synchronization and jammer

8/6/2019 Synchronization and Jammer

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` All stations transmit data on same frequency, but atdifferent times

` Needs time synchronization

` Pros users can be given different amounts of bandwidth

mobiles can use idle times to determine best base station

can switch off power when not transmitting

` Cons synchronization overhead greater problems with multipath interference on wireless

links



` Timing problems require a mechanism to synchronize thetransmitter and receiver

` Two solutions exist Asynchronous

Synchronous

` Both methods are concerned with timing issues` How does the receiver know when the bit period begins

and ends?

` Small timing difference becomes more significant over time

if no synchronization takes place between sender andreceiver

` Synchronization occurs on the data link layer



` Used in serialcommunication

` Data transmitted 1character at a time

` Character format is usually1 start & 1+ stop bits, plusdata of 5-8 bits

` Character may include

parity bit

` Timing needed only withineach character

` Resynchronization isaccomplished with each

start bit` Uses simple, cheap

technology

` Wastes 20-30% of

bandwidth



` Used in parallelcommunication

` Large blocks of bitstransmitted without

start/stop codes` Synchronized by a clock

signal or clocking data

` Data framed by preamble(opening)/ postamble(closing) bit patterns

` More efficient than

asynchronous` Overhead typically below

5%

` Used at higher speeds thanasynchronous



` Low-speed terminals and PCs commonly useasynchronous transmission inexpensive

` Large systems and networks commonly usesynchronous transmission overhead too expensive; efficiency necessary

error-checking more important



` THE ADVANCED COMMUNIC ATION SYSTEM ISVASTLY USED NOWADAYS

` UNFORTUNATELY THE COMMUNIC ATIONSYSTEM IS ALSO USED AGAINST THESOCIETY AND HUMANITY EVEN FORPERSONAL GAINS



` CELL PHONES, GPS SYSTEM AND RADIOCOMMUNIC ATION ARE NOW WIDELY USED BYTERRORIST GROUPS



y Voltage-controlled oscillator - Generates the radio signal thatwill interfere with the cell phone signal

y Tuning circuit - Controls the frequency at which the jammer broadcasts its signal by sending a particular voltage to theoscillator

y Noise generator - Produces random electronic output in aspecified frequency range to jam the cell-phone network signal(part of the tuning circuit)

y RF amplification (gain stage) - Boosts the power of the radiofrequency output to high enough levels to jam a signal



` India: government and schools use jammers.

` United States: illegal to operate, manufacture,import, or offer for sale, with fines of up to $11,000

and imprisonment of up to one year.` Pakistan: legal inside banks, often used also in

libraries

` United Kingdom: illegal to use, but legal to own



J AMMER IS AN ABSTRACT IDEA OF J AMMING

ANY LINK.THUS J AMMER C AN BE C ATEGORIZE

IN A NUMBER OF WAYS

WE BRING FORTH A FEW IMPORT ANT OF THEM



` CELL-PHONE FUNCTIONS IN AWAY THAT

THE SIGNAL IS C ARRIED FROMB ASE ST ATION

TO SATELITE AND B ACK DOWNTO THE RECEIVER VIA THESERVICE TOWERS.

` CELL PHONE J AMMERS J AM THE

DOWN LINK

SIGNALS DENYINGCOMMUNIC ATION



It produces the frequency at the cell frequency

It causes interference and cancel out signals.

Hopping of frequency occurs to block frequency band.

Interrupt the communication between base station andmobile.

Call and SMS is barred.



Power Supply

IFSection

RFSection



` It blocks unwanted signals.

` It is used to maintain peace & silence.

` It is used to interrupt terrorist communication.

` It is used in security purpose .



` It can be used for blocking signal illegaly.

` It can be used for tech-war.

` It can be used for self benefit.

synchronization and jammer

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