performance of voice over internet protocol (voip) in wireless local area network (wlan)

7/30/2019 Performance of Voice Over Internet Protocol (VOIP) in Wireless Local Area Network (WLAN)

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PERFORMANCE OF VOICE OVER INTERNET PROTOCOL (VOIP) IN

WIRELESS LOCAL AREA NETWORK (WLAN)

ONG JAW FEE1

This report is submitted in partial fulfillment o f the requirements for the

Bachelor o f C omputer Science (Computer Networking)

FACULTY OF lNFORMATION AND COMMUNICATION TECHNOLOGY

UNIVERSITI TEKNIKAL M ALAYSIA MELAKA



ABSTRACT

In this project, the suitability of 802.11b networks to carry real time voice

traffic communication will be assessed using the Internet Protocol, where in the

network the voice session have to share the link with data, video and voice.

Measurements of the quality of voice are performed in the 802.11 wireless networks

compared to the wired kind of network. Measurements are focused on the threemajor Voice over Internet Protocol (VoIP) parameters: loss, delay and jitter. The

environment factors such as the distance between nodes, network traffic and other

obstacles are also being considered when carrying out this research. Due to the

unpredictable nature of the wireless environment, providing Quality of Service (QoS)

service is a challenging task. Voice M i c s more susceptible to the three major

performance QoS parameters: delay, jitter and packet loss in the wireless domain

than data traffic. In order to ensure the QoS of VoIP in wireless LAN, some

experimental investigations have been carried out to test on the performance

limitations in establishing VoIP in wireless LAN. All these experimental testing have

been done under three varying scenarios network which are working under an idealand real condition. The analysis is based upon the software that are being used in this

project, Clearsight analyzer and Ethereal, from packet loss, jitter and delay

measurements. According to the results, measures and graphs of packet delay, packet

jitter and lost packet rate show the performance limitations when VoIP runs in

wireless LAN. VoIP is a multimedia application that requires timely servicing of the

voice traffic even when using QoS enforcement. As a result, a dedicated bandwidth

with several time constraints is the main conditions for VoTP in wireless LAN

environment to avoid the degradation of performance of VoIP service in the

received signal.



ABSTRAK

Dalam projek ini, kesesuaian rangkaian 802.11b akan dikaji untukmenghantar komunikasi trafik suara masa nyata dengan menggunakan InternetProtocol, dimana rangkaian pembawa voice session, mesti dikongsi untuk m embawadata, video dan suara. Suatu teknik sukatan kualiti suara digunakan dalarn rangkaian

tanpa wayar 802.11 berbanding dengan rangkaian wayar. Sukatan berkenaanterturnpu kepada tiga parameter VoIP yang utama: loss, delay dan jitter. Faktorpersekitaran seperti jarak antara dua titik, trafik rangkaian dan halangan-halanganlain juga merupakan faktor yang perlu diambil kira sem asa menjalankan kajian ini.Oleh sebab sifat yang tidak stabil persekitaran rangkaian tanpa wayar, untukmemenuhi permintaan kualiti perkhidmatan (00s) VoIP-WLAN merupakan suatutugas y-g agak mencabar. Prestasi trafik suara boleh dipengaruhi oleh tigap w e t e r Q oS yang utama seperti delay, jitter dan packet loss terutarnanya dalamr ~ g k a i a nanpa wayar berbanding dengan rangkaian yang menghantar data sahaja.Untuk mengenal pasti kualiti perkhidmatan VoIP dalam LAN tanpa wayar,

eksperimen telah dijalankan untuk menguji had-had kepada prestasi penggunaanYoIP. Uji kaji telah dilakukan dengan tiga senario yang berbeza dalarn keadaan idealdan nyata. Analisa dilakukan berdasar kepada perisian yang digunakan dalam projek,iaitu Clearsight analyzer dan Ethereal untuk m engukur delay, packet loss dan jitter.Merujuk keputusan yang didapati, ukuran dan graf-graf packet delay, packet jitterdan lost packet dilakar menunjukkan prestasi VoIP yang terhad pada LAN tanpawayar. VoIP ialah sejenis aplikasi multimedia yang memerlukan ketepatan masadalam penghantaran trafik suara walaupun menggunakan penguatkuasaan QoS.Sebagai keputusan, lebar jalur dedikasi dengan kekangan masa merupakan keadaan

utama bagi VoIP dalam persekitaran LAN tanpa wayar bagi mengelakkan prestasiperkidmatan VoIP m enurun pada isyarat yang diterima.



