SCMA中的消息传递算法MPA仿真程序

function[X,repeat_times]=MPA(y,sigma2)%初始化参数X=zeros(6,2);Lx=zeros(4,24);Ly=zeros(4,24);itera_max=10;%最大迭代次数itera_count=0;L_getx=zeros(1,4);L_gety=zeros(3,4);rota_angle=[1,exp(1i*2*pi/3),exp(1i*4*pi/3)];F=[111000;100110;010101;001011];forrow_index=1:4r=1;forcolumn_index=1:6ifF(row_index,column_index)==1F(row_index,column_index)=rota_angle(r);r=r+1;endendendglobalcdbook1cdbook2cdbook1=[0.4472+1.3416*1i,1.3416-0.4472*1i,-1.3416+0.4472*1i,-0.4472-1.3416*1i];cdbook2=[1.3416+0.4472*1i,0.4472-1.3416*1i,-0.4472+1.3416*1i,-1.3416-0.4472*1i];%00100111%cdbook=[-1-1i,1-1i,-1+1i,1+1i];c4=de2bi(0:3);%00100111%map=[111000;200110;020201;002022];fork1=1:4fork2=1:6ifF(k1,k2)~=0Ly(k1,(k2-1)*4+1)=0.25;Ly(k1,(k2-1)*4+2)=0.25;Ly(k1,(k2-1)*4+3)=0.25;Ly(k1,(k2-1)*4+4)=0.25;endendend%X_before2=zeros(1,12);X_before1=ones(1,12);X=X_before1-1;%主程序foritera_count=1:itera_max%*******************************更新Lx*****************************forrow_index=1:4x_loca=find(F(row_index,:));%存放每一行非零位置，即与y有关系的xfort=1:3column_index=x_loca(t);ent_k=[123];ent_k(t)=[];fork=1:3%此函数换位置L_gety(k,1)=Ly(row_index,(x_loca(k)-1)*4+1);L_gety(k,2)=Ly(row_index,(x_loca(k)-1)*4+2);L_gety(k,3)=Ly(row_index,(x_loca(k)-1)*4+3);L_gety(k,4)=Ly(row_index,x_loca(k)*4);end%计算四个概率值,3个x有64种符号的全排列x_map=zeros(1,3);forx_k=1:4%当前求得xk，对应tx_map(t)=const_map(x_k,row_index,x_loca(t));%星座映射fork2=1:4x_map(ent_k(1))=const_map(k2,row_index,x_loca(ent_k(1)));%星座映射fork3=1:4x_map(ent_k(2))=const_map(k3,row_index,x_loca(ent_k(2)));%星座映射x_map_rota=x_map.*rota_angle;y_map=sum(x_map_rota);temp=L_gety(ent_k(1),k2)*L_gety(ent_k(2),k3);dif_y(k2,k3)=y(row_index)-y_map;Lx_xk_temp(k2,k3)=temp*exp(-0.5/sigma2*(abs(dif_y(k2,k3)))^2);endendLx(row_index,(column_index-1)*4+x_k)=sum(sum(Lx_xk_temp));end%标准化normalizationlamada=1/(Lx(row_index,(column_index-1)*4+1)+Lx(row_index,(column_index-1)*4+2)+Lx(row_index,(column_index-1)*4+3)+Lx(row_index,(column_index-1)*4+4));Lx(row_index,(column_index-1)*4+1)=lamada*Lx(row_index,(column_index-1)*4+1);Lx(row_index,(column_index-1)*4+2)=lamada*Lx(row_index,(column_index-1)*4+2);Lx(row_index,(column_index-1)*4+3)=lamada*Lx(row_index,(column_index-1)*4+3);Lx(row_index,(column_index-1)*4+4)=lamada*Lx(row_index,(column_index-1)*4+4);endend%***********************更新Ly****************************************forcolumn_index=1:6y_loca=find(F(:,column_index))';%加了转置存放每一列非零位置，即与x有关系的yfort=1:2row_index=y_loca(t);%计算四个概率值fork=1:2ifk~=tL_getx(1)=Lx(y_loca(k),(column_index-1)*4+1);L_getx(2)=Lx(y_loca(k),(column_index-1)*4+2);L_getx(3)=Lx(y_loca(k),(column_index-1)*4+3);L_getx(4)=Lx(y_loca(k),(column_index*4));endendfork1=1:4Ly(row_index,(column_index-1)*4+k1)=L_getx(k1);end%必须进行标准化lamada=1/(Ly(row_index,(column_index-1)*4+1)+Ly(row_index,(column_index-1)*4+2)+Ly(row_index,(column_index-1)*4+3)+Ly(row_index,(column_index-1)*4+4));Ly(row_index,(column_index-1)*4+1)=lamada*Ly(row_index,(column_index-1)*4+1);Ly(row_index,(column_index-1)*4+2)=lamada*Ly(row_index,(column_index-1)*4+2);Ly(row_index,(column_index-1)*4+3)=lamada*Ly(row_index,(column_index-1)*4+3);Ly(row_index,(column_index-1)*4+4)=lamada*Ly(row_index,(column_index-1)*4+4);endendend%***********************判断一次X***********************fort=1:6y_loca=find(F(:,t));p00=Lx(y_loca(1),(t-1)*4+1)*Lx(y_loca(2),(t-1)*4+1);p10=Lx(y_loca(1),(t-1)*4+2)*Lx(y_loca(2),(t-1)*4+2);p01=Lx(y_loca(1),(t-1)*4+3)*Lx(y_loca(2),(t-1)*4+3);p11=Lx(y_loca(1),(t-1)*4+4)*Lx(y_loca(2),(t-1)*4+4);p=[p00,p10,p01,p11];%[~,K]=max(p);%X_judge(t,:)=c4(K,:);X_judge_out(t,:)=[log((p10+p11)/(p01+p00)),log((p01+p11)/(p10+p00))];end%X=reshape(X_judge',1,12);%ifitera_count1%ifX_before1==X%repeat_times=itera_count;%itera_count=itera_max;%%end%elseifitera_count==itera_max%repeat_times=itera_max;%end%end%end%endrepeat_times=10;X=reshape(X_judge_out',1,12);end