TRAINING REPORT

OF

SIX MONTHS INDUSTRIAL TRAINING, UNDERTAKEN

AT

BHARTI, AIRTEL

IN

TECHANICAL DEPARTMENT

ON

SUBMITTED IN PARTIAL FULFILLMENT OF THE DEGREE

OF

BACHELOR OF TECHNOLOGY

IN

ELECTRONICS AND COMMUNICATION ENGINEERING

Under the Guidance of: Submitted By: Name: Mr. Nitin Singla Name: Avika Dhingra (Y3216)Designation:Engg N/W Consulting University Roll No:-305042355Department: TECH Deptt.

CHANDIGARH-PATIALA NATIONAL HIGHWAY,VILL. JHANSLA, TEHSIL RAJPURA,

DISTT. PATIALA 140401

ACKNOWLEDGEMENT

Training in an organization like “BHARTI” which is fuelled by the individuals with so

much zest & energy, “teaming” up to form a formidable force, was in itself a true

learning experience which is going to help me immensely in my career. There is no

substitute to “Teamwork”; this is one of the many lessons I learnt during my training in

“BHARTI MOBILE Ltd”. A formal statement of acknowledgment is hardly sufficient to

express my gratitude towards the personalities who have helped me to undertake and

complete my training.

I would like to thank and express my gratitude towards the personalities who have helped

me to undertake and complete my training. Firstly, I would like to thanks Mr.Ashwani

Shukla (Tech Head) for granting me the permission to work as a Trainee in this

esteemed company

I express my gratitude towards my guide Mr. Bhupinder Pal singh(DGM

TECHNICAL) for his help and support to complete.

I am equally thankful to Er. Nitin Singla(Engg N/W Consulting) for his help and

support. He provided me valuable guidance and helped me during my entire training

period. He worked as an advisor and offered his help when needed.

I am also thankful to Mr. Shivesh verma, Mr.Ajay Pal (Senior Engg.-tech deptt) for

providing me technical knowledge.

The six months at Airtel gave me intense understanding of mobile communication and

the cellular technology concepts.

Special thanks to the talented people at Airtel. They were growing source for inspiration

for me throughout the development process of this project.

AVIKA DHINGRA

PREFACE

With the ongoing telecom revolution where innovations are taking place at the blink of an

eye, it is impossible to keep the pace with the emerging trends. In organization where

Making Things Right in the first instance is the driving motto, perfection and accuracy

are inevitable.

Excellence is an attitude that the whole of the human race is born with. It is the

environment that makes sure that whether the result of this attitude is visible or

otherwise. A well planned, properly executed and evaluated industrial training helps a lot

in inculcating a professional attitude. It provides a linkage between the student and

industry to develop an awareness of industrial approach to problem solving, based on a

broad understanding of process and mode of operation of organization.

During this period, the students get the real, first hand experience for working in the

actual environment. Most of the theoretical knowledge that has been gained during the

course of their studies is put to test here. Apart from this, the students get an opportunity

to learn the latest technology, which immensely helps them in building their career.

I had the opportunity to have a real experience on many ventures, which increased my

sphere of knowledge to a great extent. I was entrusted with a real life project, working on

which had finally made me step into the ongoing telecom revolution and gradually

become a part of it. And all the credit goes to organization Bharti – which in true self

made the telecom revolution happen.

I.CI.COMPANYOMPANY P PROFILEROFILE

“As we spread wings to expand our capabilities and explore new horizons, the

fundamental focus remains unchanged: seek out the best technology in the world

and put it at the service of our ultimate user: our customer.”

Sunil Bharti Mittal

1.1 Bharti Enterprises

Bharti Enterprises, India’s leading telecom conglomerate has been at the forefront of

technology and has revolutionized with its world class services.Established in 1976,

Bharti Enterprises has been a pioneering force in the telecom sector with many firsts and

innovations to its credit. Working on the principle of providing end to end

communication solution across the telecom value chain from manufacture of hardware to

development of telecom software and from fixed line to cellular and wireless services, e-

commerce, broadband, domestic long distance, undersea cable, infrastructure

development and business solutions. Bharti Enterprises under cable chairmanship of

Sunil Bharti Mittal is the only company to have brought to India the excellence and

expertise of leading Telecom players of the world., Bharti Telecom, the manufacture

division of Bharti is the largest sets under the brand name Beetel. Bharti televentures, the

services division of bharti has major interests in Basic, long Distance and Cellular,

Broadband and Infrastructure Operations in the country.

Spearheading the Indian telecom revolution for two decades

Highlights of history, collaborations and achievements are given below.

1996

BTNL’s winning bid for Madhya Pradesh Service Area for Fixed Line telephone

services.   

Formed Casio Bharti Mobile Communications Limited a joint venture with Casio

& Mitsui of Japan to manufacture & market Radio Pagers.

Formed Bharti Duraline Pvt. Ltd., a Joint Venture with Duraline Corporation,

USA to manufacture HDPE Ducts.   

Formed a Joint Venture Company Bharti Tele-Ventures Ltd. with Telecom Italia,

Italy to promote various telecom projects in India. 

BTNL commercially launched cellular services in Himachal Pradesh.  

1997

British Telecom joined the Consortium of Bharti Cellular. 

BTNL granted License for Madhya Pradesh Fixed Line services. 

Bharti & BT formed a joint venture Bharti BT Limited for a VSAT project. 

Bharti Global granted the license to operate comprehensive telecom services in

Seychelles as Second Operator.

1998

First ever Indian Private Fixed Line Service launched in Indore, Madhya Pradesh

on 4th June, 1998 by BTNL. 

Bharti BT Internet Limited formed to offer Internet & E-Commerce Services in

collaboration with British Telecom. 

Services launched in Seychelles on 12th December, 1998. 

British Telecom consolidated its shareholding in Bharti Cellular.

1999

Bharti BT Internet launches Mantra Online Internet services in May. 

EM Warburg Pincus, one of the largest International Private Equity Investors,

joins BTVL. 

Acquired controlling stake in J T Mobiles - Cellular Operator in Andhra &

Karnataka (Now Bharti Mobile Limited). 

Intel takes Equity stake in Bharti Tele-Spatial and Bharti Telesoft.

2000

New York Life International takes stake in Bharti Cellular. 

Launch of AIRTEL and MAGIC brands in Karnataka and Andhra Pradesh. 

Bharti Telesoft opened its overseas offices in UK & USA. 

Acquire controlling stake in Sky cell, Chennai 

Singapore Telecom decides to invest in Bharti and becomes partner in BTL &

BTVL. 

2001

Entered into a joint venture with Singapore Telecom International for Submarine

Cable project between India and Singapore  

Acquired cellular operation from Spice Cell in Kolkata. 

Acquired eight cellular licenses as fourth operator for the circles of Mumbai,

Maharastra, Gujarat, Haryana, UP (West), Kerala, Tamil Nadu and Madhya

Pradesh. 

Acquired four licenses to offer basic services in Delhi, Haryana, Tamil Nadu and

Karnataka circles. 

Bharti launches India’s first private sector national long distance service under the

brand name India One 

Bharti Launched Touchtel in Haryana.

2002

Bharti launched cellular services in Punjab  

Bharti listed on the National stock Exchange, Bombay Stock Exchange and the

Delhi Stock Exchange on February 18, 2002. 

Bharti received a letter of intent from the Government of India to provide

international voice services.

2003

GPRS launched successfully in PUNJAB.

Bharti launches MMS and GPRS services in its cellular service.

Bharti merges its fixed line, long distance and Broadband services into one Bharti

Infotel Ltd. Bharti started its internet service under name Mantra Power Net.

Bharti enters deal with a Russian company, Zveza for ISD service.

2004

Bharti touches snowy heights in Jammu & Kashmir.

Bharti expands from Kolkata to all of West Bengal & Sikkim.

Bharti covers the sands of Rajasthan.

Bharti launched India’s first 2.4GHz band cordless phone.

Bharti starts across the globe.

Bharti is the ‘Emerging Company of the Year’ at the ET Awards 2003-04.

2005

Launch of its GSM mobile service Airtel in North East and Assam.

Launch of fixed line service at UP east.

EDGE to offer data transfer speeds of up to 200 kbps.

1.2 Northern Region

After touching the hearts of more than 1 million customers and winning the Techies

Award for Best Cellular Services for four consecutive years, Bharti Cellular has reached

Punjab- the land of colors, festivals, industrious people and emerging opportunities,

Haryana- the place of handicrafts & textile industry, and Himachal Pradesh the

ultimate destination for nature lovers.

Punjab is said to be a sweet home-coming for Bharti, launched on Feb 8, 2002. With

over 25000 bookings on day 1 and having 50,000 customers in just 75 days it is already

on an expressway to success.

Ahead of competitors in Himachal, and with grand start in Haryana, Bharti is here to take

care of communication needs and live up to the true spirit of Northern Region of

Excellence.

CEO Bharti Mobile Ltd. Northern Region

Corporate functions

J&K SitesPunjab Sites

Haryana Sites

H.P. Sites

Finance

Customer Care

Marketing

HR

IT

Technical

Project Management

I.2.1) Network Switching System NSS

forms the core of all the technical departments with the maintenance & working of all the

MSC functions. NSS functions are divided into 4 sub departments:

Roaming: Roaming deals with the mobile roaming facility of the

MS, which is the major facility provided to the mobile subscribers.

It deals with the national & international launches, roaming related

definitions, problems. It also deals with the SMS functioning

within other networks too.

VAS (Value Aided Services): Various services like news, cricket update are the services provided to the mobile users. VAS team deals

With maintenance & upgrade of the system. It deals with the creation of new

dialog boxes etc.

Hardware Team: It deals with the maintenance of all the MSC’s, RBSC’s,

various links etc. they monitor & rectify all the hardware alarms & also

responsible for their gradation.

TECHNICAL DEPARTMENT

NETWORK SWITCHING SYSTEM (NSS)

NETWORK PLANNING

OPERATION MAINTAINENCE &CONTROLLING (OMC)

OPERATION AND MAINTAINENCE (O&M)

I.2.2) Operation and Maintenance

Operation and Maintenance (O&M) is a department which deals in installing new sites

and maintaining them for trouble free working. when ever a new site is to be installed, it

the duty of the O&M to check that all the things required for the integration of the site are

available .Once the place where the new site is to be integrated is fixed by the planning

department, it is the job of the O&M to ensure that the site is ON AIR.

It is the job of the planning department to survey that whether there is a need for site

expansion, TRU addition, site cascading or a new site is to be placed. According to the

need O&M is informed and task is completed. Where indoor coverage is not proper

O&M team installs repeater on that location.

Once the site is operational then it is the duty of O&M to ensure the proper working of

the site. If there is any failure, then it is the duty of the O&M to eradicate the cause, it can

be an external or an internal alarm.

I.2.3) Operation and Maintenance Center

The OSS (Operation & Support System) is the Ericsson product for the GSM Operation

and Maintenance Center (OMC).For GSM system administration, OSS supports the

operator with functions such as mobile subscriber, & cellular network administration &

alarm handling.

I.2.3.1 Basic Functions of OMC

SITE MONITERING

FAULT MANAGEMENT

ALARM MONITORING

MOBILE SUBSCRIBER DATA ADMINSTRATION

CONFIGURATION CHANGES

SWITCH BACKUPS

CASCADING BTS SITES

These are the main functions of OMC. The OSS Server connects BSC (Base Station

Controller) along with all other R_BSC (Remote BSC) to the exceed software in OMC,

where all the above mentioned functions are observed and worked upon manually.