CHAPTER I

INTRODUCTION

1.1 ProjectBackground

The world is becoming increasingly Internet Protocol (IP) oriented, with a

large number of devices getting networked every day. At the same time, individuals

are starting to favor smaller and lighter devices such as laptops since they are

portable and not too bulky compared to the normal desktop computers. As their

modalities and patterns of use get shaped, there is a trend of doing some researches

of the performance of the Voice over IP (VoIP) service whenever the distance of the

wireless laptops are getting bigger to a certain distance with coverage of wireless that

can provide the good quality of VoIP service. Thus communicating through VoIP

can be more reachable between these devices in the same Local Area Network

(LAN) environment.

VoIP is one of the fastest growing Internet applications today. It has two

fundamental benefits compared with voice over traditional telephone networks.

First, by exploiting advanced voice compression techniques and bandwidth sharing

in packet-switched networks, VoIP can dramatically improve bandwidth efficiency.

Second, it facilitates the creation of new services that combine voice communication

with other media and data applications like video, white boarding and file sharing.

At the same time, driven by huge demands for portable access, the Wireless

LAN (WLAN) market is taking off quickly. Due to its convenience, mobility and

high speed access, WLAN represents an important future trend for the Internet access.



As a result of the convergence of these two trends, we believe VoIP overWLAN is poised to become an important Internet application. Before that can

happen, however, two technical problems need to be solved. The first is that the

system capacity for voice can be quite low in WLAN. The second is that VoIP traffic

and data traffic from traditional applications such as Web and e-mail can interfere

with each other and bring dow n VoIP performance.

As we know, when deploying VoIP in this environment, one of the

challenges is meeting the performance requirements to provide the best condition

which meet w ith the Quality of Service (QoS) in V oIP. When roaming around in a

wireless network environment, at som e point the mobile device will have to switch

access point that i s being associated with due to the m edia in wireless network is not

constant. These media may be very different and each of it will face an additional

problem such as the delay, jitter and losses as a network problem that can affect the

voice quality of the VoIP service that is being used a t that time.

Voice quality is an end-to-end matter with various network equipment,

ptotocols and policies. The performance of voice service is sensitive to delay, and the

voice quality can tolerate some dropped packets within a certain limit of packet loss

rdte.

It is supposed that delays are made small enough to make two wayscdfiversation possible. Beside that, it is important to know how long it takes for a

packet to trave l through a network.

The quality of a voice call is not only depends on network conditions, but

also on the perceptual characteristic of the end users and how these network

impairments affect the user's perception. Other factors are the user's expectation,

since the mood and human m emory can increase or decrease the perceived quality.



1.2 Problem Statements

The coverage of the wireless LAN is limited. As a result, we need to do a

research on the quality of the VoIP service as the distance of the device (laptops) are

getting bigger. To maintain the quality of service (QoS) in VoP, we need to find out

which length of distance is the most suitable distance to get the best service of Vow.

Besides, the performance of the VoIP service must be monitored to ensure that every

packets that being sent by the sender can be received by the receiver without any loss

of information. There may be a problem if the distance between two devices getting

bigger, the quality of the VoIP can be degraded to a certain extend based on the

wireless LAN environment. This research aimed to come out with a graph to observe

every packets of information that is sent by VoIP service whenever there are any

changes of distance between these two laptops in a Wireless LAN (WLAN)

environment.

