Partial sampling MMSE interference suppression in asynchronousmulticarrier CDMA system

摘要

Linear minimum mean square error (LMMSE) receivers fornasynchronous multicarrier code division multiple access (MC-CDMA) systemnunder frequency-selective Rayleigh fading channel is studied. Thenperformance of this LMMSE receiver is evaluated and shown to be superiornto that of the other two schemes, equal-gain combining (EQC) andnmaximum-ratio combining (MRC). However, a perfect timing estimation ofnthe desired user is needed for these receivers, as a misaligned samplingninterval of these receivers results in severely self intersymbolninterference (ISI) and intercarrier interference (ICI) for the desirednsignal at the output. In order to remove the timing acquisitionnrequirement of a receiver for an asynchronous MC-CDMA system, wenproposed a novel partial sampling MMSE (PS-MMSE) receiver. Numericalnresult shows that the PS-MMSE receiver without timing knowledge providesnsignificantly stronger interference suppression capability than thenLMMSE receiver with known timing. Moreover, a so-called reducedncomplexity partial sampling MMSE (RPS-MMSE) receiver is proposed to makenthe number of the receiver's taps independent of the number ofnsubcarriers. Results show that with a proper grouping parameter, a muchnless complicated RPS-MMSE receiver achieves almost the same performancenas the PS-MMSE receiver. Thus, one is able to implement an MMSE receivernwithout a prior timing requirement to perform multiuser detection fornthe MC-CDMA system in an asynchronous scenario at the expense of anslight complexity increase