Further results on binary convolutional codes with an optimum distance profile (Corresp.)

Fixed binary convolutional codes are considered which are simultaneously optimal or near-optimal according to three criteria: namely, distance profile
d
, free distance
d_{ \infty}
, and minimum number of weight
d_{\infty}
paths. It is shown how the optimum distance profile criterion can be used to limit the search for codes with a large value of
d_{\infty}
. We present extensive lists of such robustly optimal codes containing rate
R = l/2
nonsystematic codes, several with
d_{\infty}
superior to that of any previously known code of the same rate and memory; rate
R = 2/3
systematic codes; and rate
R = 2/3
nonsystematic codes. As a counterpart to quick-look-in (QLI) codes which are not "transparent," we introduce rate
R = 1/2
easy-look-in-transparent (ELIT) codes with a feedforward inverse
(1 + D,D)
. In general, ELIT codes have
d_{\infty}
superior to that of QLI codes.