1、TIA/EIA INTERIM STANDARD Minimum Performance Standards for Text Telephone Signal Detector and Text Telephone Signal Regenerator TIA/EIA/IS-84O-A (Revision of TIA/EIA/IS-840) SEPTEMBER 2001 TELECOMMUNICATIONS INDUSTRY ASSOCIATION +. . I ,“. Repesenting the telecommunications industiy in association w
2、ith the Electionic Industries fiance Elsctrrrnk Industries Alliance NOTICE TIA/EIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products,
3、 and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publications shall not in any respect preclude any member or nonmember of TIMEIA from manufacturing or selling products not conforming to such Standa
4、rds and Publications, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than TIA/EIA members, whether the standard is to be used either domestically or internationally. Standards and Publications are adopted by TIA/EIA in accordance with the Ameri
5、can National Standards Institute (ANSI) patent policy. By such action, TIA/EIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard or Publication. TIA/EIA INTERIM STANDARDS TIA/EIA Interim Standards contain information deemed
6、 to be of technical value to the industry, and are published at the request of the originating Committee without necessarily following the rigorous public review and resolution of comments which is a procedural part of the development of a TIA/EIA Standard. TIA/EIA Interim Standards should be review
7、ed on an annual basis by the formulating Committee and a decision made on whether to proceed to develop a TIA/EIA Standard on this subject. TIMEIA Interim Standards must be cancelled by the Committee and removed from the TIMEIA Standards Catalog before the end of their third year of existence. Publi
8、cation of this TIMEIA Interim Standard for trial use and comment has been approved by the Telecommunications Industry Association. Distribution of this TIMEIA Interim Standard for comment shall not continue beyond 36 months from the date of publication. It is expected that following this 36 month pe
9、riod, this TIA/EIA Interim Standard, revised as necessary, will be submitted to the American National Standards Institute for approval as an American National Standard. Suggestions for revision should be directed to: Standards & Technology Department, Telecommunications Industry Association, 2500 Wi
10、lson Boulevard, Arlington, VA 2220 1. (From Project No. 4721-RV1, formulated under the cognizance of the TIA TR-45.3 Subcommittee on Time Division Digital Technology.) Published by OTELECOMMUNICATIONS INDUSTRY ASSOCIATION 200 1 Standards & Technology Department 2500 Wilson Boulevard Arlington, VA 22
11、20 1 PRICE: Please refer to current Catalog of EIA ELECTRONIC INDUSTRIES ALLIANCE STANDARDS and ENGINEERING PUBLICATIONS or call Global Engineering Documents, USA and Canada (1-800-854-7179) International (303-397-7956) All rights reserved Printed in U.S.A. TIMEINIS -840 -A Con tents . 1 . Introduct
12、ion 1 2 . Text Telephone Extension to TIAEIA-136-410 Vocoder 2 3 . Test Resources, Utilities and Conditions 3 4 . Test Procedure for Testing Detector 3 5 . Stop Bit Range . 4 Input Level Range . 4 Robustness to Music 5 . . Requirements for Text Telephone Signal Detector 4 5.3 Phase Change . 5 5.5 St
13、ability 5 5.6 Frequency Variation 5 Bit Duration Variation . 6 Worst Case Variations . 6 Character Sequence Independence 6 Starting Silence 6 Baud Rate Interoperability . 6 5.12 Typing Mode . 6 Typing Mode in 50 Baud Mode 7 6 . Test Procedure for Testing Regenerator 7 7 . Requirements for Text Telep
14、hone Signal Regenerator 8 Nominal Signal Regeneration 8 Stop Bit Range . 9 Bit Duration Variation . 9 Worst Case Variations . 9 Baud Rate Interoperability . 9 Typing Mode and Mark Hold Tone Generation 9 5.1 5.2 5.4 5.7 5.8 5.9 5.1 O 5.1 1 5.13 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Typing Mode and Mark Hold To
15、ne Generation for 50 Baud Mode . 10 Test Procedure for Testing Tandem Operation 10 Requirements for Tandem Operation . 11 9.1 Tandem Operation . 11 9.2 8 . 9 . Tandem Operation in 50 Baud Mode 12 Test Procedure for Testing Degraded Channel Performance . 12 11.1 Slow Fading . 14 Slow Fading in 50 Bau
16、d Mode 14 Annex A (Normative) Test Vectors for Checking Minimum Performance . 15 Input Test Vectors for Text Telephone Signal Detector . 15 Input Test Vectors for Text Telephone Signal Regenerator 20 Input Test Vectors for Tandem Operation . 24 Input Test Vectors for Degraded Channel Testing 24 10 .
