PROJECT REPORT

(Project semester July-December 2011)

RELIANCE GSM MAINTAINENCE

Submitted by:

Malkeet Singh

Registration no.10804149

Program 159

Section E28T7

Under the guidance of Mr. Manik Bhardwaj (Cluster Lead)

DEPARTMENT OF ECE

Lovely School of TECHNOLOGY AND SCIENCES

Lovely Professional University, Phagwara

DECLARATION

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I hereby declare that the project work entitled “RELIANCE GSM MAINTAINENCE” is an authentic record of my own work carried out at ALCATEL LUCENT MANAGED SOLUTIONS PVT. LTD. as requirement of Industry Internship project for the award of degree of B.Tech, Lovely Professional University, Phagwara, under the guidance of Mr. Manik Bhardwaj during July-December, 2011.

(_________)

MALKEET SINGH

Reg. No.10804149

Date: 09/09/2011

Certified that above statement made by the student is correct to the best of our knowledge and belief.

_________________ _______________

Faculty Coordinator Industry Coordinator

ACKNOWLEDGEMENT

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The work on this project report has been an exciting, sometimes challenging, but always interesting experience .It has been made possible by many other people, who have supported me.

I am very grateful to my institute’s faculty members Mr. MANIK BHARDWAJ who has given me the chance to participate in several interesting field projects and various seminars. They have supported me with encouragement and many fruitful discussions .I would also like to express my sincere thank him for his invaluable experience and advice.

Finally, I wish to thank my parents for their continuous support and encouragement.

TABLE OF CONTENTS

INTRODUCTION TO COMPANY (Alcatel Lucent)

INTRODUCTION TO ENGINEERING DEPARTMENT

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JOB RESPONSIBILITIES OF ENGINEERING EMPLOYEES PLANNING AND IMPLEMENTATION ENGINEERING FRONT DESK NSS OMC-R BSS MAINTENANCE NETWORK PERFORMANCE AND OPTIMISATION RF PLANNING AND OPTIMISATION

STUDY OF BSC Network availability Necessity Risk Factors Routine maintenance Alarms Types of Alarms

STUDY OF BTS CARDS

HUAWEI BTS Hardware structure COMMON SUBSYSTEM DOUBLE TRANSCEIVER SUBSYSTEM (DTRU) RF SUBSYSTEM (DAFU: Antenna front -end unit) VARIOUS CARDS ARE

WORK PROFILE

MAJOR PROJECTS DONE TILL NOW

Neighboring (GSM & CDMA SITES) Planning Of New BTS in Punjab Addition of TRX in BTS Generation of Trouble Ticket

FUTURE WORK

1. INTRODUCTION TO COMPANY (Alcatel Lucent)

Alcatel-Lucent is a global telecommunications corporation. It provides telecommunications solutions to service providers, enterprises and governments around the world, enabling these customers to deliver voice, data and video services. The company focuses on fixed, mobile, and converged broadband networking hardware, IP technologies, software, and services. It leverages

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the technical and scientific expertise of Bell Labs, one of the largest innovation and R&D houses in the communications industry. Alcatel-Lucent has operations in more than 130 countries. Its headquarter is located at Paris, France

Alcatel-Lucent was formed when Alcatel merged with Lucent Technologies on December 1, 2006. However, the company as a whole has been a part of telecommunications industry since the late 19th century.

Applications Division

Approximately half of the Application Division consists of the enterprise business and Network Applications. Services include subscriber data management, digital media, payment sorting, and customer experience management for telecoms. Content delivery networks (CDN) are becoming a increasingly large part of the Division as network traffic complexity calls for denser routers.

Network Division

Alcatel-Lucent wire line network services provides optical networking, service provider routing, and broadband access to the telecommunications industry, and other industries that require networking capabilities such as the energy and transportation industry. Wireless services emphasize growing backhaul and router businesses as companies like Verizon, AT&T, and Sprint are focused on 4G/LTE rollout.

• Applications Group - Develops software for Carriers such as digital home management and rich media applications and for Enterprises to enable deployment of applications to transform their customer service capabilities.

• Networks Group - Telecommunications products for wire line, wireless and convergent service providers.

Enterprise and Strategic Industries Group - Provides enterprises with communications solutions such as unified communications and contact centers, IP telephony, performance management software and security solutions.

Services Group - Offers professional telecommunications services to carriers that encompass the entire network lifecycle.

In India, Alcatel Lucent takes the responsibility of providing telecommunication solutions to RELIANCE COMMUNICATION (RCOM).

COMPETITION

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Company has one of the broadest portfolios of product and services offerings in the telecommunications equipment and related services market, both for the carrier and non-carrier markets. Their addressable market segment is very broad and their competitors include large companies, such as Avaya, Cisco Systems, Ericsson, Fujitsu, Huawei, ZTE and Nokia Siemens Networks (NSN). Some of the competitors, such as Ericsson, NSN and Huawei, compete across many of the product lines while others - including a number of smaller companies - compete in one segment or another. In recent years, consolidation has reduced the number of networking equipment vendors, and the list of competitors continues to change as the intensely competitive environment drives more consolidation.

The technological advancement, product and service quality, reliable on-time delivery, product cost, flexible manufacturing capacities, local field presence and long-standing customer relationships are the main factors that distinguish competitors within each of their segments in their respective markets. In today’s tight-credit environment another factor that may serve to differentiate competitors, particularly in emerging markets, is the ability and willingness to offer some form of financing.

COMPANY’S LINK

Alcatel-Lucent's revenue stands at Rs 3,500 crore. The significant revenue rise can be attributed to several factors such as main orders, smooth integration of the two entities, retaining main clients, retaining crème of the employees and introduction of a new brand that signified the two organizations flowing into each other.

During the year 2006-07, when final integration completed and a brand new look unveiled, the telecom infrastructure giant bagged some of the major coveted orders in the Indian telecom industry. The main deals grabbed recently by Alcatel-Lucent include BSNL's GSM expansion of 3 mn lines, MTNL's 2G and 3G expansion of 2 mn lines, Reliance Communications' CDMA maintenance, Tata Teleservices' hosted IP contact center solution, Bharti's transmission expansions, ICICI Bank's largest single site outsourced contact center, Reserve Bank of India's 1,000 users enterprise solution, etc. In the transmission segment, most of the deployments by Bharti Airtel and Tata Teleservices were by Alcatel-Lucent.

South Asia is the fifth largest regional unit in Alcatel-Lucent and this is significant as Asia contributed 15% of Alcatel-Lucent's global revenue in 2006. Globally, services contributed 16%, enterprises 9%, convergence 12%, wireless 32%, and wire line 31%.                                                                                                                 

Alcatel-Lucent's global market rankings: #1 in wire line, #3 in wireless, and #2 in services, are recognized in India too. Thanks to all major orders, Alcatel is the undisputed leader in many segments in India. Some of the major orders with mobile operators are in the pipeline that could foster its future as well.

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1.1 INTRODUCTION TO ENGINEERING DEPARTMENT

Engineering department of Alcatel Lucent provides 24 hours Network availability, with optimized performance, to all the customers of Reliance Communications.

This department has six sections:

1. BSS (Base Station System)2. OMC-R (Operations and Maintenance for Radio)3. EFD (Engineering Front Desk)4. NSS (Network Switching Centre)5. Planning and implementation6. Performance

BSS is involved in the maintenance of the GSM Network. It involves daily routines like Preventive Maintenance, Weather proofing, Site Expenditures, Fuel availability, Power availability, etc. These people if required also do any reconfiguration.

Operation Maintenance & Control is there for the daily/weekly/monthly maintenance and operations of the radio. It consolidates the network outages/changes. It handles alarms and notifications for the same are sent to the concerned regions. It escalate faults and monitors the overall network to ensure maximum network availability. It keeps the updated information of sites, cells, carriers and PSTNs in the network.

Engineering Front Desk is the front desk for the Engineering department. Any customer complaints or queries from any other department have to go through this for evaluation. EFD has to give feedback on customer related problems to the customer care on daily basis.

Network Switching System is involved in the maintenance of the Switch, over which all the calls of the Spice customers are routed in the Network. Operation & Maintenance of NSS equipment comprising of MSC , OMCs, VMS, SMSC & ACD. It also performs IREG testing for both national and international roaming partners and to assist IT & NRMG in post commercial scenario. It provides support to Billing and reconciliation, Performance Team and EFD in solving customer problems. It also ensures provisioning of statistics.

