A New Medium Access Control Protocol for TDD Mode Wideband CDMA Wireless Local Area Networks

Transcription

1 A New Medum Access ontrol Protocol for TDD Mode Wdebnd DMA Wreless Locl Are Networks In F. Akyldz nd Xudong Wng Brodbnd nd Wreless Networkng Lb, School of Electrcl nd omuter Engneerng Georg Insttute of Technology, Atlnt, GA 332, USA Ph: , Fx: , Eml: {n, wxudong}@ee.gtech.edu ABSTRAT It s well known tht TDD mode wdebnd DMA s rtculrly suted for wreless locl re networks (LANs). In ths er medum ccess control (MA) rotocol s roosed for wreless multmed LANs tht re bsed on TDD mode wdebnd DMA. In order to mnmze nterference exerenced by cket nd to stsfy bt error rtes (BERs) of multmed trffc, mnmumower llocton lgorthm s derved to determne the receved ower levels of code chnnels tht re llocted to moble termnl. Bsed on the mnmumower llocton lgorthm, the mxmum system ccty s nvestgted, whch onts out tht both rte nd BERschedulng s requred n order to cheve mxmum system ccty. Usng mnmum ower llocton nd rte nd BERschedulng, new cket schedulng scheme s roosed to ccommodte ckets n tme slots. Smulton s crred out to evlute the roosed MA rotocol. Results show tht the roosed MA rotocol gretly mroves the erformnce of TDD mode wdebnd DMA wreless multmed LANs. 1 INTRODUTION Wreless Locl Are Networks (LANs) hve mny dvntges over legcy wred LANs. However, due to the wreless envronment, secl desgn requrements need to be consdered for the network rotocols of wreless LANs. One of the key tsks s to desgn medum ccess control (MA) rotocol, whch delvers multmed trffc wth heterogeneous qulty of servce (QoS) requrements. urrently severl stndrds such s IEEE [1] nd Bluetooth [2] hve been develoed for wreless LANs. However, none of them s good t QoS suort for multmed trffc. Thus, to develo wreless LAN tht suort multmed trffc wth heterogeneous QoS requrements s stll n ongong reserch toc. HerLAN/2 [3] cn suort multmed trffc. However, t s TDMA network, whch lcks the dvntges of DMA network, eseclly those of wdebnd DMA network [4]. As secfed n the Unversl Moble Telecommunctons System (UMTS), tme dvson dulex (TDD) mode wdebnd codedvson multleccess (DMA) s well suted for mcro or cocell Ths work s suorted by NSF under grnt R nd by YAMARAW under grnt E wreless envronments wth hgh trffc densty [5]. Thus, t cn be used s bsc rdo ccess technque for wreless LANs. In ths er, we focus on wreless LANs bsed on TDD mode wdebnd DMA, where tmedvsondma (TDDMA) s used n both ulnk nd downlnk trnsmssons. In rtculr we roose new MA rotocol for ulnk trnsmsson n such wreless LAN. Recently severl MA rotocols [6], [7] hve been roosed for TDDMA systems. In [6], wreless multmed MA rotocol wth bt error rto schedulng (WISPER) s roosed. The schedulng scheme does not consder ower control for users n the sme tme slot becuse t ssumes tht the ower levels of receved sgnls n one tme slot re the sme. It contns novel cket schedulng scheme, whch ms to stsfy the heterogeneous bt error rtes (BER) of multmed trffc nd mrove the system throughut t the sme tme. Snce ower control n ech tme slot s not consdered, system throughut s not mxmzed. In [7], generc otml resource mngement roblem for TDDMA s defned. Becuse t s mrctcl to fnd the otml soluton to the roblem, subotml lgorthm s roosed bsed on the bnckng scheme [7]. omred to WISPER, ths lgorthm consders dfferent fxed receved ower levels for dfferent servce tyes. However, t does not mnmze the receved ower level for ech moble termnl. To develo new MA rotocol for TDD mode wdebnd DMA wreless LANs, we frst derve mnmumower llocton lgorthm tht mnmzes the nterference exerenced by ech cket n tme slot. Dfferent from the ower llocton lgorthm n [8], our lgorthm consders both multle servce tyes nd multle rtes for ech servce tye. The ower control of our lgorthm s only led to the ulnk receved ower levels of moble termnls. The ulnk trnsmtted ower level corresondng to the trget receved ower level cn be determned by usng oen nd closedloo ower control schemes [9], [10]. Bsed on the mnmumower llocton lgorthm, the mxmum ccty of tme slot s nvestgted, whch onts out tht both rte nd BERschedulng s necessry. Wth rte nd BERschedulng nd mnmumower llocton lgorthm, new cket schedulng scheme s roosed. It mxmzes the system

