Some properties of Rényi entropy over countably infinite alphabets
Problems of Information Transmission
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This paper deals with the problem of universal lossless coding on a countable infinite alphabet. It focuses on some classes of sources defined by an envelope condition on the marginal distribution, namely exponentially decreasing envelope classes with exponent . The minimax redundancy of exponentially decreasing envelope classes is proved to be equivalent to . Then, an adaptive algorithm is proposed, whose maximum redundancy is equivalent to the minimax redundancy.