Receiver-Initiated Energy Harvesting MAC Protocols: Survey

The Internet of Things (IoT) is a new technology in which several Internet-enabled IoT devices are placed to monitor the environment and the information collected through them is used for different applications. Some applications include smart towns, smart buildings, agriculture and transport, to say a few. The majority of IoT devices are small in size with a limited battery capacity. As the number of IoT devices increases, the data sensing and interaction between these devices also increases, causing the problem of depletion of batteries for IoT devices. Replacing the batteries of these devices is not a viable solution; rather Energy Harvesting (EH) provides a promising solution for battery dependent devices. EH is the process that generates energy using renewable resources from the nearby environment to power IoT devices. While energy harvesting powers the IoT devices, the MAC layer activities such as sensing, idle listening, collision are responsible for consumption of most of the power. Availability of energy sources required for energy harvesting is not guaranteed all the time and equivalently a need to focus upon the designing of MAC protocol also becomes mandatory. Hence, the interplay of MAC protocols and EH techniques is a critical aspect of energy harvesting. Various MAC protocols are designed by the researchers to address the power consumption issues. Out of different categories of MAC protocols, asynchronous receiver-initiated MAC protocol are considered very important for time critical applications as they cause very less delay. This paper provides a comprehensive overview to analyze and summarize the energy harvesting receiver-initiated MAC protocols.