Single-Carrier Frequency Domain Adaptive Antenna Array for Distributed Antenna Network

Transcription

1 Sngle-Cae Fequeny Doman Aaptve Antenna Aay fo Dstbute Antenna etwok We Peng Depatment of Eletal an Communaton ohoku Unvesty Sena, Japan Fumyuk Aah Depatment of Eletal an Communaton ohoku Unvesty Sena, Japan Abstat In ou pevous stuy, we popose a sngle-ae fequeny oman aaptve antenna aay (SC-FDAAA) fo e onventonal ellula netwok. It has been pove at e SC- FDAAA an effetvely suppess e ntefeng sgnals fom oe uses n a seveely fequeny seletve fang hannel. In s pape, we stuy e SC-FDAAA fo stbute antenna netwok (DA) an two DA SC-FDAAA shemes ae popose. hey ae, namely, stbute SC-FDAAA an unfe SC- FDAAA. he pefomanes of e two DA SC-FDAAA shemes ae ompae by ompute smulatons an e esults show at e unfe SC-FDAAA has bette bt eo ate (BER) pefomane. Keywos-stbute antenna netwok; uplnk eteton; fequeny oman aaptve antenna aay I. IRODUCIO he taget ata ate fo e next geneaton weless ommunaton system s up to 1Gbps. o ealze suh a hgh ata ate, ee ae two majo poblems. On one han, ue to e mult-pa fang, e weless hannel s haateze by sevee fequeny seletvty [1]. As a esult, t s neessay to suppess e nte-symbol ntefeene (ISI) at e eeve. he ISI an be suppesse by tme oman equalzaton tehnques suh as maxmum lkelhoo sequene estmaton (MLSE) [2]. Howeve, when e ata ate neases, e numbe of esolvable pas neases as well an hene, e omplexty of MLSE gows exponentally. Compae to e tme oman equalzaton tehnques, e fequeny oman equalzaton (FDE) has muh less omplexty whh s not a funton of e hannel fequeny seletvty. On e oe han, e ata tansmsson between e moble use an e base staton (BS) suffes fom e ntefeene fom e n-ell uses as well as e o-hannel ntefeene (CCI) [3] (e n-ell ntefeene an CCI togee s alle mult-aess ntefeene (MAI)). In ou pevous stuy [4], we have popose a sngle-ae fequeny oman aaptve antenna aay (SC-FDAAA) algom fo e uplnk tansmsson fo onventonal ellula systems. It has been shown at e SC-FDAAA algom an aheve goo pefomane n e pesene of MAI n a seveely fequeny seletve fang hannel. On e one han, huge tansmt powe wll be eque to ealze e hgh ata ate f e ell oveage s kept unhange. On e oe han, f e tansmt powe s kept unhange, en e ell oveage has to be eue geatly. Dstbute antenna netwok (DA) [4] was popose as a soluton to nease e ell oveage whle mantanng e low tansmt powe. In e DA, a numbe of antennas ae stbute n eah ell an stbute antennas ae onnete w e DA ental poesso (whh s smla to e BS n e onventonal ellula system). he moble use an ommunate w e neaby loate antennas even when t s at e ell ege. heefoe, e tansmt powe n e DA an be kept low whle e oveage of e ell an be geatly nease. In s pape, we wll stuy e SC-FDAAA fo DA. wo DA SC-FDAAA shemes wll be popose. By usng stbute SC-FDAAA, e SC-FDAAA weght fo eah atve luste of antennas wll be geneate espetvely an en e post SC-FDAAA sgnals wll be ombne; whle by usng e unfe SC-FDAAA, e AAA weght fo all atve lustes of antennas wll be unfomly geneate. he pefomane of e popose DA SC-FDAAA shemes wll be onfme an ompae by ompute smulatons. he est of e pape s oganze as follows. he system moel of DA wll be esbe n Seton II. he two DA SC-FDAAA shemes wll be popose n Seton III. An smulaton esults fo e ahevable bt eo ates (BER) ae shown n Seton IV. Fnally, e pape wll be onlue by Seton V. II. SYSEM MODEL he same ae fequeny s euse n ffeent ells to utlze e lmte spetum effently [5]. he ellula systems w fequeny euse fatos (FRFs) of 1, 3, 4 an 7 ae shown n Fg. 1. he ommonly use fst laye CCI moel s use hee,.e., only e CCI fom e fst laye neghbong ells wll be onsee an e numbe of CCI wll be B =6. In aton, DA s assume n eah ell an e DA stutue s shown n Fg. 2. he stbute lustes of antennas ae onnete to e DA ental poesso by optal fbes. o lowe e ost, eah luste s smply ompose of multple /10/$ IEEE 264

