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A TRAINING BASED TRANSMISSION PERIOD SETTING PROTOCOL
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Transcript of A TRAINING BASED TRANSMISSION PERIOD SETTING PROTOCOL
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8/13/2019 A TRAINING BASED TRANSMISSION PERIOD SETTING PROTOCOL
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A Training B
Gua
Graduate School
744 Mot
ji
ky
ABSTRACT
We have proposed Intermittentnsmission (IPT forwarding) a
packet relay method for wirel
In IPT forwarding, a sourcepackets to a destination node
time interval (IPT duration) sinterference between relay no
packets simultaneously are
frequency reuse is realized,about an improvement of sys
put. However, the optimumsetting for each node is a diffiwhich was not solved adequate
paper, we propose a new trainiduration setting protocol wh
some training packets to seoptimum IPT durations for eaalso extend the proposed
wireless backhauls applyingantennas. The proposed proto
ated both with computer simulaexperiments. Evaluation resulthe proposed protocol is noeffective but also practical.
KEYWORDSMulti-Hop, Ad-Hoc, Wirele
IPT Forwarding, Training Pack
1 Introduction
The high-speed data transan order of 100Mbps envisi
next generation wireless co
system will restrict the cell rthan 100m (a class of pico- c
sed Transmission Period Setting Prot
gri Jin, Li Gong, Hiroshi Furukawa
of Information Science and Electrical Engineer
Kyushu Universityoka, Nishi-ku, Fukuoka, 819-0395 Japan
[email protected],[email protected]
Periodic Tra- an efficient
ss backhaul.
node sendsith a certain
o that signales that send
reduced and
hich bringsem through-
PT durationcult problemly yet. In this
ng based IPTich employs
arch for thech node. Weprotocol for
directionalcol is evalu-
tion and withs show thatt only very
ss Backhaul,
et, FDA.
ission withned for the
munication
adius to lessell), which
Fig. 1Wireless backhaul
increases the number of ce
cover the service area. Dmany base nodes consid
infrastructure costs, thus c
must be key success factbroadband systems.
In recent years, wirel
systems have drawn great i
of the key technologies tostructure costs for next gen
band systems [1]2. Inhaul, base nodes have the
relay packets by wireless,
them, called core nodes, sways to connect the wirel
with outside backbone
Internet) by cables. Upwar
ginnated from the mobile tcell phone) which are asso
of the base nodes and dioutside network are relaintermediate relay nodes
until they reach the core
ward packets originated fronetwork and directed to a
inal in the wireless backha
the core nodes and rela
84
col
ing,
system.
lls needed to
ployment ofrably raises
ost reduction
r for future
ss backhaul
terest as one
reduce infra- ration broad-
ireless back- capability to
and a few of
erve as gate- ess backhaul
etwork (i.e.
packets ori-
rminals (e.g.ciated to one
ected to theyed by theslave nodes)
odes. Down-
the outsidemobile term-
l are sent by
ed by slave
International Journal on New Computer Architectures and Their Applications (IJNCAA) 1(1): 84-96The Society of Digital Information and Wireless Communications, 2011 (ISSN 2220-9085)
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85
nodes until they reach the final node to
which the mobile terminal is associated
(Fig. 1). By connecting base nodes bywireless links, flexibility of the base
nodes deployment is realized and total
infrastructure costs are reduced due tothe reduction in cable constructions [2].
Wireless backhauls traditionally have
been studied in the context of SpatialTDMA (STDMA) and the Ad Hoc
network. STDMA can achieve collision
free multi hop channel access by a well
designed time slot assignment for each
cell [3]. However, such planning isnot feasible in real systems because ofthe irregular cell forms in real environ-
ments. Additionally, frame synchroniza-tion must be managed carefully in
STDMA, which induces rather difficultoptimization issues [9]. With regard to
the Ad-Hoc network, many studies have
contributed to improve its performance.In [6], Li et al. have indicated that an
application of IEEE802.11 to wireless
multihop network fails to achieveoptimal packet forwarding due to severe
packet loss. In [7], Zhai et al. have
proposed a new packet scheduling algor-ithm called Optimum Packet scheduling
for Each Traffic flow (OPET) which can
achieve an optimum scheduling of
packets by assigning high priority ofchannel access to the current receiver.
