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Propagation Model Development and Radio Planning for Future WiMAX Systems Deployment in Beirut American University of Beirut Final Year Project Spring 2006 Advisor: Prof. Walid Y. Ali-Ahmad Group: Mohamed Hasna, 200300514 Ali Dabbous, 200300532 Adel Yammout, 200300530 Imad Atwi, 200300534 Submitted on: 23.05.2006

Propagation Model Development and Radio Planning for ... · WiMAX Deployment in Beirut.” The report demonstrates the advantages of WiMAX ... design project. This chapter covers

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Propagation Model Development and Radio Planning for Future WiMAX

Systems Deployment in Beirut

American University of Beirut

Final Year Project Spring 2006

Advisor: Prof. Walid Y. Ali-Ahmad Group: Mohamed Hasna, 200300514

Ali Dabbous, 200300532 Adel Yammout, 200300530 Imad Atwi, 200300534

Submitted on: 23.05.2006

ii

Abstract

This report talks about what has been achieved during this year regarding the project assigned by Cedarcom; “Propagation Model Development and Radio Planning for future WiMAX Deployment in Beirut.” The report demonstrates the advantages of WiMAX compared to other wireless broadband access systems in non line of sight (NLOS) scenarios. Moreover, the report sheds light on the literature survey done in this project and the analysis made to come up with the most suitable propagation model. The propagation model developed is divided into two main parts: outdoor and indoor models. The outdoor model is based on the ITU-525 model for the calculation of the received free space electric field and Deygout 94 for diffraction losses. The indoor model takes into consideration the two main construction materials in Beirut buildings: concrete and glass. The model was validated through several field measurements done in Salim Slem and Ras AlNabe’ areas. The complete model was implemented in a stand-alone software that can be linked to ICS Telecom using a dynamic linked library (dll).

iii

Acknowledgements

We would like to express our gratitude to Dr. Walid Y. Ali Ahmad, Ms. Maha

Wazen, and Mr. Raed Dabbous for their support and assistance in the development of our final year project.

iv

Contents

Abstract ii

Acknowledgements iii

1 Introduction 1

1.1 Problem Definition…………………………………………………………….1

1.2 Objectives of the project………………………………………….……………2

1.3 Report Structure………………………………………………………………..2

2 Literature Survey 4

2.1 WiMAX Technology Overview…………………………………....…………..4

2.2 Electromagnetic Wave Propagation…………………………..……………..…7

2.2.1 Free Space Propagation …………………………………..…...……..7

2.2.2 Reflection…………………………………………….……………….8

2.2.3 Diffraction…………………………………………….………..……..9

2.2.4 Fresnel Zone and Path Clearance …………………..………….…...10

2.3 Propagation and Channel Models……………………………………….……12

2.3.1 Theoretical Models……………………………………….…………12

2.3.2 Empirical Models……………………………………….…………..12

2.3.3 Physical Models…………………………………………….………13

2.4 Propagation Environment Models……………………………………………15

2.4.1 Topography…………………………………………………………15

2.4.2 Building and other structures ………………………………………15

2.4.3 Morphology…………………………………………………………16

v

2.4.4 Atmospheric and meteorological conditions……………..…………16

2.5 ATDI Manual + ITU-R 525/526 models……………………………….…….16

2.5.1 Free Space model …………………………………….……………..17

2.5.2 Diffraction Geometry…………………………….………………….18

2.5.3 Subpath Attenuation…………………………………..…………….19

3 Design alternatives: Comparison and Analysis 20

3.1 Empirical vs. Physical models………………………………………………..20

3.2 Conclusion……………………………………………………………..……..21

4 Budget 22

4.1 Hardware Equipment…………………………………………………………22

4.2 Software………………………………………………………………………22

5 Measurements 23

5.1 Measurement setup………………………………………..……….…………23

5.1.1 Measurement Material…………………………………..…………..23

5.1.2 Measurement Procedure………………………………….…………25

5.1.3 Measurement Cases………………...…………………….…………26

5.1.4 Calibration………..………………...…………………….…………27

6 Implementation 29

6.1 Outdoor Model………………………………………..……….…………...…29

6.2 Indoor Model………………………………………..……….………………..29

vi

6.2.1 Glass Model…………………………………….…………………...29

6.2.2 Concrete Model………………………………..……….…………...33

6.3 Implementation of the model in software………………..……….…………..41

6.3.1 Net Link Thread………………..……….…………………………...44

6.3.2 Data Processor Thread………………..……….…………………….44

6.3.3 GUI Thread………………..……….………………………………..45

6.3.4 Graphics Engine Thread………………..……….…………………..49

7 Evaluation 53

8 System Constraints 56

9 Conclusion 57

Bibliography 58

vii

List of Figures 2.1 OFDM technology. ………………………………….……………….…………...5

2.2 The Effect of Sub-Channelization………………………………….……………..5

2.3 Relative Cell Radii for Adaptive Modulation…………………...………………...6

2.4 Two-dimensional geometry showing specular reflection………….……………...8

2.5 Reflection and Scattering from a Rough Surface…………………..………..……9

2.6 Wave being diffracted using the Wedge Model……………..….………………...9

2.7 RF Propagation and Fresnel Zone…………………………..……..……………..10

2.8 LOS demonstration…………………………………………..…………………..10

2.9 OLOS demonstration……………………………………………….……………11

2.10 NLOS demonstration……………………………………..……….……………..11

2.11 Overhead view of the ten-ray model……………………………….…………….14

2.12 ICS Telecom propagation model menu………………………………………….17

2.13 Clearance ratio……………………………………………..……….……………18

2.14 Radius of fresnel ellipsoid………………………………………….……………18

2.15 Subpath Attenuation Method……………………………………….……………19

5.1 Equipment used for the measurements……………………………..……………23

5.2 Receiver antenna.………………………………………………………………...24

5.3 CPE.……………………………………………………………………………...24

5.4 GPS Unit.……………………………………………………………………...…25

5.5 Measurement Setup………………………………………………………………26

5.6 Measurement positions.……………………………………………………….…28

6.1 Multi ray internal successive model used.…………………………………….…31

6.2 Attenuation of glass vs. thickness at normal incidence: f = 2.6 GHz, er= 5.…….31

6.3 Attenuation of glass vs. frequency at normal incidence: thickness = 1 cm , er=

5……………………………………………………………………………….….32

6.4 Attenuation of glass vs. Incident angle of the following parameters: thickness = 1

cm , er= 5, frequency = 2.6 GHz.………………………………………………..32

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6.5 Effect of w/c ratio on the real part of the dielectric constant at one day

for PCC.………………………………………………………………….………34

6.6 Attenuation of concrete vs. thickness of the following parameters: er= 5, s = 0.05

S/m frequency = 0.890 GHz.……………………………………………….……35

6.7 Attenuation of concrete vs. incident angle of the following parameters: er= 5, s =

0.05 S/m.…………………………………………………………………………36

6.8 Attenuation of concrete vs. incident angle of the following parameters: er= 5, s =

0.1 S/m.………………………………………………………………………..…36

6.9 Averaged Attenuation of concrete vs. frequency of the following parameters:

thickness = 10.2 cm, 20.3 cm, 30.5 cm.……………………………………….…38

6.10 Averaged Attenuation of concrete vs. frequency of the following parameters:

thickness = 10.2 cm, 20.3 cm, 30.5 cm after correlating with the above

measurement.………………………………………………………………….…39

6.11 The two kinds of reinforcements that were taken into consideration. Slightly

reinforced concrete consisting of 14 cm spacing between metal rods, and heavily

reinforced consisting of 7 cm spacing between metal rods. The two specimens are

taken from [Stone].………………………………………………………………40

6.12 Averaged Attenuation of slightly (14 cm) and heavily (7cm) concrete vs.

frequency of the following parameters: thickness = 20.3 cm……………………41

6.13 The solution displayed on ICS Telecom after receiving the solution from the

dll………………………………………………………………………………...42

6.14 GUI.………...…………………………………………………………………....43

6.15 Data set section.……………………………………………………….…………44

6.16 Terrain creation group box…………………………………………………….…45

6.17 Terrain file specification…………………………………………………………46

6.18 Antenna properties group box……………………………………………………46

6.19 Antenna properties…………………………………………………….…………47

6.20 Graphics options group box…………………………………………………...…47

6.21 Calculation options group box…………………………………………...………48

6.22 Indoor model parameters………………………………………….…..…………48

6.23 Calculation Output…………………………………………………....….………49

ix

6.24 2D terrain image……………………………………………………..………..…50

6.25 3D model……………………………………………………………..….….……51

6.26 WireFrame Model……………………………………………………..…………51

6.27 WireFrame model with fresnel zone……………………………………………..52

7.1 Attenuation of glass vs. frequency at normal incidence: thickness = 1.3 cm , er=

5…………………………………………………………………………………..53

7.2 Attenuation of glass vs. frequency at normal incidence: thickness = 1.9 cm , er=

6…………………………………………………………………………………..54

1

Chapter 1

Introduction

The ever growing demand for high speed data connection to drive many of the

businesses, personal uses, and much more, precipitated an unprecedented growth in the area of telecommunications. Many technologies bloomed such as optical fiber, coaxial cable, twisted pair, and wireless. These technologies have become an integral part of any developed nation and are as fundamental as a country’s water and electrical grids. Wireless systems have gained a lot of concentration and advancement in the last few years. Broadband wireless will revolutionize people's lives by enabling a high-speed connection directly to the information they need, whenever and wherever they need it. WiMAX (Worldwide Interoperability for Microwave Access) is a technology for “wireless” broadband. It is an evolving standard for point-to-multipoint wireless. [1]

As with every communication system, the design should be accurate to provide better coverage and better performance. Propagation and channel models are fundamental tools for designing any fixed broadband wireless communication system. The channel model predicts what will happen to the transmitted signal as it goes through a certain channel to reach the receiver. Its main purpose it to predict what kind of distortion and weakening will the channel have on the transmitted signal. [2] Depending on these results, the system performance will be evaluated, determining whether it meets the performance goals and objectives or not. If it does not, the system design can be modified accordingly to before the system is built.

