Channel Coding: Theory, Algorithms, and Applications

This fraction can also be interpreted as the probability that a randomly chosen interleaver is able to break the error path in the second encoder, or, similarly, as a factor reducing the bit error probability, namely the interleaver gain.

By extension, considering a data sequence with weight $w\ge 2$, the interleaver gain becomes

$\frac{K}{\left(\begin{array}{c}\hfill K\hfill \\ \hfill w\hfill \end{array}\right)}\simeq w!K^{1-w}$

so that we can affirm that for large $K$ the most likely weights in PCCC code sequences are, in the order of their ...