Research Of Media Access Control In Cognitive Radio Networks

Cognitive radio (CR) is an intelligent wireless communication system that can be aware of its environment and adapt to the input stimuli, and has been intensively studied as a promising strategy to solve the scarcity of spectrum. It can obtain the access of licensed spectrum which is unoccupied or partially occupied as a secondary user (SU). Media access control algorithm in cognitive radio network (CRN) can greatly improve the utility of spectrum resource and satisfy the communication quality of primary user (PU).In this thesis, we illustrate the media access control algorithm in CRN. In order to improve the high computation complexity and delay of centralized scheme, we proposed least square based joint admission control and power allocation algorithm. In this algorithm, our target is to maximum the number of secondary accessing users while satisfying the certain QoS and power constraint. Different from the existing ways, we transform the problem into a least square optimization problem with constraints. For the distributed scheme, we study the power allocation algorithm with game theory and proposed the power allocation based on game theory. We set weighted summation of capacities as the utility function for maximizing the capacity of the network. However, CRs should setup maximum transit power constraints to prevent overdose interference to PU. Comparing the existing maximum transit power constraints, the proposed constraints set each SU's maximum transmit power corresponds to the transmission gain between PU and SU, respectively. Simulation results show the superior performance of the proposed algorithms over the existing algorithms.