Content for  TS 48.020  Word version:  16.0.0

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1  ScopeWord‑p. 6

The present document defines rate adaptation functions to be used in PLMN Base Station Systems (BSS) transcoders and IWF
  • for adapting radio interface data rates to the 64 kbit/s used at the A-interface in A/Gb mode and
  • for adapting radio interface data rates to the Iu interface in GERAN Iu mode in accordance with TS 43.010.
The number of Base Station System - Mobile-services Switching Centre (BSS - MSC) traffic channels supporting data rate adaptation may be limited. In this case some channels may not support data rate adaptation. Those that do, shall conform to this specification.

2  References, abbreviations and definitions

2.1  References

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TR 21.905: " Vocabulary for 3GPP specifications ".
TS 22.034: "High Speed Circuit Switched Data (HSCSD) - Stage1"
TS 43.010: "GSM Public Land Mobile Network (PLMN) connection types".
TS 23.034: "High Speed Circuit Switched Data (HSCSD) - Stage2".
TS 44.021: "Rate adaption on the Mobile Station Base Station System (MS BSS) interface".
TS 24.022: "Radio Link Protocol (RLP) for Circuit Switched Bearer and Teleservices".
TS 45.003: "Channel coding".
TS 27.001: "General on Terminal Adaptation Functions (TAF) for Mobile Stations (MS)".
TS 48.008: "Mobile Switching Centre Base Station System (MSC BSS) interface; Layer 3 specification".
TS 29.007: "General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)".
ITU-T Recommendation V.110: "Support of data terminal equipment's (DTEs) with V-Series interfaces by an integrated services digital network".
ITU-T Recommendation I.460:-Multiplexing, rate adaption and support of existing interfaces.
TS 48.060: "In-band control of remote transcoders and rate adaptors for full rate traffic channels"
TS 25.415: "UTRAN Iu Interface user plane protocols".

2.2  AbbreviationsWord‑p. 7

For the purposes of the present document, the following abbreviations apply:
Frame Pattern Substitution
Frame Start Identifier
Zero Sequence Position

2.3  Definitions

For the purposes of the present document, the following terms and definitions apply.
Stream of data with explicit or implicit numbering between splitter and combine functions.
A physical full rate channel on the radio interface (TCH/F) independent of the contents.
A interface circuit:
The 8 bits that constitute one 64 kbps circuit on the A interface.
A interface subcircuit:
One specific bit position or one specific pair of bit positions within the A interface circuit.
EDGE channel:
A general term referring to channels based on 8PSK modulation; i.e. TCH/F28.8, TCH/F32.0, and TCH/F43.2.

3  General approach

3GPP TS 43.010, clause 6 defines the PLMN connection types necessary to support the data and telematic services in a PLMN operating in A/Gb mode or GERAN Iu mode.
Within the BSS , transcoder and IWF, there are several data rate adaptation functions which are combined as shown in TS 43.010 as part of a connection type.
These functions are RA0, RA1, RA1/RA1' , RA1'' , RA1'/RA1", RA1'/RAA", RA1', RAA", RA1'/RAA', RAA' , RAE and RA2. The RA2 function is equivalent to that described in ITU-T Recommendation V.110. In addition, splitting/combining, padding and inband numbering functions as defined in TS 44.021 and multiplexing as defined herein are used in cases where more than one channel is allowed.
The RA1/RA1', RA1'/RA1", RA1'/RAA" and RA1'/RAA' are relay functions used as indicated in TS 43.010.
The BSS uses the information contained in the ASSIGNMENT REQUEST message on the A-interface (see TS 48.008) to set the "E bits" and to map the "D bits" as shown below, as well as to choose the correct channel coding.

4  The RA0 Function

The RA0 function is specified in TS 44.021.

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