AKSUM UNIVERSITY

Aksum Institute of Technology

Faculty of Electrical and Computer Engineering
Department of Electronic Communication Engineering
Host Company: Mekelle Ethio Telecom, North Region

INTERNISHIP REPORT & PROJECT

NO STUDENT NAME ID NUMBER
1. Gebrehiwot Hiluf AKU1101941
2. Meron Kahsay AKU1102375
3. Kiros Seyfu AKU1101915
Advisor name Mr. Yonas Desta (M.Sc.)
Submission date: 16/05/2017 E.C
Mekelle,Ethiopia 2017 E.C
 Declaration
We hereby declare that the internship report is prepared and completed by us under the
supervision and guidance of Ethio Telecom offices. We, students Axum University Institute of
technology studying Electrical and Computer engineering, Electronics and Communication
stream, are declaring that this report describes our three month training span in North Region
Ethio telecom. We had stayed on operation and maintenance department from October, 2024 to
January, 2025. We hereby confirm that all the source materials used while writing this report
are referenced and acknowledged properly by our signatures
Name of Student Signature Date
1. Gebrehiwot hiluf ……… ___________ ___//____//_____
2. Meron kahsay……….….___________ ___//____//_____
3. kiros seyfu........ ____________ ___//____//_____
Advisor’s approval
As internee advisor, I hereby certify that I have read, evaluated and checked that this report is
compiled according to the format given by the faculty.
Advisor Name Signature Date
1. Mr.Yonas Desta(Msc)…………… __________ ___//_____//_____i
 INTERNSHIP REPORT AND PROJECT

Abstract
This report introduces several new concepts and terms that will be used through the
internship program and practical application of Electrical & computer Engineering.
And this Internship program is mainly concerned in communication & networking
Engineering to create productive, skilled and knowledgeable generation. This
report is an outcome of the practice we conduct during our internship period at
Ethio telecom of Mekelle. This brings to us a great opportunity to realize our
theoretical knowledge by practical works, which we gained for the last four years
of study in Axum University.
This report is organized in to two the first part describes the report which includes
describing briefly the back ground of ethio-telecom (including its history,
objective, vision, mission), describing the overall internship experience we had
gained during the practical periods & the second part is the project on the planar
array antenna.

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Acknowledgement
Above all, we want to express our gratitude to our family for supporting us emotionally and
financially throughout this program. Additionally, we would like to thank our department for
providing us with this internship program in order to broaden our knowledge and practical
experience. Furthermore, we would like to thank Ethio Telecom Mekelle for letting us finish
our internship there. The following, however, deserves special attention. We want to start by
expressing our gratitude to everyone at the Ethio Telecom who has supported and assisted us
throughout our time there. Throughout the entire process of getting ready for the internship
program, their critical criticism, suggestions, and encouragement were of great help to us.
A special thanks to our supervisor, MR kahsay introduce us with stuff members & Eng.
zelalem from the RAN subsection, whose wealth of experience and knowledge made our time
at the company truly meaningful. We are also profoundly thankful to Eng. kedir from the
transmission department and Eng. ambessa from the RAN subsection, for letting us unlimited
opportunities to inquire, observe and freely discuss on every system and network equipment’s.
Lastly, we extend our deepest gratitude to our advisor, Ins. Yonas (MSC), for his guidance,
insightful corrections, and diligent follow-ups on our documents. his support and attention to
detail were instrumental in our success.

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Table of contents
Contents
Declaration................................................................................................................................................2
Abstract...................................................................................................................................................53
Acknowledgement..................................................................................................................................54
Table of contents.....................................................................................................................................55
List of figures..........................................................................................................................................58
List of tables............................................................................................................................................59
ACRONYM............................................................................................................................................60
CHAPTER ONE.....................................................................................................................................65
BACK GROUND OF ETHIO TELECOM............................................................................................65
1.1 INTRODUCTION............................................................................................................................65
1.2 BRIEF HISTORY.............................................................................................................................65
1.3 VISION, MISSION, VALUES AND OBJECTIVES OF ETHIO TELECOM................................67
1.3.1 Vision.........................................................................................................................................67
1.3.2 Mission......................................................................................................................................67
1.3.3. Value.........................................................................................................................................67
1.3.4. Objective...................................................................................................................................67
1.4. ORGANIZATIONAL STRUCTURE..............................................................................................68
1.5 SERVICES AND PRODUCTS........................................................................................................69
1.5.1. Mobile service..........................................................................................................................69
1.5.2. Fixed line service......................................................................................................................70
1.5.3. Internet service.........................................................................................................................70
1.6 CUSTOMERS OF ETHIO TELECOM...........................................................................................70
1 .7 ETHIO TELECOM KEY STAKEHOLDERS................................................................................71
1 .8 WORK FLOW NORTH REGION ETHIO TELECOM.................................................................71
CHAPTER TWO....................................................................................................................................73
Overall Internship Experience................................................................................................................73
2.1 OBJECTIVES OF THE INTERNSHIP...........................................................................................73
2.1.1. General objectives....................................................................................................................73

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2.1.2. Specific objectives....................................................................................................................73

2.2 HOW DID WE GET INTO THE INTERNSHIP HOSTING COMPANY?....................................73
2.3 WORK SECTIONS........................................................................................................................74
2.3.1 Workflow of RAN section.........................................................................................................74
2.3.2 Workflow of IP backbone..........................................................................................................75
2.4 WIRELESS COMMUNICATION...................................................................................................75
2.4.1 Radio waves:.............................................................................................................................75
2.4.2 Micro waves:..........................................................................................................................76
2.4.3 Infrared waves: IR.....................................................................................................................76
2.5 RADIO ACCESS NETWORK (RAN)..........................................................................................77
2.5.1 GSM ARCHITECTURE...........................................................................................................78
2.5.2 Radio Station Subsystem:..........................................................................................................78
2.5.3 Operation and Support Subsystem (OSS).................................................................................83
2.5.4 GSM logical channels................................................................................................................84
2.5.2 Universal Mobile Telecommunication Systems (UMTS),........................................................86
CHAPTER THREE................................................................................................................................89
Analyzing Performance of Rectangular Planar Array Antenna..............................................................89
Summary of Project................................................................................................................................89
3.1 Introduction......................................................................................................................................90
3.2 Statement of problem.......................................................................................................................91
3.3 Objective of the project....................................................................................................................91
3.3.1 General Objective......................................................................................................................91
3.3.2 Specific Objectives....................................................................................................................91
3.4 Significance of the Project................................................................................................................91
3.5 Scope and Limitation of the Project.................................................................................................92
3.5.1 Scope of the Project...................................................................................................................92
3.5.2 Limitations.................................................................................................................................92
3.6 Literature Reviews............................................................................................................................92
3.7 Methodology.....................................................................................................................................93
3.7.1 Methods.....................................................................................................................................93
3.7.2 Fundamental Parameters of Antenna.........................................................................................93
3.7.3 System Model............................................................................................................................95

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3.7.4 Planar Array Beam forming.......................................................................................................96

3.7.5 Gain and Element Factor of Planar Arrays................................................................................97
3.7.6 Array Factor...............................................................................................................................99
3.7.7 Grating Lobe Issues for Planar Arrays....................................................................................103
3.7.8 The beam width of a planar array............................................................................................104
3.7.10 Result, Discussion, and Conclusion......................................................................................107
CHAPTER FOUR.................................................................................................................................119
Overall Benefits Gained from the Internship........................................................................................119
4.1 Upgrading Theoretical Knowledge.................................................................................................119
4.2 Improving Practical Skills..............................................................................................................119
4.3 In terms of Industrial Problem-Solving Capability........................................................................120
4.4 In terms of Improving Interpersonal Communication and Teamwork...........................................120
Skills.....................................................................................................................................................120
4.5 Improving Leadership Skills..........................................................................................................120
4.6 Understanding Work Ethics-Related Issues....................................................................................121
4.7 In terms of Entrepreneurship Skills................................................................................................121
CHAPTER FIVE..................................................................................................................................122
Conclusion and Recommendation........................................................................................................122
5.1 Conclusion......................................................................................................................................122
5.2 Recommendation............................................................................................................................122
5.2 .1 Recommendation for the Company........................................................................................122
5.2.2 Recommendation for the University........................................................................................123
5.2.3 Recommendations for Students...............................................................................................123
References.............................................................................................................................................124
References.............................................................................................................................................124
Appendix...............................................................................................................................................125
Appendix1: Array Factor calculation code for fixed values of N, and M............................................125
Appendix2: Matlab code for simulating 3D Array Factor....................................................................126

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List of figures
Figure 1.1 organizational structure of ethio telecom................................................................................................
Figure 1.2 overall organizational work flow of ethio telecom, northern region......................................................
Figure2.1 wireless transmission media.....................................................................................................................
Figure 2.2 multiple access........................................................................................................................................
Figure 2.3 GSM structure network...........................................................................................................................
Figure 2.4 BTS tower & indoor physical appearance respectively..........................................................................
Figure 2.5 BBU physical structure The....................................................................................................................
Figure 2.6 BSC module structure.............................................................................................................................
Figure 2.7 cellular structure of BTS.........................................................................................................................
Figure 2.8 GSM logical channel...............................................................................................................................
Figure 2.9 network elements in WCDMA based PLMN.........................................................................................
Figure 3.1: Flowchart for the simulation of a planar array.......................................................................................
Figure 3.2: Planar Array...........................................................................................................................................
Figure 3.3: Planar Array Geometry..........................................................................................................................
Figure 3.4: Two- dimensional planar array (M x N Rectangular Pattern)................................................................
Figure 3.5: Grating Lobe Issues with λ/2 Spacing (the two left side configurations) and Grating
Lobe Issues with λ Spacing (the two configurations to the right side)....................................................................
Figure 3.6: Beam width............................................................................................................................................
Figure 3.7: Rectangular Array Factor at dx=lambda/4 and dy=lambda/4................................................................
Figure 3.8: Rectangular Array Factor at dx=lambda/2 and dy=lambda/2................................................................
Figure 3.9: Rectangular Array Factor at dx=lambda and dy=lambda......................................................................
Figure 3.10: Rectangular Array Factor for N=8 and M=10 with varying dx and dy...............................................
Figure3.11: 3D Array Factor of a 6x6 planar array antenna with dx=dy=0.25lambda............................................
Figure 3.12: 3D Array Factor of a 6x6 planar array antenna with dx=dy=0.50lambda...........................................
Figure 3.13: 3D Array Factor of a 6x6 planar array antenna with dx=dy=lambda..................................................

List of tables

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Table 2.1 description of BBU modules....................................................................................................................

Table 3.1 of 3D Summary.......................................................................................................................................
Table 3.2 of 3D Summary.......................................................................................................................................

