Mbility Detection Using GSM

8/6/2019 Mbility Detection Using GSM

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October University for Modern Sciences and Arts

Faculty of Engineering

Electrical Communication and Electronics systems

“GSM based mobility detection”A graduation project

Submitted in partial fulfillment of B.Sc degree Requirements in electrical

communication and electronics systems

Prepared By

1-Ibrahim Mohamed El kheir Ibrahim 073234

2-Mahmoud Ragaei Mohamed 073080

3-Karim Mohamed Abd-Elquader 074171

Under supervision of

Dr: Khalid Fawzy



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Chapter 1

Introduction

1.1 Introduction

Mobility detection using Global System for Mobile Communication (GSM) traces is a

new technique that uses the advantage of GSM wide coverage to detect mobility by only

having a cellular phone.

The usual way for a person who wants to detect his motion is a device called pedometer,

this device measures steps taken by the user (or “step count”), and this device is clipped

to the user’s waistband, above the thigh’s midline. This restriction can effect the desire of

the user to have such a device, for example a user might not like the look of it hanged in

his waist or doesn’t have a place to clip it on, (wearing a dress for example).

Mobile phones don’t have this kind of restrictions, as the user can have it anywhere with

him even inside a bag, we also don’t consider that the cell phone will be always with the

user, for example being at home doesn’t recommend holding the phone, but the idea of

providing a pedometer-like functionality when outside home can be useful to give a high

level report of the user’s daily movement, and this kind of info can be used for various

kind of applications.

The GSM based mobility detection allows us to add a pedometer-like capability to cell

phones, and our goal is having more and more accuracy for mobility detection.



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Chapter 2

Mobile communication systems

2.1 Introduction

Mobile radio communication began with Guglielmo Marconi’s and Alexander Popov’s

experiments with ship-to-shore communication in the 1890’s. Land mobile

Radiotelephone systems have been used since 1921 when the Detroit City Police

Department installed a system [2.1].since then the radio systems importance have

increased for voice and data communications. The mostly used frequency spectrum in

modern mobile systems is high frequency band (UHF and above) because there are more

available bandwidth at these frequencies. In the United States this includes cellular

telephone systems operating at 800-900 MHz and personal communication system (PCS)

at 1800-2000 MHZ, and a variety of unlicensed devices, including wireless LANs, in the

ISM bands at 902-928 MHz and 2.4-2.4835 GHz.

2.2 The wireless communication link

A wireless communication link includes a transmitter, a receiver, and a channel, as shown

in fig.2-1, adapted from [2.x].quantization, coding and decoding are only performed in

digital systems. Most links are full duplex and include a transmitter and a receiver or a

transceiver at each end of the link.

In mobile communication system at least one of the transceivers is mobile. It may be on

board a vehicle that can move at high speeds, or it may be handheld unit used by a

pedestrian. Basic types of systems include base/mobile, peer-to-peer, repeater, and

mobile satellite systems. In a base/mobile system, a base station connected to a public

network communicates with a mobile unit. This gives the mobile unit access to the public



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network. More than one mobile at a time can be supported if a different channel (such as

narrow band of spectrum) is assigned to each user. In most systems channels are assigned

to users as needed rather than giving each user a dedicated channel that is reserved for

that user at all times.

2.3 The spectrum debate

Spectrum is a commodity owned by national regulatory bodies established by the

governments of different countries. The national regulatory bodies cooperate with each

other through the international organizations which make sure that national spectrum

regulations provide the means for interoperability and that harmful interference between

different countries is avoided. Currently, the radio regulations unit under the international

telecommunications union (ITU) is in charge of the spectrum management decisions on

an international level. [2.]

In the last world radio communication conference (WRC’07) less than 600 MHz of

bandwidth has been allocated to mobile communication systems. Further bandwidth

allocation exclusively to mobile communication systems is not likely because spectrum

below 5 GHz is already congested.

2.3 cellular system concepts

Traditional mobile service was structured similar to television broadcasting, its contents

is high power transmitter located at the highest region in an area and broadcast in a radius

of up to fifty kilometers. The cellular concept structured the mobile telephone network in

a different way. the cellular system idea was about subdividing the whole area to small

regions each called “cell” and in each cell there will be a low-power transceiver

(BTS).for example subdividing a region in to 100 small regions (cells) with low power



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transmitters using twelve conversations (channels) each, the system capacity theoretically

will increase from 12 conversation –or voice channels using one powerful transmitter –to

1200 conversations (channels) using one hundred low-power transmitters. Figure (Y1)

Shows a metropolitan area configured as a traditional mobile telephone network with one

high power transmitter.

