15.2 RTP payload type negotiation at network side of IWF
29.0073GPPGeneral requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)Release 17TS
If a call is determined to be a data call other than faxsimile or Modem (i.e. TMR "UDI") by the offerer, the SDP offer shall contain a single m-line with only the CLEARMODE payload type (see IETF RFC 4040 [92]).
If a call is determined to be a faxsimile or Modem call by the offerer, the SDP offer shall contain an m-line including only the PCM codec. For faxsimile, the offer may include an additional m-line including the t38 payload type (see ITU-T Recommendation T.38 [96] and IETF RFC 3362 [97]).
If an offerer is not able to determine if a call is a data call or a speech call (TMR "3.1 kHz Audio"), it shall only offer speech codec(s) including the PCM codec. If the PCM codec is offered in combination with other speech codecs, the OoBTC procedures in Clauses 6.12 and 9.3 of TS 23.153 [91] are applicable,
For SCUDIF (see TS 23.172 [83]), the "vnd.3gpp.clearmode" RTP payload type (see Annex C) shall be offered together with speech codec(s) in a single SDP m-line. The OoBTC procedures in Clause 9.3 of TS 23.153 [91] are applicable.
Annex A (informative):
SDLs
The following SDLs are intended to assist in the interpretation of the text in subclause 10.2.2 and are not intended to indicate implementation requirements. Therefore these SDLs are informative only.
Figure A.1 (Sheet 1 of 1): Procedures in the HLR
Figure A.2 (Sheet 1 of 1): Procedures in the MSC/VLR
Annex B (informative):
General mapping of V.24 circuits to channel status bits
In the data transfer state, status bits SA, SB and X can be used to convey channel control information associated with the data bits. Table C1 shows the general mapping scheme between the V.24 circuit numbers and the status bits in the IWF. A binary 0 corresponds to the ON condition, a binary 1 to the OFF condition. The specific mappings for the various PLMN bearer types are given elsewhere in the present document.
Since the V.24 circuits that are outputs from a DCE are inputs to a DTE (and vice versa), this mapping is the reverse of that used in the MT (3GPP TS 27.002, 3GPP TS 27.003).
For example, CT 109 is an output from the modem in the IWF and maps on to SB towards the MT. In the MT, SB is mapped on to CT 109 which is an input to the attached DTE.
Table B1: General mapping scheme at the IWF
|
Status bit |
Status bit |
Signal at IWF modem interface |
|
SB |
105 (note 3) |
|
|
X (note 1) |
106 |
|
|
SA |
107 |
|
|
SA |
108 |
|
|
SB |
109 |
|
|
X |
133 (notes 2 and 3) |
|
|
NOTE 1: The condition of X towards the UE may also be affected by the state of any transmit buffer in the IWF. NOTE 2: The condition of CT 133 towards the modem may also be affected by the state of any receive buffer in the IWF or layer 2 flow control condition between the MT and IWF. NOTE 3: CT105 and CT133 are assigned to the same connector pin on both the standard 25 pin connector (ISO/IEC 2110 [78]) and the commonly used 9 pin connector (annex B). When this pin is used for CT133 at the DTE/MT interface then on the MT side of the interface CT 105 is treated as being always in the ON condition. SB towards the IWF will therefore also always be ON. Similarly, when this pin is being used for CT105 then on the MT side of the interface CT 133 is treated as being always in the ON condition. X towards the IWF will therefore also always be ON. As circuit 133 is used only in duplex operation and circuit 105 is used only in half duplex operation (which is not supported by the PLMN) there should be no conflict. |
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Annex C (normative):
RTP payload type for SCUDIF in SIP-I based CS core network