F8-Technical Session III: Wireless AdHocNetworks Hybrid Networks: Cellular-Relay Architecture

Peer-to-peer communication networks suchassensor networks, personal areanetworks andwireless local areanetworks arecharacterized bymulti-hop wireless communications inwhich information may-be routed fromsource todestination viamultiple wireless links. Ontheother handcellular networks aresingle-hop networks inwhichwireless communication isbetween themobile nodeandthebasestation only. Convergence will beamaintheme offuture networks that provide ubiquitous high rate services seamlessly through converged technologies. Motivated bythis wepropose cellular network architectures withmultihoptransmission fromthebasestation toterminals andvice versa through relays. Relays arenetwork elements (fixed ormobile) orother userterminals that havesignificantly moreintelligence than repeaters andarecapable ofstoring andforwarding data andmaking scheduling androuting decisions. Relay nodes arenotconnected tothewireline network through aback-haul connection, buthavetorely onwireless transmission tocommnunicate tothebasestation. Wediscuss avariety ofdeployment scenarios involving multi-hop transmission through relays. Cellular-relay networks could besuchthat therelay toterminal links usedifferent spectrum than base toterminal links. Forexample, therelays could communicate tothe terminals through awireless local areanetwork using theIEEE802.11 airinterface, inwhichcasethe relays arelike access points andusetheunlicensed band, while thebase station transmits totherelays using thelicensed cellular network spectrum. Inthis model, mobile terminals areassumed tohavebothcellular andIEEE802.11 interfaces, which isbecoming increasingly common. Analternative scenario isonein which thetwokinds ofhops usetwodifferent carriers within thespectrum assigned tothecellular network operator. Itisalso possible todeploy relays insuch awaythat noadditional carrier orspectrum isrequired andtransmissions frombasestation torelays andrelays touser terminals usethesamespectrum. Capacity gains areachieved evenihsuchascenario because oftheadditional effective spectrum reuse that is obtained duetothespatial separation oftherelays andtheir lower transmit powercompared tothat ofthe basestation. Wepresent adetailed description ofsuchasystem including thesignaling scheme andthe medium access protocol forhigh-speed packet data applications. Finally wediscuss benefits ofrelay based cellular network architectures formulticast traffic Inthis model, themulticast throughput isnotlimited by thelink quality oftheuserattheedge ofthecell since transmission happens through appropriately selected relays.