Multiplexing II
- 1. Prof.Neeraj Bhargava Abhishek Kumar Department of Computer Science School of Engineering & System Sciences, MDS, University Ajmer, Rajasthan, India
- 2. In telecommunications and computer networks, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource. For example, in telecommunications, several telephone calls may be carried using one wire. Multiplexing originated in telegraphy in the 1870s, and is now widely applied in communications. In telephony, George Owen Squier is credited with the development of telephone carrier multiplexing in 1910. The multiplexed signal is transmitted over a communication channel such as a cable. The multiplexing divides the capacity of the communication channel into several logical channels, one for each message signal or data stream to be transferred. A reverse process, known as demultiplexing, extracts the original channels on the receiver end.
- 3. A device that performs the multiplexing is called a multiplexer (UX), and a device that performs the reverse process is called a demultiplexer (DEMUX or DMX). Fig* Multiple low data rate signals are multiplexed over a single high data rate link, then demultiplexed at the
- 4. Multiple variable bit rate digital bit streams may be transferred efficiently over a single fixed bandwidth channel by means of statistical multiplexing. This is an asynchronous mode time-domain multiplexing which is a form of time-division multiplexing. Digital bit streams can be transferred over an analog channel by means of code- division multiplexing techniques such as frequency-hopping spread spectrum (FHSS) and direct-sequence spread spectrum (DSSS). In wireless communications, multiplexing can also be accomplished through alternating polarization (horizontal/vertical or clockwise/counterclockwise) on each adjacent channel and satellite, or through phased multi-antenna array combined with a multiple-input multiple-output communications (MIMO) scheme.
- 5. Space-division Multiplexing Frequency-division Multiplexing Time-division Multiplexing Polarization-division Multiplexing Orbital Angular Momentum Multiplexing Code-division Multiplexing
- 6. In wired communication, space-division multiplexing, also known as Space-division multiple access is the use of separate point-to-point electrical conductors for each transmitted channel. Examples include an analogue stereo audio cable, with one pair of wires for the left channel and another for the right channel, and a multi-pair telephone cable, a switched star network such as a telephone access network, a switched Ethernet network, and a mesh network. In wireless communication, space-division multiplexing is achieved with multiple antenna elements forming a phased array antenna. Examples are multiple-input and multiple- output (MIMO), single-input and multiple-output (SIMO) and multiple-input and single-output (MISO) multiplexing.
- 7. thus increasing the total peak bit rate by the factor k. Different antennas would give different multi-path propagation (echo) signatures, making it possible for digital signal processing techniques to separate different signals from each other. These techniques may also be utilized for space diversity (improved robustness to fading) or beamforming (improved selectivity) rather than multiplexing.
- 8. Frequency-division multiplexing (FDM) is inherently an analog technology. FDM achieves the combining of several signals into one medium by sending signals in several distinct frequency ranges over a single medium. In FDM the signals are electrical signals. One of the most common applications for FDM is traditional radio and television broadcasting from terrestrial, mobile or satellite stations, or cable television. Only one cable reaches a customer's residential area, but the service provider can send multiple television channels or signals simultaneously over that cable to all subscribers without interference. Receivers must tune to the appropriate frequency (channel) to access the desired signal. A variant technology, called wavelength-division multiplexing (WDM) is used in optical communications. Frequency-division Multiplexing
- 9. Fig* Frequency-division multiplexing (FDM): The spectrum of each input signal is shifted to a distinct frequency range.
- 10. Time-division multiplexing (TDM) is a digital (or in rare cases, analog) technology which uses time, instead of space or frequency, to separate the different data streams. TDM involves sequencing groups of a few bits or bytes from each individual input stream, one after the other, and in such a way that they can be associated with the appropriate receiver. If done sufficiently quickly, the receiving devices will not detect that some of the circuit time was used to serve another logical communication path.
- 11. Fig* Time-division multiplexing (TDM): The spectrum of each input signal is shifted to a distinct frequency range.