Single Symbol-Based Hybrid Reconfigurable Intelligent Surface-Assisted Millimeter Wave Channel Estimation

Current schemes for the hybrid reconfigurable intelligent surface (RIS) assisted mmWave communication system select a limited number of RIS elements to connect to a single radio frequency (RF) chain. This is done to estimate the channels of the base station (BS)-mobile station (MS) and MSRIS separately. However, these schemes do not take full advantage of the reconfigurable characteristics of RIS elements, and require a large number of training symbols to achieve more accurate estimation performance. To tackle these problems, we propose a single symbol-based hybrid RIS-assisted mmWave channel estimation scheme. Firstly, we subtly exploit the dynamic programmable and reconfigurable characteristics of RIS elements based on the structure of a single RF chain, so as to obtain equivalent multi-dimensional received signals. Then, the angular parameters and path gains of multiple paths of the channel can be estimated within a single pilot symbol, using atomic norm minimization (ANM), the alternating direction method of multipliers (ADMM), and the least square (LS) algorithms to achieve fine-grained sensing of the channel. Numerical results show that the proposed scheme achieves favorable channel estimation performance compared to existing hybrid RIS schemes within a single pilot symbol period.