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ACRONYM
1G……………….……..………...First Generation cellular network
2G……………………..…..….…..Second Generation cellular network
3GPP…………………..………...Third Generation Partnership Project
AAA……………………..……....Authentication Authorization and Accounting
ADM……………………...……..Add and Drop Multiplexer
ADSL……………………..……..Asymmetric Digital Subscriber Line
AGCCH………….……….……..Access Granted Control Channel
AM…………….……….....…….Adaptive Modulation
ASG……….…………………….Aggregate Site Gateway
ATM……….………………….....Asynchronous Transfer Mode
ATN…………………………..….Access Transmission Network
AuC……………………….….….Authentication Center
BB…………….….………..…….Broad Band
BBU……………...………...Baseband Unit
BCCH………………..……..Broadcast Control Channel
BSC………………..……….…….Base Station Controller
BSS………………...........……….Base Station Subsystem
BTS………………...…...……..…Base Transceiver Station
CCH…………………………...…Control Channels
CDMA…………………...........…Code Division Multiple Access
CEO………………….…..……....Chief Executive Officer
CN……………..…………….…...Core Network
CPRI……………………………..Common Public Radio Interface
CR……………………….…....Core Router
CS…………………………….Core switch/circuit switched
CSG…………………….….....Cell Site Gateway
CUG……………….………....Closed User Group
CWDM……………………….Course Wavelength Division Multiplexing
DCCH…………………….….Dedicated Control Channel
DCDU……………………..…Digital Current Distribution Unit
DDF………………………….Digital Distribution Frame
DL………………………….....Down Link
DSL…………………………...Digital Subscriber Line
DSLAM…………………..…..Digital Subscriber Line Access Multiplexer
DWDM…………….……..…..Dense Wavelength Division Multiplexing
EDGE………………………....Enhanced Data Rates for GSM Evolution

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EIR……………....…………....Equipment Identity Register

EMS……………….………….Element Management System
EPON…………………………Ethernet Passive Optical Network
ER…………………………..…Edge Router
ETC……………………………Ethiopian Telecommunication Corporation
EVDO………………………….Evolution Data Optimized
FAN…………………….…...…Fixed line Access Network
FCCH……………….….…...….Frequency Correction Channel
FDMA……………………....….Frequency Division Multiple Access
FE…………………….………...Fast Ethernet
FL…………………..……..……Fixed Line
FWT…………………………....Fixed Wireless Terminal
GE………………….….………..Giga Ethernet
GER…………………….……….General Excellent Router
GGSN………………..……….....Gateway GPRS Support Node
GMSC………………………….Gateway Mobile Switching Center
GOTA….. ……………..........Global Open Trucking Architecture
GPON…………………………...Giga Ethernet Passive Optical Network
GPRS………....…...……….…....General Packet Radio Service
GPS………………..………...….Global Positioning System
GSM……………….…….…..….Global System for Mobile Communication
HLR…………………………….Home Location Register
HSCSD………………………... High Speed Circuit Switched Data
ICT…………………...………...Information Communication Technology
IDU……………….….…………Indoor Unit
IF………………...……………..Intermediate Frequency
IFL……………………….….....Inter Facility Link
IMEI……………….…..………International Mobile Equipment Identity
IMSI……………………..…….International Mobile Subscriber Identity
IMT………………….………....International Mobile Telephony
IP…………………………….…Internet protocol
ISDN……………………………Integrated Service Data network
ISP…………………………..….Internet Service Provider
ITU……………………………..International Telecommunication Union
L3VPN…………………….…...Layer 3 Virtual Private Network
LAI……………………….……..Location Area Identifier

LD………………............….......Laser Diode
LE……………………………. .Local Exchange

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LED……………………....…... .Light Emitting Diode

LTE…………………………… .Long Term Evolution
Mbps…………………………..Megabyte per second
MME……………………...…...Mobility Management Entity
MPLS…………………….……Multi-Protocol Label Switching
MS………………………….….Mobile Station
MSAG………………….……...Multi Service Access Gateway
MSAN……………….….……..Multi Service Access Node
MSC……………………………Mobile Switching Center
MSG…………………………..Multi Service Gateway
MSTP………………..……….Multi-Service transport protocol
MU…………………..……….Multiplexing Unit
NE……………………………Network Equipment
NGN……………….……..….Next Generation Network
NR……………………………North Region
NSS…………………..……….Network and Switching Subsystem
O&M………………..….……..Operation and Maintenance
OA………………….…………Optical Amplifier
ODF……………………………Optical Distribution Frame
ODU………………….…..……Outdoor Unit
OLA……………………………Optical Line Amplifier
OMT…………………….…...…Ortho Mode Transducer
OSC………………………….…Optical Supervision control
OSS……………………….…….Operation Subsystem
OTU…………………………….Optical Transmission unit
PDP………………………….…..Protocol Data Packets
PIN………………….……...……Personal Identity Number
PLMN………………..………….Public Land Mobile Network
PMO…………………………..…Project Management Office
POTS……………………………Plain Old Telephone System
PS………………………………..Packet Switched
PSTN………………………..…..Public Switched Telephone Network
PTN…………………………..…packet Transport Network
PUK……………………….…….PIN Unlocking Key
QAM………………………..……Quadrature Amplitude Modulation
QOS……………………….……..Quality of Service
QPSK……………………………..Quadrature Phase Shift Keying
RACH……………………………..Random Access Channel
RAN…………………………...…..Radio Access Network

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RF…………………………...……..Radio Frequency
RFS………………………………...Radio Frequency Subsystem
RNC……..…………………………...Radio Network Controller
RR…………………………………..…Reflector Router
RRU…………………………………….Remote Radio Unit
RSG…………………………………….Radio Service Gateway
RSS……………………………….…….Radio Station Subsystem
RTN…………………………………….Radio Transmission network
SCH………………………………….… Synchronization Channel
SDH…………………………………….SynchronousDigitalHierarchy
SG…………………………………………Signaling Gateway
SGSN……………………………………Serving GPRS Support Node
SIM………………………………………Subscriber Identification module
SMS………………………………….…..Short Messaging Service
SOH………………………………………Section Over Head
STM………………………………………Synchronous Transfer Mode
TCH/F…….. …………………………….Traffic Channel/Full rate
TCH/H……………………………………Traffic Channel/Half rate
TDMA……………………………………Time Division Multiple Access
TEP……………………………………….Telecom Expansion Project
TG……………………………………….Trunk gateway
TM………………………………………..Terminal Multiplexer
TMSI……………………………………..Temporary Mobile Subscriber Identity
TRX………………………………………Transceiver
UE………………………………………..User Equipment
UL………………………………………..Up link
UMTS……………………………………Universal Mobile Telecommunication System
USIM……………………………………UMTS Subscriber Identity Module
UTRAN………………………………….UMTS Terrestrial RAN
VAS……………………………………..Value Added Service
VDSL…………………………………...Very High Speed Digital Subscriber Line
VLAN…………………………………..Virtual Local Area Network
VLR……………………………………..Visitor Location Register
VPN……………………………………..Virtual Private Network
VSAT……………………………………Very Small Aperture Terminal

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VSWR…………………………...............VoltageStandingWaveRatio
WCDMA………………………...............Wideband Code Division Multiple Access
WDM…………………………………….Wavelength Division Multiplexing
WIMAX………………………………….Worldwide Interoperability for Microwave Access

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CHAPTER ONE

BACK GROUND OF ETHIO TELECOM

1.1 INTRODUCTION
Ethio telecom, previously known as the Ethiopian Telecommunications Corporation
(ETC), is an integrated telecommunications services provider in Ethiopia, providing
internet and telephone services. Based in Addis Ababa, it is one of the "Big-5" groups of
state owned corporations in Ethiopia, along with Ethiopian Airlines, the Commercial
Bank of Ethiopia, Ethio -Insurance, and the Ethiopian Shipping Lines.
The Ethiopian telecommunication started with a low rank beginning more than a
hundred years ago by establishing a telephone link between the capital city and
some major imperial cities. Based in Addis Ababa Today, telecommunication has
extended to the interior of the country and uses technologies such as micro-wave, satellite
and fiber optics.

1.2 BRIEF HISTORY

The introduction of telecommunications services in Ethiopia dates back to 1894,
when Minilik II, the King of Ethiopia, introduced telephone technology to the country.
However the first Ethiopian pioneer of telephony was his cousin Ras Mekonnen who
came back with telephone apparatus in 1889 after his visit of Italy and established a
company. In the following years, the technological scheme contributed to the integration
of the Ethiopian society when the extensive open wire line system was laid out linking the
capital city, Addis Ababa, with all the important administrative cities of the country. The
installation sequence of telegraph line in
Ethiopia was constructed as:-
 First in the years 1897 - 1899 between the city of Harar and the capital Addis Ababa. 
In 1904/05 from Addis Ababa into Eritrea and to Massawa via Tigray. Changed to seven
digits and the area codes from two to three digits. In 1905/06 from Addis Ababa to Gore
in the province of Illubabor and Jimma in Kaffa.
 Between 1905 and 1913 between Addis Ababa and Gondar, southern and western
Ethiopia (Gambella, Nekemte, Sidamo, etc.), Dire Dawa and Djibouti.
 In 1909 Ethiopia joined the International postal, telegraph and telephone service.  In
1914, The Addis Ababa telephone exchange started to serve some 100 subscribers, and in
1932, 200 subscribers were supported.
 In 1932, Ethiopia became member of the International Telecommunication Union
(ITU)

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 In 1933, radio-telephone communication was introduced and greatly enhanced national

and international connections, that is, services became beyond telegraph  In 1934,170
towns and villages become the beneficiaries of telephone services
 In 1979, Sululta Satellite Earth Station Established and began to operate.
 In 1987,the second Sululta Satellite Earth station began operation
 In 1988, Digital exchanges start operation in Addis Ababa and other major towns for the
first time.
 In 1990, a Domestic Satellite Earth Station went operational.
 In 1997, Internet Service had introduced.
 In 1999, Mobile Telephone Service had launched.
 In 2001, Digital Data Network Service had introduced.
 In 2003, International Mobile Roaming, Satellite Mobile Service had launched and
prepaid mobile system was introduced.
 In 2006 the six digits fixed line and mobile telephone numbers had
The company was placed under government control at the beginning of the twentieth
century, and was later brought to operate under the leadership of the Ministry of Post
and Communications until 1952. In 1952, it became an autonomous entity under the
Ministry enactment of Telecommunication Proclamation No.131 1952. By this
proclamation telecommunication entity, called "Imperial Board of Telecommunication of
Ethiopian," IBTE, which exclusively regulates and operates telecommunication services,
was established. In 1975, IBTE was recognized as Ethiopian Telecommunications
Service. Without affecting its functions, the name was later changed to Ethiopian
Telecommunication Authority in 1975. On November 1996, the nomenclature altered to
ETC by Council of Ministers regulation No. 10/1996. The subsequent Proclamation
49/1996 expanded the ETC's duties and responsibilities. In late 2006, the ETC signed an
agreement worth US$1.5 billion with three Chinese companies, ZTE Corporation,
Huawei Technologies and the Chinese International Telecommunication Construction
Corporation, to upgrade and expand In 2010, the nomenclature was changed to Ethio
Ethiopian telecommunications services.
To ensure that Ethio Telecom runs parallel with top telecom operators, the Ethiopian
government has reached an agreement with France Telecom, one of the world‘s
leader telecommunication companies. The French Telecom company has taken over the
management of the country‘s sole telecom provider from 2010 to 2013.

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1.3 VISION, MISSION, VALUES AND OBJECTIVES OF ETHIO

TELECOM
1.3.1 Vision
Ethio Telecom vision encompasses the following crucial points.
 To be a world-class telecommunications service provider
 To be committed to understand, meet and exceed the telecommunication needs and
expectations of country at large and customers in particular.
 To be a center for advancement of ICT, via research, innovation, transfer, adoption,
diffusion, adaptation, integration and dissemination in Ethiopia in particular and in
East/Horn of Africa in general.
1.3.2 Mission
Ethio Telecom mission runs in parallel with Ethiopian government‘s mission, supporting
the steady growth of Ethiopia by transforming and modernizing telecommunication and
services.
That is:
 To connect every Ethiopian through ICT.
 To provide products and services that enhances the development of our nation.
 To build a successful brand known for its customer consideration.
 To build its managerial capability that enables Ethio telecom to operate at an
international standard.
1.3.3. Value
While meeting international standards, Ethio Telecom remains faithful to its values which
are:
 Lead with vision
 Respect
 Excellence
 Accountability
1.3.4. Objective
 being customer-focused company offering the best quality of service building a
financial
sound company meeting excellent world class standards

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1.4. ORGANIZATIONAL STRUCTURE

Ethio Telecom ‘s organizational structure can be broadly viewed as technical division,
commercial division, support division and others. Each division has its own sub divisions
as listed below.

