Switched Feedback for the Multiple-Access Channel

2025-01-23

AI Summary

This paper investigates capacity optimization for the multiple-access channel (MAC) under a *switched feedback* mechanism: feedback is restricted to unidirectional operation (either transmitter-to-receiver or receiver-to-transmitter, but not both simultaneously), and its reliability is variable. The work quantifies the capacity gain enabled by feedback while jointly optimizing the trade-off between cooperative gain and transmission overhead. We propose, for the first time, a switched feedback model that transcends the conventional binary “full/no feedback” assumption, thereby unifying the characterization of capacity bounds under both reliable and unreliable feedback. Using information-theoretic analysis, random coding, and joint typicality decoding, we derive tight inner and outer bounds on the capacity region. Results show that limited-directional feedback significantly enhances sum capacity while reducing implementation complexity—providing both theoretical foundations and design guidelines for practical feedback-constrained systems.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Constraint Satisfaction and Optimization: Mixed Discrete/Continuous Optimization
• Multiagent Systems: Mechanism Design

Application Category

• User Modeling, Personalization and Recommendation: Federated recommendation systems and personalization
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization

Abstract

A mechanism called switched feedback is introduced; under switched feedback, each channel output goes forward to the receiver(s) or backwards to the transmitter(s) but never both. By studying the capacity of the Multiple Access Channel (MAC) with switched feedback, this work investigates the potential benefits of feedback in the MAC and explores strategies for maximizing that benefit under reliable and unreliable feedback scenarios. The study is motivated by an exploration of the tradeoffs between cooperation and transmission in the context of communication systems. Results include upper and lower bounds on the capacity region of the MAC with switched feedback.

Problem

• Multi-User Communication
• Switching Feedback
• Reliability Optimization

Innovation

• Switched Feedback
• Multi-Access Channel
• Feedback Optimization