The present invention provides a frequency-diverse single-carrier modulation scheme that extends the usable SNR range of severely distorted channels. This scheme is advantageous for applications in which when the SNR is low and the transmitted spectrum contains unusable regions (e.g., spectral nulls due to radio-frequency interference ingress or egress). In one embodiment, the symbol baud rate is selected in order that unusable portions of the frequency response of the transmission channel are mapped onto usable portions of the frequency response of the transmission channel.