부산대학교 도서관

Millimeter-wave transceivers use large antenna arrays to form high-directional beams and overcome severe attenuation. A large array size leads to a costly initial beam alignment process if no prior information about beam directions is available. To eliminate the overhead associated with realignment, beam tracking is a common approach to keep the beams tightly coupled. Beam tracking becomes more difficult as the beams get narrower since slight misalignment leads to significant degradation in SNR as the beam coherence times are short. As a result, beams may lose alignment before they can be readjusted periodically with the aid of pilot signals. We propose a model where the receiver adjusts beam direction “continuously” over each physical-layer sample according to a carefully calculated estimate of the continuous variation of the beams. Our approach contrasts the classical methods, which fix the beams in the same direction between pilots. In our approach, the change of direction is configured using the estimate of variation rate via a Continuous-Discrete Kalman filter. Our method incurs no additional pilot overhead, yet, the performance of beam tracking and the resulting effective SNR are improved significantly. In typical situations, we achieve 4–7 dB enhancement in SNR and MSE reduction up to 99.5%.