MULTIPLEACCESSPERFORMANCE OFFH/NCMFSK WITHLISTDECODING

MultipleAccess (MA)performance of list metricdecodingis evaluatedforfrequency hopped (FH), noncoherentM-ary frequency shift keying (NCMFSK). In a listdecoding receiver, the demodulatorconstructsan energy-ordered list of thechannelsymbols, and the decoderthen awardseachsymbola score based on itsrankinginthislist.We consideredtwo cases: in one, thedecoder assignsthesame setof scores on eachuse of the channel;in the other,thedecoderis adaptiveand assignsmetricswhichawardone of M sets of scores depending on howmany energy detectoroutputswere believedto have containeduser signals. We showthatin a fadingenvironment a listdecodingsystemcan accommodatefive times more users thanthe best hard decisionsystem, and that an adaptivemetricdoublesthecapacityof the staticlistmetric.