Jordan University of Science and TechnologyElectrical Engineering DepartmentGSM-900 Mobile JAMMERDone By:Ahmad JisrawiSupervised By:Dr. Nihad Dib Table of ContentsIntroduction ……………………………………………………………………… 2Mobile Jamming and Disablers Techniques……………………………………… 3GSM-Mobile JAMMING Requirements…………………………………………. 7Design and Implementation of GSM Mobile JAMMER………………………….11RF-Section ………………………………………………………………..11Voltage controlled oscillator……………………………………....12RF-Power Amplifier………………………………………………13Antenna…………………………………………………………....15IF-Section………………………………………………………………... 18Triangular wave generator……………………………………….. 18Noise Generator…………………………………………………... 20Signal mixer and DC-offset Circuit………………………………..21Power Supply………………………………………………………………24Conclusions………………………………………………………………………...26References………………………………………………………………………….271 INTRODUCTIONA GSM Jammer is a device that transmit signal on the same frequency at witch theGSM system operates, the jamming success when the mobile phones in the area wherethe jammer is located are disabled.Communication jamming devices were first developed and used by militar y. Wheretactical commanders use RF communications to exercise control of their forces, an enemyhas interest in those communications. This interest comes from the fundamental area ofdenying the successful transport of the information from the sender to the receiver.Nowadays the mobile jammer devices are becoming civilian products rather thanelectronic warfare devices, since with the increasing number of the mobile phone usersthe need to disable mobile phones in specific places where the ringing of cell phonewould be disruptive has increased. These places include worship places, universitylecture rooms, libraries, concert halls, meeting rooms, and other places where silence isappreciated.Mosques are example for the places were mobile jammer would be a great solution,although mosques asks politely from prayers to disable their mobile phone during theprayer ,see figure (1), some people forget and the ringing phone o f their mobile phonebecome very annoying specially during the praying time.Figure 1: Typical sign used in places wheremobile phone are not allowed2 Mobile Jamming and Disablers TechniquesThere are different approaches to prevent mobile phones from ringing in specific area,the main five appro aches used or being developed are described in RABC Mobile &Personal Communications Committee’s (M&PCC) meeting of June 22, 1999 [1], thesetechniques are summarized in this section :1-Type "A" DeviceIn this device we ov erpower cell phone's signal with a stronger signal, This typeof device comes equipped with several independent oscillators transmitting‘jamming signals’ capable of blocking frequencies used by paging devices as wellas those used by cellular/PCS systems’ control channels for call establishment.When active in a designated area, such devices will (by means o f R F interference)prevent all pagers and mobile phones located in that area from receiving andtransmitting calls. This type of device transmits only a jammin g sign al and has verypoor frequency selectivity, which leads to interference with a larger amount ofcommunication spectrum than it was originally intended to target.Technologist Jim Mahan said, “Ther e are two types. One is called b rute forcejamming, which just blocks everything. The problem is, it’s like power-washing theairwaves and it bleeds over into the public broadcast area. The other puts out a smallamount of interference, and you could potentially confine it within a single cellblock. You could use lots of little pockets of small jamming to keep a facility undercontrol.”2-Type "B" DeviceThis device also called "Intelligent Cellular Disablers devices", and it does nottransmit an interfering signal on the control channels. The device basically works asa detector, and it cap able to communicate with the cellular base station. When the3 device detects the presence of a mobile phone in the "silent" room; a prevention ofauthorization of call establishment is done by the software at the base station. Thedevice signals the base station that the target user is in a ‘quiet’ room; therefore, donot establish the communication. Messages can be routed to the user’s voice- mailbox, if the user subscribes to a voice- mail service. This process of detection andinterruption of call estab lishment is done during the interval normally reserved forsignaling and handshaking.This intelligent device as it’s name imply can recognize emergency calls and alsocan allow specific pre-registered users to use their mobile phones for a specifiedduration. Although