Republic of Iraq

Ministry of Higher Education & Scientific Research

Al-Mamon University College

Electronic and Communication Engineering Department

Improving the quality of service

A project submitted to the Electronic and Communication Engineering Department /Al-Mamon University College in partial fulfillment to the requirement for the degree of B.S.C. in Electronic and Communication Engineering.

BY

Mohammed Luay Abdulmunem

Supervised byM.Sc Hind Salim

MAY 2013

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Dedication

Thanks for god to make me end my research and I

wish to be an effective man in community.

I gift this research to my father , mother and sisters for

there support in house, and I gift it to all my friend and

especial gift for all my teacher in the collage for there

effort to leading me to be an engineer .

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AcknowledgementFirst of all, thanks to Allah for his guidance that enables me to

complete my research. I would like to express my deepest gratitude

and appreciation to my supervisor “M.SRHendsalem "for her

continuous help, his encouragement, and his valuable i advice during

this work. I would like to express my appreciation to the Al-

Mammon College University / Electronic and Communication

Engineering Department staff for their help and support. Special

thanks to my family and my friends for their encouragements.

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Supervisor Certificate

I certify that this project entitled improving the quality of service was prepared

under my supervision at the Electronic and Communication Engineering

Department in Al-Mamon University College, as a partial fulfillment of the

requirements needed to award the degree of B.Sc. in Electronic and

Communication Engineering

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Examination Committee Certificate

We certify that we have read this project entitled" Improving the quality of GSM service" and as examination committee, examined the students

1- Mohamed LuayAbdulmunem 3- Mohamed Salam farj2- Mahmud MezherJirjees 4- NooraldineAbdAlalahAraf

In its content and that in our opinion; it meets the standard of a project for the degree of B.Sc. in Electronic and Communication Engineering.

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Abstract

In this project we will define the GSM as the global system for mobile

communication that used for make a call between two person in the word and

we try to improve a good quality for GSM serves by solving the problems that

effect on the signal like multipath propagation ,shadowing and propagation

delay and we try to solve the co-channel interference and the traffic affect

solving all this factor will improve the quality of service.

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List of Abbreviation

List of f i

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Global System for Mobile CommunicationsGSMshort message serviceSMSThe Mobile Station MS

The Base Station Sub-systemBSSThe Network Switching Sub-systemNSS

Base Transceiver StationBTSmobile equipmentME

subscriber identity moduleSIMBase Station ControllersBSCMobile Switching CentreMSCVisitor Location RegisterVLRHome Location RegisterHLRAuthentication CentreAUC

Equipment Identity RegisterEIRGateway MSCGMSC

Mobile Switching CentreMSCfrequency modulationFm

Frequency Division Multiple AccessFDMATime Division Multiple AccessTDMA

Code Division Multiple AccessCDMAOrthogonal frequency-divisionOFDMGaussian minimum shift keying GMSK

ultra-high-frequencyUHFpublic switched Telephone network PSTN

mobile station rooming numberMSRN

Figures table

NAME OF FIGURENOMBER OF FIGURECHAPTER ONE FIGURE

BSS1.1GSM FAMILY RADIO BAND SPECTRUM

1.2

CHAPTER TWO FIGUREFREQQUENCY RE-USE2.1FREQUENCY RE-USE PATREN

2.2

FREQUENCY RE-USE DISTANCY

2.3

HANDOVER TYPE2.4REASUNE OF HANDOVER

2.5

HAND OVER PROPEGATION

2.6

FDMA MODULATION2.7TDMA MODULATION2.8CDMA MODULATION2.9OFDM MODULATION2.10

CHAPTER THREE FIGUREMULTYPATH PROPEGATION EFFICT

3.1

SPEECH PROCESS IN MOBILE STATION

3.2

ANTINNA RECEVER DIVERSITY

3.3

SHADOWING3.4PROPEGATION DELAY EFFICT

3.5

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List of contents

Chapter one introduction to GSM system10

1.1 Introduction to GSM 111.2 GSM history 121.3 GSM structure 131.4 GSM frequency spectrum 161.5 GSM specification 171.6 BENEFITS Of GSM 17

