5 Domains in UMTS

23.1013GPPGeneral Universal Mobile Telecommunications System (UMTS) architectureRelease 17TS

The following figure shows the basic domains in UMTS as described in this clause.

NOTE: The domains identified in the figure will generally result from an evolution of existing network infrastructures. The core network domain may result from evolutions of existing network infrastructures, e.g., a GSM infrastructure, a N-ISDN infrastructure, a B-ISDN infrastructure or a PDN infrastructure. The evolution of these infrastructures may be performed via the use of IWUs, hidden within the domains shown in the figure.

Figure 1: UMTS domains and reference points

Cu = Reference point between USIM and ME

Iu = Reference point between Access and Serving Network domains

Uu = Reference point between User Equipment and Infrastructure domains, UMTS radio interface

[Yu] = Reference point between Serving and Transit Network domains

[Zu] = Reference point between Serving and Home Network domains

5.1 Domain split

A basic architectural split is between the user equipment (terminals) and the infrastructure. This results in two domains: the User Equipment Domain and the Infrastructure domain.

User equipment is the equipment used by the user to access UMTS services. User equipment has a radio interface to the infrastructure. The infrastructure consists of the physical nodes which perform the various functions required to terminate the radio interface and to support the telecommunication services requirements of the users. The infrastructure is a shared resource that provides services to all authorised end users within its coverage area.

The reference point between the user equipment domain and the infrastructure domain is termed the "Uu" reference point (UMTS radio interface).

NOTE: The description assumes an access interface based on UTRA. However, the physical and functional separation described in this document is general and is applicable also if other access technologies are used.

5.2 User equipment Domain

This domain encompasses a variety of equipment types with different levels of functionality. These equipment types are referred to as user equipment (terminals), and they may also be compatible with one or more existing access (fixed or radio) interfaces e.g. dual mode UMTS-GSM user equipment. The user equipment may include a removable smart card that may be used in different user equipment types. The user equipment is further sub-divided in to the Mobile Equipment Domain (ME) and the User Services Identity Module Domain (USIM).

The reference point between the ME and the USIM is termed the "Cu" reference point.

For the purpose of UMTS Cellular networks the following definition applies:

User Equipment is a device allowing a user access to network services. For the purpose of 3GPP specifications the interface between the UE and the network is the radio interface. A User Equipment can be subdivided into a number of domains, the domains being separated by reference points. Currently defined domains are the USIM and ME Domains. The ME Domain can further be subdivided into several components showing the connectivity between multiple functional groups. These groups can be implemented in one or more hardware devices. An example of such a connectivity is the TE – MT interface. Further, an occurrence of User Equipment is an MS for GSM as defined in TS 24.002 [3].

The figure below shows the Functional Model for the User Equipment, UE.

Figure 1a: Functional Model for the User Equipment

The 07- and 27-series refer to physical instances of this Functional Model. The figure below shows an example of a physical configuration as it could be used in these specifications. The boxes, in this figure, refer to physical elements. The names within brackets are just provided to map the functional blocks from the figure above onto physical elements.

Figure 1b: Example of physical configuration

5.2.1 Mobile equipment Domain

The Mobile Equipment performs radio transmission and contains applications. The mobile equipment may be further sub-divided into several entities, e.g. the one which performs the radio transmission and related functions, Mobile Termination, MT, and the one which contains the end-to-end application or (e.g. laptop connected to a mobile phone), Terminal Equipment. TE. This separation is used in the description of the functional communication in figure 3 but no reference point is defined in this specification.

5.2.2 USIM Domain

The USIM contains data and procedures which unambiguously and securely identify itself. These functions are typically embedded in a stand alone smart card. This device is associated to a given user, and as such allows to identify this user regardless of the ME he uses.

5.3 Infrastructure Domain

The Infrastructure domain is further split into the Access Network Domain, which is characterised by being in direct contact with the User Equipment and the Core Network Domain. This split is intended to simplify/assist the process of de-coupling access related functionality from non-access related functionality and is in line with the modular principle adopted for the UMTS.

The Access Network Domain comprises roughly the functions specific to the access technique, while the functions in the Core network domain may potentially be used with information flows using any access technique. This split allows for different approaches for the Core Network Domain, each approach specifying distinct types of Core Networks connectable to the Access Network Domain, as well as different access techniques, each type of Access Network connectable to the Core Network Domain.

The reference point between the access network domain and the core network domain is termed the "Iu" reference point.

NOTE: The split into the User Equipment Domain, the Access Network Domain and the Core Network Domain is consistent with the GMM report.

5.3.1 Access Network Domain

The Access Network Domain consists of the physical entities which manage the resources of the access network and provides the user with a mechanism to access the core network domain.

Additional reference points within the access domain may be identified in other specifications.

5.3.2 Core Network Domain

The Core Network Domain consists of the physical entities which provide support for the network features and telecommunication services. The support provided includes functionality such as the management of user location information, control of network features and services, the transfer (switching and transmission) mechanisms for signalling and for user generated information.

[Note: Much more could/should be written about the reference points between the core network and other networks].

The core network domain is sub-divided into the Serving Network Domain, the Home Network Domain and the Transit Network Domain.

The reference point between the serving network domain and the home network domain is termed the [Zu] reference point.

The reference point between the serving network domain and the transit network domain is termed the [Yu] reference point.

Additional sub-divisions and reference points within the core network domain may be identified in other specifications. Serving Network Domain

The serving network domain is the part of the core network domain to which the access network domain that provides the user’s access is connected. It represents the core network functions that are local to the user’s access point and thus their location changes when the user moves. The serving network domain is responsible for routing calls and transport user data/information from source to destination. It has the ability to interact with the home domain to cater for user specific data/services and with the transit domain for non user specific data/services purposes. Home Network Domain

The home network domain represents the core network functions that are conducted at a permanent location regardless of the location of the user’s access point.

The USIM is related by subscription to the home network domain. The home network domain therefore contains at least permanently user specific data and is responsible for management of subscription information. It may also handle home specific services, potentially not offered by the serving network domain.

NOTE: Most of the functionality associated with the service provider role according to the UMTS role model (ref UMTS 22.01), is normally contained within the home network domain. Transit Network Domain

The transit network domain is the core network part located on the communication path between the serving network domain and the remote party. If, for a given call, the remote party is located inside the same network as the originating UE, then no particular instance of the transit domain is activated.