telecommunication training report

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UNIVERSITY OF MORATUWA

Faculty of Engineering

Non-GPA Module 399: Industrial Training

TRAINING REPORT

Presented By

Hasanga Udesh Gunawardhana

Index No : 060147J

Field of Study : Electronic & Telecommunication Engineering

Training Establishment : Mobitel (Pvt) Ltd

Training Period : 13.10.2008 – 27.03.2009

Date of Submission : 08.04.2009


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Preface

This is the training report which includes the experiences and details about the

training that I underwent in Mobitel (Pvt) Ltd. The industrial training is a great experience for

an engineering undergraduate to improve his knowledge and learn the engineering practices.

This report contains three chapters namely, Introduction to Mobitel (Pvt) Ltd,

Training Experiences and Conclusion. Some of the chapters are divided into sub divisions

according to the guidelines.

The first chapter describes the Mobitel Company profile. It contains the details about

its history, present status, strengths and weaknesses of Mobitel (Pvt) Ltd. This also includes

about the profitability and the usefulness of the company towards the society.

In the second chapter, I describe the experience that I have gathered during the

training period. This chapter is divided into sub divisions to describe the theoretical and

practical knowledge that I have gathered in different divisions of Mobitel (Pvt) Ltd.

Sometimes it is difficult to explain some practical work that I did during the training period.

Third chapter is the conclusion of the report. This chapter summarizes the training

that I underwent in Mobitel (Pvt) Ltd. It also contains some feedback regarding the training

program conducted as a collaboration of NAITA and the Training Division, University of

Moratuwa.


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Acknowledgement

First, I would like to thank the Training Division of University of Moratuwa for

organizing and coordinating this kind of a training program to give the industrial exposure.

Not only organizing the event, Training Division gave a good introduction and pointed out

the objectives of the Industrial training before we participate in the training program. I would

like to specially thank Eng. N.A. Wijeyewickrama, Director, P. Gunawardena and S.A.S.

Punchihewa, Senior Lecturers of Training Division for their great support within the training

period to make it a success.

I would also like to thank NAITA for their cooperation towards Training Division to

organize a good Industrial Training Program for us.

Then I would like to convey my sincere thank to Eng. A.T.L.K Samarasinghe, Head,

Dept of Electronic & Telecommunication Engineering, and Eng. N. Abeysinghe, Lecturer,

who coordinated and guided us in our training program and helped us to earn a great

experience in the industry. I would also like to thank to Ms. Chamanthi Karunasekara,

Lecturer, for visiting us during the training and advising us to gain a good Industrial Training.

I would like extend my thank to all the staff in Mobitel starting from Mr. Rasantha

Hettithanthrige, Senior General Manager in Mobitel Engineering Division. Special thank

should go to Mr Rasika, Supervisory Engineer – Service Quality, for coordinating the

training program in Mobitel.

Thanks for all of my training colleagues who were at Mobitel for making my training

period a successful and enjoyable training period with full of joy.

Thank You.

Hasanga Udesh Gunawardhana

08/04/2009


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Table of Contents

1. Introduction to Mobitel (Pvt) Ltd .................................................................................. 1

1.1.

Overview of the Company .......................................................................................... 1

1.2. Vision and Mission of Mobitel (Pvt) Ltd .................................................................... 2

1.3. History of Mobitel (Pvt) Ltd ....................................................................................... 2

1.4.

Organizational Structure ............................................................................................. 3

1.5.

Hierarchical Levels ..................................................................................................... 4

1.6. Present Performance of Mobitel (Pvt) Ltd .................................................................. 5

1.7. Strengths and Weaknesses .......................................................................................... 6

1.8.

Profitability.................................................................................................................. 7

1.9.

Usefulness to Sri Lankan Society................................................................................ 7

1.10.

Suggestions to Improve the Performance ................................................................ 7

2. Training Experiences ....................................................................................................... 9

2.1. Transmission Operations Division ............................................................................ 10

2.1.1. Brief Description about the Division ................................................................. 10

2.1.2.

Experience in this Division ................................................................................ 10

2.2. Value Added Services (VAS) Division ..................................................................... 12


2.2.2. Experience in the Division ................................................................................. 12

2.3.

Radio Network Design (RND) Division ................................................................... 14


2.3.2. Network Planning .............................................................................................. 14

2.3.3. Cell Planning ...................................................................................................... 16

2.3.4. Frequency Planning ........................................................................................... 21

2.3.4.1. Frequency Reuse ............................................................................................. 21

2.3.4.2 Interference in Mobile Networks ............................................................... 22

2.3.4.3 Frequency Hopping ................................................................................... 22

2.3.5. Installations ........................................................................................................ 27

2.3.6. Optimization and Tuning ................................................................................... 29

2.3.6.1

Drive Tests .................................................................................................. 29

2.3.6.2 Defining Handovers and Measurement Frequencies .................................. 30

2.3.6.3

System Upgrades and Expansions .............................................................. 30


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2.3.6.4 Customer Complaints ................................................................................. 31

2.3.7. Other practical experiences within the stay at RND Division ........................... 38

3. Conclusion ...................................................................................................................... 40

List of Figures………………………………………………………………………………..v

List of Tables…………………………………………………………………………………v

Annex 1………………………………………………………………………………………vi

Annex 2……………………………………………………………………………………...vii

Abbreviations………………………………………………………………………………viii


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LIST OF FIGURES

Figure 1.1 – Organizational Structure in Mobitel…………………………………………….. 3

Figure 1.2 – Engineering Divisional Structure…………………………………...................... 3

Figure 1.3 – Mobitel 2G and 3G coverage distribution as at 20.03.2009…………………….. 5

Figure 2.1 – Universal Mobile Telecommunication System (UMTS)……………................... 13

Figure 2.2 – Block Diagram for Radio Network Planning……………………….................... 15

Figure 2.3 – Directional and Sector Cell Arrangement……………………………….............. 17

Figure 2.4 – Site database of the TEMS cell planner………………………………................. 18

Figure 2.5 – Coverage Predictions of Chunnkam Site in Jaffna………………........................ 19

Figure 2.6 – Height Profile can be used check the line of sight………………………………. 19

Figure 2.7 – Mobitel Sites in Katunayaka area in MapInfo GUI…………............................... 23Figure 2.8 - Distribution of Channels………………………………………............................ 25

Figure 2.9 – Frequency plan using 6 site clusters on MapInfo GUI………………………….. 26

Figure 2.10 – Diplexer arrangement used in the Pussellawa 3G installation………................. 27

Figure 2.11 – Wall-mounted RRU and 2 Diplexers fixed to the cable rack…………….......... 28

Figure 2.12 – Equipment connections in a Standard Drive Tool Kit…………………………. 29

Figure 2.13 - The GUI of the TEMS drive test tool kit which describes GSM parameters....... 32

Figure 2.14 - Map of the TEMS drive test tool which is dynamically drawn………………… 32

Figure 2.15 – WinFIOL GUI…………………………………………………………………. 34

Figure 2.16 – Customer Complaint Management Prompt……………………………………. 35

Figure 2.17 – Test phone of the TEMS tool kit………………………………......................... 36

Figure 2.18 – Handover performance of the cells using BUSINESS OBJECTS software…… 37

Figure 2.19 – The GUI of the Web base document which gives details of equipment………. 39

Figure A 1.1 – Organizational Structure of the Engineering Division……………………….. iv

Figure A 2.1 – 4/12 cell pattern………………………………………………………………. v

Figure A 2.2 – 3/9 cell pattern……………………………………………………………….. v

LIST OF TABLES

Table 2.1 – Training Schedule………………………………………………………... 9

Table 2.2 – Frequency Bands used in GSM………………………………………….. 21


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CHAPTER 1

1.

