Duty-Cycle-Aware Real-Time Scheduling of Wireless Links in Low Power WANs

Low Power Wide Area Networks (LPWANs) are an excellent fit to city-scale IoT applications—offering a long range, long battery life of several years, and a data rate of 25-50kbps, which is sufficient to carry IoT traffic. However, a practical limitation in realizing a LPWAN-based real-time wireless network is the duty-cycle limit that is imposed on the sub-1GHz band by the FCC. In this paper, we overcome this challenge by proposing the first duty-cycle-aware wireless link scheduling algorithm for real-time LPWANs that considers the urgency of the packets as well as the availability of the channels. The proposed algorithm is implemented in a five-node city-wide test-bed in multiple realworld scenarios. Simulation results are provided to quantify its performance under different settings (e.g. larger networks, variety of workloads, and multiple baselines). In both real-world deployments and simulations, the proposed scheduling algorithm has outperformed all the baselines in terms of link schedulability, deadline misses, and buffer size.