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PRESENTATION ON

GSM, CELL PLANNING & FREQUENCY REUSE

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Contents:1. GSM 1.1. What is GSM? 1.2. GSM Phases 1.3. GSM specifications 1.4. GSM system architecture 1.5. GSM network areas 1.6. GSM service area 1.7. Advantages of GSM over Analog system

1.8. GSM Radio technology

2. Cell Planning 2.1. Cell Planning 2.2. Types of cell planning 2.3. Cell Planning Process 2.4. Cell cluster3.Frequency reuse 3.1.what is frequency reuse 3.2.Example of frequency reuse

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1. GSM

1.1 What is GSM ?

Global system for mobile communication (GSM) is a globally accepted standard for digital cellular communication which is based on Time Division Multiple Access (TDMA) technique.

GSM is a second generation cellular standard developed to cater voice services and data delivery using digital modulation.

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• GSM devices range from mobile telephones to data cards that allow devices to connect and communicate with the GSM system.GSM mobile devices may include the capability to use GSM radio channels on different frequency bands.

• Mobile Telephones - Portable devices that can be used for voice communication.

• PCMCIA Air Cards - Cards that can slide into computers to provide data services.

• Embedded Radio Modules - Radio assemblies that can be built-in or installed in devices such as laptop computers, video cameras, or digital signage displays.

• External Radio Modems - Assemblies that can be connected to other devices through USB, Ethernet, or other connection types to provide data services.

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1.2. GSM PHASES

In the late 1980s, it was decided that GSM would be released in phases to complete the specifications for the entire range of GSM services & features that originally planned.

There are three GSM phases; Phase 1, Phase 2 & Phase 2+.

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1.3. GSM Specifications

Frequency bands:

– GSM 900: • 890 – 915 MHz: Uplink (MS transmit) • 935 - 960 MHz: Downlink (MS receive)

– GSM 1800: • 1710 - 1885 MHz: Uplink• 1805 - 1880 MHz: Downlink

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1.3. GSM Specification(cont.)

• Carrier Bandwidth : 200 Khz• Duplex Distance : 45 Mhz• Channels / carrier: 8• No. of RF carriers : 124• Access Method : TDMA/FDMA• Modulation Method : GMSK• Modulation data rate : 270.833 Kbps

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1.4. GSM network areas:

In a GSM network, the following areas are defined:

Cell: Cell is the basic service area: one BTS covers one cell. Each cell is given a Cell Global Identity (CGI), a number that uniquely identifies the cell.

Location Area: A group of cells form a Location Area. This is the area that is paged when a subscriber gets an incoming call. Each Location Area is assigned a Location Area Identity (LAI). Each Location Area is served by one or more BSCs.

MSC/VLR Service Area: The area covered by one MSC is called the MSC/VLR service area.

PLMN: The area covered by one network operator is called PLMN. A PLMN can contain one or more MSCs.

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1.5. GSM SERVICE AREA

The GSM service area is the entire geographical area in which a subscriber can gain access to a GSM network. The GSM service area increases as more operators sign contracts agreeing to work together.

International roaming is the term applied when an MS moves from one PLMN to another.

fig: relations between areas in GSM04/10/2023

1.6. GSM System Architecture

BSC

BSC

MSC

MS

MS

MS BTS

BTS

BTS

GMSC

PSTNISDNPDN

EIRAUC

HLR

VLR

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1.6. GSM System Architecture(cont.)

• Mobile Station (MS)Mobile Equipment (ME)

Subscriber Identity Module (SIM)• Base Station Subsystem (BSS)

Base Transceiver Station (BTS)

Base Station Controller (BSC)• Network Switching Subsystem(NSS)

Mobile Switching Center (MSC)

Home Location Register (HLR)

Visitor Location Register (VLR)

Authentication Center (AUC)

Equipment Identity Register (EIR)

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1.4. GSM system architecture

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1.7. Advantages of GSM over Analog system

• Capacity increases• Reduced RF transmission power and longer battery life.• International roaming capability.• Better security against fraud (through terminal validation and

user authentication).• Encryption capability for information security and privacy.• Compatibility with ISDN, leading to wider range of services

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1.8. GSM Radio Technology

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2. Cell Planning2.1. What is Cell Planning?

•Cell planning means building a network able to provide service to the customers wherever they are. •The main issue of the cellular network Planner is achieving the maximum capacity whilst maintaining an acceptable grade of service and good speech quality.

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Three types of cells are used in cell planning :

Macro cells :Have a typical coverage range from 1to 35 km. Normally the site location is on a hilltop or a rooftop.

Micro cells :Have a typical coverage range from 0.1 to 1 km , it can maintain indoor coverage in the lower levels of a building.

Pico cells :It supplies coverage in indoor environment. Pico cells are used when the capacity need is extremely high in certain hot spots.

2.2. Types of Cell planning

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2.3. Cell Planning Process

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There are four steps in cell planning:1. Traffic And Coverage Analysis2. Nominal Cell Plan3. Surveys4. System Design

2.3. Cell Planning Process(cont.)

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A cellular system is based on re-use of frequencies. All the available frequencies are divided into different frequency groups so that a certain frequency always belongs to a certain frequency group. The frequency groups together form a cluster.

A group of neighboring cells using all the frequencies available in the system frequency band is called a cluster of cells.

By repeating the cluster over and over again a cellular network can be built.

2.3. Cell cluster

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2.3. Cell cluster(cont.)

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3. Frequency Re-Use3.1. Frequency re-use

A frequency used in one cell can be re-used in another cell at a certain distance. This is known as frequency re-use.

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References:

Wireless and Cellular TelecommunicationsWillium C.Y.Lee

GSM System SurveyEricsson

Wireless CommunicationTheodore S.Rappaport (2nd Edition)

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