DATA COMMUNICATION TERMINOLOGIES DATA CHANNEL IT IS THE COMPUTER PATH OR MEDIUM USED TO CARRY DATA (OR INFORMATION) FROM ONE DEVICE TO ANOTHER • THE FULL FORM OF BIT IS BINARY DIGIT. BITS • IT CAN BE 0 OR 1 • DATA SWITCHES BETWEEN TWO VOLTAGE LEVELS. RETURN-TO-ZERO (RZ) FORMAT AND NON-RETURN-TO – ZERO (NRZ) FORMAT • DATA IS REPRESENTED BY A PHYSICAL QUANTITY IN THE DATA CHANNEL. • IN ELECTRICAL LINKS- VOLTAGE OR CURRENT • OPTICAL SYSTEMS- INTENSITY OF LIGHT • WIRELESS RADIO LINKS- PHASE AND FREQUENCY OF A SIGNAL CARRIER. • IF BINARY DATA SWITCHES BETWEEN +3 V AND +0.2 V, THEN IT IS AN EXAMPLE OF NRZ FORMAT. SYMBOLS • A SYMBOL IS ONE OF THE SEVERAL VOLTAGE, CURRENT, INTENSITY, PHASE OR FREQUENCY VALUES. • NUMBER OF TIMES A SIGNAL CHANGES STATE PER SECOND • (OR) NUMBER OF SIGNAL OR SYMBOL CHANGES PER SECOND. BAUD • FOR SIGNALS WITH ONLY TWO POSSIBLE STATES ONE BAUD IS EQUIVALENT TO ONE BIT PER SECOND. • BAUD WAS USED TO MEASURE DATA TRANSMISSION SPEED. HOWEVER NOW BPS (BITS PER SECOND) IS USED. • UNIT TO MEASURE SPEED AT WHICH THE DATA IS TRANSFERRED. • BITS TRANSFERRED IN A SINGLE SECOND. • BITS PER SECOND- bps BITS PER SECOND (bps) • BYTES PER SECOND- Bps • KILO BITS PER SECOND- kbps • KILO BYTES PER SECOND- Kbps • MILLION BITS PER SECOND- mbps • MILLION BYTES PER SECOND- Mbps BANDWIDTH • DIFFERENCE BETWEEN THE HIGHEST AND LOWEST FREQUENCIES OF A TRANSMISSION CHANNEL • DIRECTLY PROPORTIONAL TO THE AMOUNT OF DATA TRANSMITTED OR RECEIVED PER UNIT TIME • DIRECTLY PROPORTIONAL TO THE COMPLEXITY OF DATA FOR A GIVEN SYSTEM PERFORMANCE. • A MODEM THAT WORKS AT 57,600 bps HAS TWICE THE BANDWIDTH THAN A MODEM THAT WORKS AT 28,800 bps. BROADBAND AND NARROWBAND • HIGH BANDWIDTH CHANNELS – BROADBAND • LOW BANDWIDTH CHANNELS - NARROWBAND • THEY REPRESENT AMOUNT OF DATA TRANSFERRED PER SECOND DATA TRANSFER RATES • 1 KB = 1024 BYTES • 1 MB = 1024 KILOBYTES • 1 GB = 1024 MEGABYTES • 1 TB = 1024 GIGABYTES
