Sign in Subscribe

QCI Quality Class Identifier

Last updated on 

The Quality Class Identifier (QCI) is a parameter used in Long-Term Evolution (LTE) and 5G networks to differentiate and prioritize different types of traffic. QCI is a key element in the Quality of Service (QoS) framework, which ensures that various services and applications receive the appropriate level of performance and resource allocation within the network.

In both LTE and 5G, QCI is a 3-bit field that is included in the packet header of user plane data packets. It provides a total of eight possible values ranging from 1 to 9, with 9 being reserved for future use. Each QCI value represents a specific QoS class with predefined characteristics and priorities.

The QCI values are designed to support different types of services and applications based on their requirements for latency, packet loss, and reliability. The following are the standard QCI values commonly used in LTE and 5G networks:

  1. QCI 1: This value is assigned to real-time, delay-sensitive applications such as voice over LTE (VoLTE). It requires the lowest latency and packet loss rate and has the highest priority in terms of resource allocation.
  2. QCI 2: It is used for conversational video services, which also require low latency and low packet loss but may have slightly less stringent requirements compared to QCI 1.
  3. QCI 3: This value is typically assigned to applications that require interactive real-time communication, such as video conferencing and online gaming. QCI 3 has a moderate level of latency and packet loss tolerance.
  4. QCI 4: It is used for non-real-time services that require good quality and moderate latency, such as web browsing and email.
  5. QCI 5: This value is assigned to bearers carrying mission-critical services, where reliability and availability are crucial. Examples include public safety applications and emergency services.
  6. QCI 6: It is used for services with significant data transfer requirements, such as file downloads and software updates. QCI 6 has a relatively high packet loss tolerance but maintains a reasonable level of latency.
  7. QCI 7: This value is assigned to applications that require high-quality streaming services, such as high-definition video streaming. QCI 7 has a moderate level of packet loss tolerance but still maintains good quality.
  8. QCI 8: It is used for services with elastic traffic, where a certain level of degradation is acceptable. QCI 8 provides a best-effort type of service with high data transfer capability.

These QCI values help the network operator prioritize and allocate network resources based on the specific requirements of different services and applications. The network equipment and policies are configured to treat traffic with different QCI values differently, ensuring that critical applications receive the necessary quality and performance while efficiently utilizing the available network capacity.

It's important to note that the exact characteristics and priorities associated with each QCI value may vary slightly depending on the network operator's specific implementation and policies.