The maximum bandwidth for NR is 100

The maximum bandwidth for NR is 100MHz for FR1 and 400MHz for FR2. Bandwidth parts (BWP) operation has been introduced in NR Rel-15. Up to 4 BWPs for uplink or downlink can be semi-statically configured for a UE. Different numerology configurations can be set for each BWP and the BWP ID can be dynamically indicated by a DCI. It is well known that, the BWP with very small bandwidth is very suitable for the applications with lots of small data packets transmission and low power consumption might be achieved. The BWP with very large bandwidth is used to transmit the huge data packet. Therefore, for the case of no data arrival or small data packets transmission, UE would perform PDCCH monitoring, reporting CSI and receive small data packets and so on in small BWP. For large data packets scheduling, UE performs BWP switching based on the DCI indication. The DCI can be a normal DCI, e.g., a Rel-15 DCI, or a power saving DCI.
The bottleneck of the current DCI based BWP switching is the PDSCH reception performance in the large BWP upon BWP switching. As the bandwidth difference between the small BWP and the large BWP can be very different, the channel large-scale parameters and the CSI acquired in the small BWP may not be identical to the large BWP, especially when the channel is frequency-selective. Hence to guarantee the performance of the PDSCH reception in the large BWP, a simple but efficient solution is to trigger aperiodic CSI-RS for channel tracking or CSI reporting for target BWP in BWP switch as shown in Fig. 2. The aperiodic CSI-RS can locate just before the PDSCH of the target BWP and guarantee sufficient time for UE calculation of the channel parameters. Note that for this mechanism, UE still just processes one BWP at a given time.