research article coexistence of 3g repeaters with lte...

Hindawi Publishing CorporationThe Scientific World JournalVolume 2013 Article ID 185372 8 pageshttpdxdoiorg1011552013185372

Research ArticleCoexistence of 3G Repeaters with LTE Base Stations

Woon-Young Yeo1 Sang-Min Lee2 Gyung-Ho Hwang3 and Jae-Hoon Kim4

1 Department of Information and Communication Engineering Sejong University 98 Gunja-dong Gwangjin-guSeoul 143-747 Republic of Korea

2Network Technology RampD Center SK Telecom 9-1 Sunae-dong Bundang-gu Seongnam 463-838 Republic of Korea3 Department of Computer Engineering Hanbat National University San 16-1 Dukmyung-dong Yuseong-guDaejeon 305-719 Republic of Korea

4Department of Industrial Engineering Ajou University Yeongtong-gu Suwon 443-749 Republic of Korea

Correspondence should be addressed to Jae-Hoon Kim jayhoonajouackr

Received 25 August 2013 Accepted 8 October 2013

Academic Editors A Gonzalez and J Zhang

Copyright copy 2013 Woon-Young Yeo et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Repeaters have been an attractive solution formobile operators to upgrade their wireless networks at low cost and to extend networkcoverage effectively Since the first LTE commercial deployment in 2009 many mobile operators have launched LTE networks byupgrading their 3G and legacy networks Because all 3G frequency bands are shared with the frequency bands for LTE deploymentand 3G mobile operators have an enormous number of repeaters reusing 3G repeaters in LTE networks is definitely a practicaland cost-efficient solution However 3G repeaters usually do not support spatial multiplexing with multiple antennas and thus itis difficult to reuse them directly in LTE networks In order to support spatial multiplexing of LTE the role of 3G repeaters shouldbe replaced with small LTE base stations or MIMO-capable repeaters In this paper a repeater network is proposed to reuse 3Grepeaters in LTE deployment while still supportingmultilayer transmission of LTE Interestingly the proposed network has a highercluster throughput than an LTE network with MIMO-capable repeaters

1 Introduction

Long Term Evolution (LTE) is a radio platform that allowsmobile operators to achieve much higher peak data rates andbetter spectral efficiency than those of the third generation(3G) networks (eg WCDMA and cdma2000) [1] LTE wasinitiated by theThird Generation Partnership Project (3GPP)in 2004 and is now commercially deployed or in progressworldwide LTE is an OFDM-based radio-access technologythat supports scalable bandwidth up to 20MHz andmultiple-input multiple-output (MIMO) transmission with up tofour antennas It provides high peak data rates with apotential for 300Mbps on the downlink by using 20MHz andfour transmit antennas LTE was further improved to LTE-Advanced which was standardized in 2010 as part of 3GPPRelease 10 features [2] LTE-Advanced is not defined as newspecification series but built on existing LTE specifications

As in othermobile communication systems cell planningfor an LTE network is focused on extending LTE coverage

at minimum cost Repeaters permit mobile operators toupgrade their 3G and legacy networks to LTE at low costand to extend LTE coverage effectively Because most of 3Gmobile operators will eventually upgrade their networks toLTE and existing 3G frequency bands are shared with thefrequency bands identified for LTEdeployment [3 4] reusing3G repeaters in the LTE network may be a practical andcost-efficient solution However it is difficult to use the 3Grepeaters directly in the LTE network because LTE requiresMIMO transmission with multiple antennas To supportMIMO transmission repeaters should also support the samenumber of antenna ports as a base station (BS) If repeaters arenotMIMO-capable they can act as a keyhole and the channelrank in repeater coverage is reduced to one [5] Becausemobile operators have an enormous number of 3G repeatersfor their own 3Gnetworks high investment costs are requiredto replace 3G repeaters with small LTE BSs orMIMO-capablerepeaters In this paper a repeater network is proposed to

2 The Scientific World Journal

Codeword 1

Codeword 2

Layermapping

Precoding(W)

Antennamapping

OFDMmodulation

OFDMmodulation(s1)

(s2) s2

s1 s9984001

s9984002

r1

r2

+

+

r1 s9984001

r2 s9984002

Figure 1 Basic structure of LTE multiantenna transmission (2 times 2 antenna configuration)

reuse 3G repeaters instead of the high-cost equipment andtake advantage of multiantenna transmission of LTE

2 Multiantenna Transmission

The use of multiple antennas is one of the key technolo-gies to achieve LTE performance targets [6] Multiantennatransmission in LTE can be described as a mapping of mod-ulated symbols to different antenna ports Figure 1 illustratesdownlink multiantenna transmission that supports spatialmultiplexing of up to two layers in a 2 times 2 antenna configu-ration A codeword is an independently encoded data blockcorresponding to a single transport block (TB) delivered froman L2 protocol A spatial layer is one of the different streamsgenerated for spatial multiplexing and layer mapping is aprocess of distributing codewords over multiple spatial layersbased on the number of antenna ports Precoding can be usedto improve signal isolation at the receiver side and providemapping of the spatially multiplexed streams to transmitantennas (including beam-forming) The precoded symbolsaremapped to appropriate antenna ports by antennamappingand reference symbols (119903

1and 119903

2) are inserted within an

OFDM time-frequency gridThe number of layers may range from a minimum of one

up to multiple layers The number of layers is often referredto as the transmission rank and LTE can adaptively controlthe transmission rank according to channel conditions suchas received signal quality and fading correlation betweenantennas In a 2 times 2 antenna configuration there are four2 times 1 precoding matrices for rank-1 transmission and three2times2matrices for rank-2 transmission as shown in Table 1 [7]Codebook index 0 for rank 2 (ie identity matrix) is not usedin a closed-loop operation but only applied to an open-loopoperation When closed-loop precoding is configured eachuser equipment (UE) can report a suitable transmission rankby rank indication (RI) and a precoding matrix by precod-ing matrix indication (PMI) based on reference signal mea-surements However RI and PMI are only recommendationsand the BS does not have to follow the RIPMI provided bythe UE

