The document describes a proposed device called a "sniffer" that can detect and track lost mobile phones. The sniffer would function as a small base station using a different frequency than nearby cell towers. It includes a transceiver, unidirectional antenna, and software to store and search for the IMEI of lost phones. When in range of a lost phone, the sniffer would mimic a base station and authenticate with the phone, allowing it to track the phone's location to recover it. The sniffer aims to provide a cost-effective solution to the growing problem of lost and stolen mobile phones.

1. Department of Telecommunication engineering
SEMINAR ON SNIFFERS
Session : 2014-1015
Presented by Under the guidance of
NAME : Amarjeet Paul Mrs.Archana Mane.
Associate professor

2. Contents.
• Introduction.
• About IMEI.
• Designing for the sniffer.
- sniffer base station.
- design of unidirectional antenna.
- software for tracking
• Working of the sniffer device.
• Advantages.
• Disadvantages.
• Conclusion.
• References.

3. Introduction.
• One of the most interesting things about cell phone is that it is really 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 of communication.
• But however the technology has not yet answered the loss or misplacement of the
lost mobile phone which is significantly increasing. Hence in this seminar we try to
look for a probable solution.
• 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.

4. About IMEI.
• IMEI stands for international mobile equipment identity.
• It is a 15 digit unique code.
• When a mobile is switched on , this unique IMEI number is transmitted to the
base station.
• In the base station it is being checked against a database for the black listed or
grey listed numbers in the network’s EIR (Equipment identity register).
• EIR then determines whether the phone can log into the network to make and
receive calls.
• One can check the IMEI number of the device by dialling *#06#.
• If the IMEI matches with the EIR number in the database then the network is
bound to restraint the number .
• Grey list numbers : allows the phone to be used but the device is under constant
surveillance and tracking with the help of SIM card.
• Black list numbers : Complete termination of network facilities.

5. Designing for the Sniffer.
• As stated earlier , this proposal is about detection of lost mobile phone.
• For this purpose we are designing a new device known as Sniffers.
• The sniffer device is to be designed with high precision and the size should be
reduced for easy mobility for the purpose of detection.
• The device can be called as MOBILE BASE STATION.
• The Sniffer thereby includes the following component :
1. Sniffer base station.
2. Unidirectional Antenna.
3. Tracking software.

6. 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 cell
it is currently present.
• Frequency to be operated by the sniffer trans receiver is 9000Mhz.
• Mobile phones as well as base station have low power transmitter. So sniffer should
also have low power transmitter.
• This thereby helps in reducing the interference with devices in the same cell.

7. 2. Design of unidirectional antenna.
• Though the trans receiver plays an important role in the detection of mobile phones
, but however the unidirectional antenna plays an important role.
• The unidirectional antenna acts like the eye of the sniffer device for the purpose of
detecting lost mobile phones . Hence taking this into account we could say ,
unidirectional antenna was an important part in a sniffer device.
• Antenna is a device which is used to transmit and receive data at a particular
frequency range .
• In general , the antenna transmit power depends on the lobe pattern that varies from
one antenna to another.
• The lobe pattern is a two dimensional diagram that is used to show the radiation
pattern.
• The radiation pattern of an unidirectional antenna is as follows :

8. Unidirectional antenna radiation pattern (figure 1).

9. Unidirectional Antenna Radiation Pattern.
• Antenna radiation plots can be quite complex because in the real world they are
three-dimensional.
• However, to simplify them a Cartesian coordinate system (a two-dimensional
system which refers to points in free space) is often used. Radiation plots are most
often shown in either the plane of the axis of the antenna or the plane perpendicular
to the axis and are referred to as the azimuth or "E-plane" and the elevation or "H-
plane" respectively.
• An antenna plot is like a road map. It tells you where the radiation is concentrated.
Patterns are usually referenced to the outer edge of the plot which is the maximum
gain of the antenna. This makes it easy to determine other important antenna
characteristics directly from the plot.
• As it is evident from the graph that the sniffer uses an standard 40 decibels gain
antenna . Since the lobe is much thinner it is focused toward a single direction.
Hence an unidirectional antenna.

