Chaos for low probability of detection communications

Many methods for using chaos as a communications signal have been suggested, but all suffer from the difficulty in synchronizing the transmitter and receiver. Chaotic signals are broad band and unpredictable, making them potentially useful when the goal is low interference communications or even low probability of detection (LPD) communications. In this work, a set of randomly chosen chaotic sequences is used to synchronize a chaotic transmitter to a receiver. Once synchronization is achieved, two methods are presented for encoding information. Simply multiplying the chaotic signal by ±1 is used to encode the binary signals 1 or 0. The binary information is recovered by cross correlating the transmitted signal with the synchronized signal in the receiver. This encoding technique offers the same bit error performance as binary phase shift keying (BPSK). The data rate can be increased by creating orthogonal signals from different components of a multidimensional chaotic system. Cyclostationary properties of these signals and differential chaos shift keying (DCSK) are analyzed to show possible signatures that would make the signal easily detectable.