VLSF Decoding with Reliability Guarantees over Correlated Noncoherent Fading Channels

2026-04-17

AI Summary

This work addresses the challenge of achieving provably reliable decoding for variable-length stop-feedback (VLSF) codes over noncoherent correlated fading channels with memory. To this end, the authors develop a practical decoding rule grounded in the evolution of information density. Recognizing that channel memory precludes exact computation of information density, they derive—for the first time—finite-blocklength upper and lower bounds on information density that hold uniformly over input–output sequences. The lower bound is operationally meaningful, while the upper bound yields a quantifiable relaxation gap. By integrating tools from stochastic process concentration inequalities and stopping-time theory, the proposed framework is validated on Gauss–Markov fading channels, quantifying the impact of fading correlation on decoding performance and enabling a reliability-guaranteed VLSF decoding mechanism.

Technology Category

• Machine Learning: Information Theory
• Cognitive Modeling & Cognitive Systems: Neural Spike Coding
• Reasoning under Uncertainty: Sequential Decision Making

Application Category

• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Web learning to rank, online learning, and counterfactual learning for ranking
• Web Mining and Content Analysis: Content-based information diffusion

Abstract

This paper studies reliability-guaranteed decoding for variable-length stop-feedback (VLSF) codes over correlated noncoherent fading channels. The decoding rule is based on the evolution of the information density associated with a given channel input-output realization. Due to channel memory, exact evaluation of this information density is intractable. To enable constructive decoding, computable finite-blocklength lower and upper bounds on the information density that hold uniformly over time along each input-output sequence are derived. The lower bound enables a stopping-time analysis for VLSF decoding and has an operational meaning, while the upper bound provides a reference for the relaxation gap, which is explicitly characterized. As a concrete application, the Gauss-Markov fading channel with Gaussian signaling is considered to numerically investigate the stopping-time distribution and the impact of fading correlation on decoding performance.

Problem

• VLSF decoding
• reliability guarantees
• correlated noncoherent fading channels
• information density
• stopping-time

Innovation

• VLSF decoding
• information density bounds
• noncoherent fading channels
• stopping-time analysis
• channel correlation