## 3 System Model
### Structure of Proposed Scheme  
In CR, PUs can influence greatly the performance of CC selection schemes. This means that sensing the PUs' signal is taken into account when we design the resource scheduling scheme. The proposed framework of the resource scheduling is illustrated in Figure 3 based on the structure SBLS proposed in [12]. The functionality of the resource controller (RC) is to manage the users' buffers. In each RC, there is a serving queue for each user. The resource pool of RC is composed of RBs which belong to the CC that are controlled by RC. Each RC reads data from its serving queue to form transmission blocks for its serving users. The role of spectrum sensing and channel state detection (SS & CSD) is to  
Figure 1: Structure of JQS. Figure 2: Structure of DQS. sense PUs, estimate the channel quality of CCs and feed back the result to the CC selection. The sensor network is adopted in SS & CSD for sensing the presence of PUs; the sensor nodes perform sensing to determine the status of the PUs locally and send their results to the SU, which use the SA technology for SU data transmission in the CR network. The results of SS & CSD are the presence of PUs and the channel quality of CCs, and these results are fed back to the CC selection. We take each CC as an independent carrier, so there should be the same number of RCs and CCs in the system. The resource that is contained in each RC's resource pool is from only one of the CCs. The whole resource scheduling structure is a three-level scheduling structure. Unlike the structure of the DQS, the first level of the resource scheduling structure is the packet scheduling for SUs' data, which carries out the SUs' data packet and sends the packet to the second level; the size of the packet is determined by the result of the second level. The second level is the CC selection, which is in charge of the CR user allocation between the CCs. There is a component carrier configuration and switching process and a dispatching process in the CC selection. The task of the component carrier configuration and switching process is to configure and switch the number of CCs based on the SUs' traffic QoS guarantees. The third level is in charge of the burst data transmission, and is handled by each RC. In the proposed resource scheduling structure, CR users are not served by the fixed RC any more. The dominant RC of one CR user can be changed in the burst-level but its number is still one. This means that, among all the serving queues for CR user \(k\) in different RCs, there is only one filled with one burst for CR user \(k\). The size of the burst is calculated based on the results of SS & CSD. The specific resource scheduling procedure in the proposed resource scheduling structure is as follows. At the beginning of the procedure, the CR users' buffers are firstly updated if there are new arrival SU data and the packet scheduling is carried out. After that, the dispatching condition is checked. Before the dispatching, the component carriers configure and switching process is implemented to configure and switch the number of CCs based on the SUs' traffic QoS guarantees. The dispatching will happen only if some CCs are not used by PUs and there are still CR users' data waiting for transmission. RT-CCCS selects one of the idle CCs as the dominant CC and assigns the user data with priority to the dominant CC. Every time only one of the idle CCs will be selected as the dominant CC, only the burst in the head of CR user buffer will be dispatched, and the burst will be dispatched to the dominant CC. Repeat this cycle until all CCs are not idle. When the data transmission  
Figure 3: The resource scheduling structure of the RT-CCCS scheme. in a CC has not been finished or there is a PU signal in the CC, the corresponding CC cannot be selected as the dominant CC. In essence, the way for the proposed resource scheduling structure to improve the resource utilization is to decrease the traffic dispatching granularity and change the dominant RC when the PUs' signal arises in the CCs.