Streaming Video over a Wireless Network So what is the problem!! WPI CS Research Rugby Bob Kinicki...
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Streaming Video over aWireless Network
So what is the problem!!
WPI CS Research Rugby
Bob Kinicki
November 30, 2004
Research Rugby November 30, 2004 2
CC-Wireless Rugby Team CC-Wireless Rugby Team prop hooker
Feng Li Mingzhe Li wireless measurement wireless bandwidth estimation
flanker flanker Jae Chung Yubing Wang
congestion control retransmissions
scrumhalfRobert Kinickiprotocols
flyhalf Huahui Wu weak side wing FEC Emmanuel Agulow-level wireless
fullback
Mark Claypoolmultimedia
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OutlineOutline Motivation – the Future Streaming Video over Wireless What Problems? Background
– Layered network architecture– Networking ‘religious’ tenets– Measurement and Tools– Streaming multimedia primer– Introduction to wireless networks
Focus: Wireless Bandwidth Estimation Discussion ??
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Streaming VideoStreaming Video
Ser ver Cl i ent
Video Frames
Net wor k Cl oud
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Streaming Video over Wireless
Streaming Video over Wireless
Ser verCl i ent
Video Frames
Wired network AP
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Networking Protocol LayersNetworking Protocol Layers
Application Layer: Real Player,Windows Media Player, MPEG
Transport Layer: TCP, UDP
Network Layer: IP
Data Link Layer (MAC): 802.3, 802.11b, 802.11g
Measurement and Tools
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Wireless Streaming Multimedia Lab
Topology Wireless Streaming Multimedia Lab
Topology
IDC
Windows 2003 server(saco)
Windows media server Real streaming Server Quick time Darwin Windows IIS server Ethereal
DVD DVD Player
VCR
Video Camera
Mobile station(yangtze)
WM Tracker Real Tracker Ethereal
Wireless sniffer(seine)
Ethereal Monitor Mode
Access point Video capture
NAT Router(streamit)
WPI Campus Network
Emulated Internet
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CHub
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C Switch
NFS Server(york)
Packet Sniffer(merlot)
Media Client(???)
WM Tracker Real Tracker Ethereal
Slide courtesy of Mingzhe’s PEDS presentationMonday October 25,2005
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Wireless Measurement StudyWireless Measurement Study
Research Rugby November 30, 2004 10
Preliminary Wireless MeasurementsPreliminary Wireless Measurements
Application Layer
Network Layer
Data Link Layer
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Video Streaming ChoicesVideo Streaming Choices
Media Player or Real Player TCP or UDP Single layer encoding or multilayer
encoding
MediaPlayer™ vs. RealPlayer™ A
Comparison of Network Turbulence
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Time (seconds)
Ban
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Kbit
s/se
c.)
Real Player (284K)
Real Player (36K)
Windows Media Player (323K)
Windows Media Player (49K)
Real vs WMP Playout RateReal vs WMP Playout Rate
RealPlayer buffers at a higher rate
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Video Compression StandardVideo Compression Standard
I 0 B 00 B 01 P 1 B 10 P 2 I 0
MPEG– Popular compression standard– Intra-compression and inter-compression– Three types of frames: I, P and B– Group Of Pictures (GOP)
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340 Kbps Clip - Bottleneck Capacity 725 Kbps340 Kbps Clip - Bottleneck Capacity 725 Kbps
< 0.001 packet lossAfter 15 seconds
TCP Friendly?
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548 Kbps Clip - Bottleneck Capacity 725 Kbps548 Kbps Clip - Bottleneck Capacity 725 Kbps
~ 0.003 packet loss for WSM~ 0.006 packet loss for TCP
after 15 seconds
Not TCP- Friendly!
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1128 Kbps Clip - Bottleneck Capacity 725 Kbps1128 Kbps Clip - Bottleneck Capacity 725 Kbps
Responsive to Capacity?
Wireless Networks
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Wireless IssuesWireless Issues
Higher error rates - Bursty? Hidden terminal problem Variable bandwidth Mobile versus stationary MAC layer saturation
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Hidden Terminal ProblemHidden Terminal Problem
802.11 Solution to the Hidden Terminal Problem– Use a four-way handshake: RTS-CTS-DATA-ACK where the
RTS and CTS packets are significantly smaller than the average data packet.
– The maximum number of RTS retransmissions is set to 7.
However, the 802.11 protocol will still have problems if the MAC layer becomes saturated!!
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Rate Constrained TFRCRate Constrained TFRC A seven-hop chain network was simulated. The TFRC sending rate is manually constrained. The MAC layer saturates at 300Kbps.
Wireless Bandwidth Estimation
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Performance DefinitionsPerformance Definitions
The capacity, Ci , of hop i is the maximum possible IP layer transfer at that hop. Namely, the bit rate for transferring MTU-sized IP packets.
The available bandwidth, Ai , of a link relates to the unused capacity of a link during a time period.
The Bulk-Transfer-Capacity (BTC) is the maximum throughput obtainable by a single TCP connection.
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Bandwidth Estimation TechniquesBandwidth Estimation Techniques
Variable Packet Size (VPS) probing: used to measure minimum RTT’s to all hops on path.
• pathchar, pchar, ... Packet pair probing: each packet pair consists of
two packets of the same size sent back-to-back. The goal is to measure the dispersion of a packet pair.
Packet train probing: extends packet-pair probing by using multiple back-to-back packets.
Self-Loading Periodic Streams (SLoPS): send a train of packets (k=100) equal-sized packets at a rate R. Sender continues to vary R to get it close to A.
Trains of Packet Pairs (TOPP): send many packet pairs at gradually increasing rates from source to sink.
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Packet DispersionPacket Dispersion
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Bandwidth Estimation TechniquesBandwidth Estimation Techniques
pathchirp: uses an exponentially spaced chirp probing train and launches m packet chirps where each chirp is made up of N UDP probe packets each of size P bytes.
pathchirp discards all chirps with dropped packets!
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Bandwidth Estimation and VideoBandwidth Estimation and Video Currently, bandwidth estimation used in
Windows Media Player– Capacity estimation before streaming starts– Uses packet pair
Mingzhe’s Research : new approach to bandwidth estimation to improve performance of video over wireless networks.
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Discussion ?Discussion ?