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INDOOR PROPAGATION PREDICTION AND MEASUREMENTS WITHINMULTISTORY BUILDING FOR WIRELESS LAN APPLICATIONS
ABDUSAMEA I.A OMER
UNIVERSITI TEKNOLOGI MALAYSIA
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PSZ 19:16 (Pind. 1/97)
UNIVERSITI TEKNOLOGI MALAYSIA
BORANG PENGESAHAN STATUS TESIS
INDOOR PROPAGATION PREDICTION ANDJUDUL:
MEASUREMENTS WITHIN MULTISTORY BUILDING
FOR WIRELESS LAN APPLICATIONS
SESI PENGAJIAN: 2006 / 2007
Saya ABDUSAMEA I.A OMER
mengaku membenarkan tesis (PSM/ Sarjana/ Doktor Falsafah)* ini disimpan di PerpustakaanUniversiti Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut:
1. Tesis adalah hakmilik Universiti Teknologi Malaysia.2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan
pengajian sahaja.3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara
institusi pengajian tinggi.4. **Sila tandakan ()
SULIT(Mengandungi maklumat yang berdarjah keselamatan ataukepentingan Malaysia seperti yang termaktub di dalamAKTA RAHSIA RASMI 1972)
TERHAD(Mengandungi maklumat TERHAD yang telah ditentukanoleh organisasi/ badan di mana penyelidikan dijalankan)
TIDAK TERHAD
Disahkan oleh
(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)
Alamat Tetap:408 S47 KTC UTM
SKUDAI JOHOR MALAYSIA
PROF. DR. THAREK BIN ABD. RAHMAN
81310 Nama Penyelia
11 MAY 2007 11 MAY 2007Tarikh: Tarikh:
CATATAN: * Potong yang tidak berkenaan.** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak
berkuasa/ organisasi berkenaan dengan menyatakan sekali sebab dan tempohtesis ini perlu dikelaskan sebagai SULIT atau TERHAD.
Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjanasecara penyelidikan, atau disertasi bagi pengajian secara kerja kursus danpenyelidikan, atau Laporan Projek Sarjana Muda (PSM).
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I hereby declare that I have read this project report and in my opinion this project
report is sufficient in terms of scope and quality for the award of the degree of
Master of Engineering(Electrical-Electronics & Telecommunication)
Signature :..
Supervisor : PROF DR.THAREK BIN ABDUL RAHMAN
Date : 11 May 2007
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INDOOR PROPAGATION PREDICTION AND MEASUREMENTS WITHIN
MULTISTOY BUILDING FOR WIRELESS LAN APPLICATIONS
ABDUSAMEA I.A OMER
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering (Electrical-Electronics & Telecommunication)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
MAY 2007
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ii
I declare that this project report entitled Indoor propagation prediction and
measurements within multistory building for wireless LAN applications is the result
of my own research except as cited in the references. The project report has not been
accepted for any degree and is not concurrently submitted in candidature of any other
degree.
Signature :
Name : ABDUSAMEA I.A OMER
Date : 11 MAY 2007
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To
My Beloved Parents , Brothers and Sisters
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iv
ACKNOWLEDGMENT
In the name of Allah, Most Gracious, and Most Merciful
Praise be to Almighty Allah (Subhanahu Wa Taala) who gave me the
courage and patience to carry out this work. Pease and blessing of Allah be upon his
last prophet Mohammed (Sallulaho-Alaihe Wassalam) and all his companions
(Sahaba), (Razi-Allaho-Anhum) who devoted their lives towards the prosperity and
spread of Islam.
My deep appreciation and heartfelt gratitude goes to my supervisor,
PROF.DR THAREK BIN ABDUL RAHMAN for his kindness, constant endeavor,
and guidance and the numerous moments of attention he devoted through out thiswork.
I extend my deepest gratitude to my close friend, Eng. Ibrahim Abuharba for
his encouragement and motivation. Also I would like to thank friends and stuff in
wireless communication center (WCC) for their help facilities and for providing
conductive working environment
Family support plays a vital role in the success of any individual. I would like
to convey a heartfelt thanks to my parents, brothers, and other family members
including all my uncles, ants and their families; their prayers and encouragement
always helped me take the right step in life.
A heartfelt gratitude and acknowledgement are due to the Libyan community
in UTM, Skudai for their kindness, care, valuable advices and cooperation, which
generates a similar environment as what I left.
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v
ABSTRACT
In recent years, the possibility of using radio for data and voice
communications inside the buildings has become an attractive proposition. A
prerequisite to the design of indoor radio communication systems is knowledge of
indoor propagation characteristics. These characteristics can be used to determine theoptimum location of the base station antenna for a desired coverage within a
building. Propagation prediction within buildings is made difficult by the occurrence
of various propagation phenomena which depend on specific building structures. In
this project the investigation for WLAN system is done for three different buildings
inside University of Technology Malaysia. The Site Ware Technology's site specific
propagation prediction tool is a three-dimensional (3-D) ray tracing code employing
modified shoot and bounce ray(SBR) method know as the Vertical Plane Launch
(VPL) will be used to predict indoor propagation effects with different building
structures to show the prediction of the path loss and the time delay spread for
WLAN system inside these buildings, also a comparison between the real time
measurements using AirMagnet software and the prediction using VPL software
has been done for verification and the AutoCAD tool with the help of Ms Excel, was
used to measure all the building's dimensions for highly accurate building database.
The results from both prediction and measurement are in form of numbers, so Matlab
has been used to present these outputs in 2D display. Finally, based on the evaluation
results, we provide a set of recommendations that might help to improve this work
and fulfill the indoor user requirements.
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ABSTRAK
Syak kebelakangan ini , penggunaan radio untuk komunikasi data dan suara
dalam bangunan telah menjadi suatu proposisi yang menarik . factor yang diperlukan
dalam rekaan sistem komunikasi radio dalaman adalah pengetahuan tentang karakter-
karakter perambatan dalaman . karakter- karakter ini boleh digunakan dalam
penentuan lokasi optima antena stesen asas bagi sesuatu , rangkuman dalam
bangunan yang diinginkan ramalan perambatan dalam bangunan menjadi sukar
dengan kejadian pelhagi fenomena perambatan yang bergantung kepda struktu
struktu spesifik bangunuan . dalam projek ini ,siasatan sistem WLAN dilaksanakan
untuk tiga bangunan yang berbeza dalam Universiti Teknologi Malaysia . alat
ramalan perambatan lokasi spesifik oleh site ware technology ialah tiga dimensi
(3D)ray tracing kod yang menggunakam modifikasi shoot dan bounce ray(SBR) cara yang juga dikenali sebagai Vertical Plane Launch (VPL). la akan
digunakan dalam meramal efek-efek perambatan dalaman dengan pelbagai Stnrkuer
beugunan berbeza whtuk menunjukkan ramalan path loss dan time delay opread
bagi sistem WLAN dalam bengunan serta perbandingan antara pengukuran sebener
menggunalcan software dilaksanakan untuk tujuan verifikasi. Dengan bantuan Ms
Excel, alat antocad digunakam untuk mengukur samua dimensi bengunan untuk
memperoleh dadbase bangunan yang dalam bentuk numbor-nombor. Oleh itu,
Matlab digunakan untuk menunjuklcan output-output ini dalam pameran secara 2D.
Akhir sekali dengan berpandutcan hasil-hasil evausasi, satu set cadangan membina
dalam meningkatkan kerja ini dan mencapai kehendak-kehendak pengguna dalaman
akan dibekalkan.
