Multi-sink mobile wireless sensor networks

Abstract

In pervasive systems, as they are getting smaller and smaller, computers can be found about everywhere, but their presence is not noticed because the technologies are often embedded within items. One of the smallest embedded computers is a wireless sensor node, which is a passive sensing device capable of communicating wirelessly with other devices. A wireless sensor network is typically composed of many tiny sensor nodes, often no bigger than a credit card. Applications of sensor networks have emerged in many domains ranging from environmental monitoring to industry manufacturing. Typically, in a wireless sensor network, sensor nodes generate data about a phenomenon and relay streams of data to a more resource rich device, namely a data sink, for processing. Early sensor networks have been modeled as having a single, predefined, stationary sink. In recent years there has been renewal of interest in using multiple sinks to achieve power saving. The improvements of stationary wireless sensor networks in conjunction with the advances developed by the distributed robotics and low power embedded systems communities have led to a new class of Mobile Wireless Sensor Networks that can be utilized for a wide range of scenarios such as vehicular applications and emergency response, which require reliable and timely collection of data. Mobile Wireless Sensor Networks are similar to their stationary counterparts, thus are governed by the same energy and processing limitations, but require the development of a new generation of algorithms targeting at constantly changing network topologies due to sink and/or sensor mobility. This thesis focuses on the efficient data extraction and dissemination in multi-sink wireless sensor networks by handling mobility of sensors and sinks. We start with analyzing the characteristics of multi-sink sensor networks. We propose a set of algorithms that enable multi-sink sensor network to self-organize efficiently in the presence of mobility and adapt to dynamics in order to increase the functionality of the network. Our contributions include an algorithm for load balancing in multi-sink sensor networks, a protocol for query dissemination towards an area of interest combined with methods that are used to handle mobility efficiently in a tree-based routing, and a data dissemination protocol that tackles sink mobility in a sensor network.