2 ode Dvson TDD boundry TDD boundry Ulnk Frme k Downlnk Frme k Ulnk Frme k+1 Downlnk Frme k N u 1 2 N d 1 2 N u 1 2 N d Tme Dvson Lc Lc Dt Slot Request Slot ontrol Slot Fgure 1: Frme structures of the MA rotocol ccty, stsfes the heterogeneous BER requrements, nd mroves the QoS metrcs of multmed trffc. The er s orgnzed s follows. In Secton 2, we descrbe the bsc MA rotocol for TDD mode wdebnd DMA wreless LANs. A mnmumower llocton lgorthm s derved n Secton 3 where the mxmum system ccty s lso nvestgted. A new cket schedulng scheme s roosed n Sectons 4. The erformnce of the roosed MA rotocol s evluted n Secton 5. The er s concluded n Secton 6. 2 THE MA PROTOOL FOR UPLINK TRANSMIS SION IN A DMA WIRELESS LAN We consder TDD mode wdebnd DMAbsed wreless LAN. The frme structure of such network s shown n Fgure 1, where ulnk nd downlnk re multlexed n tme dvson. In the ulnk frme, the request slot s used by moble termnls to send requests to the bse stton. In the downlnk frme, control slot s used by the bse stton to send feedbck messges to moble termnls. The oston of the control slot, reresented by, deends on the rocessng ower of the bse stton. Multcode (M) oerton s used n the ulnk., whch s the sme s UMTS TDD mode [11]. Snce ech code chnnel suorts one bsc rte, n order to cheve multrte, severl code chnnels need to be generted through subcode conctenton [12] for ech user. Wth subcode conctenton, the selfnterference mong the codes of the sme user s voded [12]. In the MA rotocol, severl conflctng QoS rmeters such s BER vlues, verge cket delys, nd verge cket loss rtos re consdered. In ddton, system throughut needs to be mxmzed. Snce our reserch s focused on ulnk trnsmsson, dynmc TDD s not consdered n our roosed rotocol. The new MA rotocol s oerted s follows: Request for Trnsmsson. A moble termnl sends trnsmsson request before t trnsmts btch of ckets. The trnsmsson request cn be sent n the request slot or ggybcked n dt tme slot. The number of ckets nd tmeout vlue of ths btch of ckets re secfed n the trnsmsson request. Pcket Schedulng. After the bse stton collects the trnsmsson requests from ll moble termnls durng n entre ulnk frme length, t uses cket schedulng scheme to determne how the ckets of multmed lctons re ccommodted n ech tme slot. The cket scheduler s rte nd BERschedulng scheme nd s lso bsed on mnmumower llocton for ech code chnnel. It mxmzes the system ccty nd stsfes the heterogeneous BER requrements of multmed trffc. Downlnk Feedbck. After schedulng for cket trnsmsson s comleted, the bse stton sends the results bck to the moble termnls through the control slot n the downlnk frme, whch s erformed by brodcstng. It should be noted tht the feedbck nformton for ech termnl ncludes the termnl ID, ssgned tme slots, the number of ckets n ech ssgned tme slot, nd the receved ower level of ech code chnnel. Pcket Trnsmsson. When moble termnl gets the ermsson for cket trnsmsson, t enters the cket trnsmsson stte nd trnsmts ckets n the secfed tme slots wth the llocted ower level. When the bse stton receves such ckets, t forwrds them to the desred destnton. The ckets tht hve not been trnsmtted n the current frme needs to wt for ermsson n the next frme. As descrbed n the oerton rocedures of the MA rotocol, new lgorthms re requred for the cket schedulng scheme. 3 THE MINIMUMPOWER ALLOATION ALGO RITHM In tme slot code chnnels of dfferent moble termnls nterfere wth ech other, so ower llocton to these code chnnels need to be controlled so tht BER requrements of dfferent moble termnls cn be stsfed, nd tht ower level of ech code chnnel s mnmzed. To solve ths roblem, severl lgorthms hve been roosed. The ower llocton scheme roosed n [8] consders only moble termnls wth the sme BER requrement. An lgorthm s derved n [13] to suort moble termnls wth heterogeneous BER requrements n the sme tme slot. It does not consder subcode conctenton. In ths secton, we derve new lgorthm tht stsfes heterogeneous BER requrements of multmed servces by lloctng mnmum ower level to ech code chnnel. The mxmum ccty of tme slot s lso nvestgted.

