1、 TIA STANDARD Transport of TIA-825-A Signals over IP Networks TIA-1001 October 2004 TELECOMMUNICATIONS INDUSTRY ASSOCIATION The Telecommunications Industry Association represents the communications sector of NOTICE TIA Engineering Standards and Publications are designed to serve the public interest
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14、EIN, INCLUDING WITHOUT LIMITATION ANY AND ALL INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES (INCLUDING DAMAGES FOR LOSS OF BUSINESS, LOSS OF PROFITS, LITIGATION, OR THE LIKE), WHETHER BASED UPON BREACH OF CONTRACT, BREACH OF WARRANTY, TORT (INCLUDING NEGLIGENCE), PRODUCT LIABILITY OR OTHERW
15、ISE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. THE FOREGOING NEGATION OF DAMAGES IS A FUNDAMENTAL ELEMENT OF THE USE OF THE CONTENTS HEREOF, AND THESE CONTENTS WOULD NOT BE PUBLISHED BY TIA WITHOUT SUCH LIMITATIONS. i Transport of TIA-825-A signals over IP Networks CONTENTS 1 Scope . 1 2 N
16、ormative References . 1 3 Definitions. 2 3.1 Version of Standard 3 4 Abbreviations 3 5 Textphone-Over-IP Functions. 3 5.1 Signal Converter. 4 5.2 Codec 4 5.3 T.140 encode/decode 4 5.4 RFC 2793 bis 4 5.5 RTP 4 5.6 UDP 4 5.7 Optional Functions . 4 5.7.1 SSE Protocol 4 5.7.2 SPRT IP-TLP. 4 6 Connection
17、 and Network Scenarios 5 6.1 Service and Performance requirements for TIA-1001 . 5 6.2 Audio and Text functionality . 5 6.2.1 Text in Both Directions 5 6.2.2 Text and Voice Alternating in opposite directions 5 6.2.3 Text and Voice Alternating in the same direction . 5 6.3 Interactive Voice Response
18、System and DTMF signalling Support 5 7 Transport Methods 5 7.1 Audio Mode 5 7.2 VBD Mode . 6 7.3 Text Relay Mode 6 8 VBD Operation 6 9 Text Relay Operation 6 9.1 IP Transport for Text Relay 6 9.2 Text Relay Throughput 6 9.3 TIA-825-A encoding requirements 6 9.4 Cleardown in Text Relay 6 9.5 Optional
19、 use of SPRT. 7 10 Gateway to Gateway Protocol definitions and procedures 7 11 Gateway Capability and Call Set-up messages . 7 11.1 TIA-1001 Version 7 11.2 VBD parameters. 7 12 SSE Reason Identifier Codes. 7 13 Call Set up procedures. 7 14 Call discrimination procedures 7 15 Call Discrimination SDL
20、Diagrams 8 15.1 SDL for Payload Type Switching 8 15.2 SDL for optional SSE. 10 Annex A (normative) . 15 Annex B (normative) . 18 Annex C (normative) . 19 Annex D (informative). 20 Annex E (informative) . 24 Annex F (informative) . 25 iii FORWARD (This forward is not part of this Standard) This Stand
21、ard was developed by TIA technical sub-committee TR-30.1, Modems, under project number PN-3-0098. TIA-1001 1 1 Scope This Standard defines the requirements for the reliable transport, using Text Relay, of Textphones using TIA-825-A signals, and other signaling associated with Baudot TDDs, across IP
22、networks that connect two or more PSTNs (Figure 1). The Standard describes the functionality of Text Telephony Gateways, which connect between the PSTN and an IP network. This Standard also provides the ability for switching between TIA-825-A signals and voice during a call. The Standard defines Tex
23、t Relay for TIA-825-A to TIA-825-A Textphone connections with Voice Band Data (VBD) being supported only as a means to support connections that include at least one non TIA-825-A terminal or one gateway that does not support TIA-1001 or ITU-T Recommendation V.151. Figure 1 Typical TIA-1001 Applicati
24、on 2 Normative References The following standards contain provisions which, through reference in this text, constitute provisions of this Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this Standard a
25、re encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. ANSI and TIA maintain registers of currently valid national standards published by them. TIA-825-A, A Frequency Shift Keyed Modem For Use On The Public Switched Telephone Network ITU-T
