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1、JOINT INTERIM STANDARD GMR-2 Series 06 (06.001) Speech Coding Specifications: Basic Rate Speech: Basic Rate Speech Processing Functions IS-J-STD-781-Series 6 NOVEMBER 2001 TELECOMMUNICATIONS INDUSTRY ASSOCIATION Rcprewnting the telennimunicationv indusiry in aysociaion with the Electronic Indusiria
2、Alliance Elsctron ic Ind wtries. Allia nee EUROPEAN TELECOMMUNICATIONS STANDARDS INSTITUTE Copyright Telecommunications Industry Association Provided by IHS under license with EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 23:51:24 MDTNo reproduction or networking
3、 permitted without license from IHS -,-,- NOTICE FROM THE TELECOMMUNICATIONS INDUSTRY ASSOCIATION TIA/EIA Engineering Standards and hblications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and im
4、provement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and hblications shall not in any respect preclude any member or nonmember of TIA/EIA from manufacturing or selling products not con
5、forming to such Standards and hblications, nor shall the existence of such Standards and hblications preclude their voluntary use by those other than TIA/EIA members, whether the standard is to be used either domestically or internationally. Standards and hblications are adopted by TIA/EIA in accord
6、ance with the American 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 hblication. Note: The users attention is called to the possibiliS, that
7、compliance with this document may require use o f one or more inventions covered by patent rights. By publication o f this standard, Interim Standard, or TSB, no position is taken with respect to the validio o f those claims or o f any patent rights in connection therewith. The patent holder) so far
8、 identified have, however, filed statements o f willingness to grant licenses under those rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such licenses. Details may be obtained from the standards developer. TIA/EIA AND JOINT INTERIM STANDARDS Joint In
9、terim Standards contain information deemed 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 an American National
10、 Standard (ANS). Interim Standards should be reviewed on a periodic basis by the formulating Committee and a decision made on whether to proceed to develop a TIA/EIA Standard on this subject. Interim Standards must be upgraded or cancelled by the Committee before the end of their third year of exist
11、ence. hblication of this Joint Interim Standard for trial use and comment has been approved by the Telecommunications Industry Association. Distribution of this Joint Interim Standard for comment shall not continue beyond 36 months from the date of publication. It is expected that following this 36
12、month period, this Joint 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 the second digit (m) is incremented for all other types of changes,
13、 i.e. technical enhancements, corrections, updates, etc. Intellectual Property Rights The users attention is called to the possibility that compliance with this Interim Standard may require use of an invention covered by patent rights. By publication of this Interim Standard, no position is taken wi
14、th respect to the scope or validity of such patent claims or of any patent rights in connection therewith. One or more parties have notified the TIA that they hold patent rights applicable to this Interim Standard. Each patent holder has, however, filed a statement of willingness to grant a license
15、under these rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such licenses. A copy of the statement may be obtained from the TIA. Basic Rate Speech Processing Functions vi Copyright Telecommunications Industry Association Provided by IHS under license
16、with EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 23:51:24 MDTNo reproduction or networking permitted without license from IHS -,-,- TINEIA IS-781.06.001 1 Scope This TS provides an overview of the speech processing requirements applicable to the basic rate chan
17、nel of the GMR-2 system. The speech processing functions in the GMR-2 system include the following: Speech transcoding, which includes a speech encoder that converts digitised speech samples into a compressed binary bit stream and a speech decoder that converts a compressed binary bit stream into di
18、gital speech samples. Discontinuous transmission (DTX), which is used to reduce the transmission rate during periods of voice inactivity. VAD, which is used to identi periods of voice activity, as required by DTX. CNI, which is used to convey the characteristics of the background noise from the tran
19、smit end to the receive end of the connection, in an effort to reduce the modulation of background noise that would otherwise occur with DTX. Lost speech frame substitution and muting, which is used to mask transmission errors and stolen frames. Detection and regeneration of single-frequency and dua
20、l-tone multifrequency (DTMF) signals. The high level description given in this TS relates to the Digital Voice Systems, Inc.s (DVSIs) AMBETM 3600 bps voice codeddecoder 7. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the pres
21、ent document . References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific. For a specific reference, subsequent revisions do not apply. For a non-specific reference, subsequent revisions do apply. il GMR-2 O 1.004: “GEO-Mobile Radio inter
22、face specifications: Abbreviations and acronyms” NOTE: This document is not yet published GMR-2 03.050: “GEO-Mobile Radio Interface Specifications; Transmission planning aspects of the speech services in the Public Satellite Mobile Network (PSMN) system” NOTE: This document is not yet published GMR-
23、2 05.003 : “GEO-Mobile Radio Interface Specifications; Channel Coding” NOTE: This document is not yet published GMR-2 05.005: “GEO-Mobile Radio Interface Specifications; Radio Transmission and Reception NOTE: This document is not yet published GMR-2 05.008: “GEO-Mobile Radio Interface Specifications
24、; Radio Subsystem Link Control NOTE: This document is not yet published 21 31 41 51 61 71 ITU-T Recommendation G.711 (1 1/88): “Pulse Code Modulation (PCM) of voice frequencies” Digital Voice Systems,Inc. hitu : / T w . d s i i . caid Basic Rate Speech Processing Functions 1 Copyright Telecommunicat
25、ions Industry Association Provided by IHS under license with EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 23:51:24 MDTNo reproduction or networking permitted without license from IHS -,-,- TINEIA IS-781.06.001 3 3.1 Definitions and abbreviations De fi ni tions F
26、or the purpose of this standard, the following definitions apply: Frame: Time interval of 20 ms corresponding to the time segmentation of the basic rate speech transcoder, also used as a short term for a traffic frame. Traffic Frame: Block of 72 information bits transmitted on the basic rate speech
27、traffic channel. SID Frame: Frame characterised by the SID (Silence Descriptor) code word. It conveys information on the acoustic background noise. SID Code Word:Fixed bit pattern, for labelling traffic frame as a SID frame. SID Field: The bit position of the SID code word within a SID frame. Speech
28、 Frame: Traffic frame that cannot be classified as a SID frame. Bad Traffic Frame: Good Traffic Frame: Good Speech Frame: Valid SID Frame: of comfort noise parameters at any time. Unusable Frame: Lost SID Frame:An unusable frame received when the RX DTX handler is generating comfort noise and a SID
29、frame is expected (Time Alignment Flag, TAF = 1). Lost Speech Frame: An unusable frame received when the RX DTX handler is passing on traffic frames directly to the speech decoder. VAD Flag: flag = O) of voice activity. SP F1ag:Boolean flag, generated by the TX DTX hmdler, indicating whether the cur
30、rent frame of data should be transmitted by the RSS. Definitions of other terms used in this TS can be found in GMR-2 01.004 i. A traffic frame flagged BFI = 1 (Bad Frame Indication) by the Radio Subsystem. A traffic frame flagged BFI = O by the Radio Subsystem. A good traffic frame which is not an
31、accepted SID frame. A good traffic frame flagged with SID = 1 by the DTX handler. This frame is valid for updating A bad traffic frame that is not an accepted SID frame. Boolean flag, generated by the VAD algorithm, indicating the presence (VAD flag = 1) or absence (VAD 3.2 Ab brevi at ions For the
32、purposes of this present document, the following abbreviations apply: BFI Bad Frame Indication DTX Discontinuous Transmission DVSI Digital Voice Systems Inc. GSM MES Mobile Earth Station PCM Pulse Code Modulated PLMN Public Land Mobile Network PSTN Public Switched Telephone Network RF Radio Frequenc
33、y RX Receive RSS Radio Subsystem SACCH Slow Associated Control Channel SID Silence Descriptor SP flag Speech flag TAF Time Alignment Flag TX Transmit VAD Voice Activity Detector Global System for Mobile conmunications For abbreviations not given in this sub-section see GMR-2 01.004 11 Basic Rate Spe
34、ech Processing Functions 2 Copyright Telecommunications Industry Association Provided by IHS under license with EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 23:51:24 MDTNo reproduction or networking permitted without license from IHS -,-,- TINEIA IS-781.06.001 G
35、eneral Figure 4-1 presents a reference configuration where the various speech-processing functions are identified. In Figure 4-1, the audio parts including analogue to digital and digital to analogue conversion are included to show the complete speech path between the audio input/output in the Mobil
36、e Earth Station (MES) and the digital interface of the PSTN. The detailed specification of the audio parts is considered in GMR-2 03.050 2. These aspects are only considered to the extent that the performance of the audio parts affects the performance of the speech transcoder. TX DTX handler SP flag
37、 DTX -+ wntrol Info TRANSMIT SIDE RX DTX handler GSS side only 8 bit / A-law or b-law MES side only GMR-203050 RECEIVE SIDE Figure 4-1 : Reference Configuration 1) 8 bit A-law or y-law PCM (ITU-T rec G.711 6), 8 O00 sampleds 2) 13 bit uniform PCM, 8 O00 sampleds 3) Voice Activity Detector (VAD) flag
38、 4) Encoded speech / SID (Silence Descriptor) frame, 50 frame Basic Rate Speech Processing Functions 5 Copyright Telecommunications Industry Association Provided by IHS under license with EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 23:51:24 MDTNo reproduction o
39、r networking permitted without license from IHS -,-,- TINEIA IS-781.06.001 The average interference level over the air interface is reduced, leading to better Radio Frequency (RF) spectrum efficiency; Spacecraft power utilisation on the L-band forward link is optimised. The overall DTX mechanism is
40、implemented in the DTX handlers (Transmit (TX) and Receive (RX) and requires the following functions: 1) A Voice Activity Detector (VAD) on the TX side; 2) Evaluation of the background acoustic noise on the TX side, in order to transmit characteristic parameters to the RX side; 3) Generation of comf
41、ort noise on the RX side during periods where the radio transmission is turned off. In addition to these functions, if the parameters arriving at the RX side are detected to be corrupted by errors, the speech or comfort noise shall be generated from substituted data in order to avoid sound defects f
42、or the listener. The transmission of comfort noise information to the RX side is achieved by means of a Silence Descriptor (SID) frame. The SID frame is transmitted at the end of speech bursts and serves as an end of speech marker for the RX side. In order to update the comfort noise characteristics
43、 at the RX side, SID frames are transmitted at regular intervals also during speech pauses. Transmissions of the SID frames are at a much lower rate than speech traffic rate, leading to minimal additional overhead. This also serves the purpose of improving the measurement of the radio link quality b
44、y the Radio Subsystem (RSS). The DTX handlers interwork with the RSS using flags. The RSS is controlled by the transmitter keying on the TX side, which performs pre-processing functions on the RX side. The speech flag (SP) indicates whether the information bits (voice/noise/or tones) are to be trans
45、mitted over the link. The SP flag is calculated from the VAD flag by the TX DTX handler. 6.2 Transmit (TX) Side A block diagram of the TX side DTX functions is shown in Figure 6.2-1. TX DTX Handler Vocoder D TX Contro Information Bits 72 D SP Flag 1 TX Radio Subsystem I Channel Coding I SP Flag Moni
46、toring Figure 6.2-1: Block diagram of the Transmit Side DTX functions The TX DTX handler continuously passes traffic frames, individually marked by the SP flag, to the radio subsystem (RSS). The scheduling of the frames for transmission on the air interface is controlled by the RSS alone, on the bas
47、is of the SP flag as described in subsection 6.2.1. Note that the GSM SP flag indicated “Speech”; here the definition has been broadened to indicate which should be transmitted, regardless of content (i.e., speech or SID). Basic Rate Speech Processing Functions 6 Copyright Telecommunications Industr
48、y Association Provided by IHS under license with EIALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 23:51:24 MDTNo reproduction or networking permitted without license from IHS -,-,- TINEIA IS-781.06.001 Speech Speech Speech SID SID SID 6.2.1 Function of the TX DTX ha
49、ndler Fm The VAD shall operate continuously in order to assess whether the input signal contains speech or not. The output is a binary flag (VAD flag = 1 or VAD flag = O, respectively) on a frame-by-frame basis. Regardless of the state of the VAD flag, the DTX handler shall pass all frames to the RS