QoS Class Identifier
QoS Class Identifier (QCI) is a mechanism used in 3GPP Long Term Evolution (LTE) networks to ensure bearer traffic is allocated appropriate Quality of Service (QoS). Different bearer traffic requires different QoS and therefore different QCI values, with 9 different QCI values currently specified.[1]
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 (GBR) or non-Guaranteed Bit Rate (non-GBR), 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 (QCI) by the network. The QCI is a scalar that is used within the access network (namely the eNodeB) 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 Layer parameters in the relevant Evolved Packet Core (EPC) core network nodes (for example, the PDN Gateway (P-GW), Mobility Management Entity (MME) and Policy and Charging Rules Function (PCRF) ), by preconfigured QCI to Differentiated Services Code Point (DSCP) mapping. According to 3GPP TS 23.203, 9 QCI values are standardized and associated with QCI characteristics, in term of packet forwarding treatment that the bearer traffic receives edge-to-edge between the UE and the P-GW. Scheduling priority, 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".
| QCI | Resource Type | Priority | Packet Delay Budget | Packet Error Loss | Example Services |
|---|---|---|---|---|---|
| 1 | GBR | 2 | 100ms | 10−2 | Conversational Voice |
| 2 | GBR | 4 | 150ms | 10−3 | Conversational Video |
| 3 | GBR | 3 | 50ms | 10−3 | Real Time Gaming |
| 4 | GBR | 5 | 300ms | 10−6 | Non-Conversational Video (Buffered Streaming) |
| 5 | non-GBR | 1 | 100ms | 10−6 | IMS Signalling |
| 6 | non-GBR | 6 | 300ms | 10−6 | Video (Buffered Streaming) TCP-Based (for example, www, email, chat, ftp, p2p and the like) |
| 7 | non-GBR | 7 | 100ms | 10−3 | Voice, Video (Live Streaming), Interactive Gaming |
| 8 | non-GBR | 8 | 300ms | 10−6 | Video (Buffered Streaming) TCP-Based (for example, www, email, chat, ftp, p2p and the like) |
| 9 | non-GBR | 9 | 300ms | 10−6 | Video (Buffered Streaming) TCP-Based (for example, www, email, chat, ftp, p2p and the like) |
Every QCI (GBR and Non-GBR) is associated with a Priority level. Priority level 1 is the highest Priority level. If congestion is encountered, the lowest Priority level traffic would be the first to be discarded.
References
- ↑ "3GPP TS 23.203 Policy and Charging Control Architecture". Retrieved 14 January 2015.
http://www.3gpp.org/DynaReport/23203.htm