However, the overhead imposed by the
complicated hand-shake process decrea-ses frequency reuse efficiency. In [8],
Bansal et al. have indicated that the
throughput of wireless multihop networkdecreases as the hop count increases.
On the other hand, we have proposed
Intermittent Periodic Transmission (IPT
forwarding, [9]) as an efficient packetrelay method with which the system
throughput can achieve a constant value.
In IPT forwarding, source node intermit-tently sends packets with a certain time
interval (IPT duration), and each inter-
mediate relay node forwards the relay
packet immediately after the reception ofit. The frequency reuse space attained by
the method is proportional to the given
IPT duration. In [10], a series ofexperiments have been carried out to
confirm the effectiveness of the method
with real testbed. IPT forwarding isfurther enhanced with the combinations
of MIMO transmission [11] and direc-
tional antenna [12].
IPT duration is the most importantparameter for applying IPT forwarding
method. In [13], a collision free IPT
duration setting method was proposed
and evaluated with computersimulations. However, the method is not
feasible since it introduced some newMAC packets, which makes it difficult
to be implemented with general WLAN
modules without any modifications.
Additionally, system throughput is notguaranteed to be maximized by the IPT
durations attained by the method.
In this paper, we propose a new IPTduration setting protocol which employs
training packets to search the optimum
IPT durations for each slave node. Withthese IPT durations, the end to end
throughputs for each slave node are
maximized. A new metric for the train-
ing process is also presented. Then weextend the proposed protocol for wire-
less backhauls using directional antennas
introduced in [12]. The proposed prot-ocol is evaluated with both computer
simulations and experiments on a real
testbeds.The rest of this paper is organized as
follows. Section 2 explains the principle
of IPT forwarding and the collision freeIPT duration setting protocol proposed
in [13]. Section 3 explains the proposed
protocol in detail. In section 4 we extend
the proposed protocol for a wireless
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backhaul system applying
antennas. In section 5, we
proposed protocol with bosimulations and experiment
concludes this paper.
2 Intermittent Periodic TrIn this section, we expla
ciple of IPT forwarding aloconventional packet relay
collision free IPT duration
hod proposed by [13] is also
2.1 Principle of IPT forwarIn order to clearly explain
of IPT forwarding, we ill
packet relay mechanism oftional CSMA/CA based met
forwarding in Fig. 2 andpectively.
In the two figures, 9 nodes
placed and instantaneous p
on the route are shown inwith time. All the packets t
re-formatted in advance to h
time length.In the case of the conventi
/CA based method, the s
sends packets with a randosion period of P_CNV and
mediate relay node forwar
packets from its preceding
random backoff period. InIPT forwarding, the source
mits packets intermittently
transmission period of P_Iintermediate relay node
forwards the received pack
preceding node withoutperiod. No synchronization
for both the conventional
IPT forwarding method.In the conventional met
transmission space, which i
the distance between relay
transmit packets at the same
directional
evaluate the
h computer. Section 6
nsmissionn the prin-
ng with theethod. The
setting met-
introduced.
dinghe principle
strated the
the conven- od and IPT
Fig. 3, res-
are linearly
acket relays
accordancebe sent are
ve the same
onal CSMA
ource node
m transmis- each inter-
ds received
ode with a
the case ofnode trans-
ith a certain
T and eachmmediately
ts from the
ny waitingis required
ethod and
od the co-
defined as
nodes that
ime, is not
Fig. 2 Packet relay mec
in conventional met
Fig. 3 Packet relay mec
in IPT forwarding
Fig. 4 Performance compar
conventional method and IP
fixed. In such situations, paoccurs due to co-channel i
the co-transmission space i
0 2 4
Throughput
Hop Count
Conventional Method
1.
