Banglalink Operation & Maintenance (O&M)

Operation & Maintenance

Chapter 1: Introduction

1.1 Introduction:

Telecommunication is transmission of signal over a distance for the purpose of communication. In

modern times, telecommunication typically involves the use of electronic devices such as the

telephone, television, radio or computer. Telecommunication network means a combination of a set

of nodes and links that establish telecommunication between two or more points.

Internship is a partial requirement of graduation program. It brings a great opportunity for the

student to get some amazing and excellent ideas about the practical working field. The main and

challenging task is to prepare Internship Report by which a graduate can reflect the ability in the

field of telecommunication efficiently.

Internship is similar to a training program, after receiving theoretical knowledge; Students are

trained to use their knowledge in real situations. Thus they understand the appropriate application

of what they have studied from the books. It is an obligatory requirement of graduation program. It

is a great opportunity for the students to build a relationship between theoretical and practical

knowledge. Through the internship program we get the chance to raise our confident level.

Knowing the proper way to handle the practical job life is another great achievement.

This report is prepared for internship based on my internship experience. I did my internship at

Banglalink which is one of the biggest cellular service suppliers in Bangladesh after Grameenphone.

Through this internship besides experience it was great opportunity to get a glimpse of Banglalink.

I worked there focusing on operation and maintenance system of Banglalink included NMC,

Network subsystem (NSS). In this report mainly I highlight the BSS and NMS system.

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Chapter 2: Overview of Banglalink

2.1 Background of Banglalink

Banglalink is the second largest cellular service provider in Bangladesh after

Grameenphone. This was founded in 1998 and is based in Dhaka, Bangladesh.

Previously, it was a known as Sheba Telecom Pvt Ltd than had been providing

GSM (Global Service of Mobile) service in Bangladesh since 1998. As of

September 2, 2004, Banglalink GSM Ltd. operates as a subsidiary of Orascom

Telecom Now it is a wholly owned subsidiary of Orascom Telecom.

As of November, 2009, Banglalink has a subscriber base of 12.99 million. Banglalink’s Network is

covering 486 Thanas reasonably and 61 districts, covering a total population of around 90%

million.

Banglalink had 1.03 million connections until December, 2005. The number of Banglalink users

increased by 257 per cent and stood at 3.64 million at the end of 2006, making it the fastest

growing operator in the world of that year. In August, 2006, Banglalink became the first company to

provide free incoming calls from BTTB for both postpaid and prepaid connections. On August 20,

2008, Banglalink got past the landmark of 10 million subscriber base.

2.2 Making a difference

The biggest barrier today for people is the cost of handsets. We will strive to lower the total cost of

owning a mobile. We are here to help make a difference in people’s lives by providing affordable

and reliable connectivity solutions. We will strive to connect people and link their lives by listening

to them and by understanding their needs. We are here to help you speak your language.

2.3 Company Strategy

The basic strategy of Orascom Company is for the overall coverage of both urban and rural areas. It

builds continue coverage, cell after cell, with an intention to bring the whole country under its

network. Though the priority of the intensity of coverage varies from area to area, the basic strategy

of cell-to-cell coverage is applied through the whole country.

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2.4 Vision

To be a leading provider of telecommunication services all over Bangladesh with satisfied

customers, shareholder, and enthusiastic employees.

2.5 Mission

Lead the industry and exceed customer expectations by providing the best wireless services,

making life and business easier.

2.6 Numbering Scheme

Banglalink uses the following numbering scheme:

+88019N1N2N3N4N5N6N7N8

Where,

880 is the ISD (International Subscriber Dialling) code for Bangladesh and is needed only in

case of dialing from outside Bangladesh.

19 is the access code for Banglalink as allocated by the Government of Bangladesh. Omitting

+880 will require using 0 in place of it instead to represent local call, hence 019 is the

general access code.

N1N2N3N4N5N6N7N8 is the subscriber number.

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Technical division

NSS

Planning Access Network

NMC

Radio frequency measurement

RoamingPower HLSSoft switch

NSS

NMS

Radio frequency planning

TransmissionBSSBSS IN-VAS

IT


2.7 Technical Division of Banglalink:

Fig2.1: Organizational structure of Banglalink

Technical department of Banglalink is divided into four divisions. These are IT (Information

Technology), Access Network, Planning, and Network Management Subsystem (NMS). Planning

contains NSS, BSS and Transmission. The Access network handles radio frequency planning and

radio frequency measurement. Operation and Maintenance is divided into four divisions. These are

NSS, BSS, NMC and IN-VAS. The NSS subdivisions are Soft switch, Power, Roaming and HLS.

Network Management Subsystem (NMS) is responsible for the proper maintenance of the MSC, BSC,

BTS and optical fibers.

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Chapter 3: GSM Overview

3.1 History:

Global system for mobile communication (GSM) is a globally accepted standard for digital cellular

communication. GSM is the name of a standardization group established in 1982 to create a

common European mobile telephone standard that would formulate specifications for a pan-

European mobile cellular radio system operating at 900 MHz. It is estimated that many countries

outside of Europe will join the GSM partnership.

Cellular is one of the fastest growing and most demanding telecommunications applications.

Throughout the evolution of cellular telecommunications, various systems have been developed

without the benefit of standardized specifications. This presented many problems directly related

to compatibility, especially with the development of digital radio technology. The GSM standard is

intended to address these problems.

From 1982 to 1985 discussions were held to decide between building an analog or digital system.

After multiple field tests, a digital system was adopted for GSM. The next task was to decide

between a narrow or broadband solution. In May 1987, the narrowband time division multiple

access (TDMA) solution was chosen.

In 1989, GSM responsibility was transferred to the European Telecommunications Standards

Institute (ETSI) and phase I of the GSM specifications were published in 1990. The first GSM

network was launched in 1991 by Radiolinja in Finland with joint technical infrastructure

maintenance from Ericsson. By the end of 1993, over a million subscribers were using GSM phone

networks being operated by 70 carriers across 48 countries.

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3.2 Brief History of GSM:

Following table shows many of the important events in the rollout of the GSM system; other events

were introduced, but had less significant impact on the overall systems.

Years Events1982 CEPT establishes a GSM group in order to develop the standards for a pan-European cellular

mobile system.1985 A list of recommendations to be generated by the group is accepted.1986 Field tests are performed to test the different radio techniques proposed for the air interface.1987 Time Division Multiple Access (TDMA) is chosen as the access method (with Frequency Division

Multiple Access [FDMA]). The initial Memorandum of Understanding (MoU) is signed by telecommunication operators representing 12 countries.

1988 GSM system is validated.1989 The responsibility of the GSM specifications is passed to the European Telecommunications

Standards Institute (ETSI).1990 Phase 1 of the GSM specifications is delivered.1991 Commercial launch of the GSM service occurs. The DCS1800 specifications are finalized.1992 The addition of the countries that signed the GSM Memorandum of Understanding takes place.

Coverage spreads to larger cities and airports.1993 Coverage of main roads' GSM services starts outside Europe.1994 Data transmission capabilities launched. The number of networks rises to 69 in 43 countries by

the end of 1994.1995 Phase 2 of the GSM specifications occurs. Coverage is extended to rural areas.1996 June: 133 network in 81 countries operational.1997 July: 200 network in 109 countries operational, around 44 million subscribers worldwide.1999 Wireless Application Protocol came into existence and 130 countries operational with 260

million subscribers2000 General Packet Radio Service (GPRS) came into existence.2001 As of May 2001, over 550 million people were subscribers to mobile telecommunications2002 GSM introduced for 800MHz band. First Multimedia Messaging Services go live. 95% of nations

worldwide have GSM networks. 400 billion SMS messages sent in the year.2003 First EDGE networks go live. GSMA creates new CEO-level Board.

2004 GSM surpasses One billion customers. More than 50 3GSM networks live.

2005 GSM surpasses 1.5 billion customers. First HSDPA network goes live. Over 100 3GSM networks launched. 120+ 3GSM handset models launched or announced.

2006 GSM surpasses two billion customers. Over 120 commercial 3GSM networks in more than 50 countries and almost 100 million subscriptions. GSMA membership exceeds 900 companies (including over 700 operators).

2007 Heading towards 2.5 billion GSM connections. First GSMA Mobile Asia Congress held in Macau

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SAR, China. 2008 More than 55,000 visitors to the GSMA’s Mobile World Congress in Barcelona.

GSM surpasses 3 Billion connections

Table3.1: Brief list of GSM history

3.3 Characteristics & Specifications:

Frequency band—the frequency range specified for GSM is 1,850 to 1,990 MHz (mobile station

to base station).

Duplex distance—Duplex distance is the distance between the uplink and downlink

frequencies. A channel has two frequencies, 80 MHz apart.

Channel separation—Channel separation is the separation between adjacent carrier

frequencies. In GSM, this is 200 kHz.