3 , L,,, t t 3.1 SINR of Multmed Trffc We ssume tht tyes of servces re suorted n TDD mode DMA wreless LAN, nd the trget sgnl to nterferencelusnose rto (SINR) tht stsfes the BER requrement of servce s. For moble termnl suortng servce, the mxmum llowed number of code chnnels s ssumed to be. Thus, such moble termnl cn hve code chnnels wth. Gven moble termnl tht hs code chnnels nd suorts servce, the ower level for ech code chnnel s denoted by, nd the nterference level of one out of the code chnnel s denoted by. onsderng subcode conctenton, the nterference exerenced by moble termnl only comes from the codes of other moble termnls [12], so cn be exressed by ower levels! # $& '( ) $ * } s +.(/ !5!7689: (1) where 3! s the number of moble termnls tht hve code chnnels for the trnsmsson of servce. On the rght hnd sde of Equton (1), the summtons cture the ower levels of the code chnnels of ll moble termnls n the system, nd the second term s the totl ower level of the moble termnl under consderton. In ddton to nterference, code chnnel lso exerences nose. We ssume tht the nose ower level of code chnnel, denoted by ;, s the sme for ll moble termnls nd s gven by ; =<?>@5A (2) where < > s the onesded ower sectrl densty of nose, A s the bndwdth of sred sgnl. Snce both nterference nd nose cn be roxmted by zeromen Gussn rocesses, the SINR for code chnnel t the recever outut, denoted by B, s [8] B DFEHG I : JKL MONQP (3) where R s the rocessng gn. Substtutng Equtons (1) nd (2) nto Equton (3), the SINR B s B 2 SUT 1WV9X SUY 1 Z V9X!\[ 1 G Z N 1 G Z^] N EGI JKL M < (4) _ s the bndwdth of the sgnl wth bsc trnsmsson rte, br. 3.2 The MnmumPower Allocton Algorthm The objectve of the mnmumower llocton lgorthm s to determne the mnmum ower level of ech code chnnel whle BER requrements or trget SINRs of multmed servces re stsfed. In order to stsfy BER requrements of multmed servces, the recever outut SINR B for one out of the code chnnel must be lrger thn or equl to the trget SINR,.e., B dc. Thus, from Equton (4) we hve S T : 1WV9X S Y 1 Z V9X!\[ 1 G Z N 1 G Z ] N EHGI c 9&e (5) JKL M <?>@ _ Defne uxlry vrbles fg wth fh cj for k &. Then, Equton (5) s equvlent to the followng equton: S T : 1&VlX S Y 1 Z VlX!\[ 1 G Z N 1 GZ ] N EHGI JKL M <m>@ _ After some lgebr, we hve 6.(/ !5: JKL M q 1rsQ1ut Thus, f the followng constrnt holds z.(/ 0+1 n o M fgwe (6) M vw R M f : + kxyrd< t (7) {3 JKL! M q 1zr:s1 (8) the ower level of ech code chnnel s gven by + JKL vw Rd<?>@ _ M q ErsE S, S 0+1 }6!\[ 1 G Z e (9) z.~/! r JK 1 t Otherwse, no soluton exsts becuse the ower level ( must be lrger thn zero. By nlyzng Equton (9), s mnmzed when f for b ƒ&. Thus, the mnmum ower level!^ tht stsfes the trget SINR s!\ JKL vw Rd< M q E S, S 0 1 6!\[ 1 G Z e (10) z.(/! r JK t To gurntee the exstence of!^, the followng constrnt must hold:, 021 {3 JKL! e (11) z.(/!.~/ M q 1 whch comes from Equton (8) when f:ˆ &. We defne Š!!! r JKŒ for s the normlzed ccty consumed by moble termnl tht uses code chnnels to trnsmt ckets of servce n tme slot. Thus, Equton (11) becomes.(/ 021 3:! Š! e (12) Snce S 0+1 3! Š! s the overll normlzed ccty consumed by ll moble termnls tht suort servce, Equton (11) mles tht, n order to cheve mnmumower llocton for moble termnls n tme slot, the overll normlzed ccty consumed by ll moble termnls must be less thn.

