The Research On Key Technologies Of Dynamic Spectrum Access

With the rapid development of wireless communication services, spectrum has become one of the most important and scarce resources. However, the current fixed spectrum policy cannot meet the tremendous demands of spectrum accesses. To increase the spectrum efficiency, secondary usage method of the licensed spectrum has been explored, which can be referred to as Dynamic Spectrum Access (DSA). The secondary users in DSA can perform spectrum sensing to detect the "white spaces" of the under-utilized spectrum, and opportunistic access the spectrum. Hence, this technology can be used to enhance the spectrum utilization rate, and revive the lack of spectrum resources in future wireless communication.This thesis focuses on the key technologies of DSA and spectrum sharing. Based on the concept of spectrum pooling in DSA, we propose a spectrum sharing system with opportunistic accesses. In order to satisfy with the real-world application, non-real-time and real-time secondary users with heterogeneous quality-of-service (QoS) requirements are defined in our system. Since each primary user's requiring channel may be occupied by two types of secondary users, the primary user uses different schemes to solve the collision. A 4-dimentional Markov chain model is used to analyze the system performance. Numerical results show that our system can obtain a better tradeoff between improving the spectrum efficiency and guaranteeing the primary user's access priority.Given the higher QoS requirements of real-time service in secondary usage, we propose a new Call Admission Control (CAC) strategy which reserves channels not only for primary users but also for real-time secondary users. Numerical results show that the proposed CAC strategy can improve the system performance significantly, and achieve a better tradeoff between the maximum admission rate of non-real-time and real-time secondary users.