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Enhancing Voice over WLAN via
Rate
Adaptation and Retry Scheduling
I. INTRODUCTION
 Investigate the characteristics of VoIP traffic and the
limitations of state-of-the-art rate adaptation ...
II. EXISTING SYSTEM
 VoWLAN
 Characteristics of VoIP Traffic are voice codec and mouth-to-ear
delay and performance metr...
III.PROPOSED SYSTEM
 Two novel features for VoWLAN, namely, fast decrease
(FD) and retry scheduling (RS), to improve the ...
IV.ENHANCING QOS OF VOWLAN
A.Limitations of the Existing Rate Adaptation Algorithms
 Slow response of ARF based algorithm...
B . Rate Adaptation: Fast Decrease
C . Retransmissions: Retry Scheduling
D . Retry Scheduling Chain (RS Chain)
Repeated delay the sixth transmission until the next VoIP
frame arrival.
V. PERFORMANCE EVALUATION: NS-3
SIMULATION
A. Comparing Algorithms
 ARF-Based Families
 FER-Statistics-Based Families
 ...
B. Static Topology
 Fast Decrease and Retry Scheduling
 All the schemes are revised by using FD or both FD and
RS.
 R-s...
Retry Scheduling Chain
 The gain of the RS diminishes as the number of contenting
stations increases.
 The VoIP station...
C. Random Topology with Heterogeneous Traffic Types
 Five static VoIP stations and five static data stations are
randomly...
D. Mobile Topology
 Straight-line scenario and Random mobility scenario
E. Effects on Various VoIP Codecs
 R-score of ARF, RRAA, and their variants for the four
codecs.
Observe that the revise...
F. Hidden terminal environment
VI.PERFORMANCE EVALUATION:
MADWIFI IMPLEMENTATION
A. Implementation of Adaptive RTS
 MAC service data unit (MSDU) is acco...
B. Implementation of Retry Scheduling
 To implement retry scheduling revised MadWiFi is used.
 MadWiFi first delivers th...
C. Experimental Results
 Static environment
By comparing AgileARF with other algorithms performance
is different due to ...
 Mobile environment with heterogeneous traffic
The R-score of proposed iRTS algorithm is close to case that
VoIP station...
VII.CONCLUSION
 Investigate the characteristics of VoWLAN systems, and
discuss the pros and cons of the existing rate ada...
VIII.FUTURE ENHANCEMENT
 Extension of the proposed approaches for real-time video
traffic, whose QoS is also very sensiti...
IX.REFERENCES
[1] B. Kim et al., “Enhancing QoS of Voice over WLANs,”
Proc. IEEE Int’l Symp. a World of Wireless, Mobile a...
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Enhancing Voice over WLAN via Rate Adaptation and Retry Scheduling

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Investigate the characteristics of VoWLAN systems, and discuss the pros and cons of the existing rate adaptation algorithms regarding the VoIP traffic.

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Enhancing Voice over WLAN via Rate Adaptation and Retry Scheduling

