Most deployed sensor networks consist out of thousands of nodes. Each node has restricted resources (computing power, energy …). Despite this, each node must be able to transmit its collected data (temperature, humidity …) through the network towards a central system. Because of the large scale of these networks, an automatic configuring system could be convenient. To do so we can rely on the latest developments in wireless networks.
The latest adaptations of wireless standards, such as Wimax (IEEE 802.16e) and WiFi (IEEE 802.11n), are dealing with multipath diversity, MIMO (Multiple Input, Multiple Output) and beamforming to improve its performance. Therefore, the concept of antenna arrays is introduced in these standards. It would be of great benefit if these techniques could be deployed in RF Sensor Networks. This results in less contentions and a higher throughput of the data transported in wireless sensor networks. The use of antenna arrays might also allow localisation of objects, if the sensor is within reach of multiple access points by means of ‘Angle of Arrival (AoA)’. The latter is point of discussion in this work.
Localisation with AoA is based on the concept of beamforming i.e. the effect of combining multiple antenna elements to steer beams in a desired direction, the location of the object. In this research a distinction is made between two types of nodes. First, the intelligent anchor nodes having a well-known fixed position and supporting an antenna array. Typically these nodes are net powered. Second, the simple mobile devices with only one battery powered antenna element and changing position. Multiple intelligent anchor nodes, operating in receive mode, co-operate to track the position of the transmitting mobile node.