LoRaWAN Relaying: Push the Cell Boundaries

Although LoRa modulation is known for its robustness allowing devices to communicate kilometers away, it suffers from coverage issues especially where density of gateways is low or in dense urban areas. However, a simple 2-hop LoRaWAN communication can seamlessly extend the network coverage and even improve both data extraction rate (DER) and energy consumption. Experiments in this paper figure out cases under non line of sight (NLoS) conditions where relaying performs better. Regarding the exponential increase of airtime with the spreading factor (SF), as soon as a 2-hop SF7 link allows a better DER as a single hop SF8 link, it becomes more attractive to use a relay. Indeed, energy consumption is linked to the airtime - or the amount of time to send a frame - explaining the energy efficiency with the 2-hop relaying protocol. To verify this assert, LoRa network coverage with a testbed in urban environmens is first compared. Then, simulations help to study energy consumption according to the case study. Results prove that relaying effectively gives better results under NLoS conditions, particularly in dense areas, by improving the DER. It also highlights the limits of LoRa in urban areas where the DER can be under 0.5 using SF12 and with less than a kilometer range.