2 antennas an e sgnal poessng wll be ae out by e DA ental poesso. It s assume at ee ae D atve lustes of antennas an eah antenna luste s equppe w antennas; ee ae U uses wn eah ell an eah use s equppe w one omn antenna. SC-FDAAA tansmsson s a blok tansmsson. A blok fang hannel between eah use an eah luste of antennas s assume,.e., e hannel emans unhange ung e tansmsson peo of a blok. In s pape, e symbol-spae sete tme epesentaton of e sgnal s use. Assumng an L pa hannel, e mpulse esponse of e hannel between e u use an e m antenna of e luste an be expesse as Moble use DA Cental Poesso Optal fbe h L, (1) ( τ ) = h δ ( τ τ ) u, m, u, m,, l l l = 0 whee h u, m,, l an τ l ae e pa gan an tme elay of e l pa, espetvely. h u, m,, l follows e omplex Gaussan = 1, whee E{} L stbuton an satsfes { } 1 E h 2 l = 0 u, m,, l epesents e expetaton. It s assume at e tme elay s a multple ntege of e symbol uaton an τ l = l. he ylpefxe (CP) blok sgnal tansmsson s use to make e eeve symbol blok to be a ula onvoluton of e tansmtte symbol blok an e hannel mpulse esponse as well as to avo nte blok ntefeene (IBI). It s assume at e CP s longe an e maxmum pa elay of e sgnal. In e followng, we omt e nseton an emoval of e CP fo e smplty. Fgue 2 DA stutue. he baseban equvalent eeve sgnal blok m, ( t) ; t = 0 ~ of symbols at e m antenna of e { } antenna luste s gven by L = δ ( ) t P h s t l m, 0 0, 0, m,, l 0 l = 0 U L uδu, u, m,, l u u= 1 l = 0 + P h s t l B U L, u δ, u, u, m,, l u m, = 1 u = 0 l = 0 + P h s t l + n t l, (2) whee su ( t ) an P u ae e tansmt sgnal an tansmt sgnal powe of e u use ( u = 0 ~ U ), espetvely; an P, u s e tansmt sgnal an tansmt sgnal powe of e u use n e s u o-hannel ell; δ 0, epesents e stane between e ese use an e antenna luste; δ epesents e stane between e ntefeng use, an e luste;, u, δ an h,,, u m l s e stane an hannel gan between e CCI use an e luste. α epesents e pa loss exponent n B. o smplfy e analyss, no shaowng loss s assume. nm, ( t ) s e atve whte Gaussan nose (AWG). Let e tansmt sgnal fom e u = 0 use be e ese sgnal, an e tansmt sgnals fom e oe uses be e ntefeng sgnals. he fequeny oman epesentaton of (2) s gven by Fgue 1 Cellula system. whee U = + R k H k S k H k S k m, 0, m, 0 u, m, u u= 1 B U = 1 u = 0 + H k S k + k u, m,, u m,, (3) 265

3 1 Su ( k) = Pu δu, su ( t)exp j2 k π t = 0 1 S, u ( k) = P,, exp 2 u δ u s u t j k π t = 0 L (4) Hu, m, ( k ) = hu, m,, l exp j2π k. l = 0 t = 0 L Hu,,,,, exp 2 m k = hu m l j π k l = 0 t = m, ( k) = nm, ( t)exp j2π k t = 0 he fst tem n (3) s e ese sgnal, e seon tem s e MAI, e tem s e CCI an e last tem s e nose omponent. he eeve sgnal veto at e luste R ( k ) = R0, ( k ), R1, ( k ) L R 1, k s en expesse n e veto fom as U ( k ) = 0, ( k ) S0 ( k ) +, ( k ) S ( k ) R H H u u u= 1 B U = 1 u = 0 ( k ) S ( k ) ( k ) + H +, u,, u whee Hu, ( k ) = Hu,0, ( k ) Hu,1, ( k ) L Hu, 1, k an ( k) ( k ) ( k ) L ( k ) w [ ] = 0, 1,, epesentng e tanspose opeaton. III. DA SC-FDAAA In s seton, e SC-FDAAA algom fo onventonal ellula system wll be esbe at fst; en e stbute SC-FDAAA an unfe SC-FDAAA