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Cost efficient dimensioning of integrated fixed and mobile...
Transcript of Cost efficient dimensioning of integrated fixed and mobile...
Tom Pallini
mobile networksCost efficient dimensioning of integrated fixed and
Academiejaar 2011-2012Faculteit Ingenieurswetenschappen en ArchitectuurVoorzitter: prof. dr. ir. Daniël De ZutterVakgroep Informatietechnologie
Master in de ingenieurswetenschappen: computerwetenschappen Masterproef ingediend tot het behalen van de academische graad van
Begeleiders: dr. ir. Bart Lannoo, dr. ir. Koen CasierPromotoren: prof. dr. ir. Mario Pickavet, dr. ir. Sofie Verbrugge
Acknowledgments
I would like to take this opportunity to thank all the people supporting me in any way during the
writing of this dissertation. Without them, and their support and guidance, this dissertation would
not have been completed.
First of all, I would like to thank my promoters Dr. Ir. Sofie Verbrugge and Prof. Dr. Ir. Mario Pickavet
for giving me the opportunity to work on this interesting subject and providing me everything I
needed to complete this study.
I would also like to express my deepest gratitude to my advisors Dr. Ir. Bart Lannoo and Dr. Ir. Koen
Casier for their great suggestions, valuable information and useful feedback. I was truly amazed by
the amount of time they spent helping me and I’m very grateful to them.
Special thanks go out to Ir. Ger Bakker, director of Unet, who showed me around his company and
gave me all the information I needed to complete my studies.
Last, but by no means least, I thank my friends and family for their support and encouragement.
Especially my sister Katia, who made it possible I could fully focus on my dissertation, and my
girlfriend Marie for giving me endless support and for her profound understanding.
Authorization for loan
“The author gives permission to make this master dissertation available for consultation and to copy
parts of this master dissertation for personal use. In the case of any other use, the limitations of the
copyright have to be respected, in particular with regard to the obligation to state expressly the
source when quoting results from this master dissertation.”
Tom Pallini, may 2012
Cost efficient dimensioning of integrated fixed and mobile networks
by
Tom Pallini
Masterproef ingediend tot het behalen van de academische graad van Master in de ingenieurswetenschappen: computerwetenschappen
Academiejaar 2011–2012
Promotoren: Prof. Dr. Ir. M. PICKAVET, Dr. Ir. S. VERBRUGGE
Scriptiebegeleiders: Dr. Ir. B. LANNOO, Dr. Ir. K. CASIER
Faculteit Ingenieurswetenschappen en Architectuur Universiteit Gent
Vakgroep Informatietechnologie
Voorzitter: Prof. Dr. Ir. D. DE ZUTTER
Summary
In this dissertation we build a tool that computes an optimal dimensioning of a mobile
network, which is interconnected by a fixed network, based on geographical information. The
cost modeling of this dimensioning is also done by the tool. We perform techno-economic
analyses with the tool in two distinguishing cases: a rural and an urban case. We discuss
and compare two types of wireless technologies: LTE-advanced and Wi-Fi and the influence
of their MIMO-configuration, their height, the requested data rate, the adoption and the
considered area. The developed dimensioning tool finds a balance between the costs of the
wireless network and the costs of the fixed network. These costs play an important role in the
result. In both cases LTE-advanced turns out to be the best option although one should be
careful with the uncertainty involving the price of the 2.6GHz-band license. A choice between
Transmit Diversity and Spatial Multiplexing should be made when using MIMO. We
discovered that this choice depends of the chosen wireless technology and the given
scenario.
Key words
Dimensioning, wireless networks, fiber networks, MIMO, economic analyses
Cost Efficient Dimensioning of integrated
fixed and mobile networks
Tom Pallini
Supervisors: dr. ir. Sofie Verbrugge, prof. dr. ir. Mario Pickavet, dr. ir. Bart Lannoo,
dr. ir. Koen Casier
Abstract – In this article a comparison of wireless
technologies is made by computing the dimensioning of a
mobile network, along with the fixed network
interconnecting its antennas, in different types of cases and
comparing the costs. A dimensioning tool based on GIS-
data was developed to perform these calculations.
Keywords – Dimensioning, wireless networks, fiber
networks, MIMO, economic analyses
I. INTRODUCTION
More and more people use their smartphones or
tablets to surf on the internet and use bandwidth-
consuming applications. That’s why the demand of high
data rates in mobile networks is increasing rapidly.
These high data rates generate a lot of traffic between
the base station and its backhauling connection.
Therefore, there’s a need to connect these base stations
to an optical fiber network, which can handle very large
data rates.
In this paper we combine the optimal dimensioning of
a wireless network with the dimensioning of the fixed
fiber network which interconnects its base stations. Two
different cases have been evaluated, one in an urban
environment and the other in a rural area.
II. TECHNOLOGIES
A. LTE-advanced
LTE-advanced is a mobile communication standard
developed by the 3rd
Generation Partnership Project
(3GPP) [1]. To satisfy the enhanced peak data rates
LTE-advanced uses Carrier Aggregation to create a
bandwidth of up to 100 MHz. In the downlink OFDMA
is used, while in the uplink LTE-advanced uses SC-
FDMA to make the user equipment less complex and
more power-efficient. LTE-advanced supports MIMO.
In this paper 8x2 MIMO is used. Note that a license is
required when operating a LTE-advanced network.
B. Wi-Fi
Wi-Fi is a technology that allows devices to transfer
data over a wireless network. Wi-Fi is per definition any
WLAN product that is based on the IEEE 802.11
standards. The 802.11n standard was released in 2009
to create a next generation Wi-Fi capable of much
higher throughputs than other IEEE 802.11 standards.
By using 4x4 MIMO, allowing channels of up to 40
MHz, using more OFDM subcarriers and improving the
coding rates, a maximum data rate of 600 Mbps is
possible. Next to the higher data rates, a higher range
was achieved with 802.11n. In this paper 4x2 MIMO is
used as standard configuration.
C. Transmit Diversity and Spatial Multiplexing
Multiple Input Multiple Output (MIMO) is a
technique where more than one antenna at receiver and
transmitter side is used to transfer data between them.
Two techniques are used in this paper to benefit from
MIMO: Spatial Multiplexing (SM) and Transmit
Diversity (TD). TD results in a higher range of the base
station, while SM increases the capacity.
D. Passive Optical Network
A Passive Optical Network (PON) is a point-to-
multipoint optical network architecture in which all the
equipment between two endpoints of the network is
passive. PONs are used in this paper to interconnect the
base stations of the mobile network.
III. THE DIMENSIONING TOOL
We created a dimensioning tool based on GIS data
that can handle many different types of requests with
many different inputs. An important point was to
support the gradual roll-out of the networks, which is
made possible in the created dimensioning tool. The
tool first calculates the required base stations for a
target year and it will use this information to calculate
the optimal locations for the years between the first and
the target year. By using the information of the target
year, only base stations and fiber eventually needed in
the target year will be installed in earlier years
Based on the tool, we worked out some cases,
discussed in the next section, to show the power and the
possibilities of the tool.
IV. RESULTS
A. City of Ghent
We used the tool to look at the composition of the
costs when deploying an LTE-advanced network in
Ghent (157 km2) over 5 years. As shown in Figure 1,
the biggest cost is the fiber cost, which is responsible
for 45% of the total cost. This cost is linearly related to
the amount of fiber that is installed, so this amount
should be made as small as possible. The fixed network
clearly has a big impact on the total cost.
3%
45%33%
15%4%
Equipment Fiber
Fiber
Installation BSs
Maintenance BSs
License
Figure 1 Composition of costs case Ghent
In another scenario, the center of the city of Ghent, an
area of 7 km2, is assumed as the input area, where we
look at a comparison of LTE-advanced and Wi-Fi.
Different scenarios per technology, all with different
data rates, were investigated, 13 in total. The downlink
data rate varies from 1 to 13 Mbit/s and the uplink
bitrate is always one fifth of the downlink bitrate.
A comparison of the costs of all these scenarios is
given in Figure 2. As we see in the graph, at lower
downlink bitrates LTE-advanced is the cheaper
solution, but when the data rate is higher than 7 Mbit/s
Wi-Fi gives us the cheapest solution. We can state that
the cost of both technologies at data rates between 5 and
10 Mbit/s are more or less the same, but with lower or
higher rates, the chosen technology has more impact on
the total cost. Note that for LTE-advanced, a license
cost of €341,818 is taken into account.
0
0,5
1
1,5
2
2,5
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Co
sts
(M€
)
Bitrate download (Mbit/s)
Wi-Fi LTE-advanced
Figure 2 Comparison costs LTE-a vs Wi-Fi
We also inspected what the achieved coverage in the
different experiments was. We discovered that Wi-Fi
has many problems reaching the desired coverage at
high bitrates. We noticed that at data rates higher than
11 Mbit/s, the coverage of LTE-advanced also gets
below the demanded coverage of 99%. We can
conclude that the reached coverage of LTE-advanced is
always higher or equal than the coverage of Wi-Fi.
Only comparing the costs made us doubt between the
technologies when the data rates are high, but
comparing the reached coverage shows that at the high
data rates LTE-advanced performs better. So in any
case, LTE-advanced seems to be the better choice to
cover the city center of Ghent, although the exact price
of the license can have a big impact, but this is
discussed in subsection C.
B. Rural area
In the second case we tested the tool on a more rural
area of 35 km2 in Flevoland. We connected all farmers
in a given area to provide a triple-play package,
resulting in 25 Mbit/s downlink per house, and
compared different types of technologies to make this
connection. Coverage (at a lower bitrate) of the mobile
network is also provided on the fields of the farmers.
We also inspected the influence of SM and TD
Table 1 gives an overview of the results of the
different scenarios. It is quite clear that LTE-advanced
(LTE-a) with SM is the best technical choice. It
outperforms all other technologies. Not only the Capex
is lower, but also the yearly Opex is better than in the
other scenarios. Note that in this case the license cost is
estimated at €766.
Table 1 Comparison scenarios rural case
LTE-a SM LTE-a TD Wi-Fi SM Wi-Fi TD
# BSs 4 8 68 47
Km fiber 4.5 6 36.8 28.4
Capex €409,279 €712,576 €1,820,789 €1,328,672
Opex €21,000 €42,000 €44,200 €30,550
We can also conclude that SM and TD have a big
impact on the performance of the wireless networks. A
basic rule is that areas with a high demand of data
transfer, due to the high density or the demanded data
rate, need SM to increase the ranges of the antennas.
While in areas where the demand of data is lower, TD
seems a good method to increase the ranges. We
discovered that the choice between the two depends on
the area and the situation, but also on the chosen
technology.
C. Influence of license cost and adoption
We estimated the license fee for the city of Ghent at
€341,818. In a pessimistic view, we assume that the
license can cost €1,504,000, while a best-case scenario
gives us a value of €113,939.The worst-case scenario
results in an increase of 15.5% of the total cost, and the
best-case scenario is 3% lower than the reference
scenario. It is clear that the license cost has a big
influence on the final cost.
We also discovered that the adoption has a great
impact on the resulting cost. The total cost under a
lower adoption is 32% lower, and it is 27% higher
under a higher adoption. Spending some money in
making a good prediction of the adoption is definitely a
good choice.
V. CONCLUSION
This article gives a good view on how important the
fiber network is when dimensioning a fixed-wireless
network and shows that one should consider different
technologies and different settings of them. It also
shows the influences of the license fees and the
predicted adoption when deploying such a network.
REFERENCES
[1] ITU, “Framework and overall objectives of the future
development of imt-2000 and systems beyond imt-2000,” ITU
Recommendation ITU-R M.1645, 2003.
[2] P. E. Mogensen et al., “Lte-advanced: The path towards
gigabit/s in wireless mobile communications,” Wireless
Communication, pp. 147-151, 2009.
Kostenefficiënte dimensionering van
geïntegreerde vaste en mobiele netwerken
Tom Pallini
Begeleiders: dr. ir. Sofie Verbrugge, prof. dr. ir. Mario Pickavet, dr. ir. Bart Lannoo,
dr. ir. Koen Casier
Abstract – In dit artikel worden er verschillende
draadloze technologieën vergeleken door de
dimensionering van een mobiel netwerk, waarvan de
antennes verbonden zijn door een vast netwerk, te
berekenen in verschillende soorten gebieden en hun kosten
te vergelijken. Er werd hiervoor een dimenioneringstool
gemaakt dat werkt op basis van GIS-data.
Trefwoorden – Dimensionering, draadloze netwerken,
glasvezel netwerken, MIMO, economische analyses
I. INTRODUCTIE
Meer en meer mensen gebruiken hun smartphones of
tablets om op het internet te surfen en belastende
applicaties te gebruiken. Daarom is de vraag naar hoge
data-rates in mobiele netwerken snel aan het stijgen.
Deze hoge data-rates genereren veel traffiek tussen de
antennes en hun backhaul-connectie. Daardoor is er een
nood om deze antennes te verbinden aan een optisch
glasvezel-netwerk dat hele hoge data-rates aankan.
In deze paper combineren we de optimale
dimensionering van een draadloos netwerk met de
dimensionering van een vast netwerk dat diens antennes
interconnecteert.
II. TECHNOLOGIES
A. LTE-advanced
LTE-advanced is een mobiele communicatie
standaard ontwikkeld door het 3GPP [1]. LTE-
advanced gebruikt Carrier Aggregation om een
bandbreedte van maximaal 100 MHz te creëeren. In de
downlink wordt er OFDMA gebruikt en in de uplink
gebruikt LTE-advanced SC-FDMA om de apparatuur
van de gebruiker minder complex en energie-zuiniger te
maken. LTE-advanced ondersteunt MIMO en in deze
paper wordt er een 8x2 MIMO-configuratie gebruikt.
Merk op dat er een licentie nodig is wanneer men een
LTE-advanced netwerk opereert.
B. Wi-Fi
Wi-Fi is een technologie dat apparaten toelaat om
data te transfereren over een draadloos netwerk. Wi-Fi
is per definitie elk WLAN-product dat gebaseerd is op
de IEEE 802.11 standaarden. De 802.11n standaard is
gelanceerd in 2009 met als doel een next-generation
Wi-Fi te maken dat veel hogere data hoeveelheden
aankan dan eerdere standaarden. Door 4x4 MIMO te
gebruiken, kanalen van maximaal 40MHz toe te laten,
meer OFDM subcarriers te gebruiken en de codeer-rates
te verbeteren, is er een maximale data-rate van 600
Mbps mogelijk. In deze paper zullen we voor Wi-Fi een
4x2 MIMO-configuratie gebruiken.
C. Transmit Diversity en Spatial Multiplexing
Multiple Input Multiple Output (MIMO) is een
techniek waarbij meer dan één antenne bij de ontvanger
en de zender wordt gebruikt om data te transfereren.
Twee technieken worden gebruikt in deze paper om
voordelen te halen uit MIMO: Spatial Multiplexing
(SM) en Transmit Diversity (TD). TD resulteert in een
hoger bereik van het basis station en SM verhoogt de
capaciteit.
D. Passief Optisch Netwerk
Een Passief Optisch Netwerk (PON) is een punt-tot-
multipunt optisch netwerk architectuur waarbij al de
apparatuur tussen twee eindpunten van het netwerk
passief is. PONs worden in deze paper gebruikt om de
antennes van het netwerk met elkaar te verbinden.
III. DE DIMENSIONERINGSTOOL
We hebben een dimensioneringstool gemaakt,
gebaseerd op GIS-data, dat verschillende soorten
scenarios kan verwerken. Een belangrijk punt was om
een graduele uitrol van het netwerk te ondersteunen. De
tool berekent eerst het nodige aantal basis stations voor
het doeljaar en gebruikt dit om de optimale locaties te
bepalen voor de jaren ervoor. Door de informatie van
het doeljaar te gebruiken, zullen enkel basis stations en
glasvezel dat uiteindelijk nodig is in het doeljaar,
geïnstalleerd worden in de eerdere jaren.
M.b.v. deze tool werkten we enkele cases uit om de
mogelijkheden van de tool aan te tonen. Deze cases en
hun evaluatie zijn weergegeven in de volgende sectie.
IV. RESULTATEN
A. Stad Gent
We gebruikten de tool om de samenstelling van de
kosten te bekijken wanneer we een LTE-advanced
netwerk in Gent (157 km2) uitrollen over 5 jaar. Zoals te
zien op Figuur 1 is de glasvezelkost goed voor 45% van
de totale kos, wat veel is. Deze fiber-kost heeft een
lineair verband met het aantal km glasvezel dat
geïnstalleerd is, dus voor een optimale kost moet deze
afstand zou zo klein mogelijk zijn. Het vaste netwerk
heeft dus duidelijk een grote invloed op de totale kost.
3%
45%33%
15%4%
Equipment Fiber
Fiber
Installation BSs
Maintenance BSs
License
Figuur 1 Samenstelling van kosten case Gent
In een ander scenario nemen we het centrum van Gent
(7km2) als input en we vergelijken er twee draadloze
technologieën: LTE-advanced en Wi-Fi. We
onderzochten 13 verschillende scenarios per
technologie, elk met een andere data-rate. De downlink
data-rate laten we variëren van 1 tot 13 Mbit/s, waarbij
de uplink data-rate steeds een vijfde daarvan bedraagt.
Figuur 2 geeft een vergelijking van de kosten van al
deze scenarios. We zien in de grafiek dat bij lagere
bitrates LTE-advanced de goedkopere oplossing is,
maar wanneer de data-rate hoger dan 7 Mbit/s is, dan
geeft Wi-Fi ons de goedkoopste oplossing. We kunnen
zeggen dat tussen de 5 en de 10 Mbit/s de kosten van
beide technologieën ongeveer gelijk zijn, maar bij
hogere of lagere data-rates heeft de gekozen technologie
meer impact op de totale kost. Merk op dat voor LTE-
advanced een licentie-kost van €341.818 meegerekend
werd.