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vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENTS ivABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF SYMBOLS xv
LIST OF APPENDENCES xvii
1 INTRODUCTION 1
1.1 Overview 11.2 Problem Statement 2
1.3 Objective of the Project 21.4 Scope of the Project 2
1.5 Methodology of the Project 3
1.5.1 Site Survey 3
1.5.2 Data Collection of Multistory buildingusing AutoCAD
3
1.5.3 Excel Files 3
1.5.4 VPL Simulation 3
1.5.5 Real time measurement 4
1.6 Organization of the Thesis 6
2 LITERATURE REVIEW 7
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viii
2.1 Wireless Local Area Network (WLAN) 7
2.1.1 Introduction 7
2.1.2 Benefits of Wireless LANs 7
2.1.3 Architecture of a Wireless LAN 8
2.1.3.1 Stations 8
2.1.3.2 Access Points (APs) 8
2.1.3.3 Wireless Clients 9
2.1.3.4 Basic Service Set 9
2.1.3.5 Independent Basic Service
Set 9
2.1.3.6 Infrastructure Basic Service
Set9
2.1.3.7 Extended Service Set 10
2.1.3.8 Distribution System 10
2.2 IEEE 802.11 Standards 10
2.3 Indoor Radio Wave Propagation 12
2.3.1 Reflection: 13
2.3.2 Diffraction: 142.3.3 Refraction 152.3.4 Scattering 15
2.3.5 Indoor Path Loss 16
2.3.6 Free Space Los 16
2.3.7 Line of Site Path Loss 18
2.3.8 Obstructed Path Loss 192.3.9 Doppler frequency shift 20
2.3.10 Multipath and Fading Effects 22
2.3.11 Delay Spread 24
2.3.12 Raleigh Fading 252.3.13 Rician Fading 25
2.3.14 Related work 26
3 RAY TRACING SOFTWARE AND 30
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x
5.1 Conclusion 635.2 Future Work
64
REFERENCES 65
Appendices A - F 67-167
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xi
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 WLAN standards 12
2.2 2.4 GHz Signal Attenuation 20
2.3 Diffierent Between two types of ray tracing models 29
3.1 Part of WCC building database 363.2 Example of the receivers database 37
3.3 Interior building database 39
3.4 Simulation Command input 40
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xii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
1.1 AirMagnet Software with Laptop 4
1.2 Flow chart of the methodology 5
2.1 Access Point infrastructure 8
2.2 Wireless Local Area Network Architecture using anInfrastructure BSS
10
2.3a Reflected Signal on partial reflective surface 13
2.3b Reflected Signal on perfect reflective surface 13
2.4 Diffraction of a Signal 14
2.5 Refracted wave 15
2.6 Scattered Wave front on an I-beam 16
2.7 Free Space Radiating Point Source 17
2.8 2.4GHz Typical Path Loss 18
2.9 Multiple Floors Indoor Path Loss 19
2.10 Doppler frequency shift effect 22
2.11 Multipath signal in indoor environment 22
2.12 Small Scale Fading 24
2.13 Impulse response and frequency transfer function of a
multipath channel.24
2.14 Measurement system by Symbol 26
2.15 Signal level without pepole 27
2.16 Signal level with present pepole 27
2.17 Effect opening and closing the door 28
3.1 Two-Ray Model 31
3.2 Ray generation in horizontal plane (Liang and Bertoni
1998)33
3.3 Flow chart of ray-tracing simulation based on the VPL 34
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xiii
method (Liang and Bertoni 1998)
3.4 Sample of the AUTOCAD Building map of WCC 36
3.5 AutoCAD Receiver location map 37
3.6 Command input simulation 41
4.1 Example of power and delay spread output 44
4.2 Example of impulse response output 45
4.3 Example of ray path information output 46
4.4 Example of AirMagnet measurement (Kolej Perdana) 47
4.5 Simulation Path Loss for Mobile Lab room (WCC) 48
4.6 Time delay spread for Mobile Lab room (WCC) 49
4.7 Simulation Propagation predictions Path Loss for
(WCC) 49
4.8 Time delay spread for WCC 50
4.9 Kolej Perdana First floor Path loss propagation
predication at 2400MHz Carrier Frequency 50
4.10 Kolej Perdana Second floor Path loss propagation
predication at 2400MHz Carrier Frequency 51
4.11 Kolej Perdana Third floor Path loss propagation
predication at 2400MHz Carrier Frequency 51
4.12 Kolej Perdana Forth floor Path loss propagation
predication at 2400MHz Carrier Frequency 52
4.13 Kolej Perdana Fifth floor Path loss propagation
predication at 2400MHz Carrier Frequency 52
4.14 Kolej Perdana Sixth Floor Path loss propagation
predication at 2400MHz Carrier Frequency 53
4.15 Kolej Perdana Seventh Floor Path loss propagation
predication at 2400MHz Carrier Frequency 53
4.16 Kolej Perdana All the seven Floors Path loss
propagation predication at 2400MHz Carrier Frequency 54
4.17 Kolej Perdana-One Floor Path loss propagation
predication at 2400MHz Carrier Frequency (Based on
assumption that the building is only one floor) 54
4.18 Kolej Perdana One Floor Path losses Comparison 55
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xiv
between 1 ray (blue) model and 2 ray model (red)
propagation predication at 2400MHz Carrier Frequency
4.19 Time delay spread for the First Floor Kolej Perdana 55
4.20 Time delay spread for the Second Floor Kolej Perdana 56
4.21 Time delay spread for the Third Floor Kolej Perdana 56
4.22 Time delay spread for the Fourth Floor Kolej Perdana 57
4.23 Time delay spread for the Fifth Floor Kolej Perdana 57
4.24 Time delay spread for the Sixth Floor Kolej Perdana 58
4.25 Time delay spread for the Seventh Floor Kolej Perdana 58
4.26 Time delay spread for All the Seven Floors Kolej
Perdana 59
4.27 Kolej 11 All the four Floors Path loss propagation
predication at 2400MHz Carrier Frequency 59
4.28 Time delay spread for all the four Floors Kolej 11 MA7 60
4.29 comparison between real-time measurements and
simulation for Kolej Perdana 61
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xv
LIST OF SYMBOLS
WLAN - wireless local area networks
WCC - Wireless Communications Center
IEEE - Institute of Electrical and Electronic Engineering
ETSI - European Telecommunications Standards Institute
VPL - Vertical Plane Launch
Wi-Fi - Wireless Fidelity
LOS - Line of sight
OFDM - Orthogonal frequency division multiplexing
DSSS - Direct sequence spread spectrum
Pt - Transmitting power
Pr - Receiving power
Gt - Transmitter antenna gain
Gr - Receiver antenna gain
Ar - Effective aperture of antenna
- Wavelength
C - Velocity of light
dB - Decibels
- Incidence angle
f - Frequency
ht - High of receiver antenna
hr - High of transmitter antenna
A - Attenuation factor
- Ground reflection coefficient
r1, r2 - Phase path distance along
h - Fresnel zone radius to the knife edge
o - Free space wavelength
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d - Distance difference
1d - Distance from transmitter to obstacle
2d - Distance from transmitter to obstacle
- Delay spread
v - Speed of portable
fc - Carrier frequency
L - Path loss
L0 - Reference loss
Li - Floor loss factor
D - Distance
h(t) - Impulse response
nA - Amplitude of signal
n - Arrival time
n - Arrival phase
iE - Received field amplitude
oE - Transmitting field strength
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xvii
LIST OF APPENDICES
APPENDIX TITLE PAGE
A WIRELESS COMMUNICATION CENTER
SIMULATION DATABASES67
B KOLEJ PERDANA SIMULATION DATABASES 76
C KOLEJ 11 MA7 BUILDING SIMULATION
DATABASES 91D RAY TRACING PROPAGATION PREDICTION 104
E AIR MAGNET SOFTWARE
F AUTOCAD IMPLEMINTATION 130
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CHAPTER 1
INTRODUCTION
1.1 Overview
The past decade has witnessed a phenomenal growth in wireless
communication. Indoor wireless communication - such as is associated with personal
communication (PCS) and wireless local- area networks (LANs) - is exploding
rapidly. The need for an efficient way to evaluate radio propagation in buildings is
increasing. It is also critical to optimize the locations of the base stations required toensure satisfactory system performance. Consequently, radio-propagation prediction
for indoor environments, which forms the basis for optimizing the location of the
base stations, has become an important research topic.