26、 F.703, Multimedia conversational services ITU-T H.245, Control protocol for multimedia communication ITU-T H.323, Packet-Based Multimedia Communications Systems ITU-T T.140, Protocol for multimedia application text conversation ITU-T V.18, Operational and interworking requirements for DCEs operatin
27、g in the text telephone mode. ITU-T V.150.0, Modem-over-IP networks: Foundation IP NetworkPSTN Network PSTN Network TDD using TIA-825-A TDD usingTIA-825-A Text TelephonyGatewayText TelephonyGatewayTIA-1001 2 ITU-T V.150.1, Procedures for the end-to-end connection of V-series DCEs over an IP network
28、ITU-T V.152 (draft), Procedures for supporting Voice-Band Data over IP networks T1.209-2003, Operations, Administration, Maintenance, and Provisioning (OAM this is optional and cannot be relied upon. The default condition for transmitting into the PSTN shall be 45.45bit/s. This rate can be changed t
29、o 50 bit/s if it is discovered that the terminal is operating at 50 bit/s. The only dependable portion of a signal for the detection of TIA-825-A is receiving a space frequency for 22ms. This is an 1800Hz tone and there are other occurrences of the use of 1800Hz as modem tone (i.e. V.22 bis, V.32 an
30、d V.34). However, due to restrictions in modem start-up procedures these will not occur without other tonal signals causing a response. It is reasonable to expect that detection of an unprovoked 1800Hz tone is indicative of a TIA-825-A text telephone. The transmission of characters using TIA-825-A i
31、s carrierless. That is each key depression on the text telephone causes the transmission of a complete character including start and stop bits. Depending upon the rate of character input either single or concatenated characters may be received from the TDM side of a gateway. Concatenated characters
32、may occur when characters have been pre-recorded such as text based IVR. A first character is defined as the first received in any N-block of characters, where N is =1. A TIA-1001 Gateway shall not cause the deletion or insertion of text characters from the TDM to IP side when supporting text teleph
33、ony transmission by VBD or Text Relay. The method of discrimination of a TIA-825-A signal is implementation specific. The principle requirement during the discrimination procedure is to detect and verify reliably the presence of TIA-825-A within a maximum time. The discrimination should prevent exce
34、ssive leaking of the TIA-825-A signal. The maximum amount of leakage is based upon ensuring that a complete character is not transmitted to the remote terminal. Therefore maximum leakage time is one character time minus one bit time. E.g., For TIA-825-A 45.45 bit/s then this is (7-1)*(1/45.45) = 132
35、 ms. 15 Call Discrimination SDL Diagrams This section provides the SDL processing description for the procedures defined by the call discrimination call flows as described in Annex D. The SDL diagram definitions are the same as used in ITU-T Recommendation V.150.1. 15.1 SDL for Payload Type Switchin
36、g The SDL diagrams in Figures 3 5 represent the procedures for the default mode of operation using Payload Type Switching. For Payload Type Switching mode there are three defined states: Audio (a) VBD (v) Text Relay (t) TIA-1001 9 (a)Tone1800State (a)(a)UnrecognizedLine signal(v )ReceivedT.140Charac
37、terfrom modemPT=TRPT=audiosilencePT=TR(t)PT=VBDPT=VBDPT=VBDPreferredmode isVBDPT=VBD(v )NOYESFigure 3 SDL for PTS State a PT=Speech(a)(v)State (v)Figure 4 SDL for PTS State v TIA-1001 10 (t)Send T.140character(t)Drop BaudotCarrier onTDM(a)ReceiveT.140CharacterPT=SpeechReceiveT.140characterfrom Modem
