Study And Simulation On Transform Domain Communication System

Being one of the Cognitive Radio (CR) transceiver technologies, the Transform Domain Communication System (TDCS) is an interference-avoiding technology which is suitable for the variety of the electromagnetic environment, because it can actively avoid the jammed frequencies by environmental sampling, spectral estimation, thresholding and notching, and design the communicating signal in transform domain. Basing on the random phase mapping, the pseudorandom (PR) phase vector can respectively give a random phase to every spectrum component in TDCS, and the Basis Function (BF) can make TDCS to communicate with each other in Multiple Access Environment (MAE). TDCS has the characteristic of Low Probability of Intercept (LPI) and the capability of anti-jamming. It gives an available method of solving current spectrum resource scarcity.Firstly, we investigate the spectral estimation methods of TDCS in this paper, which are modeled, simulated and evaluated in Matlab after we propose a model which can simulate the TDCS electromagnetic environment.Secondly, we analyse the characteristic of the PR phase vector and the BF after their basic theories are introduced. Ulteriorly, we discuss the parameter choice, the Multiple Access Capability (MAC) and the symbol demodulation of TDCS, and propose the Least Common Multiple Phase Mapping (LCMPM) and the Equal Interval Phase Mapping (EIPM), which all can generate the BF of TDCS and are simulated in Matlab.Thirdly, we analyse the characteristic of the narrowband block interference, broadband block interference and frequency hopping interference in TDCS after the synchronization detection and symbol demodulation methods are introduced, and we propose two models which can generate the corresponding jamming signal. Ulteriorly, we give the mathematical description of obtaining some or other user signal from the TDCS multiple access signals and analyse the anti-jamming capability of TDCS. In Matlab, we simulate the the anti-jamming performance in Additive White Gaussian Noise (AWGN) and multi-path fading channels.Computer simulation results show that the Autoregressive Moving Average (ARMA) spectral estimation is more suitable for part spectrum available case, whenas the Autoregressive (AR) spectral estimation is more suitable for all spectrum available case, both the LCMPM and the EIPM can generate the BFs in TDCS, and TDCS can effectively combat the narrowband block interference, the broadband block interference and the frequency hopping interference in AWGN and multi-path fading channels as long as it can obtain sufficient spectrum. In a word, TDCS is a spectrum agile and broadband Code Division Multiple Access (CDMA) technology.