Software deployment

Application layer

Operations management

Reliability (semiconductor)

Engineering

Power (physics)

Telecommunications

Physics

Scheduling (production processes)

Air interface

Wireless

Latency (audio)

Network packet

Quantum mechanics

Operating system

Computer science

Low latency (capital markets)

Base station

Physical layer

Computer network

Telecommunications link

Standardization

IEEE Wireless Communications

URLLC is a new service category in 5G to accommodate emerging services and applications having stringent latency and reliability requirements. In order to support URLLC, there should be both evolutionary and revolutionary changes in the air interface named 5G NR. In this article, we provide an up-to-date overview of URLLC with an emphasis on the physical layer challenges and solutions in 5G NR downlink. We highlight key requirements of URLLC and then elaborate the physical layer issues and enabling technologies including packet and frame structure, scheduling schemes, and reliability improvement techniques, which have been discussed in the 3GPP Release 15 standardization.

Ultra-Reliable and Low-Latency Communications in 5G Downlink: Physical Layer Aspects