Low-Complexity Mobile User Tracking in Quantized mmWave MIMO Systems

The deployment of large-scale arrays in millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems has enabled highly accurate localization by reaping the benefits of high angular resolution. However, the use of massive antennas in mmWave systems results in expensive hardware costs and computational burdens. This paper considers mobile user localization in quantized mmWave MIMO systems, where each base station (BS) antenna is equipped with low-resolution analog-to-digital converters. The proposed approach integrates the beamspace model with off-grid information to capture channel sparsity in the angular domain. The temporal correlation of angle-of-arrival (AoA) is characterized by a Markov process for moving users. To estimate channel gains and time-varying AoAs, while keeping the computational complexity low, we further develop generalized approximate message passing and AoA tracking methods. In dense multipath environments, determining line-of-sight (LoS) paths for precise localization poses a challenge. To address this issue, we propose a fast direct localization based on LoS identification that can also be applied when the LoS paths of some BSs are obstructed. In the final stage, the moving user locations are recovered via triangulation. Simulation results validate the effectiveness of the proposed algorithms and showcase the feasibility of implementing quantized mmWave systems for localization purposes.