Experimental Measurement of the Capacity for VoIP Traffic in IEEE 802.11 WLANs

We measured the capacity for VoIP traffic in an 802.11b test-bed and compared it with the theoretical capacity and our simulation results. We identified factors that have been commonly overlooked in past studies but affect experiments and simulations. We found that in many papers the capacity for VoIP traffic has been measured via simulations or experiments without considering those factors, showing different capacity in each paper. After these corrections, simulations and experiments yielded a capacity estimate of 15 calls for 64 kb/s CBR VoIP traffic with 20 ms packetization interval and 34 calls to 36 calls for VBR VoIP traffic with 0.39 activity ratio.

[1]  Paul T. Brandy.  Model for Generating On‐Off Speech Patterns in Two‐Way Conversation , 1969 .

[2]  Malathi Veeraraghavan,et al.  Support of voice services in IEEE 802.11 wireless LANs , 2001, Proceedings IEEE INFOCOM 2001. Conference on Computer Communications. Twentieth Annual Joint Conference of the IEEE Computer and Communications Society (Cat. No.01CH37213).

[3]  DongyanChen,et al.  Supporting VoIP Traffic in IEEE 802 . 11 WLAN with EnhancedMedium Access Control ( MAC ) for Quality of Service , 2003 .

[4]  Héctor L. Velayos,et al.  Techniques to Reduce IEEE 802 . 11 b MAC Layer Handover Time , 2003 .

[5]  Prathima Agrawal,et al.  Voice performance in WLAN networks - an experimental study , 2003, GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489).

[6]  Sachin Garg,et al.  An experimental study of throughput for UDP and VoIP traffic in IEEE 802.11b networks , 2003, 2003 IEEE Wireless Communications and Networking, 2003. WCNC 2003..

[7]  Fouad A. Tobagi,et al.  Capacity of an IEEE 802.11b wireless LAN supporting VoIP , 2004, 2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577).

[8]  Thierry Turletti,et al.  IEEE 802.11 rate adaptation: a practical approach , 2004, MSWiM '04.

[9]  Henning Schulzrinne,et al.  Using dynamic PCF to improve the capacity for VoIP traffic in IEEE 802.11 networks , 2005, IEEE Wireless Communications and Networking Conference, 2005.

[10]  Ratul Mahajan,et al.  Measurement-based characterization of 802.11 in a hotspot setting , 2005, E-WIND '05.

[11]  Manpreet Singh,et al.  Overview of the ORBIT radio grid testbed for evaluation of next-generation wireless network protocols , 2005, IEEE Wireless Communications and Networking Conference, 2005.

[12]  Henning Schulzrinne,et al.  Balancing uplink and downlink delay of VoIP traffic in WLANs using Adaptive Priority Control (APC) , 2006, QShine '06.