Performance Improvement of DS-CDMA Systems Using Two Dimensional Bernoulli Chaotic Spreading Sequence

A major goal of a spread spectrum communication system is to protect communication signals against interference and exploitation by unintended listeners. In fact, Low Probability of Detection and Low Probability of Intercept are two important parameters for increasing performance of the system. In DS-CDMA, these goals are reached by multiplying the data information and spreading sequences. Chaotic sequences, with its unique properties, have numerous applications in building spreading codes. Before, using one-dimensional Bernoulli sequence as spreading code is proposed. The main feature of this sequence is its negative autocorrelation at lag of one. Efficiency of the system based on these codes will be increased comparing with other known codes. On the other hand, employing the complex chaotic sequences as a spreading sequence also has been discussed in several papers. In this paper, the use of two-dimensional Bernoulli chaotic sequences as a spreading code is proposed. The quality of a multiuser synchronous and asynchronous DS-CDMA will be evaluated by applying these sequences in AWGN and fading channel. Simulation results indicate the improved performance compared with conventional spreading codes like Gold codes and also other similar complex spreading sequences.