Beam Alignment via Phase Matching

Millimeter-wave (mmWave) with phase array systems are utilized to increase the data rate in wireless communication systems. With the larger phase array, narrower beams can be generated to compensate for the path loss and boost the effective SNR. In order to perform beamforming, however, one must find the Angle of Arrival (AoA). In this paper, we consider the problem of initial beam alignment and CSI acquisition for (sub-)mmWave communication over a single-path channel with a single RF-chain. A three stage adaptive alignment algorithm based on the posterior probability, called Adaptive Phase Matching, is proposed. The algorithm maps the candidate angles of arrivals onto a simple constellation on the complex plane adaptively. The proposed scheme generalizes HiePM to both account for practically feasible antenna patterns as well as utilize the phase information. Furthermore, an upper bound of the expected search time for any given alignment resolution and error probability is derived.