86
anism
od.
anism
.
ison of the
forwarding
cket collisionterference if
shorter than
6 8
IPT Forwarding
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the required frequency reu
shown in Fig. 2. On the ot
the case of IPT forwardinreadily understood that the
sion space could be contr
transmission period of P_given to the source node,
Fig. 3 in which reuse space
be 3.Reduction of the packet c
help to reduce retransmissi
consequently help to improv
performance. If an adequattion is set in the core node, i
to remove interference b
channel relay nodes that s
simultaneously. If the IPTequal to the threshold, t
throughput observed at thenode can be maximized.
Fig. 4 schematically sho
alized throughput versus
feature of the conventionalIPT forwarding for the syste
and 3. In Fig. 4, constant IP
applied for all slave nodesresultant throughputs ar
same [9].
2.2 Collision free IPT duraAs discussed earlier, i
achieve optimal performan
node should set an adduration for each slave nod
the optimum IPT duration fo
node depends on many efactors such as channel ch
node placements, antenna di
so on. To make IPT forwarpractical, an automatic I
setting method is require
problem, a collision freebeen proposed to automatica
durations for each node in [1
e space, as
er hand, in
it can beco-transmis-
lled by the
PT that iss shown in
s assume to
llisions will
ns and will
e the system
IPT dura- t is possible
etween co-
end packets
duration ise resultant
destination
s the norm-
hop count
method ands in Fig. 2
duration is
nd thus theall the
ion settingorder to
e the core
quate IPTe. However,
r each slave
vironmentalracteristics,
rections and
ing methodT duration
d. To this
rotocol haslly find IPT
].
In this subsection, we w
duce the collision free prot
indicate its drawbacks.
Fig. 5Collision Free IPT dur
1) Summary of collision fThree new MAC layer p
(Request to Stop Sending
CTP (Clear to Pilling UPCTPACK (CTP ACKn
packet, are defined in [13
shaking algorithm is emplthe IPT duration for each n
As shown in Fig. 5, w
duration setting started the(node 1) continuously send
to the destination node (
certain IPT duration. If atransmission fails in an
node (e.g. node 4 in Fi
interference, the node se
packet to the source node todata packets. The source n
the sending of data packets
after reception of the RTSsends a CTP packet to th
node. The CTP packet is r
same way as that for dat
therefore the destination nthat all the relaying data
cleared out from the syste
of the CTP packet. The desimmediately sends a CTPA
the source node on receptio
packet. After receiving tpacket, the source node
87
ll first intro-
col and then
tion setting.
ree method
ckets, RTSSpacket and
packet andwledgement)
and a hand
oyed to findde.
hen the IPT
source nodedata packets
ode 7) with
data packetintermediate
. 5) due to
ds a RTSS
stop sendingode suspends
immediately
S packet ande destination
elayed in the
packet and
de can knowpackets are
by reception
tination nodeCK packet to
n of the CTP
e CTPACKncreases the
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88
IPT duration by one step and resumes
the sending of data packets. This process
repeats until no data packet forwardingfailure occurs in the relaying route.
2)
Drawbacks of the collision freemethodAlthough the collision free method
can obtain certain IPT durations forwireless backhaul, it has some severe
drawbacks as described below.
1) Since new MAC layer packets areintroduced, it is difficult to be
implemented by general wireless
interface modules.
2)
The packet transmission state isconfirmed by checking the MAC
state of each node. However,existing MAC drivers (e.g. MAD
WiFi Driver) do not provide such
functions.
3) System throughput is not guaranteedto be maximized by applying the IPT
durations attained by the method.
Any modification to existing standards
will cause extra costs. Since one of the
major advantages for wireless backhaulis the ability to reduce costs, a new IPT
duration setting method which is not
only practical but also exploits the
optimum system performance isrequired.
3 Throughput maximization IPT du-
ration setting protocolIn this section, we propose a new
training based IPT duration settingprotocol which maximizes the end to end
throughput for each slave node. The
proposed protocol employs some train-ing packets and performs a series of
training process to search the optimum
IPT duration for each slave node. During
the training process, core node continu-
ously sends a number of training packets
to each slave with an IPT duration which
increases gradually until the end to endthroughput from the core node to the
slave node reaches the maximum value.
