A Complexity Reduced ML Detector on OFDM-CDM Systems in Mobile Channel

Orthogonal frequency-division multiplexing (OFDM) is one of the most promising techniques for the 4-th generation mobile system. When the OFDM system is applied to cellular environment, it is required to make the transmission scheme robust to other-cell interference (OCI). The use of code division multiplexing (CDM) has been considered to mitigate the OCI in OFDM systems. In cell boundary, it is desirable to design OFDM-CDM transceiver scheme to reduce the effect of OCI. In this paper, we consider transceiver schemes for cell boundary users in the OFDM-CDM downlink. We propose a simplified maximum likelihood (ML) detection scheme that can nearly achieve full ML detection performance. In addition, a new spreading code is proposed for BPSK modulation, yielding a receiver gain of about 1dB regardless of detection schemes. Finally, the performance of the proposed schemes is verified by computer simulation.