Design And Implementation Of GMSK-LDPC System Based On FPGA

With the rapid development of communications technology in the world today,people have increasingly higher requirements for the effectiveness and reliability of communications,and Ultrashort Wave Communication System with superior performance have emerged.On the one hand,the superiority of the Ultrashort Wave Communication System is large signal power,high frequency of information transmission and wide system bandwidth.On the other hand,it has high stability,good reliability,strong anti-interference ability,and outstanding anti-damage ability.At the same time,it also takes into account the economy and practicability.Therefore,it has been highly valued and widely used in both military and civilian fields.Since the adoption of a high-performance coding method and digital modulation technology has a non-negligible impact on improving the effectiveness and reliability of the system,this article explores and researches the channel coding,digital modulation technology in the Ultrashort Wave Communication System.LDPC code has the advantages of good error performance,low implementation complexity,and flexible parameter settings.It has been practically applied in a variety of communication standards,and LDPC code can also be seen in deep space communications,mobile communications,space communications,and magnetic storage;The GMSK modulation has many advantages such as constant envelope,continuous phase,narrow bandwidth,good spectrum characteristics and strong ability to resist noise.It is a modulation method stipulated by the GSM standard.It plays an important role in digital communication,spread spectrum communication,wireless communication,burst communication,aerospace measurement and control,and satellite automatic identification systems.Therefore,the GMSK-LDPC cascade technology is adopted in the development and design of the Ultrashort Wave Communication System in this paper,and an in-depth study has been carried out on it.Starting from the background and significance of the research content,this article briefly describes the Ultrashort Wave Communication System,and at the same time reviews the development history and research status of LDPC codec and GMSK modulation and demodulation.Then,the key technologies are studied,namely digital modulation,coding and synchronization,etc.,and the technical scheme of the ultrashort wave communication system developed and designed in this paper is determined.Then take spread spectrum and channel equalization technology as examples to further explore the key technologies in the more complex Ultrashort Wave Communication System.From the perspective of theoretical research,the basic definition and graphical representation of LDPC code are reviewed,and different design methods of check matrixes are introduced.And we compared the coding methods based on the check matrix and the generator matrix,and then studied the LDPC coding performance under different parameter conditions with the help of simulation.Then,we carried out in-depth research on decoding,and compared the error performance of various decoding algorithms and different iteration times in combination with simulation.At the same time,the definition and principle of GMSK modulation and the realization method of digital quadrature modulation are explained in detail,and the influence of different parameters of Gaussian filter on GMSK modulation is studied.Finally,different GMSK demodulation algorithms are studied,and the error performance between them is compared.Through the above research,a solid theoretical foundation has been laid for FPGA-based hardware implementation and application in this article.In this paper,combining with the needs of the engineering project,the overall design of the Ultrashort Wave Communication System is described in detail.The hardware implementation of the GMSK-LDPC cascade system based on FPGA is completed,at the same time,the Ultrashort Wave Communication System is realized by combining communication modules such as framing,digital up-down conversion,and receiving end signal synchronization,and relying on the host computer for functional verification and performance testing to ensure the validity and reliability of the communication between the sender and receiver.