Computer Communication Networks

Introduction:

The objective of the project is to develop a GSM (Global system for mobile communication) based mobile jammers and for that we have researched Final year projects and aims to collect the summary of the projects.

GSM (Global System for mobile communication):

GSM is divided in to Main three parts

1.  Switching System (SS):

Switching systems includes the following Authentication center (AUC), Equipment identity register (EIR), Visitor Location Register (VLR), Mobile service switching Center (MSC), Home location register (HLR).

2. Base Station System (BSS):

It controls the radio packets functionalities and includes Base Station Controllers (BSC) and Base Transceiver Stations (BTS)

3. Operation and support system (OSS):

It has an operation maintenance center (OMC) which is integrated and implemented with OSS which manages and controls the operation and monitoring the systems and network.

Additional Functional Elements:

Additional functional elements also considered as a part of GSM which includes the following elements.

·         MESSAGE CENTRE (MXE)

·         MOBILE SERVICE NODE (MSN)

·         GATEWAY MOBILE SERVICE SWITCHING CENTRE (GMSC)

·         GSM INTERNETWORKING UNIT (GIWU)

Jammers with its classification:

Following types of devices are available in the jammers:

·         Type ‘A’ Devices: ‘jammers’

·         Type ‘B’ Devices: ‘intelligent cellular disablers’

·         Type ‘C’ Devices: ‘intelligent beacon disablers’  

·         Type ‘D’ Devices: ‘Direct Receive and Transmit Jammers’

·         Type “E” Devices: ‘EMI Shield – Passive Jamming’

How Jammer works:

Mobile usually works on the frequency (800-1800MHz in ASIA and EUROPE and 1900MHz in US) so It generates the anti-frequency which cancel out the signals from the base station to mobile or mobile to base station. Mobile is generally working on the full-duplex transmission in which two frequencies are coming simultaneously one for talking and one for listening so if one of the frequency is jammed then the mobile is confused, either to receive or to send signals.

            In order to work properly jammer frequency should be roughly equal to the signal frequency. This can be calculated by jamming to signal ratio (J/S), which enables the jammer to block the frequency of transmission.

J/S = P_jG_jrG_rjR²_trL_rB_r / P_tG_trG_rtR²_jrL_jB_j

P_j   = jammer power, P_t  = transmitter power, G_jr = antenna gain from jammer to receiver, G_rj = antenna gain from receiver to Jammer, G_tr = antenna gain from transmitter to receiver, G_rt = antenna gain from receiver to transmitter, B_r  = communications receiver bandwidth, B_j  = jamming transmitter bandwidth, R_tr = range between communications transmitter and receiver, R_jt = range between jammer and communications receiver, L_j  =  jammer signal loss (including polarization mismatch), L_r  = communication signal loss.

Jammer Design:

The following diagram shows the basic design of Jammer design.

1.  Power Supply:

It provides the available power supply to IF and RF frequencies. It includes Rectifier, Filter and Regulator.

2. IF Section:

The main parts of the IF-Section are Triangular Wave Generator, Noise Generator, Signal Mixer and DC offset.

3. RF-Section:

Mobile jammers important part is RF-section which has Voltage controlled Oscillator (VCO), RF power amplifiers, Attenuators and Antenna. 

Conclusion:

Jammers are effective to prevent the people using mobile phone within an organization with a short range official implementation.