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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 the shadow region but however this method using modern 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.
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 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.
2. 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 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.
3. 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 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. 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, θ , Ф ) .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 any direction is given by the pointing vector and is equivalent to
Total of the power that is being radiated by the antenna is given
The average power that gets radiated is given as
Φ(avg)=W/4π (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.
The power gain of the antenna is given as
The ratio of power to the directivity is referred as a measure of efficiency of the antenna
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 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
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 mobile is transmitting.