Using orthogonalized voice for simultaneous transmission of voice and data

Voiceband channels are frequently used for data transmission, even though they were not designed for such a use. The reason is very simple; such channels already exist. It is also clear that such channels when used for data transmission can not be used at the same time for voice transmission, and vice versa. However, there are a lot of applications where simultaneous transmission of voice and data through the existing voiceband channel is needed. In this work we propose a method for simultaneous transmission based on orthogonalization of the voice signal. A comprehensive assessment of the orthogonal voice which includes subjective measures shows that the orthogonal signal may have full intelligibility while its quality is only slightly degraded. The MOS for orthogonal voice is in the range 2.5–3.9 and depend on the data transmission parameters.