Modulation—Modulation is the process of sending a signal by changing the characteristics of a

carrier frequency.

Transmission rate—GSM is a digital system with an over-the-air bit rate of 270 kbps.

Access method—GSM utilizes the time division multiple access (TDMA) concept. TDMA is a

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

particular time slot.

Speech coder—GSM uses linear predictive coding (LPC). The purpose of LPC is to reduce the

bit rate. The LPC provides parameters for a filter that mimics the vocal tract. The signal passes

through this filter, leaving behind a residual signal. Speech is encoded at 13 kbps.

3.4 GSM Frequencies:

In principle the GSM system can be implemented in any frequency band. However there are several

bands where GSM terminals are, or will shortly be available. GSM networks operate in a number of

different frequency ranges Most 2G GSM networks operate in the 900 MHz or 1800 MHz bands.

Furthermore, GSM terminals may incorporate one or more of the GSM frequency bands listed below

to facilitate roaming on a global basis.

Parameters P-GSM 900 E-GSM 900 GSM 1800 GSM 1900

Uplink frequency 890-915 MHz 880-915 MHz 1710-1785 MHz 1850-1910 MHz

Down link frequency

935-960 MHz 925-960 MHz 1805-1880 MHz 1930-1990 MHz

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Channel spacing 200 kHz 200 kHz 200 kHz 200 kHz

Carrier Frequency 124 174 374 299

Duplex Distance 45 MHZ 45 MHZ 95 MHZ 80 MHZ

Table 3.2: GSM frequencies

GSM-900 uses 890-915 MHz to send information from the mobile station to the base station

(Uplink) and 935-960 MHz for the other direction (downlink), providing 125 RF channels spaced at

200 kHz. Duplex spacing of 45 MHz is used.

In Bangladesh cellular operators use the 900 and 1800 MHz frequency bands for GSM

communication. The 900 MHz frequency band is further classified into two parts:

E-GSM 900

P-GSM 900

Fig3.1: GSM interface

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In Bangladesh cellular operators use P-GSM 900 frequency.

3.5 GSM Interfaces:

Um interface: The air or radio interface standard that is used for exchanges between a

mobile (ME) and a base station (BTS / BSC).

Abis interface: Abis interface is a BSS internal interface linking the BSC and a BTS. It

allows control of the radio equipment and radio frequency allocation in the BTS.

A interface: To provide communication between the BSS and the MSC the A interface are

used. The interface carries information to enable the channels, timeslots and the like to be

allocated to the mobile equipments being serviced by the BSSs.

B interface: The B interface exists between the MSC and the VLR. The interface is used

whenever the MSC needs access to data regarding a MS located in its area.

C interface: The C interface is located between the HLR and a GMSC or a SMS-G. When a

call originates from outside the network, i.e. from the PSTN or another mobile network it

has to pass through the gateway so that routing information required to complete the call

may be gained. In addition to this, the MSC may optionally forward billing information to

the HLR after the call is completed and cleared down.

D interface: The D interface is situated between the VLR and HLR

E interface: The E interface provides communication between two MSCs. The E interface

exchanges data related to handover between the anchor and relay MSCs.

F interface: The F interface is used between an MSC and EIR. The communications along

this interface are used to confirm the status of the IMEI of the ME gaining access to the

network.

G interface: The G interface interconnects two VLRs of different MSCs.

H interface: The H interface exists between the MSC the SMS-G. It transfers short

messages.

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Chapter 4: Performance of Banglalink

4.1 GSM in Banglalink Components:

Banglalink was known as Sheba Telecom Pvt Ltd than had been providing GSM (Global Service of

Mobile) service in Bangladesh since 1998. Orascom Telecom have bought 100% share of Sheba

telecom in 2004 and give its new name as Banglalink. Banglalink Uses GSM technology. The GSM

technical specifications define the different entities that form the GSM network by defining their

functions and interface requirements. Banglalink performances are divided into five parts. These

are,

Mobile Station

Base Station Subsystem (BSS)

Network subsystem(NSS)

Operation & Maintenance (O&M)

IT

Fig 4.1: Performance of Banglalink

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Fig4.2 : General architecture of GSM network

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Fig4.3: Physical view GSM Architecture

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4.1.1 Mobile Station:

The MS (Mobile Station) is a combination of terminal equipment and subscriber data. The terminal

equipment as called ME (mobile equipment) and the subscriber’s data is stored in SIM.

So therefore, ME+SIM=MS

Fig 4.4: Mobile station

The mobile station (MS) consists of the mobile equipment (the terminal) and a smart card called

the Subscriber Identity Module (SIM). The SIM provides personal mobility. So that the user can

have access to subscribed services irrespective of a specific terminal. By inserting the SIM card into

another GSM terminal, the user is able to receive calls at that terminal, make calls from that

terminal, and receive other subscribed services. The mobile equipment is uniquely identified by the

International Mobile Equipment Identity (IMEI). The SIM card contains the International Mobile

Subscriber Identity (IMSI) used to identify the subscriber to the system, a secret key for

authentication, and other information. The IMEI and the IMSI are independent, thereby allowing

personal security.

4.1.2 Base Station Subsystem (BSS):

All radio-related functions are performed in the BSS, which consists of base station controllers

(BSCs) and the base transceiver stations (BTSs).

Base Station Controllers (BSC) —The BSC provides all the control functions and physical

links between the MSC and BTS. It is a high-capacity switch that provides functions such as

handover, cell configuration data, and control of radio frequency (RF) power levels in base

transceiver stations. A number of BSCs are served by an MSC.

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Base Transceiver Stations (BTS) —The BTS handles the radio interface to the mobile

station. The BTS is the radio equipment (transceivers and antennas) needed to service

each cell in the network. A group of BTSs are controlled by a BSC.

4.1.3 The Network Switching Subsystem (NSS):

The Network switching system (NSS), the main part of which is the Mobile Switching Center (MSC),

performs the switching of calls between the mobile and other fixed or mobile network users, as well

as the management of mobile services such as authentication.

Fig4.5: Network Switching Subsystem

The switching system includes the following functional elements.

4.1.3.1 Home Location Register (HLR)

The HLR is a database used for storage and management of subscriptions. The HLR is considered

the most important database, as it stores permanent data about subscribers, including a

subscriber's service profile, location information, and activity status. When an individual buys a

subscription in the form of SIM then all the information about this subscription is registered in the

HLR of that operator.

4.1.3.2 Mobile Services Switching Center (MSC)

The central component of the Network Subsystem is the MSC. The MSC performs the switching of

calls between the mobile and other fixed or mobile network users, as well as the management of

mobile services such as such as registration, authentication, location updating, handovers, and call

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routing to a roaming subscriber. It also performs such functions as toll ticketing, network

interfacing, common channel signaling, and others. Every MSC is identified by a unique ID.

4.1.3.3 Visitor Location Register (VLR)

The VLR is a database that contains temporary information about subscribers that is needed by the

MSC in order to service visiting subscribers. The VLR is always integrated with the MSC. When a

mobile station roams into a new MSC area, the VLR connected to that MSC will request data about

the mobile station from the HLR. Later, if the mobile station makes a call, the VLR will have the

information needed for call setup without having to interrogate the HLR each time.

4.1.3.4 Authentication Center (AUC)

The Authentication Center is a protected database that stores a copy of the secret key stored in each

subscriber's SIM card, which is used for authentication and ciphering of the radio channel. The AUC

protects network operators from different types of fraud found in today's cellular world.

4.1.3.5 Equipment Identity Register (EIR)

The Equipment Identity Register (EIR) is a database that contains a list of all valid mobile

equipment on the network, where its International Mobile Equipment Identity (IMEI) identifies

each MS. An IMEI is marked as invalid if it has been reported stolen or is not type approved.

4.1.3.6 Gateway Mobile Switching Center (GMSC)

A Gateway mobile services switching center is a node used to interconnect two networks. The

Gateway is often implemented in an MSC.

4.1.4 Operation and Maintenance (O&M):

The operations and maintenance center (OMC) is connected to all equipment in the switching

system and to the BSC. The implementation of OMC is called the operation and support system

(OSS).

Here are some of the OMC functions:

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Administration and commercial operation (subscription, end terminals, charging and

statistics).

Security Management.

Network configuration, Operation and Performance Management.

Maintenance Tasks.

The operation and Maintenance functions are based on the concepts of the Telecommunication

Management Network (TMN) which is standardized in the ITU-T series M.30. Following is the

figure which shows how OMC system covers all the GSM elements.

Fig4.6: Operation & Maintenance system

The OSS is the functional entity from which the network operator monitors and controls the

system. The purpose of OSS is to offer the customer cost-effective support for centralized, regional

and local operational and maintenance activities that are required for a GSM network. An important

function of OSS is to provide a network overview and support the maintenance activities of

different operation and maintenance organizations.

