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Modul 3 SmallScaleFading - WCS Edited RPA

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    Modul 3

    Small Scale Fading

    Wireless Communication System

    1

    Faculty of Electrical Communication

    IT Telkom

    October 2012Modul 3 Small Scale Fading

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    Subject

    a. Introduction Fading Channel Manifestationsb. Small Scale Fading

    c. Kl sifik si Sm ll Sc le F din

    2

    Modul 3 Small Scale Fading

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    Multipath Components

    Component 2

    Component 1

    Radio Signals Arriving from different directions to receiver

    3

    Component N

    Receiver may be stationary or mobile.

    Modul 3 Small Scale Fading

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    Multipath Components

    At a receiver point

    Radio waves generated from the same transmitted signalmay come

    from different directions

    with different propagation delays

    with ossibl different am litudes random

    4

    with (possibly) different phases (random)

    with different angles of arrival (random).

    These multipath components combine vectorially at the

    receiver antenna and cause the total signal to fade

    to distort

    Modul 3 Small Scale Fading

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    5

    Modul 3 Small Scale Fading

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    6 Multipath Propagation

    In general, the received signal at the receiver point is the sum of the directsignal and the number of signals reflected from various objects. In mobilecommunication, reflection will be caused by:

    Surface terrain

    Buildings Moving objects as an example vehicle

    Wave reflection magnitude and phase will change, depending on thereflection coefficient, the wave trajectory, and also depending on the angle of

    Modul 3 Small Scale Fading

    . ,terms of:

    Amplitude, depending on the magnitude of reflection coefficient Phase, depending on the phase change of reflection and the

    path distance difference between the direct wave and the

    reflected waveThe worst condition occurs when the direct wave and reflection wave hasthe same magnitude and different phases 180o. In such conditions, betweenthe direct wave and the reflected waves will occur eliminate each other(complete cancellation)

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    7

    Phase difference of 180o

    occur if there are differences in the path distancetraveled by the waves as follows:

    =

    2

    )1n2(d

    The best condition is achieved if the direct wave and reflection wave has thesame phase or a multiple of 360o (In Phase Combination). Difference distancedirect wave and reflection on this condition can be expressed as follows:

    Multipath Propagation

    Modul 3 Small Scale Fading

    = nd where:n = 1,2, 3, etct = wave length

    The variation of wave amplitude and phase depending on thevariety of conditions and due to various factors, which causeFading occurs, we will discuss in this module.

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    Amplitudo

    Amplitudo sinyal terimatergantung dari lokasi danfrekuensi

    Jika antena bergerak,maka lokasi x akanberubah linear terhadap

    Small Scale Fading8

    Frekuensi Waktu

    wa u x= v

    Parameters:

    probability of fades

    duration of fades bandwidth of fades

    Modul 3 Small Scale Fading

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    9 Modul 3 Small Scale Fading

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    Delay Spread Model dan Time Varying Model

    Fokus pada multipath fading, disebabkan 2 hal:

    Time spreadingsinyal Akibat sinyal datangdengan delay yang berbeda-beda, dianalisis denganDelay Spread Model

    Time varying of channel akibat pergerakan,

    Karakterisasi Kanal Multipath10

    ana s s engan me ary ng o e

    Evaluasi/analisis biasa dilakukan dalam

    Domain waktu, dan

    Domain frekuensi

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    11

    Delay Spread Model

    To know the characteristics of channel delay, usually conducted Channel

    sounding (with impulse response)

    Maximum excess delay digitize into N groups of paths, each path separated

    Multipath channel

    Small Scale Fading

    Modul 3 Small Scale Fading

    .

    The model used to analyze signals with BW < 1/(2).

    The total power received is the sum of all multipath components, if the

    components can be resolved / processed.

    If the signal BW BW al multipath channel can not be overcome

    SIRCIM (Simulation ofIndoorRadioChannelIMpulse response)

    SMRCIM (Simulation ofMobileRadioChannelIMpulse response.)