Planning and Implementation Department is involved in planning and implementation of sites in the most cost effective way and handing over to field maintenance staff as per procedures. It also conducts propagation tests for new planned sites and carries out advanced planning and ordering of BTS, Microwave and other associated equipment

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according to site planning and business plan. It also carries out the Drive tests of new sites.

Performance department is there to keep a check on the Network performance and to enhance the performance when required from time to time. It collects GSM statistics viz. Call statistics, interface statistics, processor utilization statistics from GSM network entities and displays them for analysis. It monitors network traffic and equipment loading and provides necessary information for network management and planning. It is involved in RF planning and optimization

1.2 JOB RESPONSIBILITIES OF ENGINEERING EMPLOYEES

PLANNING AND IMPLEMENTATION Overall responsibility of network planning and rollout as per business plans. Planning and implementation of sites in the most cost effective way and handing over to

field maintenance staff as per procedures. To conduct propagation test for new planned sites. Drive testing of new sites and submission of its report to planning group.

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Planning &

Implementation

Planning &

Implementati

on

ng & iimple

Implementati

on

Job

Responsibilities

Engineering

Front desk

Network

Switch

system

Network Maintenance

N/W

Performance

OMC-R

OMC -

R

Advance planning and ordering of BTS, Microwave and other associated equipment according to site planning and business plan

Co-ordination with sales, marketing, customer services and site acquisition & build group for smooth process of delivering new sites.

To work on network traffic statistics for trending, identification of in-fill sites and prediction of future requirements.

ENGINEERING FRONT DESK To interact with customer care and solve customer problems. To give feedback on customer related problems to the customer care on daily basis. To escalate any kind of problems/faults occurring in the network to the customer care. To analyze the problems from customer view. To escalate faults to the concerned person and track the faults.

NSS Operation & Maintenance of NSS equipment comprising of MSC, OMC-S, VMS, SMSC

& ACD. To Perform IREG testing for both national and international roaming partners and to

assist IT & NRMG in post commercial scenario. Support to Marketing in planning and implementation of new features in the network. Billing and reconciliation support. Managing POI related issues. Planning and executing system H/W & S/W upgrades. Liaison with BSNL and TEC. Providing support to Performance Team. To ensure provisioning of statistics. To support EFD in solving customer problems.

OMC-R

To handle alarms, escalate faults and overall monitoring of network to ensure maximum network availability.

Basic level co-ordination of OMC, BSS outages planned/unplanned and to ensure service availability at all the time.

To perform operation and maintenance of OMC, DXX, EMOS & other systems. To perform daily/weekly/monthly routines of OMC-R. To consolidate the network

outages/changes into weekly and monthly reports. Ensuring documentation, database integrity and backup management of all NMS systems. To keep the updated information of sites, cells, carriers and PSTNs in the network. To maintain the updated copy of DDF and microwave diagram for the whole network.

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To create database for BSCs, XCDRS, BTSs and their devices.

BSS MAINTENANCE

To ensure the maximum Network Availability & reduce downtime to minimum. To perform routine Maintenance activities on the BSC, BTS, Microwave and Backbone

Sites. To handle all alarms which are generated at any site in the area of responsibility. To handle all Power related problems in all sites. To maintain all intercity and intercity links. To implement all upgrades in the network (BSS site specific) Asset management (Tools, testers, manuals etc) To suggest any changes in the network required to enhance the coverage and

performance. To assist in any implementation activities as the case may be.

NETWORK PERFORMANCE AND OPTIMISATION To collect GSM statistics viz. Call statistics, interface statistics, processor them for

analysis. To monitor network traffic and utilization statistics from GSM network entities and

archiving them in a database and displaying equipment loading. To provide necessary information for network management and planning. To introduce new features and control network up gradation. To forecast on network growth and capacity planning. To send reports to network operations manager. To interact with EFD in solving customer problems.

RF PLANNING AND OPTIMISATION To test network performance using various testing equipment including TEMS, E74XX

from Agilent etc. Post processing of drive test data using analyzing tools like Insight and MapInfo etc. To familiarize with call classification and duration. To make test data available to performance department for analysis. To ensure correct operation of all test equipment before drive test. To ensure that drive test technicians understand responsibilities and are well trained on

respective duties. Liaison with OMC on problem areas on daily basis.

2. TECHNOLOGY RELATED TO LIVE PROJECT

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2.1 STUDY OF GSM

i. PRINCIPLE

A cellular telephone system links a mobile subscriber to the public telephone system or to another cellular system mobile subscriber. Information sent between the MS subscriber and the cellular network uses radio communication. This removes the necessity of the fixed wiring used in orthodox and conventional telephone installation.

ii. INTRODUCTION

Global System for Mobile Communications is a digital cellular standard that uses time-division (TDMA and FDMA) to carry eight simultaneous calls on the same frequency. It was developed in order to create a common European mobile telephone standard but it has been rapidly accepted worldwide. It is a digital form of communication which uses the electromagnetic spectrum to carry the data. It is a 2-way microwave transmission form of communication which has the capability to connect to PSTNs as well.

GSM is an open, non-proprietary system that is constantly evolving. One of its great strengths is the international roaming capability. This gives consumers seamless and same standardized same number contact ability in more than 159 countries. GSM satellite roaming has extended service access to areas where terrestrial coverage is not available.

GSM differs from first generation wireless systems in that it uses digital technology and time division multiple access transmission methods. Voice is digitally encoded via a unique encoder, which emulates the characteristics of human speech. This method of transmission permits a very efficient data rate/information content ratio.

High bandwidth services are already becoming available through 2G technologies. The development path to 3G is clearly mapped out and brings with it the possibilities of sophisticated data and multimedia applications. The GSM standard will continue to evolve; I with wireless, satellite and cordless systems offering greatly expanded services. These will include high speed, multimedia data services, inbuilt support for parallel use of such services and seamless integration with the Internet and wire line networks.

iii. DIGITAL ACCESS SCHEMES IN GSM

As earlier stated, GSM is a digital form of communication which makes use of the microwaves to transmit and receive information. The normal modulation technique is that our voice or speech, which in technical terms is called as traffic is superimposed over a high frequency carrier. Now this modulated signal is trans received by the mobile equipment.

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The digital technique overcomes the analog technique if we consider the following. In analog case, the frequency once allocated cannot be used by a different user whereas in case of GSM, one carrier frequency is able to support up to 8 users.

GSM makes use of two techniques, namely

FDMA - Frequency Division Multiple Access In this technique, the available band is broken down into smaller frequency bands of equal value. Such one band is called the ARFCN.

TDMA – Time Division Multiple Access This digital technique allows for each ARFCN to support up to eight mobile subscribers simultaneously

Frequency Division Multiple Access (FDMA) refers to the fact tat each Base Transreciever Station is allocated different radio frequency channels. Mobile Phones in adjacent cells (or in the same cell) can operate at the same time, but are separated according to the frequency. The FDMA method is employed by using multiple carrier frequencies, 124 in GSM 900 and 374 in GSM 1800.

Time Division Multiple Access (TDMA) as the name suggests, is a method of sharing a resource (in this case a radio frequency) between multiple users, by allocating a specific time (known as time slot) for each user. This is in contrast to the analogue mobile systems where one radio frequency is used by a single user for the duration of the conversation. In TDMA systems each user either receives or transmits bursts of information only in the allocated time slot. These time slots are allocated for speech only when a user has set up the call. Some timeslots are, however, used to provide signaling and location updates etc. between calls.

The timeslots in the TDMA are divided into two logical channels depending on the priority of the information and they exercise some kind of control depending on their responsibilities. These logical channels are:

Dedicated channels

Common Channels

When a subscriber switches on his mobile phones and receives a call. This simple act of switching on the phone involves the following steps:

1. The mobile scans all the radio frequencies and measures them.

2. It selects the frequency with the best quality and tunes to it.

3. With the help of a synchronization signal in a TDMA frame, the mobile synchronizes itself to the network.

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The synchronization information required by this process is broadcast by the network and analyzed by the mobile.

Registration and authentication are the next steps and they consist of the following operations:

1. A point to point connection must be set up. The mobile station makes a request for a channel to establish the connection.

2. The network acknowledges the request and allocates a channel. The mobile receives and reads this information.

3. The mobile then moves to the allocated channel for further transaction with the network. The next steps are registration and authentication.

