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Emprcl Any of Brodbnd ) MIOCnnel n OudoorInoor Scero

o Fnnz M Dng n R P sDeparamento de Ingeniera de Comuncacioes, Laboratoros de I+D de Telecomuncacones

Uiversida e CantabraPlaza de la Cenca s 5 Santader, SpainE-ma: fernanos@uncan.es;domngom@uncanes;torresrp@uncan.es

Abstrct

Ths paper presnts the expermnta characterzation of a wdeband x MO chanel n typca ndooroutdoo scenarios nthe 5 GHz band The transmittr array emulates a base staton postoned on the terrace of a buldng, and the recevrarray stuated inside a nearby buldng, represents the en-user termnal In a prevous work, the authors analyzed theadvantages attanable wth a x MMO channel compared to a SSO channel for the case of arrowba wreess systems nthese types of nvironments whout line-of-sight (NLOS) The new results for the wideband chanel show that as n thenarrowband se, the capacty egradation due to penetration osses can be practcaly compensaed for by the gai of a xMIMO channe Furthermore the frequency dvrsity attanabe n the case of wdeban systems appears as newcontrbuton, renforcing th concuson obtaned for the narrowband case

Ths paper so presnts a stochstc x IMO wdebad chann-modelin method that epresents a novl smpfcatonwth respect to other wdeand MIMO models The resulting models are acurate, but also easy to mplement andcomputatonay efcent Usng this method utdoorndor channel models are obtaned from a measurements campan onra MIO chnne in dfren envronmnts he emprica data an the ms presente n th par wi be vey useful nthe delymnt of futur and present broadbnd fxed wreless-access systems BWAS

Keywords lectromagnet propagaton; and moble rado propagaton fcors; lad moble rad diversty systems; MIMOsystems;communcaton chanes;channel moes;WMAX;broadband fxed wireess-access systems; wreless LA

Ituct

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Antennas and Ppagatn Magazine Vol 52, No.6 Dcmbr 2010

[3] T rdon o ovrg rng r prolm ordploymn mnl d o l o mmry ndoor

nd odoor ovrg n prvo p pr [4] or tdd py rdon o SSO (nglnp nglotp) nrond rl ym n odoorondoor nvronmno lnog (LOS). o dgrdonn prlly ompnd or gn o 22 MMOnnl. For rl opror WMAX gly dq ndreng nolog or dployng mropolnr rlnor T l vron o drd lrd onmpl poly o ng to nnn n rnmon nd/or rpon. ovr or rr dplomn o nry

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moes s paer cuses on the 35 GHz band in which WiMAXsystems operate, a band for which the authors are unaware of theexistence of any other outdoor-indoor IMO measurement campaign

As previous work, the authors developed an experimentasetup based on the use of generalpurpose instrumentation forwideband channel caracterization As a second step, sing le-inutsingle-output (SISO) wideband channel models, using the tappeddelayine (TDL) approach for outdoorindoor environents i n thecontext of wireless metropoitanarea network systems, were

developed [8] Now, in this paper we present the experientalcharacterization and modeling of wideband 22 MIM channes intypica indoor-outdoor scenarios A 2 MIMO channe measurement system is presented, hich was deveoped using genera-purpose equipment that can be found in any reasonably equippedmicrowave laboratory This is in sharp conrast with the measurement systems devel ped ad hoc by arge aboratories or companie s,and which are still very expensive The design of the measuremets campaign and its subsequent impementation were of aclearly practical nature or engineering perspective), which, without compromising its scienti c rigor, focused on veri ing andhighligting the beets that a relatively simpe MIMO system(only 22 atennas) might have on wireless metropolitan-areanetwork systems Ths oers data of pactical use, such as the

expected peetration osses in buidings in the 35 GHz band, andthe realistic capacity vaues avaiabe in the outdoor-indoor 22IMO channel

