Radio Frequency Based Direction Sensing Using Massive MIMO

Navigation systems have been widely used in modern applications in which the moving speed and direction estimations are two key steps. Instead of using traditional device-based orientation sensor such as accelerometer and magnetometer to estimate the moving direction, this paper presents a novel radio frequency (RF) signal-based moving direction sensing scheme by using 5G massive multiple input and output (MIMO) system. We first explore the energy distribution of the received signal in massive MIMO in both near- and far-field scenarios. The energy distribution in near-field is proved to be highly related to the geometric shape of the antenna deployment. In contrast, the energy distribution turns out to be a stationary sinc-like focusing beam in far-field scenario. Inspired by such an observation, we develop a novel method to estimate the speed of a moving target with respect to a single based station. The moving direction can be further determined by jointly considering the speed estimation results and the geometric property of the locations between the target and nearby base stations. Finally, numerical simulations show that the proposed RF-based method can achieve high accuracy in which the moving speed estimation error is less than 1.5m/s while the moving direction estimation error is within 2 degrees.