Chapter two GSM techniques18

2.1 GSM coverage192.1.1 Frequency reuse20

2.2 Handover 222.2.1 Type of hand over 222.2.2 Reasons for handover 232.2.3 Decision criteria 23

2.3 GSM modulation 252.4 Traffic load and cell size292.4.1Traffic capacity versus coverage 302.5 Call establishment 31

Chapter three improving the quality of signal32

3.1 The link between MS and BTS 333.1.1Multipath propagation 33

3.1.1.1 viterbi equalisation 343.1.1.2 Interleaving 353.1.1.3 Frequency hopping 353.1.1.4 Antenna receiver diversity 36

3.1.2 Shadowing 373.1.2.1Shadowing effect 37

3.1.3 Propagation delay 373.2 The link between BTS and BSC 383.3 The link between BSC and MSC39

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Chapter four the conclusion 40

4.1Conclusion 41

References 42

Chapter one

Introduction to GSM

The Global system of mobile communication

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Chapter one introduction

1.1 Introduction to GSM GSM: stands for Global System for Mobile Communications. The original French acronym stands for Group Special Mobile. It was originally developed in 1984 as a standard for a mobile telephone system that could be used across Europe.It is now an international standard for mobile service. It offers high mobility. Subscribers can easily roam worldwide and access any GSM network. It is a digital cellular network. At the time the standard was developed it offered much higher capacity than the current analog systems. It also allowed for a more optimal allocation of the radio spectrum, which therefore allows for a larger number of subscribers. It offers a number of services including voice communications, Short Message Service (SMS), fax, voice mail, and other supplemental services such as call forwarding and

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caller ID.Currently there are several bands in use in GSM. 450 MHz, 850 MHZ, 900 MHz, 1800 MHz, and 1900 MHz are the most common ones. some bands also have Extended GSM bands added to them, increasing the amount of spectrum available for each band. There are many arguments about the relative merits of analogue versus digital, but for my mind it comes down to this: Analogue sounds better and goes further, Digital doesn't sound as good, but does a whole lot more.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.

1.2 GSM HistoryDuring the early 1980s, analog cellular telephone systems were experiencing rapid growth in Europe, particularly in Scandinavia and the United Kingdom, but also in France and Germany. Each country developed its own system, which was incompatible with everyone else's in equipment and operation. This was an undesirable situation, because not only was the mobile equipment limited to operation within national boundaries, which in a unified Europe were increasingly unimportant, but there was also a very limited market for each type of equipment, so economies of scale and the subsequent savings could not be realized.The Europeans realized this early on, and in 1982 the Conference of European Posts and Telegraphs formed a study group called the Group Special Mobile (GSM) to study and develop a pan-European public land mobile system. The proposed system had to meet certain criteria: Good subjective speech quality Low terminal and service cost Support for international roaming Ability to support handheld terminals Support for range of new services and facilities Spectral efficiency ISDN compatibility

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In 1989, GSM responsibility was transferred to the European Telecommunication Standards Institute and phase I of the GSM specifications were published in 1990. Commercial service was started in mid-1991, and by 1993 there were 36 GSM networks in 22 countries. Although standardized in Europe, GSM is not only a European standard. Over 200 GSM networks (including DCS1800 and PCS1900) are operational in 110 countries around the world. In the beginning of 1994, there were 1.3 million subscribers worldwide which had grown to more than 55 million by October 1997. With North America making a delayed entry into the GSM field with a derivative of GSM called PCS1900, GSM systems exist on every continent, and the acronym GSM now aptly stands for Global System for Mobile communications.The developers of GSM chose an unproven (at the time) digital system, as opposed to the then-standard analog cellular systems like AMPS in the United States and TACS in the United Kingdom. They had faith that advancements in compression algorithms and digital signal processors would allow the fulfillment of the original criteria and the continual improvement of the system in terms of quality and cost. The over 8000 pages of GSM recommendations try to allow flexibility and competitive innovation among suppliers, but provide enough standardization to guarantee proper interworking between the components of the system. This is done by providing functional and interface descriptions for each of the functional entities defined in the system.

1.3 GSM structureA GSM network is made up of three subsystems:The Mobile Station (MS)The Base Station Sub-system (BSS) - comprising a BSC and several BTSs The Network and Switching Sub-system (NSS) - comprising an MSC and associated registers

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The Mobile Station (MS)The mobile station consists of:• mobile equipment (ME)• subscriber identity module (SIM)The SIM stores permanent and temporary data about the mobile, the subscriber and the network, includingThe Base Station Sub-System (BSS)The BSS comprises:• Base Transceiver Station (BTS)• One or more Base Station Controllers (BSC) The purpose of the BTS is to:• provide radio access to the mobile stations• manage the radio access aspects of the systemBTS contains:• Radio Transmitter/Receiver (TRX)• Signal processing and control equipment• Antennas and feeder cables

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Fig-1.1- BSSThe BSC:• allocates a channel for the duration of a call maintains the call:• monitoring quality• controlling the power transmitted by the BTS or MSgenerating a handover to another cell when requiredSilting of the BTS is crucial to the provision of acceptable radio coverage.