I.2.4) Network Planning:

The main purpose of the Planning Department is to survey whether there is a need for site

expansion, TRU addition, site cascading, or a new site is to be placed.

I.2.4.1. The working of Network Planning department includes:-

Planning & Implementation of sites.

Transmission Planning.

Drive Tests.

Generation & Analysis of Daily Performance Report.

Site Performance Analysis.

Performance Tuning & Optimization of Network.

II. WII. WIRELESSIRELESS C CONCEPTSONCEPTS

II.1 Transmission

Transmission means transmitting of information from one point to another .i.e. from

source to destination and vice versa. This can be done with the help of Transmission lines

and Transmission media. The block diagram is as follows .The arrow represents

Transmission line.

Wireless communication is the answer to the people who need to be online all the

time. For such Mobile user’s twisted pair, coax and fiber optics are of no use. Wireless

has the basic advantage in most of the circumstances. Running a fiber to a building is

difficult due to terrain and length of fiber, henceforth wireless is preferable.

II.2 Radio Transmission

Radio waves are easy to generate, can travel long distances, and penetrate buildings

easily, so they are widely used for communication. Radio waves are omni directional,

meaning that they travel in all directions from the source, so the transmitter and

receiver do not have to be carefully aligned. The properties of radio waves are

frequency dependent. At low frequencies, radio waves pass through obstacles, but the

power falls off sharply with distance from the source, roughly as 1/r3. in air. At high

frequencies, radio waves tend to travel in straight lines and bound off obstacles.

II.2.1 Microwave Transmission

Microwave communication is used for long distance communications, cellular

telephones, television distribution. Unlike radio waves at lower frequencies,

microwaves do not pass through buildings well. Some waves are refracted off low

lying atmospheric layers and take slightly longer to arrive than direct waves. This

effect is known as multipath fading.

Information source

Transmitter Media Receiver Destination

II.2.2 Infrared and Millimeter Waves

Unguided infrared and millimeter waves are used for short-range communication. The

remote controls used on televisions, VCRs and stereos all use infrared

communications. They are relatively directional, cheap and easy to build and the

major drawback is they do not pass through solid objects.

II.3 Introduction to Analog and Digital

II.3.1 Analog Information

Analog information is continuous and does not stop at discrete values. An example of

analog information is time. It is continuous and does not stop at specific points. An

analog watch may have a second-hand which does not jump from one second to the next,

but continues around the watch face without stopping.

II.3.2 Analog Signals

An analog signal is a continuous waveform which changes in accordance with the

properties of the information being represented.

II.3.3 Digital Information

Digital information is a set of discrete values. Time can also be represented digitally. However, digital time would be represented by a watch which jumpsfrom one minute to the next without stopping at the seconds. In effect, such a digital watch is taking a sample of time at predefined intervals.

II.3.4 Digital Signals

For mobile systems, digital signals may be considered to be sets of discrete waveforms.

II.4 Advantages of Using Digital

Human speech is a form of analog information. It is continuous and changes in both

frequency (higher and lower pitches) and amplitude (whispering and shouting). At first,

analog signals may appear to be a better medium for carrying analog information such as

speech. Analog information is continuous and if it were to be represented by discrete

samples of the information (digital signal), then some information would be missing (like

the seconds on the digital watch). An analog signal would not miss any values as it too is

continuous. All signals, analog and digital, become distorted over distances.

In analog, the only solution to this is to amplify the signal. However, in doing so, the

distortion is also amplified. In digital, the signal can be completely regenerated as new,

without the distortion.

The problem with using digital signals to transfer analog information is that some

information will be missing due to the technique of taking samples. However, the more

often the samples are taken, the closer the resulting digital values will be to a true

representation of the analog information. Overall, if samples are taken often enough,

digital signals provide a better quality for transmission of analog information than analog

signals.

II.5 Frequency Bands

II.5.1 Radio Channel

A mobile station communicates with a base station via a radio channel. A radio channel is

a bi-directional radio transmission path. Each radio channel has two distinct frequencies;

one for downlink and one for uplink.

Downlink is defined as the transmission path from the base station to the mobile station,

while uplink is defined as the transmission path from the mobile station to the base

station.

The base station transmits on one frequency while the mobile station transmits on another

frequency. This creates a full duplex communication path. That is, simultaneous

communication in both directions.

II.5.2 Frequency Spectrum

Different frequency bands are used for GSM 900, GSM 1800 and GSM 1900. An

operator applies for the available frequencies or, as in the United States; the operator

buys frequency bands at an auction

GSM 900GSM 900 GSM1800GSM1800 GSM 1900GSM 1900

Uplink frequencyUplink frequency 890-915 MHz890-915 MHz 1710-1785 MHz1710-1785 MHz 1850-1910 MHz1850-1910 MHz

Downlink frequencyDownlink frequency 935-960 MHz935-960 MHz 1805-1880 MHz1805-1880 MHz 1930-1990 MHz1930-1990 MHz

II.6 Terminology

II.6.1 Duplex Distance

The distance between one uplink frequency and its corresponding downlink frequency is

called the duplex distance. The duplex distance varies for different frequency bands, refer

to table below:

II.6.2 Channel Separation

The distance between adjacent frequencies on either the uplink or downlink is called

channel separation. Channel separation is 200 kHz, regardless of the standards mentioned

above. This separation is necessary to reduce interference between channels.

In addition to the duplex distance, every mobile system includes a channel separation.

This is the distance on the frequency band between channels being transmitted in the

same direction. This is required in order to avoid the overlapping of information in one

channel into an adjacent channel.

The length of separation between two channels is dependent on the amount of

information which is to be transmitted within the channel. The greater the amount of

information to transmit, the greater the amount of separation required.

From the figure above, it can be seen that the information to be sent is modulated around

the carrier frequency of 895.4 MHz. The same is true of the information to be sent on

895.6 MHz. To avoid interference between the two sets of information, a separation

distance of 200 kHz is required. If less separation were used, they would interfere and a

caller on 895.4 MHz may experience crosstalk or noise from the caller on 895.6 MHz.

II.6.3 Transmission Rate

The transmission rate over the air is 270 kbit/s. This is true for GSM 900, GSM 1800 and

GSM 1900. The amount of information transmitted over a radio channel over a period of

time is known as the transmission rate. Transmission rate is expressed in bits per second

or bit/s.

II.6.4 Access Method

Ericsson has chosen the Time Division Multiple Access (TDMA) method for all Ericsson

GSM networks. TDMA allows several different calls to share the same frequency i.e.

TDMA is a technique in which several different calls may share the same carrier. Each

call is assigned a particular time slot. Most digital cellular systems use the technique of

Time Division Multiple Access (TDMA) to transmit and receive speech signals. With

TDMA, one channel is used to carry a number of calls, each call using that channel at

designated periods in time. These periods of time are referred to as time slots. Each MS

on a call is assigned one time slot on the uplink frequency and one on the downlink

frequency.

The information sent during one time slot is called a burst. In GSM, a TDMA frame

consists of 8 time slots. This means that a GSM radio carrier can carry 8 calls.

II.6.5 Modulation Method

The modulation method used in GSM is Gaussian Minimum Shift Keying (GMSK). It is

a digital modulation form, that is, the information sent is digital. It can be data or

digitized speech. The modulator can be looked upon as a phase modulator. The carrier

changes phase depending on the information bits sent into the modulator. GMSK

includes the desirable feature of a constant envelope modulation within a burst. To get

smooth curve shapes when changing the phase, the baseband signal is filtered with a

Gaussian shaped passband. GMSK provides narrower bandwidth compared to ordinary

MSK, but it has less resistance against noise.GSM radio interface uses Gaussian

Minimum Shift Keying or GMSK.  This is produced by passing the bipolar bit stream

through a low pass filter with a Gaussian transfer function and then using the filtered data

stream to control a Voltage Controlled Oscillator (VCO). It has the advantage that very

little of the output power is in out of band frequencies.

This is similar to conventional MSK, where the input binary symbols cause the phase of

the transmitted signal to change linearly from its starting state to ±л /2 over an input

symbol period T. The phase change for GMSK is also ±л/2  but the change requires three

symbol times to complete. This smoothing of the phase trajectory greatly reduces the

relative magnitude of the side lobes of the power spectrum of GMSK and is a primary

reason that GMSK was selected by GSM

In GMSK the signal amplitude or envelope is constant. GMSK is usually demodulated

coherently. The demodulator must handle a phase trajectory that is much longer than one

symbol period. A single modulator input symbol influences the modulator output for

approximately three symbol times - overlap of symbols, or controlled Inter Symbol

Interference - ISI. The demodulator must consider a sequence of symbols when

estimating the demodulator output symbol, rather then considering a single symbol at a

time. The controlled intersymbol interference is only a part of the GSM intersymbol

interference problem. Multipath propagation also produces delay spread in a mobile

communications system. For GSM signaling reliability is required in a two-equal-ray

multipath environment with differential delay of nearly four symbol periods (16 µs). An

equalizer is used in the demodulator to eliminate this Inter Symbol Interference

II.7 Transmission Problems:

Many problems may occur during the transmission of radio signal they are:

II.7.1 Path Loss

Path loss occurs when the received signal becomes weaker & weaker due to increasing

distance between MS and BTS, even if there are no obstacles between the Tx & Rx

antenna.

II.7.2 Shadowing

Shadowing occurs when there are physical obstacles including hills & buildings between

the BTS & MS. The obstacles create a shadowing effect which can decrease the received

signal strength. When the MS moves, the signal strength fluctuates depending on the

obstacles between the MS & BTS.

II.7.3 Multipath Fading

This occurs when there is more than one transmission path to the MS & BTS& therefore

more than one signal arriving at the receiver. This may be due to buildings or mountains,

either close to or far from the receiving device.

Rayleigh fading & Time dispersion are forms of multipath fading.

Rayleigh Fading

This occurs when a signal takes more than one path between the MS & BTS antennas. In

this case, the signal is not received on the line of sight path directly from the Tx antenna,

rather it is reflected off buildings & is received from several different paths. It occurs

when the obstacles are close to the Rx antenna.

Time Dispersion

Time dispersion is another problem relating to multiple paths to the Rx antenna of either

an MS or BTS.However, in contrast to Rayleigh fading, the reflected signal comes from

an object far away from the Rx antenna. It causes Inter Symbol Interference (ISI) where

consecutive bits interfere with each other making it difficult for the Rx to determine

which symbol is the correct one.

II.7.4 Time Alignment

Each MS on a call is allocated a time slot on a TDMA frame. This is an amount of time

during which the MS transmits information to the BTS. The information must also arrive

at the BTS within that time slot. The time alignment problem occurs when part of the

information transmitted by an MS does not arrive within the allocated time slot. Instead,

that part may arrive during the next time slot & may interfere with information from

another MS using that other time slot. It is caused by a large distance between the MS &

the BTS. Effectively, the signal cannot travel over the large distance within the given

time.

II.8 Solutions to Transmission Problems:

II.8.1 Channel Coding

In digital transmission, the quality of the transmitted signal is often expressed in terms of

how many of the received bits are incorrect. This is called Bit Error Rate (BER).BER

defines the % of the total no. of received bits which are incorrectly detected. This %

should be as low as possible.

Channel coding is used to detect & correct errors in a received bit stream. It adds bits to

the message. These bits enable a channel decoder to determine whether the message has

faulty bits, & to potentially correct the faulty bits.