In rank-2 transmission with a 2 times 2 antenna configura-tion data symbols (119904

1and 1199042) from two different codewords

aremapped to the first and second layers respectively If a UEdoes not support rank-2 transmission due to poor channelquality rank 1 can be used to improve the SINR by diversitygains In the case of rank-1 transmission only one codeword(1199041) is mapped to a single layer and one of the precoding

Table 1 Precoding matrices (W) for two antenna ports

Codebook index 0 1 2 3

Rank 1 1

radic2

[1

1]1

radic2

[1

minus1]1

radic2

[1

119895]1

radic2

[1

minus119895]

Rank 2 1

radic2

[1 0

0 1]1

2[1 1

1 minus1]1

2[1 1

119895 minus119895] mdash

matrices for rank 1 is applied to adjust antenna weightingLetting y be the received signal on each subcarrier at the UEa general transmission model is described by

y=[ℎ11 ℎ12ℎ21ℎ22

] [1199041015840

1

1199041015840

2

] + [1198991

1198992

]

=

HW1199041+ n for rank 1

HW[1199041

1199042

] + n for rank 2

(1)

where ℎ119894119895denotes the channel fading coefficient between the

119894th receive antenna and the 119895th transmit antenna 11990410158401and 11990410158402

are output symbols after precoding and 119899119894is the combined

noise and interference at the 119894th receive antenna H is the2 times 2 channel matrix W is the precoding matrix in Table 1and n represents the combined noise and interference vectorat the UE In order to detect and receive wanted signals atthe receiver linear and nonlinear algorithms can be useddepending on implementation and complexity of the receiver[8]

In LTE the control region in a subframe (1ms) carriesL1L2 signaling necessary to control uplink and downlinkdata transmission and transmit diversity is generally appliedto the signaling [1] In a 2 times 2 antenna configuration thetransmit diversity is based on Space-Frequency Block Coding(SFBC) Two consecutive modulation symbols 119904

1and 1199042 are

mapped directly to the 119896th and (119896 + 1)th subcarriers respec-tively on the first antenna port On the second antenna portminus119904lowast

2and 119904lowast1are mapped to the corresponding subcarriersThe

received SFBC signals on the 119896th and (119896 + 1)th subcarriersy(119896) and y(119896+1) respectively are given by

y(119896) = [ℎ(119896)

11ℎ(119896)

12

ℎ(119896)

21ℎ(119896)

22

] [1199041

minus119904lowast

2

] + n(119896) (2)

y(119896+1) = [ℎ(119896+1)

11ℎ(119896+1)

12

ℎ(119896+1)

21ℎ(119896+1)

22

] [1199042

119904lowast

1

] + n(119896+1) (3)

The Scientific World Journal 3

where ℎ(119896)119894119895

and n(119896) have the same definitions as (1) Assumingthat the MIMO channel is quasistatic (ie ℎ(119896)

119894119895asymp ℎ(119896+1)

119894119895) it

is possible to use a simple decoder to achieve the frequencydiversity of SFBC In addition the orthogonal design of SFBCcan support maximum likelihood (ML) detection based onlinear processing at the receiver [9]

3 Coexistence of 3G Repeaters inLTE Networks

Repeaters have been an essential building block of com-munication systems for a long time The most significantadvantages of repeaters are their fast deployment capabilityand cost efficiency Typically repeaters are implanted in thenetwork optimization phase when network coverage needsto be improved Hence classical applications of repeatersare related to coverage enhancement that targets providinga strong signal to remote areas where wireless signal strengthis relatively weak

Generally a repeater system consists of two parts a donorunit and a remote unit The repeater system transparentlyconveys and amplifies wireless signals between a BS and UEsThe donor unit captures a BS signal via a direct couplernear the BS and transmits the amplified signal to the remoteunit typically via an RF signal (RF repeater) or fiber opticcables (fiber optic repeater) The remote unit will reconvertthe received signal into an RF signal and send the signal torepeater coverage The uplink signal is also amplified andretransmitted to the BS in the opposite direction

In 3GPP technical specifications LTE is designed tooperate in all the frequency bands defined for 3G networks [34] In FDD bands 1ndash14 19ndash22 and 25 can be applied to bothLTE and 3G systems and four additional operating bandsare reserved for LTE deployment Although other frequencybands can be undertaken depending on regional and localconditions LTEwill be deployed in the same frequency bandsas 3G and other legacy cellular technologies Moreover mostof 3G repeaters can support a wide working bandwidth (eg20MHz) that corresponds to multiple carriers of 3G systemsThus it is a reasonable cost-efficient solution to reuse the3G repeaters when upgrading 3G networks to LTE Howeverthere is a critical problem that 3G repeaters cannot coexistwith LTE networks conventional 3G repeaters have only oneantenna port and usually do not support spatial multiplexingIn order to support the spatial multiplexing of LTE the roleof 3G repeaters should be replaced with small LTE basestations or MIMO-capable repeaters Two of possible waysto reuse conventional 3G repeaters are (1) configuring rank-1transmission over all service areas and (2) installing multiple3G repeaters at a repeater site to support multiple antennaportsThe first method does not guarantee full capacity of theLTE system and the second is unrealistic due to its excessivecost of reengineering

The proposed repeater architecture is devised to over-come the problemof capacity degradationwhen conventional3G repeaters are connected to the LTE BS The basic ideaof the proposed network is to extract multiple rank-1 datastreams from the BS antenna ports and deliver each of them

to one or more repeaters Before introducing the proposedscheme assume that in rank-2 transmission with a 2 times2 antenna configuration each BS antenna port is simplyconnected to a separate repeater without precoding (ieW = I) Because one codeword for each spatial layer can betransmitted transparently to separate repeater coverage it isexpected that a UE in the repeater coverage can receive itsdata by a normal rank-1 operation However the UEmay notreceive the data because each antenna port contains only asingle reference signal (RS) pattern for a specific spatial layerFor example the second antenna port does not contain 119903

1(RS

for antenna port 1) which is critical for rank-1 transmissionBasically both of the two RS patterns (119903

1and 1199032) are necessary

to decode the data symbol when two transmit antenna portsare configured at the BS

