zero mean AWGN modification

how do i modify the following code for a zero mean transmitted pulse of total length T, as shown below. (The pulse amplitude levels are +1 and -1.) Generate zero mean AWGN using randn ( ) function. Select noise variance such that the noise effect is clearly visible in the output plot as in Figure 2.5 (in page 22). Obtain the matched filter output using frequency domain processing (i.e. you have to use only fft and ifft functions). Show plots similar to those obtained with Example 2.8. Generate a set of 100 random transmitted bits of 0 and 1. (In a similar way as done in Q2.) Obtain sampled matched filter output (at t=T) for each transmitted bit. Plot the generated sequence and matched filer output (100 values) in stem plots. Comment on your results with respect to the effect of noise.

if true    
% Example 2.8   .....
%  +++++    Match Filter Receiver for PAM Signals    +++++++
%   (Note: This is a digital simulation of the analog receiver)
%   For analog representation the  Bit period, T is selected as 100 samples.
%          ----------------------------------------  
clear all ; close all;
s1 =  3*ones(1,100) ;                   % Transmitted signal s1
s0 = -3*ones(1,100) ;                   % Transmitted signal s0
hh = 3*ones(1,100) ;                  % impulse response 
xx = [0:101] ;
figure(1); 
subplot(3,1,1); plot(xx,[0 s0 0]) ; axis([-50 150 -4 4]); grid;
title('Transmitted Signal for bit=0');
subplot(3,1,2); plot(xx,[0 s1 0]) ; axis([-50 150 -4 4]); grid;
title('Transmitted Signal for bit=1');
subplot(3,1,3); plot(xx,[0 hh 0]) ; axis([-50 150 -4 4]); grid;
title('Matched Filter');
xlabel('Time (in arbitrary units)');
r0 = conv(s0, hh);   % correlation between bit=0 received signal & pulse shape 
r1 = conv(s1, hh);   % correlation between bit=1 received signal & pulse shape
xx2 = [0:198];
figure(2); 
subplot(2,1,1); plot(xx2,r0,[100 100],[-1000 1000],'r--') ; axis([-50 250 -1000 1000]); grid;
title('Matched Filter output for bit=0');
subplot(2,1,2); plot(xx2,r1,[100 100],[-1000 1000],'r--') ; axis([-50 250 -1000 1000]); grid;
title('Matched Filter output for bit=1');

end