x) operation and flexible (on per-slot basis) scheduling of Rx/Tx frame split. Slot/mini-slot structure A key enabler for low-latency scheduling is the concept of mini-slots, especially when applied in <7 GHz spectrum. A mini-slot is a subset of the (typically 14) symbols within the scheduling interval, typically 2, 4, or 7 symbols. The example in Fig. 11-1 shows a 2-symbol mini-slot. A (URLLC) mini-slot can be used to interrupt a "normal" slot [e.g., used for Enhanced Mobile Broadband (eMBB) transmission], analogous to frame preemption in (wired) TSN transmission. Preemption indication Downlink Control Information indicators are used to indicate preemption events in the next slot to other User Equipment (UE). Uplink grant-free transmission Traditional UL (UE to gNB) transmission in 3GPP systems is grant based. This means that the UE sends a scheduling request to which the gNB responds with a grant allocation-a time/frequency slot in which the UE is allowed to transmit user data. This handshake adds unwanted latency. Two mechanisms are introduced to remove this latency: type 1 or semi-persistent sched- uling (SPS, similar to LTE) where UL grants are regularly scheduled in an Radio Resource Control (re) )configured pattern as well as type 2 scheduling where additional L1 signaling is used for fast modification of semipersistently allocated resources. This additional L1 signal- ing (de)activates the grant for a specific UE. High reliability The first step to achieve high reliability is to get a good link quality, as defined by signal-to- interference and noise ratio (SINR). Increasing the UE SINR is done through known radio techniques such as increased RF power, antenna diversity, adding redundancy, and SO on. 1 Slot PDSCH Symbol 2-symbol slot FIGURE 11-1 Mini-slot configuration. Chapter 11 Differentiation by use case Antenna diversity at UE. Having multiple receive/transmit antennas in combination with rank 1 (single user, single stream) transmission increases the diversity order and SINR at the UE under fading ch