Dynamic SSK-BPSK System Under Transmitter Correlated Nonidentical Rayleigh Fading

Abstract

Space shift keying (SSK) is a recent multiple-input multiple-output (MIMO) modulation scheme where information is conveyed by the index of the activated antenna. An advantage of SSK transmitter is that it requires only one radio frequency (RF) chain. To achieve transmit diversity in such a single RF chain two antenna transmitter, modulation is dynamically changed between SSK and a modified form of binary phase shift keying (BPSK) based on channel condition in dynamic SSK-BPSK (DSB). DSB achieves second-order transmit diversity which is attributed to the statistical independence of sum and difference of independent and identically distributed complex Gaussian channel vectors. In order to study the impact of correlated and nonidentically distributed channel vectors on the transmit diversity of DSB, we consider transmitter correlated nonidentical Rayleigh fading in this work. We derive the bit error rate (BER) expression of DSB and the probability of using BPSK in DSB for the considered fading channel. Using asymptotic BER expressions, we study the diversity order of DSB. Results show that the transmit diversity of DSB is unaffected by the transmitter correlation when channel fading is identical, but nonidentical fading affects transmit diversity. Finally, we corroborate our analyses with simulation results.