1. M3: Practical and Reliable Multi-Layer Video Multicast over Multi-Rate Wi-Fi Network
Menghan Li*, Dan Pei, Xiaoping Zhang
Beichuan Zhang, Zhi Wang, Hailiang Xu, Zihan Wang
Thank you for the introduction. Good morning, everyone! My name is limenghan and I’m from Tsinghua University.
Today I would like to present my paper “…”
First, I’m going to introduce the research background of this work.
2018/12/3
IWQoS 2016

2. Video Multicast over Wi-Fi
Wi-Fi is a universal solution for the last-hop access networks
Account for 66% of IP traffic by 2020
Global public Wi-Fi hotspots: 7.8 million in 2015
In large and public assembly places
Multiple users view the same popular events via the same APs
Unicast-based solution does not scale and wastes bandwidth
Wi-Fi has been a universal solution for the last-hop access networks.
With the rapid growth of mobile devices and the wide deployment of Wi-Fi hotspots, in large and public assembly places, people may view the same popular events via the same APs.
In this scenario, unicast-based solution does not scale and wastes a lot of bandwidth
2018/12/3
IWQoS 2016

3. Video Multicast over Wi-Fi
Wi-Fi is a universal solution for the last-hop access networks
Account for 66% of IP traffic by 2020
Global public Wi-Fi hotspots: 7.8 million in 2015
In large and public assembly places
Multiple users view the same popular video via the same APs
Unicast-based solution does not scale and wastes bandwidth
Supporting video multicast over deployed Wi-Fi networks
Therefore, supporting video multicast over deployed Wi-Fi networks faces the actual demand.
2018/12/3
IWQoS 2016

4. Wi-Fi’s multi-rate nature
90Mbps C2
AP/802.11n
150Mbps C1
6.5Mbps
Due to Wi-Fi’s multi-rate nature, clients with different channel qualities can support different PHY rates. C3
-50dBm
-55dBm
-80dBm
2018/12/3
IWQoS 2016

5. Limitations of single-layer video multicast
The video quality is limited by the client with the worst channel quality
90Mbps C2
AP/802.11n
150Mbps C1
2000Kbps
4000Kbps
8000Kbps
H.264/AVC
6.5Mbps
Therefore, in traditional single-layer-coded video streams, all clients have to settle with the lowest video rate limited by the client with the worst channel quality. C3
-50dBm
-55dBm
-80dBm
2018/12/3
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6. Scalable Video Coding (SVC)
SVC is a multi-layer-coded video coding scheme
One base layer with the lowest video quality
Several enhancement layers that can increase video frame rate, resolution or picture quality BL
EL1
EL2
SVC
SVC is a multi-layer-coded video coding scheme
SVC video stream has a mandatory base layer with the lowest video quality, and several optional enhancement layers that can increase video frame rate, resolution or picture quality.
2018/12/3
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7. SVC video multicast over Wi-FiBL
EL1
EL2
SVC
90Mbps
EL1 C2
EL2
AP/802.11n BL
It is natural to use SVC and enable the AP to multicast the mandatory base layer at the lowest bit rate supported by the client with the worst channel, and multicast optional enhancement layers at higher bitrates supported by those clients with better channel qualities.
There have been several papers to propose SVC video multicast with rate adaptation mechanisms. C1
6.5Mbps C3
-50dBm
-55dBm
Lim et al., TMC 2012
Kuo et al., TCSVT 2015
-80dBm
2018/12/3
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8. SVC video multicast over Wi-FiBL
EL1
EL2
SVC
90Mbps
EL1
Need to modify MAC protocol
Impractical to be deployed C2
EL2
AP/802.11n BL
However, these solutions need to modify MAC protocol and are impractical to be deployed. C1
6.5Mbps C3
-50dBm
-55dBm
Lim et al., TMC 2012
Kuo et al., TCSVT 2015
-80dBm
2018/12/3
IWQoS 2016

9. Pseudo-broadcast (PB)
A multicast approach based on Wi-Fi unicast
No need to modify MAC protocol
The AP explicitly selects a client as the unicast receiver
Others clients listen for the packets in the promiscuous mode AP
Receiver
Listener
Unicast
Sniff
Pseudo-broadcast is a multicast approach based on wifi unicast, it does not need to modify mac protocol.
The basic ideas are, The AP explicitly select a client as the unicast receiver, usually, this receiver is the client with the worst channel quality.
And other clients listen for the packets in the promiscuous mode.
2018/12/3
IWQoS 2016

