Performance of adaptive fuzzy-based code allocation for 2-D spreading OFCDM mobile communication systems

In this paper, we investigate the multiuser performance in a 2-D spreading orthogonal frequency coded division multiplexing (OFCDM) communication system over frequency and time selective fading channels. To compromise between the diversity gain and the multiple access interference (MAI), we propose an adaptive fuzzy logic to infer adequate 2-D spreading codes and to assign the orthogonal variable spreading factor (OVSF) codes to active users for OFCDM mobile communication systems. Simulation results show that the proposed fuzzy-based code allocation (FBCA) scheme can not only suppress the MAIs induced by the non-orthogonality but also exploit the diversity gain over time and frequency selective fading channels and then outperforms the orthogonal code allocation (OCA) scheme at all system load.