9 Function and information flows

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

The following functional flows deal with the initial phase of CTS where roaming is not supported. In this case the DPLMN, HPLMN and the CTS operator need to be the same. If they are the same then this allows the CTS reference model to be simplified as the CTS FRA can be integrated in to the CTS SN thus simplifying the signalling model. The CTS specifications shall provide means to ensure that DPLMN, HPLMN and CTS operator are the same entity.

When there is no indication on the status of the CTS frequencies (i.e. licensed or licensed exempt), the following recommendations are applicable to all cases.

9.1 CTS FP management

9.1.1 CTS FP Initialisation

CTS FP initialisation can be envisaged in two phases.

The data flow diagram below shows the flows required for CTS FP initialisation.

Figure 9: CTS FP initialisation

1 The CTS-FP subscriber wants to initialise a CTS-FP. He triggers an MMI procedure. The CTS-SN telephone number is used by the CTS-FP to contact the CTS-SN. The IFPSI is given to the CTS-SN.
The CTS-SN authenticates the CTS-FP by addressing the CTS-HLR using the IFPSI.

2 In absence of location information the CTS-FRA allocates a temporary GFL.
The CTS-FP is temporarily initialised. Confirmation of the initialisation is performed in future signalling when location information can be provided and a correct GFL allocated.

9.1.2 Update of CTS FP frequencies

The data flow diagrams below shows the flows required for gathering the DPLMN surrounding cells and the updating the CTS FP GFL.

Figure 10: CTS MS Home cell reporting

1 The CTS MS remembers the cells it last camped on from the DPLMN and the time it left each cell.

2 This cell information is given to the CTS FP during signalling exchanges during attachment for example.
In addition if the MS has received a CTS-SN Telephone Number (see 9.2 CTS management for CTS MS) from the DPLMN then this will also be given.

Figure 11: CTS FP update

1 The CTS-FP calls the CTS-SN.
If a CTS-SN Tel No has been received from the DPLMN, then this number is used.

2 Authentication of the CTS FP is made by the CTS SN and HLR

3 DPLMN information is given by the CTS FP for location purposes

4 GFL is updated and the CTS-FP authenticates the CTS-SN.
This procedure also forms part of the CTS-FP initialisation procedure where the Temporary GFL (allocated during the first initialisation) is replaced by the GFL based on location information.

9.2 CTS management for CTS MS

The GSM PLMN controls the MS as to whether it can operate CTS. When the CTS-MS access the GSM PLMN it will receive signalling which informs the CTS-MS whether it can perform CTS operations.

Figure 12

1 The MS performs a location update in the DPLMN.

2 Authentication is performed.

3 If CTS is allowed in the PLMN, or this particular MS has the CTS subscription then the MSC sends CTS info to the MS. The CTS-SN Tel No is optional and indicates the telephone number for this LA/Cell to which The CTS-FP should contact.

4 The location update is accepted.

9.3 CTS integration to Fixed Mobile Convergence applications

In order to use CTS for FMC applications it is suggested that a hook be provided in order to facilitate FMC applications. To this end it is envisaged to allocate a FMC Telephone Number, for instance on the CTS-FP SIM.

9.4 Functions related to MS in idle mode for support of CTS

9.4.1 Cell selection and reselection

The definition of a "suitable cell", as defined in GSM 03.22, is extended with the following criterion:

An CTS-MS with SIM indicating CTS subscription shall always try to select the cell with the highest CTS FP priority according to the information stored on the SIM. The CTS selection parameters last received from the CTS FP shall be used to calculate the selection criteria for the corresponding CTS cell.

9.4.2 DPLMN Cell information gathering

As the CTS-MS roams through the DPLMN it shall gather information as to the cells it has passed through. This cell information is stamped with the time that the MS either left the cell or lost GSM coverage with the cell. The figure below shows the required functional behaviour.

When the CTS-MS gives this information to the CTS-FP the time information is presented by using the relative time (for example: Cell X was last camped on 5 minutes ago).

Figure 13: DPLMN cell information gathering

In this figure the cells reported to the CTS FP are as follows:

  • Cell D left at T-td
  • Cell C left at T-tc
  • Cell B left at T-tb
  • Cell A left at T-ta

9.4.3 CTS local mobility

The presence and absence of a CTS-MS needs to be determined by the CTS-FP as part of the local CTS mobility procedures.

9.4.3.1 CTS attachment

CTS attachment is a procedure by which a CTS-MSs presence is made known to the CTS-FP. The attachment to a CTS-FP is made by the CTS-MS when the CTS-MS comes within coverage of the CTS-FP.

The CTS Attach procedure shall replicate the protocol as expected as in GSM, with the exceptions to the local security procedures defined in [4].

Figure 14: CTS Attachment

1 The CTS-MS comes within coverage of the CTS-FP and initiates attachment.

2 Local authentication is performed see ([4]).

3 The CTS attachment is accepted.

9.4.3.2 CTS detachment

CTS detachment is a procedure by which a CTS-MSs non presence is made known to the CTS-FP. When a CTS-MS is attached the CTS-FP shall regularly ensure that the CTS-MS is within CTS-FP coverage, if the CTS-MS is found to be out of coverage the CTS-FP will mark the CTS-MS as detached. If the MCTS-MS is powered down within coverage of the CTS-FP the CTS-MS shall perform the CTS detach procedure.

Figure 15: CTS MS detachment

1 The CTS-MS when powered down within coverage of the CTS-FP indicates that it no longer is attached.

Figure 16: CTS-FP detected detachment of CTS-MS

  1. The CTS-FP pages and finds that the MS is not present. The CTS-MS is marked as detached.

9.5 Functions related to active mode support of CTS

9.5.1 MS connection establishment for MT and MO calls.

When calls are established the CTS FP shall perform Authentication and Ciphering as specified in 03.20.

9.5.2 Handover

Handover between instances of CTS radio interfaces shall be supported by the CTS MS when the same CTS FP controls these CTS radio interfaces.

9.6 Overview of signalling

Security procedures such as authentication, ciphering and key distribution are defined in order to protect the GSM network and the user communication. CTS operation is initialised by downloading operation control information into the CTS-FP. The operator can change and de-activate CTS operation via the GSM Radio Interface or via the access network.