Anti-spoofng algorithm design from the block diagram

I am currently working on designing an anti-spoofing algorithm, but I don't know how to write the code according to this block diagram from a literature. Would someone help me with it, how to transfer these information into coding or how to draw this block diagram on SIMULINK?

[Peter O]

Can you post the block diagram?

[zihan LI]

Oh I am so sorry i fogot this important part.

Answer 1

[Ravi]

Hi Zihan LI,

We can define a function that takes input the signals data ‘S’, the sampling number ‘N’, and the error threshold, ‘epsilon’. Here, S(i, k) represents the carrier frequency of the ith signal at the kth time slot.

Please note that MATLAB uses one-based indexing.

From the first flow chart, we can observe the following.

1. Relative discrepancies are computed.
2. Difference between relative discrepancies for every two signals ‘i', and ‘j’ at every time slot ‘k’ is calculated.
3. For every pair of signals, the count of the number of time slots for which the relative difference falls with the threshold is maintained.
4. If the count exceeds 2N/3, they are marked as spoofed signals.

The code for the first flow chart looks as follows:

function pair = spoofed(S, N, epsilon)
    pair = [];
    S_cap = abs(S(:, :) - S(:, 1));
    
    for i = 1:N
        for j = 1:N
            Nij = 0;
            for z = 1:N
                diff = abs(S_cap(i, z) - S_cap(j, z));
                if diff < epsilon
                    Nij = Nij + 1;
                end
            end
            if Nij > (2 * N / 3)
                disp('signal ' + num2str(i) + ' and signal ' + num2str(j) + ' are spoofed');
                pair = [i, j];
            end
        end
    end
end

In the second flow chart, we are computing the sum of squares of relative differences for every pair of signals at each time slot, and checking if the sum falls below the threshold. The code for the second flow chart looks as follows:

function pair = spoofed(S, N, epsilon)
    S_cap = abs(S(:, :) - S(:, 1));
    for i = 1:N
        for j = 1:N
            x = S_cap(i, :) - S_cap(j, :);
            Eij = sum(x.*x);
            if Eij < epsilon
                disp('signal ' + num2str(i) + ' and signal ' + num2str(j) + ' are spoofed');
                pair = [i, j];
            end
        end
    end
end

I hope this answer helps!