Application Of Polar Codes In Power Line Communication System

With the rapid development of new technologies such as the internet of things(IoT),the advantages of power line communication(PLC)have become increasingly apparent,and related technologies have once again become hot spots for scholars at home and abroad.The popularity of some large amount of data services,such as virtual reality,ultra-high definition video streaming,puts forward higher requirements for the overall performance of the communication systems.However,the harsh channel and noise environment on the power line has limited the rate and reliability of the data carried by it,and the current PLC system is hard to meet the development needs of emerging services.Polar codes are currently the only class of coding scheme that have been proved to be able to reach Shannon capacity.They have certain advantages over conventional PLC system's Turbo codes or low density parity check(LDPC)codes both in complexity and decoding performance.The introduction of polar codes into the PLC system is bound to be one of the trends in the development of PLC technology.Based on the application of polar codes to the PLC system,this thesis mainly solves two major problems: one is the problem of constructing the polar codes in the PLC channel;the other is the rate compatibility problem of the polar codes in the PLC system.The specific research work is as follows:1.Aiming at the problem that the existing algorithms can not realize the low complexity construction of polar codes in PLC channel,an improved low complexity polar codes construction algorithm is proposed in this thesis based on the polarization weight.This algorithm extends the Beta-expansion method,which originally can only be applicable to Gaussian channel,and makes it can be applied to PLC systems with single carrier and orthogonal frequency division multiplexing(OFDM)modulation,respectively.2.For the problem that the polar codes cannot adapt to the change of channel state due to the limitation of code length,a low complexity rate-compatible polar codes structure is proposed.The used rate matching algorithm does not need to re-estimate the reliability of the sub-channels,which greatly reduces the complexity of the algorithm compared to the traditional algorithm.At the same time,the new puncturing pattern and bit selection structure take advantage of a variety of puncturing modes to ensure decoding performance under various code rates and puncturing numbers.3.The rate matching algorithm is further optimized by combining the requirements of the PLC system and the characteristics of the polar codes.The polar codes rate matching structure with low code rate is used to replace the bits replication technology of the current HomePlug-PLC system,which not only reduces the system signaling overhead,but also improves the decoding performance under the short codes.In addition,the limitation of the maximum code length avoids excessive decoding complexity.When the maximum code length is exceeded,the same structure as that of rate matching is used to implement the bits repetition,and no extra system overhead is caused.4.Integrating all the techniques proposed in this thesis,the OFDM-PLC system coding solution based on polar codes is given.Through theoretical analysis and numerical simulation under the PLC channel,it is verified that the proposed solution is superior to the duo-binary Turbo codes of HomePlug-PLC system in terms of complexity and performance.