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Experimental Results on IP-layer Enhancement to Capacity of VoIPv6 over IEEE 802.11b WLAN. Presented for WiNMee’05 April 3, 2005 Youngjune Gwon , James Kempf, Raghu Dendukuri, and Ravi Jain [email protected] DoCoMo USA Labs. Summary. Motivation Limited VoIP capacity of wireless LAN - PowerPoint PPT Presentation
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Experimental Results on IP-layer Enhancement to Capacity of
VoIPv6 over IEEE 802.11b WLAN
Presented for WiNMee’05
April 3, 2005
Youngjune Gwon, James Kempf, Raghu Dendukuri, and Ravi Jain
[email protected] USA Labs
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 2
Summary Motivation
– Limited VoIP capacity of wireless LAN– Limited availability of experimental measurements
• Many existing studies based on analytical modeling or simulations
– Unstudied impact of IP or higher layer enhancements• Most focused on modifying 802.11 MAC
Our contributions– One of the first experimental results for VoIPv6 over
802.11b– Proposed use of IP or higher layer enhancement schemes
• ROHC and Silence Suppression (SS)– Analytical capacity model using ROHC, SS, IPv6, 802.11b,
and G.711 parameters– Experimental validation
Key technical results– Achieved best-case capacity improvement of 140 %
without MAC modification or PCF– Analytical model more optimistic about capacity than the
actual by 20%
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 3
Outline Motivation Related work Capacity enhancement Hole and Tobagi upper-bound Experimental methodology Results Conclusion
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 4
Motivation Today’s WLAN is being used not only for data
(TCP) but also for voice and other real-time multimedia
Maximum capacity of VoIPv4 over WLAN (Vo4WLAN) is 6
– Assuming G.711 with frame duration of 10 msec and 802.11b
Higher layer solutions to improve VoIP capacity unstudied
– Compared to many existing enhancements by modifying 802.11 MAC
Limited availability of experimental measurements
– Few in Vo4WLAN– What about VoIPv6 over WLAN (Vo6WLAN)?
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 5
Related Work
Capacity Evaluation Studies
Capacity Enhancement
SchemesAnalytical/simulation-based
Experimental
802.11 MAC modifying*
Higher layer enhancing
Vo4WLAN
Garg and Kappes (ICC’03), Hole and Tobagi (ICC’04)
Anjum et al. (GLOBECOMM’03), Newmann (Network World Fusion)
Aad et al. (INFOCOM’01), Suzuki et al. (PIMRC’01), Veeraraghavan et al. (INFOCOM’01), Yeh et al. (ICC’02), Anjum et al. (GLOBECOMM’03)
Any work?
Vo6WLAN
Any work?
Our work Our work
(*) IEEE 802.11 Task Group E (TGe)formed to define 802.11e
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 6
Capacity Enhancement Robust Header Compression (ROHC) – RFC
3095– 60 byte RTP/UDP/IPv6 headers fully compressed to
1 – 2 bytes
Silence Suppression (SS)– More than 50 % of telephone speech is silent– Enabled by Speech Activity Detector (SAD)
• When silence detected, need not transmit packets (perfect SS), or transmit minimal bits only
Access router/AP(ROHC compressor)
Mobile wireless host(ROHC decompressor)
Wireless link
Voice payload + RTP/ UDP/ I P headers (uncompressed)
Voice payload + ROHC Header (compressed) Voice payload + Restored RTP/
UDP/ I P headers (uncompressed)
Reference header
Reference header
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 7
Hole and Tobagi Upper-bound
N = upper-bound VoIP capacity in 802.11 R = generated voice packets / sec Tvoice = voice packet transmission time over wireless link SIFS = short interframe space TACK = acknowledgment frame time DIFS = DCF interframe space TSLOT = slot duration CWMIN = number of minimum random slots picked during backoff
22
1
MINSLOTACKVOICE
CWTDIFSTSIFSTR
N
Total voice packet transmission timeover WLAN link from caller/callee
CSMA/CA wireless mediumaccess time
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 8
Analytical Vo6WLAN Capacity Hole and Tobagi upper-bound capacity for
Vo6WLAN– Assume VoIPv6 over 802.11b, G.711 with 10 msec
voice frame (80-byte voice payload), ROHC (header = 1.5 byte), perfect SS
Vo6WLAN schemes
1Plain
2ROHC only
3SS only
4ROHC +
SS
Upper-bound capacity, N
6 7 13 14
Capacity improvement
- 17 % 117 % 133 %
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 9
Experimental Methodology Real wireless IPv6
testbed Voice traffic
– Speech generation
• ITU-T Recommendation P.59
– G.711 codec– Carried over
RTP/UDP/IPv6 Data traffic
– Based on a web traffic model
• Choi and Limb (ICNP’99)
• Observed peak per client data rate of 30 kbps
– Carried over HTTP/TCP/IPv6
Co-located
Access router
I EEE 802.11bAccess Point
I Pv6 router
…….14 mobile wireless I Pv6
hosts
I Pv6 hosts
I Pv6 hosts I Pv6 hosts
Webserver
ROHCComp/decomp
ROHCComp/decomp
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 10
Results
Experimental notes– Started from 5 calls and incrementally add a call to 14 total calls
• Call = caller/callee pair of one wireless and one wired nodes– Number of web clients matches number of wireless nodes– Captured all transmitted and received packets
• Measuring packet loss and latency– Computed MOS for each case
• Used ITU E-model• MOS > 3 to determine capacity
Validation of analytical model– More optimistic than experimental results by 20 %
Capacity improvement– 17 % (ROHC) to 140 % (ROHC + SS)
Background web traffic
Vo6WLAN schemes
1Plain
2ROHC only
3SS only
4ROHC + SS
No 6 (6) 7 (7) 12 (13) 13 (14)
Yes 5 6 10 12Note: values in ( ) represent analytical upper-bound
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 11
Obtaining Experimental Capacity
5 6 7 8 9 10 11 12 13 141
1.5
2
2.5
3
3.5
4
4.5Downlink MOS vs. total number of voice sessions
Number of VoIP sessions (calls)
MO
S
No ROHC, no SS, no web traffic (I)
No ROHC, no SS, with web traffic (II)With ROHC, no SS, no web traffic (III)
With ROHC, no SS, with web traffic (IV)
No ROHC, with SS, no web traffic (V)
No ROHC, with SS, with web traffic (VI)With ROHC, with SS, no web traffic (VII)
With ROHC, with SS, with web traffic (VIII)
© 2005 by DoCoMo Communications Laboratories USA, Inc. Confidential proprietary. All rights reserved. Youngjune Gwon 12
Conclusions Presented experimental VoIPv6 over 802.11b Proposed use of IP or higher layer
enhancement schemes– ROHC and Silence Suppression (SS)
Instantiated analytical model for VoIP capacity in wireless LAN
– Using ROHC, SS, IPv6, 802.11b, and G.711 parameters
Validated experimentally Key technical results
– Achieved best-case capacity improvement of 140 %
– Vo6WLAN capacity predicted by analytical model is off by 20 %