Chaotic Modulation for Satellite Communications (S

A new approach to satellite communications (SATCOM) can be realized by use of chaotic modulation methods. Covert SATCOM signals are a growing area of interest. Low probability of detection and interception (LPI/LPD) are becoming critically important for SATCOM operation in unfriendly territory. New research has identified chaotic modulation techniques as having great promise to reduce transmit spectral energy while adding to the data security of the link. One of the ways to improve LPI/LPD is to use chaotically timed pulse sequences. Called Chaotic Pulse Position Modulation (CPPM), each pulse has an identical shape but the time delay between them varies chaotically. Because information in contained entirely in the timing between pulses, the distortions that affect the pulse shape will not significantly influence the ability of the chaotic pulse generators to synchronize. Therefore, chaotic synchronization can be achieved using realistic channels and at the same time bandpass filters can be used for noise reduction. Variations on CPPM are described: using CDMA applied to the pulses, chaotic amplitude decision boundaries, rate adaption techniques, and a variation on Paired Carrier Multiple Access (PCMA). Together these techniques promise to increase bandwidth, increase security, and increase the covert appearance of SATCOM signals.