fix_soft_1664qam24.m

stbc在2发2收

%  表示t2*r4系统,码率= 1;
%  运用<<<<<<软判决译码>>>>>>>
% 16qam 64qam
% 记住：这是定点仿真，小数点位置要相同才可以加，即，整数和整数加。（而整数又不可以超过Max_value～Min_value的值）
clear
clc

snr_min=0;
snr_max=30;
stepsize = 2.5;
%----------------量化参量-----------------------------%
Ofdm_bits = 10000;       %一个ofdm符号长度
Mod_type = 6;           %qam调制有三种情况(2=4qam,4=16qam,6=64qam);
Max_quantity_bits = 8;
Max_value = 2^(Max_quantity_bits-1);
Min_value = -Max_value;
Sub_max_value = 2^(Max_quantity_bits-2);
Sub_min_value = -Sub_max_value;

Max_add_value = 2^(2*Max_quantity_bits-1);
mult_flow_num = 0;
add_flow_num = 0;
%-------------全局参量--------------------------------%
Tx_num = 2;             %发送天线个数,这里仅仅是赋一个默认的初始值
Rx_num = 2;             %接收天线个数
Time_length = 2;        %进行正交编码的时隙长度,这里仅仅是赋一个默认的初始值(2 or 4)
Source_length = Tx_num*Ofdm_bits*Mod_type;  %信源输出码子个数(映射前)
pqam_length = Ofdm_bits*Mod_type;            %每根天线所需的码子个数(映射前)

sig_code = zeros(Tx_num,pqam_length);
sig_code = randint(Tx_num,pqam_length);

table16 = [1+j, 3+ j, 1+3j, 3+3j,...
        1-j, 1-3j, 3- j, 3-3j,...
        -1+j,-1+3j,-3+ j,-3+3j,...
        -1-j,-3- j,-1-3j,-3-3j];
table64 = [1+j, 3+ j, 1+3j, 3+3j, 7+1j, 5+ j, 7+3j, 5+3j, 1+7j, 3+7j, 1+5j, 3+5j, 7+7j, 5+7j, 7+5j, 5+5j,...
        1-j, 1-3j, 3- j, 3-3j, 1-7j, 1-5j, 3-7j, 3-5j, 7- j, 7-3j, 5- j, 5-3j, 7-7j, 7-5j, 5-7j, 5-5j,...
        -1+j,-1+3j,-3+ j,-3+3j,-1+7j,-1+5j,-3+7j,-3+5j,-7+ j,-7+3j,-5+ j,-5+3j,-7+7j,-7+5j,-5+7j,-5+5j,...
        -1-j,-3- j,-1-3j,-3-3j,-7- j,-5- j,-7-3j,-5-3j,-1-7j,-3-7j,-1-5j,-3-5j,-7-7j,-5-7j,-7-5j,-5-5j];
table16 = table16/sqrt(10);
table64 = table64/sqrt(42);
table16 = round(table16*Max_value)/Max_value;
table64 = round(table64*Max_value)/Max_value;
switch Mod_type
    case 4
        for i=1:Tx_num
            for n=1:Ofdm_bits
                table_index = sig_code(i,(n-1)*Mod_type+1)*8+sig_code(i,(n-1)*Mod_type+2)*4+...
                    sig_code(i,(n-1)*Mod_type+3)*2+sig_code(i,(n-1)*Mod_type+4);
                qam_code(i,n) = table16(table_index+1);
            end
        end
    case 6
        for i=1:Tx_num
            for n=1:Ofdm_bits
                table_index = sig_code(i,(n-1)*Mod_type+1)*32+sig_code(i,(n-1)*Mod_type+2)*16+...
                    sig_code(i,(n-1)*Mod_type+3)*8+sig_code(i,(n-1)*Mod_type+4)*4+...
                    sig_code(i,(n-1)*Mod_type+5)*2+sig_code(i,(n-1)*Mod_type+6);       
                qam_code(i,n) = table64(table_index+1);
            end
        end  
end

stbc_code = zeros(Time_length,Tx_num,Ofdm_bits);         %stbc 编码矩阵
for m=1:Tx_num            
    stbc_code(1,m,:) = qam_code(m,:); 
end
stbc_code(2,1,:) = -conj(qam_code(2,:));
stbc_code(2,2,:) = conj(qam_code(1,:)); 

ch_scale = sqrt(Tx_num);
stbc_code = stbc_code/ch_scale;