10. Pseudo-broadcast (PB)
A multicast approach based on Wi-Fi unicast
No need to modify MAC protocol
The AP explicitly selects a client as the unicast receiver
Others clients listen for the packets in the promiscuous mode
Only PB-based single-layer video multicast
Low overall video quality AP
Receiver
Listener
Unicast
Sniff
However, existing PB-based solutions selecting one receiver only support single-layer video multicast and still suffer from low overall video quality.
Chandra et al., ICNP 2009
Sen et al., NSDI 2010
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11. Design Goal Limitations of existing solutions
Being impractical to deploy (Modify protocol)
Low overall video quality (Single-layer video multicast)
In summary, existing approaches suffer from either being impractical to deploy and low overall video quality in existing multi-rate Wi-Fi networks.
2018/12/3
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12. Design Goal Limitations of existing solutions
Being impractical to deploy (Modify protocol)
Low overall video quality (Single-layer video multicast)
M3: Multi-layer video Multicast with Multi-receiver pseudo- broadcast
Practical: No change to protocol
Reliable: All clients can view the video smoothly
Optimized: Maximize the overall video quality
Therefore, we propose M3 and use multi-receiver pseudo-broadcast to realize a practical and reliable multi-layer wifi video multicast solution.
Our design goal is to maximize the overall video quality received by all clients.
2018/12/3
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13. Outline Background Challenges M3 system design Results Conclusion
In the following, I will present some design challenges faced by M3
2018/12/3
IWQoS 2016

14. Challenge 1: How to improve pseudo-broadcast’s reliability
PB cannot guarantee the reliability for listeners
The first challenge is how to improve …
We use the following results to verify that PB cannot guarantee the reliability for listeners.
The mean value of minimum packet delivery ratio in one block
Block size is 100 packets
2018/12/3
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15. Challenge 1: How to improve pseudo-broadcast’s reliability
PB cannot guarantee the reliability for listeners
Receiver’s RSSI is more lower than listener’s RSSI
Higher probability to receive the packets
From this figure, we can see that when the receiver’s RSSI is more lower than the listener’s RSSI, the listener has a higher probability to receive packets.
The mean value of minimum packet delivery ratio in one block
Block size is 100 packets
2018/12/3
IWQoS 2016

