RFLTE QoS and QCI Overview
This page provides a basic overview of LTE Quality of Service (QoS) and the LTE QoS Class Identifier (QCI). It covers LTE QCIs, including QCI-1, QCI-2, QCI-3, QCI-4, QCI-5, QCI-6, QCI-7, QCI-8, and QCI-9.
LTE QoS allows for the differentiation of both LTE subscribers and the services they use. This means premium subscribers can be prioritized over basic subscribers, and real-time services can be prioritized over non-real-time services.
In an unloaded network, there are typically no issues for LTE subscribers concerning service provision. The real challenge arises when the network becomes congested. This is where LTE QoS becomes crucial. As network load increases, prioritization determines which subscribers and services perform well and which do not. Similar to other systems, LTE QoS also impacts admission control decisions. Connections with guaranteed QoS require larger resources and may be blocked if insufficient resources are available.
Table 1 outlines the QoS parameters associated with each LTE bearer type. QoS is applied between the User Equipment (UE) and the PDN gateway within the LTE network.
LTE QoS Parameters
| Feature | GBR | Non-GBR |
|---|---|---|
| QoS Class Identifier | Supported | Supported |
| Allocation and Retention Priority | Supported | Supported |
| Guaranteed Bit Rate | Supported | |
| Maximum Bit Rate | Supported | |
| APN Aggregate Maximum Bit Rate | Supported | |
| UE Aggregate Maximum Bit Rate | Supported |
Table 2 (below) illustrates the relationship between QCI and its associated set of QoS characteristics. 3GPP adopted this approach to reduce both the signaling overhead and the number of possible parameter combinations.
LTE QCI Table (QCI-1 to QCI-9)
| LTE QCI | Resource Type | Priority | Packet Delay Budget | Packet Error Loss Rate | Example Services |
|---|---|---|---|---|---|
| QCI-1 | GBR | 2 | 100ms | Conversational voice | |
| QCI-2 | GBR | 4 | 150ms | Live streaming of conversational voice | |
| QCI-3 | GBR | 3 | 50ms | Real-time gaming | |
| QCI-4 | GBR | 5 | 300ms | Non-conversational video (Buffered streaming) | |
| QCI-5 | Non-GBR | 1 | 100ms | IMS signaling | |
| QCI-6 | Non-GBR | 6 | 300ms | Video (buffered streaming), TCP-based applications | |
| QCI-7 | Non-GBR | 7 | 100ms | Voice, video (live streaming), interactive gaming | |
| QCI-8 | Non-GBR | 8 | 300ms | Video (Buffered streaming), TCP-based applications | |
| QCI-9 | Non-GBR | 9 |
As mentioned, the LTE QCI determines whether bearers are categorized as Guaranteed Bit Rate (GBR) or Non-GBR. The priority associated with each QCI is applied when forwarding packets across the LTE network, with a priority of 1 being the highest.
The Packet Delay Budget defines the upper bound for packet delay between the UE and the PCEF within the PDN gateway. An average delay of 20ms between the eNodeB and PCEF is assumed, and the remaining delay budget is available for the RAN (Radio Access Network).
LTE QCI table-2 also mentions the Packet Error Loss Rate, which is defined as the percentage of higher-layer packets lost during periods when the network is not congested.
LTE QoS References
- 3GPP TS 36.300
- 3GPP TS 23.401
- 3GPP TS 23.203