1.3 Objectives

We conduct measurements of critical parameters that affect the quality of

voice over wireless networks, namely loss, delay and jitter. Delay has the important

ch&acteristics that once introduced it cannot be hidden or minimized, hence it is

important to know where exactly it is introduced into the system. Loss on the other

hand can be compensated for typically by adding redundancy to the transmitted

signal allowing some of the received signal to be reconstructed at the receiver.

This research explores the causes of the degradation of those parameters, and

finds an optimal condition of the environment for software, hardware to be deployed

in order to improve voice performance of VoIP over Wireless LAN (WLAN).

Therefore, this research will be done due to the purpose:



i. To maintain the coverage of wireless network in order to provide a good

quality of VoIP service in a LAN. The coverage of the wireless network is

limited and not too constant, so we need to set up a good wireless LAN

environment to ensure the quality of service in VoIP is up to standard.

ii. To analyze the quality of VoIP when the distance between the devices are

getting bigger as the delay, jitter and packet loss will cause the performance

of VoIP degrades. When we located two devices (laptops) in a certain

distance, a testing will be made to check if the quality of the VoIP is satisfied.

The length of distance can be varied in order to get the best quality of service

for VoIP service.

iii. To map the coverage of the wireless network for a VoIP service to

communicate between devices. We can get a brief coverage of the Wireless

LAN (WLAN) to enable the two laptops to communicate in a wireless

efivironment although there may be a loss of data when transmitted through

VoIP service whenever the distance has being changed.

1.4 Scopes

The scopes of this research topic are included the following:

i. The performance of VoIP- This performance of VoIP will be measured in the term of loss rate,

delay of data and jitter using the specialized quality of service (QoS)

Measurement Tools.



ii. The distance of the laptops- The length of distance between the two laptops will be changed from

time to time to test on the quality of the VoIP service in a Wireless

LAN (MAN) environment.

iii. The coverage of wireless- The coverage distance of the wireless network may be different due to

some factors such as walls, windows and interference sources and

with typical open-air operating distances of 100 to 500 meter or 300

to 1500 feet (Trulove,2002).

iv. The brand of the laptops

- In this research, the laptops that is being used has been specified to

ensure that the communication in VoIP service between these two

devices is constant and not affected by any hardware or software issue

due to the differences for the brand of laptops.

1.5 Project Significance

This research will be used as a guideline for those users who wish to use

VoIP service in a Wireless LAN (MAN) environment to enable the quality of the

VoIP service is always being fulfilled within the coverage of distance. In addition,

for those Network Expert, this research can be studied more in depth to solve the

problem that deal with the quality of service (QoS) in VoIP service as the length of

distance between these two wireless devices are getting bigger and the ways to

improve it without any loss of data or delay during the transmission of voice packets.



1.6 ExpectedOutput

In this research, we need to find out that the reason of degradation of those

parameters during the conversation in VoIP service such as the traffic and distance of

each node to access point. In the normal condition, we can expect that the closer the

devices to the access point the stronger the signal will be received. When the distance

of the devices are getting bigger, the quality of the VoIP service will be degraded in

the term of loss packet, delay of voice packets and jitter.

1.7 Conclusion

As the Internet growing fast recently, VoIP just like PCs, web access, e-mail

will grow out of the enterprise market and get into the residential market. It is

because this technology can be considered as a cheaper, simpler, and more

cohvenient to use and it is expected to replace the legacy network idiastructure.

However the appeal of the efficiencies of VoIP and Wireless Network (802.11)

cannot be ignored and the end result may be very well being a mix of technology.

The following chapter is the Literature Review and Methodology in order in

completing this research. This chapter can be viewed as an important element in the

development process as it can used as a guideline to the researcher. The method that

is being used to do this research will include the facts that we have found in any

journals or articles in researching in this topic and the requirements in doing this

research will be stated out as well.



