QoS Improvements of VoIP in WiFi

Networks

Undergraduate Students: Chris Higgins, Linda Tran

Ph.D. Student Advisor: Ala KhalifehFaculty Advisors: Prof. Kevin Tsai, Prof.

Henry Lee

SummarySummary• Introduction: VoIP/VoWLAN, Introduction: VoIP/VoWLAN,

802.11, 802.11e802.11, 802.11e• 11stst Quarter: Linux, MADWiFi, Quarter: Linux, MADWiFi,

testing tools, design, building testing tools, design, building knowledge baseknowledge base

• 22ndnd Quarter: Soekris, Quarter: Soekris, Configurations, Testbed setupConfigurations, Testbed setup

• Results: Knowledge, future Results: Knowledge, future goals, directiongoals, direction

MotivationMotivation

To study and improve the To study and improve the QoS (Quality of Service) QoS (Quality of Service) performance of Voice performance of Voice over IP (VoIP) traffic in over IP (VoIP) traffic in Wireless Local Area Wireless Local Area Networks (WLAN).Networks (WLAN).

VoIP* in the WLAN* (VoWLAN)VoIP* in the WLAN* (VoWLAN)

-Wireless Access Point (AP)-Network Devices

• Computers• Scanners• Printers• Blackberries• Etc.

*VoIP: Voice Over IP*WLAN: Wireless Local Area Network

ApplicatioApplicationsns

Background• Integration of VoIP with WLAN (VoWLAN)

– Benefits•Cost-effectiveness•Mobility•Use already available “common infrastructure” (Lin et

al. 1)

– Problems•Limited Distribution Coordination Function (DCF) and

Point Coordination Function (PCF) in 802.11 WLAN systems impacting VoIP traffic

•High packet loss and delays (jitter and end-to-end)•Tradeoff between security protocols and delays

802.11 Protocol Architecture802.11 Protocol Architecture

-Unbiased distribution of resources between Access Class (AC) Parameters:

•Voice•Video•Background•Best Effort

1.PCF: Point Coordination Function (Initial provision for priority traffic, unimplemented in legacy 802.11 hardware)

2.DCF: Distributed Coordination Function (Global scheme for traffic resource sharing in legacy routers)

802.11• DCF and PCF operates on a “listen-

before-talk scheme” (Mangold 1) known as CSMA/CA

• Wait a fixed amount of time before sending, according to the DCF/PCF interframe space (DIFS/PIFS)

• Ready to Send (RTS) and Clear to Send (CTS) phase, where the access point and endpoint basically have a small exchange that reserves the medium for use

802.11e (802.11 Enhancements)

• Uses Hybrid Coordination Function (HCF), a combination of DCF and PCF.

• Contention-based channel access known as Enhanced Distributed Channel Access (EDCA) is located in the CP

• Controlled channel access known as HCF Controlled Channel Access (HCCA) encompasses both the CP and CFP

• Direct Link Protocol (DLP) which allows two computers in a Basic Service Set (BSS) to directly communicate and avoid network loading

802.11e: QoS Support Standard802.11e: QoS Support Standard(Current IEEE Draft)(Current IEEE Draft)

1.1. Voice (VO)Voice (VO)2.2. Video (VI)Video (VI)3.3. Best Effort (BE)Best Effort (BE)4.4. Background (BK)Background (BK)

ACAC

*DIFS: DCF Interframe Space*AIFS|AC: Arbitration Interframe Space

Parameters Being Measured

•Packet loss: arriving packets or already-queued packets dropped (Kuros, 19)

•Jitter: variability of packet delays within the same packet stream (570)

•End to end delay: delay from source to destination (43)

11stst Quarter: Quarter: Linux, MADWiFi, Testing Linux, MADWiFi, Testing Tools, Design, Building Tools, Design, Building

Knowledge BaseKnowledge Base

Operating SystemOperating System

LinuxLinux Fedora Red Hat – Core 5 (2.6.18-Fedora Red Hat – Core 5 (2.6.18-

1.2200.fc5)1.2200.fc5)x84_64: 64 bit architecture x84_64: 64 bit architecture i386: 32 bit architecturei386: 32 bit architecture

Linux kernel device driver for Linux kernel device driver for Atheros-based Wireless LAN devices Atheros-based Wireless LAN devices

