Design And Implementation Of Baseband Processing In TDMA System Based On System Generator

Satellite communication has a wide range of applications in emergency communications,for its advantages of wide coverage,not restricted by geographical conditions,not easy to be damaged,and various types of services that can be carried.Different application scenarios often require different transmission rates to carry differentiated service.If communication system can switch multi-rate transmission and multi-modulation modes online,it will make the equipment more versatile.TDMA is widely used in satellite communications.It's very suitable for handling burst communication services because of the advantages such as single carrier frequency multiplexing,no intermodulation interference,and high throughput and so on.Therefore,this article intends to design a TDMA communication system that supports multi-modulation and multi-rate transmission,and then implement the system on FPGA.The traditional FPGA development process is complicated and difficult to debug.How to make FPGA development more efficient and convenient is the direction of iterative upgrade of development tools.This paper will design the physical layer protocol of the TDMA system,and use the System Generator to implement the hardware based on the modular design idea.The main work is as follows:1.Research on the key technologies of the physical layer of the multi-mode TDMA system.Based on engineering practice,this paper discusses the key technologies used in the system,such as frequency offset estimation and timing synchronization technology of short-term burst signals,multi-rate signal processing technology,phase-locked loop technology,etc.Lay a theoretical foundation for the physical layer protocol design of the system2.Multi-mode TDMA system physical layer protocol design and software simulation.This paper clarifies the design goals,and formulates detailed technical indicators and performance indicators,and gives the design ideas of key modules and the overall scheme of the system.Based on the modular design concept,the key modules of channel encoding and decoding,modulation and demodulation,DUC and DDC,and synchronization processing are designed.Then this paper carries on the software simulation to the signal acquisition,frequency offset estimation,timing synchronization and other modules to determine the key parameters and test the performance of the module.Finally,the overall process of the system is simulated.After simulation verification,the system can capture the frame probability of over 99% under the condition of 15 d B,and the frequency offset estimation accuracy reaches one ten thousandth of the symbol rate.3.Graphical rapid development based on System Generator.According to the functional analysis of the system,this paper determines the workflow and hardware structure of each module.Then it uses the combination of System Generator and Verilog to complete the development of the whole process of sending and receiving,including channel coding and decoding,modulation and demodulation,shaping filtering,matching filtering,DUC and DDC and other modules.The flow chart and schematic diagram of each module are given.It provides a solution for the rapid development of FPGA.4.Test and verify the system and analyze the results.This article deploys the algorithm to FPGA,and then designs typical application scenarios for functional testing and performance testing.Functional testing includes internal data loopback test and external data sending and receiving tests,both of which can realize normal communication between the sender and receiver;performance tests include bit error rate test and frequency offset estimation test under different SNR ratio conditions,all of which can meet the performance indicators of system design.