Introduction to Mobitel (Pvt) Ltd

1.1. Overview of the Company

Mobitel (Pvt) Ltd is Sri Lanka’s National Mobile Service Provider which is embedded

with world’s best technology and a wider coverage which covers 70% of Sri Lanka. Starting

as the second mobile service provider, Mobitel has continuously introduced new services and

trends to the Sri Lankan community.

Mobitel (Pvt) Ltd was launched as a collaboration between Sri Lanka Telecom (SLT)

and Telstar Australia in 1993. In 2002, Sri Lanka Telecom acquired Mobitel (Pvt) Ltd and

since then it is a fully owned subsidiary of Sri Lanka Telecom.

Starting with the Analog Base systems, Mobitel (Pvt) Ltd was grown rapidly and

upgraded the network with GSM (Global System for Mobile) technology in 2004. Mobitel

(Pvt) Ltd continued this improvement further and launched the first 3.5G (3.5 Generation)network in South Asian region by 2007. Mobitel envisaged and introduced Mobile

Broadband Service to Sri Lanka. By doing that, Mobitel spanned its solutions into Voice,

Data and Entertainment.

Mobitel has done a great service to Sri Lankan community with postpaid and prepaid

packages along with a variety of value added services. With the introduction of revolutionary

packages like SMART 5 for prepaid users and UPAHARA for Government staff, Mobitel

won the hearts of Sri Lankan people and improved its customer base up to 2.7 million by the

end of 2008. Mobitel recorded a net profit of Rs. 1.17 billion in 2008, compared to the net

profit of Rs. 0.25 billion in 2007.

As the National Mobile Service Provider, Mobitel is viewing the entire county as one

family under the new tagline “We Care Always” and it will take Sri Lanka towards the ICT

world with best technological leadership.


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1.2. Vision and Mission of Mobitel (Pvt) Ltd

According to its vision “To Lead Sri Lanka towards an info-com and knowledge rich

society through our service offerings” , Mobitel has practically become the leader in mobile

communication in Sri Lanka with the best of technology, coverage and support.

“Care, Share and Deliver” is the mission that Mobitel is carrying out as the National

Mobile Service Provider. Mobitel can achieve this with its technology and the dynamic,

proactive staff who are working under the slogan of “We Care Always”.

1.3. History of Mobitel (Pvt) Ltd

Mobitel (Pvt) Ltd was initially started as a collaboration between SLT and Telstra

Australia in 1993 where SLT had 40% of its shares. In 2002, SLT acquired Mobitel (Pvt) Ltd

and since then it is a 100% owned profitable subsidiary of Sri Lanka Telecom.

Mobitel started its service by an AMPS/ TDMA network and provided a stable

network with full of reliability. As the technology improves, Mobitel introduced this new

technology to its network. As a result, GSM 1800 network was introduced in 2004 with

GPRS and EDGE technologies enabled. In 2005, Mobitel started to use GSM 900 band formobile communication. Mobitel was not limited to voice communication. They tested and

introduced new value added services such as SMS, MMS along with the GSM launch. Other

than these services, Mobitel is well known for its reliability, quality of service and customer

support. As a result, Mobitel became very popular in Sri Lanka and named as the fastest

growing mobile network in South Asia.

In 2006, Mobitel introduced 3G technology to its network. In 2007, following the new

trends in fast changing technology, Mobitel introduced the first 3.5G network in South Asia

by making a turning point in Sri Lankan Mobile Communication Market. Mobitel introduced

the first 3.5G network in South Asia with an investment of over US$ 300 million. With the

introduction of 3.5G network, Mobitel started a new era in Sri Lankan Mobile

Communication market. With this technology, many value added services were introduced

and Mobitel started to provide Mobile Broadband connections using this network.


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1.4. Organizational Structure

According to Fig 1.1, Mobitel is composed of with several divisions with well defined

tasks. From these divisions, Engineering, Marketing and Sales Divisions are spanned to

regional levels.

Mobitel (Pvt) Ltd

Engineering

Human

Resources

MarketingCustomer Care

Sales &

Distribution

Finance

Information

Syatems

Leagal

Service QualityCooperate

Planning

Figure 1.1 – Organizational Structure in Mobitel

Figure 1.2 – Engineering Divisional Structure

Engineering Division

Core Systems

Network Operations

Service Quality

Network Planning &

Implementation

Radio Network

Planning &

Optimization

Projects

Transmission Network

Planning

Core System

Planning

Switching

Operations

Field Network

Operations

BTS

Operations

Transmission

Operations

Product Development

& Customer Solutions


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In Figure 1.2, the Engineering Divisional Structure is mentioned. In the Engineering

Division, Network Planning & Implementation Division and Network Operation Division are

the major sub divisions. Other sub divisions are responsible for improving the services and

adding values to the services. A detailed organizational structure is included in Annex 1.

1.5. Hierarchical Levels

Here is the List of Hierarchical Levels that is related with Mobitel Engineering

Divisional Structure.

Chief Executive Officer

Senior General Manager

General Manager

Manager

Assistant Manager

Supervisory Engineer

Senior Engineer

Engineer

Senior Technical Officer

Technical Officer

Technician

Technical Assistant

Senior Rigger

Rigger

Some new hierarchical levels are also introduced recently. But these are the levels that

the staff in the Mobitel is still used to.


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1.6. Present Performance of Mobitel (Pvt) Ltd

Today, Mobitel (Pvt) Ltd is in a commanding position in the Sri Lankan Mobile

Telecommunication Market. These days most of the Mobile Service Providers are suffering

as a result of the world’s economic crisis. But for Mobitel it is different. If we compare the

net profit of Mobitel in 2008 and 2007, it has improved its net profit by 4 times. This is

because Mobitel has understood the requirement of the customers.

These days Mobitel is well known for providing Mobile Broadband Services. These

broadband connections are supplied under High Speed Packet Access (HSPA) technology

which is embedded in the 3.5G network. Using these connections we are capable of achieving

14.4Mbps on downlink and up to 1.98Mbps on uplink. With the future upgrades, these speeds

will be improved more. Today, video calls have become a normal thing to Mobitel users as

the rates are affordable although the technology is advanced.

Other than providing voice and data services, today Mobitel works as a solution

provider for most of the companies. Mobitel has a special division called Product

Development and Customer Solutions which is responsible for this work. Small Office Home

Office (SOHO) networks and Mobile Eye are some of the new solutions that they have

introduced to the market.

Fig 1.3 – Mobitel 2G and 3G coverage distribution as at 20.03.2009

2G Coverage Distribution 3G Coverage Distribution


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Mobitel is also well known for its wider coverage. With the introduction of 3G and

3.5G technologies, Mobitel didn’t stop the expansion of the GSM network. They also

expanded the 2G coverage parallel to the 3G coverage. Today, Mobitel covers more than

70% of Sri Lanka and 95% of the population exhibiting its role as the National Mobile

Service Provider.

Mobitel is always innovative in introducing new packages. UPAHARA, a post paid

package which is dedicated for government staff has become a major topic in the society. The

army forces, government servants and pensioners experience the facilities of this package.

Most of them appreciate the service that is offered by Mobitel.

1.7. Strengths and Weaknesses

When we consider the strengths of Mobitel, the presence of a dynamic, proactive staff

is a big asset for Mobitel. Bulk of the staff is willing to work without any time restrictions.

