Nonlinear observer design for synchronization and information recovery in communication systems using contraction theory

This paper proposes new LMI conditions for state and input recovery of a particular class of nonlinear systems. The convergence approach is presented under the original framework of the contraction theory and the conditions are derived thanks to the differential mean value theorem. This method is more general and more easily implementable than an original method, presented in [1], for the same class of systems. It is applied with success on two numerical examples of chaotic systems with unknown input, used for information encryption and decryption. Experimental results, based on a basic communication setup, are also included.