When your phone connects to an LTE network, one of the first things it does is establish a Default EPS Bearer.
What is the Default EPS Bearer?
It’s the basic connection that every LTE device gets when it attaches to the network. This bearer provides a “best-effort” quality of service (QoS) for general internet traffic. It is non-GBR (Guaranteed Bit Rate), meaning it doesn’t reserve specific bandwidth.
How is the Default EPS Bearer Established?
- Attach Request: The UE sends an attach request to the Mobility Management Entity (MME).
- Session Creation:
- The MME contacts the Serving Gateway (SGW) and Packet Gateway (PGW) to create a session.
- The PGW assigns an IP address and links it to the Access Point Name (APN)
- QoS parameters for the default bearer, such as QCI and ARP, are set by the PGW based on the user’s subscription from the HSS.
- Activate Bearer: The MME sends the “Activate Default Bearer Request” to the UE, completing the process
What’s Inside the EPS Bearer?
Each EPS bearer includes:
- QoS Parameters: Defined by the QCI (QoS Class Identifier), which determines latency, priority, and reliability.
- APN Connectivity: The APN links the UE to the internet or private networks through the PGW. The PGW enforces QoS rules and routes data traffic.
APN (Access Point Name)
- Operators use multiple APNs to separate traffic types,
one APN for enterprise applications and another for consumer internet.
EPS Bearer Types
-
Default EPS Bearer
Created automatically when the UE attaches to the LTE network.
Provides always-on connectivity via a default APN often used for general browsing and background apps. -
Dedicated EPS Bearer
Established for specific applications needing tailored QoS, such as VoLTE or video streaming.
Works alongside the default bearer to prioritize critical services.
Why QoS Matters…
QoS in LTE ensures applications like video calls, streaming, or browsing get the right treatment. For example:
- A Default EPS Bearer with QCI 9 is for basic internet browsing.
- A Dedicated Bearer can be set up for applications needing guaranteed bandwidth, like VoLTE, with QCI 1.
How Many EPS Bearers Can a UE Handle?
A UE can support up to 11 EPS bearers simultaneously (1 default + up to 10 dedicated), depending on the operator’s configuration and the device’s capabilities, But By Standard it’s only 8 bearers.
That’s it 
Slide 1. EPS
Slide 2. EPS
Slide 3. LTE UE States
Slide 4. EPS Session
Slide 5. EPS
Slide 6. APN
Slide 7. QoS
Slide 8. QoS for Operators
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