  Spatial Modulation (SM) can utilize the index of the transmit antenna (TA) to
transmit additional information. In this paper, to improve the performance of
SM, a non-uniform constellation (NUC) and pre-scaling coefficients optimization
design scheme is proposed. The bit-interleaved coded modulation (BICM) capacity
calculation formula of SM system is firstly derived. The constellation and
pre-scaling coefficients are optimized by maximizing the BICM capacity without
channel state information (CSI) feedback. Optimization results are given for
the multiple-input-single-output (MISO) system with Rayleigh channel.
Simulation result shows the proposed scheme provides a meaningful performance
gain compared to conventional SM system without CSI feedback. The proposed
optimization design scheme can be a promising technology for future 6G to
achieve high-efficiency.
