Performance of adaptive transmit power control in π/4 DQPSK mobile radio systems in flat Rayleigh fading channels

摘要

In this paper we theoretically study and analyze adaptive transmit power control schemes forπ/4 shifted differentially encoded QPSK based mobile radio transmissions with both coherent and differential detection under flat Rayleigh fadingconditions. By assuming the power control to be fast enough to compensate for Rayleigh fading, we develop theoretical general expressions for average relative transmitted power and average bit error rate (BER) for different levels of power control. Theanalytical results indicate the average transmit power for a given BER of 10{sup}(-3) can be reduced to a maximum of 7-9 dB relative to the conventional constant transmit power scheme. The approximate conditional BER expression, assumed for differentialdetection, is found to be very close representation of the exact BER expression available in the literature.