% Lab1 Matlab - Digital Communication Systems Course
% Team:
% Abdullah Mohamed Abdullah - 1557
% AbdelRahman Tarik ElBakri - 2447
% Ahmed Tawfieck - 1386

function Lab1(Num_of_Bits, SNR_Begin, SNR_Step, SNR_End)

    % BER matrix containing BER per SNR
    BER = [];

    for SNR = SNR_Begin:SNR_Step:SNR_End
        % Generate <Num_of_Bits> random bits
        Tx_Bits = randi([0 1], 1, Num_of_Bits);

        % Calculate AWGN power
        AWGN_Power = Gen_AWGN(Tx_Bits, SNR);

        % Apply AWGN to the transmitted signal
        Rx_Bits = Tx_Bits + AWGN_Power;

        % Decide whether the received bit is 1 or 0 with threshold 0.5
        Rx_Bits = Rx_Bits > 0.5;

        % Calculate BER Comparing between transmitted and received signals
        BER = [BER biterr(Tx_Bits, Rx_Bits)];

    end

    % Plot SNR against BER on a logarithmic scale Y-axis
    semilogy([SNR_Begin:SNR_Step:SNR_End], BER);
    ylabel('BER');
    xlabel('SNR (dB)');
    grid;
end

% Defining local function to calculate AWGN
function NoisePower = Gen_AWGN(Tx_Bits, SNR)
    % Calculating transmitted signal power
    Ptx = mean(Tx_Bits.^2);

    % Calculate AWGN power
    NoisePower = sqrt(Ptx/(2*SNR)) * [randn(size(Tx_Bits)) + 1j * randn(size(Tx_Bits))];

end