Receiver Design and Performance Analysis of Multiplicative Superposition Signaling Scheme for Heterogeneous-Speed Users

On the two-user multiple-input multiple-output (MIMO) broadcast channel, when one user with low mobility (called the static user) knows the exact channel state information (CSI) whereas the other user with high mobility (called the dynamic user) does not know CSI, a novel multiplicative superposition signaling scheme could obtain additive degree of freedom. Based on this novel signaling scheme, different types of receivers over an two-Heterogeneous-Speed-User MIMO broadcast channel are investigated in this study. At the dynamic user, the non-coherent maximum likelihood detection (NCMLD) is used. At the static user, we propose two hard detection scheme based on NCMLD-ML and NCMLD-Minimum-Mean-Square-Error (MMSE), respectively. We derive the union bound of the symbol error rate for the optimal hard detection scheme and the upper bound of that for the MMSE-based hard detection scheme. To avoid the error-propagation problem in the hard detection schemes, we also propose a low-complexity soft detection scheme based on the conditional expectation and MMSE (CE-MMSE). Simulation results show that the NCMLD-ML scheme outperforms the NCMLD-MMSE scheme and CE-MMSE scheme. Furthermore, CE-MMSE scheme has a better error performance than NCMLD-MMSE in the low signal-to-noise ratio region at the expense of higher complexity which is inconsiderable when compared with NCMLD-ML scheme. The numerical and simulation results verify the correctness of the theoretical analysis.