4 , M 3.3 Mxmum cty of Tme Slot In ths secton, we nvestgte the mxmum ccty n terms of the number of code chnnels tht cn be suorted n tme slot when the mnmumower llocton lgorthm s used. s the number of moble termnls tht use Snce 3! code chnnels to suort servce tye n tme slot, the number of moble termnls of ll servce tyes n the tme slot cn be descrbed by vector 3 / / &3!?W3, 0 T. If denotes the number of code chnnels of ll moble termnls n tme slot, t s gven by z.~/ 0+1 {3! (13) When mnmumower llocton s used, must stsfy the constrnt n Equton (11). As result, n order to mxmze, we need to solve the the followng otmzton roblem: fnd ostve vector 3 / /&3! W3, 0 T tht stsfes S, S 021.(/ 3!!! r JK 3 / / W3! &3, 0 T c (14) nd mxmzes the objectve functon n Equton (13). Accordng to the lner rogrmmng theory, s mxmzed t one of the extreme onts of the ostve vector 3 / / W3! &3, 0 T. By nvestgtng the constrnt n Equton (11), we know the set of extreme onts conssts of the vectors such s JKL! r JK M q X! 0 T r JKΠ0 T T.! r JKΠSubsttutng n extreme ont, e.g.,! JKL, nto Equton (13), the vlue of s q 1. Thus, the mxmum vlue of, denoted by, s b ( M vw R From Equton (15), we know tht b M vw R W $ u e (15) (16) whch mles tht s cheved when ll moble termnls use the mxmum llowed number (.e. ) of code chnnels to trnsmt ckets. Ths henomenon cn be exlned s follows. When moble termnls use mxmum number of code chnnels, the number of dfferent moble termnls n tme slot s mnmzed. onsderng subcode conctenton, mutul nterference between code chnnels s lso mnmzed. Wthn ths result n mnd, when desgnng cket scheduler, we need rteschedulng,.e., moble termnl must use s mny code chnnels s ossble n tme slot to trnsmt ckets. Also from Equton (15), we know tht mustjkl be cheved t JKL nd wth M q 1 M q 1 & nd the vector 3 / / W3!?&3, 0 T & Ths result mles tht servce s the only servce tht cn be ccommodted n the sme tme slot; otherwse, the mxmum ccty cnnot be cheved. In order to gurntee ths, BERschedulng s necessry n the cket scheduler,.e., ckets wth dfferent BER requrements must be ccommodted n dfferent tme slots. It should be noted tht s not necessry to be the servce wth the lest strngent BER requrement. In summry, n order to effcently utlze the ccty of tme slot n multcode TDDMA system, both BER nd rteschedulng re requred. Wth such schedulng scheme, the otml result s tht moble termnls trnsmttng ckets n the sme tme slot hve the sme BER requrement nd use mxmum llowed code chnnels. However, when other QoS rmeters such s cket dely nd cket loss rto re consdered, the otml result cnnot be lwys cheved. It s ossble tht ether moble termnls wth dfferent BER requrements trnsmt ckets n the sme tme slot, or moble termnls do not use mxmum llowed code chnnels. In such stutons, mxmum ccty! cnnot be cheved. However, snce the mnmumower llocton lgorthm s embedded n the scheduler, the ccty of tme slot cn stll be utlzed s effcently s ossble. In the next secton, we use mnmumower llocton nd the concet of rte nd BERschedulng to desgn cket scheduler for the MA rotocol of TDD mode wdebnd DMA wreless LANs. 4 THE PAKET SHEDULER The cket scheduler conssts of cket rortzer nd rte nd BERschedulng scheme. The rortzer s used to determne the rorty of ech btch of ckets ccordng to QoS rmeters. Then ll btches of ckets re servced from the hghest rorty towrds the lowest rorty. After btch s selected by the cket scheduler, the rte nd BERschedulng scheme determnes the rorte tme slots nd the number of code chnnels to ccommodte ckets of ths btch. The ccty of ech tme slot nd the receved ower level of ech code chnnel re determned on the bss of the mnmumower llocton lgorthm. 4.1 Pcket Prortzer In order to reduce dely nd cket loss rto, the rorty of btch of ckets needs to be nversely roortonl to the remnng tme of the btch. However, f the remnng tme of two dfferent btches s the sme, the btch wth more ckets must hve hgher rorty. It should be noted tht fr queung lgorthm cn lso be used to determne the rorty of ech btch. However, ts comlexty s much hgher. 4.2 Rte nd BERSchedulng Scheme Suose tht btch s the frst beng selected by the cket rortzer. The schedulng scheme needs to llocte rorte tme slots nd code chnnels to the ck