Figure y1: early mobile telephone system architecture

2.3.1 Mobile telephone system using the cellular concept

Interference problems caused by mobile units using the channel (frequency band) in

adjacent areas proved that all channels could not be reused in every cell. Areas had to be

skipped before using the same channel again, although this would affect the efficiency,

frequency reuse idea was still a viable solution to the problems of mobile telephony

systems.

.

.

.

.

.



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2.3.2 Cellular system architecture

The quality of service of the cellular system needed to be improved and support more

users in their systems due to the increase in demand and the poor quality of existing

service. Due to the limitation in the availability of the frequency spectrum, efficient use

of the required frequencies was needed for mobile cellular coverage.

Cells

A cell is the basic geographic unit of cellular system.

The term cellular comes from the honeycomb shape, and that’s the shape the coverage

region is divided to. Cells are base stations transmitting over a small geographic area that

are represented as hexagons. Each cell size varies depending on the landscape. Because

of constraints imposed by natural terrain and man –made structures, the true shape of

cells is not perfect hexagon.

Clusters

A cluster is a group of cells. The whole system numbers of channels are reused within a

cluster. Figure (y2) illustrates a seven cell cluster.

Figure y2: A seven cell cluster



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Frequency reuse

Because only a small number of radio channels frequencies were available for mobile

systems, engineers had to find a way to reuse radio channels. The solution the industry

adopted was called frequency reuse.

The concept of frequency reuse is based on assigning to each cell a group of radio

channels used within a small geographic area. Cells are assigned a group of channels that

is completely different from neighboring cells. The coverage area cells are called foot

print . This foot print is limited by a boundary so that the same group of channels can be

used in different cells that are far enough away from each other so that their frequencies

do not interfere as in figure (y3)

Figure: y3

Cells with the same number have the same set of frequencies. Here, because number of

available frequencies is 7, the frequency reuse factor is 1/7. That is ,each cell is using 1/7

of available cellular channels.

Cell splitting



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As service area becomes full of users,This approach is used to split a single area into

smaller ones. In this way, urban centers can be split in to as many areas as necessary in

order to provide acceptable service levels in heavy traffic regions, while larger,less

expensive cells can be used to cover remote rural regions figure (y4).

Figure: y4

Hand off

The final obstacle faced the engineers in the development of cellular network is, when a

subscriber move from one cell to another during a call. As adjacent areas do not use the

same RF channel, a call would drop if it wasn’t transferred to another radio channel.

So when a user crosses the line between adjacent cells during a call, the call is transferred

to another frequency channel to maintain the call, this process is called handoff figure(y5)



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Figure y5

2.4 signal coverage

At the frequency band VHF and the above frequency band the signal propagate by the

line of sight. And when the light of sight is blocked the signal propagates using reflected,

diffraction and scattered signals dominating. Ray tracing and FDTD are very complex

techniques that used to module this effects by using a lot of detail about the environment.

2.4.1 large scale path loss

Friis transmission equation is used to describe the relation of the power received in the

free space. It state that: (2.1)

It’s the received power.

It’s the transmitted power.

It’s the gain of the receiver.



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It’s the gain of the transmitter.

The remaining term is the inverse of the path loss, and accounts for spherical spreading

loss of the transmitted wave due to propagation over the transmit-receive distance R, and

the effective aperture of the receiving antenna, Ae=λ 2/(4πGr )

In obstructed environments the pathloss is often modeled as

(2.2)

The first term represent the free-space path loss at some at some reference distance d0

and the exponent y (sometimes n is used) is determined empirically by a curve fit to

measured data.

2.4.2 Shadowing

At a given distance from the transmitter, variations about the mean path loss will occur

due to obstruction by objects in the environment. This can be modeled using a lognormal

Distribution about the mean value of large-scale path loss that is predicted by a Distance-

dependent model like the one in (2.2). The probability distribution function (pdf) of the

received power is then given by

Equation 3

Where pr is the received power in dB and pr0 is the mean received power, also in dB. A

standard deviation cpr of 6 to 8 dB is typical.

