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1 Beh, KC., an, C., Nicolaou, M., Aou, SMD., & Doufexi, A. (9). Powe efficient MIMO technique fo 3GPP LTE and beyond. In Intenational Confeence on Vehicula Technology, Fall 9, Anchoage, Alaka (pp. 1-5). Intitute of Electical and Electonic Enginee (IEEE). DOI: 1.119/VETECF Pee eviewed veion Link to publihed veion (if available): 1.119/VETECF Link to publication ecod in Exploe Bitol Reeach PDF-docuent Univeity of Bitol - Exploe Bitol Reeach Geneal ight Thi docuent i ade available in accodance with publihe policie. Pleae cite only the publihed veion uing the efeence above. Full te of ue ae available:

2 Powe Efficient MIMO Technique fo 3GPP LTE and Beyond K. C. Beh, C. an, M. Nicolaou, S. Aou, A. Doufexi Depatent of Electical & Electonic Engineeing, Univeity of Bitol, Bitol, United Kingdo. Abtact: Envionental iue and the need to educe enegy conuption fo loweing opeating cot have puhed powe efficiency to becoe one of the ajo iue of cuent eeach in the field of wiele netwok. The objective of the Geen Radio eeach pogae (Coe 5) of Mobile VCE i to delive educed powe conuption of adio acce netwok. Thi pape attept to how that an efficient exploitation of ultiple antenna technique and ultiue diveity in both the tie, fequency a well a the pace doain can ignificantly eae the powe equieent of a bae tation, whilt aintaining the ae level of evice. Diffeent MIMO taniion and pecoding chee popoed fo LTE, achieving vaying degee of ultiue diveity ae exained. I. INTRODUCTION Thee ae cuently 4 billion obile phone ue in the wold. The enegy conuption and cabon dioxide eiion ha becoe a ajo concen fo wiele netwok indutie a the nube of obile phone ue inceae. The Mobile VCE Viion docuent tate that a typical 4-hou obile phone netwok in the UK conue appoxiately 4 MW, excluding the powe conued by the ue handet [1]. The woldwide telecounication induty i cuently eponible fo 183 illion tone o.7% of cabon dioxide eiion, which ae inceaing at a apid ate []. In addition, the inceaed enegy pice inceae the opeating cot of cellula yte. In ode to develop oe powe efficient and envionental fiendly wiele netwok, the Coe 5 eeach pogae of Mobile VCE i et to focu on the Geen Radio concept. It ai to delive high data ate evice with a 1- fold eduction in powe conuption ove cuent wiele counication netwok, theeby educing CO eiion and opeating cot without copoiing (and pefeably ipoving) the Quality of Sevice (QoS) fo ue. Achitectue and technique ae the two coplientay doain in thi pogae and the latte one i of paticula inteet to thi pape. LTE i a next ajo tep in obile adio counication, and will be intoduced a Releae 8 in the 3d Geneation Patnehip Poject (3GPP) [3]. The new evolution ai to educe the delay, ipove pectu flexibility and futhe educe the cot fo opeato and end ue. Soe of the taget of the tandad include a peak download ate of up to 36.4 Mbp fo 4x4 antenna and 17.8 Mbp fo x antenna fo evey Mz of pectu. In the uplink, a peak upload ate of 86.4 Mbp i expected. Intead of the fixed pectu in the peviou eleae, LTE ai to uppot a calable bandwidth fo 1.5Mz up to Mz. The objective of thi pape i to invetigate the capabilitie of vaiou ultiple antenna taniion and pecoding technique in cobination with ultiue diveity to educe the total powe conuption needed fo a wiele yte opeation and ipove enegy efficiency. The ue of the MIMO taniion technique can ignificantly ipove the yte pefoance, eliability o both. One