09-06-2012, 02:17 PM
Sniffer for Detecting Lost Mobiles
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ABSTRACT:
The main scope of this paper is to detect the lost mobiles. Each and every day thousands of
mobiles get misplaced or lost, though effective way for the blocking of the lost mobile to prevent
unauthorized person from making and receiving the calls has been done by the manufacturers of
the mobile with the help of International Mobile Equipment Identifier (IMEI) has been done but
however there has been no development or very little progress for the detection of the misplaced
mobile phone. For the detection of lost mobile SNIFFER plays a vital role .The sniffer device
has to be designed precisely and size should be reduced for easy mobility for the purpose of
detection .The device can be called as a mobile Base station that includes Sniffer Base station,
Unidirectional antenna , Tracking software. The sniffer is a small base station that includes
transceiver section. It should operate at a frequency which is much different from the frequency
of the current cell in which the operation of detection is being carried out. The directional
antenna is an important device that is to be designed and used as it plays a major role.
There are certain boundary conditions that have to be qualified for the identification of lost
mobile like the power of the mobile should be good enough, the mobile phone should not be in
theshadow region but however this method usingmodern technologies and devices.
Our paper seems to be a bit costlier for initial setup but the cost is gradually reduced
when effectively and efficiently utilized for the purpose of detection.
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INTRODUCTION
One of the most interesting things about cell phone is that it is really a radio an extremely
sophisticated radio, which uses some band of frequency that has the basic working similar to the
ordinary cordless phone. The mobile cellular communication has been appreciated since its birth
in the eary 70’s and the advancement in the field of VLSI has helped in designing less power,
smaller size but efficient transceiver for the purpose of communication. But however the
technology has not yet answered the loss or misplacement of the lost mobile phone which is
significantly increasing. In this paper we discuss the problem and the probable solution that
could be done. The IMEI number is a unique number that is embedded in the mobile phone the
main purpose of which is the blocking of calls that is made by unauthorized person once the
mobile is reported as stolen but here we use it effectively for the purpose of detection.
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II. ABOUT IMEI
The GSM MoU’s IMEI(International Mobile Equipment Identity)numbering system is a 15 digit
unique code that is used to identify the GSM/DCS/PCS phone. When a phone is switched on,
this unique IMEI number is transmitted and checked against a data base of black listed or grey
listed phones in the network’s EIR (Equipment ID Register). This EIR determines whether the
phone can log on tithe network to make and receive calls. To know the IMEI number the *#06#
has to be pressed, the number will be displayed in the LCD screen; it is unique to a mobile
phone. If the EIR and IMEI number match, the networks can do a number of things. For example
grey list or blacklist a phone: 1. Grey listing will allow the phone to be used, but it can be tracked
to see who has it (via the SIM information). 2. Black listing the phone from being used on any
network where there is an EIR match.
III. DESIGNING FOR THE SNIFFER
As stated this proposal is about the detection of lost mobile phone and for this purpose
we are designing a new device called the Sniffer. The sniffer device has to be designed precisely
and size should be reduced for easy mobility for the purpose of detection. The device can be
called as a mobile base station that includes the following important
components:
1. Sniffer base station
2 .Unidirectional antenna
3 .Tracking software
3.1 SNIFFER BASE STATION:
The sniffer is a small base station, it includes transceiver section. It should operate at a
frequency that is much different from the frequency of the current cell in which the operation of
detection is being carried out. Some of the main important things are the frequency that has to be
generated by the transceiver section is around 900MHz range which is a VHF range and it is
necessarily to design the oscillator circuit for that frequency range .Another important is the
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cooling that has to be provided to the circuit while designing the circuit that is to be operated at
900MHz range of frequency. Hence proper design of base station is an important thing in the
design of the sniffer. Mobile phones as well as the base station has low power transmitter is also
transmitting at low power. The transmitter of the sniffer has to be a low power transmitter. This
helps in the process of reducing the interference of the device with the devices that are in the
other cells.
3.2 DESIGN OF UNIDIRECTIONAL ANTENNA:
Though the transceiver in a sniffer plays an important role in the detection of the mobile
phone but however it is the directional antenna that has a major role in the design of the
transmitter. The directional antenna acts as the eyes for the sniffer for the purpose of the
detecting the lost mobile phones. Hence the proper design of the directional antenna is required.
