thodology. Note that the time-critical scenario out of all of these is the discrete automation one which demands a 1-ms latency and 99.9999% reliability. Building blocks to achieve these three KPIs are highlighted in the next chapters, which include: optimized numerology and integrated frame structure fast turnaround through mini-slots effficient control and data resource sharing grant-free UL transmission advanced channel coding schemes and interference management Note that not all building blocks need to be used to be able to support industrial use cases. A mix and match of capabilities is expected to be standardized and developed to sup- port specific market verticals. See the "Further Reading" section for a reference to the 3GPP study item that discusses these topics in more detail. Orthogonal frequency division multiplexing numerologies One area where 5G/NR is different from 4G and previous standards is in support of flexible numerology, where the subcarrier spacing (SCS) can be changed, mainly to support opera- tion in different frequency bands. The 15-KHz SCS provides similar numerology to Long- Term Evolution (LTE), where at higher SCS, more symbols are placed in a single subframe (Table 11-2). As the SCS increases, the slot time (minimum scheduling interval) decreases, allowing for lowering of system latency. In addition, NR defines the concept of a mini-slot (aka nonslot) of 1. 13 symbols that allows for even lower scheduling latency. As such, low-latency sched- uling can be achieved by picking a more aggressive numerology or by moving to mini-slot- based scheduling. Table 11-2 Orthogonal frequency division multiplexing numerologies in 5G/NR. Subcarrier spacing (KHz) Symbol duration (us) Cyclic prefix Minimum scheduling interval (symbols) Minimum scheduling interval (ms) 0.125 0.125 352 Open Radio Access Network (O-RAN) Systems Architecture and Design Beyond changing numerology, 3GPP has other mechanisms to reduce latency. Think about Frequency Division Duplexing (FDD) (as opposed to Time Division Duple