Raptor Codes encoding/decoding method suitable for medium/short code lengths of additive white Gaussian noise channel

Abstract

The invention discloses a Raptor Codes encoding / decoding method suitable for medium / short code lengths of an additive white Gaussian noise channel. According to the method disclosed by the invention, the degree distribution of the inner codes, i.e. LT (Linear-Time) Codes, of the Raptor Codes which are more suitable for the medium / short code lengths is proposed; and the improved PEG (Progressive Edge-Growth) algorithm is used for encoding the inner codes, i.e. the LT codes, of the Raptor Codes, wherein the encoding manner consists of two PEG encoding manners, i.e. independently carrying out PEG composition on the LT Codes and carrying out the PEG composition on the LT Codes through combining with outer codes, i.e. LDPC (Low Density Parity Check) Codes, thus the problem that excessive shortloops appear in a Tanner graph, caused by randomly selecting information packets in an LT encoding stage, is solved. With the adoption of the method disclosed by the invention, the effectiveness for the transfer of soft information when the BP (Background Processing) iterative decoding is carried out is therefore enhanced, the performance better than that of a random composition manner is obtained, and the more reliable transmission for the rateless codes with the medium / short code lengths is realized.

Description

technical field [0001] The invention relates to the field of wireless communication, in particular to a Raptor Codes encoding and decoding method with medium and short code lengths suitable for an additive white Gaussian noise channel. Background technique [0002] When designing traditional channel coding, it is necessary to first estimate the channel parameters through channel state information (CSI), and then design a linear block code with a fixed code rate R, such as LDPC code, RA code, convolutional code, etc. Due to the instability of the channel state, the actual channel parameters may be larger or smaller than the estimated channel parameters. In the former case, reliable transmission cannot be achieved, and a block code with a lower code rate needs to be used; in the latter case, resource Wasteful because higher rate linear block codes can be used. In order to make linear block codes transmit more reliably and efficiently, a puncturing technique based on LDPC cod...

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Problems solved by technology

Ravi Palanki proposed Raptor Codes suitable for AWGN (see "Rateless codes on noisy channels", Available at www.merl.com / papers / TR2003-124 / ), and gave a suitable degree distribution, due to this degree distribution It is obtained under the assumption that there is no cycle in the Tanner graph. In the case of a long code length, this assumption can be approximately established. In actual situations, due to hardware limitations, short codes are usually selected. In short and medium code lengths, the Raptor Codes internal code LT code randomly selects several pre-coded packets to construct a large number of short loops, which is harmful to the independent propagation of information in the BP algorithm, and in short and medium code lengths Under the circumstances, this degree distribution method is not reasonable enough.

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