16. Challenge 1: How to improve pseudo-broadcast’s reliability
PB cannot guarantee the reliability for listeners
RSSI
-50
-55
-60
-65
-70
-75
-80
-85
50.1
51.6
45.8
30.2
3.5
52.3
50.5
49.2
14.3
1.6
55.9
60.2
46.4
28.4
3.8
0.9
0.2
-66
72.8
75.5
62.4
47.4
20.9
6.6
92.1
94.1
88.9
80.9
41.0
23.8
90.1
96.5
87.9
84.1
83.5
53.4
15.7
95.1
96.3
89.6
91.4
94.3
89.0
45.9
12.9
95.7
99.0
93.7
96.7
96.9
90.7
56.3
And from this table, we can get more detailed results.
Even if the receiver has the lowest RSSI, it is difficult to ensure that the listener has a PDR of 100%.
Difficult to ensure a PDR of 100%
2018/12/3
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17. Challenge 1: How to improve pseudo-broadcast’s reliability
PB cannot guarantee the reliability for listeners
RSSI
-50
-55
-60
-65
-70
-75
-80
-85
50.1
51.6
45.8
30.2
3.5
52.3
50.5
49.2
14.3
1.6
55.9
60.2
46.4
28.4
3.8
0.9
0.2
-66
72.8
75.5
62.4
47.4
20.9
6.6
92.1
94.1
88.9
80.9
41.0
23.8
90.1
96.5
87.9
84.1
83.5
53.4
15.7
95.1
96.3
89.6
91.4
94.3
89.0
45.9
12.9
95.7
99.0
93.7
96.7
96.9
90.7
56.3
Choose the receiver whose RSSI is lower than the listener’s RSSI
To improve PB’s reliability, first, the sender must choose the receiver …
Difficult to ensure a PDR of 100%
2018/12/3
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18. Challenge 1: How to improve pseudo-broadcast’s reliability
PB cannot guarantee the reliability for listeners
RSSI
-50
-55
-60
-65
-70
-75
-80
-85
50.1
51.6
45.8
30.2
3.5
52.3
50.5
49.2
14.3
1.6
55.9
60.2
46.4
28.4
3.8
0.9
0.2
-66
72.8
75.5
62.4
47.4
20.9
6.6
92.1
94.1
88.9
80.9
41.0
23.8
90.1
96.5
87.9
84.1
83.5
53.4
15.7
95.1
96.3
89.6
91.4
94.3
89.0
45.9
12.9
95.7
99.0
93.7
96.7
96.9
90.7
56.3
A combined application-layer
Forward Error Correction (FEC) and
Automatic Repeat-reQuest (ARQ) mechanism
Then, we use a combined application-layer FEC and ARQ mechanism to further reduce the data loss for listeners.
Difficult to ensure a PDR of 100%
2018/12/3
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19. Challenge 2: How to choose receivers and assign SVC layers
Maximize the overall video quality with limited bandwidth
Video rate of each SVC layer
Goodput of each client
𝐺𝑃 2 C2 AP
𝐺𝑃 1 BL
EL1
EL2
SVC C1
The second challenge is how to choose …
When we get the video rate of each SVC layer and the goodput of each client, we need to assign SVC layers to proper receivers, and our aim is to maximize the overall video quality with limited bandwidth.
𝑉𝑅 1
𝐺𝑃 3 C3
-50dBm
𝑉𝑅 2
-55dBm
𝑉𝑅 3
-80dBm
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20. Challenge 2: How to choose receivers and assign SVC layers
Use binary integer linear programming to derive an optimal map between SVC layers and receivers 1 2 L
SVC layers
Receivers R1 R2 RH
Here, we use binary integer linear programming to derive an optimal map between SVC layers and receivers.
The target is to maximize the total video rate received by all clients.
Maximize the total video rate received by all clients
2018/12/3
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21. Challenge 3: How to adapt to the network dynamics
Measure the goodput of each receiver
𝐺𝑃=𝑇𝑃∙ 𝑃𝐷𝑅 𝑚𝑖𝑛
𝑃𝐷𝑅 4
𝑃𝐷𝑅 2 C4 C2
Listener
Listener
𝑇𝑃 1 C1
𝑃𝐷𝑅 3 AP
The third challenge is how to adapt …
To measure the receiver’s goodput, we need to get the receiver’s TCP throughput and all other listener’s pdr. C3
Receiver
Listener
2018/12/3
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22. Challenge 3: How to adapt to the network dynamics
Measure the goodput of each receiver
𝐺𝑃=𝑇𝑃∙ 𝑃𝐷𝑅 𝑚𝑖𝑛
𝑃𝐷𝑅 4 / 𝑃𝐷𝑅 4 ′
𝑇𝑃 2 / 𝑃𝐷𝑅 2 C4 C2
Listener
Receiver/Listener
𝑇𝑃 1 C1
𝑃𝐷𝑅 3 / 𝑃𝐷𝑅 3 ′ AP
To optimize the overall video quality, we need to get the goodput of each potential receiver. C3
Receiver
Listener
2018/12/3
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23. Challenge 3: How to adapt to the network dynamics
Measure the goodput of each receiver
𝐺𝑃=𝑇𝑃∙ 𝑃𝐷𝑅 𝑚𝑖𝑛
𝑃𝐷𝑅 4 / 𝑃𝐷𝑅 4 ′
𝑇𝑃 2 / 𝑃𝐷𝑅 2 C4 C2 C5
Listener
Receiver/Listener
𝑇𝑃 1 C1
𝑃𝐷𝑅 3 / 𝑃𝐷𝑅 3 ′ AP
And when the new client arrives or other network conditions change, we only have a little time to re-evaluate system settings to approach the optimized target. C3
Receiver
Listener
2018/12/3
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24. Challenge 3: How to adapt to the network dynamics
Measure the goodput of each receiver
𝐺𝑃=𝑇𝑃∙ 𝑃𝐷𝑅 𝑚𝑖𝑛
𝑃𝐷𝑅 4 / 𝑃𝐷𝑅 4 ′
𝑇𝑃 2 / 𝑃𝐷𝑅 2
A dynamic feedback mechanism to collect some necessary statistics from clients C4 C2 C5
Listener
Receiver/Listener
𝑇𝑃 1 C1
𝑃𝐷𝑅 3 / 𝑃𝐷𝑅 3 ′ AP
Here, we use a dynamic feedback mechanism to collect some necessary statistics from clients. C3
Receiver
Listener
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25. Outline Background Challenges M3 system design Results Conclusion
In the following, I will present M3 system design in detail.
2018/12/3
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26. M3 system design C2 C1 Challenges Solutions AP …… Pseudo-broadcast
Practicability AP
Reliability
First, to be practical to deploy in existing wifi networks, M3 uses pseudo-broadcast to perform video multicast.
SVC layer 1
SVC layer 2
SVC layer 3 ……
Optimization
Dynamics
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27. M3 system design C2 C1 Challenges Solutions AP …… Pseudo-broadcast
layer1
FEC
layer2
Practicability
FEC AP
Reliability
To improve PB’s reliability, for a specific SVC layer in one video chunk, M3 adds some necessary FEC packets and then sends them to the corresponding receiver.