4.1.5 Information Technology (IT):

The IT department, as is evident from the name, is in charge of all hardware and software and

program requirement of all departments.

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Chapter 5: The Base Station System

5.1 Introduction:

The GSM base station controller (BSC) provides the control functions and physical links between

the mobile services switching center (MSC) and the base transceiver station (BTS). It provides

functions such as handover, cell configuration data and control of radio frequency (RF) power

levels in base transceiver stations. A number of base station controllers (BSCs) are served by a

single mobile services switching center (MSC).

The base station subsystem (BSS) is the section of a traditional cellular telephone network which is

responsible for handling traffic and signaling between a mobile phone and the network switching

subsystem. The BSS carries out transcoding of speech channels, allocation of radio channels to

mobile phones, paging, transmission and reception over the air interface and many other tasks

related to the radio network.

The Base Station System (BSS) is responsible for all the radio related functions in the system, such

as:

Radio communication with the mobile units

Handover of calls in progress between cells

Management of all radio network resources and cell configuration data.

5.2 BSS Components:

Ericsson’s BSS consists of three components. This are,

Base Station Controller (BSC): the BSC is the central node within a BSS and co-ordinates

the actions of TRCs and RBSs.

Transcoder Controller (TRC): the TRC provides the BSS with rate adaptation capabilities.

This is necessary because the rate used over the air interface and that used by MSC/VLRs

are different - 33.8 kbits/s and 64 kbits/s respectively. A device, which performs rate

adaptation, is called a transcoder.

Radio Base Station (RBS): an RBS acts as the interface between MSs and the network, by

providing radio coverage functions from their antennae.

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http://en.wikipedia.org/wiki/Air_interface

http://en.wikipedia.org/wiki/Reception

http://en.wikipedia.org/wiki/Transmission

http://en.wikipedia.org/wiki/Paging_(telecommunications)

http://en.wikipedia.org/wiki/Transcoding

http://en.wikipedia.org/wiki/Network_switching_subsystem

http://en.wikipedia.org/wiki/Network_switching_subsystem

http://en.wikipedia.org/wiki/Mobile_phone

http://en.wikipedia.org/wiki/Cellular_network


The term RBS used only for if the system using Ericsson vendor. Banglalink operator used RBS

system. If there is any vendor system used then it’s called BSC.

Fig 5.1: BSS in Ericssons GSM systems

5.2.1 Base Station Controller and Transcoder Controller:

The Ericsson BSC product family consists of a combined BSC/TRC and a remote BSC (without tr

nscoders). The transcoders are pooled, meaning they can be allocated on demand – Full rate, Half

rate, Enhanced Full Rate, AMR (Adaptive Multi Rate) Full Rate or AMR Half Rate. There two main

options available for implementing the TRC and BSC in Ericssons BSS:

BSC/TRC: A combined BSC and TRC. This is suitable for medium and high capacity

applications, e.g. urban and suburban area networks. The node can handle up to 1,020

transceivers (TRXs). 15 remote BSCs can be supported from one BSC/TRC.

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Stand-alone BSC and stand-alone TRC: The stand-alone BSC (without transcoders) is

optimized for low and medium capacity applications and is a complement to the BSC/TRC,

especially in rural and suburban areas. It caters for up to 500 TRXs. The stand-alone TRC is

located at the MSC/VLR to increase transmission efficiency. A stand-alone TRC can support

16 remote BSCs.

Fig 5.2: TRC utilization and transmission rates in BSS

5.2.2 Transcoder Controller (TRC):

TRC function:

The primary functions of a TRC are to perform transcoding and to perform rate adaptation.

Transcoding:

As previously explained, the function of converting from the PCM coder information (following A/D

conversion) to the GSM speech coder information is called transcoding. This function is present in

both the MS and the BSS.

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Rate Adaptation:

Rate adaptation involves the conversion of information arriving from the MSC/VLR at a rate of 64

kbits/s to a rate of 16 kbits/s, or transmission to a BSC (for a full rate call). These 16 kbits/s

contains 13 kbits/s of traffic and 3 kbits/s of in band signaling information. This is an important

function. Without rate adaptation the links to the BSC would require four times the data rate

capabilities. Such transmission capabilities form an expensive part of the network. By reducing the

rate to 16 kbits/s, it is possible to use one quarter of the transmission links and equipment.

In Ericssons GSM systems, the TRC contains units, which perform transcoding and rate adaptation.

These hardware units are called Transcoder and Rate Adaptation Units (TRAUs). All TRAUs are

pooled, meaning that any BSC connected to the TRC can request the use of one of the TRAUs for a

particular call.

The TRC also supports discontinuous transmission. If pauses in speech are detected, comfort noise

is generated by the TRAU in the direction of the MSC/VLR. In GSM mobile systems, the transcoder

(TRA) is located in the GSM/BSS.

5.2.2.1 TRAU (Transcoding Rate and Adaptation Unit):

The Transcoding Rate and Adaptation Unit. (TRAU) protocol is an

entity that performs a transcoding function for speech channels and

RA (Rate Adaptation) for data channels. It works as follows: when

the transcoders/rate adaptors are positioned remote to the BTS, the

information between the Channel Codec Unit (CCU) and the remote

Transcoder/Rate Adaptor Unit (TRAU) is transferred in frames with

a fixed length of 320 bits (20 ms). These frames are denoted "TRAU

frames". Within these frames, both the speech/data and the TRAU

associated control signals are transferred.

The Abis interface should be the same if the transcoder is positioned

1) at the MSC site of the BSS or if it is positioned 2) at the BSC site of

the BSS. In case 1), the BSC should be considered as transparent for

16 kbit/s channels.Fig 5.3: TRAU

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In case of 4,8 and 9,6 kbit/s channel coding when data is adapted to the 320 bit frames, a

conversion function is required in addition to the conversion/rate adaptation specified in GSM

08.20. This function constitutes the RAA. In case of 14,5 kbit/s channel coding, no RAA rate

adaptation is required because V.110 framing is not used.

The TRAU is considered a part of the BSC, and the signaling between the BSC and the TRAU (e.g.

detection of call release, handover and transfer of O&M information) may be performed by using

BSC internal signals. The signaling between the CCU and the TRAU, using TRAU frames as specified

here, is mandatory when the Abis interface is applied.

5.2.2.2TRAU Feature Overview:

High fault tolerance due to 2n redundancy in central

parts and n+1 redundancy in line interfaces

Sophisticated redundancy concept. Hardware faults

have no impact on existing calls

Easy system upgrade through software download

Handling of different software loads at a time

Addition of line interfaces and BTSs without traffic

interruption

Various Abis interface configurations (star, multidrop,

loop)

Various transmission media (e.g., microwave,

PCM30/PCM24, satellite)

One LMT for all entities

Queuing and priority

IMSI/Cell tracing

Short Message Service (SMS)

SMS cell broadcast

Multiband operation

Support of hierarchical cell structure (up to 16 different priority levels)

Support of VAD/DTX

Full support of all existing and upcoming GSM data services: HSCSD, GPRS, EDGE

ASCI

Fig 5.4.: Front view of TRAU

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Full-rate, half-rate, enhanced full-rate, AMR

A interface pools supported

Other GSM services up to phase 2+

Tandem-free operation

Prepared for location services

5.2.2.3 TRAU interfaces:

5.2.2.4 TRAU function:

The functions inside the TRAU are:

"Remote Transcoder and Rate Adaptor Control Function" (RTRACF);

"Remote Speech Handler Function" (RSHF);

The RAA function in case of 4,8 and 9,6 kbit/s channel coding;

The RAA' function in case of 14,5 kbit/s channel coding;

The RA2 function;

The transcoder function.

Optionally the TFO functions (see GSM 08.62).

The protocol header structure of the TRAU protocol is as follows:

8 7 6 5 4 3 2 1 octetsSynchronize 1

2Syn Frame Type 3

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5.2.2.5 Synchronize:

The frame synchronization is obtained by means of the first two octets in each frame, with all bits

coded binary "0", and the first bit in octet no. 2, 4, 6, 8, ... 38 coded binary "1".

5.2.2.6 Frame Type:

The Frame Type:

25681416202226272831

Full RateO&M Adaptive Multi-RateDataIdle SpeechIdle SpeechData 14.5Data Enhanced Full RateO&M Full RateExtended Data

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Fig 5.5: TRAU Configuration

5.3 Base Transceiver Station

The Base Transceiver Station (BTS) handles the radio

interface to the mobile station. The BTS is the radio

equipment (transceivers and antennas) needed to service

each cell in the network. A group of base transceiver stations

(BTSs) is controlled by a base station controller (BSC).

