nding ACK/NACK transmission from UE (as shown Fig. 4.58). Depending on the frame structure, some UE data processing can be done in parallel with PDSCH reception in order to allow faster HARQ ACK/NACK transmission. For example, for front-loaded DM-RS pattern and slot-based scheduling with subcarrier spacing of 15 kHz, it can be shown that PDCCH processing, the demodulation/detection of the symbols other than the last symbol of PDSCH can be performed in T1 = TFFT + Tdemodulation + Tdecode + TUL-HARQ + Tother where TFFT, Tdemodulation, Tdecode, TUL-HARQ, and Tother denote the processing time for FFT/IFFT per symbol, the demodulation time for one symbol, the decoding time for one symbol code blocks, the processing time for uplink ACK/NACK, and the other implementation-specific processing times, respectively. For the non-slot-based scheduling (e.g., two-symbol mini-slot) and subcarrier spacing kHz, it can be shown that the UE processing requirement T2 = TPDCCH + 2Tdemodulation Tdecode + TUL-HARQ Tother where TPDCCH denotes the 546 Chapter 4 PDCCH DM-RS DM-RS PDSCH PDCCH processing (FFT, demodulation, decoding) PDSCH FFT Channel estimation Demodulation Decoding Uplink processing N1 OFDM symbols 14 OFDM symbols N1 for (front-loaded DM-RS) initial transmission N1 (3 OFDM symbols) 2 OFDM symbols) Decoding Other TB in 2 Initial transmission processing symbols N1 for initial transmission Other Retransmission Decoding TB in 14 OFDM symbols processing N1 for One slot retransmission DM-RS PDSCH DM-RS N = 13 OFDM symbols Short-PUCCH for HARQ-ACK DM-RS PDSCH DM-RS T1: control element N1 = 13 OFDM symbols processing, etc. T2: LDPC decoding T3: HARQ-ACK feedback processing Figure 4.58 UE processing time components (front-loaded DM-RS, slot-based scheduling, and 15 kHz SCS). New Radio Access Physical Layer Aspects (Part 2) 547 processing time for PDCCH including decoding, demodulation, and parsing. The above pro- cessing time calculation was done under certain conditions which may vary in different sce- narios. There is no limit fo