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MAKERERE UNIVERSITY
FACULTY OF TECHNLOGY
DEPARTMENT OF ELECTRICAL ENGINEERING
BSC ELECTRICAL ENGINEERING
SECOND YEAR INDUSTRIAL TRAINING REPORT
AT
WARID TELECOM UGANDA
BY
MUSANJE GASTER
08/U/453
JUNE-AUGUST 2010
ii
DECLARATION
I MUSANJE GASTER do declare that this work is original from Warid Telecom Uganda and it has
never been presented in any institution of higher learning for the award of any degree unless
otherwise where the respective authors have been acknowledged.
MUSANJE GASTER
08/U/453
Signature…………………………………... Date…………………………………..
This work has been submitted with the approval of:
FACULTY SUPERVISOR
MR.G. MARK KAGARURA
MAKERERE UNIVERSITY
Signature………………………… Date…………………………….
MR.TONNY LULE
ENGINEERING DEPARTMENT
WARID TELECOM
Signature…………………………. Date……………………………..
iii
DEDICATION
This work is dedicated to Mr. Robert Kigala, my Lord and Saviour Jesus Christ who has seen me
through all this years in good health and who gave me wisdom and knowledge to qualify for
this course. This work is also dedicated to my mum Ms. Robinah Mbabazi, sisters, brothers and
all my friends we have been training with at Warid Telecom Uganda who have been of great
encouragement to me.
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ACKNOWLEDGEMENTS
First I would like to acknowledge my supervisors Mr. Mark Kagarura and Mr. Tonny Lule for their
contribution and guidance in this work, and all the Engineering staff of WARID TELECOM
UGANDA for their never ending support for this field work.
In a special way, I would like to thank the Human Resource Department of Warid Telecom
Uganda, through whose hands I was offered this opportunity to train with this company; special
thanks go to Ms. Brenda Nagawa for the tireless efforts she made to coordinate the whole
process and for ensuring my due welfare during my stay at the company.
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PREFACE
This is a second year industrial training report. The training was carried out in Warid Telecom as
from: 21st June 2010 to 9th September 2010.
This report consists four chapters.
Chapter one gives a general background information, vision, goal, core values, policies,
coverage map and organisation of WTU. It also entails the objectives of Industrial Training.
Chapter two covers the theoretical concepts of radio communication. Among the theory
includes that of GSM systems, the history of GSM, GSM Frequencies, services provided by GSM,
SMS Architecture,GSM architecture that includes: the mobile station,Base station
subsytems,Network Switching Subsytems, MSC,VLR, HLR, AuC,GSMS,EIR and GSM Network
Interfaces. It also includes theoretical knowledge on GPRS, WiMAX,Wi-Fi,Transmission
Systems,VSAT‟s and Fiber optics.
Chapter three is about the practical activities carried out in the field that included; network
monitoring which involved using Ericsson‟s WinFOIL management sytem and Huawei‟s
iMANAGER,using the AKILI work flow, using INALA, using IMC-ESDER V2.05, field operations
that included site surveys, using various Engineering tools like Map-Info and PathLoss.
Chapter four is about the achievements and challenges faced at the work place during the
training period. It also includes the recommendations and the conclusion.
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ACRONYMS
WTU Warid Telecom Uganda
AUC Authentication Centre
BSC Base Station Controller
BTS Base Transceiver Station
BBS Battery Backup System
BSC Base Station Controller
BS Base Station
BSS Base Station Controller
CDMA Code Division Multiple Access
DCCU Direct Current Connection Unit
DRU Dual Radio Unit
DTX Discontinuous Transmission
DXU Distribution Switch Unit
EIR Equipment Identity Register
EDGE Enhanced Data Rates for Global Evolution
FCU Fan Control Unit
FDMA Frequency Division Multiple Access
GPS Global Position System
GSM Global System for Mobile communication
GMSC Gaussian Minimum Switching Centre
HLR Home Location Register
IDU Indoor Unit
ISDN Integrated Service Digital Networks
MS Mobile Station
MoU Memorandum of Understanding
MSC Mobile services Switching Centre
NMC Network Management Centre
NSS Network Switching System
OMC Operation and Maintenance Centre
ODU Outdoor Unit
PSU Power Supply Unit
PSTN Public Switched Telephone Network
RBS Radio Base Station
RU Replaceable Unit
RF Radio Frequency
RX Receiver
SS Switching System
TDMA Time Division Multiple Access
VLR Visitor Location Register
WIMAX Worldwide Interoperability Multiple Access
WIFI Wireless Fidelity
3 G Third generation
4 G Fourth generation
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TABLE OF CONTENTS
DECLARATION ............................................................................................................................................. ii
DEDICATION ............................................................................................................................................... iii
ACKNOWLEDGEMENTS .............................................................................................................................. iv
PREFACE ...................................................................................................................................................... v
ACRONYMS ................................................................................................................................................ vi
CHAPTER ONE: WARID TELECOM UGANDA ................................................................................................ 1
1.1 BACKGROUND AND INTRODUCTION .................................................................................................... 1
1.1.1 VISION ................................................................................................................................................ 1
1.1.2 GOAL .................................................................................................................................................. 2
1.1.3 CORE VALUES ..................................................................................................................................... 2
1.1.4 POLICIES ............................................................................................................................................. 2
1.1.5 COVERAGE MAP ................................................................................................................................. 2
1.1.6 THE WARID LOOK ............................................................................................................................... 3
1.2 OBJECTIVES OF INDUSTRIAL TRAINING ................................................................................................. 3
1.3 ORGANISATION OF WARID TELECOM ................................................................................................... 4
1.4 ENGINEERING DEPARTMENT ................................................................................................................ 5
CHAPTER TWO: GSM NETWORK ARCHITECTURE ........................................................................................ 6
2.1 HISTORY ................................................................................................................................................ 6
2.1.1 GSM Frequencies ............................................................................................................................... 7
2.1.2 Services provided by GSM .................................................................................................................. 7
2.2 SMS Architecture. ................................................................................................................................. 8
2.2 ARCHITECTURE OF GSM ........................................................................................................................ 8
2.2.1 Mobile station .................................................................................................................................... 8
2.2.2 Base Station Subsystem ..................................................................................................................... 9
2.2.3 Network Switching Subsystem (NSS) ............................................................................................... 11
2.2.4 MSC .................................................................................................................................................. 12
2.2.5 VLR ................................................................................................................................................... 12
2.2.5 HLR ................................................................................................................................................... 12
2.2.6 AuC................................................................................................................................................... 13
2.2.7 GMSC ............................................................................................................................................... 14
2.2.8 EIR .................................................................................................................................................... 14
2.3 GSM NETWORK INTERFACES............................................................................................................... 15
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2.4 GPRS ................................................................................................................................................... 17
2.4.1 GPRS Class Types .............................................................................................................................. 18
2.4.2 HSCSD .............................................................................................................................................. 18
2.4.3 EDGE ................................................................................................................................................ 18
2.5 WiMAX ................................................................................................................................................ 19
Wireless Network Topologies ................................................................................................................... 19
2.5.2 Wireless Technologies ..................................................................................................................... 20
Issues with Wireless Networks ................................................................................................................. 21
Wireless Broadband Access (WBA) ........................................................................................................... 21
2.5.5 Wi-Fi ................................................................................................................................................. 21
2.5.6 WiMAX Speed and Range................................................................................................................. 22
Why WiMAX? ............................................................................................................................................ 22
Comparison Table ..................................................................................................................................... 23
2.6.16 Fiber Optics .................................................................................................................................... 37
3.1 INTRODUCTION ................................................................................................................................... 38
3.2 NETWORK OPERATIONS CENTER (NOC) .............................................................................................. 39
3.3 USING WinFIOL TO PERFOM NETWORK MONITORING....................................................................... 39
3.5 USING iMANAGER FOR NETWORK MONITORING. .............................................................................. 43
3.8 FIELD OPERATIONS ............................................................................................................................. 45
3.9 RF PLANNING DEPARTMENT. .............................................................................................................. 46
3.9.3 SITE SURVEYS ................................................................................................................................... 48
CHAPTER FOUR: ACHIEVEMENTS, CHALLENGES, RECOMMENDATIONS AND CONCLUSION .................... 53
4.4 RECOMMENDATIONS ......................................................................................................................... 54
4.5 CONCLUSION....................................................................................................................................... 54
REFERENCES .............................................................................................................................................. 55
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LIST OF FIGURES
FIGURE 1 WTU COVERAGE MAP AS AT AUGUST 2010. (WWW.WARIDTEL.CO.UG/COVERAGEMAP) ....................................... 3
FIGURE 2 WTU LOOK. ...................................................................................................................................................... 3
FIGURE 3 SHOWING HIERARCHICAL ORGANIZATION OF WTU ............................................................................................. 5
FIGURE 4 SHOWING HIERARCHICAL ORGANIZATION OF ENGINEERING DEPARTMENT ............................................................ 5
FIGURE 5 SMS ARCHITECTURE .......................................................................................................................................... 8
FIGURE 6 TOWER WITH GSM AND MICROWAVE ANTENNAS AT NALUMUNYE. ................................................................... 10
FIGURE 7 BSS NETWORK TOPOLOGIES. ........................................................................................................................... 11
FIGURE 8 NSS ................................................................................................................................................................ 11
FIGURE 9 GENERAL ARCHITECTURE OF THE GSM NETWORK. ............................................................................................ 14
FIGURE 10 GSM NETWORK INTERFACES. ......................................................................................................................... 15
FIGURE 11 GPRS NETWORK ARCHITECTURE. ................................................................................................................... 17
FIGURE 12 WIMAX RECEIVER ......................................................................................................................................... 25
FIGURE 13 WIMAX NETWORK ARCHITECTURE. ............................................................................................................... 27
FIGURE 14 VARIATIONS OF THE RAY CURVATURE AS A FUNCTION OF K ............................................................................... 29
FIGURE 15 MICROWAVE LINK DESIGN PROCESS ............................................................................................................... 30
FIGURE 16 WINFOIL WINDOW. ...................................................................................................................................... 40
FIGURE 17 WINFOIL WINDOW DISPLAYING THE ALLIP: PRCA-53 COMMAND .................................................................... 40
FIGURE 18 WINFOIL WINDOW DISPLAYING THE RXASP: MOTY=RXOTG COMMAND .......................................................... 41
FIGURE 19 WINFOIL WINDOW DISPLAYING THE RLCRP: CELL=ALL COMMAND ................................................................. 42
FIGURE 20 AN EXAMPLE OF A TYPICAL ALARM, GENERATED AT A GPRS SITE, MONITORED USING THE IMANAGER TOOL. ...... 43
FIGURE 21 AN INTERFACE SHOWING THE DIFFERENT ALARMS AND THEIR DETAILS ............................................................... 44
FIGURE 22 INALA WINDOW ........................................................................................................................................... 44
FIGURE 23 IMC-ESDER WINDOW .................................................................................................................................. 45
FIGURE 24 MAP INFO SCREENSHOT ................................................................................................................................. 48
FIGURE 25 SITE SURVEY AT NATETE. ................................................................................................................................. 48
FIGURE 26 THE CURRENT WTU NETWORK AS AT AUGUST 2010....................................................................................... 52
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LIST OF TABLES
TABLE 1 GPRS CLASS, SLOTS AND MAXIMUM DATA TRANSFER SPEED ................................................................................ 18
TABLE 2 COMPARISON OF WIMAX AND WI-FI. ............................................................................................................... 23
TABLE 3 THE VARIOUS FREQUENCY BANDS. ...................................................................................................................... 36
TABLE 4 COMMON ALARMS VIEWED ON IMANAGER. ........................................................................................................ 43
TABLE 5 ACTIVITIES CARRIED OUT IN THE RF PLANNING DEPARTMENT. .............................................................................. 49
1
CHAPTER ONE: WARID TELECOM UGANDA
1.1 BACKGROUND AND INTRODUCTION
WARID Telecom Uganda (WTU) is owned by WARID Telecom International Limited which is a
subsidiary of the Abu Dhabi Group one of the largest business groups in the Middle East with
49% and Essar group 51% shareholder percentages respectively. WTU takes pride in being
backed by the Abu Dhabi Group that also has various investments on the African continent
including Uganda, Congo and Ivory Coast. The group also deals in other investments like
hospitality, property management, oil explorations and supplies, banking, sports, financial
services and automobiles.