II.8.2 Interleaving

Channel coding is most effective in detecting & correcting single errors & short error

sequences. It is not suitable for handling longer sequences of bit errors. For this reason, a

process called interleaving is used to separate consecutive bits of a message so that these

are transmitted in a non-consecutive way.

II.8.3 Timing Advance

This is a solution specifically designed to counteract the problem of time alignment. It

works by instructing the misaligned MS to transmit its burst earlier than it normally

would.

In GSM, the timing advance information relates to bit times. Thus an MS may be

instructed to advance its transmission by a certain no. of bit times. The maximum in

GSM is 63 bit times.

II.9 Analog to Digital (A/D) Conversion

One of the primary functions of an MS is to convert the analog speech information into

digital form for transmission using a digital signal. The analog to digital (A/D) on version

process outputs a collection of bits: binary ones and zeros which represent the speech

input.

The A/D conversion is performed by using a process called Pulse Code Modulation

(PCM). PCM involves three main steps:

Sampling

Quantization

Coding

II.9.1 Sampling

Sampling involves measuring the analog signal at specific time intervals.

The accuracy of describing the analog signal in digital terms depends on how often the

analog signal is sampled, among other things. This is expressed as the sampling

frequency. The sampling theory states that:

To reproduce an analog signal without distortion, the signal must be sampled with at

least twice the frequency of the highest frequency component in the analog signal

Normal speech mainly contains frequency components lower than 3400 Hz. Higher

components have low energy and may be omitted without affecting the speech quality

much. Applying the sampling theory to analog speech signals, the sampling frequency,

should be at least 2 x 3.4 kHz = 6.8 kHz. Telecommunication systems use a sampling

frequency of 8 kHz, which is acceptable based on the sampling theory.

II.9.2 Quantization

The next step is to give each sample a value. For this reason, the amplitude of the signal

at the time of sampling is measured and approximated to one of a finite set of values. The

figure below shows the principle of quantization applied to an analog signal. It can be

seen that a slight error is introduced in this process when the signal is quantized or

approximated. The degree of accuracy depends on the number of quantization levels

used. Within common telephony, 256 levels are used while in GSM 8,192 levels are used.

II.9.3Coding

Coding involves converting the quantized values into binary. Every value is represented

by a binary code of 13 bits (213= 8192). For example, a quantized value of 2,157 would

have a bit pattern of 0100001101101:

II.9.4 Summary of A/D Conversion

The result from the process of A/D conversion is 8,000 samples per second of 13 bits

each. This is a bit rate of 104 kbits/s. When it is considered that 8 subscribers use one

radio channel, the overall bit rate would be 8 x 104 kbits/s = 832 kbits/s. Recalling the

general rule of 1 bit per Hertz, this bit rate would not fit into the 200 kHz available for all

8 subscribers. The bit rate must be reduced somehow - this is achieved using

segmentation and speech coding.

The coding used here is HDB-3 coding & 2.048 Mbit bit streams are used.

The details of 2.048 Mbit Streams or E1 as they are called is given below.

II.10 Transmission Line

Transmission lines are considered to be impedance-matching circuits designed to deliver

power from the transmitter to the antenna, and maximum signal from the antenna to the

receiver. Any system of wires can be considered as forming one or more transmission

lines.

II.10.1 Types of Transmission Lines

There are two types of commonly used transmission lines

a) Parallel-wire (balanced) line

Balanced lines require the use of three terminals rather than two. One conductor

(shield) will be connected to ground, and the signal will be carried by two

identical conductors which carry the same voltage but with opposite polarity with

respect to ground. The line is said to be balanced since the two signal carrying

conductors are of equal (though opposite) potential Balanced lines are useful for

eliminating unwanted noises. Balanced lines have an impedance of 120 ohm.

b) Coaxial (unbalanced) line

An unbalanced line uses only two conductors with one being at or near ground

potential, while the other conductor is the hot or high side of the line. The line is

said to be unbalanced because the two conductors are of unequal potentials with

respect to the ground. Unbalanced lines have an impedance of 75 ohm.

II.11 Transmission Media

The transmission media used in AIRTEL are

Microwave

Optical fibre

Copper cable

II.11.1 Microwave

Radio link is the name for a microwave radio connection between two points. Radio link

is typically available for 2, 4, 8, 16, 34, 140 and 155 (SDH) Mbit/s capacities. The

Ericsson radio link product is called MINI-LINK and is used extensively in mobile

networks in the Asia-Pacific region.

Microwave links are further divided into two parts:

Intercity: Here we have a radio link from city to city .RF is low. Diameter of

antenna is large & Hop distance is more

Intracity: Here we have a radio link within city. RF is high. Diameter of antenna

is small & Hop distance is less.

II.11.2 Copper Cable

Relatively short repeater distances characterize metal cable systems. Two common cable

types are pair cable and coaxial cable. The factor limiting the repeater distance in twisted

pair cable systems is interference between PCM signals, whereas in coaxial systems it is

the attenuation of the signal .For out-doors applications pair cable is pre-dominant,

whereas coaxial cable is mainly used for in-door applications. In general, pair cable is

used for longer distances and coaxial cable for shorter distances. For both cables the

possible distance decreases with higher capacity.

II.11.3 Optical Fiber

Optical fiber offers high capacity, low attenuation and is insensitive to electromagnetic

disturbances. The two wavelengths mainly used in fiber optical systems are 1310 nm and

1550 nm as the fiber attenuation is minimal at these two wavelengths. Optical fibers are

usually divided into multi and single mode fibers Single mode fibers are used extensively

in telecommunication connections

III.GLOBAL SYSTEM FOR MOBILE COMMUNICATION

The Global System for Mobile communications is a digital cellular communications

system. It was developed in order to create a common European mobile telephone

standard but it has been rapidly accepted worldwide. GSM was designed to be compatible

with ISDN services.

III.1 History of Cellular Mobile Radio and GSM

The idea of cell-based mobile radio systems appeared at Bell Laboratories (in USA) in

the early 1970s. However, mobile cellular systems were not introduced for commercial

use until the 1980s. During the early 1980s, analog cellular telephone systems

experienced a very rapid growth in Europe, particularly in Scandinavia and the United

Kingdom. Today cellular systems still represent one of the fastest growing

telecommunications systems.

But in the beginnings of cellular systems, each country developed its own system, which

was an undesirable situation for the following reasons:  

The equipment was limited to operate only within the boundaries of each country.

The market for each mobile equipment was limited.

In order to overcome these problems, the Conference of European Posts and

Telecommunications (CEPT) formed, in 1982, the Group Special Mobile (GSM) in order

to develop a pan-European mobile cellular radio system (the GSM acronym became later

the acronym for Global System for Mobile communications). The standardized system

had to meet certain criteria:

Spectrum efficiency

International roaming

Low mobile and base stations costs

Good subjective voice quality

Compatibility with other systems such as ISDN (Integrated Services Digital

Network)

Ability to support new services

Unlike the existing cellular systems, which were developed using an analog technology,

the GSM system was developed using a digital technology.

In 1989 the responsibility for the GSM specifications passed from the CEPT to the

European Telecommunications Standards Institute (ETSI). The aim of the GSM

specifications is to describe the functionality and the interface for each component of the

system, and to provide guidance on the design of the system. These specifications will

then standardize the system in order to guarantee the proper networking between the

different elements of the GSM system. In 1990, the phase I of the GSM specifications

were published but the commercial use of GSM did not start until mid-1991.

The most important events in the development of the GSM system are presented in the

table.

Year Events

1982CEPT establishes a GSM group in order to develop the standards for a pan-

European cellular mobile system

1985 Adoption of a list of recommendations to be generated by the group

1986Field tests were performed in order to test the different radio techniques

proposed for the air interface

1987

TDMA is chosen as access method (in fact, it will be used with FDMA) Initial

Memorandum of Understanding (MoU) signed by telecommunication

operators (representing 12 countries)

1988 Validation of the GSM system

1989 The responsibility of the GSM specifications is passed to the ETSI

1990 Appearance of the phase 1 of the GSM specifications

1991 Commercial launch of the GSM service

1992Enlargement of the countries that signed the GSM- MoU> Coverage of larger

cities/airports

1993 Coverage of main roads GSM services start outside Europe

1995 Phase 2 of the GSM specifications Coverage of rural areas

From the evolution of GSM, it is clear that GSM is not anymore only a European

standard. GSM networks are operational or planned in over 80 countries around the

world. The rapid and increasing acceptance of the GSM system is illustrated with the

following figures:  

1.3 million GSM subscribers worldwide in the beginning of 1994.

Over 5 million GSM subscribers worldwide in the beginning of 1995.

Over 10 million GSM subscribers only in Europe by December 1995.

Since the appearance of GSM, other digital mobile systems have been developed. The

table charts the different mobile cellular systems developed since the commercial launch

of cellular systems

Year Mobile Cellular System

1981 Nordic Mobile Telephony (NMT), 450>

1983 American Mobile Phone System (AMPS)

1985 Total Access Communication System (TACS) Radio COM 2000 C-Netz

1986 Nordic Mobile Telephony (NMT), 900>

1991Global System for Mobile communications> North American Digital Cellular

(NADC)

1992 Digital Cellular System (DCS) 1800

1994 Personal Digital Cellular (PDC) or Japanese Digital Cellular (JDC)

1995 Personal Communications Systems (PCS) 1900- Canada>

1996 PCS-United States of America>

III.2 Cellular System

III.2.1 Cell

In a cellular system, the covering area of an operator is divided into cells. A cell

corresponds to the covering area of one transmitter or a small collection of transmitters.

The size of a cell is determined by the transmitter's power. The concept of cellular

systems is the use of low power transmitters in order to enable the efficient reuse of the

frequencies. In fact, if the transmitters used are very powerful, the frequencies can not be

reused for hundred of kilometres as they are limited to the covering area of the

transmitter. The frequency band allocated to a cellular mobile radio system is distributed

over a group of cells and this distribution is repeated in all the covering area of an

operator. The whole number of radio channels available can then be used in each group

of cells that form the covering area of an operator. Frequencies used in a cell will be

reused several cells away. The distance between the cells using the same frequency must

be sufficient to avoid interference. The frequency reuse will increase considerably the

capacity in number of users. In order to work properly, a cellular system must verify the

following two main conditions:

The power level of a transmitter within a single cell must be limited in order to

reduce the interference with the transmitters of neighbouring cells. The

interference will not produce any damage to the system if a distance of about 2.5

to 3 times the diameter of a cell is reserved between transmitters. The receiver

filters must also be high performance.

Neighbouring cells can not share the same channels. In order to reduce the

interference, the frequencies must be reused only within a certain pattern.

In order to exchange the information needed to maintain the communication links within

the cellular network, several radio channels are reserved for the signalling information.

III.2.2 Types of Cells

The density of population in a country is so varied that different types of cells are used:

Macro cells

Micro cells

Selective cells

Umbrella cells

Macro Cells

The macro cells are large cells for remote and sparsely populated areas.

Micro Cells

These cells are used for densely populated areas. By splitting the existing areas into

smaller cells, the number of channels available is increased as well as the capacity of the

cells. The power level of the transmitters used in these cells is then decreased, reducing

the possibility of interference between neighboring cells.

Selective Cells

It is not always useful to define a cell with a full coverage of 360 degrees. In some cases,

cells with a particular shape and coverage are needed. These cells are called selective

cells. A typical example of selective cells is the cells that may be located at the entrances

of tunnels where coverage of 360 degrees is not needed. In this case, a selective cell with

coverage of 120 degrees is used.

