ETSI TR 126 928 V16.1.0 (2021-01)

5G; Extended Reality (XR) in 5G (3GPP TR 26.928 version 16.1.0 Release 16)

RTR/TSGS-0426928vg10

General Information

• Status: Not Published
• Technical Committee: 3GPP SA 4 - Codec
• Current Stage: 12 - Completion
• Completion Date: 19-Jan-2021

Standards Content (Sample)

TECHNICAL REPORT
5G;
Extended Reality (XR) in 5G
(3GPP TR 26.928 version 16.1.0 Release 16)

3GPP TR 26.928 version 16.1.0 Release 16 1 ETSI TR 126 928 V16.1.0 (2021-01)

Reference
RTR/TSGS-0426928vg10
Keywords
5G
ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: [phone]  Fax: [phone]

Siret N° 348 623 562 00017 - NAF 742 C
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° 7803/88

Important notice
The present document can be downloaded from:
http://www.etsi.org/standards-search
The present document may be made available in electronic versions and/or in print. The content of any electronic and/or
print versions of the present document shall not be modified without the prior written authorization of ETSI. In case of any
existing or perceived difference in contents between such versions and/or in print, the prevailing version of an ETSI
deliverable is the one made publicly available in PDF format at www.etsi.org/deliver.
Users of the present document should be aware that the document may be subject to revision or change of status.
Information on the current status of this and other ETSI documents is available at
https://portal.etsi.org/TB/ETSIDeliverableStatus.aspx
If you find errors in the present document, please send your comment to one of the following services:
https://portal.etsi.org/People/CommiteeSupportStaff.aspx
Copyright Notification
No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying
and microfilm except as authorized by written permission of ETSI.
The content of the PDF version shall not be modified without the written authorization of ETSI.
The copyright and the foregoing restriction extend to reproduction in all media.

© ETSI 2021.
All rights reserved.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its Members.

