Voice quality of interconnected North-American cellular, European cellular, and public switched telephone networks

The nonlinear nature of low-rate parametric speech coding has rendered questionable analytical methods for estimating the end-to-end voice quality of interconnected telecommunications networks. Instead, quantification of transmission performance appears to require direct subjective evaluation of the pertinent conditions of interest. At the same time, the rapid growth of cellular communications has highlighted the need to characterize the quality of switched networks when cellular terminals are attached at the networks´ termination nodes. The voice quality of interconnected North-American and European digital cellular systems over national and international transmission facilities is quantified. From these assessments it was concluded that cellular networks employing the TIA IS-54 8 kbit/s VSELP or the GSM 13 kbit/s RPE-LTP algorithms may meet the end-to-end quantization distortion allocation criteria when interconnected with the switched network