# Early Detection for Optimal-Latency Communications in Multi-Hop Links

## TL;DR

This paper introduces an early-detection scheme for multi-hop wireless links that reduces latency by detecting symbols before transmission ends, maintaining reliability within finite-blocklength constraints.

## Contribution

It proposes a novel sequential-test based early-detection method tailored for finite-blocklength regimes in low-latency wireless communications.

## Key findings

- Average detection time is smaller than a symbol duration.
- Reliable detection before transmission end in multi-hop links.
- Latency reduction without exceeding error probability threshold.

## Abstract

Modern wireless machine-to-machine-type communications aim to provide both ultra reliability and low latency, stringent requirements that appear to be mutually exclusive. From the noisy channel coding theorem, we know that reliable communications mandate transmission rates that are lower than the channel capacity. To guarantee arbitrarily-low error probability, this implies the use of messages whose lengths tend to infinity. However, long messages are not suitable for low-latency communications. In this paper, we propose an early-detection scheme for wireless communications under a finite-blocklength regime that employs a sequential-test technique to reduce latency while maintaining reliability. We prove that our scheme leads to an average detection time smaller than the symbol duration. Furthermore, in multi-hop low-traffic or continuous-transmission links, we show that our scheme can reliably detect symbols before the end of their transmission, significantly reducing the latency, while keeping the error probability below a predefined threshold.