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WIRELESS NETWORK PERFORMANCE EVALUATION
FOR FCSIT LABS
ANIZA BINTI YUSUP
This project is submitted in partial fulfillment of
the requirements for the degree of Bachelor of Computer Science with Honours
(Network Computing)
Faculty of Computer Science and Information Technology
UNIVERSITI MALAYSIA SARAWAK
2006
ACKNOWLEDGEMENTS I thank my supervisor, Dr Tan Chong Eng, for his advices, the knowledge he shared and his continuous support during the accomplishment of this project. I also thank Mr Sapiee Hj. Jamel, for his opinions and suggestions and also to my examiner, Puan Azni for her comments and guidelines. Information from other member of Faculty of Computer Science and Information Technology (FCSIT) UNIMAS, including Mr Razeki Jelihi and Mr Zulkifli Ahmat are also appreciated. My heartfelt thank also goes to Mr Kamarulzaman Sharif of CICTS, UNIMAS for his willingness to share information. Finally, I wish to express my sincere gratitude to my beloved family for their loving support as well as understanding and patience and not forgotten to all of my friends for their encouragement and helpful opinions during the course of my undergraduate study.
i TABLE OF CONTENTS ACKNOWLEDGEMENTS i TABLE OF CONTENTS ii LIST OF FIGURES vi LIST OF ABBREVIATIONS x ABSTRACT xii ABSTRAK xiii
1 Chapter 1.0 Introduction 1.1 Project Descriptions 1 1.2 Problem Statement 2 1.3 Project Objective 2 1.4 Project Scope 3 1.5 Contributions of the project 3 1.6 Expected Outcome 4 1.7 Dissertation Organization 4 1.8 5 Summary 6 Chapter 2.0 Literature Review 2.1 Wireless LAN (WLAN) 6 2.2 IEEE 802.11 Standards 6 2.2.1 IEEE 802.11a 7 2.2.2 IEEE 802.11b 8
ii 2.2.3 IEEE 802.11g 9 Wireless LAN Technology 10
2.3.1 Infrared (IR) LANs 10
2.3.2 Spread Spectrum LANs 11
2.3.3 Narrowband Microwave 14
Wireless LAN Configuration 14
2.4.1 Ad Hoc Configuration 14
2.4.2 Infrastructure Configuration 15
2.5 Wireless LAN Problems 17
2.6 Performance Evaluation on Wireless LANs 19
2.7 Summary 24
2.3 2.4 26
Chapter 3.0 Methodology 3.1 Tool 26
3.2 Project Procedure 29
3.3 Summary 31
32
Chapter 4.0 System Analysis 4.1 Objective of the Simulation 32
4.2 Current Lab Configuration 32
4.3 Physical Network Arrangement. 34
4.4 Hardware Configuration 35
4.4.1 The D­Link AirPlus DWL­900AP+ 35
Access Point Configuration iii 4.4.2 The D­Link AirPlus DWL­520+ PCI 39
Adapter Configuration 4.5 Requirement Specifications 42
4.5.1 Access Point 42
4.5.2 Wireless LAN Card 43
Summary 44
4.6 Chapter 5.0 The Proposed Lab Configuration 45
5.1 The Evaluation Parameters 45
5.2 Network Traffic 47
5.3 Node Configuration 49
5.4 Discrete Event Simulation 51
5.5 The Proposed Network Layout 52
5.6 Simulation Results 56
5.6.1 Scenario 1 : Using One Access Point 56
5.6.2 Scenario 2 : Using Two Access Points 60
5.6.3 Scenario 3 : Using Three Access Points 64
5.6.4 Scenario 4 : Using Four Access Points 68
5.6.5 Scenario 5 : Using Five Access Points 72
Traffic Analysis 76
5.7.1 WLAN Throughput 76
5.7.2 Email Download and Upload Response Time 78
5.7.3 FTP Download and Upload Response Time 80
5.7.4 HTTP Page Response Time 82
5.7 iv 5.8 5.7.5 Summary of all simulation results 83
Summary 84
CHAPTER 6.0 Conclusion and Future Work 85
6.1 Project Achievements 85
6.2 Problems Faced 86
6.3 Future Work 86
6.4 Overall Project Conclusion 87
BIBLIOGRAPHY 89
REFERENCES 91
APPENDIX Appendix A : Wireless Access Point Specifications 94
Appendix B : Wireless Card Specifications 95
v TABLE OF CONTENTS ACKNOWLEDGEMENTS i TABLE OF CONTENTS ii LIST OF FIGURES vi LIST OF ABBREVIATIONS x ABSTRACT xii ABSTRAK xiii
