Convolutional spectral shaping

A new spectral shaping technique, convolutional spectral shaping (CSS), is introduced. In CSS, equivalence classes of possible sign bit sequences are represented by a coset of a convolutional code and a search through the trellis of the code is used to pick a sequence from the selected coset to approximate a target spectral shape for transmission. Simulation results are included to illustrate the performance of CSS. A version of CSS has been adopted by the International Telecommunication Union (ITU) in the pulse code modulation (PCM) modem standard V.90.