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    12

    h(d,t)x(t) y(d,t)

    Received signal, is a function of distance (d) and time (t)

    +

    == d)t,d(h)(x)t,d(h)t(x)t,d(y

    =

    Small Scale Fading - Multipath Channel Impulse Response Model

    Modul 3 Small Scale Fading

    , ,

    =t

    d)t,t.v(h)(x)t,t.v(y

    Assumption of constant v, then d is only a function of velocity (v) andtime (t)

    ==t

    d)t,t.v(h)(x)t,t.v(h)t(x)t(y

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    ( ) ( ) = +=N

    1k k0krtf2cosate

    Received signal can be expressed as follows :

    Where,=

    Multipath Signal Analysis, Assumptions: Vehicles without moving

    Small Scale Fading multipath signal analysis1313

    10/3/2012 13

    N = number of track multipathak , k = amplitude and phase of the kth

    multipath component-k

    ( ) ( ) = +=N

    1k k0kr tf2cosate

    ( ) ( ) ( ) ( ) ( )k0k0k0 sintf2sincostf2costf2cos =+Recall :

    Modul 3 Small Scale Fading

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    ( ) ( ) ( ) ( ) ( ) == =N

    1k kk0

    N

    1k kk0rsinatf2sincosatf2coste

    ( ) ( ) ( )tf2sinYtf2cosXte 00r = X

    Yr

    Small Scale Fading multipath signal analysis1414

    10/3/2012 14

    Asuming :N Large N (many paths) theoretically infinite, practically > 6k uniformly distributed in (0 to 2)ak respectively can be compared (no one is quite dominant)X and Y are mutually independent identical distributed Gaussian

    Then :

    22 YXrEnvelopeSinyal +== RAYLEIGH distibuted!!

    Identically Independently Distributed(IID)

    Modul 3 Small Scale Fading

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    as c eory _ ma ca e a ng multipath signal analysis

    Mobile RadioPropagation

    The received signal is a sum of real

    signals that have experienceattenuation, reflection, refractionand diffraction according to its path.

    Mobile station movement

    15

    Rayleigh Distribution

    ( )( )

    ( )

    >

    Coherence time < periodesimbol

    Variasi kanal lebih cepat darivariasi sinyal baseband

    Doppler spread periode

    simbol

    Variasi kanal lebih lambat darivariasi sinyal baseband

    Modul 3 Small Scale Fading

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    22%------------------

    % fading parameters%------------------

    c_light = 3E8; % speed of light (m/s)

    v = 10; % vehicle's speed (kph)

    B = 40; % number of bit per slot

    R = 60; % bit rate (kbps)

    T = 1/(R*1E3); % symbol duration (s)

    f = 1.8; % carrier frequency (GHz)

    fd = (v*1E3/3600)*f*1E9/c_light; % Doppler freq (Hz)

    N = 34;

    N0 = (N/2 - 1)/2;alpha = pi/4;

    xc = zeros(len,1);

    xs = zeros(len,1);

    sc = sqrt(2)*cos(alpha);

    ss = sqrt(2)*sin(alpha);

    ts = 0:len-1;

    ts = ts'.*T + round(rand(1,1)*10000)*T;

    wd = 2*pi*fd;

    xc = sc.*cos(wd.*ts);

    xs = ss.*cos(wd.*ts);

    Fading Simulator : Jakes Method22

    Modul 4 Small Scale Fading

    %-----------------------

    % variable in simulation

    %-----------------------

    Tp = 1000; % number of data slot

    len = B*Tp; % number of symbol (Bsymbols/slot)

    % function y = fading(len, fd, T)

    %--------------------------

    % parameter in Jakes Method

    %---------------------------

    for lx =1:N0

    wn = wd*cos(2*pi*lx/N);

    xc = xc + (2*cos(pi*lx/N0)).*cos(wn.*ts);

    xs = xs + (2*sin(pi*lx/N0)).*cos(wn.*ts);

    end;

    y = (xc + i.*xs)./sqrt(N0+1);

    %plot fading signalfigure(1);

    plot(ts*T,abs(y));

    title('Fading Signals')

    xlabel('time (sec)')

    ylabel('amplitude')

    Modul 3 Small Scale Fading

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    mu a on esuSignal Analysis on Rayleigh Channel

    Mobile station speed 5km/hour,fd=4,023Hz

    mobile station speed25km/hour, fd=20,27Hz

    23

    Mobile station speed 100km/hour, fd=80,52Hz Amplitude fluctuation (Fading) will increase asthe mobile station (MS) speed increase, it can

    be seen as follow:

    MS speed 5km/hour, fd=4,023Hz.Received signal will achieve maximalattenuation 11db, amplitude fluctuation is notoccurs many times.

    MS speed 25km/hour, fd=20,27Hz.Received signal will achieve maximalattenuation 13dB, amplitude fluctuation is moreoften than MS 25km/hour.

    MS speed 100km/hour, fd=80,52Hz.Maximal attenuation 17dB, amplitudefluctuation is the most often in this threeexperiment.

    Modul 3 Small Scale Fading

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