A class of m-ary asymmetric symbol error correcting codes constructed by graph coloring

Non-binary m-ary symbols such as alphabets and numeric characters are used in man-machine interfaces, e.g., keyboards and optical character readers (OCR). Since errors in m-ary data are generally asymmetric, m-ary asymmetric symbol error control codes are applicable for man-machine interfaces. Asymmetric symbol error locating codes for character recognition have been proposed by Saowapa, Kaneko and Fujiwara (see Trans. of IEICE A, vol.J84-A, no.1, p.73-83, 2001). This paper proposes a new type of m-ary asymmetric symbol error correcting codes constructed by colorings of an error directionality graph which expresses a set of asymmetric symbol errors. The proposed codes can be applied to m-ary data with fixed character strings, such as, postal codes, bank account numbers, and article numbers