Network Switching System (NSS)Key elements of the NSS:• Mobile Switching Centre (MSC) with:Visitor Location Register (VLR)• Home Location Register (HLR) with:• Authentication Centre (AuC)• Equipment Identity Register (EIR)• Gateway MSC (GMSC)Mobile Switching Centre (MSC) The Functions of the MSC:• Switching calls, controlling calls and logging calls• Interface with PSTN, ISDN, PSPDN• Mobility management over the radio network and other networksRadio Resource management - handovers between BSC

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1.4 GSM frequency spectrumAccording to the resolution of the World Radio communication Conference in 1978, the European Telecom Authorities primarily reserved two frequency bands of twice 25 MHz• 890 MHz to 915 MHz from mobile to the network,• 935 MHz to 960 MHz from base stations to the mobiles for use by cellular system. By 1990, a newly allocated band of twice 75 MHz (1710 MHz to 1785MHz for uplink and1805 MHz to 1880 MHz for downlink) was formed for the Digital CommunicationSystem This is a version of GSM suited to the 1800 MHz frequency band. This application was initiated in the United Kingdom Furthermore FCC has granted band of twice 60 MHz (1850 MHz to 1910 MHz for uplink and 1930 MHz to 1990 MHz for downlink) devoted to GSM networks

Fig (1.2 ) GSM family Radio band spectrum

1.5 GSM Specifications Frequency band: The frequency range specified for GSM is 1,850 to 1,990 MHz (mobile station to base station). Duplex distance: The duplex distance is 80 MHz. Duplex distance is the distance between the uplink and downlink frequencies. A channel has two frequencies, 80 MHz apart. Channel separation: 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. This is done in GSM via Gaussian minimum shift keying (GMSK). Transmission rate:

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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. The purpose of linear predictive coding 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.1.6 BENEFITS Of GSM GSM was designed to grow and meet the needs of new technologies. GSM is currently composed of EDGE, 3GSM, and GPRS. Each member of the family is designed to solve a particular need. EDGE is an upper level component used for advanced mobile services such as downloading music clips, video clips, and multimedia messages. GPSR is designed for “always-on” systems that are needed for web-browsing. 3GSM is the GSM running on third generation standards for multimedia services.In addition to growing, GSM was designed with security in mind. Older cellular systems were analog based and therefore very susceptible to security attacks. It was common for attackers to eavesdrop and intercept people’s conversations and data. Even worse yet, attackers were capable of stealing customer IDs to make fraudulent calls.

Chapter two

GSM techniques

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Chapter twoGSM techniques

2.1 GSM coverage The provision of wireless telephony network in a serving area

requires planning and design in the most effective manner. In the design process the service providers generates a set of system requirements concerning the type of the desired system (e.g. Global system for Mobile Communication GSM, Code Division Multiple Access CDMA etc.), The main principle inside cellular network is replacement of a single high power transmitter by many small power transmitters and In this case each low power transmitter covers a small area or small range called a cell. Cellular networks are completely based on the technique of frequency reuse, so that the narrow radio spectrum will get maximum use, as shown in Fig. below

Fig (2.1) frequencies re-use In cellular radio networks, a small area is covered by one base

station and other base stations are installed with small overlapping areas. Neighboring cells require using different frequencies to evade interference, but the same frequency can be reused in distant cells. The entire coverage area is splitter into many small hexagonal cells so that to increase the capacity of entire network and a decrease in the reuse of frequency

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2.1.1Frequency reuse

Fig (2.2) frequencies re-use patternChannels are reused at regular distance intervals. The mechanism that governs this process is called frequency planning.The slide shows an example of N =12 frequency plan where the available frequencies of a GSM network are placed.This set of 12 cells is called a frequency reuse pattern and is generally used for BCCH frequency plan. The frequency reuse distance

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Fig (2.3) frequencies re-use distance

D=R (√3 N )

D:Reuse distance

R: the Diameter of one cell N: number of sell in one cluster

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2.2Handover

Fig (2.4) Hand over typeThe handover isthe process of transferring an ongoing call or data session from one channel connected to the core network to another.

