A transmitter comprises a channel encoder to encode data bits; a modulator to modulate the encoded data bits, wherein the modulator selects one of a first modulation scheme and a second modulation scheme for each of a plurality of time slots; wherein, for each time slot, the channel encoder: includes a prefix and a suffix at the beginning and end, respectively, of the encoded data bits corresponding to the respective time slot, the prefix and the suffix being selected based on the selected modulation scheme for the respective time slot; and passes the prefix, the encoded data bits, and the suffix to the modulator; wherein, for each time slot, the modulator: modulates the prefix, the encoded data bits, and the suffix received from the channel encoder according to the selected modulation scheme for the respective time slot; and applies a window function to the prefix and the suffix.