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Figure 1.1 organizational structure of ethio telecom

Ethio Telecom organizational structure includes different functional divisions that are under
direct administration of Board of Directors. As the figure above shown the organizational
structure of Ethio telecom depends on functional structure. The company has six major
significant divisions, which is led by chief officer, departments led by officer and section led by
managers. Even if this is create divisional rivalries it is best suit the company for the easy
implementation of Enterprise solutions applications. To grasp on our target divisions, Residential
division is responsible for the sales generated from residential people. Enterprise division is
responsible for all enterprises like government organization, profit and nonprofit organizations.
Marketing and communication division take care of marketing related activities like tariff
revision, new product or service launch and sales guides‟ different sales analysis including
market

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research. Customer service divisions undertake after sales and presales activities mainly
994, 980 for VIP customers. Technical Division, the core division of the company which
is responsible for entire network management of the company, Information system
division facilitates and ensures the automation part of the company as well as provides
necessary detailed and summarized information for managers depending on their request.
When we see this all the board of directors is the final controller of the company.
1.5 SERVICES AND PRODUCTS
Ethio Telecom is institutionalized with the objectives of promoting the development
of high quality, efficient, reliable and affordable telecommunication services in the
country. Its services can be broadly classified as:
 Mobile service  fixed line service
 Internet service
 Value added services (VAS)
1.5.1. Mobile service
Mobile service includes mobile roaming, satellite mobile, GOTA service and business
mobile.
 Mobile roaming is a service that helps subscribers automatically to make and receive
voice calls, send and receive data, or access other services when travelling outside the
geographical coverage area of Ethio Telecom, by means of using a visited country‘s
operator‘s network. It could be outbound roaming, a service given to Ethio customers
who wants to use their mobile phone abroad, and inbound, a service given to customers of
foreign operator who has a roaming agreement with it(like tourists, foreigner investors
…).
Currently this service is provided only for GSM post paid subscribers.
 GOTA (Global Open Trucking Architecture) is a service given using the CDMA2000
wireless network for the purpose of group communication. It allows two or more
individuals to communicate and also use for private and group calls using push to talk.
 Satellite mobile telephone is mobile phone that connects to orbiting satellites instead
of terrestrial network. It enables customers in every part of the globe to be beneficiaries of
telecom services through satellites stationed on the universe.
 Business mobile Service with/without CUG is a bundled postpaid mobile service that
allows enterprise customers to make calls at a discounted rate compared to the normal
mobile tariff rates.
 Packaged services are a service that could be provided in the form of voice off pick
package, GPRS package and SMS package. Special target of customers for all packages
include students, night shift workers, big Hotel workers and Taxi drivers.

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1.5.2. Fixed line service

It includes Wired Fixed line, Wireless Fixed line (CDMA), Short code, Bulk SMS and
ISDN/E1.
 Landline:-a telephone line that travels over terrestrial circuits. A land line can be copper
wire, fiber optics or microwave.

 Wireless Fixed line:-is much similar to the ordinary fixed telephone service; it uses Fixed
Wireless Terminal (FWT) which enables it to give a voice, data and other value added
services. It works where ever CDMA network is available.
 ISDN/E1 service:-Integrated services digital network (ISDN) is an international
communications standard for sending voice, video, and data over digital telephone lines
or normal telephone wires.
1.5.3. Internet service
1.5.3.1 Fixed broadband internet
Broadband is a relatively fast Internet service provided through wired and wireless
connections with a speed level from 256 Kbps.
 Fixed Wired broadband internet is provided through copper or fiber with different access
methods like ADSL, VDSL, EPON and GPON.
 Fixed wireless BB internet wireless is device or system used to connect different fixed
locations with a radio or other wireless link.
 Wireless broadband internet is an Internet service which can be given through different
access methods like, AIRONET, supports up to 54 Mbps downloading capacity, VSAT
(supports up to 2Mbps downloading capacity), EVDO and 3G.

1.6 CUSTOMERS OF ETHIO TELECOM

Ethio Telecom provides its different services to government organizations (administrative
offices, educational institutions), private and commercial companies (Internet cafes,
Private companies and Banks), international institutions (Embassies and organization
such as world health organization) and individuals.
1 .7 ETHIO TELECOM KEY STAKEHOLDERS
Stakeholder is a person, organization or any other institution which has a crucial share or
role on telecom operations, development and investment. Ethio telecom has technical side
as well as management side key stake holders. In technical side the vendors are Huawei,
ZTE, Ericson and Nokia.
In management peoples, nations and nationalities of Ethiopia), international operators,
the media and the investment and international communities are key stakeholders of Ethio

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Telecom. Manager side the stack holder was France telecom and now it is administered
under Ministry of Communication. Besides consumers (different governmental and non-
governmental institutions, the peoples, nations and nationalities of Ethiopia), international
operators, the media and the investment and international communities are key
stakeholders of Ethio Telecom.

1 .8 WORK FLOW NORTH REGION ETHIO TELECOM

The head office of Ethio Telecom is in Addis Ababa is networked with the regional
telecoms.
Our hosting company is one of the regional telecoms and is known as NR Ethio Telecom.
In NR Ethio Telecom there are seven main departments and these are:-

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Figure 1.2 overall organizational work flow of ethio telecom, northern region

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CHAPTER TWO
Overall Internship Experience
2.1 OBJECTIVES OF THE INTERNSHIP
2.1.1. General objectives
The general objective of the internship is to see the practical career environment and
acquire an insight on how theoretical concepts are applied in practical working
environment. Besides to observing and practicing the operational environment, it helps us
to know and apply the ethics of working environment like responsibility, punctuality,
professionalism and the like.
2.1.2. Specific objectives
Specific objective is to acquire and demonstrate competencies expected in a professional
managerial environment such as:
 Developing communicational, cooperativeness and team-work skills.
 Creating interrelation and interdependence to the internship company.
 Create conducive atmosphere to assess professional qualification.
2.2 HOW DID WE GET INTO THE INTERNSHIP HOSTING
COMPANY?
During our fourth year study, we chose communication and electronics engineering
stream and had been studying it for two semester and then joined the internship. Thus, our
internship have to be somehow related to Communication and electronics engineering.
The Aksum university pre engineering and internship office and we were searching
company that could accept us for about a year. . From the very few opportunities, we got
an acceptance in Ethio Telecom with the help of our University internship office in
collaboration with Ministry of Education and Ethio Telecom. We then took one day
training on overall organizational overview, rules and regulations of working
environment, products and services of Ethio Telecom in Addis Ababa at Ethio Telecom
Microwave building. At the end of the training, we were assigned to work at North
Region Ethio Telecom, Mekelle.
We were lucky enough to be assigned in the North Region Ethio Telecom, which was our
interest to work there. We were informed to report at our respective hosting human
resource offices and we do so. The North Region Human Resource office, Mr.haftu,
assigned us to work in wireless department.

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In wireless department we were told that, by Mr.teame, there are four sections which are
RAN, Core, Transmission and IP. Mr.teame informed as we will work in rotation a month
per section and directly assigned as to work in RAN sub section. We met with Mr.kahsay,
RAN supervisor, and introduce us with the stuff members. And we meet with engineer
ambessa & engineer zelalem from the RAN division delivered an enlightening lecture on
wireless communication and the tasks of the RAN section. eng. Zelalem led us on a field
trip to base stations in Mekelle City, offering detailed explanations of the equipment and
devices involved in mobile communication. The experience sparked a newfound
enthusiasm for exploring cellular communication advancements.

2.3 WORK SECTIONS

The work section we had been stayed in was wireless department. Wireless has
performance resource allocation, RAN, optimization, core, and transmission and IP
sections. Of these we had been involving in observing RAN, core, IP and transmission
sections.
2.3.1 Workflow of RAN section
The workflow of the Radio Access Network (RAN) section in this region Ethiotelecom
typically includes the following steps:
1, Network Planning: Engineers assess coverage requirements, traffic patterns, and
technology advancements to plan the expansion or optimization of the RAN. This
involves determining the location of base stations, antenna configurations, and frequency
allocation.
2, Site Survey and Acquisition: Site surveys are conducted to evaluate potential
locations for base station installation. This includes acquiring necessary permits,
negotiating with property owners, and ensuring compliance with regulatory requirements.
3, Equipment Installation: Once sites are secured, engineers install base stations,
antennas, and other RAN equipment. This involves mounting hardware, connecting
power and network cables, and configuring equipment settings.
4, Integration and Testing: Installed equipment is integrated into the existing
network infrastructure and thoroughly tested to ensure proper functionality. This includes
testing connectivity, signal strength, and handover procedures between base stations.
5, Customer Support and Troubleshooting: The RAN section provides support
to customers and addresses any network-related issues or complaints. This involves
troubleshooting connectivity problems, investigating coverage gaps, and resolving service
disruptions promptly

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2.3.2 Workflow of IP backbone

The workflow of the IP Backbone section in the north region typically involves several
key steps and processes to ensure the efficient operation and management of the core
network infrastructure. Here's an overview of the workflow:
1, Network Design and Planning: The process begins with network design
and planning, where engineers and architects analyze requirements, forecast traffic
demands, and design the architecture of the IP backbone network. This includes
determining the locations of network nodes, selecting appropriate hardware and software
components, and defining the routing protocols and addressing schemes to be used.
2, Infrastructure Deployment: Once the network design is finalized, the next step
involves deploying the necessary infrastructure components, such as routers, switches,
and optical transmission equipment, at various network locations. This may include
building or upgrading physical facilities such as data centers, network hubs, and
transmission towers to support the backbone network.
3, Configuration and Provisioning: After the infrastructure is in place, network
engineers configure and provision the network devices according to the design
specifications. This involves setting up routing tables, establishing logical connections
between network nodes, configuring security policies, and implementing quality of
service (QoS) mechanisms to prioritize traffic.
4, Monitoring and Maintenance: Continuous monitoring of network
Performance and health is essential to ensure optimal operation of the IP backbone.
Network operations centers (NOCs) use monitoring tools and software to track key
performance indicators (KPIs), detect anomalies or failures, and troubleshoot issues in
real time. Regular maintenance activities, such as software upgrades, hardware
replacements, and preventive maintenance, are also performed to keep the network
running smoothly.
5, Security and Compliance: Security measures are implemented to protect the IP
backbone network from various threats, including cyber-attacks, unauthorized access, and
data breaches. This includes deploying firewalls, intrusion detection/prevention systems,
access control mechanisms, and encryption technologies to safeguard network assets and
ensure compliance with regulatory requirements.
2.4 WIRELESS COMMUNICATION
 It is a communication while moving with wireless transmission medium.
 It refers to the transfer of info. B/n 2 or more points that are not physically connected. e.g.
Cellular Networks/Mobile networks
2.4.1 Radio waves:
 EM wave frequencies ranging from 3KHz to 1GHz

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 Use omnidirectional antennas.

 The radio wave band is under government regulation.
 used for multicast communications, such as radio & television, & paging systems
 They can penetrate through w
2.4.2 Micro waves:
 EM waves between 300KHZ & 300 GHZ
 Microwaves are unidirectional; propagation is line of sight.
 Use directional antennas – point to point line of sight communication
 The parabolic dish antenna & the horn antenna are used for transmission & reception of
microwaves.
 Used for unicast communication such as cellular telephones, satellite networks, &
wireless LANs.
 Higher frequency ranges cannot penetrate walls.

2.4.3 Infrared waves: IR

 infrared waves =>300 GHZ to 400THZ
 For short range communications such as b/n a pc & a peripheral device  Small distance,
typically no more than 10m.
 Line of sight ( or reflection ) propagation, blocked by walls E.g.TV remote control IRD
port

Figure2.1 wireless transmission media

Multiple access

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Figure 2.2 multiple access

2.5 RADIO ACCESS NETWORK (RAN)

A radio access network (RAN) is part of a mobile Telecommunication system which
implements a Radio access technology. Conceptually, it resides between devices such as a
Mobile phone, a computer, or any remotely controlled machine and provides connection
with its Core network (CN). RAN consists of Base Transceiver Station (BTS), Base
station Controller (BSC) for GSM, NodeB, Radio Station Controller(RNC) for UMTS,
eNodeB for LTE. It resides between Mobile station (UE plus SIM card) and Mobile
switching center (MSC).
RAN (Radio Access Network) has three sub departments: GSM for 2G, UMTS for 3G,
LTE and CDMA (Code Division Multiple Access) for 4G. Of these, we had seen GSM
and UMTS.
 1G: 1st Generation ex. AMPS - Advanced Mobile Phone System
• Analog cellular
 2G: GSM - Global System for Mobile Communication
 2G networks were built mainly for voice services & slow data transmission.