Umbrella Cells

A freeway crossing very small cells produces an important number of handovers among

the different small neighboring cells. In order to solve this problem, the concept of

umbrella cells is introduced. An umbrella cell covers several micro cells. The power level

inside an umbrella cell is increased comparing to the power levels used in the micro cells

that form the umbrella cell. When the speed of the mobile is too high, the mobile is

handed off to the umbrella cell. The mobile will then stay longer in the same cell (in this

case the umbrella cell). This will reduce the number of handovers and the work of the

network. A too important number of handover demands and the propagation

characteristics of a mobile can help to detect its high speed.

III.2.3 Location Area

The Location Area (LA) is defined as a group of cells. The system uses LA to search for

subscribers in active state. When there is a call for a mobile station, a paging message is

broadcast to all cells belonging to a specific LA.

A LA is the part of the network in which a mobile station may move around freely

without reporting its location to the network. Different location areas can be identified by

the system using the Location Area Identity (LAI).

III.2.4 MSC SERVICE AREA

An MSC service area is made up of a number of LAs and represents the geographical part

of the network controlled by one MSC. In order to be able to route a call to an MS, the

subscriber’s MSC service area is also recorded and monitored. The subscriber’s MSC

service area is stored in the HLR.

III.2.5 PLMN SERVICE AREA

A Public Land Mobile Network (PLMN) service area is the entire set of cells served by

one network operator and is defined as the area in which an operator offers radio

coverage and access to its network. In any one country there may be several PLMN

service areas, one for each mobile operator’s network.

III.2.6 The Geographical Areas of GSM Network

The figure presents the different areas that form a GSM network.

 

 

 

As it has already been explained a cell, identified by its Cell Global Identity number

(CGI), corresponds to the radio coverage of a base transceiver station. A Location Area

(LA), identified by its Location Area Identity (LAI) number, is a group of cells served by

a single MSC/VLR. A group of location areas under the control of the same MSC/VLR

defines the MSC/VLR area. A Public Land Mobile Network (PLMN) is the area served

by one network operator.

III.3 The Transition from Analog to Digital Technology

In the 1980s most mobile cellular systems were based on analog systems. The GSM

system can be considered as the first digital cellular system. The different reasons that

explain this transition from analog to digital technology are presented in this section.

III.3.1 The Capacity of the System

Cellular systems have experienced a very important growth. Analog systems were not

able to cope with this increasing demand. In order to overcome this problem, new

frequency bands and new technologies were proposed. But the possibility of using new

frequency bands was rejected by a big number of countries because of the restricted

spectrum (even if later on, other frequency bands have been allocated for the

development of mobile cellular radio). The new analog technologies proposed were able

to overcome the problem to a certain degree but the costs were too important.

The digital radio was, therefore, the best option (but not the perfect one) to handle the

capacity needs in a cost-efficiency way.

III.3.2 Compatibility With Other Systems Such as ISDN

The decision of adopting a digital technology for GSM was made in the course of

developing the standard. During the development of GSM, the telecommunications

industry converted to digital methods. The ISDN network is an example of this evolution.

In order to make GSM compatible with the services offered by ISDN, it was decide that

the digital technology was the best option.

Additionally, a digital system allows, easily than an analog one, the implementation of

future improvements and the change of its own characteristics.

III.3.3 Aspects of Quality

The quality of the service can be considerably improved using a digital technology rather

than an analog one. In fact, analog systems pass the physical disturbances in radio

transmission (such as fades, multipath reception, spurious signals or interferences) to the

receiver. These disturbances decrease the quality of the communication because they

produce effects such as fadeouts, cross talks, hisses, etc. On the other hand, digital

systems avoid these effects transforming the signal into bits. This transformation

combined with other techniques, such as digital coding, improves the quality of the

transmission. The improvement of digital systems comparing to analog systems is more

noticeable under difficult reception conditions than under good reception conditions.

III.4 The GSM Network

III.4.1 Architecture of the GSM System

The GSM technical specifications define the different entities that form the GSM network

by defining their functions and interface requirements.

The GSM network can be divided into four main parts:

The Mobile Station (MS).

The Base Station Subsystem (BSS).

The Network and Switching Subsystem (NSS).

The Operation and Support Subsystem (OSS).

.

 

 

Architecture of the GSM network

 

III.4.1.1 Mobile Station

A Mobile Station consists of two main elements:

The mobile equipment or terminal.

The Subscriber Identity Module (SIM).

a) The Terminal

There are different types of terminals distinguished principally by their power and

application:

The `fixed' terminals are the ones installed in cars. Their maximum allowed

output power is 20 W.

The GSM portable terminals can also be installed in vehicles. Their maximum

allowed output power is 8W.

The handheld terminals have experienced the biggest success thanks to their

weight and volume, which are continuously decreasing. These terminals can emit

up to 2 W. The evolution of technologies allows to decrease the maximum

allowed power to 0.8 W.

b) The SIM

The SIM is a smart card that identifies the terminal. By inserting the SIM card into

the terminal, the user can have access to all the subscribed services. Without the SIM

card, the terminal is not operational.

The SIM card is protected by a four-digit Personal Identification Number (PIN). In

order to identify the subscriber to the system, the SIM card contains some parameters

of the user such as its International Mobile Subscriber Identity (IMSI).

Another advantage of the SIM card is the mobility of the users. In fact, the only

element that personalizes a terminal is the SIM card. Therefore, the user can have

access to its subscribed services in any terminal using its SIM card.

III.4.1.2 The Base Station Subsystem

The BSS connects the Mobile Station and the NSS. It is in charge of the transmission

and reception. The BSS can be divided into two parts:

The Base Transceiver Station (BTS) or Base Station.

The Base Station Controller (BSC).

a) The Base Transreceiver Station

The BTS corresponds to the transceivers and antennas used in each cell of the

network. A BTS is usually placed in the centre of a cell. Its transmitting power defines

the size of a cell. Each BTS has between one and sixteen transceivers depending on

the density of users in the cell.

b) The Base Station Controller

The BSC controls a group of BTS and manages their radio resources. A BSC is

principally in charge of handovers, frequency hopping, exchange functions and

control of the radio frequency power levels of the BTSs.

III.4.1.3 The Network and Switching Subsystem

Its main role is to manage the communications between the mobile users and other users, such as mobile users, ISDN users, fixed telephony users, etc. It also includes data bases needed in order to store information about the subscribers and to manage their mobility. The different components of the NSS are described below.

a) The Mobile Services Switching Subsystem (MSC)

It is the central component of the NSS. The MSC performs the switching functions of the network. It also provides connection to other network

b) The Gateway Mobile Services Switching Subsystem (GMSC)

A gateway is a node interconnecting two networks. The GMSC is the interface between the mobile cellular network and the PSTN. It is in charge of routing calls from the fixed network towards a GSM user. The GMSC is often implemented in the same machines as the MSC.

c) Home Location Register(HLR)

The HLR is considered as a very important database that stores information of the

subscribers belonging to the covering area of a MSC. It also stores the current location of

these subscribers and the services to which they have access. The location of the

subscriber corresponds to the SS7 address of the Visitor Location Register (VLR)

associated to the terminal.

d) Visitor Location Register(VLR)

The VLR contains information from a subscriber's HLR necessary in order to provide the

subscribed services to visiting users. When a subscriber enters the covering area of a new

MSC, the VLR associated to this MSC will request information about the new subscriber

to its corresponding HLR. The VLR will then have enough information in order to assure

the subscribed services without needing to ask the HLR each time a communication is

established.

The VLR is always implemented together with a MSC; so the area under control of the

MSC is also the area under control of the VLR.

e) The Authentication Centre (AuC)

The AuC register is used for security purposes. It provides the parameters needed for

authentication and encryption functions. These parameters help to verify the user's

identity.

f) The Equipment Identity Register (EIR)

The EIR is also used for security purposes. It is a register containing information about

the mobile equipments. More particularly, it contains a list of all valid terminals. A

terminal is identified by its International Mobile Equipment Identity (IMEI). The EIR

allows then to forbid calls from stolen or unauthorized terminals (e.g., a terminal which

does not respect the specifications concerning the output RF power).

g) The GSM Interworking Unit (GIWU)

The GIWU corresponds to an interface to various networks for data communications.

During these communications, the transmission of speech and data can be alternated.

III.4.1.4 The Operation and Support Subsystem

The OSS is connected to the different components of the NSS and to the BSC, in order to

control and monitor the GSM system. It is also in charge of controlling the traffic load of

the BSS.

However, the increasing number of base stations, due to the development of cellular radio

networks, has provoked that some of the maintenance tasks are transferred to the BTS.

This transfer decreases considerably the costs of the maintenance of the system.

III.4.2 BSS Interfaces

There are four primary interfaces within the BSS where traffic and signalling information

is received and transmitted. The A interface exchanges information between the

MSC/VLR and the TRC, the A-ter Interface between the TRC and BSCs, the A-bis

Interface transmits information between the BSC and BTS, while the Air Interface

operates between the BTS and MS.

a) A – Interface

The A-Interface provides two distinct types of information, signalling and traffic,

between the MSC and the BSS. The speech is transcoded in the TRC and the SS7

signalling is transparently connected through the TRC or on a separate link to the BSC.

b) A-TER INTERFACE

The A-ter interface is the link between the TRC and the BSC. In the TRC the speech is

transcoded from 64 kbit/s to 16 kbit/s. 13 kbit/s of speech information and 3 kbit/s of in-

band signalling information.

c) A-BIS Interface

The A-bis Interface is responsible for transmitting traffic and signalling information

between the BSC and the BTS. The transmission protocol used for sending signalling

information on the A-bis interface is Link Access Protocol on the D Channel

d) AIR Interface

The Air Interface uses the Time Division Multiple Access (TDMA) technique to transmit

and receive traffic and signalling information between the BTS and MS. The TDMA

technique is used to divide each carrier into eight time slots. These time slots are then

assigned to specific users, allowing up to eight conversations to be handled

simultaneously by the same carrier.

III.4.3 The GSM Functions

In this paragraph, the description of the GSM network is focused on the different

functions to fulfill by the network and not on its physical components. In GSM, five main

functions can be defined:

Transmission.

Radio Resources management (RR).

Mobility Management (MM).

Communication Management (CM).

Operation, Administration and Maintenance (OAM).

III.4.3.1 Transmission

The transmission function includes two sub-functions:

The first one is related to the means needed for the transmission of user

information.

The second one is related to the means needed for the transmission of signalling

information.

Not all the components of the GSM network are strongly related with the transmission

functions. The MS, the BTS and the BSC, among others, are deeply concerned with

transmission. But other components, such as the registers HLR, VLR or EIR, are only

concerned with the transmission for their signalling needs with other components of the

GSM network. Some of the most important aspects of the transmission are described in

section 5.

 

III.4.3.2 Radio Resources Management(RR)

The role of the RR function is to establish ,maintain and release communication links

between mobile stations and the MSC.The elements that are mainly concerned with the

RR function are the mobile station and the base station. However as the RR function is

also incharge of maintaining a connection even if user moves from one cell to another,

the MSC,incharge of handovers,is also concerned with the RR functions.

The RR is also responsible for the management of the frequency spectrum and the

reaction of the network to changing radio environment conditions. Some of the main RR

procedures that assure its responsibilities are :

Channel assignment, change and release.

Handover.

Frequency hopping.

Power-level control.

Discontinuous transmission and reception.

Timing advance.

a) Handover

The user movements can produce the need to change the channel or cell,

especially when the quality of communication is decreasing. This procedure of

changing the resources is called handover. Four different types of handovers can

distinguish:

Handover of channels in the same cell.

