DETECTION OF LOST MOBILE USING SNIFFERS

PURPOSE OF THE CIRCUIT

Each and every day thousands of mobiles get misplaced or lost.

misplacement of the lost mobile phone which is significantly increasing.

To detect unauthorized use of mobile phones.

THEORY BEHIND THE CIRCUIT

Presence of RF radiations in the atmosphere due the operation of many electronic devices, radio and telecommunication devices.

The circuit can compare the normal RF in the room as well as the strong RF emitted by the mobile phone.

WHAT IS THE RF LEVEL FROM MOBILE PHONE?

Mobile phone uses 2.5 GHz RF signals in the Microwave range for two way communications.

with a wavelength of 30cm at 872 to 2170 MHz.

When mobile phone => active =>signal is transmitted=>encoded signal=>network database => it is stored=> base station.

It will keep the connection with the base station having strongest transmission.

HOW THE SNIFFER DETECT MOBILE RADIATION?

Figure1: Diagram showing RF detection in Digital Multimeter

From C2

R2

R3 C3

C4

To IC1

T1

10K

15K 10uF

10uFBFR 96

Figure2:Preamplifier stage using Microwave detector Transistor BFR96

R4

R5

IC1

IC1

VR1

C5

D2

18K

18K

TL0 71

1M

100uF

IN 4148

From

C3

To VR2

3

24

7

6

Feed back

Potential Divider

12V

6V

Inverting Amplifier

with Feedback

Figure3: Second Amplification using High gain Inverting Amplifier

For the detection of lost mobile International Mobile Equipment Identifier (IMEI) is used.

The IMEI number is a unique number that is embedded in the mobile phone.

The GSM IMEI 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).

EIR determines whether the phone can log on to the network to make and receive calls.

If the EIR and IMEI number match, the networks can do a number of things.

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.

DESIGNING FOR THE SNIFFER

It includes the following important components:

1. Sniffer base station 2. Unidirectional antenna 3. Tracking software

1. SNIFFER BASE STATION

The sniffer is a small base station, it includes transceiver section.

The frequency of the transceiver section is around 900MHz range, for that frequency range,

a) It is necessary to design the oscillator circuit.

b) The cooling that has to be provided to the circuit.

2. DESIGN OF UNIDIRECTIONAL ANTENNA:

The directional antenna acts as the eyes for the sniffer for the purpose of the detecting the lost mobile phones.

Antenna is a device which works at specified frequencies range for transmitting or receiving the data signal.

Antennas transmit power depending on lobe pattern which varies from one antenna to the other.

The other important thing that has to be taken into account is:

1. The Directivity of the antenna 2. The gain of the antenna 3. The ohmic loss of the antenna 4. The power gain of the antenna 5. The effective area of the antenna

BOUDARY CONDITION

The power of the mobile should be good enough.

The mobile phone should not be in the shadow region.

BENIFITS

The sniffer device has to be designed precisely and size should be reduced for easy mobility for the purpose of detection.

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.

LIMITATION

It 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.

WHAT IS THE RANGE OF THE CIRCUIT?

For properly, assembled, fixed set it can detect the RF variation around 8 meters radius.

If two units are set in the room, it can cover 16-20 meters which is sufficient to cover the whole area the room.

SNIFFER CAN ALSO BE USED IN……

Packet analyzer, computer software or hardware that can intercept and log traffic passing over a digital network.

A program that tracks a person straight to their IP and computer.

Equipment used in a car's tailpipe during an emissions test.

Equipment used as leak detector in vacuum technique.

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. www.gsmworld.com

5. http://ericsson.com