USING COMBINATORIAL OPTIMIZATION TO DESIGN GOOD UNIT-MEMORY CONVOLUTIONAL-CODES

A new method to design good unit-memory convolutional codes is present ed. It is based on the decomposition of the original problem into two easier subproblems, which can be formulated as optimization problems a nd solved by new efficient heuristic search algorithms. The efficacy o f the new method is demonstrated by a table containing 33 new unit-mem ory convolutional codes (n, k) with 5 less-than-or-equal-to k less-tha n-or-equal-to 8, rates R = k/n between 1/4 and 7/9, and complete memor y (M = k), as well as 12 new linear block codes. Most of the new codes found have maximum free distance.