Pruned-trellis search technique for high-rate convolutional codes

A new method to search for high-rate convolutional codes is achieved by means of a pruned trellis. This makes possible a reduced search procedure that can not be accomplished by standard methods. This new search technique makes use of the concept of the expanded column distance function of a convolutional code. By use of this search procedure, codes are found with an optimum distance profile followed by a maximisation of d_free. A number of systematic convolutional codes of high rates 3/4, 4/5, 5/6, 6/7 and 3/5 are found and listed in this paper.