Long Term Evolution (LTE) has been designed to support only packet-switched services.
It aims to provide seamless Internet Protocol (IP) connectivity between user equipment (UE) and the packet data network (PDN),without any disruption to the end users’ applications during mobility.
The term “LTE” encompasses the evolution of the Universal Mobile Telecommunications System (UMTS) radio access through the Evolved UTRAN (E-UTRAN)
it is accompanied by an evolution of the non-radio aspects under the term “System Architecture Evolution” (SAE), which includes the Evolved Packet Core (EPC) network. Together LTE and SAE comprise the Evolved Packet System (EPS).
Together LTE and SAE comprise the Evolved Packet System (EPS).
EPS uses the concept of EPS bearers to route IP traffic from a gateway in the PDN to the UE. A bearer is an IP packet flow with a defined quality of service (QoS) between the gateway and the UE.
The E-UTRAN and EPC together set up and release bearers as required by applications.
EPS provides the user with IP connectivity to a PDN for accessing the Internet, as well as for running services such as Voice over IP (VoIP).
An EPS bearer is typically associated with a QoS.
Multiple bearers can be established for a user in order to provide different QoS streams or connectivity to different PDNs.
A VoIP bearer would provide the necessary QoS for the voice call, while a best-effort bearer would be suitable for the web browsing or FTP session.