Algorithm for fairness in schedule lengths of sink-rooted trees in multi-sink heterogeneous wireless sensor networks

Abstract

Sensor networks are used for observing some region of interest. Sensors sense different physical quantities and send to base station or sink. The tree based networks with TDMA as MAC protocol are preferable because of simplicity of tree and guaranteed data access in TDMA. Often sensor networks are multi-sink and multi-attribute networks. Multi-sink network means more than one sinks are present and so multiple sink-rooted trees are formed. When more than one types of nodes are deployed in the network, the network is known as heterogeneous network or multi-attribute network. Sometimes node density or heterogeneity is not uniform across entire network. As a result of non-uniform node distribution or non-uniform heterogeneity distribution, schedule lengths of sink-rooted trees are very different. Nodes part of trees with small schedule length will get more frequent transmission turns compared to those which belong to trees with large schedule length. To ensure fairness in terms of transmission opportunities, it is desired that schedule lengths should be balanced. In this work, an algorithm named as Schedule Length Balancing for Multi-sink HeTerogeneous networks (SLBMHT) is presented to balance schedule lengths. The SLBMHT algorithm is evaluated through simulations. It is found that the SLBMHT algorithm results in 8–56% reduction in schedule length difference of trees. It also results in 2–17% energy savings during data transmission phase. Only demerit is increase in control overhead. But as resulting increase in energy consumption is not much, it is overcome by savings in data energy consumption. Thus network lifetime is likely to increase.