Channel modeling is a very pragmatic endeavor, since a model is developed to adequately depict the system performance. Therefore, a designer needs to appropriately choose a model to address the design problem at hand. Failing to do so will result in poor design, poor coverage, impaired system performance, and dissatisfied customers. [2] Thus we can see how crucial the choice and application of the appropriate propagation models is in order to ensure proper system performance before the roll out.

1.1 Problem Definition

As was mentioned in the introduction, channel modeling is a very crucial step in a wireless system planning. Therefore the selection of the appropriate channel model should be given careful though and analysis.

Cedarcom, a wireless internet provider, proposed a project to work on the development of a channel model for future WiMAX deployment in Beirut which will be in the 3.5 GHz range. Currently, they are running a pre WiMAX network which is a Single Carrier 802.16a at the mentioned range. The main criterion for the design at hand is the new frequency range that WiMAX operates in and the unique environment where it will be deployed. Some of the channel models used for system planning were initially designed for much lower frequency ranges such as the 900, 1800, and 2.5 GHz range.

Chapter 1. INTRODUCTION

2

Very few models were initially designed with the intention to apply them to high frequency ranges and even fewer were tested at such frequencies. Thus, no sufficient research and development has been done so far in this new frequency range, and few of the channel models apply correctly to this scenario. In addition, channel models have varied dependency on the environment information, as we shall see later in this report. Therefore, we need to come up with the most suitable channel model which accurately depicts the system performance under a certain environment before WiMAX system rollout in the area of Ras Beirut.

1.2 Objectives of the project

The main objective of this project is to come up with the most accurate channel model at 3.5GHz for WiMAX deployment in Ras Beirut. The model should take into consideration various outdoor and indoor scenarios. The outdoor propagation model should encompass line of sight and non-light of sight cases. The indoor model should take care of different obstruction materials in Beirut buildings which are mainly concrete and glass. The model will be implemented using an external program which is linked to the software provided by Cedarcom Company, by a dynamic linked library loaded by the program. The program should have a user friendly interface that allows any network planner engineer having little experience in building construction materials to easily specify the indoor model parameters. The model must be verified by several field measurements that include outdoor and indoor cases in Ras Beirut. The developed propagation model should prove to be accurate to within ± 3 dB of the measurements done.

1.3 Report Structure

Chapter two introduces the subjects we have researched that are relevant to our design project. This chapter covers the WiMAX features in addition to its advantages over other broadband wireless systems, which makes it overcome the impediments for NLOS scenarios. In addition, an introduction is given on the parameters that affect signal attenuation as it passes in the channel such as reflection, diffraction, and freespace loss. Depending on these parameters, three main categories of propagation models are defined: theoretical, empirical, and physical. Since physical models require various databases on the environment ranging from terrain information to rain rates, they are discussed in details in this section. Finally, this chapter introduces the physical model that Cedarcom is currently using as the propagation model which is the ITU-R 525 along with subpath and diffraction models.

After the literature survey, three main propagation models are realized: theoretical, empirical, and physical. Chapter 3 discusses these alternatives, compares them and selects the most suitable model adhering to our design specs.

Chapter 4 discusses the required budget for our project. Measurements are crucial for building or verifying any propagation model,

accordingly chapter 5 discusses the measurement equipment and the procedure followed to have a correct measurement, which is crucial for the tuning of our model of choice.

Chapter 1. INTRODUCTION

3

Chapter 6 discusses the development of the model and the implementation of the model in the program.

Chapter 7 talks about the evaluation of the model via relating them to the measurements done and other references.

Chapter 8 sheds light on the economical, environmental, social and sustainability constraints that faced us during the design and implementation of the project.

Finally, chapter 9 concludes the report by giving an overall summary and the results we obtained.

4

Chapter 2

Literature Survey

2.1 WiMAX

WiMAX, or Worldwide Interoperability for Microwave Access, is a form of broadband wireless access which is based on the IEEE 802.16 standard for wireless metropolitan-area networks (MANs). Unlike many technologies in the broadband wireless access domain that provide only line of sight (LOS) coverage, the technology behind WiMAX has been optimized to provide excellent non line of sight (NLOS) coverage. As a result, WiMAX products are able to support downlink data rates of 65 Mbits/s at close range to 16 Mbits/s at distances of 9 to 10 km, which is enough bandwidth and transmission range to deliver high-speed simultaneous access to voice, data, and video services to hundreds of businesses or thousands of residences. [3, 4, 5]

WiMAX is able to overcome the impediments found in NLOS propagation and deliver such high speed access using the following technologies and techniques:

� OFDM technology. � Sub-Channelization. � Directional antennas. � Transmit and receive diversity. � Adaptive modulation. � Error correction techniques. � Power control.

Orthogonal Frequency Division Multiplexing (OFDM)

OFDM is a multi-carrier transmission technology that provides a superior means of

transmitting wireless information in high multi-path environments in 2-11 GHz frequency range. OFDM works by dividing the data stream into several parallel bit streams. Each bit stream is carried by a separate subcarrier and all subcarriers transmit in unison and simultaneously. The figure below depicts exactly how OFDM works in WiMAX. [6, 7]

Chapter 2. LITERATURE SURVEY

5

Figure 2.1. OFDM technology. [6]

Advantages of OFDM: [6, 8, 9]

� Multi-carrier multiplexing and transmission technique � Achieves high spectral efficiency and data rates � Has high resilience to RF interference � Eliminates multi-path distortion effectively � Minimizes frequency selective fading (FSF) � Eliminates Inter Symbol Interference (ISI)

Sub-Channelization

WiMAX supports subchannelization which means that instead of transmitting on all

192 data subcarriers, you can transmit on just a subset. As a result, the system achieves greater range by using the same amount of power over fewer carriers. Since we have a power limitation in the CPE, balancing the power in the uplink and downlink can be done by concentrating the power over fewer subcarriers in the uplink. The mechanism of subchannelization is very well depicted in the figure below. [3] Figure 2.2 The Effect of Sub-channelization. [4]

Chapter 2. LITERATURE SURVEY

6

Directional Antennas

The effectiveness of using directional antennas over omni-directional antennas have

been proven and successfully deployed in several scenarios that operate under significant NLOS fading. This is due to several advantages found in directional antennas. [4] Advantages of Directional Antennas

� Increase of link availability compared to omni-directional antennas � Decrease of the delay spread at both the Base Station and the CPE � Suppression of any multi-path signals that arrive in the sidelobes and backlobes.

Transmit and Receive Diversity

Diversity schemes are used to take advantage of multi-path and reflections signals

that occur in NLOS conditions. In transmit diversity; several antennas are placed at the transmitter side with a separation between them that guarantees independent fading between the transmitted signals across the wireless channel. This reduces the fade margin requirement and combats interference. The same scheme applies for receive diversity where several antennas are placed at the receiver side instead of being placed at the transmitter side. This helps in overcoming fading and reducing pathloss. [4, 10]

Adaptive Modulation

Adaptive modulation allows the WiMAX system to adjust the signal modulation

scheme depending on the signal to noise ratio (SNR) condition of the radio link. The highest modulation scheme is used when the radio link is high in quality. This gives more capacity for the system. During a deep signal fade, the WiMAX system can transfer to a lower modulation scheme to maintain the connection quality and link stability. “This feature allows the system to overcome time-selective fading.” The main feature of adaptive modulation is that it allows us to transmit at higher data rates during best case conditions as opposed to having a fixed scheme which transmits always at low data rates to account for the worst case conditions. [4]

Figure 2.3 Relative Cell Radii for Adaptive Modulation [4]

Chapter 2. LITERATURE SURVEY

7

Error Correction Techniques

WiMAX utilizes several error correction techniques in its receiver structure to reduce

the signal to noise ratio requirements and significantly improve the bit error rate (BER) performance of the system. These techniques, such as the Strong Reed Solomon FEC and convolutional coding, are used to recover frames in error which may have been lost due to deep fades in the channel. [11, 12]

Power Control

WiMAX incorporates several power control algorithms to reduce the overall power

consumption of the CPE, thus decreasing potential interference with other co-located units. This improves the overall performance of the system dramatically. It is implemented by the base station sending power control information to each of the CPEs to regulate the transmit power level to a fixed threshold. Concerning a LOS scenario, the transmit power of the CPE is approximately proportional to its distance from the base station. However in the NLOS scenario, this level depends on many other factors such as the obstructions lying in the path between the CPE and the base station. [4]

After presenting a general introduction about the WiMAX wireless system and shedding light on its different attributes, the following section will discuss the physical properties of the electromagnetic waves. These electromagnetic waves are the main carriers of data in wireless communication system.

