IEEE IOT JOURNAL [ACCEPTED: JULY 2019] 1 Enhancing the Energy-Efficiency and Timeliness of IoT Communication in WiFi Networks Jaykumar Sheth and Behnam Dezfouli Internet of Things Research Lab, Department of Computer Science and Engineering, Santa Clara University, USA
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[email protected] Abstract—Increasing the number of IoT stations or regular higher data rates, which justifies the adoption of this standard stations escalates downlink channel access contention and queu- in applications such as medical monitoring and industrial ing delay, which in turn result in higher energy consumption and control [3], [19]. The higher data rate also reduces the duration longer communication delays with IoT stations. To remedy this problem, this paper presents Wiotap, an enhanced WiFi access of transmissions and increases sleep intervals. point that implements a downlink packet scheduling mechanism. The traffic prioritization and power saving mechanisms of In addition to assigning higher priority to IoT traffic compared 802.11 fall short in IoT applications. From the timeliness point to regular traffic, the scheduling algorithm computes per-packet of view, 802.11 differentiates between real-time (e.g., voice priorities to arbitrate the contention between the transmission and video) and elastic (e.g., email, file transfer) flows by of IoT packets. This algorithm employs a least-laxity first (LLF) scheme that assigns priorities based on the remaining wake-up defining voice, video, best-effort, and background access cat- time of the destination stations. We used simulation to show egories. However, these access categories only accommodate the scalability of the proposed system. Our results show that the four traffic categories of regular (non-IoT) user devices Wiotap achieves 37% improvement regarding the duty cycle of and cannot differentiate the existence of IoT traffic.