Especially the regional officers are doing a great service to maintain a stable and reliable

network. Engineers and Technical officers are given an international training before they are

assigned to a certain job. This will make the staff aware about the new technology and the

new trends in the world which is good for the company.

Being a subsidiary of SLT, it has a great amount of strengths. Mobitel is capable of

sharing the resources of SLT such as towers, buildings, transmission links and other network

equipment. SLT has some influence in the management of Mobitel. This can be a big asset

when Mobitel faces some kind of a crisis.

The major weakness that I have seen in the Mobitel Engineering Division is the lack

of staff. Most of the engineers and technical officers are busy with their work and

assignments. Sometimes they have no time to explain something to a trainee or a new comer

like us. The absence of a party to supervise the sub-contractors is a big weakness in Mobitel.

Another weakness that I have noticed is, Mobitel needs to get permission from SLT for most

of its work. Sometimes the work is getting delayed because of that. If these things can be

eliminated, it will help Mobitel to develop more.


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1.8. Profitability

Most of the Telecom companies and Mobile Service Providers like to forget the

situation of the company during the last year. They have perceived a decline in profitability in

2008. But for Mobitel that year was a year to stand up with success. With the introduction of

UPAHARA package, Mobitel was able to increase its customer base up to 2.5 million.

Mobitel recorded a net profit of Rs. 1.17 billion in the end of 2008, compared to the net profit

of Rs. 0.25 billion in 2007.

1.9. Usefulness to Sri Lankan Society

Being the National Mobile Service Provider, Mobitel offers a bunch of services to SriLankan community at a very convenient rate with a variety of packages. Other than providing

the requirement of mobile communication in Sri Lanka, Mobitel engaged with a lot of

community projects in Sri Lanka.

Mobitel engaged with University of Colombo and launched M- Learning to address

the shortcomings in learning through technology. Also Mobitel provides mobile broadband

connections to E-NANASALA in rural areas and connect the people to the global village.

Not only that, Mobitel also engages with lot of charity work. Mobitel has done a donation to

Cancer Society Sri Lanka recently.

Mobitel is also well known for giving sponsorship to good community work such as

exhibitions and sports competitions. Mobitel was the principle sponsor of EXPOSE 2008,

engineering exhibition, which was conducted by Dept of Electronic & Telecommunication

Engineering, University of Moratuwa.

1.10. Suggestions to Improve the Performance

As I mentioned in the weaknesses, the lack of staff is a major issue in Mobitel.

Especially the Engineering Division staff is not adequate. If they recruit qualified people for

these vacancies, it will improve the performance of Mobitel.


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Sub- Contractors appearance is another weakness that I have noticed. If the work of

sub-contractors can be done using Mobitel staff, it would be beneficial in the network’s point

of view.

Another thing that Mobitel should think is the number of regions that they have. They

have divided the operations in Sri Lanka into 5 regions which are not adequate. Since the

network is expanding rapidly, the no of sites under a one region increases. Then the regional

officers will be busy with lot of sites and some of their work may get missed. Therefore

number of regions should be increased along with the network expansion.


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CHAPTER 2

2.

Training Experiences

Under the Industrial Training at Mobitel (Pvt) Ltd, I was able to explore three major

sections of the company. They are as follows,

Transmission Operations Division

Value Added Services (VAS) Division

Radio Network Design (RND) Division

At the beginning of the training, we were given a schedule that covers almost all the

divisions in the Engineering Division of Mobitel (Pvt) Ltd. But that was continued for only

three weeks. Then each of our trainees was asked to choose a one division to continue the

training. Under that criterion, I had to choose Radio Network Design Division to continue the

training. The final training schedule that I underwent is as follows,

Table 2.1 – Training Schedule

Division Reporting to (Mr.) Designation From To Duration

Transmission Chrisantha Silva Senior

Engineer

13.10.08 19.10.08 1 weeks

Value Added

Services (VAS)

Mohamed Fawaz Senior

Engineer

20.10.08 26.10.08 1 weeks

Radio Network

Design (RND)

Dhananjaya

Ponnamperuma

Manager 27.10.08 27.03.09 22 weeks

According to this training schedule, the bulk of my training period was spent in the

Radio Network Planning Division. In the other two divisions, I was only able to explore the

division in a very abstract level.


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2.1. Transmission Operations Division

2.1.1. Brief Description about the Division

This division is responsible of providing error free connections between the network

nodes such as MSCs, BSCs and Base Stations. Installation and maintenance of the core

network is the major work under their scope.

This division has day work as well as night work as the installations and upgrades are

done in the night to minimize its effect to the subscribers. I was in this division for a one

week. Within that period, I was not able to work with the network nodes. But I was able to

learn the tasks of this division in a very abstract level.

Transmission Operation Division Staff

Manager

Senior Engineer

Engineer

Technical Officers

Riggers

2.1.2. Experience in this Division

When I first went to this division, Mr. Bhathiya, an engineer of this Division

explained about the Mobitel Network and described the major work carried out by this

division. Then he showed us the MUX (Multiplexer/De multiplexer) network that they are

maintaining and how to analyze the alarms generated by this network. He also explained us

how to react depending on the alarms. Here are some of the experiences that I got from this

division.

Feeder Replacement in Koratota Mobitel Site

In this short training period at Transmission operations division, I was able to

participate in a feeder replacement in Koratota Mobitel Site. The feeders of this site were


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damaged and we replaced the feeder cables. This is my first site visit. Mr. Suresh, a technical

officer explained the equipment inside the cabin and the cabling used in the cabin. He also

explained the details about obsolete TDMA equipment which was present inside the cabin.

After replacing the feeders, earthing was done by Mr. Kelum, a rigger in Mobitel. Finally, the

alarm was cleared ensuring the successful installation.

Performed a Preliminary Acceptance Test (PAT) in MSC 4

I was also able to participate in a PAT with Mr. Bhathiya. He explained the

importance of performing the PAT. Since the installations are done by third party companies

it is important to check all the hardware and software before the handover take place. In the

PAT, we checked whether the equipments are correctly connected in the cabinet. Also we

were interested in the power supply, grounding and wiring in the cabinet. We tested the

voltages from the power supply and the earthing using a millimeter.

Apart from these hardware issues, we also tested the software related alarms of the

equipment which is generated in case of an emergency. We checked these alarms by

detaching cables and switching off the main power supply.

Finally, a document related with the PAT was filled by Mr. Bhathiya by commenting

about the installations. If the comments are not positive from the engineer, they have to redo

the installation part under the comment.

Optimization of Transmission links

Mr. Bhathiya explained us how to optimize a transmission network. Transmission in a

mobile service network is done by E1s. E1 is PCM link which is composed with 32 time

slots. Each has a capacity of 64 kb/s. As an optimizing work, we were asked to find out

available free continuous time slots in an E1 path. Mr. Bhathiya helped us to complete that

optimizing work successfully.


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2.2. Value Added Services (VAS) Division


This division is responsible for Value Added Services that are offered by Mobitel to

its subscribers. SMS, MMS, GPRS, International Roaming, Video Calls, TV on Mobile and

E-channeling are some of the value added services. Other than that, this division has a sub

division called Product Development and Customer Solutions. Handling the cooperate

customers and developing new services to the network is done by this division. I was trained

in this division for one week and got an overview of this division. That period was not

enough to explore the division in detail.

VAS Division Staff

Head

Senior Manager

Manager – Core Systems

Manager - Product Development & Customer Solutions

Senior Engineers

Engineers – VAS Operations

Engineers - Network Systems

Engineers – Product Development & Customer Solutions

Technical Officers

2.2.2. Experience in the Division

As I first came to the division, Mr. Shavin an engineer in this division explained the

services and the major tasks of this division. First, he explained the elements in the network

and described their features. Then he explained how SMS and MMS work. He also explained

about the transactions that are made between the Nodes while a customer gets these services.

