Transform Domain Communication System And Application Research

Anti-interference is the eternal topic of wireless communications, and the current mainstream anti-interference technology is spread-spectrum technology. However, spread spectrum(Direct Sequence Spread Spectrum, DSSS) can only use a section of continuous spectrum in which the interference can only be weakened, and can not be avoided. In order to avoid the interference of frequency band and be able to take advantage of non-continuous spectrum, TDCS(Transform Domain Communication System) has been proposed. In the TDCS, the transceivers form a joint design at both ends, the transmitter end only assigns the signal energy to the bands which have not been interfered, and the receiver also only receives the spectrum with the signals energy, thus avoiding interference and interference with other users. In recent years, to solve the emergence of the spectrum congestion as a result of a large number of wireless business and to improve the utilization of the frequency, Cognitive Radio(CR) technology has been proposed. OFDM(Orthogonal Frequency Division Multiplexing) and TDCS are considered as the most suitable transmission technology in the application scene of cognitive radio. So the study of TDCS in the application of cognitive radio is veryimportant. The main topics in this thesis are as follows:The basic components, working principle, the functions of each module and practical implementation method of the TDCS were Introduced .The theoretical and simulation analysis about the TDCS BER in the Gaussian white noise channel were done. At the same time, this thesis studied systematicly the TDCS for the narrow-band interference suppression method and simulated the TDCS performance in the case of narrow-band interference.This thesis focuses on analysing the practical implementation approach of control channel which is used to transmit CR control information. The channel model, interference management, parameter selection principles and methods were given. It was proposed to build the control signal of the CR by using the DSSS. And the capacity of control channel were analysed. From the result of the simulation, when the density of CR is not very high, it can give more chances for SU to access the control channel.This thesis also discusses the problems of the TDCS based on OFDM in the cognitive radio to transmit data. By using this technology, signaling transmission can be achieved without additional control channel. It can exchange the spectrum perception results when the results of the transceivers at both ends are inconsistent.After the transceivers got each other's perceptions results, by using the intersection of available spectrum to transmit data, it could overcome the effects on the performance of TDCS when the electromagnetic environment which the transceivers at both ends in are inconsistent. Then the thesis also analysed and simulated the mechanism, process and performance of the TDCS transmission technology based on OFDM used to exchange the perception results. According to the analysis, we can make the conclusion that using the TDCS as a signal transmission scheme is appropriate.