Throughout this paper we assume thatthe route of wireless backhaul is already
decided before the IPT duration setting
starts and will not change during theprocess of the protocol.
3.1Variables and parametersWe defined the following variables
and parameters in the new protocol.
1) Training packet2)
Number of training packets:N3) Training time for each node: T
4) Training metric for each node: TM5) IPT duration for each node: D
(micro second)
6) Training Step in the process: (micro second)
In these variables, the training packetis defined as OSI link layers data packet
with the length of 1450 Byte and
identified by sequence number. Theparameters TM and D are initialized
whenever new training begins for a new
slave node. The training metric TM,
which is described latter in detail, is usedas the criterion for the training process.
3.2Details of the protocolAs shown in Fig. 1, wireless backhaul
can be considered as the union of a few
sub systems each of which is consistedof a core node and several slave nodes
belonging to it (i.e. each slave node is
connected to the outside network via the
other slave nodes intermediately andfinally through the core node by wireless
multihop fashion). We call the sub sys-
tems a mesh clusters (Fig. 6) throughoutthis paper and the IPT duration setting is
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performed for each mesh clu
tively in the same way.
Fig. 6Mesh cluste
Now let us consider a
with a core node C and anodes {S1, S2, , Sn}. For
node S {S1, S2, , Sn}, tprocess is executed .
Step1: The core node C in
training metric TMas -1.0
Das D0for the slave nodeD0is a small non-negative
Step2: The core node C send
packets which have th
number of 1, 2, ,Nto thScontinuously with the IP
Step3: Whenever the slareceives a training pack
destined to it, S records t
number and the packet rece
Step4:If the reception of traidestined to itself is finishe
node Ssends a report packe
node C which contains tnumber and reception tim
of the first training packetand the sequence number atime (Seq2, T2) of the l
packet it received. The
training packets receiv
duplication, Num, is alsothe report packet.
ster respect-
.
esh cluster
set of slaveeach slave
e following
itializes the
nd initialize
S, in whichalue.
s N training
sequence
slave nodedurationD.
e node St which is
e sequence
tion time.ing packets
d, the slave
t to the core
e sequence(Seq1, T1)
it receivedd reception
ast training
number of
d without
included in
Step5: When the core nod
report packet from the sla
estimates actual training tSas below.
Fig. 7Core node behavior du
/ 2
According to the estimtime T, a new training me
ated as below.
After the computation of
metric, the training processtwo cases based on the v
TM.
a) If , thfinishes the training
the IPT duration ofand move to the trai
slave node.b) If , th
increases the IPT durreplace the training m
and repeat
Step2Step5.
89
e C receives
ve node S, it
me spent for
ing training.
1 1
2 (1)
ated trainingric is calcul-
new training
branches intolue of New_
core node Cor S and set
as ning of next
core node C
tion D by ,tric TMwith
s the above
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Step6:Thecore node Crepea
Step2Step5 until the traithe slave nodes is finished.
In Fig.7, we showed the be
core node during training pr3.3Features of the proposeWe make some explanat
new proposed protocolsubsection.
1) Throughout the trainingassume that the syste
provide packet relay seronly training related pac
the system.2) During the training proc
packet losses occur, the
packet received by the s
could be different with t
by the core node C. Forthe actual training time
estimated as in Step5. In
is the average traitransmission time and
start time and end time
mented by , which ccomplements T.