Theproposed architecture is illustrated in Figure 2 assum-ing a 2 times 2 antenna configuration which is one of the maintransmission configurations in the LTEnetwork Before beingconnected to each repeater the BS signal is processed by anoperation called post-processing which is an inverse opera-tion of precoding for repeaters and is expressed as Wminus1

119903in

Figure 2 Although there are three precoding matrices spe-cified for rank 2 in Table 1 we set a precoding matrix forrepeater coverageW

119903 as follows

W119903=Wminus1119903=1

radic2

[1 1

1 minus1] (4)

Original data symbols (1199041and 1199042) can be extracted from 1199041015840

1

and 11990410158402by the post-processing operation In addition due to

the post-processing and mutually exclusive positions of RSthe first repeater path contains 119903

1radic2 119903

2radic2 and 119904

1 and

the second path contains 1199031radic2 minus119903

2radic2 and 119904

2 Now each

repeater path contains all reference symbols and wanted data(1199041or 1199042) which are required for normal rank-1 transmission

in a 2 times 2 antenna configuration The post-processing by (4)can be understood as an addition of the two antenna ports forthe first repeater path and a subtraction for the second pathThe post-processing is a fixed operation so that it is appliedto all signals generated by the BS and has a meaning only tothe UEs in repeater coverage Note that the post-processingis performed at the end of OFDM modulation and does notmodify the BS modem structure

As for scheduling the entire bandwidth is shared bya BS and the associated repeaters The minimum unit ofscheduling in LTE is a time-frequency block correspondingto one subframe and one resource block (RB 180 kHz) Ifsome RBs are reserved for the BS (or repeater) coverage theycannot be allocated to the repeater (or BS) coverage TheBS scheduler should select an appropriate precoding matrixdepending on the UE location W

119903in (4) is selected for

the UEs in repeater coverage whereas one of the precodingmatrices in Table 1 is adaptively selected for the UEs in BScoverage If the repeater coverage is selected for schedulingtwo different codewords for the first and second repeaterpaths are provided to the layer mapping block If there is noUE in one of the two repeater areas just one codeword istransmitted over repeater coverage In the proposed scheme


Codeword 1

Codeword 2

Layermapping

Precoding(W)

Antennamapping

OFDMmodulation

OFDMmodulation(s1)

(s2) s2

s1 s9984001

s9984002

r1

r2

+

+

r1 s9984001

r2 s9984002

Repeater 1

Repeater 2

Post-processing

(Wminus1r )

r1radic2

r2radic2

s1

r1radic2

minusr2

radic2 s2

Figure 2 Proposed architecture supporting 3G repeaters

because an unwanted signal is also radiated in the unsched-uled coverage it can act as interference to the UEs in othercoverage In addition the UE location needs to be known inadvance to the BS scheduler because the transmission rankand precoding information may be different depending onthe UE locationThe UE location can be tracked by an uplinksounding reference signal (SRS) which is used by the BS forchannel state estimation After comparing the power levelsfrom three receiving paths (one BS path and two repeaterpaths) the BS considers the service area having the highestSRS power level as the scheduling target for the UE

Before proceeding to performance evaluation it shouldbe verified that UEs in repeater coverage have no problem inreceiving data and control signals in the proposed scheme Asfor data transmission transmission mode 4 (TM-4 closed-loop codebook-based precoding) with rank-1 precoding isapplied to the UEs in repeater coverage The codebookindices 0 and 1 for rank 1 in Table 1 correspond to thecolumn vectors of W

119903in (4) and they are selected for the

precoding information of the first and second repeater pathsrespectively Letting y

1and y2denote the received signals at a

UE in the first and second repeater coverage respectively

y1= [ℎ1

ℎ2

] 1199041+ n1

(5)

= (1

radic2

[ℎ1ℎ1

ℎ2ℎ2

])(1

radic2

[1

1]) 1199041+ n1 (6)

y2= [ℎ1

ℎ2

] 1199042+ n2

(7)

= (1

radic2

[ℎ1minusℎ1

ℎ2minusℎ2

])(1

radic2

[1

minus1]) 1199042+ n2 (8)

where ℎ119894is the channel fading coefficient between a repeater

and the 119894th receive antenna of the UE and n119895represents the

combined noise and interference vector in the 119895th repeatercoverage The received signal from a repeater is simplyexpressed as (5) and (7) and each can be decomposed intothe product of a channel matrix and a precoding matrix asin (6) and (8) The channel coefficients in (6) and (8) are

obtained by measuring the RS in repeater coverage Note thatthe original reference symbols are scaled down by a factorof radic2 in the repeater coverage due to the post-processing Itis interesting that the inverted RS estimation for the secondrepeater coverage in (8) is compensated by codebook index1 for rank 1 in Table 1 Because the received signal at the UEhas the same form as (1) for rank-1 transmission data symbolscan be recovered by a normal rank-1 operation of TM-4 Nowassuming the TM-4 operation supporting rank adaptation inBS coverage TM-4 can be applied to all UEs in the proposednetwork regardless of the UE location

In the case of the downlink L1L2 signaling control sym-bols should be received correctly even in the repeater cover-age Letting y(119896)

1and y(119896)2

denote the received SFBC signals onsubcarrier 119896 in the first and second repeater coverage respec-tively the received control signals can be expressed as follows

y(119896)1=1199041minus 119904lowast

2

radic2

[ℎ(119896)

1

ℎ(119896)

2

] + n(119896)1

(9)

= (1

radic2

[ℎ(119896)

1ℎ(119896)

1

ℎ(119896)

2ℎ(119896)

2

])[1199041

minus119904lowast

2

] + n(119896)1 (10)

y(119896+1)1=1199042+ 119904lowast

1

radic2

[ℎ(119896+1)

1

ℎ(119896+1)

2

] + n(119896+1)1

(11)

= (1

radic2

[ℎ(119896+1)

1ℎ(119896+1)

1

ℎ(119896+1)

2ℎ(119896+1)

2

])[1199042

119904lowast

1

] + n(119896+1)1 (12)

y(119896)2=1199041+ 119904lowast

2

radic2

[ℎ(119896)

