QCI (QoS Class Identifiers) and Priority Levels Explained

What is QCI?

QCI stands for Quality of Service Class Identifier (sometimes abbreviated as QoS Class Identifier).

The quality of service identifiers are numbers that range from 1-9 that designate how cellular traffic should be prioritized on LTE networks.

The QCI mechanism was developed by the 3rd Generation Partnership Project (3GPP), a collaborative project between seven telecommunications standard development organizations. These organizations work together to create the technical specifications and standards for cellular networks. They developed standards for the 2G, 3G, 4G, LTE-Advanced, and 5G networks.

The QCI mechanism was developed to make sure LTE networks could appropriately allocate resources to handle different tasks on the network.

For example, voice calls require low latency but can handle some data loss, while video streaming demands high bandwidth and low jitter.

QCI values have five different parameters to make sure the cellular network can meet the needs of specific tasks:

• Resource Type: Either Guaranteed Bit Rate (GBR) or Non-Guaranteed Bit Rate (Non-GBR). Having a GBR means the task is guaranteed to have a certain speed or higher on the network. Having a non-GBR means that the data speeds may fluctuate.
• Priority Level: A number from 1 to 9 that designates the priority on the network. 1 is the highest priority and 9 is the lowest priority.
• Packet Delay Budget (PDB): The maximum acceptable time delay for a packet, measured in milliseconds. A packet is basically a chunk of data being transmitted on the network. Time-sensitive applications have a PDB of 50 milliseconds. Less time-critical services have a PDB of up to 300 milliseconds.
• Packet Error Loss Rate (PELR): The acceptable rate of lost packets. This is typically expressed as a probability or percentage and is often written as a power of 10. For example, a PELR of 10-6 indicates one packet lost per million packets.
• Example Services: The type of service or application for which the QCI value is typically used.

Why Are QCI Values Important?

QCI values allow cellular carriers to manage limited network resources appropriately.

For example, assigning high-priority QCI values to military members and first responders ensures they can communicate and access the internet during emergencies.

Another example is using higher QCI values for voice tasks compared to data tasks. This allows concert-goers to successfully place a phone call on a cellular network at the concert, even if the network is too congested for cellular data to load.

Using QCI values helps maintain the quality of service on the network even as resources become constrained.

What Are the QCI Values and Their Use Cases?

Here is a full table that lists out the nine QCI values used on LTE networks as well as the example services that would use each QCI value:

And here are all the QCI values sorted by their priority level on the network:               

How Do Wireless Networks Use QCI Values?

The three major mobile networks in the United States are AT&T, T-Mobile, and Verizon.

Here is how each of these networks uses QCI values:

AT&T QCI Values and Priority Levels

• QCI 6: This is the highest priority level on the AT&T network. It is reserved for AT&T FirstNet plans. AT&T FirstNet is a cell service designed for military members and first responders. These people need higher access on the cellular network to communicate during emergencies. The AT&T Business Unlimited Premium plan also includes QCI 6 data.
• QCI 7: This is the second-highest priority level on the AT&T network, and it is the highest priority level available on AT&T's consumer plans. QCI 7 is included in AT&T's Unlimited Elite 2.0 plan. AT&T also offers it on its other postpaid plans via the AT&T Turbo add-on for $7 per month.
• QCI 8: This is the third-highest priority level on AT&T. It is generally marketed as "priority" or "premium" data on AT&T's plans. Plans with QCI 8 include AT&T Premium 2.0, AT&T Extra 2.0, AT&T Prepaid Unlimited Ultra, Cricket Supreme Unlimited, Red Pocket's plans, and US Mobile Unlimited Premium Dark Star.
• QCI 9: This is the lowest priority tier on the AT&T network. It is considered deprioritized data. Plans with QCI 9 data include most plans from AT&T MVNOs.

T-Mobile QCI Values and Priority Levels

• QCI 6: This is considered priority data on the T-Mobile network. Plans with QCI 6 include T-Mobile Experience More 2.0, T-Mobile Experience Beyond 2.0, all T-Mobile Prepaid plans, and all Google Fi plans.
• QCI 7: This is considered deprioritized data on the T-Mobile network. Plans with QCI 6 include T-Mobile Essentials 2.0, T-Mobile Essentials Saver 2.0, all Metro by T-Mobile plans, all Mint Mobile plans, and nearly all other plans from MVNOs that run on the T-Mobile network.
• QCI 8: This is reserved for hotspot data use on the T-Mobile network.
• QCI 9: This is extra deprioritized data reserved for high-data users. If you use more than 50GB on T-Mobile Essentials, T-Mobile Prepaid Unlimited, T-Mobile Prepaid Unlimited Plus, or Mint Mobile Unlimited, or more than 35GB on most of Metro's plans, then you will be knocked down to QCI 9. T-Mobile Home Internet is also under QCI 9.

Verizon QCI Values and Priority Levels

• QCI 7: This is the highest priority available on the Verizon network. Verizon reserves it exclusively for Frontline customers.
• QCI 8: This is considered priority data on the Verizon network. Plans with QCI 8 include Verizon Simplicity, Verizon Unlimited Plus, Verizon Unlimited Ultimate, Verizon Prepaid Unlimited Plus, Visible+, Visible+ Pro, all Xfinity Mobile plans, all Spectrum Mobile plans, US Mobile Unlimited Premium Warp, and more.
• QCI 9: This is deprioritized data on the Verizon network. Plans with QCI 9 data include Verizon Unlimited Welcome, Visible Base, and most other plans from Verizon MVNOs.

Full List of All QCI Values for All Cell Phone Plans (That I've Tested)