Indoor radio propagation is not influenced by weather conditions, such as
rain, snow, or clouds, as is outdoor propagation, but it can be affected by the layout
in a building, and especially by the use of different building materials. Owing to thereflection, refraction, and diffraction of radio waves by objects such as walls,
windows, doors, and furniture inside the building, the transmitted signal often
reaches the receiver through more than one path, resulting in a phenomenon known
as multipath fading [1].
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2
1.2 Problem Statement
Wireless LAN have become widely spread over the last few years, it has been
one of the most significant research topics to investigate how radio waves propagate
inside office environments, since local objects like pillars, walls, doors and windows
may reduce the link performance of such low power systems.
The existing for indoor environments is that the signal propagated from the
transmitter antenna will experience many different signal transformations and paths
with a small portion reaching the receiver antenna. Awareness of this process will
assist the user to better understand radio performance limitations.
1.3Objective
This project is aiming to predict and measure the signal strength of wireless
LAN in a multi storey building (Kolej Perdana) in the University Of Technology
Malaysia in order to Obtain best efficiency and coverage of indoor propagation for
wireless LAN systems.
1.4 Scope of project
To provide proper study of wireless LAN propagation signal in multi storey
building, in which the signals are traced , and to build the database of a multi storey
building by using AUTOCAD and MS EXCEL Software; the simulation results will
be Presented by using MATLAB software for visualizing; The prediction will be
done at a carrier frequency 2.4GHz (based on IEEE 802.11 b/g standards) the
simulated result will be compared with the real time measurements that obtained
using Air magnet software In order to Analyze the simulated result.
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3
1.5 Project Methodology
1.5.1 Site Survey
Site survey involved in locating the place to be measured. As initial stage of
this project Wireless Communication Center (WCC) in Universiti Teknologi
Malaysia was the first place to be tested.
In the second stage of this project (kolej perdana) will be our target in the
following sections the procedures that have been taken in order provide a good
evaluation of coverage are introduced.
1.5.2 Data Collection of Multistory building
Building data base was provided by WCC as DWG file (DraWinG) witch
will be imported to CAD so all the measurements of the building dimensions can be
obtained easily.
1.5.3 Excel Files
Upon having the dimensions of the multistory building with the help of
AUTOCAD the dimensions are entered into an excel file , after words a file.txt can
be generated to be imported to VPL .
1.5.4 VPL Simulation
Firstly selecting up the parameters for VPL such as increment angel betweensuccessive rays, operating frequency (in our case 2.4 GHZ), fresnel zone width first
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4
and second zone, antenna type (in our case monopole) Secondly, simulation is
carried out and the outcome of the simulation is tested If no errors, the results can be
plotted by using MATLAB two of the most graphs that will be plotted are path loss
and time delay spread .
If error occurs, then simulation must be repeated by changing either the
parameters of the VPL or the TXT file that was generated by Excel.
1.5.5 Real time measurement
Figure1.1 AirMagnet Software with Laptop
With the use ofAir Magnet software, real time measurements can be conducted to
measure the actual strength andpath loss of the signal.
Once the real time test has finished a comparison will be done with the predicted
result, the comparison will be in terms of path loss and time spread delay Upon this
comparison, an analysis can be done to evaluate the tested positions for Access
Points and Receivers to be located for best coverage Final recommendations can be
made to improve the performance of the network.
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5
Compare between
measured &
simulated results
Data Collection
Using AutoCAD
NO
Result Analysis
Collecting
parameters
Done
Measurements using
Air magnet software
Generate Excel files
Building database Receiver point databaseInterior building data base
YESSimulation
Using VPL
Success
UPDATING
DATABASE
Illustrate simulation
result using "MATLAB"
Site Survey
Figure1.2 Flow chart of the methodology
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For
Simulat
ion6
1.6 Organization of the Thesis
Chapter 1 contains some brief overview of WLAN systems In addition to this, the
problem statement , objective and the scope of the research have been described.
Finally, the flow chart of how the work of this project has been carried out was also
illustrated.
The literature review is performed in chapter 2. Some introduction about the
WLAN architecture and propagation paths and WLAN propagation mechanism are
introduced such as reflection, refraction, diffraction, delay spread and multipath
fading, the last part shows a summary of some related works.
Chapter 3 contains the some Propagation Models and brief explanation about
vertical plane launch method , the types of databases needed for the simulation are
described and some examples are provided also the outputs of the simulation
software are briefly described and the command input for the simulation software
have been provided.
Chapter 4 contains the results from VPL, result from AirMagnet software,
Visualization result in 2D by Matlab, in this chapter also include some analysis that
is done based on the wireless communication principles and fundamentals.
Finally, Chapter 5 contains the summary of the thesis and also includes some
suggestions for future work.
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CHAPTER 2
LITERATURE REVIEW
2.1 Wireless Local Area Network (WLAN)
2.1.1 Introduction
A wireless LAN or WLAN is a wireless local area network, which is the
linking of two or more computers without using wires. It uses radio communication
to accomplish the same functionality that a wired LAN has. WLAN utilizes spread-
spectrum 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 be connected to the
network this technology is becoming more and more popular, especially with the
rapid emergence of small portable devices such as PDA (Personal Digital
Assistants)[4].
2.1.2 Benefits of Wireless LANs
Wireless LANs offer users an array of benefits ranging from cost efficiency
to seamless integration with other networks.
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called the SSID which is a 32 byte (maximum) character string. Example: linksys
(the default SSID for Linksys routers).
2.1.3.8 Distribution System
A distribution system connects Access Points in an extended service set. A
distribution system is usually a wired LAN but can be a wireless LAN.
Figure 2.2: Wireless Local Area Network Architecture using an Infrastructure BSS
2.2 IEEE 802.11 Standards
IEEE 802.11 is a family of specifications for WLANs developed by the
Institute of Electrical and Electronics Engineers. The 802.11 standard specifies the
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Parameters for both the physical and medium access control (MAC) layers of a
WLAN [3]. The physical layer handles the transmission of data between nodes. The
MAC layer consists of protocols responsible for maintaining the use of the shared
medium. Work on 802.11 began in 1987 within the IEEE 802.4 group.
There are three physical layers for WLANs: two radio frequency
specifications (RF -direct sequence and frequency hopping spread spectrum) and one
infrared. Most WLANs operate in the 2.4 GHz license-free frequency band and have
throughput rates up to 2 Mbps. There are various versions of the 802.11 standard. A
brief description of the more popular revisions is given below.
A. 802.11a: 802.11a operates at radio frequencies between 5 GHz and 6 GHz
[6]. The modulation scheme used is orthogonal frequency-division multiplexing
(OFDM). OFDM, also called multicarrier modulation, uses multiple carrier signals at
different frequencies, sending some of the bits on each channel. This is similar to
Frequency Division Multiplexing (FDM). The only difference between FDM and
OFDM is that in OFDM all the sub-channels are dedicated to a single data source.
The data rates vary based on the noise level, distance from the transmitting antenna,
and the propagation environment. Possible data rates for 802.11a are 6, 9, 12, 18, 24,
36, 48, and 54 Mbps. Maximum range for this standard is 200 feet.
B 802.11b: 802.11b often called Wi-Fi, being the most popular of all the
standards, operates in the 2.4 GHz frequency [7]. It is an extension of the 802.11
standard. Typical data rates for 802.11b are 5.5 and 11 Mbps. The modulation
scheme used is Direct Sequence Spread Spectrum. The chipping rate is 11 MHz, the
same as in 802.11, providing the same occupied bandwidth. Although the data rates
are slower than 802.11a, the range is higher, up to 300 feet. The frequency band used
(2.4 GHz) can have significant interference problems from such devices as
microwave, cordless phones, and Bluetooth devices.
