Traditional wireless networks form the wireless counterpart of wired networks, in which providing infrastructure is the main functionality. High bandwidth is the primary goal and the unlimited power supply is an important characteristic of traditional wireless networks. On the other hand, Wireless Sensor Networks (WSNs) are used for environmental monitoring under, sometimes, harsh environmental conditions. Their focus does not lie on providing high bandwidth, but achieving low energy consumption as well as autonomous functioning and self-deployment. The sensor nodes of a WSN are inexpensive devices, with low memory and processing capabilities and a low bandwidth. It is often costly or impossible to replace batteries and therefore WSNs need to run autonomously for many years on a limited energy source. Data, in the form of environmental sensor readings, is sent from sensor nodes to the data sink –also named gateway. The sink forms the gateway between the WSN and the end-user application. These sink nodes have more capabilities than normal sensor nodes, i.e. they can communicate directly with each other via a high-speed link, have more processing power, and are powered by an unlimited energy source. The final destination of all sensor data generated in the sensor nodes is the data sinks in the network. In some situations the application demands more than one sink in the network, in other situations a multi-sink network is created as the result of merging two single-sink networks. In all situations it has certain benefits to add additional sinks to the network, although they can easily turn into drawbacks if the routing protocol is not suited for multi-sink networks. The aim of the research set out in this thesis, is to develop an efficient routing protocol which utilises the existence of multiple sinks in the network. Therefore this thesis presents the Partition-Based Network Load Balanced routing protocol (P-NLB), a novel routing protocol for routing in large scale multi-sink WSNs.
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