grm@drutx.UUCP (Geraldo Ramon de Martine) (02/26/85)
can anyone explain the difference between "time-division" and "frequency-division" multiplexing in laymans' terms? either mail or net posting is OK... -- mail: ihnp4!drutx!grm
js2j@mhuxt.UUCP (sonntag) (02/27/85)
> can anyone explain the difference between "time-division" and > "frequency-division" multiplexing in laymans' terms? > either mail or net posting is OK... > mail: ihnp4!drutx!grm Its really a pretty simple concept. Suppose you want to send several signals through one channel. One way is to use time-division multiplexing, in which signal A uses the channel for a certain amount of time, signal B uses it next, etc. An example of this is television, where a given channel passes signals from commercial A, then commercial B, ... , commercial G,.., then some mindless program gets ten minutes, and it more or less repeats. Another way to share a single channel is frequency division multiplexing. In this scheme, each signal is mixed from the baseband to a seperate carrier frequency, and they are all added together to go through the channel. At the other end of the channel, bandpass filters centered at the correct carrier frequencies seperate the signals, and they are mixed back down to the baseband. Television is an example of this as well, though in a different way. Think of 'channel' above as the path through the air from the transmitter to your antenna. Changing the channel on your television changes the center frequency of the bandpass on the input and the frequency which is used to mix the bandpass output back down to the baseband. -- Jeff Sonntag ihnp4!mhuxt!js2j "Would you like to swing on a star? Carry moonbeams home in a jar? And be better off than you are? Or would you rather be a fish?"
rpw3@redwood.UUCP (Rob Warnock) (02/28/85)
> can anyone explain the difference between "time-division" and > "frequency-division" multiplexing in laymans' terms? > mail: ihnp4!drutx!grm [then follows a nice reply by Jeff Sonntag <ihnp4!mhuxt!js2j>] Just to complete the orthogonalization, let us not forget "space-division" multiplexing, which allows multiple communications to proceed at the same time on the same frequencies, but at different places. Examples are: multiple wires in a bus, multiple T-1 trunks between COs, tight-beam point-to-point microwave or laser links, and (very important!) multiple lanes in a road. ;-} (Polarization-division multiplexing, widely used in satellite transmission, is generally viewed as a form of space-division, but can be thought of as frequency-division by choosing a suitable definition of "vector frequency".) Note that highways exhibit both time- and space-division muxtiplexing, but as the discrete nature of the objects carried thence implies an extremely wide spectrum in the DeBroglie-wave representation, frequency- division cannot be usefully employed while maintaining the identity of the wave packets. Of course, from time to time some unfortunate experimenters do (unsuccessfully) try... ;-} ;-} Rob Warnock Systems Architecture Consultant UUCP: {ihnp4,ucbvax!dual}!fortune!redwood!rpw3 DDD: (415)572-2607 USPS: 510 Trinidad Lane, Foster City, CA 94404