0
0,5
1
1,5
2
2,5
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Co
sts
(M€
)
Bitrate download (Mbit/s)
Wi-Fi LTE-advanced
Figuur 2 Vergelijking kosten LTE-a en Wi-Fi
We onderzochten ook wat de bereikte dekkingsgraad
was in de verschillende experimenten. We ontdekten dat
Wi-Fi veel meer problemen heeft om de vereiste
dekkingsgraad van 99% te behalen bij hoge data-rates.
We merkten dat bij data-rates hoger dan 11 Mbit/s de
dekking van LTE-advanced ook onder de gewenste
dekkinsgraad gaat. We concluderen wel dat de bereikte
dekking van LTE-advanced steeds hoger of gelijk aan
de bereikte dekking van Wi-Fi is.
Door enkel de kosten te vergelijken hadden we
twijfels over de keuze van de technologie bij hoge data-
rates, maar wanneer we ook de dekkingsgraad in
rekening brengen, zien we dat LTE-advanced eigenlijk
beter presteert bij die hoge data-rates. We kunnens dus
stellen dat LTE-advanced steeds de betere optie lijkt om
het centrum van Gent te dekken, al kan de exacte prijs
van de licentie hier een grote invloed op hebben, maar
dit wordt uitgelegd in sectie C.
B. Landelijk gebied
In een tweede case hebben we de tool gebruikt om
een landelijk gebied in Flevoland uit te werken. We
hebben alle boeren in een gegeven gebied
geconnecteerd om zo een triple-play pakket aan te
bieden, wat resulteert in 25 Mbit/s downlink per huis, en
verschillende technologieën vergeleken om deze
connectie te maken. Er wordt ook dekking (aan een
lagere bitrate) voorzien op de velden van de boeren. We
onderzochten ook de invloed van SM en TD.
Tabel 1 geeft een overzicht van de resultaten van de
verschillende scenarios. Het is duidelijk dat LTE-
advanced (LTE-a) met SM de beste optie is. Niet alleen
de Capex is lager, maar ook de jaarlijkse Opex ligt lager
dan in de andere scenarios. Merk op dat in dit geval de
licentie-kost geschat is op €766.
Tabel 1 Vergelijking scenarios landelijke case
LTE-a SM LTE-a TD Wi-Fi SM Wi-Fi TD
# BSs 4 8 68 47
Km fiber 4,5 6 36,8 28,4
Capex €409.279 €712.576 €1.820.789 €1.328.672
Opex €21.000 €42.000 €44.200 €30.550
We kunnen ook concluderen dat SM en TD een grote
impact hebben op prestatie van de draadloze netwerken.
Een basisregel is dat gebieden met een hoge vraag aan
data-uitwisseling, door de hoge dichtheid of de vereiste
data-rate, SM nodig hebben om het bereik van de
antennes te vergroten. Terwijl dat wanneer deze vraag
lager ligt, TD een goede methode lijkt om het bereik te
vergroten. We ontdektden dat de keuze tussen SM en
TD afhangt van het gebied en de situatie, maar ook van
de gekozen technologie.
C. Invloed van de licentie-kost en de adoptie
We hebben de licentie-kost voor Gent geschat op
€341.818. In een pessimistische kijk, veronderstellen
we dat de licentie €1.504.000 kan kosten en in het beste
geval kost ze €113.939. Het slechtste geval resulteert in
een stijging van 15,5% van de totale kost en het beste
geval ligt 3% lager. Het is duidelijk dat de licentie-kost
een grote invloed kan hebben op de totale kost.
We ontdekten ook dat de adoptie een grote invloed
heeft op de resulterende kosten. De totale kost bij een
lagere adoptie ligt 32% lager en ze is 27% hoger bij een
hogere adoptie. Betalen voor een goede voorspelling
van de adoptie is aan te raden, zo kan men onnodige
kosten vermijden, of het netwerk beter aanpassen aan de
vraag.
V. CONCLUSIES
Dit artikel biedt een goede kijk op het belang van
glasvezel-netwerken wanneer men een vast-mobiel
netwerk dimensioneert en toont dat men zeker ook
verschillende technologieën en instellingen moet
beschouwen. Het geeft tevens het belang van de
licentie-kost en de voorspelde adoptie aan.
REFERENTIES
[1] ITU, “Framework and overall objectives of the future
development of imt-2000 and systems beyond imt-2000,” ITU
Recommendation ITU-R M.1645, 2003.
[2] P. E. Mogensen et al., “Lte-advanced: The path towards
gigabit/s in wireless mobile communications,” Wireless
Communication, pp. 147-151, 2009.
Table of Contents
1. Introduction ......................................................................................................................... 1
2. Background .......................................................................................................................... 2
2.1 Technology ............................................................................................................................... 2
2.1.1 Wireless techniques ......................................................................................................... 2
2.1.2 Wireless technologies ...................................................................................................... 7
2.1.3 Optical Fiber ................................................................................................................... 10
2.1.4 GIS and Shapefiles .......................................................................................................... 12
2.2 Dimensioning ......................................................................................................................... 12
2.2.1 Technical modeling of the wireless technology ............................................................. 13
2.2.2 Genetic algorithm .......................................................................................................... 15
2.2.3 Minimum spanning tree ................................................................................................. 16
2.3 Economic ................................................................................................................................ 16
2.3.1 Prices and costs .............................................................................................................. 17
2.3.2 Adoption ........................................................................................................................ 19
2.3.3 Investment analysis ........................................................................................................ 20
3. The dimensioning tool ......................................................................................................... 21
3.1 Wireless Tool .......................................................................................................................... 21
3.1.1 User data and GIS data .................................................................................................. 22
3.1.2 Technical parameters and technical modeling .............................................................. 23
3.1.3 Costs, other inputs and cost modeling .......................................................................... 23
3.1.4 Dimensioning ................................................................................................................. 24
3.2 TESS framework ..................................................................................................................... 25
3.2.1 The area module ............................................................................................................ 26
3.2.2 The costing module ........................................................................................................ 27
3.2.3 The evaluation module .................................................................................................. 27
3.2.4 Importance to master thesis .......................................................................................... 27
3.3 The wireless-fixed dimensioning tool .................................................................................... 28
3.3.1 Input ............................................................................................................................... 29
3.3.2 Core of the tool .............................................................................................................. 31
3.3.3 Output ............................................................................................................................ 34
3.4 Optimizations ......................................................................................................................... 34
3.4.1 Speed.............................................................................................................................. 34
3.4.2 Splitting the target area ................................................................................................. 37
3.4.3 Downside of the density coverage ................................................................................. 37
3.5 Conclusion .............................................................................................................................. 38
4. Integration of fixed and mobile networks ............................................................................. 39
4.1 Urban case ............................................................................................................................. 39
4.1.1 Input ............................................................................................................................... 39
4.1.2 City of Ghent .................................................................................................................. 43
4.1.3 Wi-Fi vs. LTE-advanced ................................................................................................... 46
4.1.4 Conclusion ...................................................................................................................... 49
4.2 Rural case ............................................................................................................................... 50
4.2.1 Input ............................................................................................................................... 50
4.2.2 Comparison of technologies .......................................................................................... 54
4.2.3 Conclusion ...................................................................................................................... 58
5. Refined economic analyses .................................................................................................. 59
5.1 Influence of expected adoption ............................................................................................. 59
5.2 Influence of cost of extra MIMO antennas ............................................................................ 62
5.3 Influence of license cost ......................................................................................................... 63
6. Conclusion and future work ................................................................................................. 64
Table of abbreviations
4G 4th generation mobile telecommunications
AON Active Optical Network
ASK Amplitude Shift Keying
BIPT Belgian Institute for Postal Services and Telecommunications
BPSK Binary Phase Shift Keying
BS Base Station
CA Carrier Aggregation
Capex Capital Expenditures
CoMP Coordinated Multipoint
CP Cyclic Prefix
DL Downlink
EDGE Enhanced Data rates for GSM Evolution
FDD Frequency Division Duplex
FDMA Frequency Division Multiple Access
FTTB Fiber To The Business
FTTB Fiber To The Business
GIS Geographic Information System
GSM Global System for Mobile Communication
IBCN Internet Based Communication Networks and Services
IEEE Institute of Electrical and Electronics Engineers
IMT International Mobile Telecommunications
IPTV Internet Protocol TeleVision
IRR Internal Rate of Return
ITU International Telecommunication Union
LTE Long Term Evolution
LTE-a LTE-advanced
MIMO Multiple Input Multiple Output
MISO Multiple Input Single Output
MST Minimum Spanning Tree
MU-MIMO Multi User-Multiple Input Multiple Output
NPV Net Present Value
ODF Optical Distribution Frame
OFDMA Orthogonal Frequency Division Multiple Access
OLT Optical Line Terminal
ONT Optical Network Terminal
ONU Optical Network Unit
Opex Operational Expenditures
PAPR Peak-to-Average Power Ratio
PON Passive Optical Network
PSK Phase Shift Keying
QAM Quadrature Amplitude Modulation
QPSK Quadrature Phase Shift Keying
SC-FDMA Single Carrier-Frequency Division Multiple Access
SIMO Single Input Multiple Output
SISO Single Input Single Output
SM Spatial Multiplexing
SU-MIMO Single User-Multiple Input Multiple Output
TD Transmit Diversity
TDD Time Division Duplex
TDM Time Division Multiplexing
TDMA Time Division Multiple Access
TESS Transactional Environmental Support System
TESS Techno Economic Software Suite
UE User Equipment
UL Uplink
UMTS Universal Mobile Telecommunication System
VOIP Voice Over IP
VPN Virtual Private Network
WDM Wavelength Division Multiplexing
WLAN Wireless Local Area Network
XDSL (any type of) Digital Subscriber Line
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1. Introduction
Wireless technologies are evolving fast the latest years and next generation wireless networks are
being deployed all over the world. More and more people use their smartphones or tablets to surf on
the internet and use bandwidth-consuming applications, e.g. to watch video files online. Many
people would like to be able to do this anywhere, at any time. That’s why the demand of high data
rates in mobile networks is increasing rapidly. Nowadays, we already see deployments of fourth
generation (4G) networks, which are able to cope with those high demands. In the future even
networks of higher generations will be deployed that have higher data rate capacities.
New technologies also allow the ranges of the base stations of these wireless networks to be larger
than before. This means that more people can be served with just one base station. Giving each of
the people in this coverage area a high data rate generates a lot of traffic between the base station
and its backhauling connection. Therefore, there’s a need to connect these base stations to an
optical fiber network, which can handle very large data rates. Fiber networks are also becoming
popular because they can deliver a very high bandwidth. Installing a fiber infrastructure to support
the base stations has the advantage that it will certainly meet the data rate requirements of the
current wireless networks as well as of future generations.
A typical approach in network planning starts from an optimal placement of the wireless access
points followed by a separate planning in which they will look to connect the base stations to a fixed
network. The cost of this fixed connection is often underestimated.
In this master thesis we combine the optimal dimensioning of a mobile network with the
dimensioning of the fixed fiber network which interconnects the base stations. Because the demands
and the usage of a network grow every year, a gradual roll out of the network should be possible.
Based on predictions of the amount of customers and the data rate and coverage demands of every
year, we aim to find the most cost efficient roll-out of the wireless and fixed networks.
A tool was developed that is able to dimension wireless-fixed networks and perform a detailed cost
modeling of this dimensioning. We made this tool as flexible and generic as possible, so it can be
used in many different scenarios and under many different technologies for both the fixed and
wireless equipment.
After the development of such a tool some exemplary cases are set out to show the power and the
possibilities of the tool. Two different cases have been evaluated, one in an urban environment and
the other in a rural area. The tool offers solutions – the placement of the antennas and fiber and the
costs – of the dimensioning of these areas under different technologies and perform some refined
economic analyses on these results.
The results of our study show that the optimal dimensioning depends on different factors, the most
important one being the chosen technology, which has a great impact on the ranges of the antennas,
but also on the final cost of the network. The choice of this technology is influenced greatly by the
license costs needed when operating in a licensed band. Other factors, such as the MIMO-
configuration and the expected adoption of the network influence the cost of the network and
should be studied before deploying a fixed-mobile network.
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2. Background
Dimensioning both wireless and fiber networks requires knowledge of both topics. First, an overview
of the technology background is given, starting with the information of fourth generation (4G)
wireless technologies. As the fixed network is an optical fiber network, background on fiber networks
is added. Both networks are dimensioned in a different way and section 2.2 discusses the algorithms
and techniques needed to dimension them. Finally, the cost modeling of the dimensioned network is
also an important part since cost efficiency is desired when rolling out networks. In section 2.3 we
give the required definitions and information of some investment analysis terms used throughout
this dissertation.
2.1 Technology
The chapter of the technology background consists of four sections. Section 2.1.1 discusses the
techniques that will be used in the newest wireless technologies and those technologies are given in
section 2.1.2. The base stations of the wireless networks under these technologies will be
interconnected using optical networks. Information about techniques and latest developments of
optical networks is given in section 2.1.3. The final section takes a quick look at the usage of
Geographical Information Systems used in the tool of this master thesis.
2.1.1 Wireless techniques
The main goal of this thesis is to dimension a wireless network. Many different wireless technologies
exist and many new ones will arise in the future, each having their own characteristics. The choice of
the technology might be crucial when deploying a network. Requirements of such networks grow
pretty fast in time and choosing a technology that can cope with these growing demands is
important. This section sets out the techniques used in the different wireless technologies that are
deployed in the cases discussed later in the dissertation.
Duplexing
In mobile communication there is an explicit distinction in the two directions of communication:
from the base station (BS) to the user, the downlink (DL), and the other way around, which is called
the uplink (UL). Providing this two-way communication is called duplexing and the following two
techniques can be used for it:
Time Division Duplex (TDD) [1] will use the same frequency band in the DL and the UL, but assigns
different timeslots to both directions as shown in Figure 2.1. Between the UL and DL timeslots, a
guard interval is implemented to prevent UL and DL interference. This is indicated as GP (Guard
Period) in the close-up of the bandwidth allocation on the figure.
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Figure 2.1: Time Division Duplex [2]
Frequency Division Duplex (FDD) [1] will use two frequency channels to communicate between user
and BS. Figure 2.2 clearly shows that one frequency band will be assigned to the DL and one to the
UL. A guard band separates both bands to prevent interference between UL and DL. This is indicated
in the figure as the duplex frequency distance.
Figure 2.2: Frequency Division Duplex [2]
Modulation scheme
Digital modulation is the process of translating digital data to an analogue signal. This process is
necessary if the digital data needs to be transferred over a medium that only allows analogue
transmission, e.g. a wireless medium [1].
Phase Shift Keying (PSK) uses different shifts of the phase of the signal to represent the data. Shifting
over 180° is called Binary PSK (BPSK), which is shown in Figure 2.3 (a). Only 1 bit is coded per shift.
Figure 2.3 (b) shows Quadrature PSK (QPSK), where higher bitrates can be achieved because 2 bits
are coded per phase shift, but the more symbols used in the phase domain, the harder it will get to
separate them and decoding errors are more likely to occur after the analogue transmission.
Another modulation scheme is Quadrature Amplitude Modulation (QAM), which is a multilevel
coding that uses both phase shifts and differences in amplitude to code the data [1]. Two examples
of QAM are shown in Figure 2.3, where (c) gives 16-QAM using a 4-bit multilevel coding and (d)
shows 64-QAM, which implements a 6-bit multilevel coding. Here too, a higher bit-level corresponds
with a higher bitrate, but is more sensitive to modifications of the analogue signal due to
transmission.
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Figure 2.3: Modulation schemes
Multiple Access
Different ways exist to share the wireless medium amongst its users. In some current technologies
Code Division Multiple Access (CDMA) is used, which uses codes with certain characteristics to
separate different users in code space and enable access to a shared medium without interference
[1]. In modern technologies following two techniques are used:
Orthogonal Frequency Division Multiple Access (OFDMA) creates slots in the time-frequency space
and assigns users to a different number of sub-carriers as shown in Figure 2.4. An advantage over
CDMA is that it can handle multipath interference with more robustness and less complexity at the
user side. If there is less complexity in the receiver, it will become cheaper and will need less power.
OFDMA will also achieve a higher MIMO spectral efficiency (see further).
Figure 2.4: OFDMA
Single Carrier-Frequency Division Multiple Access (SC-FDMA) is an adapted form of OFDMA [3] and
their difference is explained in Figure 2.5 [4]. On the left side, N (in this case 4) adjacent 15 kHz
subcarriers are each modulated the OFDMA symbol period by one QPSK data symbol. After one
OFDMA symbols, holding 4 QPSK symbols, a Cyclic Prefix (CP) or guard period is inserted to make
sure there’s no interference between the symbols and the next four symbols are transmitted in
parallel. SC-FDMA signal generation begins with a special linear pre-coding process but then
continues as OFDMA. The right side of the figure shows that SC-FDMA transmits the four data
symbols in series at 4 times the rate, with each symbol occupying N times 15 kHz bandwidth. As the
figure shows, SC-FDMA is clearly a single carrier (which explains the SC prefix) and OFDMA is a multi-
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carrier. Note that the SC-FFMA symbol length has the same length as the OFDMA symbols, but it
contains N sub-symbols.
The complexity of SC-FDMA is comparable to OFDMA, but the peak-to-average power ratio (PAPR) of
the transmitted signal in OFDMA is higher due to parallel transmission. This means that in SC-FDMA
the transmit power is more efficient, resulting in a longer battery life. SC-FDMA is an attractive
alternative to OFDM, especially in uplink communication where lower PAPR greatly benefits the
transmit power efficiency and costs of the mobile terminal.
Figure 2.5: OFDMA and SC-FDMA [5]
Carrier Aggregation
Carrier Aggregation (CA) allows to aggregate two or more component carriers of the same or
different bandwidth into a carrier with a larger spectrum [6]. In Figure 2.6 we see that 5 carriers are
aggregated to create a larger carrier with a higher maximum bandwidth. Subcarriers of different
bands or consecutive subcarriers of the same band can be aggregated to form a bigger carrier. This
way, a larger bandwidth can be used in UL and DL. This technique is used in modern wireless
technologies, e.g. LTE-advanced (see section 2.1.2).
