MOBILITY MANAGEMENT ENTITY (MME)
The MME can be a signaling-only entity, thus user IP packets don't glance at the MME. Its main function would be to manage the UE's mobility. Also, the MME also performs authentication and authorization; idle-mode UE tracking and reachability; security negotiations; and NAS signaling. An advantage of the separate network element for signaling is that operators can grow signaling and traffic capacity independently. A comparable benefit will also be accomplished in HSPA Release 7's direct-tunnel architecture, where the SGSN turns into a signaling-only entity.
EFFICIENT QoS
An important aspect for any all-packet network is a mechanism to guarantee differentiation of packet flows based on its QoS requirements. Applications such as video streaming, HTTP, or video telephony have particular QoS needs, and must receive differentiated service on the network. With EPS, QoS flows called EPS bearers have established yourself involving the UE along with the P-GW. Each EPS bearer is a member of a QoS profile, and it is composed of a radio bearer plus a mobility tunnel. Thus, each QoS IP flow (e.g., VoIP) is going to be of a different EPS bearer, along with the network can prioritize packets accordingly. The QoS procedure for packets arriving from the Internet is just like that relating to HSPA. When receiving an IP packet, the P-GW performs packet classification based on parameters including rules received from the PCRF, and sends it through the proper mobility tunnel. Based on the mobility tunnel, the eNB can map packets towards the appropriate radio QoS bearer.
EPS SEAMLESS MOBILITY
Seamless mobility is clearly an important consideration for wireless systems. Uninterrupted active handoff across eNBs may be the first scenario one typically considers. However, other scenarios such as handoffs across core networks (i.e., P-GW, MME), transfer of access technologies, and idle mobility are important scenarios paid by EPS.
SEAMLESS ACTIVE HANDOFFS
EPS enables seamless active handoffs, supporting VoIP and other real-time IP applications. Since there is no RNC, an interface between eNBs is employed to guide signaling for handoff preparation. Furthermore, the S-GW behaves for an anchor, switching mobility tunnels across eNBs. A serving eNB maintains the coupling between mobility tunnels and radio bearers, as well as maintains the UE context1. As preparation for handoff, the origin eNB (eNB 1) sends the coupling information as well as the UE context to the target eNB (eNB 2). This signaling is triggered by the radio measurement in the UE, indicating that eNB 2 includes a better signal. Once eNB 2 signals it's ready to perform the handoff, eNB 1 commands the UE to switch the air bearer to eNB 2. For your eNB handoff to finish, the S-GW must update its records with all the new eNB that is certainly serving the UE. With this phase, MME coordinates the mobility-tunnel switch from eNB 1 to eNB 2. MME triggers the update in the S-GW, based on signaling received from eNB 2 indicating that the radio bearer was successfully transferred.
Visit Session Persistence or Seamless connectivity for more.