CHAPTER I1

LITERATURE REVIEW AND PROJECT METHODOLOGY

2.1 Introduction

In this chapter, we will discuss and study about the quality of service (QoS) of

the Voice over IP (VoIP) service, the distance of coverage in Wireless Local Area

Network (WLAN) and the method we used in executing this research. To complete a full

thesis topic, we need to do more research and study more on that topics or terms in order

to understand the research topic more clearly. Those researches that we have gathered

such as ournals or articles can be used as a guideline to ensure that the research can be

executed successfully. We need to study more in depth in the area of scope for this

research topic, its main objective, find out the system requirement of this research topic

and a comparison canbe

made if there is any similar research topic which has been donebefore this.

To fulfill the requirements in executing this research, there are a few tasks which

need to be done in order to complete this chapter. Firstly, we need to search for

particular information through Internet, reference books and journals that published

through article in Internet. Besides this, this research also can be done by comparing

with other existing research so that we can do some enhancements on it to make it better

and valuable for future market research. All these information can be used as a source

and guideline in completing this research.



The techniques which are being used in executing this research play an important

role as it can be used as a research element whether the techniques are something that

have never been learned before or those that are currently used in the market. For the

methodology part, every step that is being used in executing this project will be stated

out clearly from the beginning of planning until producing the end product and getting

the desired result. The method that used may be varied from other research thesis but

with the same purpose or vice versa. The project requirements are those equipments or

tools that needed in executing this research such as the hardware, so h a r e and network

requirements. These requirements enable a project can be planned properly before

carrying out and developing it.

There is a session named project schedule and milestone which allow students to

plan their project according to the time frame and organize their time table wisely so that

they managed to complete the project in the duration of time given. As a result, each

student must plan their project according to the schedule and follow it in order to

complete the project.

As a conclusion, this chapter allows students to search for the particular

information about the existing research and try to figure out its weaknesses or enhance itto a more valuable research in the market. Therefore, this chapter can be used as a

reference to study the current research and then come out with our own new idea that is

unique and totally different from those that are currently can be found easily in our life

or environment.



2.2 Facts and Findings

In this section, some researches will be studied for its clarity and reliability

before they are being used in the thesis paper. All the facts that have been found must be

based on the research that has been done for which the students is enrolled in. Each

statement that has written in the thesis papers must be based on the facts no matter it is

based on any reading materials either in the journals, articles, referencebooks or through

Internet. Some of the research that has been done based on the topic, Performance of

Voice over Internet Protocol (VoTP) in Wireless Local Area Network (WLAN), is being

shown as below:

2.2.1 Domain

In this section, we will be identified a few keywords which are related with the

research topic. The main terms that we are going to stress out in this research paper are

shown as below:

2.2.1.1 Voice over Internet Protocol (VoIP) in W ireless Local Area

Network (WLAN)

VoIP in WLAN refers to the provisioning of voice services across wireless LANs,

usually 802.1]-based (also knows as voice over Wi-Fi). A VoIP in WLAN system works

by translating a Private Branch exchange (PBX) telephone call to IP packets and sends

these IP packets over an 802.11 WLAN. The phones with 802.11 or softphones will

reassemble those pack& and output the audio to the user. The reverse path is similar,

but without the synchronous timing of a telephone network.



In computing, a softphone is a software for making telephone calls over the

Internet using a general purpose computer, rather than using dedicated hardware. A

softphone is often designed to behave like a traditional telephone which sometimes may

be appeared as an image of a phone or with a display panel and buttons with which the

user can interact. A softphone is usually used with a headset connected to the sound card

of the Personal Computer (PC) (Wikipedia, 2007).

This new technology can bring a lot of benefits to people. It has all the

advantages of VoIP systems but with a greater mobility. Mobility usually means

increased productivity since it also reduces the cost for deployment of wired phones.

