how to do sampling for the output of matched filter?

clc;
clear all;
close all;
tp=2.2676*10^-3;

Ts=22.6757*10^-6;
fc=4000;
Tc=(1/fc);
fs=44100;
n=0:Ts:1000;
fp=(1/tp);
w=2*pi*fp;
p=sin(w*n*Ts);
p(find(p<0))=0;
figure(1)
subplot(3,1,1);
plot(n,p);
data = randi([0,1],1,1000);
a=[];
for k=1:2:1000
    if data(k)==0 && data(k+1)==0
        a=[a 1];
    elseif data(k)==0 && data(k+1)==1
        a=[a i];
    elseif data(k)==1 && data(k+1)==0
        a=[a -1];
    elseif data(k)==1 && data(k+1)==1 
        a=[a -i];
    end
    
end
figure(2)
subplot(3,1,2);
y_s=conv(a,p);
Trm=min(numel(n),numel(y_s))
n=n(1:Trm);
y_s=y_s(1:Trm);
plot (n,real(y_s), '-',n,imag(y_s), '--');
%% modulation of 2 signals
figure(3)
subplot(3,1,3);
in_phase_carrier=cos(2*pi*fc*n*Ts);
q_phase_carrier=sin(2*pi*fc*n*Ts);
y_m=real(y_s).*in_phase_carrier+imag(y_s).*q_phase_carrier;
plot (n,real(y_m), '-');
subplot(3,2,3);
plot(n,imag(y_m), '--');
noise=sqrt(.25)*rand(1,length(y_m));
%power of signal
%pav=sum(y_m.^2)/length(y_m);
%et=sum(y_m.^2)/fs;
%  Es=((y_m).^2);
%  EsNo=((noise).^2);
%  Eb=Es.*110/2;
%  snr=sqrEb./EsNo;
%  
%  snrdb=snr(y_m,noise);
%snrdb=1:20;
% snrlin=10.^(snrdb./10);
%eb=sum(y_m.^2)/length(y_m);
% No=Es/snrlin;
% multipath channel
u=0.00022676;
g=5/60;

n1=(u-n);
in_phase_carrier_rec=cos(2*pi*fc*n1*Ts);
q_phase_carrier_rec=sin(2*pi*fc*n1*Ts);
y_mn1=(real(y_s).*in_phase_carrier_rec)+(imag(y_s).*q_phase_carrier_rec);
figure(4)
subplot(4,1,4);
r = (sqrt((1-g)^2))*y_m+y_mn1*g+noise;
plot(n,r);
%% demodulation of signal
subplot(4,2,4);
r_dm_in=real(r).*in_phase_carrier;
plot(n,r_dm_in,'-');
r_dm_out=imag(r).*q_phase_carrier;
plot(n,r_dm_out,'--');
%% fft of signal
L=length(r_dm_in);
NEFT=2^nextpow2(L);
r_dm_in_fft=abs(fft(r_dm_in,NEFT));
freq = fs/2*linspace(0,1000,NEFT/2+1);
subplot(4,3,4);
plot(freq,r_dm_in_fft(1:length(freq)),"LineStyle","--");
%% match filter
figure(5)
 o=5;
 b=438;
 a=442
 subplot(5,1,5);
 r_filt=filter(b,a,r_dm_in);
 plot(n,r_filt);
 subplot(5,2,5);
 r_filt_img=filter(b,a,r_dm_out);
 plot(n,r_filt_img);
c = xcorr(r_dm_in,n);
plot(c);
%snrdb=1:1:20;
%snrlin=10.^(snrdb/10);

%% sampling
%sampling in phase

how to proceed with sampling??