of the popula MIMO technique i pace-tie block coding (STBC) which i able to achieve full tanit diveity and enable eliable counication. Thu in LTE, an Alaouti [4][5] baed Space-Fequency Block Coding (SFBC) technique i popoed in the tandad and it will be conideed in thi pape. Anothe technique that i alo popoed in the LTE tandad i patial ultiplexing (SM) which ai to inceae the ultiate pectal efficiency. A nube of MIMO pecoding technique, which can be potentially applied to LTE, ae exained in te of thei cobined pectal and powe aving efficiency. Rando Beafoing (RB), widely exained in [4][7][8][9] ha hown capabilitie in achieving patial ultiue diveity gain and patial ultiplexing (SM) gain. With uch lowe feedback equieent than the conventional eigenbeafoing, the tanitte applie a ando pecoding atix to the tanitted ignal and elect the bet ue only baed on effective SNR (ESNR) feedback indicating channel quality. By uing a linea eceive to epaate the MIMO patial laye, allowing allocation of laye of the ae lot to diffeent ue, an additional laye ultiue diveity gain i extacted, enabling what i called Layeed Rando Beafoing (LRB). Recently, an altenative MIMO cheduling and pecoding ethod ha been popoed fo the Long Te Evolution (LTE) of 3G yte [1], that incopoate an ipoved inteface between the Phyical (PY) and the Data Link Contol (DLC) laye in ode to povide inceaed uppot fo on deand quality of evice (QoS) [11]. In [1], a pecoding ethod fo a MIMO-OFDMA chee ha been popoed in accodance to the LTE tandad [1]. Thi pecoding ethod elie on the ue of a known (by both bae tation and obile) codebook of unitay atice, which i deteined offline, geneated accoding to a Fouie bai that povide unifo coveage aco a ecto. The eaining of thi pape i oganied a follow: Section II intoduce the yte and channel odel paaete. Section III povide a bief deciption of the conideed MIMO taniion and pecoding chee. Section IV peent theoetical analyi of the capabilitie of conideed chee to aintain QoS unde diffeent aveage SNR condition. Siulation eult ae peented in ection V. Section VI dicue the iplication of eouce allocation to the BS powe conuption baed on the analyi of peceding ection. Thi pape conclude in ection VII. II. SYSTEM AND CANNEL MODEL The pefoance analyi i pefoed on the downlink of a 3GPP LTE Othogonal Fequency Diviion Multiple Acce (OFDMA) yte. The total yte bandwidth i divided into ub-channel, denoted a phyical eouce block (PRB), /9/$5. 9 IEEE

3 which ae then allocated to diffeent ue fo ultiple acce pupoe. The key paaete of the conideed LTE OFDMA downlink yte ae given in Table 1. Thee ae 5 PRB in the 1Mz yte, each coniting of 1 adjacent ub-caie. Intead of feeding back the channel quality indicato (CQI) fo all the ub-caie, a ingle CQI (calculated fo the aveage quality of the 1 ub-caie) can be fed back fo each PRB and i aued to be pefectly known at the BS. Pefect channel etiation i alo aued. A 4 bit Cyclic Redundancy Check (CRC) enable eo detection at the eceive. Due to the inceaed coputational coplexity and the inignificant gain of powe contol in the fequency doain dynaic allocation, equal powe allocation i aued thoughout the iulation. The channel odel ued in the iulation i the Spatial Channel Model Extenion [13] (SCME) Uban Maco cenaio which i pecified in 3GPP [14]. SCME povide a educed vaiability tapped delay-line odel which i well uited fo link level a well a yte level iulation. A low patially coelated channel i aued fo all the ue