Got something confused simulating the match filter in base-band transmission system.

I'm trying to simulating the match filter on matlab. the pulse shape is SRRC and the signal is 4Pam,here is my problem:after the match filter in the receiver the information is partly missing. I am wondering if someone could help figure out why. Thanks.

Here is the main function

% recfilt.m: undo pulse shaping using correlation
str='This is Steven';                     % message to be transmitted
m=Fletters2pam4(str); N=length(m);        % 4-level signal of length N
M=10; mup=zeros(1,N*M); mup(1:M:end)=m;   % oversample by M
L=10; ps=Fsrrc(L,1,M);                    % blip pulse of width M
x=filter(ps,1,mup);                       % convolve pulse shape with data

y=xcorr(x,ps);                          % correlate pulse with received signal
z=y(N*M:M:end)/(pow(ps)*M);             % downsample to symbol rate and normalize
mprime=Fquantalph(z,[-3,-1,1,3])';      % quantize to +/-1 and +/-3 alphabet
Fpam2letters(mprime)                    % reconstruct message
sum(abs(sign(mprime-m)))                % calculate number of errors

Fletters2pam4.m

% letters2pam4.m: encode a string of ASCII text into +/-1, +/-3

function f = letters2pam4(str);          % call as Matlab function
N=length(str);                           % length of string
f=zeros(1,4*N);                          % store 4-PAM coding here
for k=0:N-1                              % change to "base 4"
  f(4*k+1:4*k+4)=2*(dec2base(str(k+1),4,4))-99;
end

pam2letters.m

% pam2letters.m: reconstruct string of +/-1 +/-3 into letters

function f = newpam2letters(seq)

S = length(seq);
off = mod(S,4);

if off ~= 0
sprintf('dropping last %i PAM symbols',off)
seq = seq(1:S-off);
end

N = length(seq)/4;
for k = 0:N-1
f(k+1) = base2dec(char((seq(4*k+1:4*k+4)+99)/2),4); 
end

f = char(f);

Fpow.m

function y=pow(x)
% y=pow(x) calculates the power in the input sequence x
y=sum(x.^2)/length(x);

Fquantalph.m

function y=quantalph(x,alphabet)
% function  y=quantalph(x,alphabet)
% quantize the input signal x to the alphabet 
% using nearest neighbor method
% input x - vector to be quantized
%       alphabet - vector of discrete values that y can take on 
%                  sorted in ascending order
% output y - quantized vector
[r c] = size(alphabet); if c>r, alphabet=alphabet'; end
[r c] = size(x); if c>r, x=x'; end
alpha=alphabet(:,ones(size(x)))';
dist=(x(:,ones(size(alphabet)))-alpha).^2;
[v,i]=min(dist,[],2);
y=alphabet(i);

Fsrrc.m

function s=Fsrrc(syms, beta, P, t_off);

% s=srrc(syms, beta, P, t_off);
% Generate a Square-Root Raised Cosine Pulse
%      'syms' is 1/2 the length of srrc pulse in symbol durations
%      'beta' is the rolloff factor: beta=0 gives the sinc function
%      'P' is the oversampling factor
%      't_off' is the phase (or timing) offset 

if nargin==3, t_off=0; end;                       % if unspecified, offset is 0
k=-syms*P+1e-8+t_off:syms*P+1e-8+t_off;           % sampling indices as a multiple of T/P
if (beta==0), beta=1e-8; end;                     % numerical problems if beta=0
s=4*beta/sqrt(P)*(cos((1+beta)*pi*k/P)+...        % calculation of srrc pulse
     sin((1-beta)*pi*k/P)./(4*beta*k/P))./...
   (pi*(1-16*(beta*k/P).^2));

[sandhya]

Hey i have problem in making the code for generation of PAM signals can you help with it.