10 CTS Architecture

03.563GPPCTS Architecture DescriptionGSM Cordless Telephony System (CTS), Phase 1Stage 2TS

10.1 CTS Elements

10.1.1 CTS Fixed Part

CTS Fixed Part (CTS-FP) is the logical and physical element, which provides the link to the access network. For this purpose it controls on the one side one or more CTS Radio Interface and on the other side one or more access network interface. The interworking between both interfaces is implemented in the CTS-FP interworking Function.

Figure 17: The CTS-FP and its main functional entities

Figure 17bis: The CTS-FP connected to GSM

10.1.2 CTS Mobile Station

The CTS Mobile Station (CTS-MS) is the logical and physical element which provides to the user cordless access to the fixed network or the GSM network. The CTS-MS consists of GSM Mobile Equipment and a GSM-SIM, both with additional CTS capabilities.

Figure 18: The CTS-MS and its main functional entities

10.1.3 CTS controlling and supporting network entities

In order to control and support the CTS, the following functional entities are situated in the GSM network:

  • the CTS-AuC is the functional entity for performing authentication of the CTS-FP SIM;
  • the CTS-HLR is the functional entity which contains the data base of the CTS-FP subscribers of the CTS operator. This data base is related to subscription management (including related security control). It may contain additional information, e.g. subscriber specific CTS operation information;
  • the CTS-SN is mainly a routing functionality. It provides the interface to the CTS-FP(s) via the access network. The CTS SN also provides the security functions for secure signalling of CTS specific operation information on the CTS access network interface;
  • the CTS FRA is considered to be the location of frequency allocation for the CTS operation.

Figure 19: CTS supporting functional entities

10.2 CTS Interfaces

10.2.1 CTS Radio Interface (Um*)

The CTS Radio Interface is used for local communication between CTS MS and the CTS FP. It provides a cordless connection between these two elements. This interface is referred to as Um* in the CTS specifications.

According to GSM 02.56 [2], the CTS Radio Interface is a modified GSM Radio Interface. CTS is to operate in the GSM frequency spectrum of the DPLMN operator or in an license exempt frequency band.

The physical characteristics of the CTS Radio Interface are similar to those of the GSM Radio Interface. The aspects of the radio interface are described in [5].

The Um* interface shall be future proof to support services to be implemented in later phases such as data and fax services etc.

10.2.2 GSM Radio Interface (Um)

On the GSM Radio Interface the CTS-MS shall behave according to the GSM standards. As required in GSM 02.56 [2], means of the GSM Radio Interface shall be used to exchange information relevant for operation control of the CTS. User communication via the GSM Radio Interface is covered by the GSM specifications and not considered in the CTS specifications. The GSM Radio Interface is referred to as Um in the CTS specifications.

10.2.3 CTS Access Network Interface

The Access Network Interface is the connection of the CTS-FP to the Fixed or mobile Network for user communication. According to GSM 02.56 [2], this interface shall also be used to transport information which is relevant for operation control. The Fixed Network Interface is referred to as Cf in the CTS specifications.

10.2.3.1 Physical characteristics of the CTS Fixed Network Interface

The physical characteristics of the Fixed Network Interface, e.g. signal levels, shall correspond to national standards.

10.2.3.2 Physical characteristics of the CTS GSM Network Interface

In the case of a CTS-FP connected to GSM, the physical characteristics of the GSM Network Interface, e.g. signal levels, shall correspond to GSM standards.

10.2.4 Network internal interfaces

10.2.4.1 Interface CTS SN/CTS HLR (Cd)

The Cd interface between the CTSSN and the HLR may use existing MAP procedures to receive challenge/response pairs to be used for the authentication of the CTS FP SIM when communication is performed via the access network.

10.2.4.2 Interface CTS SN/CTS HLR (Cd’)

Cd’ interface between CTS SN and CTS HLR. The interface is used for CTS FP subscription control.

10.2.4.3 Interface CTS SN/CTS FRA

This interface is used when download of radio parameters shall be performed to the CTS-FP via application signalling.

10.2.4.4 Interface CTS FRA/BSC

This interface is used when download of radio parameters shall be performed to the CTS-FP via GSM layer 3 signalling.

10.3 CTS sub-systems

The CTS can be split in two subsystems, the local CTS and the supervising CTS:

  • the local CTS consists of a CTS-FP and one or several CTS-MS, which are enrolled at the CTS-FP.
    The main aspect of the local CTS is that the user communication is provided via the CTS Radio interface and the CTS Access Network Interface;
  • the supervising CTS consists of the functional entities to control CTS operation. The main aspect of the supervising CTS is the control of the operation of the local CTS such as:
  • control of the frequencies used by the CTS-FP on the CTS Radio Interface;
  • control of the CTS FP subscription (of the SIM) of the CTS FP;
  • control of the CTS MS subscription (of the SIM) of the CTS MS.

Figure 20: CTS Subsystems

10.4 Network Access

As the purpose of the CTS, the Access Network is accessed by the CTS-MS via the CTS-FP for user communication.

A CTS-MS can, depending on services subscribed, access the GSM network for user communication. This case is covered by the GSM specifications and not considered in the CTS specifications.

According to GSM 02.56 [2], control of the CTS operation can be carried out either via the GSM Network or via the Access Network. In the latter case the Access Network is as a transit network CTS operation control.

A co-ordination between the GSM Network and the Access Networks is not required.