Figure 2.6: Carrier Aggregation [7]
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MIMO
A key feature in 4G wireless communication is the use of multiple antennas on the transmitter and
the receiver. Multiple Input Multiple Output (MIMO) is a technique where more than one antenna at
receiver and transmitter side is used to transfer data between them (see Figure 2.7). This benefits
the spectral efficiency greatly. Using only one antenna at both sides is called Single Input Single
Output (SISO). Other variants like Single Input Multiple Output (SIMO) and Multiple Input and Single
Output (MISO) or also possible, but in this dissertation we will focus on MIMO. The notation of a
MIMO configuration with Y antennas on the transmitter and Z antennas at the receiver is: YxZ MIMO.
The antennas in MIMO can be used in different ways [6]. A distinction has to be made about the
amount of users using the antennas at a given time. Single User-MIMO (SU-MIMO) assigns the time-
frequency resources to one user only. This user can now reach a maximal spectral efficiency. Multi
User-MIMO (MU-MIMO) allocates different users in the same time-frequency resource. This way,
more users can transfer data at the same time. Different techniques exist to benefit from MIMO,
Spatial Multiplexing (SM) and Transmit Diversity (TD) being two common techniques explained
further.
Figure 2.7: SISO, SIMO, MISO and MIMO [8]
TD is a technique that uses the multiple antennas to send replicas of a given data stream [9]. As
shown in Figure 2.8, all antennas will send the same stream, but coded differently across space and
time, and the receiver can now make a better decision by combining the received signals. This results
in a higher range of the BS.
Figure 2.8: Transmit Diversity [10]
SM will split a given data stream into pieces and will send each fragment with a different antenna as
shown in Figure 2.9. Each data stream is now independent of each other. This increases the capacity
of the MIMO-link.
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Figure 2.9: Spatial Multiplexing [10]
In Spatial Multiplexing, the maximum data rate of the normal configuration will be multiplied by the
number of antennas that can transmit at the same time. This in contrast to Transmit diversity, which
doesn’t change the data rate but adds positive input gains to the antenna, resulting in a higher range.
2.1.2 Wireless technologies
Nowadays there are many different wireless technologies. We are now at breakthrough of the fourth
generation (4G) of telecommunication systems. Figure 2.10 gives an overview of the generation of
telecommunication systems that have already been deployed. The first generation (1G) was a
collection of analogue systems. Of the second generation (2G) systems the Global System for Mobile
Communications (GSM) standard is the most used one. Nowadays many third generation (3G)
networks are rolled out. Enhanced Data Rate for GSM Evolution (EDGE) and Universal Mobile
Telecommunication System (UMTS) are the most known examples of 3G systems. In this section we
will point out the requirements for the 4G systems as defined by IMT-advanced, and discuss LTE-
advanced, a 4G standard. We also take a look at the Wi-Fi standard, which matches the 4G data
rates.
Figure 2.10: Overview of generations of telecommunication systems [11]
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IMT-advanced
International Mobile Telecommunications (IMT)-advanced is a global framework made by the
International Telecommunication Union (ITU) to set the requirements for a 4G system. Its
predecessor is IMT-2000, a framework for 3G systems. Figure 2.11 shows the goals for the successor
of IMT-2000. IMT-advanced aims to achieve a higher mobility and higher data rate than IMT-2000.
Figure 2.11: IMT-2000 and IMT-advanced [12]
The most important properties of IMT-advanced are [13]:
a high degree of commonality of functionality worldwide while retaining the flexibility to
support a wide range of services and applications in a cost efficient manner
compatibility of services within IMT and with fixed networks
capability of interworking with other radio access systems
high quality mobile services
user equipment suitable for worldwide use
user-friendly applications, services and equipment
worldwide roaming capability
enhanced peak data rates to support advanced services and applications (100 Mbit/s for high
and 1 Gbit/s for low mobility were established as targets for research)
These features enable IMT-Advanced to address evolving user needs and the capabilities of IMT-
Advanced systems are being continuously enhanced in line with user trends and technology
developments.
LTE-advanced
One technique that meets the IMT-advanced requirements is Long Term Evolution (LTE) advanced
[14]. LTE-advanced is a mobile communication standard developed by the 3rd Generation Partnership
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Project (3GPP). An important demand was that LTE-advanced would remain compatible with LTE, a
3G standard that meets the demands of the IMT-2000 framework. To satisfy the enhanced peak data
rates LTE-advanced uses Carrier Aggregation to have a bandwidth of up to 100 MHz. Note that using
CA increases the complexity of the User Equipment (UE). In the downlink OFDMA is used, while in the
uplink LTE-advanced uses SC-FDMA to make the UE less complex and more power-efficient. LTE-
advanced supports MIMO of up to 8x8 in the DL and 4x4 in the UL. Coordinated Multipoint (CoMP)
transmission and reception techniques are also introduced. CoMP techniques try to decrease the
interference by communicating through the backhaul network between the Base Stations, which
increases the performance [15]. To enhance the coverage in difficult conditions, such as big buildings
or the UE being indoor, LTE-advanced uses relaying. A relay node is connected to the Base Station
through a fixed or wireless link, while the user connects wirelessly to the relay node. Figure 2.12
shows a relay situation with a wireless link between the base station and the relay node.
Figure 2.12: Relaying [7]
Wi-Fi
Wi-Fi is a technology that allows devices to transfer data over a wireless network. Wi-Fi is per
definition any Wireless Local Area Network (WLAN) product that is based on the IEEE (Institute of
Electrical and Electronics Engineers) 802.11 standards. IEEE 802.11 is a set of standards for
implementing WLAN communication in the 2.4, 3.6 and 5 GHz frequency bands, which are license-
free. The first standard, 802.11-1997, dates from 1997 and was able to reach 2 Mbps. Many releases
of the 802.11 standard exist, some much more popular than others. Following releases are the most
common ones. The first one that was widely accepted was 802.11b, which was released in 1999
along with 802.11a. The first operated in the 2.4 GHz band and could achieve 11 Mbps, the latter in
the 5GHz band with a maximum net rate of about 20 Mbps. In 2003 802.11g was released to reach
data rates of up to 54 Mbps. 802.11n was released in 2009 by IEEE to create a next generation Wi-Fi
capable of much higher throughputs than other IEEE 802.11 standards. By using 4x4 MIMO, allowing
channels of up to 40 MHz, using more OFDM subcarriers and improving the coding rates, a maximum
data rate of 600 Mbps is possible. Next to the higher data rates, a bigger range was achieved with
802.11n. More next generation releases are being developed and will be released in the future.
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2.1.3 Optical Fiber
The goal of this thesis is to interconnect the wireless network with a fiber-optical network. Two types
of optical access networks can be distinguished: Active Optical Networks (AONs) and Passive Optical
Networks (PONs). An AON uses electrically powered switching equipment to manage signal
distribution and direct signals to specific customers. A PON, on the other hand, uses optical splitters
to separate and collect the optical signals as they move through the network and does not contain
electrically powered equipment. PONs are more efficient than AONs because each fiber optic strand
can serve up to 32 users. They also have a low building cost relative to AONs along with lower
maintenance costs. That’s why we chose PONs over AONs as the backhauling networks in this
dissertation.
This section will explain how a PON works and will set out the different types of PONs. The
equipment needed for a PON will also be listed and discussed in this section.
Passive Optical Network
A Passive Optical Network (PON) (Figure 2.13) is a point-to-multipoint optical network architecture in
which all the equipment between two endpoints of the network are passive. A single optical fiber can
serve multiple premises by using unpowered optical splitters. Different types of PONs can be
distinguished according to the Division Multiplexing method. A common type is Time Division
Multiplexing PON (TDM-PON), which assigns a time-slot to each subscriber. Wavelength Division
Multiplexing PON (WDM-PON) (Figure 2.14) is a newer technique where each subscriber is assigned a
different wavelength [16]. The advantage of this method is that WDM-PON can be seen as an
aggregation of per wavelength point-to-point connections between each subscriber and the central
office.
Figure 2.13: Passive Optical Network
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Figure 2.14: WDM-PON [17]
Figure 2.15 shows the equipment model used in this dissertation. The model shows the central office
and all the equipment needed to connect one fiber to this central office with a PON. Assume the X at
the splitter in the figure is equal to 32, which is a common configuration for a PON splitter. The most
important components of the model are explained underneath.
Figure 2.15: Equipment model of a PON
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Optical Line Termination
An Optical Line Termination (OLT) is a device which serves as the service provider endpoint of a PON.
It has two main functions:
It performs conversion between the incoming signals received from the service provider’s
equipment to the signals used in the optical network.
It coordinates the multiplexing between the Optical Network Units (ONUs).
Optical Network Unit and Optical Network Terminal
An Optical Network Unit (ONU) performs conversion between the incoming optical signal from an
optical network and the in-house cabling at the customer’s premises. An Optical Network Terminal
(ONT) is a special case of an ONU that serves a single subscriber, instead of multiple subscribers.
Optical Distribution Frame
An Optical Distribution Frame (ODF) is a fiber optic management unit used to organize the fiber optic
cable connections. An ODF exists of an ODF rack and several ODF slots.
2.1.4 GIS and Shapefiles
A Geographic Information System (GIS) is a system designed to capture, store, manipulate, analyze,
manage and present all types of geographical data. A shapefile, short for Esri1 shapefile, is a
geospatial vector data format for GIS software. Shapefiles store primitive geometrical data types of
points, polylines and polygons. These three data types are used to represent many different
geographic elements, points for example can represent water wells, while a river can be shown as a
line and the polygon could be a lake or an ocean. Each data type can also have a series of attributes
that describe the items, e.g. the name.
In this thesis, shapefiles are used to represent possible locations of antennas and fiber and
geographical data that contain attributes, e.g. demographic data. These shapefiles will be used in the
dimensioning tool discussed in chapter 3 and the different files used in this study will be discussed in
chapter 4 when introducing the different cases.
2.2 Dimensioning
An important step in deploying a network is dimensioning it: making the decision where to place the
components of a network. How this works depends on the type of network and the type of its
components. In this thesis we have to dimension a wireless network in combination with an optical
fiber network.
The wireless dimensioning consists of two steps: first a technical modeling is performed to determine
the data rates and the ranges of the antennas and then the optimal locations of the base stations
have to be found. Section 2.2.1 discusses the techniques used for the technical modeling. To find the
optimal locations of the base stations this master thesis uses a heuristic algorithm to select an
optimal solution from a set of possible locations. This heuristic algorithm is explained in section 2.2.2.
1 Esri is a software development and services company providing GIS software and geodatabase management
applications. Esri developed and regulates the shapefile format as an open standard for data interoperability.
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The fiber dimensioning in this master thesis depends upon these optimal locations of the antennas.
Given these locations, the optimal interconnection is searched. This is the interconnection that has
the minimal total cost, which is linearly linked to the distance and can be optimally calculated with a
Steiner Tree. In this dissertation, we used an approximation of the Steiner Tree by using the Minimal
Spanning Tree. Section 2.2.3 explains the concept of a Minimal Spanning Tree and gives an algorithm
to calculate it.
2.2.1 Technical modeling of the wireless technology
The technical modeling of the wireless technology consists of two parts: finding the possible data
rates and determining the maximum range of the antennas. The possible data rates for every
modulation scheme of the given technology are used to determine the number of users that one
base station can cover. Finding the maximum range of a base station consists of two steps: first a link
budget is calculated and then the maximum range can be found based on this link budget and a path
loss model.
Bitrate
The bitrate depends of the properties of the used technology. The formula differs for TDD and FDD:
when using TDD an extra factor – the DL:UL ratio – has to be added. The formula [18] is given
underneath. The code rate refers to the amount of information located in the data stream. A code
rate of k/n means that for every k useful bits (holding information), n bits are generated by the
coder, resulting in n-k redundant bits. A lower code rate is more resistant to errors due to the higher
number of redundant bits and thereby results in higher ranges. M is the number of symbols in the
modulation scheme, e.g. for 16-QAM, M is 16, and for QPSK, M is 4.
(
)
( )
With BW the bandwidth in hertz
n the sampling factor
Ndata the number of available subcarriers
NFTT the total number of subcarriers
k/n code rate
M number of symbols in modulation scheme
G the guard interval
Link budget
The first step in calculating the maximum range is computing the link budget. In the link budget the
gains and losses of the transmitter, through the medium to the receiver are taken into account. The
maximum allowed path loss PLMAX that a signal can suffer and will still be detectable by its receiver
will be calculated. The path loss is given in the formula underneath. It sets out the relationship
between the emitted power and the received power of the signal.
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The input power, gains, losses and margins are input parameters that are known when selecting a
certain technology and a certain configuration of it. These parameters are discussed later when their
values will be used. The receiver sensitivity is a combination of the thermal noise, receiver noise and
receiver implementation loss. The receiver sensitivity is different for each modulation scheme and
it’s the reason why higher modulation schemes achieve lower ranges.
When using Transmit Diversity, the ranges are increased, due to a higher PLMAX. Two extra gains are
added to the link budget: a cyclic combining gain of 3dB and a MIMO gain. The MIMO gain depends
from the amount of transmitter and receiver antennas and its formula is given underneath.
( )
Path loss model
The PLMAX is used to determine the ranges of the antennas by using a path loss model. A path loss
model defines the relationship between the range of an antenna and the path loss. This thesis will
use the Erceg model [19], which has different types of configurations, each responsible for a different
terrain type. The formula for the Erceg model is given underneath [20]. Three different types of
terrain categories are defined in this model: A, B and C. Category A is developed for a hilly terrain or
moderate-to-heavy tree density, while Erceg C models a mostly flat terrain with light tree densities
and category B is somewhere in between these two. The difference in these categories is determined
by the three parameters a, b and c and there values for each different category is given in Table 2.1.
In this dissertation we only use the Erceg C model, but we use two different values for AF (the
correction factor of the environment).When calculating the path loss in an urban area, AF is set to
3dB, while in rural areas AF is equal to -5dB.
With the wavelength (in meter)
the path loss variable: = (a – b x hBS + c/hBS)
hBS the height of the Base Station
a, b, c constants that represent the terrain type
d the distance between the user and the Base Station (in meter)
d0 = 100m
f the frequency (in MHz)
hm the height of the Mobile Station (in meter)
AF the correction factor of the environment
s the shadowing fading component that takes into account the signal variations
between different locations on an equal distance of the transmitter
Category A Category B Category C
a 4.6 4.0 3.6
b 0.0075 0.0065 0.0050
c 12.6 17.1 20.0 Table 2.1: Numerical values of Erceg model parameters [19]
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2.2.2 Genetic algorithm
To dimension the wireless network we need to select a number of locations from a collection of
possible antenna locations that will result in a network that meets the demands when installing an
antenna on the selected locations. In many cases there are many possible antenna locations and the
number of antennas needed to cover a certain area is unknown. Computing every possible solution
and comparing the results will therefore be a very time-consuming assignment (e.g. for selecting 10
antenna locations from 20 possible locations already leads to more than 1013 possibilities to be
checked). A better way to approach this problem is using a heuristic algorithm, which won’t run over
every possible solution but will try and find an optimal – but not necessarily the best – solution in a
smart way. In this thesis we use the genetic algorithm to find a good solution to our dimensioning
problem.
A genetic algorithm is a search heuristic that mimics the process of natural evolution. The algorithm
is part of the larger class of evolutionary algorithms. The evolution of a genetic algorithm starts from
a population, consisting of randomly generated solutions. In each generation, the fitness of every
solution in a population is evaluated. In this master thesis this fitness function will be a combination
of the total coverage and the cost of a solution. The best solution (based on the fitness) needs to be
saved and only overwritten if a better solution is found. In a next step solutions with the lowest
fitness values are removed. Multiple solutions are then stochastically selected from the remaining
population and modified to form a new population. The population is now used in the next
generation of the algorithm. The solutions selected from a previous generation will be called the
parents. The evolution in a generation will happen through a genetic operator invoked on the
parents: either a mutation or a cross-over. This will result in the children or the offspring, which are
the solutions of the current generation.
Figure 2.16 shows a graphical explanation of both genetic operators. Consider a solution as a string
of bits with a fixed size – the amount of possible antenna locations –, where each bit is associated
with a possible antenna location. When a bit equals 1, an antenna on the corresponding location
would be installed if the solution would be implemented. A crossover is the operation where two
parents will swap a piece of their string resulting in two children that are a combination of both
parents, as shown on the left side of Figure 2.16. In a mutation, a child is formed from a parent by
changing the value of a randomly chosen bit in the string.
The algorithm stops when a satisfactory fitness level is reached or when a predefined maximum
number of generations has been reached. Note that it is not certain that a satisfactory solution has
been found at this maximum number of generations.
Figure 2.16: Crossover and mutation
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2.2.3 Minimum spanning tree
In order to calculate the cost of a fiber network, a fast way of estimating the installation length has to
be added to the dimensioning tool. For this we work with a minimal spanning tree, which is defined
as follows:
A spanning tree of a connected, undirected graph is a connected sub graph that connects all the
vertices together. If we assign weights to the edges, we can calculate the MST of the graph, which is
the spanning tree with the lowest total weight.
There are many existing algorithms for calculating such a minimal spanning tree fast. We worked
with the Kruskal algorithm which is explained in [21]. Define n as the number of vertices we need to
connect. The algorithm follows these steps:
Create a set F, which is empty
Create a set S containing all the edges of the graph
While S is not empty or F is not yet a spanning tree of size n-1
o Remove the edge with minimum weight from S
o If F is empty or if it connects to just one or none of the trees of F, add the edge to F
o If the edge connects two different trees of F, remove those trees from F and add the
new tree to F, which is the combination of the two original trees and the edge
o Else: throw the edge away
F now contains one element: the MST of the graph
As the dimensioning tool is also built to cope with gradual roll-out scenarios, where the parts of the
network that were already installed in an earlier year need to be taken into account to form the
extended network, this algorithm had to be changed in the following manner:
In the first step, add the given sub graph to the set F.
