Index exceeds the number of array elements. Index must not exceed 1.

I got "Index exceeds the number of array elements. Index must not exceed 1." problem in the line 36 at the code below:

% Define constants
c = 3e8; % Speed of light

% Define scenario parameters (adjust these as needed)
f = 2e9; % Operating frequency
d_BS_IRS = 100; % Distance between BS and IRS (meters)
d_IRS_UE = 50; % Distance between IRS and UE (meters)

% Define IRS element properties
material = "metal"; % Choose "metal" or "plastic"
element_spacing = 0.5; % Spacing between elements (meters)

% Function to calculate reflection coefficient
function reflectionCoefficient = getReflectionCoefficient(material, theta)
  if strcmp(material, "metal")
    reflectionCoefficient = ones(size(theta));
  elseif strcmp(material, "plastic")
    reflectionCoefficient = 0.5 * ones(size(theta));
  else
    error("Invalid material type");
  end
end

% Simulate for different incident angles
theta_range = -30:0.5:30; % Range of incident angles (degrees)
theta = deg2rad(theta_range); % Convert to radians

% Calculate path lengths for each angle
path_length_BS_IRS_UE = d_BS_IRS + d_IRS_UE;
path_length_BS_IRS_reflect_UE = 2 * sqrt(d_BS_IRS^2 + d_IRS_UE^2)

path_length_BS_IRS_reflect_UE = 223.6068

% Loop through angles and calculate phase shifts for perfect reflection
phase_shifts = zeros(size(theta));
for i = 1:length(theta)
  % Ideal phase shift for constructive interference at UE
  phase_shifts(i) = 2*pi*f/c * (path_length_BS_IRS_reflect_UE(i) - path_length_BS_IRS_UE); %(!!!ERROR!!!!)
end

Index exceeds the number of array elements. Index must not exceed 1.

% Simulate reflection with material properties
reflection_coefficients = getReflectionCoefficient(material, theta);

% Plot results (modify for desired visualization)
figure;
plot(theta_range, abs(reflection_coefficients).^2, 'DisplayName', material);
xlabel('Incident Angle (degrees)');
ylabel('Reflected Power (normalized)');
title('Reflection Coefficient vs. Incident Angle');
legend;

Here is the error line:

phase_shifts(i) = 2*pi*f/c * (path_length_BS_IRS_reflect_UE(i) - path_length_BS_IRS_UE); %(!!!ERROR!!!!)

Answer 1

[Torsten]

path_length_BS_IRS_reflect_UE(i) does not exist for i > 1 because path_length_BS_IRS_reflect_UE is a scalar value, namely 223.6068.

Answer 2

[Image Analyst]

Why do you think path_length_BS_IRS_reflect_UE = 2 * sqrt(d_BS_IRS^2 + d_IRS_UE^2) should have a value for i = 2m 3m etc, when you defined it as a single number:

path_length_BS_IRS_reflect_UE = 2 * sqrt(d_BS_IRS^2 + d_IRS_UE^2)

You say that you want to compute the path length for each angle but you are not using the angle theta in any way whatsoever when you do

% Calculate path lengths for each angle
path_length_BS_IRS_UE = d_BS_IRS + d_IRS_UE;
path_length_BS_IRS_reflect_UE = 2 * sqrt(d_BS_IRS^2 + d_IRS_UE^2)

so those two variables are simply single numbers, not vectors.