Iterative Equalization Technology Research In Short-wave Communication

Shortwave communications can provide users with high-quality,high-reliability,and affordable communication lines,and it has always been an important part of global information dissemination.The short-wave channel is characterized by multipath propagation,severe fading and time-varying dispersion.The effective combination of the filter and the corresponding technology to eliminate the signal distortion caused by intercode interference.Based on the mil-std-188-110c standard,this paper attempts to design an iterative equalizer which is easier to realize and suppress the interference of short-wave channel.This paper first summarizes the background and status quo of shortwave communication research,and makes an overall introduction to the research on equilibrium algorithm at home and abroad.Then the physical characteristics and basic characteristics of the short-wave channel are analyzed,and the structure of the baseband transmitter and the Watterson channel model of the MIL-STD-188-110C are introduced,as well as the simulation methods of the specific operation.This paper attempts to design a more easily realized channel estimation and iterative equilibrium algorithm based on mil-std-188-110c standard.The main work of this paper is as follows.1.This paper first analyzes the commonly used adaptive equalization and indirect equalization methods.It is found that using indirect equalizer not only outperforms the adaptive equalizer in SNR gain,but also does not increase the computational complexity.so choose indirect equalization methods.This article then introduces two additional improvements.2.Firstly,a bidirectional RLS and bidirectional LMS joint LS estimation algorithm is proposed for the time-varying of short-wavelength channels and MIL-STD-188-1 10C.For the sparseness of HF channels,a method for deleting unnecessary paths based on Gaussian distribution is proposed.Taking into account the size of the complexity,which depends on the size of the feedforward coefficient and the length of the window length,the bidirectional LMS combined with LS estimation algorithm based on a method for deleting unnecessary paths based on Gaussian distribution is selected,and the performance is better than that of the linear least squares estimation using linear interpolation(the gain increases by about 1.8dB when the bit error rate is 1.0E-4 under QPSK).3.The second improvement is the bidirectional structure,which makes full use of the useful information contained in each path signal.Because the Turbo equalizer needs to change the traditional equalizer,decoder,and deinterleaving blocks into the SISO(soft-in-soft-out)module and the modulator block is also changed,However,the hard iterative structure is not as complicated as the Turbo,and the amount of computation is greatly reduced with some loss of performance.The final equalizer model meets all the requirements of the ITU-Poor standard channel under the MIL-std-188-110c standard,the performance is higher after combining it with the iterative structure(the gain increases by about 1.3dB when the bit error rate is 1.0E-5 under QPSK).The final equalizer model meets all the requirements of the ITU-Poor standard channel under the MIL-std-188-110c standard.