The company was successfully inaugurated on the 9th of January 2008; it launched its services on
the 7th February 2008 and started its operation late that year. In November 2006 WARID
Telecom Uganda Limited was awarded its public infrastructure and public service provider
licenses which incorporated mobile, fixed, internet, email and international communication
services and within 15 months, WTU had completed the installation of hundreds of base
stations, commercially launched and had introduced a number of services to the public.
Warid Telecom, serving both the corporate and consumer markets is committed to bringing the
best of global communications to Uganda through its comprehensive portfolio of services that
include voice and data services over fixed ,wireless and internet platforms.
The subscribers of Warid Telecom while travelling internationally stay in touch with their families
and business through our one of the largest international roaming networks at over 126
destinations. Warid Telecom has established this network by entering into roaming partnerships
with 179 leading international mobile service operators around the world.
The company provides value for money, innovative and customer relevant telecommunication
services so as to achieve a new and modern corporate identity that is congruent with the
dynamic changes taking place within the telecom industry. It is working hard to become the
preferred choice as a universal communications solution.
1.1.1 VISION
WARID Telecom‟s vision is to “become the leader in national communications arena with a
strong international presence.”
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1.1.2 GOAL
WARID Telecom‟s goal is to provide an unequalled level and variety of communications services
that add value to the lives of all Ugandans.
1.1.3 CORE VALUES
WARID Telecom„s brand values include:
Quality: At WARID Telecom Quality is a prerequisite. This is reflected by optimum levels of
support and expertise provided by our highly skilled and motivated team of professionals,
reinforced by maximum network quality, coverage and connectivity.
Innovative: WTU constantly looks to doing things differently and in a better way through its
competitive promotional offers like Daboline mobile phone, Double the fun etc.
Customer friendly: Our countrywide Sales and Customer Care centres provide instant problem
solving and customer support from our highly trained Customer Care.
Simple: WTU is always open and honest.
Transparent: WTU enjoys working and succeeding together by building close relationships with
its customers.
1.1.4 POLICIES
Warid Telecom believes in working with strategic partners and employees for long term
relationships. As a consequence of the above Warid Telecom is looking for the following to
deliver its vision:
Strategic vendors and partners to assist in rolling out these services in a timely and efficient
manner with a focus on turnkey solutions and premium propositions.
Strong partners to assist in launching these services and creating effective sales and
marketing/business development opportunities for all to operationally and financially gain;
consultants and experts to deliver this vision; well rounded employees who wish to become part
of this adventure.
1.1.5 COVERAGE MAP
WTU‟s network coverage is constantly being upgraded as we strive to connect the entire
country in the shortest ever time by a telecommunications network provider in Uganda.
3
Figure 1 WTU Coverage Map as at August 2010. (www.waridtel.co.ug/coveragemap)
1.1.6 THE WARID LOOK
An evolution that strengthens the Warid identity while keeping the customers in focus. The logo
encompasses the expanding nature of Warid Telecom. Warid Telecoms‟ slogan is “We Care”.
Figure 2 WTU Look.
1.2 OBJECTIVES OF INDUSTRIAL TRAINING
Industrial training involves a planned systematic development of the knowledge, understanding,
skills, attitude and behaviour pattern required by an individual to perform a given job or task. It
is carried out with the aim of achieving the following goals;
The following are the objectives of doing Industrial Training:
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1. To get hands on experience and learn how to work with the different tools used in the
field.
2. To achieve interpersonal relationships so as to create a network of professional contacts
that could help the student at a further date to access opportunities in the field.
3. To build proactive public relations and corporate responsibility.
4. To allow students to develop the spirit of teamwork, and Solidarity in order to satisfy a
certain cause.
5. To enable the student to acquire basic skills and techniques of the Practical work
performed in the field by the experts. Through co-creating with those already
experienced, we are able to develop our practical capabilities as well.
6. To enable the student relate the theoretical knowledge and practical aspects of
Telecommunication Engineering.
7. To acquire developmental ideas like starting up small scale firms/ industries and are able
to manage them with an insight of self employment.
8. To make a professional development contribution to the upcoming professionals by
providing both hands on skills and theoretical knowledge of the different engineering
aspects.
9. To help in talent management thus nurturing young, dynamic individuals to propel in
their career aspiration thus a professional development
1.3 ORGANISATION OF WARID TELECOM
ENGINEERING
COUNTRY GENERAL MANAGER
FINANCE I.T CHIEF COMMERCIAL
OFFICER
HUMAN RESOURCE PROJECT MANAGEMENT
OFFICE
STRATEGIC PLANNING LEGAL DEPT
SALES MARKETING CUSTOMER
SERVICES
PRODUCT, SERVICES
5
Figure 3 Showing hierarchical organization of WTU
1.4 ENGINEERING DEPARTMENT
Figure 4 Showing hierarchical organization of Engineering department
6
CHAPTER TWO: GSM NETWORK ARCHITECTURE
2.1 HISTORY
The GSM story starts in 1982, when the Confederation of European Posts and
Telecommunications (CEPT) in the Conference Des Administrations Europeans Des Posts et
Telecommunications assembled a research group with intentions of researching the mobile
phone system in Europe. This group was called Group Spécial Mobile (GSM).It was to develop
the specification for a Pan-European mobile communications network capable of supporting the
many millions of subscribers likely to turn to mobile communications in the years ahead. It had
to meet the following criteria:
1. Good subjective speech quality
2. Low terminal and service cost
3. Support for international roaming
4. Ability to support hand held terminals
5. Support for range of new services
6. Spectral efficiency
7. ISDN compatibility
The European Commission endorsed the GSM Project in 1984. One year later, France, Italy, the
U.K. and West Germany signed a joint agreement to develop GSM.
Early 1987 brought an agreement on the basic parameters of the GSM standard, and the GSM
MoU was promoted. A total of 15 members from 13 countries committed to deploying GSM
through the Pan European Digital Conference. Validation trials in 1988 proved that GSM
technology was viable, and in 1989 the Groupe Spécial Mobile became a technical committee
within the European Technical Standards Institute (ETSI), which helped to define GSM as an
internationally accepted digital cellular telephony standard. The acronym GSM was then
changed from Group Spécial Mobile to Global Systems Mobile Telecommunications (GSM).
Network operator Radiolinja in Finland placed the first GSM call in 1991. The following year,
Telstra Australia became the first non-European operator to sign the GSM MoU, and Telecom
Finland and Vodafone (UK) signed the first international roaming agreement. During the same
year, the first SMS using GSM was sent.
By 1993, 32 networks were using GSM in 18 different countries or territories, and the first true
hand terminals meeting the standard were launched commercially.
7
2.1.1 GSM Frequencies
There are five major GSM frequencies that have become standard worldwide. They include
GSM-900, GSM-1800, GSM-850, GSM-1900 and GSM-400.
1. GSM-900 and GSM-1800 are standards used mostly worldwide. It is the frequency
European phones operate on as well as most of Asia and Australia.
2. GSM-850 and GSM-1900 are primarily United States frequencies. They are also the
standard for Canada GSM service and countries in Latin and South America. Most of
the Cingular network operates on GSM 850, while much of T-Mobile operates at
GSM-1900. T-Mobile however, has roaming agreements with Cingular. Meaning in
the case of no service at GSM-1900, the phone will switch to GSM-850 and operate
on Cingular‟s network.
3. GSM-400 is the least popular of the bunch and is rarely used. It is an older frequency
that was used in Russia and Europe before GSM-900 and GSM-1800 became
available. There are not many networks currently operating at this frequency.
WTU has launched its cellular services based on 900 and 1800 GSM technologies to optimise
the utilisation of frequency, thus ensuring the highest quality and service at all times.
2.1.2 Services provided by GSM
From the beginning, the planners of GSM wanted ISDN compatibility in terms of the services
offered and the control signalling used.
The most basic teleservice supported by GSM is telephony. As with all other communications,
speech is digitally encoded and transmitted through the GSM network as a digital stream. There
is also an emergency service, where the nearest emergency-service provider is notified by
dialling three digits (similar to 911).
1. Bearer services: Typically data transmission instead of voice. Fax and SMS are examples.
2. Teleservices: Voice oriented traffic.
3. Supplementary services: Call forwarding, caller ID, call waiting and the like.
4. Data Services (CSD, USSD, SMS)
A variety of data services is offered. GSM users can send and receive data at rates up to 9600
Kbps to users on POTS (Plain Old Telephone Service), ISDN, Packet Switched Public Data
Networks, and Circuit Switched Public Data Networks using a variety of access methods and
protocols such as X.25 or X.32. Since GSM is a digital network, a modem is not required
between the user and GSM network although an audio modem is required inside the GSM
network to interwork with POTS.
