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Azimuth Confidential

Voice over Wi-Fi andWi-Fi to Cellular Roaming

Wi-Fi Voice ConferenceParis, May 2005

Fanny Mlinarsky



Slide 2 Azimuth Confidential

Cell-WiFi Convergence

Dual-ModeHandset

BaseStation

Controller (BSC)

IPNetwork

CallGateway

Cellular Network

CoreMobile

Network

• Significant Cell-WiFi Convergence effortsfuse WiFi, IP and cellular technologies

– Single phone works indoors and out

– Better coverage indoors at lower cost

VoIP

Cellular Wi-Fi




Cell-WiFi Convergence Standards

*3rd Generation Partnership Project

• 3GPP GAN (generic access network),a.k.a. UMA (unlicensed mobile access)

– An extension of GSM/GPRS3GPP* to Wi-Fi

– Alcatel, AT&T Wireless,British Telecom, Cingular,Ericsson, Kineto Wireless,Motorola, Nokia, Nortel Networks,

O2, Rogers Wireless, Siemens,Sony Ericsson, T-Mobile US

• 3GPP WLAN Interworking (IMS) – VoIP, SIP-based

– SBC, Bellsouth, Cingular, Rogers (Canada), Telefonica (Mexico), Mobilkom

(Austria), GoMobile (Malta), Azaire Systems

• SCCAN (seamless converged communication across networks) – First converged system

– Proxim, Motorola, Avaya




VoWiFi IP-Based Systems

• VoWiFi – WiFi phones available since 1999

– Cisco, Symbol, Spectralink

• Most IP PBXs useproprietary protocols – Cisco SCCP

(skinny call control protocol)

– Alcatel UA

– NEC Protims

– Avaya CCMS – Nortel UniStim

– Siemens CorNet IP

– Mitel MiNet

– Spectralink SVP

• Standard IP telephony protocols – Session Initiation Protocol (SIP)

– H.323

– Media Gateway Control Protocol (MGCP)




Voice Network Requirements• Minimize bursty packet loss by control ling roaming time

802.11r Fast Roaming

802.11k Radio Resource Measurement (RRM)

802.11i Pre-authentication

• Maintain isochronous nature of voice packet

streams by controlling delay, jitter and packet loss

802.11e Quality of Service (QoS) prioritization




IEEE 802.11 Standards

802.11a (’99)

54 Mbps

5GHz PHY

802.11b (’99)

11 Mbps

2.4GHz PHY

PHY

Published

802.11g

54 Mbps

2.4GHz PHY

802.11i

Security

802.11f

Inter AP

802.11h

DFS & TPC

Current

Work

MAC

Study

Groups

APF SG

ADS SG

802.11u

WIEN SG

802.11p

WAVE

802.11v

WNM

802.11e

QoS

802.11k

RRM

802.11r

Fast Roam

802.11s

Mesh

802.11 (’99)

MAC +

2Mbps PHY

802.11T

Test

Methods

802.11nHigh

Throughput

(>100 Mbps)802.11m

Maint




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




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




WFA and IEEE Timeline

Q1/05 Q2/05 Q3/05 Q4/05 Q1/06 Q3/06 Q4/06Q2/06

Multimedia

Enablers

Security

Core Wi-Fi

Functionality

Voice & DataConvergence

WMM (802.11e-based QoS)

802.11h+d

Wi-Fi Protected Access (WPA) (802.11i-based Security)

WPA2 (full 802.11i)

802.11a+b+g (basic wireless LAN IEEE Specs)

11e

Wi-Fi Cellular Convergence (WCC)

Extended EAP (Enterprise)

Simple Configuration

Voice over Wi-Fi

WMM Power Save

11k

Consumer Electronics Framework phase 1

Consumer Electronics Framework phase 2

11n

Public Access

11r

WMM Scheduled Access

11s11p

IEEE

Standards




Voice Quality

• ITU-T Voice Quality Standards – MOS (mean opinion score)

uses a wide range of humansubjects to provide a subjectivequality score (ITU-T P.800)

– PESQ (perceptual speech quality measure)sends a voice pattern across a network andthen compares received pattern to the originalpattern and computes the quality rating (ITU-T P.862)

– E-Modelcomputes Rating Factor or R-Factor as a functionof delay and packet loss;R-Factor directly translates into MOS (ITU-T G.107)