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Once a subscriber is registered in the network and the authentication is successful, calls can be set up. In the case of a mobile terminated call, the subscriber has to be paged. This process is described below:

1. The network sends a paging message to all the Base Transreciever Station (BTS) within the Location Area (LA) where the subscriber is registered.

2. The mobile station answers the paging message by sending a service/channel request.

3. The network acknowledges this request and again an authentication is needed. A dedicated signaling channel is assigned in order to transmit the data related to the call.

4. A traffic channel is assigned for the conversation.

During the conversation, the mobile measures the signal strength of adjacent carriers and sends measurement reports to the Base Station Controller (BSC). A channel must be dedicated also for this function.

The Multiple Access Scheme defines how the GSM radio frequency can be shared by different simultaneous communication between different mobile stations located in different cells. GSM uses a mix of Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) combined with frequency hopping for its Multiple Access Scheme. Each user is given a pair of frequencies (one for uplink and one for downlink) and a time slot during a time frame. The time frame provides the basic unit of logical channels.

iv. FREQUENCY ALLOCATION

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There are two frequency bands of 25 MHz each that have been allocated for the use of GSM. The band 890 - 915 MHz is used for the uplink direction (from the mobile station to the base station). The band 935 - 960 MHz is used for the downlink direction (from the base station to the mobile station).

Figure 1: GSM Frequency Bands

v. FDMA and TDMA

FDMA divides the frequency spectrum into small slices, which are assigned to the user. Since the radio spectrum is limited and users do not free their assigned frequency until they are completely finished with it, the number of users in the system can be quickly limited. As the number of users increases, the required frequency spectrum also increases. TDMA allows many users to share a common channel. The unit of time in TDMA is called a burst. Each user is assigned its own burst within a collection of bursts called a frame.

a. Carrier Frequencies

GSM uses TDMA within a FDMA structure. As a result, different users can transmit using the same frequency, but they can't transmit at the same time. A 25MHz frequency band is divided using an FDMA scheme into 124 one-way carrier frequencies. Each base station is assigned one or more carriers to use in its cell. A 200kHz frequency band separates the carrier frequencies from each other. Normally, a 25MHz band should be divisible into 125 carrier frequencies but in GSM the 1st carrier frequency is used as a guard band between GSM and other services that

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might be working on lower frequencies.  

Figure 2: Frequency Division in the Uplink Spectrum

b. Bursts

Each carrier frequency is then divided according to time using a TDMA scheme. Each of the carrier frequencies is divided into a 120ms multiframe. A multiframe is made up of 26 frames. Two of these frames are used for control purposes, while the remaining 24 frames are used for traffic.  

Figure 3: Structure of a Multiframe   Each frame can in turn be divided into 8 bursts, and each of the 8 bursts is assigned to ta single user. In a TDMA system, a burst is the unit of time, and each burst lasts for approximately 0.577 ms.  

Figure 4: Structure of a Frame

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2.1.1 TYPES OF GSM NETWORK• GSM-900 (CHANNELS 124,SPACING 45MHZ)• DCS -1800 (CHANNELS 374 ,SPACING 95MHZ)• PCS -1900(USED IN USA)

i. GSM-900:• Uplink: 890 MHz – 915 MHz (25 MHz)• Downlink: 935 MHz – 960 MHz (25 MHz)• Uplink-Downlink distance: 45 MHz• Frequency Division Multiple Access• Channels are 200 kHz wide.• 124 pairs of channels• Time Division Multiple Access• 8 connections each channel• Theoretical 124*8 = 992 channel to use.

ii. GSM-1800:

• Uplink: 1710- 1785MHz• Downlink: 1805- 1880MHz• Uplink-Downlink distance: 95 MHz• 374 pairs of channels

iii. GSM-1900:• Uplink: 1850 - 1910 MHz• Downlink: 1930 - 1990 MHz

2.1.2 DIFFERENCE IN UPLINK AND DOWNLINK FREQUENCIES

Mobile is operated on a battery with low power and therefore it sends signals on low (uplink) frequencies whereas a base station is driven by high power and can easily send signals on high(downlink) frequencies. This can be verified by Friis equation which says Transmitted power and Transmitted frequency are directly proportional. Other reasons are:

1) On the Earth Station we have to penetrate the atmosphere to reach the satellite station. So we need a lot of power to be generated...This is only possible with the help of High power transmitter circuits, which cannot be installed on the satellite, so uplink is at higher frequency with high power.

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2)Now as the frequency is increased the amount of interference caused by the atmosphore reduces, as higher frequency signal has more signal energy in it....so it can penetrate the atmosphere more easily(the same reason why we use modulation with higher frequency).

3) Unwanted distortion like rain (main cause of attenuation), fog, other frequency in neighborhood, etc. cause distortion, so we have to count to these factors and increase the frequency band to 100-1000 GHz range...

Now the Satellite is a small piece of equipment and needs to be light weight...so it cannot have high power amplifiers on board so by default the frequency is lower than uplink...

2.1.3 GSM FEATURES

There are many features associated with GSM technology due to which it is bar far the most leading mobile communication technology in the world today. GSM technology facilitates with high speed integrated data, voice data, fax, mail, voice male and mostly used SMS feature. GSM also make sure that all the communication made between networks are secured and protected from intruders and frauds.One of the major advantages of GSM technology which changed the way we looked mobile phones at the beginning. GSM actually brought the concept of being Mobile way beyond the limits. It enabled us to communicate across the continents.

GSM supports multiple frequency levels like 900 MHz, 1800 MHz, 1900 MHz. 1900MHz frequency is used in North America where as 1800MHz is used in other parts of the world. Different frequency bands are used by different mobile phone operators. If you are using Mobile phone which supports 1800MGz and operators are available on this band, phone can be used the network, where as if phone is out of the range of the frequency band on mobile operator frequency than you need to have phone that supports the frequency. To avoid such cases one should always adopt to have mobile phones that support multiple frequency bands.

Some Important features:

i. SYSTEM FEATURES

1. Roaming: The roaming feature allows a user to make and receive calls in any GSM network and to use the same user-specific services worldwide.

2. Handover: In a cellular network, the radio and fixed voice connections are not permanently allocated for the duration of a call. Handover or handoff as it is called in North America, means

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switching an ongoing call to a different channel or cell. The execution and measurements required for handover are a basic function of the RR protocol layer. There are four different types of handovers in GSM, which involve transferring a connection between:

a. Channels (timeslots) in the same cell (intra-BTS handover)b. Cells under the control of the same BSC (inter-BTS handover).c. Cells under the control of different BSCs, but belonging to the same MSC (inter-BSC

handover)d. Cells under the control of different MSCs (inter-MSC handover)

Handovers can be initiated by either the BSC or the MSC (as a means of traffic load balancing). During its idle timeslots, the mobile scans the broadcast control channel of up to 16 neighboring cells, and forms a list of the six best candidates for possible handover, based on the received signal strength. This information is passed to the BSC and MSC, at least once per second, and is used by the handover algorithm.

The decision on when to initiate a handover is a function of the following parameters:

receive quality, receive level.

Successful handovers in GSM can take place at propagation speeds of up to 250 km/h.

3. Frequency hopping: The mobile station has to be frequency-agile, meaning it can move between different frequencies in order to transmit and receive data, etc. A normal handset is able to switch frequencies 217 times per second. GSM makes use of this frequency agility to implement slow frequency hopping, where the mobile and the BTS transmit each TDMA frame on a different carrier frequency. The frequency hopping algorithm is broadcast on the broadcast control channel. Since multipath fading is dependent on the carrier frequency, slow frequency hopping helps alleviate the problem.

In addition, co-channel interference is in effect randomized. The broadcast and common control channels are not subject to frequency hopping and are always transmitted on the same frequency.

4. Authentication: Authentication normally takes place when the MS is turned on with each incoming call and outgoing call. A verification that the »Ki« (security code) stored in the AuC matches the »Ki« stored in SIM card of the MS completes this process.

The user must key in a PIN code on the handset in order to activate the hardware before this automatic procedure can start.

5. Frequency Reuse: There are a limited number of frequencies available to each Base Station Subsystem and they must be distributed between the cells to ensure a balanced coverage throughout the BSS.

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The frequencies have to be reused. If you do not distribute the frequencies properly throughout the network the result will be a high level of interference caused by overlapping frequencies. To avoid this, the GSM network includes a specification of the Frequency reuse patterns, one of which is presented in figure below.