SVC layer 1
SVC layer 2
SVC layer 3 ……
Optimization
Dynamics
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28. Reliable pseudo-broadcast with FEC
FEC coding
One coding block <--> One SVC layer in a video chunk
A (n, k) block, containing k source packets and (n-k) overhead packets k
n-k
>=k
Briefly introduce the principle of FEC coding. One coding block is corresponding to one SVC layer in a video chunk.
For one block, containing …, if the client receives more than any k packets, then k source packets can be successfully recovered.
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29. Reliable pseudo-broadcast with FEC
FEC coding
One coding block <--> One SVC layer in a video chunk
A (n, k) block, containing k source packets and (n-k) overhead packets
Minimum packet delivery ratio in one block ( 𝐵𝑃𝐷𝑅 𝑚𝑖𝑛 ) k
n-k
>=k
Here, we introduce a concept of minimum packet delivery ratio in one block.
For example, we divide the same piece of data into blocks with different sizes for transmission. When the block size is 6, the minimum BPDR is 50 percent. And that is 75 percent when the block size is 12.
To evaluate the transmission stability of PB, we need to measure the listener’s minimum BPDR for a specific block size.
50%
75%
Block size：6
Block size：12
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30. Goodput measurement of PB
PB’s goodput
To guarantee that all listeners can recover all video chunks
FEC overhead: 𝑂=(1−𝐸( 𝐵𝑃𝐷𝑅 𝑚𝑖𝑛 ))/𝐸( 𝐵𝑃𝐷𝑅 𝑚𝑖𝑛 )
The expected goodput: 𝐸(𝐺𝑃)=𝑇𝑃∙𝐸( 𝐵𝑃𝐷𝑅 𝑚𝑖𝑛 )
To guarantee that all listeners can recover all video chunks, we use the expected minimum BPDR to calculate FEC overhead, and then measure TCP throughput to get the expected goodput. Here, we just consider the listener whose RSSI is higher than the receiver’s RSSI.
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31. Goodput measurement of PB
PB’s goodput
To guarantee that all listeners can recover all video chunks
FEC overhead: 𝑂=(1−𝐸( 𝐵𝑃𝐷𝑅 𝑚𝑖𝑛 ))/𝐸( 𝐵𝑃𝐷𝑅 𝑚𝑖𝑛 )
The expected goodput: 𝐸(𝐺𝑃)=𝑇𝑃∙𝐸( 𝐵𝑃𝐷𝑅 𝑚𝑖𝑛 )
Experiment setups
Send 100 blocks via TCP
TCP payload: 1448 Bytes
Block size: 100 packets
The ratio of decodable blocks
We conduct a verification test and use the ratio of decodable blocks to determine if the actual goodput achieves the expected value.
We can observe the results under the red line, when the receiver’s RSSI is lower than negative 65 dBm, listeners can almost decode all blocks, namely the actual goodput is very close to the expected value. However, not all listeners can decode all blocks.
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32. M3 system design C2 C1 ARQ Challenges Solutions AP …… layer1 FEC
Pseudo-broadcast
Practicability
FEC AP
Reliability
ARQ
If the listener does not receive enough packets to decode the SVC base layer, in order to ensure the smooth video playback, it will send an ACK to request additional FEC packets. And M3 will unicast these FEC packets to the listener.
SVC layer 1
SVC layer 2
SVC layer 3 ……
Optimization
Dynamics
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33. M3 system design -50dBm -60dBm -70dBm -80dBm C4 C3 C2 C1 Challenges
Solutions
Pseudo-broadcast
Practicability
FEC AP
Reliability
ARQ
To optimize the overall video quality, M3 first creates an RSSI-based client hierarchy to clearly define the service set of each receiver.
SVC layer 1
SVC layer 2
SVC layer 3 ……
Client Hierarchy
Optimization
Dynamics
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34. RSSI-based client hierarchy
A receiver’s Service Set
Receiver itself
All listeners whose RSSI values are higher than the receiver’s RSSI
Constraints
(1) 𝑆𝑆 1 contains all M3 clients
(2) 𝑆𝑆 ℎ ⊃ 𝑆𝑆 ℎ+1 and 𝐺𝑃 ℎ < 𝐺𝑃 ℎ+1
The creation of client hierarchy
All clients are sorted by an ascending order of RSSI
The number of effective client hierarchy: 1
Level 1: 𝑅 1 →( 𝑅𝑆𝑆𝐼 1 , 𝑆𝑆 1 , 𝐺𝑃 1 ) ⋯
Level ℎ: 𝑅 ℎ →( 𝑅𝑆𝑆𝐼 ℎ , 𝑆𝑆 ℎ , 𝐺𝑃 ℎ )
For a receiver’s service set, consisting of the receiver itself and all listeners whose RSSI values are higher than the receiver’s RSSI
To create the client hierarchy, all clients are sorted by an ascending order of RSSI
And then we can use two constraints to get only one effective client hierarchy.
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35. M3 system design -50dBm -60dBm -70dBm -80dBm C4 C3 C2 C1 SS1 SS4 SS2
Challenges
Solutions
SS3
Pseudo-broadcast
Practicability
FEC AP
Reliability
ARQ
For an effective client hierarchy, we can find the optimal map between SVC layers and receivers.
SVC layer 1
SVC layer 2
SVC layer 3 ……
Client Hierarchy
Optimization
BIP
Dynamics
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36. Binary integer linear programming
Define an allocation matrix to represent the map between SVC layers and receivers
The objective is to maximize
The constraints are
(C1) Smooth playback
(C2) SVC decoding dependencies
(C3) One layer can be sent only once
(C4) All clients can at least receive
the SVC base layer
Total Video Rate
We define an allocation matrix to represent the map between SVC layers and receivers, and then use binary integer linear programming to solve the optimization problem.
The objective is to maximize …
There are four constraints.
C1 is to ensure …
C2 is to ensure …
C3 is to ensure that …
And C4 is to guarantee that …
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37. The parameters used in the algorithm
The vide rate (𝑉𝑅) of SVC layers
