How can I put three different tau_rms in this code and draw them in one picture? (each tau_rms = 5*10^(-9), 30*10^(-9), 80*10^(-9), when SNR_MMSE is same as 30.)

No_PKT = 3000;                          % Number of packets for simulation
NSYM_PKT = 50;                          % Number of OFDM symbols in a packet for information data
FFT_SIZE = 64;                          % FFT size
BW = 20 * 10^(6);                       % System bandwidth, 20MHz, fixed
Ts = 1/BW;                              % Sampling interval in second unit
GI_LEN = 16;                            % Guard interval in Ts unit, fixed
subcarrier_spacing = 1/(FFT_SIZE * Ts); % Subcarrier spacing in Hz unit
N_data_subcarrier = 48;                 % Number of data subcarriers, fixed
N_pilot_subcarrier = 4;                 % Number of pilot subcarriers, fixed
pilot = [1 1 -1 1];                     % pilot symbols
modulation = '16QAM';                    % BPSK, QPSK, 16QAM, 64QAM
%===================================== Channel Environments ======================================
Channel_type = 'Rayleigh';             % 'Rayleigh' for Rayleigh channel and 'AWGN' for AWGN channel
Ch_est_mode = 'LS';                  % 'Perfect' for perfect channel estimation, 'MMSE', 'LS'                          
%============================= MMSE filter parameters ==============================
SNR_MMSE = 30;                         % SNR for MMSE filter in dB
beta = 1;                              % beta = E[x^2] * E[1/x^2]
tau_rms = 100 * 10^(-9);                % rms delay for MMSE filter in second unit  
%=================================================================================== 
SNR = [10: 2: 30];                     % SNR or Es/No for simulation
switch Channel_type
    case 'AWGN'
        No_Path = 1;
        PATH_DELAY = 0;                   % Relative delay in nano second unit
        PATH_GAIN = 0;                    % in dB        
    case 'Rayleigh'
        No_Path = 4;                             % Number of multi-paths
        PATH_DELAY = [0, 50, 200, 350];          % Relative delays in nano second unit
        PATH_GAIN = [0, -5.4, -10.3, -17.6];     % Relative gains in dB unit, 33ns 
        PATH_DELAY = round( PATH_DELAY * 10^(-9) / Ts); % Relative delays in Ts unit
end
switch modulation
    case 'BPSK'
        Mod_level = 1;
        normalize_factor = 1;
        
    case 'QPSK'
        Mod_level = 2;
        normalize_factor = sqrt(2);
        
    case '16QAM'
        Mod_level = 4;
        normalize_factor = sqrt(10);
        
    case '64QAM'
        Mod_level = 6;
        normalize_factor = sqrt(42);       
end
         
% MMSE filter generation based on exponential delay profile models
[MMSE_filter] = MMSE( SNR_MMSE, tau_rms, subcarrier_spacing, beta );
[preamble ifft_input_LTS ] = preamble_gen( FFT_SIZE );  % preamble generation
length_preamble = length(preamble);
for isnr = 1 : length(SNR)             % loop for SNR or Es/No
    
    Es = 10 ^ ( SNR(isnr) / 10 );      % symbol energe in linear scale
    
    seed = 1;
    randn('seed',seed);
    
    bit_err_total = 0;   
    
    for ifn = 1 : No_PKT                % loop for packet
      
        data = randn(1, N_data_subcarrier * NSYM_PKT * Mod_level) > 0; % binary data generation for each packet
        % symbol mapping and frame formating by modulation level
        [ifft_input] = symbol_mapping( data, pilot, FFT_SIZE, N_data_subcarrier, NSYM_PKT, Mod_level, normalize_factor );       
        % Inverse FFT
        [ifft_sig] = inverse_fft( ifft_input, FFT_SIZE, NSYM_PKT );
        
        % Guard insertion and parallel to serial conversion
        [tx_sig] = guard_insertion( ifft_sig, FFT_SIZE, NSYM_PKT, GI_LEN );
        
        tx_sig = [ preamble tx_sig ]; %cascading preamble and ofdm signals
        
        % Generating fading signals
        [fade] = fading_gen( Channel_type, PATH_GAIN, PATH_DELAY );
        % Generating a received signal 
        [rx_sig, rx_sig_no_noise] = rx_sig_gen( tx_sig, fade, Es, FFT_SIZE, GI_LEN, NSYM_PKT, length_preamble, Ts );
  
        % Guard removal
        [guard_removed_sig, guard_removed_sig_no_noise, guard_removed_LTS] = guard_removal( rx_sig, rx_sig_no_noise, FFT_SIZE, NSYM_PKT, GI_LEN );            
        % FFT at the receiver
        [fft_sig, fft_sig_no_noise, fft_LTS] = forward_fft( guard_removed_sig, guard_removed_sig_no_noise, guard_removed_LTS, FFT_SIZE, NSYM_PKT );
     
        % Channel estimation
        [est_channel] = channel_est( fft_LTS, ifft_input_LTS, fft_sig_no_noise, ifft_input, Ch_est_mode, MMSE_filter, NSYM_PKT );
  
        % Channel compensation and symbol demapping
        [est_data] = symbol_demapping( fft_sig, est_channel, NSYM_PKT, Mod_level, normalize_factor );
        
        % Counting the number of error bits
        bit_err = sum(data ~=est_data);
        
        bit_err_total = bit_err_total + bit_err;
        
        if  mod(ifn, 10) == 0
            Accumulated_BER = bit_err_total / ( N_data_subcarrier * NSYM_PKT * Mod_level * ifn )
        end  
    end   
    BER(isnr) = bit_err_total / (N_data_subcarrier * NSYM_PKT * Mod_level * No_PKT) 
end
semilogy(SNR,BER,'r-o');
xlabel('Es/No (dB)');
ylabel('BER');
axis([10 30 10^(-4) 10^(0)]);
grid on

Answer 1

[Jeffrey Clark]

@zoopzdd, as in most cases where you want to apply multiple values in code methods invoked that aren't intended to receive multiple values in one call, you need to:

1. change the variable to a vector of the values; and
2. find where/how the variable is currently used and decide where/how you can loop over the vector values; and
3. if this results in generating more outputs than you currently accumulate how will you keep track of the new ones or will a max/min/mean etc be used.

So maybe 1:

tau_rms = [5,30,80] * 10^(-9); % rms delays for MMSE filter in second unit

maybe 2 and 3:

% MMSE filter generation based on exponential delay profile models
[preamble ifft_input_LTS ] = preamble_gen( FFT_SIZE );  % preamble generation
length_preamble = length(preamble);
BER = zeros(length(SNR),length(tau_rms)); % predefine outputs for known lengths
figure % use one for all plots
for itau = 1 : length(tau_rms)         % loop over tau
    [MMSE_filter] = MMSE( SNR_MMSE, tau_rms(itau), subcarrier_spacing, beta );
    
    for isnr = 1 : length(SNR)         % loop for SNR or Es/No
        % ...
        BER(isnr,itau) = bit_err_total / (N_data_subcarrier * NSYM_PKT * Mod_level * No_PKT);
    end
    semilogy(SNR,BER(:,itau),'-o'); % use auto color assignment within one plot
    hold on
end
% ...