1

ℎ(119896)

2

] + n(119896)2

(13)

= (1

radic2

[ℎ(119896)

1minusℎ(119896)

1

ℎ(119896)

2minusℎ(119896)

2

])[1199041

minus119904lowast

2

] + n(119896)2 (14)

y(119896+1)2=1199042minus 119904lowast

1

radic2

[ℎ(119896+1)

1

ℎ(119896+1)

2

] + n(119896+1)2

(15)

= (1

radic2

[ℎ(119896+1)

1minusℎ(119896+1)

1

ℎ(119896+1)

2minusℎ(119896+1)

2

])[1199042

119904lowast

1

] + n(119896+1)2 (16)


where ℎ(119896)119894 n(119896)1 and n(119896)

2have the same definitions as (5)ndash(8)

Note that precoding is not applied to transmit diversity ofSFBC The transmitted symbols from the first and secondrepeaters are addition and subtraction of the two SFBCsymbols respectively on each subcarrier scaled down by afactor of radic2 The channel coefficients in (10) (12) (14) and(16) are obtained by measuring the RS in repeater coverageas explained in data symbol decoding Because the receivedSFBC signal from a repeater can be expressed as a normalSFBC signal in (2) and (3) the control symbols in repeatercoverage can be recovered by the same estimation techniqueas in the BS coverage Now we can see that all UEs in theproposed network can receive downlink signaling regardlessof the UE location

4 Results

Thesimulation framework is based on theVienna LTE systemlevel simulator [10] and includes additional procedures andalgorithms used in the proposed scheme We consider abasic hexagonal layout composed of BSs and repeatersFigure 3 shows the network layout for the simulation TheBSs and repeaters are located at the center and vertices ofthe hexagonal area respectively with an omni-directionalantenna (or antennas) A cluster consists of one BS and tworepeaters connected to the BS 18 clusters are added aroundthe central cluster and statistics are only collected from thecentral cluster In the proposed scheme one repeater in acluster is connected to the first repeater path (120572) and theother repeater to the second path (120573) In other conventionalrepeater networks a single type of repeater is connected to theBS and transmits the same signal as the BS 3G repeaters haveone transmit antenna BSs andMIMO-capable repeaters havetwo transmit antennas and they support spatial multiplexingwith rank adaptation UEs have two receive antennas

Themain simulation parameters are summarized in Table2The path loss is based on an urban macrocell with a carrierfrequency of 2GHz and a BS antenna height of 15m aboveaverage rooftop level [11] Shadowing is not considered inthis simulation and the microscale fading uses a pedestrianA channel at 3 kmh The distance between a BS and neigh-boring repeaters is 1000m A system bandwidth of 10MHzis assumed which corresponds to 50 RBs The BS transmitsat full power (119875

119887= 40W) over the entire bandwidth The

repeater power (119875119903) is usually lower than the BS power

and some typical power levels will be selected for repeatersWe assume two OFDM symbols for the control region ina subframe with a normal cyclic prefix (CP) configurationMIMO modeling is based on a zero forcing (ZF) receiverThe level of interference may be different depending on theoperation modes of neighboring nodes For example theintercell interference caused by rank-2 transmission is slightlyhigher than that by rank-1 transmission based on the channelmodel in [10] Thus in this simulation the surroundingnetwork nodes are assumed to be of rank 1 and rank 2 withprobability 05 and 05 respectively if they support rankadaptation (ie LTE BSs and MIMO-capable repeaters)

The scheduling policy is a proportional fair (PF) sched-uler which maximizes the total throughput while offering

Table 2 Simulation parameters

Parameters ValuesPath loss model 1281 + 376 log

10(119909) 119909 in km

Microscale fading Pedestrian A channel at 3 kmhIntersite distance 1000mSystem bandwidth 10MHz (50 RBs)BS power (119875

119887) 40W (fixed)

Repeater power (119875119903) 1 to 40W (variable)

MIMO receiver modeling Zero forcingTraffic generation Full bufferScheduling policy Proportional fairUE noise figure 9 dBThermal noise minus174 dBmHz

certain fairness among UEs The UE with the highest 119901value (ratio of instantaneous data rate to average data rate)is selected for each RB In the proposed scheme the BSscheduler compares the 119901 value for the BS coverage withthe sum of the two 119901 values for the 120572 and 120573 repeatersThe BS scheduler selects the coverage with a higher valueWhen the repeater coverage is selected by the scheduler thecorresponding RB is shared by two UEs having the highest 119901value in each repeater area If there is no UE in one of the tworepeater areas the scheduler selects just one UE having thehighest 119901 value in the other repeater area

Because the OFDM-based repeater network can be con-sidered a simplified form of a single-frequency network(SFN) all signals that arrive at the receiver within a CP aretreated as useful [12] In this simulation the repeater networkis assumed to be well engineered so that all downlink signalsin a cluster arrive at the UE within the CP However inthe proposed scheme the received signals from the BS 120572-repeater and 120573-repeater can interfere with one another evenif they arrive within the CP

Figure 4 compares the cluster throughput as a function ofdistance from the BS (or repeater)The repeaters transmit thesame power as the BS (119875

119903= 40W) and twoUEs in each cover-

age are located at the same distance from the BS (or repeater)As the distance increases the cluster throughput decreasesdue to the degradation of signal quality The MIMO-capablerepeater produces a higher throughput than the 3G repeaterdoes however the difference becomes smaller as the distanceincreases The reason is that only the UEs near the BS (orrepeater) can support rank-2 transmission and the propor-tion of rank-2 transmission decreases rapidly in the MIMO-capable repeater network At a distance of 200m 20 ofRI reported from the UEs is classified as rank 2 and theaggregate TB size of rank-2 transmission is only slightly largerthan that of rank-1 transmissionThe situation becomes evenworse at 250m where only 5 of RI is classified as rank 2

The proposed scheme is the best among the three repeaternetworks The cluster throughput is higher than otherrepeater networks even if the distance increases The reasonis that the proposed scheme can be considered a similar formof multiuser MIMO transmission over repeater coverageWhen repeater coverage is selected by the BS scheduler


