Calculating the radius of a link budget

Hi there, how would I calculate the cell radius of a link budget?

I have a given link budget but just on the uplink. Would I need to use the satellite link budget app within MATLAB or is there a way to code this?

Thanks in advance,

P.S. not a beg for code, just a point in the right direction would be helpful please?

Answer 1

[Athanasios Paraskevopoulos]

Hello! To calculate the cell radius of a link budget, particularly in a telecommunications context like satellite communications, you typically need to consider several factors from the link budget analysis.

1. Start by understanding all components of your given link budget. This includes the transmitter power, antenna gains, frequency of operation, path loss, and any losses due to the environment or equipment.

2. The key factor in calculating the cell radius is understanding the path loss. For satellite communications, this often involves models specific to satellite paths, which can include free-space loss calculations adjusted for atmospheric and rain attenuation.

3. Use the formula for path loss, \( L = 20 \log_{10}(d) + 20 \log_{10}(f) + 92.45 \), where \( d \) is the distance in kilometers and \( f \) is the frequency in GHz. This formula gives you a basic idea of how path loss increases with distance and frequency.

4. From your link budget, determine the maximum allowable path loss that still maintains the minimum required signal quality at the receiver.

5. Rearrange the path loss formula to solve for \( d \) (distance) when you set the path loss to its maximum allowable value. This gives you the maximum coverage radius for a single cell.

Here's a very basic outline of what the code structure might look like:

% Constants
c = 3e8; % Speed of light in meters per second
frequency = 2e9; % Frequency in Hz (e.g., 2 GHz)

% Link Budget Parameters
Pt = 10; % Transmitted power in dBm
Gt = 15; % Transmitter antenna gain in dB
Gr = 20; % Receiver antenna gain in dB
Pr_min = -100; % Minimum required received power in dBm

% Convert frequency to GHz for the path loss formula
frequency_GHz = frequency / 1e9;

% Calculate free-space path loss at a specific distance
calculate_path_loss = @(d) 20*log10(d) + 20*log10(frequency_GHz) + 20*log10((4*pi)/c);

% Estimate the maximum distance where the received power is still above the sensitivity
% Solve for distance d such that Pr_min = Pt + Gt + Gr - Path Loss
d_max = 10 ^ ((Pt + Gt + Gr - Pr_min - 20*log10((4*pi)/c) - 20*log10(frequency_GHz)) / 20);

% Display the maximum cell radius
fprintf('The maximum cell radius is approximately %.2f meters.\n', d_max);

The maximum cell radius is approximately 212266468729675.34 meters.

This script is quite simplified and assumes you've converted all your powers and gains into the same units (typically dBm or dBW). Adjust it according to your specific parameters and losses.