Handover of cells controlled by the same BSC.

Handover of cells belonging to same MSC but controlled by different BSC.

Handover of cells controlled by different MSCs.

Handovers are mainly controlled by the MSC. However in order to avoid unnecessary

signalling information, the first two types of handovers are managed by the concerned

BSC (in this case, the MSC is only notified of the handover).

The mobile station is the active participant in this procedure. In order to perform the

handover, the mobile station controls continuously its own signal strength and the signal

strength of the neighboring cells. The list of cells that must be monitored by the mobile

station is given by the base station. The power measurements allow deciding which

The best cell is in order to maintain the quality of the communication link. Two basic

algorithms are used for the handover:

The `minimum acceptable performance' algorithm. When the quality of the

transmission decreases (i.e. the signal is deteriorated), the power level of the

mobile is increased. This is done until the increase of the power level has no

effect on the quality of the signal. When this happens, a handover is performed.

The `power budget' algorithm. This algorithm performs a handover, instead of

continuously increasing the power level, in order to obtain a good communication

quality.

III.4.3.3 Mobility Management

The MM function is in charge of all the aspects related with the mobility of the user,

specially the location management and the authentication and security.

a) Location Management

When a mobile station is powered on, it performs a location update procedure by

indicating its IMSI to the network. The first location update procedure is called the IMSI

attach procedure.

The mobile station also performs location updating, in order to indicate its current

location, when it moves to a new Location Area or a different PLMN. This location

updating message is sent to the new MSC/VLR, which gives the location information to

the subscriber's HLR. If the mobile station is authorized in the new MSC/VLR, the

subscriber's HLR cancels the registration of the mobile station with the old MSC/VLR.

A location updating is also performed periodically. If after the updating time period, the

mobile station has not registered, it is then deregistered.

When a mobile station is powered off, it performs an IMSI detach procedure in order to

tell the network that it is no longer connected.

b) Authentication and Security

The authentication procedure involves the SIM card and the Authentication Centre. A

secret key, stored in the SIM card and the AuC, and a ciphering algorithm called A3 are

used in order to verify the authenticity of the user. The mobile station and the AuC

compute a SRES using the secret key, the algorithm A3 and a random number generated

by the AuC. If the two computed SRES are the same, the subscriber is authenticated. The

different services to which the subscriber has access are also checked.

Another security procedure is to check the equipment identity. If the IMEI number of the

mobile is authorized in the EIR, the mobile station is allowed to connect the network.

In order to assure user confidentiality, the user is registered with a Temporary Mobile

Subscriber Identity (TMSI) after its first location update procedure.

III.4.3.4 Communication Management (CM)

The CM function is responsible for:

Call control.

Short Message Services management.

a) Call Control (CC)

The CC is responsible for call establishing, maintaining and releasing as well as for

selecting the type of service. One of the most important functions of the CC is the call

routing. In order to reach a mobile subscriber, a user dials the Mobile Subscriber ISDN

(MSISDN) number which includes:

a country code

a national destination code identifying the subscriber's operator

a code corresponding to the subscriber's HLR

The call is then passed to the GMSC (if the call is originated from a fixed network) which knows the HLR corresponding to a certain MISDN number.The GMSC asks the HLR for information helping to the call routing. The HLR requests

this information from the subscriber's current VLR. This VLR allocates temporarily a

Mobile Station Roaming Number (MSRN) for the call. The MSRN number is the

information returned by the HLR to the GMSC. Thanks to the MSRN number, the call is

routed to subscriber's current MSC/VLR. In the subscriber's current LA, the mobile is

paged.

 b) Short Message Service Management

In order to support these services, a GSM network is in contact with a Short Message

Service Centre through the two following interfaces:

The SMS-GMSC for Mobile Terminating Short Messages (SMS-MT/PP). It has

the same role as the GMSC.

The SMS-IWMSC for Mobile Originating Short Messages (SMS-MO/PP).

III.4.3.5 Operation, Administration and Maintenance

The OAM function allows the operator to monitor and control the system as well as to

modify the configuration of the elements of the system. Not only the OSS is part of the

OAM, also the BSS and NSS participate in its functions as it is shown in the following

examples:

The components of the BSS and NSS provide the operator with all the

information it needs. This information is then passed to the OSS which is in

charge of analysing it and control the network.

The self test tasks, usually incorporated in the components of the BSS and NSS,

also contribute to the OAM functions.

The BSC, in charge of controlling several BTSs, is another example of an OAM

function performed outside the OSS.

III.5 The GSM Radio Interface

The radio interface is the interface between the mobile stations and the fixed

infrastructure. It is one of the most important interfaces of the GSM system.

One of the main objectives of GSM is roaming. Therefore, in order to obtain a complete

compatibility between mobile stations and networks of different manufacturers and

operators, the radio interface must be completely defined.

The spectrum efficiency depends on the radio interface and the transmission, more

particularly in aspects such as the capacity of the system and the techniques used in order

to decrease the interference and to improve the frequency reuse scheme. The

specification of the radio interface has then an important influence on the spectrum

efficiency.

III.5.1 Frequency Allocation

Two frequency bands, of 25 MHz each one, have been allocated for the GSM system:

The band 890-915 MHz has been allocated for the uplink direction (transmitting

from the mobile station to the base station).

The band 935-960 MHz has been allocated for the downlink direction

(transmitting from the base station to the mobile station).

But not all the countries can use the whole GSM frequency bands. This is due principally

to military reasons and to the existence of previous analog systems using part of the two

25 MHz frequency bands.

III.5.2 Multiple Access Scheme

The multiple access scheme defines how different simultaneous communications,

between different mobile stations situated in different cells, share the GSM radio

spectrum. A mix of Frequency Division Multiple Access (FDMA) and Time Division

Multiple Access (TDMA), combined with frequency hopping, has been adopted as the

multiple access scheme for GSM. FDMA and TDMA

Using FDMA, a frequency is assigned to a user. So the larger the number of users in a

FDMA system, the larger the number of available frequencies must be. The limited

available radio spectrum and the fact that a user will not free its assigned frequency until

he does not need it anymore, explain why the number of users in a FDMA system can be

"quickly" limited.

On the other hand, TDMA allows several users to share the same channel. Each of the

users, sharing the common channel, is assigned their own burst within a group of bursts

called a frame. Usually TDMA is used with a FDMA structure.

In GSM, a 25 MHz frequency band is divided, using a FDMA scheme, into 124 carrier

frequencies spaced one from each other by a 200 kHz frequency band. Normally a 25

MHz frequency band can provide 125 carrier frequencies but the first carrier frequency is

used as a guard band between GSM and other services working on lower frequencies.

Each carrier frequency is then divided in time using a TDMA scheme. This scheme splits

the radio channel, with a width of 200 kHz, into 8 bursts. A burst is the unit of time in a

TDMA system, and it lasts approximately 0.577 ms. A TDMA frame is formed with 8

bursts and lasts, consequently, 4.615 ms. Each of the eight bursts, that form a TDMA

frame, are then assigned to a single user.

III.5.6 Channel Structure

A channel corresponds to the recurrence of one burst every frame. It is defined by its

frequency and the position of its corresponding burst within a TDMA frame. In GSM

there are two types of channels:

III.5.6.1 Physical Channel

The path used to carry information between a Mobile Station and a Base Transceiver

Station is known as the Physical Channel. Each timeslot on a TDMA frame is called a

physical channel. Therefore, there are 8 physical channels per carrier frequency in GSM.

Physical channels can be used to transmit speech, data or signalling information.

A physical channel may carry different messages, depending on the information which is

to be sent. These messages are called logical channels. For example, on one of the

physical channels used for traffic, the traffic itself is transmitted using a Traffic Channel

(TCH) message, while a handover instruction is transmitted using a Fast Associated

Control Channel (FACCH) message.

III.5.6.2 Logical Channel

There are 12 logical channels in the system. Two are used for traffic, nine for control

signalling and one for message distribution.

Many types of logical channels exist; each designed to carry a different message to or

from an MS. All information to and from an MS must be formatted correctly, so that the

receiving device can understand the meaning of different bits in the message. For

example, as seen previously, in the burst used to carry traffic, some bits represent the

speech or data itself, while others are used as a training sequence.

Two types of logical channels are:

The traffic channels used to transport speech and data information.

The control channels used for network management messages and some

channel maintenance tasks.

Channel Structure

a) Traffic Channel (TCH)

Full-rate traffic channels (TCH/F) are defined using a group of 26 TDMA frames called a

26-Multiframe. The 26-Multiframe lasts consequently 120 Ms. In this 26-Multiframe

structure, the traffic channels for the downlink and uplink is separated by 3 bursts. As a

consequence, the mobiles will not need to transmit and receive at the same time which

simplifies considerably the electronics of the system.

The frames that form the 26-Multiframe structure have different functions:

24 frames are reserved to traffic.

1 frame is used for the Slow Associated Control Channel (SACCH).

The last frame is unused. This idle frame allows the mobile station to perform

other functions, such as measuring the signal strength of neighbouring cells.

Half-rate traffic channels (TCH/H), which double the capacity of the system, are also

grouped in a 26-Multiframe but the internal structure is different.

Once call set-up procedures have been completed on the control physical channel, the MS

tunes to a traffic physical channel. It uses the Traffic Channel (TCH) logical channel

There are two types of TCH:

Full rate (TCH): transmits full rate speech (13 kbits/s). A full rate TCH

occupies one physical channel.

Half rate (TCH/2): transmits half rate speech (5.6 kbits/s). Two half rate

TCHs can share one physical channel, thus doubling the capacity of a cell.

Traffic Channels (TCH) carry either speech or data. There are two types of traffic

channels: FULL RATE and HALF RATE. TCH can be located in any time slot on any

frequency defined in the cell, except for the first time slot (TS0) on the first carrier (C0). )

The full-rate traffic channel (TCH) handles encoded speech or data. The TCH

information is transmitted at a bit rate of 33.8 kbps. With a half-rate channel, a mobile

station will only use every second time slot (every other one is idle). As a result, two

mobile stations will be able to use the same physical channel for calls leading to a

doubling of the capacity on the channel.

b) Control Channels

According to their functions, four different classes of control channels are defined:

Broadcast channels.

Common control channels.

Dedicated control channels.

Associated control channels.

1. Broadcast Channels (BCH)

The BCH channels are used, by the base station, to provide the mobile station with the

sufficient information it needs to synchronize with the network. Three different types of

BCHs can be distinguished:

The Broadcast Control Channel (BCCH), which gives to the mobile station the

parameters needed in order to identify and access the network

The Synchronization Channel (SCH), which gives to the mobile station the

training sequence needed in order to demodulate the information transmitted by

the base station

The Frequency-Correction Channel (FCCH), which supplies the mobile station

with the frequency reference of the system in order to synchronize it with the

network

2. Common Control Channel

The CCCH channels help to establish the calls from the mobile station or the network.

Three different types of CCCH can be defined:

The Paging Channel (PCH). It is used to alert the mobile station of an incoming

cal

The Random Access Channel (RACH), which is used by the mobile station to

request access to the network

The Access Grant Channel (AGCH). It is used, by the base station, to inform the

mobile station about which channel it should use. This channel is the answer of a

base station to a RACH from the mobile station

3. Dedicated Control Channels (DCCH)

The DCCH channels are used for message exchange between several mobiles or a mobile

and the network. Two different types of DCCH can be defined:

The Standalone Dedicated Control Channel (SDCCH), which is used in order to

exchange signalling information in the downlink and uplink directions.

