Experiment-2 Analysis of power received w.r.t distance for different path loss exponents Aim: Analyze the power received at the receiver w.r.t to the distance for different path loss exponents. Software used: Matlab b!ective of the experiment:
To understand understand large scale fading environment and attenuation of the signal strength for different path-loss exponent w.r.t. w.r.t. distance. "heory: Path loss normally includes propagation losses caused by the natural expansion of the radio wave front in free space (which usually takes the shape of an ever-increasing sphere), absorption losses (sometimes called penetration losses), when the signal passes through media not transparent to electromagnetic waves, waves , diff diffracti raction on losses when part of the radio wave front is obstructed by an opaue obstacle, and losses caused by other phenomena. The signal radiated by a transmitter may also travel along many and different paths to a receiver receiver simultaneou simultaneously! sly! this effect effect is called called multipath multipath.. "ultipath can either increase or decrease received received signal signal strength, strength, dependin depending g on whether whether the individu individual al multipa multipath th wave fronts interfere interfere constructively or destructively. The total power of interfering waves in a #ayl #ayleigh eigh fading scenario vary uickly as a function of space (which is known as small scale fading fading), ), resulting in fast fades which are very sensitive to receiver position $n the study of wireless communications, path loss can be represented by the path loss exponent, whose value is normally normally in the range of % to & (where % is for propagation propagation in free space, & is for relatively lossy environments and for the case of full reflection from the earth surface'the socalled called flat-e flat-eart arth h model model). ). $n some some enviro environme nments nts,, such such as build building ings, s, stadi stadium umss and and other other indoo indoor r environments, the path loss exponent can reach values in the range of & to . n the other hand, a tunnel may act as a waveguide, resulting in a path loss exponent less than %.
*s a resu result lt of this this it is foun found d that that the the signa signall decr decrea ease sess in a way way that that is invers inversel ely y proportional to the suare of the distance from the source of the radio signal.
Free space path loss formula
The free space path loss formula or free space path loss euation is uite simple to use. +ot only is the path loss proportional to the suare of the distance between the transmitter and receiver, but the signal level is also proportional to the suare of the freuency in use. #S$% & '()d* +, 2 & '()df* c, 2
P is the ree space path loss d is the distance of the receiver from the transmitter (metres) / is the signal wavelength (metres) f is the signal freuency (0ert1) c is the speed of light in a vacuum (metres per second)
ecibel version of free space path loss euation
"ost # comparisons and measurements are performed in decibels. This gives an easy and consistent method to compare the signal levels present at various points. *ccordingly it is very convenient to express the free space path loss formula, P, in terms of dec ibels.. #S$% 'd/, & 20 lo10 'd, 3 20 lo10 'f, 3 42.((
2here3 d is the distance of the receiver from the transmitter (km) f is the signal freuency ("01) $ower 5eceived: 6$r7 & 6pt7 3 68t7 3 68r7 9 6#S$%7
Pr 4 #eceived power Pt 4 Transmitted power 5t 4 5ain of the transmitting antenna 5r 4 5ain of the receiving antenna
Al1orithm:
Matlab code:
%LARGE SCALE PATH LOSS clear all; close all; clc; d = 1000:1000:30000; Pt=2;
%Transmted Po!er
"or n=1#$:0#$:3
Pr=Pt&1#'&d#(n));%"orm*la "or rece+ed ,o!er Prd- = 10#lo.&Pr);%co+ertn. to d- scale
,td-=10#lo.&Pt);%co+ertn. to d- scale ,ld-= ,td-/Prd-;
".*re&1);
,lot&dPrd-);%,lot "or rece+ed ,o!er +s dstance
old all;
.rd on; le.end&n=1#$n=2#0n=2#$n=3)
ttle&Rece+ed ,o!er "or ""erent ,atloss e4,onents);
4la-el&5lometers); 6la-el&Rece+ed Po!er &d7));
".*re&2);
,lot&d,ld-);%,lot "or ,atlloss +s dstance
old all;
.rd on; le.end&n=1#$n=2#0n=2#$n=3)
ttle&Patloss anal6ss "or ""erent ,atloss e4,onents);
4la-el&5lometers); 6la-el&Patloss &d7));
end
$lots:
5esult:
