The Research Of Cooperative Spectrum Sensing Information Transmission Scheme Based On Cyclic Delay Diversity

Radio Spectrum is non-renewable natural resources, and its total size is limited, with the rapid development of wireless communication networks, spectrum shortage has become increasingly evident. CR (Cognitive Radio) technology improve the utilization of spectrum resources through surrounding radio environment and dynamic using of unlicensed spectrum which is unoccupied currently. In order to detect and exit the "spectrum hole" in time, as the core technology of cognitive radio, the accuracy and the validity of spectrum sensing technology is particularly important. In the cooperative spectrum sensing system, the transmission efficiency of detection information will greatly reduce if CR users are in multipath fading environment, it will influence the reliability of spectrum sensing directly.In the cooperative spectrum sensing system, the reliability of the system sensing depends not only good detection methods, but also the transmission program of detection information. In the information transmission phase of cooperative spectrum sensing, the exiting transmission programs of detection information need to select appropriate transmission model based on different detection scene and the detection model, leading to different information encoding scheme, encode design is complex and inflexible.For different number of CR user, the thesis analyses a unified detection information transmission model, and combines with the characteristics of detection information, researches a full diversity cooperative spectrum sensing information encoding scheme based on cyclic delay. The scheme achieves the full diversity of system by pre-coding and cyclic delay, the coding design is simple, and the detection model may be unified because of the unified transmission model, it has more universal significance for higher flexibility.The thesis analyses the characteristics of cooperative spectrum sensing system, equivalents the CR users and fusion center to transmitting antennas and receive antenna of "virtual MIMO" system, achieves space and frequency diversity using multiple sub-carrier transmission, frequency domain pre-coding, OFDM, cyclic delay technology, reduces the error and mission of detection information in multipath fading environment. Finally, simulations prove that the full diversity detection transmission scheme of the thesis can indeed reduces false detection probability and misses detection probability, and improves the reliability of spectrum sensing.