Ruting i trådløse sensornettverk

In military operations, there is a great need for protecting military positions. This is typically accomplished by a balanced combination of physical protection, surveillance and elimination of the threat. The use of electronic sensors is an important means to achieve early warning of intrusions and thus reduced reaction time. There is a variety of sensor types on the market intended for the detection of intrusion. Among these are wireless sensors preferable for protecting temporary camps and positions.Wireless sensors provide shorter deployment time and greater freedom regarding sensor placement compared to wired systems. Furthermore, a large number of sensors can be deployed, which can reduce the false-alarm probability when combined with other techniques such as data aggregation. Wireless sensors do on the other hand introduce a range of communication challenges. Considering that wireless sensors are battery powered and often abundant, it is very important that the communication protocols are energy efficient and scalable. The routing protocol ensures that messages (alarms and measurements) produced in the sensor network is transported from the sensor to the desired recipient. This report investigates the following issues related to routing and energy efficiency in wireless sensor networks: i) Simultaneously positioning and routing; ii) data aggregation; iii) interoperability with external systems; iv) sink node placement and routing in a multi-sink network; and v) communication interferred environment. A number of simulations and laboratory experiments are performed to address these issues. The main purpose of this work has been to find methods for efficient routing in sensor networks while ensuring good energy utilization. One the recommended ways to achieve this is to use multiple sink nodes in the network. The use of multiple sinks provides both high efficiency and redundancy. Multiple sinks can also be combined with data aggregation. Another main conclusion is that cross-layer optimizations between the routing protocol and other protocols can contribute both to a significant performance improvement and to increase the functionality in the sensor network. For example, cross layer optimizations can enable data aggregation, which provides prolonged network lifetime, and a location service, which is a necessary feature in many sensor networks. One last recommendation in the report applies to military sensor networks subjected to interference or jamming. The report recommends a hybrid routing protocol for this purpose. This protocol provides a good balance between packet delivery rate and energy efficiency, both in circumstances when the network is subjected to high interference and when it is subjected to low interference.