Millimeter-wave transceivers use large antenna arrays to form narrow high-directional beams and overcome severe attenuation. Narrow beams require large signaling overhead to be aligned if no prior information about beam directions is available. Moreover, beams drift with time due to user mobility and may need to be realigned. Beam tracking is commonly used to keep the beams tightly coupled and eliminate the overhead associated with realignment. Hence, with periodic measurements, beams are adjusted before they lose alignment. 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. In our approach, the change of direction is updated using the rate variation prediction of beam angles via three different solutions. Our approach incurs no additional overhead in pilots, yet, the performance of beam tracking is improved significantly. Numerical results reveal an SNR enhancement associated with reducing the MSE of the beam directions. In addition, our approach reduces the pilot overhead by 60% and up to 87% while achieving a similar total tracking duration as the state-of-the-art.

翻译：毫米波收发器利用大规模天线阵列形成窄高定向波束以克服严重衰减。若无波束方向先验信息，窄波束需消耗大量信令开销以实现对准。此外，波束会因用户移动性随时间漂移，可能需要重新对准。常规使用波束跟踪来保持波束紧密耦合，消除重新对准带来的开销。因此，通过周期性测量，可在波束失准前进行调整。我们提出一种模型，其中接收器根据精心计算的波束连续变化估计，在每个物理层样本上“连续”调整波束方向。该方法通过三种不同方案利用波束角度的速率变化预测来更新方向变化。我们的方法在导频中不引入额外开销，但显著提升了波束跟踪性能。数值结果表明，波束方向均方误差的降低带来了信噪比提升。此外，在达成与现有技术相当的总跟踪时长前提下，我们的方法将导频开销降低60%至87%。