In this paper, for a single-input multiple-output (SIMO) system aided by a passive reconfigurable intelligent surface (RIS), the joint transmission accomplished by the single transmit antenna and the RIS with multiple controllable reflective elements is considered. Relying on a general capacity upper bound derived by a maximum-trace argument, we respectively characterize the capacity of such \rev{a} channel in the low-SNR or the rank-one regimes, in which the optimal configuration of the RIS is proved to be beamforming with carefully-chosen phase shifts. To exploit the potential of modulating extra information on the RIS, based on the QR decomposition, successive interference cancellation, and a strategy named \textit{partially beamforming and partially information-carrying}, we propose a novel transceiver architecture with only a single RF front end at the transmitter, by which the considered channel can be regarded as a concatenation of a vector Gaussian channel and several phase-modulated channels. Especially, we investigate a class of vector Gaussian channels with a hypersphere input support constraint, and not only generalize the existing result to arbitrary-dimensional real spaces but also present its high-order capacity asymptotics, by which both capacities of hypersphere-constrained channels and achievable rates of the proposed transceiver with two different signaling schemes can be well-approximated. Information-theoretic analyses show that the transceiver architecture designed for the SIMO channel has a boosted multiplexing gain, rather than one for the conventionally-used optimized beamforming scheme.Numerical results verify our derived asymptotics and show notable superiority of the proposed transceiver.

翻译：摘要：本文研究了由无源可重构智能表面（RIS）辅助的单输入多输出（SIMO）系统，其中考虑由单发射天线与具有多个可控反射单元的RIS共同实现的联合传输。基于最大迹论证推导出的通用容量上界，我们分别刻画了该信道在低信噪比或秩一场景下的容量，并证明此时RIS的最优配置为采用精心选择相移的波束赋形。为挖掘RIS上调制额外信息的潜力，基于QR分解、串行干扰消除以及一种称为"部分波束赋形、部分信息承载"的策略，我们提出了一种新型收发机架构，该架构仅在发射端使用单个射频前端，使得所考虑信道可视为矢量高斯信道与多个相位调制信道的级联。特别地，我们研究了一类具有超球面输入支撑约束的矢量高斯信道，不仅将现有结论推广至任意维实空间，还给出了其高阶容量渐近表达式，由此可对超球面约束信道的容量及所提收发机在两种不同信号方案下的可达速率进行良好近似。信息论分析表明，为SIMO信道设计的收发机架构具有提升的复用增益，而非传统优化波束赋形方案中的单位复用增益。数值结果验证了所推导的渐近表达式，并表明所提收发机具有显著优越性。