The Base Transceiver Station, or BTS, contains the

equipment for transmitting and receiving of 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 picocell will

have several transceivers (TRXs) which allow it to serve

several different frequencies and different sectors of the cell (in the case of sectorised base

stations). A BTS is controlled by a parent BSC via the Base Station Control Function (BCF). The BCF

is implemented as a discrete unit or even incorporated in a TRX in compact base stations. The BCF

provides an Operations and Maintenance (O&M) connection to the Network Management System

(NMS), and manages operational states of each TRX, as well as software handling and alarm

collection.

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, 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 intra cell handover (HO)

can be fully handled. The advantage in this case is less load on the expensive Abis interface.

The BTSs are equipped with radios that are able to modulate layer 1 of interface Um; for GSM 2G+

the modulation type is GMSK, while for EDGE-enabled networks it is GMSK and 8-PSK.

Fig 4.6: BTS

Fig 5.6: BTS

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Antenna combiners are implemented to use the same antenna for several TRXs (carriers), the more

TRXs are combined the greater the combiner loss will be. Up to 8:1 combiners are found in micro

and pico cells only.

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 BCCH

(Broadcast Control Channel).

5.3.1 Sectorisation

By using directional antennas on a base station, each pointing in different directions, it is possible

to sectorise the base station so that several different cells are served from the same location.

Typically these directional antennas have a beamwidth of 65 to 85 degrees. This increases the

traffic capacity of the base station (each frequency can carry eight voice channels) whilst not greatly

increasing the interference caused to neighboring cells (in any given direction, only a small number

of frequencies are being broadcast). Typically two antennas are used per sector, at spacing of ten or

more wavelengths apart. This allows the operator to overcome the effects of fading due to physical

phenomena such as multipath reception. Some amplification of the received signal as it leaves the

antenna is often used to preserve the balance between uplink and downlink signal.

5.4 Base Station Controller

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The Base Station Controller (BSC) provides, classically, the intelligence

behind the BTSs. Typically a BSC has 10s or even 100s of BTSs under its

control. The BSC handles allocation of radio channels, receives

measurements from the mobile phones, controls handovers from BTS to

BTS (except in the case of an inter-BSC handover in which case control is

in part the responsibility of the Anchor MSC). 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)

(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 BSC is undoubtedly the most robust element in the BSS as it is

not only a BTS controller but, for some vendors, a full switching

center, as well as an SS7 node with connections to the MSC and

SGSN (when using GPRS). It also provides all the required data to

the Operation Support Subsystem (OSS) as well as to the performance measuring centers.

A BSC is often based on a distributed computing architecture, with

redundancy applied to critical functional units to ensure

availability in the event of fault conditions. Redundancy often

extends beyond the BSC equipment itself and is commonly used in

the power supplies and in the transmission equipment providing

the A-ter interface to PCU.

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

Fig 5.7: HUAWEI BSC 6000

Fig 5.8: Ericsson BSC

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BSC. This data is obtained directly from radio planning engineering which involves modeling of the

signal propagation as well as traffic projections.

5.4.1 Transcoder

Although the Transcoding (compressing/decompressing) function is as standard defined as a BSC

function, there are several ven dors which have implemented the solution in a stand-alone rack

using a proprietary interface. This subsystem is also referred to as the TRAU (Transcoder and Rate

Adaptation Unit). The transcoding function converts the voice channel coding between the GSM

(Regular Pulse Excited-Long Term Prediction, also known as RPE-L PC) coder and the CCITT

standard PCM (G.711 A-law or u-law). Since the PCM coding is 64 kbit/s and the GSM coding is 13

kbit/s, this also involves a buffering function so that PCM 8-bit words can be recoded to construct

GSM 20 ms traffic blocks, to compress voice channels from the 64 kbit/s PCM standard to the 13

kbit/s rate used on the air interface. Som e networks use 32 kbit/s ADPCM on the terrestrial side of

the network instead of 64 kbit/s PCM and the TRAU convert accordingly. When the traffic is not

voice but data such as fax or email, the TRAU enables its Rate Adaptation Unit function to give

compatibility between the BSS data rates and the MSC capability.

However, at least in Siemens' and Nokia's architecture, the Transcoder is an identifiable separate

sub-system which will normally be co-located with the MSC. In some of Ericsson's systems it is

integrated to the MSC rather than the BSC. The reason for these designs is that if the compression of

voice channels is done at the site of the MSC, fixed transmission link costs can be reduced.

5.4.2 Packet Control Unit:

The Packet Control Unit (PCU) is a l ate addition to the GSM standard. It performs some of the

processing tasks of the BSC, but for packet data. The allocation of channels between voice and data

is controlled by the base station, but once a channel is allocated to the PCU, the PCU takes full

control over that channel.

The PCU can be built into the base station, built into the BSC or even, in some proposed

architectures, it can be at the SGSN site.

5.5 BSS interfaces:

Fig 5.9: Front view of BSC

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Fig 5.10: BSS interfaces

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BSS interfaces are:

Um: The air interface between the mobile station (MS) and the BTS. This interface uses LAPDm

protocol for signaling, to conduct call control, measurement reporting, handover, power control,

authentication, authorization, location update and so on. Traffic and signaling are sent in bursts of

0.577 ms at intervals of 4.615 ms, to form data blocks each 20 ms.

A: The interface between the BSC and MSC. It is used for carrying traffic channels and the BSSAP

user part of the SS7 stack. Although there are usually transcoding units between BSC and MSC, the

signaling communication takes place between these two ending points and the transcoder unit

doesn't touch the SS7 information, only the voice or CS data are transcoded or rate adapted.

Ater: The interface between the BSC and transcoder. It is a proprietary interface whose name

depends on the vendor (for example Ater by Nokia), it carries the A interface information from the

BSC leaving it untouched.

Gb: Connects the BSS to the SGSN in the GPRS core network.

5.6 Base Station Antenna:

Antennas play a very important part in a communications system, coupling energy between a

transmitter or receiver and the propagation medium. While an antenna can be as simple as a piece

of wire, more suitable antenna designs are available. Matching the correct antenna to the set

ensures maximum radiated power. In practice, different designs suit a different application, which

has led to the design and development of a great many different types of antenna.

An antenna ideally has the following characteristics (particularly when deployed as part of a mobile

communications system):

Directionality and gain: A compromise must be made between saving transmitter power

(having high gain) and requiring high alignment accuracy or directionality (difficult to

achieve in the field).

Bandwidth: The antenna should preferably not require readjustment when the frequency

is changed (within limits of course).

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http://en.wikipedia.org/wiki/GPRS_core_network

http://en.wikipedia.org/wiki/Signalling_System_7

http://en.wikipedia.org/wiki/Authorization

http://en.wikipedia.org/wiki/Authentication

http://en.wikipedia.org/wiki/Power_control

http://en.wikipedia.org/wiki/Handoff

http://en.wikipedia.org/wiki/Mobile_station

http://en.wikipedia.org/wiki/Um_Interface


Low sidelobes: The radiation pattern should have limited power in other than the desired

direction to limit eavesdropping, direction finding, jamming and mutual interference.

Size: Antennas should be small and robust for ease of handling.

A base station antenna can be either:

Omni-directional Antenna

Sectoring antenna

5.6.1 Omni-directional Antenna

An omnidirectional antenna is an antenna system which radiates power

uniformly in one plane with a directive pattern shape in a perpendicular

plane. A GSM omni antenna is an omni-directional base station antenna.

An Omni antenna is used for cells that are required to cover the whole

area around a base station. Omni-directional cell-served by a BTS with

an antenna which transmits equally in all directions.

5.6.2 Sectoring Antenna

A GSM omni antenna is a directional base station antenna. A sectoring antenna

is used in GSM cells that cover only part of the area around a base station. A

sectoring antenna often has a beam width of approximately 120 degrees. From

the front, the sectoring antenna is usually rectangular.

Fig 5.12: Sectoring Antenna

Fig 5.11: Omni Antenna

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http://en.wikipedia.org/wiki/Antenna_(electronics)


Chapter 6: Network Management Subsystem

6.1 Introduction:

Network switching subsystem (NSS) (or GSM core network) is the component of a GSM system that

carries out call switching and mobility management functions for mobile phones roaming on the

network of base stations. It is owned and deployed by mobile phone operators and allows mobile

devices to communicate with each other and telephones in the wider Public Switched Telephone

Network or (PSTN). The architecture contains specific features and functions which are needed

because the phones are not fixed in one location.

The NSS originally consisted of the circuit-switched core network, used for traditional GSM services

such as voice calls, SMS, and circuit switched data calls. It was extended with overlay architecture to

provide packet-switched data services known as the GPRS core network. This allows mobile phones

to have access to services such as WAP, MMS, and Internet access.

Mobile networks require an efficient and easy-to-use operation and maintenance (O&M) system

because:

Mobile networks are extremely complex

The structure of a mobile network is often altered to allow for extension and optimization of

the network

Mobile network operators demand the reduction of O&M costs.

