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Protograph based LDPC codes with minimum distance linearly growing with block sizeWe propose several LDPC code constructions that simultaneously achieve good threshold and error floor performance. Minimum distance is shown to grow linearly with block size (similar to regular codes of variable degree at least 3) by considering ensemble average weight enumerators. Our constructions are based on projected graph, or protograph, structures that support high-speed decoder implementations. As with irregular ensembles, our constructions are sensitive to the proportion of degree-2 variable nodes. A code with too few such nodes tends to have an iterative decoding threshold that is far from the capacity threshold. A code with too many such nodes tends to not exhibit a minimum distance that grows linearly in block length. In this paper we also show that precoding can be used to lower the threshold of regular LDPC codes. The decoding thresholds of the proposed codes, which have linearly increasing minimum distance in block size, outperform that of regular LDPC codes. Furthermore, a family of low to high rate codes, with thresholds that adhere closely to their respective channel capacity thresholds, is presented. Simulation results for a few example codes show that the proposed codes have low error floors as well as good threshold SNFt performance.
Document ID
20060044424
Document Type
Conference Paper
External Source(s)
Authors
Divsalar, Dariush
Jones, Christopher
Dolinar, Sam
Thorpe, Jeremy
Date Acquired
August 23, 2013
Publication Date
November 28, 2005
Meeting Information
IEEE GlobeCom 2005(St Louis, MO)
Distribution Limits
Public
Copyright
Other
Keywords
minimum decoding
protograph
Low-density parity-check (LDPC) codes