LAUSR

LoRa, as a representative Low-Power Wide Area Network (LPWAN) technology, has emerged as a promising platform for connecting the Internet of Things (IoTs). It enables low-rate communications over upto tens of kilometers with a 10-year battery lifetime. However, practical LoRa deployments suffer from collisions, given the dense deployment of devices and the wide coverage area. We propose CoLoRa, an approach to decompose large numbers of concurrent transmissions from one collision and enable multi-packet reception in LoRa networks. At the heart of CoLoRa, we utilize the packet time offset to disentangle collided packets. CoLoRa incorporates several novel techniques to address practical challenges. (1) We translate time offset, which is difficult to measure, to frequency features that can be reliably measured. (2) We propose a method to extract peak features from low-SNR LoRa signals iteratively. (3) We address frequency shift incurred by carrier frequency offset and time offset for LoRa decoding. We implement CoLoRa on USRP N210 and evaluate its performance in both indoor and outdoor networks. CoLoRa is implemented in software at the base station, and it can work for COTS LoRa nodes. The evaluations show that CoLoRa improves the network throughput by 3.4× compared with Choir and 14× compared with LoRaWAN.