Jamming detection

3 thoughts on “Jamming detection

  1. We need an option to detect jamming
    attempts and I need your advice,

    Today we’re using the command JDR=4
    to detect jamming the problem is that this type of detection is not sufficient,
    the modem ( GE863/4/5 ) alert even when there in no GSM network.


    We need the ability to detect PMR or
    any type of detection (mentioned below) and not when the GSM network is not


    Jamming Techniques for


          1. Brute force

    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 /
    PCSsystems’ 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.


    2. Intelligent cellular

    Unlike Brute force jamming,
    Intelligent cellular disablers 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 Intelligent cellular
    disablers 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.

    When the base station sends the
    signaling transmission to a target user, the device after detecting
    simultaneously the presence of that signal and the presence of the target user,
    signals the base station that the target user is in a ‘quiet’ room; therefore,
    do not establish the communication. Messages can be routed to the user’s voice-
    mail box, if the user subscribes to a voice-mail service. This process of
    detection and interruption of call establishment is done during the interval
    normally reserved for signaling and handshaking. For ‘emergency users’, the
    intelligent detector device makes provisions for designated users who have
    emergency status. These users must pre-register their phone numbers with the
    service providers. When an incoming call arrives, the detector recognizes that
    number and the call are established for a specified maximum duration, say two
    minutes. The emergency users are also allowed to make out going calls.
    Similarly, the system is capable of recognizing and allowing all emergency calls
    routed to “911”.


    3. Intelligent Beacon

    Unlike the above mentioned jammers,
    Intelligent Beacon Disablers devices do not transmit an interfering signal on
    the control channels. The device, when located in a designated ‘quiet’ area,
    functions as a ‘beacon’ and any compatible terminal is instructed to disable its
    ringer or disable its operation, while within the coverage area of the beacon.
    Only terminals which have a compatible receiver would respond and this would
    typically be built on a separate technology from cellular/PCS, e.g., cordless
    wireless, paging, ISM, Bluetooth. On leaving the coverage area of the beacon,
    the handset must re-enable its normal function.


    4. Direct receive &

    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.


    5. Emi shield (passive

    This technique is using EMI
    suppression techniques to make a room into what is called a "Faraday cage".
    Although labor intensive to construct, the Faraday cage essentially blocks, or
    greatly attenuates, virtually all electromagnetic radiation from entering or
    leaving the cage – or in this case a target room or vehicle. 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 was a way to receive and decode the 911 transmissions, pass
    by coax outside the room and re-transmitted.


    Please advice.

    Thanks for the help & Best


    1.  Some of the techniques I’m afraid cannot be discriminated from standard lack of coverage or BS out of order.

      I’m thinking about  "5. Emi shield (passive jamming)" where the Faraday cage blocks or attenuates the GSM signal. The same situation you can have in an area where there is no coverage.

      Also in the  "4. Direct receive & transmit" since the jammer can behave like a small BS, it would be probably not possible to detect the difference from a real BS.


      We should collect much more information about how all these jammer devices work and interract with the network and the cell phones. 

    2. I’m afraid some of the jamming techniques used cannot be discriminated from the standard behavior of a GSM infrastructure.


       I’m thinking about "5. Emi shield (passive jamming)" where the the Faraday cage blocks or attenuates the GSM signal. It should be quite similar to the behavior of a phone moving to an area with lack of coverage.


      Also  for  "4. Direct receive & transmit", since the jammer can behave like a small BS, it could be quite difficult or not possible to understand if it is a fake BS or a real one.


      Anyway we should get more information about all the jammer devices and the way they work and interact with the network and the mobile station, to understand if there is any possible way to detect it.