2.2.1Type of hand over1- Intra-Cell Handover: the MS is handed over to another channel on the same cell, under the same BTS.2- Intra-BTS Handover: the MS is handed over to another channel on a different cell, under the control of the same BTS.3- Intra-BSC Handover: the MS is handed over to another channel on a different cell, under the control of a different BTS of the same BSC4- Inter-BSC Handover: the MS is handed over to another channel on a different cell, under the control of a different BSC of the same MSC.

5- Inter-MSC Handover: the MS is handed over to another channel on different cell, under another MSC of the same PLMN.

2.2.2Reasons for handover

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Fig(2.5) Reasons of hand over2.2.3Decision criteria• Bad quality.• Weak signal strength.• Cell boundaries (Distance).• Power budget (optimization).• Traffic constraints.

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Fig (2.6) hand over preparation

To avoid losing a call in progress, when the Mobile Station leaves the radio coverage of thecell in charge.

Procedure: Three steps:• Handover decision (based on measurements results).• Choice of the target cell.• Handover execution.

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2.3GSM modulation The first commercial cellular system (GSM 1)used the FM

modulation and it used the FDMA as Access method.

Fig (2.7) FDMA modulationWith Frequency Division Multiple Access (FDMA), different signals are assigned Frequency channels. FDMA is a basic technology in the Analog Advanced Mobile Phone System with FDMA; each channel can beassigned to only one user at a time.

The second generation of GSM it used the TDMA but the modulation is changed from analog to digital and it used the

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GMSK as modulation technique

Fig (2.8) TDMA modulation

In Time Division Multiple Access (TDMA), it makes use of the same frequencyspectrum but allows more users on the same band of frequencies by dividing the time into slots” and shares the channel between users by assigning them different time slots.TDMA is utilized by Digital-Advanced Mobile Phone System and GlobalSystem for Mobile communications (GSM).

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A new technique discovered and lead to Appearance a new generation of GSM named as "2.5 GSM" this technique is the CDMA

Fig (2.9) CDMA modulationIn Code Division Multiple Access (CDMA), each user is assigned a differentPseudo random binary sequence that modulates the carrier , spreading the spectrum of the waveform and giving each user a unique code pattern. This technology is used in ultra-high-frequency (UHF) cellular telephone systems in the800-MHz and 1.9-GHz bands.

Research ledtoa new access method, it’s the Orthogonal frequency-divisionmultiplexing (OFDM) and that led to

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Appearance the 3G of GSM

Fig (2.10) OFDM modulation   Advantages:• The transmission is not affected by the channel.• High transmission bitrates.• Chance to cancel any cannel if is affected by fadingDisadvantages:• High synchronism accuracy.• Multipath propagation must be avoided in other orthogonally not be Affected.• Large peak-to-mean power ratio due to the superposition of all subcarrier signals, this can become a distortion problem

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2.4 Traffic load and cell sizeThe more traffic generated, the more base stations will be needed to service the customers. The number of base stations for a simple cellular network is equal to the number of cells. The traffic engineer can achieve the goal of satisfying the increasing population of customers by increasing the number of cells in the area concerned, so this will also increases the number of base stations. This method is called cell splitting itis the only way of providing services to a burgeoning population. This simply works by dividing the cells already present into smaller sizes hence increasing the traffic capacity. Reduction of the cell radius enables the cell to accommodate extra traffic. The cost of equipment can also be cut down by reducing the number of base stations through setting up three neighboring cells, with the cells serving three 120° sectors with different channel groups.

Mobile radio networks are operated with finite limited resources (the spectrum of frequencies available). These resources have to be used effectively to ensure that all users receive service, that is, the quality of service is consistently maintained. This need to carefully use the limited spectrum brought about the development of cells in mobile networks, enabling frequency re-use by successive clusters of cells. Systems that efficiently use the available spectrum have been developed e.g. the GSM system. It can be defined spectral efficiency as the traffic capacity unit divided by the product of bandwidth and surface area element, and is dependent on the number of radio channels per cell and the cluster size (number of cells in a group of cells) however the efficiency of the one cell can be calculate in this equation

WhereNc is the number of channels per cell, BW is the system bandwidth, and Ac is Area of cell.