Operational modes: station, ap, ad-Operational modes: station, ap, ad-hoc, monitor, and wireless hoc, monitor, and wireless distribution stationdistribution station

Allows modification of EDCA Allows modification of EDCA parameters (follows the WMM-WiFi parameters (follows the WMM-WiFi Multimedia standard)Multimedia standard)

Two laptop dual-boot PCsTwo laptop dual-boot PCs Equipped with Windows XP and Equipped with Windows XP and

Fedora Core 5 (2.6.18-1.2200)Fedora Core 5 (2.6.18-1.2200) Currently Ethernet cable Currently Ethernet cable

enabled network to test program enabled network to test program functionalityfunctionality

Preliminary Testbed Preliminary Testbed SetupSetup

Wireless Connections

• Hardware:– Linksys Router

• WRT54GS

– Linksys PCI card• WMP54G (For Desktop AP).

• Software:– MADWiFi (Atheros Chipset software/drivers)

Available Tools• Interface Monitoring

– Ethereal*

• TCP/UDP Traffic Generators– Thrulay*– Iperf*– Netperf

• VoIP Traffic Generators– RTP Tools – VoIP Generator

*Refers to programs chosen to be used

Iperf• It measures UDP

and TCP bandwidth performance

• Reports bandwidth, delay jitter, datagram loss.

• Can be run in bi-directional mode

Iperf Testing Commands

•Server Side:–Iperf –s -u –i 60 (s = server, u = UDP)

•Client Side:–Iperf –u -c 192.168.1.X –t 1000 -i 60 –b <1..2000> (c = client, u = UDP, t = test time, b = bandwidth)

Thrulay• Sends bulk

TCP or UDP streams over network

• Measures RTT, throughput, and jitter

Thrulay Testing Commands

• Server Side:– Thrulayd

•must locate and be in the “thruldayd” folder.

•find –iname thrulayd (in root ‘/’ folder)• ‘cd’ into that directory•Execute ‘./thrulayd’•No confirmation screen will pop up, it will

be implied the server is running.• Client Side:

– Thrulay –t60 –l40 <host I.P.> (t = test time, l = packetsize)

ThruLay: Preliminary Test

ID Begin, s End, s Throughput (Mb/s) RTT delay, ms Jitter

( 0) 0 1 93.313 19.173 4.001

( 0) 1 2 93.318 17.833 5.629

( 0) 2 3 94.366 17.197 5.624

( 0) 3 4 93.841 16.195 5.614

( 0) 4 5 94.362 21.049 5.596

( 0) 5 6 93.318 21.116 5.59

( 0) 6 7 94.368 16.561 5.52

( 0) 7 8.001 93.318 16.103 5.603

( 0) 8.001 9 94.395 16.125 5.524

( 0) 9 10.001 94.331 16.069 5.517

( 0) 10.001 11.001 93.849 16.085 3.999

( 0) 11.001 12.001 93.317 20.001 4

( 0) 12.001 13.001 94.366 16.358 4

( 0) 13.001 14.001 93.842 20.001 4

( 0) 14.001 15.001 94.366 16.982 4

( 0) 15.001 16.001 93.317 16.015 4

Parsing Program Parsing Program (For ThruLay Output)(For ThruLay Output)

use strict;use strict;use Spreadsheet::WriteExcel;use Spreadsheet::WriteExcel;

my ($inFile, $outFile) = @ARGV;my ($inFile, $outFile) = @ARGV;

if ((!defined $inFile)||(!defined $outFile))if ((!defined $inFile)||(!defined $outFile)){{ print "ERROR... USAGE -> grep.pl <infile> <outfile>\n";print "ERROR... USAGE -> grep.pl <infile> <outfile>\n"; exit;exit;}}

open (INI, "<$inFile")|| die "ERROR... Unable to open '$inFile' for reading.\n";open (INI, "<$inFile")|| die "ERROR... Unable to open '$inFile' for reading.\n";

