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2 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 583 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 7 Ch Kyun Ng, Nor Kamarah Noordn, Borhanuddn Mohd Al, and Sudhanshu Shkhar Jamuar Dpartmnt of Computr and Communcaton Systms Engnrng, Faculty of Engnrng, Unvrst Putra Malaysa, Malaysa. Dpartmnt of Elctrcal Engnrng, Faculty of Engnrng, Unvrst Malaya, Malaysa. X. Introducton It s wll known that cllular mobl phon systms hav volvd from G and G that us frquncy and tm dvson multpl accss (FDMA and DMA) systms rspctvly, to cod dvson multpl accss (CDMA) of thrd gnraton (3G) systms (Chn t al., 6). Furthrmor, th xplotaton of spatal dvrsty from th mrgnc of advanc antnna tchnologs such as smart antnna and spac tm sgnal procssng hav gvn rs to nduc anothr multpl accss schm calld spac dvson multpl accss (SDMA) systms (Fang, ). Among ths schms, th systm capacty and spctrum ffcncy ar th ky factors to compar th prformancs of varous mobl communcaton systms. Snc rado frquncy (RF) spctrum s a lmtd rsourc, ths tchnqus hav approachd thr fundamntal lmtatons. Flxbl utlzaton of such rsourcs n spac, tm and cod has ld to grat mprovmnt n systm capacty. For a gvn bandwdth, th systm capacty for narrowband rado systms such as FDMA and DMA s dmnson or bandwdth lmtd. In contrast, th systm capacty of CDMA and SDMA systms s ntrfrnc lmtd. Any rducton n ntrfrnc n CDMA and SDMA systms convrts drctly and lnarly nto ncrasd capacty (Yu t al., 4), (Chn t al., 8). Multpl accss schms such as FDMA and DMA ncras thr systm capacty and spctrum ffcncy by dvdng th dffrnt ntwork plannng phass mor clarly nto ndvdual parts to allow dffrnt frquncs to b usd at dffrnt tm momnts (Castada & Lara, 8). In CDMA systms, th sam frquncy s usd smultanously n adjacnt clls and th ntrfrnc lvl should b takn nto account n th covragplannng phas (Nmla & Lmpann, 3). Furthrmor, cll splttng and sctorsaton to form SDMA systms wth us of drctonal antnna could also rsult n ncras of systm capacty and spctrum ffcncy ovr th omndrctonal antnna systm (Godara,

3 584 rnds n lcommuncatons chnologs 997). Although ths approachs do sgnfcantly ncras th systm capacty and spctrum ffcncy, ach schm bascally s attmptng a mor ffcnt us of th sam rsourc. It s wll known that CDMA systm s charactrzd as bng ntrfrnc lmtd. Indpndnt smultanous transmssons by mobl usrs at dffrnt locatons n a cll gv rs to th nar-far phnomnon. o combat th nar-far problm, powr control s usd to nsur qual sgnal lvls ar rcvd from all mobl usrs at dffrnt locaton (Hashm & Sousa, 997). hrfor, powr control s consdrd th most mportant systm rqurmnt for CDMA systms to ncras th systm capacty on th rvrs lnk by ovrcomng th nar-far problm (Camron & Wornr, 996), (Uthansakul, ). Snc all th clls can oprat wth th sam channl n CDMA cllular ntwork, a sgnfcant sourc of ntrfrnc apart from traffc n ts own cll s th traffc from nghbourng clls. hus, th systm capacty of CDMA systms s dtrmnd by th amount of co-channl ntrfrnc that t can tolrat, whch s comprsd of ntra-cll ntrfrnc and ntr-cll ntrfrnc (Wu t al., 998). If th traffc load n nghbourng clls s rducd, mor traffc can b accptd n th obsrvd cll (Chatovch & Jabbar, 999). Howvr, bcaus of powr control from obsrvd cll bas staton (BS), transmttng a hgh powr lvl n rvrs lnk may rsult n hgh ntrfrnc to nghbourng cll BS (Hashm & Sousa, 997). hrfor, n CDMA systms, f th capacty of a sngl cll ncrass t crats hghr ntrfrnc to ts nghbourng clls and thus mpacts thr capacty. Othr approach that shows a proms for substantal capacty nhancmnt s th us of spatal fltrng wth xplotaton of smart antnna at cll st BS (Zhng t al., 996). Hnc, th dploymnt of SDMA systm has bn rcognsd as on of th most promsng tchnqus for controllng co-channl ntrfrnc n cllular systms, ladng to th rqurd systm capacty mprovmnt (Lbrt & Rappaport, 998). h bamformng ablty of smart antnna tchnology has bn adaptd to ncras th gan of th dsrd sgnal whl null ntrfrnc sourcs rsultng n th mprovmnt of th systm capacty (Huang t al., ). h narrow bams from smart antnna ar strd toward dsrd usrs n ordr to fltr out ntrfrnc causd by co-channl usrs locatd n th sam cll and from adjacnt clls (Galvan-jada & Gardnr, ). Howvr, n ordr to achv an dal SDMA systm, smart antnna must carfully form ts radaton pattrns to captur th dsrd usr and to nullfy suffcntly ntrfrng usrs. hrfor, th smart antnna rqurs hgh accuracy n propagaton channl rspons stmaton (Cho t al., ). If thr ar N lmnts antnna array usd n a smart antnna systm, t s only possbl to accommodat N usrs n rvrs lnk (Rapajc, 998), (Km t al., ). Actually n th randomnss of mobl usrs dstrbuton, ths s not always possbl to lmnat ntrfrrs by null-strng n th corrspondng arrval drctons. Hnc, thr wll b a probablty of two or mor mobl usrs locatd nar to ach othr. hs mans that th co-channl ntrfrncs wll occur among ths mobl usrs whn adaptv bams strng smart antnna ar mployd. On th othr hand, th prsnt of sdlobs from smart antnna systm wll furthr rduc th sgnal to ntrfrnc rato (SIR) prformanc of ach mobl usr. Hnc, mor sdlobs ntrfrncs ar radatd n th drcton of th dsrd usr man lob pattrn. hs sdlobs ntrfrncs can sgnfcantly rduc th systm capacty f multpl bams ar synthszd from smart antnna to accommodat th dnsty of mobl usrs n a partcular ara.

