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Method for a double-look-up table design for LDPC decoding

IP.com Disclosure Number: IPCOM000124314D
Publication Date: 2005-Apr-15
Document File: 2 page(s) / 21K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a double-look-up table design for low-density parity check (LDPC) decoding. Benefits include improved functionality and improved performance.

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Method for a double-look-up table design for LDPC decoding

Disclosed is a method for a double-look-up table design for low-density parity check (LDPC) decoding. Benefits include improved functionality and improved performance.

Background

              Conventionally, low-density parity-check (LDPC) techniques are famous for their excellent performance in communication systems. LDPC code can be graphically represented by a bipartite Tanner graph, comprising variable nodes on one side, and check nodes on the other side. Its decoding algorithm, the so-called message-passing algorithm, operates in an iterative manner between the variable nodes and the check nodes. A key function used in these operations is defined by the following equation:

              Implementing LDPC techniques in real time applications is not realistic due to the time-consuming log and tanh functions.

              A requirement of the look-up table (LUT) design is to keep it small while the decoding performance is acceptable. Simulation indicates that to achieve a reasonable performance, an LUT must be above 1000 (x=0.01:0.01:10). This restriction adds difficulty to the implementation because the LUT must be built for each check node, and an application typically has hundreds of check nodes.

Description

              The disclosed method is a double-LUT design. It is based on the fact that the  function is quite flat after x=1, while it is steep before x=1. Specifically, the symmetry point is x=0.88 (see Figure 1)....