A novel precoding scheme for downlink multi-user spatial modulation system

Spatial Modulation is a newly developed concept for multi-antenna systems, which could greatly reduce the signal processing complexity and hardware implementation burden faced by these systems today. To improve the spectral efficiency of spatial modulation system, a novel precoding scheme for downlink multi-user system is proposed in this paper. The precoding scheme not only cancels the inter-user interference, but also preserves the information embedded both in constellation symbols as well as in transmit antenna indexes, decomposing the system into independent single-user spatial modulation systems. Simulation results show that with a high transmission rate, the proposed scheme offers a smaller bit error rate than multi-user Zero Forcing precoding in practical SNR region. With the same base station antenna number and single-antenna user number, it also outperforms Zero Forcing precoding in terms of achievable sum rate. Furthermore, systems using our scheme could achieve a multi-user gain over single-user spatial modulation system.