2.2 Electromagnetic Wave Propagation

In wireless communications, the information that is transmitted from one end to another propagates in the form of electromagnetic (EM) waves. The amplitude, phase, or frequency (wavelength) of a wave can all be modified to represent the information. As a result, it is very fundamental to understand EM waves and how they get from one place to another in order determine the performance of a wireless link. [2]

2.2.1 Free Space Propagation

Free-space transmission is a principal consideration in basically all fixed broadband

wireless communication systems. Although free space primarily means a vacuum, it can be practically implemented in short-range space-wave paths between elevated terminals. In free space, the signal gets attenuated as it travels from the transmitter to the receiver. This attenuation factor is characterized by the free space pathloss given by: Free space path loss = PLf = PR/PT = GTGR (λ / 4πr) 2 [2]

The free space pathloss is characterized by the following:

� Inversely proportional to square the distance � Proportional to the wave length (λ) � Proportional to the antenna gains (GT and GR)

Chapter 2. LITERATURE SURVEY

8

However, free space propagation alone cannot depict what will exactly happen to the

signal as it travels from the transmitter to the receiver as there are many effects that can substantially impact the communication link performance. [2]

2.2.2 Reflection

Reflection is one of the most important wave propagation phenomena involved in

almost every type of fixed wireless systems. [2] There are two basic reflection types:

� Specular reflection from smooth surfaces. � Reflections (scattering) from rough surfaces.

2.2.2.1 Specular Reflection

As we can see in Figure 2.4, reflection occurs when a signal intersects the ground, a

wall or any other surface that that does not have any edges or discontinuities. The reflection takes place on the ‘specular point’ where the angle of incidence of the transmitted wave equals the angle of reflection of the reflected wave. [2]

2.2.2.2 Reflections from Rough Surfaces

In the real world, seldom do we encounter reflections along a smooth surface.

However, most of the times, we encounter surfaces that have random variations as in the earth’s surface or have systematic variations such as in the walls and roofs of artificial structures. In severe scenarios, the surface may appear to be a pure scatterer. The degree of roughness is given by the Rayliegh criterion:

0sin8 γ

λ≥Rh [2], where Rh is the difference in the maximum and

minimum surface variations; 0γ is the angle between the incident ray and the surface

(Fig. 2.5).

Figure 2.4. Two dimensional geometry showing specular reflection [2]

Chapter 2. LITERATURE SURVEY

9

2.2.3 Diffraction

Diffraction is an important wave propagation mechanism which can occur to any

propagating wave in wireless communications. Diffraction only happens when an object partially blocks the path of a propagating wave. Since our environment deals with a non-line of sight scenario, we will be heavily relying on diffraction in our study. There are typically two models used in a wireless system design to model diffraction [2].

2.2.3.1 Wedge Diffraction

In city propagating environments, diffracting wedges are considered a very important

feature. Wedge diffraction occurs at the corner of buildings, at the edge of walls where they intersect roofs, and at the junction of walls with the ground or street. The picture below depicts what happens to a wave under wedge diffraction.

The wedge diffraction scheme, although highly computational, is used to find the

diffraction attenuation for an obstructed interference path over a rooftop edge or the parapet of a building. Moreover, experimental results have demonstrated the validity of the wedge diffraction calculation in predicting signal levels on a certain path obstructed by a building corner. [2]

Figure 2.6 Wave being diffracted using the Wedge Model.[2]

Figure 2.5 Reflection and Scattering from a rough

surface. [2]

Chapter 2. LITERATURE SURVEY

10

2.2.3.2 Knife-edge Diffraction

Knife-edge diffraction is a special case of the wedge diffraction. i.e. when the interior

angle of the wedge is assumed to be zero. Because of its resulting simplicity and speed of calculation efficiency, knife-edge diffraction is used in many propagation models. The knife-edge diffraction scheme is used as a model for many obstructed path circumstances including paths with terrain obstructions such as gently rolling hills that have very little resemblance to a knife-edge. [2]

2.2.4 Fresnel Zone and Path Clearance

A crucial design objective in a fixed wireless design is to achieve adequate path

clearance for the link. This means that any point along the path between the transmitter and the receiver should have a certain distance from any obstacle along the path.

As a result, a wireless link could fall to one of three categories, which are determined by the obstacles’ positions with respect to the Fresnel zone. Fresnel zone is the locus of the points where the diffracted path length is multiples of 180 degrees different from the direct path length. As shown in Figure 2.7, the fresnel zones form elliptically shaped solids of revolution around the transmit-receive propagation path. In concept, the first fresnel zone is the zone where the significant power is transmitted, meaning that the power available at the receiver will be diminished if the first fresnel zone is significantly obstructed or blocked. A general criterion for link system design is to set the path clearance so that a radius equal to 60% of the first fresnel zone is unobstructed. This is so called the 0.6 first fresnel zone criterion. [2, 13]

The first fresnel zone with the 0.6 criterion is depicted in the following figure:

Figure 2.7 RF Propagation and Fresnel Zone [14]

LOS (Line of Sight)

Figure 2.8 LOS demonstration [6]

Chapter 2. LITERATURE SURVEY

11

LOS Attributes: � Requires 60% Fresnel (1st) zone clearance � Diffraction losses are negligible � Free space signal attenuation determines coverage

OLOS (Obstructed Line of Sight)

Figure 2.9. OLOS demonstration [8]

OLOS Attributes :

� Fresnel zone obstruction- above the 60% mark � Diffraction Losses are from 0-6dB � Requires higher tower heights � Seasonal effects due to the nature of the obstruction

NLOS (Non Line of Sight)

Figure 2.10 NLOS demonstration [14]

NLOS Attributes

� More propagation loss � Higher delay spread � Higher ISI (Inter Symbol Interference) � Pronounced multipath distortion

Chapter 2. LITERATURE SURVEY

12

� Higher Tx power required to meet SNR/BER limits In the next section, we will present the various propagation and channel models which are built on the basis of the afore discussed EM wave characteristics.

2.3 Propagation and Channel Models

Propagation and channel models are fundamental tools for designing any fixed broadband wireless communication system. It basically predicts what will happen to the transmitted signal while in transit to the receiver. These models are divided into three basic classifications: theoretical, empirical, and physical. [13]

2.3.1 Theoretical Models

These models are based on some theoretical assumptions about the propagation

environment. Theoretical models are not suitable for planning communications systems to serve a particular area because there is no way to relate the parameters of these models to physical parameters of any particular propagation environment. They do not directly use information about any specific environment, thus it can be useful for analytical studies of the behavior of communication systems under a wide variety of channel response circumstances. An example of a theoretical model is the “tapped delay line” model in which densely spaced delays and multiplying constants and tap-to-tap correlation coefficients are determined on the basis of measurements or some theoretical interpretation of how the propagation environment affects the signal. [2]

2.3.2 Empirical Models

Empirical models are based on observations or measurements. Measurements are typically done in the field to measure path loss, delay spread, or other channel characteristics. Empirical models are widely used in mobile radio and cellular system engineering. Many cellular operators have ongoing measurements or drive-test programs that collect measurements of signal level, call quality, and network performance which are then used to refine empirical propagation models used in the system-planning tool. Parameters included in empirical models are distance, frequency, base antenna height, CPE height, and number of buildings. [2] An example of an empirical model is the “Cost-231 Hata “model which was devised as an extension to the “Hata-Okumura” model. The Hata-Okumura model is developed for the 500 to 1500 MHz frequency range using measurements done by Okumura and equations fitting to the path loss curves by Hata. [15, 16, 17] The Cost-231 model also has correction for urban, suburban and open areas. The basic path loss equation for urban areas is:

mbmb CdhahhfL +××−+−×−×+= 10101010 log)log55.69.44(log82.13log9.333.46

)8.0log56.1()7.0log1.1( 1010 −×−×−×= fhfah mm

where

Chapter 2. LITERATURE SURVEY

13

mC = 0 dB for medium sized city and suburban centers with moderate tree density, 3 dB

for metropolitan centers. f = frequency in MHz d = distance from the base station to the receiver (remote terminal) in kilometers.

bh = height of the base station (hub) above ground in meters.

mh = height of the receiver (remote terminal) above ground in meters. [2]

3.3.2.1 Empirical Model Building

Formulation of propagation loss accounting for all potential propagation

parameters

For example: fwaL mkPkPknRkfkGkdBP 625141031021 )(loglog)( +++×+×++=

where f = operating frequency

aG = Antenna Gain

R = propagation distance

1P , 2P = angle of incidence to a wall

nw, mf = number of walls and floors b/w Tx and Rx. k1… k6 = coefficients to be determined using some regression technique.

Measurement Setup

Depict different scenarios according to parameters defined, i.e. for the height parameter, measurements are taken from places with different heights; for the frequency parameter, measurements are taken for different frequencies.

Determination of propagation loss

Evaluation of the path loss coefficients is done using linear regression or root mean square methods. These regression techniques will fit the measurements in a curve that will clearly show the model. [2]

2.3.3 Physical Models

Physical models are the most widely used propagation models for fixed broadband wireless systems. They rely on the basic principles of physics rather than statistical outcomes from experiments to find the EM field at a point. Databases of terrain elevations, clutter heights, atmospheric refractivity conditions, and rain intensity rates are all used in the design process. Physical models may or may not be site specific. Non site specific models uses physical principles of EM wave propagation to predict signal levels in a generic environment in order to develop some simple relationships between the characteristics of that environment. On the other hand, when particular elements of the propagation environment between the transmitter and receiver are considered, the modal is considered site specific.

