Experimental Feasibility Study of Motion Sensor-Aided mm-Wave Beam Tracking

Abstract

The spectrum-rich millimeter-wave (mm-wave) bands are being considered for next generation mobile networks. However, due to the high path loss at these frequencies, mm-wave systems rely on highly directional antennas, making precise antenna alignment a major issue. To provide seamless connectivity for mobile users, efficient beam tracking is thus crucial. In this paper we propose using motion sensor data to track small-scale rotational user motion and to thus correct mm-wave antenna misalignment at the mobile station (MS). To this end, we study in detail the characteristics of typical MS rotational motion using an Android app and mm-wave urban measurement data. We thereby evaluate the effectiveness of MS-based beam tracking, in terms of link stability and link quality, and derive practical engineering bounds on tracking delay and sensor accuracy. We show that, in order to make motion sensor-aided beam tracking beneficial, the tracking delay and sensor error must not exceed 30 ms and 1.2°, respectively, for our 10° antenna system. Although these requirements are within the capabilities of state-of-the-art MEMS chips, they cannot be guaranteed by the Android sensor API, suggesting that direct low-level access to the sensors should be provided to support mm-wave beam tracking.