Hybrid RSSI-AoA Positioning System with Single Time-Modulated Array Receiver for LoRa IoT

Abstract

In this paper, we propose a hybrid received signal strength indication (RSSI) - angle of arrival (AoA) positioning system with only one time-modulated array (TMA) receiver for LoRa IoT devices. The proposed system has the advantage of simpler hardware configuration than a conventional multiple receiver-based positioning system since it uses only one TMA receiver. Additionally, our system does not require clock synchronization because it depends on RSSI and AoA information. The TMA receiver consists of two antennas and a single-pole double-throw (SPDT) switch. The two antennas receive the signal from the target under the control of the SPDT switch and harmonic components are generated by the switching frequency of the switch. RSSI and AoA parameters can be calculated using fundamental and harmonic components. Using the RSSI and AoA of the target, the coordinates of the position are calculated by a Lab Viewprogram in real-time. In order to evaluate the performance of this system, we conducted experiments to find the position of a LoRa end-device in an outdoor environment. From the results, we confirmed that the positioning of the LoRa end-device could be precisely estimated using only one TMA receiver.