3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and
of the 3GPP Organizational Partners.
oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and
of the oneM2M Partners. ®
GSM and the GSM logo are trademarks registered and owned by the GSM Association.
ETSI
3GPP TR 26.928 version 16.1.0 Release 16 2 ETSI TR 126 928 V16.1.0 (2021-01)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Legal Notice
This Technical Report (TR) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities. These shall be
interpreted as being references to the corresponding ETSI deliverables.
The cross reference between 3GPP and ETSI identities can be found under http://webapp.etsi.org/key/queryform.asp.
Modal verbs terminology
In the present document "should", "should not", "may", "need not", "will", "will not", "can" and "cannot" are to be
interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
3GPP TR 26.928 version 16.1.0 Release 16 3 ETSI TR 126 928 V16.1.0 (2021-01)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword. 7
Introduction . 7
1 Scope . 8
2 References . 8
3 Definitions of terms, symbols and abbreviations . 10
3.1 Terms . 10
3.2 Abbreviations . 10
4 Introduction to Extended Reality . 12
4.1 XR Terms and Definitions . 12
4.1.1 Different Types of Realities . 12
4.1.2 Degrees of Freedom and XR Spaces . 13
4.1.3 Tracking and XR Viewer Pose Generation . 18
4.1.4 XR Spatial Mapping and Localization . 18
4.2 Quality-of-Experience for XR . 19
4.2.1 Immersiveness and Presence . 19
4.2.2 Interaction Delays and Age of Content . 22
4.3 XR Delivery in 5G System . 23
4.3.1 General Delivery Categories . 23
4.3.2 5G System and Radio Functionalities for XR . 23
4.3.3 Quality-of-Service in 5G . 25
4.3.4 5G Media Delivery . 28
4.3.5 Edge Computing . 28
4.4 XR Engines and Rendering . 28
4.4.1 Introduction . 28
4.4.2 Briefly on Rendering Pipelines . 30
4.4.3 Real-time 3D Rendering . 31
4.4.4 Network Rendering and Buffer Data . 31
4.5 2D Compression Technologies . 32
4.5.1  Core Compression Technologies . 32
4.5.2 Format and Parallel Decoding Challenges . 33
4.6 3D and XR Visual Formats . 34
4.6.1 Introduction . 34
4.6.2 Omnidirectional Visual Formats . 34
4.6.2.1 Introduction . 34
4.6.2.2 Definition . 34
4.6.2.3 Production and Capturing Systems . 35
4.6.2.4 Rendering . 35
4.6.2.5 Compression, Storage and Data Formats . 35
4.6.2.6 Quality and Bitrate considerations . 36
4.6.2.7 Applications . 36
4.6.3 3D Meshes . 36
4.6.3.1 Introduction . 36
4.6.3.2 Definition . 36
4.6.3.3 Production and Capturing Systems . 37
4.6.3.4 Rendering . 37
4.6.3.5 Storage and Data Formats . 37
4.6.3.5.1 Introduction . 37
4.6.3.5.2 PoLYgon (PLY) File Format . 37
4.6.3.6 Texture Formats . 38
4.6.3.8 Bitrate and Quality Considerations . 38
ETSI
3GPP TR 26.928 version 16.1.0 Release 16 4 ETSI TR 126 928 V16.1.0 (2021-01)
4.6.3.7 Applications . 39
4.6.4 Point Clouds . 39
4.6.5 Light Fields . 39
4.6.6 Scene Description . 39
4.6.7 Production and Capturing Systems for 3D Mesh and Point Clouds . 40
4.6.7.1 Overview . 40
4.7 3D and XR Audio Formats . 42
4.8 Devices and Form Factors . 43
4.8.1 Device Types . 43
4.8.2 Power Consumption . 46
4.9 Ongoing Standardisation Work. 47
4.9.1 Related Work in 3GPP . 47
4.9.2.1 Introduction . 47
4.9.2 Related Work External of 3GPP . 47
4.9.2.1 Introduction . 47
4.9.2.2 MPEG . 47
4.9.2.2.1 Introduction . 47
4.9.2.3 Khronos . 48
4.9.2.4 W3C WebXR. 48
4.10 XR Use Cases . 48
4.11 Summary of Remaining Issues addressed in this Document . 50
5 Core Use Cases and Scenarios for Extended Reality . 50
5.1 Introduction. 50
5.2 Offline Sharing of 3D Objects . 51
5.2.1 Summary of Use cases . 51
5.2.2 Description . 51
5.2.3 Potential Normative Work . 52
5.3 Real-time XR Sharing . 53
5.3.1 Summary of Use Cases . 53
5.3.2 Description . 53
5.3.3 Potential Normative Work . 54
5.4 XR Multimedia Streaming . 55
5.4.1 Summary of Use Cases . 55
5.4.2 Description . 55
5.4.3 Potential Normative Work . 56
5.5 Online XR Gaming . 56
