PUB - Publikationen an der Universität Bielefeld

Write-efficient memories (WEM) were introduced by Ahlswede/Zhang as a model for storing and updating information an a rewritable medium. We strengthen the capacity theorem by providing a full control of the rates of the spreads, Next we address and settle the storage capacity region problem under the average costs constraint for the case of many users who write on the memory in an arbitrary order, where neither the encoder nor the decoder knows the previous content of the memory, The combinatorial essence is a diametric theorem for several families. Finally we present a storage capacity theorem for several persons using the memory in cyclic order. (C) 1997 Academic Press.