Channel outage performance of QPSK and π/4-DQPSK in a multipath fading environment

Channel outage probabilities for QPSK and π/4-DQPSK are evaluated in a Gaussian profiled multipath fading channel with additive white noise by computer simulation. Assuming a minimum acceptable bit error rate of 10^-5, it is found that even with a very small normalised delay spread d´=0.05, the channel outage probability is greater than 10^-3. Using 4-branch switched diversity this can be reduced such that channel outage is less than 10^-5 with d´<0.2 (QPSK) or 0.13 (π/4-DQPSK)