LoRa Mesh Network with Time-Efficient Medium Utilization for IoT Building Monitoring System

Flexibility, reliability, large coverage, and low cost are critical traits for low-power wide-area networks (LPWANs). The network infrastructure is the prerequisite for implementing the Internet of Things (IoT) end device (ED) in building monitoring systems. Long range (LoRa) is one of the best candidates for LPWAN, but the lack of a mesh network limits its potential, especially on the cost. Multiple medium access control (MAC) protocols with various features were proposed to handle the collision problem in LoRa mesh networks. New evaluation methods were established to verify the MAC protocols in the highly contentious period in which network extenders (NEs) compete for idle medium in a mesh network. The experiments consisted of 30 NEs with overlapping coverage, whereas in real-life applications, usually, coverage overlap of only two to three NEs occurs. The performance of the proposed MAC protocols was evaluated by comparing their packet delivery ratios (PDRs) and data throughput values (bps). The best MAC protocol, namely, carrier-sense multiple access (CSMA)/collision avoidance (CA) with assigned distributed interframe spacing (DIFS), achieved a PDR of approximately 100% and data throughput of approximately 2500 bps. The proposed LoRa mesh network can serve as the basis of low-latency, low-collision, wide-coverage IoT monitoring, and control systems. A real commercial large-scale building was deployed by this proposed network with 205 devices located across 23 continuous floors with single gateway as a deployment test. The test period spans over six months and an overall PDR of 92% is obtained, which outperforms previous research in terms of duration, scales, and PDR.