Research On The Modulation And Demodulation Technology Of D8PSK Based On Air-ground Datalink

Air-Ground Datalink System has always been one of the major means of communication for civilaviation. The low transmission rate, character-oriented application make ACARS can not meet the thedemand of Air-Ground communication today. Therefore, the International Civil Aviation Organization(ICAO) puts forward several new kinds of Air-Ground Datalink System to solve these problems.VDLM2is the next generation of civil aviation air-ground data link and has already been applied in thefield of international civil aviation. Civil Aviation Administration of China(CAAC) will graduallyimplement VDL M2.There are only several corporations abroad who supply the equiments of Air-Ground DatalinkSystem and the core technology has been monopolized by Western Countries. With localization of thedatalink advised by CAAC and the development requirements of our large aircraft, the research on thetechnology of Air-Ground Datalink System shall be promoted with a tough requisite. Due to the weakfoundation of relative research and technology accumulation lag, The study of Air-Ground Datalinkshould start from basic technology. As a wireless communication system, the performance ofdemodulation technology in physical layer determines the overall performance of the VDL M2system.The physical layer of VDL M2uses differetial8Phase Shift Keying (D8PSK) technology to modulatethe signal. On the basis of the documents ICAO issued, this research focuses on the demodulationtechnology of D8PSK signal. By comparing the anti-noise performance of different modulationscheme in the noise environment defined by ICAO, this paper establish the optimal modulation anddemodulation technology of D8PSK signal in Air-Ground Datalink System and implement thetechnology by simulating, providing support for localization of the datalink and the developmentrequirents of our large aircraft.Demodulating the signal based on the constellation defined by ICAO requires a lot ofcomparison operations. Therefore, the demodulation efficiency is low. this paper proposes twoschemes to improve the demodulation efficiency of D8PSK signal and analyzes the advantages anddisadvantages of the two kinds of schemes respectively. It is verified that the two kinds of schemesare efficient and will not cause loss of anti-noise performance.