4 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 585 h wrlss channl usually charactrzd by th path loss, shadowng and fadng (Furstn t al., 994). In urban aras, multpath propagaton s common, whrby th rcvr obsrvs a numbr of cops of th transmttd sgnal, ach wth a dffrnt tm dlay (Adach t al., 5). hs provds a form of multpath fadng. In a dgtal communcaton systm, th dlay-sprad of multpath propagaton could also caus ntrsymbol ntrfrnc (ISI) (Ln & Chrnakov, 998). h charactrstcs of th spradng squncs n CDMA systm provd a crucal ffct on th prformanc of th whol communcaton systms. hs sgnatur squncs n gnral dtrmn how much ntrfrnc s rcvd at a rcvr from othr mobl usrs and nflunc th xtracton capablty of th dsrd sgnal from nos-lk spctrum (X & Rahardja, 5). On th othr hand, snc th rvrs lnk of a CDMA systm s usually asynchronous, n th sns that th arrval tms for ach mobl usr sgnal ar dffrnt (hompson t al., 996), (Cho t al., 7). hrfor, th spradng squncs of CDMA systms ar charactrzd wth ISI as wll as multpl accss ntrfrnc (MAI) (Ptrson t al., 995), (Guo & Wang, 8). In multpath propagaton nvronmnt, multpl cops of transmttd sgnal arrv at rcvr wth dffrnt tm dlay wll caus ISI. A MAI occurs f th orthogonalty among spradng squncs s lost (Ishda t al., ). h MAI s causd by asynchronous n a CDMA systm whr ach mobl usr wll obsrv ntrfrnc from all othr mobl usrs n th systm, snc th transmttd sgnal wll not b orthogonal n dlay-sprad nvronmnt (hompson t al., 996). radtonal CDMA spradng squncs such as m-squnc (Golomb, 99), Gold cods (Gold, 967), and Kasam cods (Kasam, 966), xhbt non-zro cross-corrlaton whch rsults n hgh MAI n asynchronous rvrs lnk transmsson. Anothr famly of orthogonal cods s consttutd by Walsh cods (Harmuth, 97) and orthogonal Gold cods (Popovc, 997), do rtan thr orthogonalty n th cas of prfct synchronzaton, but also xhbt non-zro cross-corrlaton n asynchronous transmsson (W t al., 5). Rcntly, an attractv famly of larg ara synchronzd (LAS) CDMA spradng squncs s ntroducd n (L, 3) has xhbtd zro corrlaton zon (ZCZ) or ntrfrnc fr wndow (IFW) nar zro dlay tm offst, rsultng n zro ISI and MAI wthn th IFW. h LAS spradng squnc s consttutd by th combnaton of Larg Ara (LA) cod (L, 999) and Loosly Synchronous (LS) cod (Staňczak t al., ). Mor spcfcally, th ntrfrnc-fr n CDMA systm only bcom possbl whn th maxmum channl-nducd dlay-sprad s wthn th dsgnd IFW duraton. Howvr, n th systm dsgn spcally usng omndrctonal antnna, not all multpath sgnal componnts arrv wthn IFW tm offst. Snc th total duraton of IFW xprssd n trms of th numbr of chp ntrvals dpnd on th mnmum zro paddng mplantd btwn non-zro pulss ntrval, thus th numbr of mnmum zro paddng must b ncrasd to maxmum dlay-sprad of th channl n LAS squnc n ordr to accommodat all multpath sgnal componnts. hs mpls that th duty rato of LAS spradng squncs s low whn th numbr of mnmum zro paddng s ncrasd. hrfor, a spcfc drawback of LAS-CDMA s that ts rlatvly ffcnt orthogonal cods dmandd n wrlss systms ar lmtd, and hnc rduc ts spctrum ffcncy. Bsds that, th mplmntaton of LAS squncs s vry complx that addtonal componnts ar ncssary. hr hav bn many multpl accss systms for th cllular systm dsgnd to mprov ts systm prformanc. Svral works hav bn carrd out to show th mprovmnt n th systm capacty usng th jont multpl accss systm. A carful slcton of jonts

5 586 rnds n lcommuncatons chnologs multpl accss from two or mor ndvdual systms can dtrmn th ftnss of th jont systm. Intrfrnc-lmtd systms such as CDMA and SDMA ar suscptbl to tm of arrval (OA) and angl of arrval (AOA) of ndvdual usr sgnals. hus, a non-unform traffc can svrly dgrad th prformanc of CDMA and SDMA systms. In ths chaptr, a jont multpl accss of CDMA and SDMA systm s proposd. h prformanc of ths jont multpl accss systm s also vulnrabl to th non-unform traffc. Although th prformanc of ths jont multpl accss systm has bn prvously studd n svral paprs (Lbrt & Rappaport, 994), (Naqub t al., 994), (Buracchn t al., 996) and (Ng & Sousa, 998), non of thm consdrs to valuat th most ralstc of systm prformanc n ths jont multpl accss. In ths chaptr, a nw approach calld dynamc spac-cod multpl accss (DSCMA) systm arsng from th combnaton of CDMA and SDMA systms s dsgnd, and ts systm prformancs ar thn nvstgatd. An nnovatv approach to lmnat th xstng ntrfrncs n DSCMA systm s ntroducd. h spradng squncs of Larg Ara Synchronous Evn rnary (LAS-E), whch xhbtd an ntrfrnc fr wndow (IFW) n thr corrlaton, ar xplotd hr. h spatal sgnatur from smart antnna narrowr bam s xplotd to drv all th multpath propagaton sgnals to arrv wthn th IFW n rvrs lnk transmsson. h sz of IFW s adaptabl wth th sz of smart antnna bamwdth through dynamc spac-cod (DSC) algorthm. hrfor, th rsult of combnd domnant sgnatur from DSCMA systm wll yld a prfct ntrfrnc cancllaton so that th systm capacty ncrass dramatcally.. h Proprts of Orthogonal CDMA Squncs radtonal ways of sparatng multpl accss sgnals n tm or frquncy such as DMA and FDMA ar rlatvly smpl by makng sur that th sgnals ar orthogonal and nonntrfrng. Howvr, n CDMA dffrnt mobl usrs occupy th sam bandwdth at th sam tm. hy ar sparatd from ach othr through th us of a st of orthogonal squncs. wo wavforms x and y ar sad to b orthogonal to ach othr f thr crosscorrlaton, R xy () ovr prod s zro n tm shft (L, 998), whr R xy ( ) lm x( t) y( t ) dt () In dscrt tm, th two squncs x and y ar orthogonal f thr cross product R xy () ovr prod s zro (Wang t al., 7). h cross product of R xy ( ) s dfnd as R xy ( ) x( t) y( t ) () As an xampl, th followng two squncs or cods, x and y ar orthogonal. x,,, (3) y,,, (4)

6 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 587 Hnc, thr cross-corrlaton s zro. R xy () = ( )( ) + ( )(+) + (+) (+) + (+) ( ) = (5) In ordr for th st of cods to b usd n a multpl accss schm, an addtonal proprty s ndd. In addton to th zro cross-corrlaton proprty, ach cod n th st of orthogonal cods must hav an qual numbr of +s and s (Faruqu, 996). hs scond proprty gvs that partcular cod th psudorandom natur. A drct squnc CDMA (DS-CDMA) systm sprad th basband data by drctly multplyng th basband data pulss wth a pudorandom or PN squnc that s producd by a PN cod gnrator. A sngl puls or symbol of th PN wavform s calld a chp, whr th chp rat s much hghr than th data bt rat (L, 99).. Wlch Bound n CDMA Systms h CDMA systm s a multpl accss schm n whch svral ndpndnt usrs accss a common communcaton channl by modulatng thr data symbols wth prassgnd spradng squncs. h rcvr obsrvs th sum of th transmttd sgnals n addtv wht Gaussan nos (AWGN) channl. h dcodr for a gvn mobl usr trats th sum of th ntrfrng sgnals from othr mobl usrs as nos. h spradng squncs ar chosn to crat good sngl usr channls for th ndvdual codng systms. In fact, howvr, th channl cratd by th spradng squncs s suscptbl to MAI (Rupf & Massy, 994). In 974, Wlch n (Wlch, 974) had shown that th lowr bound for th accptabl sdlobs of auto-corrlaton and cross-corrlaton functons ar st around SF, whr SF s th spradng factor or procssng gan of th systm. hs lowr bound s calld as Wlch bound (L, 3). Sgnatur squncs that maxmz th sum capacty n th uplnk of CDMA systms n AWGN channl ar known to satsfy Wlch s bound on th total squard corrlaton wth qualty (Hath t al., 4).. LAS-E Squncs h orgnal LAS cods proposd n (L, 999) ar synthszd by sdng LS cods n LA cods to mprov t spctrum ffcncy. An N LA cods ar synthszd n such a mannr that th p N p non-zro pulss from m-squncs orntd ar postond as shown n abl. hs arrangmnt forms a confguraton of LA N, K, L ) whr K s th ( p c mnmum numbr of zro paddng n puls ntrval of non-zro pulss whch dtrmn th sz of IFW dlay-sprad n trm of chps, whl havng a total cod lngth of L chps. c