When the world is introducing voice to IP networks, VoIP in WLAN has the same

problems as VoIP regarding of the deployment method. Some characteristics of wireless

networks can cause some additional difficulties. As a result, there are several major

issues that needed to be solved before this technology can be fully accepted.

i. Latency can induce VoIP performance degradation as users roam. This latency is

usually caused by the reauthentication that required when associating with a new

access point. International Telecommunication Union (ITU) recommends that the

total latency in a voice call should not exceed 150 milliseconds. In VoIP inWLAN

practice, the delay of roaming and authentication should be kept under 50

milliseconds (Khan and Lang, 2004).

ii. Lack of Quality of Service (QoS) mechanisms. In order to keep the real time features

of voice traffic, voice packets should be assigned higher priority then normal data

packets to maintain the quality of voice. In this sense, QoS is needed. Currently,

there is no standard way of doing this. However, Institute of Electrical and

Electronics Engineers (IEEE) is developing a QoS standard called 802.1 1e and it is

expected to be a new technology that can carry the voice packets without any



QoS problem. In 802.1 le, two different types of QoS are provided. One is prioritized

QoS, which uses priority tagging to place different types of traffic in different queues.

Although voice gets priority treatment, it cannot get a reserved bandwidth as it is not

guaranteed that low priority frames will always wait until all higher priority frames

are transmitted, so in order to provide better service to streams with higher priority, a

reserved bandwidth may be helpful solution. The other one is called parameterized

QoS, which effectively reserves a certain amount of bandwidth for a certain stream

(Khan and Lang, 2004).

iii. Limited number of voice calls. Due to the capability of access points for handling

calls simultaneously, the number of calls is limited. Currently, when the number of

calls reach around thirty, an access point becomes overloaded, thus the quality

degrades. With 802.1 1a, 802.11g and 802.1 1h standards coming into the picture, this

problem will be solved to a certain extent.

Although VoIP in WLAN has a few problems especially in performance, it still

has a bright future and would appear to have a broad market sooner or later. With the

decreasing of cost for deployment and the introduction of new products and services,

VoIP inWLAN

will surelybe

accepted more widely.

2.2.1.2 Voice over Internet Protocol (VoIP)

Voice over Internet Protocol, also called VoIP, IP Telephony, Internet Telephony,

Broadband Telephony, Broadband Phone and Voice over Broadband, is the routing of

voice conversations over the Internet or through any other IP-based network.



There are two types of Public Switched Telephone Network (PSTN) to VoIP

services: Direct Inward Dialing (DID) and Access Numbers. DID will connect the caller

directly to the VoIP user while Access Numbers require the caller to input the extension

number of the VoIP user. Access Numbers are usually charged as a local call to the

caller and free to the VoIP user while DID usually has a monthly fee. There are also

DIDs that are free to the VoIP user but chargeable to the caller (Wikipedia, 2007).

VoIP can facilitate tasks that may be more dificult to achieve using traditional

networks:

Ability to transmit more than one telephone call down the same broadband-

connected telephone line. This can make VoIP a simple way to add an extra

telephone line to a home or ofice.

b Incoming phone calls can be automatically routed to user's VoIP phone,

regardless of where the users are connected to the network.

Call center agents using VoIP phones can work from anywhere with a

suficiently fast and stable Internet connection.

VoIP is location independent, only an Intemet connection is needed to get a

connection to a VoIP provider.

VoIP phones can integrate with other services available over the Internet,

including video conversation, message or data file exchange in parallel with the

conversation, audio conferencing, managing address books and passing

information whether other (e.g. friends or colleagues) are available online to

interested parties.



Since the User Datagram Protocol (UDP) does not provide a mechanism to

ensure that data packets are delivered in sequential order or provide QoS guarantees,

VoIP implementations face problems dealing with latency and jitter. This can be proved

especially when the satellite circuits are involved due to long round trip propagation

delay (400 milliseconds to 600 milliseconds for geostationary satellite). The receiving

node must restructure IP packets that may be out of order, delayed or missing while

ensuring that the audio stream maintains a proper time consistency. This hnctionality is

usually accomplished by means of a jitter buffer (Wikipedia, 2007).

Another challenge is routing VoIP traffic through firewalls and address

translators. Private Session Border Controllers are used along with firewalls to enable

VoIP calls to and from a protected enterprise network. As an example, Skype uses a

proprietary protocol to route calls through other Skype peers on the network, allowing it

to traverse symmetric Network Address Translators (NATs) and firewalls. Other

methods to traverse firewalls involve using protocols such as Simple Traversal of UDP

Through NATs (STUN) which is a network protocol that allowing a client behind a

NAT (or multiple NATs) to find out its public address. This information is used to set up

UDP communication between two hosts that are both behind NAT routers (Wikipedia,

2007).