1 234 5

7 8

9

6

•

1 234 5

7 8

9

6

•

1 234 5

7 8

9

6

•

1 234 5

7 8

9

6

•

1 234 5

7 8

9

6

• 1 234 5

7 8

9

6

•

• •

•

•

•

•

•

• •

•

Figure 3: Frequency reuse pattern example

The next step involves the dimensioning of the Location Areas. This is carried out according to the traffic characteristics of each area. The final phase is the dimensioning of the Fixed Network on the basis of the traffic requirements and dimensioning of the entire radio network.

Some other features are:

• Improved security function• Low cost mobile sets and base station• High quality speech• Compatibility ISDN & other telephone company service• Higher calling capacity• Support for international roaming

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2.1.4 GSM SYSTEM ARCHITECTURE

A GSM network can be divided into three groups: The mobile station (MS), the base station subsystem (BSS) and the network subsystem. They are characterized as follows:

1. The mobile station (MS):A mobile station may be referred to as a handset, a mobile, a portable terminal or mobile equipment (ME). It also includes a subscriber identity module (SIM). Each SIM card has a unique identification number called IMSI (International Mobile Subscriber Identity). The SIM card contains the identification numbers of the user, a list of the services that the user has subscribed to and a list of available networks. In addition, the SIM card contains tools needed for authentication and ciphering and, depending on the type of the card, there is also storage space for messages such as phone numbers, etc. In addition, each MS is assigned a unique hardware identification called IMEI (international mobile equipment identity). Besides providing a transceiver (TRX) for transmission and reception of voice and data, the mobile also performs a number of very demanding tasks such as authentication, handover, encoding and channel encoding.

2. The base station subsystem (BSS):

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The base station subsystem (BSS) is made up of the base station controller (BSC) and the base transceiver station (BTS). GSM uses a series of radio transmitters called BTSs to connect the mobiles to a cellular network. Their tasks include channel coding/decoding and encryption/decryption. A BTS is comprised of radio transmitters and receivers, antennas, the interface to the PCM facility, etc. The BTS may contain one or more transceivers to provide the required call handling capacity. A cell site may be omni directional or split into typically three directional cells. A group of BTSs are connected to a particular BSC which manages the radio resources for them. Today's new and intelligent BTSs have taken over many tasks that were previously handled by the BSCs. The primary function of the BSC is call maintenance. The mobile stations normally send a report of their received signal strength to the BSC every 480 ms. With this information the BSC decides to initiate handovers to other cells, change the BTS transmitter power, etc.

3. The network subsystem (NSS): It acts like a standard exchange in a fixed network and additionally provides all the functionality needed to handle a mobile subscriber. The main functions are registration, authentication, location updating, handovers and call-routing to a roaming subscriber. The signaling between functional entities (registers) in the network subsystem uses Signaling System 7 (SS7). If the MSC also has a gateway function for communicating with other networks, it is called Gateway MSC (GMSC).

4. The home location register (HLR):

It is a database used for management of mobile subscribers. It stores the international mobile subscriber identity (IMSI), mobile station ISDN number (MSISDN) and current visitor location register (VLR) address. The main information stored there concerns the location of each mobile station in order to be able to route calls to the mobile subscribers managed by each HLR. The HLR also maintains the services associated with each MS. One HLR can serve several MSCs.

5. The visitor location register (VLR):

It contains the current location of the MS and selected administrative information from the HLR, necessary for call control and provision of the subscribed services, for each mobile currently located in the geographical area controlled by the VLR. A VLR is connected to one MSC and is normally integrated into the MSC's hardware.

6. The authentication center (AUC):

It is a protected database that holds a copy of the secret key stored in each subscriber's SIM card, which is used for authentication and encryption over the radio channel. The AUC provides additional security against fraud. It is normally located close to each HLR within a GSM network.

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7. The equipment identity register (EIR):

The EIR is a database that contains a list of all valid mobile station equipment within the network, where each mobile station is identified by its international mobile equipment identity (IMEI). The EIR has three databases:

White list: approved, error-free IMEIs, without restrictions.

Black list: Unapproved or bad/stolen handsets.

Grey list: for handsets/IMEIs that are uncertain.

2.1.5 Services Provided by GSM:

Telecommunication services can be divided into Bearer Services, Teleservices, and Supplementary Services. Call diversion, caller identification, encrypted speech, fax and error protected data are a few examples of current and new services provided by the GSM.

Supplementary services are provided on top of teleservices or bearer services, and include features such as caller identification, call forwarding, call waiting, multiparty conversations, and barring of outgoing (international) calls, among others. 

1 Teleservices:

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A Teleservices utilizes the capabilities of a Bearer Service to transport data, defining which capabilities are required and how they should be set up.

The most basic Teleservice supported by GSM is telephony. There is an emergency service, where the nearest emergency service provider is notified by dialing three digits (similar to 911). The Telephony Teleservice and Emergency Teleservice cover normal speech calls. These are both the fundamental services for making ordinary telephone calls, but they are separated because of a special need for Emergency calls.

When a call is made from a GSM Mobile Station, the type of service requested is indicated in the set-up message. This means that the GSM operator has the option to treat emergency calls differently by allowing mobile equipment without a SIM card to make them.

The ISDN, on which GSM is based, has a great deal of potential for other information and data services. These are the videotext, teletex, and electronic mail services. The Videotex, Teletex and Advanced Message Handling Teleservices provide these for in GSM. The last of these covers the electronic mail requirements.

This Advanced Message Handling Teleservice (or the Electronic Mail Teleservice) is designed to allow quite long messages. GSM has one more Teleservice that is designed for short, paging type messages. This Teleservice, called Short Message Service (SMS), is by far the most widely used and flexible. The SMS Teleservice was originally defined to utilise some spare signalling capacity in GSM. However, it soon became apparent that SMS would become a key service in differentiating GSM from any other cellular service. SMS is effectively an international paging service, overlaid on top of the GSM network, with the capability to send, as well as receive, messages.

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SMS is a bidirectional service for sending short alphanumeric (up to 160 bytes) messages in a store and forward fashion. For point to point SMS, a message can be sent to another subscriber to the service, and an acknowledgement of receipt is provided to the sender. SMS can also be used in a cell broadcast mode, for sending messages such as traffic updates or news updates. Messages can be stored in the SIM card for later retrieval.

 2 Supplementary Services:

The supplementary services basically consist of call forwarding and call barring.

Call Forwarding:

The Call Forwarding Supplementary Service is used to divert calls from the original recipient to another number, and is normally set up by the subscriber himself. It can be used by the subscriber to divert calls from the Mobile Station when the subscriber is not available, and so to ensure that calls are not lost. A typical scenario would be a salesperson turns off his mobile phone during a meeting with customers, but does not with to lose potential sales leads while he is unavailable.

Call Barring:

The concept of barring certain types of calls might seem to be a supplementary disservice rather than service. However, there are times when the subscriber is not the actual user of the Mobile Station, and as a consequence may wish to limit its functionality, so as to limit the charges incurred. Alternatively, if the subscriber and user are one and the same, the Call Barring may be useful to stop calls being routed to international destinations when they are routed. The reason for this is because it is expected that the roaming subscriber will pay the charges incurred for international re-routing of calls. So, GSM devised some flexible services that enable the subscriber to conditionally bar calls.

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 The newer GSM services were not all generally available by the GSM operators at the time of writing and comprise: 

3. Number Identification:

Calling Line Identification Presentation: This service deals with the presentation of the calling party's telephone number. The concept is for this number to be presented, at the start of the phone ringing, so that the called person can determine who is ringing prior to answering. The person subscribing to the service receives the telephone number of the calling party.

Calling Line Identification Restriction: A person not wishing their number to be presented to others subscribes to this service. In the normal course of event, the restriction service overrides the presentation service.

Connected Line Identification Presentation: This service is provided to give the calling party the telephone number of the person to whom they are connected. This may seem strange since the person making the call should know the number they dialled, but there are situations (such as forwardings) where the number connected is not the number dialled. The person subscribing to the service is the calling party.

Connected Line Identification Restriction: There are times when the person called does not wish to have their number presented and so they would subscribe to this person. Normally, this overrides the presentation service.

Malicious Call Identification: The malicious call identification service was provided to combat the spread of obscene or annoying calls. The victim should subscribe to this service, and then they could cause known malicious calls to be identified in the GSM

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network, using a simple command. This identified number could then be passed to the appropriate authority for action. The definition for this service is not stable.

4. Multi-Party:

This service is similar to a conference type service, in that several calls may be connected with all parties talking to each other. However, there are enough differences, caused by its application in the mobile environment, for it to be known by a different name.

