An Adaptive MLSD Receiver Employing Noise Correlation

A per-survivor processing (PSP) maximum likelihood sequence detection (MLSD) receiver is developed for a fast time-varying frequency selective Rayleigh fading channel with colored additive noise which follows an auto-regressive (AR) model with unknown parameters. The correlation between noise samples is exploited to considerably enhance the performance of the communications. The maximum likelihood criterion is employed based on unknown noise parameters. This criterion has some desired properties, e.g., it has a unique joint minimum at the true values of the channel and the noise parameters. The new PSP-MLSD algorithm detects the input data and jointly estimates the noise and the channel parameters all together. The proposed structure can be viewed as a traditional PSP-MLSD receiver combined with an adaptive whitening filter. In a colored noise environment, this scheme offers faster tracking property, more accurate estimation of the channel and a substantially lower error probability compared with the traditional PSP-MLSD structure. The Signal-to-Noise-Ratio (SNR) improvement achieved by the proposed receiver, which can be called the Noise Whitening Gain (NWG), is almost equal to the ratio of the energy of the additive noise to the energy of the unpredictable noise component. The squared of the NWG gives also an accurate approximation for the BER improvement ratio obtained by using the proposed algorithm compared with traditional one.