17-11-2012, 03:05 PM
GSM 900 Mobile Jammer
[attachment=40014]
INTRODUCTION
A GSM Jammer is a device that transmit signal on the same frequency at which the GSM
system operates, the jamming success when the mobile phones in the area where the jammer is
located are disabled.
Communication jamming devices were first developed and used by military. Where
tactical commanders use RF communications to exercise control of their forces, an enemy has
interest in those communications. This interest comes from the fundamental area of denying the
successful transport of the information from the sender to the receiver.
Nowadays the mobile jammer devices are becoming civilian products rather than
electronic warfare devices, since with the increasing number of the mobile phone users the need
to disable mobile phones in specific places where the ringing of cell phone would be disruptive
has increased. These places include worship places, university lecture rooms, libraries, concert
halls, meeting rooms, and other places where silence is appreciated.
OPERATION
Jamming devices overpower the cell phone by transmitting a signal on the same
frequency as the cell phone and at a high enough power that the two signals collide and cancel
each other out. Cell phones are designed to add power if they experience low-level interference,
so the jammer must recognize and match the power increase from the phone. Cell phones are
full-duplex devices, which mean they use two separate frequencies, one for talking and one for
listening simultaneously. Some jammers block only one of the frequencies used by cell phones,
which has the effect of blocking both. The phone is tricked into thinking there is no service
because it can receive only one of the frequencies. Less complex devices block only one group
of frequencies, while sophisticated jammers can block several types of networks at once to head
off dual-mode or tri-mode phones that automatically switch among different network types to
find an open signal. Some of the high-end devices block all frequencies at once and others can be
tuned to specific frequencies.
To jam a cell phone, all you need is a device that broadcasts on the correct frequencies.
Although different cellular systems process signals differently, all cell-phone networks use radio
signals that can be interrupted. GSM, used in digital cellular and PCS-based systems, operates in
the 900-MHz and 1800-MHz bands in Europe and Asia and in the 1900-MHz (sometimes
referred to as 1.9-GHz) band in the United States. Jammers can broadcast on any frequency and
are effective against AMPS, CDMA, TDMA, GSM, PCS, DCS, iDEN and Nextel systems. Oldfashioned
analog cell phones and today's digital devices are equally susceptible to jamming.
Disrupting a cell phone is the same as jamming any other type of radio communication. A cell
phone works by communicating with its service network through a cell tower or base station.
Cell towers divide a city into small areas, or cells. As a cell phone user drives down the street,
the signal is handed from tower to tower.
Dept.
MOBILE JAMMING TECHNIQUES
Type "A" Device: JAMMERS
In this device we overpower cell phone's signal with a stronger signal, This type of
device comes equipped with several independent oscillators transmitting ‘jamming signals’
capable of blocking frequencies used by paging devices as well as those used by cellular/PCS
systems’ control channels for call establishment. When active in a designated area, such devices
will (by means of RF interference) prevent all pagers and mobile phones located in that area
from receiving and transmitting calls. This type of device transmits only a jamming signal and
has very poor frequency selectivity, which leads to interference with a larger amount of
communication spectrum than it was originally intended to target. Technologist Jim Mahan said,
“There are two types. One is called brute force jamming, which just blocks everything. The
problem is, it’s like power-washing the airwaves and it bleeds over into the public broadcast area.
The other puts out a small amount of interference, and you could potentially confine it within a
single cell block. You could use lots of little pockets of small jamming to keep a facility under
control.”
Type “B” Device: INTELLIGENT CELLULAR DISABLERS
Unlike jammers, Type “B” devices do not transmit an interfering signal on the control
channels. The device, when located in a designated ‘quiet’ area, functions as a ‘detector’. It has a
unique identification number for communicating with the cellular base station. When a Type “B”
device detects the presence of a mobile phone in the quiet room; the ‘filtering’ (i.e. the
prevention of authorization of call establishment) is done by the software at the base station.
Type “D” Device: DIRECT RECEIVE & TRANSMIT JAMMERS
This jammer behaves like a small, independent and portable base station, which can
directly interact intelligently or unintelligently with the operation of the local mobile phone. The
jammer is predominantly in receiving mode and will intelligently choose to interact and block
the cell phone directly if it is within close proximity of the jammer.
This selective jamming technique uses a discriminating receiver to target the
jamming transmitter. The benefit of such targeting selectivity is much less electromagnetic
pollution in terms of raw power transmitted and frequency spectrum from the jammer, and
therefore much less disruptive to passing traffic. The jam signal would only stay on as long as
the mobile continues to make a link with the base station, otherwise there would be no jamming
transmission – the technique forces the link to break or unhook and then it retreats to a passive
receive mode again.
GSM-MOBILE JAMMING REQUIREMENTS
Jamming objective is to inject an interference signal into the communications frequency so
that the actual signal is completely submerged by the interference. It is important to notice that
transmission can never be totally jammed - jamming hinders the reception at the other end. The
problem here for the jammer is that only transmitters can be found using direction finding and the
location of the target must be a specific location, usually where the jammer is located and this is
because the jamming power is never infinite. Jamming is successful when the jamming signal denies
the usability of the communications transmission. In digital communications, the usability is denied
when the error rate of the transmission cannot be compensated by error correction. Usually a
successful jamming attack requires that the jammer power is roughly equal to signal power at the
receiver. The effects of jamming depend on the jamming-to-signal ratio (J/S), modulation scheme,
channel coding and interleaving of the target system. Generally Jamming-to-Signal ratio can be
measured according to the following Equation.
