1. Chapter 7 Channel organization

2. Group members  Bilal Ahmed  Mehmal javed  Faisal khan janjua  Harris bashir

3. Bilal Ahmed 1421-211252

4. Topics we will cover  Parallel Methods  Serial Methods  Synchronization  Some Advantages  Some Disadvantages

5. Channel Organization  If we want to send data from one point to another point. There are two methods to do it:  Parallel method  Serial method

6. Parallel Method  In parallel method all the data will sent at once.  If we want to send 8 bit it will use 8 wires to sent data of 8 bit.  Each wire carry 1 bit at a time. 0 0 1 0 1 1 1 0

7. Cont’d  In parallel method, devices will be closer to each other.  E.g. Data transmission between computer and printer.  In parallel link a separate line is used as a clock signal. Its work is to inform the user when data is available (DA).  Another line may be used by the receiver to inform the sender that data has been used, and ready for next data (DU).  The exchange of signals such as DA (Data Available) and DU (Data Used) between sender and receiver is called handshake.  Rare used because of cost issues but mostly used inside computers.

8. Harris Bashir 1421-211004

9. Parallel Method ( Parallel wires)

10. Advantages and Disadvantages  Advantage:  Parallel is faster than serial because more then one bit sent at a time.  Parallel transmission is good only for short links and examples are found in all the computer.  Disadvantage:  More wires needed.  Expensive.  not good for long distance.

11. Serial Method  Each bit is sent over a single wire, one after the other.  One bit at a time.  So we need one communication channel only.  Close or far dose not create problem.  Data transfer speed is low as compared to parallel method.  Less expensive as compared to parallel because less wire are used.

12. Mehmal Javed 1421-311079

13. Serial wire

14. Cont’d  Data will be sent like this in serial:  In serial method there is no signal line is used to send information about time so in this two methods are use:  Asynchronous  Synchronous 0111000001

15. What is Synchronization Synchronization is technology that is designed to synchronize a single set of data between two or more devices, automatically copying changes back and forth. Example:  Contact list synchronization. Requirements:  two or more devices.  Local or between network.

16. Faisal Khan Janjuah 1421-211003

17. Synchronous  The term synchronous is used to describe a continuous and consistent timed transfer of data blocks.  The synchronous signaling methods use only 1 signal.  The receiver uses transitions on that signal to figure out the transmitter bit rate and timing, and set a local clock to the proper timing.  A pulse from the local clock indicates when another bit is ready.

18. Cont’d The timing needed for synchronous connections is obtained from the devices located on the communication link. All devices on the synchronous link must be set to the same clocking. The following is a list of characteristics specific to synchronous communication:  There are no gaps between characters being transmitted.  Timing is supplied by modems or other devices at each end of the connection.  Special synchronous characters precede the data being transmitted.  The synchronous characters are used between blocks of data for time session purposes.

19. Asynchronous The asynchronous signaling methods use 2 different signals. A pulse on one signal indicates when another bit of information is ready on the other signal. The term asynchronous is used to describe the process where transmitted data is encoded with start and stop bits, specifying the beginning and end of each set (set of data).

20. Cont’d When data is transferred by sender (a binary 0), the receiving system knows that data characters are going to follow. It is for this reason that the start bit, which precedes the data character, is always a space bit (binary 0) and that the stop bit, which signals the end of a character, is always a mark bit (binary 1). The following is a list of characteristics specific to asynchronous communication:  Each character is preceded by a start bit and followed by one or more stop bits.  Gaps or spaces between characters may exist.

21. Cont’d

22. Pros and Cons AdvantagesDisadvantages Asynchronous transmission  Simple, doesn't require synchronization of both communication sides  Cheap, because Asynchronous transmission require less hardware  Set-up is faster than other transmissions, so well suited for applications where messages are generated at irregular intervals, for example data entry from the keyboard and the speed depends on different applications.  A high proportion of the transmitted bits are uniquely for control purposes and thus carry no useful information until all data is transferred. Synchronous transmission  Fast and reliable for data security.  Slightly more complex  Hardware is more expensive

23. We welcome sensible questions