2.4.3 Multipath effects: fading, intersymbol interference, and Doppler spread

One of the distinctive features of a mobile radio channel is multipath propagation,

in which the received signal consists of multiple reflected, diffracted, and scattered

components, as well as (possibly) a direct line-of-sight component. Because all these



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components travel different distances and encounter different reflections, their phases are

different. The relative phases of the received signals change as the mobile moves.

Depending on the relative phases of the signals, they can reinforce each other or cancel

each other. In the latter case a fade results. As the receiver is moved the received signal

power undergoes variations, resulting in a fading envelope that can be measured.

Diversity systems that use signals received by two or more antennas can combat this

effect.

The difference in path length between multipath components causes them to arrive with

different delays. This causes intersymbol interference in digital systems, if the difference

is significant in relation to the symbol period. The amplitudes of the multipath

components also differ because they undergo different path losses. The received signal

can be represented as a superposition of all the received components as follows:

Equation………………………………….. (2.4)

where x(t) is the received signal, αn(t) is the time-varying attenuation coefficient of the nth

path, φn(t) is the time-varying phase shift associated with the n th path, s(t) is the original

transmitted signal, and τ n(t) is the time-varying delay of the nth path.

Two parameters that can be used to describe the delay characteristics of a channel are

mean excess delay and rms delay spread. Mean excess delay is given by

Equation……………………………………………………………………………… (2.5)

Where τ min is the minimum excess delay, and RMS delay spread is given by

Equation ……………………………………………………………………………. (2.6)



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Radio waves transmitted to or from a moving user undergo a shift in frequency if the

transmit-receive distance changes with time. The difference in frequency of the received

signal and the transmitted signal is called the Doppler shift and is given by

Equation ……………………………………………………………………………. (2.7)

Where dl/dt is the rate of change in the distance between the transmitter and receiver. In a

multipath channel the angles of arrival of the multipath components are different and in

general each has a different Doppler shift. This results in a Doppler spread.



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Chapter 3

Global System for Mobile

(GSM)



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GSM

3.1 Introduction

Global System for Mobile (GSM) is the second-generation cellular system standard

provided by Europe. GSM is the world’s most popular 2G technology since it is the first

cellular system to specify digital modulation and network level architectures and services.

GSM’s success has exceeded the expectations of virtually everyone. GSM was first

introduced in to the European market in 1991. By the end of 1993, several non-European

countries in South America, Asia, and Australia had adopted GSM. Figure (3.1) shows

the GSM worldwide coverage. GSM uses narrowband Time Division Multiple Access

(TDMA) for voice and Short Messaging Service (SMS).[rappaport]

Fig (3.1) GSM worldwide coverage (darker areas)

3.31 What is GSM?



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GSM (Global System for Mobile communications) is the world’s most popular

standard for mobile cellular systems.

• GSM stands for Global System for Mobile communications and it is a digital

cellular system adopted for transmitting and receiving mobile voice and data

services.

• GSM is a circuit-switched system divides each 200 kHz channel into eight 25

kHz time slots.

• The GSM operates in the 900 MHz and 1.8 GHz bands in Europe and the 1.9

GHz and 850 MHz bands in the US.

• GSM is used by over 1.5 billions of people across more than 212 countries.

• The GSM standard uses the narrowband Time Division Multiple Access

(TDMA) technique for transmitting signals.

• GSM provides voice and data services including Roaming service (Roaming

is a service provided to GSM subscribers to enable them to use their GSM

phone number in other network).

A GSM digitizes and compresses data, then sends it through channel with two other

streams of user data, each in its own time slot. It operates at either 900 MHz or 1800

MHz frequency band.

3.32 Why GSM?

GSM provide the following:

• Improve spectrum efficiency through frequency reuse.

• International roaming.



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• High-quality speech.

• Compatibility with Integrated Services Digital Network(ISDN) and other

telephone services

• Low-cost mobile sets.

• Accept some little updates to perform better.

• Integrated Services Digital Network(ISDN) compatibility.

3.33 GSM and mobility detection

In addition to the previous advantages of GSM system, GSM may be used for positioning

and for detecting the mobility of a subscriber. If we look at earlier positioning and

mobility detection systems, we will find that Global Positioning System (GPS) is the

leader wireless technology in this field.

