Transmission Media Sharing When can you share? –High Medium capacity Why share ? –Less transmission costs –More cost-effective transmissions How would you share? –Multiplexing

Multiplexing vs. No Multiplexing

Multiplexer

Types of Multiplexing Frequency Division Multiplexing (FDM) Wave Division Multiplexing (WDM) Time Division Multiplexing (TDM) –Synchronous –Asynchronous (Statistical TDM)

Frequency Division Multiplexing Analog signaling & transmission. Total bandwidth = sum of input bandwidths + guard bands. Modulates signals to different frequency Uses –Radio broadcasting and television

FDM - Multiplexer

FDM - Demultiplexer

TDM - Synchronous

TDM - Asynchronous

Inverse Multiplexing Takes data stream from one high speed line & breaks it into portions that can be sent over multiple lower speed lines simultaneously.

Multiplexing and Inverse Multiplexing

Analog Services Analog switched –Dial- up, voice networks –PSTN – Public Switched Telephone Network Analog Leased –Conditioned Lines

Multiplexing Efficiency Multiplex signals from lower bandwidth into high bandwidth lines Many analog lines into fewer bigger channels FDM used Hierarchical structure

Analog Hierarchy

Digital Service Less sensitive to interference 3 Types Digital Service –Switched/56 Service –DDS - Digital Data Service –DS Digital Signal Service

DS Hierarchy

DS T Lines are Digital Lines for Digital Transmission to deliver DS Service. –T1 = DS-1 = 1.544Mbps –T2 = DS-2 = 6.312Mbps –T3 = DS-3 = Mbps –T4 = DS-4 = Mbps