
Vocoder
IMBE™ by DVSI is the P25 Vocoder
– Model-based like virtually all vocoders
Optimized for Low Bit Rate Apps (< 4.8 kbps)
Breakdown
– 20 ms frame (50 frames per second)
– 88 vocoder bits
– 56 error control bits (unequal protection)
– 48 signaling bits
– 192 bits x 50 frames/s = 9600 bps
BER Estimator Used for Frame-by-Frame Decisions
– Smoothed estimator weighs past, present, future frames
– Has implications for performance metrics
Comentarios a estos manuales