Performance Evaluation of DS-CDMA Receivers Using Genetic Algorithm

Abstract

Direct sequence-code division multiple access (DS-CDMA) technique is used in cellular
systems where users in the cell are separated from each other with their unique spreading
codes. In recent times DS-CDMA has been used extensively. These systems suffers from
multiple access interference (MAI) due to other users transmitting in the cell, channel inter
symbol interference (ISI) due to multipath nature of channels in presence of additive white
Gaussian noise(AWGN). Spreading codes play an important role in multiple access capacity
of DS-CDMA system. M-sequences, gold sequences etc., has been traditionally used as
spreading codes in DS-CDMA. These sequences are generated by shift registers and periodic
in nature. So these sequences are less in number and also limits the security.
This thesis presents an investigation on use of new type of DS CDMA receiver called Genetic
Algorithm based DS-CDMA receiver. Genetic Algorithm is robust optimization technique
and does not fall into local minima hence this gives better weight optimization of any system.
This Thesis investigates the performance of GA based DS-CDMA communication using gold
code sequences.
Extensive simulation studies demonstrate the performance of the different linear and
nonlinear DS-CDMA receivers like RAKE receiver, matched filter (MF) receiver, minimum
mean square error (MMSE) receiver using gold sequences and the performance have been
compared with GA based receiver.