5GC basic self-study series | 5GC basic QoS

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Introduce the basic framework and implementation of QoS in 5GC

Introduction to basic concepts and terms related to 5G network and QoS
Comparison of 5G network and 4G network QoS architecture
Main QoS parameters in 5G network
Mapping process of uplink and downlink traffic in 5G network

Words written in the front: What is the QoS guarantee about?

To put it bluntly, Qos is money and cost.

For operators, QoS is bandwidth. It is also one of the most valuable assets of operators, and the cost of bandwidth is also one of the most expensive.
For users, QoS is the fee paid. To put it bluntly, the more money you give, the better the QoS experience. No extra charge, only best-effort QoS service.

According to QoS and payment characteristics, there are the following categories:

No additional payment (paid by users or partner companies): No additional QoS guarantee. Usually Non-GBR. Such as WeChat, QQ, NetEase Cloud Classroom, Douyin Small Video, etc. More than 99% of APPs on mobile phones belong to this category.
Additional payment: There is additional QoS guarantee. Can be GBR. Such as the cooperation with online games such as the glory of the king carried out in some places.
A service guaranteed by QoS without additional payment: usually a free service strongly supported by operators. Such as VoLTE.

Basic concepts related to QoS in 5G

SDF: Service Data Flow

It is all kinds of traffic generated by various APPs on the mobile phone. Such as WeChat, iQiyi, IMS voice, etc.

Qos Flow：

The best granularity to achieve QoS differentiation guarantee in 5G network (4G is based on EPS bearer).
Different QoS Flows correspond to different QoS forwarding treatments.
It is up to the operator to decide how to divide the Qos Flow. Usually, the SDF of the homogeneous class is divided into one QoS Flow.
Homogeneous SDF: That is, the QoS requirements (bandwidth, delay, etc.) are the same. In addition, it depends on whether to pay. If there is no additional payment, even if the QoS requirements are the same, it is not necessarily divided into the same QoS Flow. For example, even if the WeChat phone book and VoNR voice are homogeneous services, they may be assigned to two different QoS Flows.

QFI: Qos Flow ID. Qos Flow logo. User plane service flows with the same QFI receive the same forwarding treatment. The value range is 0~63.

4G vs 5G QoS Architecture

5G terminal service and QoS mapping example

Main QoS parameters in 5G

GFBR: Guaranteed bit rate for QoS Flow. The minimum guaranteed rate promised by the network side. Traffic exceeding the GBR will be discarded when congested, and traffic exceeding the GBR but less than the MBR can pass when there is no congestion.

MFBR: The maximum bit rate of QoS Flow. If the MBR is exceeded, the traffic will be dropped.

UE-AMBR: The upper limit of the maximum bit rate of all Non-GBR QoS Flows of the UE.

Session-AMBR: The upper limit of the maximum bit rate of all Non-GBR QoS Flows under a single PDU session of the UE.

5QI: QoS level identification in 5G. Evolved from 4G's QCI.

ARP: Assign and hold priorities. Determines the priority for establishing and maintaining QoS Flow during congestion.

RQA: Reflected QoS attribute. Used to indicate whether the QoS Flow applies reflective QoS

Notification control: Notification control. When the RAN side cannot provide guarantee for GFBR (for example, the wireless network quality is poor), it needs to send a notification to the core network side.

Maximum Packet Loss Rate: (upstream/downstream) the maximum tolerable packet loss rate.

Some examples of standard 5QI and QoS mapping

Mapping diagram of service data flow and bearer in 3GPP - 4G

Mapping diagram of service data flow and bearer in 3GPP - 5G

Basic concepts related to QoS in 5G (traffic mapping) - QoS Rule

QoS Rule and PDR: Rules for classifying and mapping uplink/downlink data packets on the terminal and network side.

Downlink direction: The UPF performs specific classification and mapping tasks according to the PDR issued by the SMF. (If there is no matching PDR, the UPF will discard the downstream data packet)

Uplink direction: The UE is responsible for performing specific classification and mapping, which can be classified and mapped according to the QoS Rule delivered by the network side or the QoS Rule derived by the UE itself.

The Qos Rule derived from UE itself is called UE Derived Qos Rule, and the corresponding concept is called reflective Qos.

Basic Concepts Related to QoS in 5G (Traffic Mapping) - Reflective QoS

Reflective QoS: means that the UE derives uplink classification rules according to the received downlink user plane data, and does not need to be delivered by the network side, thereby reducing network signaling overhead. The related parameters involved are: RQI, UE Derived Qos Rule, RQA, etc. And requires terminal support.

UE Derived QoS Rule: The QoS rule derived by the UE according to the received downlink user plane data is used to classify and map uplink data packets.

UE Derived Qos Rule contains the following parameters:

1) 1 UL Packet Filter

2） QFI

3) Priority