GPS uses information about signal propagation time between a set of satellites and

GPS receiver. GPS receiver is able to compute its position with the accuracy of about 8 m

(“GPS Performance“, 2008, p. 22). However, GPS has long start-up times (up to a few

minutes) and does not work indoors and in dense urban areas, which limits GPS's

applicability for ubiquitous location-based services. While providing a good accuracy,

time-based systems usually require custom hardware and expensive installation.

Moreover, GPS works only when and where there is an unobstructed line of sight to four

or more GPS satellites.

One of the most pioneering projects in Received Signal strength Indication (RSSI)-

based is GSM, as it could be successfully applied for indoor localization by using RSSI



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fingerprinting. System recalibration may be required as a GSM network operator can

change its topology.

In our approach, we make a good use of GSM advantages and try to detect the

mobility of MS by using GSM RSSI from some users by some nearby BSs. The

algorithm and methods used for mobility detection will be illustrated later in chapter 4.

3.2 GSM System Architecture

The GSM system architecture consists of four basic interconnected subsystems that

interact between themselves and with other users.

The subsystems are:

• The Base Station Subsystem(BSS)

• The Network Switching Subsystem(NSS)

• The Operation Support Subsystem(OSS)

• The Mobile Station(MS)

The BSS provides and manages radio transmission paths between the Mobile Stations

(MS) and the Mobile Switching Center (MSC). BSS also manages the radio interface

between the mobile stations and all the subsystems. BSS consists of many Base Stations

Controllers (BSCs) which connect the MS to NSS via the MSCs.

The NSS manages the switching functions of the system and provide the ability of MSCs

to communicate with other networks such as the Public Switching Telephone Network

(PSTN) and ISDN.

The OSS supports the operation of GSM and allows the system to monitor, diagnose, and

troubleshoot.



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The MS consists of the mobile equipment and a smart card called Subscriber Identity

Module (SIM)

Figure (3.2) shows simple network architecture

Fig (3.2) GSM network architecture [GSM history ref]

3.3 Radio link aspects

GSM originally used two 25 MHz cellular bands set aside for all countries, but it is used

in many other bands. The 890-915 MHz band was for subscribers –to-base transmissions

(reverse link), and the 935-915 MHz band was dedicated for base-to-subscriber

transmissions (forward link).

3.3.1 Traffic channels

Traffic channels are used to carry speech and data traffic. The traffic channels is a group

of Time Division Multiple Access (TDMA) frames. The length of the 26-frame is 120

ms, which is the length of a burst period.



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Fig (3.3) Bursts, TDMA frames, and multiframes organization for data and control

channels

3.3.2 Multiple access

Since the spectrum is scarce and shared by all users, a technique must be provided to

divide the bandwidth among as many users as possible. The GSM system adopted the

method of combining Time-and Frequency –Division Multiple Access (TDMA/FDMA).

FDMA part divides every 25 MHz bandwidth into 124 carrier frequencies spaced 200

KHz apart, these carrier frequencies are divided in time by a TDMA scheme .

3.3.3 GSM control channels

Control channels are common channels that could be accessed both by idle and dedicated

modes of mobile. The common control channels are used in the idle mode to to exchange

the signaling information required to change to dedicated mode. Mobile in dedicated

mode are monitoring the surrounding base stations for handover and other information.

The common control channels include:



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• Broadcast control channel: That channel operates on the forward link of a certain

GSM frames.

• Frequency Correction Channel (FCCH) and Synchronization Channel (SCH)

Used to synchronies the mobile to the time slot structure of a cell by defining the

boundaries of burst periods, and the time slot numbering. Every cell in a GSM

network broadcasts one FCCH and one SCH, which are by definition on time slot

number 0 (within a TDMA frame).

• Random Access Channel (RACH)

Used by mobile to request access to the network.

• Paging channel(PCH)

Used to alert the MS of an incoming data or call.

• Access Grant Channel(AGCH)

These channels are used by the base station to provide forward link

communication to the mobile, and caries data that instructs the mobile to operate

in particular physical channel with a particular didcated control channel.

3.4 Signal processing in GSM

3.4.1 Speech coding: the GSM speech coder is based on the Residually

Excited Linear Predictive coder (RELP), which is enhanced by

including a Long-Term Predictor (LTP). The GSM speech coder takes

the advantage of the fact in a normal conversation; each person speaks

on average for less than 40% of the time. GSM operates in a

discontinuous transmission mode which provides a longer subscriber



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battery life and reduces instantaneous radio interference as the GSM

transmitter is not working during silent periods by using a voice

activity detector (VAD)

3.4.2 Channel coding for data channels:

The coding provided for GSM full rate data channels is based on

handling 60 bits of user data at 5 ms intervals.