Operation and Support System (OSS) provides an efficient and easy-to-use O&M system. OSS is an

application within the Telecommunications Management and Operations Support (TMOS) product

family. The main purposes of the GSM OSS are to provide a network overview and support the

maintenance activities of different operation and maintenance organizations.

6.2 TMOS

6.2.1 Telecommunications Management Network (TMN):

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http://en.wikipedia.org/wiki/Multimedia_Messaging_Service

http://en.wikipedia.org/wiki/Wireless_Application_Protocol

http://en.wikipedia.org/wiki/Circuit_Switched_Data

http://en.wikipedia.org/wiki/Short_message_service

http://en.wikipedia.org/wiki/GSM_services

http://en.wikipedia.org/wiki/Core_network

http://en.wikipedia.org/wiki/Public_Switched_Telephone_Network

http://en.wikipedia.org/wiki/Public_Switched_Telephone_Network

http://en.wikipedia.org/wiki/Telephone

http://en.wikipedia.org/wiki/Mobile_phone_operator

http://en.wikipedia.org/wiki/Base_Station_subsystem

http://en.wikipedia.org/wiki/Roaming

http://en.wikipedia.org/wiki/Mobile_phones

http://en.wikipedia.org/wiki/Mobility_management

http://en.wikipedia.org/wiki/Telephone_exchange

http://en.wikipedia.org/wiki/GSM


TMOS is defined as the Ericsson management and operations support solution for public

telecommunications networks. TMOS has been developed in accordance with Telecommunications

Network Management (TMN) standards. TMN specifies an O&M network which is:

Centralized

Separate from the telecommunications network

Connected to the telecommunications network via standardized interfaces.

One of the basic principles of the TMN system architecture is the network model concept. This

means that the physical network elements (NEs) such as MSCs are represented in a model of the

network. Databases are used to store data about NEs.

6.2.2 TMOS Structure and Functions:

TMOS consists of a “family” of management application systems for different telecom networks. For

example,

Service Management Application System (SMAS) for Intelligent Networks (IN).

eXchange Management system (XM) for switched networks.

Cellular Management Application System (CMAS) for cellular mobile networks.

All TMOS application systems are built on the TMOS PlatForm (TPF). The TPF comprises all

hardware and software for interaction with a telecommunications network. The platform is a multi-

computer system based on industrial standards, such as UNIX and SQL.

The TMOS Development Platform (TDP) makes it possible for the operator to create market specific

functions using the C++ Application Programming Interface (API).

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Fig 6.1: Structure of TMOS

TMOS resides in several independent computers that are connected over a Local Area Network

(LAN) or Wide Area Network (WAN). TMOS communication with the NEs is based on the Open

System Interconnection (OSI) model. OSS is connected directly, or via the PSTN, to the MSCs, HLRs,

BSCs and AUC/EIRs. Communication with BTSs is provided via BSCs. Additionally, other Ericsson

certified nodes are supported. These include the MXE, MIN nodes and the DXX.

TMOS performs the following functions in line with TMN recommendations:

Configuration management

Fault management

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Performance management

Security management

Accounting management

6.2.3 Advantages of TMOS:

TMOS has largely consisted of demands from operators for a network maintenance system, which

will give lower maintenance and personnel costs. The most significant advantages of TMOS are:

It gives the user the ability to remotely and centrally control NEs, subscribers, traffic, etc.

In a large network, optimal performance is impossible to achieve without a support system

like TMOS.

TMOS is easy to use, employing menus, forms and graphics to interact with the operators.

New TMOS functions are continuously being developed which means that the system adapts

to new and changing conditions and requirements.

6.3 OSS Structure and Functions:

OSS (Operation Support System) is the product name for Ericssons O&M (Operation and

Maintenance) system for cellular networks. OSS consists of Exchange Management System (XM)

features and Cellular Management Application System (CMAS) features built on top of the TMOS

Platform (TPF).

The GSM network contains many NEs that may be spread over a large geographical area.

OSS enables centralized, remote controlled O&M of all NEs in a uniform and user-friendly

manner.

OSS is physically implemented on a LAN consisting of servers and workstations.

The functions provided by the graphical user interfaces of OSS are translated into

commands, which are then sent to one or several NEs.

OSS is not one tool, rather 50 different applications used by different staff for operating the

network.

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Fig 6.2: Structure of OSS

Although the GSM network is complex, OSS is easy to use. OSS consists of about 50 applications that

can be used to solve different tasks. It offers menus, windows and graphics with which the

operators can interact. No long, complicated commands are needed to operate the system.

6.4 NMC and OMC:

According to GSM specifications, a system such as OSS can be seen as a two level management

function that provides centralized control of the network. The levels are:

Network Management Center (NMC): NMC staff can concentrate on long-term system-wide

issues.

Operation and Maintenance Center (OMC): OMCs concentrate on short-term regional issues.

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Fig 6.3: NMC and OMC

In OSS, the OMC and NMC functions can be combined in the same physical installation or

implemented at different sites.

6.5 OSS Applications:

OSS includes applications for the supervision, configuration and performance management in a

cellular network. In addition to the applications for handling a cellular network, OSS also provides

basic functions. For example, alarm handling and file transfer. The figure below shows most of the

OSS applications.

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Fig 6.4: OSS applications

Radio Network Management main features are:

Central administration to optimize the use of skilled personnel

Supervision of network operation for planning purposes

Network performance measurement

Traffic recording and analysis of measurement and event data

Cellular network configuration

OSS maximizes service quality in cellular networks by providing a centralized facility for

network configuration, administration, performance measurement, and maintenance of the

network components.

Radio Network Management is achieved through the following different applications listed below:

Basic OSS-Node Administration (BOA)

Cellular Network Administration (CNA)

Cellular Network Administration Interface (CNAI)

CNA / Move BSC

Work Task Package (WTP)

Radio Network Recording Functions (RNR)

Network Statistics, Analyzer

Network Statistics, Statistical Measurement Initiator and Administration (SMIA)

Network Statistics, Statistical Gateway (SGw)

Network Statistics, Statistical Data Mart (SDM)

Network Statistics, Performance Alarms

BTS Configuration Management (BCM)

BTS Hardware Management (BHW)

BTS Alarm Management (BAM)

BTS Software Management (BSW)

Frequency Allocation Support (FAS)

Frequency Optimization Expert (FOX)

Neighboring Cell Support (NCS)

Neighboring Cell List Optimization Expert (NOX)

Measurement Result Recording (MRR)

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6.6 Configuration Management Applications

6.6.1 Cellular Network Administration (CNA):

Cellular Network Administration (CNA) is an application within OSS that is used to:

Plan and operate the cellular part of the GSM network

Plan major future changes off-line

Implement new cells or new parameter values in the network

CNA is one of the most powerful OSS applications. It registers new cells and maintains cell

parameters in an efficient and controlled manner. In large PLMNs the amount of network data is

huge. CNA provides an efficient tool for handling cell data consisting of approximately 200

parameters per cell. Most of these parameters identify the cell and control the cell behavior. The

operator can edit cell parameters and cell related parameters through a table mode, a menu mode

and a geographical mode that displays cell shapes and cell parameters on top of map layers.

6.6.2 CNA Network Model Structure and Areas:

Network structure and parameters change over time. Operators are not just interested in the

current set-up, but also interested in information about previous set-ups and possible future ones.

Therefore, OSS provides the following three different views of the network:

Valid Area: The valid area represents the current cellular network. That is, it provides

current information about the cell parameters in the network. There is only one valid area

corresponding to each cellular network. The valid area is used when retrieving information

about current network parameter values and as a basis when creating a new planned area.

Planned Area: Planned area represents planned changes in the cellular network. This area

is used for off line planning of large network changes. It is locked and connected to one user

at a time.

Fallback Area: Fallback area is a snapshot of the valid area at a specific moment and

reflects an historical view of the network. A fallback area can be created for back-up

purposes before an update to the network takes place. It is also possible to create a new

planned area from a fallback area.

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Fig 6.5: CNA area concept

6.6.3 Consistency check:

The CNA consistency check automatically performs separate validity checks on the networks

parameters. It ensures that the values of parameters are valid and that they are within predefined

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intervals. All parameters are checked against parameter consistency rules. The consistency check

can be performed on:

· Area level (Valid and Planned Area)

· MSC

· BSC

· Cell level

A consistency report generates warnings but does not prevent a faulty value from being entered.

Consistency checks can be performed on all parameters or only on new parameters.

6.6.4 CNA Interface (CNAI):

The Cellular Network Administration Interface (CNAI) tool serves as an import and export interface

to the CNA application. It provides easy exchange of information between the OSS and an external

system. For example, CNAI could be used to transfer a file of cell parameter data from the external

cell planning application, TEMS, into the OSS. Otherwise, the cell parameter data from TEMS would

have to be manually entered using CNA.

6.7 BTS Management Application:

The BTS Management application supports operator’s daily BTS-related operations in the network.

