On good convolutional codes of rate 1/2, 1/3, and 1/4

Tables are given of convolutional codes of rates 1/2, 1/3, and 1/4 and with generator polynomials of degrees from 6 to 15 (constraint lengths from 7 to 16). This is partly with a view to the use of these codes in direct-sequence spread-spectrum systems, since the asymptotic coding gains of very low-rate convolutional codes are not significantly better than the gains of codes of rate 1/3 and 1/4. Although the free distances of previously published codes are optimal some of the codes given here have fewer adversary paths at the free distance. The improvement in performance is very slight