Punctured and Irregular High-Rate Gallager Codes
David J C MacKay
Gallager codes with rates about 0.9 and
block length about 2000 or 4000 bits have previously
been shown to have promising performance [cite{MacKayHighRate98}].
In this paper we investigate puncturing as a possible
method for increasing the rate of such codes.
At
low signal-to-noise ratios, high-rate punctured Gallager codes appear to
be inferior to unpunctured Gallager codes constructed `beyond
the Steiner limit'.
We find evidence, however, that the punctured codes have superior performance
at higher signal-to-noise ratio.
We also explore the possible benefits of irregular constructions.
For these rates
and blocklengths, it seems
hard to beat regular Gallager codes.
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