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Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Date: January 18, 2005
Performance of Voice over 802.11 Networks
Author: Fanny Mlinarsky, Azimuth Systems
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Discussion Outline
• VoIP and VoWiFi history
• Cell-WiFi convergence
• Voice network requirements
• Emerging voice standards– Quality of Service– Security– Roaming
• VoWiFi performance and certification testing
• Future trends and opportunities
WiFiCell
VoIP
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
VoIP-Data Convergence
PSTN
Traditional PBX Proprietary
Digital Phones
Corporate LAN
Internet
Server
Router
PSTNPSTN
Traditional PBX Proprietary
Digital Phones
Corporate LAN
Corporate LAN
InternetInternet
ServerServer
Router
PSTNPSTNIP Phones
Corporate LAN
Corporate LAN
InternetInternet
Server
Router
Telephony Server
Traditional Enterprise connectivity
VoIP converges telephony and data networks
First VoIP products emerged in 1996
PSTN = Public Switched Telephone Network
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
VoWiFi - Legacy PBX Systems• VoWiFi manufacturers
– Cisco, Symbol, Spectralink– Spectralink WiFi phones
available since 1999– 802.11b only for now
• Most IP PBXs use proprietary protocols
– Cisco SCCP (skinny call control protocol)
– Alcatel UA– NEC Protims– Avaya CCMS– Nortel UniStim– Siemens CorNet IP– Mitel MiNet
• Standard IP telephony protocols– H.323– Media Gateway Control Protocol (MGCP)– Session Initiation Protocol (SIP)
PBX
Telephony gateway
Telephony server
Ethernet Network
PBX
Telephony gateway
Telephony server
Ethernet Network
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Voice over WiFi Use Cases• SOHO
– WiFi or WiFi-Cell handset, soft phone– Service providers: Vonage, ATT CallVantage, Net2Phone– 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
Net2Phone WiFi handset
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Cell-WiFi Convergence Standards• SCCAN - seamless converged
communication across networks– First converged system – Proxim, Motorola, Avaya
• UMA - unlicensed mobile access– An extension of GSM/GPRS
to WiFi– Alcatel, AT&T Wireless, British
Telecom, Cingular, Ericsson, Kineto Wireless, Motorola, Nokia, Nortel Networks, O2, Rogers Wireless, Siemens, Sony Ericsson, T-Mobile US
UNC Server
Internet
DSL/Cable ModemRouter
AP
Wi-Fi
UMA-enabled components:- UNC (UMA Network Controller) server - Handset
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Voice Network Requirements
• Client– Range
– Power-save
– Fast roaming
• Infrastructure– Call capacity
– Delay, jitter, packet loss
– Power-save
– Fast roaming
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
IEEE 802.11 Standards for VoWiFi
802.11r Fast Roaming802.11k Radio Resource Measurement (RRM)802.11i Pre-authentication
802.11e Quality of Service (QoS) prioritization
Minimize bursty packet loss by controlling roaming time
Manage power consumption
Maintain isochronous nature of voice packetstreams by controlling delay, jitter and packet loss
802.11e Power-save
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
QoS Protocols• WMM (Wireless MultiMedia)
– Subset of 802.11e– Specifies 4 priorities: voice (highest), video, background, best effort (lowest)– Wi-Fi certification has started in September 04
• AC (Admission Control)– Subset of 802.11e– Enables APs to reject calls when call capacity is reached
• WMM SA (WMM Scheduled Access)– Subset of 802.11e– Specifies polling mechanism to optimize bandwidth utilization– Wi-Fi certification expected in July 05
• APSD (Automatic Power Save Delivery)– Subset of 802.11e– Unscheduled APSD works with WMM– Scheduled APSD works with WMM-SA
• SVP (Spectralink Voice Priority)– Proprietary prioritization scheme that combines priority mechanism with tight
synchronization to optimize bandwidth utilization
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Security Protocols• WPA
– Subset of 802.11i– TKIP, WEP– EAP-TLS, PSK (pre-shared key)– WPA Enterprise (TLS, PSK)– WPA Personal (PSK)
