- LTE EPS is a connection-oriented transmission network and, as such, it requires the establishment of a “virtual” connection between two endpoints (e.g. a UE and a PDN-GW)
- This virtual connection is called an “EPS Bearer”
- It provides a “bearer service”, i.e. a transport service with specific QoS attributes.
- The LTE QoS parameters associated to the bearer are: QCI, ARP, GBR and AMBR.
A data radio bearer transports the packets of an EPS bearer between a UE and an eNB in LTE.
When a data radio bearer exists in lte, there is a one-to-one mapping between this data radio bearer and the EPS bearer/E-RAB in lte.
An S1 bearer transports the packets of an E-RAB between an eNodeB and a Serving GW.
An S5/S8 bearer transports the packets of an EPS bearer between a Serving GW and a PDN GW.
The QoS parameters associated to the bearer are: QCI, ARP, GBR and AMBR.
Eps bearer in lte
- A low priority signaling (message) bearer (SRB1)
- A high priority signaling (message) bearer (SRB2)
- A data radio bearer (DRB), i.e. a bearer for IP packets
Eps in lte
Part of the bearer establishment procedure are authentication and activation of encryption.
The required data for this process is retrieved by the base station (the eNodeB or eNB in 3GPP talk) from the Access Gateway (aGW), or more precisely from the Mobility Management Entity (MME).