1、W 3404583 0080475 40T E Released: July 1,1993 GSM 06.11 Version 4.0.1 Date: May 1993 Work Item No: Key words: European digital cellular telecommunication system (phase 2); Substitution and Muting of Lost Frames for Full Rate Speech Channels ETSI European Telecommunications Standards institute ETSI S
2、ecretariat: F - 06921 Sophia Antipolis Cedex . France TP. + 33 92 94 42 00 TF. + 33 93 65 47 16 Tx. 47 00 40 F This is an unpublished work the copyright in which vests in the European Telecommunications Standards Institute.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 ETS
3、I 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 008047b 346 Pago 3 GSM 06.11 (4.0.1): May 1993 Contents o.
4、 SCOPE 1, GENERAL 2. REQUIREMENTS 2.1. FIRST LOST SPEECH FRAME 2.2. SUBSEQUENT LOST SPEECH FRAMES 2.3. FIRST LOST SID FRAME 2.4. SUBSEQUENT LOST SI0 FRAME 3. EXAMPLE SOLTiON Previous page is blank W 3404583 0080477 282 111 Paga s GSM 08.1 1 (4.0.1): May 1993 o. SCOPE mis teciuiical specification def
5、ines a frame substitution and muting procedure which shall be use by the RX DTX handler when one or more lost speech or CID frames are received from the radio subsystem. The requirements of this technical specification are mandatory for implementation in all GSM Base Station Systems and Mobile Stati
6、m. 1. GENERAL The definitions of terms used in this technical specification can be found in GSM 06.31. The purpose of the frame substitution is to conceal the effect of lost frames. The purpose of muting the output in the case of several last frames is to indicate the breakdown of the channel to the
7、 user. 2. REQUIREMENTS 21. FIRST LOST SPEECH FRAME Normal decoding of last speech frames would resuit in very unpleasant noise effects. In order to improve the subjectbe quality, the first lost speech frame shall be substitided with either a repetition or an extrapoiation of the pievious good speech
8、 frame(s). Lost sw frames shell nd be delivered to the speech decoder, nor shall me output be muted direcy. 22 SUBSEQUENT LOST SPEECH FRAMES For subsequent lost speech frames, a muting technique shall be used that will gradua& decrease the output level, resulting in silencing of the outpd after a ma
9、ximum d 320 ms. Section 3 gives an example soiution. 23. FIRST LOST SI0 FRAME A single lost CID frame shall be substituted by the last valid SI0 frame and the procedure for valid SID frames be applied 8s Mbed in GSM 06.31. 24. SUBSEQUENT LOST SI0 FRAME Foc the seconb last SI0 frame, a muting techniq
10、ue shall be use on the comfort noise that will gradually decreasr ttm artpit levei, resulting in silencing of the outpu aiter a maximum of 320 ms. Section 3 gives For sutmqm# kat SI0 frames, the muting of the outpr shall be maintained 3. EXAMPLE SOLUTION For guidance, an example solution is given. T
11、he first lost speech frame is replaced at the speech decoder input by the previous good speech frame. Normal decoding is then performed. The mung procedure to be used in the case of subsequent lost speech frames or for comfort noise frames following the second lost CID frame is as follaws: The pseud
12、dogarithmic encoded Mock amplitude Xmaxcr (GSM 08.10), coded on the interval from O to 63, is decreased with a constant value d=4 in each frame, dawn to tb lawest piMe value. Consequently, Xmaxcr will be reduced gradually, and the output muted after 8 maximum of 320 ms. The Previous page is blank =
13、3404583 0080478 119 Q Page 6 GSM 06.11 (4.0.1): May 1993 grid position parameters are chosen randomiy between O and 3 during this time. For subsequent unusable frames, after the frame where Xmaxcr reached the lowest possible value, “silence frames are passed from the FM DTX handler to the speech dec
14、oder to guarantee a low output level under all conditioris. The silence frame is defined in table 31. Log area ratio 1 = 42 Log area ratio 2 = 39 Log area ratio 3 = 21 Log area ratio 4 = 10 Log area ratio 5 = 9 Log area ratio 6 = 4 Log area ratio 7 = 3 Log area ratio 8 = 2 LTP gain =o LTP lag = 40 G
15、rid position = 1 Block amplitude - O RPE pulse no. 1 = 3 RPE pulse no. 2 = 4 RPE pulse no. 3 = 3 RPE pulse no. 4 = 4 RPE pulse no. 5 = 4 RPE pulse no. 6 = 3 RPE pulse no. 7 = 3 RPE pulse no. 8 = 3 RPE pulse no. 9 = 3 RPE pulse no. 10 = 4 RPE pulse noe 11 = 4 RPE pulse no. 12 = 3 RPE pulse no. 13 - i - I I I I 1 I I I I I I I I- repeated for each subsegment I I l I I 1 - I Table 91. Encoded parameters (GSM 06.1 o) of the silence frame