ITU-T PESQ Model




ITU-T E-Model (G.107)




E-Model Parameters

0 … 200- A Advantage Factor

35 … 8535dB(A)Pr Room Noise at the Receive Side

35 … 8535dB(A)PsRoom Noise at the Send Side

--64dBmpNfor Noise Floor at the Receive Side

-80 … -40-70dBmOpNcCircuit Noise referred to 0 dBr-point

0 … 200%PplRandom Packet-loss Probability

1 … 401-BplPacket-loss Robustness Factor

0 … 400-IeEquipment Impairment Factor

1 … 141-qduNumber of Quantization Distortion Units

0 … 5000msTa Absolu te Delay in echo-free Connect ions

0 … 5000msTMean one-way Delay of the Echo Path

0 … 10000msTr Round-Trip Delay in a 4-wire Loop

5 ... 110110dBWEPLWeighted Echo Path Loss

5 …6565dBTELRTalker Echo Loudness Rating

-3 … +33-Dr D-Value of Telephone Receive Side

-3 … +33-DsD-Value of Telephone, Send Side

13 … 2318dBLSTRListener Sidetone Rating

10 … 2015dBSTMRSidetone Masking Rating

-5 … +14+2dBRLRReceive Loudness Rating

0 … +18+8dBSLRSend Loudness Rating

Permitted RangeDefault ValueUnit Abbr.Parameter

G.107 – Default values and permit ted ranges for the parameters




R-Factor to MOS Conversion




VoWiFi Performance

• QoS vs. capacity

• QoS vs. range

• QoS vs. WiFi-WiFi roam

• QoS vs. WiFi-cell roam




VoWiFi Call Capacity Test

Features

Test Diagram Test Results

Test Description: Capacity vs. QoS Performance of Wi-Fi infrastructure

• 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





Features



• Verifies the ability of infrastructure

to prioritize voice traffic and to

reject or redirect calls when

capacity is reached• Test APs, wireless switches and

other infrastructure devices

• Measures infrastructure capacity

vs. R-Factor and MOS quality

scores computed from the

measured packet loss rate, delay

and jitter + click to enlarge





Features









scores computed from the

measured packet loss rate, delay







Features









scores computed from themeasured packet loss rate, delay







Features















VoWiFi Handset Range Test

Features


Test Description: Quality of Voice Transmission over Wi-Fi as a

Function of Path Loss, Roaming and Traffic Load

• Automatically validates Voice over

Wi-Fi performance in minutes

• Standard benchmark test to analyze

rate adaptation of handset and AP pair

• Shows R-Factor and MOS

performance of real time voice stream

- measures packet loss, delay and

jitter to formulate MOS score

• Precise RF control allows for

measurement of true range

performance based on actual WiFi-

enabled handsets+ click to enlarge





Features












• Precise RF control allows formeasurement of true range







Features


















VoWiFi Roaming Test

Test Description: Roaming Performance of Wi-Fi Handsets

Features

• Measures the roaming time and

quality of voice vs. roam

• Detailed breakdown of the roaming

time helps optimize roaming algorithm

• Motion and fail-over roaming

emulation of real world scenarios

• Precise RF control and distributed

monitoring present a wealth of

information on handset performance

as a function of motion

Test ResultsTest Diagram




Roaming Process

AP1 AP2max

min

At ten

Path to AP1

Path to AP2

t TRANSITION

t SCAN

Last data packet

before roam

t ASSOCIATE

t ROAM

Data rate transition

First data packet

after roam

Test cycle

t DATA

AP1




Sample Roaming Test ResultsFastest roaming c lient - 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

R o a m T

i m e ,

S e

c o n d s

Assoc Resp > Data

Assoc Req > Resp

Auth Resp > Assoc Req

Auth Req > Resp

Probe > Auth Req

Data > First Probe




Cell-WiFi Handover Test

Complete WiFi and

VoWiFi

performance,conformance

and certification

QoS vs. WiFi-to-cellhandover

Cellular test




Wi-Fi is Proliferating

• Environments

– SOHO

– Enterprise – Public access

– Outdoor campus

– MAN/WAN

– Transportation

– Military

• Triple-play Applications

– Data

– Voice

– Video




VoWiFi Call Capacity




VoWiFi Handset Range

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