Chapter 4.3 Yani

Embed Size (px)

Citation preview

  • 8/17/2019 Chapter 4.3 Yani

    1/16

    4.3 MultiplexingOutlines

    FDM

    TDM

    WDM

  • 8/17/2019 Chapter 4.3 Yani

    2/16

    Introduction

    Definition

    1. The transmission of information from one ormore source to one or more destination over

    the same medium.

    2. The process which two or more signals

     are combined for transmission over a single

    communications path.

    3. A process where multiple analog message

    signals or digital data streams are combined into

     one signal with the aim is to share an

    expensive resource.

    http://en.wikipedia.org/wiki/Multiplexing 

  • 8/17/2019 Chapter 4.3 Yani

    3/16

    Make the communications ver economical

    b transmitting thousands of independentsignals over a single transmission line.

    Three predominant was to multiplex

    1. !re"uenc Division Multiplexing #!DM$

    2. Time Division Multiplexing #TDM$

    3. %avelength Division Multiplexing #%DM$

  • 8/17/2019 Chapter 4.3 Yani

    4/16

    Multiplexing allows several analog signals to

    be processed b one analog&to&digitalconverter #AD'$ ( ).g. *everal phone calls ma be transferred using

    one wire.

    The multiplexed signal is transmitted over acommunication channel which ma be a

    phsical transmission medium.

  • 8/17/2019 Chapter 4.3 Yani

    5/16

    The multiplexing divides the capacit of the

    low&level communication channel into severalhigher&level logical channels+ one for each

    message signal or data stream to be

    transferred.

     A reverse process+ known as demultiplexing+can extract the original channels on the

    receiver side.

  • 8/17/2019 Chapter 4.3 Yani

    6/16

     A multiplexing techni"ue ma be further extendedinto a multiple access method or channel access

    method. ( ).g. Time Division Multiple Access #TDMA$

    Multiple access method makes it possible forseveral transmitters connected to the same

    phsical medium to share its capacit.

  • 8/17/2019 Chapter 4.3 Yani

    7/16

    'oncept of multiplexing

  • 8/17/2019 Chapter 4.3 Yani

    8/16

    Frequency Division Multiplexing (FDM)

    ,redominantl used in analog

    communications.%idel used in !M stereo broadcast.

    'ompatibilit with mono&receivers.

    -e"uires onl a slight increase in %.

    /reat advantage in increasing sstem

    capacit.

  • 8/17/2019 Chapter 4.3 Yani

    9/16

    Transmitting end of an !DM *stem

  • 8/17/2019 Chapter 4.3 Yani

    10/16

    ,rocess ( )ach signal assigned s different carrier

    fre"uenc.

     ( Modulated carrier fre"uencies are combined fortransmission over a single line b M0.

     (  At -x+ a D)M0 separates channels b their

    fre"uencies routes them to the proper endusers.

  • 8/17/2019 Chapter 4.3 Yani

    11/16

      ime-Division Multiplexing

    This technique combines time-domainsamples from different message signals

    (sampled at the same rate) and transmitsthem together across the same channel.

    Performed using a commutator (switch).

    t the receiver a decommutator (switch)is used in s!nchronism with thecommutator to demultiplex the data.

    ver! sensitive to s!mbol dispersion" thatis" to variation of amplitude withfrequenc! or lac# of proportionalit! ofphase with frequenc!. This problem ma!be solved through equali$ation of both

    magnitude and phase.

  • 8/17/2019 Chapter 4.3 Yani

    12/16

    Time Division Multiplexing (TDM)4ffers greater sstem improvement.

    'apable of combining various protocols different

    tpes of signals onto a single high speed

    transmission link. ( ).g. voice and data

    More efficient than !DM

    % Methods used to s!nchroni$e the operations ofmultiplexing and demultiplexing & organi$e the

    multiplexed stream of data as frames with a

    special pattern. The pattern is #nown to the

    receiver and can be detected ver! easil!.

  • 8/17/2019 Chapter 4.3 Yani

    13/16

    ,rocess (

    The transmission must be digital in nature. ( To transmit telephone conversations #voice is

    analog signal$ Analog signal is converted to digital and transmitted

    -econverted into analog at the -x telephone.

  • 8/17/2019 Chapter 4.3 Yani

    14/16

    'loc# diagram of DM-P(M

    communication s!stem

  • 8/17/2019 Chapter 4.3 Yani

    15/16

    Drawbacks ( /reater complexit.

     ( /reater transmission % re"uired.

  • 8/17/2019 Chapter 4.3 Yani

    16/16

    Wvelengt! Division Multiplexing

    (WDM)

    'ost effective wa to increase the capacit of

    fiber optic communications.Make use of the optical fiber5s available %

    b multiplexing man wavelengths along a

    single mode optical fiber channel.

    )ach wavelength of light can transmitencoded information at the optimum data

    rate.