Ms. Chamanthi, an engineer in this division explained us about the Intelligent Node

(IN). She described the importance of IN and how it is used in the network. IN is a network

node that is responsible for keeping the details of pre-paid users and allowing them to access


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the network. The details about pre-paid cards (pin numbers) are also inserted in the databases

of IN. She also explained how call forwarding and other network related services are

provided from the network.

Mr. Gihan, an engineer in this division explained about the Universal Mobile

Telecommunication System (UMTS). He also described about the General Packet Radio

Service (GPRS) and the protocols used in this system to do perform transactions. Mr. Gihan

explained us about mobility, resource and session management that are required to maintain a

stable GPRS connection with good quality.

Within the training period at VAS division, I also learned about the international

roaming. An engineer explained how Mobitel makes roaming agreements with operators in

other countries. He also explained about the documents that are transferred between the two

parties who involve in the roaming agreement. He described how the transactions are made in

the network to successfully work international roaming.

InternetSGSN

HLR

GGSN

GPRS

Backbone

SS7

MSC

/VLRGMSC

PSTN

NetworkBSC

BTS

BTS

UMTSUTRAN

BSC

APM

APM

Figure 2.1 – Universal Mobile Telecommunication System (UMTS)


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2.3. Radio Network Design (RND) Division


Radio Network Design Division is responsible for supplying a good access layer to

the customers to access the network without any difficulties. To maintain a good and stable

radio network, RND division performs network related work such as planning, monitoring

and analyzing. Apart from that, the customer complaints are also handled and claimed by

RND division. The bulk of my training period was spent in this division and earned a good

knowledge and experience related to Radio Networks.

RND Division Staff

General Manager

Manager – Radio Network Planning

Manager – Transmission Planning

Supervisory Engineers – Radio Network Planning

Senior Engineers – VAS Planning, Power Planning, Civil Planning

Technical Officers

2.3.2. Network Planning

Radio network is the access layer of a mobile network. This is the layer which is

accessed by the subscribers to get the services from the mobile service provider. In radio

network planning, there are two major factors that the designer has to consider. They are as

follows,

Capacity

Coverage

We can understand that it is not practical to setup one huge tower in a mountain and

provide the radio network with a wider coverage. If we setup the network like that,

subscribers will not be able to take calls as the network will be congested due to limitations in

hardware. Also, since there is a single tower, the mobile devices of far-away subscribers


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should be very powerful to transmit the signals to reach the tower. This could be harmful to

the subscribers. Now we can see that Capacity and Coverage cannot be achieved at the same

time. We should address these two factors separately.

If we are interested in setting up a radio network in an urban area, capacity is the

major concern, because the density of subscribers is higher in these areas. But if we want to

provide the services in a rural area, coverage is the major concern as the subscriber density in

that area is smaller.

The first stage of network planning is nominal planning. At this stage, we select the

appropriate areas for sites by looking at maps and height contours. We can also use a

software tool to choose these locations. Then we have to perform a site survey to get the

exact location to set up the base station. In a site survey, we have to go to the nominal

locations that we have obtained and check whether is there a need of radio network in that

area. In the site survey, we are interested in providing coverage to populated areas such as

companies, banks & etc. If we can find a good place based on our requirements, we can

implement the site there. Otherwise, nominal planning and resurveying have to be done until

we meet the requirement. Finally optimizing and tuning of the implemented sites have to be

done to supply a good quality of service.

No Location/ Problem

in the nominal plan

Capacity/

Coverage

Requirements

Site Surveying

Final Plan

Implementation

Optimization

Nominal Plan

Figure 2.2 – Block Diagram for Radio Network Planning


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Practical Experience gained in Network Planning

In my training period at this division, I was lucky enough to engage in the Network

Planning area. I was given 6 sites to be planned in Colombo and Greater Colombo Areas to

fill the coverage gaps in these areas. In preparing the nominal plan Mr. Nalinda, a supervisory

engineer and Mrs. Madhuka helped me. We prepared the nominal plan using the Google

Earth as the Colombo area can be clearly seen by that tool. Then I got the nominal

coordinates from the Google Earth and insert them to my GPS (Global Positioning System)

module. I also inserted the nearby on-air site locations to the GPS module to find a proper

location to fill the coverage gaps. Then I started the surveying process along with a site

acquisition officer who is responsible for acquiring the locations and negotiating with site

owners.

In the site survey, we were interested in finding roof-top buildings because it is

difficult to construct a tower in Colombo area. We went to the nominal planned locations

with the help of the GPS module and started finding locations around the nominal coordinate.

When we survey these sites, we looked at several factors of the building such as height, floor

space for cabin and poles, availability of obstacles to block the beam of signal, availability of

nearby Mobitel sites to get the point to point transmission links and etc. We had to repeatedly

look these aspects until we get the best location. We also looked several optional locations for

a site. After selecting the correct location, I recorded the GPS coordinates, height of the

building and other important details of the location. Finally I showed these details to Mr.

Nalinda/ Mrs. Madhuka to check whether there is any issue regarding the locations. With

their approval implementation of the site takes place after getting the TRC permission. I

completed 6 new site surveys and updated their status in TEMS cell planner database. Before

I went to site surveys in my own, I was trained by Mr. Kanchana and Mr. Chaminda to find

appropriate site locations in the most effective manner.

2.3.3. Cell Planning

Cell planning plays a major role in radio network planning. “Cell” is normally

referred to the region that can get the coverage from an antenna. There are two types of cells.

They are,


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Directional Cell

Sector Cell

In a Directional cell, the main concern is the coverage. The radio frequency generated

by the base station is equally distributed in all directions using an antenna. Normally these

cells are implemented to supply in-building coverage.

In the Sector Cell arrangement, the capacity is also addressed along with coverage.

Also the coverage in these cells is not equal in all directions from the Base Station. We can

create maximum of three Sector cells from a BTS which are operating in three different radio

frequencies.

These cells are theoretically said to be hexagonal and operates with a one Broadcast

Control Channel (BCCH). But they are not hexagonal in practice. Cell planning is done to

optimize the radio interface in a cell. A software tool can be used to verify cell planning of a

cell.

Cell planning is done with the information of the site surveys and the feedbacks from

drive tests and customer complaints. There are several parameters which are involved in cell

planning. They are as follows,

Antenna Type and beam width of the antenna

Azimuth

Down tilt (Electrical / Mechanical)

Height of the Antenna

Transmitting power of the antenna

Figure 2.3 – Directional and Sector Cell Arrangement

Base Station

Cell A

Cell BCell C

Directional Cell Sector Cells


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We can change these parameters of an antenna to get an optimal cell. For an example,

we can change tilt of the antennas to change the size of the cell. When the tilt is 0 degrees,

theoretically the sector cell size is infinite but practically it is nearly 35 km. Also, we can

change the azimuth (Direction) of the antenna such that it is serving to a populated area rather

than directing it to a marsh or a forest. Antenna power can be also used to change the size of

the cell.

We can test these parameters and the values using a cell planning software tool.

Mobitel uses TEMS (TEst Mobile Systems) cell planner which is proprietary software of

Ericsson. In this software we can perform coverage predictions and other cell-related work.

Final results from these software related simulations can be implemented to achieve an

optimized cell.

Within my training at the RND division, we were allowed to use the TEMS cell

planner software without doing any changes to its database. Mr. Lasitha and Ms. Harshani

helped us in using this software. We added new sites and set their flags and performed

coverage predictions by changing the antenna types and other properties. We can also obtain

height profiles to check the line of sight using this software.