The Slow Associated Control Channel (SACCH). It is used for channel

maintenance and channel control.

  4. Associated Control Channel

The Fast Associated Control Channels (FACCH) replaces all or part of a traffic channel

when urgent signalling information must be transmitted. The FACCH channels carry the

same information as the SDCCH channels

III.6 Basic Traffic Cases

One of the most important tasks in mobile telephony system, is to continuously keep

track of where mobile stations are located. One primary function of MSC and VLR is to

store information, such as location area, about different mobile stations.

It is the responsibility of mobile station to always inform the network about changes in its

location and it must also continuously verify, that its is tuned to the strongest frequency.

Key Terms

a) Idle Mode: The mobile station is ON but not in conversation.

b) Active Mode: The mobile station is ON and in conversation.

c) Detached: The mobile station is switched OFF.

d) Roaming: When the mobile station moves around the network it is referred to as

roaming.

e) Handover: The process in which a call is passed from one cell to another.

f) Registration: The mobile station roaming around the network must inform the

network when it enters a new location area.

g) Paging: a message broadcasted by the MSC/VLR to inform the mobile station

about an incoming call.

Registration and Roaming

Mobile stations are constantly moving around in cellular network. This action of moving

around and changing the connection over the air interface is called roaming. Each time

mobile station changes Location Area (LA) it must inform the system of its new location.

This process is called registration (or location updating). Roaming and registration are

always performed in IDLE mode.

In order to choose the best radio base station, the mobile station continuously measures

the signal strength on frequencies belonging to each of the surrounding cells. When the

signal strength in the current cell becomes weaker than the signal strength in the

surrounding cells, the mobile station tunes to new base station with better signal strength.

a) Call to a Mobile Station

The difference between making a call to a mobile subscriber and a PSTN network

subscriber is that the mobile subscriber location is unknown. Therefore, the mobile

station must be paged before a connection can be made. The steps in a call setup

procedure from a PSTN subscriber to mobile station are listed below:

1) The PSTN subscriber dials the mobile subscriber’s number. The GMSC receives

the call.

2) The GMSC queries the HLR for the information needed to route the call to the

serving MSC/VLR.

3) The GMSC routes the call to MSC.

4) MSC checks VLR for the location area of the mobile station.

5) MSC contacts the mobile station via BSC and BTS by sending a page request.

6) The mobile station responds.

7) BSC selects a traffic channel and then orders the mobile station to tune to this

traffic channel. The mobile station generates a ringing signal and when the

subscriber answers the speech connection is established.

b) Call from a Mobile Station

When a mobile station wishes to establish a speech call, the following steps are

performed:

1) Mobile subscriber dials the number.

2) MSC/VLR receives a message requesting access.

3) MSC/VLR checks if the mobile station is authorised to access the network. If so,

mobile station is activated, or ON.

4) The dialled number is analysed by MSC/VLR, which in turn initiates a call setup

to the PSTN network.

5) MSC/VLR asks BSC to allocate a free traffic channel. This information is

forwarded to BTS and the mobile station.

6) The person receiving the call answers and a connection is established.

III.7 Radio Base Station (RBS)

The RBS handles the radio interface to the mobile station. One RBS can serve 1, 2 or

3 cells. A group of RBSs is controlled by 1 BSC. Ericsson has 2 base station families,

and they are RBS 2000 and RBS 200.

III.7.1 RBS 2202:

The RBS 2202 is a member of the RBS 2000 family and is used in indoor applications

with up to six transceivers. It can be configured for omni cells or multi-cells up to three-

sector cells.

Multicabinet configurations with two cabinets and up to 12 transceivers are also

supported. The RBS 2202 can be installed in any indoor environment. It can coexist in a

network with Ericsson’s RBS 200 series of base stations. It can also easily replace the

indoor cabinet models RBS 200 and RBS 205. RBS 2202 uses the same replaceable units

as all RBSs in the RBS 2000 Macro family. Should a hardware failure make a service

visit necessary, the unit can be easily replaced. RBS 2202 supports all the standard

features of the RBS 2000 family, such as:

Frequency Hopping

Receiver Diversity

Duplex Filters

Dynamic Power Regulation

Discontinuous Transmission/Reception

RBS 2202 is designed to apply to the most common voltage systems. In order to reduce

the cabinet size, all required transmission equipment and backup battery must be housed

outside the RBS 2202 cabinet. The RBS 2202 cabinet contains the radio equipment,

power supply and the climate equipment (fans). RBS 2202 is designed to fulfill

applicable parts of the GSM and the JTC standards.

Product Architecture:

The RBS 2202 cabinet, see the figure above, consists of the radio cabinet mounted on a

base frame. On top of the cabinet it is possible to mount a cowl. The radio cabinet

contains a number of units. These are all easily accessible from the front of the cabinet.

The base frame is used as a mounting base. It is mounted on the floor in order to hold the

radio cabinet in place.

The connection field, see Figure above, is located on top of the radio cabinet and includes

cable entries for antenna feeders (plates A, D, H and J), transmission cables (plate C) and

power supply (plate B).

In between plate B and C there is a +24 V DC power filter for connection of +24 V DC

power supply voltage or battery backup (when using AC mains supply).

The top cowl covers the connection field and contributes to a clean cabinet look.

a) Climate System

The climate system includes fans and air filter for cooling.

b) Combining and Distribution Unit (CDU)

The Combining and Distribution Unit (CDU) is the interface between Transceivers

(TRUs) and the antenna system. The CDU allows several TRUs to share antennas.

c) Distribution Switch Unit (DXU)

The Distribution Switch Unit (DXU) is the central control unit of the RBS. There is one

DXU per RBS. In multi cabinet configurations the DXU is located in the Master Cabinet

only.

d) Energy Control Unit (ECU)

The Energy Control Unit (ECU) controls and supervises the power equipment (PSU,

BFU, battery, AC Connection Unit) and climate equipment (fans, heater, cooler and heat

exchanger). The ECU observes alarm signals from power and climate system. The

purpose of the ECU is to protect equipment within the RBS from conditions that could

reduce lifetime and reliability. The ECU protects the equipment during power failure

conditions and cold-start up.

e) Internal Distribution Module (IDM)

The IDM handles the distribution and fusing of system voltage (+24V DC).

f) Power Supply Unit (PSU)

The PSU rectifies the AC power supply voltage to the regulated DC voltage.

g) Transceiver Unit (TRU)

The Transceiver Unit (TRU) is a transmitter/receiver and signal processing unit which

transmits and receives the radio frequency signals that are passed to and from the mobile

station. The TRU has one transmit antenna terminal and two receive terminals.

III.8 Integration of Base Station System (BSS)

When a new site is to be installed, firstly the right place for the site is planned by the

planning department .It includes right height, TX and Rx frequency of the microwave

antenna. The site is installed mainly on top of the building so that the total height may be

achieved by subtracting the height of the building from the total height from where the

antenna is to be installed i.e. if we have planned to mount an antenna at a height of 30

mts and the height of the building selected is 18 mts ,so we have to built an tower of

(30mts -18mts) 12 mts .

+MainsPowerPanel

DCPowerSupplyUnit

BatteryBackup

BTS

antenna

BTS Cabin/Shelter/Room

AirCon

CDU

TRU

DXU

A site mainly consists of following:

Shelter

Dg

Tower (including antenna)

Shelter

For the shelter we use four cemented base which are raised from ground to a height

approx. 11/2 feet two metal rails run over this base the shelter is mounted over this by

metal nails the Back side of the shelter has an AC exhaust fans mounted over by two

metal nails . As the shelter is at a height of 11/2 feet so we use 3 to 4 stairs for getting into

the shelter conveniently.

Diesel Generator

It is one of the important components used in a site. It is used in case of power

breakdown, in that case it starts automatically and when the mains are ok, it stops

automatically .the specifications of the Dg are:

AC generator: - 50 Hz, 1500 RPM, 240 V, 15 KVA.

Tower

For constructing the tower we firstly construct a concrete square wall of 3 -4 feet. The

thickness is such that it can withhold the weight of the antenna. It is painted by orange

and white colour as it the standard for any antenna using microwave frequency. The two

antennas i.e. the GSM and the microwave antenna is installed on top of the tower using

moulds. The jumper cables are connected from top of B.T.S and then connected to the

feeder cable which is routed through the cable tray on to the top of the tower then further

connected by the jumper to the antenna.

III.9 Supplementary Services

GSM supports a comprehensive set of supplementary services that can complement and

support both telephony and data services. Supplementary services are defined by GSM

and are characterized as revenue-generating features. A partial listing of supplementary

services follows.

Call Forwarding: This service gives the subscriber the ability to forward incoming calls

to another number if the called mobile unit is not reachable, if it is busy, if there is no

reply, or if call forwarding is allowed unconditionally.

Barring of Outgoing Calls: This service makes it possible for a mobile subscriber to

prevent all outgoing calls.

Barring of Incoming Calls: This function allows the subscriber to prevent incoming

calls. The following two conditions for incoming call barring exists: barring of all

incoming calls and barring of incoming calls when roaming outside the home PLMN.

Advice of Charge (AOC): The AOC service provides the mobile subscriber with an

estimate of the call charges. There are two types of AOC information: one that provides

the subscriber with an estimate of the bill and one that can be used for immediate

charging purposes. AOC for data calls is provided on the basis of time measurements.

Call Hold: This service enables the subscriber to interrupt an ongoing call and then

subsequently re-establish the call. The call hold service is only applicable to normal

telephony.

Call Waiting: This service enables the mobile subscriber to be notified of an incoming

call during a conversation. The subscriber can answer, reject, or ignore the incoming call.

Call waiting is applicable to all GSM telecommunications services using a circuit-

switched connection.

Multiparty Service: The multiparty service enables a mobile subscriber to establish a

multiparty conversation-that is, a simultaneous conversation between three and six

subscribers. This service is only applicable to normal telephony.

GPRS (General Packet Radio Service): The General Packet Radio Service (GPRS) is a

new no voice value added service that allows Mobile Phones to be used for sending and

receiving data over an Internet Protocol (IP)-based network. GPRS as such is a data

bearer that enables wireless access to data networks like internet, enabling users to access

E-mail and other internet applications using mobile phones. With GPRS we can enjoy a

continuous wireless connection to data networks (internet) and access our favorite

websites, entertainment services and other web applications. GPRS uses a packet-mode

technique to transfer high-speed and low-speed data and signaling in an efficient manner.

GPRS does not mandate changes to an installed MSC base. The radio interface resources

can be shared dynamically between speech and data services as a function of service load

and operator preference.

HARDWARE ARCHITECTURE

The hardware consists of a number of RUs and buses.

LOCAL BUSES

The local bus offers internal communication between the DXU, TRUs and ECU.

Examples of information sent on this bus are TRX Signaling, speech and data.

TIMING BUS

The timing bus carriers air timing information from the DXU to the TRUs.

X- BUS

The X – bus carrier’s speech/data on a time slot basis between the TRUs. This is used for

base band frequency hopping.

CDU BUS

The CDU bus connects the CDU to the TRUs and facilitates interface and O&M

functions. It transfers alarms and RU specific information between the CDU and TRU.

POWER COMMUNICATION LOOP

The power communication loop consists of optical fibre cables and carriers control and

supervision information between the ECU, PSUs and the BFU.