%-----------------------迭代开始 信噪比 由小到大------------------------%

iterative_length = 0;
table16 = table16*Max_value;
table64 = table64*Max_value;
table64 = fix(table64*128/138);
for snr_db_step =snr_min:stepsize:snr_max    % 信噪比从snr_min--snr_max
    iterative_length = iterative_length+1
    %------------(省略CP头和训练序列)上信道,乘性噪声------------------------%
    
    rec_code = zeros(Time_length,Rx_num,Ofdm_bits);
    channel_mul_noice = zeros(Tx_num,Rx_num,Ofdm_bits);
    ch_mul_noice = sqrt(0.5)*(randn(Tx_num,Rx_num,Ofdm_bits)+j*randn(Tx_num,Rx_num,Ofdm_bits));
    for n = 1:Time_length 
        for m = 1:Ofdm_bits
            rec_code(n,:,m) = stbc_code(n,1:Tx_num,m)*ch_mul_noice(1:Tx_num,1:Rx_num,m);
        end
    end
    
    %---------------------信号功率统计,加高斯白噪声----------------------------%
    sig_pante_pow = 0;
    for n = 1:Rx_num
        Agwn = sqrt(10^(-snr_db_step/10)/2)*(randn(Time_length,1,Ofdm_bits)+j*randn(Time_length,1,Ofdm_bits));
        rec_code(:,n,:) = rec_code(:,n,:) + Agwn;      
    end
    
    rec_code = rec_code*ch_scale;
    
    %%%%%%%%%%%%%%%%%%%%%%%%%% 定点仿真 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    
    %------------------------接收信号并进行stbc译码----------------------------%
    max_rec_code = max(max(max(max(real(rec_code),imag(rec_code)))));
    max_rec_code = fix(max_rec_code/fix(max_rec_code+0.5)*Max_value)/Max_value*fix(max_rec_code+0.5);
    rec_code = rec_code/max_rec_code;   % 信号归一化
    rec_code = fix(rec_code*Max_value);
    max_ch_noice = max(max(max(max(real(ch_mul_noice),imag(ch_mul_noice)))));
    max_ch_noice = fix(max_ch_noice/fix(max_ch_noice+0.5)*Max_value)/Max_value*fix(max_ch_noice+0.5);
    ch_mul_noice = ch_mul_noice/max_ch_noice;
    ch_mul_noice = fix(ch_mul_noice*Max_value);
    
    rec_code_r = real(rec_code);
    rec_code_i = imag(rec_code);
    ch_mul_noice_r = real(ch_mul_noice);
    ch_mul_noice_i = imag(ch_mul_noice);
    demap_int = zeros(Tx_num,Ofdm_bits);
    
    compare_tempt = zeros(Time_length,2); 
    result_index = zeros(1,Time_length);
    if Mod_type == 4
        star_index_length = 16;
    end
    if Mod_type == 6
        star_index_length = 64;
    end
    for n = 1:Ofdm_bits       
        decode_tempt_r = zeros(1,2);      % Time_length = 2
        decode_tempt_i = zeros(1,2);
        m = reshape(ch_mul_noice(:,:,n),1,Tx_num*Rx_num);              % 8 = Tx_num*Rx_num=2*4
        tempt_scale = 1;
        %ch_sum = norm(m)^2*(max_ch_noice*max_ch_noice);
        for r =  1:Rx_num        
            %decode_tempt(1,1) = decode_tempt(1,1) + rec_code(1,r,n)*conj(ch_mul_noice(1,r,n))+ conj(rec_code(2,r,n))*ch_mul_noice(2,r,n);            
            mult_tempt(1,1) = rec_code_r(1,r,n)*ch_mul_noice_r(1,r,n);
            mult_tempt(1,2) = rec_code_i(1,r,n)*ch_mul_noice_i(1,r,n);
            mult_tempt(1,3) = rec_code_r(2,r,n)*ch_mul_noice_r(2,r,n);
            mult_tempt(1,4) = rec_code_i(2,r,n)*ch_mul_noice_i(2,r,n);
            