1 Chapter 1.0 Introduction 1.1 Project Descriptions 1 1.2 Problem Statement 2 1.3 Project Objective 2 1.4 Project Scope 3 1.5 Contributions of the project 3 1.6 Expected Outcome 4 1.7 Dissertation Organization 4 1.8 5 Summary 6 Chapter 2.0 Literature Review 2.1 Wireless LAN (WLAN) 6 2.2 IEEE 802.11 Standards 6 2.2.1 IEEE 802.11a 7 2.2.2 IEEE 802.11b 8
ii 2.2.3 IEEE 802.11g 9 Wireless LAN Technology 10
2.3.1 Infrared (IR) LANs 10
2.3.2 Spread Spectrum LANs 11
2.3.3 Narrowband Microwave 14
Wireless LAN Configuration 14
2.4.1 Ad Hoc Configuration 14
2.4.2 Infrastructure Configuration 15
2.5 Wireless LAN Problems 17
2.6 Performance Evaluation on Wireless LANs 19
2.7 Summary 24
2.3 2.4 26
Chapter 3.0 Methodology 3.1 Tool 26
3.2 Project Procedure 29
3.3 Summary 31
32
Chapter 4.0 System Analysis 4.1 Objective of the Simulation 32
4.2 Current Lab Configuration 32
4.3 Physical Network Arrangement. 34
4.4 Hardware Configuration 35
4.4.1 The D­Link AirPlus DWL­900AP+ 35
Access Point Configuration iii 4.4.2 The D­Link AirPlus DWL­520+ PCI 39
Adapter Configuration 4.5 Requirement Specifications 42
4.5.1 Access Point 42
4.5.2 Wireless LAN Card 43
Summary 44
4.6 Chapter 5.0 The Proposed Lab Configuration 45
5.1 The Evaluation Parameters 45
5.2 Network Traffic 47
5.3 Node Configuration 49
5.4 Discrete Event Simulation 51
5.5 The Proposed Network Layout 52
5.6 Simulation Results 56
5.6.1 Scenario 1 : Using One Access Point 56
5.6.2 Scenario 2 : Using Two Access Points 60
5.6.3 Scenario 3 : Using Three Access Points 64
5.6.4 Scenario 4 : Using Four Access Points 68
5.6.5 Scenario 5 : Using Five Access Points 72
Traffic Analysis 76
5.7.1 WLAN Throughput 76
5.7.2 Email Download and Upload Response Time 78
5.7.3 FTP Download and Upload Response Time 80
5.7.4 HTTP Page Response Time 82
5.7 iv 5.8 5.7.5 Summary of all simulation results 83
Summary 84
CHAPTER 6.0 Conclusion and Future Work 85
6.1 Project Achievements 85
6.2 Problems Faced 86
6.3 Future Work 86
6.4 Overall Project Conclusion 87
BIBLIOGRAPHY 89
REFERENCES 91
APPENDIX Appendix A : Wireless Access Point Specifications 94
Appendix B : Wireless Card Specifications 95
v ABSTRACT There are lots of factors that can affect the performance of wireless network, such as the internal and external interference, user capacity and the application load itself. The focus of the project is to examine the effect of the various heavy applications running on Wireless LAN clients in FCSIT Lab to the wireless LAN throughput and the response time for Email, FTP and HTTP applications. The project used OPNET Modeler version 10.0 to simulate the wireless network, based on the existing network configuration in FCSIT Labs. The model must be closely similar to the real one and the challenge was, to be able to make sure that the network configurations that are being modeled really match the existing one. There are five scenarios created for the project, each with different number of Access Points. The performance of the Wireless LAN found to have improved by adding more Access Point to the wireless network. However, the response time for each application was still long, even though the WLAN throughput has improving. High application response time might be caused by too many clients running heavy applications at the same time and accessing the Internet simultaneously. Choosing a suitable applications load and number of users per Access Point is an important consideration to enable the user to achieve the maximum throughput and experience better network performance.