C 802.11g: 802.11g is the newest member of the 802.11 family. This standard
combines the best of 802.11a and 802.11b. Like 802.11b, 802.11g operates in the 2.4
GHz frequency and can achieve ranges up to 300 feet, but like 802.11a, it reaches
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speeds up to 54 Mbps. 802.11g uses a hybrid complementary code keying OFDM
modulation [8].
D 802.11i: 802.11b uses Wired Equivalent Privacy (WEP) protocol to address
security concerns. WEP itself is more or less an implementation of encryption with
built-in message authentication and data integrity systems. The sheer number and
variety of vulnerabilities discovered within WEP shows what could arise when
security is not designed from the ground up. The future of wireless LAN security is
currently being entrusted to 802.11i [9] [10]. IEEE is developing this wireless LAN
standard, which focuses strictly on security and improving upon the protocols offered
by the previous 802.11 standards. There are three main areas that the IEEE 802.11i
wants to improve on over 802.11b: 1) authentication, 2) key management and 3) data
transfer. All of these areas were severely lacking in WEP.
Table 2.1: WLAN Standards
Protocol Release Date Frequency Bandwidth
IEEE 802.11 1997 2.4 GHz 1, 2 Mbps
IEEE 802.11a 1999 5 GHz
6, 9, 12, 18, 24,
36, 48, 54 Mbps
IEEE 802.11b 1999 2.4 GHz 5.5, 11 Mbps
IEEE 802.11g 2003 2.4 GHz6, 9, 12, 18, 24,
36, 48, 54 Mbps
IEEE 802.11n expected mid-2007 2.4 GHz 540 Mbps
2.3 Indoor Radio Wave Propagation
The propagated electromagnetic signal in the indoor environment can
undergo three primary physical modes. These are reflection, diffraction, and
scattering [3]. The following definitions assume small signal wavelength, large
distances (relative to wavelength) and sharp edges for a Typical indoor scenario. the
free space wavelength at 2.4 GHz is 4.92 inches. This wavelength relative to flat
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surfaces is sufficiently small for wave propagation mechanisms to hold true.
Typically, the distances between walls, floors and ceilings are on the order of 10 feet
or greater, and the office environment contains many vertical and horizontal edges
and surfaces.
2.3.1 Reflection:
The propagated signal striking a surface will either be absorbed, reflected, or
be a combination of both. This reaction depends on the physical and signal
properties. Physical properties are the surfaces geometry, texture and material
composition. Signal properties are the arriving incident angle, orientation, and
wavelength.
Figure 2.3a. Reflected Signal on partial reflective surface
Object surface
Figure 2.3b Reflected Signal on perfect reflective surface
Perfect conductors will reflect the entire signal. Other materials will reflect
part of the incident energy and transmit the rest. The exact amount of transmission
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and reflection is also dependent on the angle of incidence, material thickness and
dielectric properties. Major contributors to reflection are walls, floors, ceilings and
furniture.
2.3.2 Diffraction:
As shown in Figure. 2.4. A diffracted wave front is formed when the
impinging
Figure 2.4: Diffraction of a Signal
Transmitted signal is obstructed by sharp edges within the path. Diffraction
occurs when obstacles are impenetrable by the radio waves. Based on Huygens's
principle, secondary waves are formed Behind the obstructing body even though
there is no line of site [3]. Indoor environments contain many types of these edges
and openings, both orientated in the vertical and horizontal planes. Thus the resultant
diffracted signal is dependent on the geometry of the edge, the spatial orientation, as
well as dependent on the impinging signal properties. Such as amplitude, phase and
polarization. The result of diffraction of a wave at an obstacle edge is that the wave
front bends around and behind the obstacle edge. Diffraction is best demonstrated by
the radio signal being detected close to the inside walls around corners and hallways.
This phenomenon can also be attributed to the waveguide effect of signals
propagating down hallways.
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2.3.3 Refraction
The Figure 2.5 below shows Another phenomenon common to most radio
waves is the bending of the waves as they move from one medium into another in
which the velocity of propagation is different. This bending of the waves is called
refraction.
Figure 2.5: refracted wave
2.3.4 Scattering:
If there are many objects in the signal path, and the objects are small relative
to the signal wavelength, then the propagated wave front will break apart into many
directions. The resultant signal will scatter in all directions adding to the constructive
and destructive interference of the signal that is illustrated in Figure. 2.6 Most
modern office construction contains pressed steel I-beams throughout the wall
supports. Furthermore, construction materials such as conduit for electrical and
plumbing service can add to the scattering effect.
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Figure 2.6: Scattered Wave front on an I-beam
2.3.5 Indoor Path Loss
Path loss is difficult to calculate for an indoor environment. Again, because
of the variety of physical barriers and materials within the indoor structure, the signal
does not predictably lose energy. The path between receiver and transmitter is
usually blocked by walls, ceilings and other obstacles. Depending on the building
construction and layout, the signal usually propagates along corridors and into other
open areas. In some cases, transmitted signals may have a direct path (Line-of-Site,
LOS) to the receiver. LOS examples of indoor spaces are; warehouses, factory floors,
auditoriums, and enclosed stadiums. In most cases the signal path is obstructed.
2.3.6 Free Space Loss
Fundamental to indoor path loss analysis is the free space loss. If the
transmitting antenna were ideally a radiating point source in space, the propagated
surface wave front will exit the point source in a spherical pattern as shown in
Figure. 2.7. The spherical signal energy reduces as the square of the distance. FreeSpace Path Loss (FSPL) is defined as: Spherical radiating wave front
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Fig. 2.7- Free Space Radiating Point Source
2)4
(
dFSPL
= (1)
Whered is distance in meters between the transmitter and receiver, and (lambda) is the wavelength in meters. This equation also implies that as the
frequency increases the loss will be proportionally higher. Relating frequency to
wavelength:
f
c= (2)
Where c is the speed of light, m/s, and frequency, f = cycles per
second.
8103=c
The wavelength of the 2.4 GHz sinusoid is:
=0.125 meters,=12.5 centimeters or=4.92 inches.Free space loss defined in decibels is :
Free Space Loss = 10 log (FSPL) (3)
Where FSPL is from equation 1.
Free Space Loss (FSL) = 40 dB @ 1 meter
Accordingly, the Free Space Loss (FSL) = 60 dB @ 10 meter Therefore, the
free space loss 1 meter away from the transmitter is 40 dB! Thereafter, the signalattenuates at a rate of 20 dB per decade.
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2.3.7 Line of Site Path Loss
For a LOS office scenario, the path loss is given
Figure 2.8 - 2.4GHz Typical Path Loss
(4)
Where FSLref is the free space loss in dB determined in the far field of the
antenna. Usually for indoor environments, this is calculated to be 1 or 10 meters as
shown in equation (3). dtr is the distance between the receiver and transmitter. The
symbol n1 is a scaling correction factor which is dependent on the attenuation of
the propagation environment. In this case, equation (4) is for large indoor spaces.
The n1 factor has been determined from empirical data collected and can be found in
the excellent reference by; [2] T. Rappaport. For line of site application in hallways
the n1 factor has been determined to be less than 2. This is due to the waveguide
effect provided by properties of hallways or corridors. Figure 2.8 shows the free
space attenuation in dB for a typical indoor application. The curve represents variousLOS path losses. The first segment represents the path loss due to free space. The
second and last segments represent a more lossy path. The instantaneous drop
demonstrates the loss due to obstruction of the LOS path.
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2.3.8 Obstructed Path Loss
Obstructed path loss is much more difficult to predict, especially for the
myriad of different indoor scenarios and materials. Therefore, different path loss
models exist to describe unique dominant indoor characteristics. Based on free space
loss and the three propagation phenomenon, the path loss models also account for the
effects of different building types. Examples are multi-level buildings with windows,
or single level buildings without windows.
