Optimal Power and Modulation Adaptation Policies with Receiver Diversity over Rayleigh Fading Channel

Abstract

<p>Efficient bandwidth utilization is paramount in wireless communication systems, particulary in fading<br />environments, since fading is one of the major constraints that impair communication in wireless systems.<br />The bandwidth efficiency of a wireless communication system can be enhanced significantly by employing<br />power and modulation adaptation policies with diversity combining gain. In this work, first we examine an<br />analytically-derived solution for Maximum Combining Ratio (MRC) diversity technique for the capacity per<br />unit bandwidth. Then, we design an adaptive transmission system to utilize the diversity combining gain while<br />retaining the target BER by adapting power and constellation size using continuous power, channel inversion<br />with fixed rate and continuous power and disrecte-rate. By considering the effect of diversity combining<br />gain, the designed system yields a reasonable spectral efficiency with respect to target BER that grows as<br />the number of diversity levels increase. Furthermore, the presented results show continuous power and<br />discrete-rate adaptation policy reduces probability of outage unlike its achieved spectral efficiency is close<br />to other selected policies, which ratifies the optimized switching thresholds and makes it best candidate for<br />imperfect channel conditions.</p>