3.4.3 Channel coding for control channels

GSM control channels messages are defined to 184 bits long, and are

encoded using a shortened binary cyclic fire cod, with a half-rate

convolution coder.

3.4.4 Interleaving

Interleaving is used to minimize the effect of sudden fades on the

received data. A total of 456 encoded bits within each 20 ms speech frame

or control message frame are broken into eight 57 bit sub-blocks.

3.4.5 Ciphering

Used to modify the content of eight interleaved blocks using

encryption techniques which is known for particular mobile station

and base transceiver station

3.4.6 Burst formatting

Burst formatting adds some binary data to the ciphered blocks, in order to

help equalization and synchronization of the received signal.

3.4.7 Modulation



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The modulation scheme used by GSM is 0.3 GMSK, where 0.3 describes

the 3dB bandwidth of the Gaussian pulse shaping filter.

3.4.8 Equalization

Equalization is performed at the receiver with the help of the training

sequence transmitted in the midamble of every time slot.

3.4.9 Demodulation

The transmitted data is demodulated with the aid of synchronization

data provided by the burst formatting.

3.5 Impairments to radio transmission

The problem with radio transmission is that it is impossible to control the transmission

environment. The impairments are a lot and the most difficult problem that these

impairments are a function of time. The following are some of the problems with radio

transmission [].

3.5.1 Path loss

It the amplitude of a signal diminishes when a signal travel a long distance away from the

transmitter. Due to path loss it hard to get enough signal strength in a large cell. but, the

path loss has an advantage in the same time, without the path loss the principle of

frequency reuse couldn’t be applied for the GSM cellular system.

One of the path loss effects could be appeared in the Fresnel Zone.

3.5.1.1 Fresnel Zone

The Fresnel zone is a 3-dimensional area that exists around the line of sight of a

transmitted radio signal. Its shape is similar to a rugby ball.



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Fig (3.4)Fresnel zone

Any objects that lie within the Fresnel zone, e.g. buildings, trees, ground, water, will

degrade the transmitted signal. The maximum diameter of the Fresnel Zone varies with

distance between the antenna and diminishes of the frequency rises. For practical system

a minimum of 60% clear Fresnel zone is acceptable, in the same time the losses is high.

Therefore, the transmitter power will be needed to be raised or the receiver sensitivity

must be increased.

Table (3.1) losses experienced by signals that lie within mobile telephone frequencies.

900 MHz

Fresnel zone diameter Freespace loss (dB) Fresnel zone dia

16 ft (7 m) 81 11 ft (5.4 m

32 ft (12 m) 96 21 ft (8.4 m

68 ft (23 m) 110 43 ft (15.2 m



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95 ft (31 m) 116 59 ft (20 m)

138 ft (42 m) 122 87 ft (27 m)

192 ft (59 m) 128 118 ft (36 m

For a successful transmission to happen, no objects should be within the Fresnel Zone,

including the ground. Therefore, the antenna height must be such that the Fresnel zone

does not touch the ground.

For a long transmitting distance, the antenna height must be increased to keep the Fresnel

Zone clear.

In the figure(3.5), trees obstruct the line of sight. The received signal will be severely

attenuated.

Fig (3.5) incorrect installation[z]



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Fig (3.6)[z]

Figure (3.6) shows Incorrect Installation, the first Fresnel zone is partially obscured. The

received signal will suffer attenuation.

Fig (3.7)[z]

Fig (3.7) shows correct installation. The first Fresnel zone clears the trees.

3.5.2 Slow fading

Is called also slow fading or lognormal fading. Obstacles that are shadowing the radio

path between the transmitter and receiver will cause slow variations in the signal strength.

3.5.3 Time dispersion

Mountains and other massive bodies reflect the signal. The MS will receive both a direct

radio signal and the reflected one. The two signals will arrive at different times, which

could cause individual bits to overlap with each other.