Figure 2.9: Multiple Floors Indoor Path Loss
It has been shown (See Figure. 2.9) that the propagation loss between floors
begin to diminish with increasing separation of floors non-linearly. The attenuation
becomes less per floor as the number of floors increases. This phenomenon is
thought to be caused by diffraction of the radio waves along side of a building as the
radio waves penetrate the buildings windows. Also, a variety of different indoor
configurations can be categorized for buildings with enclosed offices, or office
spaces consisting of a mix of cubicles and enclosed rooms. Examples of attenuation
through obstacles for various materials are shown in the table below.
Indoor path loss has been shown to be exponential as shown in Fig. 2.8. In
specific cases the models can show deterministic limits. However, in majority of the
cases the obstructed path loss is determined through empirical means followed by
corresponding refinements to the mathematical model.
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Table 2.2: 2.4 GHz Signal Attenuation
Window Brick Wall 2 dBMetal Frame Glass Wall into Building 6 dBOffice Wall 6 dB
Metal Door in Office Wall6 dB
Cinder Block Wall 4 dBMetal Door in Brick Wall 12.4 dBBrick Wall next to Metal Door 3 dB
2.3.9 Doppler frequency shift
When a signal source producing waves at a frequency f and an observer
move relative to one another, the frequency measured by the observer (f) depends
on the details of the relative motion; this change in frequency is known as the
Doppler Shift.
The Doppler shift equations shown below work for any wave moving in a
medium, when the motions of the source and observer are along the line joining
them. In the equations below, v, vo, and vs,are the speeds of mobile unit, observer
and source relative to the medium; if the medium (e.g. air) is moving, vo and vs
should be measured with respect to the medium.
If the observer is moving and the source is stationary, the measured frequency
is:
f = f(v v
O)
v
(1)
where the upper sign corresponds to an approaching observer and the lower
sign corresponds to a receding observer.
If the source is moving and the observer is stationary, the measured frequency
is:
f = fv
(v m vS )(2)
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where the upper sign corresponds to the source approaching and the lower
sign corresponds to the source receding from the observer.
More generally, where both the source and observer are moving:
f = f(v v
O)
(v m vS)
(3)
Note that the signs in the numerator and denominator are independent of each
other. Use the following general rules for the signs: in the numerator, the upper sign
is used if the observer is moving towards the source and the lower sign if moving
away from the source; in the denominator, the upper sign is used if the source is
moving towards the observer and the lower sign if moving away.
An easy way to remember the signs is simply to remind oneself whether or
not the the observed frequency is going to want to increase or decrease and use
whichever signs do that. For example, when an observer is moving away from a
source, the waves are going to move across it at a slower rate than if it was sitting
still, which means the observed frequency is going to decrease. In order for that to
happen mathematically, the numerator in Eq. (3) needs to decrease, so clearly we
want to use the (-).
Similarly, if a source is moving toward an observer, its going to smoosh
the waves together as it emits them, which means an increase in observed frequency.
This will be accomplished by making the denominator in Eq. (3) smaller, which
requires using the (-) again.
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Figure 2.10: Doppler frequency shift effect
2.3.10 Multipath and Fading Effects
Figure 2.11: Multipath signal in indoor environment
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As a transmitted radio wave undergoes the transformation process presented
in the indoor Environment it reaches the receiving antenna in more than one path,
thus giving rise to Multipath. Relating Multipath to propagation models and path loss
employs stochastic theory and probability distribution functions (PDF). A somewhat
understated view of the Multipath effect is; signal variations within a building, where
there are no clear line of site signal paths between the receiver and transmitter,
approximate a Rayleigh distribution. For receivers and transmitters that have line of
site signal paths, the distribution is Rician[3].
A Rayleigh distribution function describes a process where a large number of
incident rays (as seen at the receiver antenna) add randomly with respect to
amplitude and time. A Rician distribution is similar to a Raleigh PDF except that a
Rician PDF contains a strong dominant component. Usually the dominant component
is the direct line of sight or ground reflection ray [5].
Multipath introduces random variations in the received signal amplitude over
a frequency bandwidth. Multipath effects also vary depending on the location of the
antenna as well as the type of antenna used. The observed result of random signal
distributions, as seen by the WLAN radio receiver, will be the in and out variation
(fading) of the signal (See Figure 2.12). Variations as much as 40 dB can occur.
Fading can be very rapid or slow. This depends on the moving source and the
propagation effects manifested at the receiver antenna. Rapid variations over short
distances are defined as small-scale fading. With respect to indoor testing, fading
effects are caused by human activities and usually exhibit both slow and fast
variations. Sometimes oscillating metal bladed fans can cause rapid fading effects.
Applications of the WLAN radio indoors can either be fixed or mobile. Thus, small-
scale fading effects can be further described using Multipath time delay spreading.
Since the signal can take many paths before reaching the receiver antenna, the
signals will experience different arrival times. Thus, a spreading in time (as well as
frequency) can occur. Typical values for indoor spreading are less than 100
nanoseconds. Different arrival times ultimately create further degeneration of the
signal. Finally, those who are involved in the wireless discipline whether as a
designer or a user must be aware of construction materials, interiors and exteriors,
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and locations of a building to best position WLAN radio equipment. For optimal
performance the user should also consider work activities ultimately.
Figure 2.12 - Small Scale Fading
The WLAN user needs to understand the relationship between indoor propagation
effects and how WLAN performance is affected.
2.3.11 Delay Spread
Because ofmultipath reflections, the channel impulse response of a wireless
channel looks likes a series of pulses. In practice the number of pulses that can be
distinguished is very large, and depends on the time resolution of the communication
or measurement system.
Figure 2.13 Impulse response and frequency transfer function of a multipath
channel.
In system evaluations, we typically prefer to address a class of channels with
properties that are likely to be encountered, rather than one specific impulse
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response. Therefor we define the (local-mean) average power which is received with
an excess delay that falls within the interval (T, T+ dt). Such characterization for all
Tgives the "delay profile" of the channel.
The delay profile determines the frequency dispersion, that is, the extent to
which the channel fading at two different frequenciesf1 andf2 is correlated.
2.3.12 Raleigh Fading
Rayleigh fading , also called fast fading , is commonly used to describe
multipath fading in a two way radio communication system that occurs when there id
not a clear path between the transmitter and the receiver . Rayleigh fading describes
the statistical distribution of the radio signals power as received by a radio receiver.
Rayleigh fading occurs when two or ore waves from the transmitter are reflected and
form standing wave pairs in space, when the standing pairs occur, the signals are
summed in amplitude, which causes irregular signal strength variations, which then
usually results in a reduction in signal strength.
Rayleigh fading occurs when the receiving antenna moves through
constructive wave fronts. The receivers susceptibility to fading is a function of
frequency of oration and the receiver bandwidth. the higher the frequency , the
shorter the distance id between wave crests, the wider the bandwidth, the susceptible
the receiver is to fading . a value of 5dB is typically used in accounting for Rayleigh
fading in the link budget.
2.3.13 Rician Fading
Rician fading describes the statistical energy distribution of direct wave path
from a transmitter to a receiver. This is also referred to as the light of sight path, and
it represents the variation in signal strength that occurs when the path from a
transmitter to a receiver is not obstructed . Rician fading describes a condition thatoccurs when one dominant signal arrives at the receiver with several other weaker
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multipath signals. Rician fading is not that common in two way communication
because building or other objects usually obstruct a line of sight to the source.
2.3.14 Related works
A lot of works has been done on the radio propagation prediction. Although
the concept is the same, a lot of techniques has been proposed by a lot of reseachers.
In this section, some of the previous work is introduced to illustrate these diiferent
techniques for prediction. This will eventually lead to fully understanding the
propagation prediction measurements.
Martin , Stanislav and Pavel (Technical University ,Ireland) ,They srarted on
a site survey based on empirical measurements or planning using a software tool
with build-in signal propagation models.
Measurement Equipment
1- RF-Site Survey Software Tool
2- Measurement system by Symbol
Figure 2.14 Measurement system by Symbol
They investigated two models of propagation redictions These Methods are:
1- 1-Manual Deployment using A Site Survey based on Empirical
Measurements (Network is Up and running )
2- 2-Using Software Tool with built-in Signal propagation models
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The first method is based on the empirical and semi-empiricalmodels which
are primarily based on statistically processed representative measurements. As the
most popular examples, One-Slope and Multi-Wall models .