17、 1 1 . Requirements for Degraded Channel Performance 13 11.2 Fast Fading 14 1 1.3 11.4 Fast Fading in 50 Baud Mode . 14 A.l. A.2. A.3. A.4. I TIA/EIA/IS -840 -A II TIA/EIA/IS -840 -A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
18、43 44 1. Introduction Text telephones enable persons with hearing issues to communicate over conventional telephone lines, using written text messages. There are two types of text telephones: TTY (TeleTYpe) and TDD (Telecommunications Device for the Deaf). TTYs are basically mechanical teleprinters
19、and TDDs are their electronic counterparts. In this document, the term “Text Telephone“ refers to TTY, TDD, or both devices. Virtually all text telephones support “5-bit operational mode“ using Baudot code. In this operational mode, the communication channel is half-duplex with no channel turnaround
20、. The modulation is frequency shift-keyed (FSK) without carrier. This FSK uses 1400 Hz for a binary 1 and 1800 Hz for a binary O. A bit duration of either 20 or 22 ms (k0.4 ms) is used, providing a nominal data signaling rate of either 50 or 45.45 bits per second or baud, respectively. The bit durat
21、ion of 22 ms is used in the United States. Each character consists of 5-bit sequence preceded by one start bit at the frequency of 1800 Hz and followed by a minimum of one stop bit at 1400 Hz. There are two shift codes: letters sequence (1 11 11) and figures sequence (1 1 O 1 1). Passing the Baudot
22、tones through the present TIA/EIA-136 digital mobile systems results in strongly distorted received tones. Telecommunication Industry Association (TIA) has coordinated the efforts to find a favorable solution to improve the TTY/TDD signaling in TIA/EIA- 136 digital wireless system. This document is
23、to accompany the extension to TIA/EIA- 136-410 TDMA Enhanced Full-Rate Voice Codec (hereafter referred to as the text telephone extension) to improve the TIA/EIA- 136 digital wireless systems performance for text telephone signals. The text telephone extension consists of text telephone signal detec
24、tor, speechhext telephone signal encoder (modified TIA/EIA- 136-4 1 O encoder), speechhext telephone signal decoder (modified TIA/EIA-136-4 1 O decoder), and the text telephone signal regenerator. The speechhext telephone signal encoder and decoder are modified versions of TIA/EIA- 136-4 1 O encoder
25、 and decoder respectively. In this document the term detector refers to text telephone signal detector and the term regenerator refers to text telephone signal regenerator. The speechhext telephone signal encoder and decoder, as sf.igswn in Figure 4, shall be implemented as specified in IS-813-L4. H
26、ereafter, the term encoder is used for speechhext telephone signal encoder and the term decoder is used for referring to speechhext telephone signal decoder. In this document the term detector refers to text telephone signal detector. However, the detector and the regenerator need not be implemented
27、 in bit-exact manner. This document describes the minimum performance requirements for the detector and the regenerator. Annex A of this document describes test input vectors and reference output vectors for the detector and the regenerator. All detectors and the regenerators used for implementation
28、 of text telephone I extension of TIA/EIA- 136-4 1 O vocoder shall meet the minimum performance requirements specified in this document. Section 2 gives a brief description of the text telephone extension of TIA/EIA- 136-4 1 O vocoder. Section 3 specifies the test resources and utilities needed. Sec
29、tion 4 describes the test procedure for verifying minimum performance requirements for the detector. Section 5 describes the minimum performance requirnts for the detector. Section 6 describes the test procedure for verifying minimum performance requirements for the regenerator. Section 7 specifies
30、the minimum performance requirements for the regenerator. Section 8 describes the test procedure for testing tandem operation and degraded channel performance. Section 9 describes the performance requirements for tandem operation. Section 1 O describes the performance 1 TIA/EIA/IS -840 -A I I PCM i
31、I I I I I Text Telephone I I Signal Detector TTY i 2 requirements for various degraded channel conditions. Annex A describes the test vectors to be used for testing various performance requirements for text telephone extension. 3 4 2. Text Telephone Extension to TINEIA-I 36-41 O Vocoder I I I Speech
32、/ I Channel j Telephone D Signal I Text Encoder i I Encoder I I 5 6 I I I I I I i I 7 I I Text TTY Text BFI Speech/ I BFI I Telephone Char Telephone Flag Text Regenerator Handler .Char Signal I i Channel Signal SignalBFI TTY Telephone i Decoder 4- 8 I 9 Decoder pkt. j 10 11 12 13 14 PCM 4- 15 16 17
33、18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 I I I I I Text Telephone Extension l for Speech I Encoder I Figure 1. Text Telephone Extension The speech/text telephone signal encoder takes a frame of 160 samples (corresponding to 20 ms of speech data) in PCM format as input. These frame
