Seamless Sensor Network Communications

Wireless communication systems must operate under challenging conditions. For instance, communication between two ground personnel within an urban environment may not be possible; there may be severe fading or attenuation due to the numerous obstacles present. At the same time, this lack of connectivity is seen as unacceptable from the perspective of the radio operator. A recent concept undergoing active research is to increase the reliability of radio systems by making them cooperative. Generally, instead of having a single radio bear the entire burden of communication, coordinated operation between itself and surrounding radios will better accomplish its tasks. Such a concept is the basis for our work on cognitive multiple-input multiple-output (MIMO). Here, a distributed set of radios are able to simultaneously transmit coded data streams that are coherently combined at a central multi-antenna collector. Although the technique may be able to be applied to other radio systems, our current target application is wireless sensor networks (WSNs). Due to the limited resources available to individual wireless sensor nodes, each is severely limited in terms of power and range. In the proposed technique, we take advantage of the gains in information capacity offered by MIMO to increase link reliability.