PAM汇报——

%需要设置的参数：
%       path:图像路径
%       Rs:发送信号的波特率
%       EsN0：平均符号能量与高斯白噪声功率的比值（单位：dB）

clear;close all;
path = 'cameraman.tif';
Rs = 1000;
EsN0 = 8;

%image to binary sequence
img = imread(path);
[img_seq,height,width] = img2seq(img);

%Hamming
hamming_seq = hamming(img_seq);

%mod & awgn & demod
[send_seq,]=pam4_send(img_seq,Rs,EsN0);
rev_seq=pam4_rev(send_seq,Rs);
    %Hamming
[send_seq_ham,] = pam4_send(hamming_seq,Rs,EsN0);
rev_seq_ham = pam4_rev(send_seq_ham,Rs);

%DeHamming
rev_seq_deham = dehamming(rev_seq_ham);

%performance evaluation
num_errors = sum(img_seq ~= rev_seq);   
BER = num_errors / length(img_seq); 
    %Hamming
num_errors_ham = sum(img_seq ~= rev_seq_deham(1:height*width*8));   
BER_ham = num_errors_ham / length(img_seq); 

%binary sequence to image
recover_image = seq2img(rev_seq,height,width);
figure(1)
% subplot(1,2,1);
imshow(recover_image);
title(sprintf('Es/N0=%ddB  Recovered Image  BER=%.2f%%',EsN0,BER*100));
    %Hamming
recover_image_ham = seq2img(rev_seq_deham,height,width);
figure(2);
% subplot(1,2,2);
imshow(recover_image_ham);
title(sprintf('Es/N0=%ddB Recovered Image -Hamming  BER=%.2f%%',EsN0,BER_ham*100))

%需要设置的参数：
%       path:图像路径
%       Rs:发送信号的波特率
%       EsN0：平均符号能量与高斯白噪声功率的比值（单位：dB）
close all;clear;
path = 'cameraman.tif';
Rs = 1000;

% image to binary sequence
img = imread(path);
[img_seq,height,width] = img2seq(img);
%Hamming
hamming_seq = hamming(img_seq);

%SpecialChannel
    %img_seq
rev_seq = img_seq;
sector_num = ceil(length(rev_seq)/16);
rev_seq = [rev_seq,zeros(sector_num*16-length(rev_seq))];
for index = 1:sector_num
    random_index = randi([1,16]);
    rev_seq((index-1)*16+random_index)=~rev_seq((index-1)*16+random_index);
end
num_errors_sp1 = sum(rev_seq ~= img_seq);   
BER_SpecialChannel1 = num_errors_sp1 / length(img_seq); 
    %Hamming
hamming_seq_sp = hamming_seq;
jie = length(hamming_seq)/16;
for index = 1:jie
    random_index = randi([1,16]);
    hamming_seq_sp((index-1)*16+random_index)=~hamming_seq_sp((index-1)*16+random_index);
end
num_errors_sp2 = sum(hamming_seq ~= hamming_seq_sp); 
BER_SpecialChannel2 = num_errors_sp2 / length(hamming_seq); 

%DeHamming
rev_seq_deham = dehamming(hamming_seq);
rev_seq_deham_sp = dehamming(hamming_seq_sp);

 %performance evaluation
num_errors = sum(img_seq ~= rev_seq(1:height*width*8));  
BER = num_errors / length(img_seq); 
    %Hamming No noise
num_errors_ham = sum(img_seq ~= rev_seq_deham(1:height*width*8));   
BER_ham = num_errors_ham / length(img_seq); 
    %Hamming Special Channel
num_errors_ham_sp = sum(img_seq ~= rev_seq_deham_sp(1:height*width*8)); 
BER_ham_sp = num_errors_ham_sp / length(img_seq);


%binary sequence to image
recover_image = seq2img(rev_seq,height,width);
figure(1);
imshow(recover_image);
title(sprintf('Recovered Image  BER=%.4f',BER))
    %Hamming No noise
recover_image_ham = seq2img(rev_seq_deham,height,width);
figure(2);
imshow(recover_image_ham);
title('Recovered Image -Hamming')
    %Hamming Special Channel
recover_image_ham_sp = seq2img(rev_seq_deham_sp,height,width);
figure(3);
imshow(recover_image_ham_sp);
title(sprintf('Recovered Image -Hamming  BER=%.4f',BER_ham_sp))