xii ABSTRAK Terdapat banyak faktor yang memberi kesan kepada rangkaian tanpa wayar, seperti gangguan dalaman atau luaran, bilangan pengguna serta beban aplikasi itu sendiri. Fokus projek ini adalah untuk menganalisa kesan daripada penggunaan pelbagai aplikasi yang berat, yang dijalankan oleh pelanggan dalam rangkaian lokal tanpa wayar (Wireless LAN) di dalam Lab FCSIT, trehadap jumlah data yang di terima serta masa respon untuk aplikasi Email, FTP dan HTTP. Projek ini menggunakan OPNET Modeler versi 10.0 dalam menjalankan simulasi untuk rangkaian tanpa wayar, berdasarkan konfigurasi rangkaian yang telah sedia wujud di Lab FCSIT. Model yang digunakan perlulah menyamai model yang sebenar dan cabarannnya adalah untuk memastikan konfigurasi yang dimodelkan benar­benar menyamai yang sedia wujud. Terdapat lima senario telah dimodelkan untuk projek ini, di mana setiap satunya menggunakan bilangan ‘Access Point’ yang berbeza. Terdapat peningkatan dari segi kualiti rangkaian tanpa wayar dengan penambahan bilangan ‘Access Point’. Walaubagaimanapun, masa respon untuk setiap aplikasi masih panjang. Ini mungkin disebabkan terlalu banyak pelanggan menggunakan aplikasi yang berat pada masa yang sama dan mengakses Internet secara serentak. Memilih aplikasi yang serta bilangan pelanggan yang sesuai adalah penting untuk memastikan bilangan data yang diterima semaksismum mungkin dan peningkatan dalam kualiti rangkaian.
xiii LIST OF ABBREVIATIONS BS S B SS Ba si ic c S Se er rv vi ic ce e S Se et t B as CB R C BR Co ns st ta an nt t B Bi it t R Ra at te e C on CC K C CK Co mp pl le em me en nt ta ar ry y K Ke ey yi in ng g C om CS MA A/ /C CA A C SM Ca rr ri ie er r S Se en ns se e M Mu ul lt ti ip pl le e A Ac cc ce es ss s w wi it th h C Co ol ll li is si io on n A Av vo oi id da an nc ce e C ar DE S D ES Di sc cr re et te e E Ev ve en nt t S Si im mu ul la at ti io on n D is DH CP P D HC Dy na am mi ic c H Ho os st t C Co on nf fi ig gu ur ra at ti io on n P Pr ro ot to oc co ol l D yn DB PS SK K D BP Di ff fe er re en nt ti ia al l B Bi in na ar ry y Ph as se e S Sh hi if ft t K Ke ey yi in ng g D if P ha DC F D CF Di st tr ri ib bu ut te ed d C Co oo or rd di in na at ti io on n F Fu un nc ct ti io on n D is DI FS S D IF Di st tr ri ib bu ut te ed d I In nt te er r­ ­f fr ra am me e S Sp pa ac ce e D is DQ PS SK K D QP Di ff fe er re en nt ti ia al l Q Qu ua ad dr ra at tu ur re e P Ph ha as se e S Sh hi if ft t K Ke ey yi in ng g D if DS D S Di st tr ri ib bu ut te ed d S Sy ys st te em m D is DS SS S D SS Di re ec ct t S Se eq qu ue en nc ce e S Sp pr re ea ad d S Sp pe ec ct tr ru um m D ir DS SS S/ /H HR R D SS Hi gh he er r R Ra at te e D Di ir re ec ct t S Se eq qu ue en nc ce e S Sp pr re ea ad d S Sp pe ec ct tr ru um m H ig ES S E SS Ex te en nd de ed d S Se er rv vi ic ce e S Se et t E xt FT P F TP Fi le e T Tr ra an ns sf fe er r P Pr ro ot to oc co ol l F il GF SK K G FS Ga us ss si ia an n F Fr re eq qu ue en nc cy y Sh if ft t K Ke ey yi in ng g G au S hi HT TP P H TT Hy pe er rt tT Te ex xt t T Tr ra an ns sf fe er r P Pr ro ot to oc co ol l H yp IB SS S I BS In de ep pe en nd de en nt t S Se er rv vi ic ce e S Se et t I nd IE EE E I EE In st ti it tu ut te e o of f E El le ec ct tr ri ic ca al l a an nd d E El le ec ct tr ro on ni ic c E En ng gi in ne ee er rs s I ns IR I R
In fr ra a R Re ed d I nf IS M I SM In du us st tr ri ia al l, , S Sc ci ie en nt ti if fi ic c a an nd d M Me ed di ic ca al l B Ba an nd d I nd LO S L OS Li ne e o of f S Si ig gh ht t L in MA C M AC Me di iu um m A Ac cc ce es ss s C Co on nt tr ro ol l M ed OF DM M O FD Or th ho og go on na al l F Fr re eq qu ue en nc cy y D Di iv vi is si io on n M Mu ul lt ti ip pl le ex xi in ng g O rt OP NE ET T O PN Op ti im mi iz ze ed d N Ne et tw wo or rk k E En ng gi in ne ee er ri in ng g T To oo ol l O pt PB CC C P BC Pa ck ke et t B Bi in na ar ry y Co nv vo ol lu ut ti io on na al l C Co od di in ng g P ac C on PC F P CF Po in nt t C Co oo or rd di in na at ti io on n F Fu un nc ct ti io on n P oi PP P P PP Po in nt t t to o P Po oi in nt t P Pr ro ot to oc co ol l P oi RF R F Ra di io o F Fr re eq qu ue en nc cy y
