Abstract
Thisworkexaminestheuseoftwo-waytraininginmultiple-inputmultiple-output(MIMO)wirelesssystemstodiscriminatethechannelestimationperformancesbetweenalegitimatereceiver(LR)andanunauthorizedreceiver(UR).Thisthesisextendsuponthepreviouslyproposeddiscriminatorychannelestimation(DCE)schemethatallowsonlythetransmittertosendtrainingsignals.ThegoalofDCEistominimizethechannelestimationerroratLRwhilerequiringthechannelestimationerroratURtoremainbeyondacertainlevel.Ifthetrainingsignalissentonlybythetransmitter,theperformancediscriminationbetweenLRandURwillbelimitedsincethetrainingsignalshelpbothreceiversperformestimatesoftheirdownlinkchannels.Inthiswork,weconsiderinsteadthetwo-waytrainingmethod-ologythatallowsboththetransmitterandLRtosendtrainingsignals.Inthiscase,thetrainingsignalsentbyLRhelpsthetransmitterobtainknowledgeofthetransmitter-to-LRchannel,butdoesnothelpURestimateitsdownlinkchannel(i.e.,thetransmitter-to-URchannel).Withtransmitterknowledgeoftheestimatedtransmitter-to-LRchannel,artificialnoise(AN)canthenbeembeddedinthenullspaceofthetransmitter-to-LRchanneltodisruptUR’schannelestimationwithoutseverelydegradingthechannelestimationatLR.Basedontheseideas,two-wayDCEtrainingschemesaredevelopedforbothreciprocalandnon-reciprocalchannels.TheoptimalpowerallocationbetweentrainingandANsignalsisdevisedunderbothaverageandindividualpowerconstraints.Numericalresultsareprovidedtodemonstratetheefficacyoftheproposedtwo-wayDCEtrainingschemes.