1、 TIA-895-B (Revision of TIA-895-A) July 2011CDMA Tandem Free Operation NOTICE TIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products,
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18、NTAL ELEMENT OF THE USE OF THE CONTENTS HEREOF, AND THESE CONTENTS WOULD NOT BE PUBLISHED BY TIA WITHOUT SUCH LIMITATIONS. Revision History Date Revision Description November 2000 A.S0004-0 v1.0 Support for Tandem Free Operation. March 2002 A.S0004-A v2.0 Removal of TDMA text, addition of support fo
19、r DTMF Tones and TFO version numbering. August 2002 A.S0004-B v2.0 Support for SMV and codec mismatch resolution/optimization. January 2011 A.S0004-C v1.0 Support for EVRC-B, EVRC-WB that a certain course of 14 action is preferred but not necessarily required; or (in the negative form) that a certai
20、n possibility or 15 course of action is discouraged but not prohibited. “May” and “need not” indicate a course of action 16 permissible within the limits of the standard. “Can” and “cannot” are used for statements of possibility 17 and capability, whether material, physical, or causal. 18 3 Referenc
21、es 19 References are either normative or informative. A normative reference is used to include another 20 document as a mandatory part of a 3GPP2 specification. Documents that provide additional non-essential 21 information are included in the informative references section. 22 3.1 Normative Referen
22、ces 23 The following standards contain provisions which, through reference in this text, constitute provisions of 24 this standard. At the time of publication, the editions indicated were valid. All standards are subject to 25 revision, and parties to agreements based upon this document are encourag
23、ed to investigate the 26 possibility of applying the most recent editions published by them. 27 1 3GPP2 C.S0009-0, Speech Service Option Standard for Wideband Spread Spectrum Systems, 28 December 1999. 29 2 3GPP2 C.S0014-D v3.0, Enhanced Variable Rate Codec, Speech Service Options 3, 68, 70, and 30
24、73 for Wideband Spread Spectrum Systems, October 2010. 31 3 3GPP2 C.S0020-A v1.0, High Rate Speech Service Option 17 for Wideband Spread Spectrum 32 Communications Systems, April 2004. 33 4 3GPP2 C.S0030-0 v3.0, Selectable Mode Vocoder Service Option for Wideband Spread 34 Spectrum Communication Sys
25、tems, January 2004. 35 1cdma2000is the trademark for the technical nomenclature for certain specifications and standards of the Organizational Partners (OPs) of 3GPP2. Geographically (and as of the date of publication), cdma2000is a registered trademark of the Telecommunications Industry Association
26、 (TIA-USA) in the United States. TIA-895-B 2 5 cdma2000 Standards for Spread Spectrum Systems: 1 3GPP2 C.S0001-E v2.0, Introduction to cdma2000 Standards for Spread Spectrum Systems, June 2 2010. 3 3GPP2 C.S0002-E v2.0, Physical Layer Standard for cdma2000 Spread Spectrum Systems, June 4 2010. 5 3GP
27、P2 C.S0003-E v2.0, Medium Access Control (MAC) Standard for cdma2000 Spread 6 Spectrum Systems, June 2010. 7 3GPP2 C.S0004-E v2.0, Signaling Link Access Control (LAC) Standard for cdma2000 Spread 8 Spectrum Systems, June 2010. 9 3GPP2 C.S0005-E v2.0, Upper Layer (Layer 3) Signaling Standard for cdma
28、2000 Spread 10 Spectrum Systems, June 2010. 11 3GPP2 C.S0006-D v2.0, Analog Signaling Standard for cdma2000 Spread Spectrum Systems, 12 September 2005. 13 6 3GPP2 A.S0014-D v2.0, Interoperability Specification (IOS) for cdma2000 Access Network 14 Interfaces Part 4 (A1, A1p, A2, and A5 Interfaces), A
29、ugust 2009. 15 7 3GPP TS 28.062: In-band Tandem Free Operation (TFO) of Speech Codecs; Version 4.2.0, 16 December 2001. 17 8 GSM 08.62: Digital cellular telecommunication system (Phase 2+); Inband Tandem Free 18 Operation (TFO) of Speech Codecs; Version 7.0.0, February 1999. 19 3.2 Informative Refer
30、ences 20 3GPP2: X.S0004-000-E v9.0, Mobile Application Part (MAP), June 2009. 21 22 23 24 TIA-895-B 3 4 Terminology 1 4.1 Definitions 2 For the purposes of the present document, the following definitions apply. 3 2G is a 2ndgeneration wireless systems. 4 3G is a 3rdgeneration wireless systems. 5 Dec
31、oder provides reconstruction of a speech signal from a compressed format according to an 6 appropriate algorithm. 7 Encoder provides compression of a speech signal into a new format for bandwidth efficiency according 8 to an appropriate algorithm. 9 Error Concealment Indicator (ECI) is used to signa
32、l that a TFO frame does not contain valid speech 10 parameters. 11 EVRC-B is a narrowband Enhanced Variable Rate Codec corresponding to speech service option 68, 12 capable of operating at multiple average rates or capacity operating points. Refer to 2. 13 EVRC-WB is a wideband Enhanced Variable Rat
33、e Codec, corresponding to speech service option 70, 14 capable of operating at one wideband mode and two narrowband modes interoperable with EVRC-B 2. 15 EVRC-NW is a narrowband-wideband Enhanced Variable Rate Codec, corresponding to speech service 16 option 73, combining the wideband capability of
