FLUID: Slack-based Low-latency Delivery

2026-05-05

AI Summary

This work addresses the high transmission latency incurred by traditional ARQ protocols in high packet-loss networks, where successful delivery requires complete reception of all data packets. To overcome this limitation, the authors propose FLUID, a novel protocol that integrates fountain codes with receiver feedback and introduces a tunable slack parameter ε. FLUID employs a control strategy based on the Loss-Product Rule, enabling early termination of transmission before all original packets are received. This approach achieves bandwidth efficiency comparable to ideal ARQ while substantially reducing block delivery delay, demonstrating pronounced performance gains particularly under persistent multi-round packet loss conditions.

Abstract

We introduce FLUID (Fountain LiqUId Delivery), a protocol that uses fountain coding and receiver feedback for low-latency delivery of data blocks over lossy networks. Idealized Automatic Repeat reQuest (ARQ) protocols are bandwidth-optimal in the single-path setting, but must deliver every packet in a block and therefore can require additional rounds under packet loss. FLUID uses a controlled amount of slack to relax this all-packets requirement, allowing delivery to finish once enough encoded packets have been received. This yields substantially tighter delivery latency while remaining deterministically close to the ARQ bandwidth optimum. FLUID is controlled by a slack parameter $\epsilon$. Under the Loss-Product Rule, delivery finishes once the product of packet loss fractions across transmission rounds falls below $\epsilon$. Thus, FLUID can finish delivery in a small number of rounds even when every round experiences packet loss, while $\epsilon$ controls the gap between FLUID and bandwidth-optimal ARQ.

Problem

• low-latency delivery
• lossy networks
• Automatic Repeat reQuest
• fountain coding
• delivery latency

Innovation

• fountain coding
• low-latency delivery
• slack-based protocol
• Loss-Product Rule
• bandwidth efficiency