1 Congestion Control and Adaptive Retransmission for Multimedia Streaming over Wireless Networks...
-
Upload
georgiana-wells -
Category
Documents
-
view
224 -
download
0
Transcript of 1 Congestion Control and Adaptive Retransmission for Multimedia Streaming over Wireless Networks...
1
Congestion Control and Adaptive Retransmission for Multimedia Streaming over Wireless Networks
Kamal Singh, Árpád Huszák, David Ros, César Viho and Jeney Gábor
IRISA/INRIA, Rennes, France BUTE, Budapest, Hungary
2
Agenda
Overview Congestion control for Video Flows Adaptive retransmissions and
wireless loss estimation Results Conclusion and Future Work
3
Agenda
Overview Congestion control for Video Flows Adaptive retransmissions and
wireless loss estimation Results Conclusion and Future Work
4
Overview: Next Generation Wireless Network
Users of Voice, TCP, …
Video Streaming anywhere in the cell
“Hotspots” with high bandwidth
5
Overview: Wireless Problems in the context of Video Streaming
Problems due to the use of IP IP doesn’t support real time streaming
requirements
Problems due to radio conditions Scarce and time varying bandwidth Congestion, wireless losses & large delay
6
Overview: Video Streaming
Video Streaming
• Delay & Jitter• Bandwidth, Congestion• Packet loss
constraints
7
Overview: Video Streaming …
Video Streaming
• Underflow• No Playout
• Packet losses will cause quality distortion
8
Agenda
Overview Congestion control for Video Flows Adaptive retransmissions and
wireless loss estimation Results Conclusion and Future Work
9
Congestion Control for Video Flows
Motivation• Variable bandwidth, delay …• Congestion, packet losses
How can applications adapt to the network conditions?
10
Existing Schemes
Congestion control for video TCP: Retransmissions, rate oscillations, …
TFRC [Floyd 2000] Sending Rate is calculated by a TCP model
Better Rate Stability
TCP Friendly
11
Problems: Wireless Losses
Problem: Two types of losses in wireless Networks Packet drops due to congestion Packet drops due to bad channel conditions
Node B
Router
Wireless loss
Wireless network
IP Packets IP Queue
Congestion loss
12
Problems …
Inefficiency for TCP, TFRC … Cannot distinguish between these losses. Reduce their sending rate on loss.
How to distinguish Wireless losses from congestion losses? Previous Work have used Round Trip Time
variations: May not be reliable ARC [O. B. Akan et al. 04]: Sending Rate
(S) is calculated using w :
ARC: How to calculate w ?
,
13
Differential dropping in the DiffServ Assured Forwarding (Green, Yellow & Red)
Video applications mark their packets
Wireless Loss Estimation (Background: DiffServ)
Drop Red packets
Drop Red + Yellow packets
Rarely drop Green packets
I B P B P
Increasing Congestion
14
Wireless Loss Estimation Wireless Loss Estimation in DiffServ (WLED)
Networks: [VTC 2006]
Red packets are dropped first on congestion
Wireless loss rate (w) is correlated with green loss rate
If loss of yellow packets is not significant
Estimate w for ARC using green loss rate
15
WLED: Improves link utilization
There is no change in other properties: TCP friendliness, loss rate, rate stability
But, works only with DiffServ aware applications
WLED
WLED
TFRC
TCP
16
Agenda
Overview Congestion control for Video Flows Adaptive retransmissions and
wireless loss estimation Results Conclusion and Future Work
17
Adaptive retransmissions and wireless loss estimation
We improved link utilization in case of wireless losses.
But, lost data still deteriorates the quality!
Solution: We integrate a scheme to retransmit the lost data.
18
Adaptive retransmissions and wireless loss estimation …
Retransmission Scheme If packet has the possibility to arrive before its
deadline No congestion Enables retransmission schemes Congestion Disable retransmission
Example Scenario:
19
Adaptive retransmissions and wireless loss estimation …
Depending on: Available Bandwidth shown by Congestion
Control scheme Amount of I, P and B frames in video files
Retransmit either I frames I + P frames or All frames
WLED scheme integrated
20
Adaptive retransmissions and wireless loss estimation : Transport protocol
DCCP (Datagram Congestion Control Protocol) Sequence numbers Feedback/ACK vectors Useful for loss detection
Retransmissions done at the application layer
21
Adaptive retransmissions and wireless loss estimation : Simulation details
NS2 Dumbbell topology with 1Mbps of link
with 40ms delay Packet losses simulated in the wireless
link Reference Video: 360kbps “Mother
and Daughter” encoded using H.264
FTP and WWW flows as background
22
Agenda
Overview Congestion control for Video Flows Adaptive retransmissions and
wireless loss estimation Results Conclusion and Future Work
25
Agenda
Overview Congestion control for Video Flows Adaptive retransmissions and
wireless loss estimation Results Conclusion and Future Work
26
Conclusion and Future Work
Used a wireless loss estimation scheme integrated with a retransmission scheme Obtained better video quality
Future Work Performance of WLED + retransmission in real
network Congestion control and adaptive
retransmission for MPEG4-scalable video codec (SVC)