The Design And Research Of Cognitive OFDMA Wireless Communication System Based On Sora

Nowadays, as the shortage of spectrum resource becomes a serious problem, how to save the spectrum resource and how to utilize the spectrum more efficiently have been a hot topic. The appearance of cognitive radio provides a solution of this problem. Cognitive radio, as a technology of spectrum access and spectrum sharing intelligently, consists of two kinds of users. One is primary user, also called authorized user, and the other is secondary user, who senses the activities of primary users, decides the free spectrum and communicates on it without disturbing the primary user. This mechanism makes full use of the free authorized spectrum and relieves the pressure of spectrum shortage significantly. During recently years, cognitive radio has been developed quickly, and several sensing algorithms have been put forward. But there are few platforms in reality to test and verify them in real environment. So, we design and implement a cognitive OFDMA wireless communication system on the Sora platform, which emphasizes the features of cognitive mechanism, implements the algorithms of spectrum sensing and dynamic access, and supports multi-user communication. This platform is put into operation and test our algorithms' feasibility and performance.Firstly, the physical algorithms are introduced in the context. Physical algorithms are the key to the transmission of communication system. While all existing algorithms are designed for fixed spectrum access and couldn't be used directly in cognitive system, we should develop the physical algorithms for our system. These algorithms are mainly focused on how to guarantee the reliability of synchronization and equalization in cognitive system with dynamic spectrum access without disturbing the primary user. The result of theoretical simulation as well as the constellations of receiving data is demonstrated to verify the effect of these algorithms.Secondly, we also introduce the design and implementation of algorithms of spectrum sensing and spectrum access, which is the core algorithm of cognitive system. Meanwhile, we improve the theoretical model of those algorithms according to the features of engineering implementation in reality to make it easier to fulfill and gain better performance. Then, the procedures of sensing, transmitting and receiving are described in detail, as well as the parameters and performance. Also, the occupation of spectrum by secondary user and the constellations of receiving data are shown to imply that our system platform is well operated.At last, we introduce the hardware and software implementation of our cognitive system. Besides the brief introduction of architecture of Sora platform, it is focused on the software programming and convert of state machine. To improve the efficiency of program, some software technologies are adopted. Finally, we show some methods to test our system and the test result.