Transmission Interface

There are three alternatives to choose from concerning the "transport network

interface":

T1 1.5 Mbit/s, 100, with internal synchronization

T1 1.5 Mbit/s, 100, with PCM synchronization

E1 2 Mbit/s, 75, with PCM synchronization

E1 2 Mbit/s, 120, with PCM synchronization

External Connections

All external connectors are located on top of the cabinet. External interfaces of RBS 2202

are indicated in the figure below.

DESCRIPTION OF UNITS

DISTRIBUTION SWITCH UNIT (DXU)

The Distribution Switch Unit (DXU) is the RBS central control unit. There is one DXU

per RBS. It provides a system interface by cross connecting either a 2 Mbps or 1.5 Mbps

transport network and individual slots to their associated transceivers.

DXU

This unit consists of functions common to one RBS. These include:

Interface to BSC

Distribution switch

Timing unit

Local bus interface

Concentration of the control links (LAPD signalling) to the BSC

Collection of up to 16 external alarms

Operation and Maintenance Terminal (OMT) interface

Keeps the database with the cabinet configuration

With these functions the DXU establishes the connection to the BSC (the PCM link) and

cross connects individual time slots to certain transceivers.

A timing reference for the RBS is generated by extracting the synchronization

information from the PCM link or from an internal source.

In addition, for easy maintenance of inventory, there is a database containing information

about installed hardware. This Installation Data Base (IDB) contains each RU identity,

physical position, and related configuration parameters.

The BSC controls the configuration of the DXU.

IV. WORK PROFILEIV. WORK PROFILE

My training area was performance monitoring i.e. the network planning department.

Airtel Planning Section controls Punjab, Haryana, Himachal Pradesh and Jammu

Kashmir. One of the key functions of Airtel Planning Section is to analyse the

performance of these networks on daily and weekly.

I was mainly associated with analysis of performance reports and studying the parameters

associated with these reports and their formulas for Punjab Network. For this the study of

GSM was essential.

IV.1 Nature of the Work Done

IV.1.1 REPORT GENERATION

Report generation is a key function of Airtel Planning Section for Analysis of Network

Performance. Reports are generated from Business Objects on daily and weekly basis.

Report generation includes refreshing of data from Business Objects manually then

manipulating it as required. Minimization of Work load includes automatically saving the

required data in text files whenever data is refreshed from Business Objects manually and

executing Macros in Microsoft Excel which will save the data in Microsoft Excel in

required format.

IV.1.2 TREND ANALYSIS

The trend analysis is done so that the sudden changes can be easily found out as it is very

difficult to analyse the data. For the trend analysis, PAT and BSC analysis was made,

which gave the graphical presentation of the data. PAT provides the cell wise graphical

trend and BSC Analysis presents a BSC’s wise trend. This saves the time and the changes

can be easily located. If there is sudden change then the analysis is done on the basis of

data. The data is averaged over the period of specific days and is compared to the present

data thus the cells can be found out which are causing the change in the normal trend.

Now once these cells are identified further process of fault localization is done with the

help of CNA (Cellular Network Administration) and CHA (Command Handling

Application). CHA and CNA are a part of OSS applications.

By analysing these reports the optimization is carried out. These reports identifies the top

cells that are contributing to increase or decrease of values of parameters, that are

analysed , thus by monitoring these cells the problem can be found and the network

performance can be improved.

The Punjab Network is divided into 18 BSCs and 8 MSCs.

The 18 BSCs are as followed:

BSC1

JALBSC1

PBBSC2

PBBSC3

R_ASR

R_ASR2

R_BAT

R_GDPR

R_HSPR

R_JAL

R_KKPR

R_LUD

R_LUD2

R_PAT

R_PHAG

R_PWL

R_SNGR

R_VAR

The 8 MSCs are as follows:

MSC1

MSC2

MSC3

MSC5

JALMSC1

PBGMSC1

PBGMSC2

PBGMSC3

Out of the above mentioned MSCs three are GMSCs- PBGMSC1, PBGMSC2 and

PBGMSC3.

IV.2 Software Used

IV.2.1BUSINESS OBJECTS 5.0: The reports that are used to analyse the network are

generated using Business objects software. It is a front end which presents the data from

the OSS server database. Business Objects is an integrated query, reporting and analysis

solution for business professionals to access the data from databases, directly from

desktop and present and analyses this information in a Business Objects.

IV.3 Reports used for Performance Analysis

The performance is monitored on:

Daily basis

Weekly basis

The reports that are generated daily are:

BSC Drop

BSC Analysis

Cell Analysis

Network Performance (NWP)

Network Comparison

Idle Channel Measurements (ICM)

Bouncing Busy Hour (BBH)

Average

BSC Hourly

Showcase

The weekly performance is analyzed by:

Expansion Report

Micro

IV.4 Basic Steps for Generating a Report

1. Run Business Objects from the shortcut created on the desktop.

2. Select the open option from the File menu.

3. The appropriate report is then opened from the required folder.

4. The opened report is then refreshed using refresh data button.

5. All the values are manually entered at each user prompt. If data is to be retrieved for

day wise, then resolution should be Day, if week wise then the resolution should be week

and if hourly wise then enter resolution hour. Enter Dates for “from” and “to” from where

data is to be retrieved.

The value button can guide the user about all the valid values that can be entered in these

prompts.

Click OK and data will be retrieved on the basis of entered values from OSS Server.

6. The refreshed report is then copied using ‘Copy All’ command from the Edit menu.

7. The raw Excel file is then opened, and the content of the appropriate sheet is replaced

by the refreshed data.

8. All the above steps are repeated for all the above mentioned reports.

IV.5 Details of the Reports Generated on Daily Basis

IV.5.1 BSC Drop

BSC Drop Report is generated BSC wise to analyse network of Punjab. This report gives

information for following parts.

CNDROP

TNDROP

Drop 1

Drop 3

The parameters used in this report are as follows:

Parameter DescriptionCNDROP This parameter gives the total number of dropped calls on

SDCCH.

TNDROP This parameter gives the total number of dropped calls on TCH.

DROP 1 This parameter gives the percentage of SDCCH dropped calls with respect to total number of call attempts.

DROP 3 This parameter gives the percentage of dropped calls on TCH with respect to successful call attempts.

The BSC Drop report gives us Drop1 & Drop3 for NBH hour.

NBH hour is the busiest hour of the day for a particular network.

/

IV.5.2 BSC Analysis

This report gives us reasons for Drop1& Drop3 BSC wise for Punjab network for NBH.

The parameters used in this report are as follows:

a) Drop1

Parameters Description

SDCCH Drop This parameter gives the percentage of SDCCH dropped calls with respect to total number of call attempts.

Total No. of Dropped SDCCH Connections

This parameter gives the total number of dropped calls on SDCCH.

SDCCH Erlang Minutes per Drop

It tells what was the intensity of traffic over drop calls

Handover Lost of all SDCCH Drop

It gives the percentage of calls that were not assigned either serving or target cell (i.e. call was dropped) with respect to total call attempts.

SDCCH Drop due to TCH Congestion

This parameter gives the total number of dropped calls due to congestion on TCH .

Drop Reason, Low SS It gives the percentage of dropped calls due to low signal strength of the total number of dropped calls

Drop Reason, Bad Quality

It gives the percentage of dropped calls due to bad quality of the total number of dropped calls

Drop Reason, Excessive TA

It gives the percentage of dropped calls due to excessive timing advance of the total number of dropped calls

Drop Reason, Other ` It gives the percentage of dropped calls due to other reasons (e.g. hardware failure etc.) of the total number of dropped calls.

b) Drop3

Parameters DescriptionTCH Drop This parameter gives the percentage of dropped calls on

TCH with respect to successful call attempts.

TCH Traffic (Erlang)

Total No. of Dropped TCH Connections

This parameter gives the total number of dropped calls on TCH.

TCH Erlang Minutes per Drop

It tells how much traffic is being offered over each drop.

Drop Reason, Low SS It gives the percentage of dropped calls due to low signal strength of the total number of dropped calls.

Drop Reason, Bad Quality

It gives the percentage of dropped calls due to bad quality of the total number of dropped calls

Drop Reason, Suddenly Lost Connections

It gives the percentage of dropped calls due to the sudden loss of connection.

Drop Reason, Excessive TA

It gives the percentage of dropped calls due to excessive timing advance of the total number of dropped calls

Drop Reason, Other It gives the percentage of dropped calls due to other reasons (e.g. hardware failure etc.) of the total number of dropped calls.

IV.5.3 Cell Analysis

This report gives us reasons for Drop1& Drop3 Cell wise for Punjab network for NBH.

The reasons for Drop1 and Drop3 are same as that of BSC analysis.

IV.5.4 Network Performance

It consists of sheet NW Performance.

a) NW Performance

It consist of 18 BSCs, no. of sites in each BSC, no. of cells and no. of TRXs.It gives us

the total traffic in each BSC. It also shows us the busiest hour for each BSC and gives us

the traffic for each BSC in those hours respectively.

It also gives us the following parameters for a particular day, the day before and the same

day the previous week:

Parameter DescriptionAverage Traffic It gives us the average traffic for 24 hours

Traffic in NBH It gives us the traffic in the Network busy hour.

Cell BBH Traffic (Erlangs)

Traffic in each cell for its BBH hour.

NBH % Drop 3 This parameter gives the percentage of dropped calls on TCH with respect to successful call attempts.

NBH % Drop 1 This parameter gives the percentage of SDCCH dropped calls with respect to total number of call attempts.

TCH Congestion Time (SEC)

It tells the time in seconds for which the TCH channel is not allocated for an attempt i.e. the time for which there is non idle channel is present for an allocation attempt for TCH.

SDCCH Congestion Time (SEC)

It tells the time in seconds for which the SDCCH channel is not allocated for an attempt i.e. the time for which there is non idle channel is present for an allocation attempt SDCCH. .

No. of Cells with blocking (2%-5%) and (>5%) Cell BBH

No. of cells blocked.

%TCH Congestion (TCH Cong SECS)

It gives the TCH congestion with respect to total number of TCH allocation attempts (including call setup after directed retry)

%SDCCH Congestion (SD Cong SECS)

It gives the SDCCH congestion with respect to total number of SDCCH seizure attempts.

Handover Success Rate

It tells the percentage of successful attempts to the total attempts for handover.

SDCCH Assignment Success Rate

It gives the percentage of successful SDCCH call attempts with respect to the total attempts for SDCCH

IV.5.5 Bouncing Busy Hour(BBH)

BBH is the busiest hour of a particular BSC. It may vary from BSC to BSC.

The parameters involved are:

Parameter DescriptionTrim cell It gives the name of the cell

BSC It gives the name of BSC in which the cell is located.

BBH Erlang It gives the amount of traffic in a particular cell in the bouncing busy hour.

TCH Congestion It gives the TCH congestion with respect to total number of TCH allocation attempts (including call setup after directed retry)

Drop1 This parameter gives the percentage of dropped calls on SDCCH with respect to total number of call attempts.

Drop3 This parameter gives the percentage of dropped calls with respect to the successful calls on TCH.

TCH Assignment Success Rate

It gives the percentage of successful TCH call attempts with respect to the total attempts for TCH.

Handover Success Rate

It gives the percentage of total number of successful handover attempts to the total number of attempts for handover.

4.5.6 AverageIt gives us the average value of traffic for each cell for 24 hours. The parameters involved

in this report are same as in BBH except for bbherl we have avgerl.

