XORLoRa: LoRa Backscatter Communication with Commodity Devices

Abstract

In this paper, we present XORLoRa which firstly achieves backscatter communication with commodity LoRa devices while keeping these devices communicating normally. The basic idea of this XORLoRa is encoding data with frequency shifting. The frequency shifting operation can change the encoded data while not destroy the structure of the LoRa packet. Thus, the backscattered signal can be received by a commodity device. As the backscattered signal is shifted out from the center frequency, the commodity devices can communicate normally. In order to mount the tag data onto the commercial LoRa signal, we present a novel encoding strategy. We also reveal the relation between the number of loads on the tag and the strength of frequency harmonics which are generated by the frequency shifting operation. Based on this relation and encoding strategy, we implement a hardware prototype to test the performance of XORLoRa. It turns out that XORLoRa can cover a range of 30m with 10dBm transmit power in an indoor environment. The communication distance can be extended to over 500m with 30dBm power in open space.