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

A two-timeslot NRF 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 NRF information symbols. In timeslot 2, the same block of information symbols are transmitted using either MPSK or MQAM by activating all Nt 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.