Design And Implementation Of Rateless Polar Code Based On LT Code

Since Shannon come up with the Shannon theorem,finding the channel coding method whose channel capacity can reach the Shannon limitation is always popular in the field of communication.Michael Luby proposes LT code in 2002,which is the first kind of realizable digital fountain codes.Digital fountain code is Rateless.LT code is a kind of non-system code based on the irregular sparse bipartite graph.Erdal Arikan proposed polar codes in 2009.The complexity of coding and decoding method of polar codes is linear time,and its channel capacity can reach Shannon's limitation in binary erasure channel.Research about polar codes become another hotspot in the direction of channel coding and decoding in the field of communication.In wireless communication,deep space communication,network and other fields,data multicast and distribution scenarios have high requirements for the performance of rateless code.As polar code is an excellent forward error correction code,the research about its application in multicast and distribution scenarios has important significance.This thesis design a rateless polar code based on LT codes,which can qualify the application in multicast,multicast and distribution scenarios.This thesis mainly study the digital logic implementation of decoding unit of rateless polar code.This thesis first introduces two LT decoding algorithms: confidence propagation decoding algorithm and gaussian elimination decoding algorithm,and compares their decoding success rate in different number of received coded groups.Then,this thesis mainly introduces the successive cancellation,a low-complexity decoding algorithm of polar code and a simplified calculation method of logarithmic likelihood ratio,the minimum algorithm.Moreover,this thesis introduces the application of polar codes in multicast scenario,using polar codes as inner codes and LT codes as outer codes.Polar codes and LT codes are cascaded to realize rateless polar codes.This thesis also introduces the hardware logic implementation of rateless polar codes.In the logic implementation of the decoding unit,This thesis choose the successive cancellation-decoding algorithm as the polar codes decoding algorithm and simplifies the logarithm-likelihood ratio operation with the minimum sum algorithm.In the design of LT code decoding unit,propagation decoding algorithm is used as decoding algorithm.Given to the sparsity of correlative information of coded group and information group,This thesis realize the linked list data structure by digital logic to tradeoff between performance and resources.At last,the throughput of a single decoder unit introduced in this thesis is 7.31 Mbps with the system clock at 300 M Hz.