5. Communication of Interest:

This service is provided on GSM to enable groups of subscribers to only call each other. In this way, intrusions can be limited only to those members who wish to talk to each other. 

6. Charging:

This service was designed to give the subscriber an indication of the cost of the services as they are used. Furthermore, those Service Providers who wish to offer rental services to subscribers without their own Subscriber Identity Module (SIM) can also utilize this service in a slightly different form.

7. Additional Information Transfer:

This service allows the subscriber to send and receive information to and from the person with whom they have an active call. The amount of information is limited, but may include text (such as names and addresses), and numbers (such as telephone numbers). 

8. Call Offering:

The call transfer service allows the subscriber to transfer or forward a call to another party. This party can be either another GSM Mobile Station or indeed, a person on a different network. One of the difficulties with this service is the billing ramifications. If A calls B, and B asks to be transferred to C, then it is not clear who should be charged for the rest of the call (A, who initiated the call but is no longer a participant, or B, who asked for the call transfer. To charge B is technically difficult.)

2.2 STUDY OF CDMA: CODE DIVISION MULTIPLE ACCESS

Code Division Multiple Access (CDMA) is a digital wireless technology that was pioneered and commercially developed by QUALCOMM. CDMA works by converting speech into digital information, which is then transmitted as a radio signal over a wireless network. Using a unique

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code to distinguish each different call, CDMA enables many more people to share the airwaves at the same time - without static, cross-talk or interference. CDMA was adopted by the Telecommunications Industry Association (TIA) in 1993. CDMA wireless was commercially introduced in 1995. CDMA is very fast growing wireless technology. Code Division Multiple Access, a cellular technology originally known as IS-95, competes with GSM technology for dominance in the cellular world. There are now different variations, but the original CDMA is now known as cdma One. A newer version of this with more speed is now known as cdma20000. In 1999, the International Telecommunications Union selected CDMA as the industry standard for new "third-generation" (3G) wireless systems. The selected technology variation are called W-CDMA (wideband CDMA) and TD-SCDMA .wideband CDMA forms the basis of UMTS 3G networks. Many leading wireless carriers are now building or upgrading to 3G CDMA networks. May 2001 there were 35 million subscribers on cdma One systems worldwide. At year 2003 over 100 million consumers worldwide rely on CDMA communications.

232 bit is used in CDMA.

Code division multiple access, a cellular technology originally known as IS -95, competes with GSM technology for dominance in the cellular world.

We now have CDMA 2000 and its variants like 1XEV, 1XEV-DO, and MC 3X. the refer to variants of usage of a 1.25 MHz channel. 3x uses a 5 MHz channel.

Developed originally by QUALCOMM, CDMA is characterized by high capacity and small cell radius, employing spread spectrum technology and a special coding scheme.

2.3 TRANSMISSION MEDIA

There are four types of media that can be used in transmitting information in the telecommunications world:

Copper wire

Coaxial cable

Optical fiber

Wireless

Earlier, copper wire was the only means of transmitting information. Technically known as unshielded twisted pair (UTP), this consisted of a large number of pairs of copper wire of varying size in a cable. The cable did not have a shield and therefore the signal primarily the high-frequency part of the signal was able to leak out.

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Coaxial cable consists of a single strand of copper running down the axis of the cable. This strand is separated from the outer shielding by an insulator made of foam or other dielectrics. A conductive shield covers the cable. Usually an outer insulating cover is applied to the overall cable.

Fiber is the third transmission media. Whereas transmission over copper utilizes frequencies in the megahertz range, transmission over fiber utilizes frequencies a million times higher. This difference permits transmission speeds of immense magnitudes. Transmission speeds of as high as 9.9Gbps have become common place in the industry today. The tremendous capacity of fiber certainly makes for more efficient communications; however, placing so much traffic on a single strand makes for greater vulnerability. Most of the disruptions in the long-distance network are a result of physical interruption of a fiber run.

Wireless communications is the final option as a transmission medium. This can take several forms: microwave, synchronous satellites, low-earth-orbit satellites, cellular, personal communications service (PCS), etc. In every case, however, a wireless system obviates the need for a complex wired infrastructure. In the case of synchronous satellites, transmission can take place across oceans or deserts. With microwave there is no need to plant cable, and in mountainous territories this is a significant advantage. Cellular and PCS afford mobility. There are advantages and disadvantages to each.

3. GSM vs. CDMA TECHNOLOGY

GSM is a very straightforward standard, whereas CDMA is somewhat complicated. The key difference between the two is that GSM is a standard and CDMA is a technology, but GSM has attained some technology status over the years. So, what is the difference between GSM and CDMA?

3.1 GSM EXPLAINED:

GSM is a 'cellular' technology, that is, the entire coverage area is divided into various hexagonal shaped cells (hence the popular name 'cell phones'). Every cell has a corresponding network tower, which serves the mobile phones in that cellular area. For example: Imagine a honeycomb on a tree in a hexagonal-shaped garden. The garden has many flowers. The honeybees collect the nectar from the flowers and deposit it in the honeycomb. Your mobile phones are like the flowers, the network tower is like a honeycomb, and the bees are the signals.

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3.2 CDMA EXPLAINED: As the name suggests (Code Division Multiple Access), there are many devices which use the same spread spectrum (hence multiple access). There is one physical channel and a special code for every device in the coverage network. Using this code, the signal of the device is multiplexed, and the same physical channel is used to send the signal (the codes may or may not change). For example: There is a street on which many buses ply. Obviously, the bus will have many commuters, and they will have to buy the tickets to travel on the bus. In CDMA, the commuter is like your mobile phone, the tickets are your codes, the bus is a multiplexed carrier signal, and the street is the spread spectrum.

3.3 GSM vs. CDMA Comparison: Call Quality: This is an area where CDMA scores substantially over GSM. Statistics are hugely in favor of CDMA. Various factors such as echoes, call dropping, or voice distortion are almost non-existent in CDMA, whereas in GSM, there is a high probability of errors. To give you an analogy, the bus on the street will continue to ply even when it's full, but if the honeycomb has reached full capacity, the honey cannot be deposited.

Carriers: GSM is one up on CDMA as far as carriers are concerned. The law requires CDMA carriers to provide handsets to users, for which the users cannot change their carriers. Whereas, GSM users can change their carriers whenever they want.

Network: It's an ongoing battle between the two. Both the technologies are continuously improving the qualities of their network and adding various aspects to it as well.

Worldwide: There is a special number that every GSM compatible device in the world can call in case of an emergency. That number is 112. But in CDMA, this cannot be implemented because of certain technological limitations.

Battery Life: GSM, being a relatively simpler technology, uses less amount of cell phone battery than CDMA.

Coverage: GSM and CDMA, both have similar network coverage areas. They are present almost everywhere. The service providers of both technologies are striving hard to cover whatever areas are left.

Speed: Both GSM and CDMA are rapidly improving their capabilities in this regard. Both have introduced 3G mobile phones in their fold. Both are competing to gain space in this area.

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Building Penetration: Again, during the initial days, both technologies couldn't find building penetration, but after research in signaling systems, and through experience, service providers of both technologies have been able to give decent service to the mobile phones in buildings.

3.4 GSM vs. CDMA: Which is better?

Both have their good qualities and bad qualities. GSM has some limitations where call quality is concerned, but GSM can be easily implemented and easily integrated into existing technology. Whereas, CDMA is little difficult to implement. By my estimation, GSM has an upper hand. So, the answer to the question, "GSM vs CDMA which is better?" is GSM.

Mobile communication has had a huge impact on modern-day industry. GSM and CDMA technologies have unleashed mobile communication worldwide, and the technological competition between GSM vs. CDMA has resulted in the improvement of services for the user.

4. VOLTAGE STANDING WAVE RATION (VSWR)

In telecommunications, standing wave ratio (SWR) is the ratio of the amplitude of a partial standing wave at an antinode (maximum) to the amplitude at an adjacent node (minimum), in an electrical transmission line.

The SWR is usually defined as a voltage ratio called the VSWR, for voltage standing wave ratio. For example, the VSWR value 1.2:1 denotes maximum standing wave amplitude that is 1.2 times greater than the minimum standing wave value. It is also possible to define the SWR in terms of current, resulting in the ISWR, which has the same numerical value. The power standing wave ratio(PSWR) is defined as the square of the VSWR.