Other data services include Group 3 facsimile as described in ITU-T recommendation T.30, which
is supported by use of an appropriate fax adaptor.
8
A unique feature of GSM not found in older analog systems, is the Short Message Service (SMS).
SMS is a bidirectional service for short alphanumeric (up to 160 bytes) messages. Messages are
transported in a store-and-forward fashion. For point-to-point SMS, a message can be sent to
another subscriber to the service and an acknowledgement of receipt is provided to the sender.
SMS can also be used in a cell-broadcast mode for sending messages such as traffic updates or
news updates. Messages can also be stored in the SIM card for later retrieval.
2.2 SMS Architecture.
Figure 5 SMS Architecture
2.2 ARCHITECTURE OF GSM
A GSM network is composed of several functional entities whose functions and interfaces are
specified. The GSM network can be divided into three broad parts:
1. Mobile station
2. Base station subsystem
3. Network subsystem
2.2.1 Mobile station
The Mobile Station (MS) consists of the physical equipment used by a PLMN subscriber to
connect to the network. It comprises of the Mobile Equipment (ME) and the Subscriber Identity
Module (SIM). The ME forms part of the Mobile Termination (MT) which, depending on the
application and services, may also include various types of Terminal Equipment (TE) and
associated Terminal Adapter (TA).
9
The SIM stores permanent and temporary data about the mobile, the subscriber and the
network, including: IMSI, MSISDN, Authentication key (Ki) and algorithms for authentication
check.
The mobile equipment has a unique International Mobile Equipment Identity (IMEI), which is
used by the EIR. Security is provided by the use of an authentication key and by the
transmission of a temporary subscriber identity (TMSI) across the radio interface where possible
to avoid using the permanent IMSI identity.
The IMEI may be used to block certain types of equipment from accessing the network if they
are unsuitable and also to check for stolen equipment.
A number of GSM terminal types are defined within the GSM Specification. They are
distinguished primarily by their power output rating. There are five terminal power classes
between 0.8W to 20W.
Under control of the system, the MS is able to carry out:
1. RF power control to reduce co-channel, adjacent channel and interference and increase
MS battery life.
2. Frequency hopping, to reduce the effects of fading and interference.
3. Discontinuous transmission for allowing the MS's transmitter to be switched off during
speech pauses hence reducing interference and increasing MS battery life
2.2.2 Base Station Subsystem
The base station sub system comprises of the Base Station controller (BSC), one or more Base
Transceiver Stations (BTSs) and Transcoding equipment (TCE) to convert full- and half-rate
coded speech to 64 Kbit/s PCM.
The purpose of the BTS is to provide radio access to the mobile stations and manage the radio
access aspects of the system. It also provides timing synchronization to ensure that TDMA
transmissions from MS at various ranges arrive at precisely the right time.
BTS contains Radio Transmitter/Receiver (TRX), Signal processing and control equipment,
Antennas and feeder cables.
10
Figure 6 Tower with GSM and Microwave antennas at Nalumunye.
The BSC has the following functions:
1. Controls one or several BTS‟s.
2. Allocates a channel for the duration of a call.
3. Maintains the call
4. Monitors quality
5. Controls the power transmitted by the BTS or MS
6. Generates a handover to another cell when required
Base stations are linked to the parent BSC in one of several standard network topologies. The
actual physical link may be microwave, optical fiber or cable. Planning of these links may be
done using a tool such as PathLoss.
Chain: cheap and easy to implement. One link failure isolates several BTSs
Ring: Redundancy gives some protection if a link fails. More difficult to roll-out and extend ring
must be closed.
Star: Most popular configuration for first GSM systems .Expensive as each BTS has its own link.
One link failure always results in loss of BTS.
11
Figure 7 BSS Network Topologies.
2.2.3 Network Switching Subsystem (NSS)
The central component of the network subsystem is the Mobile Switching Center (MSC). It acts
as a normal switching mode of the PSTN or ISDN and additionally provides all the functionality
needed to handle a mobile subscriber such as registration, authentication, location updating,
handovers and call routing to a roaming subscriber. These services are provided in conjunction
with several functional entities which together form the NSS.
The following are the elements of NSS: Mobile Switching Centre (MSC), Visitor Location Register
(VLR), Home Location Register (HLR), Authentication Centre (AuC), Equipment Identity Register
(EIR), Gateway MSC (GMSC) .These elements are interconnected by means of an SS7 network
Figure 8 NSS
12
2.2.4 MSC
The Mobile Switching Centre is an exchange which performs all the switching and signaling
functions for mobile stations located in a geographical area designated as the MSC area.
Functions of the Mobile Switching Centre (MSC)
1. Switching calls, controlling calls and logging calls
2. Interface with PSTN, ISDN, PSPDN
3. Mobility management over the radio network and other networks
4. Radio Resource management that includes handovers between BSCs
5. Billing Information
6. Controlling handover between different BSCs
7. Exchanging signaling information and interworking with other networks.
2.2.5 VLR
Each MSC has a VLR, but one VLR may serve several MSCs. A Visitor Location Register is a
database serving temporary subscribers within an MSC area
Functions of the Visitor Location Register (VLR)
1. VLR stores data temporarily for mobiles served by the MSC. Information stored
includes: IMSI, MSISDN, MSRN, TMSI, LAI, the location area where the mobile station
has been registered. This data item will be used to call the station.
2. Supplementary service parameters
2.2.5 HLR
Is a database in charge of the management of mobile subscribers. A PLMN may contain one or
several physical HLRs depending on the number of mobile subscribers, the capacity of the
equipment and the organization of the network. However, even if the HLR comprises
geographically separated hardware, it logically forms a single virtual database.
Two kinds of information are stored there:
a) The subscription information.
b) Location information enabling the charging and routing of calls towards the MSC where the
MS is located (e.g. the MSRN, VLR address, MSC address, Local MS Identity).
Functions of the HLR
13
1) Stores details of all subscribers in the network, such as:
• Subscription information
• Location information: MSRN, VLR, MSC
• International Mobile Subscriber Identity (IMSI)
• MSISDN number (The IMSI or the MSISDN may be used as a key to access the information in
the database for a mobile subscription. )
• Tele -service and bearer service subscription information
• Service restrictions
• Supplementary services
2) Together with the AuC, the HLR checks the validity and service profile of subscribers
HLR Implementation
One HLR in a network may be split regionally .The data base can also contain other information
such as: Teleservices and bearer services subscription information and Service restrictions (e.g.
roaming limitation)
The HLR contains the parameters attached to these services. Supplementary services parameters
need not all be stored in the HLR.
However, it is considered safer to store all subscription parameters in the HLR even when some
are stored in a subscriber card.
Notice that the VLR stores the current Location Area of the subscriber, while the HLR stores the
MSC/VLR they are currently under. This information is used to page the subscriber when they
have an incoming call.
2.2.6 AuC
The Authentication Centre (AuC) is associated with an HLR, and stores an identity key for each
mobile subscriber registered with the associated HLR. This key is used to generate data which
are used to authenticate the IMSI and a key used to cipher communication over the radio path
between the mobile station and the network.
14
2.2.7 GMSC
A Gateway Mobile Switching Centre (GMSC) is a device which routes traffic entering a mobile
network to the correct destination. The GMSC accesses the network‟s HLR to find the location of
the required mobile subscriber. A particular MSC can be assigned to act as a GMSC.
The GMSC routes calls out of the network and is the point of access for calls entering the
network from outside. If a network, delivering a call to the PLMN cannot interrogate the HLR
directly, the call is routed to an MSC. This MSC will interrogate the appropriate HLR and then
route the call to the MSC to which the mobile station is affiliated. The MSC which performs the
routing function to the actual location of the MS is called the Gateway MSC (GMSC). The choice
of which MSCs can act as Gateway MSCs is for the operator to decide (i.e. all MSCs or some
designated MSCs).
2.2.8 EIR
EIR is a database that stores a unique International Mobile Equipment Identity (IMEI) number for
each item of mobile equipment. The EIR controls access to the network by returning the status
of a mobile in response to an IMEI query. Possible status levels are: White-listed where the
terminal is allowed to connect to the network, Grey-listed where the terminal is under
observation by the network for possible problems and Black -listed where the terminal has
either been reported stolen, or is not a type approved for a GSM network. The terminal is not
allowed to connect to the network.
Figure 9 General Architecture of the GSM Network.
15
2.3 GSM NETWORK INTERFACES
Figure 10 GSM Network Interfaces.
The following are the GSM Network Interfaces.
1. Um Interface: The interface between the MS and the BSS.
2. Abis Interface used between the BSC and BTS. The interface also allows control of the
radio equipment and radio frequency allocation in the BTS.
3. A Interface: The interface between the MSC and its BSS. The BSS-MSC interface is used
to carry information concerning: BSS management, call handling and mobility
management.
4. B (MSC-VLR) Interface: The VLR is the location and management data base for the
mobile subscribers roaming in the area controlled by the associated MSC(s). Whenever
the MSC needs data related to a given MS currently located in its area, it interrogates
the VLR. When the MS initiates a location updating procedure with an MSC, the MSC
informs its VLR which stores the relevant information.
5. C (MSC-HLR) Interface: The Gateway MSC must interrogate the HLR of the required
subscriber to obtain routing information for a call or a short message directed to that
subscriber.
6. D (HLR-VLR) Interface: This interface is used to exchange the data related to the
location of the mobile station and to the management of the subscriber. The main
service provided to the mobile subscriber is the capability to set up or to receive calls
16
within the whole service area. To support this, the location registers have to exchange
data. The VLR informs the HLR of the location of a mobile station managed by the latter
and provides it (either at location updating or at call set-up) with the roaming number of
that station. The HLR sends to the VLR all the data needed to support the service to the
mobile subscriber. The HLR then instructs the previous VLR to cancel the location
registration of this subscriber
7. E (MSC-MSC) Interface: When a mobile station moves from one MSC area to another
during a call, a handover procedure has to be performed in order to continue the
communication. For that purpose the MSCs have to exchange data to initiate and then
to realize the operation. After the handover operation has been completed, the MSCs
will exchange information to transfer A-interface signaling as necessary.
8. F (MSC-EIR) Interface: used between MSC and EIR to exchange data in order that the
EIR can verify the status of the IMEI retrieved from the Mobile Station.
9. G (VLR-VLR) Interface: When a mobile subscriber moves from a VLR area to another
Location, registration procedure will happen. This procedure may include the retrieval of
the IMSI and authentication parameters from the old VLR.
