1、 STD*EIA TSBL37-ENGL 2000 m 3234600 0655233 b42 TIA/EIA TELECOMMUNICATIONS SYSTEMS BULLETIN Clarification of DTX Receive Handling in TINEIA-136 TSBl17 MAY 2000 TELECOMMUNICATIONS INDUSTRY ASSOCIATION /- Reprcscnhng the iderommumicitions industry io isaciitioa with the Eleclonic Endusbin AUisnee Elic
2、tronic Industri- Alliance STDmEIA TSBLL7-ENGL 2000 3234600 Ob55232 ,567 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 produ
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9、of the TIA TR-45.3 Subcommittee on Time Division Digital Technology.) Published by OTELECOMMUNICATIONS INDUSTRY ASSOCIATION 2000 Standards and Technology Department 2500 Wilson Boulevard Arlington, VA 22201 PRICE: Please refer to the current Catalog of ELECTRONIC INDUSTRIES ALLIANCE STANDARDS and EN
10、GINEERING 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. STD-EIA TSBLL7-ENGL 2000 3234600 Ob55213 4L5 D TSB-117 Clarification of DTX Receive Handling in TINEIA-1 36 Table of Contents z 1. STATEME
11、NT OF PROBLEM 1 5 2. PROPOSED SOLUTION 1 i STD-EIA TSB117-ENGL 2000 3234600 Oh55214 351 H I IO II I2 13 I4 I5 16 17 18 19 20 21 22 2; 21 25 TSB-117 Clarification of DTX Receive Handling in TINEIA-1 36 1. Statement of Problem Support of the Discontinuous Transmission with Comfort Noise (DTX/CN) featu
12、re in TIAEIA- 136-4 1 O and TIAEIA- 136- 133-A may result in potential audio artifacts if the synchronization of the Voice Coder parameter reset on each side of the air interface is not insured. The potential to encounter unsynchronized Voice Coder parameters may exist if the receive DTX handler rel
13、ies on the radio channel entering the DTX Low state as the action that initiates the parameter reset. Given the non-deterministic nature of non-speech events detected by the Voice Activity Detector in the mobile station, there is no guarantee that detection of a non-speech event actually results in
14、the radio channel entering the DTX Low state. This may occur if the non-speech event does not persist long enough for the channel to discontinue transmission, and results in the Comfort Noise Parameter message being immediately followed by speech. It is also recognized that due to radio channel cond
15、itions, reception of a transmitted FACCH message is not always guaranteed. The language presented in TIAEIA- 136- 133-A, section 1 and in TIAEIA- 136-4 10, sections 6.4,6.4.1, 6.4.2, and 6.4.3.4, may not clearly identi the appropriate procedural responses to these conditions. The proposed solution r
16、ectifies these conditions, by refining the procedural aspects related to support of the DTX/CN feature. The first refinement clearly identifies receipt of the Comfort Noise Parameter message by the base station as the primary action initiating the Voice Coder parameter reset by the receive DTX Handl
17、er. The second refinement provides a DTX Indication to the entity utilizing the channel that the radio channel has entered the DTX Low state. The receive DTX Handler may use this as an inferred confirmation of the receipt of a Comfort Noise Parameter message, for the purpose of resetting the Voice C
18、oder parameters. 26 2. Proposed Solution 27 28 6.4 Operations on the receive side The changes to TIAlEIA-136-41 O, Sections 6.4, 6.4.1, and 6.4.2 are presented below. 29 30 31 32 side DTX handler. The radio receiver shall determine if the received traffic frame is either a speech frame or CN paramet
19、er message frame. It shall also set a bad frame indicator flag to 1 if the he is unusable. Frame information and the bad frame indicator flag are passed to the receive 33 6.4.1 31 The following text . I escribes the implementation in the bit-exact 35 reference C code. Example solution for classifica
20、tion of speech and CN traffic frames I. 36 37 Regardless of their context (speech, CN parameter message, other FACCH messages or none), the radio receiver continuously passes the received traffic frames to the receive side 1 1 2 O 1 :I Invalid combination Good speech frame Valid CN parameter Unusabl
21、e frame message 5 6 7 8 9 IO II 12 I3 11 15 16 17 18 19 20 21 22 23 24 25 26 27 28 i 29 30 31 32 TSB-117 Clarification of DTX Receive Handling in TINEIA-136 DTX handler, individually marked by various preprocessing function with 3 flags. These are the speech frame Bad Frame Indicator (BFI) flag, the
22、 CN parameter Bad Frame TSB-117 Clarification of DTX Receive Handling in TINEIA-1 36 The changes to TIA/EIA-136-41 O, Section 6.4.3.4 are presented below. 6.4.3.4 CN synthesis and updating The CN synthesis procedure uses the speech decoder algorithm with the following modifications: The fixed codebo
23、ok gain values (see Section 3.1) ax replaced by the random excitation gain value received in the CN parameter message. The fured codebook excitation (see Section 3.1) is replaced by the locally genemted random excitation as described in Section 6.4.3.2. The random excitation is filtered by the RESC
24、synthesis filter, as described in Section 6.4.3.3. The adaptive codebook gain value (see Section 3.1) in each subframe is set to O. The pitch delay value (see Section 3.1) in each subframe is set to 60. The LP filter parameters used (see Section 3.1) at those decoded from the CN parameter message. T
