Dispersion of the Gilbert-Elliott channel

Channel dispersion plays a fundamental role in assessing the backoff from capacity due to finite blocklength. This paper analyzes the channel dispersion for a simple channel with memory: the Gilbert-Elliott communication model in which the crossover probability of a binary symmetric channel evolves as a binary symmetric Markov chain, with and without side information at the receiver about the channel state. With side information, although capacity is invariant to the chain dynamics, dispersion is shown to be the sum of two terms: due to the Markov chain dynamics and due to the the randomness in the error generation, respectively.