Iterative MAP multiuser detection for constant modulus constellations in synchronous CDMA

The paper generalizes our previous work on BPSK (Blunt, S.D. and Ho, K.C., Proc. IEEE ICASSP, p.2313-16, 2002) to multiuser detection for constant modulus constellations in synchronous CDMA communication systems based on maximum a posteriori (MAP) estimation. The known finite alphabet of discrete transmitted symbols is approximated as a stochastic parameter with Gaussian distributions centered at the true values of the symbol constellation. This allows for the development of a MAP estimator that takes a priori knowledge of the symbol constellation into account in order to improve estimation accuracy. We examine the performance of the proposed algorithm for BPSK, QPSK, and 8PSK and compare the results with other well-known multiuser detection techniques.