5 & Btch s selected. Ste 1 serch emty tme slot or BER k tme slot from the frst tme slot to the lst one Ste 2 All tme slots re serched? Get the tme slot wth smllest An emty or BER k tme slot s found? lculte Ste 3 All tme slots re serched? For ny tme slot from the frst one to the lst one clculte All tme slots re serched? Ste 5 J = Udte vrbles: J m = m + J J T k = T f m, J k, J + 1 = 0 J = J J J >? J >? = J = Ste 4 Get the tme slot wth smllest J = J J = 0 or no code chnnels vlble? Schedulng for btch s comlete. The tme slot becomes non vlble tme slot to the moble termnl tht owns btch Fgure 2: The rocedures of the rte nd BERschedulng scheme. Tble 1: ttons Used n the Schedulng Scheme The terton number of the schedulng scheme. The number of code chnnels tht cn be used n tme slot for btch before the th terton. The number of code chnnels used by btch n tme slot before nd fter the th terton, resectvely. The number of ckets ccommodted n n terton. The number of ckets n btch before nd fter the th terton, resectvely. The number of moble termnls usng code chnnels n tme slot to suort servce tye before nd fter the th terton, resectvely. ets of ths btch. In order to trnsmt s mny ckets s ossble n tme slot, the rte nd BERschedulng scheme s used to llocte code chnnels n dfferent tme slots to btch. To smlfy descrtons of the schedulng scheme, some nottons re defned n Tble 1. Severl tyes of tme slots re lso defned s follows: Emty Tme Slot. If there re no ckets ccommodted n tme slot, the tme slot s clled n emty tme slot. Otherwse, t s nonemty tme Tme Slot. A tme slot s tme slot f the most strngent BER requred by the ckets n ths tme slot +. navlble Tme Slot. A nonemty tme slot s clled nonvlble tme slot to moble termnl f the moble termnl hs used the mxmum llowed number of code chnnels n ths tme slot. Accordng to ths defnton, nonvlble tme slot s not vlble to secfc moble termnl nsted of to ll moble termnls. As shown n Fgure 2, the rte nd BERschedulng scheme works tertvely untl ll ckets n btch re ccommodted or no code chnnel s vlble for btch n the current ulnk frme. If no code chnnel s vlble nd there re remnng ckets n btch, these ckets re servced n the next ulnk frme. However, f btch tmes out n the next frme, the remnng ckets must be dscrded. As shown n Fgure 2, ech terton of the schedulng scheme ncludes the followng stes: Ste 1. An emty or E tme slot s serched from the frst tme slot towrds the lst one of the ulnk frme to ccommodte ckets of btch so tht the ckets n the sme tme slot belong to the sme servce tye. If such tme slot s found, s clculted nd comred to &,.e., the number of ckets n btch. If & c, ckets n btch re ccommodted n the tme slot. In such wy, the moble termnl tht owns btch uses s mny code chnnels n tme slot s ossble. If &, nother emty or E tme slot s serched untl c s stsfed. After ste 1 succeeds, &,.e., ll code chnnels left for btch re used, nd thus, the corresondng tme slot becomes nonvlble tme slot to the moble termnl tht owns btch. In ths ste f some emty or E tmes slots re found, but none of them stsfes & c, the schedulng roceeds to ste 2. If nether n emty nor E tme slot s found, ste 3 s nvoked. Ste 1 erforms both rte nd BERschedulng.