It can be distinguished by its use of a graphical browser which shows the internal base station

structure.

The graphical browser enables the operator to navigate through the BTS/Transceiver Remote

Interface (TRI) managed object structure in a consistent and efficient way. The BTS Management

consists of:

BCM: BTS Configuration management

BSW: BTS Software management

BHW: BTS Hardware management

BAM: BTS Alarm Management

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Fig 6.6 : BTS Management Family

6.7.1 BTS Configuration Management (BCM)

The BTS configuration Management (BCM) application offers a centralized interface to handle BTS

configuration. BCM provides the operator with a user friendly view of the BTS/TRI managed objects

and their different parameters throughout the network. BCM helps the operator in the following

areas:

Introduction of a new BTS. When a new BRS is added to the system, BTS related data must

be entered by the operator. This includes software, hardware, future expansion options etc.

Reconfiguration of an existing BTS. BTS reconfiguration follows the same procedures as for

a new BTS. In this case, only the new data values are entered by the operator.

Servicing of a BTS. The operator has the ability to enable or disable the entire BTS or

subordinate parts of the BTS to perform network service. From the browser, the user may

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block individual boards of a BTS structure all the way up to the entire BTS. Deblocking is

also possible.

6.7.2 Base Station Software Management (BSW)

The BTS software management (BSW) feature caters for the downloading and handling of BTS

related software in a centralized manner. Software can be read into the OSS and stored there for

subsequent transfer to the BTS via the BSCs.

BSW enhances the operator’s control over BTS related software, and reduces the overall risk of

introducing errors when updating or maintaining the software. BSW includes functions for:

Storing and administering BTS software in the OSS.

Retrieving all relevant information about the stored packages

Loading BTS software.

Displaying BTS software status.

Displaying BTS software history.

Automatically updating software register.

Providing search capabilities.

6.7.3 Base Station Hardware Management (BHW)

The BHW application provides the operator with a hardware register of the installed BTS

Replacement Units (RU). BHW enables the operator to perform the following task:

Audit the installed BTSs

Search and compare on various BTS criteria

Compare installed hardware.

By using the BHW application, the user can easily identify RUs, their revisions and serial numbers

installed on a site.

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Fig 6.7: BTS Software Management

6.7.4 Base Station Alarm Management (BAM)

The BTS Alarm Management (BAM) application provides support for handling the alarm reporting

function in the BSC. This allows the operator to configure the BTS alarm reporting and make the

fault finding process easier by filtering and customizing the alarm flow.

BAM contains functions for:

Configuration of BTS alarm reporting

Interworking with fault management

BTS error log administration

Retrieving suppressed alarms

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6.8 Separation of BTS Software Download and Upgrade

This feature enables the operator to perform a BTS software upgrade in two steps by introducing

the possibility to separate the software download and upgrade. By using this feature the operator

is able to perform software download during busy times and only start the new software at quiet

times, e.g. at night. The key points of the feature are:

Simplify BTS software upgrade

Different command interfaces

Download BTS software

Start (upgrade) the downloaded BTS software

Backward compatible

There is a new observation alarm when software is loaded but not started. This alarm will cease

when all managed objects are started.

6.9 Operation and Maintenance Features

6.9.1 Remote Function Change:

The remote function change feature introduces a radically new way to upgrade software. Instead of

sending a rollout team on-site to upgrade the software by following an implementation procedure

described on paper, the upgrade team can now sit at the OMC site and supervise the execution of a

software program that remotely upgrades the software in the target exchange.

Using OSS applications, an upgrade team can supervise the remote upgrade of at least 30 exchanges

in parallel from one OSS terminal.

The upgrade procedure is performed using software scripts. The OSS plays a key role. The upgrade

is monitored and controlled by the OSS application Software Management Organizer (SMO).

6.9.2 Real Time Event Data:

The Real Time Event Data features will provide access to radio network events on a real time basis.

The feature together with the OSS feature, Real Time Performance Monitoring (R-PMO), will

provide an effective and user friendly way of monitoring network performance in real time from

the OMC site. The feature complements the already existing possibilities of performance

measurements and recordings in the BSC and OSS.

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The feature introduces a reporting mechanism in the BSC that provides information about events in

the radio network, i.e. event data, on a real time basis. The event data is time stamped, which

makes it possible to monitor the speech quality immediately before and after a parameter change

has been introduced. The feature complements the already existing performance measurement

and recording functions in the BSC and OSS, by providing faster access to event data.

At the OSS site, the operator can view the event data in graphs and tables print and save it by using

R-PMO functions. Performance warnings can also be set in the OSS to monitor network

disturbances. By using the feature, feedback from radio network design and optimization activities

are available instantly.

6.10 Fault Management Applications

Fault Management is collecting alarms and is connected all NEs (Network Elements) that it is

necessary to supervise and where to take action on alarms. Available tools within OSS fault

management are described below.

6.10.1 Network Alarm Status viewer:

A common operator task is to supervise the network alarm status and to act upon incoming alarms.

All alarms, including internal and external alarm are routed to OSS. Alarms from NEs will be

forwarded to OSS if the alarms in the NE are defined to be routed to the OSS and if the alarms are

defined in the OSS as expected output from the NE.

Depending on alarm severity and operator defined parameters, an alarm bell can be activated. It is

also possible to filter alarms so that only certain alarms are presented. The alarms are presented on

a graphical map of the operating area, called Network Status Presentation (NSP). The alarms are

displayed next to the affected NE. Different symbols are used to depict different alarm-categories:

6.10.2 Alarm severity When to take action

Critical Action must be taken immediately

Major Action must be taken as soon as possible

Minor Action should be taken when there is time, or the situation should be observed

Warning Take corrective action during routine maintenance

Indeterminate an alarm has been generated for which there no alarm severity is defined in the

system

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6.10.3 Fault Management

Fault Management is the all-inclusive name for the different alarm handling functions (Alarm

Handling). Events reported from NEs, as well as data link faults, external alarms and OSS internal

errors are processed and distributed to the following end-user services:

Alarm Viewer

Alarm Status Viewer

The user can view the alarms with the Alarm Viewer, which consists of three applications with

graphical user interfaces: the Alarm List Viewer, the Alarm Log Browser and the Alarm Status

Matrix.

With Alarm List Viewer, the user can view details of the current alarms, and also handle these

alarms. With the Alarm Log Browser, the user can search for specific alarms in the alarm log and

view details and statistics of these alarms. With the Alarm Status Matrix, the users can overview the

current alarm situation in the network in a compressed view.

The Alarm Status Viewer presents the current alarm in the Geographical and Logical Network

Information Presentation (GNIP) framework, which provides maps showing each supervised object

at its geographical position and views showing the logical relation between supervised objects also.

The Alarm Viewer and the Alarm Status Viewer can also be displayed by a Windows NT

workstation, but the main process is still executed in the UNIX server. An important feature of

Alarm Handling is the capability of other Operations Support Systems to subscribe to specific

alarms handled by OSS.

6.11 Performance Management Applications

Some performance management functions within OSS:

Network Statistics Analyzer (NWS)

Performance Management Traffic Recording (PMR)

Measurement Results Recording (MRR)

Frequency Allocation Support (FAS)

Neighboring Cell Selection and handling (NCS)

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6.11.1 Network Statistics Analyzer (NWS)

NWS is a set of reports in network planning and engineering. The reports focus on presenting data

used for managing, planning, and engineering a cellular network. The reports are divided into

three categories, giving different target groups reports especially designed for their needs:

Management reports

Planning and engineering reports

Operation reports

6.11.2 Performance Management Traffic Recording (PMR)

PMR provides detailed performance analysis of the radio network. The observed performance is

related to traffic behavior, such as setup of connections, handovers, and increased rate of dropped

calls. PMR provides support for the following Radio Network Recording (RNR) functions:

Mobile Traffic Recording (MTR): This provides measurement reports for identified MSs

(up to 64). This gives the operator the possibility to trace certain MSs to identify the causes

of problems. It can also be used to study network behavior in different situations by tracing

measurements from test mobiles. PMR takes short-term measurements on individual IMSIs.

Cell Traffic Recording (CTR): This gives the operator the possibility to study the network

behavior in certain cells by tracing measurements from up to 16 cells at the same time.

Channel Event Recording (CER): The performance of channel allocation functions in the

BSC can be studied, and improvements can be identified to increase the capacity and quality

of the network.

6.11.3 Mobile Results Recording (MRR)

Mobile Results Recording (MRR) is a graphical tool which supports the supervision of network

performance and trouble shooting by enabling the recording of radio characteristics such as:

Uplink/downlink signal strength

Uplink/downlink path loss

Power level used by MS

6.11.4 Frequency Allocation Support (FAS)

The interference level in GSM networks has to be kept to a minimum in order to achieve a high

speech quality. Due to increased network complexity, it is difficult to perform frequency planning to

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increase the capacity without increasing interference levels. Frequency Allocation Support (FAS) is

a tool that supports the operator in performing efficient frequency planning so that tighter

frequency re-use and less interference levels in the network can be achieved.