3.5.4 Co-channel interference



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The co-channel interference appears because of using the same transmitting frequency in

more than one cell, which is well known as frequency reuse. Frequency reuse is one of

the cellular concepts that provide a regular reuse of the frequencies allocated to the

service as shown in figure (3.8)

Fig (3.8) Frequency re use plan for c=3, with hexagonal cells

Chapter 4

The algorism of detection the traffic jams

4.1 Introduction



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The traffic jam is the problem of cars’ slow motion in certain places due to different

reasons. So our first step is to detect the speed of a chosen sample of mobile phones in

cars in the streets, so we can know the average of speed of the cars in these streets. In

other words we can know the streets that suffer from overcrowding. But before we start

to detect the speed of the mobile phones we have to choose them carefully to be sure that

our sample is for mobile phones in cars not mobile phone cared by a walking people or

stationary mobile phones.

4.2 Sampling Operation

Before we start the speed detection processes we must chose our sample that we are

going to make our processes on it. The first condition in our sample that this mobile

phone is in car, not cared by walking man or stationary mobile phone. The second

condition is to be sure that this car is moving in the specific street and in a specific

direction.

To be sure that the mobile phone is in car not cared by walking man or stationary mobile

phone, we must make two steps

1. To be sure that this mobile phone was moving by a speed come close to the

average car speed of the last cell.

2. If the speed that we detect for this mobile phone is aberrant from the other we will

remove this mobile phone from our sample.

Cars in all the cells are not moving in the same direction. But, I need to know the speed

of cars in every direction in the same cell individually. So our second step is to set an

individual sample of mobile phones in cars for every direction by choosing the sample

from mobile phones in cars according to the cell that it comes from.



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4.3 Speed Detection Processes

Mobility detection using everyday GSM traces [1] was the best algorism in detecting the

speed of moving mobile phones which depends on the change of the power that received

by the base station from the mobile phone. The received power by the base station from

the mobile phone as we indicate in chapter 2 depend on more than one factor but the only

factor that changes when moving is the distance. So when we calculate the change of

power it gives us an indication on the rate of change of distance, which is the speed. So

we can deals with power as the distance and we can use Euclidean distance to calculate

the change in power.

Euclidean distance [2] is considered to be the main rule that used to detect the length

between any two points in any space (either two dimensional planes or three dimensional

spaces). The Euclidean distance was discovered by the Alexandrian Greek mathematician

Euclid or the father of geometry (323-283 BC).

Euclid states that the distance between any two points in space is the line of segment that

connects the two points. So if we have two points A and B with coordinates A= (A1, A2

………, An) and B= (B1, B2 ………, Bn) then the distance between them (by using

Euclidean distance will be)

d(A,B)=

So in this algorism he used Euclidean distance by assume that the two points in Euclidean

distance is two consecutive positions of the mobile phone and its coordinates is the power

received from the base station. In the paper of mobility detection using GSM after he use

Euclidean distance the answer was that in picture 4.1



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Picture 4.1 after research and calculation from the team of research they say that this

picture is” average Euclidean distance between consecutive measurements during a

stationary period, slow/fast walking periods and slow/medium/fast driving periods.”[1]

We noticed that the answer of Euclidean distance overlap at some speed so we start to

detect seven different features that indicate the speed of the car exactly. To detect this

features we must put the answer of the Euclidean distance in window consist of 10, 60,

and 300 answer of Euclidean distance according to the area of the cell and the length of

the street.

This feature is:

1. The answer of the Euclidean distance between two consecutive points.

2. Using spearman rank correlation coefficient between the two consecutive points.





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7. Measure the Euclidean distance between the first and the last value of the

Euclidean distance in the window.

4.3 traffic jam detection

After we detect the speed of the cars we start our final step by using this speed to

detect the traffic jam. Our main problem was that base stations after long distance it

starts to loss the signal of the mobile phone. So we try to solve this problem by using

our speed detection algorism more than one time on the same mobile phone by

change the base station that receive the signal of the mobile phone so if one base

station loss the signal of the mobile we can remove it so we can continue the speed

detection without any problem.



References

[2.1] W. C. Jakes, Microwave Mo-bile Communications, AT&T, 1974, (reprinted by

IEEE Press, Piscataway, NJ).

[2.3] Mehdi. Bennis, spectrum sharing for future mobile cellular systems, oulu 2009,

c347.

[2.2] J. G. Proakis, Digital Communications, McGraw-Hill, New York, 1989.

For further info. Contact us on:

[email protected]

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Mbility Detection Using GSM

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