Sniffer for Detecting Lost Mobiles

Sniffer for detecting lost Mobiles.

ABSTRACT:

The main scope of this paper is to detect the lost

mobiles. Each and every day thousands of mobilesget misplaced or lost, though effective way for theblocking of the lost mobile to prevent unauthorizedperson from making and receiving the calls hasbeen done by the manufacturers of the mobile withthe help of International Mobile EquipmentIdentifier (IMEI) has been done but however therehas been no development or very little progress forthe detection of the misplaced mobile phone.For the detection of lost mobile SNIFFERplays a vital role .The sniffer device has to bedesigned precisely and size should be reduced foreasy mobility for the purpose of detection .Thedevice can be called as a mobile Base station thatincludes Sniffer Base station, Unidirectionalantenna , Tracking software. The sniffer is a smallbase station that includes

transceiver section.Itshould operate at a frequency which is muchdifferent from the frequency of the current cellin which the operation of detection is beingcarried out. The

directional antenna is animportant device that is to be designed and used asit plays a major role.

There are certain boundary conditionsthat have to be qualified for the identification oflost mobile like the power of the mobile should begood enough, the mobile phone should not be in the

shadow region but however this method using

modern technologies and devices.

Our paper seems to be a bit costlier for initial setupbut the cost is gradually reduced when effectivelyand efficiently utilized for the purpose of detection.

1. 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 early 70’s and

the advancement in the field of VLSI has helped

in designing less power, smaller size but

efficient transceiver for the purpose ofcommunication.But however the technology has notyet answered the loss or misplacement of the lostmobile phone which is significantly increasing.In this paper we discuss the problem and theprobable solution that could be done. The IMEInumber is a unique number that is embedded inthe mobile phone the main purpose of which isthe blocking of calls that is made byunauthorized person once the mobile is reportedas stolen but here we use it effectively for thepurpose of detection.

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 database of black listed or grey listed phones in thenetwork’s EIR (Equipment ID Register). This

EIR determines whether the phone can log on to

the 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 thedetection of lost mobile phone and for thispurpose we are designing a new device called theSniffer. The sniffer device has to be designedprecisely and size should be reduced for easymobility for the purpose of detection.The device can be called as a mobile basestation 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, itincludes transceiver section. It should operate ata frequency that is much different from the frequency of the current cell in which theoperation of detection is being carried out.Some of the main important things arethe frequency that has to be generated by thetransceiver section is around 900MHz rangewhich is a VHF range and it is necessarily todesign the oscillator circuit for that frequencyrange .Another important is the cooling that hasto be provided to the circuit while designing thecircuit that is to be operated at 900MHz range offrequency. 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 playsan important role in the detection of the mobilephone but however it is the directional antenna

that has a major role in the design of thetransmitter. The directional antenna acts as the

eyes for the sniffer for the purpose of thedetecting the lost mobile phones. Hence theproper design of the directional antenna isrequired. 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 lobepattern 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 necessarythat the transmitter should be a low powertransmitter. The Gain and directivity areintimately related in antennas. The directivity ofan antenna is a statement of how the RF energyis focused in one or two directions. Because theamount of RF energy remains the same, but isdistributed over less area, the apparent signalstrength is higher. This apparent increase insignal strength is the antenna gain. The gain ismeasured in decibels over either a dipole (dBd)or a theoretical construct called an Isotropicradiator (dBi). The isotropic radiator is aspherical signal source that radiates equally wellin all directions. One way to view the omnidirectional pattern is that it is a slice takenhorizontally through the three dimensionalsphere.The graphical representation of Radiationpattern of the unidirectional antenna is shown infigure. The spherical co-ordination system has three main components for the patternrepresentation and they are (R, _ , _ ) .The shapeof the radiation system is independent of R, aslong R is chosen to be sufficiently large andmuch greater than the wavelength as the largestdimension of the antenna. The magnitude of thefield strength in any direction varies inverselywith R. A complete radiation pattern requires thethree dimensional representation. The otherfactors that are to be taken into account duringthe development of the antenna for the sniffershould be the gain and the directivity .As thesefeatures have a greater effect while designing theantenna. The gain of the antenna is defined as theability of the antenna to radiate the power in aparticular 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 beingradiated 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 thedirection in which there is maximum gain for theradiation that is being radiated, the gain of theantenna is given as a function of the angles. Thedirectivity value is constant for a particulardirection. In addition to the directivity and thegain of the antenna the other important thing thathas to be taken into account is the power that isbeing radiated by the antenna. The total power isgiven 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 theantenna.

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 antennashould be properly designed as this causes morepenetration of the electromagnetic radiation and

thus it might have some effect in the near by

cells.The effective area of the antenna isanother important factor that is mainly required inthe receiving antenna and it may be referred as theeffective aperture or capture area and is related tothe directive gain of the antenna through therelation

A=gd_2/4

Since the sniffer device that is constructedis a device that has both the transmitting and thereceiving antenna. Effective gain has to be taken

into account and this shows the ability of theantenna to capture the signal that the lost mobile

is transmitting.

