ALLYS: All You can Send for Energy Harvesting Networks

Abstract

The energy harvesting technology enables nodes to gather energy from a surrounding environment, and store excessive energy for later use. With the energy harvesting technology, the MAC protocol design paradigm shifts from “how to reduce energy consumption” to “how to optimize performance with harvested energy.” Legacy MAC protocols such as Framed Slotted Aloha (FSA) and Dynamic FSA (DFSA) does not consider energy harvesting and therefore may not work optimally in a network with energy harvesting nodes. In this paper, we propose a novel All You can Send (ALLYS) protocol for an energy harvesting network. ALLYS uses fixed frame size, but the slot transmission probability is adjusted by a sink node to control the channel access of contending nodes. A sink node broadcasts not only the frame size but also the transmission probability, so that a node can transmit more than once in an opportunistic manner fully utilizing the harvested energy. At the end of a frame, a sink node estimates the number of nodes accessing the channel and provides an appropriate transmission probability so as to reduce the collision probability preventing from the excessive contention among the nodes. We have evaluated the throughput, delay, and energy efficiency of the proposed ALLYS through analysis and simulations, and it is shown that ALLYS can greatly improve the throughput, delay, and energy efficiency in a wide range of operating conditions for wireless networks or Internet of Things (IoT).