In this paper, we propose a novel cross-layer frame-work for Multi-user 360-degree video streaming over cellular networks. At the content layer, Scalable Video Coding is utilized to encode a tile into multiple layers. At the transport layer, the tiles' layers are delivered to users in hybrid unicast/multicast mode. The experiment results show that the proposed method can improve the average viewport quality by up to 4.85% compared to state-of-the-art methods.

1. A Cross-Layer Framework for Multi-user
360-degree Video Streaming over Cellular
Networks
Duc Nguyen,Nguyen Viet Hung, Truong Thu Huong, Truong Cong Thang
Tohoku Institute of Technology, Japan
East Asia University of Technology, Vietnam
Hanoi University of Science and Technology, Vietnam
The University of Aizu, Japan
hungnv@eaut.edu.vn
ducnguyen@tohtech.ac.jp

2. Outline
 Introduction
 Proposed Method
 Evaluation
 Conclusions and Future Work
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3.  360-degree video is the main content
type in Virtual Reality.
 Live 360 video streaming allow users
to feel like they are in a different place
rather than in their true location.
(Immersive Telepresence Experience)
 Enabling remote participations of live
events (e.g., music, sports)
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Introduction

4. 4
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 Two key challenges of 360 video live streaming
 360 video has an extremely high data rate
 Need to stream simultaneously to many users
Introduction
360 video bitrates at different
resolutions (Mbps)
User #1
User #2
User #N
…
…
Live streaming to multiple users
Research Question:
How to deliver live 360 video to
users over resource-constrained
networks (e.g., cellular networks)?

5. 5
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 Cross-Layer Live 360 Video Streaming Framework
Proposed Method
Content Layer
• Spatially divide 360 video into tiles
• Encode individual tiles using
Scalable Video Coding
Transport Layer
• Deliver tiles’ layers in hybrid
unicast/multicast mode

6. Proposed Method
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Flat video
360-degree video are converted to flat video using
CubeMap Projection
Converted video is divided into small parts called tiles
(24 tiles)

7. Proposed Method
• Content Layer
• Tiles are encoded into a base layer
and K multiple enhancement layers
• Base layer
• Minimum quality
• Enhan. Layer
• Improved Quality
• Require base layer and all
previous enhance. layers
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8. 8
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 Network Layer
 Tiles’ layers needed by all users: multicast
 Other tiles’ layers: Unicast
Proposed Method
High
Quality
Low
Quality
User #1
User #2
Conventional Method
Unicast
Enhance.
Layer
Base
Layer
User #1
User #2
Proposed Method
Unicast
Multicast

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 Tiles’ layers Delivery Mode
Proposed Method
Delivery Mode Required Network
Resources
Unicast
(Layer k of tile n to user m)
𝑅𝑛𝑘
𝜎𝑚
Multicast
(Layer k of tile n to all users)
𝑅𝑛𝑘
min(𝜎1, 𝜎2, … , 𝜎𝑚)
Bitrate
Spectral
Efficiency of
user m

10. Tile Layer Selection Problem:
Choose 1) tiles’ layers and 2) delivery mode (unicast or
multicast) so as to maximize a quality objective and to satisfy a
set of constraints
ICCE2022
Tile Layer
Selection
Algorithm
Layer 0
(Base layer)
Layer 1
Tiles’ layers
…
Layer K
…
…
Quality
objective Constraints
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Proposed Method
User #1
User #2
User #N
…
…
…

11. Optimization problem
Objective function
𝑊
𝑚𝑛 is the weight of tile n for user m
𝑄𝑛𝑘 is the quality of layer k of tile n
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12. Quality metrics
ICCE2022
 Viewport layer
𝐾𝑚𝑛
∗ is the layer selected for tile n for user m
 Viewport quality
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13. Evaluation Settings (1)
 We use a 360-degree video of 60-second long, and with a
size of 2880x1920 in CubeMap format.
 A video is divided into 24 tiles
 Each tile with a size of 480x480.
 Individual tiles are encoded into a base layer and 4
enhancement layers (K=4) with the bitrate (quality).
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14. Evaluation Settings (2)
 The number of users M is set to 15.
 The spectral efficiency 𝜎𝑚 of the user m from [0.02,
0.031, 0.05, 0.079, 0.116, 0.155, 0.195, 0.253,
0.318, 0.36, 0.439, 0.515, 0.597, 0.675, 0.733]
Set R from 250 Mbps to 700 Mbps.
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15. Evaluation Results
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[3] N. Kan, C. Liu, J. Zou, C. Li, and H. Xiong, “A Server-Side Optimized Hybrid
Multicast-Unicast Strategy for Multi-User Adaptive 360-Degree Video Streaming,” in 2019
IEEE ICIP, Taiwan, 2019, pp. 141–145.
[4] A. Majidi and A. H. Zahran, “Optimized Joint Unicast-Multicast Panoramic Video
Streaming in Cellular Networks,” in 2020 IEEE ICNP, Madrid, Spain, 2020, pp. 1–6.

16. Evaluation Results
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[3] N. Kan, C. Liu, J. Zou, C. Li, and H. Xiong, “A Server-Side Optimized Hybrid
Multicast-Unicast Strategy for Multi-User Adaptive 360-Degree Video Streaming,” in 2019
IEEE ICIP, Taiwan, 2019, pp. 141–145.
[4] A. Majidi and A. H. Zahran, “Optimized Joint Unicast-Multicast Panoramic Video
Streaming in Cellular Networks,” in 2020 IEEE ICNP, Madrid, Spain, 2020, pp. 1–6.

17. Conclusions and Future work
Conclusions
 Proposed a novel cross-layer framework for Multi-user VR video
streaming over cellular networks
Scalable Video Coding
delivery of tiles in the hybrid mode (unicast/multicast).
Improve the average viewport quality by up to 4.85% compared to
state-of-the-art methods.
Future work
 Extend the proposed method to support the scenario with a massive
number of users
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18. Thank you for your
attention!
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