SWR is used as an efficiency measure for transmission lines, electrical cables that conduct radio frequency signals, used for purposes such as connecting radio transmitters and receivers with their antennas, and distributing cable television signals. A problem with transmission lines is that impedance mismatches in the cable tend to reflect the radio waves back toward the source end of the cable, preventing all the power from reaching the destination end. SWR measures the relative size of these reflections. An ideal transmission line would have an SWR of 1:1, with all the power reaching the destination and no reflected power. An infinite SWR represents complete reflection, with all the power reflected back down the cable. The SWR of a transmission line is measured with an instrument called an SWR meter, and checking the SWR is a standard part of installing and maintaining transmission lines.

i. Relation to the Reflection Coefficients

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The voltage component of a standing wave in a uniform transmission line consists of the forward wave (with amplitude Vf) superimposed on the reflected wave (with amplitude Vr).

Reflections occur as a result of discontinuities, such as an imperfection in an otherwise uniform transmission line, or when a transmission line is terminated with other than its characteristic impedance. The reflection coefficient Γ is defined thus:

Γ is a complex number that describes both the magnitude and the phase shift of the reflection. The simplest cases, when the imaginary part of Γ is zero, are:

Γ = − 1: maximum negative reflection, when the line is short-circuited, Γ = 0: no reflection, when the line is perfectly matched,

Γ = + 1: maximum positive reflection, when the line is open-circuited.

For the calculation of VSWR, only the magnitude of Γ, denoted by ρ, is of interest. Therefore, we define

ρ = | Γ | .

The voltage standing wave ratio is then equal to:

As ρ, the magnitude of Γ, always falls in the range [0,1], the VSWR is always ≥ +1.

The SWR can also be defined as the ratio of the maximum amplitude of the electric field strength to its minimum amplitude, i.e. Emax  / Emin .

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Figure. VSWR reading with stable value

Figure: VSWR reading with faulty value

ii. Practical Implication of SWR

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The most common case for measuring and examining SWR is when installing and tuning transmitting antennas. When a transmitter is connected to an antenna by a feed line, the impedance of the antenna and feed line must match exactly for maximum energy transfer from the feed line to the antenna to be possible. The impedance of the antenna varies based on many factors including: the antenna's natural resonance at the frequency being transmitted, the antenna's height above the ground, and the size of the conductors used to construct the antenna.

When an antenna and feed line do not have matching impedances, some of the electrical energy cannot be transferred from the feed line to the antenna. Energy not transferred to the antenna is reflected back towards the transmitter. It is the interaction of these reflected waves with forward waves which causes standing wave patterns. Reflected power has three main implications in radio transmitters: Radio Frequency (RF) energy losses increase, distortion on transmitter due to reflected power from load and damage to the transmitter can occur.

Matching the impedance of the antenna to the impedance of the feed line is typically done using an antenna tuner. The tuner can be installed between the transmitter and the feed line, or between the feed line and the antenna. Both installation methods will allow the transmitter to operate at a low SWR, however if the tuner is installed at the transmitter, the feed line between the tuner and the antenna will still operate with a high SWR, causing additional RF energy to be lost through the feed line.

.

Figure: VSWR meter for measuring VSWR

5. STUDY OF BSC

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A BSC may control several BTS; the maximum number of BTS which may be controlled by one BSC is not specified by GSM.

Typically a BSC has tens or even hundreds of BTSs under its control. The BSC handles allocation of radio channels, receives measurements from the mobile phones, and controls handovers from BTS to BTS.

A key function of the BSC is to act as a concentrator where many different low capacity connections to BTSs (with relatively low utilization) become reduced to a smaller number of connections towards the mobile switching center (MSC) (with a high level of utilization). Overall, this means that networks are often structured to have many BSCs distributed into regions near their BTSs which are then connected to large centralized MSC sites.

The databases for all the sites, including information such as carrier frequencies, frequency hopping lists, power reduction levels, receiving levels for cell border calculation, are stored in the BSC. This data is obtained directly from radio planning engineering which involves modeling of the signal propagation as well as traffic projections.

The BTSs and BSC may either be located at the same cell site “Colocated” or located at different sites “Remote”. In reality most BTSs will be remote as there are many more BTSs than BSCs in a network.

Another BSS configuration is the Daisy Chain. A BTS need not communicate directly with the BSC which controls it, it can be connected to the BSC via a chain of BTSs.

The BSC's will be finally connected to the MSC. So for example, when a call is made from a fixed line to mobile, it is routed from PSTN to MSC, then to BSC and BTS and to Mobile. The BSC controls various functions of BTS and Mobile, like assigning a channel for call, handover etc.

The Base Station Controller though controls the BTS which is radio equipment, but the BSC itself is not radio equipment It has no radio elements inside it. The BSC has processor boards and PCM interfaces to provide connections to all the BTS's and also on the other side to the MSC. The BSC has a major role to play in switching traffic circuits from the Abis to the A interface. The BSC may also have optionally a TRAU, if transcoding is to be done at the BSC. Different configurations are shown in the diagram shown on next page.

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I. Operations of BSC Power Management – to handle all Power related problems at the site such as record of

power supplied by Generator, battery or Mains. Money Management –Maintaining the Electricity and the site maintenance bills. Preventive Maintenance Management and Maintenance of Transmission Equipment such as ODU’s Capacity Additions such as more adding more TCU’s. Maintenance of inter & intra City Microwave & Fiber Links. Redundancy Planning Maintenance of Spares such as various controller cards, TCU’s & ODU’s. Handling of Alarms at all Sites such as high temperature, fire alarm, rectifier failure.

The various duties performed in BSS department are: To ensure the maximum Network Availability & reduce downtime to minimum. To perform routine Maintenance activities on the BSC, BTS, Microwave and Backbone

Sites. To handle all alarms which are generated at any site in the area of responsibility. To handle all Power related problems in all sites. To maintain all intercity and intracity links. To implement all upgrades in the network (BSS site specific) Asset management (Tools, Testers ,manuals etc)

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II. Network availability:

Network availability is the main duty which ensures that full signal is available at all the sites at each hour of the day. It also takes care to reduce the downtime to the minimum so that if full network is not available at any particular time, at any particular site or station then due care is taken to find out and rectify the problem. This helps to provide maximum network within the minimum possible time.

III. Necessity:

Maximum network availability is one of the prime functions of BSS. If maximum network availability is not ensured then mobiles will not be able to function properly bringing the communication to a standstill. Routine checkup of BTS and backbone sites is necessary to ensure proper and optimum working of various machineries and equipments. It also helps to keep under check any error which may creep in unknowingly.

IV. Risk Factors:

The major risk factor involved is the failure of proper functioning of the mobiles as well as the congestion occurring due to downlink of the particular network. If routine checkup is not done then some small malfunctioning, not rectified in time, can lead to a major internal problem bringing the process of communication to a standstill.

So it’s very necessary to have routine checkup of BTS sites.

V. Routine maintenance:

Routine maintenance of the BTS sites is another essential activity. Routine checkup of the BTS sites is done by the engineers even if there is no detectable error in the performance of various machines and instruments.

VI. Alarms

In OMC all type of alarms are monitored 24 hours. The Base Station System (BSS) MMI alarm messages are text strings that are sent to the Operations and Maintenance Centre (OMC) or to a Local Maintenance Terminal (LMT) on-site from the master processor. Alarm messages are generated when a specific fault condition occurs within a BSS or the OMC.

i. Types of alarm messages:There are two types of alarm messages: hardware and software.

a) Hardware alarm messages:

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Hardware alarm messages are generated when specific hardware fault conditions are detected by various digital modules within BSS network.

b) Software alarm messages:

Software alarm messages are generated when specific software fault conditions are detected by the processor.

ii. Types of Alarms

a) Critical

Indicates that a service-affecting condition has occurred. Immediate corrective action by the OMC operator or a field representative on-site is required. For example, when an item critical to the proper functioning of the system fails and is completely Out Of Service (OOS), the device must be restored to service as soon as possible. Critical alarms includes like Fire Alarm etc.

b) Major

Indicates that a service-affecting condition has occurred. Urgent corrective action is required. For example, if a device has severely degraded in terms of the capability to function, the device must be restored to service.

c) Minor

Indicates the existence of a non-service-affecting fault. Corrective action should be taken to avoid a more serious fault. For example, if a device is not currently degrading in terms of service, the service capability of the device may eventually be affected.

d) Warning

Indicates the detection of a potential or impending service-affecting fault frequently before any significant effects have been noticed. Corrective action should be taken to monitor and diagnose the problem to prevent it from becoming a more serious, service-affecting fault condition.

e) Clear

Indicates the clearing of a previously reported alarm after a fault condition has been resolved. For example, an alarm could be cleared from a Network Element (NE), and the severity level at the OMC would then be set to clear.

