Tomohiko Saito

A Note on Construction of Orthogonal Arrays with Unequal Strength from Error-Correcting Codes

Orthogonal Arrays (OAs) have been playing important roles in the field of experimental design. It has been known that OAs are closely related to error-correcting codes. Therefore, many OAs can be constructed from error-correcting codes. But these OAs are suitable for only cases that equal interaction effects can be assumed, for example, all two-factor interaction effects. Since these cases are rare in experimental design, we cannot say that OAs from error-correcting codes are practical. In this paper, we define OAs with unequal strength. In terms of our terminology, OAs from error-correcting codes are OAs with equal strength. We show that OAs with unequal strength are closer to practical OAs than OAs with equal strength. And we clarify the relation between OAs with unequal strength and unequal error-correcting codes. Finally, we propose some construction methods of OAs with unequal strength from unequal error-correcting codes.

A Linear Programming bound for Unequal Error Protection codes

In coding theory, it is important to calculate an upper bound for the size of codes given the length and minimum distance. The Linear Programming (LP) bound is known as a good upper bound for the size of codes. On the other hand, Unequal Error Protection (UEP) codes have been studied in coding theory. In UEP codes, a codeword has special bits which are protected against a greater number of errors than other bits. In this paper, we propose a LP bound for UEP codes. Firstly, we generalize the distance distribution (or weight distribution) of codes. Under the generalization, we lead to the LP bound for UEP codes. And we show a numerical example of the LP bound for UEP codes. Lastly, we compare the proposed bound with a modified Hamming bound.

A note on automatic construction algorithms for orthogonal designs of experiments using error-correcting codes

Abstract In the field of experimental design, it is important to construct orthogonal designs. In this paper, we propose a new algorithm to construct orthogonal design. This algorithm uses Ukita’s algorithm, which is essentially based on projective geometries, and uses orthogonal designs constructed by error-correcting codes. We show some numerical examples of the proposed algorithm, and show that the proposed algorithm can construct good orthogonal designs with low complexity even if there are high order effects.