Replacement strategies for minimizing maintenance cost and maximizing sensor network lifetime

Recent advances and development of wireless sensor network are based on low-cost, low-power and multifunctional solutions of the sensor nodes. Sensor Networks are very much data concentric and dependent on the performance of the sensor nodes. Sensing the network, processing data and broadcasting to other nodes are common jobs for the sensor node. The positions of the node are not fixed in the network but dynamic based on different algorithms applicable in different situations. As a result, the topology of sensor network changes very frequently. Sensor nodes perform four basic functional blocks:- sensing unit, processing unit, transceiver unit and the power unit. If any one of these block fails, then the entire network may became unstable. Sometime the solution is to repair the faulty block or to replace it by new one. Sometimes, repairing may take considerable time which leads to longer downtime and thereby, increase in the maintenance cost. On the other hand, replacements of the faulty block may reduce downtime but may enhance the cost. There should be an optimized solution for delay, beyond which the replacement cost may become less than the repair cost. This paper analyzes this issue and proposes a mathematical model to optimize the value of time t which minimizes the total cost involved in the system and ensures prolonged system life time.