  1. 1. Enhancing Voice over WLAN via Rate Adaptation and Retry Scheduling
  2. 2. I. INTRODUCTION  Investigate the characteristics of VoIP traffic and the limitations of state-of-the-art rate adaptation algorithms.  Enhance the QoS of voice over WLAN (VoWLAN).  Fast decrease and retry scheduling  NS-3 simulations and MadWiFi implementations.  Proposed schemes improve the R-score performance by up to 80%.
  3. 3. II. EXISTING SYSTEM  VoWLAN  Characteristics of VoIP Traffic are voice codec and mouth-to-ear delay and performance metric of VoIP(R=Rmax-Idelay-Iloss)  Existing rate adaptation algorithms are ARF and AdaptiveARF, CARA , RRAA, SampleRate and minstrel ,PHY assisted rate adaptation.  IEEE 802.11 MAC and QoS Provisioning.  Retransmission policy and Access category
  4. 4. III.PROPOSED SYSTEM  Two novel features for VoWLAN, namely, fast decrease (FD) and retry scheduling (RS), to improve the QoS.  Evaluate the QoS of the proposed schemes in various communication environments via network simulator (ns-3) and MadWiFi implementation results.
  5. 5. IV.ENHANCING QOS OF VOWLAN A.Limitations of the Existing Rate Adaptation Algorithms  Slow response of ARF based algorithm  PHY assisted algorithm is not feasible  RRAA cannot be fast to trace fast fading channel
  6. 6. B . Rate Adaptation: Fast Decrease
  7. 7. C . Retransmissions: Retry Scheduling
  8. 8. D . Retry Scheduling Chain (RS Chain) Repeated delay the sixth transmission until the next VoIP frame arrival.
  9. 9. V. PERFORMANCE EVALUATION: NS-3 SIMULATION A. Comparing Algorithms  ARF-Based Families  FER-Statistics-Based Families  Reference Algorithms
  10. 10. B. Static Topology  Fast Decrease and Retry Scheduling  All the schemes are revised by using FD or both FD and RS.  R-score is enhanced by applying FD while RS enhances R-score greater than 80.  RS improves the R-score of all rate adaptation algorithm by removing continuous retransmission failure.  FD and RS algorithm rarely affect mouth to ear delay of VoIP frames.
  11. 11. Retry Scheduling Chain  The gain of the RS diminishes as the number of contenting stations increases.  The VoIP stations donot need to intentionally delay the transmission.  Delaying the retransmission is good enough to improve the QoS of VoWLAN.
  12. 12. C. Random Topology with Heterogeneous Traffic Types  Five static VoIP stations and five static data stations are randomly deployed.  Both use same rate adaptation algorithm except RS feature.  Average R-score of scenario with VoIP and data stations are slightly greater due to random topology.  High chance that VoIP stations get closer to AP.
  13. 13. D. Mobile Topology  Straight-line scenario and Random mobility scenario
  14. 14. E. Effects on Various VoIP Codecs  R-score of ARF, RRAA, and their variants for the four codecs. Observe that the revised Agile ARF w/ RS and RRAA- e10-FD w/ RS achieve the R-score over 80.
  15. 15. F. Hidden terminal environment
  16. 16. VI.PERFORMANCE EVALUATION: MADWIFI IMPLEMENTATION A. Implementation of Adaptive RTS  MAC service data unit (MSDU) is accompanied with _transmit descriptor generated by MadWiFi.  Multi rate retry control PHY rate.  MRR is specified by vector (R1,C1,R2,C2,R3,C3,R4,C4).  Implementable RTS implemented in MadWiFi driver.  iRTS has two operating parameters, RTSWnd and RTSCoutner, and one decision parameter x.
  17. 17. B. Implementation of Retry Scheduling  To implement retry scheduling revised MadWiFi is used.  MadWiFi first delivers the original packet to HAL.  MadWiFi removes the copied packet when the transmission is successful and receives new packet.  Two transmit descriptors for MSDU transmission  Chances to enable/disable CTS/RTS  Group of MPDU transmission
  18. 18. C. Experimental Results  Static environment By comparing AgileARF with other algorithms performance is different due to highly fluctuating channel Highly stable
  19. 19.  Mobile environment with heterogeneous traffic The R-score of proposed iRTS algorithm is close to case that VoIP stations that use RTS.
  20. 20. VII.CONCLUSION  Investigate the characteristics of VoWLAN systems, and discuss the pros and cons of the existing rate adaptation algorithms regarding the VoIP traffic.  Fast decrease and Retry scheduling  Extensive ns-3 simulations and MadWiFi measurements  Existing rate adaptation algorithms can dramatically improve the QoS of VoWLAN.
  21. 21. VIII.FUTURE ENHANCEMENT  Extension of the proposed approaches for real-time video traffic, whose QoS is also very sensitive to its packet loss rate.  Future work on refining the RS design, i.e., jointly optimizing the delayed transmission and de-jitter buffer size.  Considering silence suppression and high-latency network, enhance the QoS of VoWLAN.
  22. 22. IX.REFERENCES [1] B. Kim et al., “Enhancing QoS of Voice over WLANs,” Proc. IEEE Int’l Symp. a World of Wireless, Mobile and Multimedia Networks (WoWMoM), June 2012. [2] Wi-Fi Alliance, http://www.wi-fi.org, online link, 2014. [3] Y. Xiao et al., “Protection and Guarantee for Voice and Video Traffic in IEEE 802.11e Wireless LANs,” Proc. IEEE INFOCOM, Mar. 2004. [4] S. Shin and H. Schulzrinne, “Call Admission Control in IEEE 802.11 WLANs Using QP-CAT,” Proc. IEEE INFOCOM, Apr. 2008. [5] J. Yu et al., “Supporting VoIP Services in IEEE 802.11e WLANs,” Proc. Int’l ICST Conf. Heterogeneous Networking for Quality, Reliability, Security and Robustness (QShine), Nov. 2009.

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