1、 ETSI TS 126 226 V15.0.0 (2018-07) Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); Cellular text telephone modem; General description (3GPP TS 26.226 version 15.0.0 Release 15) TECHNICAL SPECIFICATION GLOBAL SYSTEM FOR MOBILE COMMUNICAT
2、IONSRETSI ETSI TS 126 226 V15.0.0 (2018-07)13GPP TS 26.226 version 15.0.0 Release 15Reference RTS/TSGS-0426226vf00 Keywords GSM,UMTS ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association bu
3、t non lucratif enregistre la Sous-Prfecture de Grasse (06) N 7803/88 Important notice The present document can be downloaded from: http:/www.etsi.org/standards-search The present document may be made available in electronic versions and/or in print. The content of any electronic and/or print version
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9、nd owned by the GSM Association. ETSI ETSI TS 126 226 V15.0.0 (2018-07)23GPP TS 26.226 version 15.0.0 Release 15Intellectual Property Rights Essential patents IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information pertaining to these essenti
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12、hich are, or may be, or may become, essential to the present document. Trademarks The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners. ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, an
13、d conveys no right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks. Foreword This Technical Specification (TS) has been produced
14、by ETSI 3rd Generation Partnership Project (3GPP). The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables. The cross reference between
15、 GSM, UMTS, 3GPP and ETSI identities can be found under http:/webapp.etsi.org/key/queryform.asp. Modal verbs terminology In the present document “shall“, “shall not“, “should“, “should not“, “may“, “need not“, “will“, “will not“, “can“ and “cannot“ are to be interpreted as described in clause 3.2 of
16、 the ETSI Drafting Rules (Verbal forms for the expression of provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TS 126 226 V15.0.0 (2018-07)33GPP TS 26.226 version 15.0.0 Release 15Contents Intellectual Property Rights 2g3Foreword .
17、 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 References 5g33 Definitions and Abbreviations 5g33.1 Definitions 5g33.2 Abbreviations . 5g34 General . 6g35 The problem . 6g35.1 US regulatory issues . 6g36 The goals and objectives 7g37 Text Telephony architecture based upon CTM 7g37.1 Text
18、Telephone devices 9g37.2 Error resilient transmission in the speech path . 9g37.3 Interworking with traditional Text Telephone devices . 9g38 Technical description of CTM . 10g38.1 Overview 10g38.2 CTM transmitter . 10g38.2.1 Character set . 10g38.2.2 FEC error protection . 10g38.2.3 CTM burst struc
19、ture 11g38.2.4 Periodic muting and insertion of resynchronization sequence 12g38.2.5 Interleaver and synchronization preamble 15g38.2.6 CTM modulator 16g38.2.7 Switching between speech and data 17g38.3 CTM receiver . 17g39 CTM negotiation and inband signaling 17g39.1 Definition of control characters
20、 17g39.2 CTM availability negotiation . 18g310 Functions in the CTM environment . 18g310.1 CTM to CTM communication 18g310.2 CTM between the mobile side and a gateway 18g310.3 CTM within the transcoding equipment . 19g310.4 Cascading of CTM adapters in the speech path 19g310.5 Rerouting of a call fr
21、om a CTM supported environment to a non-supported environment 19g3Annex A (Informative): CTM Receiver 20g3A.1 Demodulator . 20g3A.2 Synchronization and de-interleaver 20g3A.3 Puncture and resynchronization . 21g3A.4 FEC error correction . 21g3Annex B (informative): Change history . 22g3History 23g3E
22、TSI ETSI TS 126 226 V15.0.0 (2018-07)43GPP TS 26.226 version 15.0.0 Release 15Foreword This technical description has been produced by T1P1. The present document is a description of the Cellular Text Telephone Modem solution for reliable transmission of a text telephone conversation via the speech c
23、hannel of cellular or PSTN networks The contents of the present document are subject to continuing work within 3GPP and may change following formal 3GPP approval. Should the 3GPP TSG modify the contents of this TD, it will be re-released by the 3GPP TSG with an identifying change of release date and
24、 an increase in version number as follows: Version x.y.z where: x the first digit: 1 presented to 3GPP for information; 2 presented to 3GPP for approval; 3 Indicates 3GPP approved document under change control. y the second digit is incremented for all changes of substance, i.e. technical enhancemen
25、ts, corrections, updates, etc. z the third digit is incremented when editorial only changes have been incorporated in the specification; ETSI ETSI TS 126 226 V15.0.0 (2018-07)53GPP TS 26.226 version 15.0.0 Release 151 Scope This Technical Specification (TS) concerns the Cellular Text Telephone Modem
26、 (CTM). CTM allows reliable transmission of a text telephone conversation alternating with a speech conversation through the existing speech communication paths in cellular mobile phone systems. This reliability is achieved by an improved modulation technique, including error protection, interleavin
27、g and synchronization. Together with recommendations ITU-T V.18 and T.140, CTM may serve for worldwide applications in text telephony. A general overview and explanations of possible implementation architectures is provided. CTM is intended for use in end terminals (on the mobile or fixed side) and
28、within the network for the adaptation between CTM and existing traditional text telephone standards. The CTM transmitter is fully specified and a bit exact C-code reference is provided. An implementation of an example CTM receiver is also described. 2 References This TS incorporates by dated and und
29、ated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this TS only when incorporated i
30、n it by amendment or revision. For undated references, the latest edition of the publication referred to applies. 1 3GPP TS 26.231: “Cellular text telephone modem; Minimum performance requirements“. 2 ITU-T Recommendation V.18 (2000-11): “Operational and interworking requirements for DCEs operating
