On Optimal Multi-user Beam Alignment in Millimeter Wave Wireless Systems

摘要: Directional transmission patterns (a.k.a. narrow beams) are the key to wireless communications in millimeter wave (mmWave) frequency bands which suffer from high path loss and severe shadowing. In addition, propagation channel mmWave frequencies incorporates only a few number of spatial clusters requiring procedure align corresponding beams with angle departure (AoD) clusters. The objective this procedure, called beam alignment (BA) is increase beamforming gain for subsequent data communication. Several prior studies consider optimizing BA achieve various objectives such as reducing overhead, increasing throughput, power consumption. While these mostly provide optimized schemes scenarios single active user, there often multiple users practical networks. Consequently, it more efficient terms overhead delay design multi-user can perform management collectively. This paper considers class where base station performs one shot scan angular domain simultaneously localize users. minimize average expected width remaining uncertainty regions (UR) on AoDs after receiving users' feedbacks. Fundamental bounds optimal performance analyzed using information theoretic tools. Furthermore, optimization problem formulated scheme, provides significant gains compared sweeping used 5G standard, proposed.