Design And Realization Of Modem Based On Meteoric Trail Communication

Meteor burst communication as a special way of communication technology, the technical system is different from other means of communication. The current application of modulation types of meteor burst communication in the field of business includes BFSK, BPSK and DBPSK. America federal standard takes DBPSK as modulation mode of meteor burst communication. In order to improve the data throughput and with various modulation systems applicable to the meteor burst channel gradually deepening, the modulation scheme is becoming more and more complex.This paper mainly introduces a kind of modem based on meteor burst communication. Firstly, it introduces the research background and the significance as well as the meteor burst communication development and current situation, mainly including the meteor burst communication introduction, advantages, development history and the current status at home and abroad. Then it explains meteor burst communication channel characteristics. In this chapter, the characteristics of meteor burst channel are analyzed from three aspects, which are meteor burst randomness, classification and channel model. The principle of the meteor burst communication is introduced. The communication system of the meteor burst communication is analyzed. And then it discusses the specific design and implementation of the modem, mainly including modulation and demodulation mode, the signal selecting technology and fast demodulation technique, in which coherent carrier extraction method and bit timing recovery method are introduced in detail. Then it introduces the implementation of adaptive variable rate system and the application of forward error correction technique in meteor burst channel, mainly including three aspects as follows:the adaptive variable rate modulation and demodulation system is designed and realized; if there is a need for meteor burst channel to carry forward error correction is demonstrated and Turbo product coding and decoding is expounded. Finally the test data and analysis is provided. Through experiment it proves that:Modem overall bit error rate (BER) performance curve and theoretical curve is less than 2dB, and the code rate error curve reflects the effect of the corresponding coding gain, modem performance indicators meet the requirements. Rate of 8kbps,16 Kbps using RS codec,32 Kbps, rate of 64Kbps using TPC codec, the signal-to-noise ratio more than 4dB bit error performance curve suddenly become steep by, product code in power and band limited communication system has a good applicability, in meteor burst communication system application are very significant.This subject adopts full duty square wave modulation BPSK/QPSK. Receiver through different code type demodulation frame head, using maximum likelihood matching filter method to identify the channel transmission rate, demodulator using distortion adaptive coherent detection system to finish the demodulation of the signal; in addition, the modem according to characteristics of burst communication design for flow star meteor trails burst channel characteristics, physical layer transmission frame structure, and the corresponding high error correcting ability of error correction coding, error correction coding coding rate according to the channel condition variable, the decoder design using soft decision method and maximize the information demodulation. Using adaptive variable rate transmission technology,on the one hand, low speed transmission can reduce the average waiting time of the system; on the other hand, the high speed data transmission and error coding with high error correcting ability can be effectively against channel fading, for further improving the system data throughput.