Research On LDPC Codes Technology Of Low Voltage Power Line Communications

As an important supporting technology in our smart grid, Power Line Communication(PLC) has being paid more and more attention.Due to widely distributed, low cost andconvenient to connected, Power Line Communication has great development potential. Powerline is initially used to transmit50/60Hz power not used to transmit data. However, comparedwith wireless communication channel, power line channel has some troubles such as strongnoise, transmission attenuation and variable impedance. Select a appropriate channel codingscheme can effectively enhance the signal of anti-interference ability, reduce system bit errorrate and improve the reliability of communication system.LDPC codes can be gotten by information sequence multiplied by generated matrix.Although LDPC check matrix is sparse, the generated matrix is not, and its coding complexityis proportional to the square of code length. It cannot meet low voltage power linecommunication system with low processing ability.In order to improve the sparsity ofgenerated matrix and reduce the complexity, so the system uses approximate lower triangularmatrix encoding method. It can be easily implemented by hardware, and can meet power linecommunication system for coding performance requirements.Although Belief Propagation decoding algorithm has a good performance, there are anumber of multiplication, so the complexity is very high and not easy to realize. Min-sumdecoding algorithm reduces the complexity, but the performance is worse than BP decodingalgorithm. For Power Line Communication channels multipath delay effects and impulsenoise, the system of LDPC-OFDM based on low-voltage power line is built. Impulse noisemodel is modeled as Middleton A.OFDM technology can solve multipath interference andimprove bandwidth efficiency.The Low Density Parity Check Codes decoding algorithm isstudied based on the system. According to the min-sum BP algorithm, a coefficient is designed to modify layered sum-product algorithm, so the layered min-sum BP algorithmbased coefficient is proposed. The algorithm is convenient to implement for its low decodingcomplexity and fast speed of iterative. The simulation shows that the algorithm not onlyachieves a better error performance under the system of LDPC-OFDM.but also improves thetransmission efficiency.