Reconfigurable intelligent surface (RIS) is envisioned to be a promising green technology to reduce the energy consumption and improve the coverage and spectral efficiency of massive multiple-input multiple-output (MIMO) wireless networks. In a RIS-aided MIMO system, the acquisition of channel state information (CSI) is important for achieving passive beamforming gains of the RIS, but is also challenging due to the cascaded property of the transmitter-RIS-receiver channel and the lack of signal processing capability of the passive RIS elements. The state-of-the-art approach for CSI acquisition in such a system is a pure training-based strategy that depends on a long sequence of pilot symbols. In this paper, we investigate semi-blind cascaded channel estimation for RIS-aided massive MIMO systems, in which the receiver simultaneously estimates the channel coefficients and the partially unknown transmit signal with a small number of pilot sequences. Specifically, we formulate the semi-blind cascaded channel estimation as a trilinear matrix factorization task. Under the Bayesian inference framework, we develop a computationally efficient iterative algorithm using the approximate message passing principle to resolve the trilinear inference problem. Meanwhile, we present an analytical framework to characterize the theoretical performance bound of the proposed approach in the large-system limit via the replica method developed in statistical physics. Extensive simulation results demonstrate the effectiveness of the proposed semi-blind cascaded channel estimation algorithm.
翻译:重新配置智能表面(RIS)被认为是一个大有希望的绿色技术,可以降低能源消耗,提高大规模多投入多输出多输出无线网络的覆盖面和光谱效率。在RIS辅助的MSIMO系统中,获取频道国家信息对于实现RIS的被动波束增益十分重要,但由于发报机-接收器频道的分级特性以及被动的RIS元素缺乏信号处理能力,因此也是具有挑战性。在这样一个系统中获取 CSI的先进方法纯粹是基于培训的纯战略,取决于一系列长的试点符号。在本文件中,我们调查了对RIS辅助的大型MIMO系统的半盲级级级级级级频道估算,在该系统中,接收器同时估计频道系数和部分未知的传输信号,而试验序列数量较少。具体地说,我们将半盲级级级级级链的频道估算作为三线矩阵的指数化计算任务。在Bayeserine 框架下,我们开发了一种基于计算效率的计算高效的代数级程程计算法,在通过IMIMIMIMF原则上,在计算出一个拟议的系统上,在逻辑上,在通过逻辑上,在逻辑上,在逻辑上,在逻辑上,我们开发了一种计算中,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,以上,以上,以上,以上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,在逻辑上,我们上,我们上,我们上,我们,