Video%20over%20Wireless

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Video over Wireless

• Sowjanya Talasila

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Topics for discussion

• Introduction
• Issues and solution
• Challenges
• Future work
• Conclusion
• References

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Video

• Video the technology of capturing, recording,
  processing, transmitting and reconstructing the
  moving pictures using celluloid film, electronic
  signals or digital media
• Quality of the video depends on the method used
  for capturing and storing

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Characteristics of video stream

• Frame rate number of still pictures per unit
  time of video
• Video resolution size of video image
• Aspect ratio dimensions of video screen and
  video picture elements
• Bits per pixel determines the number of
  distinct colors

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Contd..

• Video quality in terms of PSNR (ratio of max
  power of the video signal to the power of the
  corrupting noise)
• Bit rate (digital only) rate of information
  content in a video stream
• Higher the bit rate, better the video quality

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Introduction

• With the development of broadband wireless
  networks, attention is given to the delivery of
  video over wireless networks

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Issues

• Rate control
• Handover
• Security

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Issue 1 Rate control

• Importance of rate control
• Results in full utilization of the link by
  ensuring that sending rates are not too slow
• Prevents congestion collapse by ensuring that
  sending rates are not too aggressive

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Contd..

• Ensures fairness among the users sharing the
  common link in a given network

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TCP Friendly Rate Control (TFRC)

• This solution is proposed so that the performance
  of TCP doesnt deteriorate when both TCP and UDP
  sessions co-exist in the internet
• TFRC a non TCP connection should receive the
  same amount of bandwidth as a TCP connection if
  they traverse on the same path

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TFRC contd..

• TFRC regulates the data sending rate according to
  the network condition, expressed in terms of RTT
  and packet loss probability, to achieve same
  throughput that a TCP connection would acquire on
  the same path.

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TFRC Contd..

• The TFRC sender changes the sending rate at least
  once a RTT
• This affects the video quality

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Experimental setup
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Contd..

• Assumptions
• No cross traffic at node1 and node2
• No congestion at node1
• No congestion and queuing delay at node2 if and
  only if wireless bandwidth is underutilized

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Contd..

• The available wireless link bandwidth Bw and
  packet loss rate (caused by wireless channel
  error) Pw is a constant
• Backward path is error free and congestion free

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Contd..

• Based on the above mentioned scenario and the
  assumptions, it is proved that, one TFRC
  connection underutilizes the wireless link as the
  available bandwidth is larger than the highest
  sending rate

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Contd..

• The total throughput of the application will
  increase with the number of TFRC connections
  until it reaches the hard limit of Bw(1-Pw)
• For a particular packet size, the maximum number
  of TFRC connections to achieve proper utilization
  of the link is derived

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Contd..

• Any connection beyond this number will result in
  increase in RTT or packet loss rate and hence the
  sending rate of each connection has to be
  decreased

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Multiple TFRC (MULTFRC)

• A practical scheme called MULTFRC is developed to
  determine the optimal number of connections
• Measures RTT and adjusts the number of
  connections accordingly to utilize the wireless
  bandwidth efficiently and ensure fairness between
  the applications

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Contd..

• The proposed system consists of two subsystems
  RTT Measurement Subsystem (RMS) and Connections
  Controller Subsystem (CCS)
• Based on the RMS, CCS responds

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Comparision (One TFRC Vs MULTFRC)
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Contd..

• When there is a change in the route, say change
  in the wireless base station, the RTT changes and
  the performance of MULTFRC is affected
• Employing route change detection tools such as
  Traceroute, helps in resetting the RTT value

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Analysis of MULTFRC
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Issue 2 Handover

• Video applications are delay sensitive. Certain
  delay in handing over the mobile device to
  another access point leads to loss in data.
• In video streaming packet loss should be as
  minimum as possible
• Low latency and low packet loss are the
  critical design issues

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Handover decision based on packet delay

• Delay is used as an indicator of when loss is
  likely to occur
• UDP is used in the transport layer
• Hard handoff not preferred as there could be a
  possibility for data loss by the time the mobile
  device is handed over to the next suitable access
  point

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Experimental setup
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Experiment results
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Contd..

