Super-Resolution Angle Estimation for RIS-Aided Wideband mmWave Communications

In this paper, we investigate super-resolution angle estimation (SRAE) for reconfigurable intelligent surface (RIS)-aided mmWave communications. For the RIS-aided narrowband system, based on beam sweeping using a wide-beam codebook, we propose a two-step SRAE (TS-SRAE) scheme. In the first step, the selected optimal wide beam is refined to a narrow beam. In the second step, we develop an angle quantization error correction method. Then, for the RIS-aided wideband system, we propose an adaptive codebook design scheme, where the angle domain is divided into two regions, including the central region and the edge region, regarding the beam squint effect. Based on the beam sweeping using the adaptive codebook, we propose a two-region SRAE (TR-SRAE) scheme. In the central region, we extend the TS-SRAE scheme for angle estimation. In the edge region, we formulate the angle estimation as a maximum-a-posteriori problem, which is then solved by our developed Bayesian inference method. Simulation results demonstrate that both TS-SRAE and TR-SRAE schemes can effectively reduce the training overhead and improve the achievable rate.