Figure 2.4 – Site database of the TEMS cell planner


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We can also obtain the height profile in any direction using the height contour

database that is included in this software.

Figure 2.5 – Coverage Predictions of Chunnkam Site in Jaffna

Figure 2.6 – Height Profile can be used check the line of sight


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Practical Experience gained in Cell Planning

While I was in training at RND division, I got the opportunity to engage with a work

related to cell planning. Before we came to the training in this division, they have performed

a drive test and found out that cell planning in the Colombo and Greater Colombo region was

not optimal. Due to that reason, frequency overshooting occurs. This is occurred when the

antenna tilt is not set to the correct value and creates interference and leads to call drops. Mr.

Tharaka, an engineer explained this situation and asked us to perform a tilt and azimuth check

and adjust them to the planned values.

In Colombo region, the sites are planned in a much closed manner with higher tilt

angles, because the major concern in Colombo is the capacity as the density of subscribers in

this area is high. But as we move to the greater Colombo area, sites are separated with

reasonable distance with lesser tilt angle, because the intension is to provide the coverage in

these areas.

We started this work with two riggers who helped us by measuring and adjusting the

antenna tilts. Signal Beam from the antenna can be either tilted by physically tilting the

antenna (Mechanical Tilt) or by turning knob in the antenna (Electrical Tilt). The total tilt of

the beam will be the addition of Mechanical tilt and Electrical tilt. But sometimes the pole inwhich the antenna is fixed may also have a tilt. In such a case, the tilt of the pole is also

added to addition of the electrical and mechanical tilt. The addition of Mechanical tilt and tilt

of the pole can be measured by putting the tilt meter on the antenna. Electrical tilt can be

measured from the position of electrical tilt knob.

We also documented the details about the site such as cabin layout, site layout, cable

ladder space and tower space available. These details would be beneficial when performing a

capacity upgrade to these sites. We also got an opportunity to see the equipment and cabling

inside the cabin, while working in this down-tilting project. This work was continued for

about 10 weeks to cover 125-130 Mobitel sites in Colombo and Greater Colombo Areas and

gained a good experience about equipment and cell planning in a network.


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2.3.4. Frequency Planning

In cell planning, we are interested in changing the parameters of hardware equipment

until we meet the best results. But installing all equipment with correct parameters will not

create a stable network with reliability. As the access layer of the network which is open for

subscribers operates with radio frequencies, correct frequency plan should be implemented to

minimize the interferences and improve the call quality.

In GSM technology, there are two major frequency bands used. They are 900 MHz

band and 1800 MHz band. The frequency band allocation is as follows,

Frequency Band

(MHz)

Uplink Band

(MHz)

Downlink Band

(MHz)

Duplex Distance

(MHz)

900 890 – 915 935 – 960 45

1800 1710 – 1785 1805 - 1880 95

In GSM, these bands are divided into parts of 200 kHz blocks which are called the

carrier spacings. One block from Uplink Band and another from Downlink Band create a

Duplex channel. The separation between these two blocks is called “Duplex Distance”. For

the convenience, in frequency planning we do not refer to frequencies. Instead, we refer to

Absolute Radio Frequency Channel Number (ARFCN) which is corresponding to a Duplex

channel.

2.3.4.1. Frequency Reuse

Global System for Mobile (GSM) operates as a combination of Time Division

Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA). Each mobile

service operator gets a very limited frequency band from TRC. For a small network we can

use these frequencies without any interference. But as the network grows, there is no option

other than reusing the limited frequency band. There are standard ways to reuse frequencies.

Some of them are included in Annex 2. But sometimes we have to make some modifications

due to limitations in frequency resource and Geographical aspects of the network.

Table 2.2 – Frequency Bands used in GSM


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2.3.4.2 Interference in Mobile Networks

In general, mobile networks will have to face two types of interferences. They are as

follows,

Co-Channel Interference

Adjacent Channel Interference

Co- Channel Interference is occurred with the appearance of the same frequency from

two sectors as a result of frequency reusing. When this happens the Mobile Equipment of the

subscriber will be in an ambiguous mode and cannot identify the serving cell. This will leads

to increase in call drops and bad call quality. Co-Channel interference is indicated by a

parameter called Carrier to Interference Ratio (C/I) and recommends that to be above 9 dB.

Adjacent Channel Interference is occurred with the presence of a frequency along

with its adjacent frequency. Since the electronic filters used in radio equipment are not ideal,

some adjacent frequency components can be also filtered into the equipment and will create

ambiguity. This interference is measured by Carrier to Adjacent ratio and recommends that to

be greater than -9 dB.

2.3.4.3 Frequency Hopping

As a mobile network grows and the capacity of the network is expanded, the cell size

would be small and frequencies are reused at a very short distance. In this kind of a tightly

frequency reused network, the interference is also very high. The concept of frequency

hopping was introduced to minimize the effect of frequency collision. In frequency hopping,

the Base Transceiver Station (BTS) and the Mobile Equipment change the frequency that

they are using according to a pattern number called Hopping Sequence Number (HSN). By

doing this, we cannot stop the interference but we can reduce the effect of interference. Since

the devices hop the frequency, although there is an interference that would be only for a short

time which is insignificant.


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Practical Experience gained in Frequency Planning

Frequency Plan for GSM 900 sites in Katunayaka

After learning the above mentioned basic fundamentals about frequency planning, the

first task assigned for us was to prepare a frequency plan for GSM 900 band sites in

Katunayaka area. In this area, frequency hopping was not implemented before. Under the

new frequency plan we were asked plan frequencies along with frequency hopping. Mr.

Tharaka, an engineer defined the cluster where the frequency plan is going to implement.

We used a software package called “MapInfo” to graphically visualize the frequency

plan by loading the site database.

Making a frequency plan with frequency hopping can be divided into several stages.

They are as follows,

1.

Prepare the Broadcast Control Channel (BCCH) Frequency plan

2. Prepare the Base Station Identification Code (BSIC) plan for the sites

3.

Assignment of Hopping Sequence Numbers (HSNs) and Mobile Allocation

Index Offsets (MAIOs) to the sites and sectors

Figure 2.7 – Mobitel Sites in Katunayaka area in MapInfo GUI


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4. Assignment of frequency band for hopping

First, we started the plan with BCCH planning. BCCH is the frequency broadcasted

by a cell and Mobile equipments measure these frequencies to initiate the services with the

network. Mobitel uses BCCH frequencies starting from ARFCN 1006 – ARFCN 1023 for

GSM 900 band. Therefore we had to use these 18 channel numbers in the most effective way

by considering Co-Channel and Adjacent Channel Interference. Co-Channels and Adjacent

Channels should be separated by a reasonable distance such that a Mobile Equipment should

not receive these frequencies at the same time.

The next stage of the plan was to prepare the BSIC plan. BSIC is another parameter

which is used to identify the Base Stations which are operating on the same frequency.

Therefore with the combination of BCCH value and BSIC, we can identify the exact cell.

Normally all three sectors of a BTS are assigned with the same BSIC value. But they can be

different. In Mobitel, they use two value sets for BSIC. They are 11-17 & 61-67. Therefore

we got 14 BSIC values to be used in the network. For sites which have the same BCCH

values, the BSIC values should be planned with maximum distance of separation. Finally, the

neighboring cells in an area should not have the same BCCH and BSIC combination.

