SYLOIN: Measuring Angle of Arrival of LoRa signals using Software Defined Radio

Abstract

Several radio frequency direction finding algorithms exist for Internet of Things (IoT) applications that use angle-of-arrival (AoA) measurements to estimate target position. However, providing reliable and accurate direction system capability still remains a challenge. In this paper, we are interested in measuring the angle-of-arrival (AoA) of LoRa RF signal by using a software-defined radio (SDR) platform implemented with antenna-array interferometry method. The proposed system can determine the node’s direction using only dual interferometry antenna. The two antennas are operated by an individual universal software radio peripheral (USRP) SDR receiver. Furthermore, a new paradigm of LoRa digital carrier signal detection is investigated using GNU Radio and USRP B210 operating at a center frequency of 868 MHz. We present a solution that builds on the LoRa modulation properties to determine the presence of the user’s signal in the channel. The phase difference of the detected signal received by the two-channel USRP B210 is used to estimate the node’s AoA. The entire experimental setup was implemented in the GNU Radio Companion (GRC) and measured in a 8m 8m office environment. The measurement results show an AoA ×with a mean error of less than 5 degrees approximately. We therefore believe that our AoA system can be easily calculated in real time without the need for complicated post-processing algorithms.