3.3 SOFTWARE FOR THE TRACKING:

The software part plays a major role inthe tracking of the lost mobile phone It is thebase for the antenna to track the lost mobile themain feature of this software is that it helps inthe process of creation of the data base and thisis 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 theIMEI number of the lost mobile phone from theRAM and this ID done using the SQL query thatfetches the IMEI number. After getting the inputof the lost mobile phones IMEI number it checks the comport for getting the information whetherit obtains any signaling information from the lostdevice that might respond to the signal sent bythe snifferThe programming is done with C orJava. However the C is most preferred as it iseasily embedded with the chips. With VB thefront end is designed. The oracle SQL is the backend as it helps in retrieving the input data fromthe RAM using the query. But however the

sample program that we have designed does notuse the oracle it takes the input directly from thekeyboard and this is an example and a dummyprogram that has been created that helps in theunderstanding of how the device would work.

IV WORKING OF THE SNIFFER DEVICE

The sniffer is basically a transceiverthat works in the frequency which is in thespecial unused range that is operated by theservice provided or it can designed to operate ata frequency that is of much different frequencythan the one that is being used by the nearbycells as there may be possibility of interferenceby the device with the devices in the nearbycells. 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 operationof the mobile with the base station and there is a

BTS that acts as a middle man in the process of

communication between the mobile and theMTSO which is popularly known as MSC orMobile Switching Centre .There is always a two

way communication between devices and before

the establishment of the communication theauthentication 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 theauthentication of the handset, which is done in

EIR or the Equipment Identifier Register. Thisregister 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 twoway communication is established.The IMEI of the lost mobile phonenumber once has been reported to the serviceprovider, who keeps in track of the record of lostmobile phones. The MTSO or the MSC whichkeeps in track of all the mobile phones withIMEI number and the IMSI number has theinformation of the lost mobile phones locationwhich means the location of the cell where thelost device is because of the two waycommunication with the device the BTS of thelost device is known to MSC. From thisinformation regarding the cell in which thedevice is located the sniffer device is introduced.

Fig: 2 .The initial connection between thecellular network and lost mobile phone

The next figure or the fig 2 shows thesniffer that gets into work for the purpose ofdetection of the lost device. After theinformation regarding the IMEI number of thelost device is provided by the MTSO or MSC.This is then fed into the sniffers main memorythe sniffer’s located in particular cell gets intoaction of detecting the lost device. The snifferuses a frequency that is different from the onethat is being used by the base station and thelocated nearby cells .The base stationdisconnects the connection with the lost mobilephone, as there is a request regarding this actionfrom the EIR part of the MSC. This causes thelost device to search the BTS to get locked withsince each base station does not haveauthorization capability the lost device sendappropriate connection request signal. Nowwhen the sniffer device is being deployed andthis device has in built authorization capabilitythe lost device finds the sniffer to get itselflocked to the frequency of the sniffer .While theconnection between the sniffer and the mobilephone is established; the IMEI of the lost mobileis validated with the stored IMEI and after

successful authorization the communicationbetween the sniffer and the lost device isestablished. If the other devices in the same try

to communicate with the sniffer the access isdenied and this is done at the validation donebased on the IME. Once the communicationstarts it is mainly with the antenna and the signal

strength of the lost device the location can betracked. However the process to searching canalso be aided with the GPS system for moreaccurate and fast detectionThe main requirement is that thesniffer is operated in a frequency that is differentfrom the frequency adopted by the cell andnearby ones. Hence the interference from thenearby cell can be avoided. The directionalantenna is used in finding the location of themobile phone.

Fig 3 . The connection of the snifferdevice with the lost mobile phone.

Here the signal strength of the received signal isobtain antenna pattern is plotted once the signalof the mobile is obtained. The no. of antennapattern for different position of same mobilephone is used to find the exact location. Buthowever in this method the directional antennaused much be of a very small beam width thishelps in more accurate process ofdetection

.

Fig4 the sniffer shown in fig tries tocommunicate with the lost mobile.After getting connected with themobile it creates a virtual cell pattern and thushelps in the detection of lost mobile phones.

V .CONCLUSION:

Since the boom of the mobile phone for thepurpose of the communication there has been a

large no. of complaints regarding the mobilephone that is being lost and there has been noeffective method developed for detecting the lost

device. The given paper dealt about the idea of

development “Sniffer for the detection of lostMobile phones” paves a way by means of which

the lost mobile phones can be recovered. But theprocess of detection is yet to be developed

through the software and demo has beendeveloped and is with the authors. The demo hasbeen written in VB that gives the over view ofhow 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 theinternal architecture is of lesser complexitycompared to the base station as this mainlyinvolves the control signal and there is no need

for the voice process.The design involved the following:Design of the sniffer base station design ofunidirectional l antenna, development ofsoftware for tracking. Though this methodappears to be a little bit complex involving thedesign 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 ofthe lost mobile like the power of the mobileshould be good enough , the mobile phoneshould not be in the shadow region etc., buthowever this method can be improved by usingmodern technologies and devices.

VI . APPENDIX

IMEI: International Mobile Equipment Identifier.

SNIFFER: The small transceiver used fordetecting lost mobile phone.

IMSI: International Mobile Subscriber Identifier.

BTS: Base transceiver station.

MTSO: Mobile Telephone Switching Office.

MSC: Mobile Station Switching Controller.

VII .REFERENCES

1. Schiller , “Mobile Communication”,

Pearson Education 1 Edition, 7th reprint

-2003.

2. John D Kraus, “Electromagnetics”,

TMH,

3. Jordan et al, “Electromagnetic waves

and radiation system” , Printice Hall

4.

5.

6.