JoiuntDetermilnat'ion of Power andlDecod'ing Order for Successive Inter- andIntra-Cell Interference Cancellation

The performance of multiple accesssystems mainlydependson themanagementofinterference arising frombothintra-cell andinter-cell transmission. Successive interference cancellation (SIC)isa promising approachto manageinterference inboththepractical andinfoirmation theoretic senses. Becausethemessages ofthecellboundary usersarelikely tobedecodednotonlyattheserving base station butalsoatanadjacent basestation, itispossible to subtract inter-cell interference ofthecell boundary users before SICoftheintra-cell users. Thisisthemotivation ofourwork. Inthispaper, we first decodethemessages oftheadjacent cell boundary usersandsubtract them,andthenperform SIC within theserving users. Itshowsbetter performance compared totheconventional schemeswiththeSICwithin theserving usersonly. J.INTRODUCTION Inthecellular systems, thetransmit powercontrol has beenanessential technique, i.e., codedivision multiple access (CDMA)systems, since interference fromother users degrades thesystem performance. Inorder tosupport data services suchasafile orimagedownload, current cellular systems allocate moreresources forthedownlink traffic thanfortheuplink traffic. Duetotheincreasing downlink traffic, mostoftheprevious worksofthepowercontrol andrateallocation hasbeenconcentrated, onthedownfink einvironments (1), (2). Morerecently, Ihowever, thedemaind of theuplink traffic also increases proportional tothedownfink traffic. Duetothedynamic downlink resource allocation, morechannel feedbacks orcontrol messages areneeded. Furthermore, someapplications suchasafile orimageup- loadrequire large amount ofuplink resources. Based onthis consideration, someworks(3), (4), (5)related totheuplink powercontrol andrateallocation havebeenperformed. Indirect sequence CDMA systems, multiple-access inter- ference (MAI) causes performance loss duetothenonorthog- onality ofspreading codes. Successive interference cancel- lation (SIC) isoneofthepromising methods asapractical approach toward multiuser detection (MUD)Theiterative powercontrols forSICareproposed in(6), (7) andtheeffect ofachannel estimation error isconsidered in(8)Power controls basedonthemultirate direct sequence CDMA systems areconsidered under nonfading andfading channels in(9).