Generalized Selection Combining for Dynamic SSK-BPSK Systems

Space shift keying (SSK) is a multiple-input multiple-output (MIMO) technique in which the transmitter can be designed with a single radio frequency (RF) chain. By adaptively selecting the modulation in a two antenna transmitter as either SSK or binary phase shift keying (BPSK), dynamic SSK-BPSK (DSB) obtains second order transmit diversity. In this work, we conceive DSB with generalized selection combining (DSB-GSC) to reduce the receiver circuit complexity. Specifically, we propose the metrics of modulation selection and receiver antenna selection for DSB where the receiver is equipped with lesser number of RF chains than its antennas. The performance of DSB-GSC is analyzed with exact bit error rate (BER) expression which is validated using simulation results. From the results, we infer that DSB-GSC provides diversity order equal to twice the number of receiver antennas irrespective of the number of RF chains used at the receiver. We further infer that there is only small SNR gains attained for increasing receiver RF chains. Thus the receiver complexity of the system can be considerably reduced with a small performance loss compared to that of full complex receiver.