Chapter 2. LITERATURE SURVEY

14

An example of a physical model is the “Ray-tracing” model. Ray-tracing is not a cohesive mathematical technique but a collection of methods based on geometric optics (GO), the uniform theory of diffraction (UTD), and other scattering mechanisms, which can predict EM scattering from objects in the propagation environment. This collection of field calculation methods are drawn upon mainly because none alone can successfully deal with all the geometric features of propagation environments likely to be encountered in broadband communication systems. However, if there is an incomplete or insufficiently refined description of the propagation environment, Ray-tracing does not provide a complete and accurate calculation of the field at all locations in the environment. The five propagation primitives usually included in ray tracing are:

� Free space propagation � Specular reflection � Diffraction � diffuse wall scattering � wall transmission

In the computer implementation of a Ray-tracing model, all the rays are handled as complex electric field voltages that are affected by the magnitude and phase of the reflection and diffraction coefficients. Using the equation of the field and a database describing the propagation environment, the resulting ray trajectories from this model can be found. Several studies have been done to validate ray-tracing, generally with good results when comparing ray-tracing signal level predictions with measurement values. The primary drawback to ray-tracing models is that the computations can take some time complete, but increased processor speed has helped this situation to some extent.

Figure 2.11 Overhead view of the ten-ray model. [2]

After seeing that some of the channel models, and specifically the physical models,

require detailed databases on the environment, there is a need to present the types of databases or models that provide such information about the environment. [2]

Chapter 2. LITERATURE SURVEY

15

2.4 Propagation Environment Models Wireless system wave propagation is affected by the elements and characteristics of

the real environment in which the networks are deployed. All empirical and physical propagation models rely on information about the propagation environment to operate. Obviously, models that take into account more information about the propagation environment will probably have more accurate predictions than those that take into account less information.

The four main categories of propagation environment information that are used for designing fixed broadband wireless systems are:

1. Terrain elevations or topography. 2. Building and other structures. 3. Land use or morphology (clutter). 4. Atmospheric and meteorological conditions.[2]

2.4.1 Topography

2.4.1.1 Topographic Map

Topographic maps are the fundamental source of information of terrain elevations.

The map includes information such as lines of constant elevation or contours. These contour lines are drawn at regular spacing so that relative line density indicates how steep or shallow the terrain slope is. The raw description of the contours and a string of latitude and longitude coordinates where the elevation was found along the contour.

2.4.1.2 Terrain DEMs

A Digital Elevation Model (DEM) consists of a matrix of elevation points with fixed

spacing in either meters or seconds of latitude and longitude. Each grid point contains the elevation of the specific terrain. DEM for a given area can be developed using satellite imagery using low earth orbits ranging from 150 to 500 Km above the surface where these satellites are continuously taking photographs to collect information. The optical resolution of the photos improved from 10 m to 1 or 2 m. However the main disadvantage of DEMs is that their cost is quiet high.

2.4.2 Building and Other Structures

Building is one of the primary factors that affect short-range wireless communication

links in urban areas so detailed information about the location and heights of buildings is needed. There are two kinds of building databases:

2.4.2.1 Vector building databases

Chapter 2. LITERATURE SURVEY

16

In these databases, individual walls and roofs are represented by their latitude, longitude, and height coordinates. It has a high degree of resolution in order of cm which makes it excellent for indoor wireless systems. It can suit ray tracing models.

2.4.2.2 Canopy building databases

In these databases, building, foliage, and highway overpasses are represented by a very fine resolution regular grid of elevation points. It is not as specific as the vector building data bases, but can be easily dealt with, i.e. it is easy to build a planning software tool that can access them.

2.4.3 Morphology

Morphology or clutter databases contain information that generally classifies the

character of the land cover at a particular location on earth. These databases contains classification such as urban, densely urban, residential, forest, and agricultural. Clutter databases are in a grid matrix form similar to the terrain DEM where a clutter number is assigned to a point. Once determined, clutter databases can provide a degree of improved prediction over those obtained using terrain data alone.

2.4.4 Atmospheric and Meteorological Factors

Atmospheric refraction, rain, and fog have significant consequences on link

performance thus it is necessary to have databases that describe what conditions are likely to occur in the area where a wireless link or network is being deployed. Atmospheric refractivity depends on temperature, pressure and humidity. Maps having such measurements can be found in the ITU-R Recommendation. Rain is the primary factor in limiting the range of fixed broad band links operating above 8 GHz due to absorption. Rain-rates databases model rain as stationary events meaning that they do not describe the changing size, shape, and movement of rain cells, which make these maps very inaccurate. [2]

2.5 ATDI Manual and ICS Telecom Propagation Models

ICS Telecom is a program made by ATDI for radio planning. It contains certain propagation models (both empirical and physical) that can be used to calculate the power received by an isotropic antenna from a base station. The base station’s parameters and GPS position are specified in the program, which contains a database and map of a city which in our case is greater Beirut. In ATDI’s manual, they explain the technical conventions used in ICS Telecom and some of the propagation models used. Figure 2.12 shows the propagation model menu of ICS Telecom. Since Cedarcom possesses a DEM database of greater Beirut, they use physical models as their main propagation models. The main parameters of the physical propagation models are: � Free space model � Diffraction geometry � Subpath attenuation

Chapter 2. LITERATURE SURVEY

17

Figure 2.12 ICS Telecom propagation model menu.

2.5.1 Free space model

The free space model chosen by Cedarcom is the one described in the ITU-R P.525-2 recommendation. ITU-R, International Telecommunication Union–Radiocommunication Sector, is a union composed of more than 1500 specialists from telecommunication organizations and administrations around the world that participate in the work of Radiocommunication Sector’s study groups.

ITU-R study groups

1. Develop ITU-R Recommendations on the technical characteristics of and operational

procedures for radiocommunication services and systems. 2. Draft the technical bases for radiocommunication conferences. 3. Compile handbooks on spectrum management and emerging radiocommunication

services and systems. [18]

Conversion formulae proposed by the ITU-T P.525-2 for free space propagation [19]

� Field strength for a given isotropically transmitted power: E = Pt – 20 log d + 74.8

Chapter 2. LITERATURE SURVEY

18

� Isotropically received power for a given field strength: Pr = E – 20 log f – 167.2

� Free-space basic transmission loss for a given isotropically transmitted power and

field strength: Lbf = Pt – E + 20 log f + 167.2

� Power flux-density for a given field strength: S = E – 145.8

where Pt = isotropically transmitted power (dB(W)) Pr = isotropically received power (dB(W)) E = electric field strength (dB(µV/m)) f = frequency (GHz) d = radio path length (km) Lbf = free-space basic transmission loss (dB) S = power flux-density (dB(W/m2)).

2.5.2 Diffraction geometry

The diffraction geometry that is chosen by Cedarcom is the Deygout 94 multiple obstacle diffraction. In the case of one single knife-edge obstacle between the transmitter and the receiver, the diffraction loss can be approximated by:

( ) ( )

−++−+= 2

111log209.6 vvLd [20]

where v, the clearance ratio is

r

hv 2= (See figure 2.13)

Figure 2.13 Clearance ratio. [2]

)( 21

21

ddf

ddr

+= [1] (See figure 2.14)

Figure 2.14 Radius of Fresnel ellipsoid. [2]

Chapter 2. LITERATURE SURVEY

19

In the case of multiple edges, Deygout proposed that first we look for a primary obstacle obtained from the maximum clearance ratio v1 with respect to the line of sight between Tx and Rx, if an obstacle exists (v1 > 0), one searches for two secondary obstacles. One between Tx and the primary obstacle and the other between the obstacle and Rx. Then, this search is performed recursively on each side of the secondary obstacles. The total diffraction loss is:

( )∑= i idd vLL '

2.5.3 Subpath attenuation

Subpath attenuation is an additional correction term for the field strength, because it turned out that models with classical diffraction corrections provide too optimistic field strength values. Deygout proposed the following term:

Lgr = 20log(75000d) – 20log(πh1h2f) where d = the distance between the Tx and Rx (in km) h1, h2 = Tx and Rx antenna heights repectively (in m) f = the frequency in MHz. [20]

ICS Telecom offers some modified subpath attenuation methods. The most important method is the Standard Subpath Attenuation method where it is based on Lgr value but with a correction coefficient:

Lsp = FZ * ρ * Lgr

where ρ is the proportion of the total path that is located above the first Fresnel virtual ellipsoid, ρ = (d1+ d2+ d3+ d4)/d. Figure 2.15 below illustrates this in more detail. FZ (for Fresnel Zone) is a coefficient of reduction of this virtual ellipsoid: FZ = 1 means that the whole ellipsoid is considered, FZ = 0 means that the virtual ellipsoid reduces to the straight line of sight segment.

Figure 2.15 Subpath Attenuation Method. [2]

20

Chapter 3

Design Alternatives: Comparison and

Analysis

As described above, there exist three propagation models in our project: theoretical, empirical, and physical. Physical models are part of our alternative analysis since there is a database of greater Beirut, comprising of the DTM, clutter and building Database (5m resolution) which is provided by Cedarcom.

Theoretical models, as described above, are not intended to be applied to any real propagation scenario. They are not practical for radio planning because they don’t use information about any specific environment. In addition there is no possibility to relate the parameters of these models to physical parameters in the real world. Theoretical models are derived only from mathematical and physical theories such as the uniform theory of scattering. Therefore, the main purpose for these models is for analytical studies of the way a communication system behaves under a wide variety of channel response circumstances.

The following section presents the main pros and cons for the two remaining types of models: empirical and physical model. In addition a conclusion is made about the type of model that needs to be selected for our design project.

