Const_size=4;?%%?QAM_size?=?Const_size^2;
Constellation?=?[-（Const_size-1）:2:Const_size-1];
snr_db=[10:3:25];?
Nr?=4;?Nt=Nr;?sigma=0.41;
err_num=[0?0?0?0];
MaxIter=1000;K_size=16;
for?Iter=1:MaxIter
?H=generate_channel（NrNt）;
[QR]=qr（H）;
?noise?=?randn（Nr*21）*sigma;
?x=Constellation（unidrnd（Const_size2*Nt1））‘;
rx?=?H*x?+?noise;
n1?=?Q‘*noise;
r1?=?R*x+n1;
%%%%%%%%%%%%??K?Best?algorithm?%%%%%%%%%%%%%
[x_est1metric1]=K_best（RConstellationr1K_size）;
?x_hat?=?x_est1（:1）;
err_num（1）=?err_num（1）+sum（x_hat~=x）;

%%%%%%%%%%%%??Double?K?Best?algorithm?%%%%%%%%%%%%%
[x_est1metric21]=K_best（R（Nt+1:2*NtNt+1:2*Nt）Constellationr1（Nr+1:2*Nr）K_size）;
[Q2R2]=qr（H（:[Nt+1:2*Nt?1:Nt]））;
r2=Q2‘*rx;
[x_est2metric22]=K_best（R2（Nt+1:2*NtNt+1:2*Nt）Constellationr2（Nr+1:2*