MOBILITY MANAGEMENT ENTITY (MME)
The MME is a signaling-only entity, thus user IP packets will not glance at the MME. Its main function should be to manage the UE's mobility. Additionally, the MME also performs authentication and authorization; idle-mode UE tracking and reachability; security negotiations; and NAS signaling. A benefit of an separate network element for signaling is that operators can grow signaling and traffic capacity independently. An identical benefit may also be accomplished in HSPA Release 7's direct-tunnel architecture, the location where the SGSN becomes a signaling-only entity.
EFFICIENT QoS
A significant aspect for virtually any all-packet network is often a mechanism to guarantee differentiation of packet flows depending on its QoS requirements. Applications for example video streaming, HTTP, or video telephony have special QoS needs, and must receive differentiated service over the network. With EPS, QoS flows called EPS bearers have established yourself between the UE along with the P-GW. Each EPS bearer is associated with a QoS profile, which is consists of a radio bearer plus a mobility tunnel. Thus, each QoS IP flow (e.g., VoIP) will likely be of a different EPS bearer, along with the network can prioritize packets accordingly. The QoS process of packets arriving from the Internet is similar to those of HSPA. When receiving an IP packet, the P-GW performs packet classification determined by parameters such as rules received through the PCRF, and sends it with the proper mobility tunnel. Using the mobility tunnel, the eNB can map packets towards the appropriate radio QoS bearer.
EPS SEAMLESS MOBILITY
Seamless mobility is clearly a vital consideration for wireless systems. Uninterrupted active handoff across eNBs may be the first scenario one typically considers. However, other scenarios for instance handoffs across core networks (i.e., P-GW, MME), transfer of access technologies, and idle mobility may also be important scenarios included in EPS.
SEAMLESS ACTIVE HANDOFFS
EPS enables seamless active handoffs, supporting VoIP and other real-time IP applications. As there is no RNC, an interface between eNBs is used to support signaling for handoff preparation. In addition, the S-GW behaves as an anchor, switching mobility tunnels across eNBs. An amount eNB maintains the coupling between mobility tunnels and radio bearers, plus maintains the UE context1. As preparation for handoff, the origin eNB (eNB 1) sends the coupling information plus the UE context to the target eNB (eNB 2). This signaling is triggered by a radio measurement from the UE, indicating that eNB 2 incorporates a better signal. Once eNB 2 signals that it is willing to perform the handoff, eNB 1 commands the UE to change radio stations bearer to eNB 2. For the eNB handoff to complete, the S-GW must update its records while using new eNB that's serving the UE. Due to this phase, MME coordinates the mobility-tunnel switch from eNB 1 to eNB 2. MME triggers the update with the S-GW, dependant on signaling received from eNB 2 indicating that the radio bearer was successfully transferred.
Visit Session Persistence or Seamless connectivity for more.