7 588 rnds n lcommuncatons chnologs C C C C C C C C C C C C C C C C abl. h arrangmnt of 6 LA(6,38,847) squncs In ordr to xplot th charactrstcs of LA squncs proposd n (L, 999) wthout altrng th sz of ts IFW, a modfd vrson of th squnc such LAS-E squncs (Ng t al., 9) s mployd n DSCMA nstad of LAS-CDMA squncs proposd n (L, 3) whch xhbt a small IFW. Fgur shows th corrlaton proprts of th LAS E 6,38,88 squncs. As can b sn n ths fgurs, th corrlaton proprts of LAS E 6,38,88 squncs ar smlar to th orgnal proposd 6,38,847 LA squncs whch xhbtd a larg IFW around th orgn. h cross-corrlaton valu of LAS E 6,38,88 squnc n zro dlay sprad s 4.3 x -7. (a)

8 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 589 Fg.. Corrlaton proprts of cross-corrlaton. (b) LAS E 6,38,88 squnc; (a) auto-corrlaton and (b) 3. Rvrs Lnk Capacty of SDMA Systm h convntonal SDMA systms ncras ts capacty by spatal fltrng th ntrfrncs. h systm contnuously adapts ts narrowr bam from smart antnna systm to str ach mobl usr wth th man lob whl solatng ntrfrncs wth nulls. Hnc, SDMA s allowd to rus th lmtd rado rsourcs (frquncy, tm and cod) wthn a cll. From Equaton () n (Ng t al., 8), th nulls AOA, of th SDMA radaton pattrn occur at nulls nulls cos h N (6) whr N s th numbr of lmnts n smart antnna systm, s progrssvly phas shft, and h s any ntgr but not qual to, n, n,.. Fgurs a and b show th typcal SDMA systm for N = 8 and 3 rspctvly wth 9 o AOA of th dsrd usr. For N = 8, th nulls to accommodat ntrfrng usrs ar occurrd at 4.4 o, 6 o, 75.5 o, 4.48 o, o and o, whl th nulls for N = 3 ar occurrd at.36 o, 8.96 o, o, 4.4 o, o, 5.3 o, o, 6 o, 64.6 o, o, 7.79 o, 75.5 o, 79.9 o, 8.8 o, 86.4 o, 9 o, o, 97.8 o,.8 o, 4.48 o, 8. o,. o, 5.94 o, o,

9 59 rnds n lcommuncatons chnologs 4.3 o, 8.68 o, o, o, o, 5.5 o and o. hs fgurs show that th systm capacty, K of SDMA systm s drct proportonal to th numbr of antnna lmnts n smart antnna wth xprsson blow (Rapajc, 998) K (7) N h ntrfrng usrs ar only allowd to b locatd at null AOAs, othrws co-channl ntrfrncs btwn mobl usrs wll occur. Any addtonal mobl usr nto ths systm aftr th lmtd nulls ar fully occupd wll also caus co-channl ntrfrnc to othr mobl usrs. (a) (b) Fg.. Radaton pattrn of SDMA systm for (a) N = 8 and (b) N = 3.

10 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 59 It has bn rportd that smart antnna can synthsz a hgh drctv bam toward th dsrd usr whl nullng th ntrfrng usrs to ncras capacty. Howvr, fully nullng th ntrfrng usrs n SDMA systm do not tak plac bcaus thr ar two major ntrfrnc sourcs, whch ar sd-lobs and co-channl ntrfrncs. h ntrfrng usrs wll not always locat at th nulls of th dsrd usr radaton pattrn spcally n randomly dstrbutd traffc nvronmnt as shown n Fgur 3. Fg. 3. Co-channl and sd-lobs ntrfrncs to th dsrd usr, C from randomly locatd ntrfrng usrs of,, 3, 4,.., 6 4. Dynamc Spac Cod Multpl Accss (DSCMA) Systm Non-unformly dstrbutd traffc usually dgrads th prformanc of CDMA and SDMA systms svrly n th rvrs lnk. h mprfct corrlaton proprts of th tradtonal CDMA spradng squncs rsult n ISI and MAI at non-zro dlay sprad. h random postons of mobl usrs wll caus MAI among thm n th SDMA systm, whr postons at nulls of th dsrd usr radaton pattrn ar rarly achvd. hrfor, th non-unform traffc causs loss of orthogonalty to dstngush ach mobl usr n th convntonal ntrfrnc lmtd systms. Hr, a promsng soluton to dploy th BS wth smart antnna systm to prform th jont multpl accss of CDMA and SDMA systms s proposd. h CDMA and SDMA systms ar adaptd to ach othr dynamcally to form DSCMA systm. hs proposd multpl accss schm s a novl ntrfrnc cancllaton schm that mploy th spradng squncs of CDMA systm nto spatal sgnaturs of SDMA systm through DSC algorthm. In DSC algorthm, th sz of ddcatd IFW from LAS-E sprad squnc s

11 59 rnds n lcommuncatons chnologs adaptd dynamcally to th sz of half powr synthszd bamwdth from smart antnna bamformng systm as shown n Fgur 4. In ths jont multpl accss schm, ach usr s assgnd an LAS-E squnc wthn a hgh drctvty bam. Hnc, th ntgraton of ths two sgnatur schms, spatal fltrng and spradng squnc, crats a domnant sgnatur schm calld DSC sgnatur. hrfor, by usng ths domnant sgnatur schm, th nhrnt ntrfrncs n CDMA and SDMA systms nvronmnt can b lmnatd. Fg. 4. Prformanc of varous bamwdths n smart antnna systm ovr IFW rgon from LAS E 6,38,88 squncs. corrlaton proprty of As shown n prvous scton, th co-channl ntrfrnc btwn two mobl usrs n SDMA systm occurs whn both of thm ar locatd clos to ach othr. For xampl, assumng that th dsrd usr, C s locatd at AOA of 9 o to th smart antnna axs whl othr mobl usrs ar randomly locatd wthn th AOA of o to 8 o as shown n Fgur 3. It s obsrvd that th th usr s bam s locatd vry nar to C wth only.6 o sparaton. hs phnomnon causs co-channl ntrfrnc btwn thm whl othr mobl usrs also contrbut ntrfrncs to C through thr sdlobs radaton pattrn. It s possbl to mtgat ths co-channl ntrfrncs by CDMA spradng squncs. Howvr, all tradtonal CDMA spradng squncs ar slf-ntrfrnc systms whn all sgnals from ach mobl usr arrv at th BS n asynchronous mannr. h auto-corrlaton and crosscorrlaton proprts of tradtonal CDMA squncs ar not orthogonal at non-zro dlay

