Sustainable Tree-Based Scheduling in Solar Powered Wireless Mesh Networks

In many applications of wireless mesh networks, due to the lack of access to a permanent source of energy and the use of battery and energy harvesting equipment, energy sustainable design is very important. Duty-cycle adjustment, putting the node into sleep mode in some parts of the working period, is a method for energy saving and sustainability assurance. In this case, to exchange data between neighboring nodes, protocols for sleep scheduling are needed. In some applications of these networks, such as video surveillance applications, it is necessary to collect data from different parts of the network. Tree topology is a good option for these applications. A simple method for coordinating sleep in a tree topology is the TIME-SPLIT algorithm, at which the working time of each node is evenly divided among its children.
The proposed TIME-SPLIT scheduling algorithm does not consider the node energy limitations. In this paper, we have added the nodes duty-cycle constraint in the TIME-SPLIT algorithm to guarantee energy sustainability in tree-based wireless mesh networks. In situations where the energy status of the children is different, equal division of time leads to network inefficiency. To improve network efficiency and throughput, we provide two scheduling algorithms that take into account the conditions of the children's energy and traffic. In the first proposed algorithm, the time division is performed in relation to the duty-cycle of the children of each node. In the second algorithm, the time division is dynamically and in proportion to the traffic of the children, and the connection acceptance is more precisely performed based on its energy consumption during its lifespan. The simulation results performed by the NS3 network simulator show that in energy and tree structure imbalance conditions, where children of a node have different energy or sub tree, the proposed methods significantly (more than about 60%) increase the network’s total delivered traffic.