Multiplexing
- 1. Multiplexing ļ Many to one/one to many ļ Types of multiplexing
- 2. Multiplexing ļ It is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link. ļ Multiplexing is done using a device called Multiplexer (MUX) that combine n input lines to generate one output line i.e. (many to one). ļ At the receiving end a device called Demultiplexer (DEMUX) is used that separate signal into its component signals i.e. one input and several outputs (one to many).
- 4. Advantages of Multiplexing ļ More than one signals can be sent over single medium or link ļ Effective use of the bandwidth of medium
- 5. Multiplexing vs. No Multiplexing
- 6. Types of Multiplexing Synchronous TDM Asynchronous TDM
- 7. Frequency Division Multiplexing ļ It is an analog technique. ļ Signals of different frequencies are combined into a composite signal and is transmitted on the single link. ļ Bandwidth of a link should be greater than the combined bandwidths of the various channels. ļ Each signal is having different frequency. ļ Channels are separated by the strips of unused bandwidth called Guard Bands (to prevent overlapping).
- 8. FDM
- 9. Applications of FDM ļ FDM is used for FM & AM radio broadcasting. ļ AM frequency = 530 to 1700 kHz. ļ FM frequency = 88 to 108 MHz. ļ FDM is used in television broadcasting. ļ First generation cellular telephone also uses FDM.
- 10. FDM, Time Domain
- 14. Wave Division Multiplexing ļ WDM is an analog multiplexing technique. ļ Working is same as FDM. ļ In WDM different signals are optical or light signals that are transmitted through optical fiber. ļ Various light waves from different sources are combined to form a composite light signal that is transmitted across the channel to the receiver. ļ At the receiver side, this composite light signal is broken into different light waves by Demultiplexer. ļ This Combining and the Splitting of light waves is done by using a PRISM. Prism bends beam of light based on the angle of incidence and the frequency of light wave.
- 16. Time Division Multiplexing ļ It is the digital multiplexing technique. ļ Channel/Link is not divided on the basis of frequency but on the basis of time. ļ Total time available in the channel is divided between several users. ļ Each user is allotted a particular time interval called time slot or slice. ļ In TDM the data rate capacity of the transmission medium should be greater than the data rate required by sending of receiving devices.
- 17. TDM
- 18. Types of TDM ļ Synchronous TDM ļ Asynchronous TDM
- 19. Synchronous TDM ļ Each device is given same Time Slot to transmit the data over the link, whether the device has any data to transmit or not. ļ Each device places its data onto the link when its Time Slot arrives, each device is given the possession of line turn by turn. ļ If any device does not have data to send then its time slot remains empty. ļ Time slots are organized into Frames and each frame consists of one or more time slots. ļ If there are n sending devices there will be n slots in frame.
- 20. Synchronous TDM
- 21. Multiplexing Process in STDM ļ In STDM every device is given opportunity to transmit a specific amount of data onto the link. ļ Each device gets its turn in fixed order and for fixed amount of time = INTERLEAVING. ļ Interleaving is done by a character (one byte). ļ Each frame consist of four slots as there are four input devices. ļ Slots of some devices go empty if they do not have any data to send.
- 24. Disadvantages of STDM ļ The channel capacity cannot be fully utilized. Some of the slots go empty in certain frames.
- 25. Framing Bits
- 26. Asynchronous TDM
- 27. Asynchronous TDM ļ Also known as Statistical Time Division multiplexing. ļ In this time slots are not Fixed i.e. slots are Flexible. ļ Total speed of the input lines can be greater than the capacity of the path. ļ In ASTDM we have n input lines and m slots i.e. m less than n (m<n). ļ Slots are not predefined rather slots are allocated to any of the device that has data to send.
- 28. Frames and Addresses a. Only three lines sending data
- 29. Frames and Addresses b. Only four lines sending data
- 30. Frames and Addresses c. All five lines sending data