Design of PN Sequence Families with Bounded Correlation Properties, Using Genetic Algorithms

The communication process in spread spectrum and CDMA like systems requires PN families with good correlation properties. The research activity in this area was stimulated and many such families were developed: m-sequences, Gold, Kasami or OVSF (orthogonal variable spreading factor) codes. Some of them have been chosen to implement WCDMA mechanisms because they fulfill the requirements of good correlation and autocorrelation properties. Spreading data requests good cross correlation properties in order to avoid the interference among users that are accessing the system resources at the same time. The scrambling process requires sequences with good autocorrelation properties to ensure a proper identification of different network entities: mobile station or base station. This paper deals with a new method based on genetic algorithms that can be used to identify PN sequences families with good correlation properties adequate for WCDMA systems. Using a Gold codes-like mechanism, the family members are obtained by modulo 2 adding the first sequence with the shifted replicas of the second one