The Benefit of Decoder-Provided Pilots in Highly Dynamic Channels

2026-05-01

AI Summary

This work addresses the fundamental trade-off between estimation accuracy and data rate in fast-fading channels, where conventional training-sequence-based channel estimation is inherently limited. The authors propose a non-iterative, modulation-, coding-, and decoding-agnostic cooperative mechanism that leverages decoded codewords as soft pilots to continuously refine channel estimates in real time—without incurring any additional overhead. The approach is universally applicable to diverse forward error correction systems and its theoretical performance limits are characterized from an information-theoretic perspective. By integrating soft-output decoding with joint time–frequency domain coding, the scheme substantially enhances transmission efficiency under rapid fading: in the frequency domain, soft information improves estimation accuracy; in the time domain, shorter codes at the same code rate outperform longer ones. Extensive simulations confirm the superiority of the proposed method.

Abstract

Communications in highly dynamic channels relying on training-based channel estimation experience a trade-off between increasing channel measurement accuracy by sending more frequent training sequences and increasing data rate by sending fewer training sequences. Simultaneously, most communication systems use forward error correction to enable error detection and correction at the receiver. This paper presents decoder-provided pilots for time-varying channels by using decoded codewords as training sequences to update the channel estimate at the receiver. In contrast to approaches such as data-aided channel estimation, decision-feedback equalization, joint channel estimation and error correction, and turbo equalization, the decoder-provided pilots approach is non-iterative, which is ideal for low-latency requirements in highly dynamic scenarios. Furthermore, it is modulation-, code-, and decoder-agnostic, meaning it can be implemented on top of virtually any communication system that uses forward error correction. From an information-theoretic perspective, we derive the fundamental limits of decoder-provided pilots' ability to simultaneously sense the channel and transmit data. Simulation results demonstrate that decoder-provided pilots significantly improve performance, that when coding across frequency, soft-output can further enhance performance, and that when coding across time, short codes can outperform long codes of the same rate in fast-fading channels.

Problem

• highly dynamic channels
• channel estimation
• training sequences
• data rate
• forward error correction

Innovation

• decoder-provided pilots
• non-iterative channel estimation
• forward error correction
• highly dynamic channels
• training-free sensing