Distributed switch and stay combining with partial relay selection and signal space diversity

Spatial diversity schemes are often used to extract additional performance from wireless communication systems. Incorporating the partial relay selection (PRS) protocol into a distributed switch-and-stay combining (DSSC) cooperative communication network gives the benefit of diversity while simplifying hardware, processing and feedback requirements. Because only a single relay is ever active, the destination employs no combiner; the best relay is chosen based on first-hop relay conditions. However, achieved performance is worse than other distributed protocols, such as distributed selection combining (DSC). In this study, signal space diversity (SSD) is added to the DSSC-PRS system to provide further diversity and error performance gains, at the expense of necessitating a maximum-likelihood detector with increased complexity at the receiver. Analytical results are presented in the form of a lower bound based on the minimum distance lower bound for SSD systems and are verified with simulation. The DSSC-PRS-SSD system shows an improvement of 5 dB at a symbol error rate of 10^-4 as well as a clear diversity order improvement. Spectral efficiency of the new system with SSD is slightly decreased at low signal-to-noise ratios, but is still an improvement over other distributed schemes, such as DSC.