Statistical Time Division Multiplexing
Defintion from: thefreedictionary.com
STDM is a system developed to overcome some inefficiencies of standard time division multiplexing, where time slices are still allocated to channels, even if they have no information to transmit.
STDM uses a variable time slot length and by allowing channels to vie for any free slot space. It employs a buffer memory which temporarily stores the data during periods of peak traffic. This scheme allows STDM to waste no high-speed line time with inactive channels. STDM requires each transmission to carry identification information (i.e. a channel identifier). To reduce the cost of this overhead, a number of characters for each channel are grouped together for transmission.
["Data Communications, Computer Networks and Open Systems", Halsall & Fred, Addison Wesley, p160-161, 1995].
["Digital, Analog, and Data Communication", Sinnema & McGovern, Prentice Hall, p245, 1986].