QCI (QoS Class Identifiers) Explained

One of the primary mechanisms that LTE networks use to handle prioritization of traffic during congestion are quality of service class identifiers (also called QCI values).[1] Without getting too technical, QCI values indicate a certain priority level for traffic. Most data use by regular consumers on LTE networks will involve QCI values between 6 and 9. Within that range, lower QCI values are associated with higher-priority service. For a much more technical treatment of QCI values, see the 3GPP publication on Policy and charging control architecture.

Observed QCI Values

I’ve started to run tests to figure out QCI values associated with different carriers’ service. I hope to run test like these with more carriers in the future. More information on how I run these tests can be found here.

Carriers using AT&T’s network

Cricket Wireless

I found a QCI of 8 for regular data use on a non-unlimited Cricket plan on 5/17/2020.

Test result showing a QCI of 8 on a non-unlimited Cricket Wireless plan

Carriers using T-Mobile’s network

Google Fi

I found a QCI value of 6 for regular data use on Fi’s service on 9/17/2019.[2]

T-Mobile Connect

I found a QCI value of 6 for regular data use on a T-Mobile Connect plan on 5/14/2020.

A test run on a T-Mobile Connect plan showing a QCI of 6

Mint Mobile

I found a QCI value of 7 for regular data use with Mint Mobile’s service on 9/17/2019.

Carriers using Verizon’s network

Xfinity Mobile

I found a QCI of 9 for regular data use on a second-generation Xfinity Mobile unlimited plan on 5/19/2020.

Test showing a QCI of 9 on a second-generation Xfinity Mobile unlimited plan

Standardized QCI characteristics

The following table is a modified and abbreviated version of what appears in the 3GPP standards.[3]

QCIResource TypePriority LevelPacket Delay BudgetPacket Error Loss RateExample Services
1Guaranteed Bit Rate (GBR)2100 ms10-2Conversational Voice
2GBR4150 ms10-3Conversational Video (Live Streaming)
3GBR350 ms10-3Real Time Gaming; V2X messages
4GBR5300 ms10-6Non-Conversational Video (Buffered Streaming)
65GBR0.775 ms10-2Mission Critical user plane Push To Talk voice (e.g., MCPTT)
66GBR2100 ms10-2Non-Mission-Critical user plane Push To Talk voice
67GBR1.5100 ms10-3Mission Critical Video user plane
75GBR2.550 ms10-2V2X messages
5Non-GBR1100 ms10-6IMS Signalling
6Non-GBR6300 ms10-6Video (Buffered Streaming); TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing, progressive video, etc.)
7Non-GBR7100 ms10-3Voice; Video (Live Streaming); Interactive Gaming
8Non-GBR8300 ms10-6Video (Buffered Streaming); TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing, progressive video, etc.)
9Non-GBR9300 ms10-6Same as above
69Non-GBR0.560 ms10-6Mission Critical delay sensitive signalling (e.g., MC-PTT signalling, MC Video signalling)
70Non-GBR5.5200 ms10-6Mission Critical Data (e.g. example services are the same as QCI 6/8/9)
79Non-GBR6.550 ms10-2V2X messages
80Non-GBR6.810 ms10-6Low latency eMBB applications (TCP/UDP-based); Augmented Reality

Footnotes

  1. Other mechanisms include guaranteed bit rates, maximal bit rates, and allocation and retention priority. The excerpt below comes from page 51 of 3GPP TS 23.203 V16.1.0:
    “The service level (i.e., per SDF or per SDF aggregate) QoS parameters are QCI, ARP, GBR, and MBR.”
  2. I did this using a device that was compatible with Fi but not designated “Designed for Fi.”
  3. Based on Table 6.1.7-A: Standardized QCI characteristics from 3GPP TS 23.203 V16.1.0.