Interference in DS-CDMA systems with exponentiallyvanishing autocorrelations: Chaos-based spreading is optimal

A novel estimation of the minimum achievable interference in direct sequence-code division multiple access (DS-CDMA) systems is introduced, which holds when spreading sequences with exponentially vanishing autocorrelation are employed. This can be applied to many of the recently proposed improvements to classical maximum-length or Gold sequences, such as chaos-based spreading. Asymptotic, infinite-bandwidth results are also provided, clarifying the maximum attainable gain. Empirical evidence shows that this theoretical maximum is achieved by some chaos-based sequences which are therefore optimal.