Compilation Method of System LT Code Based on Superposition Degree

Abstract

The invention provides a system LT code compiling method based on the superposition degree. The method comprises the following compiling steps: conducting initialization, defining input nodes S, middle nodes I and redundancy check nodes R, constructing a BP translatability matrix in advance, and utilizing S=I G<ENC> to generate the I; generating the R by the I in a distribution mode through the superposition degree; using the S and the R as output nodes to be sequentially sent out. SPDD degree distribution is designed and optimized for the middle nodes of system coding, a DD doping level component is arranged in a superposition mode on the basis of WRSD degree distribution, the full coverage probability on information nodes is effectively ensured, and meanwhile the method has the advantages of ensuring linear code compiling complexity and partial recovery of the middle nodes and theoretically proving the asymptotic performance of the SPDD.

Description

technical field [0001] The invention relates to a method for compiling systematic LT codes, in particular to a method for encoding and decoding finite-length systematic LT codes based on the degree of superposition. Background technique [0002] In recent years, fountain codes, which can approach the margin of deleted channels with lower coding and decoding complexity, have attracted great attention from relevant researchers. The rate-free feature of the fountain code enables the sending end to generate unlimited coded packets for k information packets and spray them to the receiving end; while the receiving end only needs to successfully receive a little more than k coded packets to pass a simple The message passing (Belief Propagation, BP) iterative decoding algorithm restores the original information. Fountain codes extend the traditional channel error correction coding to data packets, and provide an efficient forward erasure correction transmission mechanism without fe...

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Problems solved by technology

[0003]However, the random coding method adopted by the LT code designed by Luby and the Raptor code of Shokrollahi makes it difficult for the original coding scheme to obtain the system code word structure

Therefore, Shokrollahi designed the relevant patented technology, by inversely transforming the generation matrix of the cascaded WRSD distribution (weakly robust solitary wave distribution) LT code, to obtain intermediate nodes and then construct the system Raptor code, but the inverse transformation operation of the generation matrix requires The complexity of O(k2), when the number of information nodes k is large, the coding complexity exceeds the capability of hardware-limited communication nodes

3GPP uses pseudo-random sequences to construct the generation matrix of input nodes and intermediate nodes, and proposes a Raptor code system coding scheme with minimal redundant decoding overhead, but the receiving end needs to use Gaussian Elimination (GE) decoding algorithm. When the decoding side needs O(k2) complexity

However, the above studies are all oriented to non-systematic structure LT codes

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