fo e DA wll be popose. A. SC-FDAAA he tanseve stutue of e SC-FDAAA fo e uplnk tansmsson n onventonal ellula system w antennas at e eeve s shown n Fg. 3. Afte e -pont fast Foue tansfom (FF), e eeve sgnal s tansfome nto e fequeny oman sgnal an AAA weght ontol s en pefome on eah fequeny. he objetve of e AAA weght ontol s to suppess e MAI as well as e ISI so at e sgnal to ntefeene plus nose ato (SIR) an be maxmze [4]. -pont nvese FF (IFF) s en use to obtan e tme oman sgnal estmate fo ata eson. (5) Fg. 3 SC-FDAAA uplnk tansmsson B. Dstbute SC-FDAAA fo DA he stbute SC-FDAAA eeve s shown n Fg. 4. At fst, FDAAA weght ontol s pefome on eah luste of antennas. ake e antenna luste as an example, e eeve sgnal s fst tansfome to e fequeny oman sgnal as gven n (3) ~ (5). SC-FDAAA weght ontol s en pefome on eah fequeny as = W R R% k k k (6) whee ( k ) W ( k ),, W ( k ) W =,0 L,. he AAA R% k ; = 0, L, D ae ombne as weghte sgnals { } Rˆ k = G k R % k. (7) whee ( k ) G ( k ) G ( k ) ( k ) R ( k ),, R ( k ) R % % L %. G, L, D an = 0 D = 0 he AAA weght at mnmze e mean squae eo (MSE) between R% ( k ) an e efeene sgnal S0 ( k ) (e plot sgnal wll be use as e efeene sgnal) s gven by [6] ( k ) = ( k ) ( k ) W C C, (8),, { } whee ( k ) = E ( k ) ( k ) C R R s e oelaton matx of, e eeve sgnal an ( k ) = E ( k ) S ( k ) { } C R s e, 0 oss-oelaton veto between e eeve sgnal an e efeene sgnal, an enotes omplex onjugate opeaton. he tme oman sgnal blok estmate s en obtane by - pont IFF fo ata eson, gven by 1 1 ˆ ˆ t = R( k ) exp j2π k. (9) k = 0 266

4 Cluste D-1 Cluste 0 - FF - FF - FF - FF WD 1 ( k ) W 0 ( k ) Fgue 4 Dstbute DA SC-FDAAA. C. Unfe SC-FDAAA fo DA he unfe SC-FDAAA eeve s shown n Fg. 5. In stea of pefomng SC-FDAAA on eah atve luste of antennas, e eeve sgnals fom all e atve lustes of antennas ae poesse unfomly. he unfe FDAAA weght s geneate by e DA ental poesso. In s stuy, pefet synhonzaton among e lustes of antennas s assume fo smplty. In ou futue wok, e e-synhonzaton poblem wll be aesse. G ( k ) - IFF & Data Deson weght at mnmzes e MSE between R ( k ) efeene sgnal S ( k ) s gven by 0 ( k ) ( k ) ( k ) % an e W = C C, (11) k = E{ k k } { 0 } whee C R R an C k = E R k S k. he unfe SC-FDAAA weghte sgnals n (11) s en fe to e -pont IFF an e tme oman sgnal blok estmate s en obtane fo ata eson, gven by 1 1 ˆ ˆ t = R ( k ) exp j2π k. (12) k = 0 IV. SIMULAIO RESULS In s seton, e pefomane of e stbute SC-FDAAA an unfe SC-FDAAA shemes fo DA wll be nvestgate by smulatons. he ellula stutues usng FRF =1, 3, 4 an 7 shown n Fg. 1 wll be onsee. he paametes use n e smulatons ae lste n ab. I. In s stuy, e sheulng among all lustes of antennas s not onsee an up to two ( D = 1, 2 ) atve lustes of antennas, whh ae anomly loate n a ell, ae assume fo smplty. he sheulng algom an moe omplate stuaton emans as e tops of ou futue wok. ABLE I. SIMULAIO PARAMEER Fgue 5 Unfe SC-FDAAA fo DA. he fequeny oman sgnal on e k fequeny afte e unfe SC-FDAAA weght ontol s gven by W R % =, (10) R k k k = 0 D whee ( k ) W ( k ),, W ( k ) W L s e D 1 weght ontol veto an R k R0,0L R 1,0, 0,1 1,1,, R LR L R0, DL R, D s = e fequeny oman eeve sgnal veto whh omposes of (3) fom all e atve lustes of antennas. he AAA Channel Moulaton Channel Moel QPSK Fequeny seletve blok Raylegh fang umbe of pas L = 16 Powe elay pofle Unfom Pa loss α = 3.5 umbe of o-hannel ells B = 6 umbe of antennas of moble use 1 umbe of uses pe ell U = 2 Use loaton stbuton umbe of antennas n eah luste Ranom = 4 umbe of atve lustes D = 1, 2 Dstbuton of lustes Ranom FF (IFF) ponts = 256 At fst, one atve luste of antennas s use an e BER pefomane of e uplnk tansmsson as a funton of tansmt sgnal to nose ato (SR) s shown n Fg. 6. It s shown at bette BER pefomane s aheve when lage 267