12 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 593 sprad,. hus, t shows that ntrfrnc occur among th mobl usrs n asynchronous transmsson nvronmnt. hrfor, t s ncssary to prfr spradng squncs that xhbt zro corrlaton btwn ach othr to drv all th asynchronous sgnal componnts to drop wthn th smart antnna s narrow bam maxmum propagaton dlay sprad. Hnc, a spradng squnc that xhbts larg sz of IFW s rqurd to accommodat larg bamwdth of smart antnna radaton pattrn. Consdrng Fgur 3 agan, thr s group of bams wth thrs AOA rspctvly to accommodat 7 randomly dstrbutd mobl usrs. Each bam s assgnd to dffrnt mobl usr wth an LAS squnc ordr, C, C, C3, C4, C5,, Cm, whr m s th maxmum numbr of total avalabl squnc. hs squncs ar assgnd to mobl usrs n chronologcal ordr upon thr arrval and can b rusd dynamcally whnvr ndd. o llustrat how drctv bam can mprov th rvrs lnk n a sngl cll of DSCMA systm, consdr th cas n whch ach mobl usr has an omndrctonal antnna, and th BS tracks ach mobl usr n th cll usng a drctv bam. Assum that th bam pattrn, G n formd such that th pattrn has a maxmum gan n th AOA of th dsrd usr. Such a drctv pattrn can b formd usng an N lmnts smart antnna array. Assum that K usrs n th sngl cll of DSCMA systm ar non-unformly dstrbutd throughout a cll. On th rvrs lnk, th powr rcvd from th dsrd usr sgnal s P r, wth maxmum gan of G. h rcvd powrs from K ntrfrng usrs ar gvn by r for,,..., K. hn th avrag total rcvd ntrfrnc powr, I sn at th dsrd usr AOA, at th BS s gvn by P, whr AOA of th dsrd usr. h valu of K I E G P r, (8) G s th th ntrfrnc gan lvl of smart antnna radaton pattrn sn at th al., 8) and s gvn as G can b obtand from Equaton () n (Ng t sn N k cos G ( ) (9) N sn k cos whr k s gvn as.5 for half wavlngth spacng btwn lmnts to avod th apparanc of gratng lob n th systm, and paramtr s th phas shft of th smart antnna to str th bam n drcton of th ntrfrng usr. If th prfct powr control s appld such that th rcvd powr at th BS antnna from ach mobl usr s th sam, thn Pr, Pc for ach of K usrs, and hnc th avrag ntrfrnc powr sn by th dsrd usr s gvn by K I Pc E G ()

13 594 rnds n lcommuncatons chnologs 5. Rvrs Lnk Intrfrncs n DSCMA Systm In DSCMA systm, a BS quppd wth smart antnna transmts sgnal to ach mobl usr n forward lnk transmsson usng a synthszd narrow bam and a ddcatd spradng squnc. h sgnal s prfctly synchronzd at transmsson so that t arrvs at mobl rcvr n synchronsm wth zro dlay sprad. Consquntly, du to th orthogonalts of both spatal sgnatur and spradng squnc n zro dlay sprad among th K usrs n a cll, ach mobl rcvr can dmodulat ts own sgnal wthout ntrfrnc from othr transmttd sgnals that shar th sam channl. Howvr, ths synchronsm n forward lnk transmsson cannot b mantand n rvrs lnk transmsson whr all th sgnals from K usrs ar rathr arrvd at BS n asynchronzd mannr. hus, th sgnals from th othr mobl usrs appar as addtv ntrfrnc to th dsrd usr sgnal f th orthogonalts of both spatal sgnatur and spradng squnc among thm ar loss n non-zro dlay-sprad. h rvrs lnk ntrfrncs ar twofold: th ntrfrnc arsng from K usrs n th sam cll or can b known as ntra-cll ntrfrnc, and th ntrfrnc arsng from mobl usrs n nghbourng clls or also calld as ntr-cll ntrfrnc. Hnc, th systm capacty of DSCMA s xamnd by consdrng both ntra-cll and ntr-cll ntrfrnc nvronmnts n rvrs lnk transmsson. 5. Intra-cll Intrfrnc Suppos that ach cll has K randomly dstrbutd mobl usrs. Wth th us of prfct nstantanous powr control, all K usr sgnals ar arrvng at th BS wth th sam powr lvl S wthn th sam cll. hrfor, th ntra-cll ntrfrnc, I nt from K ntrfrng usrs s gvn as I ra ( K ) S () nt In DSCMA systm, th K ntrfrncs powr lvl ar not sam n th AOA of th dsrd usr,. Nvrthlss, th ntrfrng sgnals from K usrs ar stll rcvd at th sam powr lvl S from thrs rspctv AOA through prfct powr control. Most of ths ntrfrng sgnals contrbut mrly sd-lob ntrfrncs wth G S n drcton. Som of th ntrfrng sgnals ar also rcvd at th sam powr lvl, whn thy ar at th sam AOA of th dsrd usr. G S h arbtrarly ntrfrncs lvl, G as shown n Fgur 3 wth 6 ntrfrng usrs can b analogously as multpl dots along th ln of radaton pattrn as shown n Fgur 5. hs s assumng that all radaton pattrns for all mobl usrs ar sam. Hnc, from (9) I ylds to and (), th ntra-cll ntrfrnc n AOA of mobl usr C, I nt ra K K nt ra S sn N( k cos( ) / ) ( ) S G ( ) () N sn( k cos( ) / ) ra

14 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 595 Fg. 5. h analogously random sd-lobs ntrfrncs from 6 ntrfrng usrs n AOA of th dsrd usr 5. Intr-cll Intrfrnc In th mult-cll of DSCMA systm, th ntrfrnc analyss n rvrs lnk bcoms complcatd. hs s bcaus th mobl usrs ar powr controlld by thr own cll BS. h mmbrshp of th usr s dtrmnd by th maxmum plot sgnal powr among th clls and not th mnmum dstanc from a cll BS. h mobl usrs ar connctd to a BS that offrs th lowst sgnal attnuaton rathr than th closst BS (Glhousn t al., 99). Bcaus of powr control, th ntrfrnc lvl rcvd from mobl usrs n nghbourng clls dpnds on two factors: attnuaton n th path to th dsrd usr's cll BS, and attnuaton n th path to th mobl usr's cll BS. hus, n th fourth powr law of dstanc, th usr s transmttd powr P t can b xprssd as (Chatovch & Jabbar, 999) P P r 4 ( ) t r (3) whr P r s th rcvd sgnal powr at ts BS, s th log-normal Gaussan random varabl wth zro man and standard dvaton, of 8 db, and r s th dstanc from th mobl usr to BS. Snc only avrag powr lvls ar consdrd, th ffcts of multpath I n DSCMA, consdr an fadng ar gnord. o valuat ntr-cll ntrfrnc, nt r

15 596 rnds n lcommuncatons chnologs ntrfrng usr locatd n mth nghbourng cll at a dstanc r m from ts bas staton and r from th dsrd usr bas staton BS as shown n Fgur 6. BS m Fg. 6. Intr-cll ntrfrnc nvronmnt modl. If P t s ts transmt powr, th rcvd powr S at ts BS s gvn by PG ( ) S (4) t m m ( m ) 4 rm whr Gm ( m ) s th antnna gan n th AOA of th ntrfrng usr to ts cll BS m, and s th Gaussan random varabl rprsntng th shadowng procss n ts cll. hn th ntrfrnc I rcvd at BS s gvn by m I PG ( ) (5) t m ( ) 4 r whr G ( m ) s th antnna gan of BS n th AOA of th th ntrfrng usr from mth nghbourng cll to BS, and s th Gaussan random varabl rprsntng th shadowng procss n th dsrd usr cll. Hnc, from (4) and (5), th ntrfrnc to sgnal rato, I/S s gvn by I S r r m 4 G G ( ) m ( m ) ( m ) m (6)

