iginally transmitted code blocks will be decoded: Transport Block Codeblock Segmentation Block Block Block Block Codeblock Grouping Code Block Group Code Block Group Figure 6.16 - CBG-based retransmissions The DCI includes information not only about the group of code blocks that is retransmitted but also the soft buffer. When processing the error retransmission, the new information received is traditionally combined with the previous original transmission. This combining scheme works if the codeword was retransmitted due to the Signal to Interference and Noise Ratio (SINR). If the original transmission fails since it is pre-empted by low-latency traffic, then the information from the original transmission does not correspond to the retransmission. In that case, it is better to flush the previously received information from the soft buffers rather than using a combining scheme because it corresponds to the low-latency traffic. The HARQ principle NR supports adaptive and asynchronous HARQ in both the downlink and uplink: Earliest possible re-transmission Fast A/N Figure 6.17 - A HARQ process The number of HARQ processes is configured to the device with at most 16 HARQ processes: 15 kHz 30 kHz 60 kHz 120 kHz LTE R8 PDSCH PUCCH 8; 0.57 10; 0.36 17; 0.3 20; 0.18 2.3 ms PDCCH PUSCH 10; 0.71 12; 0.42 23; 0.41 36; 0.31 NR defines two device capabilities for the minimum HARQ processing time. Initially, most devices will support the baseline capability shown in the preceding table. The following table indicates the second device capability that is defined by the specification: 15 kHz 30 kHz 60 kHz LTE R8 PDSCH PUCCH 3; 0.21 4.5; 0.16 9; 0.16 (FR1) 2.3 ms PDCCH PUSCH 5; 0.35 5.5; 0.2 11; 0.2 (FR1) A HARQ process needs to feedback multiple acknowledgments at the same time - for instance, for carrier aggregation, multiple downlink slots followed by an uplink slot. Note that the number of bits to feedback depends on the number of downlink transmissions and some of these downlink transmissions might be missed by the device. Fin