31、in the text telephone mode“. 3 3GPP TS 26.230: “Cellular text telephone modem; Transmitter bit exact C-code“. 4 ANSI TIA/EIA-825 (2000-03): “A Frequency Shift Keyed Modem for use of the Public Switched Telephone Network“. 5 ITU-T Recommendation T.140 (1998-02): “Protocol for multimedia application t
32、ext conversation, Feb. 1998“. 6 ISO/IEC 10646-1: “Information technology Universal Multiple-Octet Coded Character Set (UCS) Part1: Architecture and Basic Multilingual Plane“. 7 ITU-T Recommendation H.248 (2000-11), Annex F: “Text Telephony, Text Conversation, Fax and Call discrimination packages“. 3
33、 Definitions and Abbreviations 3.1 Definitions Cellular Text Telephone Modem: modem (consisting of transmitter and receiver) that allows the reliable transmission of text via the speech channel of cellular phone systems or PSTN networks Baudot Code: modem signal and character coding scheme of the No
34、rth American Text Telephone, as specified in ITU-T V.18 2, Annex A.1 (“5-bit operational code“) and in ANSI TIA/EIA-825 4 Text Telephone Code: modem signal and character coding scheme of any of the PSTN Text Telephone types supported by the harmonizing ITU-T Recommendation V.18 2 3.2 Abbreviations F
35、or the purposes of this TS, the following abbreviations apply: BP Band Pass CER Character Error Rate CTM Cellular Text Telephone Modem ETSI ETSI TS 126 226 V15.0.0 (2018-07)63GPP TS 26.226 version 15.0.0 Release 15FCC Federal Communications Commission FEC Forward Error Correction GSM Global System f
36、or Mobile communications HCO Hearing Carry Over Alternating transmission of speech and text. ITU-T International Telecommunication Union Telecommunication standardization sector (former CCITT) LP Low Pass PCM Pulse Code Modulation PSTN Public Switched Telephone Network TTY Text Telephone UCS Univers
37、al Multiple-Octet Coded Character Set UMTS Universal Mobile Telecommunications Systems VAD Voice Activity Detection VCO Voice Carry Over alternating transmission of speech and text 4 General Deaf, hard of hearing, and speech-impaired persons have been using specific Text Telephone (referred to as TT
38、Y in North America) equipment in the fixed network for many years to transmit text and speech through ordinary speech traffic channels. Modern digital cellular systems, however, do not provide satisfactory character error rates for text transmitted in the speech channel with the traditional modulati
39、on developed for the fixed network. The FCC under the US Government has required an urgent solution for all emergency (911) calls for one specific text telephone protocol called Baudot Code. This TS addresses these FCC requirements, and specifies a solution for the GSM and UMTS and potentially other
40、 cellular technologies. The goal is to provide a solution that can support all traditional text telephony systems worldwide. Internationally, PSTN text telephony is standardized in ITU-T V.18 2 and ITU-T T.140 5. 5 The problem Due to the fact that digital cellular phone systems are optimized for spe
41、ech signals and the radio transmission may be subject to relatively high error rates, the transmission of text telephone modem signals via the speech path in cellular networks is in some cases unsatisfactory: i.e. received messages show an unacceptably high character error rate (CER). One reason for
42、 this is that the digital cellular phones use speech coding in order to compress the signal. Since this coding is optimized for speech-like signals, modem signals are more or less distorted. A further problem is in the transmission errors and the applied error concealment in digital cellular phone s
43、ystems in case of poor channel conditions. The repetition of speech frames results in character errors or even in error propagation. The traditional text telephone modulation technique, designed years ago for PSTN lines, was not developed for these sophisticated, speech-optimized transmission channe
44、ls. Data transmission methods exist in the wireless services, but for various reasons, a text telephone transmission method for the speech path is desired. Two reasons are: 1: text telephony is acknowledged as a way to contact the emergency services, and emergency services in wireless networks are s
45、o far only defined for speech calls. 2: Alternating speech and text in a call is desired, and one simple way to accomplish that without special service support (like multimedia) is by alternating the use of the speech channel. 5.1 US regulatory issues The FCC under the US Government has required an
46、urgent solution for all emergency (911) calls for one specific text telephone protocol of the ITU-T V.18 standard, called “Baudot Code“. This TS addresses these FCC requirements and this section points out specific US regulatory issues. The minimum performance requirements for the CTM transmission a
47、re included in 1. That specification shall be applied for verifying performance. The FCC requires that the solution for cellular systems is fully compatible to traditional text telephone standards, at least it shall support Baudot modulation at 45.45 baud in the landline end. ETSI ETSI TS 126 226 V1
48、5.0.0 (2018-07)73GPP TS 26.226 version 15.0.0 Release 156 The goals and objectives CTM is developed to provide a solution that: - meets the FCC Emergency Call (911) requirements for Text Telephony; - meets the requirements for a Global solution for Text Telephony; - works with GSM AMR, EFR, and FR c
49、odecs, as well as future codecs; - is applicable for existing and future speech traffic channels in GSM and UMTS; - minimizes the impact to existing or future cellular networks; - allows roaming between networks of different operators; - provides a transmission rate of 10 characters per second according to a net bit rate of 80 bit/s; - does not introduce an additional delay of more than 800 ms for text transmission; - does not have any impact for voice transmission, i.e. speech signals must not be distorted or delayed. 7 Text Telephony architect
