Stabilization of Multi-Hop Routing Construction in Wi-SUN FAN Systems

Wi-SUN FAN (wireless smart utility network field area network) is a technical specification of Wi-SUN that introduced multi-hop M2M (machine-to-machine) transmission for advanced smart city infrastructure. To construct a multihop network, the RPL (IPv6 routing protocol for low power and lossy networks) and the ETX (expected transmission count) are adopted as routing protocol and routing metric, respectively, in Wi-SUN FAN. The combination of the RPL and the ETX may cause a node to change its parent frequently. If a node selects a parent with lower link quality, communication reliability becomes lower. To avoid the frequent parent changing problem, parent candidates of each node should be selected appropriately. In this paper, we propose two schemes to select parent candidates for each node (i.e., optimized RSL (received signal level) threshold scheme and MAC (media access control) address filtering scheme) to stabilize the multi-hop routing construction in the Wi-SUN FAN systems. The proposed schemes are experimentally evaluated in a real field in an office building using the IoT-GWs (internet of things gateways) with Wi-SUN FAN module. By using the optimized RSL threshold scheme, the number of parent changes can be reduced by up to 96% compared to the case with unoptimized RSL threshold. Also, the number of parent changes can be reduced by up to 77% with the proposed MAC address filtering scheme compared to without the proposed scheme.