Implicit Multi-hop Communication Scheme based on Overhearing in IoT LoRa Networks

Long Range (LoRa) is a Low-Power Wide-Area technology, because it is eminent for robust long-distance, low-bit rate, and low power communications in the unlicensed sub GHz spectrum used for the Internet of Things (IoT) networks. Recently, several schemes in multi-hop LoRa networks have proposed schemes with explicit relay nodes to partially mitigate the path loss and longer transmission time bottlenecks of the conventional single-hop LoRa by focusing more on coverage expansion. However, they do not consider improving the packet delivery success ratio (PDSR) and the packet reduction ratio (PRR) by using the overhearing technique. Thus, this paper proposes an Implicit Multi-hop Communication scheme based on Overhearing (IMCO) that exploits implicit relay nodes for performing the overhearing to promote relay operation. In IMCO, implicit relay nodes are selected as overhearing nodes (OHs) among end devices which have a Low spreading factor (SF) to improve PDSR and PRR for distant end devices (EDs). A theoretical framework for designing and determining the OH nodes to execute the relay operations was developed with consideration of the LoRaWAN MAC protocol. Simulation results verify that IMCO achieves better performance than the existing schemes.