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标题: OFDM的仿真程序。 [打印本页]

作者: House 时间: 2020-4-20 14:40
标题: OFDM的仿真程序。
本帖最后由 House 于 2020-4-21 14:03 编辑

OFDM的仿真程序，并且包括详细的WORD说明。有误码率和各种性能分析的做图程序。有需要的可以看看。

%a_run_design.m文件
setup                               %系统设置
QAM                               %QAM调制方式
OFDM                               %OFDM调制方式
Analysis                               %QAM和OFDM两种方式对比

1setup          %初始化部分
% setup
disp(' '), disp('------------------------------------------------------------')
disp('Simulation Setup')

% OFDM Setup -----------------------------------------------------------
fft_size = 128             % should be a power of 2 for fast computation
                              % more points = more time domain samples (smoother & more cycles)
num_carriers = 32       % should be <= fft_size/4
                              % number of carriers used for each data chunk
% new var - denotes even spacing or variations of carriers among fft points
input_type = 2;
% 1 = test input
      test_input_type = 1;
      % 1 = bit specified (binary)
            binary_data = [0 1 0 1 0 1 0 1];
      % 2 = random data stream (samples in the range of 0-255)
            num_symbols = 9;
      % 3 = sinusoidal
            frequency = 2;
            num_samples = 50;
% 2 = external file input
      file_name = 'shortest.wav';             % Name of input file
      file_input_type = 3;
            % 1 = binary (not implemented)
            % 2 = text                                     % Demo file:  'text.txt'
            % 3 = sound                               % Demo files: 'shortest.wav' & 'shorter.wav'
            % 4 = image (not implemented)

% QAM Setup ------------------------------------------------------------
do_QAM = 1;             % (1=on, 0=off)
QAM_periods = 10;       % defines the number of periods per QAM Symbos (1=2*pi)

% Channel Simulation Parameters --------------------------------------------
channel_on = 1;             % 1=on, 0=off
clip_level = 1.0;             % 0.0 - 1.0 (0-100%)
      % Max magnitude of the signal is 'clip_level' times the full magnitude of the signal
noise_level = 0.0;       % 0.0 - 1.0 (0-100%)
      % Magnitude of noise is 'noise_level' times the magnitude of the signal
% Multipath Channel Simulation
      % Good defaults when fft_size = 128 and num_carriers = 32:
      %       d1=6; a1=0.30; d2=10; a2=0.25
      d1 = 6;             % delay in units
      a1 = 0.30;       % attenuation factor - multipath signal is x% of size or original signal
      d2 = 10;             % delay for second multipath signal
      a2 = 0.25;       % attenuation factor for second multipath signal

% ****************** TEST INPUT SETUP - DO NOT MODIFY **************************
if input_type == 1
      if test_input_type == 1
            %specify BINARY input bit-by-bit
            data_in = binary_data;
      end
      if test_input_type == 2
            %random input defined by parameters
            num_levels = 255;             %number of possible levels of a symbol
                                             %must be integer between 1-255
            data_samples = round(rand(1,num_symbols)*(num_levels-1));
            data_in = zeros(1,8*length(data_samples));
            for i = 1:length(data_samples)
                     data_in(1 + (i-1)*8: (i-1)*8 + 8) = eight2bin(data_samples(i));
            end
      end
      if test_input_type == 3
            %data stream represents sine wave samples
            t = linspace(0,1,num_symbols);       %evenly space number of samples
            %take 8-bit samples of sine wave
            data_samples = round(127.5*sin(frequency*2*pi*t) +127.5);
            data_in = zeros(1,8*length(data_samples));
            for i = 1:length(data_samples)
                     data_in(1 + (i-1)*8: (i-1)*8 + 8) = eight2bin(data_samples(i));
            end
      end
end

already_made_noise = 0;       % initialization (don't change)

2、QAM.m
% QAM.m compares OFDM (multicarrier) to multi-level QAM (single carrier)
% when they transmit the same # of bits in a given time period

read             % read data for QAM - does not affect OFDM
data_in_pol = bin2pol(data_in);             % Converts binary data to polar data