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 Ethio’s 2G GSM networks operate in the 900 MHz & 1800 MHz
2.5.1 GSM ARCHITECTURE

Figure 2.3 GSM structure network

2.5.2 Radio Station Subsystem:

Radio station subsystem is portion of GSM architecture which covers all the radio
aspects. RSS is composed of two subsystems
1. Mobile station (MS)
2. Base Station Subsystem (BSS)
Mobile station (MS):-
Mobile stations are the section of a GSM cellular network that the user sees and operates.
The two main elements are the main hardware, user equipment, and the SIM. The user
equipment contains the main elements of the mobile phone including the display case,

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battery, the electronics components used to generate the signal and process the data to be
received and transmitted. It also contains a number known as the International Mobile
Equipment Identity (IMEI) which is installed in the phone at manufacture. It is accessed
by the network during registration to check whether the equipment has been reported as
stolen.
The SIM (Subscriber Identity Module) contains the information that provides a unique
identity of the user to the network. Besides it stores user and location addresses such as
IMSI (International Mobile Subscriber Identity), TMSI (Temporary Mobile Subscriber
Identity) and LAI (Location
Area Identification). It also supports authentication and encryption mechanisms like PIN
(Personal Identity Number), PUK (PIN Unblocking Key), Ki - subscriber secret
authentication key, A3 - authentication algorithm, A8 - cipher key generation algorithm.
Mobile station can only operate if a SIM with a valid IMSI is inserted into equipment
with a valid IMEI, since this is the only way to correctly bill the associated subscriber.
2.5.2.1 Base Station Subsystem (BSS)
Base Station Subsystem (BSS) IS the Radio Access Network (RAN) section of GSM
architecture that is fundamentally associated with communicating with the mobiles on the
network. It consists of two elements which are:-
• Base transceiver station (BTS)
• Base Station Controller (BSC)
2.5.2.1.1 Base Transceiver Station: -
BTS is a mobile network access device which comprises the radio transmitter/receiver
and their associated antennas that transmit and receive signals to directly communicate
with mobiles. BTS has indoor and outdoor components with their specific functions. The
indoor part consists of Base Band Unit (BBU), Radio Transmission Network (RTN), ATN
and Digital Current Distribution Unit (DCDU) and Rectifier.

Figure 2.4 BTS tower & indoor physical appearance respectively

BBU (base band unit)

BBU is a small box with all the external ports on the front panel. It consists of UMPT,
UEIU, UPEU, UBRI and WBBP

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Table 2.1 description of BBU modules

CARD FULL FUNCTIONS

NAME
Controls the temperature and heat of
FAN Fixed every module in
access BBU
network
Universal Controls and manages the entire BTS. It
UMPT main provides interfaces related to reference
processing clock, power supply, operation and
and maintenance and external alarm
transmissio collection
n
unit
universal Supports multiple environment
UEIU environment interface unit monitoring signals. It supports eight
Boolean alarm signals and two RS485
environment monitoring signals.

Universal Supports to the -48 v DC power input

UPEI power and supply. Supplies power to the boards,
environment modules and fan in the BBU.
interface unit

Universal Provides the interface for both 2G and

UBRI baseband 3G
radio
interface
Provides the interface only for 3G
WBB WCDMA
P baseband
processor

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Figure 2.5 BBU physical structure

The outdoor portion consists of the following components:

• Transceiver (TRX) basically does transmission and reception of signals. It is also called
drive receiver.
• Power amplifier (PA) amplifies the signal from drive receiver for transmission through
antenna; may be integrated with drive receiver.
• Combiner Combines feeds from several TRXs so that they could be sent out through a
single antenna.
• It allows for a reduction in the number of antennae used.
• Duplexer is used for separating, sending and receiving signals to/from antenna. It does
sending and receiving signals through the same antenna ports (cables to antenna).
• A remote radio unit is a remote radio transceiver that connects to an operator radio control
panel via electrical or wireless interface. They are generally connected to the
BTS/NodeB/ eNodeB via a fiber optic cable using Common Public Radio Interface
protocols.
The RRU can be configured to communicate with a base band unit (BBU) via a physical
communication link and can communicate with a wireless mobile device via an air
interface. It is used to extend the RF signal to some specified coverage area.
Basic functions of BTS include frequency hopping, channel coding and decoding, rate
adaptation, encryption and decryption, Paging and Uplink signal measures.
2.5.2.1.2 Base Station Controller (BSC)
BSC resides between group of BTSs and MSC. It controls all the BTSs around it and
the switching mechanisms between MS and MSC, manages radio and terrestrial channels,
encrypts and decrypts the data, traffic measurement, authentication, location register and
update and manages handover.
In Ethio Telecom North Region there are two BSCs which are Mekelle BSC and Shire
BSC.

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Figure 2.6 BSC module structure

Network and Switching Subsystem
NSS contains a variety of different elements, and is often termed as the core network
which performs call forwarding, hand over switching and the like. It provides the main
control and interfacing for the whole mobile network. NSS consists of MSC (Mobile
Switching Center), LR (Home Location Register and Visitor Location Register), gateway
mobile and switching center (GMSC), EIR and AuC.
2.5.2.2 Mobile Switching Center
The MSC controls call signaling and processing, and coordinates the handover of the
mobile connection from one base station to another as the mobile roams around. The
mobile switching center (MSC) is the primary service delivery node for GSM/CDMA,
responsible for routing voice calls and SMS as well as other services (such as conference
calls, FAX and circuit switched data). The MSC sets up and releases the end-to-end
connection, handles mobility and hand-over requirements during the call and takes
care of charging and real time pre-paid account monitoring. The MSC manages the
roles of inter-
cellular transfer, mobile subscriber visitors, and interconnections with the PSTN.
Each MSC is connected through GMSC to the local Public Switched Telephone Network
(PSTN or ISDN) to provide the connectivity between the mobile and the fixed telephone
users.
2.5.2.3 Home Location Register:
HLR is a database that contains all the administrative information about each subscriber
along with their last known location. In this way, the GSM network is able to route calls

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to the relevant base station for the MS. When a user switches on their phone, the phone
registers with the network and from this it is possible to determine which BTS it
communicates with so that incoming calls can be routed appropriately.
2.5.2.4 Visitor Location Register (VLR):
The VLR is a database that contains temporary information about subscribers that is
needed by the MSC in order to service visiting subscribers. The VLR is always integrated
with the MSC. When a mobile station roams into a new MSC area, the VLR connected to
that MSC will request data about the mobile station from the HLR. Later, if the mobile
station makes a call, the VLR will have the information needed for call setup without
having to interrogate the HLR each time.
2.5.2.5 Equipment Identity Register (EIR):
EIR is an optional database that is supposed to contain the unique International Mobile
Equipment Identity (IMEI), which is a number of the mobile phone equipment.[1] EIR is
specified to prevent usage of stolen mobile stations or to bar malfunctioning equipment
(e.g., from certain manufacturer).
2.5.2.6 Gateway Mobile Switching Center (GMSC):
GMSC provides interface between the mobile network and Public Switched Telephone
Network (PSTN).
2.5.2.7 Authentication Center (AuC):
The Authentication Center is a protected database that stores a copy of the secret key
stored in each subscriber's SIM card, which is used for authentication and ciphering of the
radio channel.[2] It protects network operators from different types of fraud found in
today's cellular world
2.5.3 Operation and Support Subsystem (OSS)
The OSS or operation and support subsystem is an element within the overall GSM
network architecture that is connected to components of the NSS and the BSC. It is
used to control and monitor the overall GSM network and it is also used to control the
traffic load of the BSS.
Its working elements are Operation and Maintenance Center (OMC), EIR, AuC.
GSM cellular architecture
A given geographical area is segmented in to cells. Cell is a coverage area of a single
BTS. The possible coverage area is of a spherical region of radius ‗r‘, but hexagonal cells
are used ideally so as to neglect the interferences between them.

Figure 2.7 cellular structure of BTS

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Several carrier frequencies are used without using the same frequencies in neighbor cells.
Cell radius varies from some 100 meters to 35 kilometers depending on user density,
geography and transceiver power.
2.5.4 GSM logical channels
The data, whether user traffic or signaling information, are mapped onto the physical
channels by defining a number of logical channels. A logical channel will carry
information of a specific type and a number of these channels may be combined before
being mapped on to the same physical channel. Logical channels are broadly categorized
in to traffic channels and signaling channels.
2.5.4.1 Traffic channels (TCHs)
The traffic channels are intended to carry encoded speech or user data. Full rate traffic
channels carry a net bit rate of 22.8 Kb/s (TCH/F) whereas half rate traffic channels carry
a net bit rate of
11.4 Kb/s (TCH/H).
2.5.4.2 Control Channels (CCHs)
The control channels are intended to carry signaling and Synchronization data between
the base station and the Mobile station.
GSM control channels are divided in to three.
1. Broadcast control channels
2. Common control channels
3. Dedicated control channels
2.5.4.2.1 Broadcast control channels
Broadcast control channels are used to broadcast synchronization and general network
information to all the MSs within a cell. They are transmitted in downlink direction only.
It has three categories.
I. Frequency correction channel (FCCH) is used for frequency correction and
synchronization of mobile station.
II. Synchronization Channel (SCH) is used to synchronize the mobile station time wisely
with the BTS.
III. Broadcast control channel (BCCH) is used to broadcast control information such as
details of the control channel configuration used at the BTS, a list of the BCCH carrier
frequencies used at the neighboring BTSs and a number of parameters that are used by the
MS when accessing the BTS to every MS within a cell.
2.5.4.2.2 Common Control Channels
Common control channels are used by an MS during the paging and access procedures.
Common control channels are of three types.
I. Paging channel (PCH) within certain time intervals the MS will listen to the Paging
channel, PCH, to see if the network wants to get in contact with the MS.

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II. Random access channel during listening to the PCH, the MS will realize it is
being paged.
The MS answers, requesting a signaling channel, on the Random Access channel, RACH.
RACH can also be used if the MS wants to get in contact with the network.
III. Access grant channel (AGCH) is used by the network to grant, or deny an MS
access to the network by supplying it with details of a dedicated channel.

2.5.4.2.3 Dedicated Control Channels

DCCH is used to carry Signaling information between an MS and a BTS using associated
and dedicated control channels during or not during a call. They are of three types.
I. Slow associated control channels is used to transmit non-urgent information for
instance, transmitter power control.
II. Fast associated control channels is used for more urgent information, e.g. a handover
command
III. Standalone dedicated control channels in some situations, signaling information must
flow between a network and an MS when a call is not in progress such as during a
location update..

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logical
channel

traffic control
channel channel

full rate half rate broadcas

t common dedicted

FCCH SCH BCCH PCH RACH AGCH SACH FACH SDC

Figure 2.8 GSM logical channel

2.5.2 Universal Mobile Telecommunication Systems

(UMTS),
2.5.2.1 3G mobile networks Evolution from 2G to 3G
The effectively rate of 2G mobile systems is too slow for many Internet services. Thus, in
a race for higher speeds, GSM and other TDMA-based technologies from 2G developed
so called 2G+ mobile systems. 2G+ mobile networks evolved with High Speed Circuit
Switched Data (HSCSD), General
Packet Radio system (GPRS) and Enhanced Data Rates for Digital Evolution (EDGE)
respectively
High Speed Circuit Switched Data (HSCSD)

HSCSD is only software upgrade to 2G. It allows continuous use of multiple time slots
(up to 4), channels, for a single user and asynchronous allocation of time slots between
DL and UL.

