Simultaneous voice and data on the general switched telephone network using framed QADM

Considerable effort has been expended to allow voice to be transmitted over a general switched telephone network (GSTN) connection simultaneous with modulated data. A new transmission technology for this purpose is introduced-framed quadrature audio/data modulation (framed QADM)-in which voice and data channels are combined as an integral part of the modulation process. The basic technology is described and two implementations, which are at different levels of maturity for standardization within the International Telecommunications Union (ITU), are presented. Finally, system attributes are discussed for framed QADM as they compare to other technologies.