Pilot-Assisted Faster-than-Nyquist Signaling for HRLLC: A Non-Asymptotic Approach

2026-08-04

AI Summary

This work addresses the performance limitations of faster-than-Nyquist (FTN) signaling in ultra-reliable low-latency communication (URLLC) with short-packet transmissions, where inter-symbol interference and imperfect channel estimation degrade reliability. For the first time, non-asymptotic information-theoretic analysis is applied to pilot-assisted FTN systems, leveraging the random coding union bound under mismatched decoding to jointly model channel estimation errors and inter-symbol interference under finite pilot overhead. The framework enables joint optimization of pilot allocation and power distribution. Numerical results demonstrate that, at a target block error rate, the proposed approach achieves up to a 2 dB signal-to-noise ratio gain over Nyquist-rate signaling, thereby confirming the practical viability of FTN for URLLC scenarios.

Abstract

This paper investigates the performance of faster-than-Nyquist (FTN) signaling within the context of hyper-reliable low-latency communications (HRLLC), specifically focusing on the challenges imposed by the short-packet regime. While traditional Nyquist-based systems maintain symbol orthogonality to prevent inter-symbol interference (ISI), FTN intentionally introduces ISI to achieve higher transmission rates. While many existing FTN studies assume perfect channel state information, this assumption is often impractical for mission-critical HRLLC. In such scenarios, a portion of the limited packet length must be reserved for pilot symbols to ensure reliable estimation. To characterize the achievable error probability while accounting for imperfect channel estimation in the short-blocklength regime, we derive the random coding union bound with parameter $s$ (RCUs) under mismatched decoding for FTN systems. The numerical results demonstrate that FTN provides up to a 2 \dB SNR gain over Nyquist signaling, provided that power allocation and pilot overhead are optimized. These findings highlight the necessity of non-asymptotic analysis for designing efficient, next-generation HRLLC-FTN systems.

Problem

• Faster-than-Nyquist signaling
• Hyper-reliable low-latency communications
• Short-packet transmission
• Imperfect channel estimation
• Non-asymptotic analysis

Innovation

• Faster-than-Nyquist signaling
• Hyper-reliable low-latency communications
• Non-asymptotic analysis
• Imperfect channel estimation
• Random coding union bound