An Overview of Physical Layer Design for Ultra-Reliable Low-Latency Communications in 3GPP Releases 15, 16, and 17

Trung-Kien Le,Umer Salim,Florian Kaltenberger

doi:10.1109/access.2020.3046773

Abstract

Ultra-reliable low-latency communication (URLLC) has been introduced in 5G new radio for new applications that have strict reliability and latency requirements such as augmented/virtual reality, industrial automation and autonomous vehicles. The first full set of the physical layer design of 5G release, Release 15, was finalized in December 2017. It provided a foundation for URLLC with new features such as flexible sub-carrier spacing, a sub-slot-based transmission scheme, new channel quality indicator, new modulation and coding scheme tables, and configured-grant transmission with automatic repetitions. The second 5G release, Release 16, was finalized in December 2019 and allows achieving improved metrics for latency and reliability to support new use cases of URLLC. A number of new features such as enhanced physical downlink (DL) control channel monitoring capability, new DL control information format, sub-slot physical uplink (UL) control channel transmission, sub-slot-based physical UL shared channel repetition, enhanced mobile broadband and URLLC inter-user-equipment multiplexing with cancellation indication and enhanced power control were standardized. This article provides a detailed overview of the URLLC features from 5G Release 15 to Release 16 by describing how these features allow meeting URLLC target requirements in 5G networks. The ongoing Release 17 targets further enhanced URLLC operation by improving mechanisms such as feedback, intra-user-equipment multiplexing and prioritization of traffic with different priority, support of time synchronization and new quality of service related parameters. In addition, a fundamental feature targeted in URLLC Release 17 is to enable URLLC operation over shared unlicensed spectrum. The potential directions of URLLC research in unlicensed spectrum in Release 17 are presented to serve as a bridge from URLLC in licensed spectrum in Release 16 to URLLC in unlicensed spectrum in Release 17.

Highlights

ULTRA-RELIABLE LOW-LATENCY COMMUNICATION (URLLC) OVERVIEW To satisfy the requirements of emerging applications such as intelligent transportation, augmented/virtual reality, industrial automation, etc., Third Generation Partnership Project (3GPP) defined three main service categories in 5G New Radio: Enhanced mobile broadband, Massive machine-type communication and URLLC
This article has described the features for URLLC in Release 15: new numerology with flexible sub-carrier spacing (SCS), new CHANNEL QUALITY INDICATOR (CQI) and MODULATION AND CODING SCHEME (MCS) tables, UL and DL transmissions at sub-slot level, preemption indication in DL Enhanced mobile broadband (eMBB) and URLLC multiplexing, UL CG transmissions with automatic repetitions
The evolution of URLLC in Release 16 is analyzed with new features to improve URLLC performance in new use cases: increasing PDCCH monitoring capability, new downlink control information (DCI) with the configurable number of bits in the fields, SEMI-PERSISTENT SCHEDULING (SPS) enhancements, sub-slot physical uplink control channel (PUCCH) transmission, UCI intra-UEmultiplexing, PUSCH Repetition Type B with back-to-back repetitions, cancellation indication (CI) and power control in UL inter-user equipment (UE) multiplexing, multiple CG configurations

Summary

Introduction

A. ULTRA-RELIABLE LOW-LATENCY COMMUNICATION (URLLC) OVERVIEW To satisfy the requirements of emerging applications such as intelligent transportation, augmented/virtual reality, industrial automation, etc., Third Generation Partnership Project (3GPP) defined three main service categories in 5G New Radio: Enhanced mobile broadband (eMBB), Massive machine-type communication and URLLC. ULTRA-RELIABLE LOW-LATENCY COMMUNICATION (URLLC) OVERVIEW To satisfy the requirements of emerging applications such as intelligent transportation, augmented/virtual reality, industrial automation, etc., Third Generation Partnership Project (3GPP) defined three main service categories in 5G New Radio: Enhanced mobile broadband (eMBB), Massive machine-type communication and URLLC In these three service categories, the physical design of URLLC is the most challenging one because two conflicting factors of reliability and latency have to be coped with at the same time. If more time domain resources are consumed due to an increase of parity check bits in the low code rates, it increases latency and reduces the system efficiency

Findings

Discussion

Conclusion