Two-Class Joint Source-Channel Coding: Expurgated Exponents with i.i.d. Distributions

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.