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Cross Layer optimization for VoIP over WLAN [Yuan Liu Zhu]

Cross Layer optimization for VoIP over WLAN [Yuan Liu Zhu]. A Presentation for Resilinets group Sarvesh Kumar Varatharajan Department of Electrical Engineering & Computer Science University of Kansas sarvesh@ittc.ku.edu. 23 September 2014. 23 September 2014. 1. 1. Abstract.

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Cross Layer optimization for VoIP over WLAN [Yuan Liu Zhu]

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  1. Cross Layer optimization for VoIP over WLAN[Yuan Liu Zhu] A Presentation for Resilinets group Sarvesh Kumar Varatharajan Department of Electrical Engineering & Computer Science University of Kansas sarvesh@ittc.ku.edu 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 1 1

  2. Abstract • Problems of VoIP over WLAN • Unacceptable voice delays when coexisting with other applications • Low voice Capacity due to heavy headers from the above layers • Cross layer schemes to improve voice capacity • Voice stream enjoys fixed bandwidth. • Voice delay is minimum • Simulation at various PHY rates over various voice codec • Proposed scheme advances throughput of voice stream 23 September 2014 Cross-layer optimization for VoIP over WLAN 2

  3. Organization of the paper • Introduction • Background • Cross Layer Optimizations • Theoretical Analysis • Simulation and Results • Conclusion 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 3 3

  4. Introduction • VoIP applications • Delay • Heavy packet headers from upper layers reduces voice capacity • 802.11 can support only limited number of VoIP connections • Capacity of G.711 VoIP using CBR model and a 20ms packet interval is only 12 calls[2] • A scheme is proposed where interaction with application layer reduces delay • Time slot reuse method to increase capacity 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 4 4

  5. Background • VoIP Overview • Overview of 802.11 and 802.11e • Related Work 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 5 5

  6. VoIP overview • Variable delay in each hop • End to end delay threshold Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 6 6

  7. Overview of 802.11 and 802.11e • Distributed Coordination function (DCF) • Contention based access • Best effort service • No QoS support • Infeasible option for VoIP • Point Coordination function (PCF) • When number of polling stations is large then higher the end to end delay • Poor performance of VoIP • Service Differentiation based on MAC schemes to classify traffic types with relative priorities 23 September 2014 Cross-layer optimization for VoIP over WLAN 7

  8. Overview of 802.11 and 802.11e • 802.11e addresses the problem of 802.11 • Hybrid Coordination Function (HCF) • Enhanced Distributed Coordinated Access( EDCA ) • Significant time delay • HCF Controlled Channel Access(HCCA) • POLL, ACK required. Additional overhead Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 8 8

  9. Related Work • VoIP over PCF[3][4] • VoIP over DCF[5] • No solutions to improve VoIP performance over HCCA of 802.11e • Paper proposes schemes to improve VoIP capacity over HCCA of 802.11e 23 September 2014 Cross-layer optimization for VoIP over WLAN 9

  10. Organization of the paper • Introduction • Background • Cross Layer Optimizations • Theoretical Analysis • Simulation and Results • Conclusion 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 10 10

  11. Cross Layer Optimization • Assumption: All nodes of WLAN have fixed and equal PHY rate • Slotted TXOP • Time Slot reuse • Packet-header Compression 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 11 11

  12. Slotted TXOP • POLL + ACK reduces VoIP capacity in HCCA • ACK unnecessary for voice • Slotted TXOP • Each node has fixed PHY rate and same voice codec Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 12 12

  13. Slotted TXOP (contd) • Minimizing time delay Reference[1] • Application layer informed about the time slot • Packaging is done before the time slot of the node 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 13 13

  14. Time-slot reuse • Voice Activity Detection(VAD) • MAC layer rarely downloads and uploads voice packet at the same time Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 14 14

  15. Time slot reuse(contd) Reference[1] Cross-layer optimization for VoIP over WLAN

  16. Packet-header compression • Typical VoIP packet at MAC layer 40 –byte IP/UDP/RTP headers while payload only 10 to 30 bytes • Packet Header Compression(PHC) • Casner’s Algorithm[6] • Most of the fields in the IP,UDP and RTP headers do not change over the lifetime of RTP session(Represent by fewer bits) • RTP header fields such as sequence number and time stamp are increased by a constant amount for successive packets • Differential coding • This algorithm can compress the header to 2 bytes 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 16 16

  17. Cross Layer Optimization • Assumption: All nodes of WLAN have fixed and equal PHY rate • Slotted TXOP • Time Slot reuse • Packet-header Compression 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 17 17

  18. Theoretical Analysis 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 18 18

  19. Theoretical Analysis 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 19 19

  20. Theoretical Analysis 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 20 20

  21. Theoretical Analysis • TRST with PHC increases network capacity compared to original TRST • If psil is large enough the network capacity of VoIP increases compared with STXOP, let alone the original HCCA scheme 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 21 21

  22. Organization of the paper • Introduction • Background • Cross Layer Optimizations • Theoretical Analysis • Simulation and Results • Conclusion 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 22 22

  23. Simulation and Results Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 23 23

  24. Simulation and Results Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 24 24

  25. Simulation and Results Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 25 25

  26. Simulation and Results Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 26 26

  27. Simulation and Results Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 27 27

  28. Simulation and Results Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 28 28

  29. Simulation and Results Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 29 29

  30. Simulation and Results Reference[1] 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 30 30

  31. Conclusion • STXOP utilizes slotted TXOP and discards POLL and ACK to system capacity • Every voice stream enjoys fixed bandwidth • Interaction with application layer reduces delay • TRST scheme proposed reutilizes silent slots to advance system performance and reduce CFP duration • Proposed scheme better than HCCA scheme • System capacity better for codec G 723.1 Cross-layer optimization for VoIP over WLAN

  32. References [1]YUAN Wen-peng, LIU Gan, ZHU Guang-xi,Cross-layer optimization for VoIP over WLAN,June 2007 Volume 1,No 1,Computer Technology and Application,ISSN1934-7332,USA [2]LIN Y.-B. and Chlamtac, I. Wireless and Mobile Network Architectures, New York:Wiley,2001 [3]Chen D., Garg S., Kappes . And M. and Trivedi K. Supporting VBR VoIP traffic in IEEE 802.11 WLAN in PCF mode. Avaya Laboratories, Basking Ridge, NJ Tech. Rep. ALR-2002-026, 2002 [4]Veeraraghavan, M., Cocker, N. and Moors, T. Support of voice services in IEEE 802.11 wireless LANs Proc. INFOCOM ‘01 Apr. 2001, 1:488-497 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 32 32

  33. References [5]Baldwin, R.O. Davis IV, N.J .Midkiff, S.F and Raines, R.A. Packetized voice transmission using RT-MAC, a wireless real- time medium access control protocol. Mobile Comput Commun. Rev 2001, 5(3):11-25 [6] Casner,S. and Jacobson, V. Compressing IP/UDP/RTP headers for low speed serial links. Proc. IETF RFC 2508, Feb 1999. 23 September 2014 23 September 2014 Cross-layer optimization for VoIP over WLAN 33 33

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