Impact oflubFlowControl onHSDPA System Performance

Therecently emerging HighSpeed Downlink Packetbuffer level Access (HSDPA)enhances conventional WCDMA systems ac- fromrunnin cording totheUMTSstandard withdatarates ofupto14MBit/s Duetoth inthedownlink direction. Thisisachieved byusingadaptive data rateon modulation andcoding aswell asafast Hybrid Automatic Repeattaratelo Request (HARQ)mechanism. Thisfunctionality isimplemented therelativel close totheairinterface intheNodeB.Inaddition tothedatacorrespondir buffer intheRNC,this requires asecond databuffer inthe flowcontrol NodeB.Consequently, aflowcontrol mechanism isneeded whichbeabletor controls theamountofdatatobetransmitted fromtheRNC's buffer totheNodeB'sbuffer. Thespatial separation ofRNCand asfast asne NodeBimposes significant signaling constraints andcontrol dead whenusLng timelimitations totheflow control mechanism. Additionally, due leadtoaratl tothetime-varying nature oftheradiochannel, thedatarate Schedulin towards aparticular usermaybehighly variable. Inthis paper,beenaddres. westudy theimpact oftheflowcontrol onsystem performance. sche We will showthatitisessential tojointly consider schedulingduling a andflow control inanHSDPAsystem astheconstraints imposedIn(3), Kold bytheflowcontrol maydominate thesystem performance.Fair (PF)scl