Universal coding for arbitrarily varying sources

The minimum universal coding redundancy for finite-state arbitrarily varying sources, is investigated. If the space of all possible underlying state sequences is partitioned into types, then this minimum can be essentially lower bounded by the sum of two terms. The first is the minimum redundancy within the type class and the second is the minimum redundancy associated with a class of sources that can be thought of as 'representatives' of the different types. While the first term is attributed to the cost of uncertainty within the type, the second term corresponds to the type itself. The bound is achievable by a Shannon code w.r.t. an appropriate two-stage mixture of all arbitrarily varying sources in the class.