Cisco Cisco Packet Data Interworking Function (PDIF) Documentation Roadmaps
MME in LTE/SAE Wireless Data Services
▀ Features and Functionality - Base Software
▄ Cisco ASR 5000 Series Product Overview
OL-22938-01
Tracking Area List Management
Provides the functions to allocate and reallocate a Tracking Area Identity (TAI) list to the UE to minimize the Tracking
Area updates.
Area updates.
The MME assigns the TAI list to a UE so as to minimize the TA updates that would be sent by the UE. The TAI list
should not be very long as this would mean that the paging load would be high. There is a trade-off between paging load
and Tracking Area Update procedures number.
should not be very long as this would mean that the paging load would be high. There is a trade-off between paging load
and Tracking Area Update procedures number.
To avoid ping-pong effect, the MME includes the last visited TAI (provided that the TA is handled by the MME) in the
TAI list assigned to the UE.
TAI list assigned to the UE.
The tracking area list assigned to different UEs moving in from the same tracking area should be different so as to avoid
Tracking Area Update message overflow.
Tracking Area Update message overflow.
Reachability Management
It provides a mechanism to track a UE which is in idle state for EPS connection management.
To reach a UE in idle state the MME initiates paging to all eNodeBs in all tracking areas in the TA list assigned to the
UE. The EPS session manager have knowledge about all the eNodeB associations to the MME and generates a list of
eNodeBs that needs to be paged to reach a particular UE.
UE. The EPS session manager have knowledge about all the eNodeB associations to the MME and generates a list of
eNodeBs that needs to be paged to reach a particular UE.
The location of a UE in ECM-IDLE state is known by the network on a Tracking Area List granularity. A UE in ECM-
IDLE state is paged in all cells of the Tracking Areas in which it is currently registered. The UE may be registered in
multiple Tracking Areas. A UE performs periodic Tracking Area Updates to ensure its reachability from the network.
IDLE state is paged in all cells of the Tracking Areas in which it is currently registered. The UE may be registered in
multiple Tracking Areas. A UE performs periodic Tracking Area Updates to ensure its reachability from the network.
Network Operation Management Functions
This section describes following features:
Overload Management in MME
Provides mechanism to handle overload/congestion situation. It can use the NAS signalling to reject NAS requests from
UEs on overload or congestion.
UEs on overload or congestion.
MME restricts the load that its eNodeBs are generating on it. This is achieved by the MME invoking the S1 interface
overload procedure as per 3GPP TS 36.300 and 3GPP TS 36.413 to a proportion of the eNodeB‘s with which the MME
has S1 interface connections.
overload procedure as per 3GPP TS 36.300 and 3GPP TS 36.413 to a proportion of the eNodeB‘s with which the MME
has S1 interface connections.
Hardware and/or software failures within an MME may reduce the MME‘s load handling capability. Typically such
failures result in alarms which alert the operator or Operation and Maintenance system.
failures result in alarms which alert the operator or Operation and Maintenance system.