RIS-assisted receive spatial modulation for high-speed railway communication

In high-speed railway (HSR) wireless communication, the rapid channel changes and limited high-capacity access cause significant impact on the link performance. Meanwhile, the Doppler shift caused by high mobility leads to the inter-carrier interference. In this paper, we propose a reconfigurable intelligent surface (RIS)-assisted receive spatial modulation (SM) scheme based on the spatial-temporal correlated HSR Rician channel. The characteristics of SM and the phase shift adjustment of RIS are used to mitigate the performance degradation in high mobility scenarios. Considering the influence of channel spatial-temporal correlation and Doppler shift, the effects of different parameters on average bit error rate (BER) performance and upper bound of ergodic capacity are analyzed. Therefore, a joint antenna and RIS-unit selection algorithm based on the antenna removal method is proposed to increase the capacity performance of communication links. Numerical results show that the proposed RIS-assisted receive SM scheme can maintain high transmission capacity compared to the conventional HSR-SM scheme, whereas the degradation of BER performance can be compensated by arranging a large number of RIS-units. In addition, selecting more RIS-units has better capacity performance than activating more antennas in the low signal-to-noise ratio regions.