Transcript doc.: IEEE 802.11-05-0033-00

doc.: IEEE 802.11-05-0033-00
Date: January 18, 2005
Performance of Voice over 802.11 Networks
Author: Fanny Mlinarsky, Azimuth Systems
[email protected]
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Discussion Outline
• VoIP and VoWiFi history
VoIP
• Cell-WiFi convergence
• Voice network requirements
• Emerging voice standards
– Quality of Service
– Security
– Roaming
Cell
WiFi
• VoWiFi performance and certification testing
• Future trends and opportunities
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
VoIP-Data Convergence
Traditional Enterprise
connectivity
Internet
Internet
Router
Router
Corporate
LAN
Corporate
LAN
Server
Server
PSTN
PSTN
Traditional
PBX
Telephony
Server
IP Phones
VoIP converges telephony
and data networks
Proprietary
Digital Phones
First VoIP products emerged in 1996
PSTN = Public Switched Telephone Network
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
VoWiFi - Legacy PBX Systems
•
VoWiFi manufacturers
–
–
–
•
Most IP PBXs use
proprietary protocols
–
–
–
–
–
–
–
•
Cisco, Symbol, Spectralink
Spectralink WiFi phones
available since 1999
802.11b only for now
Ethernet Network
Telephony
gateway
PBX
Cisco SCCP
(skinny call control protocol)
Alcatel UA
NEC Protims
Avaya CCMS
Nortel UniStim
Siemens CorNet IP
Mitel MiNet
Telephony
server
Standard IP telephony protocols
–
–
–
Submission
H.323
Media Gateway Control Protocol (MGCP)
Session Initiation Protocol (SIP)
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Voice over WiFi Use Cases
•
SOHO
–
–
–
–
•
Enterprise
–
–
–
–
–
•
WiFi or WiFi-Cell handset, soft phone
Service providers: Vonage, ATT CallVantage, Net2Phone
No handoff, low capacity, basic security
Range
WiFi or WiFi-Cell handset, soft phone
Range
Handoff speed
Call capacity
Security
Public access (WiFi hotspots)
–
–
–
–
Submission
WiFi-Cell handset, soft phone
Range
Call Capacity
Roaming issues
Net2Phone WiFi handset
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Cell-WiFi Convergence Standards
UNC Server
Internet
DSL/Cable Modem
Router
AP
Wi-Fi
Submission
• SCCAN - seamless converged
communication across networks
– First converged system
– Proxim, Motorola, Avaya
UMA-enabled
components:
- UNC (UMA Network
Controller) server
- Handset
• 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
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Voice Network Requirements
• Client
– Range
– Power-save
– Fast roaming
• Infrastructure
– Call capacity
– Delay, jitter,
packet loss
– Power-save
– Fast roaming
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
IEEE 802.11 Standards for VoWiFi
Minimize bursty packet loss by controlling roaming time
802.11r Fast Roaming
802.11k Radio Resource Measurement (RRM)
802.11i Pre-authentication
Manage power consumption
802.11e Power-save
Maintain isochronous nature of voice packet
streams by controlling delay, jitter and packet loss
802.11e Quality of Service (QoS) prioritization
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
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
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Security Protocols
• WPA
–
–
–
–
–
Subset of 802.11i
TKIP, WEP
EAP-TLS, PSK (pre-shared key)
WPA Enterprise (TLS, PSK)
WPA Personal (PSK)
• WPA2
–
–
–
–
Submission
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
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
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
IEEE 802.11 Standards
802.11h
DFS & TPC
802.11 (’99)
MAC +
2Mbps PHY
802.11i
Security
802.11f
Inter AP
MAC
PHY
802.11a (’99)
54 Mbps
5GHz PHY
802.11b (’99)
11 Mbps
2.4GHz PHY
802.11g
54 Mbps
2.4GHz PHY
802.11s
Mesh
802.11p
WAVE
802.11r
Fast Roam
802.11u
WIEN SG
802.11e
QoS
802.11v
WNM
802.11k
RRM
802.11m
Maint
802.11n
High
Throughput
(>100 Mbps)
ADS SG
APF SG
802.11T
Test
Methods
Study
groups
Current
work
Published
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
WiFi Alliance Roadmap
IEEE Standard Releases
802.11j
2004
Q4
Q3
Baseline
Security
802.11k
802.11e
2005 Q1
Q2
Q3
Q4
802.11h+d
WPA2
Extended EAP
Simple Config
QoS
WMM
Applications
WMM
Scheduled Access
Public Access
CE WCC
Phase2
Submission
Voice/
Wi-Fi
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Voice Quality
ITU-T Voice Quality Standards
– 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)
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
ITU-T PESQ Model
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
ITU-T E-Model
Packet-loss
Latency
E-Model based on ITU-T G.107
Submission
Fanny Mlinarsky, Azimuth Systems
E-Model Parameters
doc.: IEEE 802.11-05-0033-00
Parameter
Abbr.
