Wavelet multiuser detector for asynchronous DS-CDMA systems

A novel wavelet transform based multiuser detector (WTMUD) is proposed for asynchronous DS-CDMA systems in flat Rayleigh fading channels. In this approach, wavelet reconstruction and decomposition are performed on the spread signal sequences and the received signals, respectively. Using the existing multiuser detection methods and the properties of wavelet decomposition, the information bits can be recovered from received signal. In this way, a series of WTMUDs can be implemented conveniently. The computation complexity of inverting correlation matrix of asynchronous WTMUDs is the same as that of synchronous multiuser detectors. And WTMUDs can realize the bit-by-bit detection of desired users. In addition, wavelet transform can mitigate the influence of noise to improve the signal-to-noise ratio (SNR) to achieve lower bit-error-rate (BER). Simulation results show that WTMUDs' provide better performance on the aspects of BER performance and near-far resistance ability in flat Rayleigh fading channels, and larger system capacity in AWGN channels than their counterparts that do not incorporating wavelet transform.