Adaptive code length improves data freshness and throughput in noisy channels
AoI-Aware Polar Code Blind Rate Adaptation
Information Theory
Summary
Keeping data fresh and accurate during transmission is important but challenging over unreliable channels. This paper studies a method that adapts how much of a code to send based only on whether the last message was decoded successfully, without needing to know the channel conditions. They mathematically analyze how this approach balances sending enough data to be reliable against sending too much that causes delays. Their method closely matches simulations using polar codes over a noisy channel and quantifies how much performance is lost by adapting from minimal feedback.
What this means in practice
- •For wireless network engineers: Design adaptive coding schemes that balance data freshness and throughput in unreliable communication links without channel estimation.
- •For satellite communication teams: Implement blind prefix-length adaptation to maintain up-to-date transmissions over noisy satellite channels with limited feedback.
Authors
Hassan Tavakoli
Abstract
We study adaptive prefix-length selection for reliability-ordered coded transmission over $N$ coordinates, using only the $K$ most reliable, to balance age of information (AoI) against throughput. An additive-increase/decrease (AID) prefix-walk controller updates the prefix length from the last decoding outcome alone, at $O(1)$ per-slot cost with no channel estimation, inducing an irreducible birth--death chain whose mean drift fixes a unique balance point $K^\dagger$ (largest $K$ with success probability $\ge\tfrac12$), around which the stationary distribution concentrates geometrically. We derive this distribution in closed form via detailed balance and obtain exact steady-state AoI and goodput via renewal-reward analysis. Simulations on a $64$-coordinate polar code over a binary symmetric channel (BSC) confirm these predictions to within $0.3\%$. Relative to a genie-aided upper bound with perfect channel knowledge, we further quantify the goodput cost of adapting from a single feedback bit alone.