GSM-900 Mobile JAMMER

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INTRODUCTION


A GSM Jammer is a device that transmit signal on
the same frequency at witch the
GSM system operates, the jamming success when the m
obile phones in the area where
the jammer is located are disabled.

Communication jamming devices were first develop
ed and used by military. Where
tactical commanders use RF communications to exerci
se 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 civ
ilian products rather than
electronic warfare devices, since with the increasi
ng number of the mobile phone users
the need to disable mobile phones in specific place
s where the ringing of cell phone
would be disruptive has increased. These places inc
lude worship places, university
lecture rooms, libraries, concert halls, meeting ro
oms, and other places where silence is
appreciated.

Mosques are example for the places were mobile j
ammer would be a great solution,
although mosques asks politely from prayers to disa
ble their mobile phone during the
prayer ,see figure (1), some people forget and the
ringing phone of their mobile phone
become very annoying specially during the praying t
ime.


Mobile Jamming and Disablers Techniques


There are different approaches to prevent mobile p
hones from ringing in specific area,
the main five approaches used or being developed ar
e described in RABC Mobile &
Personal Communications Committee’s (M&PCC) meeting
of June 22, 1999 [1], these
techniques are summarized in this section :

1-
Type "A" Device

In this device we overpower cell phone's signal
with a stronger signal
,
This type
of device comes equipped with several independent o
scillators transmitting
‘jamming signals’ capable of blocking frequencies u
sed by paging devices as well
as those used by cellular/PCS systems’ control chan
nels 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 tha
t area from receiving and
transmitting calls. This type of device transmits o
nly a jamming signal and has very
poor frequency selectivity, which leads to interfer
ence with a larger amount of
communication spectrum than it was originally inten
ded to target.
Technologist Jim Mahan said, “There are two type
s. 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 broadca
st area. The other puts out a small
amount of interference, and you could potentially c
onfine it within a single cell
block. You could use lots of little pockets of smal
l jamming to keep a facility under
control.”


2-
Type "B" Device

This device also called "Intelligent Cellular Dis
ablers devices", and it does not
transmit an interfering signal on the control chann
els. The device basically works as
a detector, and it capable to communicate with the
cellular base station. When the
device detects the presence of a mobile phone in th
e "silent" room; a prevention of
authorization of call establishment is done by the
software at the base station. The
device signals the base station that the target use
r is in a ‘quiet’ room; therefore, do
not establish the communication. Messages can be ro
uted to the user’s voice- mail
box, if the user subscribes to a voice- mail servic
e. This process of detection and
interruption of call establishment is done during t
he interval normally reserved for
signaling and handshaking.

This intelligent device as it’s name imply can re
cognize emergency calls and also
can allow specific pre-registered users to use thei
r mobile phones for a specified
duration. Although this device sounds the best solu
tion for disabling mobile phone,
a provision is needed by the cellular/PCS service p
roviders or provision by a third-
party working cooperatively with full support of th
e cellular/PCS service providers,
allowing the detector device to be integral part of
the cellular/PCS systems.


3-
Type "C" Device

This device also called "Intelligent Beacon Disa
blers ", as in the type "B" device it
does not transmit an interfering signal on the cont
rol channels.

The device, when located in a specific "silent"
room, functions as a ‘beacon’ and
any compatible terminal is ordered to disable its r
inger or disable its operation. In
the coverage area of the beacon only terminals whic
h have a compatible receiver
would respond and this should be built on a separat
e technology from cellular/PCS,
for example Bluetooth technology. Also the handset
must re-enable its normal
function as it leaves the coverage area of the beac
on.

The need for intelligent handsets with a separat
e receiver for the beacon receiver
from the cellular/PCS receiver, make effective depl
oyment for the type "C" device
will be problematic for many years.




4-
Type "D" Device

This jammer is similar to type "A" , but with a
receiver, so that jammer is
predominantly in receive mode and when the device d
etects the presence of a
mobile phone in the "silent" room; it will intellig
ently choose to interact and block
the cell phone by transmitting jamming signal. This
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.

Thus this device much less electromagnetic pollu
tion in terms of raw power
transmitted and frequency spectrum from the type "A
" Jammer, and therefore much
less disruptive to passing traffic. This technique
could be implemented without
cooperation from PCS/cellular providers. Also this
technique has an added
advantage over Type B in that no added overhead tim
e or effort is spent negotiating
with the cellular network.


5-
Type "E" Device

This technique is using EMI suppression techniqu
es to make a room into what is
called a Faraday cage. Although labour intensive to
construct, the Faraday cage
essentially blocks, or greatly attenuates, virtuall
y all electromagnetic radiation from
entering or leaving the cage or in this case a tar
get room.

With current advances in EMI shielding techniques
and commercially available
products one could conceivably implement this into
the architecture of newly
designed buildings for so-called “quiet-conference”
rooms.

Emergency calls would be blocked unless there w
as a way to receive and decode
the Emergency Call transmissions, pass by coax outs
ide the room and re-
transmitted.


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