% check to see if num_carriers is a power of 2
is_pow_2 = num_carriers;
temp_do_QAM = 0;
if is_pow_2 ~= 2
      while temp_do_QAM == 0
            temp_do_QAM = rem(is_pow_2,2);
            is_pow_2 = is_pow_2/2;
            if is_pow_2 == 2
                     temp_do_QAM = -99;             % it is a power of 2 -> can do QAM
            end
      end
else
      temp_do_QAM = -99;       % 2 is a power of 2
end
if temp_do_QAM ~= -99
      do_QAM = 0;       % don't do it if it's not possible
      disp(' '),disp('ERROR: Cannot run QAM because num_carriers is not valid.')
      disp('    Please see "setup.m" for details.')
end

if do_QAM == 1
      tic       % Start stopwatch to calculate how long QAM simulation takes

      disp(' '), disp('------------------------------------------------------------')
      disp('QAM simulation'), disp('Transmitting')

      % Pad with zeros so data can be divided evenly
      data_length = length(data_in_pol);
      r = rem(data_length,num_carriers);
      if r ~= 0
            for i = 1:num_carriers-r
                     data_in_pol(data_length+i) = 0;       %pad input with zeros to complete last data set
            end                                                       %speed improve possible
      end
      data_length = length(data_in_pol);             %update after padding

      num_OFDM_symbols = ceil(data_length / (2*num_carriers));
      % num QAM symbols that represent equal amount of data to one OFDM symbol
      num_QAM_symbols = num_carriers / 2;
      % num samples per QAM symbol
      num_symbol_samples = fft_size / num_QAM_symbols;

      % convert polar data [-1, 1] to 4 level data [-3, -1, 1, 3]
      data_in_4 = zeros(1,data_length/2);
      for i = 1:2:data_length
            data_in_4(i - (i-1)/2) = data_in_pol(i)*2 + data_in_pol(i+1);
      end

      % define sample points between 0 and 2*pi
      ts = linspace(0, 2*pi*QAM_periods, num_symbol_samples+1);

      % Generate 16-QAM data
      % total length of 16-QAM transmission
      tx_length = num_OFDM_symbols * num_QAM_symbols * num_symbol_samples;
      QAM_tx_data = zeros(1,tx_length);
      for i = 1:2:data_length/2
            for k = 1:num_symbol_samples
                     QAM_tx_data(k+((i-1)/2)*num_symbol_samples) = data_in_4(i)*cos(ts(k)) + data_in_4(i+1)*sin(ts(k));
            end
      end

      % Do channel simulation on QAM data
      xmit = QAM_tx_data;             % ch uses 'xmit' data and returns 'recv'
      ch
      QAM_rx_data = recv;             % save QAM data after channel
      clear recv                               % remove 'recv' so it won't interfere with OFDM
      clear xmit                               % remove 'xmit' so it won't interfere with OFDM

      disp('Receiving')                      % Recover Binary data (Decode QAM)
      cos_temp = zeros(1,num_symbol_samples);             %
      sin_temp = cos_temp;                                     %
      xxx = zeros(1,data_length/4);                               % Initialize to zeros for speed
      yyy = xxx;                                                             %
      QAM_data_out_4 = zeros(1,data_length/2);             %

      for i = 1:2:data_length/2       % "cheating"
            for k = 1:num_symbol_samples
                     % multiply by carriers to produce high frequency term and original data
                     cos_temp(k) = QAM_rx_data(k+((i-1)/2)*num_symbol_samples) * cos(ts(k));
                     sin_temp(k) = QAM_rx_data(k+((i-1)/2)*num_symbol_samples) * sin(ts(k));
            end
            % LPF and decide - we will do very simple LPF by averaging
            xxx(1+(i-1)/2) = mean(cos_temp);
            yyy(1+(i-1)/2) = mean(sin_temp);
            % Reconstruct data in serial form
            QAM_data_out_4(i) = xxx(1+(i-1)/2);
            QAM_data_out_4(i+1) = yyy(1+(i-1)/2);
      end

