Partial sampling MMSE interference suppression in asynchronous multicarrier CDMA system

Linear minimum mean square error (LMMSE) receivers for asynchronous multica rrier code division multiple access (MC-CDMA) system under frequency-select ive Rayleigh fading channel is studied in this paper. The performance of th is LMMSE receiver Is evaluated and shown to be superior to that of the othe r two schemes, equal-gain combining (EQC) and maximum-ratio combining (MRC) . However, a perfect timing estimation of the desired user is needed for th ese receivers, as a misaligned sampling interval of these receivers results in severely self intersymbol interference (ISI) and intercarrier interfere nce (ICI) for the desired signal at the output. In order to remove the timi ng acquisition requirement of a receiver for an asynchronous MC-CDMA system , we proposed a novel partial sampling MMSE (PS-MMSE) receiver. Numerical r esult shows that the PS-MMSE receiver without timing knowledge provides sig nificantly stronger interference suppression capability than the LMMSE rece iver with known timing. Moreover, a so-called reduced complexity partial sa mpling MMSE (RPS-MMSE) receiver is proposed to make the number of the recei ver's taps independent of the number of subcarriers. Results show that with a proper grouping parameter, a much less complicated RPS-MMSE receiver ach ieves almost the same performance as the PS-MMSE receiver. Thus, one is abl e to implement an MMSE receiver without a prior timing requirement to perfo rm multiuser detection for the MC-CDMA system in an asynchronous scenario a t the expense of a slight complexity increase.