Toward Collision-Free LoRaWAN Communication under the Coexistence with Wi-Fi Networks

The last few years have witnessed the prosperity of low-power wide area networks (LPWANs) operating in the region-specific sub-GHz frequency bands. In particular, as one of the representatives of LPWANs, long-range WAN (LoRaWAN) has been newly developed to exploit the 2.4 GHz worldwide unlicensed band for region-independent LoRaWAN development. However, this makes LoRaWAN susceptible to signal interference caused by coexisting Wi-Fi networks that also use the 2.4 GHz band with a higher transmission power than LoRaWAN typically. As a medium access control (MAC)-layer solution to this problem, this paper proposes BeLow to enable better coexistence between LoRaWAN and Wi-Fi networks. To our best knowledge, BeLow is the first-ever LoRaWAN-oriented MAC protocol to mitigate the impact of Wi-Fi interference on LoRaWAN. Overall, BeLow seeks to exploit the silent time of Wi-Fi traffic for LoRaWAN communication. This is achieved in a probabilistic manner via a Wi-Fi traffic profiling technique at LoRaWAN gateways and a packet length adaptation approach at LoRaWAN end devices. On the other hand, BeLow also aims to avoid signal collisions among LoRaWAN end devices by including a novel channel access protocol based on Channel Activity Detection, a carrier-sensing technique tailor-made for LoRaWAN. Experimental results show that BeLow can avoid both Wi-Fi interference and LoRaWAN signal collisions well with a throughput boost of up to 120% compared to the best of our benchmark approaches.