We derive an upper bound on the reliability function of mismatched decoding for zero-rate codes. The bound is based on a result by Koml\'os that shows the existence of a subcode with certain symmetry properties. The bound is shown to coincide with the expurgated exponent at rate zero for a broad family of channel and decoding metric pairs.

翻译：我们得出了不匹配的零速率代码解码的可靠性函数的上限值。 约束值基于 Koml\'os 的结果, 该结果显示存在具有某些对称属性的子代码。 约束值显示与宽广的频道和解码度对子的排出零率指数一致 。