These new results showed that also i n the wideband case, tecaacity degradation due to penetration losses can be practicalycompensated for by the ain of a 22 IMO channe urthermore, the equency iversity attainabe in the case of widebandsystems apears as a ne contribution, reinforcing the concusionobtained for the naoan case It was experimentaly veriedthat in he case of oaan systems, the diversity ain in the equency domain imroves the outage-capacity eves of te systemwith respect to naowad systems This phenomenon was theoretically known in iea channes However, the channels anayzedwere real channes, which combine spatial and frequency correla

tion There are vey few experimental resuts on this gain in reachannels in the iterature

inally, the paper presets a stochastic 22 MIMO widebandchannelmodeling metho that uses tapped delay ines (TDL),base on 8, an a simpe spatiacorrelation matrix The modeingmetho is compared wit measured data, obtaining ood resultsAlthough the number of measured scenarios was not big enough toobtain a comlete model for genera outdoor-indoor scenarios, thispreliminary mode is of great vaue as a realistic reference, due tohe lack of information aout outdoor-indoor channe performancen fact, the model has been used for simulating dierent spacetime rocessing methods over realistic channes [9] At present, theauthors are develoing nw measurement campaigns in order to

generalize the model Te rest o f this aper i s organized as folows Section 2

describes the wideband measurement system and the scenarios inwhich the measurements were made In Section 3 , the exprimental results are presented, as wel as the analysis of the major MIMOchannel characteristics These show that caacty degradation ispractically compensated for by the gain o f the MIMO system Section 4 presents the MIMO channe-modeling method om a general point of vi ew ection 5 describes the application of the general modeing method to the outdoorindoor MIMO case based on

em an the study of its capacity inally, some conclusions aredrawn in Section 6

crs Msurmt ystm

crs

In order to perform the characterization and modeling of

MIMO broadband xed wirelessaccess channels in outdoorindoor environments, severa measurement campaigns were cariedout in the 3 5 GHz equency band, with a bandwidth of 250 MzTe measurements were made between two buildings of the University of Cantabria, separated by a distance of 120 m (igre 1)The transmitter array was positioned as a base station on the terrace of a buildi n, while the receiver, acting as the enduser terminal, was placed inside the other buiding, in three scenarios withdifferent characteristics

The rst scenario was an assembly room: an oen area withfew obstac les around the receiver array The second scenario wasan electronics laboratory, equipped with computers, workbenches,measuring euipment, and cupboards Tese two scenarios were at

a height that was around 6 m ower than the transmitter The thirdscenario was a typical oce oor, at a height of 15 m below thetransiter The inuence of the line of sight between the transmitter and the receiver was considered in the channel characterization, placing the receiver aray in three different ocal areas foreach measurement scenario The rst measurement area waslocated close to a window, opposite the transmitter, i a quasi lineofsight (QLOS) situation In this area, the line of sight wasobstcted only y a window O moving away from this windowand going into the room, the visual line of sight between thetransmitter and the receiver was ost In these conditions of nonine-of-sight (N OS), measurements were made in two local areasNLOS, in which the receiver was aready indoors in the building,but only one of the inner wals obstructed the direct sight of the

the measured data, detaiing the eects of correlation on the sys Figure . The mearemen scenarios

56 Antennas and Ppagatin Magazine Vol 52 No6, Dmbr 2010

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r._LN

ignal GenrdrTansmiter

Aen ECG433B

RfenceMHz d

Aper

Sector Anenns,G=15Bi

Minonroer

OnidiretonAntenn G 0 dBi

ReceverAglen

PNA E

Figure 2 The wideband channelmeauremn yem

transmtter; and HNLOS hardNLOS, n whch the receiver wasalso located an indoors zone of the building, but with severalpattions between the transmtter and the receiver The oor plasof the three scenarios and the dfferent areas measured were preented n detail n [4]

Msurmt ystm

A wideband measurement system, based on an AgilentECG4433B sigal generator and an Aglent PNA E8362A networkanalyzer, was use The system performed a 400tone frequencysweep in the band of nterest: 3385-3635 GHz The two ends ofthe measurement system were synchronized in equency andphase thanks to an exteal reference of 10 MHz, generated byrubidium oscillators and dsciplined by GPS receivers igure 2shows a schematic diagram of the measurement system used Thetransmitter array was made up of two sector antennas wth a gainof dBi, separated 0 and oriented towards the measurementscenaro Meawhle, the recever array was composed of two biconc ondirectonal broadband antennas, spaced 5 apart,with a gain of approxi aty 0 dBi or the 3 5 GHz bad

