Investigations on Building Robust Cognitive Radio Based Networks

Abstract

Data Communication Networks find their extensive utility in national security, newlinecommerce, education sector, social media interactions, voice telephony, Internet usage newlineand multimedia streaming. Further, in recent times there has been an exponential growth newlinein the number of its users and their demands. On the other side, with extensive developments in the field of icroelectronics, wireless transmitters and receivers have become very popular and hence increased demand for electromagnetic spectrum usage. Since much of the spectrum has been licensed to wireless networks, spectrum scarcity is an unavoidable consequence. However, a recent survey of licensed networks [1] shows that a large portion of spectrum is underutilized. If only one can have a mechanism to identify the underutilized spectral bands and utilize them effectively, there is a large free electromagnetic spectrum out there for future applications. Cognitive Radio (CR) technology addresses the issues and techniques of utilizing the otherwise underutilized spectral bands and the networks based on cognitive radio concepts are inevitable consequences. To have efficient communications over cognitive radio based networks, cognitive radios newlinemust have low probability of false alarms and missed detections, and they also must avoid newlineinterference among themselves and more importantly with the licensed or primary users. newlineIn this thesis enhanced spectrum sensing scheme was proposed and incorporated in newlinecognitive cell radio environment for increasing the capacity and to minimize the newlineinterference. Conventional spectrum sensing methods have the problem of missed newlinedetections and false alarms if there is little variation in the environment. As the secondary user has to sense the spectrum all the time, it has the past spectrum information with it. Inthe proposed enhanced spectrum sensing with the help of past spectrum information the decision is made about primary users presence or absence and applied it in different traffic scenarios to check for improved throughput.