In the second step, remove all edges from the sub graph in the set S.
All other steps remain the same.
2.3 Economic
An important part of this master thesis will handle the cost modeling of the dimensioned networks.
To do so, some economic background is required. Section 2.3.1 will set out the costs and prices of
the equipment and the installation used in this master thesis. Because the discussed wireless
technologies are new, people need to be given time to get used to its existence and they will not
always use it right away. The amount of people using a certain technology at a given time is called
the adoption. The costs and the income will depend on this adoption, which is discussed in section
2.3.2. The most frequently used operation for performing an economic analysis based on these costs
is the Net Present Value, which is formulated and explained in section 2.3.3.
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2.3.1 Prices and costs
This section sums up the prices and costs used in this thesis. First, the costs for the wireless network
are given, including the equipment costs and the rent or price for a pole to place the base station on.
The other subsection gives the costs for the equipment and installation of the optical network.
Wireless
The wireless costs depend on the chosen technology. In this master thesis we use two different
technologies: Wi-Fi and LTE-advanced, which were discussed in section 2.1.2.
The equipment of a 2x2 MIMO BS of LTE-advanced comes to a total of €30,0002. In this master thesis
we will use 8x2 MIMO LTE-advanced, which implies that for each sector on the BS 6 extra antennas
have to be placed. The costs of these extra antennas can be very dependent on the case, the vendor
and the type of contract with the vendor. We assume an extra cost of 66.67% per BS to upgrade it to
an 8X2 MIMO BS. Later, we take a look at the influence of this extra cost. For Wi-Fi, a 4x2 MIMO BS
costs €4,0003. The maintenance costs of the base stations are 10% of the equipment costs and the
average lifetime of the wireless equipment is 5 years. To install a BS and connect to the power and to
a network an installation cost of €4,000 for LTE-advanced and €2,000 for Wi-Fi is needed. This cost is
lower for Wi-Fi because the base station is smaller and easier to install.
Also the area of the cases used in this thesis has an influence on some costs. As we will see in chapter
4 we have one urban case in Ghent (Belgium) and one rural case in Flevoland (The Netherlands). A
distinction has to be made in the cost of the locations, because in Ghent we can rent locations on
poles of the Belgian Institute for Postal services and Telecommunications (BIPT) or, in case of Wi-Fi,
even just install the base stations on buildings. In Flevoland we have to install our own poles, either
just straight into the ground or a smaller pole on the roof of a building in the area.
In the case of Ghent, for a location of BIPT a yearly rental cost of €3,000 for LTE-advanced and €2,700
for Wi-Fi will be asked [18]. A new location on a building has a rental cost of €250, but also an extra
installation cost of €2,000 is required to be able to place a BS on a building. On this new location a
building permit for the installation is needed, such a permit costs €500. We will not need this permit
for a BIPT location.
In the rural case (see section 4.1.3) no poles of the government or buildings are used for placing the
base stations but new poles have to be installed. There are two options: a 100ft (33m) pole on the
ground or a 30ft (11m) pole placed on top of a roof on a building. A 100ft pole costs €10000,
consisting of €8000 equipment and €2000 placement costs. The 30ft pole costs €2500, off which
€2000 are equipment costs and €500 are paid for installation. In Table 2.2 an overview of all the
discussed costs is given.
2 This figure is based on an estimation made on rough data received from Ericsson.
3 This estimated number is based on information received from Zapfi.
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Ghent Flevoland
LTE-advanced Wi-Fi Wi-Fi new loc. LTE-advanced Wi-Fi
Base station 50000 4000 4000 50000 4000
Pole 0 0 2000 10000 2500
Installation BS 4000 2000 2000 4000 2000
Building permit 0 0 500 500 500
Total Capex 54000 6000 8500 64500 9000
Rent location 3000 2700 250 250 250
Maintenance 5000 400 400 5000 400
Total Opex 8000 3100 650 5250 650
Table 2.2: Wireless equipment and installation costs
License costs
When operating in the 2.6 GHz band, so when using the LTE-advanced technology, a license has to be
paid to use this frequency band. Determining a fixed cost per MHz is not easy, because these licenses
are auctioned in every country and depend greatly from country to country, e.g. the licenses in
Sweden were sold at almost 4 times the price as they were sold in Belgium [22]. Since we will handle
two cases in two different countries, we need to look up the license fees for both countries.
In Belgium, the licenses were auctioned in November 2011. The licenses were sold at 4.6 euro cents
per MHz-PoP, which is the bandwidth in MHz divided by the population covered [23]. So, to give an
idea, a 2x15 MHz band (3 sectors FDD) was bought for €15,040,000 and a 45 MHz band (3 sectors
TDD) is worth €22,510,000 in Belgium. The licenses are valid for 15 years.
In the Netherlands, the 2.6GHz auction happened in April 2010. Licenses were sold much cheaper
than in Belgium, averaging only 0.13 euro cents per MHz-PoP, which is derisory compared to the
Belgian price [24]. 1 MHz in the paired spectrum for the whole country was sold at an average of
€20,200, but prices were different for every bidder [25]. These licenses are valid for 20 years, but the
operators were obliged to start deploying their network within 2 years.
The exact license costs used in this dissertation depend on the case and are discussed in chapter 4.
Fiber costs
The cost for installing 1 meter fiber is estimated at €50. These costs include the digging costs and the
cost of the material of the fiber. Table 2.3 shows an overview of the costs of equipment used in the
central office. Also the average lifetime of the equipment is given. At the end of this period, the
equipment needs to be replaced. When no entry is given, the lifetime is considered infinite.
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Equipment Price Average lifetime
ODF rack €800
ODF slot €20
System rack €600
Shelf with switching fabric €5375 5 years
OLT card €2000 5 years
Control card €0 5 years
Transport card €0 5 years
Small pluggable optical port €15 5 years
Power supply €700
Layer 2 switch €650 5 years
1:32 splitter €500 5 years Table 2.3: Fiber equipment costs and lifetimes [26]
2.3.2 Adoption
User adoption is often the basis of the economical calculations since users are the main revenue
driver. The adoption is considered to be given by a general adoption model. The Gompertz model is
chosen to estimate the user adoption of Mobile internet through the years [27]. According to [28],
this adoption model gives the best fit in case of a telecom business case compared to other models.
The formula of the Gompertz model has three parameters: the inflection point (a), the slope (b) and
the market size (m). The parameters used for Ghent are shown in Table 2.4, assuming we are now
(i.e. 2012) in year 0. We will mainly use the values for the inhabitants. The formula of the Gompertz
model is given underneath and Figure 2.17 shows the shape of the Gompertz curve for the
parameters of the inhabitants.
( ) ( )
User type a b m (%)
Inhabitants 2 0.64 20.00
Students 2 0.64 33.33
Tourists 2 0.64 5.00
Industry 2 0.64 5.00
Table 2.4: Values of parameters of Gompertz model
Figure 2.17: Gompertz curve
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2.3.3 Investment analysis
When deploying a network gradually, every year costs will be made and revenues will be earned
resulting in a cash flow. Different calculations and operations can be made on this cash flow. The
most important of them all is the Net Present Value (NPV).
The NPV of cash flows is defined as the sum of the present values of the individual cash flows of
same entity [29]. A present value is the value on a given date of a payment made at other times. If
this payment is in the future the payment is discounted to reflect the time value of the money. The
discount rate used in this dissertation is 10%. The formula of NPV is given underneath.
Other instruments to measure the profitability exist, such as Internal Rate of Return (IRR), which is
the rate at which the NPV is 0. The higher the IRR, the more profitable a project is. Another
instrument is the payback period, which refers to the period of time required to repay the
investment. Shorter payback periods are preferable to longer ones. In this dissertation we only use
the NPV as an instrument for the investment analysis.
∑
( )
With t the time of the cash flow
i the discount rate
Rt the net cash flow (inflow minus outflow) at time t
N the total number of periods
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3. The dimensioning tool
The dimensioning tool is a very important part of the master thesis, because it will do the hard work
for the research. If we want to make an estimation of the costs for installing a wireless network
backhauled over a fixed fiber network and want to get a better feeling for the different tradeoffs in
this, we need to be able to calculate the optimal placement of the wireless antennas and fiber
topology. Once the amount and placement of the antennas and the topology of the fiber is available,
we can proceed to estimate the costs for such a project. With this ability in place, we are able to link
the wireless technologies (see chapter 2) to a market estimation in terms of customer adoption,
willingness to pay, expected bandwidth per user, etc. and come up with a set of profitable scenarios
(technology, placement, etc.) and their detailed business cases, which will be further explored in
chapter 4.
Finding the optimal combination of antenna placement and fiber topology on top of geographical
information system (GIS) data, is a non-trivial task and clearly an infinite amount of solutions for this
exist. For this, we have built upon an existing heuristic tool based on genetic algorithms for the
optimal placement of the wireless antennas. This tool is described in more detail in subsection 3.1.
To keep the calculation time as low as possible, only a stub calculation is used for the costs and
revenues, and a more detailed calculation is required once a good optimal candidate is found. To
accomplish this we could use the Techno-Economic Software Suite (TESS), for which we describe the
parts we used in subsection 3.2.
Both tools – wireless dimensioning and TESS – are combined and extended to form the core of the
fixed mobile dimensioning tool. Clearly here it is important to capture the requirements correctly, to
enable us to perform all simulations later on. For this the input and output has to be defined and
linked into the existing tools. Especially the code of the wireless tool had to be extended and
updated to cope with those new requirements and to enable fixed-wireless instead of wireless-only
cost estimation. The structure and details of the different elements in the tool are described in
subsection 3.3.
A final part of the key research and work on a heuristic tool is focused on reducing the runtime while
maintaining (or improving) the outcome. Subsection 3.4 details the most important runtime-
optimizations introduced in the tool. It also concludes this section and will clearly show the input,
output and runtime for different exemplary cases.
3.1 Wireless Tool
The Wireless Tool is a tool that was developed within IBCN. It was developed to find an optimal
placement of antennas in a given area when someone wants to roll out a wireless network that has
to meet a given adoption requirement and given capacity requirements in ten years. Note that the
tool assumed the network will be rolled out within the coming year, so all antennas will be placed at
once. The dimensioning of the wireless network is well handled in this tool. A detailed technical
modeling is done, based on path loss models, to determine the range of each antenna, while taking
into account the population density. The dimensioning itself is computed with a heuristic algorithm,
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which is a good choice due to the many possible solutions of a wireless dimensioning problem. This is
caused by the lack of placement restrictions for an antenna.
Since the goal of the dissertation is to determine the roll-out of a wireless network interconnected by
a fixed network, this tool is a good starting point. The tool even offers a basic calculation to connect
the base stations to given backhauling connection points. Though, in many situations these
calculations won’t give an optimal solution, so one of the main working points will be to extend this
fixed network dimensioning. Another important working point will be the flexibility of the tool, since
many parameters in this tool are hardcoded. Finally, to be able to run many experiments with this
tool, some runtime-optimizations will be needed.
Figure 3.1 shows the structure of this tool. Based on the GIS data of the area, the technical
parameters of the desired wireless technology and the costs of the antennas, a dimensioning is
made. First the modeling of the wireless technology to find the ranges of the antennas is run,
followed by the actual dimensioning – placing antennas as good as possible to cover the given area-
and eventually a cost modeling, based on the input costs. In the following sections each part of the
tool will be discussed and changes that have been made are highlighted.
Figure 3.1: Wireless tool [18]
3.1.1 User data and GIS data
The tool requires several files with GIS data (in a shapefiles format) as input. A shapefile of the target
area is needed. The area can be split into sectors, each having a different value for the number of
inhabitants, called user data in Figure 3.1. There is also an option to provide another shapefile to
determine the area to cover. Besides that, a shapefile containing the possible locations of the base
stations is needed. The tool can also process three-dimensional shapefiles to determine the height of
buildings in the area and use these buildings as possible base station locations. This will be important
| 23
when using technologies such as Wi-Fi, because the ranges of the antennas won’t always be big
enough to place them only on the public locations. Finally, the original tool also requires a shapefile
with the locations of possible backhaul connections. For every antenna installed, the closest
connection point is searched and a fiber connection is made between the antenna and this
connection point.
All of this GIS data will be used in the updated dimensioning tool, except for the shapefile containing
the possible backhauling locations, which will not be used as the fiber dimensioning will be more
detailed and requires a different input (see section 3.3.1).
3.1.2 Technical parameters and technical modeling
The technical parameters for the chosen wireless technology are stored in a spreadsheet. There are
many parameters to consider when dealing with wireless technologies. All the values of the
parameters are processed by the same calculation sheet. The sheet calculates the maximum uplink
and downlink data rates of a base station under given technologic constraints.
Based on the maximum data rates, and the demographic data from the shapefile, a range for every
possible antenna (based on the given antenna locations) is calculated. These ranges are calculated
using a path loss model, discussed in chapter 2. This range translates into a coverage area that has
the shape of a circle. So every possible antenna location now also has a given area it would cover if
the antenna is installed. This technical modeling information will be used as input for the
dimensioning of the wireless network.
3.1.3 Costs, other inputs and cost modeling
In some ways, the Wireless Tool is very limited. As mentioned before, it assumes the roll-out will be
performed all at once. Therefore, the tool will look at the demand for network connectivity over ten
years. It assumes the adoption of the network usage will be 0.2 and that the DL capacity requirement
is 5 Mbit/s, while the UL capacity is 1 Mbit/s. These settings are not easy to edit in the original tool,
because they can’t be changed in the main class. The fixed period of ten years is also hard to change,
because not only are the calculations for the adoption based on it, but also the equipment costs are
calculated based on this number. The tool has one cost as input, the antenna cost. This cost is based
on the installation cost, and 10 years of maintenance costs, all discounted with 5 percent over these
years. This implies that changing the installation or maintenance cost requires some effort too. For
the fiber a fixed cost per meter is assumed. This cost includes all equipment costs and installation
cost. The latter will be the most expensive of both, because it includes the digging costs, which –
certainly in the city – is not to be underestimated. The cost modeling of the wireless tool is rather
simple: multiplying the amount of antennas by this fixed antenna cost and adding the amount of
fiber multiplied by the fiber cost.
In the dimensioning tool of this master thesis easy changes of these parameters should be possible.
First of all, the roll-out should be able to be gradual, so every year antennas can be added, to cope
with the capacity and adoption requirements of the given year. This also makes the cost modeling
more complex, which for the antennas should be based on an installation cost and a yearly
maintenance cost and should calculate for any period what the total cost will be. To be able to have a
gradual roll-out, the requirements of capacity and the adoption should also be variable every year
instead of fixed.
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3.1.4 Dimensioning
As mentioned before, the tool uses a genetic algorithm to dimension the wireless. This algorithm
mimics normal genetics and its selection of the fittest, leading to an optimization over different
generations. Each generation, a number of solutions will be created based on solutions of the
previous generation. One solution has as its genes the placement of a number of antennas and the
total cost, considering the antenna costs and the cost of the fiber connection. In every generation,
the tool will calculate the fitness value for every solution and compare it with the current best
solution. The fitness value is a combination of the coverage fitness and the cost fitness. The coverage
fitness is the ratio of area covered by the current solution to the total area of the target input area.
The cost fitness is equal to one, subtracted by the ratio of the cost of the current solution to the
worst case cost, and this number is multiplied by 100 to get a percentage. The worst case cost is the
total cost, assuming an antenna would be installed and connected to a backhaul connection point on
every possible antenna location. To determine the total fitness value, a weight factor is calculated to
determine the influence of the cost fitness upon the total fitness. The minimum coverage is the goal
coverage, e.g. 99%, subtracted with a fixed value, e.g. 5%. The exact calculations are shown in the
formulas below. When the coverage of a solution is situated between the minimum and the goal
coverage, a quadratic ascending function decides the influence of the cost fitness. The weight is
implemented to achieve a good coverage: the closer the coverage is to the coverage goal, the higher
the fitness will become, due to the impact of the cost fitness. If the coverage of the solution is below
the minimum coverage, the cost fitness won’t have any influence on the total fitness at all.
(
)
{
(
)
This dimensioning algorithm gives good results, but the result might not always be based on fair
assumptions. Considering the cost of 1 meter fiber is set in the tool at 50€, the impact of the amount
of fiber needed to connect a base station is big. A small example scenario to highlight this impact is
given in Figure 3.2. As shown, two base stations (BS1 and BS2) have a common closest connection
point.
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Figure 3.2: Example scenario fiber cost impact
The Wireless tool will simply connect both base stations directly to the connection point (Figure 3.3).
Figure 3.3: Example scenario solution of Wireless Tool
This solution is not optimal, because obviously it is cheaper to connect BS1 to BS2 instead of directly
to the connection point as shown in Figure 3.4.
Figure 3.4: Example scenario good solution
The impact of the non-optimal solution is big, because the cost of the fiber has a big influence on the
total antenna cost. In this scenario, BS1 actually has a false cost, because in a realistic case, the last
solution will always be implemented. Because the cost of BS1 is high, it will have less chance to be
selected as an antenna that has to be installed, even though it might be optimally located to get a
good coverage. To solve this problem, we have to improve the fiber dimensioning in the tool. Some
simple changes can give us a more realistic solution and a correct cost for every antenna. These
improvements are explained in section 3.3.2.
3.2 TESS framework
The Techno Economic Software Suite (TESS) is a network cost and business modeling framework
developed by IBCN. It is designed to be able to perform a detailed cost modeling of different types of
fixed networks. The framework is currently being expanded to support the cost modeling of wireless
networks. Great effort was made to make this framework as generic as possible. That’s why every
input and output is based on an object of the class “TimeFunction”. A time function is a function in
time off which the type of value of the function can be chosen freely. Time functions are used for the
input and output of the tool and will make the cost modeling easier. Figure 3.5 shows a typical
calculation chain of TESS for a fixed network. There are three chained modules: area, cost and
evaluation.