10. H (HLR-AuC) Interface: When an HLR receives a request for authentication and
ciphering data for a Mobile Subscriber and it does not hold the requested data, the HLR
requests the data from the AuC. The protocol used to transfer the data over this
interface is not standardized.
17
2.4 GPRS
GPRS
Mast and
antennas
Base
Transceiver
Station
Base-Station
Controller
MSC
Point of
Interconnection
BTS
BSC
HLR
VLR
AUC
Home and Visitor
Location Registers
Authentication
Centre
Mobile
Switching
Centre
EIR Equipment Identity
Register
OMC/NMC
Operations & Maintenance Centre
Network Management Centre
POI
Mobile
Station
TRU
ABis
uM
A Interface
DTI
Data Transmission Interface SMS-GMSC
SMS-IWMSC
Short
Message
Service
PCU
GGSN
SGSN
Gb
Figure 11 GPRS Network Architecture.
General Packet Radio Service (GPRS) is a packet oriented mobile data service available to all
users of the 2G cellular communication systems as well as in the 3G systems. It provides data
services over the GSM infrastructure with additional equipment implemented. These are:
PCU: It‟s a part of the BSC (Added on if GPRS service is to be deployed) that converts IP type
packets to the GSM radio interface format.
SGSN: Routes packet data between MS and GGSN, mobility management, session management
and charging.
GGSN: Carries out the functions of IP Gateway functionality. Routes and forwards data between
MS and the internet, IP address allocation, charging.
The data packets are sent over a Packet Data Channel (PDCH). Unlike in CS (Circuit Switched)
GSM, a user is not bound to a single TCH, if 1 or more timeslots are available, they can be
assigned to a user to send or receive data. 8 timeslots are available per carrier. On the Um
interface, you can have timeslots dedicated to GPRS or have dynamic allocation of resources but
always, voice connections have a higher priority.
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2.4.1 GPRS Class Types
The class of a GPRS phone determines the speed at which data can be transferred. Technically
the class refers to the number of timeslots available for upload (sending data from the phone)
or download (receiving data from the network). The timeslots used for data are in addition to
the slot that is reserved for voice calls. These timeslots are available simultaneously, so the
greater the number of slots, the faster the data transfer speed. Because GPRS transmits data in
packets, the timeslots are not in use all the time, but are shared amongst all users of the
network. That increases the overall data capacity of the network, and it also means that you are
billed for the quantity of data transmitted, not the time that you are online. It may mean that
during busy times, data transfer rates slow down, because the network will give priority to voice
calls.
The most common GPRS classes in use are as follows:
Table 1 GPRS class, slots and maximum data transfer speed
GPRS CLASS SLOTS MAX.DATA TRANSFER SPEED
Class 2 3 8 - 12 kbps upload / 16 - 24 kbps download
Class 4 4 8 - 12 kbps upload / 24 - 36 kbps download
Class 6 4 24 - 36 kbps upload / 24 - 36 kbps download
Class 8 5 8 - 12 kbps upload / 32 - 40 kbps download
Class 10 5 16 - 24 kbps upload / 32 - 48 kbps download
Class 12 5 32 - 48 kbps upload / 32 - 48 kbps download
Generally speaking, the higher the GPRS class, the faster the data transfer rates.
2.4.2 HSCSD
HSCSD enables data to be transferred more rapidly than the standard GSM (Circuit Switched
Data) system by using multiple channels. The maximum number of timeslots that can be used is
four, giving a maximum data transfer rate of 57.6 kbps (or 38.4 kbps on a GSM 900 network).
HSCSD is more expensive to use than GPRS because all four slots are used simultaneously - it
does not transmit data in packets. Because of this, HSCSD is not as popular as GPRS and is
being replaced by EDGE.
2.4.3 EDGE
EDGE or EGPRS provides data transfer rates significantly faster than GPRS or HSCSD. EDGE
increases the speed of each timeslot to 48 kbps and allows the use of up to 8 timeslots, giving a
maximum data transfer rate of 384 kbps. In places where an EDGE network is not available,
GPRS will automatically be used instead. EDGE offers the best that can be achieved with a 2.5G
network, and will eventually be replaced by 3G.
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2.5 WiMAX
WiMAX is broadband wireless technologies based on IEEE 802.16 specification and it is expected
to deliver high quality broadband services.
Wireless means transmitting signals using radio waves as the medium instead of wires. Wireless
technologies are used for tasks as simple as switching off the television or as complex as
supplying the sales force with information from an automated enterprise application while in
the field. Now cordless keyboards and mice, PDAs, pagers and digital and cellular phones have
become part of our daily life.
Some of the inherent characteristics of wireless communications systems which make it
attractive for users are given below:
Mobility: A wireless communications system allows users to access information beyond their
desk and conduct business from anywhere without having wire connectivity.
Reachability: Wireless communications systems enable people to be better connected and
reachable without any limitation of any location.
Simplicity: Wireless communication systems are easy and fast to deploy in comparison to
cabled network. Initial setup cost could be a bit high but other advantages overcome that high
cost.
Maintainability: Being a wireless system, you do no need to spend too much to maintain a
wireless network setup.
Roaming Services: Using a wireless network system you can provide service any where any
time including train, busses, aeroplanes etc.
New Services: Wireless communications systems provide new smart services like SMS and
MMS.
Wireless Network Topologies
There are basically three ways to setup a wireless network.
Point-to-point Bridge: As you know a bridge is used to connect two networks. A point-to-
point bridge interconnects two buildings having different networks. For example, a wireless LAN
bridge can interface with an Ethernet network directly to a particular access point.
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Point-to-multipoint Bridge: This topology is used to connect three or more LANs that may be
located on different floors in a building or across buildings.
Mesh or ad hoc network: This network is an independent local area network that is not
connected to a wired infrastructure and in which all stations are connected directly to one
another.
2.5.2 Wireless Technologies
Wireless technologies can be classified in different ways depending on their range. Each wireless
technology is designed to serve a specific usage segment. The requirements for each usage
segment are based on a variety of variables, including Bandwidth needs, Distance needs and
Power.
Wireless Wide Area Network (WWAN)
This network enables you to access the Internet via a wireless wide area network (WWAN)
access card and a PDA or laptop.
These networks provide a very fast data speed compared with the data rates of mobile
telecommunications technology, and their range is also extensive. Cellular and mobile networks
based on CDMA and GSM are good examples of WWAN.
Wireless Personal Area Network (WPAN)
These networks are very similar to WWAN except their range is very limited.
Wireless Local Area Network (WLAN)
This network enables you to access the Internet in localized hotspots via a wireless local area
network (WLAN) access card and a PDA or laptop.
It is a type of local area network that uses high-frequency radio waves rather than wires to
communicate between nodes.
These networks provide a very fast data speed compared with the data rates of mobile
telecommunications technology, and their range is very limited. Wi-Fi is the most widespread
and popular example of WLAN technology.
Wireless Metropolitan Area Network (WMAN)
This network enables you to access the Internet and multimedia streaming services via a
wireless region area network (WRAN).
21
These networks provide a very fast data speed compared with the data rates of mobile
telecommunication technology as well as other wireless network, and their range is also
extensive.
Issues with Wireless Networks
There are following three major issues with Wireless Networks.
Quality of Service (QoS): One of the primary concerns about wireless data delivery is that, like
the Internet over wired services, QoS is inadequate. Lost packets and atmospheric interference
are recurring problems wireless protocols.
Security Risk: This has been another major issue with a data transfer over a wireless network.
Basic network security mechanisms like the service set identifier (SSID) and Wireless Equivalency
Privacy (WEP). These measures may be adequate for residences and small businesses but they
are inadequate for entities that require stronger security.
Reachable Range: Normally wireless network offers a range of about 100 meters or less. Range
is a function of antenna design and power. Now days the range of wireless is extended to tens
of miles so this should not be an issue any more.
Wireless Broadband Access (WBA)
Broadband wireless is a technology that promises high-speed connection over the air. It uses
radio waves to transmit and receive data directly to and from the potential users whenever they
want it. Technologies such as 3G, Wi-Fi, WiMAX and UWB work together to meet unique
customer needs.
BWA is a point-to-multipoint system which is made up of base station and subscriber
equipment. Instead of using the physical connection between the base station and the
subscriber, the base station uses an outdoor antenna to send and receive high-speed data and
voice-to-subscriber equipment.
BWA offers an effective, complementary solution to wireline broadband, which has become
globally recognized by a high percentage of the population.
2.5.5 Wi-Fi
Wi-Fi stands for Wireless Fidelity. Wi-Fi is based on the IEEE 802.11 family of standards and is
primarily a local area networking (LAN) technology designed to provide in-building broadband
coverage.
22
WiMAX would operate similar to Wi-Fi but at higher speeds, over greater distances and for a
greater number of users. WiMAX has the ability to provide service even in areas that are difficult
for wired infrastructure to reach and the ability to overcome the physical limitations of
traditional wired infrastructure.
2.5.6 WiMAX Speed and Range
WiMAX is expected to offer initially up to about 40 Mbps capacity per wireless channel for both
fixed and portable applications, depending on the particular technical configuration chosen,
enough to support hundreds of businesses with T-1 speed connectivity and thousands of
residences with DSL speed connectivity. WiMAX can support voice and video as well as Internet
data.
WiMAX will be to provide wireless broadband access to buildings, either in competition to
existing wired networks or alone in currently unserved rural or thinly populated areas. It can also
be used to connect WLAN hotspots to the Internet. WiMAX is also intended to provide
broadband connectivity to mobile devices. It would not be as fast as in these fixed applications,
but expectations are for about 15 Mbps capacity in a 3 km cell coverage area.
With WiMAX users could really cut free from today‟s Internet access arrangements and be able
to go online at broadband speeds, almost wherever they like from within a Metro Zone.
WiMAX could potentially be deployed in a variety of spectrum bands: 2.3GHz, 2.5GHz, 3.5GHz,
and 5.8GHz
Why WiMAX?
WiMAX can satisfy a variety of access needs. Potential applications include extending
broadband capabilities to bring them closer to subscribers, filling gaps in cable, DSL and T1
services, Wi-Fi and cellular backhaul, providing last-100 meter access from fibre to the curb and
giving service providers another cost-effective option for supporting broadband services.
WiMAX can support very high bandwidth solutions where large spectrum deployments (i.e. >10
MHz) are desired using existing infrastructure keeping costs down while delivering the
bandwidth needed to support a full range of high-value, multimedia services.
WiMAX can help service providers meet many of the challenges they face due to increasing
customer demands without discarding their existing infrastructure investments because it has
the ability to seamlessly interoperate across various network types.
