Performance analysis of adaptive modulation and transmit antenna selection with channel prediction errors and feedback delay

Abstract

Rate-adaptive modulation and transmit antenna selection require channel knowledge at the transmitter, typically achieved using a feedback communications path from receiver to transmitter. Feedback delay in such systems causes outdated channel knowledge at the receiver and thus suboptimal switching decisions. This study evaluates the effect of degraded switching and proposes a channel prediction scheme to mitigate against delay-induced performance degradation, specifically when deployed in Rayleigh fading channels using maximum ratio combining at the receiver. Shannon capacity expressions are found and then closed form bit-error-rate and average spectral efficiency expressions derived – all derivations supporting arbitrary number of antennas at both receiver and transmitter. These expressions are developed to allow optimal switching boundaries to be determined for M-quadrature amplitude modulation rate adaptation under different degrees of channel prediction error, system arrangement and number of antennas.