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ABSTRACT

Transmitting voice through IP data network can provide significant cost savings. However if not managed properly, voice quality can degrade due to data network congestion. Voice over IP (VoIP) is gaining an ever increasing popularity. As such, it nowadays represents one of the most studied test applications in the performance evaluation of wireline and wireless networks in which the IEEE 802.11 distributed coordination function protocol or enhanced DCF protocol is used. However, since both DCF and EDCF are contention-based medium access control protocols, it is difficult for them to support the strict QoS requirement for VoIP.

In this paper we will investigate QoS indications (for voice packets), Improvement of NS2 network simulator in order to simulate statistical QoS in 802.11 MAC and Show that Uplink/Downlink problem exists in EDCF and suggest different solutions using QoS parameters (DIFS, CWmin and PF).

REFERENCES

• 1: S. Shin, and H. Schulzrinne. Experimental measurement of the capacity for VoIP traffic in IEEE 802.11 WLANs. Proc. IEEE INFOCOM 2007, Anchorage, USA, May 6-12.
• 2: Skype, http://www.skype.com, continuously updated
• 3: H. Wu, K. Tan, Y. Zhang, and Q. Zhang. Proactive scan: Fast handoff with smart triggers for 802.11 wireless LAN Proc. IEEE INFOCOM 2007, Anchorage, USA, May 6-12
• 4: http://info.iet.unipi.it/~cng/ns2voip/
• 5: http://nsnam.isi.edu/nsnam/
• 6: http://www.nsnam.org/
• 7: IEEE 802.11e Wireless LAN for Quality of Service
• 8: Reuven Cohen, Liran Katzir (Technion, Israel). Scheduling of Voice Packets in a Low-Bandwidth Shared Medium Access Network
• 9: Vasilios A. Siris. Achieving Service Differentiation and High Utilization in 802.11
• 10: Dongyan Chen, Sachin Garg, Martin Kappes and Kishor S.Trivedi. Supporting VBR VoIP Traffic in IEEE 802.11 WLAN in PCF Mode
• 11: Dongyan Chen, Sachin Garg, Martin Kappes and Kishor S. Trivedi. Supporting VoIP Traffic in IEEE 802.11 WLAN with Enhanced MAC for QoS.
• 12: http://www.cs.technion.ac.il/Courses/Computer-Networks-Lab/projects/winter2004/voip2/
• 13: IEEE 802.11E ENHANCEMENT FOR VOICE SERVICE

INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.6 SIMULATION AND MODELING
      I.6.2 Simulation Languages

General Terms:
Performance

Keywords:
ieee 802.11, mac protocol, ns-2, qos, voip