Optimization Of CDMA Based Wireless System

This paper presents an optimization problem of spreading codes (sequences) in asynchronous Direct Sequence Code Division Multiple Access (DS/CDMA) systems. Bit Error Rate (BER) is one of the performance measurements and it is related to the spreading sequences mathematically. Therefore, the performance of CDMA systems highly depends on the assignment of the unique spreading sequences to the users in which different types and subsets of sequences of a selected sequence type are designed. If the type and the subset of the sequences are not carefully designed, then the Multiple Access Interference (MAI) can be very high. Thus, the channel capacity can be reduced significantly. Hence, proper selection of the type of sequences and its sequence subset are necessary and important to achieve good performance of the system. In this paper, we will use Gold. Kasami and Multiple Spreading [1] sequences as the spreading sequences and apply the genetic algorithm to optimize the sequences such that the MAI is minimized. Although the Multiple Spreading has many advantages over the other PN code, its set of sequences still is not the best if no Genetic Algorithm is applied. Therefore it can be concluded the GA based Multiple Spreading is the best solution to produce PN codes for DS-CDMA system.