om QoS flow A remains buffered in the transmission queue of RB2 as long as RB1 contains data from QoS flow A (Step 2 in the figure). Once RB1 has no remaining data from QoS flow A, delivery of data from QoS flow A on RB2 can start (Step 3 in the figure). An example of QoS flow relocation in the uplink is depicted in Figure 7.6, where a QoS flow A initially mapped onto RB1 together with a QoS flow B is remapped to RB2 (Step 1 in the figure). After updating the mapping rules, fresh data from QoS flow A on DRB2 is buffered in the receiver as long as the end marker (depicted with M) is not received (Step 2 in the figure). Once the end marker is received, the buffered data from QoS flow A on DRB2 is delivered to the upper layers and buffering ends (Step 3 in the figure). Step 1 Step 2 Step 3 Figure 7.5 QoS relocation - downlink. 7.3 SDAP Step 1 Step 2 Step 3 buffering Figure 7.6 QoS relocation - uplink. 7.3.3 MDBV One of the new QoS characteristics introduced in 5G is the MDBV. It denotes the largest amount of data that is required to be served within a given delay and is one of the char- acteristics of the QoS profile in 5G (see Section 7.3.1 above). MDBV is used in radio admission control to assess how many delay-critical GBR bearers can be supported in parallel in a cell. If delay-critical GBR bearers started send- ing more data than initially indicated by the MDBV, the gNB would have no choice but to take the statistical variations into account when performing admission control, thereby reducing not only the number of delay-critical GBR bearers it allows, but any type of bearers for which resources need to be guaranteed. For instance, considering a delay-critical GBR service requiring 160 octets to be sent within 5 ms every second, a PDB of 5 ms, an MDBV of 160 octets, and a GBR of 1280 bit/s (160 octets/s) would be configured. Without the MDBV, the gNB would have to cope with a bit rate up to 256 6000 bit/s (160 octets/5 ms), i.e. 200 times larger. This simple example underscores the importance of the MDBV for ma