3.1 Empirical vs. Physical models

After discarding theoretical models from the analysis, empirical and physical models are left for comparison.

Empirical models use extensive measurements in making an average description of the environment to predict median path loss. Due to their simplicity, they are widely used for system equipment planning, system dimensioning, and other various generic system concept formulations. However, the usage of empirical models in our design has many drawbacks.

First, these models use parameters such as building heights, street width, and distance, making their accuracy limited.

Second, most of the widely used empirical models such as Cost 231 Hata, and Cost 231 W-I models have frequency limitations. This is due to the fact that the extensive measurements that they were based on were done in the popular or more available frequency ranges then, which is 800 to 2000 MHz. Some models such as the MMDS band model and the Stanford University Interim (SUI) have been specifically developed for the MMGD frequency band from 2.5 to 2.7 GHz. These ranges vary greatly from that of our current design which is the 3500 MHz range, under which the performance of such empirical models is unpredictable and in many cases have not been tested. [2]

Third, these empirical models suffer from various limitations such as inappropriate parameter variations, lack of correction factors for diversity in environment, and lack of the possibility to relate terrain type of the empirical model to the commonly available

Chapter 3. DESIGN ALTERNATIVES: COMPARISON AND ANALYSIS

21

clutter or terrain databases, making the method of selecting a certain category for a particular system deployment not systematic. [15, 16]

Last but not least, the empirical models are two dimensional, i.e. pathloss is described using a single equation as a function of the transmitter distance. Thus when applying the model in all directions from the transmitter and fixing the antenna height and environment used, a circular coverage area would result. However, this clearly contradicts real systems in nonhomogenous propagation environments, where the coverage area for a given base station is highly non circular, and sometimes discontinuous.

Therefore, using empirical models for our design project would give erroneous and unreliable results for our detailed, location-specific, system planning.

The last alternative for our design project is physical models. Physical models rely heavily on high resolution terrain databases to give accurate results. These models do not suffer from some of the limitations of empirical models such as the circular coverage area limit and the frequency range limit. The result of such models would be of great importance to our project since they would be location specific.

It is important to note that had the terrain databases of greater Beirut been not available, physical models would have been a feasible option. Thus the best alternative would have been to build a new empirical model. However, this model would require comprehensive measurement scenarios and would be strenuous to achieve.

3.2 Conclusion We can conclude that relying on physical models would achieve the most accurate

results compared to other propagation models under the current project circumstances.

22

Chapter 4

Budget

There was no need for a budget plan and a source of funding for our project since the

company which is sponsoring the project, Cedarcom, has provided all the hardware needed for measurement except for the omni antenna and the GPS unit that was provided by our supervisor. In addition Aperto Manager 5.3 was provided by Cedarcom, whereas ICS Telecom full license was provided via our supervisor.

4.1 Hardware Equipment The hardware provided comprised of the following main units

1. CPE (Customer Premise Equipment) 2. GPS unit: A Global Positioning Satellite 3. Connecting cables 4. 2.4 GHz omni antenna

4.2 Software The two main software programs provided are:

1. ICS Telecom 2. Aperto Manager 5.3

23

Chapter 5

Measurements

This section describes the equipment used and the followed procedure for the measurement scenarios under the pre-WiMAX fixed wireless system currently installed. It also includes the measurements that have been done throughout this semester to evaluate our model.

5.1 Measurement setup

The enhancement of the physical model will be based on measurements taken in the field, where we need specialized equipment and follow a procedure in order to correctly measure the field strength at a certain point in the environment. Correct measurements are crucial since they are the basis for tuning the model which will be used in our design.

5.1.1 Measurement Material

The picture below illustrates the equipment being used in the measurements that have been conducted.

Figure 5.1: Equipment used for the measurements.

Chapter 5. MEASUREMENTS 24

Transmit Antenna

One of the pre-WiMAX BSs currently deployed by Cedarcom will be used as the

transmit antenna. The BS is PacketWave® 1000, one of Aperto network products. The transmit antenna is located in Abraj – sector 5.

Receiver Antenna

Figure 5.2. Receiver antenna.

An isotropic (omni directional) antenna should be used for the measurements to ensure correct measuring of the signal received from the base station. Thus there would be minimal tuning of the direction of the antenna to get the correct signal. The omni direction al antenna that we had available is a 2.4 GHz omni antenna.

CPE

Figure 5.3. CPE

This unit works as a modem which converts the IF signal from the receiver to baseband and sends the data to the computer via ethernet.

Chapter 5. MEASUREMENTS 25

Computer

A computer is needed on the receiver side to measure the received signal. It should have an Ethernet card and Java Runtime Environment installed. In addition, Aperto manager software is needed to display the measured signal.

GPS Unit

Figure 5.4: GPS Unit.

To compare the measured signal with the one that the ICS software provides and that of our program, we need to get the coordinates of the measured signal to input them in the software. This is done using a GPS unit having a 5 m resolution

Cables

There are two Cat.5E cables used for connections: one with straight connectors, the other with cross connectors.

Electric wire

A basic two wire line of 1 mm width is used for power connections.

Aperto manager 5.3 Software

The software requires the presence of java runtime environment installed on the computer. It is responsible for reading the received signal strength using specific setup.

5.1.2 Measurement Procedure

The following procedure was used for measurements (see figure 5.5):

1. Connect the straight cable from the Omni antenna to the modem. 2. Connect the modem to the antenna using the cross cable. 3. Connect the modem to the computer using the cross cable.

Chapter 5. MEASUREMENTS 26

4. Connect the modem to an electric outlet of 220 V. 5. Assign a random IP address with its host to the computer. 6. Using the Aperto manager 5.3 software the following measuring specs should

be assigned: a. Designated pre-WiMAX BS: Abraj1. b. Sector of the BS: 5. c. Receiving signal frequency: 2.528 GHz.

7. Place the omni antenna in an upright position. 8. Slightly maneuver the angle of the antenna to achieve the best possible signal. 9. The average received signal in dBm will be read using the Aperto software via

a graph that displays the received signal strength vs. time. 10. Measure the location of the receiver antenna using the GPS unit.

Figure 5.5: Measurement Setup.

5.1.3 Measurement Cases

Throughout this semester, several measurements have been done on the roof tops of many buildings in Beirut. The purpose of these measurements is to evaluate our model and verify that the results given by our model adhere to real life cases through the different measurements that we have conducted.

Measurement Limitations:

The distance between the receiver antenna and the base station had to be less than 1 km in order to receive a strong signal, and therefore, our measurement cases were primarily concentrated on Salim Slem and Ras AlNabe’ areas. As previously mentioned, the omni antenna that is available is a 2.4 GHz antenna, while the sector that we are working with

Chapter 5. MEASUREMENTS 27

is 2.6 GHz. The minimum frequency that the sector can transmit is 2.528 GHz, so we used this frequency in our measurements.

5.1.4 Calibration:

In our measurement setup we have two sources of RF losses:

1. RF cable: which was estimated to be around 0.5 dB at 2.5GHz. 2. The Omni antenna optimum characterisitics are tuned for 2.4GHz; so at

2.5GHz, there is an estimated loss of 1dB approximately (pattern loss and return loss).

Thus, all our measurments were calibrated by this 1.5dB additional loss in the receiver radio front end. Below is a table that shows the different values of the signals that we have received through various measurement points.

Table 5.1: Values of the measurement cases that were conducted.

Measurement Measurement Name

Coordinates

Measured Calibrated Signal (dBm)

Wall Thickness (cm)

Behind Wall (dBm)

Attenuation (dB)

1 M1 35.50429 33.88413 -68 20 -86 18

2 M2 35.3007 33.53078 -62 30 -86 24

3 M3 35.30051 33.53092 -72 20 -91 19

4 M4 35.30343 33.53118 -67

5 M5 35.29565 33.53048 -77 15 -92 15

6 M6 35.30022 33.52581 -80

7 M7 35.29583 33.52598 -70

8 M8 35.29597 33.5301 -72 15 -90 18

9 M9 35.30023 33.53001 -78 20 -97 21

10 M10 35.29587 33.53035 -67 20 -85 18

11 M11 35.3006 33.53059 -63 30 -87 24

12 M12 35.3009 33.53039 -68

13 M13 35.30106 33.53109 -65 20 -83 18

14 M14 35.30078 33.53041 -67 15 -79 12

15 M15 35.30084 33.53099 -65 20 -85 20

16 M16 35.30175 33.53012 -71 15 -86 15

17 M17 35.30154 33.53002 -67 25 -89 22

18 M18 35.30132 33.53011 -69 15 -86 17

19 M19 35.30124 33.53104 -67 20 -87 20

Figure 5.6 below shows the points on the ATDI map that corresponds to the measurements taken in the field.

Chapter 5. MEASUREMENTS 28

Figure 5.6. Measurement positions.

29

Chapter 6

Implementation In this chapter, we will discuss how we came up with the indoor model and explain how we implemented the indoor model in addition to the outdoor model for the ICS Telecom.

6.1 Outdoor Model For the outdoor model, we have used ITU-525 for the calculation of the free space field. If there is an obstruction between the Tx and Rx, two loss components are calculated:

1. The diffraction loss using Deygout-94 method. 2. The penetration loss for the signal component that cuts through the buildings.

6.2 Indoor Model As the electromagnetic wave propagates from the outdoor medium (air) to the indoor medium (air), it passes through a certain construction material that has significant effect on the power of the incoming wave. The two predominant materials that the wave will encounter while passing from outdoor to indoor are: glass and concrete. This is typically true for our area of interest (Beirut) and throughout the region. So our focus will be on the implementation of a model for each of these two materials. There are a lot of factors to be taken into account for each of the two materials to come up with an accurate model.

