Effect of correlation and power distribution on transmitter diversity Rician and Rayleigh fading channels

In this paper we consider the effect of antenna diversity transmission in a spread spectrum system where the power radiated from each of the antennas can be varied. We look at DPSK data modulation systems. It is shown that for equal power distribution the performance of the receiver degrades as the paths become correlated for a Rayleigh fading path but improves for a Rician fading channel. It is shown numerically that there is an optimum power distribution that minimizes the BER given the data symbol energy or minimizes the requirement on the symbol energy given a BER requirement. The optimum power distribution deviates from the equal distribution solution when the paths gains are not equal.