Encoding And Decoding Technology Of Polar Codes Towards 5G Applications

With the rapid development of the internet,existing communication technical framework is challenged by the massive data stream.As a popular research topic,the 5th generation mobile communication system(5G)is mainly focusing on solving the ultra-high speed,ultra-reliable and low-lantency transmission problems.These problems put forward more requirements for channel coding,which is the core component of the physical layer of wireless communication.Derived from channel polarization phenomenon,Polar codes are the only family of codes which can theoretically achieve Shannon limits.Due to the fruitful results created by academia and industry,3GPP standardize Polar codes for control channel in 5G e MBB scenario.However,there are still some noticeable bottlenecks for the practical applications of Polar codes.Although long Polar codes can reach the Shannon limit without random encoding,short Polar codes have poor error correction capacity because of insufficient polarization.As to the relay network communication scenario,Polar coded cooperation can bring diversity gains and error correction gains simoutaineously.But until now,there are few studies on sub-codewords design for variable cooperation level.For the multiple access transmission of network communication,MAC(Multiple access channel)shares same time interval or frequency interval to send multiple users' information.Specific plans of Polar coding & decoding under MAC should be studied urgently.Aiming to the above questions,whole research is composed of three aspects:For the single link transmission,methods to improve the performance of short Polar codes are studied.To compensate the poor error performance of short Polar codes,RS codes are chosen to develop a multi-RS codes concatenation scheme of Polar codes.Specifically,the code rate of every RS frame is adaptively allocated based on the error pattern estimated by Monte-Carlo algorithm.After using the frame & intra-frame interleaver,the performance of short Polar codes under fading channels is well improved with the help of SCL-based(Successive Cancellation List decoder)joint decoder.Simulation results show that the concatenation scheme enhances the short Polar codes performance under fast fading channels.On the aspect of relay channel,the research of improving the performance of Polar coded cooperation is conducted.Under the relay channel communication scenario,few researches about Polar coded cooperation have been studied,high performance can be obtained only at 50% cooperation level.Based on the polarization channel capacity and the feature of Polar codes' minimum hamming weight,a low-complexity puncture algorithm is proposed.With the help of information refreezing algorithm,nice performance can be reached under any cooperation level(puncture number).In addition,a soft cancellation decoder(SCAN)based scheme can reduce the redundant decoding delay by cyclical redundancy check(CRC)results generated by the cooperative user.At last,the polarization phenomenon of multiple access channel and the corresponding coding & decoding techniques are well studied.On the aspect of multiple access channel(MAC),few points on the dominant face of MAC rate region can be reached using the rate splitting decoding or original channel polarization.Taking two-user MAC as an example,the monotone chain rules expansion is deployed to realize practical Polar transmission schemes of MAC that can achieve all points on the dominant face.After the polarization phenomenon of MAC is proved,recursive calculation formulas of single user can be extended to MAC.So,SC & SCL can be extended to MAC as well.The above Polar coding scheme of MAC inherits the complexity of single user coding scheme,simulation results show that MAC-SC and MAC-SCL can achieve any points on the dominant face of rate region.