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Figure 3.5: The Techno Economic Software Suite [26]
3.2.1 The area module
The area module is a hierarchical structure that can have several sub-areas. For this dissertation the
sub-areas won’t be needed. Each area consists of three smaller calculation modules: the adoption
module, the dimensioning module and the equipment tree module. The adoption module will
forecast the number of subscribers of the network for every coming year. The dimensioning module
is responsible of calculating the amount of ducts, fiber and trenching needed to deploy the network.
For now this dimensioning is based on analytical models, but IBCN is currently working on a GIS-
based dimensioning module. The last calculation module of the area module is the equipment tree
module. It consists of a tree structure that allows determining the amount of equipment needed to
connect the subscribed customers at any given time. Figure 3.6 gives an example of such a
hierarchical equipment tree structure. On every branch there is a granularity factor representing the
relationship between different levels. The lowest level equipment of the tree is connected to
drivers. A driver can be different things, e.g. the amount of customers or the amount of street
cabinets. The calculations of the tree will be based on those drivers and performed in a bottom-up
manner.
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Figure 3.6: Example of tree structure of equipment model [26]
3.2.2 The costing module
The costing module is responsible for calculating the costs of the infrastructure and operation costs.
The input of the costing module is obtained from the output of the area module. It links the amount
for equipment, cable, trenching and customers to the unit costs. Different calculations are done in
this module. First of all, the Capital Expenditures (Capex) are calculated, which is the upfront cost of
the infrastructure, including installation of the equipment and costs for deploying the network. The
re-installation costs are also part of the Capex. These costs occur when equipment has to be replaced
at the end of its lifetime. Next to the Capex, the Operational Expenditures (Opex) are computed,
which is the sum of the costs of maintenance and repair, connection and service provisioning of
customers and daily operational costs like power consumption. Finally, the revenues are calculated in
this module, depending on the number of customers the network has connected.
3.2.3 The evaluation module
The evaluation module is a final step in the TESS module chain. It allows automatically combining all
the calculation results of the cost module and determining the final results for a specified period of
time. The output consists of some predefined economic calculations like NPV, IRR, etc.
3.2.4 Importance to master thesis
The TESS framework will be an easy tool to use in the cost modeling part of the master thesis. The
flexibility given by the time functions is a great benefit using this framework and the fact that
everything is made generic also contributes to the favor of using this framework.
From the three modules in the area module, only the equipment module will be used in this
dissertation. For the dimensioning and adoption calculations we rely on the Wireless Tool, because it
is much more extended than in TESS. We have to make sure the output of the dimensioning and
adoption calculations are time functions, so we can plug those calculation steps into the calculation
chain. We connect this output to the area module, which is limited to the equipment tree module.
The driver for the equipment module is the number of base stations, which equals the number of
| 28
fiber connections with the central office, since our equipment model assumes the splitter is located
in the central office. TESS calculates the yearly Capex and Opex in the calculation module, given a
time function with the values of this driver as input. Based on this information the evaluation module
can calculate the NPV of the solution.
3.3 The wireless-fixed dimensioning tool
The new dimensioning tool has two main goals: add a better fiber dimensioning and allow the choice
to gradually expand the network over time in a cost efficient manner. The realistic fiber dimensioning
is crucial to give every possible antenna location an equal chance to get selected for the
dimensioning. The gradually expansion is also a feature that creates more realistic scenarios of
wireless network roll-outs. The tool first calculates the required base stations for a target year and it
will use this information to calculate the optimal locations for the years between the first and the
target year. By using the information of the target year, only base stations and fiber eventually
needed in the target year will be installed in earlier years. Note that the tool is also programmed to
determine a roll out over several years without first calculating a target solution. Still, the options for
this calculation are not as flexible as required in this dissertation and we are more interested to first
calculate the network required in the target year.
All these requirements resulted in a tool, of which the structure is shown in Figure 3.7. As said
before, the tool is based on the original wireless tool, and expanded in many ways to meet the
requirements for the wireless-fixed dimensioning. Section 3.3.1 will discuss the input of the tool,
while section 3.3.2 will take a more detailed view on the upgrades of the core of the tool. At last,
section 3.3.3 takes a look at what comes out of the tool.
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Figure 3.7: the dimensioning tool
3.3.1 Input
An overview of the input of the tool is given in Figure 3.8. Compared to the original wireless tool, we
added two types of input: the TimeFunctions and the equipment model. This section discusses the
changes in input compared to the original Wireless Tool.
The wireless technology input is equal to the input of the technical parameters of the original
wireless tool. There are many parameters to consider when dealing with wireless technologies. Some
parameters will remain unchanged in all the considered scenarios, which are listed in Table 3.1. The
gains and losses at the receiver and the transmitter that are needed to calculate the link budget are
given, as well as the number of sectors and the average height of the mobile station used later in this
dissertation. The fade margin is a margin that takes the temporal fading (e.g. changing weather
conditions) into account and is determined by the expected yearly availability of the system. The
noise figure is a measure for the degradation of the signal caused by the components in the
radiofrequency signal chain. Many other parameters may vary according to the considered
technology; those parameters will be discussed in the chapter of the case using the certain
technology. Note that the parameters given here can easily be changed when e.g. using a new
technology.
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Parameter Value
Base station (BS)
BS antenna gain 17 dB
BS feeder loss (Tx/Rx) 0.5 dB
Noise Figure (Rx) 2 dB
Implementation loss 2 dB
Sectors 3
Mobile station (MS)
MS height 1.5 m
MS feeder loss (Tx/Rx) 0 dB
Noise Figure (Rx) 7 dB
Implementation loss 2 dB
Margins
Fade margin 10 dB
Cell interference margin (DL) 2 dB
Cell interference margin (UL) 3 dB
Table 3.1: Fixed technical parameters
We combined the GIS data and the user data of the input of the original wireless tool into one block
and called it the GIS data. Only the shapefile with the fiber connection points will not be used
anymore. Where in some scenarios it is desired to give some connection points as input, it is not
mandatory. If one would like to give the location of existing fiber as input, the possible connections
points on this fiber network should be given as input. With this info, the tool will be able to build a
wireless network upon a given fiber infrastructure.
Many input parameters of the tool are time functions. All time functions should have the same
length in time. For every year a certain UL data rate, DL data rate, coverage and adoption can be
provided. If a parameter should remain the same over time, a constant time function can be given as
input. Due to the usage of these time functions, many different scenarios can be evaluated with the
tool; from roll-outs that have to be completed by the end of the years to roll-outs of networks that
will gradually be built during many years.
Figure 2.15 shows the equipment model which was used for the tool. Note that changing this model
in the tool is very easy. Every base station that is installed in the target area after dimensioning is
seen as an incoming fiber for this model. This input is only used in the cost modeling of the tool,
which is the last step.
As discussed before, the cost input is now somewhat different: an installation cost and a yearly
maintenance cost has to be provided for the base stations. For the fiber, there’s also a fixed cost per
meter, mainly consisting of the digging cost per meter. Along with this fixed cost, the costs of the
equipment in the central office have to be provided as input, together with their average lifetime.
Figure 3.8: Input of the dimensioning tool
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3.3.2 Core of the tool
The core of the tool is shown in Figure 3.9. A big difference to the original wireless tool is the
separation of the wireless and the fiber dimensioning. The outer loop, which runs a wireless-fixed
dimensioning over several years, is also a major modification. This was added to include the
possibility to roll out a network gradually. The first iteration is the dimensioning of the target year.
This way, we know what the network in the future will have to look like and we can base the
dimensioning of the other years upon this solution. After the target year, the tool dimensions all the
other years in ascending order, starting from the first year. Note that the tool also works without
setting a target year and just gradually adding antennas every year, based on the previous year.
Figure 3.9: Core of the dimensioning tool
Dimensioning of fiber
First of all a more realistic dimensioning of fiber was added. Therefore the Minimum Spanning Tree
between the base stations will be calculated using Kruskal’s algorithm (see section 2.2.3). Now the
distance between the base stations will affect the cost. By adding this, the tool will try to minimize
the total length of the MST between the base stations. Compared to the original wireless tool, the
dimensioning of fiber is now executed after the wireless dimensioning. In the original wireless tool it
happened all at once, just by deciding beforehand which connection point the base station will
connect to. Because now the dimensioning is split into two parts, the wireless dimensioning is more
correct, due to the fact that each base station has the same price.
Different variants of the fiber dimensioning have to be implemented. For the target year, the fiber
dimensioning is just the MST between the installed base stations and, if desired, between the fiber
connection points given as input. For the other years, we need to keep track of which fiber was
installed in the previous years, because this fiber will certainly have to belong to the solution of
| 32
future years. This is done by deleting the existing fiber from the set S and adding it to the forest F in
Kruskal’s algorithm. Now an MST between the new and old antennas is calculated and connected to
the existing fiber network. Besides that, the dimensioning of a non-target year needs an adapted
implementation of Kruskal’s algorithm, because in this case, only fiber connection that will be
installed in the target year should be chosen. So instead of having the complete graph of connections
between all selected antennas as the starting set S for Kruskal’s algorithm, set S now only contains
the fiber connections that will be needed in the future. This means, that a non-optimal amount of
fiber may be installed in the earlier years.
To make this more clear, we return to the example scenario of Figure 3.2, now assuming that both
base stations will be needed in the target year and only BS1 will be needed in the first year to meet
the requirements. This means that Figure 3.4 would be our most favorable solution of the fiber
dimensioning in the target year, which is the MST between the three points. Figure 3.10 (a) now
shows the fiber dimensioning problem of year 1. BS2 is colored gray to emphasize the fact that it is
not part of the first year’s solution, but it will be part of the solution of the target year. If we calculate
the normal MST on this scenario, we would obtain the solution shown in Figure 3.10 (b): BS1 directly
connected to the connection point. This would give the cheapest solution in terms of fiber in that
year. If now in the target year BS2 is added to the network, the fiber dimensioning will connect BS2
directly to the connection point. This will give the solution shown in Figure 3.3, which is not optimal.
To solve this problem, we use the adapted algorithm, where the starting set is restricted to the fiber
that will be needed in the future. The solution is shown in Figure 3.10 (c), which is not optimal for the
current year, because the amount of fiber could be less if BS1 is connected directly to the connection
point. But adding BS2 in the target year now doesn’t require any extra fiber to be laid, because Figure
3.4 now is the target year solution and all the fiber in this solution was already installed in year one.
Looking at it year by year, the fiber dimensioning might not be optimal, but if we look at the total
amount of fiber installed over all the years, using the adapted form of Kruskal’s algorithm in the non-
target years gives us an optimal solution.
Figure 3.10: (a) top: example scenario year 1; (b) middle: MST example scenario year 1;
(c) bottom: adapted MST example scenario year 1
| 33
Density coverage
The current formula of coverage fitness (see section 3.1.4) cannot be considered as correct because
the loss of coverage in a dense area ‘costs’ as much as the loss of coverage in a less dense area. This
problem is explained with a small example given in Figure 3.11. The total area exists of both the blue
and the red square, which we assume is 2 units big (1 unit equals the area of 1 square). The
populations of the areas shown on the Figure 3.11 are given as input in the tool, but only used to
calculate the coverage areas of the antennas. This actually explains why on the figure the coverage
area of BS2 is smaller than the one of BS1. If we had to choose to install one of both antennas,
intuitively we would select BS2, because it covers an area with 100 people living in it instead of 50 in
the area covered by base station 1.
The figure shows when we install both base stations 1 and 2, the tool would clearly value the
coverage fitness at 100. If we would now remove BS1 from the solution, the coverage fitness would
become 50%, because only 1 unit of the total area of two units would be covered. Removing BS2
results in the same coverage fitness of 50%, based on the same reasoning. Assuming that the
installation and fiber connection costs of both base stations are equal, both solutions – only installing
BS1 and only installing BS2 – will result in the same total fitness value. So running this problem with a
coverage demand of at least 50%, this will result in an outcome of one of both solutions, each having
an equal chance to be selected. This is not correct, because BS2 covers more people, so it should
always be selected by the tool.
This problem is solved by adding the density value to the coverage fitness calculations. The new
formula for coverage fitness is shown underneath. This results in a more realistic fitness value.
Applying this formula to the problem of Figure 3.11, only installing BS1 results in a coverage fitness
value of 33% and only installing BS2 a value of 67%. So using this formula in the tool always gives a
more correct and logic result of the wireless dimensioning.
Figure 3.11: Coverage fitness problem
Cost of worst case scenario
Another thing that had to be revised is the cost of the worst case scenario that was discussed in
section 3.1.4, which is needed for the calculation of the cost fitness. In the original wireless tool this
was rather basic, just adding all the costs of all the possible antennas and the cost of their connection
to the backhauling. In this case we will also need to consider the costs of all the possible antennas,
but we will use a different calculation for the total fiber cost of this worst case scenario. There can be
many possible antenna locations, so a simple calculation is preferred to save some calculation time.
Since the only requirement of a worst case scenario cost is that it has to be higher than the cost of
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any other possible case, the worst case fiber cost is the addition of the costs of a fiber connection
between each antenna and a certain point in the target area. This point can be a fiber connection
point or the first antenna location. This creates a star network of the antenna locations, which
cannot be shorter in distance than the MST between all the antennas. The total worst case scenario
cost is the sum of this fiber cost and the total antenna cost. Even if all possible antennas would be
part of the solution, its cost will still be smaller or equal than the worst case scenario cost.
3.3.3 Output
The tool has two different types of output, as we can see in Figure 3.12. One output type contains
the placement of the base stations and the fiber connections for each year of the planning. The other
– a cost modeling of the considered project – is calculated after the iterations over all the years. Both
output types are discussed in following sections.
Figure 3.12: Output of the dimensioning tool
Location of base stations and fiber
This type of output consists of shapefiles that contain the location of the base stations and fiber of
the best solution of each year. The original wireless tool already had methods to provide a shapefile
with the location of the base station and one where the coverage of each base station is displayed as
a circle. A new method is provided to create a shapefile where the fiber connections are stored.
Showing these shapefiles together with the one of the target area gives a view on the solution of the
tool.
Cost modeling
After running the genetic algorithm for every year the costs of the best solution is modeled using the
TESS framework. For each year it calculates which base stations need to be installed and which ones
were already there. The latter will have a maintenance cost for every year they are up and running.
The same thing has to be calculated for the fiber and the equipment needed for the fiber. A number
of mathematical operations for time functions available in the TESS framework are used in these
calculations. All the costs are discounted with a rate of 10% and the total cost is calculated.
3.4 Optimizations
This section discusses the main optimizations that are made in the core of the wireless tool to
increase the performance of the tool.
3.4.1 Speed
Many optimizations that have been implemented to improve the runtime are listed underneath.
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Population
The population, which is the number of solutions calculated in each generation, affects the speed of
the tool. Figure 3.13 shows a graph that gives the relation between a fitness value and the time when
this fitness value is reached for different population sizes calculated over 1000 generations. We see
that in case of a smaller population a higher fitness value is reached in a lower generation. Note that
these results are affected by the randomness of the genetic algorithm and that the results are used
to find a good population size, but this might not be the optimal one. These results were used to
estimate around which population size we have to look to find a good size to use in the tool. In the
next section we check if there is a better size than 25.
Figure 3.13: impact of population time on runtime of the tool
Efficiency
By performing some local optimizations on the solutions the tool gives better results. Every 60
generations the tool tries to optimize the solutions of the population. It checks for every active base
station if the total fitness would improve when the base station and its fiber connections are
removed from the solution. This local optimization removes base stations that don’t have a big
influence on the coverage fitness. A downside is that executing this optimization requires more
calculation time. Figure 3.14 shows a graph, again with the relation of a fitness value and the time it
is reached for a population of 25. It shows that implementing the optimization (‘full optimization’ in
the graphs’ legend) improves the result, because the fitness value reaches a higher value, but the
execution time is higher. By only performing the local optimization on the best half of the population
a better result is achieved. By best half we mean the 12 solutions that have the best fitness values at
that time. The green line on the graph shows that this optimization results in a better fitness value
and that fitness values are reached much earlier than in the case of no optimization or full local
optimization. It is clear that by implementing the ‘half’ local optimization, less time is needed to
reach a certain fitness value, which makes the tool more efficient. Note that when the term ‘local
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optimization’ is used in the remaining of this paper, it refers to the ‘half local optimization’ as
described above.
To make sure that the population size is still a good choice with the implementation of the local
optimization, we compared the runtimes of the tool again for different populations. Figure 3.15
shows the fitness-time relations for a population of 20, 25 and 30. It is clear that 25 is a good choice
of population size, because it reaches a certain fitness value earlier than the other two options and
also a higher fitness value after 1000 generations is reached.
Figure 3.14: comparison of different configurations of local optimization
Figure 3.15: comparison of population sizes with implementation of local optimization
Caching
A great optimization of speed was to cache the fitness values and only recalculate them when really
necessary. Most of the runtime of the tool is spent while calculating fitness values. The runtime
improved greatly by caching them smartly. As discussed in 3.1.4 the worst case scenario cost is
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needed for the calculation of this fitness value. In the original wireless tool this cost was calculated
every generation, but since this cost is equal in every generation, it is enough to calculate it at the
start of the genetic algorithm and caching this value to use it in the other generations. Following the
same reasoning, there is no need to recalculate the fitness values of solutions that are not changed,
so we cache these values too. The runtime is reduced thanks to the caching.
Stopping rule
Thanks to the optimization in efficiency a good solution is obtained faster than before. A stopping
rule was added to speed the tool up even more. If for a number of generations no better fitness is
found, the genetic algorithm will stop and the current best solution is selected as the optimal
solution. In this dissertation this number of generations is 350 for the dimensioning of the target year
and 200 for the dimensioning of the years before the target year. This number is lower in the years
before the target year because the number of base stations to choose from is lower and a good
solution is achieved faster.