5.5.1 Summary of Use Cases . 56
5.5.2 Description . 56
5.5.3 Potential Normative Work . 57
5.6 XR Mission Critical . 57
5.6.1 Summary of Use Cases . 57
5.6.2 Description . 58
5.6.3 Potential Normative Work . 58
5.7 XR Conference . 59
5.7.1 Summary of Use Cases . 59
5.7.2 Description . 59
5.7.3 Potential Normative Work . 60
5.8 Spatial Audio Multiparty Call . 61
5.8.1 Summary of Use Cases . 61
5.8.2 Description . 61
5.8.3 Potential Normative Work . 62
6 Mapping Extended Reality to 5G . 62
6.1 Introduction. 62
6.2 XR Processing and Media Centric Architectures . 62
6.2.1 Introduction . 62
6.2.2 Viewport-Independent delivery . 63
6.2.2.1 Architecture . 63
6.2.2.2 Use Cases in Context . 63
6.2.2.3 Basic Procedures . 63
6.2.2.4 Content Formats and Rendering . 63
ETSI
3GPP TR 26.928 version 16.1.0 Release 16 5 ETSI TR 126 928 V16.1.0 (2021-01)
6.2.2.5 Relevant QoS and QoE parameters . 63
6.2.2.6 Potential Standardisation Needs . 64
6.2.3 Viewport-dependent Streaming . 64
6.2.3.1 Architecture . 64
6.2.3.2 Use Cases in Context . 65
6.2.3.3 Basic Procedures . 65
6.2.3.4 Content Formats and Rendering . 65
6.2.3.5 Relevant QoS and QoE parameters . 65
6.2.3.6 Potential Standardisation Needs . 65
6.2.4 Viewport Rendering in Network . 66
6.2.4.1 Overview . 66
6.2.4.2 Relevant QoS and QoE parameters . 66
6.2.4.3 Potential Standardisation Needs . 67
6.2.5 Raster-based Split Rendering . 67
6.2.5.1 Architecture . 67
6.2.5.2 Use Cases in Context . 68
6.2.5.3 Basic Procedures . 68
6.2.5.4 Content Formats and Rendering . 69
6.2.5.5 Relevant QoS and QoE parameters . 69
6.2.5.6 Potential Standardisation needs . 69
6.2.6 Generalized XR Split Rendering . 69
6.2.6.1 Architecture . 69
6.2.6.2 Use Cases in Context . 70
6.2.6.3 Basic Procedures . 70
6.2.6.4 Content Formats and Rendering . 71
6.2.6.5 Relevant QoS and QoE parameters . 71
6.2.6.6 Potential Standardisation needs . 71
6.2.7 XR Distributed Computing . 71
6.2.8 XR Conversational . 72
6.3 Summary of Traffic Characteristics . 74
6.4 Analysis of existing 5QIs . 75
7 Potential Standardisation Areas . 76
7.1 General . 76
7.2 XR-Centric Device Types and Architectures . 76
7.3 Extensions to 5G Media Streaming for XR/6DoF Media . 76
7.4 Raster-based Split Rendering with Pose Correction . 76
7.5 XR conference applications . 77
7.6 Augmented Reality for New Form Factors . 77
7.7 Traffic Characteristics and Models for XR Services . 78
7.8 Social XR . 78
7.9 Generalized Split and Cloud Rendering and Processing . 79
8 Conclusions and Proposed Next Steps . 79
Annex A: Collection of XR Use Cases . 81
A.1 Introduction and Template . 81
A.2 Use Case 1: 3D Image Messaging . 84
A.3 Use Case 2: AR Sharing . 85
A.4 Use Case 3: Streaming of Immersive 6DoF . 86
A.5 Use Case 4: Emotional Streaming . 88
A.6 Use Case 5: Untethered Immersive Online Gaming . 89
A.7 Use Case 6: Immersive Game Spectator Mode . 92
A.8 Use Case 7: Real-time 3D Communication . 94
A.9 Use Case 8: AR guided assistant at remote location (industrial services) . 95
A.10 Use Case 9: Police Critical Mission with AR . 97
ETSI
3GPP TR 26.928 version 16.1.0 Release 16 6 ETSI TR 126 928 V16.1.0 (2021-01)
A.11 Use Case 10: Online shopping from a catalogue – downloading . 99
A.12 Use Case 11: Real-time communication with the shop assistant . 100
A.13 Use Case 12: 360-degree conference meeting . 102
A.14 Use Case 13: 3D shared experience . 104
A.15 Use Case 14:6DOF VR conferencing . 107
A.16 Use Case 15: XR Meeting . 110
A.17 Use Case 16: Convention / Poster Session . 114
A.18 Use Case 17: AR animated avatar calls. 119
A.19 Use Case 18: AR avatar multi-party calls . 120
A.20 Use Case 19: Front-facing camera video multi-party calls . 121
A.21 Use Case 20: AR Streaming with Localization Registry . 123
A.22 Use Case 21: Immersive 6DoF Streaming with Social Interaction . 124
A.23 Use Case 22: 5G Online Gaming party . 126
A.24 Use Case 23: 5G Shared Spatial Data . 128
Annex B: Change history . 131
History . 132

