Channel Recovery Using History Information for Hybrid Beamforming Systems

Millimeter-wave channels are angular sparse. Under practical channels, angle of arrivals (AoAs) tend to change slowly over time, while the path gain corresponding to each AoA may vary relatively fast. To exploit the property of slow AoAs variation, this paper proposes two approaches that consider measurements of current and multiple previous beam sweeping periods to improve channel recovery quality at the user equipment (UE). Given slow AoAs variation, the first approach suggests that UE update the beam sweeping codebook based on estimated AoAs to improve signal to noise ratio for the following beam sweeping. When path gains also vary slowly, the second approach suggests that UE estimate channel AoAs using both current and history measurements, and estimate path gains only using current measurement. The first approach is more robust to channel variation since it only assumes slow AoAs variation. When channel variation is small, the second approach exhibits advantage over the first one, and both outperform closed form simultaneous orthogonal matching pursuit (SOMP) proposed in [1], which only uses current measurement for channel recovery. When channel variation is relatively large, codebook update still brings gains over closed form SOMP.