      % Make decision between [-3, -1, 1, 3]
      for i = 1:data_length/2
            if QAM_data_out_4(i) >= 1, QAM_data_out_4(i) = 3;
            elseif QAM_data_out_4(i) >= 0, QAM_data_out_4(i) = 1;
            elseif QAM_data_out_4(i) >= -1, QAM_data_out_4(i) = -1;
            else QAM_data_out_4(i) = -3;
            end
      end

      % Convert 4 level data [-3, -1, 1, 3] back to polar data [-1, 1]
      QAM_data_out_pol = zeros(1,data_length);       % "cheating"
      for i = 1:2:data_length
            switch QAM_data_out_4(1 + (i-1)/2)
                     case -3
                              QAM_data_out_pol(i) = -1;
                              QAM_data_out_pol(i+1) = -1;
                     case -1
                              QAM_data_out_pol(i) = -1;
                              QAM_data_out_pol(i+1) = 1;
                     case 1
                              QAM_data_out_pol(i) = 1;
                              QAM_data_out_pol(i+1) = -1;
                     case 3
                              QAM_data_out_pol(i) = 1;
                              QAM_data_out_pol(i+1) = 1;
                     otherwise
                              disp('Error detected in switch statment - This should not be happening.');
            end
      end
      QAM_data_out = pol2bin(QAM_data_out_pol);       % convert back to binary

      % Stop stopwatch to calculate how long QAM simulation takes
      QAM_simulation_time = toc;
      if QAM_simulation_time > 60
            disp(strcat('Time for QAM simulation=', num2str(QAM_simulation_time/60), ' minutes.'));
      else
            disp(strcat('Time for QAM simulation=', num2str(QAM_simulation_time), ' seconds.'));
      end
end

3 % Run OFDM simulation
tic       % Start stopwatch to calculate how long QAM simulation takes
disp(' '),disp('------------------------------------------------------------')
disp('OFDM Simulation')
tx
ch
rx
% Stop stopwatch to calculate how long QAM simulation takes
OFDM_simulation_time = toc;
if OFDM_simulation_time > 60
      disp(strcat('Time for OFDM simulation=', num2str(OFDM_simulation_time/60), ' minutes.'));
else
      disp(strcat('Time for OFDM simulation=', num2str(OFDM_simulation_time), ' seconds.'));
end

3.1发送
% tx
disp('Transmitting')
read                         %read original data
data_in_pol = bin2pol(data_in);          % Converts binary data to polar data
tx_chunk                      %convert polar data into chunks.

% perform ifft to create time domain waveform representing data
td_sets = zeros(num_chunks,fft_size);
for i = 1:num_chunks
      td_sets(i,1:fft_size) = real(ifft(spaced_chunks(i,1:fft_size)));
end

tx_dechunk    % Construct signal to transmit by placing time domain sets in series

3.1.1 % tx_chunk %双极性数组转化成OFDM字符串
data_length = length(data_in_pol)                                  %number of symbols in original input
num_carriers
num_chunks = ceil(data_length/(2*num_carriers))       %2 data on each carrier (real and imaginary)
r = rem(data_length,2*num_carriers)
if r ~= 0
      for i = 1:num_carriers*2-r
            data_in_pol(data_length+i) = 0;       %pad input with zeros to complete last data set
      end                                                       %speed improve possible
end

% break data into chunks
chunks = zeros(num_chunks,num_carriers);       % for speed
for i = 1:num_chunks
      % *********************chunk done
      for k = 1:num_carriers
            chunks(i,k) = data_in_pol(2*num_carriers*(i-1)+k) + data_in_pol(2*num_carriers*(i-1)+k+num_carriers)*j;
      end
end

chunks
% Padding chunks with zeros so num_carriers and fft_size are compatible
% Once compatible, further spacing is simplified
num_desired_carriers = num_carriers;
num_zeros = 0;
thinking = 1;
while thinking == 1 % Continue if num_carriers and fft_size are not compatible
      if rem(fft_size/2,num_desired_carriers) == 0
            thinking = 0;
      else
            num_desired_carriers = num_desired_carriers + 1;
            num_zeros = num_zeros + 1;
      end
end

padded_chunks = zeros(num_chunks,num_carriers + num_zeros); % for speed
padded_chunks(1:num_chunks,num_zeros + 1:num_carriers + num_zeros) = chunks;

