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 = 44.736Mbps– T4 = DS-4 = 274.176Mbps