University Of Technology Control & Systems Dept. Computer Eng. Lecture No. 1 Lecturer: Hamid Mousa Data Communications Computer Eng. 3 rd class course Lecturer : Hamid Mousa Course Reference Data Communications and Networking Behrouz A. Forouzan, 4 th Edition McGraw-Hill 1-1
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. 1-2
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 1-3
Direction of Data Flow 1-4
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 Data Communications, Kwangwoon University 1-5
Point-to-point Type of Connection 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 1-6
Type of Connection 1-7
Transmission Modes 1-8
Parallel Transmission Use n wires to send n bits at one time synchronously Advantage: speed Disadvantage: cost Limited to short distances 1-9
Serial Transmission On communication channel Advantage: reduced cost Parallel/serial converter is required Three ways: asynchronous, synchronous, or isochronous 1-10
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) 1-11
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 1-12
Data Communications - Tutorial sheet Third year - computer Eng. Hamid M. Hasan March - 2012 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. 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.