Comparison of Constructions of Irregular Gallager Codes
David J C MacKay, Simon T Wilson and Matthew C Davey
The low density parity check codes whose performance
is closest to the Shannon limit are based on irregular graphs.
We compare alternative methods for constructing these graphs
and find that `super-Poisson' constructions give significantly
better empirical performance.
Low density parity check codes normally take N^2 time to encode,
because they are defined in terms of non-systematic
parity check matrices.
We investigate constructions which allow the encoding to be made
faster to see whether any performance loss results, looking
both at regular and irregular Gallager codes.
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