Experimental quantification of voice transmission quality of mobile-satellite personal communications systems

The design and analysis of an experiment, which was conducted in order to assess the subjective impact of transmission delay on mobile voice communications via a satellite, are presented. This study was conducted using simulated end-to-end propagation delays representative of low Earth orbit (LEO) and geostationary Earth orbit (GEO) networks (single and double-hop) in combination with three different speech coding technologies: 64 kb/s pulse code modulation, 8 kb/s vector-sum excited linear prediction, and 4.15 kb/s improved multiband excitation (representing wireline, cellular, and mobile satellite technologies, respectively). Subsequent analysis included computation of the cross-correlation between the delay and coding method, from which it was concluded that for “wireline-quality” and “communications-quality” circuits the transmission performance somewhat degraded as the propagation delay increased to that of a double-hop GEO circuit. However, for “communications quality” circuits employing the 4.15 kb/s speech coding algorithm, the transmission performance remained constant as propagation delay increased