Maximum likelihood channel estimation of flat Rayleigh multi-user CDMA channels

Coherent detection in CDMA mobile radio is desirable but non-trivial. We have characterised the performance of maximum likelihood channel estimation in terms of the SNR degradation as well as the average MSE performance for three types of spreading codes, namely Gold codes, PN codes and self-orthogonal PN codes. The SNR degradation is as much as 3 dB for K=60 users when Gold codes were used for channel estimation. The effect of the higher Doppler fading rate was also shown to degrade the average MSE performance by less than 1.5 dB for the three types of spreading codes. We have also shown via simulation and analysis that the self-orthogonal PN code offers the best performance for use in channel impulse response estimation for quasi-synchronous channels