Deploying Multiple Sinks in Multi-hop Wireless Sensor Networks

Due to the scarce energy supplies of a wireless sensor network (WSN) it is necessary to design the architecture and operation of the network so as to optimize the energy consumption. Since in a multi-hop WSN a sensor spends most of its energy for relaying data packets it is important to shorten the distance a packet has to travel until reaching the sink. These distances can be reduced seriously by deploying multiple sinks instead of one. In that case every sensor communicates with the closest sink. In order to achieve the shortest distances the sinks have to be deployed in a coordinated way. In this paper we give a mathematical model that determines the locations of the sinks minimizing the sensors´ average distance from the nearest sink. First we present an iterative algorithm called global that is able to find the sink locations given by the mathematical model. However, it uses global information about the network that is impractical in wide area sensor networks, thus we propose a novel iterative algorithm called lhop that carries out the sink deployment based only on the location information of the neighboring nodes while the location of the distant nodes is being approximated. We compared the two algorithms and show that lhop approaches the performance of global very closely. Another important issue is that the neighboring nodes of the sinks have a high traffic load, thus the lifetime of the network can be elongated by relocating the sinks from time to time. Based on the lhop algorithm we propose the lhop relocation algorithm for the coordinated relocation of multiple sinks. The simulation results show that the algorithm extend the network lifetime severely.