• The MN has two WLAN interfaces, so that it can
  handoff from one WLAN to another
• The MN uses soft handoff in the application
  layer, enabling the video decoder in the MN to
  present an uninterrupted video stream to the user

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Contd..
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Experimental setup
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Experimental results
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USHA and VTP

• Cost effective
• Handoff solution with minimal changes in the
  current internet infrastructure
• Adapts to the user mobility faster while
  maintaining better connectivity for established
  network sessions

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Contd..
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Contd..

• Handoff network configured using IP tunneling
  methods
• Handoff server (HS) as one end of the IP tunnel
  and Mobile Host (MH) as other end of the IP
  tunnel
• IP tunnel uses two virtual IP addresses and two
  fixed IP addresses

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Contd..

• Physical connection between HS and MH made using
  fixed IP addresses
• The handoff client is responsible for
  automatically switching the underlying physical
  connection of the virtual tunnel to new interface

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Contd..

• USHA provides seamless handoff environment
• Video Transfer Protocol (VTP) is used to adapt
  video streaming rates according to eligible rate
  estimates

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Contd..

• VTP provides substantial improvements to
  streaming performance in terms of perceived video
  quality and robustness against sudden changes in
  link capacities

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Issue 3 Security

• Transmission over wireless can be intercepted by
  any suitable device within the transmission
  radius
• If a network intruder is able to attach to
  unsecured AP, he can get access to the
• wireless network and internet connection

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MAC address filtering

• Limit the access to only identifiable network
  cards with approved MAC addresses
• Not a good solution as MAC addresses are
  broadcasted, any intruder can figure it out

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Encryption

• Only authorized receivers can understand the
  transmitted data
• WPA encryption security standard for wireless
  networks

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Novel secure wireless video surveillance system

• Video encryption is very important in WLAN
  environment since everyone can receive the video
  content and inject faked video packets

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Architecture of secure video wireless system
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Contd..

• The video source is capture by the camera nodes
  and is compressed and stored in the processor
• Authentication information and encryption key is
  embedded to this
• Camera nodes also act as routers and route the
  encrypted frames to the monitoring center

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Real-time key embedding and key detecting process
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Contd..

• New keys are embedded in I-frame (intra frame) of
  group of pictures (GOP) and directly modulated
  into the direct current component of discrete
  cosine transform (DST) coefficients of luminance
  blocks
• All GOPs will be encrypted by a selective
  encryption algorithms

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Challenges

• To improve QoS (video quality, packet loss, delay
  etc)
• High variability of network throughput
• Cost

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Future work

• Rate and quality control mechanism under lossy
  conditions
• Single physical WLAN interface to access multiple
  networks simultaneously
• In novel secure system, the misbehavior detection
  capability is limited by the computational power
  of

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Contd..

• the camera nodes. An adaptive mechanism has to
  be figured out to suit the application
• Monitoring center is the only non-distributed
  component. Some solutions must be found to scale
  the network size

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Conclusion

• Video streaming in wireless networks is one of
  the upcoming multimedia applications which is
  still in its developing stages.
• There are many areas of research to improve its
  performance over wireless networks.

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References

• Rate control for streaming video over wireless by
  Minghua Chen, Avideh Zakhor, August 2005, IEEE
  http//ieeexplore.ieee.org/iel5/7742/32173/0149785
  6.pdf?tparnumber1497856isnumber32173
• Seamless handover of streamed video over UDP in
  wireless LANs by Ger Cunningham, Philip Perry,
  Sean Murphy, Liam Murphy http//www.eeng.dcu.ie/
  perryp/pub/cunningham4.pdf

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Contd..

• Adaptive video streaming in vertical handoff by
  Chen L-J, Guang Yang, Gerla M etc, August 2004,
  IEEE http//ieeexplore.ieee.org/iel5/9259/29413/0
  1331716.pdf?tparnumber1331716isnumber29413
• A novel secure wireless video surveillance system
  based on Intel IXP425 network processor by Hao
  Yien, Xiaowen Chu, Oxtober 2005, ACM
  http//delivery.acm.org/10.1145/1090000/1089748/p6
  2-hao.pdf?key11089748key26505163411collGUIDE
  dlGUIDECFID72460738CFTOKEN4574127