The sectorization is briefly described in traffic load and cell size as a way to cut down equipment costs in a cellular network. When applied to clusters of cells sectorization also reduces co-channel interference. This is because the power radiated backward from a directional base station antenna is minimal and interfering with adjacent cells is reduced. (The number of channels is directly proportional to the number of cells.) The

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maximum traffic capacity of sectored antennas (directional) is greater than that of omidirectionalantennas as by a factor which is the number of sectors per cell (or cell cluster).

2.4.1Traffic capacity versus coverageCellular systems use one or more of four different techniques of access (TDMA, FDMA, CDMA, and OFDM). Let a case of Code Division Multiple Access be considered for the relationship between traffic capacity and coverage (area covered by cells). CDMA cellular systems can allow an increase in traffic capacity at the expense of the quality of service

In TDMA/FDMA cellular radio systems, Fixed Channel Allocation is used to allocate channels to customers. In Fixed Channel Allocation the number of channels in the cell remains constant irrespective of the number of customers in that cell. This result in traffic congestion and some calls being lost when traffic gets heavy.

A better way of channel allocation in cellular systems is Dynamic Channel Allocation which is supported by the GSM DCS and other systems. Dynamic Channel Allocation is a better way not only for handling cell traffic. Dynamic Channel Allocation allows the number of channels in a cell to vary with the traffic load, hence increasing channel capacity with little costs. Since a cell is allocated a group of frequency carries (e.g. f1-f7) for each user, this range of frequencies is the bandwidth of that cell, BW. If that cell covers an area Ac, and each user has bandwidth B then the number of channels will be BW/B. The density of channels will beThe density= BW

Ac∗B , This formula shows as the coverage area Ac are increased, the channel density decreases.2.5 Call establishmentWhen a mobile station wishes to establish a speech call, the following steps are performed.1. Mobile subscriber dials the number.2. MSC /VLR receive a message requesting access.3. MSC /VLR checks if the mobile station is authorized to initiates a call set up to the PSTN network.

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4. The dialed number is analyzed by MSC /VLR, which in turn initiates a call set-up to the PSTN network.5. MSC / VLR ask BSC to allocate a free traffic channel. This information is forwarded to BTS and the mobile station.6. The person receiving the call answer and a connection is established.

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Chapter three Improving the quality of signal in

GSM system

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CH3Improving the quality of signal

Improving the quality of signal To improve the maximum quality of service, we should resaved high quality signal.In GSM system there are three links should found to make a call between tow phone every link effect by deferent Factors those factor cause the bad call those link is

3.1 The link between MS and BTS Those problems are

· Multipath propagation· shadowing· Propagation delay.

3.1.1Multipath propagationWhenever a mobile station is in contact with the GSM network,

it is quite rare that there is a direct "line of sight" transmission between the mobile station and the base transceiver station. In the majority of cases, the signals arriving at the mobile station have been reflected from various surfaces. Thus a mobile station (and the base transceiver station) receives the same signal more than once. Depending on the distance that the reflected signals have travelled, they may affect the same information bit or corrupt successive bits. In the worst case an entire burst might get lost. Depending on whether the reflected signal comes from near or far, the effect is slightly different. A reflected signal that has travelled some distance causesinter symbol interference" whereas near reflections cause "frequency dips". There are a number of solutions that have been designed to overcome these problems.

The solutions are:1 –viterbi equalisation2- Channel coding3- Interleaving4- Frequency hopping.5- Antenna diversity

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Fig (3.1)multy path propegation effict

3.1.1.1 Viterbi equalisation Vitoria equalization is generally applicable for signals that have been reflected from far away objects. When either the base transceiver station or mobile station transmits user information, the information contained in the burst is notall user data. There are 26 bits that are designated for a "training sequence" included in each transmitted TDMA burst. Both the mobile station and base transceiver station know these bits and by qualizat how the radio propagation affects these training bits, the air interface is mathematically qualiz as a filter. Using this mathematical model, the transmitted bits are estimated based on the received bits. The mathematical algorithm used for this purpose is called"viterbiequalisation".

3.1.1.2 InterleavingInterleaving is the spreading of the coded speech into many bursts. BySpreading the information onto many bursts, we will be able to recover the data even if one burst is lost. (Ciphering is also carried out for security reasons.)

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Fig (3.2)speech processing in the mobile station

3.1.1.3 Frequency hoppingWith frequency hopping, the frequency on which the information is transmitted is changed for every burst. Frequency hopping generally does not significantly improve the performance if there are less than four frequencies in the cell.

