Fig. 6. SIR distribution for different number of sectors per cell

Transcription

1 0 0 setors per ell: setors per ell: 0 setors per ell: For 0 B (no fing), B n B s the stnr evition, the 99%-overge SIR is B,. B, n. B respetively. A onfiene nlysis for ifferent sees for lognorml fing shows vrition of up to 0. B for the 99% overge SIR vlue for the referene se. Pro.( SIR < siss) SIR (B) Fig.. SIR istriution for ifferent numer of setors per ell Pro.( Downlink SIR < siss) s.. of log norml fing: 0 B s.. of log norml fing: B s.. of log norml fing: B s.. of log norml fing: B s.. of log norml fing: 0 B Downlink SIR (B) Fig.. SIR istriution for ifferent vlues of stnr evition for lognorml show fing VI. CONCLUSION We hve shown tht setor-se resoure llotion is roust sheme tht uses the omintion of iretionl ntenns n re-use to effetively omt o-hnnel interferene in fixe wireless systems. For resonle hoies of system prmeters n SIR of out to B, the sheme elivers high throughput (with n effetive reuse ftor of one), while permitting given n of frequenies to e re-use in every setor of every ell. This sheme hs very ttrtive fetures suh s flexile setor plnning n flexile re-use ptterns for irregulr ell lyout, non-uniform trffi ensity, n esy pity growth. REFERENCES. T. K. Fong, P. S. Henry, K. K. Leung, X. Qiu n N. K. Shnkrnrynn, Bnwith Allotion in Fixe Bron Wireless Networks, Pro. of the th WINLAB Workshop on Thir Genertion Wireless Networks, New Brunswik, NJ, Mrh 0-, 99, pp.9-; revise version epte for pulition in IEEE Trns. on Communition.. X. Qiu n K. Chwl, Resoure Assignment in Fixe Wireless System, IEEE Commun. Letters, Vol., No., pp. 0-0, July 99.. K. K. Leung n A. Srivstv, Dynmi Resoure Allotion for Bron Servies in Fixe Wireless Networks, Multiess, Moility, n Teletrffi for Personl Communitions, D. Everitt n M. Rumsewiz (Eitors), Kluwer Aemi Pulishers, 99, pp I. Ktzel n M. Nghshineh, Chnnel Assignment Shemes for Cellulr Moile Teleommunition Systems: A Comprehensive Survey, IEEE Personl Communitions, pp. 0-, June 99.. W. C. Y. Lee, Moile Cellulr Teleommunitions Systems, MGrw-Hill, New York, 99.

2 SBRA sheme n provie itionl flexiility to use the limite nwith effiiently. V. DOWNLINK PERFORMANCE RESULTS We use our OPNET pket wireless simultor to numerilly evlute the interferene hrteristis of the SBRA sheme. The system stuie h three tiers of interferers for the enter ell. Re-use ptterns of three n four were stuie. Numeril results were generte for the following referene set (n some vritions s well) of prmeters: regulr hexgonl gri lyout, setors/ell, se ntenn FTB rtio = B, se ntenn emwith = 0 o, terminl ntenn FTB rtio = B, terminl ntenn emwith = 0 o, stnr evition of lognorml fing = B, pth loss exponent =, n prtil (overlpping) ntenn pttern. We stuie the ownlink n uplink performne, lthough we present only the ownlink results here. In the ownlink, we lulte performne uner the mximum o-hnnel interferene (CCI) when ll setors were trnsmitting in their orresponing sufrmes. Terminl were first ssigne to setors in the following mnner. Eh terminl ntenn ws pointe to ll ses n then ssigne to the se whih resulte in the highest SIR. Sine lognorml fing to ifferent ses ws inepenent, the ove proeure tene to minimize eep fe ses. The primry figure-of-merit is the f of the SIR, n the frtion p whih represents the terminls tht o not meet require threshol. The frtion p (trget to %) represents the outge, i.e. the vulnerle terminls tht nnot e ommote n must e remove from the system. Sine the interferene onitions re lmost stti, retrnsmissions re not useful exept for very light lo. We o not onsier power ontrol on the ownlink. Figure illustrtes the vlue of iretionl ntenns y showing the ownlink system performne with omniiretionl terminl ntenns n iretionl terminl ntenns with emwiths of 0 o, 0 o, n 0 o. For n SIR outge of % (99% overge), the SIR hieve is. B for the referene se of 0 o n B for the omni se. It is ler tht iretionl terminl ntenns re require, n lso tht terminl ntenn emwith is not very ritil in the rnge from 0 o to 0 o ; this implies wie tolerne to ntenn emwiths n pointing errors. Figure lso shows the performne for reuse of for the referene se. The 99%-overge SIR vlue inreses from. B to out. B n provies goo mrgin for vrition in ell sizes tht oul ring the o-hnnel ells slightly loser. Figure illustrtes the ritil importne of the terminl FTB rtio. The SIR urves re shown for FTB rtios of 0 B, B, n 0 B. The urves o not exee B ue to the ft tht the se ntenn FTB hs een hosen s B. For 99% overge, the hieve SIR is B,. B, n B. For eh B rop in FTB rtio, the SIR rops y out. B. This informtion is useful sine terminl ntenn with free-spe FTB rtio of 0 B hs n effetively-lower interferene suppression of B to 0 B in the presene of Pro.