A pseudo-chaotic coding/modulation method. The coding method exploits
symbolic dynamics of a chaotic map at the transmitter to encode data. The
encoding synthesizes the chaotic map based upon the data to be
transmitted. In a preferred embodiment, pseudo-chaotic iterates are
generated from a digital implementation of a Bernoulli shift map. The
output of the shift map is translated by a mapping, preferably implemented
by a digital signal processor, to allow transitions between states in a
transmitted signal to differ, and the translated map is used to drive a
modulator (for example PPM, FSK, PSK, QAM, etc.). In the specific case of
pulse-position modulation (PPM) the translated map is used to modulate
pulse train positions within a periodic synchronization frame. The
preferred embodiment uses a shift register to implement an approximation
of the Bernoulli shift map acting as a form of convolutional code with a
number of states equal to the symbolic states defined on the chaotic map.
A receiver may use fewer states and still decode the data signal, allowing
receiver scalability.