6.2.1 Glass model

As we know glass is a homogeneous material with known range of parameters. Under the frequency of our interest (2.6 GHz), the wavelength is not that small compared to the thickness of the material (couple of cms). Therefore, the transmission and reflection characteristics of this material can be approximated by a multiray model as shown in Figure 6.1. [21]. The addition of the rays results in a generalized reflection, Γg, and transmission, Tg given by:

)sin(222

)sin(222

1)1( θα

θα

jkosjks

jkosjks

geee

eee+−−

+−−

Γ−

ΓΓ−−Γ≡Γ (6.1)

)sin(222

)sin(222

1

)1(θα

θα

jkosjks

jkosjks

geee

eeeT

+−−

+−−

Γ−

Γ−= (6.2)

Where

Chapter 6. IMPLEMENTATION 30

rk ελπ2

= is the propagation constant.

002

)tan(εεµ

δωα r= is the attenuation.

λπ2

=ko is the propagation in free space.

r

ls

εθ )(sin

12

= is the path length inside the slab.

1)(sin

2

2−

=

θε r

ld is the path length difference, Figure.

rεσλ

δ60

)tan( = is the loss tangent.

Γ is the Fresnel reflection coefficient pertaining to a parallel polarization, and is given by:

)cos()cos(

)cos()cos(

12

12

it

it

θηθηθηθη

+

−=Γ

Where

2,12,1

2,1

2,1 ωεσ

ωµη

j

j

+= is the complex permittivity.

Where σ, ε, µ are the conductivity, permittivity, and permeability of the air and reflecting material and ω is the frequency of the incident radiation in radians. Given the above formulas and definitions, we can see that:

igr PP2

Γ=

igt PTP2

=

Thus, ( ) ( ) )(log10log10)(22

dBmPTPTdBmP igigt +==

Therefore, Transmission Attenuation (dB) = ( )2

log10 gT (6.3)

Chapter 6. IMPLEMENTATION 31

Figure 6.1. Multi ray internal successive model used.[21]

The following three figures are based on the glass model just described.

0.005 0.01 0.015 0.02-2.6

-2.4

-2.2

-2

-1.8

-1.6

-1.4

-1.2

-1

thickness (m)

Attenuation (dB)

Figure 6.2. Attenuation of glass vs. thickness at normal incidence: f = 2.6 GHz, εr= 5.

Chapter 6. IMPLEMENTATION 32

1 1.5 2 2.5 3 3.5 4

x 109

-2.6

-2.4

-2.2

-2

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

frequency

Attenuation (dB)

Figure 6.3. Attenuation of glass vs. frequency at normal incidence: thickness = 1 cm , εr= 5.

10 20 30 40 50 60 70 80 90-5

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

Incident angle (degrees)

Attenuation (dB)

Figure 6.4. Attenuation of glass vs. Incident angle of the following parameters: thickness = 1 cm , εr=

5, frequency = 2.6 GHz.

Chapter 6. IMPLEMENTATION 33

6.2.2 Concrete model

In theory, we can consider concrete to be a slab of a certain thickness and apply the above theoretical model to it. However, concrete is hardly a homogeneous element with predefined electrical properties. The dielectric constant of a concrete amalgamation and its equivalent electric conductivity depend on many variables such as: mixture, w/c ratio, cure time/conditions, and frequency. [22]

Frequency

The imaginary part of the dielectric constant exhibits a general increase as frequency increases. Since the effect of polarization reduces with increasing frequency, the real part of the dielectric constant decreases with frequency. Conductivity is more responsible for the loss behavior than the damping effects. Since conductivity increases with frequency (ω), the imaginary part (ε") which is given by σ/ω decreases with frequency; the increase of σ, however, is much smaller than the increase in ω. [22, 23]

Mixture

As we know, concrete is made of various mixtures of cement; each of a certain mixture has an effect. We can see from [24] that using 8 different mixes of concrete showed somehow variable results around 30% difference in attenuation that results from the different dielectric constants and conductivity exhibited by the different mixes.

Water/Cement (W/C) ratio

Cement concrete with a higher w/c ratio would be expected to have a higher dielectric constant due to higher pore water content. Even a small amount of free water significantly affects the imaginary part of the dielectric constant due to an increase in electric conductivity. [22, 25]. As we can see in the following figure, the difference of real part of the dielectric constant between the two specimens despite their close w/c ratio is shown:

Chapter 6. IMPLEMENTATION 34

Figure 6.5. Effect of w/c ratio on the real part of the dielectric constant at one day

for PCC.[22]

Cure time/ Conditions

As the curing time increases, the amount of free water in the cement decreases due to the cement hydration. The water changes from a free to an adsorbed state, which reduces ionic polarization and also conductivity due to decrease in ion production. Also, the pore structure changes with curing time. The pore sizes become very small, thus making it difficult for the movement of the free ionized water remaining in the cement. Therefore, the dielectric constant would decrease with curing time [22, 25]. After an adequate amount of time, the mixture will be fully cured, thus the changes in electrical parameters would be minimal, making the attenuation loss approximately constant from that point on.

We have researched many references such as [26-34], but found no reference that actually defines the permittivity and the electric conductivity as a function of w/c ratio, cure time and conditions, reinforcement, and frequency. Thus there was an impossibility to come up with a theoretical model of concrete that permits us to define its attenuation as a function of the above parameters, in addition to thickness and angle of incidence. Even though there are several theoretical models that tend to qualify for only a certain type of walls under certain conditions, many of them have not been actually verified against measurements. In addition, network planning engineers are not knowledgeable about the specificities of a concrete wall discussed above, and it would not be feasible to examine every type of wall in a certain area and get its attributes to achieve a successful network planning. Thus we have emphasized that our model to reflect general parameters reflecting curing time/conditions, mixture type, and w/c ratio. We have focused on developing a model that is a function of the thickness of the wall, type of reinforcement used (slightly or heavily), and frequency of the EM wave hitting the concrete specimen.

Chapter 6. IMPLEMENTATION 35

To get a starting point, we have seen from [32], the following parameters were extracted for a given homogeneous concrete wall of thickness = 17 cm at 890 MHz: εr = 3 and σ = 0.05 S/m. Thus applying the above theoretical multi ray model to these specific parameters, we find that the attenuation at normal incidence is = 9.5 dB as we can see in the following graph:

0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3

-16

-14

-12

-10

-8

-6

-4

thickness (m)

Attenuation (dB)

Figure 6.6. Attenuation of concrete vs. thickness of the following parameters: εr= 5, σ = 0.05 S/m

frequency = 0.890 GHz.

We have also computed the attenuation of concrete as a function of the angle of incidence for the above parameters and found that there is close agreement to that of what was measured in [32] especially before an incident angle of 60 degrees(see figure 6.7). The following figure shows the agreement between the theoretical and measured model.

Chapter 6. IMPLEMENTATION 36

0 10 20 30 40 50 60 70 80 90-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5

Incidence angle (degrees)

Attenuation (dB)

Theoretical

Measured

Figure 6.7. Attenuation of concrete vs. incident angle of the following parameters: εr= 5, σ = 0.05 S/m.

We have also computed the attenuation of various parameters (εr, σ) of concrete against frequencies and realized that the attenuation incurred due to the change in incidence angle is approximately the same as the one computed above. For example, the following figure shows the attenuation vs. incident angle for different parameters:

Figure 6.8. Attenuation of concrete vs. incident angle of the following parameters: εr= 5, σ = 0.1 S/m.

Chapter 6. IMPLEMENTATION 37

Thus we will take the above theoretical graph as a reference for our incidence angle loss. In order to get the frequency dependent nature of the concrete, i.e. how the concrete attenuation changes as a function to frequency, we shall use the most complete single examination of building material properties at microwave frequencies which was performed by Stone and coworkers at the US national Institute of Standards and Technology’s Gaithersburg laboratories [24]. The limitations of this study are mainly the low cure time that the concrete specimen was subjected to, thus increasing the overall attenuation greatly from what they would have been had the concrete specimen they were cured for months or years. However, we can extract several important characteristics of the average concrete mix such as the frequency dependent nature and the thickness dependent nature. In addition, we can also extract the effect of the slightly and heavily reinforced grids embedded in concrete. The following is the data extracted from [24] and its corresponding figure (see figure 6.9) from the 8 various mixtures of concrete and averaged over the three different thicknesses over the following frequency range:

Table 6.1. Average data from Stone.

Freq (GHz) Wall width (cm)

0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.5 4

10.2 9.50 11.50 12.83 13.97 14.93 15.77 16.90 18.73 20.57 22.40 24.23 24.24 24.01

20.3 22.08 24.43 26.33 28.25 29.67 30.50 31.67 36.50 41.33 46.16 50.99 51.83 52.67

30.5 36.42 37.25 38.00 38.58 38.67 38.50 38.35 46.85 55.34 63.84 72.33 84.50 85.33

Chapter 6. IMPLEMENTATION 38

0

10

20

30

40

50

60

70

80

90

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Freq (GHz)

Attenuation (dB)

10.2 cm 20.3 cm 30.5 cm

Figure 6.9. Averaged Attenuation of concrete vs. frequency of the following parameters: thickness =

10.2 cm, 20.3 cm, 30.5 cm [24].

Therefore, correlating the frequency change of the above data with the value that we have got above using the given parameter and theoretical mode ( 9.5 dB @ 17 cm thickness), we get the following data table and corresponding graph:

Table 6.2. Average calibrated data from Stone.

