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  • 8/6/2019 Communication Chanel


    Topic : Communication Channels

    Presented by:

    Saniya Adeen


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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


    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)


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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


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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 5.9megahertz to 26.1 megahertz

    Citizens band (CB) radio - 26.96 megahertzto 27.41 megahertz

    Television stations - 54 to 88 megahertz forchannels 2 through 6

    FM radio - 88 megahertz to 108 megahertz

    Television stations - 174 to 220 megahertzfor 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 stations transmission tower

    to the antennas of the television

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    Digital channel is the sending and receivingof moving images and sound by discrete

    (digital) signals

    Transmitting a broadcast signal by encodingit as zeroes and ones 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 encodestelevision 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 knownas 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 tocommunication that occurs in one direction



    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



    IN full duplex data can travel in bothdirections simultaneously

    Full duplex allows both way communication


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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 senderto only one receiver.

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    Broadcast is a type of transmission in whichinformation is sent from just one computerbut is received by all the computersconnected to the network. This would meanthat every time a computer or a node wouldtransmit 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


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  • 8/6/2019 Communication Chanel