Switched-diversity trellis-coded 8-DPSK for mobile radio applications

The performance of 64 kbit/s two-branch switched-diversity 4DPSK (differential phase shift keying) and TCM-8DPSK systems in the presence of a simulated Rayleigh fading channel are analyzed. The bit error rate (BER) is obtained as a function of switching threshold, maximum Doppler shift frequency of the channel, and interleaving buffer size. The optimum switching threshold is determined as a function of the other parameters. It is found that the location of the optimum switching threshold is nearly constant for different interleaving buffer sizes, and practically unaffected by the Doppler frequency. Using the optimum threshold, the BER-performance of the systems is determined with Doppler frequency and interleaving buffer size as parameters. One of the most significant results is that the switched-diversity trellis-coded modulation (TCM) 8DPSK system improves the switched-diversity 4DPSK performance by more than 8 dB for a BER ⩽10^-3, a Doppler frequency of 5 Hz, and an interleaving buffer size of 20×5000 symbols