On the other hand, there are some challenges that are faced by VoIP services

nowadays such as the available of bandwidth, delay or network latency, packet loss,

jitter, echo, security and reliability. All these challenges must be overcome in order to

provide a good quality of service in VoIP.

Fixed delays cannot be controlled but some delays can be minimized by marking

voice packets as being delay-sensitive. The principal cause of packet loss is congestion

which can be controlled by congestion management and avoidance. Besides this, a jitter



can be defined as variation in delay. The effects of jitter can be mitigated by storing

voice packets in a buffer (called a play-out buffer) upon arrival, before playing them out.

This avoids a condition known as buffer underrun, in which the playout process runs out

of voice data to play because the next voice packet has not yet arrived, but increases

delay by the length of the buffer. Common causes of echo include impedance

mismatches in analog circuitry and acoustic coupling of the transmit and receive signal

at the receiving end (Wikipedia, 2007).

2.2.1.3 Wireless Local Area Network (WLAN)

A wireless LAN or WLAN is a wireless local area network, which is the linking

of two or more computers without using wires. WLAN utilizes spread-spectrum or

Orthogonal Frequency Division Multiplexing (OFDM) (802.1 la) modulation technology

based on radio waves to enable communication between devices in a limited area, also

known as the basic service set. This gives users the mobility to move around within a

broad coverage area and still can be connected to the network (Wikipedia, 2007).

For the home user, wireless has become popular due to ease of installation, andlocation freedom with the gaining popularity of laptops. Public businesses such as coffee

shops or malls have begun to offer wireless access to their customers; some are even

provided as a free service. Large wireless network projects are being put up in many

major cities.

The popularity of WLANs is a testament primarily to their convenience, cost

efficiency, and ease of integration with other networks and network components. The

majority of computers sold to consumers today come pre-equipped with all necessary

wireless LAN technology.



There are many benefits of using or applying wireless LANs in the office,

campus or housing areas which include:

i. Convenience: The wireless nature of such networks allows users to access

network resources from nearly any convenient location within their primary

networking environment (home or office). With the increasing saturation of

laptop-style computers, this is particularly relevant.

ii. Mobility: With the emergence of public wireless networks, users can access the

internet even outside their normal work environment. Most chain coffee shops,

for example, offer their customers a wireless connection to the internet at little or

no cost.

i i i . Productivity: Users connected to a wireless network can maintain a nearly

constant affiliation with their desired network as they move from place to place.

For a business, this implies that an employee can potentially be more productive

as hisw her work can be accomplished from any convenient location.

iv. Deployment: Initial setup of an infrastructure-based wireless network requires

little more than a single access point. Wired networks, on the other hand, have

the additional cost and complexity of actual physical cables being run to

numerous locations (which can even be impossible for hard-to-reach locations

within a building).

v. Expandability: Wireless networks can serve a suddenly-increased number of

clients with the existing equipment. In a wired network, additional clients would

require additional wiring.



vi. Cost: Wireless networking hardware is at worst a modest increase from wired

counterparts. This potentially increased cost is almost always more than

outweighed by the savings in cost and labor associated to running physical cables.

WLAN technology, while replete with the conveniences and advantages

described above, has its share of downfalls. For a given networking situation, wireless