[attachment=40014]
INTRODUCTION
A GSM Jammer is a device that transmit signal on the same frequency at which the GSM
system operates, the jamming success when the mobile phones in the area where the jammer is
located are disabled.
Communication jamming devices were first developed and used by military. Where
tactical commanders use RF communications to exercise control of their forces, an enemy has
interest in those communications. This interest comes from the fundamental area of denying the
successful transport of the information from the sender to the receiver.
Nowadays the mobile jammer devices are becoming civilian products rather than
electronic warfare devices, since with the increasing number of the mobile phone users the need
to disable mobile phones in specific places where the ringing of cell phone would be disruptive
has increased. These places include worship places, university lecture rooms, libraries, concert
halls, meeting rooms, and other places where silence is appreciated.
OPERATION
Jamming devices overpower the cell phone by transmitting a signal on the same
frequency as the cell phone and at a high enough power that the two signals collide and cancel
each other out. Cell phones are designed to add power if they experience low-level interference,
so the jammer must recognize and match the power increase from the phone. Cell phones are
full-duplex devices, which mean they use two separate frequencies, one for talking and one for
listening simultaneously. Some jammers block only one of the frequencies used by cell phones,
which has the effect of blocking both. The phone is tricked into thinking there is no service
because it can receive only one of the frequencies. Less complex devices block only one group
of frequencies, while sophisticated jammers can block several types of networks at once to head
off dual-mode or tri-mode phones that automatically switch among different network types to
find an open signal. Some of the high-end devices block all frequencies at once and others can be
tuned to specific frequencies.
To jam a cell phone, all you need is a device that broadcasts on the correct frequencies.
Although different cellular systems process signals differently, all cell-phone networks use radio
signals that can be interrupted. GSM, used in digital cellular and PCS-based systems, operates in
the 900-MHz and 1800-MHz bands in Europe and Asia and in the 1900-MHz (sometimes
referred to as 1.9-GHz) band in the United States. Jammers can broadcast on any frequency and
are effective against AMPS, CDMA, TDMA, GSM, PCS, DCS, iDEN and Nextel systems. Oldfashioned
analog cell phones and today's digital devices are equally susceptible to jamming.
Disrupting a cell phone is the same as jamming any other type of radio communication. A cell
phone works by communicating with its service network through a cell tower or base station.
Cell towers divide a city into small areas, or cells. As a cell phone user drives down the street,
the signal is handed from tower to tower.
Dept.
MOBILE JAMMING TECHNIQUES
Type "A" Device: JAMMERS
In this device we overpower cell phone's signal with a stronger signal, This type of
device comes equipped with several independent oscillators transmitting ‘jamming signals’
capable of blocking frequencies used by paging devices as well as those used by cellular/PCS
systems’ control channels for call establishment. When active in a designated area, such devices
will (by means of RF interference) prevent all pagers and mobile phones located in that area
from receiving and transmitting calls. This type of device transmits only a jamming signal and
has very poor frequency selectivity, which leads to interference with a larger amount of
communication spectrum than it was originally intended to target. Technologist Jim Mahan said,
“There are two types. One is called brute force jamming, which just blocks everything. The
problem is, it’s like power-washing the airwaves and it bleeds over into the public broadcast area.
The other puts out a small amount of interference, and you could potentially confine it within a
single cell block. You could use lots of little pockets of small jamming to keep a facility under
control.”
Type “B” Device: INTELLIGENT CELLULAR DISABLERS
Unlike jammers, Type “B” devices do not transmit an interfering signal on the control
channels. The device, when located in a designated ‘quiet’ area, functions as a ‘detector’. It has a
unique identification number for communicating with the cellular base station. When a Type “B”
device detects the presence of a mobile phone in the quiet room; the ‘filtering’ (i.e. the
prevention of authorization of call establishment) is done by the software at the base station.
Type “D” Device: DIRECT RECEIVE & TRANSMIT JAMMERS
This jammer behaves like a small, independent and portable base station, which can
directly interact intelligently or unintelligently with the operation of the local mobile phone. The
jammer is predominantly in receiving mode and will intelligently choose to interact and block
the cell phone directly if it is within close proximity of the jammer.
This selective jamming technique uses a discriminating receiver to target the
jamming transmitter. The benefit of such targeting selectivity is much less electromagnetic
pollution in terms of raw power transmitted and frequency spectrum from the jammer, and
therefore much less disruptive to passing traffic. The jam signal would only stay on as long as
the mobile continues to make a link with the base station, otherwise there would be no jamming
transmission – the technique forces the link to break or unhook and then it retreats to a passive
receive mode again.
GSM-MOBILE JAMMING REQUIREMENTS
Jamming objective is to inject an interference signal into the communications frequency so
that the actual signal is completely submerged by the interference. It is important to notice that
transmission can never be totally jammed - jamming hinders the reception at the other end. The
problem here for the jammer is that only transmitters can be found using direction finding and the
location of the target must be a specific location, usually where the jammer is located and this is
because the jamming power is never infinite. Jamming is successful when the jamming signal denies
the usability of the communications transmission. In digital communications, the usability is denied
when the error rate of the transmission cannot be compensated by error correction. Usually a
successful jamming attack requires that the jammer power is roughly equal to signal power at the
receiver. The effects of jamming depend on the jamming-to-signal ratio (J/S), modulation scheme,
channel coding and interleaving of the target system. Generally Jamming-to-Signal ratio can be
measured according to the following Equation.