Research And Implementation Of The Key Technologies Of Real-time Cognitive Radio Platform

The existing spectrum allocation and spectrum use policy indicates, as a non-renewable resource, the spectrum resource exhausts rapidly. Inconsistent with this phenomenon, the statistics to the wireless spectrum assigned to a particular user groups reveals that some bands exist a lot of waste. The low usage of spectrum allocated and the increasing depletion of spectrum to be allocated have become an important problem that must be addressed in the future development of wireless communication.Through dynamic spectrum usage program used to increase the efficiency of spectrum utilization, cognitive radio technology has been considered to be one of the most effective methods to solve the above problems. With the combination of multi-carrier technology, it has become the key field in wireless communications today. The cognitive radio technology proposes a communication model with the coexistence of the primary user and cognitive user network. If the spectrum usage is low or if there are significant time distribution characteristics of the main users, a cognitive radio network can be deployed. Without interfering with the communication between the main users, cognitive users can effectively use the spectrum resources allocated to the main users to communicate with each other.As a dominate technology in multi-carrier communication, OFDM has drawn extensively attention. Meanwhile, it has been included in IEEE802.11standard. With the high resolution ratio of subcarriers and needless of cyclic prefix, multi-carrier communication based on filterbank has drawn increasing attention. Because of its efficient organization structure and low computational complexity of the implementation, multiphase structure of the filter bank provides the probability in real time communication. Compared with OFDM, polyphase filterbank can be both used to multicarrier communication and spectrum sensing, which decreases the demand of hardware demand of cognitive radio.Currently, some domestic and foreign research institutions and universities begin the design and develop cognitive radio platform. The advantage of the software implementation of cognitive radio platform is with a short design cycle and easy to implement. But its processing speed is often unable to meet the demand for high data rate; cognitive radio platform hardware realization can overcome the shortcomings of the software design, but meanwhile, hardware development cycle, poor scalability and algorithm changes are difficult to achieve. With the rising of the performance of the PC, the development of radio communication being processed in a computer becomes reality. The essence of software radio technology is to use a low-cost wireless terminal to process the wireless signals and transfer them to digital signals, and the baseband digital signal is processed in a general-purpose personal computer.We proposed a real time cognitive radio communication system based on the software defined radio technology. The purpose of the project is to study the reality and performance of cognitive radio in real wireless channel. Meanwhile, we studied the communication model and its relative technology. The system was developed by USRP and GNURadio. Its baseband signal processing was all developed in PC. With the system development, we studied the spectrum sensing method based on polyphase filterbank. In the end, we studied the relay selection problem in multi-carrier communication under cognitive radio.