Unit
Default
value
Permitted
range
Send Loudness Rating
Receive Loudness Rating
Sidetone Masking Rating
Listener Sidetone Rating
D-Value of Telephone, Send Side
D-Value of Telephone Receive Side
Talker Echo Loudness Rating
Weighted Echo Path Loss
Mean one-way Delay of the Echo Path
Round-Trip Delay in a 4-wire Loop
Absolute Delay in echo-free Connections
Number of Quantization Distortion Units
Equipment Impairment Factor
Packet-loss Robustness Factor
Random Packet-loss Probability
Circuit Noise referred to 0 dBr-point
Noise Floor at the Receive Side
Room Noise at the Send Side
Room Noise at the Receive Side
Advantage Factor
SLR
RLR
STMR
LSTR
Ds
Dr
TELR
WEPL
T
Tr
Ta
qdu
Ie
Bpl
Ppl
Nc
Nfor
Ps
Pr
A
dB
dB
dB
dB
+8
+2
15
18
3
3
65
110
0
0
0
1
0
1
0
70
64
35
35
0
0 ... +18
5 ... +14
10 ... 20
13 ... 23
–3 ... +3
–3 ... +3
5 ... 65
5 ... 110
0 ... 500
0 ... 1000
0 ... 500
1 ... 14
0 ... 40
1 ... 40
0 ... 20
80 ... 40
Submission
dB
dB
ms
ms
ms
%
dBm0p
dBmp
dB(A)
dB(A)
Latency
500 ms max
Packet loss
20% max
35 ... 85
35 ... 85
0 ... 20
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
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
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
MOS vs. Path Loss
5
MOS
4
3
2
1
50
55
60
65
70
75
80
85
90
Path Loss (dB)
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
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
Submission
Fanny Mlinarsky, Azimuth Systems
AP Call Capacity Test Results
% Frame Loss
doc.: IEEE 802.11-05-0033-00
# calls
Submission
Fanny Mlinarsky, Azimuth Systems
AP Call Capacity Test Results
Delay (usec)
doc.: IEEE 802.11-05-0033-00
# calls
Submission
Fanny Mlinarsky, Azimuth Systems
Jitter (usec)
AP Call Capacity
Results
doc.: IEEETest
802.11-05-0033-00
# calls
Submission
Fanny Mlinarsky, Azimuth Systems
AP Call Capacity Test Results
MOS
doc.: IEEE 802.11-05-0033-00
# calls
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
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
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Roaming Process
AP1
AP2
AP1
max
Path to AP1
Atten
Path to AP2
min
Test cycle
Data rate transition
t ASSOCIATE
t DATA
t TRANSITION
t SCAN
Last data packet
before roam
Submission
t ROAM
First data packet
after roam
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Sample Roaming Test Results
Fastest roaming client - test results reported by the Azimuth test script
0.2
Roam Time, Seconds
0.18
0.16
Assoc Resp > Data
0.14
Assoc Req > Resp
Auth Resp > Assoc Req
0.12
Auth Req > Resp
0.1
Probe > Auth Req
Data > First Probe
0.08
0.06
0.04
0.02
0
1
2
3
4
5
6
7
Roam Number
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Sample Roaming Test Results
Roam Time of Various Clients with ORiNOCO AP600
Client Cards
C
8.3
E
5
D
3
B
2.4
0.4
A
0
1
2
3
4
5
6
7
8
9
Roam Time (sec)
Multi Mode Clients (ABG)
Single Mode Clients (B only)
Submission
Fanny Mlinarsky, Azimuth Systems
doc.: IEEE 802.11-05-0033-00
Future Technology
• Environments
–
–
–
–
–
–
–
SOHO
Enterprise
Public access
Outdoor campus
MAN/WAN
Transportation
Military
• Applications
– Data
– Voice
– Video
Submission
Fanny Mlinarsky, Azimuth Systems