4 Additional network functions for call handling

03.013GPPNetwork FunctionsTS

4.1 Queuing

As a PLMN option MS originating and/or MS terminating calls may be queued at the BSS. (NOTE: this queuing is additional to that for normal call handling). However, the following condition must be met:

– for MS terminating calls the queuing must not conflict with abnormal release conditions in the fixed network. In general, calls that may have passed international circuits should not be queued, i.e. it should not be applied to calls where the originating network is not known to the PLMN.

4.2 Off-Air-Call-Set-Up (OACSU)

4.2.1 General

OACSU may be implemented in PLMNs in order to increase the call handling capacity of the PLMN.

OACSU may be implemented in PLMNs on an optional basis subject to the following conditions:

i) OACSU should not be used for calls to an international number;

ii) OACSU should not be used for incoming international calls, except where bilateral agreement has been reached to allow such an application of OACSU. For the avoidance of doubt, OACSU shall not be applied to calls where the call type or originating network is not known by the PLMN;

iii) foreign MSs not supporting the OACSU procedure should be allowed to access the PLMNs where OACSU is used;

iv) MSs supporting OACSU should be capable of operating in PLMNs where OACSU is not implemented;

v) OACSU should only be used for telephone calls.

4.2.2 Signalling procedures

Signalling procedures supporting OACSU are specified in Technical Specification GSM 04.08.

4.3 Security related services

PLMNs will offer three security related services on the radio path: confidentiality of the user identity, confidentiality of user data and confidentiality of signalling information elements and connectionless user data.

4.3.1 Identity confidentiality

This service provides for the privacy of the identities of subscribers. An intruder cannot identify which subscriber is using a certain resource on the radio path. Instead of IMSI a temporary identity is used.

4.3.1.1 Circuit switched services

This identity (TMSI) is a local number only valid in a given location area. The TMSI is allocated by the VLR and is sent to the MS in a ciphered mode, when ciphering is available as a network option. The IMSI and IMEI should also be transmitted in ciphered mode, whenever the procedure allows this, and when ciphering is available as a network option.

The structure of the TMSI is defined in Technical Specification GSM 03.03.

4.3.1.2 Packet switched services

The packet temporary mobile subscriber identity (P-TMSI) is a local number only valid in a given routing area. The P-TMSI is allocated by the SGSN and is sent to the MS in a ciphered mode, when ciphering is available as a network option.

The structure of the TLLI is defined in Technical Specification GSM 03.03.

4.3.2 User data confidentiality

This service provides for the confidentiality of anything transmitted on a traffic channel.

4.3.2.1 Circuit switched services

Encryption/decryption is done in the MS and BSS with a key which is calculated in both the MS and network. Detailed information is given in Technical Specification GSM 03.20.

4.3.2.2 Packet switched services

Encryption/decryption is done in the MS and SGSN with a key which is calculated in both the MS and network. Detailed information is given in Technical Specification GSM 03.20.

4.3.3 Signalling Information Element Confidentiality

This service provides for the confidentiality of anything transmitted on a signalling channel

4.3.3.1 Circuit switched services

Signalling information to control the service offered to a subscriber or connectionless user data can be encrypted/decrypted. Encryption/decryption is done in the MS and BSS with a key which is calculated in both the MS and the network. Detailed information is given in Technical Specification GSM 03.20.

4.3.3.2 Packet switched services

Signalling information to control the service offered to a subscriber can be encrypted/decrypted. Encryption/decryption is done in the MS and SGSN with a key which is calculated in both the MS and the network. Detailed information is given in Technical Specification GSM 03.20.

4.4 Discontinuous Reception

Discontinuous reception is a technique used to reduce the battery consumption ofMSs. The operation of the technique is specified in Technical Specification GSM 03.13. This function must be supported by the network, but is optional forMSs.

4.5 Discontinuous Transmission

Discontinuous transmission is a technique used to reduce overall interference level on the radio interface, and to reduce the battery consumption in the MSs. The operation of the technique is specified in Technical Specification GSM 05.08. This function must be supported by the MSs, whereas only the receiver requirements are mandatory in the network.

4.6 Support of DTMF

DTMF is supported as defined in Technical Specification GSM 03.14.