LANs may not be desirable for a number of reasons. Most of these have to do with the

inherent limitations of the technology which include:

i. Security: Wireless LAN transceivers are designed to serve computers throughout

a structure with uninterrupted service using radio frequencies. Because of space

and cost, the antennas typically present on wireless networking cards in the end

computersare generally relatively poor. In order to properly receive signals using

such limited antennas throughout even a modest area, the wireless LAN

transceiver utilizes a fairly considerable amount of power. This means that not

only can the wireless packets be intercepted by a nearby adversary's poorly-

equipped computer, but more importantly, a user willing to spend a small amount

of money on a good quality antenna can pick up packets at a remarkable distance;

perhaps hundreds of times the radius as the typical user. In fact, there are even

computer users dedicated to locating and sometimes even hacking into wireless

networks, known as wardrivers. On a wired network, any adversary would first

have to overcome the physical limitation of tapping into the actual wires, but this

is not an issue with wireless packets. To combat this consideration, wireless

networks users usually choose to utilize various encryption technologies

available such as Wi-Fi Protected Access (WPA). Some of the older encryption

methods, such as Wired Equivalent Privacy (WEP) are known to have

weaknesses that a dedicated adversary can compromise.



ii . Range: The typical range of a common 802.1 1g network with standard

equipment is on the order of tens of meters (Smyth, 2004). While sufficient for a

typical home, it will be insufficient in a larger structure. To obtain additional

range, repeaters or additional access points will have to be purchased. Costs for

these items can add up quickly.

i i i . Reliability: Like any radio frequency transmission, wireless networking signals

are subject to a wide variety of interference, as well as complex propagation

effects that are beyond the control of the network administrator. In the case of

typical networks, modulation is achieved by complicated forms of phase-shift

keying (PSK) or quadrature amplitude modulation (QAM), making interference

and propagation effects all the more disturbing. As a result, important network

resources such as servers are rarely connected wirelessly.

iv. Speed: The speed on most wireless networks (typically 1-108 Mbit/s) is

reasonably slow compared to the slowest common wired networks (100 Mbit/s

up to several Gbit/s). There are also performance issues caused by Transmission

Control Protocol (TCP) and its built-in congestion avoidance. For most users,

however, this observation is irrelevant since the speed bottleneck is not in the

wireless routing but rather in the outside network connectivity itself. For example,

the maximum Asymmetric Digital Subscriber Line (ADSL) throughput (usually

8 Mbitls or less) offered by telecommunications companies to general-purpose

customers is already far slower than the slowest wireless network to which it is

typically connected. That is to say, in most environments, a wireless network

running at its slowest speed is still faster than the internet connection serving it in

the first place. However, in specialized environments, the throughput of a wired

network might be necessary. Newer standards such ai 802.1 In are addressing



this limitation and will support peak throughputs in the range of 100-200 Mbitls

(Wikipedia, 2007).

2.2.2 Existing System

These days a massive deployment of VoIP is taking place over data networks.

Most of these networks are Ethernet based and running IP protocol. Many network

managers are finding it very attractive and cost effective to merge and unify voice and

data networks into one. It is easier to run, manage and maintain. However, one has to

keep in mind that IP networks are best-effort networks that were designed for non-real

time applications. On the other hand, VoIP requires timely packet delivery with low

latency, jitter, packet loss and sufficient bandwidth. To achieve this goal, an efficient

deployment of VoIP must ensure these real-time traffic requirements can be guaranteed

over new or existing IP networks.

When deploying a new network service such as VoIP over existing network,

many network architects, managers, planners, designers and engineers faced with

common strategic and sometimes challenging questions. Due to these challengingquestions, they have led to the development of some commercial tools for testing the

performance of multimedia applications in data networks. A list of the available

commercial tools that support VoIP with the two most common approaches in assessing

the deployment of VoIP into the existing network. One approach is based on first

performing network measurements and then predicting the network readiness for

supporting VoIP. The prediction of the network readiness is based on assessing the

health of network elements. The second approach is based on injecting real VoIP traffic

into existing network and measuring the resulting delay, jitter, and loss.



Other than the cost associated with the commercial tools, none of the commercial

tools offer a comprehensive approach for successful VoIP deployment. In particular,

none gives any prediction for the total number of calls that can be supported by the

network taking into account important design and engineering factors. These factors

include VoIP flow and call distribution, future growth capacity, performance thresholds,

impact of VoIP on existing network services and applications, and impact background

traffic on VoIP. The research paper attempts to address those important factors and

layout a comprehensive methodology for a successfbl deployment of any multimedia

application such as VoIP and videoconferencing. However, the research paper focuses

on VoIP as the new service of interest to be deployed in a new environment, WLAN

(Salah, 2005).