R ad x SI FS S S IF Sh or rt t I In nt te er r­ ­f fr ra am me e S Sp pa ac ci in ng g S ho SS H S SH Se cu ur re e S Sh he el ll l S ec SS ID D S SI Se rv vi ic ce e S Se et t I ID D S er TC P T CP Tr an ns sm mi is ss si io on n C Co on nt tr ro ol l P Pr ro ot to oc co ol l T ra TC P/ /I IP P T CP Tr an ns sm mi is ss si io on n C Co on nt tr ro ol l P Pr ro ot to oc co ol l/ / I In nt te er rn ne et t P Pr ro ot to oc co ol l T ra UD P U DP Us er r D Da at ta ag gr ra am m P Pr ro ot to oc co ol l U se UN II I U NI Un iv ve er rs sa al l N Ne et tw wo or rk ki in ng g I In nf fo or rm ma at ti io on n I In nf fr ra as st tr ru uc ct tu ur re e U ni WE P W EP Wi re ed d E Eq qu ui iv va al le en nt t P Pr ro ot to oc co ol l W ir WL AN N W LA Wi re el le es ss s L Lo oc ca al l A Ar re ea a N Ne et tw wo or rk k W ir WS P W SP Wi re el le es ss s S Se es ss si io on n P Pr ro ot to oc co ol l W ir WT P W TP Wi re el le es ss s T Tr ra an ns sa ac ct ti io on n P Pr ro ot to oc co ol l
W ir xi LIST OF FIGURES Figure 2.1 General Model of Spread Spectrum Digital Communication 11
System Figure 2.2 Channel use for Frequency Hoping Spread Spectrum 12
Figure 2.3 Channel use for Direct Sequence Spread Spectrum 13
Figure 2.4 Ad hoc or peer­to­peer Wireless LAN 15
Figure 2.5 Infrastructure Wireless LAN 16
Figure 2.6 Infrastructure Wireless LAN with multiple Access Points and 17
roaming Figure 3.1 OPNET Modeler versions 10.0 27
Figure 3.2 Project Editor Window 27
Figure 3.3 Tool Bar Buttons in Project Editor 28
Figure 3.4 The Project Editor Object Palette 28
Figure 4.1 Floor Plan of Lab 8 with 20 wireless PCs 33
Figure 4.2 Floor Plan of Lab 6 with 5 wireless PCs in the middle of the lab 33
Figure 4.3 Default setting of DWL­900AP 35
Figure 4.4 The LAN default setting of DWL­900AP+ 36
Figure 4.5 Default Performance Settings for DWL­900AP+ Access Point 37
Figure 4.6 MAC Filter Settings for DWL­900AP+ 37
Figure 4.7 Changing the password in Admin window 38
Figure 4.8 Current information for DWL­900AP+ Access Point 38
Figure 4.9 Configuration Utility Icons 39
Figure 4.10 Link Quality and Signal Strength on Link Info window 40
Figure 4.11 Default configuration for DWL­520+ 41
vi Figure 4.12 D­Link AirPlus DWL­900AP+ Enhanced 2.4GHz Wireless 42
Access Point Figure 4.13 D­Link AirPlus DWL­520+ Enhanced 2.4 GHz Wireless 43
PCI Adapters Figure 5.1 The Simulation Project Flow 45
Figure 5.2 The Wireless LAN Object Palette 46
Figure 5.3 Network objects used in the project 46
Figure 5.4 HTTP Application Configuration 47
Figure 5.5 Email Application Configuration 48
Figure 5.6 FTP Application Configuration 48
Figure 5.7 Wireless LAN parameters inside Modeler 49
Figure 5.8 The Profile configuration for each scenario 50
Figure 5.9 Discrete Event Simulation (DES) Configuration 51
Figure 5.10 One Access Point to support 50 clients running heavy applications 53
Figure 5.11 Two Access Points to support 50 clients running heavy 53
applications Figure 5.12 Three Access Points to support 50 clients running heavy 54
applications Figure 5.13 Four Access Points to support 50 clients running heavy 54
applications Figure 5.14 Five Access Points to support 50 clients running heavy 55
applications Figure 5.15 WLAN throughput using one Access Point. 56
Figure 5.16 Email download response time using one Access Point 57
vii Figure 5.17 Email download response time using one Access Point 57
Figure 5.18 FTP download response time using one Access Point 58
Figure 5.19 FTP upload response time using one Access Point 58
Figure 5.20 HTTP page response time using one Access Point 59
Figure 5.21 WLAN throughput using two Access Points. 60
Figure 5.22 Email download response time using two Access Points 61
Figure 5.23 Email upload response time using two Access Points 61
Figure 5.24 FTP download response time using two Access Points 62
Figure 5.25 FTP upload response time using two Access Points 62
Figure 5.26 HTTP page response time using two Access Points 63
Figure 5.27 WLAN throughput using three Access Points 64
Figure 5.28 Email download response time using three Access Points 65
