Multi-user schemes using nonlinear time-varying modulation

We propose to optimally reduce multiple access interference in multi-user systems using modulation schemes based on time-varying signals with nonlinear phase functions. This minimization is achieved by deriving constraints on the frequency modulation parameters of these signals. The success of the new method over frequency-shift keying signaling is demonstrated in frequency-hopped code division multiple access (FH-CDMA) systems. In addition, we propose to estimate the transmitted symbol information at the receiver using time-varying processing techniques based on unitary versions of the optimal periodogram spectral estimator.