t where the UE can be configured with a scheduling request slot as often as every 2 symbols. Multi-slot repetition (2, 4, or 8 repetitions) for data channels to allow retransmissions without waiting for HARQ-ACK feedback. Shorter UE processing time: 5G design facilitates UE pipelining processing to shorten the UE processing time. This is done by transmitting the DMRS at the beginning of the slot and using frequency-first mapping, which allows symbol-by-symbol processing. Table 14.9 illustrates an example of the timing delay for transmitting a packet. After packet arrival at the gNodeB, the packet can be transmitted in 8 OFDM symbols for the initial transmission. If a retransmission is needed, the entire process will consume 20 symbols. For a subcarrier spacing of 30 kHz, this corresponds to a total time of 0.7 ms. To support ultra-reliable packet reception for URLLC, 5G has specified support for the following techniques in Release 15: Table 14.9 Example timing delay for downlink packet transmission. Time (OFDM Event symbols) Packet arrival gNodeB processing time and scheduling delay Scheduling grant (PDCCH) Data transmission (PDSCH) UE processing time HARQ-ACK (PUCCH) gNodeB processing time and scheduling delay Scheduling grant for retransmission (PDCCH) Data retransmission (PDSCH) 14.11 loT Optimizations in 5G Multi-slot repetitions for the data channels and low code rate for the control channel to improve reliability. Enhanced channel state reporting with corresponding modulation and coding level to support 99.999% reliability. PDCP layer data duplication which allows a packet to be transmitted from two differ- ent carriers. Further URLLC enhancements are being studied in Release 16. They include down- link control channel enhancements (e.g. compact scheduling grants, additional repeti- tions, increased monitoring capabilities), uplink control information enhancements (e.g. enhanced HARQ, CSI feedback), uplink data channel enhancements (e.g. mini-slot level hopping), enhancements to scheduling/HARQ/CS processin