5G QoS is based on QoS Flows.
Each QoS flow is identified by QoS Flow Identifier (QFI) with in a PDU session.
There are 3 different types of QoS Flows:
1. Guaranteed Bit Rate (GBR) QoS Flows
2. Non Guaranteed Bit Rate QoS Flows.
3. Delay Critical GBR bearer: new in 5G, used for URLLC services
How 5G QoS different from 4G QoS ?
1. In 4G, QoS is based on bearers and in 5G, QoS is based on flow.
2. In 4G EPS Bearer ID is used to differentiate between different QoS, in 5G we use QFI.
Note:
1. 4G QoS is applied at EPS (Evolved Packet Service) bearer. There is one to one mapping like, for an EPS bearer, there is a corresponding EPS Radio Access Bearer (RAB), an S1 bearer and a Radio Bearer.
2. In 5G, QoS flow are mapped to AN to DRBs.
5G QoS Architecture
> In an E2E (End to End) service, a UE will be connected to external DN.
> Different E2E service will need different QoS.
> They can have one or more IP flow.
> An Service Data Flow (SDF) will be created depending upon the UE traffic.
> Every uplink and downlink packet is mapped to a QoS flow.
> Each PDN session can carry one or more QoS flow.
> QFI is used to identify a QoS flow in a PDU session.
> QoS profile is used to characterize each QoS flow.
> In 5GS a QoS flow associated with default QoS rule is required to be established for a PDU session and remains established throughout the lifetime of the PDU session.
> QFI will be unique within a PDU session.
> QFI can be dynamically allocated or equal to 5QI.
QoS configuration file
A QoS flow may be GBR or non-GBR, based on that QoS parameters can be configured as below:
Each QoS flow (GBR or non-GBR) will include:
1. 5QI
2. Assignment and Reservation Priority (ARP).
3. Reflective QoS Attribute (RQA).
For each non-GBR QoS flow will include:
1. Guaranteed Traffic Bit Rate (GFBR) – UL and DL;
2. Maximum Streaming Bit Rate (MFBR) – UL and DL;
5G QoS Example
As discussed above, we can see taht:
1. SDF (Service Data Flow) has been created between UE and DN.
2. PDU session and SDF has been created and each application will have its own SDF.
3. Multiple IP flows can be mapped to same QoS flow.
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