Then as the third stage, we assigned HSNs to these sites. HSN is a number related to a

pattern. HSN number has a range of 1-63 indicating that there are 63 different patterns for the

frequencies to hop. Normally a single HSN value is assigned to a single site. Then the same

pattern is operating in the 3 of its sectors. MAIO is also another parameter defined in sector

wise manner. MAIO defines an offset to the start frequency hopping and ensures that

minimal interference is occurred in nearby cells although they are operating in the same

hopping frequency band.

As the final part of the plan we had to define a frequency hopping band which does

not create any interference with BCCH frequencies. For that we used the default GSM 900

hopping band which is operating in GSM 900 hopping enabled sites.

Mr. Tharaka and Mr. Kanchana helped us to make this frequency plan in a very

effective manner. Finalized plan was implemented and worked successfully.


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Frequency plan for Colombo GSM 1800 sites

As a result of the successful work in the Katunayaka frequency plan, we were asked

to design a frequency plan for GSM 1800 sites in the Colombo area (CBD region). This task

was very complicated compared to the previous frequency plan. In this design, we thought of

a different approach as the site density in Colombo region is very high.

As the first step of the design, we have separated out 18 available frequency channels

from ARFCN 512 to ARFCN 529 to be used in BCCH planning. Then we divided these 18

channels into groups of three channels as follows,

Each group of these channels was assigned to a site and the three channels were used

in three sectors. This method ensured that there are no Co- Channels or Adjacent Channels in

the same site. Then we took a plot of the Colombo region and marked the GSM 1800 sites. In

that map, we drew clusters where each of these clusters contains 6 GSM 1800 sites. After

that, group numbers were assigned to the 6 sites in the cluster. As the Group 1 & 6 along with

all the adjacent groups creates adjacent frequency channel pairs, we had to be careful when

assigning these group numbers. Finally we exported what we have designed to a MapInfo

database.

Using the MapInfo GUI, we were able to observe the Co – Channels and Adjacent

Channels that may cause interference. We optimized the BCCH plan using the software tool.

Then we performed the BSIC planning, HSN planning and MAIO planning as we did for

Katunayaka frequency plan. HSN and MAIO planning were easily done as frequency

hopping was previously implemented in some of these areas. We used the previously

512 513 514 515 516 517

518 519 520 521 522 523

524 525 526 527 528 529

Group No >> 1 2 3 4 5 6

Figure 2.8 - Distribution of Channels


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designed HSN and MAIO plans and add some modifications to them to obtain an optimal

plan. Then we selected the hopping frequency band starting from ARFCN 531 such that the

hopping band does not create any interference with the BCCH frequencies.

Mr. Tharaka and Mr. Kanchana helped us to design the frequency plan successfully.

They also appreciated our ideas and encouraged us to complete it successfully.

The finalized plan was inspected by Mr. Kanchana and implemented on the network.

It is still working successfully and the call drop rates were reduced with the execution of this

frequency plan.

.

Figure 2.9 – Frequency plan using 6 site clusters on MapInfo GUI


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2.3.5. Installations

In Mobitel (Pvt) Ltd, the equipments are supplied by two major equipment providers

namely HUAWEI and ERICSSON. Most of the times, the installations are done by their sub-

contractors. But Mobitel is engaged with its own installations.

Practical Experience gained in Installation

Within the 22 weeks of my training at RND division, I got an opportunity to take part

in a 3G installation in Pussellawa site. Two 3G sectors of this site were installed at that time

and we were asked to install the third sector of that site with the help of some technical

officers.

The installation was not similar to an ordinary 3G installation. This site had already

installed GSM antennas. Two antennas were placed in the tower and the other antenna was

placed in top of a mountain with buried feeder cables. The new 3G antenna had to be placed

in top of the mountain. But there were no feeder cables for the 3G antennas. In this case, we

used a special device called “Diplexer” to solve the problem. The diplexer can act as a

frequency Multiplexer and a De-multiplexer. The diplexer arrangement that we used for the

installation is as follows,

TX/RX TX/RX

RX RX

Diplexer

Diplexer

Diplexer

Diplexer

3G feeders from the RRU

(Remote Radio Unit)

GSM feeders from the BTS

Feeders for 3G antenna

Feeders for GSM antenna

Figure 2.10 – Diplexer arrangement used in the Pussellawa 3G installation

Buried feeders for GSMinstalled previously


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First we fixed the antenna in the mountain using a pole. Then, according to Figure

2.10, we connected RXs and TX/RXs to separate diplexers and fixed 2 diplexers inside the

cabin. At the end of the buried feeders, we continued the reverse process and connected the

antennas to the diplexers using jumper cables. Those two diplexers were fixed to the pole,

which holds the antenna.

After connecting the diplexers, we started to make the fiber optic connection between

the RRU (Remote Radio Unit) and Node B/APM (Advanced Power Unit). We laid the optical

fiber and the power cables gently on the cable ladders. Then we wall mounted the RRU

inside the cabin. After fixing the RRU, we connected the ends of optical fiber into the BBU

(Base Band Unit) which is inside the APM and RRU which is located inside the cabin. Power

cable was also connected between RRU and APM. After that, insulation and earthing were

done to ensure the safety.

Figure 2.11 – Wall-mounted RRU and 2 Diplexers fixed to the cable rack

RRU

2 Diplexer fixed to

the cable rack


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After completing all the hardware work, the software related programs were installed

by Operations Division by remotely logging into the system. Finally, the newly installed 3G

sector worked successfully. In this installation, Mr. Aruna and Mr. Bhanusha, two technical

officers from Mobitel helped us a lot. They taught everything about the installation from the

start during the two days that we spent in the site. This was a great experience that I had in

the field.

2.3.6. Optimization and Tuning

In Mobitel (Pvt) Ltd, Radio Network Design division is also responsible for

optimizing and tuning the network. Since planning and optimization is done by a one team, it

is good in the network’s point of view. Because then what ever problems or drawbacks can

be eliminated in future plans. I was also able to take part in some of the optimizing work

carried out by RND division.

2.3.6.1 Drive Tests

Drive tests are performed to check the network quality and continuous network

connectivity when the mobile equipment is in move. From these tests, we can analyze

downlink interference, coverage issues and network quality. Once these problems are

identified, modifications in the network can be done to correct these problems.

In Mobitel (Pvt) Ltd, they use three Drive Test tool kits to perform the Drive tests.

They are TEMS Investigation Tool Kit, HUAWEI GENEX Probe Tool Kit, Q VOICE tool

kit. The equipment in a standard drive test tool kit are connected as follows,

Figure 2.12 – Equipment connections in a Standard Drive Tool Kit

Software installed La to

Mobile Equipment (Phone)

GPS

GPS

License Dongle


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Software installed laptop along with the license dongle is capable of monitoring and

recording the transactions which are made between the mobile equipment and the network.

The GPS module is capable of monitoring the movements that are made during the drive test.

We can observe the transactions make between the mobile equipment and the network along

with tracking data using the software that installed in the Laptop. If we want, we can record

these details to a log file and analyze later.

2.3.6.2 Defining Handovers and Measurement Frequencies

Mobitel is a mobile service provider which provides services to bunch of subscribers

who are in move. When the subscriber moves with a call, the call should be also movedwithin the neighboring cells in order to provide a continuous call without any drops. To

handover a call from one cell to another cell, the handover between these two cells should be

defined in the BSC (Base Station Controller). Otherwise the call will be dropped and can be

dialed to get a new connection.

Measurement frequencies are the frequencies that are broadcasted by each cell to its

subscribers. Then the mobile devices of the subscribers measure these frequencies and take

decisions depending on the strengths of these frequencies. These measurement frequencies

should be correctly defined in the BSC. Otherwise, although the handovers are correctly

defined between two cells, the call will be not transferred as the Mobile equipment does not

measure new cell’s control f requency (BCCH).