A synthetic SVC DASH dataset with constant bitrate
The video chunk is 2 seconds duration and consists of 5 layers
Chunk size: (120, 300, 500, 350, 800) packets
Video rate: (675, 1688, 2813, 1969, 4500) Kbps
All clients’ 𝑅𝑆𝑆𝐼
Receivers’ 𝐺𝑃
Ok, let’s take a look at some parameters used in the algorithm.
Including the video rate of SVC layers, all clients’ RSSI and Receivers’ goodput.
Here, it is difficult to measure receivers’ TCP throughput and listeners’ minimum BPDR.
𝐺𝑃=𝑇𝑃∙ 𝐵𝑃𝐷𝑅 𝑚𝑖𝑛
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38. M3 system design -50dBm -60dBm -70dBm -80dBm C4 C3 C2 C1 Challenges
Solutions
layer2
FEC
layer3
FEC
Pseudo-broadcast
layer1
FEC
Practicability
FEC AP
Reliability
ARQ
In practical application scenarios, there is not enough time to conduct a comprehensive test for all clients.
Therefore, we propose a simplified measurement method based on dynamic client feedback mechanism.
SVC layer 1
SVC layer 2
SVC layer 3 ……
Client Hierarchy
Optimization
BIP
Dynamics
Client Feedback
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39. Client feedback mechanism
Two cases in real application scenarios
New client successively joins the multicast group
Here, we consider two cases in real application scenarios.
The first case is that the newly-arriving client successively joins the multicast group every once in a while. R1
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40. Client feedback mechanism
Two cases in real application scenarios
New client successively joins the multicast group C2
When the new client arrives, the M3 server will send a special test video chunk. R1
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41. Client feedback mechanism
Two cases in real application scenarios
New client successively joins the multicast group
Test.ELs C2
Test.BL
The base layer is still sent to the current R1 to maintain the video service without interruption. And other enhancement layers are sent to the newly arrived C2. R1
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42. Client feedback mechanism
Two cases in real application scenarios
New client successively joins the multicast group
Test feedback:
RSSI & TP C2
Test feedback:
RSSI & BPDRmin
After finishing the test chunk, clients return test feedbacks. The server can get C2’s TCP throughput and R1’s minimum BPDR. R1
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43. Client feedback mechanism
Two cases in real application scenarios
New client successively joins the multicast group R1
And then M3 can change the client hierarchy. C1
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44. Client feedback mechanism
Two cases in real application scenarios
New client successively joins the multicast group
Bandwidth fluctuation impacted by background traffic
Regular feedback:
RSSI & TP R1
Regular feedback:
RSSI & BPDRmin
The second case is the available bandwidth fluctuation impacted by background traffic.
In response, all clients send regular feedbacks and enable the server to regularly update receivers’ TCP throughput and listeners’ minimum BPDR. C1
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45. Outline Background Challenges M3 system design Results Conclusion
Ok, In the following, I will present the evaluation results of M3 system.
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46. M3 performance evaluation
Performance metrics
Buffering time: the smoothness of video playback
Total video rate: the overall video quality
Experiment setups
One AP and 8 clients
a/n, 5GHz, channel 40
Non-overlapping channel
Phy rate: (6.5~144.4) Mbps
RSSI: 8 equal bins in (-46~-85) dBm
Here, we choose two performance metrics: buffering time and total video rate.
Our aim is to verify the smoothness of video playback and the overall video quality.
We deployed a real testbed in our lab. There are one AP and 8 clients. The wireless adaptors run at a 5GHz non-overlapping channel. And the RSSI range is divided into 8 equal bins.
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47. System stability when clients successively arrive
RSSI(dBm)
-46
~-50
-51
~-55
-56
~-60
-61
~-65
-66
~-70
-71
~-75
-76
~-80
-81
~-85
Client C1 C2 C3 C4 C5 C6 C7 C8
Arrival Order
C4, C1, C6, C2, C8, C5, C3, C7
We first use a random client arrival order to verify system stability when clients successively arrive.
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48. System stability when clients successively arrive
RSSI(dBm)
-46
~-50
-51
~-55
-56
~-60
-61
~-65
-66
~-70
-71
~-75
-76
~-80
-81
~-85
Client C1 C2 C3 C4 C5 C6 C7 C8
Arrival Order
C4, C1, C6, C2, C8, C5, C3, C7
New client has the lowest RSSI
A longer initial buffer duration
When the new arrival client has the lowest RSSI, it may not receive any packets until M3 server changes SVC-layer allocation and will buffer for a little longer time.
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49. System stability when clients successively arrive
RSSI(dBm)
-46
~-50
-51
~-55
-56
~-60
-61
~-65
-66
~-70
-71
~-75
-76
~-80
-81
~-85
Client C1 C2 C3 C4 C5 C6 C7 C8
Arrival Order
C4, C1, C6, C2, C8, C5, C3, C7
New client has the lowest RSSI
A longer initial buffer duration
And for any time, there is at most one client for buffering. And there is no re-buffering event occurring for all clients.
The above results show that M3 can adjust the SVC-layer allocation to provide smooth video streaming for all current clients whenever the new client arrives
No re-buffering event
2018/12/3
IWQoS 2016