16 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 597 whr th frst trm s du to th attnuaton causd by dstanc and blockag to th gvn BS, whl th thrd trm s th ffct of powr control to compnsat for th corrspondng attnuaton to ts BS. Snc and ar ndpndnt thr dffrnc has zro man and m varanc (Coopr & Nttlton, 978). h scond trm rvals th total antnna gan rcvd n th AOA of th ntrfrng usr to th BS, and ts valu s lss than unty. In DSCMA, ths scond trm wll only has a maxmum valu whn an ntrfrng usr from a nghbourng cll s locatd at th sam AOA of th dsrd usr,. hn G ( ) n (6) wll bcom 6 K m m m sn N ( k cos( m ) / ) G ( m ) (7) N sn( k cos( ) / ) For all valus of th paramtrs n (6), I S s lss than unty. If ts valu s not lss than unty thn th usr would swtch to th othr cll BS. hrfor, I n DSCMA s nt r found by summng (6) for all mobl usrs n th frst tr nghbourng clls I 6 K ( ) S r G ( ) (8) m m ( m ) nt r m r ( ) m Gm m whr Gm ( m ) = whch th gan to thrs mobl usr s DSCMA Systm Sgnallng o smplfy th drvaton, only th basband sgnal of transmttd sgnal s bng consdrd. Hnc, n DSCMA systm, th transmttd sgnal from th th usr, s (t) that occups th th spradng squnc for,,..., K can b wrttn as s ( t) Pd ( t) c ( t) t (9) Assumng that th dsrd usr s usr and all th othr K usrs ar ntrfrng usrs. h r t s a sum of th transmttd sgnals from all K usrs and corruptd by ts rcvd sgnal, addtv complx Gaussan thrmal nos, n (t) n an AWGN channl. h sgnal of ach mobl usr arrvs at a dffrnt propagaton dlay,. hus, th rcvd sgnal at th BS quppd wth smart antnna bamformng ntwork n th AOA of usr can b xprssd as K K ), t s t G ( ) nt P G ( d t c t nt r () whr G ) dnots as th radaton pattrn gan of th usr n th AOA of usr. hs ( quaton sgnfs th combnaton of CDMA and SDMA by th trms G ). Whn (

17 598 rnds n lcommuncatons chnologs G ( ) s normalzd to, th gnratd G ) wll b lss than f th th ntrfrng usr ( s not locatd at th sam AOA as usr. For a convntonal CDMA systm, G ) wll tak th valu of. hs sgnal s thn dsprad wth th spradng squnc of usr at th rcvr. A corrlaton-basd dtctor s usd to obtan th approprat dcson, z whch can b drvd as z ( r(, t) c ( t dt () ) whr s th squnc synchronzaton rror, whch dgrads th auto-corrlaton proprts. If prfct synchronzaton s assumd as n th cas of drctonal antnna, whr th multpath fadng ffct s nglctd, thn. hus, Equaton () lads to z r(, t) c ( t) dt P G ( ) d n( t) c( t) S I ( t) c ( t) K P G ( ) d ( t ) c ( t ) c ( t) dt () 7. Probablty of Error Evaluaton n DSCMA Systm ovr AWGN Channl A bt rror rat (BER) xprsson for DSCMA s drvd ovr MAI from th othr K usrs n an AWGN channl. h drvaton s prformd at th basband lvl, whch wll smplfy th analyss. From th prvous scton, th frst trm of (), S s th transmttd sgnal of usr, whr S P G ( ) d ( t) c ( t dt (3) ) Consdrng that G ( ), c ( t) and d, thus Equaton (3) bcoms S P (4) h trm n () s th nos componnt du to n (t) n AWGN channl, whch corrsponds to th dsprad trm of n (t) attrbuts to n t c t dt (5)

18 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 599 Snc n (t) s th zro man AWGN havng a varanc of N man Gaussan varabl and a varanc of Var, whch s drvd as, thus s also a zro Var[ ] E[ ] E n( t) c ( t) dt n( u) c( u) du E[ n( t) n( u)] c ( t) c ( u) dtdu (6) But E [ n( t) n( u)] s th auto-corrlaton of n (t), whr N E[ n( t) n( u)] ( t u) (7) hrfor, th varanc of (6) bcoms N Var[ ] N c N ( t u) c ( u) du ( t) c ( u) dtdu (8) h trm I n () s th MAI componnt of th K ntrfrrs, whch s gvn by I K P G ( ) d ( t ) c ( t ) c ( t) dt (9) Snc c ( t ) c ( t) dt s cross-corrlaton btwn squncs c and c, thus and d ( t ), thrfor I s rducd to c ( t ) c ( t dt R (3) ), K I P G ( R (3) ), h sgnal to ntrfrnc plus nos rato (SINR) s thn gvn as S SINR Var I (3)

19 rnds n lcommuncatons chnologs 6 hrfor, from (4), (8) and (3), th SINR for th DSCMA systm can b xprssd as,,, ) ( ) ( ) ( K K K R G P N P R G P N R G P N P SINR (33) Snc th ampltud of ach mobl usr s sgnal s P, thn th nrgy pr bt s P E b. h Equaton (33) lads to, ) ( K b R G N E SINR (34) Assumng that th combnng nos and ntrfrnc componnts hav a Gaussan dstrbuton, thn th BER s gvn as, ) ( K b R G N E Q SINR Q BER (35) whr Q(x) s th Gaussan Q-functon. For th ntrfrnc lmtd of DSCMA systm whr thrmal nos s not a factor du to N E SF N E c b (36) whr th rsultant of N E b s larg nough to caus th thrmal nos bcom nglgbl. hrfor, Equaton (35) s rducd to, ) ( K G R Q BER (37) whch s a xprsson of BER prformanc n DSCMA ovr AWGN channl.

20 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 6 8. BER Prformanc and Systm Capacty n DSCMA Systm wo dffrnt typs of BS antnna, omndrctonal antnna and smart antnna ar xplotd for BER prformanc comparson through smulaton. h systm smulaton wll valuat th BER prformanc of DSC algorthm n DSCMA by consdrng ntrfrnc from both ntra-cll and ntr-cll ntrfrncs. h BER xprssons ovr ths ntrfrncs hav bn drvd n th prvous scton. From ths BER xprssons th systm capacty n DSCMA can b stmatd by lookng at th numbr of mobl usrs that th systm can support at. BER (BER < -3 ). Snc th cll s splt nto thr sctors, th ntr-cll ntrfrnc sourcs ar only consdrd from two nghbourng clls for ach sctor. h systm chp rat s.88 Mcps rsultng at a data rat of 4.8 Kbps for squnc lngth of about 56 chps pr bt. hs data rat s usd to transmt th multmda typ data. h data transmsson wll go through a wrlss channl wth fourth powr of dstanc loss and 8 db shadowng. h voc actvty factor s not takn nto consdraton n ths smulaton. h systm paramtrs for th systm smulaton ar summarsd n abl. Cll radus, R Unty Numbr of sctors pr cll 3 Numbr of ntrfrng nghbourng clls pr sctor yp of data Multmda Spradng factor, SF About 56 Systm chp rat, W.88 Mcps Data rat, R 4.8 Kbps Path loss xponnt 4. Standard dvaton of shadowng, abl. Summary of th systm paramtrs h radaton pattrn of a smart antnna rprsnts gans of dffrnt AOA along a o azmuth span sctor. It s assumd that K sparat narrow bams and K dffrnt spradng squncs can b gnratd from BS and drctd to ach of K usrs wthn a sctor of ntrst. Assum that a sctor antnna bamwdth s o n th thr sctors pr cll confguraton. hs bamwdth sz attrbuts to a maxmum xcss dlay, max of 4 chps for chp rat, R c of.88 Mcps n sparaton of Km. hus, th corrlaton proprty, R, of th spradng squncs btwn th ntrfrng usr and th dsrd usr s randomly takn wthn 4 chps dlay sprad. Nvrthlss, whn th smart antnna s xplotd, th bamwdth bcoms narrowr as a functon of th numbr of lmnts, N. Hnc, th maxmum xcss dlay, max of ths narrowr bam wll b rducd. h maxmum xcss dlay, max for th smart antnna systm wth dffrnt numbr of lmnts, N has bn shown n abl 3. 8 db