whee 1λ pacing at the BS i eployed. In the iulation, a channel eain the ae duing a packet taniion. independently and identically ditibuted (i.i.d.) channel ealiation ae conideed in each iulation. Six odulation and coding chee (MCS) level ae conideed, a hown in Table. A x MIMO achitectue i conideed in thi pape but the analyi i eadily extendible to highe MIMO ode. Equal powe i allocated to each tanit antenna. Table 1: Paaete fo LTE OFDMA downlink Taniion Bandwidth 1 Mz Tie Slot/Sub-fae duation.5/1 Sub-caie pacing 15kz Sapling fequency 15.36Mz (4x3.84Mz) FFT ize 14 Nube of occupied 61 ub-caie Nube of OFDM ybol 7/6 pe tie lot (Shot/Long CP) CP length (μ/aple) Shot (4.69/7)x6 (5.1/8)x1 Long (16.67/56) Table : Modulation and Coding Schee Mode Modulation Cod. Rate Data bit pe tie lot (1x1), (x) Bit Rate (Mbp) 1 QPSK 1/ 4/76 8/15. QPSK 3/4 6/114 1/ QAM 1/ 8/15 16/ QAM 3/4 1/8 4/ QAM 1/ 1/8 4/ QAM 3/4 18/34 36/68.4 III. DESCRIPTION OF INVESTIGATED SCEMES A. Rando Beafoing and Layeed Rando Beafoing With low feedback equieent, ando beafoing i conideed a a ub-optial chee to [4]. A unitay atix V i geneated fo the ando channel atix and it i applied to the ub-caie of the OFDMA ignal on a PRB bai. The eceived ignal afte FFT and guad inteval eoval becoe (tie index t i oitted): Yk, = V, X + N (1) = U Dk, ( Vk, ) V, X + N whee k denote a ue index, denote a ub-caie index, (). denote the eitian function and i a atix containing ue k fequency epone of the channel between N tanit and t N eceive antenna at ub-caie. D i a diagonal atix including all the ingula value of and U and V ae the unitay atice obtained by applying Singula Value Decopoition (SVD) to. X denote an N t 1 atix containing the tanit ignal at ub-caie at the BS and N, epeent the additive coplex Gauian noie with zeo ean and vaiance ( σ ). If V i equal to V k, the V k V te becoe an identity atix and the ue k i aid to be in the tue beafoing configuation. The yte adopt a linea MMSE eceive, which ha intefeence uppeion capability. Fo a x MIMO yte, the MIMO channel can be decopoed into epaate patial laye, which can be allocated to eithe one ue fo the RB chee o to diffeent ue() fo the LRB cae. The eceived ignal Y i ultiplied by the MMSE filte G : k ( V ) ( V ) + SNR I ) ( V ) G k, = k,, k,,, () Fo data tea q at ub-caie, the ue k copute the ESINR : q E ESINRk, = (3) A σ ( k, ) qq whee A ( V ) ( V ) ( + SNR ) 1 = I., k,, E denote the aveage ybol enegy and () qj indicate the eleent located in ow q and colun j. Evey ue calculate the aveage data ate aco all ubcaie in each PRB and end it to the BS though the feedback channel. Fo PRB c, if the index of the tating ubcaie i n and finihing ub-caie i, the aveage ate of ue k i given by [8]: N q R = 1 k, c log ( 1+ ESINRk, ) n + 1 (4) = n q= 1 The BS allocate each PRB to the ue having the highet ate. In the cae of, the eouce allocation i baed on the channel gain, whee the detailed deciption i well known and hence oitted hee due to liited pace. Fo the LRB chee, the diffeent patial laye can be allocated to a diffeent ue to achieve an additional patial ultiue diveity gain. oweve, it inceae the feedback by the nube of patial laye (iniu nube of tanit and eceive antenna) copaed to the RB chee. Baed on the ESINR calculated uing equation (3), the ue k calculate the ate of each patial laye on a PRB bai [8]: R = 1 q q c log ( 1+ ESINRk ) n + 1 (5), = n Fo evey PRB, the BS allocate each patial laye to the ue whoe channel condition of the coeponding laye ae bet. C. Unitay Codebook baed Beafoing Unlike the ando unitay atix geneation, popoed fo RB and LRB yte, unitay codebook baed beafoing ugget that a pedefined et of antenna bea i to be deteined offline, which altogethe enue a good ecto coveage [11]. The popoed pe-code deign elie on the