34、s are also given to the detector. The detector detects text telephone characters in the input signal and conveys the information about the detected characters to the encoder. The encoder takes the information given by the detector and inserts it into the specific bit locations of the encoded output
35、frame of TINEIA-136-410 encoder as recommended in the text telephone extension standard. When no text telephone signal is detected by the detector, the encoded output frame of TINEIA-136-410 is not modified by the speech/text telephone signal encoder. The encoded output frame is processed by the cha
36、nnel encoder. At the receiver end, the received frame is decoded by the channel decoder. Whenever channel decoder finds that the mobile channel caused uncorrectable frame errors, it sets bad frame indication (BFI) flag for the speech/text telephone signal decoder. The decoder decodes the received fr
37、ame along with BFI flag. The decoder extracts the information about text telephone character from the received TINEIA-136-410 frame and gives the same along with BFI flag to text telephone signal BFI Handler. The BFI handler corrects any frame errors and gives the decoded character to the text telep
38、hone signal regenerator. Text telephone signal regenerator synthesizes text telephone signals for the decoded text telephone character. When the speech/text telephone signal decoder finds that the received frame represents speech signal 2 TIA/EIA/IS -840 -A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
39、18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 then the received frame is decoded using the TIA/EIA-136-410 speech decoding process and outputs the synthesized speech samples. 3. Test Resources, Utilities and Conditions The test vectors or sequences to be used for testing the minimum performance
40、 requirements for the detector and the regenerator are described in the Annex A of this document. These test vector files can be obtained from the CDROM that accompanies this standard. The reference data for testing the minimum performance shall be generated using these test sequences. The output of
41、 text telephone signal detector and/or the text telephone signal regenerator shall be compared against the reference data using the “diff utility on UNIXm and “parse-changes.exe“. The “parse-changes.exe“ program is supplied along with the test vectors. Unless otherwise specified the baud rate for th
42、e text telephone signal is 45.45 baud. 4. Test Procedure for Testing Detector The test procedure for testing the minimum performance of the text telephone signal detector is illustrated in figure 2. The test procedure shall have the following steps: 1. Input the specified tone file into the TTY rece
43、iver program (TTY-RCV) to generate the reference character file and reference TTY code file : TTY-RCV -i -t -o 2. Also input the specified tone file from step 1 into the text telephone signal detector software to generate test code and test character files. 3. Transfer the reference data files obtai
44、ned in step 1 and test data files obtained in the step 2 to a UNIXm system and run the UNIXTM utility “diff : diff -c diff -c 4. Transfer the char. diff. file and the code diff. file obtained in step 3 to PC. Run the parser on these output files : parsechanges parsechanges 5. The character error fil
45、e gives total number of characters changed, missed and added and the total number of character errors. Calculate the printable character error rate (PCER) : PCER = (No. of Char. Errors * 100.0) / (No. of Characters in Ref. Char. File) 6. The code error file gives total number of codes changed, misse
46、d and added and the total number of code errors. Calculate the total character error rate (TCER) : TCER = (No. of Code Errors * 100.0) / (No. of Codes in Ref. Code File) 3 TIA/EIA/IS -840 -A TTY Tone 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Text Telephon
47、e Signal Detector TTY-RCV I parse-changes I Test Char. File Ref. Char. File Char. Errors . I Calculate PCER I I diff (on UNIXm) v parse-changes Code Errors v Calculate TCER Figure 2. Test Procedure for Detector 5. Requirements for Text Telephone Signal Detector The minimum performance requirements f
48、or text telephone signal detector shall be tested using the test procedure described in section 4 (Test Procedure for Testing Detector) of this document. A text telephone detector shall meet the following performance requirements. 5.1 Stop Bit Range Text telephone signal detector shall detect all te
49、xt telephone characters correctly when the stop bit is set at 1.0, 1.5, and 2.0 bits. TCER and PCER shall be zero for all the cases of stop bit duration. 5.2 Input Level Range Text telephone signal detector shall detect all text telephone characters correctly when the signal level is set at 45 dBm, -40 dBm, -35 dBm, -15 dBm, -10 dBm and -5 dBm. TCER and PCER shall be zero for all the signal levels. 4 TIA/EIA/IS -840 -A 1 5 6 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 5.3 Phase Change Text telephone signal detectors performance shall not depend on the phase
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