10. Unidirectional antenna (Gain).
• In addition to the radiation pattern , the transmitter should be a low power
transmitter.
• The gain and directivity are interdependent on each other.
• An RF antenna radiates a given amount of power. This is the power dissipated in
the radiation resistance of the RF antenna. An isotropic radiator will distribute this
equally in all directions.
• For an antenna with a Unidirectional pattern, less power will be radiated in some
directions and more in others. The fact that more power is radiated in given
directions implies that it can be considered to have a gain.
• The gain can be defined as a ratio of the signal transmitted in the "maximum"
direction to that of a standard or reference antenna.
• 𝐺 = 𝐸 × 𝐷
• Where G is the gain , E is the efficiency and D is the directivity.

11. Unidirectional Antenna (directivity).
• The directivity of an antenna is an statement of how the RF energy is focused in
one or two directions.
• We know that the RF electrical energy remains the same so , if the signal to be
transmitted is transmitted over a less area , the apparent signal strength increases.
This increase in the signal strength is due to the antenna gain over a particular
direction.
• Directive gain or directivity is a different measure which does not take an
antenna's electrical efficiency into account.
• Directivity compares the radiation intensity of the antenna in one direction to that
with the values of radiation intensity from other directions.
• 𝐷 =
𝑈
𝑃/(4𝜋)
• Here D= directivity , P= Total power radiated , U = radiation intensity.
• Typical sniffer directivity is 5-8 decibels.

12. Unidirectional Antenna. (Power)
• The power radiated by the unidirectional antenna should be properly designed.
• Higher the power, higher is the penetration of electromagnetic radiations and it
might have some effect in the nearby cells.
• 𝑃 = 𝜙=0
𝜙=2𝜋
𝜃=0
𝜃=2𝜋
𝑈 𝑠𝑖𝑛𝜃 d𝜃 𝑑𝜙
• Here P = power , U is the radiation intensity.
• The effective area of an antenna is mainly required in the receiving antenna and it
may be referred as the effective aperture or capture area.
• antenna aperture or effective area is a measure of how effective an antenna is at
receiving the power of radio waves. The aperture is defined as the area, oriented
perpendicular to the direction of an incoming radio wave, which would intercept the
same amount of power from that wave as is produced by the antenna receiving it.
• Since the sniffer device is a device that has a trans receiver unit , effective gain has
to be taken into account and this shows the ability of the antenna to capture the
signal the lost mobile is transmitting.

13. 3. Software for the tracking.
• It plays a major role in the tracking of lost mobile phones.
• It is the base of the antenna to track the lost mobile .
• The main feature of the software is to create a database.
• This database is created and manipulated using a Random Access Memory.
• The mobile that has been lost has a certain IMEI number that is embedded in the
mobile processor.
• This RAM of the sniffer device stores the IMEI number of the lost mobile phone.
• Thus this acts as a database or the directory of the lost mobile phone number.
• The software is 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 a the SQL
query that fetches the IMEI number.
• After getting the input of the lost mobile IMEI number , the information whether it
obtains any signalling information from the lost mobile by transmitting a beacon
signal from the base station is retained by the sniffer.
• The programming is done with C or Java.

14. Working of sniffer device.
• The sniffer is basically a trans receiver that works in the frequency which is in the
special unused range that is allocated by the service provider .
• The sniffer can also be designed to operate at a frequency that is much different
frequency than the one that is being used in the nearby cells.
• We use different frequency to avoid the case of interference of the device with the
other mobiles that maybe operating in that particular cell or the nearby cells.
• The working of the sniffer is as follows. the figures 2 and 3 show the working of
sniffers .
• From figure 2 it gives the normal operation of the mobile with the base station and
there is a BTS that acts like a middle man in the process of communication between
the lost mobile and the MTSO which is popularly know as MSC or the Mobile
Switching Centre.
• There is always a two way communication between the devices .
• Before the establishment of communication the sim card having the IMSI and the
imei of the phone gets validated . This IMSI number aids in the authorization of the
user.

