Impact of Realistic GNSS Location Errors on REM-Based Beam Management in Urban Millimeter-Wave Networks

Millimeter-wave (mm-wave) is envisioned to provide seamless multi-Gbps connectivity for future cellular networks and relies on directional links to overcome the high path and penetration loss and the spatially sparse nature of the mm-wave channel. Initial access and seamless mobile connectivity thus require active and precise alignment of the directional antenna beams between the base station and user equipment, which imposes a significant overhead. To address this, context-aware beam management approaches have been proposed to reduce the search space of feasible beam pair links (BPLs). In this work, we evaluate the performance of location-aided beam management under realistic localization accuracy in urban environments, with errors correlated in time and space. We investigate the effect of location errors in the construction and querying of radio environment maps (REMs) for beam management by incorporating real global navigation satellite system (GNSS) measurement data for modeling location errors, to better reflect the location information quality of users in future urban cellular networks, specifically low-cost GNSS receivers in modern smartphones. Our simulation results show that the beam management performance-in terms of the throughput achieved via BPLs predicted by the REM - strictly depends on the considered level of urbanization, with a significantly worse performance in highly urbanized scenarios due to the larger and more correlated GNSS error experienced. This suggests that it is crucial to develop location-error-aware directional REM techniques for exploiting location-aided beam management in mm-wave 5G-and-beyond cellular networks.