Research On Theory And Related Key Techniques In Dynamic Spectrum Management Based On Cognitive Radio

The demand for wireless spectrum is dramatically growing with the rapid development of wireless communications. Large number of measurements show that the inefficient spectrum utilization of static spectrum allocation mode at present, which force people to explore some new spectrum management mode. The development of Cognitive Radio (CR) technology promotes the appearance of Dynamic Spectrum Management (DSM) theory. The DSM strategy based on CR is on the foundation of flexible Dynamic Spectrum Access (DSA) mechanism, and can implement efficient share and dynamic planning of resources among different radio systems. DSM technology can break through the bottleneck of spectrum resource-constrained in the development of wireless communications. It has an important theoretical and pratical significance of DSM researches.Theoretical simulation and practical measurement are combined in this dissertation. Focusing on the new DSA strategy, the influence of spectrum mobility on CR network performance, the coexistence and interference properties between CR network and licensed network, as well as the spectrum measurement and in-depth analysis, a few aspects have been studied. The main innovative achievements carried out in this dissertation are as follows:(1) A new DSA strategy is developedThis strategy, based on spectrum pool, has higher access efficiency than instant manners. The optimal capacity and update time of spectrum pool are all studied. It is found that there is quantitative mathematical relationship between optimal capacity and system efficiency. Different update strategies of spectrum pool in licensed and unlicensed frequency bands are also proposed. Through simulation the dynamic average update interval in licensed and unlicensed frequency bands are obtained.(2) A novel method to analyze spectrum mobility is proposedThis approach follows the logic thinking of mobile spectrum, spectrum handoff and communication interruption, a time relationship model of spectrum handoff is established. Equations of Spectrum Handoff Probability (SHP) in times and Communication Outage Probability (COP) are deduced. Influences of different spectrum handoff manners on COP of CR services are studied. Distinguishing from the former researches about CR service communication interruption, only spectrum handoff times exceed a certain number, communication interruption will occur. This strategy can reduce the COP of CR services.(3) Some coexistence issues between WRAN and DTV system are studiedFirstly, the network architecture, system parameters, and self-coexistence of Wireless Regional Area Network (WRAN) are investigated, and convergent performances among overlapping Base Station (BS) are simulated and validated. Then, a simple coexistent scenario between WRAN and Digital TV (DTV) is designed to analyze the interference from WRAN BS to DTV receiver. Through simulation and computation, some critical values to contral interferences are obtained. These values have directive significance to the design and deployment of WRAN.(4) New methods to measure and analyze spectrum aredevelopedAccording to the shortages of previous spectrum measurements, new methods to measure spectrum occupancy in wide-band and multi-point synchronously is proposed in this dissertation, and the tests last a whole week; the relativities of licensed services are considered when test points are selected. More importantly, data mining and in-depth analysis are carried out with the huge amounts of test data, and a channel analysis method using Channel Vacancy Duration (CVD) and Service Congestion Rate (SCR) are proposed. The spectrum relativities of 3-dimension in time, space and frequency are researched also. The correlativity between channel state and history information is discoved, and which will provide the scientific basis to channel modeling, spectrum analysis and decision of CR users.Some issues at different levels of DSM in CR network are researched in this dissertation, and the purpose is to provide the basical research results for improving spectrum efficiency and resolution of new challenges CR network faced. The mergence of CR technology and ubiquitous wireless networks in future the future will be the next study focus of author.