2.2.3 Technique

To analyze the suitability of IEEE 802.11b networks to carry out voice traffic, a

series of experiments will be performed that covering a range of factors which affecting

the voice quality, including both networks and link quality aspects. To compute the end-

to-end delay, loss and jitter at the end point, a few tools such as QoS Measurement Toolsthat can be used to achieve those goals. QoS Measurement Tools is a central component

for testing the quality voice data in a wireless VoIP Communication network. ClearSight

Analyzer is a network analyzer software that completely overlooked on everyday traffic

and issues in the network. It is designed purposely for packet decoding and network

diagnosis, monitors the network traffic transmitted over a local host and a local network

with the ability of real time packet capture and the network troubles. ClearSight

Analyzer was installed in the receiver or sender nodes through a hub to be connected to

the network to capture all the IP packets and Media Access control (MAC) frames. The

other measurement tool is Ethereal which allows user to monitor both MAC layer frames



and IP layers traffic and that it is available under an open sources license. This is due to

the fact that Ethereal has a large community supporting to its development. Ethereal was

used in the receiver and sender nodes to capture all the IP packets and MAC frames.



2.3 ProjectMethodology

The Waterfall Model derives its name due to the cascading effect from one phase

to another (Sommerville, 2004). In this model, each phase is well defined from the

starting point until the ending point with identifiable deliveries to the next phase.

Sometimes this model also can be referred as the linear sequential model or the software

life cycle as shown in the Figure 2.1.

Analysis

Designand iPlanning I

I

I Testing j,igure 2.1: Waterfall model



Requirement Analysis- All parts of analysis element will be conducted such as requirement

analysis and planning analysis. Besides that, understanding of objectives,

functions, requirements and planning of this research topic are very

important in order to produce a good quality of research paper.

Specifications

- Research specification is produced from the detailed definition of the

requirement analysis. As a result, the objectives of the research should be

studied first and try to figure out the main purpose of doing this research

and explain it briefly so that other people can understand the research

topic as well.

Design and Planning- In this stage, the hardware requirements can be determined along with a

brief idea of the architecture of the research. The hardware and software

should be linked together to execute the project. The network design will

be an overview of the project which will be used for the whole research

and it can be used as a guideline to overcome some network problems.

Implementation- In this phase, the network diagram that has design earlier will be

implemented into a real environment with the hardware and software

required. This phase is important since wrongly implemented may affect

the end result of the research. This phase can be changed according to the

hardware or software provided.



Testing- For testing phase, the VoIP in WLAN system will be tested from time to

time in order to get the best result out of it. At the mean time, the skill of

trial and error may be helpful in executing this research as this research is

an assumption for future research enhancement. This phase is critical

since the result may be depending on the implementation stage and each

time implementation has changed, so is the result of testing stage.

Documentation- After every testing session, the result of the experiments can be recorded

and a conclusion will be made at the final of this research to determine

the level of QoS for VoIP functions well in WLAN. The documentations

will be based on a series of experiment that are carried out during the

research.

2.4 ProjectRequirements

Project requirements are the sofhvares, tools or equipments that are needed to

carry out the research in order to achieve the goal of the objectives proposed at the early

stage of this research. The requirements for this research are shown as following:



2.4.1 Software Requirements

a) Equipments or Development Tools

- Skype (VoIP function)- Clearsight Analyzer

- Ethereal

- Microsoft Project 2003- Microsoft Visio 2003

b) Operating System or Sewer- Windows XP

2.4.2 Hardware Requirements

- Wireless Switch (Access Point)

- Laptops with Wireless

- Personal Computers (Pcs)

- Wireless USB adapter (for Client PC)- Category 5 (CATS) Unshielded Twisted Pair (UTP) Cable

-Switch- Router

performance of voice over internet protocol (voip) in wireless local area network (wlan)

Documents