%compute zeros_between
zeros_between = ((fft_size/2) - (num_carriers + num_zeros))/(num_carriers + num_zeros);

spaced_chunks = zeros(num_chunks,fft_size); % for speed - extra room for folding later
%add zeros_between
i = 1;
for k = zeros_between +1:zeros_between +1:fft_size/2
      spaced_chunks(1:num_chunks,k) = padded_chunks(1:num_chunks,i);
      i = i+1;
end

% folding data to produce an odd function for ifft input
for i = 1:num_chunks
      % Note: index = 1 is actually DC freq for ifft -> it does not get copied over y-axis
      spaced_chunks(i,fft_size:-1:fft_size/2+2) = conj(spaced_chunks(i,2:fft_size/2));
end

3.1.2 tx_dechunk
% tx_dechunk

% Construct signal to transmit by placing time domain sets in series
xmit = zeros(1,num_chunks*fft_size);
for i = 1:num_chunks
      for k = 1:fft_size
            xmit(k + (i-1)*fft_size) = td_sets(i,k);
      end
end

3.2 %ch.m
% ch
recv = xmit;       % channel is applied to recv, don't modify transmitted data
if channel_on == 1
      disp('Simulating Channel')
      norm_factor = max(abs(recv));       % Normalize all data before applying
      recv = (1/norm_factor) * recv;       % channel for a fair comparison
      ch_clipping                   %clipp data
      ch_multipath                   %
      ch_noise                      %
      recv = norm_factor * recv;             % Restore data magnitude for proper decoding
end

3.2.1 %ch_clipping.m
% ch_clipping
for i = 1:length(recv)
      if recv(i) > clip_level
            recv(i) = clip_level;
      end
      if recv(i) < -clip_level
            recv(i) = -clip_level;
      end
end

3.2.2 % ch_multipath                % 产生多经的方法
copy1=zeros(size(recv));
for i=1+d1: length(recv)
      copy1(i)=a1*recv(i-d1);
end
copy2=zeros(size(recv));
for i=1+d2: length(recv)
      copy2(i)=a2*recv(i-d2);
end
recv=recv+copy1+copy2;

3.2.3、%ch_noise                   %施加信道噪声
% ch_noise (operate on recv)
% random noise defined by noise_level amplitude
if already_made_noise == 0       % only generate once and use for both QAM and OFDM
      noise = (rand(1,length(recv))-0.5)*2*noise_level;
      already_made_noise = 1;
end
recv = recv + noise;

3.3 %rx.m                      %接收程序
% rx
disp('Receiving')
rx_chunk

% perform fft to recover original data from time domain sets
recv_spaced_chunks = zeros(num_chunks,fft_size);
for i = 1:num_chunks
      recv_spaced_chunks(i,1: fft_size) = fft(recv_td_sets(i,1: fft_size));
      % Note: 'round()' gets rid of small numerical error in Matlab but a threshold will be needed for a practical system
      % 2001-4-17 -- Got rid of 'round()' to do decoding more intelligently
end
rx_dechunk
output = pol2bin(output);       % Converts polar to binary
write

3.3.1 %rx_chunk.m
% rx_chunk
% break received signal into parellel sets for demodulation
recv_td_sets = zeros(num_chunks,fft_size);
for i = 1:num_chunks
      for k = 1: fft_size
            recv_td_sets(i,k) = recv(k + (i-1)*fft_size);
      end
end

3.3.2 % rx_dechunk          %并串转换
% rx_dechunk
% take out zeros_between from recv_spaced_chunks --> recv_padded_chunks
recv_padded_chunks = zeros(num_chunks, num_carriers+num_zeros);
i = 1;
for k = zeros_between +1:zeros_between +1:fft_size/2
      recv_padded_chunks(1:num_chunks,i) = recv_spaced_chunks(1:num_chunks,k);
      i = i+1;
end

