Research On VHF Data Link Transmission Technology Of Civil Aircraft Based On Software Defined Radio

As China 's civil aviation industry has entered a new stage of development,ground-to-air communication traffic has been increasing in recent years.The capacity of the Aircraft Communication Addressing and Reporting System(ACARS),which is widely used in domestic civil aviation communications,has been saturated in some urban airports.In order to solve the problem of ground-to-air digital communication for civil aircraft,ICAO requires the ground-to-air communication system to establish a VHF data link to realize the transition to the aviation telecommunication network.However,the core technology of VHF data link is monopolized by foreign countries,and related equipment depends on imports.In order to realize localization,it is necessary to research on VHF data link related technologies.This paper studies the physical layer transmission technology of VHF data link mode 4(VDL-M4)based on ICAO documents to improve the efficiency and reliability of ground-to-air communication.The VDL-M4 physical layer uses Gaussian filter frequency shift keying(GFSK)for modulation.Based on the flexible,reconfigurable and modular GNU Radio and HackRF One software radio platform,this paper studies the GFSK modulation and demodulation technology used in VDL-M4,and designs the encoding,decoding,GFSK modulation,demodulation and code for VDL-M4 Meta-synchronization and other schemes have realized the VDL-M4 digital signal transceiver system based on GFSK modulation.First,according to the ICAO documents,the VDL-M4 physical layer communication technology is researched and analyzed in depth,and the VDL-M4 communication scheme is designed according to the relevant parameters.Secondly,the hardware structure of HackRF One and the software architecture of GNU Radio are studied.The software architecture and message processing and scheduling mechanism of GNU Radio are analyzed,and module development methods are studied.Then in the software radio platform,according to the VDL-M4 communication scheme,code processing,decoding,and GFSK modulation and demodulation are modularized to design and implement M & M symbol synchronization schemes.By designing a clock tracking loop to improve the symbol synchronization module,built the VDL-M4 communication system,and completed the digital signal transmission function.Finally,the software radio platform based on VDL-M4 is tested,and the system reliability is verified through bit error rate and data packet tests,and the experimental results are analyzed.The experiment compared two kinds of symbol synchronization schemes,and tested the bit error rate of the communication system in the noise environment specified by ICAO documents.The bit error rate met the expected requirements.The transmission of data packets in real space is tested,and the results prove that the performance of communication transmission is improved by channel coding.Experiments show the engineering practical value of this research and provide technical support for data link research.