Relay Based Cooperation for Cognitive Radio Networks

Spectrum allocation has been traditionally done in a licensed fashion. But observations of spectrum usage suggest that most bands are underutilized. Cognitive Radio (CR), broadly defined as an intelligent radio which can adapt based its context has come up as a means for opportunistic (secondary) usage of spectrum. Cognitive radios are required to sense the spectrum for availability of holes and to communicate in the sensed holes without interfering with the licensed primary users of the bands. According to the network architecture, cognitive radio networks can be classified as infrastructure-based and ad-hoc networks. The infrastructure based networks rely on base-station like controller/arbiters. These arbiters collect the sensing information and decide on the band for secondary communication. The ad-hoc network does not have any infrastructure backbone. So, each user needs to have all CR capabilities and is responsible for determining its actions based on the local observation. One of the most important challenges for cognitive radio systems is to identify the presence of primary (licensed) users over a wide range of spectrum at a particular time and specific geographic location. We consider the use of cooperative spectrum sensing in cognitive radio systems to enhance the reliability of detecting primary users. With multi-hop relay, we enhance coverage, throughput and system capacity.