% take out num_zeros from padded chunks --> recv_chunks
recv_chunks = zeros(num_chunks, num_carriers);
recv_chunks = recv_padded_chunks(1:num_chunks, num_zeros+1:num_carriers+num_zeros);

% Recover bit stream by placing reconstructed frequency domain data in series
recv_dechunked = zeros(1, num_chunks*num_carriers);
for i = 1:num_chunks
      for k = 1:num_carriers
            recv_dechunked(k + (i-1)*num_carriers*2) = real(recv_chunks(i,k));
            recv_dechunked(k + (i-1)*num_carriers*2 + num_carriers) = imag(recv_chunks(i,k));
      end
end

% take out trailing zeros from output --> output
output_analog = recv_dechunked(1:data_length);
output = sign(output_analog);

3.3.3 %write             %save received data
% write
% ******************TEST OUTPUT*********************************
if input_type == 1
      if test_input_type == 1
            %already binary - do nothing
      end

      if (test_input_type == 2) | (test_input_type == 3)
            %random input    OR    sine wave samples
            output_samples = zeros(1,floor(length(output)/8));  %extra zeros are not original data
            for i = 1:length(output_samples)
                     output_samples(i) = bin2eight(output(1 + (i-1)*8: (i-1)*8 + 8));
            end
            if do_QAM == 1
                     QAM_output_samples = zeros(1,floor(length(QAM_data_out)/8));
                     for i = 1:length(QAM_output_samples)
                              QAM_output_samples(i) = bin2eight(QAM_data_out(1 + (i-1)*8: (i-1)*8 + 8));
                     end
            end
      end
end

% ******************FILE OUTPUT*********************************
if input_type == 2

      if file_input_type == 1
            %binary file output - not implemented
      end

      if file_input_type == 2
            %text file output
            output_samples = zeros(1,floor(length(output)/8));  %extra zeros are not original data
            for i = 1:length(output_samples)
                     output_samples(i) = bin2eight(output(1 + (i-1)*8: (i-1)*8 + 8));
            end
            file = fopen('OFDM_text_out.txt','wt+');
            fwrite(file,output_samples,'char');
            fclose(file);

            if do_QAM == 1
                     %extra zeros are not original data
                     QAM_output_samples = zeros(1,floor(length(QAM_data_out)/8));

for i = 1:length(QAM_output_samples)
                              QAM_output_samples(i) = bin2eight(QAM_data_out(1 + (i-1)*8: (i-1)*8 + 8));
                     end
                     file = fopen('QAM_text_out.txt','wt+');
                     fwrite(file,QAM_output_samples,'char');
                     fclose(file);
            end
      end

      if file_input_type == 3
            output_samples_big = zeros(1,floor(length(output)/8));  %extra zeros are not original data
            for i = 1:length(output_samples_big)
                     output_samples_big(i) = bin2eight(output(1 + (i-1)*8: (i-1)*8 + 8));
            end
            %convert dynamic range from 0:255 to -1:1
            output_samples = (output_samples_big-127)/128;
            %sound file output
            wavwrite(output_samples, 11025, 8, 'OFDM_out.wav')
            if do_QAM == 1
                     QAM_data_out_big = zeros(1,floor(length(QAM_data_out)/8));
                     for i = 1:length(QAM_data_out_big)
                              QAM_data_out_big(i) = bin2eight(QAM_data_out(1 + (i-1)*8: (i-1)*8 + 8));
                     end
                     %convert dynamic range from 0:255 to -1: 1
                     QAM_output_samples = (QAM_data_out_big-127)/128;
                     %sound file output
                     wavwrite(QAM_output_samples, 11025, 8, 'QAM_out.wav')
            end
      end

      if file_input_type == 4
            %image file output - not implemented
      end
end

