URLLC Enables 5G to be Embedded into Industrial Production Processes
Automated guided vehicles (AGVs) and advanced industrial robotics have been broadly deployed in today’s flexible manufacturing systems, often requiring very low communication latency and high reliability, such as 5 milliseconds (ms) end-to-end latency and 99.99% reliability for the operation of AGVs. The “augmented worker” is emerging in modern industrial processes, which entails a remote task expert providing guidance and support for field workers through augmented reality (AR) devices. The use case usually requires 10ms end-to-end latency and 99.99% reliability. However, wireline solutions will not be applicable for these use cases because mobility is also a critical requirement of each scenario.
The first mobile communications system natively designed with URLLC features is 5G. A flexible frame structure was specified in 3GPP Release 15 to enable low-latency communications. The transmission time interval (TTI) can scale from 1ms down to ~140 microseconds (a microsecond is equal to one millionth of a second) for URLLC cases. The maximum number of retransmissions can be adjusted from four to two to meet the latency requirement. The 5G standard also allows the creation of a “mini-slot” with the minimum set to only two symbols (against 14 symbols for a full slot in the usual case), which can provide fine scheduling granularity to reduce transmission latency.