BS

Cluster

120572-Repeater 120573-Repeater

Figure 3 Cell layout for performance evaluation The concept of 120572 and 120573 repeaters is used only in the proposed scheme In other repeaternetworks a single type of repeater is connected to the BS

80

60

40

20

00 100 200 300 400 500

Distance (m)

Clus

ter t

hrou

ghpu

t (M

bps)

3G repeater (rank 1 only)

Proposed schemeMIMO repeater (rank adaptation)

Figure 4 Cluster throughput at different distances Two UEs arelocated at the same distance from the BS (or repeater) in eachcoverage (six UEs per cluster)

two different data streams are transmitted simultaneously inthe 120572 and 120573 repeater areas respectively guaranteeing rank-2 transmission from the BS point of view As the distanceincreases the proportion of rank-2 transmission decreasesrapidly in the MIMO-capable repeater network but theproposed scheme can still support dual-stream transmission

by means of scheduling over repeater coverage The ratio ofselecting repeater coverage in the proposed scheme is about66 regardless of the distance Thus the performance ofthe proposed scheme can outperform the MIMO-capablerepeater network with rank adaptation The disadvantage ofthe proposed scheme is that the peak data rate in the repeatercoverage can be half of that in the BS coverage

Because the repeater power is usually lower than the BSpower it is reasonable to take the repeater power into accountfor performance evaluation Figure 5 illustrates coverageboundaries when 119875

119903is set to 1 5 10 and 40W respectively

As expected at a low value of 119875119903 the repeater coverage is rela-

tively small when compared to the BS coverage Accordinglyonly a small number of UEs will be located in the repeatercoverage if the UEs are uniformly distributed If the repeaterpower is the same as the BS power the coverage boundarybecomes a typical hexagonal structure

Figure 6 compares the cluster throughput and the edgethroughput of the three repeater networks when 30UEsare randomly distributed in each cluster 1000 different UEdistribution scenarios are applied to the simulation In Figure6(a) as the repeater power increases the cluster throughputincreases steadily in the proposed scheme More UEs will belocated in repeater coverage at a higher value of 119875

119903 Remem-

ber that two data streams can be transmitted simultaneouslyover repeater coverage in the proposed schemewhen repeatercoverage is selected for scheduling As the repeater coverageincreases the ratio of scheduling on the repeater coveragealso increases For example the ratio increases from 181 to


150010005000minus500minus1000minus1500

1500

1000

500

0

minus500

minus1000

minus1500

(a) Repeater Tx power = 1W


1500

1000

500

0

minus500

minus1000

minus1500

(b) Repeater Tx power = 5W


1500

1000

500

0

minus500

minus1000

minus1500

(c) Repeater Tx power = 10W


1500

1000

500

0

minus500

minus1000

minus1500

(d) Repeater Tx power = 40W

Figure 5 Coverage boundaries of base stations and repeaterswith different repeater power levels Squares and triangles represent base stationsand repeaters respectively Units of 119909- and 119910-axes are in meters

Proposed schemeMIMO repeater (rank adaptation)3G repeater (rank 1 only)

30

20

10

01 2 5 10 20 40

Clus

ter t

hrou

ghpu

t (M

bps)

Repeater power (W)

(a) Cluster throughput

300

200

100

01 2 5 10 20 40

W)Repeater power (


Edge

thro

ughp

ut (k

bps)

(b) Edge throughput

Figure 6 Performance comparison at different transmission power of repeaters


641 as the repeater power increases from 1W to 40W Asa result at 119875

119903= 40W the cluster throughput of the proposed

scheme is 267 higher than that of the MIMO-capablerepeater network It is interesting that the MIMO-capablerepeater network has just 13 higher throughput than the 3Grepeater network Only about 135 of RI is classified as rank1 in theMIMO-capable repeater network and thus the clusterthroughput improvement is not as significant as expect-ed

In Figure 6(b) the edge throughput is defined as thedata rate that 5 of the UEs cannot reach [11] The edgethroughput of theMIMO-capable repeater network is slightlylower than that of 3G repeater network The reason is thatthe interference caused by rank-2 transmission is slightlyhigher than that by rank-1 transmission as explained insimulation parameters The edge throughput of the proposedscheme is rather lower than those of other repeater networkswith 119875

119903= 1 2 and 5W whereas almost the same or

slightly higher with 119875119903= 10 20 and 40W This can be

explained by two factors that influence the performance of theproposed schemeThefirst factor is the increased interferencecompared to other repeater networks The received signalsfrom the BS120572-repeater and120573-repeater can interferewith oneanother in the proposed scheme because they are differentsignals This additional interference can cause degradationof the edge throughput The second factor is dual-streamscheduling over repeater coverage When repeater coverageis selected for scheduling two UEs connected to the 120572and 120573 repeaters respectively can receive downlink data atthe same time This can give the UEs in repeater coveragethe opportunity to receive more data and thus the edgethroughput can be improved At low repeater power becauseonly a small number of UEs are located in repeater coveragethe first factor is dominant over the second one At highrepeater power the dual-stream scheduling overcomes theinterference on the edge UEs and the edge throughputbecomes slightly higher than those of other networks Insummary at repeater power over 10W the cluster throughputof the proposed scheme is much higher than those of otherrepeater networks while the edge throughput is almost thesame or slightly higher

5 Conclusions

In this paper a repeater network has been proposed to reuse3G repeaters in LTE deployment and utilize themultiantennastructure of LTE effectively Because 3G repeaters usuallydo not support multiantenna transmission the proposedscheme extracts two rank-1 data streams from the BS antennaports and delivers each of them to one or more repeatersby a post-processing operation in the base station It hasbeen proved that the closed-loop codebook-based precodingand transmit diversity based on SFBC can be applied to allUEs in the proposed network Due to the simultaneous tran-smissions of multiple data streams in repeater coverage theproposed scheme showed a much higher throughput thana MIMO-capable repeater network while maintaining anacceptable level of edge throughput

Acknowledgments

This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Education Science andTechnology (2010-0006057) This research was also sup-ported by SK Telecom