4、%Analysis.m
% Analysis
disp(' '), disp('------------------------------------------------------------')
disp('Preparing Analysis')
figure(1), clf
if (input_type == 1) & (test_input_type == 1)
      subplot(221), stem(data_in), title('OFDM Binary Input Data');
      subplot(223), stem(output), title('OFDM Recovered Binary Data')
else
      subplot(221), plot(data_samples), title('OFDM Symbol Input Data');
      subplot(223), plot(output_samples), title('OFDM Recovered Symbols');
end
subplot(222), plot(xmit), title('Transmitted OFDM');
subplot(224), plot(recv), title('Received OFDM');

% dig_x_axis = (1:length(QAM_tx_data))/length(QAM_tx_data);
%       figure(4), clf, subplot(212)
%       freq_data = abs(fft(QAM_rx_data));
%       L = length(freq_data)/2;

dig_x_axis = (1: length(xmit))/length(xmit);
figure(2), clf

if channel_on ==1
      num = [1, zeros(1, d1-1), a1, zeros(1, d2-d1-1), a2];
      den = [1];
      [H, W] = freqz(num, den, 512);
      mag = 20*log10(abs(H));
      phase = angle(H) * 180/pi;

      subplot(313)
      freq_data = abs(fft(recv));
      L = length(freq_data)/2;
      plot(dig_x_axis(1: L), freq_data(1: L))
      xlabel('FFT of Received OFDM')
      axis_temp = axis;

      subplot(311),
      freq_data = abs(fft(xmit));
      plot(dig_x_axis(1: L), freq_data(1: L)), axis(axis_temp)
      title('FFT of Transmitted OFDM')

      subplot(312)
      plot(W/(2*pi),mag),
      ylabel('Channel Magnitude Response')
else
      subplot(212)
      freq_data = abs(fft(recv));
      L = length(freq_data)/2;
      plot(dig_x_axis(1: L), freq_data(1: L))
      xlabel('FFT of Received OFDM')
      axis_temp = axis;

      subplot(211),
      freq_data = abs(fft(xmit));
      plot(dig_x_axis(1: L), freq_data(1: L)), axis(axis_temp)
      title('FFT of Transmitted OFDM')
end

% if file_input_type == 4
%       figure(5)
%       subplot(211)
%       image(data_in);
%       colormap(map);
%       subplot(212)
%       image(output);
%       colormap(map);
% end

if do_QAM == 1       % analyze if QAM was done

      figure(3), clf
      if (input_type == 1) & (test_input_type == 1)
            subplot(221), stem(data_in), title('QAM Binary Input Data');
            subplot(223), stem(QAM_data_out), title('QAM Recovered Binary Data')
      else
            subplot(221), plot(data_samples), title('QAM Symbol Input Data');
            subplot(223), plot(QAM_output_samples), title('QAM Recovered Symbols');
      end
      subplot(222), plot(QAM_tx_data), title('Transmitted QAM');
      subplot(224), plot(QAM_rx_data), title('Received QAM');

      dig_x_axis = (1: length(QAM_tx_data))/length(QAM_tx_data);
      figure(4), clf

      if channel_on ==1
            subplot(313)
            freq_data = abs(fft(QAM_rx_data));
            L = length(freq_data)/2;
            plot(dig_x_axis(1: L), freq_data(1: L))
            xlabel('FFT of Received QAM')
            axis_temp = axis;

            subplot(311),
            freq_data = abs(fft(QAM_tx_data));
               plot(dig_x_axis(1: L),freq_data(1: L)), axis(axis_temp)
            title('FFT of Transmitted QAM')

            subplot(312)
            plot(W/(2*pi),mag)
            ylabel('Channel Magnitude Response')
      else
            subplot(212)
            freq_data = abs(fft(QAM_rx_data));
            L = length(freq_data)/2;
            plot(dig_x_axis(1: L), freq_data(1: L))
            title('FFT of Received QAM')
            axis_temp = axis;

            subplot(211),
            freq_data = abs(fft(QAM_tx_data));
               plot(dig_x_axis(1: L),freq_data(1: L)), axis(axis_temp)
            title('FFT of Transmitted QAM')
      end

