QoS Class Identifier


QoS Class Identifier is a mechanism used in 3GPP Long Term Evolution networks to ensure bearer traffic is allocated appropriate Quality of Service. Different bearer traffic requires different QoS and therefore different QCI values. QCI value 9 is typically used for the default bearer of a UE/PDN for non privileged subscribers.

Background

To ensure that bearer traffic in LTE networks is appropriately handled, a mechanism is needed to classify the different types of bearers into different classes, with each class having appropriate QoS parameters for the traffic type. Examples of the QoS parameters include Guaranteed Bit Rate or non-Guaranteed Bit Rate, Priority Handling, Packet Delay Budget and Packet Error Loss rate. This overall mechanism is called QCI.

Mechanism

The QoS concept as used in LTE networks is class-based, where each bearer type is assigned one QoS Class Identifier by the network. The QCI is a scalar that is used within the access network as a reference to node specific parameters that control packet forwarding treatment, for example scheduling weight, admission thresholds and link-layer protocol configuration.
The QCI is also mapped to transport network layer parameters in the relevant Evolved Packet Core core network nodes, Mobility Management Entity and Policy and Charging Rules Function ), by preconfigured QCI to Differentiated Services Code Point mapping.
According to 3GPP TS 23.203, 9 QCI values in Rel-8 are standardized and associated with QCI characteristics in terms of packet forwarding treatment that the bearer traffic receives edge-to-edge between the UE and the P-GW. Scheduling priority, resource type, packet delay budget and packet error loss rate are the set of characteristics defined by the 3GPP standard and they should be understood as guidelines for the pre-configuration of node specific parameters to ensure that applications/services mapped to a given QCI receive the same level of QoS in multi-vendor environments as well as in roaming scenarios. The QCI characteristics are not signalled on any interface.
The following table illustrates the standardized characteristics as defined in the 3GPP TS 23.203 standard "Policy and Charging Control Architecture".

QCIResource TypePriorityPacket Delay BudgetPacket Error Loss RateExample Services
1GBR2100ms10−2Conversational Voice
2GBR4150ms10−3Conversational Video
3GBR350ms10−3Real Time Gaming, V2X messages
4GBR5300ms10−6Non-Conversational Video
65GBR0.775ms10−2Mission Critical user plane Push To Talk voice
66GBR2100ms10−2Non-Mission-Critical user plane Push To Talk voice
75GBR2.550ms10−2V2X messages
5non-GBR1100ms10−6IMS Signalling
6non-GBR6300ms10−6Video TCP-Based
7non-GBR7100ms10−3Voice, Video, Interactive Gaming
8non-GBR8300ms10−6Video TCP-Based
9non-GBR9300ms10−6Video TCP-Based. Typically used as default bearer
69non-GBR0.560ms10−6Mission Critical delay sensitive signalling
70non-GBR5.5200ms10−6Mission Critical Data
79non-GBR6.550ms10−2V2X messages
80non-GBR6.810ms10−6Low latency eMBB applications ; Augmented Reality
82GBR1.910ms10−4Discrete Automation
83GBR2.210ms10−4Discrete Automation
84GBR2.430ms10−5Intelligent Transport Systems
85GBR2.15ms10−5Electricity Distribution- high voltage

Every QCI is associated with a Priority level. Priority level 0.5 is the highest Priority level. If congestion is encountered, the lowest Priority level traffic would be the first to be discarded.
QCI-65, QCI-66, QCI-69 and QCI-70 were introduced in 3GPP TS 23.203 Rel-12.
QCI-75 and QCI-79 were introduced in 3GPP TS 23.203 Rel-14.