The operator can order FAS to perform recordings of the interference levels on up to 150

frequencies in up to 2,000 cells handled by one OSS. Once the recording is complete, the result

values are reported to OSS where they are processed and presented to the operator in tabular form

or graphically on a map.

6.11.5 Neighboring Cell Support (NCS)

Handover between cells have to be based on reliable and accurate measurements to keep speech

quality high, even near cell borders. For each cell the operator has to define a list of neighboring

cells (BA-list). The MS will measure on these defined neighboring cells and deliver the

measurements to the BSC, where an evaluation of the measurements can be made in order to make

handover decisions.

Due to the increased complexity of the radio network, it is more difficult to define an optimal list

that includes all possible handover cell candidates. Neighboring Cell Support (NCS) supports the

operator with this task.

6.12 Network Management Solutions (NMS)

NMS is an open solution based on existing standards and is designed for flexibility and scalability. It

is a fundamental platform for future expansion in network size, capacity and services. The solution

efficiently supports and at the same time provides the flexibility needed to handle organizational

demands or new service demands.

An important strategic concept is to build management solutions of modular components that in

themselves are world-class and best-of-breed product applications. Solutions built from pre-

integrated components to a verified working management solution will significantly decrease the

implementation time in the operator’s network.

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Fig 6.8: NMS Structure

6.13 Billing Gateway (BWG)

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BGW Functions:

A Billing Gateway (BGW) collects billing information or Call Data Record (CDR) files from network

elements such as MSCs and forwards them to post-processing systems that use the files as input. A

BGW acts as a billing interface to the network elements in any network and its flexible interface

supports adaptation to any new types of network elements. BGW is usually connected to the

customer administration and billing systems and is handled by the administrative organization.

BGW Implementation:

In GSM systems the BGW is implemented using Unix. Like the SOG, it contains a GUI enabling simple

management of the billing information. It can also be connected to OSS for operation and

maintenance purposes.

7.1Limitation of the Internship:

Restriction is the actual meaning of Limitation. Internship needs long period of visits to work field’s

money, patience and inspiration. But, limitation from the university as well as from the

organization such as time limit, no allowances, not being an employee yet, entry restriction in

secure places our knowledge yet remains much limited within the framework of the theoretical

knowledge and it needs further practice for right application to the real field of work. The main

problems of data collection are for management restriction of the company they did not provide all

necessary data and information to the internees. As a result there is some lacking regarding the

internship some information which are confidential to the company, was not revealed for the work.

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8.1 Conclusion:

In the practical training for a period of 90 days which helps to learned a lot about the planning of a

project, designing, and implementation and present scenario in the field IT networking of

Banglalink. In this time it helps to learn a lot about the present scenario in the field of

telecommunication I gained knowledge about the technology used by the Banglalink for network

building and maintenance. At my university I learn most of the things theoretically, which does not

provides sufficient information about the subject, and students remain unaware of the problems

and errors when they go to the field. This practical training has provided me the knowledge about

various technologies in the telecommunication field. I am highly grateful to the Banglalink family

for the support and guidance given to us for the successful completion of my internship. Working in

Banglalink as an internee is really pleasant and thrilling experience, for better future in the running

world.

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9.1 APPENDIX

A

A, Asub A-interface

API Application Programming

Interface

AUC Authentication Center

B

BAM BTS Alarm Management

BCCH Broadcast Control Channel

BCF Base Station Control Function

BCM BTS Configuration

management

BGW Billing Gateway

BHW BTS Hardware management

BSC Base Station Controller

BSS Base Station Subsystem

BSW BTS Software management

BTS Base Transceiver Station

C

CCU Channel Codec Unit

CDR Call Data Record

CER Channel Event Recording

CMAS Cellular Management

Application System

CNA Cellular Network

Administration

CNAI Cellular Network

Administration Interface

CTR Cell Traffic Recording

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D

DTX Discontinuous transmission

(mechanism)

E

EIR Equipment Identity Register

ETSI European

Telecommunications Standards Institute

F

FAS Frequency Allocation Support

FDMA Frequency Division Multiple

Access

G

GMSC Gateway Mobile Switching

Center

GNIP Geographical and Logical

Network Information Presentation

GSM Global system for mobile

communication

GPRS General Packet Radio Service

H

HLR Home Location Register

I

ISD International Subscriber

Dialing

ISDN Integrated Services Digital

Network

ISO International Standard

Organization

ISUP Integrated Services Digital

Network User Part/ISDN User Part

IMEI International Mobile

Equipment Identity

IMSI International Mobile

Subscriber Identity

IN Intelligent Network

IT Information Technology

ITU International

Telecommunication Union

L

LAN Local Area Network

LMT Local Maintenance Terminal

LPC Linear predictive coding

M

ME Mobile equipment

MRR Measurement Results

Recording

MS Mobile Station

MSC Mobile services Switching

Centre, Mobile Switching Centre

MSISDN Mobile Station International

ISDN Number

MTR Mobile Traffic Recording

N

NCS Neighboring Cell Selection and

handling

NMS Network Management

Subsystem

NSP Network Status Presentation

NSS Network SubSystem

NWS Network Statistics Analyzer

S

SIM Subscriber Identity Module

O

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OMC Operations & Maintenance

Centre

OSI Open System Interconnection

OSS operation and support system

P

PCU Packet Control Unit

PDH Plesiochronous Digital

Hierarchy

PMR Performance Management

Traffic Recording

PSDN Public Switched Data Network

PSTN Public Switched Telephone

Network

PSU Power Supply Unit

Q

QOS Quality of Service

R

RBS Radio Base Station

RF Radio Frequency

RHSF Remote Speech Handler

Function

R-PMO Real Time Performance

Monitoring

RTRACF Remote Transcoder and Rate

Adaptor Control Function

RU Replacement Units

S

SMAS Service Management

Application System

SMO Software Management

Organizer

SS7 Signaling System No.7

T

TCH Traffic Channel

TCSM TransCoder & Sub-Multiplexer

TDMA Time division multiple access

TDP TMOS Development Platform

TMN Telecommunications

Management Network

TMOS Telecommunications

Management and Operations Support

TPF TMOS PlatForm

TRAU Transcoder & Rate Adaptation

Unit

TRC Transcoder Controller

TRI Transceiver Remote Interface

TRX Transceiver (board)

U

UMTS Universal Mobile

Telecommunications System

V

VLR Visitor Location Register

W

WAN Wide Area Network

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9.2 GLOSSARY

A

A-bis

Interface between the BSC and BTS in a GSM

network.

Air interface

In a mobile phone network, the radio

transmission path between the base station

and the mobile terminal.

A-interface

Interface between the MSC and BSS in a GSM

network.

AMR

Adaptive Multi-Rate codec. Developed in

1999 for use in GSM networks, the AMR

has been adopted by 3GPP for 3G.

AUC

Authentication Centre; the element within a

GSM network which generates the

parameters for subscriber authentication.

B

Bandwidth

A term meaning both the width of a

transmission channel in terms of Hertz and

the maximum transmission speed in bits per

second that it will support.

BCH

Broadcast Channels; carry only downlink

information and are mainly responsible for

synchronisation and frequency correction

(BCCH, FCCH and SCH).

BCCH

Broadcast Control Channel; the logical

channel used in cellular networks to

broadcast signaling and control information

to all mobile phones within the network.

BER

Bit Error Rate; the percentage of received bits

in error compared to the total number of bits

received .

Bit

A bit is the smallest unit of information

technology. As bits are made up using the

binary number system, all multiples of bits

must be powers of two i.e. a kilobit is actually

1024 bits and a megabit 1048576 bits.

Transmission speeds are given in bits per

second (bit/s) wirelessly.

BSC

Base Station Controller; the network entity

controlling a number of Base Transceiver

Stations.

BSS

Base Station System/Subsystem.

BTS

Base Transceiver Station; the network entity

which communicates with the mobile station.

C

CDMA

Code Division Multiple Access; also known as

spread spectrum, CDMA cellular systems

utilize a single frequency band for all traffic,

differentiating the individual transmissions

by assigning them unique codes before

transmission.

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Cell

The area covered by a cellular base station. A

cell site may sectorise its antennas to service

several cells from one location Cell site The

facility housing the transmitters/receivers,

the antennas and associated equipment.

Cell splitting

The process of converting a single cell to

multiple cells by sectorising the antennas in

the cell site or constructing additional cells

within a cell site.

Circuit switching

A method used in telecommunications where

a temporary dedicated circuit of constant

bandwidth is established between two distant

endpoints in a network. Mainly used for voice

traffic; the opposite of packet switching.

