MIMO Multi-user CDMA System with Forward Error Correction

TELECOMMUNICATION
Multiple Input Multiple Output Multi-user
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Professor:
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Abstract
Due to the heightened demand from consumers, it is a major challenge to model a
communication system that entail best resources. In code division multiple access systems,
these resources are namely power, bandwidth and code. The main limitation for Code Division
Multiple Access system is that, the system capability is exclusively dependent on the amount of
intrusion coming to an operator from other resource sharing users. Multiuser detection systems
reduce the consequence of interference and hence intensify the channel capacity as suggested in
several studies [5]–[7].
Introduction
Wireless methods are better compared to wire channels due to tractability in communication
system. MIMO transmission system offers reliable and fast output wireless link. Unlike traditional
communication, MIMO employs several antennas at the spreader and the recipient. Different data
can be conveyed via the different transmitting masts concurrently and at the same rate since there
are several transmitting receiving aerial pairs. According to Boerman [1], the entire sum of data
that can be sent is thus amplified over a channel engaging a single transmitting-receiving aerial
pair. For a MIMO to operate well, three requirements must be fulfilled. First, the setting must
allow multipath broadcast, secondly, the aerials must have adequate range in order to afford nearly
uncorrelated indications at the recipient and finally, the received signals should be powerful in
order to overcome any noise that is presented at the receiver [2]–[4]

Objective
To design and simulate MIMO multiuser CDMA system with Forward Error Correction.
Solution
Question 1
In this question we were required to design a CDMA system using matlab for both Walsh
code with spreading gain 64 and 31-gold code. Matlab code:
%% Clearing and closing any open files.
clear all
close all
clc
%% Generation of data for each
user N=30; gain_1=31;
gain_2=64; data_set=[]; for
p=1:N s=rand(1,10); r=[]; for
t=1:10 if s(t)>0.5
r=[r 1]; else if s(t)<0.5
r=[r 0]; end end
end data_set(p,:)=r; end
data_set=2*data_set-1; %% CDMA
using Walsh code
walsh=hadamard(gain_2);
signal_1=[]; for p=1:N
a=walsh(p,:); q=[];
for r=1:10
s=data_set(1,r)*a;
q=[q s]; end
signal_1=[signal_1;q];
end
% combining the signal from
each user combined_1=[]; for
t=1:29
combined_1=signal_1(t,:)
+signal_1(t+1,:); end
%% Generating Gold code
G=31; % Code length K=10;
% Number of Codes or code
sequences
%.................Generation of first perferred PN
sequence................ sd1 =randsrc(1,5,[0 1]); % First
user's seed.

PN1=[]; % Spreading code vector
of user-1 for j=1:G PN1=[PN1 sd1(1)];
if sd1(1)==sd1(4) temp1=0; else temp1=1;
end sd1(1)=sd1(2); sd1(2)=sd1(3);
sd1(3)=sd1(4); sd1(4)=sd1(5); sd1(5)=temp1; end
%.................Generation of Second perferred PN
sequence...............
sd2 =randsrc(1,5,[0 1]);
PN2=[];
for j=1:G
PN2=[PN2 sd2(1)]; if
sd2(1)==sd2(2)
temp1=0; else temp1=1;
end if sd2(4)==temp1
temp2=0; else temp2=1;
end if sd2(5)==temp2
temp3=0; else temp3=1;
end sd2(1)=sd2(2);
sd2(2)=sd2(3);
sd2(3)=sd2(4);
sd2(4)=sd2(5);
sd2(5)=temp3; end
%.........................Generation of Gold
Codes......................... Co_Mat=[]; for codes=1:K
code=[]; PN2(31)=PN2(1); for k=1:G-1
PN2(k)=PN2(k+1); end for j=1:G code=[code
xor(PN1(j),PN2(j))]; end
Co_Mat=[Co_Mat code'];
end for row=1:G for
col=1:K if
Co_Mat(row,col)==0
Co_Mat(row,col)=-1;
end
end end %
combining with the data
signa signal_2=[]; for
x=1:N b=Co_Mat(x,:);
y=[]; for v=1:10
l=data_set(1,v)*b;
y=[y l]; end
signal_2=[signal_2;y]; end
% combining the signal from each user
combined_2=[]; for z=1:29
combined_2=signal_2(z,:)
+signal_2(z+1,:); end
%% plotting figure; for u=1:3
subplot(4,1,u)
bar(signal_1(u,1:200)) if u==1
title('Signal for user 1 walsh