| Summary: | The concept of cognitive radio aims to increase the efficiency of spectrum usage. Besides, cooperation techniques, such as cooperative sensing and cooperative transmission, have been widely used to further enhance the performance of cognitive radio networks (CRNs). In the first part of the thesis, we analyze both cooperative sensing and channel accessing in a CRN with multiple primary users (PUs) and multiple secondary users (SUs). We first propose a cooperative spectrum sensing and accessing (CSSA) scheme for all the SUs. We then formulate the multi-channel spectrum sensing and channel accessing problem as a hedonic coalition formation game. The value function of each coalition takes into account both the sensing accuracy and energy consumption. In order to implement our CSSA scheme, we propose an algorithm for decision node selection. Also, we propose an algorithm based on the switch rule for the SUs to make distributed decisions on whether to join or leave a coalition. We prove analytically that all the SUs will converge to a final network partition, which is both Nash-stable and individually stable. Besides, the proposed distributed algorithms can adapt the Nash-stable partition to environmental changes. Simulation results show that our CSSA scheme achieves a better performance than the noncooperative spectrum sensing and accessing (NSSA) scheme in terms of the average utility of SUs.
In the second part of the thesis, we analyze the cooperative transmission in CRNs, where SU can be selected as the cooperative relay to assist PU’s transmission. In order to improve the performance, the PU needs to select the secondary relay and allocate time resources for cooperative transmission. Then, the SUs need to determine their strategies of random access. We first establish a model for cooperative cognitive radio networks. We then propose a cooperative transmission and random access (CTRA) scheme. Based on the sequential structure of the decision-making, we study the cooperative cognitive radio network and determine the equilibrium strategies for both the PU and SUs using the Stackelberg game. Simulation results show that both the PU and SUs achieve better performance compared with the noncooperative transmission and random access (NTRA) scheme.
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