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Data CommunicationsComputer Eng. 3rd class course

Lecturer : Hamid MousaCourse Reference

Data Communications and NetworkingBehrouz A. Forouzan, 4th Edition

McGraw-Hill

University Of TechnologyControl & Systems Dept.

Computer Eng.

Lecture No. 1Lecturer: Hamid Mousa

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Data Communications

• Data– Information presented in whatever form is agreed

upon by the parties creating and using the data.

• Data communication– Exchange of data between two devices Via some

form of transmission medium.

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Five Components of Data Communication• Message: Information(data) to be communicated• Sender• Receiver • Transmission medium: Physical path by which a message travels• Protocol: A set of rules that govern data communication

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Direction of Data Flow

Data Communications, Kwangwoon University 1-5

Data Flow

• Simplex– Unidirectional– As on a one-way street

• Half-duplex– Both transmit and receive possible, but not at the same time– Like a one-lane road with two-directional traffic– Walkie-talkie, CB radio

• Full-duplex– Transmit and receive simultaneously– Like a two-way street, telephone network– Channel capacity must be divided between two directions

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Type of Connection• Point-to-point

– Dedicated link between two devices– The entire capacity of the channel is reserved– Ex) Microwave link, TV remote control

• Multipoint – More than two devices share a single link– Capacity of the channel is either

• Spatially shared: Devices can use the link simultaneously• Timeshare: Users take turns

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Type of Connection

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Transmission Modes

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Parallel Transmission

• Use n wires to send n bits at one time synchronously• Advantage: speed• Disadvantage: cost ⇒ Limited to short distances

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Serial Transmission• On communication channel• Advantage: reduced cost• Parallel/serial converter is required• Three ways: asynchronous, synchronous, or isochronous

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Asynchronous Transmission• Use start bit (0) and stop bits (1s)• A gap between two bytes: idle state or stop bits• It means asynchronous at byte level• Must still be synchronized at bit level• Good for low-speed communications (terminal)

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Synchronous Transmission

• Bit stream is combined into “frames”• Special sequence of 1/0 between frames: No gap• Timing is important in midstream• Byte synchronization in the data link layer• Advantage: speed ⇒ high-speed transmission

Q1:An available Bandwidth of 300 kHz which spans 200 to 500 kHz , what should be the Bit rate if fullduplex Binary ASK is used with d=1, and what are the carrier frequency for the receiver and the transmitter .

Q2: answer the following 1.Show how the following data will be transmitted using Binary

ASK and PSK:- 10101011 .2.Using differential Manchester and RZ encoding methods for

the following Data: 10011011 .

Q3: An available Bandwidth of 400 kHz which spans 200 to 600 kHz , what should be the Bit rate if PSK is used with d=1, and what are the carrier frequency .

Q4: Using QAM with 8 different phases and 4 different magnitudes :-a: Draw the constellation diagram.b: Determine the data elements to signal elements ratio r .c: If the transmission rate is 64 kbps determine the baud rate.

Q5 :An available Bandwidth of 500 kHz which spans 100 to 600 kHz , what should be the Bit rate if Binary ASK is used with d=1, and what are the carrier frequency for the receiver and the transmitter .

Q6: Using QAM with 4 different phases and 4 different magnitudes :-a: Draw the constellation diagram.b: Determine the data elements to signal elements ratio r .c: If the transmission rate is 50 kbps determine the baud rate.

Q7: A multistage switch with 3 stages:-1st stage contains three (6 to 2) crossbars.2nd stage contains three (2 to 2) crossbars.3rd stage contains three (2 to 6) crossbars.a: draw the multistage switch.b:How many alternative paths can be used for any input to connect to any

output.c:Identify the blocking condition for this switch.

Data Communications - Tutorial sheetThird year - computer Eng.

Hamid M. Hasan March - 2012

Q8: Six connections with 1kbps each are to be time division multiplexed if ( 2 bit ) Unit is used determine:-

1. The duration of slot time .2. The duration of frame time.3. The transmission rate for the link.