Streaming Video over aWireless Network

So what is the problem!!

WPI CS Research Rugby

Bob Kinicki

November 30, 2004

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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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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

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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)

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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 ?