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Personal Service Environment (PSE). These components create a common set of personal preferences and profiles for users. Many applications can then reuse this information and give the user a more personalized service.
Applications. This area is where the applications servers reside, including application-specific databases and servlets.
Service management. As technology offers users more and more services, it is important to keep statistics for the users about usage and quality. In addition, it should be easy both for the operator and for the individual user to add or remove services dynamically.
Now, it should be obvious to you that a lot circulates around the service enablers.
In Chapter 1, “Basic Concepts,” we touched upon the definitions of applications and services and concluded the following:
End users consume services provided by applications, which operate on application servers and/or client devices.
In order to understand what service enablers do, we must complement the previous statement with another definition: Applications consume services that service enablers provide.
In other words, applications get additional services from the mobile network through the service enablers without interfacing directly with the network. An example would be a positioning server that adds location-based services to applications. In the same way that programming libraries give convenient developer access to different features of a computer, the service enablers give
access to features of mobile networks. The standardized APIs make it possible for an application to be compatible with a service enabler of a certain type, regardless of whether it is manufactured by Ericsson, Lucent, or somebody else. This functionality is one of the most widely anticipated features that software developers have pushed the telecommunications industry into adopting. Telecommunications networks have traditionally been very closed, and it has been difficult for third parties to get solutions into operation. The Internet model has so far not had this problem of inflexibility (but instead, a lack of structure and standardization of APIs). For example, it has been very difficult to get a micro payment standard to be accepted as a standard on the Internet.
Figure 9.7 is the same as Figure 9.5 but with the service enablers magnified.
The APIs not only make it possible to develop applications for all standardized service networks, but they also substantially raise the abstraction level. An applications developer will not need to know whether a user is equipped with a Global Positioning System (GPS) receiver or whether network -based positioning is available. A service enabler (here, a mobile positioning center or MPC) provides an API where the application can ask for the position of a user. The MPC then finds out the details by interfacing with the mobile network and with the device. If the application had interfaced directly with the network, you would also have needed to change it if you added more positioning options.
MPC is an example of a service capability server because it gives access to features that the core network provides, rather than to other service network components.
Figure 9.7 The service enabler part magnified.
Service Capability Servers
In order to make the VHE dream of personalized services for the masses come true; an open, standardized, and flexible architecture is necessary. As for most of the technologies that are primarily on 3G networks, 3GPP has performed this work. This time, however, another organization was formed in order to agree on APIs and protocols for service enablers. This group, called PARLAY, today consists of companies, and the group works closely with 3GPP and standardization (“Services to applications on application servers”). As we mentioned in the previous subchapter, a node (server) that offers such services that give access to core network features is called a service capability server. The services that such a server provides can be things such as user location, message transfer, and call control.
Figure 9.8 illustrates how the application server has access to a set of services that service capability servers offer, such as WAP gateway and gsmSCF (which
Figure 9.8 The service capability servers with OSAAPIs.
offers CAMEL Services (3GPP TS 22.078)). The architecture is sometimes called Open Services Architecture (OSA), and the APIs are all available in the 3GPP specifications (TS 22.078, TS 29.998).
As we see in figure 9.8, several SCSs can offer one service. The MPC as well as the Home Location Register Gateway (HLR-GW) offer user location services. Because the HLR is where the mobile system keeps subscriber information, it knows the cell in which the user currently exists. This information is then offered through the HLR-GW via the user location services. The MPC has this information as well, and it knows whether the user can be positioned more accurately with GPS or by using other technologies. In other words, the MPC (most of the time) can give a more exact position and thus a higher service to the application. Nodes such as the HLR-GW, which are not much more than an interface toward an existing node on the mobile network, are called OSA gateways.