Antenna is a device which works at specified frequencies range for transmitting or receiving the
data signal. In general, antennas transmit power depending on lobe pattern which varies from one
antenna to the other. The lobe pattern is a two dimensional diagrams that is used to show
radiation pattern. Radiation pattern of directional antenna is shown in fig1.
In addition to this it is necessary that the transmitter should be a low power transmitter.
The Gain and directivity are intimately related in antennas. The directivity of an antenna is a
statement of how the RF energy is focused in one or two directions. Because the amount of RF
energy remains the same, but is distributed over less area, the apparent signal strength is higher.
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This apparent increase in signal strength is the antenna gain. The gain is measured in decibels
over either a dipole (dBd) or a theoretical construct called an Isotropic radiator (dBi). The
isotropic radiator is a spherical signal source that radiates equally well in all directions. One way
to view the omni directional pattern is that it is a slice taken horizontally through the three
dimensional sphere. The graphical representation of Radiation pattern of the unidirectional
antenna is shown in figure. The spherical co-ordination system has three main components for
the pattern representation and they are (R, _ , _ ) .The shape of the radiation system is
independent of R, as long R is chosen to be sufficiently large and much greater than the
wavelength as the largest dimension of the antenna. The magnitude of the field strength in any
direction varies inversely with R. A complete radiation pattern requires the three dimensional
representation. The other factors that are to be taken into account during the development of the
antenna for the sniffer should be the gain and the directivity .As these features have a greater
effect while designing the antenna. The gain of the antenna is defined as the ability of the
antenna to radiate the power in a particular direction. The power radiated per unit area in sany
direction is given by the pointing vector and is equivalent to E2/_2 W/m2
Total of the power that is being radiated by the antenna is given as
W=__d_
The average power that gets radiated is given as _(avg)=W/4_ (watts per steradian) The
Directivity of the antenna is the direction in which there is maximum gain for the radiation that is
being radiated, the gain of the antenna is given as a function of the angles. The directivity value
is constant for a particular direction. In addition to the directivity and the gain of the antenna the
other important thing that has to be taken into account is the power that is being radiated by the
antenna. The total power is given as W and is the summation of the radiated power and the
ohmic loss of the antenna. Here the Wl represents the ohmic losses of the antenna.
Wt=Wr+Wl
The power gain of the antenna is given as
gp=4__/wt
The ratio of power to the directivity is referred as a measure of efficiency of the antenna
gp/gd=Wr/(Wr+Wl)
The power radiated by the antenna should be properly designed as this causes more penetration
of the electromagnetic radiation and thus it might have some effect in the near by cells. The
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effective area of the antenna is another important factor that is mainly required in the receiving
antenna and it may be referred as the effective aperture or capture area and is related to the
directive gain of the antenna through the relation A=gd_2/4
Since the sniffer device that is constructed is a device that has both the transmitting and the
receiving antenna. Effective gain has to be taken into account and this shows the ability of the
antenna to capture the signal that the lost mobileis transmitting.
3.3 SOFTWARE FOR THE TRACKING:
The software part plays a major role in the tracking of the lost mobile phone It is the base
for the antenna to track the lost mobile the main feature of this software is that it helps in the
process of creation of the data base and this is mainly done using a Random Access Memory.
The mobile phone that is lost has certain IMEI number that is embedded in the chip. This RAM
of the sniffer device stores the IMEI number of the lost mobile phone. Thus this acts as a data
base or the directory of the lost mobile phone number/The software that is to be designed in such
a way that the software has the input as the IMEI number of the lost mobile phone from the
RAM and this ID done using the SQL query that fetches the IMEI number. After getting the
input of the lost mobile phones IMEI number it checks the comport for getting the information
whether it obtains any signaling information from the lost device that might respond to the signal
sent by the sniffer The programming is done with C or Java. However the C is most preferred as
it is easily embedded with the chips. With VB the front end is designed. The oracle SQL is the
back end as it helps in retrieving the input data from the RAM using the query. But however the
sample program that we have designed does not use the oracle it takes the input directly from the
keyboard and this is an example and a dummy program that has been created that helps in the
understanding of how the device would work.