• WPA2– Entire 802.11i– Superset of WPA– AES support– Pre-Authentication to help with 802.11r fast
roaming
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Radio Resource Management
• 802.11k– Mechanism for stations and APs to
discover neighboring APs and to learn about their traffic load and signal conditions
– Helps 802.11r fast roaming
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
IEEE 802.11 Standards
802.11 (’99)MAC +
2Mbps PHY
802.11a (’99)54 Mbps
5GHz PHY
802.11b (’99)11 Mbps
2.4GHz PHY
PHY
Published
802.11g54 Mbps
2.4GHz PHY
802.11nHigh
Throughput(>100 Mbps)
802.11eQoS802.11i
Security
802.11f Inter AP
802.11hDFS & TPC
Currentwork
MAC
802.11kRRM
Studygroups
802.11rFast Roam
802.11sMesh
802.11TTest
Methods
802.11uWIEN SG
APF SG
802.11pWAVE
ADS SG
802.11vWNM
802.11mMaint
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
WiFi Alliance Roadmap
Baseline
Security
QoS
Applications
IEEE Standard Releases
Q3 Q1Q4 Q2 Q4Q32005
802.11e
WMM WMMScheduled Access
Public Access
WPA2
CEPhase2
2004
Extended EAP
802.11h+d
Simple Config
Voice/Wi-Fi
WCC
802.11j 802.11k
Baseline
Security
QoS
Applications
IEEE Standard Releases
Q3 Q1Q4 Q2 Q4Q32005
802.11e
WMM WMMScheduled Access
Public Access
WPA2
CEPhase2
2004
Extended EAP
802.11h+d
Simple Config
Voice/Wi-Fi
WCC
802.11j 802.11k
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Voice Quality
– 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
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
ITU-T PESQ Model
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
E-Model based on ITU-T G.107
Packet-lossLatency
ITU-T E-Model
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
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
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Phone Range vs. MOS• Vary attenuation
between the phone and the AP
• Measure packet loss, delay and jitter of a phone-AP link as a function of path loss
• Use ITU-T E-Model to compute R-Factor and MOS vs. range
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
MOS vs. Path Loss
1
2
3
4
5
50 55 60 65 70 75 80 85 90
Path Loss (dB)
MO
S
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Measuring Call Capacity
• Emulate voice traffic from multiple phones
• Emulate background data traffic
• Measure delay, jitter and packet loss* vs. number of calls and background traffic
* Per IETF RFCs 2544, 2889
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
AP Call Capacity Test Results
# calls% F
ram
e L
oss
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
AP Call Capacity Test Results
Dela
y (
usec)
# calls
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
AP Call Capacity Test ResultsJi
tter
(usec)
# calls
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
AP Call Capacity Test ResultsM
OS
# calls
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Measuring Roaming Time
• Emulate motion of the phone using programmable attenuators
• Monitor source and destination WiFi channels and Ethernet
• Derive roaming time from data captures
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Roaming ProcessAP1 AP2
max
min
Atten
Path to AP1
Path to AP2
t TRANSITION
t SCAN
Last data packetbefore roam
t ASSOCIATE
t ROAM
Data rate transition
First data packetafter roam
Test cycle
t DATA
AP1
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Sample Roaming Test ResultsFastest roaming client - test results reported by the Azimuth test script
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
1 2 3 4 5 6 7
Roam Number
Ro
am T
ime,
Sec
on
ds
Assoc Resp > Data
Assoc Req > Resp
Auth Resp > Assoc Req
Auth Req > Resp
Probe > Auth Req
Data > First Probe
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Sample Roaming Test ResultsRoam Time of Various Clients with ORiNOCO AP600
8.3
5
3
0.4
2.4
0 1 2 3 4 5 6 7 8 9
A
B
D
E
C
Clie
nt
Ca
rds
Roam Time (sec)
Single Mode Clients (B only)
Multi Mode Clients (ABG)
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Submission
Future Technology
• Environments– SOHO– Enterprise– Public access– Outdoor campus– MAN/WAN– Transportation– Military
• Applications– Data– Voice– Video
