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Streaming Video over a Wireless Network So what is the problem

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Introduction to wireless networks. Focus: Wireless Bandwidth Estimation. Discussion ? ... Higher error rates - Bursty? Hidden terminal problem. Variable bandwidth ... – PowerPoint PPT presentation

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Title: Streaming Video over a Wireless Network So what is the problem


1
Streaming Video over aWireless NetworkSo what
is the problem!!
  • WPI CS Research Rugby
  • Bob Kinicki
  • November 30, 2004

2
CC-Wireless Rugby Team

  • prop hooker
  • Feng Li Mingzhe Li
  • wireless measurement wireless
    bandwidth estimation
  • flanker

    flanker
  • Jae Chung Yubing Wang
  • congestion control
    retransmissions
  • scrumhalf
  • Robert Kinicki
  • protocols

  • flyhalf

  • Huahui Wu
  • weak side wing FEC
  • Emmanuel Agu
  • low-level wireless

3
Outline
  • 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 ??

4
Streaming Video
Video Frames
5
Streaming Video over Wireless
Video Frames
Wired network
AP
6
Networking 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

7
Measurement and Tools
8
Wireless Streaming Multimedia Lab Topology
Slide courtesy of Mingzhes PEDS
presentation Monday October 25,2005
9
Wireless Measurement Study
10
Preliminary Wireless Measurements
Application Layer
Network Layer
Data Link Layer
11
Video Streaming Choices
  • Media Player or Real Player
  • TCP or UDP
  • Single layer encoding or multilayer encoding

12
MediaPlayer vs. RealPlayer A Comparison of
Network Turbulence
13
Real vs WMP Playout Rate
RealPlayer buffers at a higher rate
14
Video Compression Standard
  • MPEG
  • Popular compression standard
  • Intra-compression and inter-compression
  • Three types of frames I, P and B
  • Group Of Pictures (GOP)

15
340 Kbps Clip - Bottleneck Capacity 725 Kbps
lt 0.001 packet loss After 15 seconds
TCP Friendly?
16
548 Kbps Clip - Bottleneck Capacity 725 Kbps
Not TCP- Friendly!
0.003 packet loss for WSM 0.006 packet loss
for TCP after 15 seconds
17
1128 Kbps Clip - Bottleneck Capacity 725 Kbps
Responsive to Capacity?
18
Wireless Networks
19
Wireless Issues
  • Higher error rates - Bursty?
  • Hidden terminal problem
  • Variable bandwidth
  • Mobile versus stationary
  • MAC layer saturation

20
Hidden 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!!

21
Rate Constrained TFRC
  • A seven-hop chain network was simulated.
  • The TFRC sending rate is manually constrained.
  • The MAC layer saturates at 300Kbps.

22
Wireless Bandwidth Estimation
23
Performance 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.

24
Bandwidth Estimation Techniques
  • Variable Packet Size (VPS) probing used to
    measure minimum RTTs 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 (k100) 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.

25
Packet Dispersion
26
Bandwidth 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!

27
Bandwidth Estimation and Video
  • Currently, bandwidth estimation used in Windows
    Media Player
  • Capacity estimation before streaming starts
  • Uses packet pair
  • Mingzhes Research new approach to bandwidth
    estimation to improve performance of video over
    wireless networks.

28
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