Optimum multiuser detection for MC-CDMA systems using sphere decoding

Abstract

The maximum likelihood joint detection of all users in a multi-carrier code division multiple access (MC-CDMA) system has a prohibitive complexity, growing exponentially with the number of users, when it is performed using an exhaustive search. In this paper, a novel ML multiuser detection algorithm is proposed, whose complexity is a polynomial function of the number of users and is independent of the modulation size. The MC-CDMA system is modelled using a sphere packing lattice representation and an efficient lattice decoder, called the sphere decoder, is applied to jointly detect all users. Simulation results are proposed up to 64 users transmitting 16-QAM symbols.