Research On Serial Cascade Continuous Phase Modulation Transmission Technology

Continuous Phase Modulation is a memory modulation with has high spectral efficiency and constant envelope characteristics.CPM can be used in nonlinear amplifiers with high power efficiency and improve power efficiency significantly.These advantages enable CPM technology to be well applied in weak signal communication environment such as satellite communication and deep space communication.CPM is usually cascaded with error-correcting codes to form SCCPM.It inherits the advantages of CPM spectrum and high power utilization,and further improves the transmission reliability of the system.In this paper,the cascade system of CPM and LDPC codes is taken as the research object,from the perspective of Single-h CPM and Multi-h CPM,the SCCPM system is studied and improved in terms of complexity and parameter performance.Considering the recursive structure of CPE obtained by Rimoldi decomposition method,a non-recursive structure is designed to reduce the influence of recursive structure on error propagation in LDPC cascaded Single-h CPM system.Considering that cascade systems need decoding algorithms with the lowest complexity,the decoding algorithm based on dynamic information update strategy is given,among which SVNF-RBP algorithm has advantages in complexity and bit error performance.On the basis,non-recursive CPM and SVNF-RBP algorithm are applied to SCCMP system.Aiming at many parameters of the system,a joint parameter optimization method is proposed,which provides a feasible idea on how to select parameters to improve system performance.For LDPC cascaded Multi-h CPM system,the PAM decomposition waveforms of Multih CPM signals are given.Based on the optimal demodulation of PAM decomposition,two suboptimal demodulation schemes are designed to reduce the complexity of the receiver at the cost of a small performance loss.On the basis,in order to reduce the computation in the process of modulation and demodulation of the cascaded system,the designed titled phase representation of Multi-h CPM signal is used at the modulation end.In the receiving terminal,a suboptimal demodulation method balancing complexity and performance loss is designed.Simulation results show that the LDPC code cascaded Multi-h CPM system presented in this paper has significant performance advantages compared with the LDPC code cascaded Singleh CPM system under the condition of low SNR.Moreover,compared with the optimal PAM demodulated Multi-h CPM cascade system,the LDPC cascade Multi-h CPM presented in this paper significantly reduces the demodulation complexity.Comparing Multi-h CPM and Singleh CPM systems,although Multi-h CPM implementation is more complex,it also has better spectrum performance and bit error performance.Both of them can be cascaded with errorcorrecting codes to obtain excellent,and suitable systems can be selected according to different communication scenarios and requirements.