Performance Enhancement of Cognitive Radio System by distributed interference compensation with MAC Layer Node Cooperation

Abstract

The cognitive radio, built on a software-defined radio, is defined as an intelligent wireless communication system that is aware of its environment and uses the methodology of understanding- by-building to learn from the environment and adapt to statistical variations in the input stimuli. Thus the two most popular research areas when it comes to cognitive radios are spectrum sensing and interference management and resource allocation. Spectrum sensing is the ability to find available frequencies/timeslots to transmit in. Research in the area of interference management and resource allocation consists of how to allocate power in channels to maximize capacity while minimizing interference to other users. This thesis will explore the aspect of interference and resource management in cognitive radio, to see how this can be exploited to enhance the performance of a cognitive radio system. Especially the aspect of simultaneous transmission between secondary (cognitive) and primary users is of interest, as this could potentially enhance the performance of cognitive systems. So, this thesis proposed an algorithm which utilizes Medium Access Control layer mechanisms for message exchange between secondary nodes that operate in license exempt spectrum bands, in order to achieve interference mitigation. Also, this thesis successfully implements Fuzzy Logic to Cognitive radio in order to deal with complex and vague environmental conditions.