A communication system (20) comprises a transmitter (22) and a receiver (24). The transmitter (22) comprises a source of information symbols (30); a pulse shaping wave function generator (32); and a combiner (34) configured to express the information symbols received from the source as signals which are shaped in time and frequency domains by the wave function. The pulse shaping wave function generator (32) is configured to provide a wave function which has the Nyquist property and has a same shape as its own Fourier transform. The combiner (34) is configured to combine the wave function with a stream of digital data symbols to produce a filtered stream for transmission by the transmitter.