Research On CPM-SC-IFDM Transmission Scheme In Scattering Channel

The tropospheric scattering channel has been widely used in various remote and emergency communications fields because of its long communication distance and strong antiinterference ability.However,the loss in the tropospheric scattering channel is large,and the channel has time-selective and frequency-selective fading.Therefore,the SC-IFDM technology with time-frequency joint frame is considered as the transmission scheme of the channel.And because Continuous phase modulation(CPM)has many excellent characteristics: it keeps the envelope constant,the phase changes continuously,and has high power efficiency and spectral efficiency.What's more,CPM has both coding and modulation characteristics.Ultimately,combining CPM with SC-IFDM can take full advantage of both.Therefore,this paper mainly studies the CPM-SC-IFDM transmission scheme under the tropospheric scattering channel.The main contents are as follows.Firstly,the paper analyzes the basic characteristics of the tropospheric scattering channel and the channel model is given according to the basic characteristics.On this basis,the sevenpath simulation model of the scattering channel is given.Then,this paper studies the traditional CPM scheme,introduces the phase state,modulation scheme and parameter selection of CPM.On this basis,it analyzes the problems existing in the traditional CPM scheme applied in the scatter channel.Finally,the transmission scheme of CPM-SC-IFDM is given,and the corresponding system block diagram and frame structure are given.Secondly,this paper studies the frequency domain equalization algorithm of CPM-SC-IFDM transmission scheme.A least squares channel estimation algorithm based on mean interpolation is given.Then,the equalization algorithm based on orthogonal decomposition,the equalization algorithm based on Laurent decomposition,the equalization algorithm based on oversampling are studied and the simulation performance under the scatter channel are analyzed.At last,a frequency domain equalization algorithm based on precoding is presented.Differential precoding is performed before CPM modulation,which greatly reduces the bit error rate performance of the system while maintaining the complexity of the receiver.Finally,the low complexity demodulation algorithm of CPM-SC-IFDM transmissionscheme is researched in this paper.The theoretical analysis and implementation of optimal demodulation are studied,and the influence of different parameters on the bit error rate performance of optimal demodulation is studied.The Laurent decomposition is then used to reduce complexity on the basis of optimal demodulation.In this paper,a low complexity demodulation algorithm based on threshold decision is presented.Under the premise of no loss of bit error rate performance,the number of filters and the number of grid searches for Viterbi decoding can be reduced at the same time,which greatly reduces the complexity of demodulation.