Hierarchical Beam Alignment in Single-User MIMO Single-Carrier Frequency Division Multiple Access Terahertz Communication Systems

Single-carrier frequency division multiple access (SC-FDMA) is a promising technique for high data rate Terahertz (THz) communications in future beyond 5G systems. Beam alignment (BA) is considered as a mandatory solution to establish a reliable communication link in SC-FDMA THz communication. However, existing BA methods introduce a large latency in searching for the optimal beam. In this paper, we propose a multi-armed bandit algorithm referred to as hierarchical beam alignment (HBA) for single-user SC-FDMA THz systems to reduce the beam alignment latency. HBA utilizes a hierarchical structure in the adopted codebook and the prior knowledge regarding the frequency-selective fading of the channel to speed up the BA process. Both theoretical analysis and simulation results illustrate that HBA converges to the optimal beam with high probability. The latency introduced by HBA is significantly lower compared to an exhaustive search method.