This work studies the asymptotic sum-rate performance of a multi-user reconfigurable intelligent surface (RIS) assisted-multiple-input single-output (MISO) downlink system under imperfect CSI and Rayleigh and Rician fading. We first extend the existing least squares (LS) ON/OFF channel estimation protocol to a multi-user system, where we derive minimum mean squared error (MMSE) estimates of all RIS-assisted channels over multiple sub-phases. We also consider a low-complexity direct estimation (DE) scheme, where the BS obtains the MMSE estimate of the overall channel in a single sub-phase. Under both protocols, the BS implements maximum ratio transmission (MRT) precoding while the RIS phases are studied in the large system limit, where we derive deterministic equivalents of the signal- to-interference-plus-noise ratio (SINR) and the sum-rate. The derived asymptotic expressions reveal that under Rayleigh fading, the RIS phase-shift values do not play a significant role in improving the sum-rate but the RIS still provides an array gain. However, under Rician fading, we show that RIS provides both array and reflect beamforming gains. A projected gradient ascent-based algorithm is used to optimize the phase-shifts under both ON/OFF and DE protocol. Simulation results show that the DE of the overall channel yields better downlink performance when considering large systems.

翻译：这项工作研究多用户可重新配置智能表面(RIS)协助多输出单发单发单发系统在不完善的 CSI 和Raylei和Rician 退退退状态下连接系统下线系统中的无症状总和率表现。我们首先将现有的最低正方(LS) ON/OFF频道估算协议扩展至多用户系统,我们从该系统中得出所有RIS辅助渠道在多个子阶段的最低平均正方差(MMSSE)估计值。我们还考虑低兼容性直接估算(DE)方案,即BS在单一子阶段获得总信道MMSE估计值。根据这两项议定书,BS实施最大比率传输(MRT)预编码,同时在大型系统限度内研究TRIS阶段,我们从中得出信号对干涉加营养比率(SIN)和基于总和比率的确定性等值。从分析中得出的弱性表示,在Rayliele Flax 下,在改进整个轨道的预测性平流中,我们提供的SLISLA(RRA) 和递增) 下递增成果。