1、3404583 0080484 412 Released: July 1,1993 GSM 06.31 Version 4.0.1 Date: May 1993 Work Item No: Key words: European digital cellular telecommunication system (phase 2); Discontinuous Transmission (DTX) for Full Rate Speech Transmission Channels ETS I European Telecommunications Standards Institute ET
2、SI Secretariat: F - 06921 Sophia Antipolis Cedex . France TP. + 33 92 94 42 00 TF. + 33 93 5 47 16 Tx. 47 00 40 F This is an unpublished work the copyright in which vests in the European Telecommunications Standards Institute. All rights reserved. The information contained herein is the propetry of
3、ETSI and no part may be reproduced or used except as authorised by contract or other written permission. The copyright and the foregoing restriction on reproduction and use extend to all media in which the information may be embodied. = 3404583 0080485 359 Page 3 GSM 06.31 (4.0.1): May 1993 Contents
4、 0.SCOPE 5 1.GENERAL 5 1.2. NAMING CONVENTION 5 1.2.1. Definition of general terms 6 1.2.2. Definition of terms on the receive side 6 1.1, GENERAL ORGANISATION . 5 2 . TRANSMITSIDE 6 2.1. GENERALOPERATION 7 2.1 . 1. Functions of the TX DTX handler . 7 2.1.2.FunctionsoftheTXradiosubcystem. 9 3.RECEIV
5、ESIDE . 10 3.1. GENERAL OPERATlON 1 0 3.1 .i . Functions of the RX radio subsystem . .i 1 3.1.2. Functions of the RX DTX handler . 1 1 Previous page is blank - - 3404583 0080486 295 Paga 5 GSM 08.31 (4.0.1): May 1993 O. SCOPE This technical specification gives a description of the general baseband c
6、pwation of full rate speech traffic channels in the transmitter and in the receiver of GSM Mobile Stations and Base Statim Systems during DiscorRinuous Transmission (OW. Foc clartty, the description is structured according the Mock diagrams in figures 2-1 and 3-1. Excep in the case described next, t
7、his structure of distributing the various functions between system entities is nd mandatory for implementation, as long as the operation on the air interface and on the speech decoder output remains the same. In the case of Base Statim Systems where the speech transcoder is located remuteiy in the B
8、ase Station Contrdler, the implementation of the interfaces between the DTX Handlers and the Radio Subsystem (RSS) as described in this technical specificatiori togehm with ail their flags is mandatory, being a part of the A-bis- interface as described in GSM 08.60. In this cae the various ags also
9、serve to avoid additional delays. The DTX functions described in this technicd specification are mandatory for implementation in all GSM Mobile Stations. The receiver requirements are mandatory for implementation in all GSM Base Station Systems, the transmitter requirements only for those where down
10、link DTX will be USBd. DTX sMl be in operation in GSM Mobile Statim if commanded so by the nework, see GSM 04.08. 1. GENERAL Discontinuous Transmission is a mechanism which allows the radio transmitter to be switched off most of the time during speech pauses for the following two purposes: - to save
11、 power in the Mobile Station - to reduce the overall interference level on the air. 1.1. GENERAL ORGANISATION The overall DTX mechanism described in this technical specification requires the fdlwing functioris: - a Voice Activity Detedor on the transmit side, - evaiuatiori of the background acwstic
12、noise on the transmit side, in order to transmit characteristic parameters to the receive side, - generstkn m the receive side cd a similar noise, called comfort noise, during periods where the radio trm b a. The VdceAethrity Deector is defined in GSM 06.32 Voice Activity Detection, the comfort nois
13、e functions in GSM a12 Comfort Noise Aspects. Both are based partty on the speech transcoder and its internal variables, defined in GSM 06.1 O GSM Full Rate Speech Trarrscoding In addition to these unctiarrs, if the parameters arriving at the receive side are detected to be seriousiy corrupted by er
14、rors, the speech or comfort noise must be generated from substituted data in ad- to avoid sefiousty annoying effects foc the listener. This funah s defined in GSM 06.11 Subsr;tution and Muting of Lost Frames. An overall description of the speech processing parts can be found in GSM 06.01 Speecn c.oc
15、essing functions - General description. 1.2 NAMING CONVENTION This Section lists the definitions of terms relevant for the DTX fwictim, as used in his and :?e iechnical 3404583 0080487 121 = Page 6 GSM 06.31 (4.0.1): May 1993 specifications mentioned above. 1.2.1. Definition of general terms - Frame
16、 Time inteival of 20 msec. catrespwxling to the time segmentation of the full rate speech transcoder (GSM W.lO), ais used as a short term for a traffic frame. Traffic frame: Block of 260 information bits (sea GSM 05.03) transmitted on the full rate speech traic channel. SID (Silence Descriptor) fra
17、me: Frame characterized by the SID code word. it conveys information on the acoustic background noise. SI0 code word Fixed bit pattern defined in GSM 06.12, for labelling a traffic frame as a SI0 frame. SID field The ba positions defined in GSM C6.12, of the CID codeword within a SI0 frame, Speech f
18、rame: TrMc frame that cannot be classified as a SID frame. 1.2.2 Definition of terms on the receive side Bad traffic frame: A traffic frame flagged BFI-1 (Bad Frame Indication) by the Radio Subsystem. Good trafiic frame: A traffic frame flagged BFt4 by the Radio Subsystem. Good speech frame: A good
19、traffic frame which is na an accepted SID frame. Accepted SI0 frame: Traffic frame in which the SID field deviates in less than 16 bit posiuoris from the SI0 code word (flag SIDSS, then this last last SI0 frame shall repeateiy be passed to the RSS, wiul a new updated SI0 %ne is available (N+1 corrse
20、cuuVe frames marked with VAD=O).This reduces the activity on the air in cases where shat backqound noise spikes are taken for speech, by avoiding the hangoveP waiting for the SI0 frame computation (see also fig 2-3: Note that fig 2-3 chows as exampie the longest possible speech burst withad hangover
21、). = 3404583 0080490 7Lb Page 9 GSM 06.31 (4.0.1): May 1993 ? ? ?O 12 3 4 5 6 7 8.- 22232425260 I SXDavCngUrg period Fig 2-3. Handllng of short speech bum (Neepa = 16 The binary TAF flag (Tme Alignment Flag) marks with TAF4 those traffic frames that are aligned with the SACCH muttiframe structure as
22、 described in the technical specifications referenced in section 2.1 2. 3.1 2. Fundions of the RX DTX handler The RX DTX Handler is responsible for the overall DTX operation on the receive side, which shall be as follows: * whenever a gocd speech frame is detected, the DTX Handler shall pass it dire
23、ctly on to the speech decoder. * When lost speech or lost CID frames are detected, the substituan and muting procedure defined in GSM 06.1 1 shall be applied Valid SID frames shall result in comfort noise generatiari, as defined in GSM 06.12, until the next SI0 frame is expected FAF=l) OT god speech
24、 frames are detected. Owing this ptid, the FIX DTX handler shall ignore any unlsable frames delivered by the Radio Subsystem. * An invalid SI0 frame shail be substitiffed by the Isst valid SI0 frame and the ptocedure foi valid CID frames be applied NOTE: If the first SID frame Mer a svh bust (a series of good speech frames) is invalid, then the comfort noise parameters can be taken from the last valid St0 frame o( from te krot received good speech frame which, because d the VAD hangover time (see GSM 6.32), may be suppossd to contain noise only.