In the second one, it is more based on software planning (using a propagation
model) which is much more convenient and cost-effective way to deploy a wireless
network than a site survey with lots of measurements and empirical decisions. Using
simulations many different configurations of the network can be tested with no
expenses to find an optimal solution.
The Measurements that were conducted during the test are RSSI, Coverage ,
Data Rate , Signal quality. The fillowing graphs illustrated some of these
measurements.
Figure 2.15 :signal level without pepole
Figure 2.16 :signal level with present pepole
At first, the measurements were performed without the presence of people.
The doors were opened and closed and the orientation of the notebook was changed
in order to nvestigate how it would distort received signal strength. In the Figure .
2.16 and 2.17 the 5 dB variations due to the "door state" can be clearly seen. Few
high attenuation peeks were caused by a sporadic movement of people at the corridor
which was difficult to prevent even in such a limited area.
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Figure 2.17: effect opening and closing the door
It is understood from the graph that the effect opening and closing the door
can be even more distinct when hand-held device is used. The influence on how it is
held, i.e. shadowed by a user, is tremendous. This will give us a real picture of how
accurate our measurements can be.
Eventaully, they have came with these conclusions; Empiriacal measurements
are more precise since they include real environment e.g. people movement , doors
open and closed
However, it is very time consuming (expensive) and usually it is feasible to
perform measurements in limited number of location .
They have recommended for reliable network, both of these methods might
be used in order to fully get an optimised network. In the next table, a summary of
some papers survey is illustrated.
Two main options are available for the implementation of a ray tracing
model known as ray launching , and point to point ray tracing .
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Table 2.3 diffierent Between two types of ray tracing models
MMeetthhoodd Raytracing p to p Ray launching
AAddvvaannttaaggee More accurateSimple computational
time
DDiissaaddvvaannttaaggeeExtremely high
computational time
Less accurate
For the measurements of the ray tracing, it is a commonly used computational
method for site specific prediction of the radio channel characteristics of wireless
communication system. this provides time delay and path loss of the arrival
information for multi path reception condition.
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CHAPTER 3
RAY TRACING SOFTWARE AND SIMULATION
3.1 Propagation Models
3.1.1 Two-Ray tracing Model
Site specific propagation models are based on electromagnetic-wave
propagation theory to characterize indoor radio propagation. Unlike statistical
models, site specific propagation models do not rely on extensive measurement, but a
greater detail of the indoor environment is required to obtain an accurate prediction
of signal propagation inside a building. In theory, electromagnetic-wave propagation
characteristics could be exactly computed by solving Maxwells equations with the
building geometry as boundary conditions. Unfortunately, this approach requires
very complex mathematical operations and requires considerable computing power,
beyond that of current microcomputers. Hence it is not economical for the
characterization of indoor radio wave propagation. Therefore, approximate numerical
methods are of interest. Ray tracing is an intuitively appealing method for calculating
radio signal strength, time-invariant impulse response, root mean square (RMS)
delay spread and related parameters in an indoor environment [12].
The concept of ray-tracing modeling is based on the fact that high-frequency
radio waves behave in a ray-like fashion. Therefore, signal propagation can be
modeled as ray propagation. By using the concept of ray-tracing, rays may be
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(3.1)
Where Pt is the transmitted power, r1 is the direct distance from the transmitter to the
Receiver, r2 is the distance through reflection on the ground, and ( ) is the
reflection coefficient depending on the angle of incidence and the polarization.
The reflection coefficient is given by
(3.2)
Where = 90- and a = 1/ or 1 for vertical or horizontal polarization,
respectively. r Is a relative dielectric constant of the reflected surface the signal
strengths from theoretical and empirical models.
3.1.2 Vertical-Plane-Launch MethodVertical-Plane-Launch (VPL) method provides a full three dimensional (3-D)
solution with computationally fast way to determine contributing rays and yields an
accurate propagation prediction. The VPL method considers specular reflections
from vertical surfaces and diffraction at vertical edges. It also allows approximation
of diffraction at horizontal edges along the plane of incidence.
The advantage of the VPL over full 3-D shoot and bounce ray (SBR) method
is that it can handle many multiple forward diffraction at horizontal edges. Besides
this, the VPL method provides many other advantages. The VPL method is
applicable for rooftop antenna and areas with mixed building heights that can not be
properly handled by vertical-plane/slant-plane (VP/SP) approximation[14].
The VPL method applies standard shoot and bounce method only at thehorizontal plane and use deterministic approach to determine the vertical
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displacement of ray paths. This method is based on assumption that building walls
are approximately almost vertical.
Figure 3.2 indicates that 2-D rays are generated in horizontal directions from the
source. This method generates a binary tree at intersection point of vertical plane and
exterior surface of building at intersection point, two planes are generated where one
follows the incidence direction and the other one follows the direction of specular
direction.
The vertical path direction can be found based on buildings profile and use
deterministic equation to calculate the vertical displacement and received signal
strength.
Figure 3.2: Ray generation in horizontal plane (Liang and Bertoni 1998)
3.1.3 Algorithm of Simulation Software
The ray architecture is described by the flow chart shown in the Figure 3.3,
the program architecture is divided into three modules that are found intersections
with walls module, find receiver module, and find diffracting corner module.
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hence away from the building and receivers. These simplifications are made because
it is believed that the rays do not contribute to the total received power in a micro
cellular environment, or they occur very infrequently, and their inclusion would
substantially increase the model complexity and computation time.
3.2 Databases for Simulation
There are four types of databases needed to run this simulation completely:
building database, receiver database Interior building database and antenna radiation
pattern database. The building database gives relative location of the building within
the predication area, whereas the receiver database contains the coordinates of the
receiver points. Interior building database is used to model the effect of the building
details on the ray path. Antenna radiation pattern database gives the radiation pattern
of the antenna at every one degree. Since we use monopole antenna and transmitter
and receivers inside a building, terrain elevation database and antenna radiation
pattern database will be ignored, while building interior database will be used [15].
3.2.1 Building database
The building database is comprised of a single American Standard Code for
Information Interchange (ASCII) file which contains six columns of integer and
floating point numbers that represent the building. The first column is a unique
building identity number that must be different from the building number before and
after. The second and third columns are the X and Y coordinates are entered as a
relative position from some arbitrary fixed reference position of the database
coordinate system.. The fourth column is the Z coordinates which representing the
height of the top of the building above the reference plane and the fifth column is Z
which representing the vertical distance that the corner of the building extends
downward from Z, are assigned to each (X; Y) point, while final column in the
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database is representing the relative dielectric constants. The recommended
dielectric constant is 6 because it provides the least error compared to value [15].
Figure 3.4: sample of the AUTOCAD Building map of WCC
Table 3.1:part of WCC building database
Building ID X Y Z Z PL
1 24.961 2.5 3 3 6
1 38.887 2.5 3 3 6
1 38.887 12.937 3 3 6
1 38.072 12.937 3 3 61 38.072 14.637 3 3 6
1 38.887 15.062 3 3 6
1 38.887 26.844 3 3 6
1 24.961 26.844 3 3 6
1 24.961 2.5 3 3 6
2 30.352 20.672 3 3 6
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3.2.2 Receiver Database
The receiver file is also in multi-column format, with each line containing
the coordinates of a single receiver point. The first column represents the receiver
number and the following three columns represent the location of the receiver in x,y
and z coordinates, with respect to the building database coordinate system. The z
value of the receiver point is the height of the ground at the point and not absolute
height of the receiver. The height of the receiver above the ground, which is
specified by the user, is added to the z value to get the height of the receiver [15].
