Radio communications via channels already occupied by traditional telecommunication systems can be achieved by using ultra-wideband (UWB) radio where extremely wideband wavelets are used in order to reduce the power spectral density (psd) of transmitted signal. Since the recovery of these UWB carriers is not feasible, noncoherent demodulation techniques have to be used. The letter evaluates and compares the noise performances of the feasible noncoherent UWB modulation schemes, namely, that of the noncoherent pulse polarity modulation and the transmitted reference system.

In order to demodulate a Differential Chaos Shift Keying (DCSK) signal, the energy carried by the received chaotic signal must be determined. Since a chaotic signal is not periodic, the energy per bit carried by the chaotic signal can only be estimated, even in the noise-free case. This estimation has a non-zero variance that limits the attainable data rate. In this paper the DCSK technique is combined with frequency modulation in order to overcome the estimation problem and to improve the data rate of DCSK modulation.