34、EVRC-WB, the multiple capacity operating point 17 capability of EVRC-B, and capability for discontinuous transmission in circuit-switch domain 2. 18 Mobile is a standalone unit communicating with the BTS over an air interface in a digital wireless 19 communication system. In this document it is inte
35、rpreted as a mobile station or a fixed wireless terminal. 20 PCM sample is an 8-bit value representing the A_Law or _Law coded sample of a speech or audio 21 signal; sometimes used to indicate the time interval between two PCM samples (125s). 22 PSTN interface is used to denominate the 64 kbps PCM l
36、ink from/to the TRAU. Note that PSTN 23 interface does not necessarily mean a connection to a PSTN, but is a general description for a digital 64 24 kbps PCM line. 25 TFO frame is used equivalent to “TFO TRAU frame“. TFO frames are transmitted between TFO 26 Partners (e.g. TRAUs). 27 Transcoder is a
37、 unit for housing the encoder and the decoder required for digital wireless transmission. 28 Transcoder and Rate Adapter Unit (TRAU) is a unit that performs speech encoding and decoding on 29 the network side of the communications system according to the codec standard selected. 30 TRAU frame is use
38、d equivalent to “TRAU speech frame“. TRAU frames are transmitted between 31 TRAU and TRX. 32 TTL is used to denote the link between the TRAU and the TRX, independent of the system. 33 4.2 Acronyms 34 For the purposes of the present document, the following acronyms apply. 35 BS Base Station BSC Base
39、Station Controller BTS Base Transceiver System TIA-895-B 4 CDMA Code Division Multiple Access COP 0 Capacity Operating Point 0 CRC Cyclic Redundancy Check DS0 Digital Signal Level 0 DTMF Dual Tone MultiFrequency ECI Error Concealment Indicator EVRC Enhanced Variable Rate Codec 2 EVRC-WB Enhanced Var
40、iable Rate Codec Wideband EVRC-NW Enhanced Variable Rate Codec Narrowband-Wideband GSM Global System for Mobile Communication HHO Hard Handoff IPE In Path Equipment LPC Linear Predictive Codec LSB Least Significant Bit MS Mobile Station MSC Mobile Switching Center PCM Pulse Coded Modulation PCM_Sile
41、nce either PCM_Alaw_Silence, or PCM_Law_Silence, dependent on application PSTN Public Switched Telephone Network Q8 Speech Codec Service Option 1 for cdma2000 at 8 kbps 1 Q13 Speech Codec Service Option 17 for cdma2000 at 13.3 kbps 3 SDU Selection/Distribution Unit SMV Selectable Mode Vocoder Speech
42、 Service Option 56 4 TCME TFO Circuit Multiplication Equipment TDMA Time Division Multiple Access T_Bits Time Alignment bits TFO Tandem Free Operation TFO_ACK TFO Acknowledgement message TFO_FILL TFO Fill message TFO_TRANS TFO Transparent Mode message TFO_NORMAL TFO Normal Mode message TFO_DUP TFO (
43、Half) Duplex Mode message TFO_REQ TFO Request message TFO_SYL TFO Sync Lost message TRAU Transcoder and Rate Adapter Unit TRX Radio transceiver station TTL TRAU-TRX-Link UMTS Universal Mobile Telecommunications System VoIP Voice over IP 1 TIA-895-B 5 5 General Approach 1 5.1 Background 2 In the case
44、 of mobile-to-mobile (MS-MS) calls in networks without TFO, the speech signal is encoded 3 within the first MS for transmission on the air interface, and decoded within the associated first TRAU. 4 The PCM samples are then transported within the fixed part of the network to the second TRAU using 64
45、5 kbps traffic links. This second TRAU encodes the speech signal a second time for the transmission on the 6 second air interface, and the associated second mobile station decodes it again. The two codecs (encoder-7 decoder pair) of the connection are in “Tandem Operation“. 8 Tandem Free Operation o
46、vercomes the disadvantage of degraded speech quality caused by the two 9 consecutive encoding/decoding processes required in Tandem Operation. 10 Tandem Free Operation does not necessarily decrease processing delay. PCM is still sent, 11 synchronized to the coded speech, e.g. for easy TFO in/out. 12
47、 Tandem Free Operation requires a bi-directional “transparent“ digital channel or path between the 13 TRAUs. Devices within these paths need to be transparent or switched off for the TFO messages and the 14 TFO frames. To guarantee this digital transparency with out-of-band signaling is not trivial.
48、 In 15 particular, out-of-band signaling has insufficient speed to fall back to normal operation in case of sudden 16 interruption of the transparency of the links. 17 This TFO recommendation defines therefore an inband signaling protocol, which 18 tests if: 19 - an MS-MS call is given; 20 - the pat
49、hs between the TRAUs are digitally transparent; 21 - both TRAUs support TFO; 22 - the speech codecs on both radio legs are identical. 23 establishes the TFO connection by: 24 - commanding the paths to go transparent; 25 - bypassing the decoder/encoder functions within the TRAUs. 26 provides a fast fall back procedure for sudden TFO interruption. 27 28 Although Tandem Free Operation only requires changes to the TRAUs, network IPEs may also need to 29 be modified to be compliant with TFO. 30 5.2 Principle of Tandem Free Operation 31 The TRAU shall b
