Statistical multiplexing

by gowtham 2010-02-18 19:13:27

Statistical multiplexing is a type of communication link sharing, very similar to dynamic bandwidth allocation (DBA). In statistical multiplexing, a communication channel is divided into an arbitrary number of variable bit-rate digital channels or data streams. The link sharing is adapted to the instantaneous traffic demands of the data streams that are transferred over each channel. This is an alternative to creating a fixed sharing of a link, such as in general time division multiplexing (TDM) and frequency division multiplexing (FDM). When performed correctly, statistical multiplexing can provide a link utilization improvement, called the statistical multiplexing gain.

Statistical multiplexing is facilitated through packet mode or packet oriented communication, which amongst others is utilized in packet switched computer networks. Each stream is divided into packets that normally are delivered asynchronously in a first-come first-serve fashion. Alternatively, the packets may be delivered according to some scheduling discipline for fair queuing or differentiated and/or guaranteed quality of service.

Statistical multiplexing of an analog channel, for example a wireless channel, is also facilitated through the following schemes:

* Random frequency-hopping orthogonal frequency division multiple access (RFH-OFDMA)
* Code-division multiple access (CDMA), where different amount of spreading codes or spreading factors can be assigned to different users.

Statistical multiplexing normally implies "on-demand" service rather than one that preallocates resources for each data stream. Statistical multiplexing schemes do not control user data transmissions.

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