Types of Communication channel

—Communication channel is a connection between transmitter and receiver through which Data can be transmitted.

—Communication channel also called as communication media or transmission media

Other types are Under Water Acoustic Channels, Storage Channels like magnetic tapes, magnetic disks etc.

Twisted-pair cable;

Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboringpairs ...

• —One of the wires carries signal, the other is used only as a ground reference.
• —Number of twists per unit length determines the quality of the cable.

Coaxial cable;

Coaxial cable, or coax (pronounced /ˈkoʊ.æks/), is a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables also have an insulating outer sheath or jacket.

•Used for both analog and digital signals
•Effectively used at higher data rate and higher bandwidth
•For analog signals need amplifiers every few km
•For digital signals requires repeater every 1km

Optical fiber;

a thin glass fibre through which light can be transmitted.

Terrestrial microwave;—

• Requires fewer repeaters 
• Use a parabolic dish to focus a narrow beam. 
• —1-40GHz frequencies

—

Broadcast Radio;

• —Radio frequency range is 3kHz to 300GHz 
• —Use broadcast radio of 30MHz - 1GHz, for: —

1. FM radio 
2. —UHF and VHF television 

• —Is a unidirectional 
• —Suffers from multipath interference 
• Reflections from land, water, other objects 
• ——Are used for multicasts communications, such as radio and television, and paging system.

Satellite communication;

A communications satellite is an artificial satellite that relays and amplifies radio telecommunications signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth.

—Receives on one frequency, and transmits on another frequency
—eg. uplink 5.925-6.425 GHz & downlink 3.7-4.2 GHz
•Height 35,784km
•Spaced at least 3-4° apart