ETSI
3GPP TR 26.928 version 16.1.0 Release 16 7 ETSI TR 126 928 V16.1.0 (2021-01)
Foreword
This Technical Report has been produced by the 3rd Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
Introduction
This Technical Report collects information on eXtended Reality (XR) in the context of 5G radio and network services.
Extended reality (XR) refers to all real-and-virtual combined environments and associated human-machine interactions
generated by computer technology and wearables. It includes representative forms such as augmented reality (AR),
mixed reality (MR), and virtual reality (VR) and the areas interpolated among them. In this Technical Report, baseline
technologies for XR type of services and applications are introduced outlining the QoE/QoS issues of XR-based
services, the delivery of XR in the 5G system, and an architectural model of 5G media streaming defined in TS 26.501.
In addition to the conventional service category, interactive, streaming, download, and split compute/rendering are
identified as new delivery categories. A survey of 3D, XR visual and audio formats is also provided.
Use cases and device types are classified, and processing and media centric architectures are introduced. This includes
viewport independent and dependent streaming, as well as different distributed computing architectures for XR. Core
use cases of XR include those unique to AR and MR in addition to those of VR discussed in 3GPP TR 26.918, ranging
from offline sharing of 3D objects, real-time sharing, multimedia streaming, online gaming, mission critical
applications, and multi-party call/conferences. Based on the details in the report, proposals for potential standardisation
areas are documented.
ETSI
3GPP TR 26.928 version 16.1.0 Release 16 8 ETSI TR 126 928 V16.1.0 (2021-01)
1 Scope
The present document collects information on eXtended Reality (XR) in the context of 5G radio and network services.
The primary scope of the present document is the documentation of the following aspects:
- Introducing Extended Reality by providing definitions, core technology enablers, a summary of devices and
form factors, as well as ongoing related work in 3GPP and elsewhere,
- Collecting and documenting core use cases in the context of Extended Reality,
- Identifying relevant client and network architectures, APIs and media processing functions that support XR use
cases,
- Analysing and identifying the media formats (including audio and video), metadata, accessibility features,
interfaces and delivery procedures between client and network required to offer such an experience,
- Collecting key performance indicators and Quality-of-Experience metrics for relevant XR services and the
applied technology components,
- Drawing conclusions on the potential needs for standardisation in 3GPP.
2 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.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TR 26.918: "Virtual Reality (VR) media services over 3GPP".
[3] 3GPP TS 26.118: "3GPP Virtual reality profiles for streaming applications".
[4] ARCore, https://developers.google.com/ar/
[5] ARKit, https://developer.apple.com/arkit/
[6] 3GPP TR 22.842: "Study on Network Controlled Interactive Service in 5GS".
[7] 3GPP TR 26.247: "Transparent end-to-end Packet-switched Streaming Service (PSS); Progressive
Download and Dynamic Adaptive Streaming over HTTP (3GP-DASH)".
[8] 3GPP TS 23.501: "System Architecture for the 5G System".
[9] Schuemie, Martijn J., Peter Van Der Straaten, Merel Krijn, and Charles A.P.G. Van Der Mast.
“Research on Presence in Virtual Reality: A Survey.” CyberPsychology & Behavior, Vol. 4, No.
2. April 2001.
[10] Ching, Teo Choong. "The Concept of Presence in Virtual Reality." Medium. 27 August 2016.
[11] Sparks, Matt. "Don't Break the Spell: Creating Presence in Virtual Reality" Learning Solutions
Magazine, 17 July 2017.
[12] 3GPP TS 26.501: "5G Media Streaming Architecture".
ETSI
3GPP TR 26.928 version 16.1.0 Release 16 9 ETSI TR 126 928 V16.1.0 (2021-01)
[13] 3GPP TS 22.173: "IP Multimedia Core Network Subsystem (IMS) Multimedia Telephony Service
and supplementary services; Stage 1".
[14] 3GPP TS 26.114: "IP Multimedia Subsystem (IMS); Multimedia Telephony; Media handling and
interaction".
[15] 3GPP TR 22.891 "Feasibility Study on New Services and Markets Technology".
[16] Khronos, "The OpenXR Specification", Jan 25, 2020,
https://www.khronos.org/registry/OpenXR/specs/1.0/html/xrspec.html#introduction
[17] W3C, "WebXR Device API", https://www.w3.org/TR/webxr/
[18] Rolland, Jannick & Holloway, Richard & Fuchs, Henry. (1994). Comparison of optical and video
see-through, head-mounted displays. Proceedings of SPIE - The International Society for Optical
Engineering. 10.1117/12.197322.
[19] "Cloud Gaming: Architecture and Performance", Ryan Shea and Jiangchuan Liu, Simon Fraser
