A code C/spl sube/Z/sup n//sub 2/, where Z/sub 2/={0,1}, has unidirectional covering radius R if R is the smallest integer so that any word in Z/sup n//sub 2/ can be obtained from at least one codeword c/spl isin/C by replacing either 1s by 0s in at most R coordinates or 0s by 1s in at most R coordinates. The minimum cardinality of such a code is denoted by E(n,R). Upper bounds on this function are here obtained by constructing codes using tabu search; lower bounds, on the other hand, are mainly obtained by integer programming and exhaustive search. Best known bounds on E(n,R) for n/spl les/13 and R/spl les/6 are tabulated.
['Patric R. J. Östergård', 'Esa Antero Seuranen']
Unidirectional covering codes