Content for TS 26.261 Word version: 18.0.0
0 Introduction
1 Scope
2 References
3 Definitions of terms, symbols and abbreviations
3.1 Terms
3.2 Symbols
3.3 Abbreviations
4 Interfaces
4.1 General
4.2 Air interfaces
4.3 Acoustical interfaces
4.4 Electrical interfaces
...
...
0 Introduction p. 5
TS 26.261 specifies minimum performance requirements for the electro-acoustic characteristics of LTE, NR and WLAN terminals when used to provide immersive services. The performance requirements are specified in the main body of the text; the test methods and test considerations are described in TS 26.260.
1 Scope p. 6
The present document specifies minimum performance requirements for the electro-acoustic characteristics of LTE, NR and WLAN terminal. It is applicable to any terminal capable of supporting wideband, super-wideband or fullband immersive services.
The set of minimum performance requirements enables a guaranteed level of speech quality while taking possible physical limits of the terminal design into account. Some performance objectives are also defined if such design limits can be overcome.
The present document covers both conversational services based on MTSI / telepresence and non-conversational services.
2 References p. 6
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.
[1]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TS 26.260: "Objective test methodologies for the evaluation of immersive audio systems"
[3]
TS 26.114: "IP Multimedia Subsystem (IMS); Multimedia Telephony; Media handling and interaction".
[4]
TS 26.131: "Terminal Acoustic Characteristics for Telephony; Requirements".
[5]
ETSI TS 103 739 (2021-10) V1.4.1: " Transmission requirements for wideband mobile wireless terminals (handset and headset) from a QoS perspective as perceived by the user".
[6]
ETSI TS 103 740 (2021-10) V1.4.1: "Transmission requirements for wideband mobile wireless terminals (hands-free) from a QoS perspective as perceived by the user".
3 Definitions of terms, symbols and abbreviations p. 6
3.1 Terms p. 6
For the purposes of the present document, the terms given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.
For the purposes of the present document the terms wideband, super-wideband and fullband refer to test signals associated with the corresponding operating codec modes in TS 26.260.
The overload point (maximum load capacity) is for the purposes of this document defined as the RMS level of a digital representation of a full-scale pure tone at the input of the IVAS encoder. The overload point is defined in TS 26.260.
For the purposes of the present document, the term electrical interface is defined as an analogue or digital access to a UE, which allows injecting and capturing signals electrically instead of through an acoustical interface. The interface can be either analogue (wired) or digital (wired or wireless). The purpose of this interface is to connect a separate device (typically a headset), which provides a receiver and transmitter.
Stereo panorama:
The spatial image of a stereo signal, in which the sound source directions lie in a range from -100% (left) to 100% (right).
3.2 Symbols p. 7
dB
Decibel
Hz
Unit of frequency (Hertz)
ϕ
Azimuth angle (phi)
θ
Elevation angle (theta)
TR
UE delay in receiving direction
TS
UE delay in sending direction
ζ(ϕ)
Estimate for a single source direction in the stereo panorama that is physically positioned in direction ϕ relative to the capturing device
3.3 Abbreviations p. 7
For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
DTX
Discontinuous Transmission
EVS
Enhanced Voice Services
HATS
Head and Torso Simulator
ILD
Interaural Level Difference
ISM
Independent Stream with Metadata
ITD
Interaural Time Difference
IVAS
Immersive Voice and Audio Services
MASA
Metadata-Assisted Spatial Audio
OMASA
Objects (ISM) with Metadata-Assisted Spatial Audio
OSBA
Objects (ISM) with Scene-Based Audio
POI
Point of Interconnection (with PSTN)
RLR
Receive Loudness Rating
SBA
Scene-Based Audio
SLR
Send Loudness Rating
WLAN
Wireless Local Area Network
4 Interfaces p. 7
4.1 General p. 7
The interfaces required to define immersive terminal electro-acoustic characteristics are shown in TS 26.260. These are the air interface and the point of interconnect (POI). The interfaces are shown for different types of immersive formats.
Measurements can be made using the system simulator (SS) described in TS 26.260. For conversational services, MTSI aspects are specified by TS 26.114.
4.2 Air interfaces p. 7
The same air interfaces as in clause 4.2 of TS 26.131 apply.
4.3 Acoustical interfaces p. 8
The acoustical interfaces are described in clause 5.4.2 of TS 26.260.
4.4 Electrical interfaces p. 8
The electrical interface UE is considered in this specification and details on standardized analogue (wired) and digital (wired and wireless) electrical interfaces can be found in TS 26.260. For the electrical interface, the POI in sending / receiving direction is respectively defined as the input / output of the reference coder of the system simulator.
Any of the UE types mentioned in clause 4.3 providing an electrical interface can be considered as Electrical Interface UE.