15. Working of sniffer device.
• The second authentication is that of the EIR or the equipment identity 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 handset , a two way communication is established.
• The IMEI of the lost mobile phone number 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 the IMEI
number and the IMSI number searches for the matching of the IMEI of the lost mobile
phones.
• Once the said imei and is entered in the MSC , it searches for the BTS which is currently
housing the lost mobile and if the mobile is turned on the mobile is being authenticated
by the BTS , compares the imei of the mobile with that given to the MSC and then
immediately forwards the IMSI and the cell location of the mobile phone to the MTSO.
• The mtso then indicated the sniffer that the LOST MOBILE CELL HAS BEEN
FOUND.
• The sniffer is now activated .

16. Initial connection between cellular network and the lost
mobile phone ( figure 2).

17. Working of Sniffer device.
• The next figure shows how the sniffer now gets into the work .
• After receiving the information about the lost mobile from the MSC. The sniffer now
goes to the cell where the lost mobile phone is currently in.
• It is to be noted that prior to the sniffer entry into the cell the lost phone was in direct
contact with the BTS , but it was not able to use the network resources.
• Once the sniffer is about to enter the cell the BTS completely severs its connection to the
lost mobile phone.
• This results in the Lost mobile to search for any nearby BTS to get locked with to access
the network resources.
• Since all the BTS present in the area have their own authorisation protocols , the lost
mobile is unable to connect with any BTS as it is already now being black listed.
• Now when the sniffer device is being deployed , this device has in built authorization
capability.
• The mobile phone now mistake the sniffer for a BTS . And once the mobile phone
mistakenly sends an authentication request to the sniffer , The sniffer locks itself to the
mobile phone.

18. Working of Sniffer device.
• There may be a chance of error so when the mobile phone locks on to the sniffer
and vice versa , the sniffer compares the imei got from the authorization request and
the imei stored in its RAM.
• If the both IMEI matches , the sniffer now is set in TRACKING MODE.
• The sniffer now with the help of Its antenna starts searching for the lost mobile by
comparing the Signal strength . It now functions as a RADAR.
• If other device try to communicate with a sniffer (mistaking it for a BTS) , the
access is immediately denied using the authentication systems.
• It is to be mentioned that the process of searching can be aided with the GPS or the
GLOBAL POSITIONING SYSTEM for pinpoint and fast detection of the lost
mobile phone.
• It is very important that the sniffer uses a different frequency from any of the cells
to avoid interference.
• So ideally the frequency is above 9000 Mhz. this range is reserved by the service
provider and is used for this sort of purposes.

19. Connection Between Sniffer and the lost mobile phone.

20. Sniffer : Virtual Cell Pattern.
• After connecting to the device , the sniffer also creates a virtual cell pattern and
thus helps in the detecting of the lost mobile phones.

21. Advantages.
• It is cost effective
• It has good performance
• It has low power consumption.
• Easy Mobility.

22. Disadvantages.
• The design is kind of complex.
• Precision designing needed.
• Modifying the system is complex.

23. Conclusion.
• Since the boom of the mobile phones for the purpose of communicating , there has
been an large number of complaints in the cases of mobile theft and misplacement.
• This is a present day problem and it was very important to address the said issue.
• The given documents gives us an idea to recover a lost mobile phone , thereby
ending the myth that the mobile phone cannot be recovered once lost.
• This document is effective because it can be applied to all kind of mobile phones be
it the old cell phones or the newer model smart phones.
• This method might appear a bit complex and expensive involving the design of the
sniffer but considering the prospect of large scale detection the overall cost for
designing and detection scales down considerably.

24. References.
• Schiller, “ Mobile communication”, Pearson Education 1st Edition, 7th reprint –
2003.
• John D. Krauss , “ Electromagnetic”, TMH.
• Jordan et al , “ Electromagnetic waves and Radiation System”, prentice hall.
• www.gsmworld.com
• Ericsson.com
• www.cisco.com
• www.google.com
• MVJCE Central Library.

25. .