Design And Simulation Implementation Of High-Speed Wireless Data Transmission System

Near space has an important strategic value, and it can provide a strong support for large capacity data transmission. To achieve high-speed data transmission, the current research direction is the use of a higher frequency communication band and a better performance of the modulation and coding schemes. The advantages of selecting a higher Ka-band frequency are not only available bandwidth, but also the interference of small, narrow beam, small size of terminal equipment, etc. But rainfall can affect large rain attenuation for Ka-band signal. To fight the rain attenuation, a current research is the use of Adaptive Coding and Modulation（ACM） technology.Firstly, study six kinds of digital modulation: BPSK, QPSK, 8PSK, 16 PSK, 16 QAM and 32 QAM, four kinds of error control coding: convolution code, R-S codes, Turbo codes and LDPC codes, and ITU-R rain attenuation model.Then research the composition and working parameters of data transmission units based on the subject background. Design system’s overall programme and the specific programmes. From the rain attenuation value, data transmission distance, transmit power, antenna size and efficiency, various aspects of the link loss, receiver quality factor, link margin, demand rate, coding and modulation, and other multiple indicators, design the system parameters. For the communication link analysis, determine the system operating point. System tradeoff analysis of different design parameters is also carried out.On the basis of simulating performance of Modulation and Coding Schemes（MCS） of three encoding scheme corresponding to various modulations, propose the selection scheme of the number of MCS finite set based on normalized signal to noise ratio E₀/N_b and bandwidth efficiency η. After selection process, get 2MCS finite set which consists of 6 groups of better performance MCS. Then compare it with 3MCS of one encoding scheme corresponding to various modulations, and it is concluded that the paper’s performance of ACM is better, but engineering implementation is more difficult. In order to realize ACM, combined with the research of this paper, propose two criteria for switching threshold of MCS: the meeting E₀/N_b standard and the meeting η standard.Finally, system simulation platform is built by using MATLAB/ SIMULINK software to verify the correctness and feasibility of the scheme design and parameters design of the high-peed data transmission system in the near space. Under background of power limitation of supersonic aircraft in near space, the operating process of system adaptive coding and modulation is compared under two different rainfall conditions. Then propose a scheme of the near space high-speed wireless data transmission system which meets the 600 Mbps transmission rate, and it has the guiding significance of engineering design.