References

[1] E Dahlman S Parkvall and J Skold 4G LTELTE-Advancedfor Mobile Broadband Elsevier Academic Press Boston MassUSA 2011

[2] S Parkvall A Furuskar and E Dahlman ldquoEvolution of LTEtoward IMT-advancedrdquo IEEE Communications Magazine vol49 no 2 pp 84ndash91 2011

[3] 3GPP TS 25101 v1090 ldquoUser Equipment (UE) radio transmis-sion and reception (FDD)rdquo July 2013

[4] 3GPP TS 36101 v10110 ldquoEvolved Universal Terrestrial RadioAccess (E-UTRA) User Equipment (UE) radio transmissionand receptionrdquo July 2013

[5] D Chizhik G J Foschini and R A Valenzuela ldquoCapacities ofmulti-element transmit and receive antennas correlations andkeyholesrdquoElectronics Letters vol 36 no 13 pp 1099ndash1100 2000

[6] S Sesia I Toufik and M Baker LTEmdashThe UMTS Long TermEvolution From Theory to Practice John Wiley amp Sons Chich-ester UK 2011

[7] 3GPP TS 36211 v1070 ldquoLTE Evolved Universal TerrestrialRadio Access (E-UTRA) Physical channels and modulationrdquoFebruary 2012

[8] A Sibille C Oestges and A Zanella MIMO From Theory toImplementation Academic Press Burlington Mass USA 2010

[9] SM Alamouti ldquoA simple transmit diversity technique for wire-less communicationsrdquo IEEE Journal on Selected Areas in Com-munications vol 16 no 8 pp 1451ndash1458 1998

[10] J C Ikuno M Wrulich and M Rupp ldquoSystem level simulationof LTE networksrdquo in Proceedings of the 71st IEEE VehicularTechnology Conference (VTC rsquo10) pp 1ndash5 May 2010

[11] 3GPP TS 36942 v1030 ldquoEvolved Universal Terrestrial RadioAccess (E-UTRA) Radio Frequency (RF) system scenariosrdquoJune 2012

[12] M Batariere K Baum and T P Krauss ldquoCyclic prefix lengthanalysis for 4G OFDM systemsrdquo in Proceedings of the 60thIEEE Vehicular Technology Conference (VTC rsquo04) pp 543ndash547September 2004

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



Codeword 1

Codeword 2

Layermapping

Precoding(W)

Antennamapping

OFDMmodulation

OFDMmodulation(s1)

(s2) s2

s1 s9984001

s9984002

r1

r2

+

+

r1 s9984001

r2 s9984002

Figure 1 Basic structure of LTE multiantenna transmission (2 times 2 antenna configuration)

reuse 3G repeaters instead of the high-cost equipment andtake advantage of multiantenna transmission of LTE

2 Multiantenna Transmission

The use of multiple antennas is one of the key technolo-gies to achieve LTE performance targets [6] Multiantennatransmission in LTE can be described as a mapping of mod-ulated symbols to different antenna ports Figure 1 illustratesdownlink multiantenna transmission that supports spatialmultiplexing of up to two layers in a 2 times 2 antenna configu-ration A codeword is an independently encoded data blockcorresponding to a single transport block (TB) delivered froman L2 protocol A spatial layer is one of the different streamsgenerated for spatial multiplexing and layer mapping is aprocess of distributing codewords over multiple spatial layersbased on the number of antenna ports Precoding can be usedto improve signal isolation at the receiver side and providemapping of the spatially multiplexed streams to transmitantennas (including beam-forming) The precoded symbolsaremapped to appropriate antenna ports by antennamappingand reference symbols (119903

1and 119903

2) are inserted within an

OFDM time-frequency gridThe number of layers may range from a minimum of one

up to multiple layers The number of layers is often referredto as the transmission rank and LTE can adaptively controlthe transmission rank according to channel conditions suchas received signal quality and fading correlation betweenantennas In a 2 times 2 antenna configuration there are four2 times 1 precoding matrices for rank-1 transmission and three2times2matrices for rank-2 transmission as shown in Table 1 [7]Codebook index 0 for rank 2 (ie identity matrix) is not usedin a closed-loop operation but only applied to an open-loopoperation When closed-loop precoding is configured eachuser equipment (UE) can report a suitable transmission rankby rank indication (RI) and a precoding matrix by precod-ing matrix indication (PMI) based on reference signal mea-surements However RI and PMI are only recommendationsand the BS does not have to follow the RIPMI provided bythe UE

In rank-2 transmission with a 2 times 2 antenna configura-tion data symbols (119904

1and 1199042) from two different codewords

aremapped to the first and second layers respectively If a UEdoes not support rank-2 transmission due to poor channelquality rank 1 can be used to improve the SINR by diversitygains In the case of rank-1 transmission only one codeword(1199041) is mapped to a single layer and one of the precoding

Table 1 Precoding matrices (W) for two antenna ports

Codebook index 0 1 2 3

Rank 1 1

radic2

[1

1]1

radic2

[1

minus1]1

radic2

[1

119895]1

radic2

[1

minus119895]

Rank 2 1

radic2

[1 0

0 1]1

2[1 1

1 minus1]1

2[1 1

119895 minus119895] mdash

matrices for rank 1 is applied to adjust antenna weightingLetting y be the received signal on each subcarrier at the UEa general transmission model is described by

y=[ℎ11 ℎ12ℎ21ℎ22

] [1199041015840

1

1199041015840

2

] + [1198991

1198992

]

=

HW1199041+ n for rank 1

HW[1199041

1199042

] + n for rank 2

(1)

where ℎ119894119895denotes the channel fading coefficient between the

119894th receive antenna and the 119895th transmit antenna 11990410158401and 11990410158402

are output symbols after precoding and 119899119894is the combined

noise and interference at the 119894th receive antenna H is the2 times 2 channel matrix W is the precoding matrix in Table 1and n represents the combined noise and interference vectorat the UE In order to detect and receive wanted signals atthe receiver linear and nonlinear algorithms can be useddepending on implementation and complexity of the receiver[8]