( SIR < siss) Pro.( SIR < siss) Fig. Reution of interferene using iretionl ntenn t the terminl K= (omni ntenn) K= (BW: 0egrees) K= (BW: 0 egrees) K= (BW: 0 egrees) K= (BW: 0 egrees) terminl FTB rtio: 0 B terminl FTB rtio: B terminl FTB rtio: 0 B SIR (B) SIR (B) Fig.. SIR istriution for ifferent terminl FTB rtios strong lol stterers. Figure shows the SIR results for ifferent numers of setors. The % SIR outge for, 0, n setors re. B, B, n. B respetively. Agin, the SIR penlty is smll for lrger numer of setors, thus estlishing the fesiility of setor growth. Fig. shows the effet of lognorml show fing. Besies vrying the signl n interferene onitions t the terminl, ertin fing onitions n lso use terminl to hnge setors. Thus, extreme ses of verse fing (low signl, high interferene) re voie y the mroiversity offere y setor seletion.

3 iffiulty in system growth for shemes suh s SRA [], where setor splitting my upset the reful leling sequene neessry to mnge interferene. With setor splitting, the opertions of the SBRA metho remins unhnge. This is mjor vntge ompre to ell splitting whih requires new ses n re-pointing of terminl ntenns. If iretionl ntenns re use t the se, setor splitting woul require hnging of setor ntenns, wheres if multi-em smrt ntenns re use t the se, it my e possile to reonfigure the ntenns t the of setor splitting without nee for replement. Consier system with ses instlle in n irregulr fshion, s might e the se ue to onstrints of ville lotions n non-uniform trffi ensity. This oul give rise to irregulr ell sizes n shpes. The SBRA sheme n e implemente with suffiient performne mrgin to ommote this in strightforwr mnner. In generl, the numer of jent ells n the mount of ommon ounry with eh oul vry. We now show how pity n e enhne in other prts of n irregulr system if reuse requirements vry ross the system. We use n exmple system lyout shown in Figure in whih K= (the mximum numer of reuse ptterns) is require. Cells re lele with one of the four ell types (leling ptterns),, n. A susript is e purely to ientify eh ell, i.e. n use the sme leling ptterns. Note tht ells,,, re the only group of ells in whih eh ell is very lose to ll others in the group; thus the ells lmost meet t one point n require the four ifferent lels. In other ses, it is rther thn ells tht meet t ounry. As result, ells hve neighors whih use totl of either two or three ifferent ptterns; ells with neighors using only two lels re either ege-ells or woul hve n even numer of neighoring ells. As n illustrtion, the neighors of ell use type or, while the neighors of ell use,, or. As isusse ove, setors in ell,, n woul e lele y n, n, n, n n, respetively, whih re not shown in the figure. Figure epits slots whih re groupe into eight sufrmes n setor with lel i oul use only slots of sufrme i. However, this stright-forwr pproh my result in wste of nwith in some ells. We now explore the nonuniform leling to improve the nwith usge n system throughput s follows. To illustrte the ie, let us onsier ouple of exmples. First, ssume tht ell (e.g., ell oes not hve neighoring ell with leling pttern. In this se, sufrme n normlly use y ell n e ivie into six mini-frmes, inexe y to s shown in Figure. Thus, in ition to sufrme n, ell n lso use slots of mini-frme n. (It is unerstoo tht setors with lel n in ell trnsmit only in slots of sufrme or mini-frme n, respetively.) This is fesile euse trnsmission in the mini-frmes in ell is not interfere y ny first-tier neighoring ells. Further, ell n use slots in sufrme n s well s those in mini-frme n. Similrly, s shown in Figure to e, the orresponing () () () () (e) Time slots for ells with lels of leling ptterns No neighour with -leling pttern No neighour with -leling pttern No neighour with -leling pttern No neighour with -leling pttern Fig.. Non-uniform leling for irregulr ell lyouts sufrme n e ivie into mini-frmes n use y ells with no neighors hving the ssoite leling pttern. In n extreme sitution, if ell hs only one neighor, it n use slots in two sets of two mini-frmes, erive from four sufrmes tht oul hve een use y the missing neighors. Note tht this non-uniform reuse onept is ifferent from slot reuse in TSRP [] lthough the two onepts n ertinly e merge in hyri sheme. Speifilly, the TSRP sheme llows ifferent reuse ptterns for ifferent terminls, epening on their reeption qulity. However, the ivision of the totl nwith for ifferent reuse ptterns is performe y onsiering ll terminls reeption in the system. In ontrst, our lolize reuse tkes ell-y-ell pproh. Thus, the Fig.. Frme strutures for enhne pity for irregulr ell lyout shown in Fig.