Freq (GHz) Wall width (cm)

0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.5 4

10.2 3.89 4.71 5.26 5.72 6.12 6.46 6.93 7.68 8.43 9.18 9.93 9.94 9.84

20.3 9.05 10.01 10.79 11.58 12.16 12.50 12.98 14.96 16.94 18.92 20.90 21.24 21.58

30.5 14.92 15.27 15.57 15.81 15.85 15.78 15.72 19.20 22.68 26.16 29.64 34.63 34.97

Chapter 6. IMPLEMENTATION 39

0

5

10

15

20

25

30

35

40

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Freq (GHz)

Attenuation (dB)

10.2 cm 20.3 cm 30.5 cm

Figure 6.10. Averaged Attenuation of concrete vs. frequency of the following parameters: thickness =

10.2 cm, 20.3 cm, 30.5 cm after correlating with the above measurement.

We have also modeled using [24] reference, the affect of slightly and heavily reinforced steel on a concrete specimen. Two cases of reinforcements are taken into consideration as we can see in the following figure:

Chapter 6. IMPLEMENTATION 40

Figure 6.11. The two kinds of reinforcements that were taken into consideration. Slightly reinforced

concrete consisting of 14 cm spacing between metal rods, and heavily reinforced consisting of 7 cm

spacing between metal rods. The two specimens are taken from [24].

Relying on the data that was measured by [24], we come up with the following graph relating the non-reinforced concrete to its corresponding slightly and heavily reinforced concrete counterparts.

Chapter 6. IMPLEMENTATION 41

0

5

10

15

20

25

30

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Freq (GHz)

Attenuation(dB)

20 cm No Rein 7 cm Rein 14 cm Rein

Figure 6.12. Averaged Attenuation of slightly (14 cm) and heavily (7cm) concrete vs. frequency of the

following parameters: thickness = 20.3 cm.

6.3 Implementation of the model in software

ICS Telecom is a program from ATDI used by Cedercom. The program includes various propagation models used to calculate the power received by an antenna when a signal is transmitted from a base station. To include our model into ICS Telecom, a dynamic linked library (dll) was created. The library is loaded from the propagation model menu of the program. When ICS Telecom needs to calculate a received power by an antenna, it sends to the dll the following structures and arrays: 1. InModel structure: This structure includes general information about the transmitter

and the receiver used to calculate the power. The structure includes: a. The number of ALT2 structures in the ALT2 array. b. The Tx’s x and y position (DTM point) c. The Tx and Rx Antenna Height

Chapter 6. IMPLEMENTATION 42

d. The Radiated Power in the direction of the receiver. e. The frequency. f. The DTM step in the x and y direction in meters.

2. ALT2 Array: The ALT2 array includes all the DTM points between the transmitter and the receiver. The ALT2 structure includes information about the DTM point. The structure includes:

a. The altitude of ground above sea level. b. The clutter code ( 0 = ground, 5 = trees, 9 = building ) c. The clutter altitude above ground. d. The x and y DTM coordinates of the point. e. The distance between the transmitter and this DTM point.

3. OutModel: This structure needs to be filled by the dll. It includes the following

fields: a. The free space field received b. The field received c. The diffraction loss

When a field strength is computed along a profile of n points between the Tx and

Rx, ICS Telecom successively calls the DLL, providing it first with a 2 element pointer of an ALT2 structure, then a 3 element pointer on an ALT2 structure (the third element is new), …, until a n element pointer is provided. Thus, the DLL is called n-1 times for a profile of length n to calculate the field received at the points between the receiver and transmitter (see figure 6.13). [20]

Figure 6.13. The solution displayed on ICS Telecom after receiving the solution from the dll.

Chapter 6. IMPLEMENTATION 43

Using the fact that each DTM point in Beirut map used by ICS Telecom has unique x and y coordinates, an idea came up to copy all the DTM points from ICS Telecom to an external program that can draw the map as a 3D model by incorporating the height and using the clutter code to specify if this point is ground, tree, water or building. So the job of the dll was to send the structures it receives to an another external program (Analyzer) that will save the DTM points, analyze the data, calculate the power received and then fill up the OutModel and return it to the dll which will then return it to ICS Telecom. This connection between the dll and the Analyzer program is done by establishing a TCP socket connection over port 4000. Therefore, the Analyzer program can be on another computer in the network and the dll will connect to it.

The Analyzer program is an eight thousand line of code program that uses the Microsoft Foundation Class, OpenGL and Windows socket libraries. The Analyzer program has two main calculation functions. In the first function, the Analyzer program calculates the field received from the data coming from the dll. In the second function, the program calculates the field received from the pre-stored data set and antenna specification in the program. The Analyzer program runs four threads in parallel. The four threads are:

1. The net link thread. 2. The data processor thread. 3. The graphical user interface (GUI) thread. (see figure 6.14) 4. The graphics engine thread.

Figure 6.14. GUI.

Chapter 6. IMPLEMENTATION 44

6.3.1 Net link thread

The net link thread takes care of listening on port 4000 for any coming connection from the dll. When a connection is established, the InModel structure and the ALT2 array are transmitted from the dll to the Analyzer program where the net link thread will save the received data into a buffer and then calculates the received power using first ITU-525 to calculate the free space received power. Then if there are any obstacles between the Tx and the Rx, Deygout-94 method will be used to calculate the diffraction loss. Then if the indoor propagation model is enabled from the main menu of the program, the concrete or glass loss will be calculated. Then the final received field will be calculated and the OutModel will be filled and return using the same TCP socket. Then the socket will be closed and the thread will wait for a new connection.

6.3.2 Data processor thread

The net link server saves the received data in a buffer. As explained before, ICS Telecom calls the dll n-1 times for a profile of n points. So the Analyzer program should be able to identify which data received belongs to the same profile to save it in the same data set. This job is the work of the data processor thread. This function was put is a separate thread so that the net link thread will not waste time in identifying which data belong to the same data set. The net link thread just saves the data in a buffer and then the data processor thread reads the data from the buffer and groups data of the same profile into one dataset. Then an entry is added in to the data set list box (see figure 6.15).

Figure 6.15. Data set section.

In the “Data set Selection” group box there are buttons that:

• Save and load the data set list into external files for future use.

• Delete a data set from the data set list.

• Empty the data set list.

• Rename a data set list, so that it can be identified easily later. When the user selects a data set from the data set list, its information is displayed in the “Data Set Information” group box. The information displayed includes the InModel fields

Chapter 6. IMPLEMENTATION 45

and the ALT2 fields of each DTM point. The buttons in this group box are used to switch between the DTM points.

6.3.3 GUI thread

The GUI thread takes care of the user input. The main dialog is divided into five main parts:

1. Data set list section. 2. Terrain file specification and creation section. 3. Antennas properties section. 4. Graphics options section. 5. Calculation section.

6.3.3.1 Data set list section

The data set list part was discussed above in the data processor thread section.

6.3.3.2 Terrain file specification and creation section

Figure 5.16 shows the terrain creation controls group box. The group box contains three buttons: 1. Create Terrain: Creates a terrain file from all the data sets in the data set list. The

algorithm saves the DTM points in a random access file in an efficient way so that they can be loaded later. If a DTM point occur more than one time in the data set list, the algorithm keeps updating the saved file with the last occurrence.

2. Update Terrain: Takes a terrain file created by “Create Terrain” and adds to it the new points from the data set list.

3. Terrain info: Displays the maximum x and y coordinates in a terrain file.

Figure 6.16. Terrain creation group box.

Coverage data were sent from the ICS Telecom to the Analyzer program using one km radius. Then using create and update terrain functions, a terrain file that contains all Beirut was created. Figure 6.17 shows the “Terrain File” group box. The “Terrain File” button specifies the terrain file that will be used for the 3D modeling. The maximum x and y coordinates in the terrain file is displayed also.

Figure 6.17. Terrain file specification.

Chapter 6. IMPLEMENTATION 46

6.3.3.3 Antennas properties section

Figure 6.18 shows the “Antenna Properties” group box.

Figure 6.18. Antenna properties group box

The group box contains 9 buttons: 1. Data Set Tx: creates a new antenna with the x and y coordinates from the first DTM

point in the data set which is selected in the data set list. 2. Data Set Rx: creates a new antenna with the x and y coordinates from the last DTM

point in the data set which is selected in the data set list. 3. New Antenna: opens the antenna properties dialog (see figure 6.19) where various

parameters of the antenna are set. The azimuth and zenith patterns are loaded from external files where for each angle the loss of the antenna is given. After setting the parameters of the antenna and pressing ok, a new antenna is created and added to the antenna list.

4. Delete Antenna: deletes the selected antenna from the antenna list. 5. Save Ant List: saves the antenna list with the properties of all the antennas in an

external file for future use. 6. Load Ant List: loads an antenna list from an external file. 7. Antenna Properties: opens the antenna properties dialog to set the various parameters

of the antenna. 8. Select Tx: select the selected antenna from the antenna list as the Tx antenna to be

used for the calculation of the power received in the second calculation function. 9. Select Rx: select the selected antenna from the antenna list as the Rx antenna to be

used for the calculation of the power received in the second calculation function.

Chapter 6. IMPLEMENTATION 47

Figure 6.19. Antenna properties.

The names and most important parameters of the selected Rx and Tx antennas are shown below the buttons.