Figure 5.29 Email upload response time using three Access Points 65
Figure 5.30 FTP download response time using three Access Points 66
Figure 5.31 FTP upload response time using three Access Points 66
Figure 5.32 HTTP page response time using three Access Points 67
Figure 5.33 WLAN throughput using four Access Points. 68
Figure 5.34 Email download response time using four Access Points 69
Figure 5.35 Email upload response time using four Access Points 69
Figure 5.36 FTP download response time using four Access Points 70
Figure 5.37 FTP upload response time using four Access Points 70
Figure 5.38 HTTP page response time using four Access Points 71
Figure 5.39 WLAN throughput using four Access Points 72
Figure 5.40 Email download response time using five Access Points 73
viii Figure 5.41 Email upload response time using five Access Points 73
Figure 5.42 FTP download response time using five Access Points 74
Figure 5.43 FTP upload response time using five Access Points 74
Figure 5.44 HTTP Page response time using five Access Points 75
Figure 5.55 WLAN throughput for the entire scenarios 76
Figure 5.56 Email download response time for the entire scenarios 78
Figure 5.57 Email upload response time for the entire scenarios 79
Figure 5.58 FTP download response time for the entire scenarios 80
Figure 5.59 FTP upload response time for the entire scenarios 81
Figure 5.60 Graph of HTTP Page response time for the entire scenarios 82
Figure 5.61 The Simulation Results 83
ix CHAPTER 1 INTRODUCTION This section is focusing on the introduction of the project including a brief explanation about the problem statement, the objectives, the project’s scope, the expected outcomes and the contribution of the project. 1.1 Project Descriptions The demand for Wireless LAN (WLAN) has increased dramatically over the past years. Most users are convinced of its benefits such as mobility, flexibility, simplicity, less cost of ownership, ease of installation and also scalability. Lots of research have been done or proposed to enhance the performance of Wireless LAN, in term of its security, roaming capabilities and etc. In Wireless LAN, the bandwidth is shared amongst the clients and sometime problems can be caused by interference and also bottleneck. The concept of this project is, to re­design existing wireless network configuration and simulate it using OPNET Modeler version 10.0. Simulations are to be conducted to test it and obtaining the expected result without even have to build a real network. The focus of the project is to examine the effect of the various applications running on Wireless LAN clients in FCSIT Lab. The overall performance might be affected by factors such as the increase number of nodes in the network, the workload of the applications and the file size. The experiments conducted in this project are important to further improve Wireless LAN performance.
1 1.2 Problem Statement Wireless LAN system currently suffers from limited bandwidth, longer response time and the wireless media is error prone. This is caused by factors such as the nature of the physical medium (air) itself, the number of users, the latency, the propagation factors i.e., range and multipath. These problems can decrease performance of Wireless LAN, like inefficient HTTP and TCP performance, packet losses, and network thrashing. It is important to find practical approaches or solutions to improve response time of Wireless LAN so that it can meet the demand of high­speed applications. Study and research on wireless network performance can bring benefit to the problems faced by the wireless network today. 1.3 Project Objective The objectives of this project are: i. Understand the basic wireless network architecture, hardware used in today’s network, learn the physical layout and topology, and use the knowledge to design and analyze the wireless network for the Faculty of Computer Science and Information Technology (FCSIT) wireless Lab. ii. Use special designing and simulation tool, OPNET Modeler version 10.0 to model Wireless LAN, simulate and analyze the expected results for every scenario created for better performance improvement.