4 . Setor leling plns n re-use ptterns shoul e roust enough to llow for the inevitle evitions from regulr ell lyout. Also, the numer n size of setors my not lwys e the sme in eh ell. III. THE SECTOR-BASED RESOURCE ALLOCATION (SBRA) SCHEME In the setor-se resoure llotion (SBRA) sheme, eh ell hs n even numer of setors with lternte leling (every other setor in ell hs the sme lel.) The sheme is presente in the ontext of -omin re-use ut lso pplies to frequeny hnnel reuse. The sheme ensures tht o-hnnel setors in other ells re kept t suffiient istne. In prtiulr, o-hnnel setors re not llowe in the first tier of neighoring ells. There is flexiility in the lyout options s expline in the next setion. To illustrte our ies, Figure () shows the SBRA sheme leling for hexgonl ell system with six setors (S = ) per ell n reuse pttern with three (K = ) types of ells. The three ell types use setor lels n, n, n n, respetively. All ells epit n essentil hrteristi of the SBRA sheme; every other setor of ell hs the sme lel. This reuse pttern of three ensures tht no two jent ells re the sme type (leling pttern), n the o-hnnel interferene is reue to eptle levels (s o-hnnel interferers re in the seon tier of ells). For hexgonl lyout, three ell types re suffiient to over ll ells in the system in self-onsistent mnner. In the -omin SBRA sheme, is ivie into slots. Eh frme onsists of K= su-frmes inexe y to for the lyout in Figure (), eh of whih ontins multiple slots. Setors with lel l n sheule pket trnsmission in slots of sufrme l. As result, eh setor n trnsmit on.% uty yle, onsuming t most one-sixth of the totl nwith. The totl network pity is inrese y the ft tht setors with ientil lel in eh ell n trnsmit simultneously. In this exmple (K =, S = ), the effetive overll re-use ftor is sine, if there re N pkets (slots) per frme, eh ell proesses (N/K) x (S/) = N pkets per frme. Note tht suh high egree of onurrent pket trnsmission n e supporte y the SBRA metho euse of the high iretivity of the ntenns. The SBRA sheme n support ifferent re-use ptterns n ifferent numer of setors. Figure () shows n exmple lyout for K = whih offers lower ohnnel interferene, whih my e neee for higher SIR threshol requirements. We now highlight other vntges of the SBRA sheme. IV. IRREGULAR SECTOR AND CELL LAYOUT & NON-UNIFORM REUSE PATTERNS The SBRA metho is pplile to irregulr setor plns where the numer of setors n their orresponing emwiths vry from ell to ell. The primry onstrint is tht eh ell shoul hve n even numer of setors. There my lso e esign onstrints for prtil ntenns whih onstrin the ifferene in ngulr sizes of jent setors. Thus, the setor setting for eh ell n e hosen to mximize the utiliztion of equipment while meeting the ntiipte trffi emn. Suh flexile setor plnning is possile euse the SBRA sheme oes not rely on the lignment of the setors in other ells. The SBRA sheme llows setor splitting, whih llows for esy growth in network pity in n existing system. When the trffi lo for setors exees pity, setors n e further split into smller setors, eh of whih hve roughly the sme pity s the originl setor. This is in ontrst to the () () Fig.. SBRA metho for reuse pttern of () n ().

