Key Technology Of Spectrum Access Scheme In Cognitive Radio Network

As a novel technology to access unauthorized spectrum, Cognitive Radio (CR) has comprehensive application background. The key technology of CR, such as spectrum access scheme, is the current research hot spot. The topic of this paper has important theoretical significance and practical significance.In this paper, the CR spectrum access technology is research in depth, and the following innovative research findings are completed:1. For perodic data transmission scheme in CR, a transmission efficiency maximum frame structure design scheme is proposed. Choose the spectrum sensing time minmium and systemic throughput maximum as the object function, construct frame structure optimized model according to realistic CR environment. The optimal spectrum sensing time, the optimal channel searching time and the optimal data transmission time are obtained by mathematical derivation and optimization methods. Numerical and simulation results claim that this frame structure design scheme can improve systemic data transmission efficiency dramatically according specific CR environment.2. For dynamic variation CR environment, a spectrum access scheme based on partially observed Markov decision process (POMDP) to maximize the throughput is proposed in multiple PUs system. Based on the first innovation in this paper, this spectrum access scheme is designed to solve aperiodic sensing, data transmission and channel handoff problem. Furthermore, a double thresholds mechanism is used to reduce the computational complexity of this scheme. Then, the differences of this scheme in single channel scenario and multi-channel scenario are introduced. Simulation results claim that this access scheme can set different thresholds according to different requirement of collision probability, and improve the spectrum utilization efficiency dramatically.3. For multi-SU and multi-PU scenario in CR, two queue models and one channel selecting scheme are proposed respectively according to the impacts of frame structure and imperfect spectrum sensing. Based on the present two kinds of error detection incidents and one kind of false alarm event, the third kind of error detection event is defined. We rectify the M/G/1queue model and obtain the M/G/1-R queue model, in which the first moment and the second moment of data transmission time of PU and SU are derived. Moreover, a multi-priority bubble-queuing access scheme (B-M/G/1-R) based on systemic cost is proposed whose sorting method can minimize the systemic cost. And, in multiple channel scenarios, a channel selection scheme (M/G/1-LI) based on data transmission interrupted times is proposed in which the non-contradictory certification between interrupted times and latency is proposed. Furthermore, the numerical and simulation results confirm that M/G/1-R model is designed reasonably, and B-M/G/1-R and M/G/1-LI can reduce the latency and interrupted times of data transmission.4, In WiMAX network, a localization algorithm for mobile nodes based on hidden semi-Markov model (HSMM) and Cell-ID vector is proposed. WiMAX network, as a station based communication system, doesn’t have domestic licensed spectrum band. Research the localization algorithm in WiMAX network, which can be used in other station based CR networks, has positive practical significance. In this part, the definition of Cell-ID vector is introduced firstly. Then, combined with districted method and HSMM, the localization algorithm, Cell-ID-HSMM, is proposed. Cell-ID-HSMM has some novel characteristics, such as simple positioning information and low hardware and software cost. Simulation results claim that Cell-ID-HSMM can enhance the positioning accuracy and provide a new function of estimating the cell residual dwell time.