21 6 rnds n lcommuncatons chnologs Numbr of lmnts, N Bamwdth, BW ( o ) Maxmum angular sprad, max ( o ) Maxmum xcss dlay, max ( s ) (chp) abl 3. Prformanc of smart antnna for varous N hs tabl showd that th narrowr bam of a smart antnna wll rduc th OA of a transmttd sgnal. hs mpls that th maxmum xcss dlay of a channl can b rducd whn mor lmnts n a smart antnna systm s xplotd. o analys th systm prformanc n DSCMA, all th smulatons ar xcutd by consdrng smart antnna systms wth N = 4, 8, 6, 3, 64 n th channl modls of AWGN, Raylgh fadng, and fadng wth dvrsty gan. h smulatons also consdr spradng squncs such as m-squnc, Gold, Walsh-Hadamard and LAS-E for prformanc comparson n DSCMA systm. For th smulaton n AWGN channl, Equaton (37) from prvous scton s usd to analys th BER prformanc n DSCMA systm. Fg. 7. BER prformanc of CDMA systm for varous spradng squncs

22 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 63 For comparson purposs, th BER of convntonal CDMA and SDMA systms wll b th frst to b valuatd. In th CDMA systm, th omndrctonal antnna gan, G ) for all mobl usrs ar normalzd to on n th whol sctor. hrfor, th BER of th CDMA systm s valuatd basd on th corrlaton proprty of th spradng squncs. Fgur 7 shows th BER prformanc of CDMA systm for varous spradng squncs. h systm capacty of th CDMA systm for ths spradng squncs for BER < -3 ar shown n abl 4. ( Squncs Capacty, N u (BER < -3 ) m-squnc 8 Gold 9 Walsh-Hadamard 58 LAS-E 4 abl 4. Systm capacty of CDMA systm for varous spradng squncs On th othr hand, n th SDMA systm, th corrlaton proprty, R, s normalzd to on bcaus t s not a factor of mprovmnt n th convntonal SDMA systm. h only paramtr that s usd to valuat BER prformanc of SDMA systm s th antnna gan of ntrfrng usrs, G ) n th drcton of th dsrd usr. hs antnna gans of ntrfrng usrs ar ( takn randomly from th radaton pattrn of smart antnna wthn th o sctor. Fgur 8 shows th BER prformanc of th convntonal SDMA for varous antnna bamwdths. h SDMA systm capacty of BER < -3 for varous bamwdths s gvn n abl 5. Fg. 8. BER prformanc of SDMA systm for varous numbrs of lmnts

23 64 rnds n lcommuncatons chnologs Numbr of lmnts, N Capacty, N u (BER < -3 ) abl 5. Systm capacty of SDMA systm for varous numbrs of lmnts In th AWGN channl, t s ncssary for DSCMA to prform n prfct synchronous mannr to obtan th orthogonalty among th mobl usrs n zro dlay sprad. Howvr, prfct synchronsms rarly xst bcaus ach mobl usr sgnal arrvs at BS rcvr wth dffrnt dlay. hrfor, th orthogonalty btwn spradng squncs s no longr hld n non-zro dlay sprad. h BER prformanc of th DSCMA systm n AWGN channl for varous spradng squncs, vs m-squnc, Gold, Walsh-Hadamard and LAS-E squncs ar shown n Fgurs 9a - 9d rspctvly. In ach fgur, th BER prformanc s valuatd by xplotng th smart antnna wth dffrnt numbr of lmnts, N = 4, 8, 6, 3 and 64 lmnts. Addtonally, th systm capacty of th DSCMA systm basd on BER < -3 for ths spradng squncs ar shown n abls 6a - 6d rspctvly. Fg. 9a. DSCMA systm BER prformanc for m-squnc wth dffrnt numbr of antnna lmnts, N n AWGN channl

24 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 65 Numbr of lmnts, N Capacty, N u (BER < -3 ) abl 6a. DSCMA systm capacty of BER < -3 for m-squnc wth dffrnt numbr of antnna lmnts, N n AWGN channl Fg. 9b. DSCMA systm BER prformanc for Gold squnc wth dffrnt numbr of antnna lmnts, N n AWGN channl Numbr of lmnts, N Capacty, N u (BER < -3 ) abl 6b. DSCMA systm capacty of BER < -3 for Gold squnc wth dffrnt numbr of antnna lmnts, N n AWGN channl

25 66 rnds n lcommuncatons chnologs Fg. 9c. DSCMA systm BER prformanc for Walsh-Hadamard squnc wth dffrnt numbr of antnna lmnts, N n AWGN channl Numbr of lmnts, N Capacty, N u (BER < -3 ) x x x x 5 abl 6c. DSCMA systm capacty of BER < -3 for Walsh-Hadamard squnc wth dffrnt numbr of antnna lmnts, N n AWGN channl

26 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 67 Fg. 9d. DSCMA systm BER prformanc for LAS-E squnc wth dffrnt numbr of antnna lmnts, N n AWGN channl Numbr of lmnts, N Capacty, N u (BER < -3 ) 4.4 x x x x x 34 abl 6d. DSCMA systm capacty of BER < -3 for LAS-E squnc wth dffrnt numbr of antnna lmnts, N n AWGN channl All th valuatd systm capacts n DSCMA systm hr ar basd on th ntrfrnc lvl that th systm can tolrant. Hnc, ths attand rsults ar not th dal systm capacty prformanc. hr ar som othr factors nd to b consdrd n conformng to ths ssu such as th totally bandwdth avalabl, th numbr of spradng squncs that can b synthszd, and th lmtaton of systm sgnal procssng. hrfor, all th attand rsults ar only sutd for th comparson purpos and ar not rprsntng th ral scnaro. In gnral, t shows that th DSCMA systm prformanc s mprovd wth spradng squncs of m-squnc, Gold, Walsh-Hadamard and LAS-E n ascndng ordr as n

