International audienceIt has been recently pointed out than the Kalman filter is a powerful tool for the synchronization of chaos, which remains a major difficulty in the development of efficient chaos based digital communication systems, capable of operating over nonstationnary channels. The input signal power fluctuations, which often causes large errors in synchronizing chaotic waveforms, is discussed in this paper. The automatic gain control will be solved in two manners, the first one relying on a modification of the chaotic dynamics and the second one by matching the second order statistics of the original chaotic spreading code. The performance of these approaches will be illustrated through numerical simulations for a symmetric chaos shift keying system (i.e. chaotic direct sequence spread spectrum). A dual Unscented Kalman filtering schemewill be achieved at the receiver to demodulate and synchronize simultaneously
