5G • Core Network
RQI
Reflective QoS Indicator
1-bit header flag in downlink packets instructing the UE to derive corresponding uplink QoS mapping rules.
Technical Explanation
When an application starts transmitting a new QoS flow in the downlink, the UPF sets the RQI bit in the GTP-U extension header over N3, and the gNodeB transfers the flag in the SDAP header over Uu. The UE observes this flag and creates an automatic uplink QoS rule mapping matching packets to that DRB.
Key Functions
- 1-bit flag in downlink packet header activating Reflective QoS
- Propagates from UPF GTP-U header to radio SDAP protocol header
- Prompts UE to derive uplink QoS Flow-to-DRB mapping automatically
Specifications
3GPP TS 23.501, TS 37.324
Interfaces
UuN3
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