Design And Implementation Of Short-Time Burst Communication Baseband Transmission System

In the age of the prevalence of electronic equipment,there are various interference factors that affect the correct transmission and reception of information.Therefore,it's of great significance to design a communication system that ensures timely and accurate transmission and reception of information in a complex communication environment.Short-time burst communication can effectively reduce the probability of information being discovered by reducing the signal transmission duration and increasing the uncertainty of signal transmission time.It has the characteristics of anti-interception,strong anti-interference ability,good reliability and high transmission efficiency.Therefore,it has been widely used in the field of military communication.This dissertation design and implements the baseband transmission system for short-time burst communication.In this thesis,the signal system scheme is formulated,including data frame structure design with high transmission efficiency,selection of symbol synchronization sequence,timing synchronization scheme,phase derotation scheme,GMSK modulation and demodulation scheme,and LDPC coding and decoding scheme.Based on the short-time burst communication system hardware platform,the baseband system of the "GMSK+LDPC code" system is implemented using the Verilog HDL language.Integrate the designed baseband system into the hardware platform for actual communication testing and sensitivity testing.The main contributions of this thesis are as follows:1.In order to meet the burst characteristics,a data frame structure with high transmission efficiency is designed.The data frame structure consists of two parts: effective information and symbol synchronization sequence.According to the data frame structure,an M-Part timing synchronization algorithm is proposed.Compared with the synchronization performance analysis of the sliding mutual timing synchronization algorithm,the comparison results show that the synchronization performance of the sliding cross-correlation timing synchronization algorithm is greatly affected by the frequency offset,and the synchronization performance of the M-Part timing synchronization algorithm is much less affected by the frequency offset than the sliding cross-correlation timing synchronization algorithm,but the complexity is higher than the sliding cross-correlation timing synchronization algorithm.2.In order to eliminate the phase error caused by frequency offset and timing recovery,two phase derotation algorithms are proposed.The anti-frequency offset performance of the two algorithms is analyzed and compared.The comparison results show that the anti-frequency offset performance of the phase derotation algorithm based on multiple sub-correlation peak phase information is better than the phase derotation algorithm based on single correlation peak phase information.3.In order to solve the problem that phase calculation consumes a lot of hardware resources and phase error accumulation during GMSK quadrature modulation,a method of waveform storage quadrature modulation is adopted as the GMSK modulation scheme.A linear approximation GMSK demodulation scheme is designed,which solves the problem of poor performance of the differential demodulation scheme.4.The check matrix of QC-LDPC code has quasi-cyclic characteristics,which better solves the problem of high coding complexity and high hardware consumption of LDPC codes with long code length.Therefore,QC-LDPC coding is adopted as the LDPC coding scheme in the design of the transmit baseband subsystem.In the design of the receiving baseband subsystem,the decoder with serial structure is used to implement the improved Min-Sum LDPC decoding algorithm,which greatly reduces hardware resource consumption and hardware implementation complexity.