In LTE the control region in a subframe (1ms) carriesL1L2 signaling necessary to control uplink and downlinkdata transmission and transmit diversity is generally appliedto the signaling [1] In a 2 times 2 antenna configuration thetransmit diversity is based on Space-Frequency Block Coding(SFBC) Two consecutive modulation symbols 119904

1and 1199042 are

mapped directly to the 119896th and (119896 + 1)th subcarriers respec-tively on the first antenna port On the second antenna portminus119904lowast

2and 119904lowast1are mapped to the corresponding subcarriersThe

received SFBC signals on the 119896th and (119896 + 1)th subcarriersy(119896) and y(119896+1) respectively are given by

y(119896) = [ℎ(119896)

11ℎ(119896)

12

ℎ(119896)

21ℎ(119896)

22

] [1199041

minus119904lowast

2

] + n(119896) (2)

y(119896+1) = [ℎ(119896+1)

11ℎ(119896+1)

12

ℎ(119896+1)

21ℎ(119896+1)

22

] [1199042

119904lowast

1

] + n(119896+1) (3)


where ℎ(119896)119894119895


119894119895asymp ℎ(119896+1)

119894119895) it








1(RS





119903in


119903 as follows

W119903=Wminus1119903=1

radic2

[1 1

1 minus1] (4)


1



1radic2 119903

2radic2 and 119904

1 and


2radic2 and 119904

2 Now each







Codeword 1

Codeword 2

Layermapping

Precoding(W)

Antennamapping

OFDMmodulation

OFDMmodulation(s1)

(s2) s2

s1 s9984001

s9984002

r1

r2

+

+

r1 s9984001

r2 s9984002

Repeater 1

Repeater 2

Post-processing

(Wminus1r )

r1radic2

r2radic2

s1

r1radic2

minusr2

radic2 s2








y1= [ℎ1

ℎ2

] 1199041+ n1

(5)

= (1

radic2

[ℎ1ℎ1

ℎ2ℎ2

])(1

radic2

[1

1]) 1199041+ n1 (6)

y2= [ℎ1

ℎ2

] 1199042+ n2

(7)

= (1

radic2

[ℎ1minusℎ1

ℎ2minusℎ2

])(1

radic2

[1

minus1]) 1199042+ n2 (8)






1and y(119896)2


y(119896)1=1199041minus 119904lowast

2

radic2

[ℎ(119896)

1

ℎ(119896)

2

] + n(119896)1

(9)

= (1

radic2

[ℎ(119896)

1ℎ(119896)

1

ℎ(119896)

2ℎ(119896)

2

])[1199041

minus119904lowast

2

] + n(119896)1 (10)

y(119896+1)1=1199042+ 119904lowast

1

radic2

[ℎ(119896+1)

1

ℎ(119896+1)

2

] + n(119896+1)1

(11)

= (1

radic2

[ℎ(119896+1)

1ℎ(119896+1)

1

ℎ(119896+1)

2ℎ(119896+1)

2

])[1199042

119904lowast

1

] + n(119896+1)1 (12)

y(119896)2=1199041+ 119904lowast

2

radic2

[ℎ(119896)

1

ℎ(119896)

2

] + n(119896)2

(13)

= (1

radic2

[ℎ(119896)

1minusℎ(119896)

1

ℎ(119896)

2minusℎ(119896)

2

])[1199041

minus119904lowast

2

] + n(119896)2 (14)

y(119896+1)2=1199042minus 119904lowast

1

radic2

[ℎ(119896+1)

1

ℎ(119896+1)

2

] + n(119896+1)2

(15)

= (1

radic2

[ℎ(119896+1)

1minusℎ(119896+1)

1

ℎ(119896+1)

2minusℎ(119896+1)

2

])[1199042

119904lowast

1

] + n(119896+1)2 (16)


where ℎ(119896)119894 n(119896)1 and n(119896)



4 Results









10(119909) 119909 in km


119887) 40W (fixed)










BS

Cluster



80

60

40

20

00 100 200 300 400 500

Distance (m)

Clus

ter t

hrou

ghpu

t (M

bps)











119903 Remem-




1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500




30

20

10

01 2 5 10 20 40

Clus

ter t

hrou

ghpu

t (M

bps)

Repeater power (W)


300

200

100

01 2 5 10 20 40

W)Repeater power (


Edge

thro

ughp

ut (k

bps)

(b) Edge throughput










5 Conclusions


Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










where ℎ(119896)119894119895


119894119895asymp ℎ(119896+1)

119894119895) it








1(RS





119903in


119903 as follows

W119903=Wminus1119903=1

radic2

[1 1

1 minus1] (4)


1



1radic2 119903

2radic2 and 119904

1 and


2radic2 and 119904

2 Now each







Codeword 1

Codeword 2

Layermapping

Precoding(W)

Antennamapping

OFDMmodulation

OFDMmodulation(s1)

(s2) s2

s1 s9984001

s9984002

r1

r2

+

+

r1 s9984001

r2 s9984002

Repeater 1

Repeater 2

Post-processing

(Wminus1r )

r1radic2

r2radic2

s1

r1radic2

minusr2

radic2 s2








y1= [ℎ1

ℎ2

] 1199041+ n1

(5)

= (1

radic2

[ℎ1ℎ1

ℎ2ℎ2

])(1

radic2

[1

1]) 1199041+ n1 (6)

y2= [ℎ1

ℎ2

] 1199042+ n2

(7)

= (1

radic2

[ℎ1minusℎ1

ℎ2minusℎ2

])(1

radic2

[1

minus1]) 1199042+ n2 (8)






1and y(119896)2


y(119896)1=1199041minus 119904lowast

2

radic2

[ℎ(119896)

1

ℎ(119896)

2

] + n(119896)1

(9)

= (1

radic2

[ℎ(119896)

1ℎ(119896)

1

ℎ(119896)

2ℎ(119896)

2

])[1199041

minus119904lowast

2

] + n(119896)1 (10)

y(119896+1)1=1199042+ 119904lowast

1

radic2

[ℎ(119896+1)

1

ℎ(119896+1)

2

] + n(119896+1)1

(11)

= (1

radic2

[ℎ(119896+1)

