Minimum probability of error demodulation for MC-CDMA

Multi-carrier code division multiple access (MC-CDMA) is an attractive choice for high speed wireless communication as it mitigates the problem of intersymbol interference (ISI) and also exploits frequency diversity. The data stream in MC-CDMA is spread using a user specific spreading sequence in the frequency domain and every chip travels on a different sub-carrier. At the receiver, the different sub-carriers have to be combined properly to form the decision variable. Minimum mean square error (MMSE) detector is a popular choice for this, but as it tries to minimize the mean square error (MSE) and not the bit error rate (BER), the BER it attains is not optimum. In this paper, we propose a minimum probability of error (MPOE) based linear multiuser detector, which tries to minimize the probability of error, by exploiting the probability density function (pdf) of the filter output. Theoretical and simulation results are presented for the MPOE detector and it can be seen that the MPOE detector outperforms the MMSE detector.