4.5.7 BSC Hourly

This report consists of Drop1, Drop3, CNDROP and TNDROP for last four days for each

hour for whole Punjab Network

V. SV. SOFTWAREOFTWARE’’SS U USEDSED

1) Business Object 5.0

2) Citrix

3) MapInfo Professional 6.0

V.1 Business Object 5.0

Business Objects is an integrated query, reporting and analysis solution for business

professionals to access the data from databases, directly from desktop and present and

analyze this information in a Business Objects. Business Objects is used for report

generation.

V.1.1 Report Generation

Report generation is a key function of Airtel Planning Section for Analysis of Network

Performance. Reports are generated from Business Objects on daily and weekly basis.

Report generation includes refreshing of data from Business Objects manually then

manipulating it as required, as this require a lot of time so the visual basic scripts were

written to minimize the work load. Minimization of Work load includes automatically

saving the required data in text files whenever data is refreshed from Business Objects

manually and executing Macros in Microsoft Excel which will save the data in Microsoft

Excel in required format. This eliminates user participation and manual operations of the

user. Minimization tools are used to minimize work load by eliminating most of overhead

from user. Repeatedly performed tasks can be removed by a series of commands and

functions that are stored in a Microsoft Visual Basic module/Script.

V.1.2 How to Generate a New Report

1. Select an option for the report layout, and then click Begin. The Specify Data Access

dialog box will appears and select Personal data files.

2. Next step is to select universe.

Universe: Semantic layer between user and a database, consisting of classes and object.

The objects in the universe map to data in the database, and enable you to build queries

on the universe. A universe represents a complete set of data and data operations.

3. Drag the parameter and counters that you want in the report as shown. You can view

SQL statements for the report you have crated by clicking SQL icon on the top.

Following interface will be shown and drag the counters and parameters which you wants

to view from left most window to top of right side window and apply condition to the

values of same parameters in lower side window.

4. Run the Report by clicking on Run and run the report for the desired time interval

5. Click the report title and give the title to the reports and add other fields in the report.

In this way the reports are generated to analyse the network, this was the core area of my

training.

V.2 OSS Citrix Server Client

Citrix is User Emulation Software, which connects a remote user to the OSS server.

Run Citrix from the shortcut created on the desktop.

V.2.1 Command Handling Terminal (CHA):

CHA is a tool available in Citrix which helps us to check the present status of the cells by

executing various commands.

1) The appropriate BSC is selected from the network elements

2) Then the required command is run.

we use Citrix. For TRU Addition and check the values of HLR .

The cells are defined in two nodes APG and IOG.

a) TRU ADDITION:

b) HLR VALUES:

V.3 MAPINFO

Map Info Professional 6.0 is software where all sites are displayed in the form of map. It

displays all sites in the Punjab Network along with their names, state highways, railways

and state boundaries.

V.3.1 Updating of MapInfo

As new sites are added time to time so the map is updated is regularly after a month.

The map is updated as follows:

1) The latest excel sheet containing all the sites is divided into four sheets each

containing 1000 cells.

2) Go to Map Info Professional 6.0 icon and open a table. Now open the first sheet from

the saved four sheets.

3) Now run the map basic program from file menu.

4) After this run create base station from query menu.

After running creates base station the map containing the sites in the given sheet is

formed.

5) The same process is repeated for the remaining three sheets. In the end all four sheets

are added up to form a final map containing all the sites.

And finally from the layer control icon in the tool bar highways, railways etc. are added.

Map info is used to locate a site, to measure distance between two sites, to find the

appropriate neighbour of a site.

VII. GVII. GAINSAINS F FROMROM T TRAININGRAINING

With the completion of this training I am now aware of the technical setup of the GSM Network. I have worked for six complete months on the software used in GSM. I was the part of one of the most happening and demanding field of communication i.e. the Global System for Mobile and spending six months into it really proved very useful to me and I have gained following things out of it:

I got an overview of the actual working of GSM network

I worked on the software which helped me in being more familiar to the practical tasks which I am supposed to do in the long run.

I learned inter department coordination and the qualities such as team work.

Training helped me increasing my working skills & stamina and also showed me the atmosphere which we have to join after completion of the degree program.

Doing all these I have acquired a lot of knowledge about the working of my department (Network Planning).Finally the main advantage of this training was that I have now opened doors for my easy entry to the giant mobile telecom industry.

VIII. BVIII. BIBLIOGRAPHYIBLIOGRAPHY

www.airtelindia.com

www.ericsson.com

Active Library Explorer (ALEX)

Ericsson system manuals

www.gsmworld.com

PROJECT UNDERTAKEN DURING INDUSTRIAL TRAINING

VI. Projects Which Were Undertaken During Industrial Training:-

1. TRU ADDITION

2. WORK PROFILE

TRU ADDITION

TRU ADDITION: It is a transmitter and signal unit which transmits and

receives the radio frequency signals.

The main functions of TRU ADDITION are:

1. Radio transmitting.

2. Radio Receiving.

3. Air interface signal processing.

4. TRX mangeme.

TRU IS DIVIDED INTO THREE SECTIONS:

1. Transceiver Unit Digital. (TRUD)

2. Transmitter Block. (TX-Block)

3. Receiver Block. (RX-Block)

1. TRUD : It serves as the TRX controller. It communicates with other RBS

components via the Local Bus, CDU Bus, Timing Bus and Bus. The digital block

performs uplink and downlink digital signal processing such as channel coding,

interleaving, ciphering, brust formatting and equalization.

2. TX-Block: It performs the downlink signal modulation and amplification.

3. RX-Block: It performs the uplink signal demodulation and then routes the

demodulated signal to the TRUD part.

In TRU Addition I worked on CITRIX which is a User Emulation Software, which

connects a remote user to the OSS server.

COMMAND HANDLING TERMINAL (CHA):

Tool available in CITRIX which helps us to check the present status of the cells by

executing various commands.

First the connection with the appropriate BSC is made by selecting BSC from

the network elements .

TRU ADDITION COMMAND LIST

1) RXTCP:MOTY=RXOTG,CELL=<CELL NAME>;

2)RXCDP:MO=RXOTG-<TG NUMBRE>;

3) SUN TOOLS >> TERMINAL ( RUN SCRIPT)

./TRU_ADDTG NO.SLOT NO.CELL NAME.BSC NO.

4) RLCHP:CELL=<CELL NAME>;

5) RLCFI:CELL= <CELL NAME>,DCHNO= Freq & Freq&…….

OR

IF MAIO IS DEFINED:---

RLCHC:CELL= <CELL NAME>,MAIO=Maio&Maio&........,Chgr=1;

6) RXESI:MO=RXOTRX-<TG NUMBER>-<SLOT NUMBER>,SUBORD;

7) RXBLE:MO=RXOTRX-<TGNUMBER>-<SLOT NUMBER>,SUBORD;

8) RLSLP:CELL=<CELLNAME>;

9) RXCDP:MO=RXOTG-<TG NUMBER>;

10) RLCFP:CELL=<CELL NAME>; ( TO CHEK THE FREQ…..) 11) RLBDP:CELL=<CELL NAME>; ( TO CHEK THE BDP……)

12) RLBDC: CELL= <CELL NAME>, NUMREQBPC=32; {#HINT 4(TRU)*8=32} 13) RXMSP:MO=RXOTG-<TG NUMBER>,SUBORD; ( IN THIS STATE BLA ( OPER 000 ( OPER 000 ( OPER 000

14) RLCHC:CELL=<CELL NAME>, HOP=ON,CHGR=1; (FOR HOP)

15) RXMOP:MO=RXOTRX-TG NO-1&&-11; For D cell

16) RLSLC:CELL=<CELL NAME>,CHTYPE=TCH,LVA=29; (LVA… VALUE)

WORK PROFILEWORK PROFILE

My training area was performance monitoring i.e. the network planning department.

Airtel Planning Section controls Punjab, Haryana, Himachal Pradesh and Jammu

Kashmir. One of the key functions of Airtel Planning Section is to analyse the

performance of these networks on daily and weekly.

I was mainly associated with analysis of performance reports and studying the parameters

associated with these reports and their formulas for Punjab Network. For this the study of

GSM was essential.

Nature of the Work Done

1 REPORT GENERATION

Report generation is a key function of Airtel Planning Section for Analysis of Network

Performance. Reports are generated from Business Objects on daily and weekly basis.

Report generation includes refreshing of data from Business Objects manually then

manipulating it as required. Minimization of Work load includes automatically saving the

required data in text files whenever data is refreshed from Business Objects manually and

executing Macros in Microsoft Excel which will save the data in Microsoft Excel in

required format.

2 TREND ANALYSIS

The trend analysis is done so that the sudden changes can be easily found out as it is very

difficult to analyse the data. For the trend analysis, PAT and BSC analysis was made,

which gave the graphical presentation of the data. PAT provides the cell wise graphical

trend and BSC Analysis presents a BSC’s wise trend. This saves the time and the changes

can be easily located. If there is sudden change then the analysis is done on the basis of

data. The data is averaged over the period of specific days and is compared to the present

data thus the cells can be found out which are causing the change in the normal trend.

Software Used

IV.2.1BUSINESS OBJECTS 5.0: The reports that are used to analyse the network are

generated using Business objects software. It is a front end which presents the data from

the OSS server database. Business Objects is an integrated query, reporting and analysis

solution for business professionals to access the data from databases, directly from

desktop and present and analyse this information in a Business Objects.

Reports used for Performance Analysis

The performance is monitored on:

Daily basis

Weekly basis

Basic Steps for Generating a Report

1. Run Business Objects from the shortcut created on the desktop.

2. Select the open option from the File menu.

3. The appropriate report is then opened from the required folder.

4. The opened report is then refreshed using refresh data button.

5. All the values are manually entered at each user prompt. If data is to be retrieved

for day wise, then resolution should be Day, if week wise then the resolution should

be week and if hourly wise then enter resolution hour. Enter Dates for “from” and

“to” from where data is to be retrieved.

The value button can guide the user about all the valid values that can be entered in these

prompts.

Click OK and data will be retrieved on the basis of entered values from OSS Server.

6. The refreshed report is then copied using ‘Copy All’ command from the Edit

menu.

7. The raw Excel file is then opened, and the content of the appropriate sheet is

replaced by the refreshed data.

8. All the above steps are repeated for all the above mentioned reports.

TABLE OF CONTENTS

1. Company Profile 1.1 Bharti Enterprises 1.2 Nothern Region 2. Wireless Concepts 2.1 Transmission 2.2 Radio Transmission 2.3 Introduction to Analog and Digital 2.4 Advantages of using Digital 2.5 Frequency Bands 2.6 Terminology 2.7 Transmission Problems 2.8 Solutions to Transmission Problems 2.9 Analog to Digital(A/D) Conversion 2.10 Transmission Lines 2.11 Transmission Media 3. Global System for Mobile Communication 3.1 History of Cellular Mobile Radio and GSM 3.2 Cellular system 3.3 The Transition from Analog to Digital Technology 3.4 The GSM Network 3.5 The GSM Radio Interface 3.6 Basis Traffic Cases 3.7 Radio Base Station (RBS) 3.8 Integration of Base Station System (BSS) 3.9 Supplementary Services 4. Work Profile 4.1 Nature of the Work Done 4.2 Software Used 4.3 Reports Used for Performance Analysis 4.4 Basic Steps for Generating a Report 4.5 Details of the Reports Generated on Daily Basis

5. Software’s Used 5.1 Business Objects 5.0 5.2 OSS Citrix Server Client 5.3 MapInfo

6. Projects undertaken 6.1 TRU addition.6.2 Work Profile

7. Gains from Training 8. Bibliography