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

Abstract

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