$outFile =~ s/\..*//;$outFile =~ s/\..*//;$outFile .= ".xls";$outFile .= ".xls";my $Book = Spreadsheet::WriteExcel->new("$outFile");my $Book = Spreadsheet::WriteExcel->new("$outFile");my @times = scalar gmtime();my @times = scalar gmtime();my($day, $month, $year) = (gmtime())[3,4,5];my($day, $month, $year) = (gmtime())[3,4,5];my $Sheet = $Book->add_worksheet(($month+1) . '-' . ($day+1) . '-' . ($year+1900));my $Sheet = $Book->add_worksheet(($month+1) . '-' . ($day+1) . '-' . ($year+1900));my $line = 1;my $line = 1;my @heading = ("ID", "Begin, s", "End, s", "Mb/s", "RTT delay, ms", "Jitter");my @heading = ("ID", "Begin, s", "End, s", "Mb/s", "RTT delay, ms", "Jitter");$Sheet->write(0,0,\@heading);$Sheet->write(0,0,\@heading);while (<INI>)while (<INI>){{ my $in = $_;my $in = $_; $in =~ s/\s+//;$in =~ s/\s+//; if ($in =~ /^[\[|\#].*/)if ($in =~ /^[\[|\#].*/) {{ next;next; }} my @words = split (/\s\s+/, $in);my @words = split (/\s\s+/, $in); $Sheet->write($line,0,\@words);$Sheet->write($line,0,\@words); $line++;$line++;}}$Book->close() or die "Error closing file: $!";$Book->close() or die "Error closing file: $!";

Bandwidth

92.6

92.8

93

93.2

93.4

93.6

93.8

94

94.2

94.4

94.6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Packet Sequence Number

Ban

dw

idth

(M

b/s

)

Round Trip Time

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Packet Sequence Number

Ro

un

d T

rip

Tim

e (

ms

)

Jitter

0

1

2

3

4

5

6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Packet Sequence Number

Jit

ter

Goals to Accomplish for 2nd Qtr.

1. Synchronization between computers (Using NTP and correction script)

2. Create a more aggressive 802.11 based software application to transport VoWLAN packets, effectively meeting a certain QoS standard

3. Create a standardized testbed for testing.4. (UROP Proposal) Create a stable 802.11e

based testbed for VoWLAN trafficking5. Solidify Tools and Metrics

1. Synchronization between 1. Synchronization between computerscomputers

Use NTP (Network Time Protocol) for Use NTP (Network Time Protocol) for initial time adjustments (multiple initial time adjustments (multiple millisecond accuracy)millisecond accuracy)

Create Synchronization Software for Create Synchronization Software for precise time measurements (microsecond precise time measurements (microsecond precision)precision)

2. 802.11 Based Software Upgrade for

VoIP•Create a more aggressive

transportation protocol for VoWLAN applications

•Duplication algorithms could provide necessary WLAN availability where current TCP/UDP transportation dominates

3. Testbed: Planned

• Desktop PC acting as an 802.11e based “access point”

• Multiple PC-embedded boards with Linux platforms based on the Soekris net4826 acting as client stations

• Atheros Chipsets/Wireless Cards• MADWiFi Enabled Wireless Drivers• Linux 2.6.8.1 Kernel

4. Proposal: Budget Justification

• The need to simulate real VoWLAN networks

• Individual endpoints (Soekris boards) are necessary for the test bed of this project

• Real life simulation of packet collision and router allocation is necessary to test fabricated protocols and allocation guidelines

Proposal: Itemized Budget

Item Price Qty Total

Soekris net4826-50 Board and Case + Tax & Shipping

$224 7 $1568

Power Supply, 12V, 1.5A, US/Canada 110V, Small Switch Mode, for all boards. + Tax & Shipping

$14 7 $98

ATHEROS WI-FI MINI-PCI WIRELESS 802.11G + Tax & Shipping

$44 7 $308

Null Modem Cable + Shipping $5 1 $5

USB to RS232 DB9 9-Pin Cable Adapter + Shipping

$10 1 $10

Power Strip $5 2 $10

TOTAL: $1999

22ndnd Quarter: Quarter: Soekris, Configurations, Soekris, Configurations,

Testbed Setup, Testbed Setup, ExperimentationExperimentation

Design ApproachDesign Approach Phase 1: Initial Network SetupPhase 1: Initial Network Setup

•Expected availability of MADWiFiExpected availability of MADWiFi•Planned EDCA parameters (802.11e Planned EDCA parameters (802.11e setup)setup)

Phase 2: Final Network Setup Phase 2: Final Network Setup •Unavailability in means of testing Unavailability in means of testing and manipulating 802.11e and manipulating 802.11e parametersparameters

•Based on EDCA parameters availableBased on EDCA parameters available

Network Setup for testing 802.11e

Synchronization

Synchronization Software

• Endpoint.pl accompies accessPoint.pl to complete the end to end network – It creates a file based on the IP address of

the host (endpoint) computer and one for the AP

• AccessPoint.pl, in turn, will send pings to various user-specified endpoints and receive pings from those endpoints.