%函数说明
%   功能：错误位置判断
%参数说明
%   输入参数
%       seq:16位二进制序列
%   输出参数
%       answer:发生错误的位置（若为0则说明无错误或0000位出现错误，若为1说明第2比特出现错误）

function [answer] = check(seq)
answer = 0;
if mod(sum(seq(2:2:16)),2)==1
    answer = answer + 1;
end
if mod(sum(seq(3:4:15))+sum(seq(4:4:16)),2)==1
    answer = answer + 2;
end
if mod(sum(seq(5:8))+sum(seq(13:16)),2)==1
    answer = answer + 4;
end
if mod(sum(seq(9:16)),2)==1
    answer = answer + 8;
end

%函数说明
%   功能：(15,11)汉明编码收端
%参数说明
%   输入参数
%       rev_seq:接收到的二进制序列
%   输出参数
%       cor_seq:纠错后的二进制序列

function [cor_se] = dehamming(rev_seq)
sector_num = length(rev_seq)/16;
cor_se = zeros(1,sector_num*11);
for i = 1:sector_num
    index_old = (i-1)*16;
    index_new = (i-1)*11;
    wrong_bit = check(rev_seq(index_old+1:index_old+16));
    if wrong_bit
        rev_seq(index_old+wrong_bit+1) = ~rev_seq(index_old+wrong_bit+1);
    end
    cor_se(index_new+1) = rev_seq(index_old+4);
    cor_se(index_new+2:index_new+4) = rev_seq(index_old+6:index_old+8);
    cor_se(index_new+5:index_new+11) = rev_seq(index_old+10:index_old+16);
end

%函数说明
%   功能：(15,11)汉明编码发端
%参数说明
%   输入参数
%       original_seq:原始二进制序列
%   输出参数
%       hamming_seq:纠错位后的二进制序列

function [hamming_seq] = hamming(original_seq)
len = length(original_seq);
sector_num = ceil(len/11);
len_pad = sector_num*11;
pad_seq = [original_seq,zeros(1,len_pad-len)];
hamming_seq = zeros(1,sector_num*16);
for i = 1:sector_num
    index_old = (i-1)*11;
    index_new = (i-1)*16;
    hamming_seq(index_new+4) = pad_seq(index_old+1);
    hamming_seq(index_new+6:index_new+8) = pad_seq(index_old+2:index_old+4);
    hamming_seq(index_new+10:index_new+16) = pad_seq(index_old+5:index_old+11);
    hamming_seq(index_new+2) = mod(pad_seq(index_old+1)+pad_seq(index_old+2)+pad_seq(index_old+4)+pad_seq(index_old+5)+pad_seq(index_old+7)++pad_seq(index_old+9)++pad_seq(index_old+11),2);
    hamming_seq(index_new+3) = mod(pad_seq(index_old+1)+pad_seq(index_old+3)+pad_seq(index_old+4)+pad_seq(index_old+6)+pad_seq(index_old+7)+pad_seq(index_old+10)+pad_seq(index_old+11),2);
    hamming_seq(index_new+5) = mod(sum(pad_seq(index_old+2:index_old+4))+sum(pad_seq(index_old+8:index_old+11)),2);
    hamming_seq(index_new+9) = mod(sum(pad_seq(index_old+5:index_old+11)),2);
    hamming_seq(index_new+1) = mod(sum(hamming_seq(index_new+1:index_new+16)),2);
end

%函数说明
%   功能：将图像转换为二进制序列
%参数说明
%   输入参数
%       img:图像
%   输出参数
%       image_seq：二进制序列
%       height:图像的高度
%       width:图像的宽度

function [image_seq,height,width] = img2seq(img)
img_bin = dec2bin(img(:))';
image_seq = double(char(img_bin(:)')) - '0';
[height,width] = size(img);

%函数说明
%   功能：将二进制序列转化为图像
%参数说明
%   输入参数
%       rev_seq：二进制序列
%       height:图像的高度
%       width:图像的宽度
%   输出参数
%       rev_image：图像

function [recover_image] = seq2img(rev_seq,height,width)
new_length = height*width;
new_array = zeros(1, new_length);
for i = 1:new_length
    start_index = (i - 1) * 8 + 1;
    end_index = i * 8;
    new_array(i) = sum(rev_seq(start_index:end_index) .* (2 .^ [7 6 5 4 3 2 1 0]));
end
recover_image = uint8(reshape(new_array,height,width));