doc.: ieee 802.11-05/1109r1 submission november 2005 fanny mlinarsky, et alslide 1 framework for...
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November 2005
Fanny Mlinarsky, et al
Slide 1
doc.: IEEE 802.11-05/1109r1
Submission
Framework for Testing Latency Sensitive Use Cases
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Date: 2005-11-09
Name Company Address Phone email Fanny Mlinarsky
Azimuth Systems
31 Nagog Park, Acton, MA 01720
(978) 263-6610
Chris Trecker Azimuth Systems
31 Nagog Park, Acton, MA 01720
(978) 263-6610
Charles R. Wright
Azimuth Systems, Inc.
31 Nagog Park, Acton MA 01720
978-263-6610
Authors:
November 2005
Fanny Mlinarsky, et al
Slide 2
doc.: IEEE 802.11-05/1109r1
Submission
Abstract
This presentation proposes a framework for testing Latency Sensitive Usage Cases (LSUCs) over 802.11 interfaces.
November 2005
Fanny Mlinarsky, et al
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Outline• Definition of LSUC• Examples of LSUCs• Voice – A An Example
– Primary Metrics– Secondary Metrics
• Proposed 802.11 LSUC Framework• Summary• References
November 2005
Fanny Mlinarsky, et al
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Definition of LSUCLatency Sensitive Usage Cases (LSUCs) are applications
whose functionality depends on and is affected by packet loss, packet delay and packet jitter across any and all networks traversed. LSUCs frequently send/receive packets at a constant packet rate.
Examples include VOIP, Video Conferencing, Internet Gaming.
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Fanny Mlinarsky, et al
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Example: VOIP
• PC-to-PC or PC-to-PSTN (services like Skype)• 802.11 Handsets• Broadband Phone Service• Enterprise VOIP Networks• Metropolitan MESH VOIP Networks
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Fanny Mlinarsky, et al
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Voice over WiFi Examples• Home
– Streaming Video– Broadband Voice– Appliance Control– Video Gaming
• SOHO– WiFi or WiFi-Cell handset, soft phone– Service providers– No handoff, low capacity, basic security– Range
• Enterprise– WiFi or WiFi-Cell handset, soft phone– Range– Handoff speed– Call capacity– Security
• Public access (WiFi hotspots)– WiFi-Cell handset, soft phone– Range– Call Capacity– Roaming issues
WiFi handset
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Fanny Mlinarsky, et al
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Primary Voice Metrics
– MOS (mean opinion score) uses a wide range of human subjects to provide a subjective quality score (ITU-T P.800)
– PESQ (perceptual speech quality measure) sends a voice pattern across a network and then compares received pattern to the original pattern and computes the quality rating (ITU-T P.862)
– E-Model computes Rating Factor or R-Factor as a function of delay and packet loss; R-Factor directly translates into MOS (ITU-T G.107)
ITU-T Voice Quality Standards
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Fanny Mlinarsky, et al
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ITU-T PESQ Model
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Fanny Mlinarsky, et al
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E-Model based on ITU-T G.107
Packet-lossLatency
ITU-T E-Model
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Fanny Mlinarsky, et al
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E-Model ParametersParameter
Abbr. Unit Default value
Permitted range
Send Loudness Rating SLR dB +8 0 ... +18 Receive Loudness Rating RLR dB +2 5 ... +14 Sidetone Masking Rating STMR dB 15 10 ... 20 Listener Sidetone Rating LSTR dB 18 13 ... 23 D-Value of Telephone, Send Side Ds 3 –3 ... +3 D-Value of Telephone Receive Side Dr 3 –3 ... +3 Talker Echo Loudness Rating TELR dB 65 5 ... 65 Weighted Echo Path Loss WEPL dB 110 5 ... 110 Mean one-way Delay of the Echo Path T ms 0 0 ... 500 Round-Trip Delay in a 4-wire Loop Tr ms 0 0 ... 1000 Absolute Delay in echo-free Connections Ta ms 0 0 ... 500 Number of Quantization Distortion Units qdu 1 1 ... 14 Equipment Impairment Factor Ie 0 0 ... 40 Packet-loss Robustness Factor Bpl 1 1 ... 40 Random Packet-loss Probability Ppl % 0 0 ... 20 Circuit Noise referred to 0 dBr-point Nc dBm0p 70 80 ... 40 Noise Floor at the Receive Side Nfor dBmp 64 Room Noise at the Send Side Ps dB(A) 35 35 ... 85 Room Noise at the Receive Side Pr dB(A) 35 35 ... 85 Advantage Factor A 0 0 ... 20
Latency500 ms max
Packet loss20% max
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Fanny Mlinarsky, et al
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Primary LSUC Metrics
Vary depending on application. R-Factor and PESQ are commonly used for voice
Some LSUCs do not have any primary metrics defined (i.e., internet gaming)
Devices/systems under test Client AP Multi-AP infrastructure (e.g. mesh)
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Fanny Mlinarsky, et al
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Secondary Metrics• Secondary Metrics for LSUCs are:
– Packet Loss– Packet Delay (in microseconds)– Jitter (RFC 1889)
• Packet Loss is measured in each direction (upstream / downstream) separately. Ideally, it should be measured from both endpoints – i.e., the transmitter and the receiver.
• Packet Delay should be measured in each direction (upstream / downstream) separately in microseconds.
• Jitter should be measured in microseconds according to RFC 1889
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Fanny Mlinarsky, et al
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Proposed LSA Testing Framework
• TGt should reference applicable Primary Metrics where possible. Should TGt recommend specific primary metrics, or is that too contentious?
• Use packet delay, loss and jitter as the secondary metrics for LSUC. Are there potentially other application specific secondary metrics?
• TGt should define the 802.11 test variables that will directly impact the Primary LSUC metrics. For example:– Signal strength– Traffic load– BSS Transitions / Fast BSS Transitions– PS-Poll / APSD– 802.11e and 802.11i specific device and system settings
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Discussion
• Is this framework acceptable?• Should this framework be used as a basis to draft a
submission into TGt ?
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Fanny Mlinarsky, et al
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References
• 11-05/949r0, “Latency-Sensitive-Application Metrics”, S. Bangolae
• 11-05/33r0, “Performance of Voice over 802.11 Networks”, Fanny Mlinarsky
• 11-05/887r0, “Video Testing Strategy”, P. Corriveau, et al
• 11-05-/177r0, “Dell IEEE 802.11 TGT Output”, P. Mehta, et al