Fast Accurate Beam and Channel Tracking for Two-dimensional Phased Antenna Arrays
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The sparsity and the severe attenuation of millimeter-wave (mmWave) channel imply that highly directional communication is needed. The narrow beam produced by large array requires accurate alignment, which can be achieved by beam training with large exploration overhead in static scenarios. However, this training expense is prohibitive when serving fast-moving users. In this paper, we focus on accurate two-dimensional (2D) beam and channel tracking problem in mmWave mobile communication. The minimum exploration overhead of 2D tracking is given in theory first. Then the time-varying channels are divided into three cases: Quasi-static Case, Dynamic Case I and Dynamic Case II. We further develop three tracking algorithms corresponding to these three cases. The proposed algorithms have several salient features: (1) fading channel supportive: they can simultaneously track the channel gain and 2D beam direction in fading channel environments; (2) low exploration overhead: they achieve the minimum exploration requirement for 2D tracking; (3) fast tracking speed and high tracking accuracy: in Quasi-static Case and Dynamic Case I, the tracking error is proved to converge to the minimum Cramer-Rao lower bound (CRLB). In Dynamic Case II, our tracking algorithm outperforms existing algorithms with lower tracking error and faster tracking speed in simulation.
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