WiMAX can provide wide area coverage and quality of service capabilities for applications
ranging from real-time delay-sensitive voice-over-IP (VoIP) to real-time streaming video and
23
non-real-time downloads, ensuring that subscribers obtain the performance they expect for all
types of communications.
WiMAX, which is an IP-based wireless broadband technology, can be integrated into both wide-
area third-generation (3G) mobile and wireless and wireline networks, allowing it to become
part of a seamless anytime, anywhere broadband access solution.
Ultimately, WiMAX is intended to serve as the next step in the evolution of 3G mobile phones,
via a potential combination of WiMAX and CDMA standards called 4G.
2.5.8 WiMAX and Wi-Fi Comparison
WiMAX is similar to the wireless standard known as Wi-Fi, but on a much larger scale and at
faster speeds. A nomadic version would keep WiMAX-enabled devices connected over large
areas, much like today‟s cell phones. We can compare it with Wi-Fi based on the following
factors.
Comparison Table
Table 2 Comparison of WiMAX and Wi-Fi.
Feature WiMAX
(802.16a)
Wi-Fi
(802.11b)
Wi-Fi
(802.11a/g)
Primary
Application
Broadband Wireless
Access Wireless LAN Wireless LAN
Frequency Band Licensed/Unlicensed
2 G to 11 GHz 2.4 GHz ISM
2.4 GHz ISM (g)
5 GHz U-NII (a)
Channel
Bandwidth
Adjustable
1.25 M to 20 MHz 25 MHz 20 MHz
Half/Full Duplex Full Half Half
Radio Technology OFDM
(256-channels)
Direct Sequence
Spread Spectrum
OFDM
(64-channels)
24
Bandwidth
Efficiency <=5 bps/Hz <=0.44 bps/Hz <=2.7 bps/Hz
Modulation BPSK, QPSK,
16-, 64-, 256-QAM QPSK
BPSK, QPSK,
16-, 64-QAM
FEC Convolutional Code
Reed-Solomon None Convolutional Code
Encryption Mandatory- 3DES
Optional- AES
Optional- RC4
(AES in 802.11i)
Optional- RC4
(AES in 802.11i)
Mobility Mobile WiMAX
(802.16e) In development In development
Mesh Yes Vendor
Proprietary Vendor Proprietary
Access Protocol Request/Grant CSMA/CA CSMA/CA
2.5.10 WiMAX - Building Blocks
WiMAX Base Station: A WiMAX base station consists of indoor electronics and a WiMAX
tower similar in concept to a cell-phone tower. A WiMAX base station can provide coverage to a
very large area up to a radius of 6 miles. Any wireless device within the coverage area would be
able to access the Internet.
The WiMAX base stations would use the MAC layer defined in the standard. A common
interface that makes the networks interoperable and would allocate uplink and downlink
bandwidth to subscribers according to their needs, on an essentially real-time basis.
Each base station provides wireless coverage over an area called a cell. Theoretically, the
maximum radius of a cell is 50 km or 30 miles however, practical considerations limit it to about
10 km or 6 miles.
WiMAX Receiver
25
A WiMAX receiver may have a separate antenna or could be a stand-alone box or a PCMCIA
card sitting in your laptop or computer or any other device. This is also referred as customer
premise equipment (CPE).
WiMAX base station is similar to accessing a wireless access point in a Wi-Fi network, but the
coverage is greater.
Figure 12 WiMAX Receiver
2.5.11 Backhaul
A WiMAX tower station can connect directly to the Internet using a high-bandwidth, wired
connection (for example, a T3 line). It can also connect to another WiMAX tower using a line-of-
sight, microwave link.
Backhaul refers both to the connection from the access point back to the base station and to
the connection from the base station to the core network.
It is possible to connect several base stations to one another using high-speed backhaul
microwave links. This would also allow for roaming by a WiMAX subscriber from one base
station coverage area to another, similar to the roaming enabled by cell phones.
The IEEE 802.16e-2005 standard provides the air interface for WiMAX but does not define the
full end-to-end WiMAX network. The WiMAX Forum's Network Working Group (NWG) is
responsible for developing the end-to-end network requirements, architecture, and protocols
for WiMAX, using IEEE 802.16e-2005 as the air interface.
The WiMAX NWG has developed a network reference model to serve as an architecture
framework for WiMAX deployments and to ensure interoperability among various WiMAX
equipment and operators.
The network reference model envisions unified network architecture for supporting fixed,
nomadic, and mobile deployments and is based on an IP service model. Below is simplified
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illustration of IP-based WiMAX network architecture. The overall network may be logically
divided into three parts:
1. Mobile Stations (MS) used by the end user to access the network.
2. The access service network (ASN), which comprises one or more base stations and one
or more ASN gateways that form the radio access network at the edge.
3. Connectivity service network (CSN), which provides IP connectivity and all the IP core
network functions.
The network reference model developed by the WiMAX Forum NWG defines a number of
functional entities and interfaces between those entities. Fig below shows some of the more
important functional entities.
Base station (BS): The BS is responsible for providing the air interface to the MS. Additional
functions that may be part of the BS are micro mobility management functions, such as handoff
triggering and tunnel establishment, radio resource management, QoS policy enforcement,
traffic classification, DHCP (Dynamic Host Control Protocol) proxy, key management, session
management, and multicast group management.
Access service network gateway (ASN-GW): The ASN gateway typically acts as a layer 2 traffic
aggregation points within an ASN. Additional functions that may be part of the ASN gateway
include intra-ASN location management and paging, radio resource management and
admission control, caching of subscriber profiles and encryption keys, AAA client functionality,
establishment and management of mobility tunnel with base stations, QoS and policy
enforcement, and foreign agent functionality for mobile IP, and routing to the selected CSN.
Connectivity service network (CSN): The CSN provides connectivity to the Internet, ASP, other
public networks, and corporate networks. The CSN is owned by the NSP and includes AAA
servers that support authentication for the devices, users, and specific services. The CSN also
provides per user policy management of QoS and security. The CSN is also responsible for IP
address management, support for roaming between different NSPs, location management
between ASNs, and mobility and roaming between ASNs.
27
Figure 13 WiMAX Network Architecture.
The WiMAX architecture framework allows for the flexible decomposition and/or combination
of functional entities when building the physical entities. For example, the ASN may be
decomposed into base station transceivers (BST), base station controllers (BSC), and an ASNGW
analogous to the GSM model of BTS, BSC, and Serving GPRS Support Node (SGSN).
2.6 TRANSMISSION
While deploying telecommunication infrastructures, the planning team will give high attention
to that kind of transmission system they will use to deliver the packet or traffic from source
address to destination.
There are basically three transmission media:
1. Microwave transmission
2. Satellite communication
3. Fiber optic.
The backbone transmission which carries out the huge traffic from the core network to the
international internet gateway, telecommunication partners etc usually will be planned to have
high scalability to anticipate increasing huge traffic in the future.
Optical fiber and Satellite transmissions are the most transmission media which are used by
telecommunication companies to carry huge traffic from the backbone network.
2.6.1 MICROWAVE TRANSMISSION
Microwave communication is the transmission of signals via radio using a series of microwave
towers. Microwave communication is known as a form of “line of sight” communication,
28
because there must be nothing obstructing the transmission of data between these towers for
signals to be properly sent and received.
Microwave Communication Technology was developed in the 1940‟s.
The technology used for microwave communication was developed in the early 1940‟s by
Western Union. The first microwave message was sent in 1945 from towers located in New York
and Philadelphia. Following this successful attempt, microwave communication became the
most commonly used data transmission method for telecommunications service providers.
Microwave communication takes place both analog and digital formats. While digital is the
most advanced form of microwave communication, both analog and digital methods pose
certain benefits for users.
Digital microwave communication utilizes more advanced, more reliable technology. It is much
easier to find equipment to support this transmission method because it is the newer form of
microwave communication. Because it has a higher bandwidth, it also allows you to transmit
more data using more verbose protocols. The increased speeds will also decrease the time it
takes to poll your microwave site equipment. This more reliable format provides for more
reliable reporting with advanced communication equipment, while also allowing you to bring in
your LAN connection when it becomes available at the site.
2.6.2 Line-of-Sight Considerations
Microwave radio communication requires a clear line-of-sight (LOS) condition. Under normal
atmospheric conditions, the radio horizon is around 30 percent beyond the optical horizon.
Radio LOS takes into account the concept of Fresnel ellipsoids and their clearance criteria.
Fresnel Zone are areas of constructive and destructive interference created when
electromagnetic wave propagation in free space is reflected (multipath) or diffracted as the
wave intersects obstacles. Fresnel zones are specified employing ordinal numbers that
correspond to the number of half wavelength multiples that represent the difference in radio
wave propagation path from the direct path.The Fresnel Zone must be clear of all obstructions.
Typically the first Fresnel zone (N=1) is used to determine obstruction loss .The direct path
between the transmitter and the receiver needs a clearance above ground of at least 60% of the
radius of the first Fresnel zone to achieve free space propagation conditions. Earth-radius factor
k compensates the refraction in the atmosphere. Clearance is described as any criterion to
ensure sufficient antenna heights so that, in the worst case of refraction (for which k is
minimum) the receiver antenna is not placed in the diffraction region
Effective Earth‟s Radius = k * True Earth‟s Radius
True Earth‟s radius= 6371 Km
k=4/3=1.33, standard atmosphere with normally refracted path (this value should be used
whenever local value is not provided)
29
Variations of the ray curvature as a function of k
Figure 14 Variations of the ray curvature as a function of k
Clearance criteria to be satisfied under normal propagation conditions
1. Clearance of 60% or greater at the minimum k suggested for the certain path
2. Clearance of 100% or greater at k=4/3
3. In case of space diversity, the antenna can have a 60% clearance at k=4/3 plus allowance
for tree growth, buildings (usually 3 meter)
2.6.3 Microwave Link Design
Microwave Link Design is a methodical, systematic and sometimes lengthy process that includes
1. Loss/attenuation Calculations
2. Fading and fade margins calculations
3. Frequency planning and interference calculations
4. Quality and availability calculations
The whole process is iterative and may go through many redesign phases before the required
quality and availability are achieved.
