MEASUREMENT AND ANALYSIS OF TIME VARIANT CHANNELS FOR WIRELESS SENSOR NETWORKS

Abstract

Wireless Sensor Networks have been identified as one of the key technologies for the 21st century. The unique qualities of Wireless Sensor Networks mean that a wide range of applications have been found for them and everyday new applications are being added. Wireless Sensor Networks are expected to become ubiquitous over the next few years. A wireless sensor network consists of a number of low-cost, low-power sensor nodes, which can perform sensing, simple computation, and communication over short distances. Wireless sensor networks are mainly power constrained as the life of sensor nodes is limited by battery life. Cooperative communications have been proposed to exploit the spatial diversity gains inher-ent in multiuser wireless systems without the need of multiple antennas at each node. Coopera-tive communications are specially desirable for resource constrained networks such as a wireless sensor network since the nodes can cooperate to optimally allocate resources so as to maximizes performance and network lifetime. A deep understanding of the channel is necessary before going into the design of the Radio for sensor networks. The fading statistics of.the propagation channels between sensor nodes are essential to determine the possible data rate, outage, and latency of sensor networks. The diversity order obtained strongly depends on the correlation properties of the channel. It is thus necessary to do a detailed study of the channel characteristics specially keeping sensor networks in mind. In this thesis we have investigated the true channel conditions for indoor (office) and outdoor (open ground) environments. These are (to the best of our knowledge) the first investigations based on measurements which look into the correlation properties of channels for sensor networks. The thesis gives a brief overview of Sensor networks and Cooperative diversity. A section on radio channel modeling is also presented for a relevant background. Measurement campaigns were carried out in indoor (office) and outdoor (open ground) environments. In theses campaigns