Application, Network, and Link Layer Measurements of Streaming Video over a Wireless Campus Network

1
Application, Network, and Link LayerMeasurements
of Streaming Videoover a Wireless Campus Network
2
Group MembersBerk BerkerEmrah
BayraktarogluS. Tuncer ErdoganMustafa Omer
KilavuzErkan Okuyan
3
I. Introduction (The Reason)

• The Reason for the Expectations about Streaming
  Video
• Decrease in price of W-LAN APs
• Increase in wireless link capabilities up to 54
  Mbps

4
I. Introduction (The Problem)

• The problem is all about
• RealNetworks Windows Streaming Media make
  decisions, but it is unclear that
• Frame Lost Rate?
• Signal Strength?
• Link Layer Bitrate?
• are more important?

5
I. Introduction (4 Hypothesis)

• This measurements study considers
• W-LANs make it difficult for streaming video to
  gracefully adapt when network conditions degrade.
• Multiple level encoding can stream better than
  videos encoded with only a single level when
  W-LAN conditions are poor.
• TCP is more effective than UDP.
• Current available estimation techniques for
  capacity are inadequate for W-LAN

6
II. Methodology (Tools)

• 1. Application Layer
• Media Tracker collects application layer data
  specific to streaming video including
• Encoding data rate
• Playout bitrate
• Time spend buffering
• Video frame rate
• Video frames lost
• Video frames skipped
• Packets lost
• Packets recovered

7
II. Methodology (Tools)

• 2. Network Layer
• UDP Ping measures
• Round-Trip time (?)
• Packet loss rate along the stream flow path
• by providing
• Constant ping rates
• Configurable ping intervals in milliseconds
• Configurable ping packet sizes

8
II. Methodology (Tools)

• 3. Wireless Data Link Layer
• WRAPI library was enhanced to collect information
  about
• Signal strength
• Frame retransmission counts and failures
• The specific W-AP that handles the wireless last
  hop to the client
• Typeperf collects
• Processor utilization
• Various network data

9
II. Methodology (Experiment)

• Experiments are done with hardware
• Windows Media Server
• Windows Media Service v9.0
• Dell laptop (Centrino Mobile CPU, Windows XP SP1,
  IEEE 802.11g Wireless Network Adapter)
• Airspace APs, providing IEEE 802.11a/b/g wireless
  service.

10
II. Methodology (Experiment)

• Experiments are done with videos of
• Two Video Clips Coast Guard Paris (Both
  352x288 resolution 30 frames per second, two
  minutes long)
• Coast Guard High Motion (5.4 skipped macro
  blocks)
• Paris Low Motion (41.2 skipped macro blocks)

11
II. Methodology (Experiment)

• Experiments are done with
• Single-Level version of videos encoded at 2.5
  Mbps to stress the wireless link
• Multiple-Level version including 11 encoding
  layers
• Streamed using TCP UDP for comparison

12
II. Methodology (Experiment)

• Campus Network Map

13
II. Methodology (Design)

• Experiments done
• Downloading a large file with wget
• To estimate the effective throughput of a TCP
  bulk transfer
• 2 clips x 2 versions x 2 transport protocols
• A final bulk download
• UDP pings to determine round-trip time and
  package lost
• 200 milliseconds apart
• 1350-byte packets for single level video
• 978-byte packets for multiple level video

14
II. Methodology (Design)

• Experiments done
• Five times x Three distinct locations x Three
  floors in the CS department
• 45 experimental results
• 360 video streams
• Locations Three laptop in good, fair, and bad
  reception locations

15
III. RESULTS

• Collected data is
• No significant statistical difference between the
  high-motion and the low-motion video.
• High-motion and low-motion does not have a
  significant effect on wireless network
  performance.

16
Categorization

• There is a cliff between signal strengths -70
  and -80 dBm

17
Categorization

• From now on, experiments are categorized in one
  of the regions Good, Edge or Bad

18
First Analysis Single-Level vs. Multi-Level
Encoding

• Multi-Level or Single-Level Encoded
• Streaming of single and multi-level encoded
  videos are compared according to their average
  frame rate in Good and Bad locations.

19
Single-Level vs. Multi-Level
20
Single-Level vs. Multi-Level
21
Single-Level vs. Multi-Level

• In a Good location, number of encoded levels have
  a very little effect, since the stream does not
  have to be scaled to a lower bitrate.
• In a Bad location, for the 2/3 of the time,
  multiple level stream has a higher frame rate
  than the single level one. (22 fps to 11 fps on
  average)

22
TCP Streaming Over UDP Streaming

• In good wireless locations, TCP streaming and
  UDP streaming have almost the same performance
• In bad wireless locations choosing one of them
  has significant impact on performance

23
TCP Streaming Over UDP Streaming

• In bad wireless locations choosing TCP
  Streaming(24fps) provides better frame rate than
  the UDP(15fps) streaming
• TCP Streaming also have lower coefficient of
  variation of frame rate than the UDP Streaming

24
TCP Streaming Over UDP Streaming
25
TCP Streaming Over UDP Streaming
26
TCP Streaming Over UDP Streaming

• TCP Streaming has better frame rates because TCP
  retransmits the data
• But, Without Built-in retransmissions,UDP does
  not recover the lost data, so loss rates occur

27
TCP Streaming Over UDP Streaming
28
TCP Streaming Over UDP Streaming
29
TCP Streaming Over UDP Streaming

• UDP uses a high data rate to fill the playout
  buffer
• AP queue grows long and AP cannot drain the
  queue, because wireless layer capacity is limited.

30
TCP Streaming Over UDP Streaming
31
TCP Streaming Over UDP Streaming

• TCP may have longer play out than the UDP for the
  same length of video
• Because in TCP, retransmissions take a lot of time

32
TCP Streaming Over UDP Streaming
33
The Challenges of Streaming over Wireless
34
TCP-Friendly Capacity

• s packet size
• R round-trip time
• p packet drop rate
• trto TCP retransmission timeout

35
Average Application Encoding Rate versus
Wireless Capacity for TCP and UDP Streams
36
Average Application Encoding Rate versus
TCP-Friendly Capacity for TCP and UDP Streams
37
Average Application Encoding Rate versus
Wireless Capacity for Multiple and Single Level
Stream
38
Average Application Encoding Rate versus
TCP-Friendly Capacity for Multiple and Single
Level Stream
39
Conclusion (4 Hypothesis) Revisited

• This measurements study considers
• W-LANs make it difficult for streaming video to
  gracefully adapt when network conditions degrade.
• Multiple level encoding can stream better than
  videos encoded with only a single level when
  W-LAN conditions are poor.
• TCP is more effective than UDP.
• Current available estimation techniques for
  capacity are inadequate for W-LAN

40
Improvement Areas

• Identifying and adapting to challenging wireless
  transmission situations.
• Understanding packet and frame burst loss
  behavior.
• Effective media scaling
• Real Media and Quick Time researches.

41
End of Presentation

• Questions?