2.3.6.3 System Upgrades and Expansions

Planning for expansions and upgrades are also done by RND division. Capacity

upgrades such as adding an extra band to a site and increasing the number of DTRUs (Double

Transceiver Units) in a site are planned by RND division. I was also engaged with a dual

band site survey which was performed to install a new band in already implemented on air

sites.


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2.3.6.4 Customer Complaints

In Mobitel (Pvt) Ltd, RND division always engaged with customer complaints

because they believe that customer complaints are good tools to optimize the network. When

a customer makes a complaint regarding an issue, the frequency plan is checked in the area

under the complaint. If there is a problem found, we can fix the problem by correcting the

plan. But if it is not found, we perform a drive test or a coverage test to identify the problem

and claim the problem. Within my stay at this division, I was able to engage with several

customer complaints and claim several complaints successfully.

Practical Experience gained in Optimizing and Network Tuning

Drive test using the TEMS drive test tool kit

Within the training period in RND division, I performed number of drive tests in

Colombo using the TEMS drive test tool kit. In a drive test, I had to connect the equipment as

shown in Figure 2.12. Since the drive test are performed using a vehicle, an inverter was

needed to get the power supply to the laptop. Once all the equipments are correctly

connected, we can start the drive test.

Drive tests can be done in two modes. They are “Active Mode” and “Idle Mode”. In

the “Active Mode”, we perform the drive test by making a call from the Mobile equipment.

But in the “Idle Mode” no calls are made.

In the drive test, we can see all the transactions that take place between the mobile

equipment and the network through the TEMS software that is installed in the laptop. In this

software,we can see the details of currently serving cell such as BCCH, BSIC, signal

receiving strength, receiving quality etc. Also we can see the details about other neighboring

cells such as their BCCHs, BSICs and receiving strengths. From this tool we can also obtain

C/I (Carrier to Interference) ratio which represents details about the interference in that area.

Since we can see the serving cell and neighboring cells with their BCCHs and BSICs

we can directly identify, Co-Channel or Adjacent channel interference that is available in

area. We can also check the effect of handovers in the active mode. If frequency hopping is

enabled in an area, we can also identify the details about frequency hopping using this tool.With the help of the GPS, we can obtain the path that we have taken during the drive test.


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Figure 2.13 - The GUI of the TEMS drive test tool kit which describes GSM parameters

Figure 2.14 - Map of the TEMS drive test tool which is dynamically drawn


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We can record all the transactions and all the events of the mobile equipment to a log

file and analyze later. From this tool kit, we can investigate the issues related with call drops,

handovers, down link interference and bad call quality. With the feedback of this software,

we can optimize the network.

I performed the first drive test with Mr. Bhanusha, a technical officer in Mobitel. He

taught me how to perform a drive test while analyzing the GSM parameters at the same time.

I liked to perform drive tests very much because we can understand how GSM works from

these tests.

Other than this drive test tool kit, Mobitel uses QVOICE and Genex Probe tool kits to

test the network. I have also worked with these tool kits and the testing procedure is common

to all these drive test tool kits.

Checking the Handovers and measurement frequencies using WinFIOL

WinFIOL is a proprietary software developed by Ericsson for maintain purposes of

Ericsson BSCs. From this software, we can log into five Ericsson BSCs in Mobitel network.

BSC is the center which controls a set of BTSs. Therefore by logging into these BSCs we canchange configuration parameters of these BTSs individually.

Within the training, we mostly dealt with handovers between cells, measurement

frequency lists and neighbor relations between cells. By using this software we checked and

defined handovers to some Mobitel sites. Defining handovers between cells is very important,

because if these handovers are not defined properly, the calls will not be transferred between

these cells and they will be dropped.

Although we defined the handovers in the BSC, the handover will not work if the

BCCH of the two cells are not included in their measurement frequency lists. Measurement

frequency list is broadcasted to from a cell to its subscribers and asked to measure the

frequencies in that list. If they are not properly configured call will be dropped. We have

checked the measurement frequency lists in all the cells under BSC 2 and BSC 5 and

removed unwanted BCCHs from some cells. Other than these details, we can also observe the

uplink interference using this software tool.


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This tool has a command-line interface and Mr. Tharaka, an engineer taught us all the

commands and tips which are related with this software. All the details about frequencies that

are used in BTSs can be seen using this terminal. We have used this software a lot while we

were designing the frequency plans.

Assigning 3G neighbors to 2G sites

We also prepared a plan to add 3G neighbors to 2G sites. The purpose of this plan was

to transfer the data traffic in the 2G network to the 3G network. In 3G, higher data rates can

be achieved at a good quality. In this plan, we defined neighbor relations between 2G cells

and 3G cells. The neighboring 3G cells of a 2G cell were added and continued this work for

all the 2G cells in Colombo and Greater Colombo regions.

Figure 2.15 – WinFIOL GUI


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Customer Complaints

Within the training period, we attended to customer complaints in two ways. We

answered to the customer complaints using a database and sometimes we went to the

customer’s premises and performed a test to find out the problem.

When customers complain to the Call center, the call center officers insert those

complaints to a database. We access that database using a software tool such as “ putty” and

upload the comments and replies to these complaints.

Using this prompt, we can reply to these complaints. When answering these

complaints, we looked at the on air sites and planned sites in the areas under complaints. If

the coverage is there, then we looked at KPIs (Key Performance Indicators) in these sites and

answered the complaints. If we cannot figure out the reason for complaint, we asked about it

from the engineers and uploaded the comments.

Other than answering the complaints using this prompt, we were asked to go to

customers premises and perform tests. I performed coverage tests and 3G data rate tests

within the training.

Figure 2.16 – Customer Complaint Management Prompt


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In the coverage test I used a TEMS test phone / Net Monitor phone to check the

coverage. This is similar to a drive test. But we only perform the test using a mobile phone.

The software installed in the phone can display the GSM parameters such as BCCH, BSIC

and receiving signal strength of serving cell and neighboring cells. From the display, we can

also look at Carrier to interference ratio which indicates a measure of interference in that

area.

In the 3G data rate testing, I went to the customer’s premises with a Laptop along

with a HSPA modem/data card and checked the data speeds using “ NetperSec” software tool.

Once I connected to the internet and start downloading a large file, a trace was made to the

IMSI (International Mobile Subscriber Identity) number in the RNC (Radio Network

Controller). Then the officers at the office also can monitor the transactions and identify the

problems. Mr. Nalinda and Mr. Deepal helped me to perform a successful test to find out the

problems related with the network.

Checking the Key Performance Indicators (KPIs) using Business Objects Tool

For maintaining a good mobile network, it is important to check the KPIs of network

frequently. There are number of KPIs for a mobile network such as call setup success rate,

Hand over success rate, call drop rate and the reason for drop and etc. In the training period

we checked these parameters using a software tool called “Business Objects”. This software

reads a database and views these parameters.

Figure 2.17 – Test phone of the TEMS tool kit

ARFCN of

the BCCH

FrequencyBSIC of theServing cell

Receiving Signal

Strength in dBm


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We used this tool to check the performance of our frequency plans. We also checked

the call drop rates and drop reasons of each cell in our frequency plan to check whether there

is any increase in call drops after implementing the frequency plan. We observed call

handover success rates in the area under our frequency plan. Then we modified the

handovers and measurement frequencies such that the call handovers are done successfully.

