Matlab Practicals for Wireless Communication

MATLAB Implementation of free space & multipath channel Model.

Case-I    Free space propagation model

INTRO –

The “free space propagation model” is used for the measurement of received signal strength when the transmitter and receiver of the communication system have clear, line of sight between the transmitter and receiver. It also confirms that there is no obstacle between the transmitter and receiver.

The free space propagation is useful for microwave radio links and satellite communication. It predicts the received power decay level as a function of the Tx-Rx separation distance.

The Friss free space equation expresses the free space power received P_R(d) by the receiver antenna that is separated from a radiating transmitter antenna that is separated from a radiating transmitter antenna by a distance d, it is given as,

P_R(d)   =   (P_T G_T G_R l*l) / ((4p)² d² L)

Where,            P_T = Transmitted power (watt)

G_T = Transmitter Gain
G_R = Receiver Gain
l = Lambda c/f (m)
c = 3 x 10⁸
f = operating frequency (Hz)
L = Loss factor (L >= 1)

f = 900MHz, Gt=Gr=1, d = 200:1:10000m, let Pt = 50W, L = 1,   Pr (d) in watt and dBm = ?

PROGRAM

clc;

close all;

clear all;

 Pt = input('enter the value of transmitted power in Pt(watt) = ')

'transmitted power in dBm = Pt1'

 Pt1= 10*log10(Pt/(1*10^(-3)))

 Gt = input('enter the value of transmitter gain Gt = ')

 Gr = input('enter the value of receiver gain Gr = ')

  L = input('enter the value of Loss Factor L = ')

  f = input('enter the value of operating frequency f(Hz) = ')

  c = 3*10^8

'ld = c/f (lambda)'

 ld = c/f

 pi = 3.14

  d = input('enter the value/range of d(m) = ')

'receiver power Pr using transmitted power in watt '

'Pr = (Pt*Gt*Gr*(ld)^2)/(((4*pi)^2)*(d^2)*L)'

Pr = (Pt.*Gt.*Gr.*ld.*ld)./(((4.*pi).^2).*d.*d.*L)

'received power in dBm = Pr1'

Pr1= 10*log10(Pr/(1*10^(-3)))

subplot(2,1,1)

plot(d,Pr)

ylabel('Radiated Power(watt)')

xlabel('Distace(m)')

title('Free Space Propagation model watt')

subplot(2,1,2)

plot(d,Pr1)

ylabel('Radiated Power(dBm)')

xlabel('Distace(m)')

title('Free Space Propagation model dBm')

RESULT 

Case-II   Multipath channel (frequency selective) model

INTRO - 

The presence of reflecting objects and scatters in the channel constantly creates a constantly changing environment that dissipates the signal energy in amplitude, phase and time. Such random phase and amplitudes of different multipath components can cause fluctuation in the signal strength.

The received signal can take a direct path or any indirect path to reach receiver. Multipath propagation increases the time required for the baseband signal to reach the receiver.

Equation for multipath channel model can be written as follows :

H(w)   =       Ö( 1 + α² + 2 α (cos (wΔt)))

Where, w = np/ Δt

 α = 2, f = 900000000 Hz, n = 0:0.01:10

PROGRAM

clc;

close all;

clear all;

 a = input('Enter the value of a=')

dt = input('Enter the value of dt=')

 f = input('Enter the value of f=')

 n = input('Enter the value of n=')

 w = (n.*(3.14))./dt

 x = cos(w.*dt)

 h = sqrt(1+(a.^2)+(2.*a.*x))

plot(w,h)

xlabel(' w ')

ylabel('  H(w) ')

title('frequency selective model')

RESULT