AWGN impairment in MATLAB

clc;
clear all;
close all;
len=input('Enter the length of the payload:');
mod=input('Enter 1 for bpsk, 2 for qpsk, 4 for 16qam, 6 for 64qam:(default:4)');
if mod==1
c1=sqrt(1);
elseif mod==2
c1=sqrt(1/2);
elseif mod==4
c1=sqrt(1/10);
elseif mod==6
c1=sqrt(1/42);
else printf('wrong entry');
end

%This part will generate binary vector as per length entered by user
data=floor(rand(1,len)+0.5);
%Mapping of binary data
mapper_out=data_mapping(data',mod,c1);
mapper_out_ori=mapper_out;
figure;plot(real(mapper_out_ori),imag(mapper_out_ori),'r+');title('ideal constellation');

snr=input('Enter SNR:');
map_out_awgn=awgn(mapper_out,snr,'measured');
figure;plot(real(map_out_awgn),imag(map_out_awgn),/'r+');title('constellation with Added AWGN');

function [map_out]=data_mapping(data,mode,fact)
input_seq = data;
switch mode
case 1
b=fact*[1 -1];
case 2
b=fact*[1+1i -1+1i 1-1i -1-1i];
case 4
b=fact*[1+1i 1+3i 1-1i 1-3i 3+1i 3+3i 3-1i 3-3i -1+1i -1+3i -1-1i -1-3i -3+1i -3+3i -3-1i -3-3i];
case 6
b=fact*[3+3i 3+1i 3+5i 3+7i 3-3i 3-1i 3-5i 3-7i 1+3i 1+1i 1+5i 1+7i 1-3i 1-1i 1-5i 1-7i 5+3i 5+1i 5+5i 5+7i 5-3i 5-1i 5-5i 5-7i 7+3i 7+1i 7+5i 7+7i 7-3i 7-1i 7-5i 7-7i -3+3i -3+1i -3+5i -3+7i -3-3i -3-1i -3-5i -3-7i -1+3i -1+1i -1+5i -1+7i -1-3i -1-1i -1-5i -1-7i -5+3i -5+1i -5+5i -5+7i -5-3i -5-1i -5-5i -5-7i -7+3i -7+1i -7+5i -7+7i -7-3i -7-1i -7-5i -7-7i];
otherwise error('wrong choice');
end

count=1;
count1=1
;
for i=1:(ceil(length(input_seq)/mode))
temp=0;
for j=1:mode
temp=bitor(temp,bitshift(input_seq(count),(j-1)));
count=count+1;
if(count>length(input_seq))
break;
end
end
map_out(count1)=b(temp+1);
count1=count1+1;
end