In the LTE network architecture, EPS (Evolved Packet System) bearers are essential for managing data traffic between the user equipment (UE) and the Packet Data Network Gateway (PDN-GW). There are two types of EPS bearers: Default EPS Bearers and Dedicated EPS Bearers. Each serves distinct roles in traffic management and QoS (Quality of Service) provisioning. Let's explore their differences and the reasons for having both.
Default EPS Bearer:
- Establishment: Established when the UE initially connects to the LTE network and remains active as long as the UE is connected.
- Purpose: Provides a basic, non-GBR (Non-Guaranteed Bit Rate) service, allowing the UE to access the internet and other IP-based services.
- QoS Level: Associated with a default QoS profile, which is applied to all data traffic in the absence of a Dedicated EPS Bearer. This QoS level is generally lower compared to dedicated bearers.
- Characteristics: Every UE has at least one default bearer per PDN connection, which ensures that there is always a path for IP traffic flow between the UE and the PDN-GW.
Dedicated EPS Bearer:
- Establishment: Can be established and released as needed, after the default bearer is set up. A UE can have multiple dedicated bearers in addition to the default bearer, each tailored for specific services or data flows.
- Purpose: Provides guaranteed QoS for services requiring higher priority, bandwidth, or lower latency, such as VoIP (Voice over IP) or video streaming.
- QoS Level: Each dedicated bearer is associated with a specific QoS Class Identifier (QCI) and optionally, a Guaranteed Bit Rate (GBR), ensuring that the network resources are allocated to meet the QoS requirements of the service.
- Characteristics: Dedicated bearers are used to segregate different types of traffic and apply specific QoS rules, allowing for more granular control over network resources and service quality.
Why We Need Both:
- Flexibility in QoS Management: The distinction allows the network to efficiently manage resources by providing a basic level of connectivity through the default bearer, while also being able to cater to specific QoS needs through dedicated bearers.
- Efficiency: Default bearers help in minimizing signaling overhead and resource allocation by serving as a continuous, basic connectivity channel. In contrast, dedicated bearers allocate resources dynamically, optimizing the network for varying traffic demands and service requirements.
- Service Differentiation: Dedicated bearers enable the network to differentiate between various traffic types and prioritize them accordingly. This is crucial for supporting a wide range of applications, from low-latency services like real-time gaming or VoIP to high-bandwidth applications like HD video streaming, ensuring that critical applications receive the necessary network resources for optimal performance.