3.4.2 Splitting the target area
If we want to run the dimensioning tool on a big area, the tool has the possibility to split the area
into smaller parts. This optimization was already part of the original wireless tool, splitting up the
wireless dimensioning of a bigger area in 9 parts, but is expanded to be able to handle splitting the
fiber network into parts. The tool can split the area into 9 parts based on the number of antenna
locations, so every part contained practically the same amount of possible antenna locations. To be
able to use the density coverage optimization and not using too much time with it, each part has to
be given the appropriate population information. For every part, a connection point (which is one of
the possible antenna locations) that is closest to the center of the target area will be selected to take
care of the connection of the fixed networks of the different parts. The genetic algorithm then runs
on all the parts and looks for a good partial solution in each part.
When these partial solutions are merged, another local optimization, which was added for this
master thesis, is performed. This local optimization checks for every active base station what the
total fitness would be if we remove it from the solution. Then we remove the base station which
gave the greatest improvement on the total fitness. These two steps are iterated until no
improvement is made by removing another base station. This local optimization gives better results
than the one discussed before, but it takes a lot more time to complete.
3.4.3 Downside of the density coverage
In section 3.3.2 we introduced the density coverage to create more correctness in the solutions. A
downside to the density coverage is that the runtime of the tool increases by these calculations. To
give an idea, an overview of the solution of the urban case discussed in section 4.1 is given in Table
3.2, once with, and once without the density coverage. It shows us that the solutions are almost the
same (except for the location of the antennas), but we see that there is a big difference in runtime.
When using the geographic coverage instead of the density coverage, the tool only needs 70% of the
time. Then again, it doesn’t’ give a correct solution.
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Geographic coverage Density coverage
Antennas in year 5 6 6
Fiber in year 5 5.4 km 5.2 km
Total cost €527,909 €523,580
Runtime 12 min 17 min
Table 3.2: Geographic coverage versus density coverage
3.5 Conclusion
To complete this master thesis a refined tool was needed to dimension a wireless network
interconnected by a fixed network. The Wireless Tool seemed a good starting point and expanding it
in various ways made it possible to make a generic fixed-wireless dimensioning tool. We also used
the TESS framework to make the inputs and outputs more generic and time-sensitive and optimized
the final tool in several ways to improve the runtime. This created a relatively fast dimensioning tool
that can handle many different types of requests with many different inputs. An important point was
to support the gradual roll-out of the networks, which is certainly possible in the created
dimensioning tool. The tool is a good starting point to consider different cases describing totally
different situations. Based on the tool, we worked out some cases to show the power and the
possibilities of the tool. These cases and their evaluation are discussed in the next chapter.
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4. Integration of fixed and mobile
networks
A powerful tool was developed to dimension an integrated fixed and mobile network. We handled
two different cases to determine the strengths of this tool and to see where improvements and
changes may be needed in future work. Two very different cases are discussed in this chapter: one
case is situated in an urban area, while in the other case the target area is rural. Many other cases
could be handled with the tool. The two distinguishing cases are used to show what the tool is
capable of.
4.1 Urban case
In most cases a broadband network is installed in an urban area. In this master thesis we determined
the gradual roll-out of a 4G network in the city of Ghent. Two different scenarios are discussed. The
first is the deployment of an LTE-advanced network in the whole city of Ghent, an area of 157 km2.
This case is used to show what the output of the tool looks like. Later in the section, we assume the
small center of the city of Ghent as the input area, where we look at a comparison of two possible
wireless technologies: LTE-advanced and Wi-Fi. This shows that the tool is capable of making a good
comparison between two technologies. Choosing the wireless technology is a key decision when
rolling out a wireless network and this tool could help make the decision easier. The chapter starts
with giving all the input and assumptions used in both scenarios.
4.1.1 Input
Area
Different types of shapefiles are used as input of the tool. First of all, the target area has to be
selected. This shapefile also contains the demographic data of the area. This is added as a property to
every different feature of the shapefile. The left side of Figure 4.1 shows the shapefile of the city of
Ghent, where each area separated by the darker lines represents one feature. The city center is
shown in green while the rest of the area is orange. Since the goal was to deploy a network in the
urban, the docks of Ghent are removed from this shapefile (they were located at the north-east
corner of the given map). The right side of Figure 4.1 shows a close-up of the center of Ghent, which
is about 7 km2.
Another shapefile that is required to run the tool is the shapefile containing the possible antenna
locations. In Ghent we can rent a location on a pole of the BIPT. The locations of those poles are
publically known and can be retrieved on the website of the BIPT. Figure 4.2 shows the shapefile
containing all the possible BIPT locations in Ghent for placing an antenna. We also use this shapefile
when solving the scenario of the center of Ghent, since all the poles in the center are also shown on
this figure. When considering the scenario in the city center, we also deploy a Wi-Fi network to
compare it with an LTE-advanced network. With Wi-Fi, we have the possibility to install the base
| 40
stations on the rooftops of buildings in the center of the city. For this, a shapefile containing 3D-data
of the center, containing the height of each building, is available. The tool selects every building that
is higher than 15m to be a possible antenna location for the Wi-Fi network.
The city of Ghent is mainly an urban environment, so we will need to use the corresponding
parameters in the Erceg C model, with the urban correction factor, explained in section 2.2.1. This is
done by setting the path loss model mode to ‘Urban’ in the tool.
Figure 4.1: Shapefiles Ghent
Figure 4.2: Antenna locations of BIPT Ghent
| 41
Requirements
A case depends on the requirements for a certain area. In this case, we look at a gradual roll-out
spread over 5 years. The data rate requirements of the scenario considering the total area of Ghent
are different every year and are listed in Table 4.1. These data rates are increasing a lot every year as
means of an example to show the influence of the data rates on the ranges of the antennas.
When considering only the center of Ghent we would like to see the influence of the required data
rate on the solution, so we consider 13 different situations per technology, each with a different data
rate requirement. The roll-out also happens in 5 years, but in each of these years the data rate is
equal. The considered data rates are given in Table 4.2.
Year 1 2 3 4 5
DL (Mbit/s) 1 2 3 4 5
UL (Mbit/s) 0.2 0.4 0.6 0.8 1
Table 4.1: Yearly data rate requirements city of Ghent
Scenario A B C D E F G H I J K L M
DL (Mbit/s) 1 2 3 4 5 6 7 8 9 10 11 12 13
UL (Mbit/s) 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6
Table 4.2: Data rate requirements of different scenarios center of Ghent (equal each year)
Another factor that influences the ranges of the antennas is the adoptions of the technology in the
area. To apply this adoption to the case the Gompertz curve given in section 2.3.2 is used as input for
both scenarios. The required coverage also has to be given as input and is equal in every year: 99%
(of the inhabitants) in both scenarios.
Wireless technology
In the scenario of the whole city of Ghent we selected LTE-advanced as the wireless technology to
show the possibilities of the tools. The base station has an input power of 46 dBm. We use the FDD
spectrum with 2x5 MHz per sector, because studies in [18] showed this is the best configuration for
this case. A MIMO configuration of 8x2 is applied and Spatial Multiplexing is used to increase the
data rates. In urban environments SM has much more use than TD, because many people are located
on small areas, so high total data rates in one coverage area are needed. The carrier frequency is 2.6
GHz, for which a license is required. All these parameters are listed in Table 4.3. The cyclic combining
gain is a gain in the link budget when using Transmit Diversity, because this increases the range. So
for Spatial Multiplexing this remains 0. The MIMO gain is also only positive if TD is used and it
depends on the number of antennas used at the transmitter and receiver, while this number doesn’t
impact the cyclic combining gain.
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Parameter Value
Input Power 46 dBm
Frequency 2.6 GHz
Duplexing FDD
Bandwidth 2x5 MHz
Base station
Tx antennas 8
Rx antennas 8
Cyclic combining gain (Tx) 0 dB
Mobile station
Tx antennas 2
Rx antennas 2
Cyclic combining gain (Tx) 0 dB
MIMO
Configuration SM
MIMO gain (Tx/Rx) 0 dB
Table 4.3: Parameters LTE-advanced FDD
When considering the scenario of the center of Ghent, we also run the tool with Wi-Fi. The
parameters are similar to the ones of LTE-advanced. The input power of the base stations are less
though, only 35 dBm instead of 46 dBm. Wi-Fi also operates in the license-free band at 2.4 GHz with
a bandwidth of 20 MHz. Wi-Fi uses TDD and has a DL:UL ratio of 0.75. Wi-Fi only uses 4 MIMO
antennas at the BS, so 4x2 MIMO is used. Spatial Multiplexing is also applied to get higher data rates,
so no extra gains are added to the link budget. All this information is listed in Table 4.4.
Parameter Value
Input Power 35 dBm
Frequency 2.4 GHz
Duplexing TDD
Bandwidth 20 MHz
Base station
Tx antennas 4
Rx antennas 4
Cyclic combining gain (Tx) 0 dB
Mobile station
Tx antennas 2
Rx antennas 2
Cyclic combining gain (Tx) 0 dB
MIMO
Configuration SM
MIMO gain (Tx/Rx) 0 dB
Table 4.4: Parameters Wi-Fi TDD
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Costs
Section 2.3.1 discusses all the costs needed and used in the cases. Table 2.2 shows the costs of the
wireless equipment used in this case. Table 2.3 contains the costs of the equipment of the fiber
network; these costs are the same for every case. The price of laying one meter fiber equals €50 per
meter.
For LTE-advanced a license is needed to operate in the 2.6 GHz band. In this case we use a 2x5 MHz
bandwidth in FDD mode, but we have to consider three sectors per base station, so we need a
license for 2x15 MHz. This license was auctioned for €15,040,000 for Belgium and is valid for 15 years
[23]. Now, we will try and estimate the value of a license for Ghent only. We could divide the total
license cost by the area of Belgium and multiply it by the area of Ghent, but this proportion is not
really fair since a license is more seen as a permission to cover an amount of people instead of an
area. The area covered is more a consequence of covering a certain amount of people. That’s why a
better estimation of the license cost would be to divide the license by the total population of Belgium
– about 11 million – and multiply it by the population of Ghent, which is around 250 thousand. This
results in a license cost of €341,818. To compare with the other method, its calculations result in a
cost of €77,348, so there is certainly a big difference in both methods. Note that these calculations
are only estimations and could be different in reality, e.g. due to touristic value of the city of Ghent
or due to the fact you can’t buy or own a license for only Ghent. Nevertheless this estimation seems
a fair indication of the license costs.
4.1.2 City of Ghent
We put all the input of the scenario of whole Ghent into our tool and let it run. An overview of the
output of the cost modeling is given in Table 4.5. The overview proofs that the higher the data rate
and the adoption are, the higher the amount of base stations will be. Deploying a network of 52
antennas, interconnected by 67 km of fiber, over a period of 5 years will cost around 7.5 million
euros. We also set out the yearly costs in a graph shown in Figure 4.3. It’s clear that the major part of
the investment happens in the first year, because the biggest part of the infrastructure – 25 antennas
and 64.5 km fiber – is installed this first year and in later years we also take a discount rate into
account. We can see that, apart from the first year, the yearly cost is higher in later years, even
though an equal cost is actually lower in a later year due to the discount. This is explained by the fact
that every year there are two input values that increase: the data rate and the adoption. So the
increase in the amount of antennas needed to cover the region is not linear, but is higher in later
years.
After year 1 2 3 4 5
Number of base stations 26 28 33 39 52
Amount of fiber (km) 64.5 66.1 67 67 67
Cumulative cost €5,306,928 €5,687,208 €6,177,708 €6,664,562 €7,468,978
Table 4.5: Overview solution case Ghent
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Figure 4.3: Yearly costs case Ghent
The visual output of the tool for each year is shown in Figure 4.4. These figures give a good view on
the way the dimensioning algorithm works. First the network for year 5 is installed, that’s why it’s
displayed first. It’s clear that the antennas in year 1 to 4 are all antennas that will eventually be
placed in year 5. Antennas placed in an earlier year will also remain in the solutions of later years.
The same reasoning is valid for the fiber. If we would dimension the fiber between the antennas
placed in year 1 without thinking about the coming years, we would determine the MST. As we can
see this is certainly not the case, because the fiber network makes some big detours. But as we
know, this is done on purpose, because in later years antennas will be placed along these detours.
This explains why almost all the fiber is installed in the first year. To reach a base station at an edge
of the area, the fiber passes through many future locations before reaching the base station. This is
confirmed by the fact that in year 2 only 1 extra fiber is installed and that in year 3 all the fiber
needed in year 5 is already placed.
That’s not the only thing that changed, because if we look closely at some of the base stations that
are both in year 1 and year 5, we notice that their ranges are smaller in year 5. This is a consequence
of the increase in data rates, which is explained by the fact that the range of an antenna is limited by
two things: the input gain of the antenna and the total data rate it has to provide. If the data rate
doesn’t exceed the maximum allowed bitrate, the range will be as high as the maximum path loss
(calculated based on the gains) allows it to be. If at a certain range, the maximum data rate is
reached, the antenna will not be able to provide any more coverage beyond this range, because it is
fully occupied. The limitation by the path loss is the same for every base station under a similar
configuration, but the limitation by the data rate depends on the demands of the area a base station
has to cover. In year one for example, all ranges are about the same, because the ranges are limited
by the path loss model. In higher years the required data transfers are higher in the center, which
decreases the range of that base station due to the need of higher modulation schemes. This is
definitely noticeable in year 5, where all the ranges in the city center are really small compared to
the ranges in the suburbs because the density in the center is much higher.
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Figure 4.4: Visual output of each year of case Ghent
To see what the influences of the different components of the network are, we set out the
composition of the total discounted cumulative cost over the 5 years in Figure 4.5. The biggest cost is
the fiber cost, which is responsible for 48% of the total cost. We made a distinction between the
costs directly dependent of the amount of fiber and the equipment costs at the central office. The
latter is only responsible for 3% of the cost. This means the amount of fiber that is installed has a
great influence on the total cost, in this case 45% and should be as small as possible. The installation
costs of the base stations are good for 33% of the total cost, while maintaining them and their
location is good for 15%. For the license we pay 4% of all the money that has to be spent.
Figure 4.5: Composition of the total cost of solution
3%
45%33%
15%4%
Equipment Fiber
Fiber
Installation BSs
Maintenance BSs
License
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4.1.3 Wi-Fi vs. LTE-advanced
In this subsection we focus on the center of Ghent only, where we calculate the deployment of two
different types of wireless networks: LTE-advanced and Wi-Fi. We would like to see which technology
is cheapest to roll it out over a period of 5 years. We have performed a comparison for different
values of bitrates, as shown in Table 4.2. It’s interesting to see which technology can handle higher
data rates, so which one is more future-proof. The results of this experiment are given in Figure 4.6.
Figure 4.6: Comparison of LTE-advanced and Wi-Fi costs under given data rates
As we see in the graph, at lower DL bitrates LTE-advanced is the cheaper solution, but when the data
rate is higher than 7 Mbit/s Wi-Fi gives us the cheapest solution. We can state that the cost of both
technologies at data rates between 5 and 10 Mbit/s are more or less the same, but with lower or
higher rates, the chosen technology has much more impact on the total cost. Note that for LTE-
advanced, the license costs are also taken into account. To give an idea in the difference of number
of base stations and km fiber that are installed in every situation, an overview of these figures is
given in Table 4.6.
Mbit/s 1 2 3 4 5 6 7 8 9 10 11 12 13
LTE- #BS 2 3 4 5 6 8 9 11 12 14 15 18 20
advanced km fiber 0.5 1.6 3.2 4.7 5.4 5.9 6.5 7 7.5 8.3 8.8 9.3 9.4
Wi-Fi #BS 20 28 35 39 43 49 57 60 62 68 72 78 74
km fiber 11 12.4 12.9 14.2 14.9 15.8 16.1 16.8 16.9 18 18 18.6 19
Table 4.6: Number of base stations and km fiber
The antennas of the two technologies clearly have a different range. Wi-Fi needs 5 to 10 times more
base stations to cover the same area. The fact that there is more fiber needed for Wi-Fi is a direct
consequence of the high number of base stations. Table 4.6 shows some strange numbers for Wi-Fi
at 12 and 13 Mbit/s. It states we need less base stations for a higher data rate if we compare both
numbers. This can be explained by inspecting what the achieved coverage in the different
experiments is. We did set the required coverage at 99%, but the fitness function discussed in section
3.1.4 doesn’t guarantee that this coverage is met. In Figure 4.7 we set out all the coverage
percentages reached in the experiment.
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Figure 4.7: Reached coverage percentage in Wi-Fi vs. LTE-advanced experiment
We can see that Wi-Fi has many problems reaching the desired coverage at high bitrates, while it
actually has many more possible antenna locations. Table 4.6 also learns us it needs many more base
stations to cover a same area, so it is quite logic that when even more BSs are needed, some parts of
the area might not get covered well enough, due to the lack of antenna locations. We can see that at
data rates higher than 11 Mbit/s the coverage of LTE-advanced also gets below 99%. We notice that
at 6 and 7 Mbit/s the coverage is above the coverage goal. This is explained by the fact that an extra
antenna can result in a better coverage than needed, but without the antenna the coverage goal
would not be reached. We can conclude that the reached coverage of LTE-advanced is always higher
or equal than the coverage of Wi-Fi. At high data rates there’s a difference of up to 2%, which results
in an incorrect comparison of the costs. We can add this achieved coverage-level in the comparison
by using the fitness formulas introduced in the tools. We have all the data needed to calculate the
fitness values, except for the worst case scenario cost, which has to be the same for both
technologies. We arbitrary chose the worst case cost as the sum between €1,500,000 and the DL
bitrate multiplied with €200,000. We chose to increase this cost with increasing bitrate because it
makes sense that more money is spent for deploying networks that can achieve higher data rates. If a
fixed worst case cost would be chosen, the fitness values of lower bitrates would be very high and
the one of higher bitrates low, while both solutions might have the same cost efficiency. The fitness
values are set out on the graph given in Figure 4.8.
