COOPERATIVE SPECTURM SENSING IN COGNITIVE RADIO NETWORKS

Abstract

Cognitive Radios is a promising technology for the opportunistic use of under-utilized spectrum since they are able to sense the spectrum and use frequency bands. For this purpose several spectrum sensing techniques are employed like Energy Detector, Matched Filter and Cyclo-Stationary feature detector. The performance of these Spectrum Sensing techniques for cognitive radios is limited by the received signal’s strength which may be severely degraded due to pathloss. In such a scenario cooperative sensing may alleviate the problem of detecting the primary user by reducing the probability of interference to a primary user. The cooperative sensing relies on the variability of signal strength at various locations. It is expected that a network of cognitive radios with sensing information exchanged between neighbors will have a better chance of detecting the primary user compared to the individual sensing. This thesis demonstrates that single node detection is not sufficiently reliable in a lossy environment and how cooperative spectrum sensing can be improved. Moreover cooperative and non cooperative spectrum sensing schemes have been compared on the basis of reliability and performance. All simulations have been carried out in MATLAB