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Topic : Communication Channels
Presented by:
Saniya Adeen
MIT01093010
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Communication is an exchange of feelings,
ideas, and information, whether by speaking,
writing, signals ,or behaviors
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� A channel is a communication medium, the
path that data takes from source to
destination.
� A channel can be comprised of so manydifferent things: wires, free space, and
entire networks
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A medium through which a message is
transmitted to its intended audience , such
as print media or broadcast (electronic)
media
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� Digital (discrete) or analog (continuous) channel
� Baseband and passband channel
� Computer network virtual channel
� Simplex communication, duplex communication
or half duplex communication channel
� Return channel
� Uplink or downlink (upstream or downstreamchannel)
� Broadcast channel, unicast channel or multicast
channels
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R adioTelevision
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Receiving an AM signal
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�AM radio - 535 kilohertz to 1.7 megahertz
� Short wave radio - bands from 5.9
megahertz to 26.1 megahertz
�Citizens band (CB) radio - 26.96 megahertzto 27.41 megahertz
�Television stations - 54 to 88 megahertz for
channels 2 through 6
� FM radio - 88 megahertz to 108 megahertz
�Television stations - 174 to 220 megahertz
for channels 7 through 13
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Radio waves have the longest wavelengths inthe electromagnetic spectrum.
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Different wavelengths of EM radiation cause
the radiation to react differently with
different materials
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Is the distribution of video signals which
transmit programs to an audience
Network transmits their signals frombroadcasting studios via satellite signals to
local stations or cable distributors. Then
broadcast signals travel over cable television
lines, satellite distribution systems or theairwaves from a station·s transmission tower
to the antennas of the television
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�Digital channel is the sending and receiving
of moving images and sound by discrete
(digital) signals
� Transmitting a broadcast signal by encodingit as zeroes and ones ² the digital code used
in computers. DTV can be compressed to
provide four, five or more channels in the
same bandwidth required for one channel ofthe current standard television. .
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�Analog (or analogue) television encodes
television picture and sound information and
transmits it as an analog signal: one in which
the message conveyed by the broadcastsignal is a function of deliberate variations in
the amplitude and/or frequency of the
signal. ...
� The video signal of analog television istransmitted in AM, while the audio is
transmitted in FM.
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� A baseband channel (or system, or network)
is a communication channel through which
digital signals are sent without frequencyshifting
� Ethernet is an example of a basebandnetwork
� A passband is the range of frequencies orwavelengths that can pass through a filter
without being attenuated
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� A logical channel number (LCN), also known
as virtual channel, is a channel designation
which differs from that of the actual radiochannel (or range of frequencies) on which
the signal travels.
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� Simplex communication refers to
communication that occurs in one direction
only
� Examples
�Commercial radio broadcast (not walkie-
talkies, etc.)
� Television broadcast
� Keyboard to CPU communication
� Internet multicast
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A half-duplex channel can send and receive,
but not at the same time. It's like a one-lane
bridge where two way traffic must give way
in order to cross. Only one end transmits at atime, the other end receives
Example:
walkie-talkies
IN full duplex data can travel in bothdirections simultaneously
Full duplex allows both way communication
simultaneously
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� In a duplex transmission channel, it is
sometimes the case that the main channel
operates only in one direction (i.e. simplex),
but that a channel of much lower capacity
(and much lower cost) operates in the
opposite direction, this is the return channel.
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� The communication going from a satellite to
ground is called downlink, and when it is
going from ground to a satelliteit is called uplink.
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�Unicast is a type of transmission in which
information is sent from only one sender to
only one receiver. In another words, Unicast
transmission is between one-to-one nodes(involving two nodes only).
� Examples of Unicast transmission are http,
smtp, telnet, ssh, pop3 where the request
for information is directed from one sender to only one receiver.
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� Broad cast is a type of transmission in whichinformation is sent from just one computer but is received by all the computersconnected to the network. This would meanthat every time a computer or a node would transmit a packet of type ¶broadcast·, allthe other computers will receive thatinformation packet.
� Examples of broadcast are many but one thatwould be best to understand here is acomputer booting up and requesting for a IPaddress
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� A type of transmission or communication in
which there may be more than one senders
and the information sent is meant for a set
of receivers� Example of Multicast based network is video
transmission network in which one computer
needs to transmit video channel to a specific
group of computers.
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The broadcast tower refers to a tall structureproviding mounting space for FM radio,AMradio antennas, and TV tower is constructed
to support Television antennasThe structure of broadcast tower
and TV tower not only meet
the requirement of broadcast
and television antenna but also isaesthetical in appearance and
coordinate with the surrounding
environment.
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