MATLAB Answers


What is correct to calculate Rate or shannon capacity?

Asked by Praveen Pawar on 18 May 2018
Latest activity Commented on by KALYAN ACHARJYA on 18 May 2018
Users are uniformly distributed in the circular area and base station is at the center. If the distance is varied then their corresponding rate should also be different. Here is the code, I am getting the approximate same rate for all users. Where is the mistake in my code? any suggestion is very thankful.
n_users=10;%no. of users
N0dbm=-124; %%%noise power
N0 = 10^((N0dbm-30)/10);
P_MBS=20;%Power in watt
MBS_XY = [0 0];
alpha=0.3; %bandwidth allocation
FREQ = 2.15;
angle_users = 2*pi*rand(n_users,1);
r_users = r_MBS*sqrt(rand(n_users,1));
%x and y coordinate of users
X_users = r_users.*cos(angle_users)+ MBS_XY(1);
Y_users = r_users.*sin(angle_users)+ MBS_XY(2);
XY_users=X_users + 1i.*Y_users;
MBS_XY = MBS_XY(1)+1i*MBS_XY(2);
%%Calculate channel gain
dist_users = abs(XY_users-MBS_XY);
path_loss = 10*alpha*log10(dist_users) + 27.3 + 26*log10(FREQ);
shadowing = 4*ones(size(dist_users));
shadowing = shadowing.*randn(size(shadowing));
sub_power_array = 10.^((shadowing-path_loss)./10); % caculate shadowing
size_h = size(sub_power_array); % caculate h
h = sqrt(0.5)*randn(size_h)+sqrt(0.5)*randn(size_h)*1j;
% final power array
channel_gain = (abs(h)).^2.*sub_power_array;
G_MBS = channel_gain;
R_MBS = log2(1+(P_MBS.*G_MBS)./N0); %%Rate or shannon capacity


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1 Answer

Answer by KALYAN ACHARJYA on 18 May 2018
Edited by KALYAN ACHARJYA on 18 May 2018

The output is not same, where you got the same results if you vary the n_user


Sir, there is no issue with the uniformly distributed random numbers. If above code is ok, then I need to find the basic conceptual answer. However, something is missing in my code. First, there is no significant variation on the basis of distance between base station (BS) and users. Second, while changing BS power from 20 to 2 watt, still, there is small change in rate.
Why do not plot Shannon's capacity limit graph, you will get the clue whether the results are OK or not?

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