The signal generator of the transmitter stae performed theequency sweep with a typica power of 0 dBm Te generatoroutput was amplied by means of a broadband ampler wth again of 30 dB to compensate for the propagaton losses or themeasurement of each MIMO channel, two sweeps were madesequentally, one wth each transmtting antenna The seletion ofthe transmitting atenna was made through an swith

At reception, a etwork analyze performed the equencysweep n parael with the transmier, capturng the 400 equencytones Taking advantage of the two analyzer inputs, the receptionwas performed simultaneously y both receive antenas Themeasurements were made in the absence of moving persons to

Anennas and Ppagatin Magazine, Vol52, No6 Dcmbr 2010

maintain the tmeinvariant chae behavr during the tme ittook for one snapshot, which was 30 seconds

To obtain the transfer nction of each of the MIMO subchannels tt(m)dm)t(m) and (m) the MIMOchannel was measured n 32 locations for each local area

The conguration and control of the measurement systemwas perfored centrally from a personal computer, wth an ad

hocdeveloped soware tool The equency swep was synchronied in both stages from this PC, and the corresponding transmitter antenna was selected and the receved data were stored adprocessed

Cpct f Msur MIMO Chs

rom the MIMO chane measurements, the channel capacitwas calculated in the three loca l areas of the di fferent scenari os The MI MO channel capacty depends on th e values of the channematrx, and on the sgnaltonoise rato SNR in the receiver Inorder to evaluate the inuence of the correlation on the performance of the MIMO chanel, a compariso of the capacity in eachof the three lcal areas was made for each scenario This compari

son was performed for two condtions of SNR: one for a xedtypical value of 20 dB, ad another or the sitespecic SNR vaues measured n each loca area When comparing the channelcapacty in derent scenarios at a xed SNR value, the eect ofthe correlation on capacity was dented In the second case , usingthe measured SNR values, the combined effect of the corrlationand the measured signaltonoi se ratio was analyzed

Cpcty fr Fx SNR

irst, the cumuative probability distriuton nction CDof the bradband channel capacity measured for a constant SNR o f

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s presente Te capacity results tained with a cmmnSNR allwed the analysis f the capacity degradatin due t theinuence the spatial c rrelatin when passing m line-f-sightt nn-line-f-sight nes

igures 35 present the capacity statistics fr the three lcalareas, fr each scenari These gures als include the cumulativepraility distributin nctin the capacit tained m twtheretical widean channel mdels, used as a reference Thesetw mdels presented uncrrelated Rayleigh fading in the spatialdmain and a different degree f crrelatin in the frequency

dmain ne ttally at in frequency (at fading), and antherttally selective in frequency (equecy selective) intly andinseparably, the measured channels underwent the eects f thespatia and frequency crrelatin, al ways shwing l wer capacitiesthan thse f the reerence channels It is wrth nting that fr acnstant SNR, wen the situatin went m line-f-sight t nnine-f-sight and thn t the mre structed hard nn-ine-fsight, the capacity curves were clser t the theretical curvesThis was due t scattering richness f the mre-bstructed situa-

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trbuon fncon n he aemblyroom cenro n lneofgh nonIne-of-gh and hard nonIneofgh areaotaned wh a 20 dB SN

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0 2 4 6 Fgure 4 The channel-capacty cumulatve probablytrbuon functon n the laboraory cenaro n lneofghnon-neofght an har nonne-of-gh area otanewth a 20 S