4 Fouie bai fo enuing unifo ecto coveage. The codebook E, conit of the unitay atix et, i.e. ( ) ( G) ( g ) V E = { VE... VE }, whee ( g ) ( g ) VE = [ ve,... v ] i the g- E, M th pecoding atix, and v ( g ) i the -th pecoding vecto in the et. Accoding to the Fouie bai, ( g ) 1 ( g ) ( g ) v = [ ( ) ] Τ w... w M M ( ) πn g (6) w g n = exp j + M G Siilaly to the RB appoach, unitay codebook baed beafoing define two ode of opeation, depending on the patial eouce allocation poce. Single ue MIMO () yte, aign both patial tea to the ae ue, ealiing Spatial Diviion Multiplexing (SDM). A oe efficient pectu utiliation can be achieved via Multi-ue MIMO (MU-MIMO), wheeby the patial dienion i exploited, in a iila fahion to LRB. MU-MIMO can alo be known a Spatial Diviion Multiple Acce (SDMA) and i expected to achieve a geate oveall yte pefoance gain. In a full feedback chee, the eving BS eceive CQI infoation egading the patial laye fo all unitay atice, allowing an oveall optiiation of the aggegate ate by electing the atix that achieve the oveall highet pectal efficiency. Siilaly to RB and LRB, evey ue calculate the aveage data ate aco all the ub-caie in each PRB and end it to the BS though the feedback channel. The aveage data ate fo the PRB can be calculated uing the equation 4-6 except that the Fouie baed unitay atice ae ued. Depending on the codebook ize G, unitay codebook baed beafoing ipoe the additional feedback equieent of tanitting a total nube of G CQI value along with the coeponding atix index fo each CQI. In ode to educe thi uplink feedback ovehead, patial feedback technique have been popoed in [1], wheeby each ue feed back CQI fo only it pefeed atix. In [15] it wa hown that patial feedback technique attain the ae pefoance a full feedback chee. Fo MU-MIMO chee the degee of patial feedback pefoance convegence to full feedback i dependent on the cobination of the nube of ue and the codebook ize G. Subequent ection will aue a ange of ue fo 1-5 and a fixed codebook ize G=. Table 3 peent the uplink feedback ovehead aociated with each of the pecoding chee invetigated in thi pape. Pefect feedback infoation i aued in the iulation. oweve in pactie, the feedback infoation i quantized to educe the aount of feedback ovehead in the uplink. In LTE, it i popoed that 5 bit ae ued to epeent each CQI [16], with only vey aginal pefoance degadation. Note that in the popoed LTE yte, SFBC i not conideed in cobination with ulti-ue diveity and theefoe it doe not equie channel feedback. IV. TEORETICAL ANALYSIS The benefit of ultiue diveity (MUD), wheeby ue ae cheduled only on thei tonget PRB have been widely tudied in liteatue e.g. [17][18]. Povided that diffeent ue expeience independent fading, the aveage yte pectal efficiency can be inceaed a a function of the nube of ue. The pecoding yte exained in thi pape achieve vaying degee of ultiue diveity. It i theefoe expected that fo a given SNR value, diffeent chee will achieve diffeent pectal efficiency. To illutate thi, Figue 1 peent theoetical pectal efficiency eult, calculated accoding to Shannon Capacity liit, fo a ange of SNR value fo a total nube of ue, K=1, fo the MIMO pecoding