50. System stability when clients successively arrive
TVR gradually increases
Measured value is very close to theoretical value
Order 1
Order 1
C4, C1, C6, C2, C8, C5, C3, C7
Order 2
C3, C1, C7, C5, C2, C6, C8, C4
We use two different random client arrival orders to show the results of total video rate, with the increase of the number of clients, TVR gradually increases and the measured value is very close to the theoretical value.
This means that M3 can effectively support the dynamic expansion of video multicast group.
Order 2
2018/12/3
IWQoS 2016

51. System stability when clients successively arrive
TVR gradually increases
Measured value is very close to theoretical value
Order 1
Order 1
C4, C1, C6, C2, C8, C5, C3, C7
Order 2
C3, C1, C7, C5, C2, C6, C8, C4
After all clients arriving, TVR of these two cases are nearly the same, to show that M3 can select proper receivers according to the specific client layout.
Final TVR of these two cases are nearly the same
Order 2
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IWQoS 2016

52. The impact of background traffic
Layout 1 C1 C2 C3 C4 C5 C6 C7 C8
Layout 1
(dBm)
-46
~-50
-51
~-55
-56
~-60
-60
~-65
-66
~-70
-76
~-75
-81
~-85
Layout 2
-61
-71
Here, we consider system stability impacted by background traffic.
The experiment process is divided into 3 phases: the first phase has no background traffic, and background traffic with different levels of intensity are introduced in the next two phases.
We choose 2 different client layouts. The main differences are those clients with worse channel qualities, whose RSSI values gradually increase.
Layout 2
2018/12/3
IWQoS 2016

