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  1. 1. Video over Wireless Sowjanya Talasila
  2. 2. Topics for discussion  Introduction  Issues and solution  Challenges  Future work  Conclusion  References
  3. 3. 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
  4. 4. 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
  5. 5. 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
  6. 6. Introduction  With the development of broadband wireless networks, attention is given to the delivery of video over wireless networks
  7. 7. Issues  Rate control  Handover  Security
  8. 8. 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
  9. 9. Contd..  Ensures fairness among the users sharing the common link in a given network
  10. 10. TCP – Friendly Rate Control (TFRC)  This solution is proposed so that the performance of TCP doesn’t 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
  11. 11. 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.
  12. 12. TFRC Contd..  The TFRC sender changes the sending rate at least once a RTT  This affects the video quality
  13. 13. Experimental setup
  14. 14. 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
  15. 15. 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
  16. 16. 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
  17. 17. 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
  18. 18. 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
  19. 19. 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
  20. 20. Contd..  The proposed system consists of two subsystems : RTT Measurement Subsystem (RMS) and Connections Controller Subsystem (CCS)  Based on the RMS, CCS responds
  21. 21. Comparision (One TFRC Vs MULTFRC)
  22. 22. 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
  23. 23. Analysis of MULTFRC
  24. 24. 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
  25. 25. 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
  26. 26. Experimental setup
  27. 27. Experiment results
  28. 28. 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
  29. 29. Contd..
  30. 30. Experimental setup
  31. 31. Experimental results
  32. 32. 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
  33. 33. Contd..
  34. 34. 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
  35. 35. 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
  36. 36. Contd..  USHA provides seamless handoff environment  Video Transfer Protocol (VTP) is used to adapt video streaming rates according to eligible rate estimates
  37. 37. Contd..  VTP provides substantial improvements to streaming performance in terms of perceived video quality and robustness against sudden changes in link capacities
  38. 38. 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
  39. 39. 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
  40. 40. Encryption  Only authorized receivers can understand the transmitted data  WPA – encryption security standard for wireless networks
  41. 41. 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
  42. 42. Architecture of secure video wireless system
  43. 43. 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
  44. 44. Real-time key embedding and key detecting process
  45. 45. 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
  46. 46. Challenges  To improve QoS (video quality, packet loss, delay etc)  High variability of network throughput  Cost
  47. 47. 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
  48. 48. 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
  49. 49. Conclusion  Video streaming in wireless networks is one of the upcoming multimedia applications which is still in it’s developing stages.  There are many areas of research to improve it’s performance over wireless networks.
  50. 50. References  Rate control for streaming video over wireless by Minghua Chen, Avideh Zakhor, August 2005, IEEE .pdf?tp=&arnumber=1497856&isnumber=32173  Seamless handover of streamed video over UDP in wireless LANs by Ger Cunningham, Philip Perry, Sean Murphy, Liam Murphy df
  51. 51. Contd..  Adaptive video streaming in vertical handoff by Chen L-J, Guang Yang, Gerla M etc, August 2004, IEEE .pdf?tp=&arnumber=1331716&isnumber=29413  A novel secure wireless video surveillance system based on Intel IXP425 network processor by Hao Yien, Xiaowen Chu, Oxtober 2005, ACM 62- hao.pdf?key1=1089748&key2=6505163411&coll=GU IDE&dl=GUIDE&CFID=72460738&CFTOKEN=457412 7