Deadline-Constrained Repeat reQuest mechanisms for wireless communication channels

Distributed (networked) control systems where data exchanges have to satisfy real-time constraints could advantageously use centralized Medium Access Control schemes implementing priority-based scheduling strategies borrowed from the operating system domain. When considering lossy channels, as in the case of wireless networks, Automatic Repeat reQuest mechanisms are needed to ensure the required levels of reliability. As retransmissions impact on bandwidth consumption and introduce latency, adequate tradeoffs between reliability and timeliness have to be determined. Some solutions have been proposed in the recent past, aimed at helping designers in finding the best compromise under given system requirements. In this paper, we generalize them as a class of Deadline-Constrained Repeat reQuest mechanisms. Lower and upper bounds on the probability of delivering data successfully (i.e., correctly and timely), in spite of transmission errors, are computed for the entire class, under specific channel conditions. These results may help designers in assessing the advantages of each solution.