A method for generating a symbol mapping table ( 14) in a memory (13) comprises: selecting an initial set of pulse train segments having a time-granularity corresponding to a second oversampling clock rate (F2), determining a frequency-domain complex energy coefficient of the pulse train segments of the initial set at the carrier frequency, selecting a subset of the pulse train segments of which the frequency-domain complex energy coefficients at the carrier frequency closely approximate the quantized complex output states of the modulation device, so that each quantized complex output state is uniquely mapped to a pulse train segment of the subset, for each pulse train segment mapped to a quantized complex output state, recording at a memory address associated to the quantized complex output state a quantized symbol (16) encoding the pulse train segment.