University; Edith C.-H. Ngai, Uppsala University; Yong Cui, Tsinghua University; IEEE
Network-July/August 2013.
[20] M. Claypool and K. Claypool. Latency and player actions in online games. Communications of the
ACM, 49(11):40–45, 2006.
[21] Quax, P., Monsieurs, P., Lamotte, W., De Vleeschauwer, D., and Degrande, N. Objective and
subjective evaluation of the influence of small amounts of delay and jitter on a recent first person
shooter game. In Proceedings of 3rd ACM SIGCOMM workshop on Network and system support
for games (New York, NY, USA, 2004), NetGames ’04, ACM, pp. 152–156.
[22] Chen, K.-t., Huang, P., Wang, G.-s., Huang, C.-y., and Lei, C.-l. On the Sensitivity of Online
Game Playing Time to Network QoS. Proceedings of IEEE INFOCOM 2006 00, c (2006).
[23] 3GPP TS 23.501: "System architecture for the 5G System (5GS)".
[24] 3GPP TS 38.300: "NR; Overall description; Stage-2".
[25] 3GPP TS 22.173: "IP Multimedia Core Network Subsystem (IMS) Multimedia Telephony Service
and supplementary services; Stage 1".
[26] 3GPP TS 26.114: "IP Multimedia Subsystem (IMS); Multimedia telephony; Media handling and
interaction".
[27] 3GPP TR 23.758: "Study on application architecture for enabling Edge Applications"
[28] 3GPP TR 23.748: "Study on enhancement of support for Edge Computing in 5G Core network
(5GC)".
[29] 3GPP TS 23.558: "Architecture for enabling Edge Applications (EA)".
[30] Recommendation ITU-T H.264 (04/2017): "Advanced video coding for generic audiovisual
services" | ISO/IEC 14496-10:2014: "Information technology – Coding of audio-visual objects –
Part 10: Advanced Video Coding".
[31] Recommendation ITU-T H.265 (12/2016): "High efficiency video coding" | ISO/IEC 23008-
2:2015: "High Efficiency Coding and Media Delivery in Heterogeneous Environments – Part 2:
High Efficiency Video Coding".
[32] 3GPP TS 26.116: "Television (TV) over 3GPP services; Video profiles". [33] Jens-Rainer Ohm,
Gary J. Sullivan, Heiko Schwarz, Thiow Keng Tan, and Thomas Wiegand, "Comparison of the
Coding Efficiency of Video Coding Standards—Including High Efficiency Video Coding
(HEVC)" IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO
TECHNOLOGY, VOL. 22, NO. 12, DECEMBER 2012.
[34] T.K. Tan, M. Mrak, R. Weerakkody, N. Ramzan, V. Baroncini, G.J. Sullivan, J.-R. Ohm, K.D.
McCann, "HEVC subjective video quality test results", IBC2014 Conference, 2014.
ETSI
3GPP TR 26.928 version 16.1.0 Release 16 10 ETSI TR 126 928 V16.1.0 (2021-01)
[35] Thiow Keng Tan ; Rajitha Weerakkody ; Marta Mrak ; Naeem Ramzan ; Vittorio Baroncini, Jens-
Rainer Ohm, Gary J. Sullivan, "Video Quality Evaluation Methodology and Verification Testing
of HEVC Compression Performance" IEEE Transactions on Circuits and Systems for Video
Technology, Volume: 26 , Issue: 1 , Jan. 2016.
[37] ISO/IEC 23090-2: "Information technology — Coded representation of immersive media — Part
2: Omnidirectional media format"
[38] S. Schwarz et al., "Emerging MPEG Standards for Point Cloud Compression," in IEEE Journal on
Emerging and Selected Topics in Circuits and Systems, vol. 9, no. 1, pp. 133-148, March 2019.
[39] Khronos, "The GL Transmission Format (glTF)", Jun 9, 2017,
https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md
[40] Long Qian, Alexander Barthel, Alex Johnson, Greg Osgood, Peter Kazanzides, Nassir Navab, and
Bernhard Fuerst, "Comparison of optical see-through head-mounted displays for surgical
interventions with object-anchored 2D-display", Int J Comput Assist Radiol Surg. 2017 Jun; 12(6):
901–910, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5891507/.
[41] 3GPP TS 22.261: "Service requirements for the 5G system".
[42] 3GPP, VR-IF and the Advanced Imaging Society's 2ND VR ECOSYSTEMS & STANDARDS
WORKSHOP, Culver City, CA, US, https://www.vr-if.org/events/3gpp-vrif-ais-workshop/.
3 Definitions of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the terms given in 3GPP TR 21.905 [1] and the following apply. A term
defined in the present document takes precedence over the definition of the same term, if any, in 3GPP TR 21.905 [1].
3.2 Abbreviations
For the purposes of the present document, the abbreviations given in 3GPP TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
3GPP TR 21.905 [1].
3DoF Three Degrees of Freedom
5QI 5G QoS Identifier
6DoF Three Degrees of Freedom
AI Artificial Intelligence
API Application Programming Interface
AR Augmented Reality
ARP Allocation and Retention Priority
ASIC Application-Specific Integrated Circuit
ASTC Adaptive Scalable Texture Compression
ATW Asynchronous TimeWarp
AVC Advanced Video Coding
BC1 Block Compression for RGB
CAD Computer-Aided Design
CBR Constant BitRate
CDN Content Delivery Network
CPU Compute Processing Unit
CTC Call for TeChnologies
DASH Dynamic Adaptive Streaming over HTTP
DL DownLink
...