Research And Implementation On Key Technologies Of High-speed MAPSK Satellite Communication System

With the growth in demand for military communications, requirements for theinformation processing speed becomes very high. In recent years, many countries havecarried out research on space technology for high-speed data transmission over600Mbps.Setting in high-speed modem pre-research project, this paper takes research andimplementation on key technologies of high-speed MAPSK satellite communication system.As the needs of high power amplifier in satellite communication, the satellitecommunication channel is a typical nonlinear channel. We use the LDPC codec technologywhich is close to the Shannon limit and the MAPSK modulation technology which has lessamplitude, and we use the pre-distortion technology to compensate for nonlinear distortion.Since the symbol rate of high-speed satellite communications system is very high, thechannel is not flat and exist group delay jitter. There is a serious Inter-Symbol Interference(ISI) between symbols, so it is necessary to add an equalizer to compensate for channeldistortion.Based on the above discussion, the research point and the main work of this paperinclude:(1) This paper analyzes the wave propagation characteristics of satellitecommunication channel, and modulated signals will cause nonlinear distortion because ofthe high-power amplifier on the satellites. According to the characteristics, this paperintroduces the coding technology and modulation technology which is suitable forhigh-speed satellite communication systems. We use LDPC coding technology for channelcoding, which has excellent performance, low decoding complexity and a parallel structureeasily achieved. We use MAPSK modulation technology (32APSK and64APSK), whichthe non-linear amplifier caused is relatively small.(2) This paper describes adaptive digital predistortion technology, includingmathematical models and linear technology of power amplifier. The two traditionalalgorithms (LMS algorithm and RLS algorithm) used in adaptive predistortion aredescribed in detail, then we give the performance simulation. Basis on this, a new RLSalgorithm based on QR decomposition is particularly suitable for hardware implementationand application of this algorithm for adaptive predistortion technology are simulated andanalysis.(3) This paper gave a basic overview of the equalization. On the research and analysis of the traditional equalization algorithm (LMS algorithm and RLS algorithm), we introducetwo adaptive blind equalization algorithm: CMA algorithm and MMA algorithms. Thesetwo algorithms are further improved to accommodate the higher order modulation, and weapply this improved algorithm for adaptive blind equalization to simulate and analysis theperformance.(4) Finally, we complete the hardware implementation of the entire system usingVHDL language on the FPGA platform. According to the design requirements and designspecifications, we develope a high-speed modem systems whose information rate is higherthan600Mbps. Focusing on adaptive predistortion technology and adaptive equalizationtechnology, we complete the hardware implementation and performance measurement. Andfinally we complete performance measurement on the overall system.