Editing Multiplexing (section)

===Code-division multiplexing===
[[Code-division multiplexing]] (CDM), [[code-division multiple access]] (CDMA) or [[spread spectrum]] is a class of techniques where several channels simultaneously share the same [[frequency spectrum]], and this spectral bandwidth is much higher than the bit rate or [[symbol rate]]. One form is frequency hopping, another is direct sequence spread spectrum. In the latter case, each channel transmits its bits as a coded channel-specific sequence of pulses called chips. Number of chips per bit, or chips per symbol, is the [[spreading factor]]. This coded transmission typically is accomplished by transmitting a unique time-dependent series of short pulses, which are placed within chip times within the larger bit time. All channels, each with a different code, can be transmitted on the same fiber or radio channel or other medium, and asynchronously demultiplexed. Advantages over conventional techniques are that variable bandwidth is possible (just as in [[statistical multiplexing]]), that the wide bandwidth allows poor signal-to-noise ratio according to [[Shannon–Hartley theorem]], and that multi-path propagation in wireless communication can be combated by [[rake receiver]]s.

A significant application of CDMA is the [[Global Positioning System]] (GPS).

[[File:telecommunication-multiplexing.svg|thumb|right|400px|Telecommunication multiplexing]]