l DCI#0 PDSCH DCI#1 DCI#2 PDSCH PDSCH Cross Carrier Scheduling CC #0 PCell CC #1 SCell CC #2 SCell DCI#0 PDSCH DCI#1 PDSCH DCI#2 PDSCH Self Carrier Scheduling Figure 5.6. L1/L2 control signaling. For a color version of this figure, see www.iste.co.uk/launay/5g.zip PCell SCell RRC Reconfiguration RRC ReconfigurationComplete DCI - MAC CE (Activation) PDSCH PDSCH DCI--MAC CE(DeActivation) Figure 5.7. Carrier aggregation procedure. For a color version of this figure, see www.iste.co.uk/launay/5g.zip 5.4.1.2. HARQ procedure HI (HARQ Indicator) information relates to the positive ACK, or negative NACK, acknowledgment of data received on the physical PDSCH channel. 158 NG-RAN and 5G-NR HI information is transmitted in the PUCCH physical channel according to one of the UCI (Uplink Control Information) formats defined in Chapter 4. In the case of carrier aggregation, the UCI control information is transmitted in the PUCCH physical channel of the primary cell PCell SO as to allow a number of DC radio channels in the downlink direction greater than the number of DC radio channels in the uplink direction. If the number of downlink CC radio channels is important, then the PUCCH channel on the uplink can be simultaneously transmitted on two radio channels PCell and SCell to avoid saturation of uplink PUCCH in the PCELL. PUCCH 1 PCell SCell SCell PUCCH 2 Figure 5.8. The transmission of acknowledgments on two PUCCH channels. For a color version of this figure, see www.iste.co.uk/launay/5g.zip 5.4.2. SUL procedure The SUL procedure consists of adding an additional radio channel for uplink direction in order to improve the uplink coverage. The SUL radio channel is on a lower carrier frequency and of lower bandwidth compared to the traditional (non-SUL) channel. The SUL channel can be a shared channel with an LTE frequency band, in the case of NR/LTE coexistence and whose spectrum is dynamically allocated by the base station (Dynamic Spectrum Sharing). DL/UL paired band No SUL Figure 5.9. SUL mode with coexistence LTE and without c