Design And Implementation Of The Forward Link Of L-DACS1 System Based On USRP

L-band digital aeronautical communication system 1(L-DACS1)is a future broadband aviation communication system based on the orthogonal frequency division multiplexing(OFDM)technology.Due to its advantages,such as large transmission capacity,high user data throughput,high information rate,etc,the L-DACS1 system is regarded as an important technical means of the future civil aviation communication system.The L-DACS1 system can provide air traffic control(ATC)for the aircraft,it also can provide data and voice communication services for the operation and control business of airlines.According to the ICAO’s recommendation,the L-DACS1 system will be deployed in the frequency gaps between the distance measuring equipment(DME)channels.Relevant studies show that DME signals will seriously interfere with the L-DACS1 receiver,which will lead to the decline of system transmission performance.Therefore,it is of great significance to study and verify the DME interference mitigation methods.In order to solve the problem that there is no convenient verification platform for the DME interference mitigation methods of the L-DACS1 system,a prototype system of the forward link of the L-DACS1 system is designed and implemented based on the universal software radio peripheral(USRP),and its effectiveness is tested and verified in the laboratory environment.The main work of this paper is as follows:Firstly,according to the L-DACS1 protocol specification,the forward link floating-point algorithm model of the L-DACS1 system and the algorithms of key units of the transmitter and receiver are given,and the transmission performance of the forward link is verified in the additive white Gaussian noise(AWGN)channel and multipath channel environment based on Matlab.Secondly,according to the above floating-point algorithm model,the forward link transmitter and receiver of the L-DACS1 system are designed and implemented based on the software radio platform of USRP,which include the scrambler,interleaver,channel encoder,modulator,OFDM modulator,synchronizer,OFDM demodulator,channel estimator,demodulator,channel decoder,deinterleaver,descrambler and other units.Finally,the forward link transmitter and receiver of the L-DACS1 system are tested and verified by text transmission in the laboratory environment.The correctness of the prototype system is verified by comparing the test results with the simulation results obtained by the forward link floating-point algorithm platform.