Research On Encoding And Decoding Algorithm Of Low-Density Lattice Codes

Frequency and spectrum resource is very precious in wireless communication environments. How to efficiently utilize these resources is a major topic in modern communications. Channel coding such as Turbo codes, LDPC codes, etc. coding schemes improve the reliability of communication by adding redundant information. However, the introduction of redundant information reduced the effectiveness of communication, resulting in lower bandwidth efficiency. Without extending signal bandwidth, Low-density lattice codes(LDLC) can obtain high coding gain and shaping gain, contributing to higher spectral efficiency. And its decoding complexity is linear in block length, which makes the LDLC a powerful coding-modulation scheme. With the background of ZTE cooperation project, the encoding/decoding algorithms of LDLC and its performance are deeply investigated in this paper, including1. The paper summarizes the development and application status of LDLC codes,outlines the basic principles of LDLC codes. On this basis, the Jacobi iteration encoding scheme and the hypercube shaping algorithm of LDLC codes are deeply studied.2. The construction algorithm of LDLC codes is studied. In order to eliminate the effect of short loops,an 8-cycle construction scheme for LDLC parity check matrix is put forward.The performances of proposed scheme are tested with the help of Matlab simulation software.3 The quantized decoder and parametric decoder of LDLC codes are studied. Both of these decoders do not have an early stopping criterion and the iteration decoders can not terminate until the maximum iteration number is reached. With the purpose of reducing the average number of iterations,an early stopping criterion for the LDLC decoders is proposed in the paper.4. The LDLC encoding and decoding system model is established and the simulations of sampling resolution, mapping method, iteration number are made to analyze the impact of the system bit error rate performance. Then the comparison between LDLC encoding/decoding scheme and Turbo-QAM scheme are made under the same spectral efficiency. Simulation results demonstrate that LDLC is a more efficient coding-modulation scheme.