.PS
# Trellis.m4
# Some trellis diagrams using pic alone without m4
# https://tex.stackexchange.com/questions/253458/latex-trellis-diagrams-for-stbcs
# https://web.archive.org/web/20150926144231/http://www.ee2.caltech.edu/Faculty/babak/courses/ee161/papers/tsc.pdf

define trellis {[ # ( nstates, psk, width, ydistance )
 ngroups = ($1)/($2)
 for s=1 to $1 do {
   A[s]: circle rad 0.02 fill 0 at (0,-s*($4))
   B[s]: circle rad 0.02 fill 0 at ($3,-s*($4)) }
 for g=1 to ngroups do {
   for i=1 to $2 do {
     for j=1 to $2 do { line from A[g+(i-1)*ngroups] to B[(g-1)*($2)+j] }
     } }
 ]}

trellis(4,4,1/2,1/2)
trellis(8,8,1,1/2) with .nw at last [].ne+(1/2,0)
trellis(16,4,3/4,1/4) with .nw at last [].ne+(1/2,0)
trellis(16,8,5/4,1/4) with .nw at last [].ne+(1/2,0)
trellis(32,4,5/4,1/8) with .nw at last [].ne+(1/2,0)

.PE