n 5G NR design to mitigate signaling overhead in the system and the memory need on the device side. With the maximum allowable values, the CSI-MeasConfig information element alone can take almost 150 kB per carrier. In contrast, the size of an LTE RRC message is usually small, for example, less than 1 kB. Consequently in Rel-15 NR, the size of an RRC message is limited to no more than 9 kB [4]. An understanding of NR's flexibility and of the challenges in UE implementation can be obtained by examining a few of the parameters in CSI-MeasConfig. Figure 13.3 shows that a UE can be configured with up to 128 trigger states for aperiodic CSI reporting at a given component carrier. Among them, 63 trigger states can be selected as the active trigger states, whereby each active trigger state can be indicated dynamically by the 13 5G Modem Design Challenges Trigger State N Up to 128 Trigger State M+ 1 Trigger States Up to 63 active Trigger States Trigger State 1 Figure 13.3 Trigger state configuration and indication for aperiodic CSI reporting. Trigger State 1 Up to 16 per CSI Associated Report Config Info 1 CSI Associated Report Config Info 2 Trigger State CSI Report Config CSI Associated Report Config Info CSI Resource Config for CMR NZP CSI-RS NZP CSI-RS CSI Report Config selection Resource Set 1 Resource Set 2 NZP CSI-RS Resource Set selection CSI Resource Config for IMR CSI IM Resource Set selection CSI-IM CSI-IM Resource Set 1 Resource Set 2 Figure 13.4 Link between trigger state for aperiodic CSI reporting and CSI report configuration. network to the UE. As shown in in Figure 13.4, in NR, up to 16 CSI reports can be requested simultaneously with a single trigger state. Further for each CSI report, the measurement resources for the desired channel and interference can be selected. As for uplink data transmission, NR supports both codebook-based transmission and non-codebook-based transmission. To address the uplink coverage shortage in some deployment scenarios, a device may also need to support the so-called Supplem