            for nnn = 1:4
                if mult_tempt(1,nnn) >= Max_add_value
                    mult_temp(1,nnn) = Max_add_value-1;
                    mult_flow_num = mult_flow_num+1;
                elseif mult_tempt(1,nnn) < -Max_add_value
                    mult_tempt(1,nnn) = -Max_add_value;
                    mult_flow_num = mult_flow_num+1;
                end
            end
            sum_tempt = (mult_tempt(1,1) + mult_tempt(1,2)+mult_tempt(1,3) +mult_tempt(1,4))/tempt_scale;              
            decode_tempt_r(1,1) = decode_tempt_r(1,1) + sum_tempt;
            
            if decode_tempt_r(1,1) >= Max_add_value
                decode_tempt_r(1,1) = Max_add_value-1;
            elseif decode_tempt_r(1,1) <-Max_add_value
                decode_tempt_r(1,1) = -Max_add_value;
            end
            
            
            mult_tempt(1,1) = -rec_code_r(1,r,n)*ch_mul_noice_i(1,r,n);
            mult_tempt(1,2) = rec_code_i(1,r,n)*ch_mul_noice_r(1,r,n);
            mult_tempt(1,3) = rec_code_r(2,r,n)*ch_mul_noice_i(2,r,n);
            mult_tempt(1,4) = -rec_code_i(2,r,n)*ch_mul_noice_r(2,r,n);
            
            for nnn = 1:4
                if mult_tempt(1,nnn) >= Max_add_value
                    mult_temp(1,nnn) = Max_add_value-1;
                    mult_flow_num = mult_flow_num+1;
                elseif mult_tempt(1,nnn) < -Max_add_value
                    mult_tempt(1,nnn) = -Max_add_value;
                    mult_flow_num = mult_flow_num+1;
                end
            end
            sum_tempt = (mult_tempt(1,1)+mult_tempt(1,2)+mult_tempt(1,3)+mult_tempt(1,4))/tempt_scale;         
            decode_tempt_i(1,1) = decode_tempt_i(1,1)+sum_tempt;               
            
            if decode_tempt_i(1,1) >= Max_add_value
                decode_tempt_i(1,1) = Max_add_value-1;
            elseif decode_tempt_i(1,1) <-Max_add_value
                decode_tempt_i(1,1) = -Max_add_value;
            end
            %decode_tempt(1,2) = decode_tempt(1,2) + rec_code(1,r,n)*conj(ch_mul_noice(2,r,n))- conj(rec_code(2,r,n))*ch_mul_noice(1,r,n); 
            mult_tempt(1,1) = rec_code_r(1,r,n)*ch_mul_noice_r(2,r,n);
            mult_tempt(1,2) = rec_code_i(1,r,n)*ch_mul_noice_i(2,r,n);
            mult_tempt(1,3) = -rec_code_r(2,r,n)*ch_mul_noice_r(1,r,n);
            mult_tempt(1,4) = -rec_code_i(2,r,n)*ch_mul_noice_i(1,r,n);
            
            for nnn = 1:4
                if mult_tempt(1,nnn) >= Max_add_value
                    mult_temp(1,nnn) = Max_add_value-1;
                    mult_flow_num = mult_flow_num+1;
                elseif mult_tempt(1,nnn) < -Max_add_value
                    mult_tempt(1,nnn) = -Max_add_value;
                    mult_flow_num = mult_flow_num+1;
                end
            end
            sum_tempt = (mult_tempt(1,1)+mult_tempt(1,2)+mult_tempt(1,3)+mult_tempt(1,4))/tempt_scale; 
            decode_tempt_r(1,2) = decode_tempt_r(1,2)+sum_tempt;
            
            if decode_tempt_i(1,2) >= Max_add_value
                decode_tempt_i(1,2) = Max_add_value-1;
                add_flow_num = add_flow_num+1;
            elseif decode_tempt_i(1,2) <-Max_add_value
                decode_tempt_i(1,2) = -Max_add_value;
                add_flow_num = add_flow_num+1;
            end
            
            mult_tempt(1,1) = -rec_code_r(1,r,n)*ch_mul_noice_i(2,r,n);
            mult_tempt(1,2) = rec_code_i(1,r,n)*ch_mul_noice_r(2,r,n);
            mult_tempt(1,3) = -rec_code_r(2,r,n)*ch_mul_noice_i(1,r,n);