chee outlined in the peviou ection. capacity i alo included fo efeence. The chee that achieve the highet degee of MUD exploitation (tie/fequency and pace) e.g. MU-MIMO and LRB achieve the highet capacity fo any given SNR value. Spectal Efficiency (bp/z) Rando Beafoing Layeed Rando Beafoing Patial Feedb. MU-MIMO SNR (db) Figue 1: Theoetical Spectal Efficiency fo and Diffeent Pecoding Schee fo K =1 Pefoance Gain Ove Single Ue (db) No.of Ue SFBC Rando Beafoing Layeed Rando Beafoing Patial Feedb. MU-MIMO Figue : Theoetical Reult of Pefoance Gain of Multiue and othe MIMO Pecoding Schee ove Single Ue Scenaio Figue how the theoetical eult of the pefoance gain of ultiue and othe MIMO pecoding chee ove ingle ue cenaio, a a function of the nube of ue at a fixed pectal efficiency of 3bp/z. The fixed pectal efficiency of 3bp/z i a faily abitay etic. It i expected that iila tend will occu fo othe pectal efficiencie, but with a change in the abolute SNR value. A tend, wheeby the pefoance gain inceae a a function of the nube of ue i obeved. It i woth to note that eouce allocation i not conideed in the cae of SFBC chee. Thi i conitent to the popoed LTE tandad whee channel dependent cheduling i not applicable to the SFBC chee [5]. A notable diffeence between chee utiliing the additional patial diveity coponent and thoe who do not can be obeved. The pefoance gain ove the ingle ue cenaio can be tanlated into a powe aving at the BS. Theoetical eult how that depending on the degee of MUD exploitation, tanit powe fo the BS could be ignificantly educed, whilt attaining the ae aveage evice level.

5 V. SIMULATION RESULTS Figue 3 how the iulated pefoance of pectal efficiency of chee and diffeent MIMO pecoding chee in the downlink of 3GPP LTE. The pectal efficiency i deived fo the achievable aveage thoughput of all the ue given the taniion bandwidth. The achievable aveage thoughput i given by, Thoughput = R(1-PER) whee R and PER ae the bit ate and the eidual packet eo ate fo a pecific ode epectively. The thoughput envelope i obtained by uing ideal adaptive odulation and coding (AMC) baed on the (thoughput) optiu witching point. Siulated eult ae vey conitent with the theoetical eult. The iulation eult how that the pectal efficiency of MIMO pecoding chee ignificantly outpefo the chee. Beide that, in line with the theoetical eult the additional patial diveity of both MU-MIMO chee and LRB chee achieve a futhe pefoance gain of -3dB copaed to SU- MIMO and RB chee. Spectal Efficiency (bp/z) Rando Beafoing Layeed Rando Beafoing Patial Feedb. MU-MIMO SNR (db) Figue 3: Siulated Spectal Efficiency fo and Diffeent Pecoding Schee fo K =1 Pefoance Gain Ove Single Ue (db) No.of Ue SFBC Rando Beafoing Layeed Rando Beafoing Patial Feedb. MU-MIMO SFBC - Multiue Figue 4: Siulated Pefoance Gain of Multiue and othe MIMO Pecoding Schee ove Single Ue Scenaio Figue 4 how the iulated eult of the pefoance gain of ultiue and othe MIMO pecoding chee ove a ingle ue cenaio, a a function of the nube of ue at a fixed pectal efficiency of 3bp/z. The iulated eult atch with the theoetical tend of Figue. Figue 4 how that a ignificant gain i obtained by exploiting ultiue diveity, accounting to 7-8dB of the powe gain. Thi can be clealy obeved in the cenaio, whee in thi cae, the pefoance gain coe olely fo the MUD gain. In addition to that, oe gain can be achieved by uing MIMO taniion technique uch a SFBC and SM. Futheoe, conideable gain can be achieved by