Research On Key Techniques Of Coded Cooperative Relay Based On Hybrid Fading And Impulsive Noise

Wireless communication and power line communication have broad application prospects in smart grid and smart home.The cooperation and combination of the two can significantly improve the resource utilization rate of communication system and the intelligent level of the network,and provide users with diversified communication services.In this paper,in wireless and power line bi-media collaborative communication system,the bidirectional relay communication combining physical layer network coding(PLNC)and LDPC code is studied,which is the key technology to obtain the diversity gain and improve the reliability of system transmission.Coding collaboration technology can improve the performance of long-distance power line communication.In order to meet the requirements of asymmetric wireless and power line bidirectional relay system,a novel physical layer network coding algorithm based on relay probability density function is proposed to reduce mixed fading and impulsive noise.Firstly,the probability density distribution of the relayed signal is analyzed and the mean and variance formulas of the relayed coded signal are deduced.Then the flatness characteristics of the relayed probability density function under different channel parameters are analyzed.The threshold method is used to simplify the multidimensional signal.At last,the algorithm simulation is carried out for the proposed algorithm.The simulation results verify the validity and reliability of the proposed algorithm.In order to solve the problem of relay performance analysis and LDPC codeword construction under mixed fading and impulse noise,an EXIT algorithm based on Gaussian mixture coding and multi-dimensional node information calculation is proposed.Firstly,the EM algorithm is used to estimate the weight,mean and variance of Gaussian model based on the mixed Gaussian estimation of the decoding initialization information under different two-way relay PLNC conditions.Then based on the multi-dimensional Gaussian mixture model and the symmetry analysis,the multi-dimensional information processing is performed on the variable node and the check node information in the traditional EXIT algorithm.Finally,the objective function and constraint conditions of LDPC codeword optimization are constructed,and the optimal codeword distribution is obtained by convex optimization algorithm.Simulation results show that the newly constructed codeword has better performance compared with the traditional rules and other irregular LDPC codes.