Complexity reduction of maximum likelihood multiuser detection (ML MUD) receivers with carrier interferometry codes in MC CDMA

Abstract

We propose to use carrier interferometry (CI) codes to reduce the complexity of the maximum likelihood multiuser detection (ML MUD) receiver in MC CDMA systems with carrier frequency offsets (CFOs). Complexity reduction is achieved by exploiting the sparsity of the cross correlation matrix of CI codes. It is shown that, for a fully loaded MC CDMA with spread gain N over a multipath channel with length L, the complexity of the ML MUD receiver grows exponentially with 2L - 1 (instead of N), where L << N in a typical setting. Moreover, an upper bound for the minimum error probability is derived. Finally, simulation results are given to corroborate theoretical results.