3) The protocol repeatstraining process by grad
sing the IPT duration fo
node until its training mthe maximum value. Si
slave node the training fi
moment when TMbegin
we set the IPT durationof one preceding step as
of Step5.4) It can also be easily r
training metric TM is
nected to the end to en
from the core node Cnode S. Since the proto
the IPT duration for eac
which maximizes its traithe end to end through
slave node is also maxi
ts the above
ning for all
avior of the
cess.d protocolons on the
in this
process, we
does not
vice so thatets exist in
ess, if someirst and last
lave node S
e ones sent
this reason,must be re-
formula (1),
ing packetthe training
are comple-
onsequently
the sameally increa-
each slave
tric reachesce for each
ishes at the
to decrease,
as the valueshown in a)
ealized thatlosely con-
throughput
o the slaveol searches
slave node
ning metric,ut of each
ized by the
calculated IPT durations
4. Extension of the proposIn this section we extend
protocol to a wireless bac
which employs directionalspecified as FDA system [1
Fig. 8 AnF-3node with 3 i
4.1 Introduction of FDA sFDA system was propos
the application of directionwireless backhaul. In the
first briefly introduce the
FDA system.InF-nFDA system (Fixe
Antennas), each node conta
interfaces and each interfac
with one directional antdirectional antennas are s
spaced and each antenna i
one of the n uniform direcover the whole space toge
assumed that the beamw
directional antenna is equthan 2/n. For illustration,
an F-3 node which contai
interfaces and 3 directionalIn FDA, packet relays
between the two interfaces
and receiver nodes whicantennas to each other, thefor switching antennas dur
During packet relay servic
receives packets from oneforwards the received pac
one of the n interfaces.
90
.
ed protocolthe proposed
haul system
antennas and].
nterfaces.
stemd to simplify
l antennas inollowing, we
principles of
d Directional
ns nwireless
e is equipped
nna. The nymmetrically
s oriented to
ctions whichher. It is also
dth of each
al to or lessFig. 8 shows
s 3 wireless
antennas.only occur
f transmitter
direct theireby no need
ing run-time.
e, each node
interface andkets through
This feature
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significantly simplifies the a
directional antennas in wirel
The authors have proprouting protocol for FDA s
specifies not only the uplin
link interfaces used in eacalso the corresponding inter
destination nodes. The autho
extended traditional IPT forhod for FDA system as belo
(a)Core node applies IPT feach of its wireless interf
(b)Core node waits for a(referred to as inter-pat
tion in the paper) when
wireless interface during
It was shown that by (a) ancollisions in FDA system ca
However, the optimization
IPT duration and inter-path
in (a) and (b) remained to be
4.2 IPT and inter-path I
setting for FDA systemWe extend the training ba
for FDA system. Throughou
we assume that system routdecided before the training p
Since in FDA system ant
ing is not required during r
IPT duration setting methodsection 3 can be directly
decide the optimum IPT dur
for each slave node (e.g. Sonly needs to execute the pr
the interface corresponding
node S.Now we consider the in
duration setting problem in (
the inter-path IPT durationdecided for each pair of sla
which core node uses differe
to relay packets. We consid
nodes S1and S2to which co
plication of
ss backhaul.
sed a newstem which
and down-
node, butfaces in the
rs have also
arding met- .
rwarding in
ace.certain time
IPT dura-
it switches
packet relay.
(b), packetbe avoided.
roblems for
PT duration
solved.
T duration
sed protocol
this section,
e is alreadyocess.
nna switch-
n time, the
proposed inapplied. To
tions in (a),
, core nodeotocol using
to the slave
er-path IPT
b), in which
should beve nodes to
nt interfaces
r two slave
e node uses
interface M1 and M2 to
respectively. The inter-path
between S1and S2is denowe assume that core n
interfaces from M1 to M2
Fig. 9. We also assume thaations for S1 and S2 are alr
and denoted asD1andD2.
Fig. 9Inter path IPT durati
The inter-path IPT dura
be large enough, so that tra
node to slave node S2does
with the traffic from core nshould also be small enou
the optimum system perfor
on this consideration, we ptraining based inter-path
setting method.
We defined the followiand parameters for the met
1) Training packet2) Number of training pa3) Training time for each4) Training metric for ea
TM1, TM2.
5) Training Step in the prAll of these variables h
meanings as defined in sethe pair of slave nodes S1
node repeats the following
Step1: Core node initializes
metric TM1 and TM2initializeDiasDi0.
