Abstract
The recent Wi-Fi HaLow technology focuses on adopting Wi-Fi for the needs of the Internet of Things. A key feature of Wi-Fi HaLow is the Restricted Access Window (RAW) mechanism that allows an access point to divide the sensors into groups and to assign each group to an exclusively reserved time interval where only the stations of a particular group can transmit. In this work, we study how to optimally configure RAW in a scenario with a high number of energy harvesting sensor devices. For such a scenario, we consider a problem of device grouping and develop a model of data transmission, which takes into account the peculiarities of channel access and the fact that the devices can run out of energy within the allocated intervals. We show how to use the developed model in order to determine the optimal duration of RAW intervals and the optimal number of groups that provide the required probability of data delivery and minimize the amount of consumed channel resources. The numerical results show that the optimal RAW configuration can reduce the amount of consumed channel resources by almost 50%.
Highlights
The concept of the Internet of Things (IoT) [1] with its tremendous number of interconnected autonomous devices has become very attractive for device vendors, mobile operators, and their customers [2]
There are many studies of Restricted Access Window (RAW) and other mechanisms introduced in the IEEE 802.11ah amendment, which evaluate the efficiency of these mechanisms via simulation [16,17], we focus on the works containing analytical approaches to estimate the network performance
Wi-Fi HaLow aims at extending the usage of Wi-Fi to the Internet of Things scenarios, which include gathering data from large numbers of autonomous energy-limited devices
Summary
The concept of the Internet of Things (IoT) [1] with its tremendous number of interconnected autonomous devices has become very attractive for device vendors, mobile operators, and their customers [2]. From the technical point of view, it is evident that the easiest way to provide Internet access for the swarm of devices is using wireless communications. It is not clear how to do it the most efficiently Since it may be difficult, if even possible, to wire thousands of devices to an electric grid, autonomous devices are typically battery-supplied and/or harvest solar, wind, or other kinds of green energy. From both technical and ecological points of view, the usage of traditional accumulators by autonomous devices is limited. Their efficiency degrades with every recharge cycle. They typically contain much mercury, cadmium, lead, or other dangerous poisonous
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