Performance improvements in cognitive radio networks through regional approach

Abstract

In modern wireless communication systems, the number of wireless users is steadily increasing, resulting in a necessary demand for more available radio spectrum. Cognitive Radio (CR) is an innovative solution toward the efficient use of spectrum, by using the same spectrum from Secondary User (SU) simultaneously with Primary User (PU) or exploiting the spectrum holes, in underlay/ overlay/ interweave paradigms. In all the cases, important consideration for performance enhancement of secondary user network, is to protect PU`s QoS. In this regard all resource management problems and solutions pertaining to normal wireless communications becomes more complicated. In this thesis two of the important link layer issues, i.e. power control in underlay CR paradigm and cooperate sensing in interweave paradigm are addressed, while considering a regional approach, which generally increases performance than conventional methods, and reduces complexity (and hence cost) than recent techniques/ algorithms. For the case of power control, we have evaluated number of regions around PU basestation (BS), differentiated by signal to noise ratio (SNR) of PU, for which we can have appropriate outage gain. This work investigated what and up to what extent we can have advantage, if we have more and more divided regions. The results obtained through extensive simulation for different PU rate constraints (both uplink and downlink), prove that we have bigger advantage of three regions over two regions, while using binary power allocation (BPA) for determining thresholds for different regions, especially when grey region is placed near the edge of the cell. But further increasing the regions might not necessarily enhance the performance further, but definitely increases complexity. We have shown performance in terms of more active SUs and outage gain for cell edge SUs in a typical environment, for both ad-hoc communications and through a CR-BS. For second part of the thesis, we have used...