• Evaluate.pl must be used to compute the delays/synchronization differences from both the access point and end point log files.

Soekris 4826• Compact, low power, low cost computer• Specifications

– 266 Mhz AMD Geode SC1100 – 256 Mbyte SDRAM, soldered on board – 4 Mbit BIOS/BOOT Flash – Board size 4.0" x 5.2"

• Software– comBIOS for operation over serial port – PXE boot rom for diskless booting

Soekris 4826

Soekris 4826• Power LED, Activity LED, Error LED

Soekris 4826

• 1 10/100 Mbit Ethernet ports, RJ-45 • 1 Serial port, DB9.

802.11a/g/b Wireless Mini PCI Card

• SENAO EMP- 8602

Mini PCI on Soekris Mini PCI on Soekris BoardBoard

Installing Fedora Linux on Soekris• Mininimal linux installation on a spare system.

• Configure system to run with only a serial console • Make it as small as possible, removing unneeded

files. • Copy that system over to an NFS server• Configure a PXEboot configuration for the Soekris

system, using the new tree as NFS root. • Boot the soekris over PXE• Partition the CF disk, and make a filesystem on it,

then copy the FS from the NFS server to the CF disk.

• Boot over PXE, but now using the CF disk as root. • Install the GRUB bootloader, and reboot from CF

disk.

EDCA Parameters (802.11e)• CWmin: a random backoff time will be

chosen between 0 and CWmin and added onto the interframe space

• CWmax: maximum CW• AIFS (similar to DIFS/PIFS in 802.11):

duration that medium must be idle before backoff countdown

• TXOPlimit: time that a station can spend transmitting on the medium once it has won transmission opportunity

*Ng and Mal, 19

How can the parameters be adjusted to fully utilize

802.11e?

• Large TXOP can allow multiple packets at each station can be transmitted at every transmission opportunity (Malone et. al., 19)– ↑ TXOP (μs), ↑ throughput

• ↑ AIFS, ↑ throughput • ↓ CWmin (smaller delay between

transmission), ↑ throughput

EDCA Parameters for 802.11e

ParameterAC1:

BackgroundAC2:

Best Effort AC3:Video

AC4:Voice

AIFS 7 3 2 2

CWmin 15 15 7 3

Cwmax 1023 1023 15 7

TXOPLimit (ms) 0 0 3008 1504

Network Setup: Network Setup: CurrentCurrent

Documentation

Installation/Configurations

• Soekris Installation– Debian PXEboot

• Full installation of Fedora Linux • MADWiFi Installation• Server setups

– DHCP– TFTP– NFS– PXEboot

•Synchronization tool

Experimental Experimental Results and Results and

AnalysisAnalysis

Bandwidth

0

2

4

6

8

10

12

1 6 11 16 21 26 31 36 41 46 51 56

Iteration

Ban

dwid

th (

Mb/

s)

1000100000010000000

Network Loading (bytes/sec)

Round Trip Time

1

10

100

1000

10000

1 6 11 16 21 26 31 36 41 46 51 56

Iteration

Rou

nd T

rip T

ime

(ms)

1000100000010000000

Network Loading (bytes/sec)

Jitter

1

10

100

1000

1 6 11 16 21 26 31 36 41 46 51 56

Iteration

Jitte

r (m

s) 1000100000010000000

Network Loading (bytes/sec)

Analysis: 802.11• Bandwidth: As the loading on the

network increases, the available bandwidth for VoIP transportation decreases.

• RTT: The round trip time has an inverse effect to the bandwidth. As the loading increases so does the RTT.

• Jitter: Just like RTT, random jitter increases as more background traffic is added.

