VSAT Satellite Signal Demodulation And Research On Turbo Coding And Decoding Alogorithm

VSAT satellite communication has the following advantages:free from geographical restrictions,flexible networking,compact size,strong scalability,etc.It has been widely used in rescue and disaster relief,ocean voyage,polar scientific research,cross-country exploration and other fields.In the VSAT satellite communication network,the master station equipment adopts DVB-S series standard,the user station equipment adopts TDMA communication mode,and uses the Turbo code.Turbo code is an ideal code type approaching the Shannon limit,which can fit the requirements of VSAT user station equipment with strong error correction ability,small time delay and easy engineering realization.In this paper,Turbo coding and decoding algorithm and TDMA communication mechanism are taken as the entry point to study the technology and method of improving VSAT satellite communication.The main work of this paper includes:(1)The VSAT satellite communication system was deconstructed and analyzed with reference to the international mainstream European dvb-rcs standard and the American IPoS standard protocol,focusing on the research of the TDMA communication mode of VSAT users and the Turbo code coding and decoding algorithm.(2)The coding structure and technical principle of Turbo code are studied,and the structural design and technical principle of component encoder,interleavers,scrambler,CRC check and eraser are discussed in detail,and the coding process of binary convolutional Turbo code is described.(3)Explore and study Turbo code coding technology,and design a reset self-synchronous scrambler with 0/256 detection,which further reduces the long consecutive 0 and 1 runs before Turbo code coding;An efficient program for calculating CRC by byte table lookup method is developed,which is nearly 17 times more efficient than the direct calculation method.Adaptive rate Turbo code is studied,and a practical application based on 100 frame CRC pass rate is listed.(4)A segmented unique code TDMA frame structure is proposed,and corresponding demodulation and burst frame detection technologies are studied.Interpolation sliding cross correlation algorithm is used to detect burst frames and estimate parameters accurately.Channel response tracking LMS algorithm is applied to achieve accurate global tracking and unlocking at the single symbol level.(5)The principle of MAP,Log-MAP and MAX-Log-MAP algorithm in AWGN channel is derived in detail,a parallel decoder structure suitable for GPU is designed,a normalized dominance algorithm of soft decision value is proposed,and the soft input Max-Log-MAP algorithm is implemented to improve the decoding quality.