Common Randomness Generation from Sources with Infinite Polish Alphabet
Wafa Labidi, Rami Ezzine, Moritz Wiese, Christian Deppe, Holger Boche
TL;DR
This work extends common randomness generation to sources with infinite Polish alphabets under one-way noisy-channel communication, deriving single-letter lower and upper bounds on the CR capacity that are tight except at at most countably many points. It builds on generalized typicality for Polish spaces and Wyner-Ziv‑style coding to achieve rates governed by $I(U;X)$ under the constraint $I(U;X)-I(U;Y) \le C(W)$ (plus vanishing terms), with the channel capacity $C(W)$ playing a key role in the trade-off. A notable contribution is the result that, if $I(X;Y)=\infty$, the CR capacity can be infinite for certain continuous-source models, illustrating a stark contrast with finite-alphabet cases. The findings provide a rigorous framework for CR generation with continuous and infinite alphabets, informing practical correlated randomness protocols in advanced communications contexts.
Abstract
We investigate the problem of common randomness (CR) generation in the basic two-party communication setting in which a sender and a receiver aim to agree on a common random variable with high probability. The terminals observe independent and identically distributed (i.i.d.) samples of sources with an arbitrary distribution defined on a Polish alphabet and are allowed to communicate as little as possible over a noisy, memoryless channel. We establish single-letter upper and lower bounds on the CR capacity for the specified model. The derived bounds hold with equality except for at most countably many points where discontinuity issues might arise.