91
elay packets
IPT duration
ed asDiandde switches
as shown in
the IPT dur-eady decided
n setting.
ion Di must
fic from core
not interfere
ode to S1.Digh to ensure
ance. Based
opose a newPT duration
ng variablesod:
ckets:Nnode: T
ch node: TM,
ocess:
ve the same
tion 3.1. Forand S2, core
rocess.
the training
as -1.0 and
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Step2:Core node sendsNtrai
continuously with the sequ
of 1, 2, ,Nto slave nodeIPT duration of D1. Then
waits forDitime. After tha
sends N training packetswith the sequence number
to slave node S2with the
ofD2.
Step3: Whenever slave nod
receive a training packet,
the sequence number and
reception time.Step4: When the reception
packet is finished, slave no
send report packets to cor
the sequence number antime (Seq1, T1) of the f
packet and the sequencereception time (Seq2, T2)
training packet they rec
number of training pack
without duplication, Num1are also included in the rep
Step5: When core node rec
packets from S1 and S2,TM1 and TM2 in the sa
shown in Step5 of section 3
calculatesNew_TM = TM1that the training process b
two cases based onNew_ T
a) If , thefinishes the training and
path IPT duration as
b) Else If increases the inter-path
Di by , replace the tra
TM with
and
above Step2Step5.
It can be easily underst
above method is an exten
training based protocol dsection 3, which searches t
inter-path IPT duration for t
ing packets
nce number
S1with theCore node
t Core node
ontinuouslyf 1, 2, ,N
PT duration
s S1 or S2
they record
the packet
of training
e S1and S2
node with
d receptionrst training
umber andof the last
eived. The
ts received
and Num2,rt packets.
ived report
t calculatesme way as
.2, and then
TM2. Afteranches into
.
core nodeet the inter-
.
, core nodePT duration
ning metric
repeats the
od that the
sion of the
iscussed ine optimum
e pair of S1
and S2. With the attained i
duration, the sum of the
throughput for S1and S2is
5 Evaluation
In this section, we evalposed protocol with both c
ulations and experiments o
bed under indoor environm
Fig. 10 Simulation site 1, stri
system.
Fig. 11 Simulation site 2, tree to
Table 1. Simulation ParMAC Model IEEE802.11a,
Retry Count =PHY Model Packet recepti
SINR level bethan 10dB.
Propagation Model 2 Ray Groun
Model.No Fading Ef12dB Attenua
Routing Method Minimum Pat
Data Packet Length 1500 Byte.
5.1Evaluation by SimulatWe assume IEEE802.11
less interface of each nodetwo simulation scenarios
topology and tree topologas shown in Fig.10 (Sce
Fig.11 (Scenario 2). The si
are models of West Buil
Campus, Kyushu-Universit
92
ter-path IPT
end to end
maximized.
ate the pro- mputer sim-
n a real test-
nt.
ng topology
ology system.
ameters.Basic Mode.
3.on fails whencomes lower
Reflection
ect.tion by a Wall.
Loss Routing.
ons
as the wire-
and deployedwith string
respectivelyario 1) and
ulation sites
ding of ITO
, Japan.
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93
Each system in the Scenarios is
consisted of only one mesh cluster. The
simulation parameters are shown inTable 1 and IPT forwarding is applied.
5.1.1
Simulation scenariosIn the first, we measured the end to
end throughput from core node to each
slave node with different IPT durationsin the two simulation scenarios using the
following formula (2).
Fig. 12 IPT durations and end to end throughput
for node 4, 5, 6 in simulation scenario 1.
Fig. 13 IPT durations and end to end throughput
for node 7, 8, 9, 10 in simulation scenario 1.
Table 2 Optimum IPT durations in simulation
scenario 1 ().
Node 4 Node 5 Node 6 Node 7
1000 1300 1600 1900
Node 8 Node 9 Node 10
1900 1900 1900
2
In the above formula This throughput,
Nr is the number of received packetswithout duplication, PL is packet length
and Tmis transmission time.
