Bidirectional and parallel decoding method of convolutional Turbo code

Abstract

The invention provides a decoding method of a convolutional Turbo code for reducing decoding time delay and saving a memory. The decoding method comprises the following steps of: simultaneously carrying out forward recursion and backward recursion in a component decoding process; dividing the forward recursion and the backward recursion into two stages with equivalent computation quantity; and sequentially calculating and obtaining posterior likelihood ratio information at the beginning of the second stage. The time delay from the beginning of recursion operation to the end of the posterior likelihood ratio information operation is shortened once compared with the traditional decoding process. Furthermore, the traditional posterior likelihood ratio operation is serial, while the posteriorlikelihood ratio operation of the invention is carried out bidirectionally and simultaneously in parallel, the required calculation time and the recursive calculation time are overlapped, and it is unnecessary to distribute additional calculation time; in addition, a bidirectional parallel structure can ensure that the memory used for storing state metric is reduced by half. Furthermore, through the calculation of splitting branch metric, redundancy calculation is reduced, and the space for storing the branch metric is reduced by half.

Description

technical field [0001] The invention belongs to the communication field, and mainly relates to channel coding, especially related technologies of Turbo code decoding. Background technique [0002] Since the concept of iterative decoding was proposed, Turbo codes have been widely studied and applied. Convolutional Turbo Code (CTC) has developed rapidly in recent years because of its higher coding efficiency, faster coding speed and greater free distance. It has been selected as the forward error correction of the physical layer by the standards 802.16e and 802.16m. pattern. [0003] Standard 802.16m chooses double binary convolution Turbo code (DB-CTC) as one of the channel coding schemes. In the systematic code DB-CTC, 2 bits of information are input in parallel at each moment of coding, and 6 bits are output. Due to the adoption of the second encoding scheme, the states before and after encoding are the same, so there is no need for a tail bit. However, these characteri...

AI Technical Summary

Problems solved by technology

Although the multiplication operation is reduced, the component decoder using the Log-MAP algorithm or the Max-Log-MAP algorithm still has a long decoding delay

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