both MU-MIMO chee and LRB whee additional patial diveity i exploited. The ue of pecoding atice can optiie the peceived gain in the eceive to achieve the additional gain. It ha to be noted that eult of Figue 4 ae pecific to the pecific cenaio (3bp/z and K=1). Ganulaitie in the PY ode election and the diffeent SNR ange that aie fo iulation eult in diffeent ode being elected fo diffeent pecoding chee, which explain the deviation of the pefoance gain fo theoetical to iulation eult. It i woth noting howeve, that by uing AMC, actual iulation eult can outpefo theoetical expectation. VI. DISCUSSION The powe efficiency of a given chee can be aociated with a cot etic, K P k R, with a coeponding Jain k k= ` powe faine index (PFI). The PFI i defined a: K Pk K 1 K l k = 1 Rk Pk = PFI = (7) Rk Thi cot etic can be conideed a the aggegate powe equied fo achieving a pecified pectal efficiency. The lowe the cot etic the highe the powe efficiency i. A tadeoff i known to exit between powe efficiency and faine. Analyi in ection IV and V, ha hown that pecoding chee that hane the benefit of ultiue diveity to a highe degee equie le tanit powe fo the BS to achieve the ae thoughput. It i thu expected that thee chee will have a lowe powe utility, which tanlate ipoved powe efficiency. In Table 4 the cot function and the coeponding vaiance ove diffeent channel ealiation i peented. Thee eult ae in accodance with Figue and 4, howing that chee eploying a highe degee of diveity achieve the lowet cot in te of powe fo poviding a fixed aount of bit. It can alo be obeved that a oe equally ditibuted cot function i obtained fo the oe powe efficient chee. ence, a highe degee of ultiue diveity not only enue an oveall ipoveent in powe efficiency but alo ipove the eliability of the cot etiation. Thi ipoved eliability can be attibuted to the fact that deep fade occuing in wiele channel ae effectively eoved fo the aggegate eceived channel ignal at the BS [17]. Schee exploiting the additional patial laye fo diveity geneate a oe flat aggegate channel, eulting in fewe deep fade and hence in a oe pedictable channel epone. Table 4: Aveage and Vaiance of the cot etic fo Diffeent Pecoding Schee Cot Metic Vaiance Rando Beafoing Layeed Rando Beafoing Patial Feedb. MU-MIMO The PFI povide an indication of how faily powe i allocated to diffeent ue with epect to thei achieved ate. Figue 5 how the cuulative ditibution function of the PFI, eaued ove a nube of channel ealiation. A PFI value cloe to unity indicate a high degee of faine. Schee utiliing the additional patial laye, e.g. LRB and

6 MU-MIMO (full feedb. and patial feedb.) achieve an oveall highe powe allocation faine, with PFI value conitently cloe to unity. ACKNOWLEDGEMENTS The autho wih to acknowledge the financial uppot of Mobile VCE. Maio Nicolaou alo wihe to thank Tohiba Reeach Euope Liited fo it financial uppot. Figue 5: Powe Faine Index fo and Diffeent Pecoding Schee VII. CONCLUSIONS The concept of geen adio i to develop envionental fiendly, low-powe and enegy efficient olution fo futue wiele netwok. Thi pape invetigate the powe efficiency of a nube of MIMO taniion and pecoding technique, SFBC, RB, LRB,, and MU-MIMO with full and patial feedback. The analyi i pefoed on the downlink of a 3GPP LTE OFDMA yte and both nueical and iulation pefoance ae peented. A detailed feedback ovehead of diffeent MIMO chee i peented. In addition, the powe efficiency of the oveall yte and individual ue ae alo