27 68 rnds n lcommuncatons chnologs convntonal CDMA systm. hs s bcaus th man squar corrlaton proprty, E for,,3,..., K btwn (K ) ntrfrng usrs and th dsrd usr ar dcrasd n ascndng ordr from ths spradng squncs. Furthr mprovmnt s xhbtd whn th numbr of lmnts, N n smart antnna s ncrasd as n convntonal SDMA systm. hs s bcaus th ntrfrnc gan factor, G ) for,,3,..., K n th drcton of ( th dsrd usr, s rducd du to th fact that th sdlob lvls of ntrfrng usrs radaton pattrn prsntd n drcton s dcrasd whl th numbr of nulls s ncras whn th numbr of lmnts n smart antnna s ncras. All th nrgs from hghr numbr of antnna lmnts, N ar transformd nto hgh gan n th man lob of smart antnna. It can b sn that thr s consdrabl mprovmnt whn th bamwdth of th smart antnna bcom narrowr. h narrowr bam from hghr numbr of antnna lmnts, N also contrbuts to th ntrfrnc rducton du to th fact that th probablty of usrs bam ntrfr to ach othr s low n narrowr bam compard to wdr bam. hrfor, hghr systm capacty can b obsrvd n DSCMA whn numbr of lmnts, N s ncrasd. And ths mprovmnt can achv as hgh as.9 x 34 usrs pr sctor whn LAS-E squncs togthr wth DSC algorthm ar usd. On th othr hand, ths s ntrstng to fnd that n tradtonal spradng squncs, thr systm prformancs suppos to b appard n randomnss bcaus of non-unform dstrbuton n thr corrlaton proprty wthn th concrnd dlay-sprad. hs s obvously occurrd n m-squncs. R, 9. Concluson It can b concludd that non-unform traffcs can svrly dgrad th prformanc of CDMA and SDMA cllular systms. h DSCMA systm dscrbd n ths chaptr s a doubl sgnaturs systm that can dstngush mor usrs by cancllng th xstng ntrfrnc n multpath nvronmnt. hs multpl accss systm uss LAS-E squncs to crat IFW nar zro dlay sprad n ts cross-corrlaton functon. In ordr to nsur all th sgnal componnts drop wthn th IFW, a narrow bam wth hghr drctvty smart antnna systm s xplotd. h sz of IFW s adaptd to th smart antnna half-powr bamwdth usng DSC algorthm. hrfor, all th ntrfrncs nducd n non-unform traffcs can b dramatcally rducd n DSCMA systm and thus rsultng n hghr systm capacty.. Rfrncs Adach, F., Garg, D., akaoka, S. & akda, K. (5). Broadband CDMA tchnqus, IEEE Wrlss Communcatons, vol., no., pp Buracchn, E. t al. (996). Prformanc Analyss of A Mobl Systm Basd on Combnd SDMA/CDMA Accss chnqu, IEEE 4th Intrnatonal Symposum on Sprad Spctrum chnqus and Applcatons Procdngs, vol., pp Camron, R. & Wornr, B. (996). Prformanc Analyss of CDMA wth Imprfct Powr Control, IEEE ransactons on Communcatons, vol. 44, pp

28 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 69 Castada-Camacho, J. & Lara-Rodrguz, D. (8). ltraffc Analyss of an Ovrlad Systm Usng CDMA and DMA Wth Cll Covrag Ara Rstrcton, IEEE ransactons on Vhcular chnology, vol. 57, no., pp Chatovch, A. & Jabbar, B. (999). Effct of Non-unform raffc Load on Erlang Capacty of CDMA, IEEE 49th Vhcular chnology Confrnc Procdngs, vol., pp Chn, H. H., Chu, H. W. & Guzan, M. (6). Orthogonal Complmntary Cods for Intrfrnc-Fr CDMA chnologs, IEEE Wrlss Communcatons, vol. 3, no., pp Chn, H. H., Chu, H. W. & Guzan, M. (8). On Nxt Gnraton CDMA chnologs: h REAL Approach for Prfct Orthogonal Cod Gnraton, IEEE ransactons on Vhcular chnology, vol. 57, no. 5, pp Cho, K. t al. (). Novl Smart Antnnas for Applyng SDMA to Cllular Mobl Communcaton Systms, IEEE Antnnas and Propagaton Socty Intrnatonal Symposum Procdngs, vol. 4, pp Cho, W., Andrws, J. G. & Hath, R. W. (7). Multusr Antnna Parttonng for Cllular MIMO CDMA Systms, IEEE ransactons on Vhcular chnology, vol. 56, no. 5, Part, pp Coopr, G. R. & Nttlton, R. W. (978). A Sprad Spctrum chnqu for Hgh Capacty Mobl Communcatons, IEEE ransactons on Vhcular chnology, vol. V-7, pp Fang, X. (). Mor Ralstc Analyss for Blockng Probablty n SDMA Systms, IEE Procdngs Communcatons, vol. 49, no. 3, pp Faruqu, S. (996). Cllular Mobl Systms Engnrng, Norwood, MA, Artch Hous. Furstn, M. t al. (994). Path Loss, Dlay Sprad, and Outag Modls as Functons of Antnna Hght for Mcrocllular Systm Dsgn, IEEE ransactons on Vhcular chnology, vol. 43, no. 3, pp Galvan-jada, G. M. & Gardnr, J. G. (). hortcal Modl to Dtrmn th Blockng Probablty for SDMA Systms, IEEE ransactons on Vhcular chnology, vol. 5, no. 5, pp Glhousn, K. S. t al. (99). On h Capacty of A Cllular CDMA Systm, IEEE ransactons on Vhcular chnology, vol. 4, no., pp Godara, L. C. (997). Applcatons of Antnna Arrays to Mobl Communcatons, Part I: Prformanc Improvmnt, Fasblty, and Systm Consdratons, Procdngs of th IEEE, vol. 85, no. 7, pp Gold, R. (967). Optmal Bnary Squncs for Sprad Spctrum Multplxng, IEEE ransactons on Informaton hory, vol. 3, no. 4, pp Golomb, S. W. (99). Shft Rgstr Squncs, Aqan Park Prss. Guo, D. & Wang, C. C. (8). Multusr Dtcton of Sparsly Sprad CDMA. IEEE Journal on Slctd Aras n Communcatons, vol. 6, no. 3, pp Harmuth H. F. (97). ransmsson of Informaton by Orthogonal Functons, Sprngr- Vrlag. Hashm, B. & Sousa, E. (997). On th Capacty of a Cllular DS/CDMA Systm undr Slow Multpath Fadng and Fxd Stp Powr Control, IEEE 6th Intrnatonal Confrnc on Unvrsal Prsonal Communcatons Rcord, vol., pp

