A cooperative communication approach to cognitive radio

Cognitive radio, whose main idea is to have intelligent devices utilize the limited resources, such as frequency spectrum in wireless channels, is becoming a groundbreaking technology. The aim of this thesis is to apply the cooperative communication techniques to the systems which consist of cognitive radio terminals and to develop new cooperative encoding and decoding protocols to reach higher data rates. Accordingly, the performance of a cognitive system where there is one primary (licensed) user and one secondary (unlicensed) user in a network is analyzed considering two approaches: maximization of the sum rate, and maximization of the rates achievable of the secondary user. Optimal power allocation policies for the cooperative cognitive multiple access channel (MAC) are obtained, and the resulting power distributions and achievable rate regions are computed via simulations.