Receiver point
Figure 3.5: AutoCAD Receiver location map
Table 3.2: Example of the receivers database
RX ID X Y Z
1 30.87 19.492 0.79
2 30.87 17.972 0.79
3 31.57 20.172 0.79
4 33.57 20.172 0.79
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5 35.57 20.172 0.79
6 37.57 20.172 0.79
7 38.405 19.472 0.79
8 38.405 18.472 0.79
9 38.405 17.472 0.79
10 30.87 13.242 0.79
11 30.87 12.242 0.79
12 30.87 11.243 0.79
13 32.567 10.572 0.79
14 34.567 10.572 0.79
15 31.57 21.172 0.79
3.2.3 Building Interior Database Format
When the floor plan of building is not known but propagation into the
interior of a building is desired it is possible to assume some assume some average
characteristics of the building. The loss associated with this general description of
the building is due mostly to the penetration through the exterior face and the interior
walls of the building. The first number represents the building and must be a integer
number. The number should correspond with the same building number as the one
being described in the building database file.
The next three numbers represent the average height of each floor, the
height of the first (or ground floor), the average width of the rooms. The following
three numbers represent the type of interior wall, type of floor and the type of
exterior walls and must be integers. Currently, the numbers that represent the wall
and floor types are use directly to determine the penetration loss. In words a wall or
floor with a number 8 means that there is -8dB of loss associated with propagation
through this material [15].
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Table 3.3: Interior building database
.
1 3 3 25 4 8 10 10 0
Number of
Building
Average height offloor and average
width of rooms
Type of wall due
to penetration loss
Number ofelevator
2 3 3 8 4 8 10 10 0
3 3 3 8 4 8 10 0.4 0
4 3 3 8 4 8 10 1 0
5 3 3 8 4 8 10 1 0
6 3 3 8 4 8 10 10 0
7 3 3 8 4 8 10 1 0
8 3 3 8 4 8 10 10 0
9 3 3 8 4 8 10 10 0
10 3 3 8 4 8 10 10 0
11 3 3 8 4 8 10 10 0
12 3 3 8 4 8 10 10 0
13 3 3 8 4 8 10 10 0
3.3 Simulation Command Input
The ray tracing program is run in DOS mode where it performs command
line execution. Three arguments are required to initialize the program with a fourth
argument being optional as shown in the first command input in Table 3.4. The first
argument is building database file name, the second argument is receiver location file
name and the third argument is output file name. The optional input is the
preprocessed data file name. The associated directory of each file name must be
defined correctly. After the program has been initialized correctly, two lines of
information are displayed as second command input in Table 3.4. If the
preprocessed input file name is not given at the initialization stage, a question will
prompt user to decide whether to have a preprocess run again [15].
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Then, the program starts requesting a series of input parameters as listed in
Table 3.4
3.4 Output of the Prediction Tool
There are 3 type of output that can be generated by the prediction program.
They are power and delay spread output, impulse response output, and ray paths
information output. Either power or delay spread output or impulse response output
files. On the other hand, ray path information outputs that contain the individual ray
paths for the receivers can be obtained together with any of the two output files. The
details of the output files are presented in the next chapter.
Table 3.4 simulation Command input
NO Command Input
1 C:\...\runvpl
[
2 Site Ware Technologies, Inc.
Site Specific Propagation Prediction Tool, ver 1.0 28SEP99
No preprocessed file was specified.
Do you want to do a preprocess run? [y/n] n
3 Enter the angle that the ray trace will increment by: 1
4 Enter the maximum number of reflections to calculate: 10
5 Enter the number of diffractions at vertical edges that will be computed: 2
6 Enter the number of operating frequencies: 1
7 Enter the value of frequency 1 [MHz]: 2450
8 Enter the Fresnel zone width used to test screens: 1
9 Consider terrain using digital elevation database? [y/n]: n
10 Compute with 2 ray model? [y/n]: n
11 Impulse Response or Power & Delay Spread Output? [i/p]: p
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12 Is a directional antenna used? [y/n]: n
13 Output individual ray path data? [y/n]: y
14 The ray paths for each receiver is in file `ray_paths___'
15 Enter the x coordinate of the transmitter: 33.38
16 Enter the y coordinate of the transmitter: 20.47
17 Enter the z coordinate of the transmitter: 2.5
18 Number of different transmitter heights at (20,30,50): 1
19 Enter height 1 of the transmitter: 0.3
20 Enter the height of the receivers: 0.1
Figure 3.6: Command input simulation
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CHAPTER 4
RESULTS AND DISCUSSION
4.1 Overview
This chapter will discuss the simulation results and the comparison between
the simulation and the real time measurements of the propagation prediction for the
WALN system in the main campus of universiti tekonologi Malaysia . The study of
the indoor propagation environmentis done in order to obtain the good accuracy,
efficiency and coverage of signal strength, a simulation firstly is done within a
mobile lab, corridor and area around inside WCC in the second stage our target was
a multistory building (kolej perdana) and in the third stage the propagation
prediction was done for (kolej 11 building MA7).
4.2 Output Result from VPL SoftwareThere are 3 types of outputs generated by VPL software. They are power
and delay spread output, impulse response output, and ray paths information.
Output. The type of result can be choose during software run, if user request the ray
path information to be saved, that will be 2 types output file. The results from power
and delay spread or impulse response out put with ray path information for every
receiver. The result of each type of output will be described in the followingsections for each type of results.
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4.2.1 Power and Delay Spread Output
This output file contains the predicted path loss for receivers, a section that
contains the different components that add together to get the total power received,
rms delay spread and mean excess delay. The results for each receiver are listed in a
multicolumn format on a single line with brief heading describing the program
execution parameters. Below the headers, the first column represents receiver
numbers while second to fourth columns list the x, y, and z coordinates for those
receivers. The fifth column is the predicted path loss value in dB. The column after
in between vertical line (|) Separators is breakdown of the total power received into
its separate components. The first two columns indicate value in watt and number of
LOS rays, the second two columns show value in watt and number of reflected rays
that arrived at receiver. The third and forth two columns indicate value in watt and
number of rays that undergo 1 and 2 vertical edge diffraction beside on top of
reflection. The final two columns of data represent the rms delay spread and the
mean excess delay in seconds.
4.2.2 Impulse Response Output
In this result, the header is same with the one used for the power and delay
spread. Below the header is the individual path information according to the
receiver. The first line is the receiver number and the x, y, and z coordinates of the
receiver. Listed below the receiver are the individual rays contributed at the receiver.
The columns represent the angle at which the ray left the transmitter and path length
of the ray in meters, the propagation time in seconds and the predicted path loss in
dB. The fifth and final column is numerical representation of the type or class of
ray.
4.2.3 Ray Path Information Output
The ray path information is stored in separate file for each receiver in every
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Simulation these outputs generate details of each ray path that arrive at a particular
receiving point. Each group of information starts with a # sign heading representing
a single ray path. The heading with a # sign shows the total path length and total
path loss associated with the ray. Information below the heading is a list of x, y, and
z coordinates for all ray segments that combine together to form a complete path
from source to receiving point. The number of ray paths that arrives at a particular
receiving point is depending on the simulation output.
Example of the power and delay spread output
Header
Meanexcessdelay
DelaySpread
Power received fordifferent components
PathLoss
Receivercoordinate
Receivernumber
Figure 4.1: Example of power and delay spread output
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Receivernumber andcoordinate
Path lossdB
PropagationTime
(seconds)
PathLength(meter)
Angle ClassOf ray
Figure 4.2: Example of impulse response output
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Coordinate
For all raySegments
Length andpath loss ofEach ray
Figure 4.3: Example of ray path information output
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4.3 Measurements result using AirMagnet
AirMagnet Software compute many type of data, IP address for access point,
signal strength, level of noise, speed, packet loss and packet retried as shown in
Figure 4.4. This data will generate to every receiver with number of output depend
to the time that use to catcher data , after that take the average of data and compare
them with result that obtain from VPL software.