25、he predictor memories of the ordinary LP parameter and fixed codebook gain quantization algorithms are reset when SP flag = “O”, so that the quantizers start from their initial states when the speech activity begins again. If a DTX-Low state indication (see TIAEIA 136-133-A, Section 1.1) is received
26、 from a lower layer entity processing the channel and is not pcceded by a valid Comfort Noise parameter message, the predictor memories of the ordinary LP parameter and fixed codebook gain quantization algorithms shall be reset and a bad franie masking procedure such as that suggested in Section 6.4
27、.4 may be applied. Updating of the CN parameters (random excitation gain, RESC parameters and LP filter parameters) occurs each time a valid CN parameter message is received, as described in Section 6.4.2. When updating the CN, the parameters above should be interpolated over the CN update period to
28、 obtain smooth transitions. Spectral dithering should be applied to the interpolated LP parameters prior to using them for CN synthesis. The adaptive tilt factor rn of the tilt compensation filter H,(z) (see Section 3.2.1) should be changed to a fixed value of m = -0.2. With these modifications, the
29、 speech decoder now synthesizes comfort noise. . 4 STDoEIA TSBLL7-ENGL 2000 3234600 Ob55218 TT7 I 2 4 5 6 7 8 9 IO II 12 li I4 15 16 17 18 19 20 21 22 2: 24 2s 26 27 28 34 35 56 37 28 39 40 41 32 43 TSB-117 Clarification of DTX Receive Handling in TINEIA-1 36 The changes to TIA/EIA-133-A are present
30、ed below. I Discontinuous-Transmission Discontinuous-Transmission refers to the ability of certain mobile stations to switch autonomously between two transmitter power-level states (DTX-High and DTX-Low). I .I Discontinuous-Transmission on a Digital Traffic Channel In the DTX-High state. the transmi
31、tter radiates at a power level indicated by the most recent power-controlling order (Initial Traffic Channel Designation message, Digital Traffic Channel Designation message, Handoff message, Dedicated DTC Handoff message, or Physical Layer Control message) received by the mobile station. In this st
32、ate, the mobile station will send CDVCC at all times. BMI support of DTX is indicated in the Handoff, Physical Layer Control, and Dedicated DTC Handoff messages. Mobile Stations on a digital traffic channel may activate DTX with Truncated Bursts, or DTX without Truncated Bursts if BMI support is ind
33、icated by a DTX Mode Information Element. When DTX is activated by a DTX Mode Information Element, the Comfort Noise feature shall be activated also. The base station may provide a DTX Indication to the higher layer entity utilizing the radio channel for each slot that DTX is active. Mobile Stations
34、 that do not support DTX Mode, or that are not on a digital traffic channel may activate DTX if BMI support is indicated by a DTX Allowed Information Element. A Mobile Station that activated DTX as a result of receiving a DTX Allowed Information Element shall not activate the Comfort Noise feature.
35、When DTX without Truncated Bursts is activated in the mobile station, in the DTX-Low state, the transmitter will remain off and the CDVCC will not be sent except for the transmission of FACCH messages. When DTX without Truncated Bursts is activated in the mobile station, all SACCH messages to be tra
36、nsmitted by the mobile station while in the DTX-Low state shall be sent as FACCH messages after which the transmitter will return to the off state unless Discontinuous-Transmission has been otherwise inhibited. I When DTX without Truncated Bursts is activated in the mobile station, and a mobile stat
37、ion desires to switch from the DTX-High state to the DTX-Low state. it may complete all in-progress SACCH messages in the DTX-High state, or terminate SACCH message transmission and resend the interrupted SACCH messages, in their entirety, as FACCH messages. When DTX with Truncated Bursts is activat
38、ed in the mobile station, while in the DTX Low state, the mobile station transmitter will remain on during transmission of the DTX Low Truncated Bursts. On a full or half rate digital traffic channel, a truncated burst will be transmitted in every assigned slot while in the DTX Low state. On a doubl
39、e rate, triple rate or multi-rate digital traffic channel, the mobile station will transmit a DTX Low truncated burst in every assigned slot in which it transmits a layer 1 SACCH field while in the DTX High state. Prior to a mobile station in the DTX High state switching to the DTX Low state, a Comf
40、ort Noise message and all other pending FACCH messages shall be entirely transmitted. The final full length burst prior to transition from the DTX High state to 8 9 STDUEIA TSBZL7-ENGL 2000 3234600 Ob552L9 933 W TSB-117 Clarification of DTX Receive Handling in TINEIA-1 36 the DTX Low state shall inc
41、lude a FACCH message, interleaved with a FACCH Word containing 6 FACCH Filler Octets. Note that while a Comfort Noise Parameter message shall always precede the transition to the DTX Low state, it does not guarantee that the transition to the DTX Low state shall occur. The initial full length burst after transition from the DTX Low to the DTX High state shall include a FACCH Word containing 6 FACCH Filler Octets interleaved with a FACCH message or voice. Note that only one half of the word containing FACCH Filler is transmitted with the final and initial full length bursts. 6