dicued and copaed fo diffeent MIMO pecoding tategie. Fo the popoed LTE yte, if no ulti-ue diveity i conideed, SFBC i a feedback fee MIMO taniion chee and achieve ignificant powe aving ove a yte. oweve, ince it doe not offe data ate ipoveent, the aving on cot pe bit i till liited. The capabilitie of thee MIMO pecoding tategie to exploit ultiue diveity in tie, fequency and pace doain vaie. It i obeved that inceaing ultiue diveity ignificantly ipove the powe efficiency. All MIMO chee benefit fo ultiue diveity and how ipoved powe efficiency a the nube of ue inceae. The MU-MIMO and LRB ae the ot powe efficient and fai chee a a eult of an additional laye patial ultiue diveity gain, although they have a lage feedback ovehead. Between MU-MIMO and LRB, MU-MIMO outpefo LRB in te of oveall powe efficiency and theefoe it i the ot powe cot efficient chee. REFERENCES [1] Mobile VCE Viion goup, Viion: Enabling the Digital Futue, Decebe 7. [] "Geen Teleco-Calling fo a Bette Futue," IDATE New 453, 5 Januay 9. [Online] &idp=334&idl=7 [3] 3GPP; Technical Specification Goup Radio Acce Netwok; (E- UTRA) and (E-UTRAN); Oveall Deciption; Stage (Releae 8), 3GPP TS 36.3 V8.8., Mach 9. [Online] [4] S. Alaouti, A Siple Tanit Diveity Technique fo Wiele Counication, IEEE JSAC, Vol. 16, No. 8, pp , 1998 [5] E. Dahlan,S. Pakvall, J. Skold, P. Being,' 3G Evolution: SPA and LTE fo Mobile Boadband', Acadeic Pe, 8 [6] C. an, A. Doufexi, S. Aou, J. A.-M. McGeehan, Joe, and Y. A.-S. Sun, Yong, "Rando Beafoing OFDMA fo Futue Geneation Cellula Counication Syte," VTC Fall 7. [7] C. an, M. Nicolaou, A. Doufexi, and S. Aou, "Reduced Feedback Oppotunitic and Layeed Rando Beafoing," IET Sat Antenna and Coopeative Counication Seina, London, UK, 7. [8] C. an, S. Aou, A. Doufexi, J. McGeehan, and Y. Sun, "Pefoance Analyi of Layeed Rando Beafoing OFDMA with Feedback Reduction," PIMRC, Sept. 7. [9] J. Chung, C.-S. wang, K. Ki, and Y. K. Ki, "A Rando Beafoing Technique in MIMO Syte Exploiting Multiue Diveity," IEEE Jounal on Selected Aea in Counication, vol. 1, pp , 3. [1] 3GPP, "Multiple Input Multiple Output (MIMO) antennae in UTRA (Releae 7)," vol. 7, TR [11]. Rohling and R. Gunheid, "Co Laye Conideation fo an Adaptive OFDM-Baed Wiele Counication Syte," Wiel. Pe. Coun., vol. 3 pp [1] Saung, "Downlink MIMO fo EUTRA."3GPP-TSG RAN WG1, Meeting#43, R [13] D. S. Bau, J. anen, and J. Salo, "An Intei Channel Model fo Beyond-3G Syte: Extending the 3GPP Spatial Channel Model (SCM)," VTC Sping 5. [14] "Spatial Channel Model fo MIMO Siulation," 3GPP TR V6.1., Sep'3 [Online] [15] M. Nicolaou, A. Doufexi, and S. Aou, "Pefoance Analyi fo Patial Feedback Downlink MIMO with Unitay Codebook Beafoing fo LTE," Intenational Wokhop on LTE Evolution, ICC 9, Deden, Geany. [16] R1-7114, "Uplink Ovehead fo CQI and MIMO Feedback in E- UTRA', uawei, RAN1 eeting #48, St. Loui, USA, Febuay, 7 [17] P. Viwanath, D. N. C. Te, and R. Laoia, "Oppotunitic beafoing uing dub antenna," Infoation Theoy, IEEE Tanaction on, vol. 48, pp ,. [18] Y. Liu and E. Knightly, "Oppotunitic Fai Scheduling Ove Multiple Wiele Channel," INFOCOM 3. Table 3: Feedback ovehead fo vaiou MIMO chee fo G= and M= Pefeed Laye 1 CQI Pefeed Laye CQI Altenative Laye 1 CQI Altenative Laye CQI Pefeed Matix Index Total bit pe PRB 5bit - 5 bit SFBC N/A (No MUD i conideed) - N/A RB 5 bit - 5bit LRB 5bit 5bit - 1bit 5 bit 5 bit bit 1 bit 5 bit 5 bit 5 bit 5 bit bit bit Patial Feedb. MU-MIMO 5 bit 5 bit - - bit 1 bit