      % Plots the QAM Received Signal Constellation
      figure(5), clf, plot(xxx,yyy,'ro'), grid on, axis([-2.5 2.5 -2.5 2.5]), hold on

%       % Overlay plot of transmitted constellation
%       x_const = [-1.5 -0.5 0.5 1.5 -1.5 -0.5 0.5 1.5 -1.5 -0.5 0.5 1.5 -1.5 -0.5 0.5 1.5];
%       y_const = [-1.5 -1.5 -1.5 -1.5 -0.5 -0.5 -0.5 -0.5 0.5 0.5 0.5 0.5 1.5 1.5 1.5 1.5];
%       plot(x_const, y_const, 'b*')

      % Overlay of constellation boundarys
      x1 = [-2 -2]; x2 = [-1 -1]; x3 = [0 0]; x4 = [1 1]; x5 = [2 2]; x6 = [-2 2];
      y1 = [-2 -2]; y2 = [-1 -1]; y3 = [0 0]; y4 = [1 1]; y5 = [2 2]; y6 = [-2 2];
      plot(x1,y6), plot(x2,y6), plot(x3,y6), plot(x4,y6), plot(x5,y6)
      plot(x6,y1), plot(x6,y2), plot(x6,y3), plot(x6,y4), plot(x6,y5)

      hold off
      title('16-QAM Received Signal Constellation and Decision Boundarys')

      binary_err_bits_QAM = 0;
      for i = 1:length(data_in)
            err = abs(data_in(i)-QAM_data_out(i));
            if err > 0
                     binary_err_bits_QAM = binary_err_bits_QAM + 1;
            end
      end
      BER_QAM = 100 * binary_err_bits_QAM/data_length;
end

figure(6), clf
if channel_on == 1
      subplot(211), plot(W/(2*pi),mag),title('Channel Magnitude Response')
      xlabel('Digital Frequency'),ylabel('Magnitude in dB')
      subplot(212), plot(W/(2*pi),phase),title('Channel Phase Response')
      xlabel('Digital Frequency'),ylabel('Phase in Degrees')
else
      title('Channel is turned off - No frequency response to plot')
end

% Compare output to input and count errors
binary_err_bits_OFDM = 0;
for i = 1:length(data_in)
      err = abs(data_in(i)-output(i));
      if err > 0
            binary_err_bits_OFDM = binary_err_bits_OFDM +1;
      end
end
BER_OFDM = 100 * binary_err_bits_OFDM/data_length;
disp(strcat('OFDM: BER=', num2str(BER_OFDM,3), ' %'))
disp(strcat('    Number of error bits=', num2str(binary_err_bits_OFDM)))

if (do_QAM == 1)
      disp(strcat('QAM:  BER=', num2str(BER_QAM,3), ' %'))
      disp(strcat('    Number of error bits=', num2str(binary_err_bits_QAM)))
end

% Display text file before and after modulation
if (input_type == 2) & (file_input_type == 2)
      original_text_file = char(data_samples')
      if do_QAM ==1
            edit QAM_text_out.txt
      end
      edit OFDM_text_out.txt
end

% Listen to sounds
if (input_type == 2) & (file_input_type == 3)
      do_again = '1';
      while ( ~(isempty(do_again)) )
            disp(' ')
            disp('Press any key to hear the original sound'), pause
            sound(data_samples,11025)
            disp('Press any key to hear the sound after OFDM transmission'), pause
            sound(output_samples,11025)
            if do_QAM == 1
                     disp('Press any key to hear the sound after QAM transmission'), pause
                     sound(QAM_output_samples,11025)
            end
            do_again = '';
            do_again = input('Enter "1" to hear the sounds again or press "Return" to end  ', 's');
      end
end

作者: YNhhU 时间: 2020-4-20 16:03
有详细的WORD说明最好了，怕我看不懂。

作者: xuzwg 时间: 2020-4-21 13:55
看看楼主分享的OFDM的仿真程序。

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