Performance comparison of space diversity and equalization techniques for indoor radio systems

By means of analytical and numerical methods, we derive the bit error rate (BER) of π/4-DQPSK systems in frequency-selective fading channels. For a theoretical analysis of the system, a simplified two-ray channel model has been used. However, both Rayleigh and lognormal distributions for the ray envelope have been considered. The system performance in the presence of antenna diversity and in combination with a new nonlinear equalizer has been evaluated. In particular, it is seen that in flat fading environments, space diversity may improve the performance by more than 10 dB at a BER=10^-3. However, for channels with a large delay spread, nonlinear intersymbol interference (ISI) is the predominant disturbance, and the performance can only be enhanced by the nonlinear equalizer