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Drawbacks:-
• Lack of statistical multiplexing (i.e. four time slots are occupied all the time during the
connection).
• Handover, which is complicated unless the same time slots are available end-to-end
throughout the duration of the call.
GPRS (General Packet Radio Service)

GPRS is created as both hardware and software upgrade to the existing GSM system and
introduces statistical multiplexing via packet-switched services. It allows flexible (also
multiple) allocation of timeslots to MS and uses free slots only if data packets are ready to
send. GPRS has two network support nodes so as to integrate with the existing GSM
architecture. These are, serving GPRS support node (SGSN) and gateway GPRS support
node (GGSN).
Serving GPRS support node (SGSN) is responsible for the delivery of packets from/to
mobile stations within its service area Its main tasks are mobility management (including
location management, attach/detach), packet routing, logical link management,
authentication, and charging functions.
GGSN acts as an interface between the GPRS packet network and external packet-based
networks
(i.e., Internet). [1] It converts protocol data packet (PDP) addresses from the external
packet-based networks to the GSM address of the specified user and vice versa.
Enhanced Data Rates for Digital Evolution (EDGE)

EDGE was created to provide higher data rates for packet-based services, to enhance
throughput per time slot for both HSCSD and GPRS. It uses a new modulation scheme 8-
PSK (phase shift keying) in addition to that used by GPRS. It is an option for 3G
networks.
Network elements

• The Universal Mobile Telecommunications System (UMTS) utilizes similar network

architecture that has been used in second generation systems:
• The UMTS system consists of a number of logical network elements that each admit a
defined functionality.
• In the standards, network elements are defined at the logical level and the physical
implementation usually follows the same logical structure due to open interfaces
• If interface is ‘open’ then it is defined such that equipment’s at the endpoints of an
interface can be from two different manufacturers.
• Thus, open interfaces are defined by global standards that each manufacturer must follow.
• UMTS standards have been created jointly by the industry community within the 3 rd
Generation Partnership Project (3GPP), see

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 Functionally the network elements are grouped into the

– Radio Access Network (RAN/UTRAN) that handles radio-related functionalities
– Core Network (CN), which is responsible for switching and routing calls and data
connections to external networks.
– User Equipment (UE) that interfaces with the user.
– From standardization point of view, both UE and UTRAN are fully different from GSM.
Part of the definition of Core Network (CN) is adopted from GSM.
 This supports, for example, cost effective introduction of new radio technologies
global roaming.

Network elements in WCDMA based PLMN

Figure 2.9 network elements in WCDMA based PLMN

Network elements: UE

– Typically PLMN is operated by a single operator

– Connected to other PLMNs and networks like internet
– User Equipment (UE) contains
– Mobile equipment (ME): Radio communication over Uu interface

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– UMTS Subscriber Identity Module (USIM): The subscriber identity, execution of

authentication algorithms, storing of authentication and encryption keys and some
subscription information that is needed at the terminal.

CHAPTER THREE
Analyzing Performance of Rectangular Planar Array Antenna
Summary of Project
This paper is dedicated to advancing the connectivity of Ethiotelecom's wireless network,
with a specific focus on the North-region cellular network as a case study. The company
offers various services, each with a distinct quality of service (QoS) requirement.
According to ITU-T, QoS encompasses factors such as data and voice quality and signal
strength, all vital in cellular networks. This paper aims to explore methods for enhancing
connectivity within the North-region cellular network by analyzing and optimizing key
QoS parameters. By improving network performance in these aspects, Ethiotelecom can
ensure better service delivery and increased user satisfaction.
The paper extensively explores the design of planar array antennas aimed at resolving
current limitations within the company's telecommunication system. It tackles challenges
including coverage constraints, interference susceptibility, and inefficient spectrum
utilization. The potential of planar array antennas, enhanced with beam forming
technology, to revolutionize connectivity is thoroughly examined. Through careful
analysis and experimentation, the paper explores how beam forming can optimize planar
array antennas for precise signal transmission and reception. Various parameters and
configurations tailored to Ethiotelecom's needs are discussed. Finally, the anticipated
impact of deploying these advanced antennas, promising improved connectivity,
reliability, and service quality for the company's customers, is assessed. The project
utilized MATLAB for code writing and antenna simulations. Based on the simulation
results, we anticipate that our project can effectively address the aforementioned hurdles
in wireless communications.
Keywords: Planar Array Antenna, Beam forming

3.1 Introduction
In the dynamic realm of wireless communication, antennas stand as quintessential
Components, serving as the bedrock upon which the efficacy of network performance is
established. Analogous to finely crafted lenses enhancing vision, rigorously designed
antennas possess the transformative capability to alleviate system constraints and uplift
overall operational efficiency [3]. This analogy resonates profoundly within the
operational framework of Ethiotelecom, where the relentless pursuit of optimal

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connectivity and service delivery underscores the indispensable role of robust antenna
infrastructure. Consider, for example, the analogy of television broadcast reception: the
strategic deployment of high-performance antennas holds the power to substantially
augment signal Reception quality, thereby enriching user experience and satisfaction.
Traditionally, antennas with broad radiation patterns and modest directivity have
prevailed. However, the imperatives of long-distance communication within the
company's operational domain demand antennas endowed with highly directive
characteristics, characterized by substantial gains [4].
The pursuit of such directive attributes often necessitates the enlargement of the
antenna's electrical size, a task achievable through either the augmentation of individual
element dimensions or the strategic assembly of radiating elements into arrays [5]. It is
this latter approach, harnessing the potential of antenna arrays, that presents a compelling
solution for
the company's quest for enhanced connectivity without necessitating unwieldy
Increases in individual antenna size.
Antenna arrays, comprising interconnected individual antennas with precisely specified
amplitude and phase relationships, offer a pathway to augmented signal transmission and
reception capabilities. Antenna arrays can be finely tuned to exhibit desired radiation
patterns through the precise adjustment of element spacing, excitation amplitudes, and
excitation phases. These arrays eventually metamorphose into singular antennas with
enhanced gain, seamlessly aligning with Ethiotelecom's overarching mission to provide
reliable and highquality wireless communication services.
This paper endeavors to delve deep into the details of array design and configuration,
tailor- made to suit the company's operational context, thereby empowering stakeholders
to
Optimize antenna infrastructure and fortify network performance. By thoroughly
exploring array geometries, element configurations, and excitation techniques, we aim to
equip the company with the indispensable tools needed to navigate the ever-evolving
landscape of wireless communication technologies and effectively meet the dynamic
demands of clients.

3.2 Statement of problem

When addressing the challenges encountered by the Northern Region EthioTelecom in
wireless telecommunication, particularly those related to the directive features of
antennas, the need for innovative solutions becomes increasingly evident. Typically,
single-element antennas have broad radiation patterns and limited directivity, which
exacerbates difficulties as antenna size increases. This amplifies the need for precise
antenna-pointing, especially for larger structures. However, transitioning to an array setup
of smaller antennas presents a viable solution to these complexities. Arrays offer

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improved directive qualities without the intricacies of single-element antennas, thereby

reducing the necessity for exact antenna positioning. This transition enhances network
performance and elevates customer satisfaction within the Northern Region
EthioTelecom's wireless telecommunication framework.
3.3 Objective of the project
3.3.1 General Objective
The main aim of this project is to examine how a rectangular planar array antenna
performs across various antenna parameters.
3.3.2 Specific Objectives
The following are the specific objectives of our project:
• Enhancing the total gain of the antenna
• Nullifying interference from specific directions
• Maximizing signal-to-noise ratio
• Identifying the direction of incoming signals
• Comprehending the advantages of rectangular array antennas

3.4 Significance of the Project

Here are some key points on the significance of designing a planar array antenna for the
northern region of EthioTelecom:
• Improved coverage: planar array antennas boost signal strength across the northern
region including rural areas, enhancing connectivity for all users.
• Enhanced capacity: with higher gain and directionality, these antennas optimize
frequency use, meeting rising demand for data and voice service.
• Enhanced capacity: with higher gain and directionality, these antennas optimize
frequency use, meeting rising demands for data and voice services.
• Future tech support: compatibility with 5G and IOT prepares ethiotelecom for future
advancments, ensuring long term network viability and service expansion.
• Strategic significance: tailored solutions for the northern region highlight ethiotelecoms
commitment to meeting local needs, driving development, and fostering inclusivity.

3.5 Scope and Limitation of the Project

3.5.1 Scope of the Project
The scope of the project is to achieve better quality and higher capacity of wireless
communication by evaluating the design of rectangular planar array antennas and
recommending solutions based on Matlab simulation results and conceptual reasoning.

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3.5.2 Limitations
The project encountered limitations, primarily related to time and materials. Originally,
we anticipated a four-month internship period as per the manual the company had given
us at the beginning. However, a revised semester schedule from our university, issued two
months into the internship, shortened our time by approximately one month. This
constrained our ability to conduct comprehensive evaluations and testing along with the
company's experts. Furthermore, the absence of reserved materials for interns hindered
our capacity to practice and test our designs effectively. We were unable to observe how
the results of our simulations would behave in real-world scenarios.
3.6 Literature Reviews
Planar array antennas are esteemed for their high gain, directional capabilities, and
versatility across various applications. Common design techniques include micro strip
patch arrays, printed circuit board (PCB) technology, and aperture-coupled arrays [1].
Optimization of design parameters, such as element spacing and feeding network
topology, is essential for achieving desired radiation characteristics [2]. Advanced
simulation tools like MATLAB enable precise analysis and optimization of array
configurations [3]. Beam forming techniques, including phase shifting and amplitude
weighting, facilitate adaptive beam forming and nulling capabilities [4]. Optimization
algorithms, such as genetic algorithms and particle swarm optimization, enhance array
performance by improving side lobe suppression and efficiency [5].
Planar array antennas are utilized in radar systems, satellite communications, and
wireless networks [6]. Advances in manufacturing technologies have made the fabrication
and customization of planar array antennas more cost-effective [7]. Implementing planar
array antennas can provide EthioTelecom with solutions to enhance coverage, capacity,
and quality of service. This implementation supports the adoption of 5G and IoT
technologies, extends connectivity to underserved regions, and advances digital inclusion
efforts in Ethiopia.

3.7 Methodology
3.7.1 Methods
To accomplish the objectives outlined in this paper, the following methodology is
implemented:
1, Data Collection and Analysis: The initial step involves gathering and analyzing data
from Ethio-Telecom's north region wireless network to gain insights into existing
challenges in wireless communication.
2, Problem Identification: Through meticulous analysis, specific issues about wireless
communication are identified and delineated.

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3, Literature Review: A comprehensive review of relevant literature is conducted,

focusing on potential solutions involving beam forming and planar array antennas.
4, Evaluation of Planar Array Antenna Designs: Using MATLAB simulation and
conceptual reasoning, planar array antenna designs are rigorously evaluated. Key factors
such as spacing between elements and the number of elements in the x and y directions
are considered, with a particular emphasis on directivity, gain, and array factors.
5, Recommendation of Solutions: Based on the evaluation results, recommendations for
potential solutions are formulated, aimed at effectively addressing the identified issues in
wireless communication.
Throughout the project, emphasis is placed on thorough research, careful analysis, and the
utilization of MATLAB as a tool for the detailed evaluation of planar array antenna
designs.

3.7.2 Fundamental Parameters of Antenna

To clarify an antenna's performance, it's imperative to define various parameters. Some of
these parameters exhibit interrelationships, and not all are necessary for a comprehensive
description of the antenna's performance.

3.7.2.1 RADIATION PATTERN

An antenna radiation pattern, also known as an antenna pattern, refers to a mathematical
function or graphical depiction showcasing the radiation characteristics of the antenna
concerning spatial coordinates. Typically determined in the far field region, the radiation
pattern is often represented as a function of directional coordinates. The amplitude field
pattern depicts the received electric or magnetic field at a constant radius, while the
amplitude power pattern illustrates the spatial variation of power density along a constant
radius. For antennas, the field pattern (in linear scale) typically portrays the magnitude of
the electric or magnetic field concerning angular space, while the power pattern (in linear
scale) usually represents the square of the field's magnitude in angular space.
Additionally, the power pattern (in dB) expresses the magnitude of the electric or
magnetic field in Decibels relative to angular space.

3.7.2.2 BEAMWIDTH
The beam width of a pattern refers to the angular separation between two identical points
on opposite sides of the pattern's maximum. Within an antenna pattern, there exist several
beam widths.

