Research On High Data Transmission Technology Based On The C-band Satellite Transponders

With the development of global satellite navigation system(Global Navigation Satellite System, GNSS), the resources of L-band which commonly used are increasingly scarce. Compared with the L-band, though C-band has larger link attenuation,its available resources are relatively abundant,and it is more suitable for studying. This article which relies on High Precision Wide Area Augmentation Service System of Beidou proposed a signal system for navigation system of C-band.After simulation, its information transfer rate up to 750 bps when the bit error rate requirements for 10-7.High Precision Wide Area Augmentation Service System of Beidou described herein is operating in C-band satellite navigation system, which consisted of the data source station, Geosynchronous orbit(GEO)satellites and ground receiving terminal.Data source station is responsible for navigation satellite observations and calculate differential corrections and other enhancement information, after coding, spreading,modulation processing, it send the information to the GEO satellite through large-diameter antenna. After receiving the information, it switch to another frequency of C-band and broadcast the information to the ground terminal. Then the ground receiving terminal demodulates and decodes to obtain the information. This paper which focused on the system makes a detailed study of the data transmission link,then doing research on coding techniques, spread spectrum technology, modem technology of data transmission, giving the simulation results at last. Specific research work of this paper is as follows:(1)Research on data transmission link of the systemThe studied system is based on C-band,so this paper compares the different points of C-band and L-band which is commonly used on satellite navigation system,then analyzes advantages and disadvantages of C-band. Taking the launch conditions and available satellites as example, this section does a detailed calculation on data transmission link. At last, means for encoding and spread spectrum can be taken are discussed by this section.(2)Research on coding technologyThis section introduces several error correction coding methods commonly used on satellite navigation system, then compares the advantages and disadvantages ofLow-Density Parity-Check(LDPC)codes, convolutional codes, Turbo codes. A cycle elimination algorithm of constructing quasi-cyclic(QC) LDPC codes is studied at last,simulation and Analysis for this algorithm is given combined the calculation result of data transmission link.(3)Research on spread spectrum technologyThis section describes the theoretical basis of spread spectrum communication.Autocorrelation of different code lengths of m-sequence is studied, selecting the m-sequence with good autocorrelation as the system’s spreading code.(4)Research on modulation technologyThis section introduces several common modulation methods of communication system, simulation and comparison to the methods is did at the same time. As a new modulation method,Time Division Data Modulation attracts a wide range of vision.Taking TDDM-BPSK modulation as an example, this section studies its generation mechanism and characteristics as well as its acquisition algorithm. Then it simulates the acquisition results of the algorithm combined with results studied beyond.(5)Verification of the signal systemA variety of factors that affect the transmission quality are analyzed and examined, the simulation results verify the feasibility of the signal system proposed in this paper under link conditions of the system.