2 1.4 Project Scope This project is focusing on the evaluation of Wireless LAN performance in the Faculty of Computer Science and Information Technology (FCSIT) wireless Lab. OPNET Modeler version 10.0 will be use to model and simulate Wireless LAN in the FCSIT Lab. The wireless clients in the lab performing activities like E­mail, File transfer and Web Browsing. The aim is to examine and evaluate the effect of various applications used inside the FCSIT Lab to the Wireless LAN’s overall performance. This includes the overall Wireless LAN throughput and response times for each application. 1.5 Contributions of the project The design and the finding of the project will be the contributions to the area of wireless networks. The performance evaluation of the Wireless LAN in FCSIT Lab will be the beginning of a more advance research to further improve the performance of Wireless LAN. In this project, the Application Layer of the Wireless LAN becomes the main focus, where the appropriate selection of tool to create and simulate the scenarios will give accurate results. By analyzing these results, any weaknesses can be detected and solutions to these problems can be found through the evaluation and studies.
3 1.6 Expected Outcome At the end of this project, the results from various configurations of WLAN parameters will be analyzed and evaluated. i. The Wireless LAN system perform under various configurations. ii. The effect of various kinds of applications being related to the Wireless LAN throughput and response time. iii. The solutions to enhance the Wireless LAN performance in FCSIT lab. iv. The best way to maintain the performance of Wireless LAN in FCSIT Lab. 1.7 Dissertation Organization Chapter 1 briefly explains all the general information of the project. The problems, the objectives, the scope of the project, its contributions and also the expected outcome are also stated in this chapter. Chapter 2 provides the background information and literature review of the related works done by previous researches and studies related to this project. Chapter 3 specifies for the Research Methodology which describes the tool being used and the methodology being applied within the project. All the procedures to conduct the experiments and simulation will also be mentioned here.
4 Chapter 4, the System Analysis will discuss all the important requirements needed to conduct the experiments, the study of the experiment and problems and also how the experimental setup being done. All boundary conditions and assumption will also be stated in this chapter. Chapter 5 is The Proposed Lab Configuration which contains the result and the analysis of the experiments performed by using the simulator. Finally, Chapter 6 is the Conclusion and Future Work that concludes remarks and discusses directions for future research. 1.8 Summary The project has been divided into 6 chapters which are Introduction, Literature Review, Methodology, System Analysis, The Proposed Lab Configuration and Conclusion and Future Work. The focus of the project is to examine and evaluate the effect of various applications used inside the FCSIT Lab to the Wireless LAN’s overall performance. This includes the overall Wireless LAN throughput and response times for Email, FTP and HTTP applications. OPNET Modeler version 10.0 will be use to model and simulate Wireless LAN in the FCSIT Lab. By analyzing the simulation results, any weaknesses can be detected and solutions to these problems can be found through the evaluation and studies.
5 CHAPTER 2 LITERATURE REVIEW This chapter provides the background and related works done by other researches. It also defines the procedures and methodology used in the project. 2.1 Wireless LAN (WLAN) Wireless LAN is a flexible data communication system that can be the replacement or alternatives to wired network. It transmits and receives data by using Radio Frequency (RF) technology and using the air itself as the medium of communications. It provides similar features and benefits of traditional LAN technology, but without any attachment or limitation of wires or cables. Wireless LAN is being widely used today, especially for applications in which mobility is important. Besides mobility, Wireless LAN offers productivities, conveniences and advantages such as flexibility, ease of installation, less cost of ownership where the long term benefits are greatest in dynamic environment which requires frequent changes and moves, and also scalability in configuring varieties of topologies to meet the needs of specific applications and installations. 2.2 IEEE 802.11 Standards Initial IEEE Standard 802.11 was published by the Institute of Electrical and Electronics Engineers (IEEE). Since it was introduced in 1997, IEEE 802.11 for Wireless LAN has seen modifications and improvements in the past years and promising a brighter wireless future. It is the standard which offers; interoperability amongst products from
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