In this first evaluation, IPT durations
are set manually for the purpose of
searching an optimum IPT duration foreach slave node. Manually taken optim-
um IPT durations are compared with the
ones to be found by the proposed prot-ocol, afterward.
We assume that no extra traffic occurs
during the measurement and the numberof transmitted packets in the above
formula is 2000.
Fig. 14Automatically calculated IPT durations
in simulation scenario 1.
Fig. 15 IPT durations and end to end throughput
for node 4, 5, 9, 10 in simulation scenario 2.
Table 3 Optimum IPT durations in simulation
scenario 2 ().
Node 4 Node 5 Node 9 Node 10
1000 1300 1300 1300
After that, we performed the proposed
protocol to calculate the IPT durations
for each slave node with the initial valueD0to be 0, to be 100.
5.1.2 Simulation resultsThe throughput vs. IPT duration for
each slave node is shown in Fig. 12, 13for scenario 1 and in Fig. 15 for scenario
2. The optimum IPT durations with
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200EndtoE
ndThroughput(Kbps)
IPT Durations (micro sec)
Node 4
Node 5
Node 6
0
1000
2000
3000
4000
5000
6000
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Endto
EndThroughput(Kbps)
IPT Durations (micro sec)
Node 7Node 8
Node 9 Node 10
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 1 2 3 4 5 6 7 8 9 10 11
IPTDuration(microsec)
Node
N = 300, 500, 1000
N = 100 N = 50
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 100200300 400500600 70080090010001100120013001400150016001700
Throughput(kbps)
IPT Durations (micro sec)
Node 4
Node 5
Node 9
Node 10
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which the end to end th
maximized are shown in
scenario 1 and in Table 3 foThe IPT durations obtai
protocol for each slave nod
in Fig. 14 for scenario 1 anscenario 2.
As shown in Fig. 14 and.
duration calculated by thezero for node 1, 2, 3 in sce
for node 1, 2, 3, 6, 7, 8 in sce
Fig. 16Automatically calculated
in simulation scenario
According to the feature of
ding, it can be easily undersIPT durations for the slave
are located within the CSthe core node could be
because for these nodes noinal problem occurs and thu
purposely adjust the packet
time in the core node. Forwe deleted the throughput
results of these nodes in Fig
15.In Fig. 14 and 16, the a
calculated IPT durations
optimum ones in Table 2 an300, 500, 1000. However, wi
small values of N(50, 100 ithe calculated IPT durati
match to the optimum obecause with such small N,
received training packets nu
varies intensively each tiestimation of training time i
enough.
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6
IPTDuration(microsec)
Node
N = 300, 500, 1000
N = 100
oughput is
able 2 for
scenario 2.ed by the
are shown
Fig. 16 for
16, the IPT
protocol isnario 1 and
nario 2.
IPT durations
2.
IPT forwar-
ood that theodes which
A range ofset to zero
idden term- no need to
ransmission
this reason,easurement
. 12, 13 and
tomatically
atch to the
3 withN=th relatively
n this case),ns do not
es. This isthe ratio of
mber and N
e and thenot precise
However, with the inc
(larger than 300 in this cas
iations are suppressed andthe calculated IPT duration
the optimum values for eac
The simulation results sadequate parameter setting
sed protocol can find the
durations for each slave nothe end to end throughput is
Fig. 17 Picomesh Lu
Table 4 Specificatio
CPU AMD
Memory D
Backhall Wireless IF IEEE8
Access Wireless IF IEEE8
OS Linu
Fig. 18 Experimental
Fig. 19Throughput measuring
5.2Evaluation by ExperiIn order to further confi
mance, we implement the
tocol into a testbed and evformance under real indoor
7 8 9 10 11
N = 50
94
ement of N
e), these var-
consequentlyconverge to
slave node.
ow that withs, the propo-
ptimum IPT
e with whichmaximized.
chBox
of LB.Geode LX800R 512MB02.11b/g/a 2
02.11b/g/a 1
x kernel 2.6
site.
system.
entsm its perfor-
roposed pro-
luate its per- environment.
