Description of Transmission Media

Description of Transmission Media

Transmission Media:

v  Transmission media are the physical pathways that connect computers, other devices, and people on a network—the highways and byways that comprise the information superhighway.

v  A transmission medium is a material substance (solid, liquidor gas) which can propagateenergywaves. For example, the transmission medium for sound received by the ears is usually air, but solids and liquids may also act as transmission media for sound.

v  The absence of a material medium (the vacuumof empty space) can also be thought of as a transmission medium for electromagnetic waves such as light and radio waves.

v  Each transmission medium requires specialized network hardware that has to be compatible with that medium.

v  In OSI reference model, each layer defines network hardware and services in terms of the functions they perform.

v  Transmission media operate at Layer 1 of the OSI model: They encompass the physical entity and describe the types of highways on which voice and data can travel.

v  Electrical signals are generated as electromagnetic waves (analog signaling) or as a sequence of voltage pulses (digital signaling). To be propagated (sent) from one location to another, a signal must travel along a physical path. The physical path that is used to carry a signal between a signal transmitter and a signal receiver is called the “transmission medium.”

There are two types of transmission media:

v  Guided media

v  Unguided media

1)    Table: Traditional Transmission Media Characteristics

Media Type Bandwidth Performance: Typical Error Rate
Twisted-pair for analog voice applications 1MHz Poor to fair (10–5)
Coaxial cable 1GHz Good (10–7 to 10–9)
Microwave 100GHz Good (10–9)
Satellite 100GHz Good (10–9)
Fiber 75THz Great (10–11 to 10–13)

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