INFORMS Keynote Capone
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Transcript of INFORMS Keynote Capone
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Politecnico di Milano
Advanced Network Technologies Laboratory
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From Pre-Planned to Self-Organizingand Green Wireless Networks
Antonio Capone
The 10th INFORMS Telecommunications
Conference
Concordia University, May 5 - 7, 2010
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Disclaimer:Engineers and Mathematicians
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Picture borrowed from:A. Eisenbltter, H.-F. Geerdes, Wireless Network Design: Solution-oriented
Modeling And Mathematical Optimization, IEEE Wireless Communications, December 2006
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Summary
Wireless networks Radio planning evolution (2G and 3G)
Coverage Planning
Capacity Planning
Self-organizing networks (4G) Complexity of network management
4G systems (LTE)
Concept of SON
Dynamic resource management
Wireless Green networks
Energy consumption
Green energy management
Conclusion
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Phones
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Mobile phones
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Cellular subscribers vs fixedlines
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0
500
1000
1500
2000
2500
3000
3500
1990 1995 2000 2005 2007 2010
Cellular
Subscribers
Telephone Lines
Source: www.etforecasts.com
M bil fi d
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Mobile vs fixed vsinternet
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60 mobile subscribers per 100 inhabitants 19fixed lines per 100 inhabitants
23internet users per 100 inhabitants
9 broadband users per 100 inhabitants
Source: ITUData: 2008
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Mobile subscribers bycountry
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Radio planning
The deployment of mobile radio networksrequired so far HUGE investments
The extension of existing network, new dataservices, and new technologies are continuing
to require a lot of money This has stimulated mobile operators to use
automatic tools for the design and theoptimization of their networks
In the last ~15 years the research communityhas proposed a large number of approaches fordesigning and optimizing wireless accessnetworks (more than 16000 results in GoogleScholar)
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Network planning tools
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Main PlanningTools:
Aircom Asset
Mentum Planet
Atoll FORSK
ATDI
WinProp
EDX Signal Pro
CelPlan
Siradel
Pathloss
Main OptimizationEngines
Actix
Capesso
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What is radio planning?
The basic decisions that must be taken duringthe radio planning phase are: Where to install base stations (or access points,
depending on the technology) How to configure base stations (antenna type,
height, sectors orientation, tilt, maximum power,
device capacity, etc.)
XX
XX
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What is radio planning? This is, however, not enough
Multiple access techniques are used to define
communication channels on the available radiospectrum
Radio resources for wireless systems are limitedand must be reusedin different areas (cells)
Resource reuse generates interference
FDMA TDMA CDMA
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Interference
Interference is the key parameter that drivesnetwork planning and optimization processes
Interference can be tolerated (goodcommunication quality) if the Signal-to-Interference and Noise Ratio (SINR)is high
enough
SIR constraint limits the number of simultaneouscommunications per cells, i.e. the systemcapacity
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GOAL:minimize costs
maximize covered traffic
inout
rec
II
PSFSINR
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2G Planning
FDMA/TDMA cellular systems adopt a two phases radioplanning
Coverage planning
Capacity planning (frequency assignment)
Coverage planning:
Select where to install base stations
Select antenna configurations
s.t. constraints on signal level in the area
Capacity planning:
Define which radio resources can be used by eachcell
s.t. SINR (quality) constraints
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Coverage Planning Many different models have been proposed for
the coverage planning
Basically all of them are based on the classicalset covering problem
With several specific features that have been
added depending on technology and service mix
15
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min Objective function:total network cost
Full coverage constraints
One configuration per site
Integrality constraints
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Coverage Planning
Example: Cell overlap
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Note that:
zih= 1if iand h are coveredby a same BS
Cell overlap may be requiredfor mobility management
Overlap can negatively affectcapacity (e.g. in WLANs)
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Capacity planning(aka frequency assignment)
After coverage planning,capacity planning is in chargeof defining which radioresources can be used by
each cell
The amount of resources(frequencies) assigned to cells
determines system capacity Frequencies can be reused,
but SINR (quality) constraintsmust be enforced
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F2
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Frequency assignment
Maximizing the simultaneoustransmission with SINRconstraints is a key problem isall wireless networks
ij
SINRij>t
However, the most popularmodels for frequencyassignment have been basedon compatibility graphs
Frequency assignment problems
are modeled as variants of the
graph coloring problems
i j
cij
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Frequency assignment
Since Graph based models do not considerSINR constrains explicitly the cumulative effectof interference is not accouter for
Compatible?
