Investigation of Continuously Variable Slope Delta (CVSD) Modulation for Voice Communications

摘要

The design of an existing 14 kbps continuously variable slope delta (CVSD) modulation voice communications system is analyzed and documented in an attempt to improve system performance. Design parameters, obtained from the hardware analysis, are used as the input variables to a CVSD computer model which computes output signal-to-noise ratio (SNR). Parameter values are then varied in an attempt to find the setting which produces the best possible SNR for the given data rate. Voice quality is measured using the Diagnostic Rhyme Test for the hardware system operating at various data rates. The results show that data rate and output filter design have the most impact on improving system performance. At the current 14 kbps data, other design parameters have minimal effect on the output SNR. Although noisy, voice quality is acceptable at 14 kbps, but certain consonant sounds, which are distorted by the CVSD processing, could present a problem depending on the system use. (Author)