The provision of services and service capabilities that is possible to offer in a network shall not be restricted by the existence of the network sharing It shall be possible for a core network operator to differentiate its service offering from other core network operators within the shared network. It shall be possible to control the access to service capabilities offered by a shared network according to the core network operator the user is subscribed to.

Service capabilities shall take account of the discontinuous and asymmetric nature of most teleservices, multimedia services and user applications and consider the overheads and signalling surge caused by frequent transmissions of small amount of data by mobile data application, in order to make efficient use of network resources (particularly radio resources).

When a large number of subscribers enter in a registration area in which they have not registered, the core and radio access network shall be able to provide a capability to optimize the mass simultaneous registration traffic at a given instance of time. The core and radio access network shall be able to keep providing the service (e.g. mobile originated and mobile terminated services) without interruption for those subscribers who are originally in the cell which receive the mass simultaneous registration traffic.

Service capabilities shall be provided in a wide range of radio operating environments (where a radio environment is characterised in terms of propagation environment, mobile equipment relative speeds and traffic characteristics). Although 3GPP aims to minimise the number of radio interfaces and to maximise commonality between them, it may utilise several radio interfaces, each optimised for different environments. Each radio interface may provide differing service capabilities. 3GPP specifications include UTRA(N) radio interface supporting two modes (TDD and FDD), an Evolved UTRA(N) radio interface and GERAN radio interface. Additionally, it may be possible to connect to the 3GPP system using radio interfaces and fixed access technologies specified outside of 3GPP. 3GPP specifications shall provide a mechanism which will enable a piece of user equipment (UE) to adapt to different radio interfaces as necessary and to determine the service capabilities available. The specifications shall also provide a mechanism which will enable a UE to select radio interfaces capable of providing appropriate service capabilities and support mobility between multiple radio interfaces.

To enable network operators to render services efficiently, dimension their networks and set tariffs that more accurately reflect radio resource usage, real time information on resource usage is needed. When requested, it shall be possible for the serving cell type (e.g. RAT), cell ID / UTRAN Service Area Identity and cell / Service Area capability usage (e.g. HSDPA, E-DCH) information to be made available to the core network. Cell / Service Area capability usage information may include, for example, user(s) identity, start and finish time of data transfer, up-link and down-link data rates, volumes of data and other statistical information.

The 3GPP core network shall be able to use these additional criteria for selecting a paging policy:

• mobility information on the UE (e.g. the UE is stationary, or moving only in a specified area)
• application characteristics that are known and trusted at the serving network (e.g. communication pattern, expected QoS (e.g. latency, reliability), and priority)
• likely location of the UE within the paging area

The UDC concept [45] supports a layered architecture, separating the data from the application logic in the 3GPP system, so that user data is stored in a logically unique repository allowing access from core and service layer entities, named application front-ends. And such unique repository shall be possible to be shared among different PLMNs that have trusted relationships. Network elements and functionalities should be designed to access profile data remotely and without storing them permanently locally, i.e. the front-ends shall work in a subscriber data-less configuration. In some cases, services may depend on user data scattered over UDC and other network elements. UDC may support the ability to access necessary network elements to fetch user data on behalf of these services, while minimizing impacts on existing Network Elements in which the data is located. Applications can subscribe to specific events which will likely occur on specific user data, and those should be notified when those events do appear. The events can be changes on existing user data, addition of user data, and so on. Third-party applications and non-trusted network elements should only be able to access the user data after proper authentication and authorization taking into account security and privacy requirements, i.e. it should be possible to present different views on the data to the parties which require access, dependent on the authorization. UDC concept is backwards compatible with 3GPP systems, i.e. it does not have an impact on traffic mechanisms, reference points and protocols of existing network elements. The UDC concept preserves user authentication and authorization of services across domains, ensuring secured users' access to network.

Due to the logical centralization of user data, it is necessary for UDC to support the provisioning of the user data, that is, user data manipulation like creation, deletion, reading, modification and other operations. Provisioning shall be possible via an external system, self-care or dynamically via applications offering e.g. user service configuration facilities. Operations carried out in the framework of UDC shall support the ACID (Atomicity, Consistency, Isolation, and Durability) characteristics.

User Data Modelling refers to the different models that apply to user data convergence: Information Models and Data Models. An Information Model denotes an abstract, formal representation of entity types, including their properties and relationships, the operations (e.g. read, write…) that can be performed on them, and related rules and constraints. In the information model, entities might have network topology relationship with each other. In order to accommodate multiple applications and services, existing and new ones, a common baseline information model shall be developed and shall, at minimum, clearly distinguish a number of concepts as entity types:

• Subscriber with relation to several users (e.g. a company and its employees),
• A user attached to different subscriptions (e.g. for a private and a professional service usage)
• A user using multiple devices (e.g. mobiles or fixed)
• Grouping of users to certain categories
• A particular user as member of a certain group
• Service providers' services provided by network operators
• Enterprise services provided by network operators

The baseline information model shall be future proof. It shall not be tied to any specific implementation of the data base or its interfaces. It shall provide flexibility (in its data structure and content), extensibility and multi-application approach. By extensible, it shall be understood that new applications and/or new service profiles can be added by the operator, if necessary. The flexibility shall permit new data for existing applications to be introduced, or modified. Data Models are practical implementations of the information model, e.g. Tree-like modelling. The common information model shall allow deriving one or more data models. A reference data model shall be standardized for the message exchange over Ud interface [50], in order to enable multivendor interoperability. Each application shall only interface the UDC for the data it is dealing with, and not be impacted by other data that UDC stores for other applications. It corresponds to the concept of a data view specific to a given application. An application can allow access by other applications to data for which it is responsible. This can be done under certain constraint customized by operators. Access to the UDC data shall be independent of the structure of the data models, i.e. the changes in the data models shall not affect the interface.