Coding against delayed adversaries

Bikash Kumar Dey, Sidharth Jaggi, Michael Langberg, Anand D. Sarwate

Abstract: In this work we consider the communication of information in the presence of a delayed adversarial jammer. In the setting under study, a sender wishes to communicate a message to a receiver by transmitting a codeword x = (x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , ..., x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> ) over a communication channel. The adversarial jammer can view the transmitted symbols xi one at a time, but must base its action (when changing x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ) on x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> for j ≤ i - Δ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> , where Δ ∈ [0, 1] is a delay parameter. In this work, we study codes for a class of delayed adversaries, and for any delay Δ > 0 present a single letter characterization of the achievable communication rate in the presence of such adversaries.