  We study the scaling behavior of coupled sparse graph codes over the binary
erasure channel. In particular, let 2L+1 be the length of the coupled chain,
let M be the number of variables in each of the 2L + 1 local copies, let l be
the number of iterations, let Pb denote the bit error probability, and let
{\epsilon} denote the channel parameter. We are interested in how these
quantities scale when we let the blocklength (2L + 1)M tend to infinity. Based
on empirical evidence we show that the threshold saturation phenomenon is
rather stable with respect to the scaling of the various parameters and we
formulate some general rules of thumb which can serve as a guide for the design
of coding systems based on coupled graphs.