IV WORKING OF THE SNIFFER DEVICE
The sniffer is basically a transceiver that works in the frequency which is in the special
unused range that is operated by the service provided or it can designed to operate at a frequency
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that is of much different frequency than the one that is being used by the nearby cells as there
may be possibility of interference by the device with the devices in the nearby cells. The working
for the device is as follows. The fig 2 &3 shows the working of the sniffer ; as given in the fig2
it gives the normal operation of the obile with the base station and there is a BTS that acts as a
middle man in the process of communication between the mobile and the MTSO which is
popularly known as MSC or Mobile Switching Centre .There is always a two way
communication between devices and before the establishment of the communication the
authentication of the SIM card that has the IMSI or the International Mobile Subscriber Identifier
.This IMSI number helps in the authorization of the user. The second authentication is the
authentication of the handset, which is done in EIR or the Equipment Identifier Register. This
register is located at the MSC and it contains the IMEI number of the lost handset and if the
signal is obtained from the normal one then the two way communication is established. The
IMEI of the lost mobile phone number once has been reported to the service provider, who keeps
in track of the record of lost mobile phones. The MTSO or the MSC which keeps in track of all
the mobile phones with IMEI number and the IMSI number has the information of the lost
mobile phones location which means the location of the cell where the lost device is because of
the two way communication with the device the BTS of the lost device is known to MSC. From
this information regarding the cell in which the device is located the sniffer device is introduced.
Fig: 2 .The initial connection between the cellular network and lost mobile phone
The next figure or the fig 2 shows the sniffer that gets into work for the purpose of detection of
the lost device. After the information regarding the IMEI number of the lost device is provided
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by the MTSO or MSC .This is then fed into the sniffers main memory the sniffer’s located in
particular cell gets into action of detecting the lost device. The sniffer uses a frequency that is
different from the one that is being used by the base station and the located nearby cells .The
base station disconnects the connection with the lost mobile phone, as there is a request
regarding this action from the EIR part of the MSC. This causes the lost device to search the
BTS to get locked with since each base station does not have authorization capability the lost
device send appropriate connection request signal. Now when the sniffer device is being
deployed and this device has in built authorization capability the lost device finds the sniffer to
get itself locked to the frequency of the sniffer .While the connection between the sniffer and the
mobile phone is established; the IMEI of the lost mobile is validated with the stored IMEI and
after successful authorization the communication between the sniffer and the lost device is
established. If the other devices in the same try to communicate with the sniffer the access is
denied and this is done at the validation done based on the IME. Once the communication starts
it is mainly with the antenna and the signal strength of the lost device the location can be tracked.
However the process to searching can also be aided with the GPS system for more accurate and
fast detection The main requirement is that the sniffer is operated in a frequency that is different
from the frequency adopted by the cell and nearby ones. Hence the interference from the nearby
cell can be avoided. The directional antenna is used in finding the location of the mobile phone.
Fig 3 . The connection of the sniffer device with the lost mobile phone.
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Here the signal strength of the received signal is obtain antenna pattern is plotted once the
signal of the mobile is obtained. The no. of antenna pattern for different position of same mobile
phone is used to find the exact location. But however in this method the directional antenna used
much be of a very small beam width this helps in more accurate process of detection
.
Fig4 the sniffer shown in fig tries to communicate with the lost mobile. After getting
connected with the mobile it creates a virtual cell pattern and thus helps in the detection of lost
mobile phones.
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V .CONCLUSION:
Since the boom of the mobile phone for the purpose of the communication there has been a large
no. of complaints regarding the mobile phone that is being lost and there has been no effective
method developed for detecting the lost device. The given paper dealt about the idea of
development “Sniffer for the detection of lost Mobile phones” paves a way by means of which
the lost mobile phones can be recovered. But the process of detection is yet to be developed
through the software and demo has been developed and is with the authors. The demo has been
written in VB that gives the over view of how the lost mobile is being detected and the software
has been written in C. The SQL has to be used for the purpose of querying and the internal
architecture is of lesser complexity compared to the base station as this mainly involves the
control signal and there is no need for the voice process. The design involved the following:
Design of the sniffer base station design of unidirectional l antenna, development of software for
tracking. Though this method appears to be a little bit complex involving the design of the sniffer
but however for large scale detection the overall effective cost of the design and the detection
scales down.
There are certain boundary conditions or criteria that have to be qualified for the
identification of the lost mobile like the power of the mobile should be good enough , the mobile
phone should not be in the shadow region etc., but however this method can be improved by
using modern technologies and devices.
