cross layer optimization for voip over wlan [yuan liu zhu]
DESCRIPTION
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 [email protected]. 23 September 2014. 23 September 2014. 1. 1. Abstract. - PowerPoint PPT PresentationTRANSCRIPT
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 1April 21, 2023 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 [email protected]
April 21, 2023 1
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 2April 21, 2023 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
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 3April 21, 2023 3
Organization of the paper
• Introduction• Background• Cross Layer Optimizations• Theoretical Analysis• Simulation and Results• Conclusion
April 21, 2023 3
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 4April 21, 2023 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
April 21, 2023 4
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 5April 21, 2023 5
Background
• VoIP Overview• Overview of 802.11 and 802.11e• Related Work
April 21, 2023 5
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 6April 21, 2023 6
VoIP overview
April 21, 2023 6
• Variable delay in each hop• End to end delay threshold
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 7April 21, 2023 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
© Sarvesh
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]
April 21, 2023 Cross-layer optimization for VoIP over WLAN 8April 21, 2023 8April 21, 2023 8
© Sarvesh
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
April 21, 2023 Cross-layer optimization for VoIP over WLAN 9April 21, 2023 9
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 10April 21, 2023 10
Organization of the paper
• Introduction• Background• Cross Layer Optimizations• Theoretical Analysis• Simulation and Results• Conclusion
April 21, 2023 10
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 11April 21, 2023 11
Cross Layer Optimization
• Assumption: All nodes of WLAN have fixed and equal PHY rate• Slotted TXOP• Time Slot reuse• Packet-header Compression
April 21, 2023 11
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 12April 21, 2023 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]
April 21, 2023 12
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 13April 21, 2023 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
April 21, 2023 13
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 14April 21, 2023 14
Time-slot reuse
• Voice Activity Detection(VAD)• MAC layer rarely downloads and uploads voice packet at
the same time
Reference[1]
April 21, 2023 14
© Sarvesh
Time slot reuse(contd)
April 21, 2023 Cross-layer optimization for VoIP over WLAN 15
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 16April 21, 2023 16
Packet-header compression
April 21, 2023 16
• 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
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 17April 21, 2023 17
Cross Layer Optimization
• Assumption: All nodes of WLAN have fixed and equal PHY rate• Slotted TXOP• Time Slot reuse• Packet-header Compression
April 21, 2023 17
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 18April 21, 2023 18
Theoretical Analysis
April 21, 2023 18
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 19April 21, 2023 19
Theoretical Analysis
April 21, 2023 19
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 20April 21, 2023 20
Theoretical Analysis
April 21, 2023 20
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 21April 21, 2023 21
Theoretical Analysis
April 21, 2023 21
• 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
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 22April 21, 2023 22
Organization of the paper
• Introduction• Background• Cross Layer Optimizations• Theoretical Analysis• Simulation and Results• Conclusion
April 21, 2023 22
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 23April 21, 2023 23
Simulation and Results
April 21, 2023 23
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 24April 21, 2023 24
Simulation and Results
April 21, 2023 24
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 25April 21, 2023 25
Simulation and Results
April 21, 2023 25
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 26April 21, 2023 26
Simulation and Results
April 21, 2023 26
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 27April 21, 2023 27
Simulation and Results
April 21, 2023 27
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 28April 21, 2023 28
Simulation and Results
April 21, 2023 28
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 29April 21, 2023 29
Simulation and Results
April 21, 2023 29
Reference[1]
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 30April 21, 2023 30
Simulation and Results
April 21, 2023 30
Reference[1]
© Sarvesh
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
April 21, 2023 Cross-layer optimization for VoIP over WLAN 31
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 32April 21, 2023 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
April 21, 2023 32
© Sarvesh
April 21, 2023 Cross-layer optimization for VoIP over WLAN 33April 21, 2023 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.
April 21, 2023 33