Communication Channels
The Communication channel may be wired or wireless .The wired connection is also called as
1. Physical Connections
a) Telephone lines
- Typically use twisted pair cables, copper wires covered with an insulating jacket
- Relatively inexpensive way to connect devices
- Now being phased out by more technically advanced and reliable media
b) Coaxial cable
- A high frequency transmission cable, can be used to replace multiple lines of twisted pair cable with one single, solid copper core.
- Can carry 80 times the capacity of one twisted pair cable
c) Fiber-optic cable
- Transmit data as a pulse of light through tiny tubes of glass
- Has over 26,000 times the capacity as one twisted pair cable
- Fiber optic cables are rapidly replacing twisted pair telephone wires
2. Wireless Connections
a) Infrared
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Use infrared light waves to communicate
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Known as a “line of sight” communication medium
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Commonly used to transmit data from a PDA to a
desktop PC
b) Broadcast radio
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Uses special sending and receiving towers called
“transceivers”
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The transceiver sends and receives many signals
from different wireless devices
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Cellular telephones communicate using this
technology
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WiFI (Wireless Fidelity aka 802.11 technologies)
are used to build wireless local area networks
c) Microwave
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Uses high frequency radio waves
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Line of sight medium
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Transmit data over relatively short distances
(within 10-20 miles) due to curvature of the earth
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Microwave signals are sometimes repeated at
microwave stations with microwave dishes
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Bluetooth is a short-range wireless
communication standard that uses microwaves to transmit data over very short
distances (less than 33 feet). This may
become popular for connecting peripheral devices to computers
d) Satellite
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Uses satellites orbiting up to 22,000 miles
above the earth to send large volumes of data
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Uplink is sending data to a satellite
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Downlink is receiving data from a satellite
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GPS (Global Positioning Systems) use satellite
data to pinpoint locations nearly anywhere on the earth. They are used for both military and
commercial navigation systems
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