Description

The advancement in technology and increasing interest in the various emerging wireless products has lead to the exponential growth in demand of limited spectrum, which is extremely difficult to satisfy through the current fixed spectrum assignment policy. Cognitive radio technology has emerged as a promising solution for the spectrum scarcity problem which enables the access of licensed spectrum band opportunistically. Cognitive radio technique helps in enabling the communication on both licensed and unlicensed channels without interfering with the licensed user. One of the important issues in cognitive radio networks is the channel assignment which is the mapping of available idle licensed channels to the unlicensed users. A dynamic channel assignment is required such that available resources are utilized effectively along with minimizing interference to the licensed user. This thesis focused on some functionalities of cognitive radio networks for the development of efficient channel assignment techniques. Different functions of cognitive radio networks depend upon each other for its effective performance. Therefore, this thesis focused on various cognitive functions like spectrum sensing, spectrum sharing and spectrum handoff to develop channel assignment methods such that the overall network performance is improved. To achieve this objective, the proposed research applied the concept of economics, contract theory, game theory and markov chain to address the various issues of spectrum channel assignment. An effective channel assignment cannot be performed until spectrum sensing is done accurately. Generally, sensing is done individually or cooperatively by the unlicensed users. Further, cooperative sensing improves the sensing reliability other than the sensing performed by any single user. The first contribution of this thesis is the design of incentive mechanism to encourage users for cooperative sensing. As sensing costs energy, the unlicensed users often do not cooperate in sensing to save their respective energies for their own transmission. To address this issue, a contract theory based incentive mechanism has been designed to encourage the unlicensed users to cooperate in the sensing process. Moreover, to reduce the communication overhead incurred in cooperative sensing only a subset of users have been selected that were enoug