Enhancing the Energy-Efficiency and Timeliness of IoT Communication in WiFi Networks

Increasing the number of Internet of Things (IoT) stations or regular stations escalates downlink channel access contention and queuing delay, which in turn result in higher energy consumption and longer communication delays with IoT stations. To remedy this problem, this paper presents WiFi IoT access point (Wiotap), an enhanced WiFi access point (AP) that implements a downlink packet scheduling mechanism. In addition to assigning higher priority to IoT traffic compared to regular traffic, the scheduling algorithm computes per-packet priorities to arbitrate the contention between the transmission of IoT packets. This algorithm employs a least-laxity first (LLF) scheme that assigns priorities based on the remaining wake-up time of the destination stations. We used simulation to show the scalability of the proposed system. Our results show that Wiotap achieves 37% improvement regarding the duty cycle of IoT stations compared to a regular AP. In addition, we developed a testbed to confirm the implementation correctness and the performance benefits of Wiotap in a network with four IoT stations and regular traffic. For the edge and cloud scenarios, our empirical evaluations show up to 44% and 38% improvement in energy and 52% and 41% improvement in delay, respectively.