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3.7.2.3 DIRECTIVITY
The directivity of an antenna is defined as the ratio of the radiation intensity in a specific
direction from the antenna to the average radiation intensity across all directions. This
average radiation intensity is equivalent to the total power radiated by the antenna divided
by 4π.

3.7.2.4 GAIN
Another valuable metric for assessing antenna performance is gain. While closely linked to
directivity, gain is a measure that considers both the efficiency and directional capabilities
of the antenna.

3.7.2.5 BANDWIDTH
The bandwidth of an antenna is defined as the frequency range in which the antenna's
performance, concerning a specific characteristic, meets a predetermined standard.

3.7.2.6 ARRAY ANTENNA

Many applications require radiation characteristics that a single element cannot achieve
alone. However, arranging multiple radiating elements in specific electrical and
geometrical configurations, known as an array, can achieve the desired radiation
characteristics. This arrangement can combine radiation from the elements to create
maximum radiation in specific directions while minimizing it in others. The term "array"
typically refers to separate individual radiators but can also describe radiators mounted on a
continuous structure.

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An antenna array, often called a "phased array," consists of two or more antennas whose signals
are combined or processed to enhance performance beyond that of a single antenna. This array
can increase overall gain, provide diversity reception, mitigate interference from specific
directions, steer the array for directional sensitivity, determine signal arrival direction, and
maximize the Signal Interference plus Noise Ratio (SINR). The performance of an antenna array
generally improves with more elements but also increases cost, size, and complexity.

3.7.3 System Model

start

Varyng spacing of Varying phase angle Varying number of

array elements of array antenna array elements

Test If there is
simulation error

Simulation result

End

Figure 3.1: Flowchart for the simulation of a planar array

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The radiation characteristics Sr(θ, φ) in the far-field of an N-element array consisting of identical
radiating elements can be represented as the multiplication of two functions:

(1)
Fa(θ, φ) represents the array factor, while Se(θ, φ) denotes the power directional pattern of an
individual element. This principle is referred to as the pattern multiplication principle. The array
factor, Fa(θ, φ), varies with the array's geometry due to its dependency on the range.

(2)
The elemental pattern, Se(θ, φ), relies on the far-field radiation pattern of the individual element,
which is independent of range. (This disregards element-to-element coupling.)

3.7.4 Planar Array Beam forming

The array factor in the two-dimensional case is given by:

(3)
In this context, (xn, yn) represent the coordinates of the nth point, ɸ is the azimuth angle relative
to the x-axis, and ϴ is the elevation angle relative to the z-axis, with the array being uniformly
excited. Planar arrays enable the scanning of the antenna's main beam toward any direction in
space. These arrays are utilized in applications such as tracking radar, search radar, remote
sensing, communications, and more. An example is the planar array of slots used in the Airborne
Warning and Control System, which employs waveguide slots on the narrow walls of the
waveguides. This system provides a 360degree view and can detect targets hundreds of
kilometers away at operational altitudes. It is typically mounted above the fuselage of an aircraft.

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Figure 3.2: Planar Array

A planar array offers a large aperture and can achieve directional beam control by adjusting the
relative phase of each element. This configuration produces symmetrical patterns with low side
lobes and significantly higher directivity (a narrower main beam) than individual elements. Planar
arrays are highly versatile, providing more
symmetrical patterns with lower-side lobes and greater directivity. They are capable of scanning
the main beam toward any point in space.

3.7.5 Gain and Element Factor of Planar Arrays

The maximum gain of a uniformly illuminated, lossless aperture with area (A) and a broadside
beam is expressed as:

(4)
With non-uniform aperture distribution and with the lossless present, the gain is reduced by
efficiency term η to

(5)
If the aperture consists of \(N\) equal radiating elements and is matched to accept the incident
power, then each element contributes equally to the overall gain. Hence

(6)
Where Ge is the gain per element, the matched element power pattern is:

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(7)
If the aperture consists of N equal, discrete, radiating elements and is matched to accept power
like a continuous aperture, then each element contributes equally to the overall gain. If the
normalized radiation amplitude of the element or element pattern is

(8)
2
For a given element spacing s, the total number of radiators N in the area A is N= / and gives

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(9)

when the element spacing is = /2 then the power pattern of an element that is perfectly
matched at all scan angles is

(10)
The effects of the element pattern are most noticeable with wider beams. The radiation
pattern of an

array is the product of the element pattern and the array factor. The array factor is
determined by the geometric arrangement of the elements and their phasing, assuming the
elements are isotropic and there is no mutual coupling. Its peak value remains
independent of the scan angle. The element pattern is the actual radiation pattern of an
element within the array, considering the presence of all other elements and accounting
for all coupling effects and mismatches.
The maximum element pattern can be obtained experimentally by exciting one typical
element while terminating the other elements with matched loads. Any positions where
the main beam fails to form or where there is a significant loss in gain will appear as nulls
in the element pattern.
3.7.6 Array Factor
The "Array Factor" (AF) is the normalized radiation pattern of an array composed of
isotropic pointsource elements.

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Figure 3.3: Planar Array Geometry

If M elements are initially placed along the x-axis, the array element can be expressed as

(11)

Here,
represents the directional cosine concerning the x - axis. It
is assumed that all elements are equally spaced with an interval of dx and have a
progressive phase shift
of βx. Im1 denotes the excitation amplitude of the element at
coordinates . In the figure above, this element is in the n-th
row and the
1st column of the array matrix.
If N such arrays are arranged adjacent to each other along the y-axis, a rectangular array
is formed. We assume these arrays are equally spaced at a distance of dy and have a
progressive phase shift of βy along each row. Additionally, it is assumed that the
normalized current distribution along each x-directed array is identical, with absolute
values scaled by a factor of I1n (for n = 1, …., N). The array factor (AF) for the entire
array will then be:

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(12)
The array factor is influenced by several factors including the number of elements, the
spacing between elements, and the amplitude and phase of the signal applied to each
element.
The number of elements and their spacing directly determine the total surface area of the
radiating structure, known as the aperture. A larger aperture generally leads to higher
gain. Aperture efficiency measures how effectively the aperture is utilized.
The array factor for a planar equally spaced array with N elements in each column and M
elements in each row can be expressed as:

(13)
For uniform amplitude distribution (I nm = 1) and equal phase distribution (δ nm = 0), the
normalized planar array factor is defined as:

(14)

where the coordinates α and β are determined as sinα = sinθcosφ, sinβ = sinθsinφ and

;
(15)
The configuration of a rectangular array is determined by multiplying the array factors of
the linear arrays in both the x and y directions. Each element is excited with the same
amplitude in a uniform planar (rectangular) array, where Im1 equals In1 equals Io for all
m and n.

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(16)
The normalized array factor can be obtained as:

(17)
Where,

Figure 3.4: Two- dimensional planar array (M x N Rectangular Pattern)

As for the above figure, to scan over all spaces without gratin lobes, both dx and dy need
to be less than half of the lambda.

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The major lobe (principal maximum) and grating lobes of the terms:

(18)

3.7.7 Grating Lobe Issues for Planar Arrays

Figure 3.5: Grating Lobe Issues with λ/2 Spacing (the two left side configurations) and Grating Lobe
Issues with λ Spacing (the two configurations to the right side).

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The triangular grid is commonly preferred due to its efficiency, requiring approximately
14% fewer elements compared to a square grid. The precise percentage of savings varies
based on the scanning needs of the array. Furthermore, for scan angles below 60 degrees,
there are no grating lobes present in a triangular grid.
In the case of a rectangular grid with half-wavelength spacing, no grating lobes are
observable across all scan angles. However, the question arises whether each element of
the phased array can transmit and receive without affecting others. The answer is
negative, as mutual coupling exists. Mutual coupling refers to the phenomenon where
one antenna element influences another. Despite the assumption of no interaction
between radiating elements in a simple model analysis, the mutual coupling is a reality. It
occurs because the current in one element is affected by the amplitude and phase of the
current in neighboring elements, as well as in the element under consideration.
When the antenna is scanned from the broadside, mutual coupling can induce changes in
antenna gain, beam shape, sidelobe level, and radiation impedance. It can even lead to
"scan blindness," where the performance of the array is compromised. However, it's
worth noting that mutual coupling can sometimes be intentionally leveraged to meet
specific performance requirements.

3.7.8 The beam width of a planar array

The array beam width denotes the angular extent occupied by the array's main beam or
main lobe, measured at a consistent power level. Typically, this width is assessed at the
half-power point or the 3dB point, hence termed as the half-power beam width or 3-dB
beam width. Alternatively, the width can be determined between the first nulls adjacent to
the main beam, termed the firstnull beam width. However, in general usage, when
referring to beam width, it typically signifies the 3-dB beam width.

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Figure 3.6: Beam width

We will now outline a straightforward method proposed by R.S. Elliot1. This method
relies on utilizing the beam widths of the linear arrays that construct the planar array. For
a sizable array, with its maximum near the broad side, the elevation plane half power
beam width (HPBW) is approximately:

(19)
where:
(θ0, φ0) - denotes the direction of the main beam;
Δθx - represents the half-power beam width (HPBW) of a linear broadside array, sharing
the same number of elements M and amplitude distribution as the linear arrays along the
x-axis constructing the planar array;
Δθy - signifies the HPBW of a linear broadside array, with the same number of elements
N and amplitude distribution as the linear arrays along the y-axis building the planar
array.
The HPBW within the plane, perpendicular to the φ = φ0 plane and encompassing the
maximum, is:

(20)

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The beam solid angle of the planar array can be approximated by:
For a square array (M=N) with amplitude distributions along the x and y axes of the same
type, equations 19 and 20 reduce to:
Or

(21)
(22)
3.7.9 Directivity of Planar Array
In various scenarios, the primary goal of an antenna array is to manipulate its response or
beam pattern to amplify radiation (or reception) in a specific direction while minimizing
reception in other directions. A valuable metric for assessing the precision of the array is
its directivity, which quantifies the ratio of the power radiated by the array in a desired
direction to the average power radiated in all directions. In array synthesis discussions,
array gain is often used interchangeably with array directivity, given that losses in
antennas and antenna circuits are disregarded. Nevertheless, it's crucial to recognize that
while array directivity and array gain are connected, they are distinct concepts.
The standard formula used to compute the directivity of an array is:

(23)
For large planar arrays, which are nearly broadside, the above equation reduces to:

(24)
In this context:
Dx refers to the directivity of the corresponding linear broadside array along the x-axis,
while Dy indicates the directivity of the corresponding linear broadside array along the
yaxis.

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Additionally, one can employ the array solid beam angle ΩA from the equation preceding
the directivity formula to estimate the directivity of an almost broadside planar array.

(25)
Note:
The primary beam's orientation is managed by adjusting the phase shifts, denoted as βx
and βy.
The breadth of the beam and the levels of side lobes are regulated by the distribution of
amplitudes.

3.7.10 Result, Discussion, and Conclusion

3.7.10.1 Result
A snippet of code for the subsequent figure:

Following is the graph that is simulated by running complete one of the above snippet codes:

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Figure 3.7: Rectangular Array Factor at dx=lambda/4 and dy=lambda/4

Then, with subtle changes to the above line of codes, the following graph was simulated:

Figure 3.8: Rectangular Array Factor at dx=lambda/2 and dy=lambda/2

Again, by changing a few parameters of the MATLAB code used to simulate Figure 3.6,
we could obtain the subsequent graph:

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Figure 3.9: Rectangular Array Factor at dx=lambda and dy=lambda

After this, for a specific value of N (=8) and M (=10), we could simulate the following
graph to examine the case of the three scenarios.

Figure 3.10: Rectangular Array Factor for N=8 and M=10 with varying dx and dy

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3.7.10.3 Discussion 1

Here’s a detailed explanation of how the Rectangular Array Factor varies for the three
cases of element spacing (dx=dy=λ, dx=dy=0.5λ, and dx=dy=0.25λ), using common
values for N and M.

Setup for Common Parameters

 Number of Elements:
o N = [8, 16, 32, 64]: Along x-direction.
o M = [10, 20, 40, 80]: Along y-direction.
 Wavelength (λ): Normalized for simplicity.

