 - STDM, or statistical time division multiplexing, is one method for transmitting
several types of data simultaneously across a single transmission cable
or line (such as a T1 or T3 line). STDM is often used for managing data
being transmitted via a local area network (LAN) or a wide area network
(WAN). In these situations, the data is often simultaneously transmitted
from any number of input devices attached to the network, including computers,
printers, or fax machines.
STDM can also be used in telephone switchboard settings to manage the
simultaneous calls going to or coming from multiple, internal telephone
lines.
The concept behind STDM is similar to TDM, or time division multiplexing.
TDM allows multiple users or input devices to transmit or receive data
simultaneously by assigning each device the same, fixed amount of time
on one of many "channels" available on the cable or line. The TDM method
works well in many cases, but does not always account for the varying data
transmission needs of different devices or users.
For example, a busy laser printer shared by many users might need to
receive or transmit data 80-90% of the time at a much higher transmission
rate than a seldom-used, data-entry computer attached to the same T-1 line.
With TDM, even though the printer's transmission needs are greater, both
devices would still be allocated the same duration of time to transmit
or receive data.
In comparison to TDM, the STDM method analyzes statistics related to
the typical workload of each input device (printer, fax, computer) and
determines on-the-fly how much time each device should be allocated for
data transmission on the cable or line. In the above example, STDM would
allocate more time to the group printer, based on its past and current
transmission needs and less time to the data-entry computer. Many believe
the STDM method is a more efficient use of total bandwidth available than
the TDM method.
The main statistics used in STDM are: each input device's peak data
rates (in kbps, or kilobytes per second), and each device's duty factors
(which is the percentage of time the device typically spends either transmitting
or receiving data).
Besides TDM and STDM, other methods for simultaneously transmitting
data on the same channel include Wavelength Division Multiplexing (WDM)
and Frequency Division Multiplexing (FDM).
| LAST UPDATED: |
31 Jul 2001
|
 |
Do you have something to add to this definition? Let us know.
Send your comments to techterms@whatis.com
|
|
More resources from around the web:
|
|
