Research On Spectrum Resources And Key Technology Of Cognitive TD-LTE System Access In UHF Band

The next-generation broadband wireless mobile communication network requires wide enough spectrum to support its communication requirements for the smooth development.TD-LTE,4G technology of China which has own intellectual property rights, the frequency resources currently available it is not only short but also at less-than-ideal frequency.. In WRC07, ITU released digital transformation through a resolution by the radio and television system of the digital dividend band (700MHz band and800MHz band) for IMT. However, the process of digitization of analog television has been slow in China, which leads to that the digital dividend band allocated to TD-LTE is difficult to use. With respect to the nations which have completed the release of the digital dividend band, the demand to solve the shortage of frequencies of TD-LTE, especially the lack of low frequency of our country is more urgentIn recent years, studies have shown that cognitive radio technology is one of the effective techniques to improve spectral efficiency and ease the spectrum supply and demand by reconfiguring the available spectrum and reusing the allocated spectrum resources, providing another way to solve the issue.The combination of cognitive radio technology and TD-LTE systems, not only help solve the shortage of spectrum and management issues, but also promote the research of cognitive radio technology on the basis of the commercial TD-LTE system. It is of great significance for next-generation broadband wireless mobile communication network to open up new spectrum resources.This paper mainly studied two aspects, one is the use of digital dividend spectrum band, the other one is one of the key technologies for cognitive TD-LTE system access-spectrum sensing algorithm. The research of digital dividend spectrum band focuses on the694-806MHz band. Firstly, selecting five typical locations in Beijing and determining the testing program according to the test site, the measurement time, measurement equipment and parameter setting. Secondly carrying out spectrum monitoring for one week. Finally, using Matlab for data processing, generating frequency channel occupancy and frequency band occupancy. Dynamic threshold method is used to distinguish signal from noise. Data processing results indicate that the highest spectrum occupancy of five locations, dense urban is only25.40%. So that the TV bands are more suitable as the candidate band for cognitive radio band to access.Secondly, the binding characteristics of broadcast digital television signals to the based on the classical spectrum sensing algorithm, an optimization algorithm is proposed, namely multi-cycle frequency cooperative spectrum sensing algorithm based on OFDM signal. The main idea of the algorithm is that, firstly using the cyclostationary feature detection to generate the verdict of single cycle frequency, then fusing all the single cyclic frequency verdicts according to the optimal Chair-Varshney fusion theory to give the final verdict. The algorithm not only improves the accuracy of the spectrum sense, but also reduces the complexity of traditional cooperative spectrum sense. The Monte Carlo simulation method is used when doing the simulation by Matlab. Simulation results show that the performance of the proposed algorithm is superior than single cycle frequency detecting results, and it still has a good detection performance even in the low SNR environment.