6. STUDY OF BTS CARDS

The base transceiver station, or BTS, contains the equipment for transmitting and receiving radio signals (transceivers), antennas, and equipment for encrypting and decrypting communications with the base station controller (BSC).

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The functions of a BTS vary depending on the cellular technology used and the cellular telephone provider. There are vendors in which the BTS is a plain transceiver which receives information from the MS (mobile station) through the Um (air interface) and then converts it to a TDM (PCM) based interface, the Abis interface, and sends it towards the BSC. There are vendors which build their BTSs so the information is preprocessed, target cell lists are generated and even intracell handover (HO) can be fully handled. The advantage in this case is less load on the expensive Abis interface.

A TRX transmits and receives according to the GSM standards, which specify eight TDMA timeslots per radio frequency. A TRX may lose some of this capacity as some information is required to be broadcast to handsets in the area that the BTS serves. This information allows the handsets to identify the network and gain access to it. This signaling makes use of a channel known as the Broadcast Control Channel (BCCH).

I. FEATURES AND FUNCTIONS:

Multiple Frequency band applications

Supports GSM 850 MHz, 900 MHz, 1800 MHz and 1900 MHz Supports GPRS and EDGE.

Networking Capacity

One BTS3012 cabinet can hold six DTRU’s (Double Transceiver Unit )i.e.12 TRX’s .The 2nd version of BTS 3012 cabinet holds up to six QTRU’s(Quadruple Transceiver Unit with each having 6 TRX support) i.e. 36 TRX’s.

Supports combined cabinets and multiple cabinets can hold up to 72 TRX’s. BTS 3012 can share cabinet with WCDMA base station. i.e. Module of WCDMA base station can be inserted in the BTS 3012 cabinet.

Network Capability Supports multiple transmission modes such as E1/T1,STM-1,Microwaveand Satellite

transmission. Supports multiple topologies such as Star, Tree, Chain, ring and Hybrid topologies. Supports A5/1 and A5/2 encryption and decryption. Supports Power boost technology (PBT) and max. Power of the TRX can reach up to

100W. Supports Diversity transmit and four diversity receive modes. Supports high receive sensitivity.

Clock and Synchronization

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The BTS 3012 clock has

Four modes: fast pull-in, locked, holdover and free run. Process the inputs of external BITS clock. Supports soft synchronization on the Um interface.

II. ANTENNA

An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter applies an oscillating radio frequency electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals that is applied to a receiver to be amplified. An antenna can be used for both transmitting and receiving.

Antennas are essential components of all equipment that uses radio. They are used in systems such as radio broadcasting, broadcast television, radio, communications, radar, cell phones, and satellite communications, as well as other devices such as garage door openers, wireless microphones, Bluetooth enabled devices, wireless computer networks, baby monitors, and RFID tags on merchandise.

Supports Remote Electric Tilt (RET) antennas. Supports dual polarization antennas. Supports Tower Mounted Amplifiers. (TMA’s) equipment.

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Figure 5: Antenna

III. BASE TRANSRECIEVER STATION

The base transceiver station, or BTS, contains the equipment for transmitting and receiving radio signals (transceivers), antennas, and equipment for encrypting and decrypting communications with the base station controller (BSC). Typically a BTS for anything other than a Pico will have several transceivers (TRXs) which allow it to serve several different frequencies and different sectors of the cell. A base station might have any number of TRXs from one to twelve. These TRXs are then configured into one, two or three cells. If aBTS is configured as one cell it is called an “omnidirectional BTS” and if it is configured as either two or three cells it is called a “sectorised BTS”.

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Figure 6: Types of BTS

The functions of a BTS vary depending on the cellular technology used and the cellular telephone provider. There are vendors in which the BTS is a plain transceiver which receives information from the MS (mobile station) through the Um (air interface) and then converts it to a TDM (PCM) based interface, the Abis interface, and sends it towards the BSC. There are vendors which build their BTSs so the information is preprocessed, target cell lists are generated and even intracell handover (HO) can be fully handled. The advantage in this case is less load on the expensive Abis interface.

Frequency hopping is often used to increase overall BTS performance; this involves the rapid switching of voice traffic between TRXs in a sector. A hopping sequence is followed by the TRXs and handsets using the sector. Several hopping sequences are available, and the sequence in use for a particular cell is continually broadcast by that cell so that it is known to the handsets.

A TRX transmits and receives according to the GSM standards, which specify eight TDMA timeslots per radio frequency. A TRX may lose some of this capacity as some information is required to be broadcast to handsets in the area that the BTS serves. This information allows the handsets to identify the network and gain access to it. This signaling makes use of a channel known as the Broadcast Control Channel (BCCH).

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Figure 7: BTS

IV. HUAWEI BTS Hardware structure

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A BTS 3012 is composed of

The Common Subsystem Double Transceiver Subsystem RF Subsystem

A. COMMON SUBSYSTEM

Consists of the BTS Common subsystem and Cabinet Top Access subsystem

Functions of Common subsystem:

Managing and controlling other subsystem and modules. Importing E1 signals. Collecting and monitoring the environment alarm. Providing clock for the BTS. Controlling the Remote Electric Tilt (RET).

Functions of Top Access subsystem:

Protecting the E1 signal from Lightning. Protecting the monitor signal from

Lightning. Importing the Boolean value and Power

supply. Connecting cabinets to form a combined

subsystem and their functions.

B. DOUBLE TRANSCEIVER SUBSYSTEM (DTRU)

Functions:

Baseband signals processing RF Receive/Transmit processing Power amplification Supports RF frequency hopping and

Baseband Frequency hopping

I. RF subsystem (DAFU: Antenna front -end unit)

Functions:

Transmits and receives the signals Connects the antenna via feeder to ANT A or ANT B interface

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Amplifies the signals (TMA)

C. VARIOUS CARDS ARE

DEMU: Environmental monitoring unit

DCSU: Combined cabinet signal connection unit

DCCU: Cabel connections unit

DATU: Antenna & control unit

DMLU Monitor signal lightning-protection unit

DTRU: Double transceiver subsystem

DDPU: Dual duplexer unit

7. WORK PROFILE

I. BTS OPERATION AND MAINTENANCE

O&M is a department which deals in installing new sites and maintaining them for trouble free working, whenever a new site is to be installed it is 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 installed 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 installed. According to the need, O&M is informed and task is completed. Where indoor coverage is not proper, O&M team installs repeaters on that location.

Punjab Connect has divided its site in 6 zones:

Bathinda zone Chandigarh zone Amritsar zone Jalandhar zone Ludhiana zone Patiala zone

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

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internal alarm. To sum up, the OMC provides a central point from which to control and monitor the other network entities (i.e. base stations, switches, database, etc) as well as monitor the quality of service being provided by the network.

There are two types of OMC these are:

OMC (R): OMC controls specifically the Base Station System. OMC (S): OMC controls specifically the Network Switching System.

i. O&M GOALS

Receive a complete and fault free network and services– System and network element acceptance test

Keep the complete network fault free– Restore faulty equipment as quick as possible (not redundant eq.)– Service availability and call setup success close to 100% (>98%)– Service interruption (drop calls) close to 0% (<1%)

Integrate planned changes with minimum service interruptions– If not possible, interruption only at night time

Focus on services, keep the complete chain available

ii. TASKS PERFORMED BY O&M TEAM

The O&M team performs the following tasks:

OPERATION

Alarm handling (NMS, monitoring of correlated alarms)

Fault detection

SW troubleshooting and contact with vendor helpdesk

Support to field maintenance

Routing and signaling changes

Frequencies and radio parameter changes

Upgrade and update changes

Performance Management (OMC or performance tools)

Analyze Statistic from BSS counters

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MAINTAINENCE

Corrective maintenance (laptop connection to equipment)

– Troubleshooting

– Spare part handling (repair and logistics)

– Drive tests and optimizing

Preventive maintenance

Quality assurance of houses and equipment

iii. FUNCTIONS OF O & M ENGINEER

a. TMA INSTALLATIONTMA stands for tower mounted amplifiers which are installed at received signal path to increase the gain of the received path. Since the battery of the MS (Mobile Station) is weak, so the output power of the MS is very low. So we need to boost up the output power level of the MS by TMA installation.

