An Inequality Useful for Proofs of Strong Converse Theorems in Network Information Theory

In this paper we provide a new inequality useful for the proofs of strong converse theorems in the network information theory. We apply this inequality to the recent work by Tyagi and Watanabe on the strong converse theorem for the Wyner-Ziv source coding problem to obtain a new strong converse outer bound. This outer bound deviates from the Wyner-Ziv rate distortion region with the order of O(1/√n) on the length n of source outputs.