Performance of an MC-CDMA system based on the complex wavelet packet and pre-equalisation technique

A novel complex wavelet packet-based MC-CDMA (CWP-MC-CDMA) system is proposed, based on the analysis of the principle of multi-carrier code division multiple access (MC-CDMA) and the use of the optimised complex wavelet packet. By making use of the reciprocity between uplink and downlink channels under the time-division duplex (TDD) schemes, the authors adopt the preequalisation technique to simplify the receiver architecture and suppress the multi-access interference (MAI) effectively. The system performance is investigated in multipath Rayleigh fading channels. The CWP-MC-CDMA scheme with the energy-controlled pre-equalisation technique is also developed due to the greater energy consumption in pre-compensating for the weak subcarriers. The theoretical analysis and simulation results show that the proposed CWP-MC-CDMA system has a superior bit-error rate (BER) performance to that of the conventional MC-CDMA system based on DFT (DFT-MC-CDMA), and the system with preequalisation also outperforms other detection-combining techniques, such as equal gain combining (EGC), maximum ratio combining (MRC), orthogonality restoring combining (ORC) and minimum mean square error combining (MMSEC).