Figure 4.8: Fitness values of Wi-Fi vs. LTE-advanced comparison
94%
95%
96%
97%
98%
99%
100%
1 2 3 4 5 6 7 8 9 10 11 12 13
Co
vera
ge
Data rate DL (Mbit/s)
Wi-Fi LTE-advanced
0
50
100
150
200
250
300
350
400
450
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Fitn
ess
val
ue
Bitrate downlink (Mbit/s)
Wi-Fi LTE-advanced
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From this graph we can conclude that LTE-advanced is always the better choice. Only comparing the
costs made us doubt between the technologies when the data rates became higher, but comparing
the fitness values shows that at the high data rates it is actually even more favorable to choose LTE-
advanced than in the lower data rates. In any case, LTE-advanced seems to be the ideal technology
for covering the city center of Ghent.
To see the composition of the costs of both technologies we compare the situation with 5 Mbit/s DL
and 1 Mbit/s UL, because both the total cost and the fitness value are about the same. Figure 4.9
shows the composition of the costs when using LTE-advanced. We see that 32% of the costs are
license fees. 28% of the money is spend on the fiber network, while 27% is dedicated to the
installation of the base stations and 13% for maintaining them. Figure 4.10 shows the same diagram
for Wi-Fi. Here, a remarkable 69% of the costs are caused by the fiber network, the biggest part to
the placement of the fiber, which is 56% of the total costs. No license costs are applicable here. The
installation and maintenance costs of the wireless network are responsible for respectively 21% and
10% of the costs.
The main factor for the high costs of LTE-advanced is the license fee and also the expensive
equipment for the base stations. Although the latter gets compensated due to the fact not many of
them are needed. If the license fees would be less in reality than estimated, we should certainly go
for LTE-advanced in the choice of technology. On the other hand, if the estimation of the license cost
is lower than in reality, we should consider Wi-Fi to cover the city center with a wireless network.
The influence of this license cost will be investigated in the next chapter.
When using Wi-Fi, the main factor is obviously the fiber network. This makes sense, because many
cheap base stations are installed through-out the city-center, and they all have to be connected to
the fiber network. Due to the high digging costs, the influence of a couple more meters of fiber is
pretty big. If these costs could be suppressed, e.g. by renting dark fiber or when an FTTH network is
available, Wi-Fi seems a good option for the network. The actual costs of this network could be
higher too, due to the abstractions made in the dimensioning: we didn’t take the roads into account.
We just took the shortest path between two points, which is straight. Considering the roads would
give us a longer trajectory of the fiber, increasing the costs. On the other hand, this abstraction is
also made when implementing LTE-advanced, so also in that scenario the costs would go up without
this abstraction.
Figure 4.9: Composition of costs LTE-advanced
23%
5%
27%13%
32%
Fiber
Equipment Fiber
Installation BSs
Maintenance BSs
License
| 49
Figure 4.10: Composition of costs Wi-Fi
4.1.4 Conclusion
The first scenario gives a good aspect on what the dimensioning tool is capable of and what type of
output the tool produces. It shows how the different years of the gradual roll-out are computed. The
second scenario shows the comparison of Wi-Fi and LTE-advanced in the city center of Ghent and
teaches us that LTE-advanced seems to be the best option, although the exact price of the license
and the equipment has a big impact. The influence of the license will be examined in chapter 5. Also
the fixed network has a big influence on the decision, as Wi-Fi will need a much longer net. So if the
costs would be significantly lower, it might be a good decision to go with Wi-Fi instead of LTE-
advanced. On the other hand we can also conclude that LTE-advanced works better at higher bitrate
demands, so it’s more future-proof than Wi-Fi.
56%
13%
21%
10%
Fiber
Equipment Fiber
Installation BSs
Maintenance BSs
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4.2 Rural case
In the second case we would like to test the tool on a more rural area. Within this dissertation there
was a close cooperation with Unet B.V. Unet is a Dutch Fiber To The Business (FTTB) company that
provides services over their fiber to small and medium sized companies. They also rent dark fiber to
other companies. On their active networks they provide services such as internet, VOIP, XDSL, IPTV,
VPN, PIN and surveillance. Unet gave us detailed information to benchmark the tool on a rural case
in Flevoland. They would like to connect all farmers in a given area and provide a triple-play package,
including internet, telephony and digital television and compare in a study different types of
technologies to make this connection. Coverage (at a lower bitrate) of the mobile network should
also be provided on the fields of the farmers. Different wireless technologies and configurations of
them are tested with the tool to find an optimal technology to meet the demands. We inspect the
influence of Spatial Multiplexing and Transmit Diversity, since in rural areas the ranges of the base
stations become important because the population is spread over the area.
4.2.1 Input
Area
The target area in Flevoland has a surface of about 35 km2. Figure 4.11 shows a satellite view of the
area limited by the road N305 in the north, by the road N301 in the east, by the N704 in the west and
by the red line drawn on the map in the south.
Figure 4.11: Sattelite view of the target area in Flevoland
Unet gave us GIS-data in which the buildings and the fiber that’s already available are given. We
made a shapefile out of this data, which is shown in Figure 4.12. We assigned the population
manually to the areas. We aim at a bitrate of 5 Mbit/s DL and 1 Mbit/s UL per person. We assign a
population of 100 to the total rural area – without the areas of the houses – assuming not more than
100 farmers will be at work at once. Each house on the shapefile has a population of 5, assuming a 10
Mbit/s channel for HDTV and three channels of 5 Mbit/s for telephony and internet usage. This
results in a total of 25 Mbit/s per house.
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Figure 4.12: Fiber available in target area
Besides that, Unet also gave as GIS data of a fiber network that they would deploy in order to
connect all the farmers in this area. The shapefile with their proposal is shown in Figure 4.13. Their
solution has the benefit that there is basically no limit in terms of data rate, but on the other hand,
they only connect farms and there would be no network access on the fields. Additionally this
solution leads to much trenching and a high final cost.
Figure 4.13: Solution Unet case Flevoland
We aim to compare their solution to a couple of solutions computed with our tool. Therefore we
need to select the possible antenna locations. We chose to select every house (or their garden) as a
possible antenna location. Making this choice, we can compare the scenario where large poles are
installed on the ground with the scenario where smaller poles are put upon roofs. This results in a
collection of about 75 possible locations shown in Figure 4.14.
Figure 4.14: Possible antenna locations case Flevoland
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A final step to prepare the geographical input is to create fiber connection points. We created
(manually chosen) points on the given fiber that crosses the area, making sure each farm near the
fiber is not too far away from a connection point. In the data received from Unet there was also an
extra connection point given at the north border of the area. This connection point is part of another
fiber line running through Flevoland that belongs to Unet. As shown in Figure 4.15 we also added
this connection point to the input.
Figure 4.15: Fiber connection points case Flevoland
Since this area is a rural area, we will need to use the correction factor in the Erceg C model that
corresponds with a rural environment. This can be done by setting the path loss model mode on
‘Rural’ in the tool.
Requirements
In this case, we are not talking about a gradual roll-out. We just want to know how many base
stations of a given technology need to be installed to meet the demands. As stated before, DL data
rate of 5 Mbit/s and an UL data rate of 1 Mbit/s is required and this at 99% coverage. The adoption
here will be 100%, because every house will pay for the use of their amount of bandwidth.
Wireless technology
In some scenarios of this case we use LTE-advanced, but this time we also use it in the TDD. The TDD-
mode in LTE-advanced works better together with the Transmit Diversity technique used in MIMO
[18]. The base stations have an input power of 46 dBm. TDD LTE-advanced also operates in the
licensed band at 2.6 GHz with a bandwidth of 15 MHz. A MIMO configuration of 8x2 is also used and
now Transmit Diversity is used to increase the range of the antennas. Note that not that many
people use the base stations at the same time, so increasing the ranges could be better than
increasing the data rate. The cyclic combining gain is now 3 dB and the MIMO gain is also positive,
due to the usage of TD. The MIMO gain depends only from the amount of transmitter and receiver
antennas and in case of 8x2 MIMO it equals 12 dB. All these parameters are listed in Table 4.7.
When using the FDD mode of LTE-advanced we refer to the previous case, where all the
technological details are set out in section 4.2.1.
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Parameter Value
Input Power 46 dBm
Frequency 2.6 GHz
Duplexing TDD
Bandwidth 15 MHz
Base station
Tx antennas 8
Rx antennas 8
Cyclic combining gain (Tx) 3 dB
Mobile station
Tx antennas 2
Rx antennas 2
Cyclic combining gain (Tx) 3 dB
MIMO
Configuration TD
MIMO gain (Tx/Rx) 12 dB
Table 4.7: Parameters LTE-advanced TDD
We use two configurations of Wi-Fi in this case. The Wi-Fi parameters used in one scenario are the
same as the ones used in the urban case, so also a 4x2 MIMO configuration, using Spatial
Multiplexing in a TDD frequency band of 20MHz. In another scenario we use the same configuration
– still operating in TDD-mode – along with Transmit Diversity instead of Spatial Multiplexing. Similar
to LTE-advanced, this adds a cyclic combining gain of 3 dB to the BS and MS parameters and a MIMO
gain of 9 dB (4x2 MIMO).
LTE-advanced base stations are placed on poles of 30m high, while Wi-Fi antennas are placed on
smaller poles of 10m on rooftops, resulting in a total height of 15m.
Costs
Table 2.2 shows the costs of the wireless equipment used in this case. Digging in a rural area is much
cheaper than digging in the streets of a city. Here, fiber can be laid in a trench next to the street
under soft ground. This is why the cost per meter fiber given in 2.3.1 is much lower for this case.
Unet also gave us some financial information about their solution, which consists only of a fiber
network. From that data we derived a price of €23.7 per meter for the installation of fiber in the
area.
Again, for LTE-advanced a license is needed. In the first scenario we use 15 MHz bandwidth in TDD
mode, but again considering three sectors, so we need a license for 45 MHz. In the Netherlands
licenses were sold at an average of €20,200 per MHz. So, €909,000 would be sufficient to have the
license for the whole country. Again, we are only deploying the network in a small part of the country
and this time, the part is not touristic or populated at all. It’s an area where about 75 farmers live,
and where the interest for a 4G network is not very high. If we take the same approach as in the
previous case, estimating the population of the given area at 250 (considering wives and kids) out of
a total of 16,736,736 people living in the Netherlands, the license cost would result in €13.6. This
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price can be neglected and might be unrealistic. If we now try the geographic approach, considering
35 km2 for the area and 41,528 km2 for the whole country, the license cost is estimated at €766. This
might be a better indication, so we will work with this price. Note that the 3G licenses in the
Netherlands will have a much smaller impact than in Belgium.
For LTE-advanced operating in a FDD-mode, with the configurations given in the urban case, only 30
MHz is needed. The same calculations as in the TDD-mode result in a license cost of €511.
4.2.2 Comparison of technologies
LTE-advanced
When using LTE-advanced in the TDD-mode and with the TD technique, the output gives us a
network with 8 antennas and about 6 km fiber shown in Figure 4.16. In this figure both the newly
installed fiber and the fiber that was already available are shown. The total cost of this solution is
€754,576, including the license cost. The total cost includes one year of maintenance and operational
costs.
Figure 4.16: Solution Flevoland case LTE-advanced TD
When we compare it to the scenario using LTE-advanced in FDD-mode, so with Spatial Multiplexing,
we observe that only 4 antennas interconnected by about 4.5 km fiber are needed. The result is
shown in Figure 4.17. This solution will also be a lot cheaper, only costing €430,279.
We stated before that we thought using Transmit-Diversity in TDD mode would give us better results,
but here we discover it’s not true. This can be explained by the fact that the required data rates are
fairly high. One house, which is just a small area on the map, demands a data rate of 25 Mbit/s. So,
10 houses for example, require 250 Mbit/s (with an adoption of 100%). As explained before, the
range of an antenna is limited by both the input gain of the antenna and the total data rate it has to
provide. In Figure 4.16 for example, the coverage-circle of the center antenna is much smaller than
the one in the top-left corner, because it serves more houses. So it seems the range-increase that TD
brings along has no influence in this situation, because the original maximum range is not even
reached due to the high rates.
On the other hand, SM creates enough bandwidth to cope with these high data rates for many users,
so the ranges won’t be constrained by the data rate, but by the maximum path loss function. As
| 55
Figure 4.17 shows, the ranges of the base stations are all about the same. This indicates they are
limited by the path loss function, instead of the maximum allowed bitrate. So in this scenario, the
ranges limited by the path loss are higher than the ones limited by the maximum data rate.
Figure 4.17: Solution Flevoland case LTE-advanced SM
Wi-Fi
A first study for Wi-Fi runs the tool with a configuration that implies Spatial Multiplexing. We
discover that when we install an antenna on every possible location given in Figure 4.14, we achieve
a coverage-percentage of 75. From the previous case we learned that the ranges for Wi-Fi are not as
high as the ones for LTE-advanced. This explains why we can’t reach the required coverage when
only using these antenna locations for Wi-Fi. Although we prefer to use the previously shown
possible locations, we created a shapefile with much more locations covering the area, assuming
poles of 15m can also be placed in the fields. The new possible locations are shown in Figure 4.18.
Note that the poles and installation costs are higher on locations that are not on rooftops of
buildings, which only require poles of 10m. So we added a cost of €1000 to cope with this problem.
Figure 4.18: Possible antenna locations case Flevoland for Wi-Fi
Using this shapefile as input and the Wi-Fi configurations implementing SM, results in a network of
68 antennas connected by almost 36.8 km fiber. Although a Wi-Fi BS is much cheaper, the total costs
will be €1,864,989, which is much higher than both scenarios using LTE-advanced. Not only is this
technology much more expensive, its optimal solution also achieves only 97.7% coverage, instead of
the 99% achieved with LTE-advance. The visual output of the solution is shown in Figure 4.19.
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Figure 4.19: Solution Flevoland case Wi-Fi SM
We notice that the ranges of the antennas are really small, which means that one antenna doesn’t
cover many houses. It’s clear that the ranges are limited by the path loss, because they are all the
same. In this scenario, TD might help increasing these ranges because the required data rate by one
base station is not so high and it increases the ranges of the antennas if they are only limited by the
path loss function.
Figure 4.20 shows the result of the scenario where TD is used. This time, only 47 antennas are
needed and about 28.4 km fiber to connect them all. This results in a total cost of €1,359,222, which
is less than the SM scenario of Wi-Fi, but still much more than the scenarios using LTE-advanced. In
this case, Transmit Diversity does help to increase the ranges and to bring down the total cost. So for
this scenario, there are fewer antennas needed when using TD than when using SM. Note that the
obtained coverage here is 98.6%.
Figure 4.20: Solution Flevoland case Wi-Fi TD
Overview of solutions
Table 4.8 gives an overview of the results of the scenarios discussed before. It is quite clear that LTE-
advanced (LTE-a) with SM is the best technical choice. It outperforms all other technologies. Not only
the Capex is lower, but also the yearly Opex is better than in the other scenarios.
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We can also conclude that SM and TD have a big impact on the performance of the wireless
networks. A basic rule is that areas with a high demand of data transfer, due to the density or the
data rate, need SM to increase the ranges of the antennas. While in areas where the demand of data
is lower, TD seems a good method to increase the ranges. We discovered that the choice between
the two depends on the area and the situation, but also on the chosen technology. This case clearly
showed that in one technology SM performs better, while in the other the choice should definitely
be TD.
LTE-a SM LTE-a TD Wi-Fi SM Wi-Fi TD
# BSs 4 8 68 47
Km fiber 4.5 6 36.8 28.4
Coverage 99.1% 99.2% 97.7% 98.6%
Capex €409,279 €712,576 €1,820,789 €1,328,672
Opex €21,000 €42,000 €44,200 €30,550 Table 4.8: Overview results Flevoland case
Influence of height
In previous scenarios, LTE-advanced base stations where placed on 30m poles and Wi-Fi antennas on
10m poles on 5m high roofs, resulting in a height of 15m. The difference between the two
constructions supporting the equipment is €7,500. This made us wonder what would happen if we
put the LTE-advanced antennas on the smaller poles, which cost much less. The ranges of the
antennas depend on this height, a higher placed antenna will reach further. We tested if placing
(probably more) antennas at 15m would be cheaper than the previous scenarios. We ran the tool
with both LTE-advanced settings, so once for SM and once for TD and retrieved the results given in
Table 4.9. We see that both scenarios are worse compared to the case when they are placed on a
pole of 30m. Again, the fact that the choice between SM and TD depends strongly on the situation is
emphasized here. With base stations placed at a height of 15m we notice that it’s actually better to
implement TD. Both the Capex and Opex are lower and fewer antennas are needed to cover the
area. Actually, when comparing the solution of the TD-scenario with its solution at 30m, we see that
there’s only one antenna difference between both solutions. When we make a similar comparison
for SM we notice a difference of 7 antennas. This is explained by the fact that only SM could benefit
from the increase of the range of the antennas by putting them higher. TD didn’t really need this
increase in range, because it didn’t get that far anyway due to the limitations caused by the required
data rates.
LTE-a SM 15m LTE-a TD 15m
# BSs 11 9
Km fiber 8.3 7.8
Coverage 99.3% 99.1%
Capex €888,640 €758,553
Opex €57,750 €47,250 Table 4.9: Solution case Flevoland with BS at 15m
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4.2.3 Conclusion
The results of our tool tell us the best way to provide the farmers a wireless connection is to use LTE-
advanced with SM, placed on 30m poles. Deploying this network would cost us around €410k with a
yearly cost of €21k. We also learned from the previous case that LTE-advanced can cope better with
increasing data rate demands, so if in the future the required data rates might go up, LTE-advanced
does seem a good choice of technology.
By studying this case we also discovered there’s no real strategy in choosing between SM and TD, but
both techniques have to be tested before making a decision. We discovered there are different
factors that influence their performances:
The chosen technology
The input power of the BS
The height of the BS
The density and the placement of the population through-out the area
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5. Refined economic analyses
In this chapter, we perform some refined economic analyses. We show how the tool can also be used
to perform such analyses. Our reference scenario is the scenario of the whole city of Ghent in the
urban case, except when studying the influence of the expected adoption. There we use the center
of Ghent as reference scenario.