1ℎ(119896+1)

1

ℎ(119896+1)

2ℎ(119896+1)

2

])[1199042

119904lowast

1

] + n(119896+1)1 (12)

y(119896)2=1199041+ 119904lowast

2

radic2

[ℎ(119896)

1

ℎ(119896)

2

] + n(119896)2

(13)

= (1

radic2

[ℎ(119896)

1minusℎ(119896)

1

ℎ(119896)

2minusℎ(119896)

2

])[1199041

minus119904lowast

2

] + n(119896)2 (14)

y(119896+1)2=1199042minus 119904lowast

1

radic2

[ℎ(119896+1)

1

ℎ(119896+1)

2

] + n(119896+1)2

(15)

= (1

radic2

[ℎ(119896+1)

1minusℎ(119896+1)

1

ℎ(119896+1)

2minusℎ(119896+1)

2

])[1199042

119904lowast

1

] + n(119896+1)2 (16)


where ℎ(119896)119894 n(119896)1 and n(119896)



4 Results









10(119909) 119909 in km


119887) 40W (fixed)










BS

Cluster



80

60

40

20

00 100 200 300 400 500

Distance (m)

Clus

ter t

hrou

ghpu

t (M

bps)











119903 Remem-




1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500




30

20

10

01 2 5 10 20 40

Clus

ter t

hrou

ghpu

t (M

bps)

Repeater power (W)


300

200

100

01 2 5 10 20 40

W)Repeater power (


Edge

thro

ughp

ut (k

bps)

(b) Edge throughput










5 Conclusions


Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Codeword 1

Codeword 2

Layermapping

Precoding(W)

Antennamapping

OFDMmodulation

OFDMmodulation(s1)

(s2) s2

s1 s9984001

s9984002

r1

r2

+

+

r1 s9984001

r2 s9984002

Repeater 1

Repeater 2

Post-processing

(Wminus1r )

r1radic2

r2radic2

s1

r1radic2

minusr2

radic2 s2








y1= [ℎ1

ℎ2

] 1199041+ n1

(5)

= (1

radic2

[ℎ1ℎ1

ℎ2ℎ2

])(1

radic2

[1

1]) 1199041+ n1 (6)

y2= [ℎ1

ℎ2

] 1199042+ n2

(7)

= (1

radic2

[ℎ1minusℎ1

ℎ2minusℎ2

])(1

radic2

[1

minus1]) 1199042+ n2 (8)






1and y(119896)2


y(119896)1=1199041minus 119904lowast

2

radic2

[ℎ(119896)

1

ℎ(119896)

2

] + n(119896)1

(9)

= (1

radic2

[ℎ(119896)

1ℎ(119896)

1

ℎ(119896)

2ℎ(119896)

2

])[1199041

minus119904lowast

2

] + n(119896)1 (10)

y(119896+1)1=1199042+ 119904lowast

1

radic2

[ℎ(119896+1)

1

ℎ(119896+1)

2

] + n(119896+1)1

(11)

= (1

radic2

[ℎ(119896+1)

1ℎ(119896+1)

1

ℎ(119896+1)

2ℎ(119896+1)

2

])[1199042

119904lowast

1

] + n(119896+1)1 (12)

y(119896)2=1199041+ 119904lowast

2

radic2

[ℎ(119896)

1

ℎ(119896)

2

] + n(119896)2

(13)

= (1

radic2

[ℎ(119896)

1minusℎ(119896)

1

ℎ(119896)

2minusℎ(119896)

2

])[1199041

minus119904lowast

2

] + n(119896)2 (14)

y(119896+1)2=1199042minus 119904lowast

1

radic2

[ℎ(119896+1)

1

ℎ(119896+1)

2

] + n(119896+1)2

(15)

= (1

radic2

[ℎ(119896+1)

1minusℎ(119896+1)

1

ℎ(119896+1)

2minusℎ(119896+1)

2

])[1199042

119904lowast

1

] + n(119896+1)2 (16)


where ℎ(119896)119894 n(119896)1 and n(119896)



4 Results









10(119909) 119909 in km


119887) 40W (fixed)










BS

Cluster



80

60

40

20

00 100 200 300 400 500

Distance (m)

Clus

ter t

hrou

ghpu

t (M

bps)











119903 Remem-




1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500




30

20

10

01 2 5 10 20 40

Clus

ter t

hrou

ghpu

t (M

bps)

Repeater power (W)


300

200

100

01 2 5 10 20 40

W)Repeater power (


Edge

thro

ughp

ut (k

bps)

(b) Edge throughput










5 Conclusions


Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










where ℎ(119896)119894 n(119896)1 and n(119896)



4 Results









10(119909) 119909 in km


119887) 40W (fixed)










BS

Cluster



80

60

40

20

00 100 200 300 400 500

Distance (m)

Clus

ter t

hrou

ghpu

t (M

bps)











119903 Remem-




1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500




30

20

10

01 2 5 10 20 40

Clus

ter t

hrou

ghpu

t (M

bps)

Repeater power (W)


300

200

100

01 2 5 10 20 40

W)Repeater power (


Edge

thro

ughp

ut (k

bps)

(b) Edge throughput










5 Conclusions


Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










BS

Cluster



80

60

40

20

00 100 200 300 400 500

Distance (m)

Clus

ter t

hrou

ghpu

t (M

bps)











119903 Remem-




1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500




30

20

10

01 2 5 10 20 40

Clus

ter t

hrou

ghpu

t (M

bps)

Repeater power (W)


300

200

100

01 2 5 10 20 40

W)Repeater power (


Edge

thro

ughp

ut (k

bps)

(b) Edge throughput










5 Conclusions


Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500



1500

1000

500

0

minus500

minus1000

minus1500




30

20

10

01 2 5 10 20 40

Clus

ter t

hrou

ghpu

t (M

bps)

Repeater power (W)


300

200

100

01 2 5 10 20 40

W)Repeater power (


Edge

thro

ughp

ut (k

bps)

(b) Edge throughput










5 Conclusions


Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation

















5 Conclusions


Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









research article coexistence of 3g repeaters with lte...

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