this device sounds the best solution for disabling mobile phone,a provision is needed by the cellular/PCS service providers or provision by a third-party working cooperatively with full support of the cellular/PCS service providers,allowing the detector device to be integral part of the cellular/PCS systems.3-Type "C" DeviceThis device also called "Intelligent Beacon Disablers ", as in the type "B" device itdoes not transmit an interfering signal on the control channels.The device, when located in a specific "silent" room, functions as a ‘beacon’ andany compatible terminal is ordered to disable its ringer or disable its operation. Inthe coverage area of the beacon only terminals which have a compatible receiverwould respond and this should be built on a separate technology from cellular/PCS,for example Bluetooth technology. Also the handset must re-enable its normalfunction as it leaves the coverage area of the beacon.The need for intelligent handsets with a separate receiver for the beacon receiverfrom the cellular/PCS receiver, make eff ective deployment for the type "C" devicewill be problematic for many years.4 4-Type "D" DeviceThis jammer is similar to type "A" , but with a receiver, so that jammer ispredominantly in r eceive mode and when the device detects the presence of amobile phone in the "silent" room; it will intelligently choose to interact and blockthe cell phone b y transmitting jamming signal. This jam signal would only stay onas long as the mobile continues to make a link with the base station; otherwise therewould be no jamming transmission.Thus this device much less electromagnetic pollution in terms of raw po wertransmitted and frequency spectrum from the type "A" Jammer, and ther efore muchless disruptive to passing traffic. This technique could be implemented withoutcooperation from PCS/cellular providers. Also this technique has an addedadvantage over Typ e B in that no added overhead time or effort is spent negotiatingwith the cellular netwo rk.5-Type "E" DeviceThis technique is using EMI suppression techniques to make a room into what iscalled a Faraday cage. Although labour intensive to construct, the Faraday cageessentially blocks, or greatly attenu ates, virtually all electromagnetic radiation fromentering or leaving the cage or in this case a target room.With current advances in EMI shielding techniques and commercially availableproducts one could con ceivably implement this into the architecture of newlydesigned buildings for so-called “quiet-conference” rooms.Emergency calls would be blocked unless there was a way to receive and decodethe Emergency Call transmissions, pass b y coax outside the room and re-transmitted.5 This passive configuration is currently legal in most worlds' countries for anycommercial or residential location; however some building may not allow this typeof construction. Table 1 shows a comparison between the differentJammer/Disablers techniques.Emer gencyRegularityTypeEfficiencyImplementationcallApprovalNot"A" Blocked LowVer y simpleallowedComplex"B" Allowed Medium Required(Required third partyCellular/PCS Services)Complex"C" Allowed High Required(Required Intelligent Handset)"D" Allowed Medium Required SimpleHigh(No sign al"E" BlockedAllowed Simpletransmitted)Table 1: Comparison between Jammer/Disabler Techniques6 GSM-Mobile JAMMING RequirementsAs discussed in part-2, jamming objective is to inject an interference signal intothe communications freq uency so that the actual signal is completely submerged bythe interference. It is important to notice that transmission can never be totallyjammed - jamming hinders the reception at the other end. The problem here for thejammer is that only transmitters can be found using direction finding and thelocation of the target must be a specific location, usually where the jammer islocated and this is because the jamming power is never infinite.Jamming is successful when the jamming signal denies the usability of thecommunications transmission. In digital communications, the usability is deniedwhen the error rate of the transmission cannot b e compensated b y error correction.Usually a successful jamming attack requires that the jammer power is roughlyequal to signal power at the receiver.The effects of jammin g depend on the jamming-to-signal r atio (J/S), modulationscheme, ch annel coding and interleaving of the target system.Gener ally Jamming-to-Signal r atio can be measured according to the followingEquation. [2]JGGPRLB2=jj rr jt rr
đang được dịch, vui lòng đợi..
![](//viimg.ilovetranslation.com/pic/loading_3.gif?v=b9814dd30c1d7c59_8619)