5 SECTOR-BASED RESOURCE ALLOCATION FOR BROADBAND FIXED WIRELESS NETWORKS Arty Srivstv, N. K. Shnkrnrynn, n Kin K. Leung {rty, shnkr, reserh.tt.om AT&T Lortories - Reserh 00 Shulz Drive, Re Bnk, NJ 00-0, USA Astrt - We present setor-se resoure llotion sheme for ron fixe wireless networks. For SIR requirements of out to B, the sheme n eliver n effetive reuse ftor of one, while permitting given spetrum to e re-use in every setor of every ell. The sheme lso offers flexile setor plnning, esy pity growth, n resses irregulr ell lyout n non-uniform trffi ensity. I. INTRODUCTION As teleommuting n Internet ess eome inresingly populr, the emn for ron pket servies will grow tremenously. Previous work [-] hs shown tht fixe ron wireless networks tht use iretionl ntenns t oth ses n terminls re n ttrtive n fesile solution for proviing suh pket servies to homes n smll usinesses. The present work is motivte y prgmti issues suh s relisti ntenn ptterns, inustry trens, non-uniform trffi ensity, pity growth methos, n irregulr ell lyout. We present simple Setor-Bse Resoure Allotion (SBRA) sheme tht resses these issues in ron fixe wireless networks. II. BROADBAND FIXED WIRELESS NETWORKS WITH DIRECTIONAL ANTENNAS Consier ron fixe wireless network where eh ell is ivie into multiple setors, eh of whih is serve y setor ntenn o-lote with se sttion t the enter of the ell. Terminls use iretionl ntenns (typil emwiths of 0 o ) mounte on the roof top n pointe to their respetive se ntenns. The rtios of front-to-k-loe gin (FTB rtio) for the se n terminl ntenns my e ifferent, n re ssume to e finite. For resons outline in [], we pik TDMA system with shre ownlink hnnel of 0 to 0 M/s tht is suitle for ron wireless systems. Time is slotte suh tht pket n e trnsmitte in eh slot. Due to high t rte n limite spetrum vilility, tritionl methos for frequeny reuse [, ] re not pplile in ron systems. This hs een strong motivtion for solutions tht n use the sme frequeny in every setor of every ell in ron wireless networks. Fesile solutions with high throughput re enle y the use of iretionl ntenns n omin reuse [, ] in whih frmes re ivie into su-frmes n use in setors in mnner nlogous to frequeny reuse. The Stggere Resoure Allotion (SRA) sheme [] uses ynmi resoure llotion lgorithm where the sme spetrum is use y every setor n ell on ynmi sis. There is speifi sequene in whih setors re lele, n speifi sheule in whih su-frmes re use in eh setor with the result tht onurrent pket trnsmissions use little interferene to eh other. In fixe wireless systems with ggressive re-use, for potentilly-uneptle frtion of terminls tht re typilly ner ell ounry, unfvorle show-fing onitions n lol-sttering effets n rete high interferene tht nnot e suffiiently suppresse y the iretivity of the terminl/se ntenns []. We refer to these terminls s vulnerle terminls. Tehniques re ville to inrese the servie overge to ommote suh terminls with eptle QoS [, ]. The Time Slot Reuse Prtitioning sheme [] uses multiple -omin re-use ptterns whih provie ifferent signl-to-interferene rtio (SIR) hrteristis. Terminls re tegorize se on SIR requirement n ssigne to ifferent -omin re-use ptterns, i.e., they use slots llote to the respetive ptterns. Vulnerle terminls thus use ptterns with higher reuse ftors. The Enhne SRA sheme [] moifies the setor leling sheme n the trnsmission sheule in the originl SRA sheme [] to ommote the vulnerle terminls. In our sheme, we use higher (K = n ove for typil ses) re-use ftors to ommote the vulnerle terminls. The resultnt pity rop is me up y onurrent trnsmissions from lternte setors in the sme ell. Our fous is on the epenene of SIR performne on vrious prmeters, riteri for setor ssignment, n prgmti issues suh s flexiility n upgres. We mke the following oservtions tht hve motivte our new setor-se resoure llotion sheme.. For typil system with SIR requirement of 0 to B, ny o-hnnel interferer in the first-tier of neighoring ells woul ontriute the most signifint interferene. For overge trgets greter thn 0%, it is neessry to remove ohnnel setors to the seon tier of ells.. Prtil setor ntenn ptterns overlp with those of jent setors of the sme ell. Thus, no two jent setors shoul use the sme hnnel.. The ommon prtie of ell splitting for pity growth in ellulr networks is not goo option for fixe wireless networks sine the existing iretionl terminl ntenns in the new ell will nee to e re-oriente to new se - huge n unesirle tsk! A etter solution is to inrese the numer of onurrent trnsmissions per ell.