38、PT=SpeechSend T.140character tomodemlast charplayedout bymodemPT=SpeechYESNOPT=VBDlast charplayedout bymodemPT=VBD(v)(t)NOYESState (t)Figure 5 SDL for PTS State t 15.2 SDL for optional SSE The SDL diagrams in Figures 6 13 define the procedures when using optional SSE. The states are defined from the
39、 viewpoint of a gateway of its own state (o) and the perceived state (p) of the peer gateway. The state is presented as (o,p). The following modes are defined: Audio (a) Text Relay (t) VBD (v) TIA-1001 11 (a,a)TIA-825ATonesdetected(t,a)(t,a, TIA-825)SSE:t(TIA-825)(t,t)(t,t,p)UnrecognizedLine signalR
40、C=UKN(v ,a)(v,a,RC)For a TIA-1001 onlygateway , any unrecognizedline signal can be used toinitiate a transition to VBD.SSE:v (RC)(v ,v )(v,v, p)Preferredmode isVBD(v ,a)NOYES(v,a, TIA-825)Block ToneFigure 6 SDL for SSE State (a,a) (t.a)SSE:T(p)(t,t)Stop Timer(a,a)SSE:v(UKN)vs (t,v)ts SSE:a(RC)as Sto
41、p TimerFigure 7 SDL for SSE State (t,a) TIA-1001 12 (t.t)Send T.140character(t.t)Drop BaudotCarrier onTDM(a.t)(a,t, NULL)SSE:a(NULL)(a,a)ReceiveT.140Character(a,a, p)UnrecognizedLine signalRC=UKN(v,t)(v,t,RC)Figure 8 SDL for SSE State (t,t) CharacterPlayedout(v ,v , p)(v ,v )Yes(t,v )No(t,v )Figure
42、9 SDL for SSE State (t,v) TIA-1001 13 (a.t)SSE:a(p)(a,a)Stop Timeras Figure 10 SDL for SSE State (a,t) (v,a)SSE:v(p)(v,v)SSE:a(RC)vs Stop TimerSSE:t(RC)(a,i)(a,a,p)(a,i,RC)EOPStop TimerOverride back toaudioUnexpectedResponseFigure 11 SDL for SSE State (v,a) TIA-1001 14 (v,t)SSE:v(p)(v,v)Stop Timervs
43、 Figure 12 SDL for SSE State (v,t) (*,*)AbortRequestRC=ABORTSSE:a(RC)(a,i)is as Timer Expired(a,i)is as Figure 13 SDL for SSE All State (*,*) TIA-1001 15 Annex A (normative) Definition of Capabilities for Use within H.245-Based Systems H.323 systems have a means of advertising the ability to transpo
44、rt text over RTP using the “t140” capability defined in H.245. However, this capability does not provide a means to advertise supported modulations, such as TIA-825-A. New enhancements to H.323 Annex G also do not define those modulations, but it does provide a means to allow another standard to adv
45、ertise its capabilities. TIA-1001 devices must be able to support the transmission of text interleaved with audio. The capability definition is shown below using H.323 Annex G: Capability name: T140Audio Capability class: Audio Capability Capability identifier type Standard. Capability identifier va
46、lue itu-t (0) recommendation (0) h (8) 323 annex(1) g (7) audio(0) maxBitRate The maxBitRate field shall be included and indicate the maximum bits per second. When using the Flow Control Command or other signals in relation to this capability, any maxBitRate field shall be interpreted to be in units
47、 of bits/sec, as opposed to the typical 100bits/sec used in H.245. This is due to the low bit rate nature of real-time text communication, including the low bit rates used by many PSTN textphone protocols. nonCollapsing This field shall not be included and shall be ignored if received. nonCollapsing
48、Raw This field shall not be included and shall be ignored if received. transport This field shall not be included. Devices may advertise the maximum characters per second via the below optional parameter: Parameter name: cps Parameter description: This is a collapsing capability. Indicates the maxim
49、um number of characters per second that may be received on a session. When carried inside an OLC (Open Logical Channel), it indicates the maximum transmission rate that the other endpoint may use if it opens a corresponding text session. Parameter identifier value: standard: 0 Parameter status: Optional Parameter type: unsignedMin Supersedes: - TIA-1001 16 The following is an optional parameter that indicates the set of supported modulations. Absence of this parameter may be interpreted to mean that all modulations are supported or