58

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:- --. IlONlOHNlOFr S -Ft Fa in- 10-12 16 bFgre 5. The M channel-capacy cumulave probablydrbon fncon n he ofce-oor cenaro n lne-ofghnon-ne-of-gh and har non-Ineof-gh area obanewh a 20 dB SNTable 0% oage and mean capacy wh a 20 B SNR 0% Mean Derence

uageCapacy

wth UpperCaci! m LOS 7 .3 8 2 3 : NLOS 80 9.5 8 NLOS 83 9.9 4

LOS 5. 4 7.4 3 9e NLOS 79 90 23

NLOS 9.4 0 2LOS 73 8 2 3

NLOS 78 92 2

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lneosght envronments n comparson wth te lneosghtareas In these areas, the capacty was very close to te upper reference lmts, wth an average capacty o between and 2 bpsHzbeo w the theoretcal lmt

An nherent caracterstc of a broadband cannel s theefect o the requency dversty, reected n an ncreased sope nthe cumulatve probablty dstrbuton ncton capacty curve,gvng rse to a gan n te outage capacty Comparng te capactyvaues or the broadband measured channes wt te at equency reerence cannel, t was obsered that the 10% outage

capacty was cose to or even surpassed the correspondng outagecapacty o IO channes wth no spatal correaton, but wth ahgh requency correlaton at requency Snce the euencyversty appeared because o a greater tme dsperson assocated,n tu, wth a greater scaerng rchness, t coud be concudedthat the mostobstructed stuatons oered the twoold advantageof presentng ess correaton n te spata and equency domans

2 Cpcty fr sur R

Secondy, te capacty o te evauated IO channes spresented, caculated usng the SR vaues measured n eac area

In combnaton, tese curves sowed te nuence on capacty ofthe spata correaton and the rea SNR gures 68 present thecumuatve probablty dstributon ncton of the capacty n tescenaros studed or each scenaro, these graphs compare thecapacty o the IO channel wth the capacty o te SISOchannels n each o f the ocal areas Ths comparson sowed thatthe use of mutple antennas n transmsson and recepton ddndeed lea to a sgncant proveent wth resect to the SISOchannel

In the prevous secton, gures 35 showed how the presenceof neosgt ncreased the spata correaton provdng lesscapacty n these areas tan n nonneofsght stuatos However, snce the propagaton n neosgt areas undergoes essattenuaton, te SNR at recepton n these areas was greater thantat btand n te nonneofsgt areas: n the measured scenaro, te SNR n ne osght areas was 15 B hger Table 2) rom te pont of vew of capacty, t coud be observed n g

1, 5ci 3

5 35

Figure 6 he channcapacity cumulativ probabiliditribution function in the aembyroom cenario in ine-ofight non-ine-of-ight and hard nonine-of-ight areaobtained ith the meaured SN

EEEAntennas and pagatin Magzine Vol. 52 No6, D cmb r 2010

9

_0.7

'5

3

20=5y

Figure 7. he M channel-capacity cumuative probabiityditribution function in the aboratory cenario in ineof-ightnon-ine-ofight and hard nonineofight area obtainedith the meaured SN

9

8

7

a: 3

%--15=Cpib

Figure 8 he channe-capacity cumuative probabiityditribution function in the oceoor cenario in ineofightnon-ineofight and hard nonineofight area obtainedwith the meaured SN.

ures 68 that atough te ceaton between subchannes waslower for nonneosght stuatons, the reducton n the SNR nthese areas ed to sgncantly ower capacty vaues In te neofsgt areas, the MIO canne tus provded a capacty ofbetween 8 and 23 bts/s/Hz, whe on passng over to the nonneosgt and ard nonneofsgt areas, te capacty n these sce

naro was reduced by between 5 and 9 bts/sHz

Comparng the capacty o the MIO channes wth tatobtaned or SISO chanels, t could be observe how te capactygan provded by te IM systems n te noneofsgt areasalwed a smar capacty as or that obtaned by te SISO system lneosght stuatons to be reaced In terms of te sgnaltonose rato, the IMO canel n nonneofsg stuatons provded a gan that compensated for te fal n SNR caused by thegreater propagato osses n te nonneofsgt areas

Table 2 shows ow n the evauatd scenaros templementaton of IO n nonlneofsght areas prove a

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abe 2 he mean capacity in SSO and MMO chan nes obtained with the mea sured SN.

SSO MMOChanne ChanneCapaciy Capacity(bpsHz) (bpsHz)

LOS 153 233 NLOS 103 162 g