30
Figure 15 Microwave Link Design process
2.6.4 Advantages of Microwave Radio
1. Less affected by natural calamities
2. Less prone to accidental damage
3. Links across mountains and rivers are more economically feasible
4. Single point installation and maintenance
5. Single point security
6. They are quickly deployed
2.6.5 Improving the Microwave System
1. Hardware Redundancy (Hot standby protection, Multichannel and multiline
protection)
2. Diversity Improvement (Space Diversity, Angle Diversity, Frequency Diversity, Cross
band Diversity, Route Diversity, Hybrid Diversity, Media Diversity)
3. Antireflective Systems
4. Repeaters (Active repeaters, Passive repeaters)
2.6.6 Basic Recommendations for Microwave Transmission
1. Use higher frequency bands for shorter hops and lower frequency bands for longer
hops
2. Avoid lower frequency bands in urban areas
3. Use star and hub configurations for smaller networks and ring configuration for
larger networks
31
4. In areas with heavy precipitation, if possible, use frequency bands below 10 GHz.
5. Use protected systems (1+1) for all important and/or high-capacity links
6. Leave enough spare capacity for future expansion of the system
7. Space diversity is a very expensive way of improving the performance of the
microwave link and it should be used carefully and as a last resort
8. The activities of microwave path planning and frequency planning preferably should
be performed in parallel with line of sight activities and other network design
activities for best efficiency.
9. Use updated maps that are not more than a year old. The terrain itself can change
drastically in a very short time period. Make sure everyone on the project is using the
same maps, datum‟s and coordinate systems.
10. Perform detailed path surveys on ALL microwave hops. Maps are used only for initial
planning, as a first approximation.
11. Below 10 GHz, multipath outage increases rapidly with path length. It also increases
with frequency, climatic factors and average annual temperature. Multipath effect
can be reduced with higher fade margin. If the path has excessive path outage the
performance can be improved by using one of the diversity methods.
2.6.7 Difficult Areas for Microwave Links
1. In areas with lots of rain, use the lowest frequency band allowed for the project.
2. Microwave hops over or in the vicinity of the large water surfaces and flat land areas
can cause severe multipath fading. Reflections may be avoided by selecting sites that
are shielded from the reflected rays.
3. Hot and humid coastal areas
2.6.8 VSAT
What is a VSAT?
The term Very Small Aperture Terminal (VSAT) refers to a small fixed earth station. VSATs
provide the vital communication link required to set up a satellite based communication
network. VSATs can support any communication requirement be it voice, data, or video
conferencing.
The VSAT comprises of two modules - an outdoor unit and an indoor unit.
32
The outdoor unit consists of an Antenna and Radio Frequency Transceiver (RFT). The antenna
size is typically 1.8 metre or 2.4 metre in diameter, although smaller antennas are also in use.
The indoor unit functions as a modem and also interfaces with the end user equipment like
standalone PCs, LANs, Telephones or an EPABX.
VSATs can typically be divided into two parts- an outdoor unit and an indoor unit. The outdoor
unit is generally ground or even wall mounted and the indoor unit which is the size of a desktop
computer is normally located near existing computer equipment in your office.
2.6.9 Outdoor Unit
The antenna system comprises of a reflector, feed horn and a mount. The size of a VSAT
antenna varies from 1.8 metres to 3.8 metres. The feed horn is mounted on the antenna frame
at its focal point by support arms.
The FEEDHORN directs the transmitted power towards the antenna dish or collects the received
power from it. It consists of an array of microwave passive components. Antenna size is used to
describe the ability of the antenna to amplify the signal strength.
The RFT is mounted on the antenna frame and is interconnected to the feed horn. Also termed
as outdoor electronics, RFT, in turn, consists of different subsystems.
These include low noise Amplifiers (LNA) and down converters for amplification and down
conversion of the received signal respectively. LNAs are designed to minimise the noise added
to the signal during this first stage of the converter as the noise performance of this stage
determines the overall noise performance of the converter unit.
The noise temperature is the parameter used to describe the performance of a LNA
Up converters and High Powered Amplifiers (HPA) are also parts of the RFT and are used for up
converting and amplifying the signal before transmitting to the feed horn. The Up/Down
converters convert frequencies between intermediate frequency (Usually IF level 70 MHz) and
radio frequency. For Extended C band, the down converter receives the signal at 4.500 to 4.800
GHz and the up converter converts it to 6.725 to 7.025 GHz. The HPA ratings for VSATs range
between 1 to 40 watts.
Interlink Facility
The outdoor unit is connected through a low loss coaxial cable to the indoor unit. The typical
limit of an IFL cable is about 300 feet.
2.6.10 Indoor Unit
33
The IDU consists of modulators which superimpose the user traffic signal on a carrier signal. This
is then sent to the RFT for up conversion, amplification and transmission. It also consists of
demodulators which receive the signal from the RFT in the IF range and demodulates the same
to segregate the user traffic signal from the carrier. The IDU also determines the access schemes
under which the VSAT would operate. The IDU also interfaces with various end user equipment,
ranging from stand alone computers, LAN's, routers, multiplexes, telephone instruments, EPABX
as per the requirement. It performs the necessary protocol conversion on the input data from
the customer end equipment prior to modulation and transmission to the RFT.
An IDU is specified by the access technique, protocols handled and number of interface ports
supported.
2.6.11 Advantages of VSATs
VSATs are an ideal option for networking because they enable Enterprise Wide Networking with
high reliability and a wide reach which extends even to remote sites.
Last Mile Problem
Let us begin with the situation where you have reliable high-speed links between city exchanges
for meeting your communication requirements. But before you begin to feel comfortable,
connections from the nearest exchange to your company's office often fail. Consequently,
stretching what is technically called the last mile problem into much
longer distances. VSATs located at your premises guarantee seamless communication even
across the last mile.
Reach
You must be well aware of the limitations faced by terrestrial lines in reaching remote and other
difficult locations. VSAT‟s on the other hand, offer you unrestricted and unlimited reach.
Reliability
Uptime of up to 99.5 percent is achievable on a VSAT network. This is significantly higher than
the typical leased line uptime of approximately 80 to 85 percent.
Time
VSAT deployment takes no more than 4-6 weeks as compared to 4 to 6 months for leased lines.
2.6.12 Network Management
Network monitoring and control of the entire VSAT network is much simpler than a network of
leased lines, involving multiple carriers at multiple locations. A much smaller number of
elements needs to be monitored in case of a VSAT network and also the number of vendors and
carriers involved in between any two user terminals in a VSAT network
34
is typically one. This results in a single point of contact for resolving all your VSAT networking
issues.
A VSAT NMS easily integrates end-to-end monitoring and configuration control for all network
subsystems.
Maintenance
A single point contact for operation, maintenance, rapid fault isolation and troubleshooting
makes things very simple for a client, using VSAT services. VSATs also enjoy a low mean time to
repair (MTTR) of a few hours, which extends up to a few days in the case of leased lines.
Essentially, lesser elements imply lower MTTR.
Flexibility
VSAT networks offer enormous expansion capabilities. This feature factors in changes in the
business environment and traffic loads that can be easily accommodated on a technology
migration path. Additional VSATs can be rapidly installed to support the network expansion to
any site, no matter however remote.
Cost
A comparison of costs between a VSAT network and a leased line network reveals that a VSAT
network offers significant savings over a two to three years timeframe. This does not take into
account the cost of downtime, inclusion of which would result in the VSAT network being much
more cost - effective. Pay-by-mile concept in case of leased line sends the costs spiralling
upwards. More so if the locations to be linked are dispersed all over the country.
Compare this to VSATs where the distance has nothing to do with the cost. Additionally, in case
of VSATs, the service charges depend on the bandwidth which is allocated to your network in
line with your requirements. Whereas with a leased line you get a dedicated circuit in multiples
of 64Kbps whether you need that amount of bandwidth or not.
2.6.12 VSAT System Architecture
A VSAT system consists of a satellite transponder, central hub or a master earth station, and
remote VSATs. The VSAT terminal has the capability to receive as well as transmit signals via the
satellite to other VSATs in the network.
Depending on the access technology used the signals are either sent via satellite to a central
hub, which is also a monitoring centre, or the signals are sent directly to VSATs with the hub
being used for monitoring and control.
2.6.13 Topologies
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The network of VSATs at different locations adopts different topologies depending on the end
applications traffic flow requirements. These topologies could be Star or Mesh.
The most popular of these is Star topology. Here we have a big, central earth station known as
the hub.
Generally the hub antenna is in the range of 6-11metre in diameter. This hub station controls,
monitors and communicates with a large number of dispersed VSATs. Since all VSATs
communicate with the central hub station only, this network is more suitable for centralized
data applications. Large organizations, like banks, with centralized data processing requirements
is a case in point.
In a mesh topology a group of VSATs communicate directly with any other VSAT in the network
without going through a central hub. A hub station in a mesh network performs only the
monitoring and control functions. These networks are more suitable for telephony applications.
These have also been adopted to deploy point to point high speed links.
However, in actual practice a number of requirements are catered to by a hybrid network
topology. Under hybrid networks a part of the network operates on a star topology while some
sites operate on a mesh topology.
2.6.14 Access Technologies
The primary objective and advantage of these networks is to maximise the use of common
satellite and other resources amongst all VSAT sites. The methods by which these networks
optimise the use of satellite capacity, and spectrum utilisation in a flexible and cost effective
manner are referred to as satellite access schemes. Each of the above topologies is associated
with an appropriate satellite access scheme. The most commonly used satellite access schemes
are:
1. Time Division Multiple Access(TDMA)
2. Frequency Division Multiple Access(FDMA)
3. Code Division Multiple Access(CDMA)
4. Demand Assigned Multiple Access(DAMA)
5. Pre-Assigned Multiple Access(PAMA)
6. Frequency-Time Division Multiple Access(FTDMA)
2.6.15 Space Segment Support
The ideal orbit for a communications satellite is geostationary, or motionless relative to the
ground. Satellites used for communications are almost exclusively in the geostationary orbit,
located at 36000 km above the equator. In line with ITU stipulations, for avoiding interference,
36
all satellites are placed 2 degree apart. This places a maximum limit of 180 satellites operating in
a geostationary orbit.
However, with a view to maximise the utilisation of orbital slots, Co-located satellites are being
deployed. Co-located satellites are separated by 0.1 degree in space or approximately 30kms.
Signal interference from the Co-located satellites is prevented by using orthogonal
polarisations. Hence ground station equipment can receive signals from two Co-located
satellites without any reorientation of the antenna. The signals can be differentiated based on
their polarisation.
Space segment: Space Segment is available from organisations which have procured satellites,
arranged launches and conducted preliminary tests in-orbit and who then operate these
satellites on commercial basis.
Transponders: Contained in the satellite body are a number of transponders, or repeaters. These
transponders perform the following functions:
1. Signal Reception - it receives the signal uplinked by a VSAT and/or hub
2. Frequency Translation - the frequency of the received signal is translated to a
different frequency, known as the downlink frequency. The frequency translation
ensures that there is no positive feedback and also avoid interference related issues.
