Study And Simulation On Transform Domain Communication System And Related Key Technologies

With the rapid development of communication technololgies, the demand for high speed communication of people is incressing, making the use of spectrum resource shows obvious growth trend. However, in wireless communication systems, besides using a certain proportion of spectrum resource, the proformance of anti-jamming communication system also becomes very important.The main trend of anti-interference technique is the spread spectrum technology, this technology is already mature and widely used in military and civilian communications. But the spread spectrum system has its own disadvantages, in order to overcome those problems, Transform Domain Communication System(TDCS) appeared.TDCS as the candidate of transmitter and receiver technololgy of Cognitive Radio, the transmitter and receiver both design the waveform, making out the interference of frequencies.The transmitter only distribute the signal energy on the spectrum which are not interference when sending signal. And the base function has the character of noise, to solve the shortage of spectrum resources in the wireless communications business and guarantee the low intercept characteristic of the system and performance of anti-interference at the same time. TDCS shows an important use in military wireless communication.The main content of this paper is about the key technologies research and simulation analysis in TDCS, including the basic principle and implementation in detail of TDCS. In view of the TDCS are studied the similarities and differences of the direct sequence spread spectrum system, frequency hopping system and OFDM in many aspects, making TDCS to the pratical technical inheritance possibile. In the aspect of research in CCSK, analyzing the qualitative and quantitative of different order of CCSK modulation when the number of available frequency is different, and the scope and trend of bit error rate change, and analyzing the degree of change using MATLAB. When the spectrum of transmitter and receiver are the same, put forward a adaptive threshold algorithm in a complex electromagnetic environment, the algorithm can extract the useable frequency and guarantee the system transmission rate at the same time, and the bit error rate can reach the optimal, using MATLAB to simulate the algorithm compared with the traditional algorithm improved ber, verified the superiority and effectiveness of the adaptive algorithm. When the spectrum of transmitter and receiver is different without spectrum interaction, build a system model of TDCS in that situation, and simulate BER loss. In the aspect of channel estimation of TDCS, I studied LS estimation algorithm and its noise reduction algorithm as well as two MMSE algorithms in the application of TDCS. Compared with MATLAB simulation verified the five methods without channel estimation error rate in the slowly varying channel improvement and is mean square errme(MSE) change trand. At the same time, as the technology gap of inserted pilot frequency domain channel estimation in TDCS, a non-uniform pilot insertion method is showed, and the non-uniform recovery algorithm, verify the effectiveness of the algorithm in the frequency selective fading channel, and compared the bit error rate with no estimation by using MATLAB simulation.Finally, the author summrise the research work, and discussed the future work direction. Moreover, show a great thankful to the people who contribute for this article.