Analysis of coded successive interference cancellation in multicarrier DS/CDMA systems

This paper presents a successive interference cancellation (SIC) scheme for a multicarrier (MC) asynchronous DS/CDMA system, wherein the output of a convolutional encoder modulates bandlimited spreading waveforms at different subcarrier frequencies. In every subband, the SIC receiver successively detects the interferers' signals and substracts them from that of the user-of-interest. The SIC receiver employs maximal-ratio combining (MRC) for detection of the desired user, and feeds a soft decision Viterbi decoder. A comparison is made among SIC-MRC, matched filter detection with maximal-ratio combining (MF-MRC), and N-tap minimum mean-squared error (MMSE) receivers with optimal tap coefficients, assuming a slowly varying, frequency selective, Rayleigh fading channel, where N is the processing gain. Analysis and simulation results show that the SIC-MRC can obtain a performance comparable to that of N-tap MMSE receivers, and both of them have better ability to suppress multiple-access interference (MAI) than does the MF-MRC. On the other hand, more powerful codes do not necessarily guarantee the better performance, since frequency diversity will decrease caused by a lower code rate. Finally, with small tracking errors, results show that SIC-MRC can still retain a performance advantage over MF-MRC.