C.5 Service interactions
23.2263GPPGlobal Text Telephony (GTT)Release 17Stage 2TS
C.5.1 Interaction with other CAMEL services
The text users can use other CAMEL services. However, with other CAMEL services using the same Detection Point as the Text Telephone service, the other CAMEL services are impacted when using CAMEL Phase 1 as presented in this document.
As for the impact on existing CAMEL services, some of the services may be impacted anyway to support text users, for example Prepaid for playing announcement in text telephone signals.
Every CAMEL service, which is expected to be used by both voice and text users, and use the same CAMEL detection point as the GTT service, is assigned two SKs, one for non-text users and another for text users. For text users the other service logic has to integrate CTM-SCP routing logic.
C.5.2 Interactions with Supplementary Services
In general, no other interactions are expected than described in the CAMEL standard.
Call Forwarding in GMSC is invoked after terminating CAMEL service invocation. This means the CTM-SRF service node is already linked in the call path. A further invocation of a mobile originated CAMEL based service will cause an additional routing to a CTM-SRF service node. This is needed to convert the text back to text telephone coding, e.g. Baudot, which is required for the following routing towards the forwarded-to-party (C-party).
C.5.3 Emergency Call interaction
New emergency call categories introduced in 3GPP Release 4 (introduced as emergency-call enhancement) have no impact on routing of emergency calls via CTM-SRF server.
New categories may be specified in order to detect text emergency calls.
C.5.4 Usage of Destination Routing Address
The Destination Routing Address CAMEL parameter is used by the service logic for two purposes.
– It contains the CTM-SRF server address to let the MSC to route the call to the CTM-SRF server.
– It contains the original B-subscriber address, to let the CTM-SRF server to use it as Called Party Number on the outgoing side.
When the service logic reconnects the CTM-SRF server, the service has to save the Nature of Address and the Numbering Plan Indicator of the original Called Party Number in the Destination Routing Address parameter.
CAMEL Phase 1 Destination Routing Address has up to 12 octets. Two octets are needed to encode Nature of Address and the Numbering Plan Indicator. This means that 10 octets are left for CTM-SRF server address digits plus Called Party Address digits. All together 20 digits are given.
An international one up to 15 digits according E.164. This results in having 5 digits left for CTM-SRF server addressing.
C.5.5 Inserting CTM/Text telephone conversion function
The CTM/Text telephone conversion function is direction oriented. A CTM modem should be connected towards the radio side and a modem for ITU‑T Recommendation V.18 [4] or any of its text telephone submodes towards the other direction. Therefore the CTM-SRF server has to distinguish between mobile terminating and mobile originating calls.
This can be achieved by either allocating different channels for the directions or make decision based on the Called number to the CTM-SRF.
C.5.6 Lawful interception
Depending on where on the route the intercept is made, and also depending on the support for CTM in the terminal, the coding in the intercept point will be transmitted in CTM modulation and coding, or native PSTN text telephone coding and modulation. Both are possible to decode, and a combined decoder can be designed.
NOTE: In some countries it is required that all PLMN specific codings are decoded before the lawful interception. In this case operators must upgrade their lawful interception equipment.
Annex D (informative):
Change history
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Change history |
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|
Date |
TSG # |
TSG Doc. |
CR |
Rev |
Cat |
Subject/Comment |
Old |
New |
|
2004-12 |
SP-29 |
– |
Upgraded to Release 6 |
5.2.0 |
6.0.0 |
|||
|
2006-03 |
SP-31 |
SP-060139 |
0003 |
– |
– |
Update of three references on real time text |
6.0.0 |
7.0.0 |
|
2008-12 |
SP-42 |
– |
– |
– |
Updated to Rel-8 version (MCC) |
7.0.0 |
8.0.0 |
|
|
2009-12 |
SP-46 |
SP-090795 |
0005 |
2 |
F |
Correction to introduce interworking and emergency aspects of GTT-IP |
8.0.0 |
9.0.0 |
|
2011-03 |
SP-51 |
– |
– |
– |
– |
Update to Rel-10 version (MCC) |
9.0.0 |
10.0.0 |
|
2012-09 |
– |
– |
– |
– |
– |
Update to Rel-11 version (MCC) |
10.0.0 |
11.0.0 |
|
2014-09 |
SP-65 |
– |
– |
– |
– |
Update to Rel-12 version (MCC) |
11.0.0 |
12.0.0 |
|
2015-12 |
– |
– |
– |
– |
– |
Update to Rel-13 version (MCC) |
12.0.0 |
13.0.0 |
|
2017-03 |
– |
– |
– |
– |
– |
Update to Rel-14 version (MCC) |
13.0.0 |
14.0.0 |
|
2018-06 |
SP-80 |
– |
– |
– |
– |
Update to Rel-15 version (MCC) |
14.0.0 |
15.0.0 |
|
2020-07 |
SP-88E |
– |
– |
– |
– |
Update to Rel-16 version (MCC) |
15.0.0 |
16.0.0 |
|
2022-03 |
SP-95E |
– |
– |
– |
– |
Update to Rel-17 version (MCC) |
16.0.0 |
17.0.0 |