Research On Key Technology Of Frequency Domain Equalization For CPM In Scattering Channel

Since tropospheric scattering channel not only has far communication distances and large transmission capacity but also has high quality of confidentiality,directionality and anti-interference ability,it was much attention in the field of military communications and emergency communications.However,the tropospheric scattering channel is also a rigorous time-varying multipath fading channel.In this case,the emergence of the single carrier frequency domain equalization(SC-FDE)technology has attracted the attention of the troposcatter communication field,which provides an effective low complexity solution for resisting channel multipath decline.And because the M-ary continuous phase modulation(CPM)signal has the constant envelope,continuous phase,high spectral utilization and power efficiency,the combination of the above two technology and play their respective advantages have a good application prospects.And add the serial concatenated coding to the CPM signal can greatly improve communication performance.Therefore,this paper mainly researches the frequency domain equalization of M-ary CPM signals in the tropospheric scattering channel.Firstly,the paper summarizes the basic characteristics of the tropospheric scattering channel,which includes loss characteristics and fading characteristics,and the channel simulation model of the seven path tropospheric scattering channel is given by using channel characteristics and channel model.And then according to the characteristics of the scattering channel analysis of the communication requirements,select the performance of a good modulation system CPM and frequency domain equalization technology SC-FDE,then the transmission system and two equalization algorithms of SC-FDE technology are researched and analyzed in detail and the simulation results under scattering channel are given.Secondly,this paper researches an oversampling frequency domain equalization algorithm of M-ary CPM signals based on chaotic interleaving.First,the frame structure of the M-ary CPM signal is designed by using the phase nulling method to keep the phase continuous.And then for the non-decomposed M-ary CPM signal which uses the oversampling frequency domain equalization algorithm,the simulation performance of the scattering channel is analyzed by using the viterbi algorithm.And on this basis,this algorithm combines the chaos interleaving method based on the Baker map,the sequence of the transmitted signal is interleaved to obtain a low correlation permutation sequence by this way,so compared to traditional block interleaving method to effectively improve the system performance.Finally,an algorithm for frequency domain equalization of serially concatenated continuous phase modulation(SCCPM)signals based on pulse amplitude modulation(PAM)decomposition is researched in this paper.Add the serial concatenated convolutional code(SCCC)to the M-ary CPM signal,and then carry on the frequency domain equalization on the basis of the PAM decomposition,on the basis of this,a chaotic-mode 2 interleaving method based on Logistic map is used to improve the bit error rate of the system compared with the commonly used pseudo-random interleaving method.The receiver uses the log maximum a posteriori(Log-MAP)algorithm to perform soft-in soft-out(SISO)iterative decoding,and compared with the another low-complexity soft-output viterbi algorithm(SOVA)and analyzed.Compared with the frequency domain equalization system of the uncoded CPM signal,the system simulation performance is significantly improved in the scattered channel.