29 6 rnds n lcommuncatons chnologs Hath, R. W. t al. (4). Constructon of Equangular Sgnaturs for Synchronous CDMA Systms, IEEE 8th Intrnatonal Symposum on Sprad Spctrum chnqus and Applcatons Procdng, pp Huang, C. t al. (). A Jont Multpl Accss Schm for Uplnk Channls of CDMA Systms, Intrnatonal Confrncs on Info-tch and Info-nt (ICII ) Procdngs, vol., pp Ishda, Y. t al. (). Wdband CDMA Bas Staton wth Co-channl Intrfrnc Cancllr, IEEE 5st Vhcular chnology Confrnc (VC -Sprng) Procdngs, vol., pp , okyo. Kasam. (966). Wght Dstrbuton Formula for Som Class of Cyclc Cods, chncal Rport R-85 (AD 63574), Coordnatd Scnc Laboratory, Unv. of Illnos, Urbana. Km, S. W. t al. (). Prformanc of Smart Antnnas wth Adaptv Combnng at Handsts for th CDMA Systm, Intrnatonal Confrnc on hrd Gnraton Wrlss and Byond Procdng, San Francsco, pp L, W. C. Y. (99). Ovrvw of Cllular CDMA, IEEE ransactons on Vhcular chnology, vol. 4, no., pp L, W. C. Y. (998). Mobl Communcatons Engnrng, McGraw Hll. L, D. (999). A Hgh Spctrum Effcnt Multpl Accss Cod, Ffth Asa-Pacfc Confrnc on Communcatons and Fourth Optolctroncs and Communcatons Confrnc (APCC/OECC '99) Procdngs, vol., pp L, D. (3). h Prspctvs of Larg Ara Synchronous CDMA chnology for th Fourth-Gnraton Mobl Rado, IEEE Communcatons Magazn, vol. 4, no. 3, pp Lbrt, J. C. Jr. & Rappaport,. S. (994). Analytcal Rsults for Capacty Improvmnts n CDMA, IEEE ransactons on Vhcular chnology, vol. 43, no. 3, pp Lbrt, J. C. Jr. & Rappaport,. S. (998). Smart Antnnas for Wrlss Communcatons, Prntc Hall PR, Uppr Saddl Rvr, NJ. Ln, S. Y. & Chrnakov, M. (998). Analytcal Approach for Multpath Dlay Sprad Powr Dstrbuton, IEEE Global lcommuncatons Confrnc (GLOBECOM 98) Procdngs, h Brdg to Global Intgraton, vol. 6, pp Nagub, A. F. t al. (994). Capacty Improvmnt wth Bas-Staton Antnna Arrays n Cllular CDMA, IEEE ransactons on Vhcular chnology, vol. 43, no. 3, pp Ng, B. & Sousa, E. S. (998). Prformanc Enhancmnt of DS-CDMA Systm for Wrlss Local Loop, IEEE Intrnatonal lcommuncatons Symposum (IS) Procdngs, vol., pp Ng, C. K., Noordn, N. K., Khatun, S., Mohd Al, B., Jamuar, S. S. & Ismal, M. (8). Drctonal Dvrsty of Smart Antnna n LAS CDMA Systms, Wrlss Prsonal Communcatons, Sprngr Nthrlands, vol. 46, pp Ng, C. K., Noordn, N. K., Mohd Al, B., Jamuar, S. S. & Ismal, M. (9). Spctrum Effcncy Enhancmnt n Dynamc Spac Codd Multpl Accss (DSCMA) Systm, Wrlss Prsonal Communcatons, Sprngr Nthrlands, 99-6 (Prnt) X (Onln), DOI.7/s

30 Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm 6 Nmla, J. & Lmpann, J. (3). Impact of th Bas Staton Antnna Bamwdth on Capacty n WCDMA Cllular Ntworks, h 57th IEEE Smannual Vhcular chnology Confrnc (VC 3-Sprng) Procdngs, vol., pp Ptrson, R. L. t al. (995). Introducton to Sprad Spctrum Communcatons, Prntc Hall Intrnatonal Edton. Popovc, B. M. (997). Effcnt Dspradrs for Mult-cod CDMA Systms, IEEE 6th Intrnatonal Confrnc on Unvrsal Prsonal Communcatons Rcord, vol., pp Rapajc, P. B. (998). Informaton Capacty of h Spac Dvson Multpl Accss Mobl Communcaton Systm, IEEE 5th Intrnatonal Symposum on Sprad Spctrum chnqus and Applcatons Procdngs, vol. 3, pp Rupf, M. & Massy, J. L. (994). Optmum Squnc Multsts for Synchronous Cod- Dvson Multpl-Accss Channls, IEEE ransactons on Informaton hory, vol. 4, no. 4, pp Stańczak, S. t al. (). Ar LAS-Cods a Mracl?, IEEE GLOBECOM Procdngs, vol., (San Antono, xas), pp , Novmbr. hompson, J. S. t al. (996). Smart Antnna Arrays for CDMA Systms, IEEE Prsonal Communcatons, pp Uthansakul, P. & Uthansakul M. (). Numbr of Elmnts n Smart Antnna Systm Effcts on Both Prfct and Imprfct Powr Control for Rvrs Lnk of CDMA Cllular Systm, h Intrnatonal chncal Confrnc on Crcuts/Systms, Computr and Communcatons Procdngs, haland. Wang, X., Ahonn,. & Nurm, J. (7). Applyng CDMA chnqu to Ntwork-on-Chp, IEEE ransactons on Vry Larg Scal Intgraton (VLSI) Systms, vol. 5, no., pp W, H. t al. (5). Intrfrnc-Fr Broadband Sngl and Multcarrr DS-CDMA, IEEE Communcatons Magazn, vol. 43, no., pp Wlch, L. R. (974). Lowr Bounds on th Maxmum Cross Corrlaton of Sgnals, IEEE ransactons on Informaton hory, vol. I-, pp Wu, J. S. t al. (998). Hot-Spot raffc Rlf wth A ltd Antnna n CDMA Cllular Ntworks, IEEE ransactons on Vhcular chnology, vol. 47, no., pp X, S. & Rahardja, S. (5). Prformanc Evaluaton for Quatrnary DS-SSMA Communcatons wth Complx Sgnatur Squncs ovr Raylgh-Fadng Channls, IEEE ransactons on Wrlss Communcatons, vol. 4, no., pp Yu, J. t al. (4). Rvrs-Lnk Capacty of Powr-Controlld CDMA Systms wth Bamformng, IEEE ransactons on Vhcular chnology, vol. 53, no. 5, pp Zhng, Z. t al. (996). Capacty Improvmnt wth Bas Staton Antnna Arrays n Cllular CDMA, IEEE 46th Vhcular chnology Confrnc, Mobl chnology for th Human Rac Procdngs, vol., pp

31 6 rnds n lcommuncatons chnologs

32 rnds n lcommuncatons chnologs Edtd by Chrstos J Bouras ISBN Hard covr, 768 pags Publshr Inch Publshd onln, March, Publshd n prnt dton March, h man focus of th book s th advancs n tlcommuncatons modlng, polcy, and tchnology. In partcular, svral chaptrs of th book dal wth low-lvl ntwork layrs and prsnt ssus n optcal communcaton tchnology and optcal ntworks, ncludng th dploymnt of optcal hardwar dvcs and th dsgn of optcal ntwork archtctur. Wrlss ntworkng s also covrd, wth a focus on WF and WMAX tchnologs. h book also contans chaptrs that dal wth transport ssus, and namly protocols and polcs for ffcnt and guarantd transmsson charactrstcs whl transfrrng dmandng data applcatons such as vdo. Fnally, th book ncluds chaptrs that focus on th dlvry of applcatons through common tlcommuncaton channls such as th arth atmosphr. hs book s usful for rsarchrs workng n th tlcommuncatons fld, n ordr to rad a compact gathrng of som of th latst fforts n rlatd aras. It s also usful for ducators that wsh to gt an up-to-dat glmps of tlcommuncatons rsarch and prsnt t n an asly undrstandabl and concs way. It s fnally sutabl for th ngnrs and othr ntrstd popl that would bnft from an ovrvw of das, xprmnts, algorthms and tchnqus that ar prsntd throughout th book. How to rfrnc In ordr to corrctly rfrnc ths scholarly work, fl fr to copy and past th followng: Ch Kyun Ng, Nor Kamarah Noordn, Borhanuddn Mohd Al, and Sudhanshu Shkhar Jamuar (). Dynamc Spac-Cod Multpl Accss (DSCMA) Systm: A Doubl Intrfrnc Cancllaton Multpl Accss Schm n Wrlss Communcatons Systm, rnds n lcommuncatons chnologs, Chrstos J Bouras (Ed.), ISBN: , Inch, Avalabl from: Inch Europ Unvrsty Campus SP R Slavka Krautzka 83/A 5 Rjka, Croata Phon: +385 (5) Fax: +385 (5) Inch Chna Unt 45, Offc Block, Hotl Equatoral Shangha No.65, Yan An Road (Wst), Shangha, 4, Chna Phon: Fax: