1、 ETSI EN 300 395-3 V1.2.1 (2005-01)European Standard (Telecommunications series) Terrestrial Trunked Radio (TETRA);Speech codec for full-rate traffic channel;Part 3: Specific operating featuresETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 2 Reference REN/TETRA-05118-3 Keywords codec, TETRA ETSI 650 Route
2、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 but non lucratif enregistre la Sous-Prfecture de Grasse (06) N 7803/88 Important notice Individual copies of the present document can be downloaded fr
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6、ight and the foregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute 2005. All rights reserved. DECTTM, PLUGTESTSTM and UMTSTM are Trade Marks of ETSI registered for the benefit of its Members. TIPHONTMand the TIPHON logo are Trade Marks currently b
7、eing registered by ETSI for the benefit of its Members. 3GPPTM is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. ETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 3 Contents Intellectual Property Rights4 Foreword.4 1 Scope 5 2 References 5 3 Definitions
8、 and abbreviations.5 3.1 Definitions5 3.2 Abbreviations .5 4 TETRA Speech encoder.6 4.1 Encoder homing function .7 4.1.1 Definition of encoder homing frame.7 4.1.2 Encoder homing7 4.2 Speech importance function .7 4.3 Comfort noise function.7 4.4 Frame stealing function8 4.5 Test mode functions .8 4
9、.6 Encryption interface .8 5 TETRA Speech decoder .8 5.1 Encryption interface .9 5.2 Decoder homing function.10 5.2.1 Definition of decoder homing frame.10 5.2.2 Decoder homing10 5.3 Missing frame generation.10 5.4 Missing frame substitution .10 5.5 Test mode functions .10 6 Signalling data block fo
10、rmat 11 7 AMR speech encoder and decoder.12 Annex A (informative): Implementation of optional features 13 A.1 Speech importance calculation.13 A.2 Voice Activity Detection (VAD) .13 A.3 Discontinuous Transmission (DTX) 13 A.4 CNF computation .13 A.5 Missing Frame Generation (MFG).13 A.5.1 Error conc
11、ealment 13 A.5.2 Comfort noise generation .14 A.6 Setting BFI .14 A.7 U-plane frame stealing .14 A.8 Receiver muting .14 A.9 Response to U-plane signalling14 Annex B (informative): Bibliography.15 History 16 ETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 4 Intellectual Property Rights IPRs essential or pot
12、entially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essentia
13、l, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/webapp.etsi.org/IPR/home.asp). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No
14、guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Foreword This European Standard (Telecommunications series) has been produced by ETSI Project Ter
15、restrial Trunked Radio (TETRA). The present document is part 3 of a multi-part deliverable covering speech codec for full-rate traffic channel, as identified below: Part 1: “General description of speech functions“; Part 2: “TETRA codec“; Part 3: “Specific operating features“; Part 4: “Codec conform
16、ance testing“. National transposition dates Date of adoption of this EN: 21 January 2005 Date of latest announcement of this EN (doa): 30 April 2005 Date of latest publication of new National Standard or endorsement of this EN (dop/e): 31 October 2005 Date of withdrawal of any conflicting National S
17、tandard (dow): 31 October 2005 ETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 5 1 Scope The present document describes all the functions associated with the TETRA speech codec, except the specification of the codec by itself which is entirely defined in EN 300 395-2 1. Clause 4 of the present document prov
18、ides a description of the functions associated with the speech encoder, while clause 5 is its counterpart for the speech decoder. Clause 6 describes the contents and the format of the signalling data block included in a stolen frame when used for transferring information relevant to the codec in a U
19、-plane signalling message. In addition, annex A provides indications and preferred solutions for the implementation of optional features. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. References are eithe
20、r specific (identified by date of publication and/or edition number or version number) or non-specific. For a specific reference, subsequent revisions do not apply. For a non-specific reference, the latest version applies. Referenced documents which are not found to be publicly available in the expe
21、cted location might be found at http:/docbox.etsi.org/Reference. 1 ETSI EN 300 395-2: “Terrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic channel; Part 2: TETRA codec“. 2 ETSI EN 300 392-7: “Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D); Part 7: Security“. 3 Definitions
22、 and abbreviations 3.1 Definitions For the purposes of the present document, the terms and definitions given in EN 300 392-2, clause 3 apply. 3.2 Abbreviations For the purposes of the present document, the abbreviations given in EN 300 392-2, clause 3 and the following apply: AMR Adaptive Multi-Rate
23、 BFI Bad Frame Indicator CNF Comfort Noise Frame DTX Discontinuous Transmission LTP Long Term Predictor MAC Medium Access Control MFG Missing Frame Generation PCM Pulse Coded Modulation RMS Root Mean Square VAD Voice Activity Detector ETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 6 4 TETRA Speech encoder
24、A diagram of the speech encoder and associated functions is given in figure 1. A more general overview is given in EN 300 395-1. The speech encoder is defined in EN 300 395-2 1 and the other functions form the speech encoder control unit. The speech encoder control unit shall have access to all the
25、internal data and functions of the speech encoder (including the input speech). COMFORT NOISEFUNCTIONTEST MODEFUNCTIONS1235Reset4ENCODER HOMINGFUNCTIONSPEECH IMPORTANCEFUNCTIONSpeech Encoder ControlFRAME STEALINGFUNCTIONENCRYPTIONINTERFACESPEECH ENCODER1) 16-bit uniform PCM, 8 000 samples/s. 2) Enco
26、ded speech frame 30 ms, 137 bits/frame. 3) Encoded speech frame in “TMD_UNITDATA_request“ message. 4) Stolen indication in “TMD_REPORT_indication“ message. 5) Test mode control. Figure 1: Overview of speech encoder specific operating features The speech encoder as defined in EN 300 395-2 1 shall rec
27、eive speech in the form of 16-bit uniform PCM at a rate of 8 000 samples per second. The coded data corresponding to each 30 ms speech frame shall be output from the speech encoder control unit via the encryption interface to the encryption unit (or directly to the MAC if encryption is not used). Th
28、e interfaces with the encryption unit, namely interface points 3 and 4 in figure 1, shall be as defined in EN 300 392-7 2, clause 7. Message “TMD_UNITDATA_ request“ is the means of conveying half-slots from the U-plane to the MAC, while “TMD_REPORT_indication“ enables the MAC to pass control informa
29、tion to the U-plane. Comfort noise parameters may be generated and their presence in the coded speech data shall be indicated by a U-plane signalling message conveyed using the frame stealing mechanism. A speech importance indication shall be provided. The presence of a homing sequence in the input
30、speech shall be recognized and the encoder reset to a defined state. All functions necessary to support conformance testing shall be implemented. ETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 7 An appropriate U_device destination address shall be set for each half slot of coded speech data to allow correc
31、t routing at the receiver. 4.1 Encoder homing function 4.1.1 Definition of encoder homing frame The encoder homing frame shall consist of 240 identical samples (corresponding to a 30 ms speech frame), each 16 bits long with the value 0x0008. NOTE: 0x0008 is a number represented in hexadecimal notati
32、on. 4.1.2 Encoder homing Whenever the speech encoder receives at its input an encoder homing frame exactly aligned with its internal speech frame segmentation, the following events shall take place: Step 1: the speech encoder performs its normal operation and produces a speech parameter frame at its
33、 output which is in general unknown; Step 2: the speech encoder shall be reset and placed in its home state by executing the reset functions “Init_Coder_Tetra( )“ and “Init_Pre_Process( )“ as defined in EN 300 395-2 1; Step 3: the speech encoder is now in its home state and any further consecutive e
34、ncoder homing frames shall result in an output speech parameter frame identical to the decoder homing frame. Applying a sequence of N encoder homing frames to the speech encoder input shall cause at least N-1 decoder homing frames at the output of the speech encoder control unit. 4.2 Speech importan
35、ce function This function shall compute an importance parameter for each speech frame. This may be done on the basis of the likely degradation in speech quality which would result from stealing that frame. The importance parameter shall take one of the values: NO_IMPORTANCE; LOW; MEDIUM; or HIGH. Ev
36、en in the case of speech frames marked “NO_IMPORTANCE“ there may be some benefit in terms of speech quality from transmission to the end user. 4.3 Comfort noise function This function may compute speech parameters which can be used for comfort noise generation at the receiver. A Comfort Noise Frame
37、(CNF) shall have the same format as a normal speech frame. The comfort noise function may also determine when a CNF should be transmitted. If Discontinuous Transmission (DTX) is employed on an uplink, then at least a CNF, or some other data, should be transmitted frequently enough that the receiving
38、 base station does not drop the connection. ETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 8 4.4 Frame stealing function Clause 6 hereafter defines the format of the signalling messages inserted by the frame stealing function used in conjunction with the codec. The following describes the normal use of the
39、se messages. SPEECH_ON is used to signal the start of active speech in the next half slot. This may be used particularly to end DTX. An alternative method of ending DTX is to recommence transmission of speech frames without specific signalling. SPEECH_OFF is used to signal the end of active speech.
40、This may be used particularly to start or maintain the channel during a period of DTX. CNF_COMMAND signals that the second half slot contains CNF. It might be used normally to signal three conditions: - to signal the end of active speech and to start comfort noise in the receiver; - to maintain the
41、channel during a period of DTX; - to update the CNF. MUTE signals the receiver to mute the speech decoder output. NOTE: U-plane frame stealing shall be disabled when required by test mode functions. 4.5 Test mode functions The test mode control input to the speech encoder control shall determine whe
42、n the codec conformance test mode is active. When the codec conformance test mode is active, the following shall apply: - the frame stealing function shall not carry out U-plane frame stealing; - the frame stealing function shall pass the encoded speech data to the encryption interface without any m
43、odification; - the speech importance function shall indicate HIGH importance for all input speech data; - encryption shall be disabled. 4.6 Encryption interface This function assembles the parameters for the message “TMD_UNITDATA_request“ for passing to the encryption unit (or directly to the MAC if
44、 encryption is not used). The parameters of this message shall each be set to one of their allowed values. 5 TETRA Speech decoder A diagram of the speech decoder and associated functions is given in figure 2. A more general overview is given in EN 300 395-1. The speech decoder is defined in EN 300 3
45、95-2 1 and the other functions form the speech decoder control unit. The speech decoder control unit shall have access to all the internal data and functions of the speech decoder. ETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 9 MISSING FRAMESUBSTITUTION25Reset 9MISSING FRAMEGENERATIONTEST MODEFUNCTIONSSp
46、eech Decoder ControlDECODER HOMINGFUNCTIONDECRYPTIONINTERFACESPEECH DECODER811) 16-bit uniform PCM, 8 000 samples/s. 2) Encoded speech frame 30 ms, 137 bits/frame. 5) Test mode control. 8) Encoded speech frame in “TMD_UNITDATA_indication“ message. 9) Bad frame indicator. Figure 2: Overview of speech
47、 decoder specific operating features The interfaces from the encryption unit (or MAC) to the speech decoder control unit, namely interface point 8 in figure 2 shall be as defined in EN 300 392-7 2, clause 7. Message “TMD_UNITDATA_indication“ is used to convey half-slots from the MAC to the U-plane.
48、The coded data corresponding to each 30 ms speech frame shall be received from the encryption unit via the encryption interface. Each received half_slot will have a U_device destination address to allow routing to appropriate device at the receiver. The speech decoder as defined in EN 300 395-2 1 sh
49、all output synthesized speech in the form of 16-bit uniform PCM at a rate of 8 000 samples per second. 5.1 Encryption interface This function receives the parameters in the message “TMD_UNITDATA_indication“ from the encryption unit (or directly from the MAC if encryption is not used). ETSI ETSI EN 300 395-3 V1.2.1 (2005-01) 105.2 Decoder homing function 5.2.1 Definition of decoder homing frame The decoder homing frame is a fixed set of parameters as described in table 1. It is the natural response of the speech encoder, starting from its home s
