Statistical Time Division Multiplexing Presenter Arlien Mc Dougal

Statistical Time Division Multiplexing Presenter: Arlien Mc. Dougal PHS 221 Prof. Jiang

Objectives • Explain what is Statistical Time Division Multiplexing • Describe how STDM work • Compare Asynchronous Multiplexing to Synchronous Multiplexing

What is Statistical Time Division Multiplexing

• Statistical Time Division Multiplexing is a process of time multiplexing where the time slots on the time division multiplexing (TDM) medium between Statistical time division multiplexing (STDM) multiplexers are dynamically allocated. • STDM multiplexers are known as asynchronous multiplexers to differentiate them from the synchronous time division multiplexers used in PSTN.

• In this allocation any input to the STDM multiplexer can be assigned to any time slot on the Time Division Multiplexing medium. • Time slots on the TDM medium are assigned to input channels that have data ready to send over the TDM medium to a distant STDM multiplexer.

HOW DOES IT WORK?

• To accomplish dynamic allocation of any input to any time slots, the TDM multiplexer places a header on the data that each input channel has ready to transmit. • The header informs that receiving STDM multiplexer which output channel is to receive the data.

ILLUSTRATION

ASYNCHRONOUS vs. SYNCHRONOUS

ASYNCHRONOUS vs. SYNCHRONOUS • Dynamically assign slots • Synchronized time slot in the TDM path • Better use of capacity. • Wastes of capacity. • Greater number of channels. • Limited number of channels. • Better utilization of composite TDM circuit. • Utilization can be improved by using a STDM and increasing the number of input channels.

QUESTIONS