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The Direct Sequence-Code Division Multiple Access (DS-CDMA) systems offer physical layer security without the need for a significant increase in computation or power requirements but, these systems suffers from multiple access interference because of other users transmitting in the cell, channel inter symbol interference and additive white Gaussian noise. Codes have an effective role in DS-CDMA system, so M-sequences; gold sequences have been used as spreading codes in DS-CDMA. These sequences by shift registers and periodic in nature are developed. However, these sequences are not enough and also limit the security. This paper presents an investigation on use of new type of sequences called chaotic sequences for DS-CDMA system. These sequences are generated by chaotic maps. First of all, chaotic sequences are easy to generate and store. For very long sequences there are needed only a few parameters and functions. Moreover, numerous numbers of sequences can be developed simply by changing its initial condition. Chaotic sequences are deterministic, reproducible, uncorrelated and random-like, which can be very helpful in enhancing the security of transmission in communication. This paper examines the use of chaotic sequences in DS-CDMA systems using various receiver techniques. Extensive simulation indicate the performance of the different linear DS-CDMA receivers like RAKE receiver, matched filter (MF) receiver and Minimum Mean Square Error (MMSE) receiver using Chaotic Sequences and Gold Sequences.

DS-CDMA Systems Performance Using Chaotic Sequence in Different Linear Receivers