hi folks... you can have an overview about the communication channels....

2. M.Tech ECE
Department of Electronics

3.  What is a Communication channel….?
• The Communication channel provides the connection
between the transmitter and the receiver.
• The physical channel may be a pair of wires that carry
the electrical signal, or an optical fiber that carries the
information on a modulated light beam, or an underwater
ocean channel in which the information is transmitted
acoustically, or free space over which the information
bearing signal is radiated by use of an antenna.

4. Communication
Transmitter Receiver
Channel

5. COMMUNICATION CHANNELS
Wired
Wireless
Acoustic Channels
Storage Channels
Twisted Pair Cable
Coaxial Cable
Optical fiber Cable
Terrestrial Microwave
Satellite Communication
Under water channels
Magnetic Tapes
Magnetic Disks

6.  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
cancelling out electromagnetic interference (EMI) from external
sources; for instance, electromagnetic radiation from unshielded
twisted pair (UTP) cables, and crosstalk between neighbouring
pairs.

7.  For a Shielded twisted pair :
Cost per node: moderate
Media and Connector size : medium to large
Maximum cable length : 100m

8.  Coaxial Cable :
• Coaxial cable, or coax 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.
• Effectively used at Higher Data
rate and higher band width.
• For Digital signals requires
repeater every 1km

9.  Optical Fiber Cable:
• A technology that uses glass (or plastic) threads (fibers) to
transmit data. A fiber optic cable consists of a bundle of glass
threads, each of which is capable of transmitting
messages modulated onto light waves.
• Optical fibers typically include a transparent core surrounded
by a transparent cladding material with a lower index of
refraction. Light is kept in the core by total internal
reflection. This causes the fiber to act as a waveguide

10. • Fibers that support many propagation paths or transverse
modes are called multi-mode fibers (MMF), while those that
only support a single mode are called single-mode
fibers (SMF).

11. • When light traveling in an optically dense medium hits a
boundary at a steep angle the light is completely reflected. This is
called total internal reflection. This effect is used in optical fibers
to confine light in the core.

12.  Terrestrial microwave:
• Terrestrial microwave communication employs Earth-based
transmitters and receivers. The frequencies used are in the
low-gigahertz range, which limits all communications to
line-of-sight.
• You probably have seen the terrestrial microwave equipment
in the form of telephone relay towers, which are placed every
few miles to relay the telephone signals across the country

13.  Satellite Communication:
• A communication satellite is a radio relay station in orbit
above the earth.
• It receives, amplifies and
redirects analog and digital
signals carried on a specific radio
frequency
• These are having different uplink
and downlink frequencies and
speed is about 1Gbps

14.  Under Water Acoustic Channels:
• Underwater acoustic communication is a technique of
sending and receiving message below water.
• There are several ways of employing such communication
but the most common is using hydrophones.
• Under water communication is difficult due to factors like
multi-path propagation, time variations of the channel,
small available bandwidth and strong signal attenuation,
especially over long ranges.

15. • In underwater communication there are low data rates
compared to terrestrial communication, since underwater
communication uses acoustic waves instead
of electromagnetic waves.

16.  Magnetic tapes :
• Magnetic tape is a medium for magnetic recording, made of
a thin magnetisable coating on a long, narrow strip of plastic
film. It was developed in Germany, based on magnetic wire
recording. Devices that record and play back audio and video
using magnetic tape are tape recorders and video tape
recorders. A device that stores computer data on magnetic
tape is a tape drive .

17.  Magnetic Disks :
• Magnetic storage (or magnetic recording) is the storage
of data on a magnetized medium. Magnetic storage uses
different patterns of magnetization in a magnetisable material
to store data and is a form of non-volatile memory. The
information is accessed using one or more read/write heads