3. Amplification - the transponder also amplifies the downlink signal.
The number of transponders determines the capacity of a satellite. The INSAT series of satellites
have typically 12 /18 transponders in various frequency bands. Each transponder typically has a
bandwidth of 40 MHz.
The various frequency bands are as below:
Table 3 The various frequency bands.
Internationally Ku-Band is a popular frequency band in use. The Ku- Band by virtue of its higher
frequency can support traffic with smaller antenna sizes in comparison to C / Ext-C Band. It is ,
however, susceptible to rain outages making it unsuitable for use in South East Asian regions.
Indian service providers are presently allowed to hire space segment only on the INSAT series
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and operate in Ext-C band only. Ext-C band is available only on the INSAT series of satellites and
is not a standard band available internationally.
Link Budgets: Ascertains that the RF equipment would cater to the requirements of the network
topology and satellite modems in use. The link Budget estimates the ground station and
satellite EIRP required. Equivalent isotropically radiated power (EIRP) is the power transmitted
from a transmitting object. Satellite ERP can be defined as the sum of output power from the
satellite‟s amplifier, satellite antenna gain and losses.
Calculations of signal levels through the system (from originating earth station to satellite to
receiving earth station) to ensure the quality of service should normally be done prior to the
establishment of a satellite link. This calculation of the link budget highlights the various
aspects. EIRP required at the transmitting VSAT, Satellite EIRP which will be required for a
desired specified gain of this receiving system. Apart from the known losses due to various
cables and inter - connecting devices, it is customary to keep sufficient link margin for various
extraneous noise which may affect the performance. It is also a safeguard to meet eventualities
of signal attenuation due to rain/snow. As mentioned earlier a satellite provides two resources,
bandwidth and amplification power. In most VSAT networks the limiting resource in satellite
transponder is power rather than bandwidth.
With all their advantages, VSATs are taking on an expanding role in a variety of interactive, on-
line data, voice and multimedia applications. Whether it is gas station service, rural telephony,
environmental monitoring, distance learning / remote training or the Internet, VSATs are truly
poised to be the Space Age Technology.
Satellite transmission is an alternative solution provided there is no optical fiber for the
backbone transmission or there is no E1 transmission via radio microwave to carry out low and
middle traffic. It‟s a high costly transmission media.
2.6.16 Fiber Optics
Optical fiber (or "fiber optic") refers to the medium and the technology associated with the
transmission of information as light pulses along a glass or plastic strand or fiber.
An optical fiber is made up of the core, (carries the light pulses), the cladding (reflects the light
pulses back into the core) and the buffer coating (protects the core and cladding from moisture,
damage, etc.). Together, all of this creates a fiber optic which can carry up to 10 million
messages at any time using light pulses.
The medium of transmission is light. Light waves have an extremely high frequency and travel at
186,000-miles (300,000Km) per second.
A single OF cable can theoretically carry trillions of bits of information every second.
38
The tiny, flexible glass or plastic fiber is coated, both for protection and to enhance its
characteristics as a reflective light wave guide.
Fiber optic cables normally carry numerous OF strands within a single enclosure.
Compared to a coaxial cable, optical fiber has the following advantages:
1. Much greater capacity. The information carrying capacity of optical fibre is thousands of
times greater than a normal copper wire. Note on the right the comparison between an
optical fiber link and a telephone cable with its hundreds of wires. Both have the same
information carrying capacity.
2. Low and very uniform attenuation (signal loss) over a wide frequency range. This greatly
simplifies amplification of the signal.
3. Virtual immunity to all types of interference
4. No problems with leakage or causing interference with other signals
5. Insensitivity to temperature variations
6. Extremely small size
7. Will not short out in bad weather or even in water
8. Low cost
9. High reliability .The fibers do not corrode or break down in moisture or salt air the way
copper wires do.
10. Light weights since they are not based on metal conductors, OF cables are lighter and
much easier to transport and install.
Fiber optics is a particularly popular technology for local-area networks. In addition, telephone
companies are steadily replacing traditional telephone lines with fiber optic cables. In the future,
almost all communications will employ fiber optics.
CHAPTER THREE: PRACTICAL WORK DONE
3.1 INTRODUCTION
This chapter comprises of the hands-on activities which were done during the training period.
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3.2 NETWORK OPERATIONS CENTER (NOC)
The NOC is a centralized interconnected operations centre where network operations
monitoring and maintenance are carried out to ensure network optimisation and performance.
The WTU is a bi-vendor network (Huawei and Ericsson) which is divided into regions with
respect to the vendor of equipment used. The NOC is divided into three sections that is the
Huawei, Ericsson and Nera NOC all with a joint aim of network monitoring and maintenance to
meet the required quality of service. In case of a fault in equipment, an alarm message is
received and this can be critical, major, minor or warning and consequently the issue is dealt
with appropriately. For the case of a critical alarm e.g. High temperature in the BTS room, a call
out is sent out to the field engineers to attend quickly to the situation.
Various tools were used in the NOC, among which included WinFIOL, iManager M2000, BSC
Local Maintenance Terminal MSOFTX 3000, AKILI, WebSMAP and UltraEdit-32.
3.3 USING WinFIOL TO PERFOM NETWORK MONITORING.
It‟s an element management system for Ericsson that runs a command line interface which
displays required parameters like; cell information status, alarm situation, GPRS connectivity of
the sites etc. The commands run in WINFOIL are stored in the ALEX libraries.
WINFOIL monitors 3 BSC‟s one in Jinja and two in Kampala.
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Figure 16 WINFOIL window.
Common commands run on WINFOIL.
Allip: prca-53; returns a printout of the existing alarms on the site.
Figure 17 WINFOIL window displaying the allip: prca-53 command
Rxasp: moty=rxotg; returns a general printout of all outstanding alarms on the corresponding
sites.
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Figure 18 WINFOIL window displaying the Rxasp: moty=rxotg command
Rlcrp: cell=all; returns a printout cell resources for all active cells within the BSC.
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Figure 19 WINFOIL window displaying the Rlcrp: cell=all command
Common alarms viewed on WINFOIL
1. Rectifier module fail
2. Genset fail to start
3. High temperature
4. BBS CLU alarm
5. Tower alarm
6. Aircon system fault
3.4 USING THE AKILI WORK FLOW TOOL.
This is a management tool that enables NOC engineers to monitor activities regarding
intrusion logs, time, reasons for intrusion, events monitoring, making call outs and all related
on-site activities.
3.4.1 Procedure for logging out a field engineer from a site.
1. The site engineer logs into the site using SMS. This is by sending a message VISIT to
197. He then receives a reply message indicating a reference number which is
automatically generated by the system to enable him access the site.
43
2. Upon completing the purpose of the intrusion such as fuelling, he calls the NOC and
gives details of the quantity of fuel fed in the generator, generator run hours and the
number of generators on site. These details are entered into AKILI where it is stored
for future reference. The site has to be checked to ensure there is no other fault
pending or caused by the engineer.
3. To use the tool feed in the URL http://10.6.35.8/intrusions then you enter a valid
login details (username and password). For a new intrusion, look for Intrusion, New
Intrusion log then get the details of the site engineer (name, company, reason for
intrusion), the current time and date and submit. You will have successfully logged in
a site engineer.
3.5 USING iMANAGER FOR NETWORK MONITORING.
iManager is also a Huawei tool used for network monitoring. When any of the equipment goes
faulty, an alarm is immediately reported to the NOC and observed via this interface.
Common alarms viewed on iManager M2000
Table 3.1: Common alarms viewed on iManager.
Table 4 Common alarms viewed on iManager.
Critical AC mains failure, No AC power
Major PSU shutdown alarms
Minor Breakdown of the communication link between
the HLR and IVR.
Warning E1/T1 issues.
Figure 20 An example of a typical alarm, generated at a GPRS site, monitored using the iManager Tool.
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Figure 21 An interface showing the different alarms and their details
3.6 USING INALA
Its software designed for fuel management. It controls Genset pumping, displays RBS
temperature, battery temperature, humidity, fuel levels, power meter reading, discharging
current, charging current and battery voltage.
Figure 22 INALA window
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3.7 USING IMC-ESDER V2.05
This was used to monitor the temperature and humidity conditions in the MSC rooms so as to
maintain system efficiency. The interface is made in such a way that it shows the position at
which each equipment is located and the current temperature and humidity of the equipment.
There is a maximum and minimum temperature and humidity above and below which is not to
be exceeded and in case it is exceeded, and escalation has to be made to the concerned
engineer to take the necessary action.
It also monitors other events and the alarms returned include infrared motion (movement within
the room), door magnetic alarm (door has been opened), filtering net maintenance (cleaning of
the air system being carried out), etc.
When an alarm is returned, it contain the following details: Site ID; Device Address; Device
Name; Device Type; Signal Name; State; Alarm meaning; Fix suggestion.
Figure 23 IMC-ESDER window
3.8 FIELD OPERATIONS
The field activities carried out included going to various sites to rectify faults, as a response to
alarms which have been detected from the NOC.
46
In this case the field engineer has to actually go to the site and carry out troubleshooting in
order to work upon a given problem and get feedback from NOC whether the alarm has ceased.
Among the sites that were visited included the following.
3.8.1 Site Visit to Kizungu
Site ID:MDKP1068
Type: Indoor
Reason for intrusion: To check on fuel levels and generator running hours and DXU alarms.
1. These alarms were being reflected at the NOC while the actual situation at the site
was different.
2. A laptop was connected to the BTS through the OMT (operation and maintenance
terminal) at the DXU (digital switching unit) using the USB cable.
3. The OMT software was opened and was used to access the BTS, where the alarm
status was then configured to the right settings through the monitoring window
option.
4. The alarms were observed for a few seconds after which they were cleared and the
site was then left.
3.8.2 Site Visit to Lubowa
Reason for intrusion: check the fuel level.
Type of site: Indoor
The fuel level for the site generator was also checked and the following values noted
• Fuel level in centimetres (1 cm = 20 litres)
• Current Genset running hours(2237)
• Running hours for which next service is to be done.
• After the purpose of the intrusion, the site was then left.
3.9 RF PLANNING DEPARTMENT.
Here the work done was aimed at network performance and optimization. Site surveys were
carried out, as well as learning how to use optimization and planning tools. Some of the tools
learnt included the following.
3.9.1 LINK DESIGN AND PLANNING USING PATHLOSS
The Pathloss Tool is used to carry out link design and planning for microwave transmission. It‟s
used for finding the line of sight between two sites and gives an estimate of the Fresnel zone.