On the site, it is located between the antenna and the BTS and it gets power from the battery bank itself. The TMA or ALNA (both designating the same unit) is an external unit mounted in the mast, close to the antenna. It amplifies the received signal to increase the overall system sensitivity and to compensate for loss in the antenna feeder. The TMA is supplied with power from the CDU and is supervised by the RBS. In addition, it connects the transmitter and receiver path to the same antenna by means of a duplex filter

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Figure 8. Tower Mounted Amplifier

b. TCC IMPLEMENTATION

When we need to cater a much larger area, we employ another transmitter at the same site and the output of both the antennas is combined through a combiner and the power transmitted. As the power increases, the coverage of the cell increases but the capacity remains the same i.e. the capacity of one TRX.

So, we employ this method when generally coverage is an issue.

c. BTS EXPANSION

BTS expansion means installing a new BTS to increase the coverage and capacity of the network. Usually a cell is divided into 3 sectors namely A, B, C. The BTS has three directional antennas installed at 1200(ideal case) from each other and serve corresponding sectors namely A, B, C. If we have to add another sector say D, we need to install the additional. TRUs as a single BTS have only 12 TRUs.

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Figure 9. Frequency Reuse

d. COVERAGE COMPLAINTS

When any problem occurs in the network at any place, the complaint is forwarded to the O&M department and details about the nature of the complaint are given. Now the O&M department accesses the RF data of the specified place from where complaint is received.

There is software named MAP INFO and GPS which tells us the exact latitude and longitudinal value of the complaint area. The MAP INFO shows us the exact complaint area and tells about the nearest cell site. The engineers at the OSS will go to the site and check for any missing hardware or damaged hardware which might be due to thefts also or fault occurred.They will check the output power levels of the transmitting antenna of the nearest site and the output power of the MS (mobile station).

The engineers at the OSS will check for the alarms(C-40, NOOP, D-40, NOOP 940) or check for the blocked TRU`s. If none of the above case occurs, then the power level of the site is increased or tilts the angle of the antenna for proper coverage or change the height of the antenna.

For poor networks in basement or any underground / Indoor place; the repeaters or the boosters are installed at that place. The repeaters can be indoor or outdoor. The gain of indoor repeater is 19 dBm. The outdoor repeater are used where large areas are to be covered e.g.- Marriage places and the outdoor repeaters are more costly than the indoor ones ranging from Rs 50,000 onwards and are installed at places which fetch more revenue for the network operators.

e. SWAP PLAN

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Swap plan is used for shifting the capacity from low utilization cells to high utilization. If in a coverage area, there are less number of MS and capacity is not fully utilized then the hardware is removed from that place and put at the place where number of MS is relatively high. Thus the TRU`s are deleted from first and subsequently added to the place where required.

f. PREVENTIVE MAINTENANCE

The operation and maintenance department also takes various preventive steps for proper working of numerous BTS lying in its region. These include continuous site monitoring, fault management, alarm monitoring, performance analysis, configuration changes, backups etc.

II. MAJOR PROJECTS DONE TILL NOW

1. Neighboring of GSM SITES

2. Planning Of New BTS in Punjab

3. Addition of TRX in BTS

4. Generation of Trouble Ticket

5. Router Configuration

6. Processing of PRE & POST data of Drive Test.

A. NEIGHBOURING OF GSM SITES:

SOFTWARE USED- BSC 6000 LOCAL MAINTENANCE TERMINAL

when a new radio base station is introduced into a communication network, said neighboring cell lists being used for facilitating handover of one or more user equipment moving between cells, each being served by a radio base station.

In a typical cellular radio system, mobile user equipment (UEs) communicates via a radio access network (RAN) to one or more core networks (CN). The radio access network covers a geographical area which is divided into cell areas, with each cell being served by a radio base station. Each radio base station, however, may serve more than one cell and cells being served by the same radio base station form a cell site. In order to maintain a radio connection with the network, the user equipment is handed over from one cell to the next when travelling through the geographical area. To facilitate handovers in cellular systems, the neighboring cells concept is introduced and is well known from the early days.

Alcatel Lucent manages 7 BSC’s of Reliance Cellular in PUNJAB:

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1. CHANDIGARH2. BATHINDA3. PATIALA4. AMRITSAR5. JALANDHAR6. LUDHIANA-17. LUDHIANA-2

STEP 1: Login to BSC softwareSTEP 2: Right click on the site name whose neighbouring is to be doneSTEP 3: Configure adjacent cell

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This window will open

STEP 4: Select the sector on which neighbouring is to be done.

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STEP 5: According to the data base enter the Site ID’S from system cells to bidirectional adjacent cells.

\

B. PLANNING OF NEW BTS IN PUNJAB

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Planning of the new BTS is done as per the requirements like

1. Coverage hole2. More congestion3. Number of users increases4. To increase the coverage or performance of the network.

If planning is complete then take the latitudes and longitudes of the site and make a report..

C. ADDITION OF TRX IN BTS

Following steps need to be executed in LMT to configure TRX

STEP 1: In navigation tree, right click cell in which TRX needs to be added. Click add TRX

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STEP 2: select site and click Set Site Device

STEP 3: Right click slot where TRX need to be added in that particular cell

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Click add boardclick TRU

STEP 4: right click newly added TRU and click Configure Board Attributes

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STEP5: Assign the TRX to required cell.

After selection click ok to exit Binding logical TRX window

STEP 6: right click DDPUclick Configure Board Attributes

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STEP 7: Add Uplink tributary 0,1 and downlink tributary TRX mapping from DTRU to DDPU

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STEP 8: Select cell as shown below and click Set Cell TRX

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STEP 9: Select the new TRX board and click cell frequency as shown below

STEP 10: Clcik frequency to assign for TRX

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Click ok to exit

STEP 11: Click TRX attributes in Configure cell TRX window

Select available frequency in assigned frequency section and click ok

Click finish to exit Add TRX window

D. TO MONITOR VARIOUS GSM ALARMS IN BSC

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Alarms Occurring at a BTS Site:

There are various types of alarms occurring at BTS site, due to either failure of any component or due to any other fault. There are mainly 8 types of alarms. These are:

1) Fire Alarm2) Main supply Failure Alarm3) Rectifier 1 Failure Alarm4) Rectifier 2 Failure Alarm5) Low Fuel Level Alarm6) Engine Fault Alarm7) High Temperature8) Air Conditioner Failure or Fault Alarm

E. MONITOR THE TRAFFIC ON DIFFERENT CHANNEL

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F. USER TRACE MANAGEMENT

SOFTWARE USED: M2000 client

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STEP1: Enter the MDN number.

Automatically this window will open

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G. GENERATION OF TROUBLE TICKET

SOFTWARE USED: ARUSER.EXETrouble Ticket is generated for the faulty hardware cards.if any hardware or card is faulty in the MSC,BTS & BSC then we have to change that card but for this, firstly we have to create trouble ticket. Then only the new card will be issued. The code is generated and mail to the Mumbai head office, so that the faulty cards can be replaced.

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H. PROCESSING OF PRE & POST DATA OF DRIVE TEST.

Drive Test offers RF Optimization services for existing GSM and CDMA network operators. This is a continuous RF engineering activity that ensures optimum network performance that meets the set Quality of Service (QoS) targets such as:

Coverage of Service Area: Urban areas, In building, Suburban areas, Roads, Rural areas. Call Success Rate

Handover failure

Rx quality

The benefits of RF Optimization service for the network operator are increased revenues and reduced costs.

Network quality is maintained resulting in higher speech quality index. Stronger competitiveness resulting in higher customer acquisitions.

Satisfied customers resulting in low churn

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RF Optimization services include the following: Study of network performances through OMC Statistics, drive tests and customer

Enquiry. Post-processing and analysis of the performance data to bench mark the network

performance against the set QoS targets and identify eventual problems.

Proposing an action plan for solving the problems. The proposed action plan may include parameter changes and/or network configuration changes and/or network Hardware elements changes.

In close coordination with the customer, implementing the proposed action plan.

Performance Verification to ensure that the optimization process has resulted in network performance improvements such that it meets the set QoS targets.

PRE DRIVE TEST GRAPH

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Figure 10.Drive test

POST DRIVE TEST GRAPH

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Figure 11. Post drive tets

Efficient network utilization resulting in reduced investment costs.

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