Adaptive fuzzy frequency hopping system

An adaptive fuzzy system generates the frequency hopping sequence for a spread spectrum communications system. The authors describe a fuzzy rule-based pseudorandom number generator. Adaptive fuzzy rules map distributions of old output frequencies to show new output frequencies. These rules, with some initial conditions and the sampling pattern that gives the previous outputs´ distribution, fix the output sequence. Each sequence has an unknown length if it repeats at all. Such sequences are hard for an eavesdropper to predict if he does not know either the rules, the initial conditions, or the sample pattern. This fuzzy system can generate a sequence uniform over any number of frequencies. The fuzzy system was tested with 100 and 1025 frequencies and compared to a shift register with linear feedback. The fuzzy system had lower chi-squared values and thus gave a more uniform or more random spread than did the shift register. The fuzzy system was easier to change and harder to intercept