Multiplexing
An IEEE 802.11g wireless router with k antennas makes it in principle possible to communicate with k multiplexed channels, each with a peak bit rate of 54 Mbit/s, 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.
Time-division multiplexing (TDM) is a digital (or in rare cases, analog) technology that 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.
Each terminal communicated at 2400 baud, so rather than acquire four individual circuits to carry such a low-speed transmission, the airline has installed a pair of multiplexers.
A pair of 9600 baud modems and one dedicated analog communications circuit from the airport ticket desk back to the airline data center are also installed.
[4] Carrier-sense multiple access and multidrop communication methods are similar to time-division multiplexing in that multiple data streams are separated by time on the same medium, but because the signals have separate origins instead of being combined into a single signal, are best viewed as channel access methods, rather than a form of multiplexing.
[7] It can potentially be used in addition to other physical multiplexing methods to greatly expand the transmission capacity of such systems.
As of 2012[update] it is still in its early research phase, with small-scale laboratory demonstrations of bandwidths of up to 2.5 Tbit/s over a single light path.
A multiple-access method makes it possible for several transmitters connected to the same physical medium to share their capacity.
Code-division multiplexing (CDM) is a technique in which each channel transmits its bits as a coded channel-specific sequence of pulses.
Several researchers were investigating acoustic telegraphy, a frequency-division multiplexing technique, which led to the invention of the telephone.
The multiplexed signal is then carried to the central switching office on significantly fewer wires and for much further distances than a customer's line can practically go.
[citation needed] Cable TV has long carried multiplexed television channels, and late in the 20th century began offering the same services as telephone companies.
In digital video, such a transport stream is normally a feature of a container format which may include metadata and other information, such as subtitles.
[citation needed] In FM broadcasting and other analog radio media, multiplexing is a term commonly given to the process of adding subcarriers to the audio signal before it enters the transmitter, where modulation occurs.
In spectroscopy the term is used to indicate that the experiment is performed with a mixture of frequencies at once and their respective response unraveled afterward using the Fourier transform principle.
In sociolinguistics, multiplexity is used to describe the number of distinct connections between individuals who are part of a social network.
A multiplex network is one in which members share a number of ties stemming from more than one social context, such as workmates, neighbors, or relatives.