Measurement Loss
for location RX-59
Figure 4.4 Example of AirMagnet measurement (Kolej Perdana)
The figure 4.4 shows the measurement in one location which is in this case location
RX-59 this receiver point have a predicted path loss -80.96 dB and real time
measurement using AirMagnet software about -80 dB , a comparison between the
predicted path loss and real time path loss will be shown later for 19 receiver point
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4.4 Result Visualization
Matlab is a high level technical computing language and interactive
environment for algorithm development, data visualization, data analysis, and
numerical computation. It includes a set of low-level file input output (I/O)
functions that are based on the I/O function of the American National Standards
Institute (ANSI) Standard C Library.
Matlab was used to extract data from the numerical input and output file
from the VPL ray tracing software. The data are then presented in a 2D graphic
display.
4.4.1 Path Loss and Time delay spread Visualization for WCC
Figure 4.5 Simulation Path Loss for Mobile Lab room (WCC)
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Figure 4.6 Time delay spread for Mobile Lab room (WCC)
Figure 4.7 Simulation Propagation predictions Path Loss for (WCC)
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Figure 4.8 Time delay spread for WCC
4.4.2 Path Loss and Time Delay Spread For KOLEJ PERDANA
Figure 4.9 Kolej Perdana First floor Path loss propagation predication at 2400MHzCarrier Frequency
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Figure 4.10 Kolej Perdana Second floor Path loss propagation predication at2400MHz Carrier Frequency
Figure 4.11 Kolej Perdana Third floor Path loss propagation predication at
2400MHz Carrier Frequency
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Figure 4.12 Kolej Perdana Forth floor Path loss propagation predication at2400MHz Carrier Frequency
Figure 4.13 Kolej Perdana Fifth floor Path loss propagation predication at 2400MHzCarrier Frequency
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Figure 4.14 Kolej Perdana Sixth Floor Path loss propagation predication at2400MHz Carrier Frequency
na Seventh Floor Path loss proFigure 4.15 Kolej Perda pagation predication at
2400MHz Carrier Frequency
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Figure 4.16 Kolej Perdana All the seven Floors Path loss propagation predication at2400MHz Carrier Frequency
Figure 4.17 Kolej Perdana-One Floor Path loss propagation predication at2400MHz Carrier Frequency
(Based on assumption that the building is only one floor)
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Figure 4.18 Kolej Perdana One Floor Path losses Comparison between 1 ray (blue)model and 2 ray model (red) propagation predication at 2400MHz Carrier Frequency
Figure 4.19 Time delay spread for the First Floor Kolej Perdana
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Figure 4.20 Time delay spread for the Second Floor Kolej Perdana
Figure 4.21 Time delay spread for the Third Floor Kolej Perdana
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Figure 4.22 Time delay spread for the Fourth Floor Kolej Perdana
Figure 4.23 Time delay spread for the Fifth Floor Kolej Perdana
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Figure 4.24 Time delay spread for the Sixth Floor Kolej Perdana
Figure 4.25 Time delay spread for the Seventh Floor Kolej Perdana
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-40
Figure 4.28 Time delay spread for all the four Floors Kolej 11 MA7
4.5 Result Analysis
4.5.1 Path Loss and Time Delay Spread
The effects of the fading due to Multipath reception condition in the indoor
environment is the main problem , firstly the propagation prediction was done in one
floor building (WCC) the results of the Path Loss and Time delay spread are presented The Figure 4.5 and Figure 4.6 , Figure 4.7 , Figure 4.8 shows that the
maximum path loss was about (-76 dB ) which is very acceptable for good coverage
, the time delay spread output as in the graphs usually the first arrival signals must
have less error due to less number of paths that the signal must go through before it
reaches the receiver point.
Secondly the Figures from number 4.9 to 4.15 shows the predicted path loss
for Kolej Perdana building its clear form this graphs that the effect of the multifloor
10-13
10-12
10-11
10-10
10-9
10-8
-60
-80
-100
-120
-140
-160
-180
4 Floors Time delay spread
Time in (n sec)
Path
Loss
(-dB)
10-7
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factor (penetration from ceiling) was from 1 dB loss to 25 dB loss depends on the
transmitter location and the material of the ceiling used . a comparison between the 7
floors are presented in Figure 4.16, the figure 4.17 One Floor Path loss propagation
predication at 2400MHz Carrier Frequency (based on assumption that the building is
only one floor) and the figure 4.18 shows one floor Path loss comparison between 1
ray model (blue) and 2 ray model (red) propagation predication at 2400MHz carrier
frequency, figures from number 4.19 to 4.25 shows the different of arriving time for
the signal in every single floor and the Figure number 4.26 shows the time delay
spread for are the 7 floors together , also figure 4.27 shows Kolej 11 building MA7
all the four floors path loss propagation predication at 2400MHz carrier frequency
From this figure we see that the effect of the multifloor factor is almost the same due
to the similarity of the ceiling material and the complexity of the building
architecture, figure 4.28 shows the time delay spread for the MA7 building.
4.5.2 Comparison between Prediction and Measurement Result
Figure 4.29 comparison between real-time measurements and simulation for
Kolej Perdana
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From Figure 4.29 for This comparison have carried out for 18 receiver point
in Kolej Perdana among the corridor the comparison between prediction and
measurement result, we find that loss from both in good agreement except some
receiver point due to Multipath fading effect phenomena, when signals arrive to
receives there are usually a combination of direct and indirect path, if
electromagnetic phase of signal same will make signal strength because it is sum of
this phase and if the electromagnetic phase for signals shift of inverse will drop
signal strength.
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CHAPTER 5
CONCLUSION
5.1 Conclusion
This chapter concludes all the work that has been carried out in this project. It
summarizes the targets achieved and shows how well this work can contribute to give
full understanding of how the propagation prediction can be done using software
based on ray tracing model for WLAN system. Also, it provides some suggestions for
future work that can help to improve this project.
The study on the indoor environmental effect, which affect the radio wave
propagation and visualization of the radio wave propagation with 2 dimensional
introduces effect of reflection, diffraction, multipath fading, also the time delay spread
and Path loss of the propagation mechanism are presented, the main issue that effects
the signal coverage in multistory building was the multifloor factor which was clear
from the obtained results.
Indoor wireless LAN coverage can be done based on the said study and the
experiments, in our days WLAN is important technology to provide higher data rate
to the indoor user.
The Indoor propagation prediction is crucial to optimize coverage prediction
and characterize indoor channel parameters.
Field measurements have been carried out to verify the simulation results.
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In the first stage of this project one floor building (WCC) was simulated for
the propagation prediction to see how the signal will be affected in such complex
office. After that in the second stage our target was multi-storey building with
complex indoor architecture (Kolej Perdana) to see how the multifloor factor can
effect the signal and also we have simulated another multi-storey building which is
near in complexity to the Kolej Perdana building which was Kolej 11 MA7 building
to see weather the effects of multifloor factor is the same or not.
5.2 Future Work
A lot of ideas can be suggested in order to improve the present work. Some of
these useful suggestions are the signal propagation prediction can be extend to bigger
area with number of single and multiple storey buildings and simulate for outdoor
transmitters to indoor receivers and vise versa .
Further investigations are needed to produce similar results for different types
of indoor environment such as office, factory or any other indoor structure also
another important issue can be considered, in order to get more accuracy which is the
effect of presence of people inside the building and the effect of the doors status
(closed or opened).
Comparison between different indoor propagation models that are currently
proposed can be done. And from the study a new channel model can be developed
which could be used for wireless networks, to provide optimal performance in a local
indoor environment.
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[9] IEEE. Wireless LAN medium access control (MAC) and physical layer
(PHY) specifications Amendment 6: Medium Access Control (MAC) security
enhancements.IEEEStandard 802.11i, 2004.
[10] J. C. Chen, M. C. Jiang, and Y. W. Liu; "Wireless LAN security and IEEE
802.11i Wireless Communications", IEEE, 12:2736, February 2005.
[11] Jorgen Bach Andersen, Theodore s