47
Below is a quick procedure of using Pathloss:
1. Click to open Pathloss icon to open, click Module on toolbar and choose map grid a
new page is displayed. Click on site data and choose site list. a new page is
displayed. Click Edit on the menu bar then select Add and feed in the site name
corresponding coordinates.
2. Click Mark site on the menu bar, a new page is displayed showing the added sites.
Create a link by clicking and holding on one of the sites and dragging along a
straight line to the next site. Left click on the line, select terrain data. A new interface
is displayed. Click on Operations and select generate profile. On the menu bar
select Module and click print profile which displays the Fresnel zone between the
two sites, path length between them, elevation and frequency.
3. To adjust antenna height, click module, select antenna heights, then adjust according
to the relief
4. To create a Link Budget, click Module on the menu bar and select summary. set the
frequency desired (6, 11, 18, or 38 GHz). Click on Module and select worksheet to
configure the channel, radio equipment, transmission line and antenna to the set
frequency and also load the rain file and in the branching network window, set the
miscellaneous losses to 1 for both sites. To view final report click on report, select
full report. The link budget will be displayed. The link should be designed as to
operate without outage for 99.9995% of the year.
3.9.2 THE MAPINFO TOOL
This Tool is used for plotting purposes. It is also used to determine the nature of relief of an
area, hence help to give information on suitable points for establishment of a new site. It has a
toolbar menu, with a variety for different tasks
Plotting is done based on the provided coordinates (longitude and latitude). Care should be
taken when specifying the coordinates so that they are not interchanged, otherwise the point
will lie outside required boundary.
48
Figure 24 Map Info screenshot
3.9.3 SITE SURVEYS
Site survey involves finding suitable locations where new sites can be built for network
optimisation and coverage. The following tools were used:
1. GPS (Global Positioning System)
2. Distance meter
3. Camera
Figure 25 Site survey at Natete.
49
Table 5 Activities carried out in the RF planning department.
Date/Supervisor(s) Work done Remarks
George Kasangaki Had a drive test to Dundu-Entebbe to ascertain a
complaint by a subscriber (Jena Poultry Farm) of
poor signal quality. The Dongle (USB license for
TEMS) is plugged into the laptop and a Sony
Ericsson mobile (for the test call) uploaded with
TEMS (software for monitoring the network) is
plugged into the laptop (having TEMS installed)
and dialled 171. TEMS displayed the various signal
status parameters (RxQual, RxLev, GSM serving
+neigh ours and other windows).
Carried out site surveys in Lubowa,Masaja and
Gaba recording site coordinates(using
GPS),tower height(using the distance
meter),field azimuth(GPS), available construction
points coordinates(GPS) ,power and road
accessibility.
Carried out site surveys in Natete, Nalumunye
and Konge recording site coordinates (using
GPS), tower height (using the distance meter),
field azimuth (GPS), available construction points
coordinates (GPS), power and road accessibility
data.
Carried out site surveys in
Nsambya.Najja,Namasuba1,Makindye,Ndeeba
and Kyengera recording site coordinates(using
GPS),tower height(using the distance
meter),field azimuth(GPS), available construction
points coordinates(GPS) ,power and road
accessibility data.
Carried out site surveys in Namasuba2 recording
site coordinates (using GPS), tower height (using
the distance meter), field azimuth (GPS),
available construction points coordinates (GPS),
power and road accessibility data.
Poor signal quality
because there is no
Warid site in Dundu.
All the existing sites
were not sharable
thus new ground
sites have to be put
up.
Possible sharing
Natete(Orange),Nalu
munye(UTL)
New ground site at
Konge.
Possible sharing at
Nsambya (Orange),
Najja (Zain, Orange).
Rooftop sites
recommended to be
constructed in
Namasuba,
Makindye, Ndeeba
and Kyengera.
Rooftop sites
recommended to be
constructed in
Namasuba2.
Ladder needed for
access to rooftop.
Compilation of
survey data is vital in
the planning process
as it provides the
possible points that
50
Compiled the data gathered during site surveys
showing Site Name, Surveyed coordinates,
proposed field azimuth, accessibility, power,
possible construction points and in case of an
existing site , the operator name site
coordinates ,azimuth , are fed into the excel
sheet.
Used Map Info professional to map locations of
the surveyed sites. Map Info Professional is a
mapping tool that uses coordinates to map
given locations. Save the survey data (you can
select say site name, coordinates and tower
height) obtained in csv format. Open map info
and select the saved file (csv) thereby creating a
tab file. Click on table, select create points and
choose the preferred site symbol, projection
(longitude/latitude WGS84), where to get the X
and Y coordinates from (longitudes or latitudes).
Open the tab file, right click, select layer control,
click on auto label and the site names will be
displayed.
can be used for
improving network
performance where
new links on the
network could be set
up and setting up
the network where it
did not exist.
With Map Info
professional you can
map various
locations easily.
Stephen Mwanje Had a presentation on optical fibers as a
medium of communication, what to consider
during installations (underground or overhead)
for economical reasons, possible interferences
considered (the interconnections, joints,
connecting cores), developing a test plan
(assurance that what is installed actually works),
maintenance (planning for restoration) and how
to deal with a growing subscriber base (data)
without overhaul of entire fiber network.
The choice of
Optical fiber
communication over
cable and
microwave lies
greatly in its higher
bandwidth, less loss
transmission, not
affected by EM
interference.
During the laying of
the fiber, manholes
should be left for
maintenance work.
Brian D'ujanga Used Pathloss in finding the Line Of Sight and
creating the Link Budget. Given the site name
and the corresponding coordinates, open
Pathloss, click Module (menu bar) and on the
dropdown list, click map grid a new page is
displayed where you click site data, on the
With Pathloss
setting up a
microwave link
between two sites
can done easily
since all the
51
dropdown menu click site list which also
displays a new page where you click Edit on the
menu bar. Select Add and feed in the site name
and corresponding coordinates. Click Mark site
on the menu bar where a new page is displayed
showing the added sites. By clicking and holding
on one of the sites create a link which upon left
clicking, select terrain data. New page is
displayed and on the menu bar click Operations
and select generate profile. A profile is
displayed without the LOS. On the menu bar
select Module and click print profile which
displays the LOS between the two sites, path
length, elevation and frequency.
To create a Link Budget, on the menu bar click
Module and select summary. Here you set the
frequency you want to use (6, 11, 18, 38 GHz).
Click on Module and select worksheet to
configure the channel, radio equipment,
transmission line and antenna to the set
frequency and also load the rain file and in the
branching network window, set the
miscellaneous losses to 1 for both sites. Upon
completion click on report (menu bar) and
select full report. The link budget will be
displayed.
necessary
parameters are put
into consideration
(terrain, rain, LOS
etc).
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Figure 26 The current WTU Network as at August 2010.
53
CHAPTER FOUR: ACHIEVEMENTS, CHALLENGES,
RECOMMENDATIONS AND CONCLUSION
4.1 ACHIEVEMENTS
Training at Warid Telecom was an eye opener to the diverse engineering field where I got to to
learn and appreciate the engineering field much more to a practical extent. With daily
advancements in technology one needs to adjust swiftly to keep abreast of the competitors in
the industry. This ensures a continuous learning process throughout the whole period.
Throughout the training I was able to understand the various concepts in the
telecommunication world for example network monitoring, network planning and optimization,
how the WIMAX, GSM, GPRS, EDGE technologies actually operate.
Though Economics is not largely looked at, it plays an important role in all engineering
activities. My training at WTU enabled to get clear-cut economic decisions for most of the
engineering activities. For instance when carrying out a site survey, you will have to
economically weigh the option of constructing a new site or sharing an existing site.
WTU trained me to be a flexible employee. Throughout the training period I was exposed to
different engineering departments participating in different activities thereby encouraging me
to be able to adjust accordingly in case of an uncertainty in any given workplace.
Further still, I learnt that the problems encountered in the telecommunications industry rarely
have unique solutions and I gained some experience on how to select the optimal solution from
the many alternatives available. For example when a site has issues with fuel, the fuel probe may
be damaged and it may necessitate you to repair the probe.
Above all, I learnt the significance of maintaining a good formal and informal relationship in an
industrial organization and how they can promote favourable human relations and teamwork.
This is enables smooth coordination among the workers and hence, smooth work flow.
4.3 CHALLENGES FACED DURING THE TRAINING
Besides the achievements there were indeed some challenges faced during the training, among
which included the following:
Limited transport means: At times there was shortage of vehicles to be used. This was especially
experienced during site surveys, hence causing some bit of delays from the actual time the
activities were to be carried out.
Insufficient projectors: some presentations were made without projectors which made the
learning process difficult.
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4.4 RECOMMENDATIONS
I would recommend that students are given a guideline of the areas that they are expected to
encounter during their industrial training period so that the company supervisor can allocate
tasks effectively.
The company should also try to begin its training period earlier than they have been doing so
that the trainee has enough time to exhaustively understand whatever has been prepared for
him/her and fully utilize the time allocated by the university to carry out the industrial training.
I would recommend that transport facilities are easily accessible for field operation activities.
Necessary equipment like projectors should be readily available to aid in presentations.
With the cut-throat competition currently in Uganda‟s telecommunications industry WTU should
consider more investment in its data handling section in order to increase the company‟s data
subscriber base through the introduction of the latest data technologies.
During the training period additional desktops should be added in the Engineering department
to assist the internee‟s in practicing the use of the Engineering tools.
Finally, WTU should continue with their policy of offering industrial training so that the
upcoming professionals, who are still at undergraduate levels get to know what goes in the field
and what is required of them as they per sue their profession.
4.5 CONCLUSION
No doubt experience as an internee in the Engineering Department of a Multinational cellular
company like WTU would serve as a step stone to better carrier in Engineering field.
Experiences such as Network Monitoring, site surveys and field operations and presentations
from Engineers would be helpful in my future assignments as a student and as well as an
Engineer.
All the Engineering aspects being considered should be balanced with an appropriate economic
figure to keep profitability the goal of the company.
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REFERENCES
1. Gunnar Heine, GSM Networks: Protocols, Terminology and Implementation, 1999,
Artech House Inc.
2. Peter Stuckmann, The GSM Evolution: Mobile Packet data Services, 2003, John Wiley and
Sons.
3. Amitabj Kumar, Mobile Broadcasting with Wimax: Principles, technology and
applications, 2008, Focal Press.
4. www.waridtel.co.ug Date Accesed 28 -07-2010