6.3.3.4 Graphics options section

Figure 6.20 shows the “Graphics Options” group box. The “Create WireFrame Model” check box specifies if the 3D model can draw a WireFrame model of the buildings. “Draw Terrain” button starts the graphics engine thread that creates the 3D model of the terrain file.

Figure 6.20. Graphics options group box.

6.3.3.5 Calculation section

Figure 6.21 shows the “Calculation Options” group Box. The “Create Data Set” button creates a new data set from the Tx and Rx antenna positions and uses the terrain file specified in the “Terrain File” group box to fill the DTM points between the Tx and Rx. From the azimuth pattern, zenith pattern, tilt, azimuth rotation and transmitted power of the Tx antenna, the radiated power in the direction of the receiver is calculated. The “FZ” field specifies the amount of the first fresnel zone that will be used for calculating the subpath attenuations. The “Building Loss” field specifies the loss of the signal in dB

Chapter 6. IMPLEMENTATION 48

when it passes in a building of one Km width. This value is used to calculate the power of the received signal when we take the signal component that passes through the building and not the diffracted component when there is an obstacle between the Tx and Rx.

Figure 6.21. Calculation options group box

The “Indoor Propagation Model” check box specifies if the indoor model calculations will be done for the two calculation functions. The “Set Indoor Model Parameters” button opens the “Indoor Model Parameters” dialog (see figure 6.22) where the obstruction material is specified as either concrete or glass. The thickness in cm of the obstruction material is specified in the thickness text field. For the glass obstruction, the relative dielectric constant and electric conductivity should be specified (default values are placed). For the concrete model, the user should choose if the concrete is not reinforced, slightly reinforced or heavily reinforced.

Figure 6.22. Indoor model parameters.

Chapter 6. IMPLEMENTATION 49

The “Calculate Received Power” button calculates the free space power received as if there was no obstruction. Then it calculates the indoor model loss. If there is an obstruction between the Tx and Rx, two loss components are calculated: 3. The diffraction loss using Deygout-94 method. 4. The penetration loss for the signal component that cuts through the buildings. For the two calculations, the final power received is calculated by subtracting the indoor model loss and the diffraction loss or the penetration loss from free space power received. All the values are displayed in the “Calculation Output” dialog (see figure 6.23). In addition the different subpath attenuations are displayed alone in the “Subpath Attenuation” group box.

Figure 6.23. Calculation Output.

6.3.4 Graphics engine thread

When “Draw Terrain” button is pressed in the “Graphics Options” group box, a new thread is created. The thread creates a new window and initializes the OpenGL interfaces. First the thread loads the terrain file that is specified in the “Terrain File” group box. It displays a 2D image of the terrain file and displays on the right the name and sector number of all the antennas in the antenna list (figure 6.24). Also on the terrain, each antenna will be drawn as a square with a small yellow line that represents the direction of the antenna. Using the mouse, the user can select which antenna is the Tx antenna and which antenna is the Rx antenna. Then the user creates, by clicking and dragging the mouse, a yellow box that represents the portion of the terrain that will be modeled in 3D. As soon as the box is specified, the graphics engine will go to its next state. In this state the graphics engine models in 3D to scale the terrain; where ground is drawn in black color, trees are drawn in green color, water is drawn in blue color and buildings are drawn in gray (figure 6.25). The “W” and “S” keys are used to move the user forward

Chapter 6. IMPLEMENTATION 50

and backward respectively. The “A” and “D” keys are used to strafe the user left and right. The “Q” and “E” keys are used to move the position of the user up and down. The “R” and “F” keys are used to increase and decrease the speed of movement. The right and left arrow keys are used to rotate the view left and right. The up and down arrow keys are used to move the view up and down. Each antenna in the antenna list is drawn as a thin line above the building and the name of the antenna is written above the line. A red line will join the chosen Tx and Rx antennas. Pressing “1”, “2” and “3” keys will draw the first fresnel zone in red, the second fresnel zone in green and the third fresnel zone in blue respectively. If “Create WireFrame Model” check box is clicked, the user can press the “L” key and the WireFrame model will be rendered (figure 6.26). Then the user can press the “P” key to turn off the 3D rendering and keep only the WireFrame Model to see how the signal cut through buildings (figure 6.27).

Figure 6.24. 2D terrain image.

Chapter 6. IMPLEMENTATION 51

Figure 6.25. 3D model.

Figure 6.26. WireFrame Model.

Chapter 6. IMPLEMENTATION 52

Figure 6.27. WireFrame model with fresnel zone.

53

Chapter 7

Evaluation

After coming up with the model, the next important step is to validate, verify and evaluate the results that the model gave and check if it adheres to the measurements that we have done. We will first present the evaluation of the glass model. Since there were no measurements involving glass attenuation, we will have to validate our multi-ray model against other references that have done some measurements on glass slabs. We will use glass measurements in [24] to correlate to our model. Thus the following is a graph relating what our theoretical model gives to what the measurement in [stone] has given:

Figure 7.1. Attenuation of glass vs. frequency at normal incidence: thickness = 1.3 cm , εr= 5.

Chapter 7. EVALUATION 54

Figure 7.2. Attenuation of glass vs. frequency at normal incidence: thickness = 1.9 cm , εr= 6.5.

Thus we can see that the error between our model and what Stone has measured is on average less than 0.5 dB. As for the concrete model, we will evaluate it using the measurements that we have done and relating it to what our program gives. The below table shows the received power of the measurements done and what our program outputs. All the measurements done were LOS cases due to the omni antenna that did not have enough gain to be able to receive MLOS signals. Our program output will be based only on ITU-525. For the case of behind wall measurements, the measurements were done on the same site rooftop but behind a non reinforced wall. The “program indoor output” in the table below is our program’s output based on ITU-525 and the loss of the implemented concrete model.

Table 7.1. Measurements and program results.

Measurement Name

Measured Calibrated

Signal (dBm)

Program Outdoor Output (dBm)

Error = Meas. – Program outdoor

(dB)

Wall thickness

(cm)

Behind Wall

(dBm)

Program Indoor Output (dBm)

Error = Behind Wall – Prog. Indoor (dB)

M1 -68 -67.67 -0.33 20 -86 -85.75 -0.25

M2 -62 -63.3 1.3 30 -86 87.6 1.6

M3 -72 -70.9 -1.1 20 -91 89 -2

M4 -67 -67.1 0.1

Chapter 7. EVALUATION 55

M5 -77 -63 -14 15 -92 -77 -15

M6 -80 -70.8 -9.2

M7 -70 -66.9 -3.1

M8 -72 -66.4 -5.6 15 -90 -80 -10

M9 -78 -68.8 -9.2 20 -97 -87.2 -9.8

M10 -67 -66.8 -0.2 20 -85 -85.1 0.1

M11 -63 -64.1 1.1 30 -87 -88.4 1.4

M12 -68 -65.4 -2.6

M13 -65 -64.4 -0.6 20 -83 82.5 -0.5

M14 -67 -67 0 15 -79 -80.5 1.5

M15 -65 -63.9 -1.1 20 -85 -82 -3

M16 -71 -70.2 -0.8 15 -86 -83.7 -2.3

M17 -67 -67.3 0.3 25 -89 -88.5 -0.5

M18 -69 -69.1 0.1 15 -86 -82.7 -3.3

M19 -67 -66.6 -0.4 20 -87 -84.7 -2.3

We can see that in most cases the error between the measurements and what our model gives is very small (within ±3 dB). However, in some of the measurements (such as M5), we can see that the program has deviated greatly due to presence of wires and metal doors that were near our measurements and would not be incorporated in a map or in our program. Thus giving rise to such erroneous measurements. If we omit these measurements we would get the following average error for the overall model = 2.8 dB.

56

Chapter 8

System Constraints

In our system design, we encountered a lot of constraints that tried to hinder our progress. However, we were able to successfully overcome all of these constraints to finally come up with required model. On the economical level, the project required sophisticated measuring equipment which obviously cost a lot. However, and since Cedarcom are the sponsors of the project, they provided us with the necessary equipment. Another important economic constraint was being able to obtain the ATDI software which cost around $20,000 to get its license. However, Prof. Walid Ali Ahmad, through his connections, was able to obtain the software for the university. As for the environmental aspect, field measurements were done during the months of February and March, therefore, we had to face heavy winds and rain on the rooftops of buildings during our measurements. As a result, we started watching the weather forecast new in order to have a vivid idea on when we will be able to perform the measurements. During the field measurements and despite the fact that we had a paper signed from the dean showing explicitly the nature of our project, we faced a problem of not being able to enter many buildings. This was primarily due to the non-helpful social characters of many people. We overcame this problem by simply choosing other building to go to. Finally, we had an important criterion to meet, which is sustainability. The model has to function properly even if many new buildings were constructed. Therefore, our design does not depend on a specific map but it can be easily customized according to user needs and demands to stay robust.

57

Chapter 9

Conclusion

In this final year project, we have implemented a propagation model that is divided into two main parts: outdoor and indoor models. The outdoor model is based on the ITU-525 model for the calculation of the received free space electric field and Deygout 94 for diffraction losses. The indoor model takes into consideration the two main construction materials in Beirut buildings: concrete and glass. The model was validated through several field measurements done in Salim Slem and Ras AlNabe’ areas. Specifically, the model was within ± 3 dB from the measurements. The complete model was implemented in a stand-alone software that can be linked to ICS Telecom using a dynamic linked library (dll). Concerning the future work to be done, additional field measurements should be performed using new WiMAX equipment in order to further develop the model and adhere to WiMAX specifications.

58

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