Maximizing the lifetime in wireless sensor networks with multiple mobile sinks having nonzero travel times

It is a known phenomenon of the wireless sensor networks that the relay sensors, the sensors neighboring directly to the sinks, spend more energy than the rest of the sensors. This causes premature death of the relay sensors which isolates the sink(s) from the rest of the network. In order to prevent isolation of the sinks due to premature death of the relay sensors, sink mobility is offered as a remedy and that has attracted the interest of many researchers. Mobility of the sinks has been the subject of numerous studies but most of them assume that the mobile sinks travel from one point to another in negligible amount of time. However, harsh and hostile environments in which wireless sensor networks are deployed force the mobility of the sinks to be limited in real applications. Velocity of the mobile sinks for the wireless sensor networks deployed in hostile environments is so slow and consequently considerable sink traveling times occur. In this study, a mathematical model is offered that takes the sink travel times into consideration and the importance of taking sink traveling times into account is illustrated especially for the slow sinks.