We investigate the effects of the performance of sensor networks on network availability and in turn evaluate the impact of protocols and network configuration on these effects. The typical wireless sensor network of the future consists of a large number of micro-sized sensors that are equipped with batteries of limited capacity. In such a network, energy consumption is one of the most important issues. Several representative protocols that are applied in ring and linear network configurations are analyzed, and explicit formulae for network availability are derived for each of them. Numerical values derived by using these formulae yielded the surprising result that backup routes do not always improve network availability. This is because the loads imposed by the backup routes on network segments that do not include dead sensor nodes reduce sensor-node lifetimes in these segments.

This paper discusses performance issues for a sensor network. It describes the unique features of the sensor network and discusses studies on its protocols. Performance measures for the sensor network are investigated and studies related to them are surveyed. As an example of performance measures, this paper analyzes a sensor network's availability, which is the probability that all the sensor nodes are working without any of them having run out of energy. An explicit formula for the sensor network availability is derived, and the optimal placement of sensor nodes is investigated.