Delay Tradeoff and Adaptive Finite Blocklength Framework for URLLC

TL;DR

This paper explores the delay components in URLLC for 6G, revealing tradeoffs among delay types, and proposes an adaptive blocklength framework with algorithms to significantly reduce over-the-air delay.

Contribution

It introduces a novel adaptive blocklength framework for URLLC that optimizes delay tradeoffs and enhances low-latency performance in 6G networks.

Findings

The framework effectively reduces over-the-air delay in URLLC scenarios.

Tradeoff analysis clarifies relationships among transmission, queuing, and retransmission delays.

Algorithms improve delay efficiency in grant-free access schemes.

Abstract

With various time-sensitive tasks to be served, ultra-reliable and low-latency communications (URLLC) has become one of the most important scenarios for the fifth generation (5G) wireless communications. The end-to-end delay from the sub-millisecond-level to the second-level is first put forward for a wide range of delay-sensitive tasks in the future sixth generation (6G) communication networks, which imposes a strict requirement on satisfying various real-time services and applications with different stringent quality of service (QoS) demands. Thus, we need to find out new delay reduction framework to satisfy the more stringent delay requirements. In this article, a state-of-the-art overview of end-to-end delay composition and delay analysis combined with access protocols are elaborated. We reveal the tradeoff relationship among transmission delay, queuing delay, and retransmission times with the change of blocklength in the finite blocklength (FBL) regime. Based on the tradeoff and combining the grant-free (GF) random access (RA) scheme, we propose the adaptive blocklength framework and investigate several effective algorithms for efficiently reducing the over-the-air delay. Numerical results show that our proposed framework and schemes can significantly reduce the over-the-air delay for URLLC.