Analysis: 802.11e• Unlike 802.11, 802.11e should alleviate

the adverse effects on the following variables for VoIP traffic.

• Bandwidth: As the loading on the network increases, the available bandwidth for VoIP transportation should remain constant or only slightly suffer.

• RTT: Even though the round trip time has an inverse effect to the bandwidth, in 802.11e RTT should minimally vary with the same test.

• Jitter: Just like RTT, random jitter should only slightly increase with the progression of tests.

Future Work• Continued wireless

testbed at UCI• Expand testbed to

video testing• Increase real time

protocols in wireless testing

• Test various network design schemes

Socioeconomic IssuesSocioeconomic Issues Socioeconomic (economic repercussions Socioeconomic (economic repercussions

resulting from social shifts)resulting from social shifts) As consumers turn toward VoIP-As consumers turn toward VoIP-

enabled technology (conglomerate enabled technology (conglomerate Internet, telephone, TV, gaming), it is Internet, telephone, TV, gaming), it is industry’s responsibility to industry’s responsibility to aggressively keep up with those aggressively keep up with those changes in order to maintain a stable changes in order to maintain a stable domestic economy and employment domestic economy and employment rate. rate. Partnership between companies Partnership between companies Domestic technological researchDomestic technological research

Social Aspect• VoIP will allow ease

of use, availability, increase performance, efficiency, and lower costs.

• This will encourage acceptance of these new technologies.

• Disadvantages: This will, however, necessitate new hardware in every aspect this affects.

Economical Issues

•Possible growth of major conglomerates

•Convergence of technologies under one medium

•Necessitates new companies with a focus on VoIP

Upcoming Activities• UROP

– Finalize Soekris boxes

– Further 802.11e testing

• Make installation/configuration documentation globally available

Knowledge GainedKnowledge Gained• Linux and its architectureLinux and its architecture

– FedoraFedora– MadWiFiMadWiFi– DebianDebian

• Wireless systems: 802.11, 802.11eWireless systems: 802.11, 802.11e• Servers: NFS, DHCP, TFTP, HTTPServers: NFS, DHCP, TFTP, HTTP• PXEboot PXEboot • Computer architectureComputer architecture• Network transportation (UDP, TCP, Network transportation (UDP, TCP,

ICMP)ICMP)

Project Website

•http://www.donjohnii.com/wireless–Programs–Configuration guides–How-To

References• Arte Marketing, Inc. “Linksys WIP300”,

www.voip-info.org/wiki/view/Linksys+WIP300. (February 21, 2007).

• AT&T. “AT&T”, http://www.corp.att.com/presskit/voip/. (February 21, 2007).

• California State Washington in St. Louis. “Wireless LANs”, http://www.cse.seas.wustl.edu/. (February 21, 2007).

• Invocom. “Medium Access Control Protocols”, http://www.invocom.et.put.poznan.pl/~invocom/C/P1-4/p1-4_en/p1-4_8_1.htm. (February 21, 2007).

• Leith, Douglas J., Malone, David, Ng, Anthony C.H. Ng. “Experimental Evaluation of TCP Performance and Fairness in an 802.11e test-bed.” SIGCOMM ’05 Workshops August. 2005: 17-22

• Kurose, James F. and Ross, Keith W. Computer Networking: A Top-Down Approach Featuring the Internet. Pearson Education. Boston, MA. 2005

• Mangold, Stefan. “Analysis of IEEE 802.11e for QoS Support in Wireless LANs.” IEEE Wireless Communications December. 2003: 40-50.

• Ohrtman, Frank. Voice Over 802.11. Boston: Artech House, 2004.

• Pan, Jianping, Pang, Ai-Chung, Yi-Bing Lin, and Shen, Xuemin. “Voice Over Wireless Local Area Network.” IEEE Wireless Communications February. 2006: 4-5.

• Smile Design. “Smile Group”, http://www.smilejogja.com/. (February 21, 2007).

• “VoIP Telephone”, http://www.logoandco.com/p/voip-telephone--iHox3AZVYOho.htm. (February 21, 2007).

Acknowledgements

• Ph.D. Student Advisor: Ala Khalifeh

• Prof. Kevin Tsai

• Prof. Henry P. Lee