Research On MAC Spectrum Sensing & Spectrum Access For Cognitive Radio Networks

Recently, wireless communications technology has rapid growth, and the demand for wirelss radio spectrum resources has greatly increased. However, the spectrum uti-lization is so low beacause of the traditional fixed spectrum assignment policy. The spectrum regulatory bodies start to search for the dynamic spectrum access technology, which can enhance the spectrum resources utilization flexibility.The cognitive radio technology is proposed to deal with the issue of spectrum effi-ciency. The core idea of cognitive radio is that the primary users can share the licensed spectrum bands with secondary users. The secondary users can dynamically adjust their wireless tranismission parameters adapt to the surrounding wireless network circum-stance. Cognitive radio technology has made big process in recent years.Based on the research of congnitive radio networks, we do some innovative work. First, we research the technology of spectrum sensing and propose a sensing period optimizaion algorithm. Then we focus on the spectrum access problem, which is the core of CR. At last, we joint these two aspects mentioned before. In this work, we apply the novel framework, mechanism and angle to study these problems, and get some effective results.1. We propose an energy efficient spectrum sensing algorithm, which apply se-lectable sensing period optimization mechanism. Here, each secondary user ap-ply the different period for channel detection according to the different channel states. On the one hand, we can enhance the spectrum resources utilization; On the other hand, the energy consumption of secondary users can stay in an accept-able range. Both the interference to PU and the energy consumption are designed as the constraints. We do lots of simulations, and the results is that, both energy consumption and spectrum utilization have the better performance by using the SSPO algorithm.2. We present a multi-user spectrum allocation and multi-channel spectrum shar-ing mechanism. The system model we confront is that secondary users have no knowledge about primary users’ behavior. We analyze the interference caused by secondary users through utilizing renewal process theory and derive the cor-responding closed-form expressions. Under the constraints of the interference to primary users and the secondary network’s stability, the queuing theory is inno-vatively utilized to obtain the maximum average data rate of SUs.3. We develop a dynamic spectrum access (DSA) strategy for CRN where prioritized traffic is considered. We divide the secondary users into different priority users depending on the type of data transmission. Primary users always have the highest access permissions for the licensed bands. We model the steady state transitions for DSA as a multi-dimensional Markov chain, which has three-state variables. And we find the factors of the blocking and dropping probabilities of the two types of secondary users.4. We propose a framework of joint multi-user spectrum sensing and multi-channel spectrum access mechanism for the secondary users. Most former works study spectrum sensing or spectrum access respectively. But these technologies have the relationship of restraint. We also study the interference to PUs caused by the dynamic access and the inaccurate spectrum sensing. We use renewal process theory and queuing theory to analysis the performance of CRN.