Minimum InterferenceFrequency AssignmentProblem (MI-FAP) andits variants modelsdirectly interferenceeffect
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3G Planning
3rd Generation Systems are based on W-CDMA(UMTS)
Two-phases approach not suitable because:
Channels are shared and there is no frequencyplanning for CDMA
Coverage depends on SINR values
Joint coverage and capacity planning
SINR constraints make the problem ageneralization of the capacitated facility
location problems
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N t k t &
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Network management &control
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Network configuration and optimization is becoming
far too complex for mobile operators
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4G Long Term Evolution
The need to plan, configure, manage a newwireless network from scratch
with up to 10 times more base stations
and many more parameters to set
simply worries mobile operators
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LTE architecture
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eNB
MME / S-GW MME / S-GW
eNB
eNB
S1
S1
S1
S1
X2
X2X2
E-UTRAN
The radio architecture
of LTE is more complex
Base stations (eNodeB)are connected alsoamong them (mesh
topology) and they have
computation capabilityto perform advancesfunctions
The presence offemto-cellscanmake the networkmanagement evenmore complicated
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LTE radio interface
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More similar to 2G than to 3G
S lf O i i N t k
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Self Organizing Network(SON)
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Self Planning
Self Configuration
Self Optimizationand Self Tuning
Self Testing andSelf Healing
Self Mantenance
PerformanceImprovement
Cost reduction
self-organizing network is a cellular network in
which the tasks of configuring, operating, andoptimizing are largely automated.
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Self Organizing Network
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Self Organizing Network(SON)
Most of the SON features are aimed at simplifyingpreoperational and operational procedures
HW configuration
SW installation and configuration
Radio basic parameters
Transport parameters
Etc.
However, the most interesting issues from ourperspective are related to the configuration and
management of radio resources
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Automaticcarrier
selectionFractional reuse Load balancing
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Dynamic assignment
The idea of self-configuring and self-optimizing
wireless network is not new!
Several Dynamic Channel Assignment (DCA)schemes have been proposed and analyzed for 2G
Channel/frequency assigned on demand based on
compatibility or interference constraints
but they have never been used in real networks
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Resource assignment in LTE
LTE-advanced offers several instrumentsto make configuration and dynamicmanagement of radio resources possible
eNBs can make measurements over the
radio interface before first resourceconfiguration
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User terminals can providemeasurements to eNBsduring system operationto dynamically selectresources
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Resource assignment in LTE
Defining both centralized and distributedself-configuration and self-optimizationmodels and algorithms for LTE is still anopen problem
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Automatic carrier selection
Channel assignment basedon position in the cell
(fractional reuse) Load balancing among cells
forcing handover
Etc.
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Green Wireless Networks
In addition to configuration, energyconsumption of wireless network is anotherissue that concerns of operators
The power consumption of cellular networks
infrastructure (base stations and core network)doubles every 4-5 years - to 60 TWh in 2008
Energy consumption of mobile telephonyoperators in Italy is 0,7% of total nationalelectric consumption, 55% of wholecommunications sector, with bills of more than300Mper year
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Energy consumption
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Radio accessand core
network
Base
Stations
80%
Mobile
Stations
Network
90%
User
Terminals
10%
Mobile
Network20%
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Energy consumption
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Energy Savings
Significant energy savings can be achieved ifparts or all components of some wirelessnetwork devices are powered off when traffic islow, and powered on based on the volume andlocation of user demand
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Energy Savings
It is also possible to partially switchoff internal modules of base stations
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Base Station
Cabinet
TRXs
Air
Conditioner
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Green Network Management
Switching on and off networkelements based on traffic level
Re-planning of the network based on
different traffic scenarios
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Green Network Management
Radio Planning models can be re-used But some additional features need to be
modeled like:
Coverage and capacity constraints
Cost of network reconfiguration
Performance Energy trade off
Etc.
Energy saving is one of the issues thatis being considered as part of SelfOrganizing Network by standardizationbodies and manufacturers
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Conclusion
The need to plan and manage newgeneration wireless network in a costeffective way is even more acute now thanin the past
Network complexity is increasing Network re-planning is required more
often also for energy saving
New design and management approachesare required
Dont let engineers play alone with thesenew challenging problems
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Politecnico di Milano
Advanced Network Technologies Laboratory
From Pre-Planned to Self-Organizingand Green Wireless Networks
Antonio Capone