6 x Ste 2. If emty or E tme slots hve been found but & c s not stsfed, then & ckets must be ccommodted n the emty or E tme slot n whch s the smllest mong ll emty nd E tme slots. Thus, tme slots wth lrger re reserved for btches wth more ckets, whch s the objectve of rteschedulng. After ths ste s successfully executed, & &,.e., no ckets re left n btch. Ste 3. If nether n emty nor E tme slot ws found n ste 1, ll tme slots re serched untl & c s stsfed. If tme slot stsfyng & c s found, ckets of btch re ccommodted n the tme slot. Otherwse, ste 4 s nvoked. As we cn see, only rteschedulng s erformed n ths ste. After ste 3 succeeds, & nd the corresondng tme slot becomes nonvlble tme slot to the moble termnl tht owns btch. Ste 4. If ste 3 fls, & ckets must be ccommodted n the tme slot n whch s the smll est. Thus, & &. Ste 5. Vrbles re udted s shown n Fgure 2. In ech terton of the schedulng scheme, s clculted ccordng to the mnmumower llocton lgorthm. After rte nd BERschedulng scheme s comleted for the whole ulnk frme, the mnmumower llocton lgorthm s used to llocte the receved ower level to ech code chnnel n tme slot. 5 PERFORMANE EVALUATION Sx trffc models tht re the sme s those n [6] hve been develoed to smulte the multmed trffc. 5.1 System Prmeters Inut Prmeters. The nut rmeters re shown n Tble 2. In ddton, the frme length of both ulnk nd downlnk s, nd the number of slots n the ulnk frme s. The sredng bnd e, wdth nd the sredng gn re nd x resectvely, nd the bsc trnsmsson rte s e. In Tble 2, < s the number of totl ckets tht re generted by n eml or dt messge. In smultons, the cll comoston of dfferent trffc tyes s the sme s tht used n n [6]. Outut Prmeters. Averge cket loss rto, verge cket dely, nd throughut re the metrcs used to evlute the erformnce of the rotocol. The verge cket dely conssts of two comonents,.e., M (17) where s the tme beng sent on lloctng tme slots to moble termnls, whle s the trnsmsson tme of cket fter tme slots re llocted. Tble 2: System Inut Prmeters Servce!! # $ Voce &('*),+ /. 0212' 1 BR Audo &(' ),4 6*&(' 5 VBR Vdeo &(' )87 6. '26 ' 4 BR Vdeo &('*),9 & & Dt ;:=< &(' ),> &?0@. 6 A 1 1 Eml 12'2:=< &(' ),> &?0@. 6 A Numercl Results Bsed on the system nut rmeters nd the trffc models, we hve smulted the roosed MA rotocol for TDD mode wdebnd DMA wreless LANs. The system outut rmeters re used to evlute the erformnce of the rotocol. We lso comre our rotocol wth WISPER rotocol [6] nd the resource llocton lgorthm roosed n [7]. Snce WISPER s FDD mode TDDMA MA rotocol, when t s led to TDD system n the smulton, ts sgnlng rocedures need to be modfed s follows: request trnsmtted from moble termnl n the ulnk frme does not receve feedbck mmedtely; the feedbck s receved n the next downlnk frme. However, the cket scheduler of WIS PER does not need ny chnge. The verge cket dely of multmed trffc s shown n Fgure 3, nd the verge cket loss rtos of dfferent tyes of rel tme trffc re llustrted n Fgure 4. It should be noted tht Fgure 4 does not nclude the results of nonreltme trffc becuse the lrge tmeout vlues of eml nd comuter dt trffc vod cket loss. The throughut of the system s shown n Fgure 5. In Fgs. 3 5, comrsons wth WISPER rotocol nd the resource llocton lgorthm n [7] re dected. Smulton results show tht the new rotocol not only mroves the system throughut but lso decreses the cket loss rto nd the verge cket dely of