Spectrum efficiency improvements in cognitive radio networks : a survey

Cognitive Radio Network (CRN) is a promising wireless communication network to utilize the unused and otherwise wasted portions of the licensed spectrum under two conditions; protecting the primary users of the licensed spectrum from harmful interference, and providing to its best effort optimum Quality of Service (QoS) to its users. However, there are so many challenges that must be tackled in order to satisfy both of conditions together. This paper provides an up-to-date survey of various techniques, algorithms, open area studies and ideas to improve the spectrum efficiency in CRNs in terms of topology and spectrum sharing strategy. To the best of our knowledge this paper is the first survey that considers the QoS provisioning from CRN perspective and the challenges involved. Conclusions about these issues and future work are presented at the end