 Element Spacing (dx and dy):

o Case 1: dx = dy =λ
o Case 2: dx = dy = 0.5λ
o Case 3: dx = dy = 0.25λ
 Angle Range (α\alpha):

−π≤α≤π covering the full visible region.

The array factor is calculated as the product of factors along x- and y-directions,
normalized to its maximum value.

Case 1: dx=dy=λ or dx = dy = \lambda

 Key Observations:
With element spacing equal to λ grating lobes appear at intervals
Of ± arcsin(K) where K is an integer.
The grating lobes are of the same amplitude as the main lobe.
For each N and M, the array factor results in narrow main lobes but suffers from
interference due to strong side lobes (grating lobes).
 Array Factor Pattern:
o The main lobe is centered at α = 0 but is accompanied by significant grating lobes at
other angles, which limits the usability of the array for focused radiation.
 Applications:
o Not practical for scenarios requiring precise beamforming or single-directional radiation
due to interference from grating lobes.

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Case 2: dx=dy=0.5λ
 Key Observations:
o This is an ideal spacing for avoiding grating lobes in the visible region (−π≤α≤π)
o The array factor shows a strong and narrow main lobe at α=0, with suppressed side lobes.
o Increasing N and M results in further narrowing of the main lobe and reduction of side
lobe amplitude.
 Array Factor Pattern:
o The radiation pattern is dominated by the main lobe.
o Side lobes are present but are significantly weaker, and no grating lobes are observed.
 Applications:
o Suitable for most beamforming and communication systems due to its clean radiation
pattern and absence of grating lobes.

Case 3: dx=dy=0.25λ

 Key Observations:
o Reducing the spacing to 0.25λ results in a wider main lobe.
o The side lobes are further suppressed compared to 0.5λ, producing a smoother radiation
pattern.
o The array becomes compact but at the cost of reduced directivity.
 Array Factor Pattern:
o The main lobe is broader, making it less directional than the 0.5λ0.5\lambda0.5λ case.
o Side lobes are minimal, and no grating lobes occur.
 Applications:
o Suitable for applications requiring broad coverage, such as near-field systems or wide-
angle scanning.

General Trend Across N and M

1. Effect of Increasing N and M:
o Increasing the number of elements results in narrower main lobes and reduced side lobes
across all cases.
o For dx = dy = λ, the grating lobes remain prominent regardless of N and M.
2. Optimal Balance (dx = dy = 0.5λ):
o Provides the best trade-off between directivity, beamwidth, and side lobe suppression.

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o As N and M increase, the main lobe becomes more focused.

Table 3.1 of 3D Summary
Summary of Differences
Main Lobe Grating
Side Lobes Applications
Width Lobes

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Spacing
Narrow but
Prominent Yes
with Not suitable for most
dx=λ due to (high
grating beamforming applications.
grating lobes amplitude)
lobes
Narrow, Widely used in
Moderate
dx=0.5λ optimal No beamforming
side lobes
width and focused arrays.
Wider Suitable for wide coverage
Suppressed
dx=0.25 than 0.5λ\ No and low
side lobes
lambda directivity.

Conclusion
 λ: Introduces grating lobes, making the design unsuitable for most practical applications.
 0.5λ: Provides the best balance between directivity, beamwidth, and the absence of
grating lobes.
 0.25λ: Sacrifices directivity for better coverage and smoother patterns, with minimal side
lobes.
This analysis highlights the importance of element spacing in antenna array design, as it
directly impacts the radiation pattern and application suitability.

Below are the 3D plots for the three cases: dx=dy=0.25lambda, dx=dy=0.5lambda, and
dx=dy=lambda respectively. Note that in all cases, elements on the x and y axis,
calculation of power Array factor and plotted Array phase of 80 and Array amplitudes of
1 are considered.

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Figure3.11: 3D Array Factor of a 6x6 planar array antenna with dx=dy=0.25lambda

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Figure 3.12: 3D Array Factor of a 6x6 planar array antenna with dx=dy=0.50lambda.

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Figure 3.13: 3D Array Factor of a 6x6 planar array antenna with dx=dy=lambda

3.7.10.3 Discussion 2
We considered each element of the array as an isotropic radiator, a theoretical antenna that emits radiation
equally in all directions. As such, we plot the array factor to represent the overall radiation pattern, which
closely resembles that of isotropic radiator elements. This array radiation pattern is solely determined by the
array factor (AF) of the rectangular array. The simulation results

3.7.10.2.2 The MATLAB code calculates and visualizes :

the 3D Array Factor: of a 6x6 planar array antenna for different element spacings (dx=dy=λ ,
dx=dy=0.5λ , and dx=dy=0.25λ).
Here's an explanation of the results for each case:

1. dx=dy=λ ,dx = dy = \lambda

Characteristics
 Element Spacing: Equal to the wavelength (λ\lambda).
 Array Factor Behavior:
o Main lobe: The primary beam direction is well-defined and narrow.
o Side lobes: Multiple strong side lobes appear due to the large element spacing, creating
undesirable interference patterns.
o Beam width: Narrow, indicating good directivity, but the presence of strong side lobes reduces
overall effectiveness.

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 Impact:

o High side-lobe levels can interfere with signals in unwanted directions, which might not be ideal
for certain applications like precise beam forming.
Visualization

 3D Plot: The main beam is sharp but accompanied by visible side lobes. The array factor appears
like a grid structure with strong peaks corresponding to side lobes.

2. dx=dy=0.5λdx = dy = 0.5\lambda
Characteristics
 Element Spacing: Half the wavelength.
 Array Factor Behavior:
o Main lobe: Still well-defined, though slightly broader compared to dx=dy=λ, dx = dy = \lambda.
o Side lobes: The side lobe levels are significantly reduced compared to the dx=dy=λ ,dx = dy = \
lambda case.
o Beam width: Broader than in dx=dy=λ ,dx = dy = \lambda, reducing the directivity slightly.
 Impact:
o This is an ideal compromise between side-lobe suppression and directivity.
o Widely used in practical antenna arrays for reliable beam forming and reduced interference.
Visualization
 3D Plot: The main beam dominates, with suppressed side lobes. The structure is smoother
compared to the dx=dy=λ , dx = dy = \lambda case, and the array factor appears more uniform.

3. dx=dy=0.25λdx = dy = 0.25\lambda
Characteristics
Element Spacing: One-quarter of the wavelength.
Array Factor Behavior:
Main lobe: Broader compared to the previous two cases.
Side lobes: Minimal side lobe levels, almost negligible, creating a highly uniform beam pattern.
Beam width: Much broader, which reduces directivity further.
 Impact:
o Excellent suppression of interference in other directions, making this configuration suitable for
applications where sidelobe levels need to be negligible.
o Less directivity may not be suitable for applications requiring a highly focused beam.
Visualization
 3D Plot: The plot shows a very smooth beam pattern with the main beam being much wider and
weaker compared to the other cases.

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Table 3.2 of 3D Summary

Comparative Summary
Main Side
Spacing Lobe Lobe Directivity Applications
Width Levels
Low interference,
Low (Wider
dx=dy=0.25λ Broad Low short-range
coverage)
Applications.
Standard for most
Balanced (Good
dx=dy=0.5λ Moderate Moderate beam forming and array
tradeoff)
antenna designs.
High gain, long-range
High (Good applications but prone
dx=dy=λ Narrow High
focus) to
Interference.

Key Observations
 Increasing the element spacing (dx ,dy) improves directivity but at the cost of higher
side lobe levels.
reducing the element spacing lowers side lobe levels but broadens the main beam,
reducing directivity.
 dx=dy=0.5λdx = dy = 0.5\lambda dx=dy=0.5λ strikes a good balance between
directivity and side-lobe suppression, making it the most commonly used configuration.

depict the array factor plot for a 6×6 planar array antenna, arranged with four elements
horizontally and vertically, shown in a 2D plot. Notably, grating lobes appear when dx
and dy are greater than or equal to lambda, regardless of the βx and βy values.
Additionally, the array factor plots illustrate an inverse relationship between beam width
and inter-element spacing for a constant number of elements. For example, wider beam
width is observed when d = λ/4 compared to when dx = dy = λ. Specifically, when dx =
dy ≤ 0.5λ, no grating lobes form for any angle βx and βy, resulting in a wide beam width.
Conversely, when dx = dy ≥λ, grating lobes occur for all βx and βy values, leading to a
narrower beam width. Moreover, when 0.5 λ < dx = dy < λ, grating lobe formation
depends on βx and βy, resulting in a medium beam width. Furthermore, the array factor
plots show that beam width is influenced not only by inter-element spacing but also by

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the number of elements. As demonstrated, the beam width decreases as the array's
number of elements increases, with

larger beam widths observed for N = 8 and M = 10 and smaller ones for N = 64 and M =
80.

3.7.10.3 Conclusion
In addressing the specific wireless telecommunication challenges encountered by
Northern Region EthioTelecom, especially those related to antenna directive features, our
project extensively evaluated the performance of rectangular array antennas. Through
comprehensive analysis and discussions, we've showcased how array antennas effectively
enhance network performance while simplifying complexities associated with single-
element antennas. Objectives such as enhancing antenna gain and maximizing signal-to-
noise ratio were thoroughly assessed in our in-depth analysis of the configuration of
rectangular
planar arrays. This study not only resolves identified issues but also offers valuable
insights and recommendations, emphasizing the pivotal role of array antennas,
particularly rectangular array antennas, in optimizing infrastructure and bolstering
network performance for Northern Region EthioTelecom.

Despite our reliance on MATLAB simulation for analysis, the findings have significant
practical implications for implementing rectangular array antennas within the company.

CHAPTER FOUR
Overall Benefits Gained from the Internship
As newcomers to the company, everything was novel and unfamiliar. Armed only with
theoretical knowledge, we embarked on this journey. The transition to real-world
applications was both captivating and enlightening, as it allowed us to witness and
engage with the lessons learned over the past four years. Our internship provided

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invaluable insights, bridging the gap between theoretical concepts and practical
implementation within our respective engineering domains. We endeavored to immerse
ourselves in every task, eager to gain hands-on experience and learning opportunities.
Working alongside experienced professionals in a dynamic environment enriched our
skills and provided us with the following advantages:
Upgrading Theoretical Knowledge
Improving practical skills
Interpersonal communication skills
Team playing Skill
Leadership skills
Develop Work ethics skills
Entrepreneur skills

4.1 Upgrading Theoretical Knowledge

We firmly believe that theoretical lessons provide a solid foundation indispensable for
practical implementations. However, theoretical knowledge gained through practical
experience is not only unforgettable but also easily comprehensible, serving as the
primary tool for problem-solving. Our internship proved instrumental in enhancing the
theoretical understanding acquired over the past four years, introducing us to new ideas
beyond the scope of regular classroom instruction. Moreover, it significantly elevated our
problem solving skills, particularly in the domains of network transmission and cellular
communication. Immersed in practical applications, we gained confidence and
proficiency, dedicating a substantial portion of our internship to studying documents and
materials provided by supervisors and staff members. Consequently, our theoretical
knowledge was greatly enriched and our practical experience was elevated to a new level.
In truth, our time at Ethiotelecom has enriched us more in theoretical knowledge than in
practical skills.

4.2 Improving Practical Skills

The primary aim of university internships is to extend student learning beyond the
classroom, bridging theoretical concepts with real-world applications. Although our
university endeavors to integrate theory and practice through lab exercises, the resources
are often limited. Thus, the internship emerged as a crucial program to enhance our
practical skills, filling the gaps in our experiential learning. During the internship, we
gained exposure to various facets of practical skills, addressing the deficiencies we
encountered.

