As for all networks supporting mobility, special functions are required for looking up the current position of a mobile terminal, for providing the moving terminal with a permanent address, and for ensuring security features such as privacy, authentication, or authorization. These and more functions are grouped and team location management.
Requirements for location management
Several requirements for location management have been identified,
Transparency of mobility: A user should not notice the location management function under normal operation. Any change of location should be performed without user activity. This puts certain constraints on the permissible time delay of the functions associated with location management. Furthermore, transparent roaming between different domains should be possible. This may include roaming between networks based on different technologies using, for example, a dual-mode terminal.
Security: In order to provide a security level high enough to be accepted for mission-critical use, a wireless ATM system requests special features. All location and user information corrected for location management and accounting should be protected against unauthorized disclosure.
This protection is especially critical for roaming profiles which allowed the precise tracking of single Terminals. As the air interface is very simple to access, special access limitations must be executed to, for example, put out public users from private wireless ATM networks. But users should also be able to define the network their terminal is allowed to access. Required security features involve authentication of users and terminals, but also access points. Additionally, encryption is required, at least between terminal and access point, But preferably end-to-end.
Efficiency and scalability: imagine wireless ATM networks with Minions of users like today's mobile phone networks. Every function and system involved in location management must be scalable and efficient. This includes distributed servers for location storage, accounting, and authentication.
Furthermore, the performance of all operations should be practically independent of network size, number of current connections, and network load. Thus, clustering of switches and hierarchies of domains should be possible to increase the overall performance of the system by dividing the load.
In contrast to many existing cellular networks, wireless ATM should work with a more efficient, integrated signaling scheme. All signaling required for location management should therefore be incorporated into the existing signaling mechanism, for example, by adding new information elements to existing messages. This allows for the utilization of the existing signaling mechanisms in the fixed ATM network which are efficient.
Identification: location management must give the means to recognize all entities of the network. Radio cells, wireless ATM networks, terminals, and switches require unique identifiers and mechanisms to exchange identity data. This specification also covers information for a terminal concerning its current location and its current point of attachment. furthermore, in addition to the permanent ATM end system address, a needs a routable temporary AESA as soon as it is outside its home network. This temporary AESA must be forwarded to the terminal's home location.
Inter- working and Standards: All location management functions must co-operate with existing ATM functions from the fixed network especially routing. Furthermore, location management in wireless ATM has to be harmonized with other location management schemes, such as location management in current GSM networks, future UMTS networks, the internet using mobile IP, or internet switch special features.
This harmonization could for instance lead to two-level location management if mobile IP is used on top of wireless ATM. All protocols used in wireless ATM for database updates, registration, etc. Have to be standardized to permit mobility across provider network boundaries. However, inside the administrative domain proprietary enhancements and optimizations could be applied.
Procedures and entities
Several entities that support location management have been identified. The mobile terminal, which is wireless for the applications considered here, executes functions to initiate location updates and participates in authentication under privacy protocols.
Many end-user mobility supporting switches are necessary to identify connection setup messages destined for the WMDs and to invoke location resolution functions. Furthermore, EMASs redirect connections, and Some of them maintain location and authentication servers.
Location servers (LS) maintain a database containing the current AESA and the permanent AESA of a WMT. They also keep track of further service-specific parameters of a terminal and user, such as quality of service of connections. Location servers may be part of an EMAS. An authentication server maintains a secure database of authentication and privacy-related information for each WMT. This also includes access to rights and equipment identification.
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