A Scheduling Method for Reducing Latency in Wi-SUN FAN Networks

The Wireless Smart Utility Network Field Area Network (Wi-SUN FAN) is a standard wireless communication technology for building large-scale outdoor multi-hop networks. Nodes in a Wi-SUN FAN network can communicate stably by performing channel hopping based on unicast and broadcast schedules. However, transmission of unicast or broadcast may be restricted according to the broadcast schedule, resulting in additional latency depending on the timing of frame generation. This paper presents a scheduling method to reduce the latency while preserving the unicast and broadcast throughput ratio. By keeping the ratio of Broadcast Interval (BI) and Broadcast Dwell Interval (BDI) unchanged, but making BDI more frequent, the time from frame creation to transmission is reduced. The method was evaluated using Wi-SUN FAN hardware, and the results showed that in one-hop communication, the latency of unicast frames decreased by up to 36% and the latency of broadcast frames decreased by up to 58%. Additionally, in a mesh network consisting of 21 devices, the roundtrip latency decreased by up to 20%.