On Lower Bounds for the Capacity of Deletion Channels

This correspondence considers binary deletion channels, where bits are deleted independently with probability d; it improves upon the framework used to analyze the capacity of binary deletion channels established by Diggavi and Grossglauser, improving on their lower bounds. Diggavi and Grossglauser considered codebooks with codewords generated by a first-order Markov chain. They only consider typical outputs, where an output is typical if an N bit input gives an N(1-d)(1-epsi) bit output. The improvements in this correspondence arise from two considerations. First, a stronger notion of a typical output from the channel is used, which yields better bounds even for the codebooks studied by Diggavi and Grossglauser. Second, codewords generated by more general processes than first-order Markov chains are considered