Parallel Soft Information Forwarding in Non-Coherent MIMO System based on Unitary Space-Time Modulation

Parallel relay is an effective way to extend wireless communication distance. Employing multiple-input multiple-output (MIMO) relay can improve communication quality on a large scale, but the communication efficiency is reduced due to channel estimation. In this study, a mutual information-based estimate-and-forward scheme is proposed based on unitary space-time modulation in MIMO system. An equivalent transmission model is also constructed by regarding that the source signal is affected by a multiplicative factor and an additive noise. Based on this equivalent MIMO model, the generalized signal-to-noise ratio and global mutual information of the forwarding schemes are calculated. Error rate and mutual information analysis show that the proposed soft information forwarding can improve the reliability of parallel relaying system and has a better error rate performance than all the existing memory-less forwarding schemes.