This paper studies expurgated exponents for joint source-channel coding of discrete memoryless sources and channels under i.i.d. random coding. We show that a two-class partitioning of source sequences, where the codeword distribution depends on the source type, achieves an exponent at least as high as that of optimal single-class coding, in which the codeword distribution is independent of the source message.

翻译：本文研究了离散无记忆信源与信道在独立同分布随机编码下联合信源信道编码的删减指数。我们证明，通过对信源序列进行两类划分，使得码字分布依赖于信源类型，所获得的指数至少不低于最优单类编码（其中码字分布独立于信源消息）的指数。