5.1 Influence of expected adoption
Figure 2.17 showed us the adoption curve we used in the cases. It represents the predictions of the
amount of people that will use the network. There doesn’t exist a prediction that is 100% certain, so
also this adoption is just estimation and possesses a certain amount of uncertainty. In this chapter
we want to take this uncertainty into account. To do so, we constructed alternative adoption curves
that represent this uncertainty. The adoption influences the range of the base stations, so a different
adoption as input will give us a different output. We will discuss the changes of the output due to
these changes in adoption.
For creating the curves, we assume that in year 0 there’s 60% chance that the regular adoption curve
will be followed, 20% that the curve will be higher than expected and 20% that it will be lower. The
differences between the curves are situated in parameter m of the Gompertz model. For the higher
curves m is 0.25 and the lower curve has 0.15 as value for m, while in the regular curve m is 0.2.
These curves and their chances are given in Figure 5.1.
Figure 5.1: Possible adoption curves year 0
This uncertainty is present in every year, so after 1 year, we should also take the uncertainty into
account. Two new curves are built for every curve created in year 0 in a similar way. Again, a higher
and a lower curve with 20% chance are made. This time, the higher curve is a composition of its
reference curve until year 1 and the Gompertz curve with an m that’s 0.05 higher but shifted down to
be equal as its reference curve in year 1. The lower curve is constructed in the same fashion. The
higher and lower curve for the regular curve (m=0.2) are shown in Figure 5.2 along with their
chances. Note that these chances have to be multiplied with the chance the reference curve appears,
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which is 60% in this case. The higher curve is displayed as RU, which is the notation for “regular-up”,
and the lower curve as RD, corresponding with “regular-down”.
Figure 5.2: Possible adoption curves year 1
This process is repeated each year for every curve that’s created in the year before. The only
difference is that every year the difference of parameter m between the higher and lower curve and
their reference curve is cut in half. This is done to cope with the fact that every year the uncertainty
is a bit less, because the predicted period that is shorter. So in year 2 the difference is 0.025 as
shown in Figure 5.3. This difference equals 0.0125 in year 3 and 0.00625 in year 4. Year 5 is the last
year of the gradual roll-out so no more prediction is made in that year.
Figure 5.3: Possible adoption curves year 2
Creating all the curves in every year results in a collection of 243 curves that are shown in Figure 5.4.
We ran the tool with the input of the urban case, in the scenario of the center of Ghent at 5 Mbit/s
DL, once for each of these curves.
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Figure 5.4: All possible adoption curves sensitivity analysis
We set out the total costs of the results along with the chance they appear on a graph shown in
Figure 5.5. The costs vary from €800,000 to about €1,500,000, which is almost double. Compared to
the reference scenario (normal adoption) – resulting in €1,180,098 – the lowest cost is 32% lower,
and the highest cost is 27% higher. Note that a higher adoption brings a higher income, because
more customers will pay for the service. So even though the cost is higher, the income is higher.
Actually, if we look at year five, the adoption varies between 0.075 and 0.275, so in case of higher
adoptions our income will be about 3.5 times as high. This means a higher adoption would be
beneficial when taking an income per person into account. Back to Figure 5.5, we notice that costs
near the reference scenario – the only one with a 0.08 chance – have more chance to appear than
scenarios with much lower or higher costs. We calculated the mean, which is the sum of the costs
multiplied by the chance they appear. The mean equals €1,170,375, so there’s €10,000 difference
between the reference scenario and the mean. This means that in reality, there’s a little more chance
the costs will be lower than expected.
Figure 5.5: Influence of expected adoption
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We conclude that the adoption has a great impact on the resulting costs. This impact is also
influenced by the license cost of €341,818. If we don’t take it into account, the reference scenario
would cost €830k and the costs of the scenarios would vary between €460k and €1,160k, which is
45% lower and 40% higher. So not considering the license costs, the impact of the adoption is even
higher. Spending some money in making a good prediction of the adoption is definitely a good
choice, especially because here we discuss a small area of 7km2, but in reality mobile networks cover
much bigger areas. If we e.g. consider the case of the whole city of Ghent where the total cost was
about €7.5 million. If you don’t study the adoption of the area and just assume the regular adoption
as used throughout this dissertation and e.g. in reality have the lowest possible adoption (as
discussed before), you actually spent 32% too much, which is about €2.4 million.
5.2 Influence of cost of extra MIMO antennas
A 2x2 MIMO BS of LTE-advanced costs about €30.000. There are many speculations about the price
of extra MIMO-antennas. As said before, when implementing 8x2 MIMO, 6 extra antennas per sector
have to be installed, so 18 antennas in total. In our cases we assumed an extra cost of 66,67% per BS
for the extra antennas, which comes down to €20,000. This extra cost depends on the vendor and on
the size of the project.
To test the influence of this project on our reference scenario (Ghent), we calculated the total costs
of the project with some other costs. In a worst-case scenario, we assume the extra antennas cost as
much as the 2x2 BS itself, resulting in €60,000 per BS. As we assume we overrated the prices of the
extra antennas, we take a look at the scenario where the extra antennas only cost 33.33% or 50%
extra, resulting in BS’s of €40,000 and €45,000. Note that the maintenance cost also change in price
when the price of the BS is adapted.
Figure 5.6 shows the resulting cost composition of the different scenarios. Obviously, the higher the
MIMO costs, the higher the total costs will be. At 100%, the total cost is €8,065,898, which is about
€600k higher; so an increase of 8% upon the original costs. When the MIMO costs are 50%, the costs
will be about 300k – or 4% – lower. When they are 33.33%, the total cost decreases by 8%, the same
amount as it increases when they are 100%. We conclude that a change in the total BS cost of 20%
corresponds with a change in the total cost of 8%.
Figure 5.6: Influence of the additional cost for extra MIMO antennas
€ 0
€ 1.000.000
€ 2.000.000
€ 3.000.000
€ 4.000.000
€ 5.000.000
€ 6.000.000
€ 7.000.000
€ 8.000.000
€ 9.000.000
33% 50% 67% 100%
Equipment Fiber
Maintenance BSs
Installation BSs
Fiber
License
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5.3 Influence of license cost
As stated before, the license cost was estimated and depends on the people living in Ghent. There
are more factors in this scenario that can influence the cost of the license. Following factors would
indicate the costs of the scenario would be higher:
1. The touristic value of the city
2. Area too small to own or buy the license for it
3. Rental costs if not an owner of a license
Other factors could mean that the cost would actually be lower:
1. Size of the area of Ghent (compared to Belgium) does matter or has an influence
2. License is valid for 15 years and the main scenario only handles a period of 5 years. So there
is still a big value of the license after these 5 years are passed
These factors give us reasons to revise our estimations of the license costs. Besides, [22] teaches us
that the price of the licenses greatly depends from the country in which it is auctioned, so it certainly
can be interesting to see what the influence of the license costs are in a general case. We estimated
the license fee for the city of Ghent at €341,818. We now recalculate the financial results for the
scenario of Ghent with different figures for this fee.
In a pessimistic view, let’s assume that the licenses in Belgium are divided by the different states and
not by the area you would want. There are ten states in Belgium, so we divide the total cost of
€15,040,000 by ten, resulting in €1,504,000. Although the license of one state could be worth more
than the license in another, East Flanders (the state of Ghent) seems a good representation of a state
with an average license-value.
The licenses in Belgium are valid for 15 years and our case only considers a period of 5 years. Let’s
assume in a best-case scenario that our network will exist for 15 years and we decide to consider the
license cost as a yearly cost. Accountants would probably not agree with this point of view, but it
makes sense to split the cost of this license into a yearly cost, since it will be used in each of those
years. This means we have to divide the €341,818 by 3. This gives us a value of €113,939.
The change in total cost is straight forward and equals the change in license cost. The worst-case
scenario is €1162k more expensive, or a total cost increase of 15.5%. The total cost of the best-case
scenario is only 3% lower, so €230k. It is clear that the license cost will have a big influence on the
results.
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6. Conclusion and future work
The goal of this study was to determine the dimensioning of a mobile network, interconnected by a
fixed optical network, and performing a cost modeling of different cases. This dimensioning is used to
compare different wireless technologies and their settings to see how they influence the result and
to see what are the costs that have the biggest impact on the total cost.
We built a generic fixed-mobile dimensioning tool that can handle many cases and requirements. It
supports gradual roll-outs and offers a detailed cost modeling. Optimizations were made to this tool
make it run faster and to gain efficiency. Due to the generic form of the tool it works good to
evaluate different cases and make comparisons between scenarios with different input.
We proved that the tool gives us what we want by deploying an LTE-advanced network in the city of
Ghent over a period of 5 years. It shows us how the different aspects of the tool work.
From this urban case we learned that the fiber network has a big impact on the total costs of the
network. Almost half of the costs are dedicated to the fixed network. We also made the comparison
between a Wi-Fi and a LTE-advanced network in the center of Ghent. We learned that LTE-advanced
is the right choice when deploying a city-wide high data rate network. Two factors could have a big
influence on this decision: the costs of the fiber network and the license fee. Lower fiber costs, e.g.
by renting dark fiber, or a higher license fee could lead to the decision of rolling out a Wi-Fi network.
Still, LTE-advanced should be chosen if the data rates of the network will have to be higher in the
future.
Next, also a rural case was considered (Flevoland). Again, a comparison was made between Wi-Fi and
LTE-advanced, but here it was very clear that LTE-advanced should always be chosen, unless the
licenses would be very high (not the case in the Netherlands). When deploying LTE-advanced, a
choice has to be made between Transmit Diversity and Spatial Multiplexing, both techniques that use
the extra MIMO-antennas. From the urban case we learned this choice depends of several factors.
First of all the mobile technology has an impact on the choice, for which the most important
parameter is the input power of the base station that has a direct influence on the range of the base
station. Also the height at which the base station is installed impacts this range. We concluded that
besides these factors, the area itself influences this decision, moreover the way the people are
spread out over the area and the density of the different parts of the area.
Finally, as several factors can greatly influence the outcome, we conducted sensitivity analyses. As a
first uncertainty, we focused on the license cost, which can have a great influence on the solution
and fluctuates a lot. The price depends on the surface, inhabitants and country where it is purchased
and whether you can buy or rent it. When the price is relatively low, LTE-advanced comes out best,
otherwise the decision could move to Wi-Fi. When using MIMO, the price of extra MIMO-antennas is
an important uncertainty. Depending on the price, more or less base stations with respectively a
lower or higher MIMO-configuration is preferable. Finally, the adoption of the network will pose
important uncertainties. We calculated the dimensioning of the network in many different scenarios,
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where e.g. the adoption after 2 years seems to be higher than expected, resulting in different types
of networks. In some scenarios costs were up to 32% lower, where in others they were 27% higher.
Variations on this parameter should be investigated on a specific case, because they can have a big
influence on the final cost of the network.
The development and usage of the tool doesn’t stop here. The tool can be expanded in many ways.
An interesting topic would be to not only use the GIS data for the wireless dimensioning, but also for
the fixed dimensioning. A shapefile with the street-layout of a given area could give a realistic view
on where to lay fiber, if an appropriate algorithm is used. This could provide an even more detailed
cost modeling.
It might also be interesting to perform more study in the field of the path loss models. Actually, when
having 3D-GIS data of an area, like we have of the center of Ghent, realistic path loss models could
be created that take the specific buildings around a BS into account. The mobile networks can be
modeled more precisely, no longer restricted to circular ranges, and will show us where the weak
spots really are.
This tool also allows comparing both the technical details of the technologies and their price. It can
easily be to calculate the deployment of future 5G networks or to compute the effect of new
techniques implemented on current wireless technologies, e.g. a mixture of Transmit Diversity and
Spatial Multiplexing.
More research in the tradeoff between TD and SM would definitely be useful too. There may exist
some logic patterns or basic rules which could explain the advantage of one technique upon the
other in a given situation.
This master thesis really gave a good view on how important the fiber network is when dimensioning
a fixed-wireless network and gives a good view on the influences of the different costs. It also shows
that one should consider different technologies and also different settings of them when deploying a
wireless network somewhere. The price of the equipment of the mobile network is not the only thing
influencing the total cost, but also the cost of the network connecting that equipment has a big
impact.
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List of figures
Figure 2.1: Time Division Duplex [2] ........................................................................................................ 3
Figure 2.2: Frequency Division Duplex [2] ............................................................................................... 3
Figure 2.3: Modulation schemes.............................................................................................................. 4
Figure 2.4: OFDMA ................................................................................................................................... 4
Figure 2.5: OFDMA and SC-FDMA [5] ...................................................................................................... 5
Figure 2.6: Carrier Aggregation [7] .......................................................................................................... 5
Figure 2.7: SISO, SIMO, MISO and MIMO [8] ........................................................................................... 6
Figure 2.8: Transmit Diversity [10] ........................................................................................................... 6
Figure 2.9: Spatial Multiplexing [10] ........................................................................................................ 7
Figure 2.10: Overview of generations of telecommunication systems [11] ............................................ 7
Figure 2.11: IMT-2000 and IMT-advanced [12] ....................................................................................... 8
Figure 2.12: Relaying [7] .......................................................................................................................... 9
Figure 2.13: Passive Optical Network .................................................................................................... 10
Figure 2.14: WDM-PON [17] .................................................................................................................. 11
Figure 2.15: Equipment model of a PON ............................................................................................... 11
Figure 2.16: Crossover and mutation ..................................................................................................... 15
Figure 2.17: Gompertz curve ................................................................................................................. 19
Figure 3.1: Wireless tool [18] ................................................................................................................. 22
Figure 3.2: Example scenario fiber cost impact ..................................................................................... 25
Figure 3.3: Example scenario solution of Wireless Tool ........................................................................ 25
Figure 3.4: Example scenario good solution .......................................................................................... 25
Figure 3.5: The Techno Economic Software Suite [26] .......................................................................... 26
Figure 3.6: Example of tree structure of equipment model [26] ........................................................... 27
Figure 3.7: the dimensioning tool .......................................................................................................... 29
Figure 3.8: Input of the dimensioning tool ............................................................................................ 30
Figure 3.9: Core of the dimensioning tool ............................................................................................. 31
Figure 3.10: (a) top: example scenario year 1; (b) middle: MST example scenario year 1; (c) bottom:
adapted MST example scenario year 1 .................................................................................................. 32
Figure 3.11: Coverage fitness problem .................................................................................................. 33
Figure 3.12: Output of the dimensioning tool ....................................................................................... 34
Figure 3.13: impact of population time on runtime of the tool ............................................................ 35
Figure 3.14: comparison of different configurations of local optimization ........................................... 36
Figure 3.15: comparison of population sizes with implementation of local optimization .................... 36
Figure 4.1: Shapefiles Ghent .................................................................................................................. 40
Figure 4.2: Antenna locations of BIPT Ghent ......................................................................................... 40
Figure 4.4: Yearly costs case Ghent ....................................................................................................... 44
Figure 4.5: Visual output of each year of case Ghent ............................................................................ 45
Figure 4.6: Composition of the total cost of solution ............................................................................ 45
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Figure 4.7: Comparison of LTE-advanced and Wi-Fi costs under given data rates ................................ 46
Figure 4.8: Reached coverage percentage in Wi-Fi vs. LTE-advanced experiment ............................... 47
Figure 4.9: Fitness values of Wi-Fi vs. LTE-advanced comparison ......................................................... 47
Figure 4.10: Composition of costs LTE-advanced .................................................................................. 48
Figure 4.11: Composition of costs Wi-Fi ................................................................................................ 49
Figure 4.12: Sattelite view of the target area in Flevoland .................................................................... 50
Figure 4.13: Fiber available in target area ............................................................................................. 51
Figure 4.14: Solution Unet case Flevoland ............................................................................................. 51
Figure 4.15: Possible antenna locations case Flevoland ........................................................................ 51
Figure 4.16: Fiber connection points case Flevoland ............................................................................. 52
Figure 4.17: Solution Flevoland case LTE-advanced TD ......................................................................... 54
Figure 4.18: Solution Flevoland case LTE-advanced SM ........................................................................ 55
Figure 4.19: Possible antenna locations case Flevoland for Wi-Fi ......................................................... 55
Figure 4.20: Solution Flevoland case Wi-Fi SM ...................................................................................... 56
Figure 4.21: Solution Flevoland case Wi-Fi TD ....................................................................................... 56
Figure 5.1: Possible adoption curves year 0 .......................................................................................... 59
Figure 5.2: Possible adoption curves year 1 .......................................................................................... 60
Figure 5.3: Possible adoption curves year 2 .......................................................................................... 60
Figure 5.4: All possible adoption curves sensitivity analysis .................................................................. 61
Figure 5.5: Influence of expected adoption ........................................................................................... 61
Figure 5.6: Influence of the additional cost for extra MIMO antennas ................................................. 62
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List of tables
Table 2.1: Numerical values of Erceg model parameters [19] ............................................................... 14
Table 2.2: Wireless equipment and installation costs ........................................................................... 18
Table 2.3: Fiber equipment costs and lifetimes [26] ............................................................................. 19
Table 2.4: Values of parameters of Gompertz model ............................................................................ 19
Table 3.1: Fixed technical parameters ................................................................................................... 30
Table 3.2: Geographic coverage versus density coverage ..................................................................... 38
Table 4.1: Yearly data rate requirements city of Ghent ........................................................................ 41
Table 4.2: Data rate requirements of different scenarios center of Ghent (equal each year) .............. 41
Table 4.3: Parameters LTE-advanced FDD ............................................................................................. 42
Table 4.4: Parameters Wi-Fi TDD ........................................................................................................... 42
Table 4.5: Overview solution case Ghent .............................................................................................. 43
Table 4.6: Number of base stations and km fiber .................................................................................. 46
Table 4.7: Parameters LTE-advanced TDD ............................................................................................. 53
Table 4.8: Overview results Flevoland case ........................................................................................... 57
Table 4.9: Solution case Flevoland with BS at 15m ............................................................................... 57