of (2) PDCCH monitoring can take place at any monitoring occasions OFDM symbol of a slot. per slot Shorter Reduction of (4), (5) The values of "the time between PDSCH and PDSCH/PUSCH HARQ-ACK" and "the time between uplink processing time grant and PUSCH" in NR can be shorter than in LTE. Preemption indication Reduction of (1) A scheduled resource can be preempted and used for latency-critical service. Front-loaded DMRS Reduction of (4) DMRS is located at the beginning of a data transmission. OFDM symbol-based Reduction of (5) The duration of PUCCH can be as short as one PUCCH OFDM symbol. 13.3.1.1 Shorter Slot Duration The subcarrier spacings supported by NR are 2H X 15 kHz with 0 < M 4. For 1, a larger subcarrier spacing Af than in LTE means a shorter OFDM symbol duration of 1/Af. This reduction can contribute to low latency. On the other hand, it requires a change of the common symbol duration and the frame structure. A shorter symbol duration directly leads to a faster baseline system. Specifically, for a shorter slot duration, the clock rate should be increased to complete the tasks scheduled in a slot. This increases the power consumption. In order to keep the clock rate at a sustainable level (for the purpose of reducing the energy demand at the device) under a tighter processing requirement, tasks can be distributed into more parallel pipes. However, such a design consumes a larger chip area and cost, and more sophisticated algorithm design is needed to handle the interaction among the pipes. Besides, function-specific hardware modules (see Figure 13.1) can be used to improve the processing speed. However, this again increases the device cost. To make the processing burden at similar levels for all subcarrier spacings, the pro- cessing time requirement is subcarrier spacing specific. For a task, more OFDM symbols are allowed for the modem to process a certain task at a larger subcarrier spacing. 13.3.1.2 Mini-Slot Transmission NR allows packet transmission over a fractional slot duration of 2-14 OFDM symbo