Multi-RF Chain Time Successive Space-Shift-Keying-M-ary Modulation: A Transmit Diversity Scheme

Abstract

A two-timeslot $N_{\text{RF}}$ radio frequency (RF) chain transmitter is proposed in this work that takes advantage of the independence of sum and difference of Gaussian random vectors to achieve second-order transmit diversity. Each RF chain in the transmitter is equipped with $N_t$ transmitter antennas such that the transmitter is capable of switching the modulation between space shift keying (SSK) and either $M$ -ary phase shift keying (MPSK) or $M$ -ary quadrature amplitude modulation (MQAM). In timeslot 1, the proposed multi-RF chain time successive SSK- $M$ -ary modulation (MRF-TSSM) uses SSK in each RF chain to transmit a block of $ N_{\text{RF}}$ information symbols. In timeslot 2, the same block of information symbols are transmitted using either MPSK or MQAM by activating all $ N_t$ antennas of every RF chain. For this system, the maximal likelihood detection metric, transmit diversity order, coding gain, and computational complexity are derived. The performance of MRF-TSSM is analyzed considering transmitter correlation using a tight upper bound of the bit error rate. The analysis is validated using simulation results, which show that MRF-TSSM achieves significant performance gains compared to some existing transmit diversity systems, and the transmit diversity of MRF-TSSM degrades only slightly even for high transmitter correlation. Furthermore, the performance of MRF-TSSM is studied with imperfect channel state information at the receiver.