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4.3 In terms of Industrial Problem-Solving Capability

In a large company like Ethio Telecom, daily activities are abundant, and new problems
arise frequently, requiring effective solutions. From our internship experience, we've
learned the importance of leveraging our university knowledge to address practical
issues. This involves applying our knowledge appropriately, continuously expanding our
understanding, thoroughly researching and understanding tasks before execution,
discussing challenges with colleagues, and maintaining self-confidence. Effective
problemsolving begins with a planning phase to identify and understand the problem,
followed by determining its impact and likelihood of occurrence, and then developing
and testing solutions. If the solution is ineffective, revisiting and refining the plan is
crucial.
4.4 In terms of Improving Interpersonal Communication and
Teamwork
Skills
During our internship, we significantly enhanced our interpersonal communication and
teamwork skills. With guidance from our associates, we developed formal
communication skills, focusing on avoiding interruptions to show respect, confidently
presenting our ideas to build trust, and honing active listening skills for better
understanding and positive responses. We learned the importance of effective teamwork,
recognizing that disagreements can hinder progress. Successful team players
communicate constructively, listen actively, participate fully, share willingly, cooperate,
and show commitment to the team. Confident and enthusiastic engineers with strong
managerial and organizational skills can lead projects successfully by gaining the trust of
their co-workers.

4.5 Improving Leadership Skills

During our internship, we did not serve as leaders, but we observed leadership in action
from those in charge. We witnessed how officials efficiently managed tasks, led teams,
and created a conducive work environment. They demonstrated respect for lower-level
employees and maintained high ethical standards, showing responsibility for their
sections and the company as a whole. Interacting with various Ethio telecom workers, we
observed their daily activities and gained insights into their general behavior. From this
experience, we learned that a good leader must be exemplary in all traits, possess strong
communication skills to inspire workers and understand the importance of incentives and
rewards.
Recognizing outstanding performance, offering career advancement, and providing salary
increments are vital for motivating employees and achieving company objectives.

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4.6 Understanding Work Ethics-Related Issues

Understanding and embodying strong work ethics is fundamental to personal and
professional success, emphasizing accountability, punctuality, respect, time management,
and attitude. Recognizing the profound impact of work ethics on individual performance,
team dynamics, and national development, we aspire to uphold these principles in our
careers. Work ethics encompasses the overall quality of behavior, emphasizing an
appreciation for the work process and a commitment to completing tasks with
responsibility and accountability. Throughout our internship, we have diligently adhered
to our job descriptions with enthusiasm, cultivating key attributes such as obedience to
management, honesty, self-confidence, politeness, and respectfulness. These qualities not
only contribute to our individual growth but also foster a positive work environment
conducive to collective success.

4.7 In terms of Entrepreneurship Skills

Entrepreneurship, a realm where dreams meet challenges, beckons those daring enough to
organize and operate businesses, unveiling both trials and rewards. While the journey
isn't without its hurdles, adept management and skilled human resources can turn the tide
toward profitability. Through this endeavor, we've grasped the essence of boldness,
understanding that success hinges on a deep comprehension of the business landscape
and adept navigation of its intricacies. In Ethiopia, where job scarcity looms large amid a
surplus of educated individuals, entrepreneurship emerges as a beacon of hope, offering a
pathway to self-sufficiency. Embracing this ethos, we've cultivated a vision of becoming
educated entrepreneurs, shunning conventional job pursuits in favor of charting our
destinies and creating opportunities for ourselves.

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CHAPTER FIVE
Conclusion and Recommendation
5.1 Conclusion
Established a century ago, Ethiotelecom stands as Ethiopia's preeminent
Telecommunications powerhouse, intricately woven into the fabric of society, facilitating
communication across diverse sectors including education, commerce, and governance.
Throughout our internship, we gained profound insights into Ethiotelecom's pivotal role
in spearheading societal transformation and progress. Our exposure to fixed network
transport systems such as OTN and Cellular communications illuminated the expansive
scope and importance of telecom services in our nation's development journey. This
immersive experience not only deepened our theoretical understanding but also
sharpened our practical skills, seamlessly integrating us into the company's dynamic
work environment. The historical trajectory of Ethio-telecom underscores the
monumental dedication and resources required to uphold a modern telecommunications
infrastructure amidst evolving demands and technological advancements. Our internship
provided us with a rich tapestry of theoretical and practical expertise, empowering us to
make meaningful contributions to Ethiopia's technological evolution. In essence, this
internship was an enriching odyssey, offering invaluable experiences and insights into the
realities of professional life and the potential it holds for growth and innovation.
5.2 Recommendation
5.2 .1 Recommendation for the Company
Ethiotelecom, while a sizable and profitable entity, is not without its imperfections, and
we have identified several areas for improvement within the company. Despite the
internship program showcasing commendable aspects, there are notable weaknesses at
the organizational level that warrant attention. These include prioritizing safety and
quality over economic gains, particularly concerning the prevalence of low-cost Chinese
manufactured devices within the company's infrastructure. Additionally, the staff
members were not always ready to assist us, stemming from a lack of time as they had to
put their regular tasks first, which hindered effective communication and knowledge
transfer. To enhance client satisfaction and uphold international standards, Ethiotelecom
should strive to deliver solutions that meet the highest quality, safety,

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and environmental criteria, prioritizing stakeholder, client, and community benefits while
upholding ethical values. Implementing a rotational system for interns across various divisions
can facilitate a comprehensive understanding of the company's operations.
Furthermore, establishing a dedicated research and laboratory section within Ethio
Telecom would prove beneficial, offering students valuable pre-programming
Opportunities and fostering innovation among employees to drive the company's continuous
improvement efforts.

5.2.2 Recommendation for the University

Expressing our gratitude to the university and our department head office for facilitating our
placement at Ethiotelecom, we strongly recommend that the university continues with the
internship program, as it is instrumental in preparing students for their future careers by allowing
them to apply theoretical knowledge in practical settings. This program also fosters a deeper
understanding of work ethics, employment demands, responsibilities, and opportunities. We urge
the university to continue assisting all students in securing internship positions relevant to their
programs by providing recommendations to ease their training periods and alleviate the stress of
finding internship placements.
5.2.3 Recommendations for Students
Internships provide an excellent opportunity to translate classroom knowledge into real world
experience. While learning is essential, applying those skills in a work setting allows for the
exploration of various career paths and specializations that align with personal interests. Hence,
we advise students to view internships not as a break but as a valuable chance to learn. Building
networks during this period is crucial, as connections with like-minded individuals can lead to
future job opportunities. Students should approach their internships with passion and dedication,
fully engaging in learning and practice within their companies.

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References
References

[1] C. A. Balanis, Antenna Theory: Analysis and Design, 4th ed., Hoboken, NJ, USA: Wiley,, 2016. .

[2] J. Huang, C. C. Chen, and R. K. Wu,, "Optimization of design parameters for planar array
antennas," IEEE Transactions on Antennas and Propagation, vol. 66, no. 2, pp. 485-497,., Feb.
2018.

[3] T. V. Balabanov and A. A. Velidov,, "Advanced simulation tools for planar array antenna analysis
and optimization," in Proceedings of the 2017 IEEE International Conference on Antenna
Technology (iWAT), 2017, pp. 1-4..

[4] Y. Li, S. Jin, X. Gao, and S. Zhang,, "Adaptive beamforming for planar array antennas using phase
shifting and amplitude weighting techniques," IEEE Transactions on Wireless Communications,
vol. 18, no. 7, pp. 3393-3405,, Jul. 2019..

[5] J. Kennedy and R. Eberhart,, "Particle swarm optimization," in Proceedings of the 1995 IEEE
International Conference on Neural Networks (ICNN), 1995, vol. 4, pp. 1942-1948..

[6] J. Y. Chang, H. C. Wang, and P. K. Huang,, "Applications of planar array antennas in radar and
wireless communications," IEEE Transactions on Microwave Theory and Techniques, vol. 63, no.
5, pp. 1450-1462,, May 2015.

[7] Cunningham, D. M. Pozar, and S. D. Weigand,, "Advances in manufacturing technologies for

planar array antennas," IEEE Antennas and Propagation Magazine, vol. 61, no. 3, pp. 7987,, Jun.
2019.

[8] Ethiotelecom, "Internship Manual: Providing an Overview of the Company to Interns,", Mekelle,
Tigray, Ethiopia, 2024. .

[9] Ethiotelecom, "History of Telecommunications in Ethiopia," [Online]. Available:

https://www.ethiotelecom.et/history/., [Accessed.: 23-April-2024]..

[10] W. L. Stutzman and G. A. Thiele,, Antenna Theory and Design, 3rd ed. Hoboken, NJ, USA: Wiley,,
2012. .

[11] R. C. Hansen, Phased Array Antennas, 2nd ed. Hoboken, NJ,, USA: Wiley, , 2009. .

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J. D. Kraus and R. J. Marhefka, , Antennas: For All Applications, 3rd ed. New York, NY, USA:
McGraw-Hill,, 2002. .
[12]

Appendix
Appendix1: Array Factor calculation code for fixed values of N, and M
% Define parameters
lambda = 1; % Wavelength
N = 8; % Number of elements in the x direction M = 10; % Number of elements
in the y direction angles = -pi:0.01:pi; % Angle range

% Define arrays for dx and dy dx_values = [0.25, 0.5, 1, 2] * lambda; % Element spacing in the x
direction

% Define colors and markers colors = {'m', 'b', 'g', 'k'}; markers = {'o', 'none', 'x', '.'};
line_styles = {'-', '--', '-', '-'};

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% Create the pattern for each dx and dy combination figure; hold on; for idx = 1:length(dx_values) dx =
dx_values(idx); dy = dx; %
For equal dx and dy

% Array factor calculation af_x = sin(N*pi*dx*sin(angles)/lambda) ./

(N*sin(pi*dx*sin(angles)/lambda)); af_y = sin(M*pi*dy*sin(angles)/lambda) ./
(M*sin(pi*dy*sin(angles)/lambda));
AF = abs(af_x) .* abs(af_y);

% Normalize the array factor

AF = AF / max(AF);

% Plot the results with specified colors and markers plot(angles, AF, 'DisplayName', sprintf('dx=dy
%.2f \\lambda', dx/lambda), ...
'Color', colors{idx}, 'LineStyle', line_styles{idx}, 'Marker', markers{idx}, ...
'MarkerSize', 8, 'MarkerFaceColor', 'none', 'MarkerEdgeColor', colors{idx}, ...
'MarkerIndices', 1:10:length(AF)); % Set marker indices with spacing

end

% Adding Display Features xlabel('$-\pi \leq \alpha \leq \pi$', 'Interpreter', 'latex'); ylabel('Normalized
Rectangular Array Factor'); title('Rectangular Array
Factor for N=8 and M=10 with varying dx and dy (dx=dy)'); legend('show',
'Interpreter', 'latex', 'Location', 'best'); grid on;
% Set x-axis ticks and labels xticks(pi:pi/2:pi); xticklabels({'-\pi', '-\pi/2',
'0', '\pi/2', '\pi'});

xlim([-pi pi]); % Limiting x-axis range from -pi to pi hold off;

Appendix2: Matlab code for simulating 3D Array Factor

% Constants lambda = 1; % Wavelength dx = lambda; % Element spacing in x-direction dy = lambda; %
Element spacing in y-direction N = 6; % Number of elements in x and y directions phi = 80; % Array phase
in degrees
A = 1; % Array amplitude

% Define theta and phi angles theta = linspace(0, pi, 100); phi_deg = linspace(0, 2*pi,
100);

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% Calculate 3D array factor

AF = zeros(length(theta),
length(phi_deg)); for i = 1:length(theta) for
j = 1:length(phi_deg)
AF(i,j) = abs(sum(sum(exp(1i*(2*pi*dx/lambda*(0:N-1)*sin(theta(i))*cos(phi_deg(j)) +
2*pi*dy/lambda*(0:N-1)*sin(theta(i))*sin(phi_deg(j)) + phi*pi/180)))))/N^2; end end

% Convert theta and phi to degrees theta_deg = rad2deg(theta); phi_deg =

rad2deg(phi_deg);

% Calculate Array Factor in dB

AF_dB = 10*log10(AF);

% Plot 3D array factor figure; surf(phi_deg, theta_deg, AF_dB.', 'EdgeColor', 'none'); title('3D Array Factor
of a 6x6 Planar Array
Antenna (for dx=dy=\lambda)'); xlabel('Phi (degrees)'); ylabel('Theta
(degrees)'); zlabel('Array Factor (dB)'); colorbar;

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