Vocoders Human voice is made up of a combination of voiced and unvoiced sounds Vocoders exploit these properties of speech production mechanism Vocoders do not respond to music, non-human sounds and tones from voice band modems PCM vs VOCODERS CDMA VOCODERS 8 kbps variable rate coder Rate 1 Rate 1/2 Rate 1/4 Rate 1/8 Cdma … Read more
The base station uses a slightly different scheme when the vocoder moves to lower rates. First, EIA/TIA-95-B CDMA base stations do not pulse their transmissions. Rather, base stations repeat the same bit patterns as many times as needed to get back to the full rate of 9,600 bps. So, if the vocoder selects a frame … Read more
Vocoders Convert Voice to/from Analog Using Data Compression There are Three CDMA Vocoders: IS-96A Variable Rate (8 kbps maximum) CDG Variable Rate (13 kbps maximum) EVRC Variable Rate (improved 8 kbps) Each has Different Voice Quality: IS-96A – moderate quality EVCR – near toll quality CDG – toll quality All digital communication systems use various … Read more