Reduced complexity iterative multi-user detector for IDMA (Interleave-Division Multiple Access) system

Interleave-Division Multiple Access (IDMA) is a multi-user scheme in which chip interleavers are the only means of user separation. The receiver involves a chip-by-chip iterative multi-user detection. Its complexity increases in a linear manner with the number of users, the number of iterations and the number of paths in the case of multipath channels. In spite of this linear increase, this can be prohibitive if a hardware implementation of the system is expected. In this paper, we propose some reduced complexity multi-user detectors for the IDMA receiver. Performance in terms of bit error rate and complexity with respect to the number of operations of the proposed detectors are compared with that of the original detector for AWGN channels. One of the proposed detectors presents the best trade-off between performance and complexity. We then extend our study in the context of multipath channels. A system combining OFDM and IDMA using this selected detector is studied and compared with the original OFDM-IDMA system. Our results show that, for high Eb/N0, the OFDM-IDMA with the selected detector can achieve the same performance as the original one with a lower complexity.