First, we find a `super--Poisson' construction which gives a small improvement in empirical performance over a random construction.
Second, whereas Gallager codes normally take N2 time to encode, we investigate constructions of regular and irregular Gallager codes which allow more rapid encoding and have smaller memory requirements in the encoder. We find that these `fast--encoding' Gallager codes have equally good performance.
Status: Published in the Proceedings of the 1998 Allerton Conference on Communication, Control, and Computing. IEEE Transactions on Communications, Vol. 10, no. 8, pp1449-1454, October 1999.