An EWFRFT-based Diversity Multiplexing Technology In Troposcatter Communication

Troposcatter communication usually requires high transmit power.Improving the signal anti-fading performance can reduce the power.Diversity technology is one of the main ways to resist channel fading.The traditional time and frequency diversity methods use extra time-frequency resources,which will reduce the communication capacity.The hybrid-carrier signal based on the classical weighted fractional Fourier Transform(WFRFT)has better anti-fading performance than the traditional single-carrier(SC)or multi-carrier(MC)signals.However,the extended HC signal without energy allocation restriction has greater potential in terms of anti-fading.Therefore,the extended Weighted Fractional Fourier Transform(EWFRFT)is applied to Troposcatter communication in this paper.Diversity multiplexing scheme based on discrete EWFRFT is studied,and the diversity gain is achieved without using additional resources.The main research contents of this paper are as follows:Firstly,the training symbol-based channel estimation and the linear equalization methods are studied.The performance of single-carrier frequency domain equalization(SC-FDE)and Orthogonal Frequency Division Multiplexing(OFDM)frequency domain equalization system is simulated under the troposcatter channels.The influence of factors such as pilot insertion modes and pilot length on system performance is also discussed.On the basis of EWFRFT continuous form,flipping and zero padding are introduced to discrete EWFRFT so that the symbol energy distribution is more uniform,and its transformation matrix expression is given.The SC-FDE and OFDM diversity multiplexing scheme based on discrete EWFRFT are studied,and the expression of symbol decision signal-to-noise ratio is derived.The simulation results show that this scheme can obtain diversity gains without reducing the system capacity.Moreover,since the proposed scheme has an averaging effect on the channel estimation error,the diversity gain is larger when the channel state information is unknown.In addition,a full frequency diversity OFDM(Frequency Diversity OFDM,FDOFDM)based on discrete EWFRFT is proposed to further improve its robustness against frequency selective fading.The system simulation is carried out under troposcatter channels and compared with the Walsh Hadamard FDOFDM.The proposed method can achieve full frequency diversity without sacrificing spectrum efficiency,and has the potential to obtain larger coding gains when combined with channel coding.Finally,the EWFRFT signal hardware demonstration platform was established to verify the key technologies of EWFRFT-based diversity multiplexing schemes.A point-to-point extended weighted fractional Fourier transform domain signal laboratory verification module is designed.The communication validity was tested on the channel simulator.The test results verify the physical realizability of the proposed scheme.