Energy efficient power allocation in sensing based spectrum sharing cognitive radio networks with imperfect csi

Abstract

Different independent measurement campaigns and regulatory bodies in the world including the Federal Communications Commission (FCC) in the United States and ofcom in the United Kingdom found that most of the radio frequency spectrums were not utilized efficiently. The frequency bands such as military, amateur radio and paging frequencies are insufficiently utilized but some other frequency bands such as cellular network bands are overloaded in most parts of the world. Independent analysis and studies were performed in some countries to confirm that observation, and concluded that spectrum utilization depends on the time and place. In the fixed spectrum allocation the frequencies are assigned to specific services, and rarely used frequencies cannot be used by the unlicensed user. On the contrast, regulatory bodies in the world have been considering whether to permit the unlicensed users to proceed in the licensed bands, provided that they cause no interferences to the licensed users. The FCC proposed Cognitive Radio (CR) as the most promising technology in this regard. CR is an intelligent wireless communication system that is aware of its surrounding environment that is outside world, and uses the methodology of understanding by-building to learn from the environment and adapt its internal states to statistical variations in the incoming RF stimuli by making corresponding changes in certain operating parameters (e.g., transmitpower, carrier-frequency, and modulation strategy) in real time, with the objective of highly reliable communications whenever and wherever needed and efficient utilization of the radio spectrum. In CR perception Primary Users (PUs) are said to be licensed users whereas Secondary Users (SUs) have less precedence to utilize this spectrum and are unlicensed users. There are in general three strategies proposed for spectrum sharing: The first one is Opportunistic Spectrum Access (OSA), in which the SUs areallowed to access the spectrum that is allocated to PUs when the spectrum is not used by