Optimal Sensing Time And Power Allocation In Sensing-based CR-OFDM Systems

In the last decade, with rapid development of wireless communication technology, the limited spectrum has turned into a scarce resource. On the other hand, due to the traditional fixed spectrum allocation policy, it has made the allocated spectrum experience low utilization. In order to solve these problems, Cognitive Radio (CR) was introduced by Dr. Joseph Mitola and has become a key technology which aims for efficient spectrum usage by allowing secondary users to access licensed frequency bands under the condition of protecting the primary users from harmful interference. Orthogonal Frequency Division Multiplexing (OFDM) is an advanced multi-carrier transmission technology which is flexible for selecting spectrum and it will provide a good platform for cognitive radio system.In this thesis, we make OFDM technology used in a sensing-based spectrum sharing transmission model and get a new CR system model, which is referred as sensing-based CR-OFDM system. And the basic structure of the new system and key technologies are described later. Furthermore, we have also studied the problem of designing the optimal sensing time and power allocation strategy under joint the average transmit and average interference power constraint, in order to maximize the ergodic throughput of the system. Finally, the simulation results of this new system model in different conditions are presented, and the relationship between the capacity of the system and all the constraints are also discussed in the last part of this thesis.