5 FRF s use. he eason s at when FRF neases, e CCI powe eues ue to e nease stane between e CCI use an e eeve antennas. Howeve, only a slght BER pefomane mpovement an be seen by neasng e FRF fom 4 to 7 an e two uves of FR=7 an 4 s vey lose to eah oe. hs s beause when e FRF beome lage an lage, e CCI powe beomes too weak to affet e BER pefomane. heefoe, e BER pefomane an not be fue mpove by neasng e FRF. Aveage BER Uplnk ansmsson wo atve lustes of antennas (D)=2 Unfe SC-FDAAA Dstbute SC-FDAAA 10-1 FRF=1 FRF=3 FRF=4 FRF= FRF=1 FRF=3 FRF=4 FRF= ansmt SR(B) Aveage BER 10-3 Uplnk ansmsson One atve antenna luste (D=1) Fgue 7 Pefomane ompason between stbute SC-FDAAA an unfe SC-FDAAA when two atve lustes of antennas ( D =2) ae use ansmt SR(B) Fgue 6 Uplnk BER pefomane when one atve luste of antennas ( D =1) s use. ext, two atve lustes of antennas ae use an e stbute SC-FDAAA sheme an unfe SC-FDAAA sheme ae stue an ompae as shown n Fg. 7. he uplnk aveage BER pefomane by usng e stbute SC- FDAAA sheme s epesente by sol uves. It s obseve at: 1) e aveage BER pefomane of two atve lustes of antennas ase has been mpove ove e ase of one atve antenna luste; s mpovement omes fom e vesty gan obtane fom e atonal luste of antennas. he uplnk aveage BER pefomane by usng e unfe SC- FDAAA sheme s epesente by e otte uves. It s obseve at: 2) e unfe SC-FDAAA sheme aheves muh bette pefomane an e stbute SC-FDAAA sheme. Howeve, to ealze e unfe SC-FDAAA sheme, e unfe weght ontol s moe omputatonally omplate. In aton, goo synhonzaton among ffeent antenna lustes s eque fo bo shemes. In s stuy, pefet synhonzaton has been assume an how to synhonze e atve antenna lustes emans as ou futue wok. V. COCLUSIOS In s pape, we have stue SC-FDAAA fo DA an popose two DA SC-FDAAA shemes. he stbute SC- FDAAA sheme pefoms e weght ontol on eah atve luste of antennas an en ombnes e weghte sgnals; whle e unfe SC-FDAAA sheme pefoms e weght ontol on e eeve sgnals fom all e atve lustes of antennas. he BER pefomane of e two popose shemes has been stue by ompute smulatons. It has been shown at 1) e BER pefomane wll be mpove by usng lage FRF, howeve, e pefomane an not be fue mpove when FRF s lage an 4, 2) bo e stbute SC-FDAAA an unfe SC-FDAAA aheve bette pefomane an e one atve luste of antennas ase, an 3) e unfe SC- FDAAA sheme aheves bette pefomane an e stbute SC-FDAAA sheme. In aton, e spetum effeny may egae as FRF neases an eefoe, how SC-FDAAA an mpove e spetum effeny s an mpotant futue stuy. Refeenes [1] J. G. Poaks, Dgtal Communatons, fou eton, ew Yok: MGaw Hll, [2] R. Pe an P. E. Geen, A Communaton ehnque fo Multpa Channels, Po. IRE, vol. 46, pp , Mah [3] F. Aah, K. akea,. Obaa,. Yamamoto an H. Matsua, Reent avanes n sngle-ae fequeny-oman equalzaton an stbute antenna netwok, IEEE ICICS 2009, pp.1-5, Mah [4] W. Peng an F. Aah, Fequeny Doman Aaptve Antenna Aay Algom fo Sngle-ae Uplnk ansmsson, IEEE PIMRC 2009, pp. 1-5, Sept [5] W. Peng an F. Aah, Mult-use hyb FRF algom fo ownlnk ellula MIMO systems, IEEE PIMRC, pp , Sept [6] J. H. Wntes, Sgnal Aquston an akng w Aaptve Aays n e Dgtal Moble Rao System IS-36 w Flat Fang, IEEE ans. Vehula ehnology, vol. 42, pp , ov