Fig (3.3) frequency hoping 3.1.1.4 Antenna receiver diversity In this case two physically separated antennas receive and process the same signal. This helps to eliminate fading dips. If a fading dip occurs at the position of one antenna, the other antenna will still be able to receive the signal. Since the distance

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between two antennas is a few meters, it can only be implemented at the Base Transceiver Station.

Fig (3.3) antenna receiver diversity

3.1.2 ShadowingHills, buildings and other obstacles between antennas cause shadowing (Also called log normal fading) Instead of reflecting the signal, theseObstacles attenuate the signal.

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fig (3.4) shadowing 3.1.2.1Shadowing effectShadowing is generally a problem in the uplink direction, because a Base Transceiver Station transmits information at a much higher powerCompared to that from the mobile station. The solution adopted to overcome this problem is known as adaptive power control. Based on quality and strength of the received signal, the base station informs the mobile station to increase or decrease the power as required. This information is sent in the Slow Associated Control channel .

3.1.3Propagation delayAs you remember, information is sent in bursts from the mobile station to the Base Transceiver Station (BTS). These bursts have to arrive at the Base Transceiver Station so that they can map exactly into their allocated time slots. However, the further away the mobile station is from the BTS, the longer it will take for the radio signal to travel over the air interface. This means that if the mobile station or base station transmits a burst only when the time slot appears, then when the burst arrives at the other end, it will cross onto the time domain of the next timeslot, thereby corrupting data from both sources. The solution used to overcome this problem is called "adaptive frame alignment". The Base Transceiver Station measures the time delay from the received signal compared to the delay that would come from a mobile station that was transmitting at zero distance from the Base Transceiver Station. Based on this delay value, the Base Transceiver Station informs the mobile station to either advance or retard the time alignment by sending the burst slightly before

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the actual time slot. The base station also adopts this time alignment in the downlink direction.

Fig (3.5) propagation delay3.2 The link between BTS and BSC

These link must be at Highrise To ensure that the link will not cut by any Physical barrier such care or the new building and because this link Holds all the information if there is any malfunction will lead to service interruptions, i prefer to use Double link if one is not work the other will Works suit and put the the transmitting antenna at high place to improve the line of sightand inarea with have rain the prefer is using the fiber optic because the heavy rain may cut the link.

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Fig (3.6) line of site

3.3 the link between BSC and MSC These link must be at High rise To ensure that the link will not cut by any Physical barrier such care or the new Building and because this link Holds all the information if there is any malfunction will lead to service interruptions, it prefer to use Double link if one is not work the other will Works suit and put the transmitting and receivers antenna at high place to improve the line ofsight and inarea with have rainthe prefer is using the fiber optic because the heavy rain may cut the link.

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Chapter four The Conclusion

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Chapter 4 Conclusion4.1Conclusion When we study the first three chapters we should know that The GSM is a Global System for Mobile Communications used for make a call between two person and like any communication system in the world it effects by different Factors those factor cause the bad call as explained in chapter two we take the GSM coverage and we learn that the coverage used is cellular system to solve the CO- channel interference and then we take the GSM modulation like FDMA, TDMA, CDMA and OFDM every one of them increased the capacity of channel and that led to apparent a new service like internet ,video call ……etc.And then we take the traffic effect on the density of channels decreases if the coverage area Ac is increased according to this formula

The density= BWA c∗BThen we take the hand over and it solve this

problems Bad quality, Weak signal strength, and Power budget .In chapter 3 I tried to solve the problems that

happened on the link between MS to BTS like the Multipath propagation, Propagation delay and Shadowing that increased the bit/error rate and finally the link between BTS and BSC and the link between BSC and MSC and how they must be at High rise To ensure that the link will not cut by any Physical barrier

such care or the new Building and because this link Holds all the information if there is any malfunction will lead to service

interruptionsAnd in areas torrential rains the prefer is using the fiber optic because the heavy rainmay cut the link.

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References

1- ASHA MEHROTRA"GSM SYSTEM ENGINEERING " British Library Data 1997 ARTECH HOUSE, INC.

2- Javier Gozálvez Sempere "An overview of the GSMSystem""Departmentof Electronic&Electrical EngineeringUniversity of Strathclyde .

3-Siegmund M. Redl"Personal Communications Handbook"1989

4-Forney, G.D. JR. "The Viterbi Algorithm"Proc. of the IEEE3, Mar.1973.

5-GSM System and Products Overview"Nortel network"

6-GSM Air interface and network planning Training Document "NOKIA"

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