We also checked these parameters, when a customer complaint is found regarding a call drop

issue. Sometimes the cells are congested in the customer’s area. Then a capacity expansion is

required to solve the problem.

Dual Band Site survey for Capacity Expansions

During the training period at Mobitel, we were asked to perform a dual band site

survey to install another additional band in some of congested sites. The main objective of

this site survey was to check the availability of resources and the space for an additional BTS.

We performed this site survey in Kalutara, Matara, Hambantota, Kandy, Anuradhapura and

Polonnaruwa regions.

Figure 2.18 – Handover performance of the cells using BUSINESS OBJECTS


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In this site survey, we documented the cabin and site layout along with spaces

available. We were interested in availability of cabin space, roxtec space, space in the vertical

and horizontal cable ladders and the tower space required for an additional antenna set. If the

site contains an outdoor BTS, we measured and documented the space available in the site to

install another outdoor BTS. We also took photographs and videos of these free spaces.

Once we came to the office, we gave these details to Mrs. Madhuka who is

responsible for Capacity expansions. This work was continued for nearly 4 weeks and had a

great experience.

2.3.7. Other practical experiences within the stay at RND Division

Represented Mobitel at EXPOSE 2008

When I was on training at RND division, I got an opportunity to represent Mobitel at

EXPOSE 2008, the engineering exhibitions conducted by Dept of Electronic &

Telecommunication Engineering of our university. In this exhibition, we demonstrated a

mobile base station called COW (Cell On Wheel). That was a mobile base station which can

be carried inside a container box. It has an adjustable tower and a cabin where the equipmentare fixed. We explained the details about this tower and its operation to the interested people

who came to learn about it.

Also I explained the exhibits at the Gadget Mart which were introduced by Mobitel.

We demonstrated the HSPA (High Speed Packet Access) modem, SOHO (Small Office

Home Office) 3G router and a special gadget called Mobile Eye. Mobile Eye is a camera that

can be accessed and controlled by taking a video call to the number of the SIM (Subscriber

Identity Module) inserted in the camera.

Ms. Gayangi and the product development team helped us by giving a small

introduction about these equipments before the exhibition.

A web based interface to look at the equipments in Major equipment rooms

Within the training at RND division, we were also asked to design a document showsthe details of the major equipment rooms (MSCs). Under this task, we started to document


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the details of MSCs (Mobile service Switching Centers) from MSC2. Then we prepared web

based document that can be accessed through a web browser to view the details. In this

document we inserted routing tables of routers, switch connections, dummy ports and other

network related parameters.

But we were not able to construct this structure for all the MSCs. We completed that

work only for MSC 2 which is located inside the Engineering Division.

5S implementation in Mobitel Engineering Division

This was a great day that we spend with everyone in the Engineering division to make

a clean organized working area. On that day, the entire staff worked as a one unit by

organizing historical data, files and other equipment. We tagged the unwanted

malfunctioning equipment and sent them to dispose.

That day was memorable for all of our trainees and earned a great experience by

associating with everyone in the division.

Figure 2.19 – A Screen shot of the Web based document which gives details of equipment


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Chapter 3

3.

Conclusion

Summary of the training experiences

I’m happy that I have successfully completed my training in Mobitel (Pvt) Ltd which

is a profitable company embedded with technology. Within this training period, I was able to

train in 3 of its major divisions. The experience that I have earned from this company was not

organized. We were not given lectures and handouts. Whatever experience that we got was

earned in a very practical way with day today work. We were allowed to work with

equipment and their software. The Mobitel staff in the engineering is very friendly and easy

to talk with. They have provided enough chances to gain the experience. They are also

willing to teach us something whenever they are free.

Out of the 24 weeks of my training, 22 weeks were spent in the Radio Network

Design (RND) Division. Therefore I had a great experience in this division compared to other

two. Since I was in this division for 22 weeks, I was able to associate most of the people in

this Division. Therefore I got a chance to engage with everyone’s work and gain experience.

With time, we were given some responsible work. I was given some areas to plan new sites

and perform site surveys for them, which was not given for trainees previously. Although I

got fewer divisions to explore, I’m happy that I got the opportunity to specialize RND

division.

More importantly, we were not asked to work in front of a computer. We were given

chances to go to sites and gain practical experience. Within my training I was able to

associate a wide spectrum of staff starting from Mangers and engineers to Riggers and

Drivers. This is the first time that I was exposed to this kind of an organizational structure.

By associating the staff in the company, I learned how to interact with different levels of

people in the society which is more important for life.

Another thing that I have earned from this training is bunch of good friends.

Especially the technical officers and engineers who helped us during the training have


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become good friends of us. We worked with a lot of synergy and on the last day, we were sad

to leave the office.

Improvement in training at Mobitel

The only thing that I propose is to continue the rotation of training in all the divisions.

This will help trainee to get an overview of the network and learn how the entire system

works. Once we have this big picture about the network, we can select the field that we like

most. Also some projects should be given to the trainees during their training period. Then

we get a chance to work in an organized manner within given time line.

Suggestions regarding the overall training program

We should appreciate the work carried out by the Training Division and NAITA. The

Industrial training is an essential module for engineering students. Sometimes the experience

that we earned in the training period may be beneficial for our final year projects. Not only

that this experience will be useful when we start working as engineers. The daily diary and

the monthly reports trained us to keep records of whatever the work that I do and they were

helpful in preparing the training report.

Instructors from the Department came and inspected the training, which is a goodthing. We were asked some questions individually regarding the work that we did. If this is

consistently happening throughout the training, it would be beneficial for us to improve our

knowledge and soft skills as well.

Overall Assessment of the training program

I’m very happy to say that my industrial training at Mobitel (Pvt) Ltd was successful.

With the instructions given by the training division and the department, I was able to

complete the training successfully. It was a very fresh experience for me to work with that

kind of an organization. Other than technical things, I was also able to earn some experiences

which would be beneficial to be a good individual in the society.


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ANNEX 1

Figure A 1.1 – Organizational Structure of the Engineering Division


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ANNEX 2

Figure A 2.1 – 4/12 cell pattern

Figure A 2.2 –

3/9 cell pattern


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ABBREVIATIONS

AMPS Advanced Mobile Phone System

APM Advanced Power ModuleARFCN Absolute Radio Frequency Channel Number

BBU Base Band Unit

BCCH Broadcast Control Channel

BSC Base Station Controller

BSIC Base Station Identification Code

BTS Base Transceiver Station

COW Cell On Wheel

DTRU Double Transceiver Unit

EDGE Enhanced Data rates for GSM Evolution

FDMA Frequency Division Multiple Access

GGSN Gateway GPRS Support Node

GPRS General Packet Radio Service

GPS Global Positioning System

GSM Global System for Mobile

HSN Hopping Sequence Number

HSPA High Speed Packet Access

ICT Information and communication technology

IMSI International Mobile Subscriber Identity

IN Intelligent Node

KPI Key Performance Indicator

MAIO Mobile Allocation Index Offsets

MMS Multimedia Messaging Service

MSC Mobile service Switching Center

MUX Multiplexer

PAT Preliminary Acceptance Test

PCM Pulse Code Modulation

RNC Radio Network Controller

RRU Remote Radio Unit

SIM Subscriber Identity Module


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SMS Short Message Services

SOHO Small Office Home Office

SSGN Serving GPRS Support Node

TDMA Time Division Multiple Access

TEMS TEst Mobile Systems

TRC Telecommunications Regulatory Commission

UMTS Universal Mobile Telecommunication System

VAS Value Added Services
http://www.trc.gov.lk/http://www.trc.gov.lk/http://www.trc.gov.lk/

telecommunication training report

Documents