53. The impact of background traffic
TVR gradually decreases
Measured value is very close to theoretical value
Layout 1 C1 C2 C3 C4 C5 C6 C7 C8
Layout 1
(dBm)
-46
~-50
-51
~-55
-56
~-60
-60
~-65
-66
~-70
-76
~-75
-81
~-85
Layout 2
-61
-71
For Layout 1, with the arrival and increasing intensity of background traffic, TVR gradually decreases and the measured value is very close to the theoretical value. This means that client feedback mechanism can effectively respond to the changes of the available bandwidth.
Layout 2
2018/12/3
IWQoS 2016

54. The impact of background traffic
TVR gradually decreases
Measured value is very close to theoretical value
Layout 1 C1 C2 C3 C4 C5 C6 C7 C8
Layout 1
(dBm)
-46
~-50
-51
~-55
-56
~-60
-60
~-65
-66
~-70
-76
~-75
-81
~-85
Layout 2
-61
-71
For Layout 2, TVR is always stable, because the available bandwidth can still support all SVC layers even in the third phase
TVR is always stable
Layout 2
2018/12/3
IWQoS 2016

55. Comparison with single-layer video multicast
M3 Layout 1
Layout 1
SVC layers: (675, 1688, 2813, 1969, 4500)Kbps
AVC streams: (675, 2149, 4314, 5496, 8319)Kbps
Here, I will introduce the comparison between M3 and single-layer video multicast.
We use an AVC DASH dataset for single-layer video multicast. And the video qualities of 5 different AVC streams are equal to 5 different SVC layers.
Here, SVC introduces 10 percent bitrate overhead for each enhancement layer.
SVC introduces 10% overhead for each enhancement layer
M3 Layout 2
Layout 2
2018/12/3
IWQoS 2016

56. Comparison with single-layer video multicast
Eliminating the coding overhead, M3 still improves TVR by over 200%
M3 Layout 1
Layout 1
SVC layers: (675, 1688, 2813, 1969, 4500)Kbps
AVC streams: (675, 2149, 4314, 5496, 8319)Kbps
For Layout 1, even if eliminating the coding overhead, M3 still improves TVR by over 200%.
The above results prove that, in the situation of big differences of channel qualities between all clients, M3 can fully utilize Wi-Fi’s multi-rate nature to effectively improve the overall video quality.
SVC introduces 10% overhead for each enhancement layer
M3 Layout 2
Layout 2
2018/12/3
IWQoS 2016

57. Outline Background Challenges M3 system design Results Conclusion
Finally, I would like to make a conclusion with this presentation
2018/12/3
IWQoS 2016

58. Conclusion
M3 – a practical and reliable multi-layer video multicast solution over multi-rate Wi-Fi network
A multicast approach via multi-receiver pseudo-broadcast
No change to APs
RSSI-based client hierarchy
Use BIP to optimize the overall video quality
Client feedback mechanism
Compared with single-layer video multicast, M3 can improve total video rate by up to 200%
In this paper, we present M3, a practical …
It is a multicast … and makes no change to APs.
M3 creates a RSSI-based client hierarchy and uses BIP to optimize the overall video quality.
Using a client feedback mechanism, M3 can adapt to the dynamic network conditions.
Compared with single …
2018/12/3
IWQoS

59. Thanks! Q&A So, that’s all for M3, and I’d like to take questions now.
Thank you.
2018/12/3
IWQoS