ech trffc tye. As trffc lod becomes hgher, the mrovement becomes more sgnfcnt. The reson s s follows. By usng the mnmumower llocton nd rte nd BERschedulng scheme, the ccty of ech tme slot s mroved. Thus, t the sme trffc lod the new scheme sends less tme to trnsmts multmed ckets. Also, due to the ncrese of ccty, more ckets cn be trnsmtted wthn ech ech frme. Snce there s no cket loss n nonreltme trffc, when the system ccty s not enough to meet the trffc lod, the verge cket dely s much more sgnfcntly ncresed thn tht of reltme trffc. In other words, when the system ccty s mroved by the new MA rotocol, the verge cket dely of nonreltme trffc wll be much more sgnfcntly reduced by the new scheme thn tht of reltme trffc. Ths hs been shown n the comrsons of verge cket delys n Fgure 3 for three dfferent rotocols. 6 ONLUSIONS In ths er, we derved the mnmumower llocton lgorthm for moble termnls tht trnsmt multmed trffc n TDD mode wdebnd DMA wreless LANs. The mxmum ccty of tme slot ws lso n

7 22 18 () Voce (b) Audo vestgted. Then we desgned new cket scheduler for the MA rotocol bsed on the rte nd BERschedulng scheme nd the mnmumower llocton lgorthm. Fnlly, smulton exerments were thoroughly crred out to evlute the erformnce of the new MA rotocol. Results llustrte tht our roosed MA rotocol gretly mroves the QoS metrcs of multmed trffc nd the system throughut (c) BR Vdeo (e) Eml (d) VBR Vdeo (f) omuter Dt Fgure 3: The verge cket dely versus cll rrvl rte. (vertcl xs: verge cket dely (msec), horzontl xs: rrvl rte of voce clls (clls/hour).) () Voce (c) BR Vdeo (b) Audo (d) VBR Vdeo Fgure 4: The verge cket loss rto of reltme trffc versus cll rrvl rte. (vertcl xs: verge cket loss rto (ercentge), horzontl xs: rrvl rte of voce clls (clls/hour).) Throughut (ckets/frme) ll Arrvl Rtes (voce clls/hour) Fgure 5: The system throughut versus the rrvl rte of voce clls. REFERENES [1] IEEE , Wreless ln medum ccess control (mc) nd hyscl lyer (hy) secfctons, [2] J. Hrtsen, The bluetooth rdo system, IEEE Personl ommunctons, , 00. [3] M. Johnsson, Herln/2 the brodbnd rdo trnsmsson technology oertng n the 5 ghz frequency bnd, techncl secfcton v 1.0, Her LAN/2 Globl Forum, [4] T. Ojner nd R. Prsd, Wdebnd cdm for thrd generton moble communctons, Artech House, [5] M. Hrdt et l., The tdcdm bsed utr tdd mode, IEEE J. Select. Ares ommun., vol. 8, , 00. [6] I.F. Akyldz, D. A. Levne,, nd I. Joe, A slotted cdm rotocol wth ber schedulng for wreless multmed networks, IEEE/AM Trns. Networkng, vol. 7,. 1 13, [7] V. Hung nd W. Zhung, Otml resource mngement n cketswtchng tdd cdm systems, IEEE Personl ommun., , 00. [8] Z. Lu et l., hnnel ccess nd nterference ssues n multcode dscdm wreless cket (tm) networks, AM/Bltzer Wreless Networks (WINET), vol. 2, , [9] F.. M. Lu nd W. M. Tm, vel srestmtonbsed ower control n cdm moble rdo system under multth envronment, IEEE Trns. Vehc. Technol., vol. 50, , 01. [10] L. Song, N. B. Mndym, nd Z. Gjc, Anlyss of n u/down ower control lgorthm for the cdm reverse lnk under fdng, IEEE J. Select. Ares ommun., vol. 19, , 01. [11] 3rd generton rtnersh roject; techncl secfcton grou rdo ccess network; rdo resource mngement strteges (relese 4), 3GPP TR , v 4.0.0, 01. [12] L I nd R. D. Gtln, Multcode cdm wreless ersonl communctons networks, n IEEE I 95, [13] X. Wng, A new schedulng scheme for the wdebnd tdcdm mc rotocol, n IEEE I 01, 01.