Codec

A word formed by combining coder and

decoder the codec is a device which encodes

and decodes signals. The voice codec in a

cellular network converts voice signals into

and back from bit strings. In GSM networks,

in addition to the standard voice codec, it is

possible to implement Half Rate (HR) codecs

and Enhanced Full Rate (EFR) codecs.

Control signal

A signal sent to a cellular phone from a base

station or vice versa which carries

information essential to the call but not

including the audio portion of a conversation.

CPU

Central Processing Unit.

E

EIR

Equipment Identity Register; a database that

contains a list of all valid mobile stations

within a network based on their IMEI.

Erlang

A dimensionless unit of average traffic

density in a telecommunications network.

ETSI

European Telecommunications Standards

Institute: The European group responsible for

defining telecommunications standards.

F

FDMA

Frequency Division Multiple Access-a

transmission technique where the assigned

frequency band for a network is divided into

sub-bands which are allocated to a subscriber

for the duration of their calls.

G

GMSC

Gateway Mobile Services Switching Centre;

the gateway between two networks.

GPRS

General Packet Radio Service; standardized as

part of GSM Phase 2+, GPRS represents the

first implementation of packet switching

within GSM, which is a circuit switched

technology. GPRS offers theoretical data

speeds of up to 115kbit/s using multislot

techniques. GPRS is an essential precursor for

3G as it introduces the packet switched core

required for UMTS.

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GSM

Global System for Mobile communications,

the second generation digital technology

originally developed for Europe but which

now has in excess of 71 per cent of the world

market. Initially developed for operation in

the 900MHz band and subsequently modified

for the 850, 1800 and 1900MHz bands. GSM

originally stood for Groupe Special Mobile,

the CEPT committee which began the GSM

standardisation process.

H

Handoff

The transfer of control of a cellular phone call

in progress from one cell to another, without

any discontinuity.

HLR

Home Location Register; the database within

a GSM network which stores all the

subscriber data. An important element in the

roaming process.

I

IMEI

International Mobile Equipment Identity.

IMSI

International Mobile Subscriber Identity; an

internal subscriber identity used only by the

network.

IMT-2000

The family of third generation technologies

approved by the ITU. There are five members

of the family: IMT-DS, a direct sequence

WCDMA FDD solution IMT-TC, a WCDMA

TDD solution IMT-MC, a multicarrier solution

developed from cdma2000 IMT-SC, a single

carrier solution developed from

IS-136/UWC-136 IMT-FT, a TDMA/TDD

solution derived from DECT.

IN

Intelligent Network.

Internet

A loose confederation of autonomous

databases and networks. Originally

developed for academic use the Internet is

now a global structure of millions of sites

accessible by anyone.

Intranet

A private network which utilizes the same

techniques as the Internet but is accessible

only by authorized users.

IP

Internet Protocol.

IPv6

The next generation of IP addressing

designed to replace the current system IPv4

which uses a 32 bit address code which limits

the number of possible addresses. IPv6 uses a

128 bit code ensuring that the possible

number of IP addresses will be virtually

limitless .

ISDN

Integrated Services Digital Network.

ISO

International Standards Organization.

ISP

Internet Service Provider.

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ITU

International Telecommunications Union.

L

LAN

Local Area Network.

LAP

Link Access Protocol.

M

MHz

Megahertz; a unit of frequency equal to one

million Hertz.

MMS

Multimedia Messaging Service; an evolution

of SMS, MMS goes beyond text messaging

offering various kinds of multimedia content

including images, audio and video clips .

MS

Mobile Station.

MSC

Mobile Switching Centre; the switching centre

of a mobile phone network, the MSC has

interfaces to the BSCs, HLR, VLR and other

MSCs.

MSISDN

Mobile Station International ISDN Number.

Multiplexing

A telecommunications technique where

several channels can be combined to share

the same transmission medium. The most

common forms are Time Division

Multiplexing (TDM) and Frequency Division

Multiplexing (FDM).

O

OTA

Over the air activation (of services and tariff

changes).

O&M

Operations and Maintenance.

OMC

Operations and Maintenance Centre.

OMC-R

The radio OMC.

OMC-S

The switching OMC.

OSI

Open Systems Interconnection; a seven layer

model for protocols defined by ISO.

P

Packet switching

A communication system wherein the

information is transmitted in packets of a set

size. These packets have address headers and

find their way to their destination by the most

efficient route through the network.

Compared to circuit switching where a

connection is occupied until the traffic

exchange is completed, packet switching

offers considerable efficiencies as

connections can be used by a number of users

simultaneously.

PCM

Pulse Code Modulation; the standard digital

voice format at 64kbit/s.

PCU

Packet Control Unit; an element in a

GPRS/UMTS network.

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PDA

Personal Digital Assistant.

PIN

Personal Identifier Number.

PLMN

Public Land Mobile Network; any cellular

operator’s network.

PMR

Private Mobile Radio communications; two-

way radio technology widely used for

dispatch and delivery services, taxi

companies and the like. See TETRA.

PSDN

Public Switched Data Network.

PSPDN

Public Switched Packet Data Network.

PSTN

Public Switched Telephone Network.

PSU

Power Supply Unit.

Q

QoS

Quality of Service; a broad term to describe

the performance attributes of an end-to-end

connection.

R

RACH

Random Access Channel; uplink only, allows

the MS to request an SDCCH in response to a

page or for a call.

RAM

Random Access Memory.

Reuse

The assignment of frequencies or channels

to cells so that adjoining cells do not use the

same frequencies and cause interference

whereas more distant cells can use the same

frequencies. Reuse expands the capacity of a

cellular network by enabling the use of the

same channels throughout the network.

S

SGSN

Serving GPRS Support Node; the gateway

between the RNC and the core network in a

GPRS/UMTS network.

SIM

Subscriber Identity Module; A smart card

containing the telephone number of the

subscriber, encoded network identification

details, the PIN and other user data such as

the phone book. A user.s SIM card can be

moved from phone to phone as it contains all

the key information required to activate the

phone.

SMS

Short Message Service; a text message service

which enables users to send short messages

(160 characters) to other users. A very

popular service, particularly amongst young

people, with 400 billion SMS messages sent

worldwide in 2002.

SS7

Signaling System Number 7 (See CCS7).

STM

Synchronous Transfer Mode.

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T

TDMA

Time Division Multiple Access; a technique

for multiplexing multiple users onto a single

channel on a single carrier by splitting the

carrier into time slots and allocating these on

a as-needed basis.

TMN

Telecommunications Management Network.

TMSI

Temporary Mobile Subscriber Identity;

covers the IMSI to prevent over-the-air

interception and tracing.

TRAU

Transcoder Rate Adapter Unit; the transport

unit for a 16kbit/s traffic channel on the A-bis

interface.

TRX

Transmitter/receiver (transceiver).

U

Um

The air interface between the BTS and the

MS in a GSM network.

UMTS

Universal Mobile Telecommunications

System; the European entrant for 3G; now

subsumed into the IMT-2000 family as the

WCDMA technology.

V

VAS

Value Added Services.

VLR

Visitor Location Register.

10.1 Bibliography:

Ericsson (2008) GSM System Survey. R5B Revised Upgrade Edition

Wireless Communication, 2nd Edition--Rappaport, Theodore S. (2006).

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Manual of GSM M900/M1800_Huawei Technologies Co.Ltd

Websites:

http://banglalinkgsm.com Date-05-04-2010 Time- 11:30

AM

http://www.tutorialspoint.com/gsm/gsm_architecture.htm Date-07-04-2010 Time- 10:30 PM

http://www.tutorialspoint.com/gsm/gsm_network_switching_subsystem.htm

Date-05-04-2010 Time- 12:45 AM

http://febby-blog.blogspot.com/2008/03/bss-bts-dan-bsc.html

Date-06-04-2010 Time- 01:30 AM

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interface-slot-burst.php Date-10-04-2010 Time- 08:15 PM

http://www.docstoc.com/ Date-10-04-2010 Time- 08:30 PM

http://www.tutorialspoint.com/gsm/gsm_operation_support_subsystem.htm

Date-10-04-2010 Time- 10:30 PM

http://ccnga.uwaterloo.ca/~jscouria/GSM/gsmreport.html Date-15-04-2010 Time- 11:30 AM

http://www.telecomspace.com/gsm.html Date-18-04-2010 Time- 09:30 AM

http://www.protocols.com/pbook/gprsfamily.htm Date-20-04-2010 Time- 10:30 PM

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Date-25-04-2010 Time- 06:30 PM

http://www.radio-electronics.com/info/cellulartelecomms/gsm_technical/gsm_interfaces.php

Date-26-04-2010 Time- 06:30 PM

http://en.wikipedia.org/wiki/Base_station_subsystem Date-27-04-2010 Time- 11:30 AM

http://www.huawei.com Date-21-04-2010 Time- 07:30 PM

http://www.gsmworld.com Date-24-04-2010 Time- 11:30 AM

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