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5.2.1 Testbed and Throughput Meas-uring Tool
The testbed is called PicoMesh
LunchBox (LB, Fig. 17). LB is the first
product of MIMO MESH Project,which the authors are working on [14].
LB is equipped with three IEEE802.11
modules, two of which are used forrelaying packets between base nodes and
the other one is used for mobile terminal
access.
Each module of LB is assigned withdifferent spectrum so that the inter-
ference between these modules could be
avoided. The hardware specification of
LB is shown in Table 4.In this experiment, we use IPerf to
measure the throughputs [15]. IPerf isfree software which can measure the end
to end throughput in various networks
with a pair of server and client. Add-
itionally, we adopt UDP mode of its twooperational modes (TCP mode and UDP
mode) and measure the throughput from
client to server.
5.2.2 Experimental ScenarioWe deployed a wireless backhaul
system with one core node and six slave
nodes in West Building of ITO Campus,
Kyushu-University, Japan (Fig. 18).
At first, we measured the end to endthroughput of each slave node with
different IPT durations by IPerf. Speci-
fically, we set up the IPerf client in a PCwhich is connected to the core node and
the IPerf server in a PC which is
connected to the slave node (Fig. 19).During the measurement, traffic flows
from IPerf client to sever and each
measuring continues 30 seconds. Wealso assume that no extra traffic occurs
during the measurement. In this first
experiment, IPT durations are set man-
ually for the purpose of searching an
optimum IPT duration for each slave
node. The optimum IPT durations are
compared with the ones to be found bythe proposed protocol, afterward.
In the next, we performed the prop-
osed protocol to calculate the IPT dura-tions for each slave node with the
training packet numberNto be 1000 and
the initial value D0 to be 1000, to be
100.
Fig. 20 IPT durations and end to end throughput
for Node 3, 4, 5, 6 in experiment.
Table 5 IPT durations searched by the
protocol () and its run time.Node 1 Node 2 Node 3 Node 4
0 0 1000 1300
Node 5 Node 6 Run Time
1300 1300 11 (sec)
5.2.3 Result of the ExperimentsThe throughput vs. IPT duration for
each slave node is shown in Fig. 20 and
the IPT durations calculated by the prop-
osed protocol and the protocols run timeare shown in Table 5.
The calculated IPT durations of node
1 and 2 are zero in Table 5, which meansthat the two nodes are located within the
CSMA range of the core node and thus
we deleted the corresponding through-puts of the two nodes in Fig. 20.
As we can see from Fig. 20 and Table
5, the calculated IPT durations match to
the optimum ones measured by IPerfwith which the end to end throughputs
reach the maximum values. With 6 slavenodes and 1000 training packets, the
0
1
2
3
4
5
6
7
8
0 200 400 600 800 1000 1 200 1400 1600 1800 2 000 2 200
Throughput(kbps)
IPT Duration (micro sec)
Node 3
Node 4 Node 5 Node 6
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protocol spent 11 seconds to finish,
which makes it practical enough in real
applications.
5 Conclusion
In this paper we proposed a new IPTduration setting protocol which can
calculate the optimum IPT duration for
each slave node automatically. The pro-posed protocol is evaluated both with
computer simulations and experiments
on a real testbed in an indoor enviro-
nment.Evaluation results show that with the
calculated IPT durations the end to end
throughput of each slave node is max-
imized. Since the protocol does notdemand modification of the existing sta-
ndards, it could be easily implementedwith general WLAN modules.
Additionally, we left the evaluation of
inter-path IPT duration setting method as
future work.
6 ACKNOWLEDGMENT
This work was supported by MIMO-MESH PROJECT under Grant of Know-
ledge Cluster Initiative implemented by
Ministry of Education, Culture, Sports,Science and Technology, Japan.
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International Journal on New Computer Architectures and Their Applications (IJNCAA) 1(1): 84-96The Society of Digital Information and Wireless Communications, 2011 (ISSN 2220-9085)