| Voice processing:
Presently, 64 kilobits per second speech is used in PSTN for transmission
of digital speech. This is achieved by taking 8000 samples per second and
quantization of each sample with 8 bits-this is known as Pulse Code Modulation.
This data rate is very high and we need to use low bit rate coding techniques
to reduce the data rates. Particularly, the last mile (end user to the Internet
server) supports small data rates such as 28.8 or 56 Kbps modems and the
actual throughput is still lower. One way of achieving low bit rate coding of speech is by removing the silence periods in the speech. This technique reduces the speech data rates by 50 to 60 percent. Fast switching of the packets can provide using frame relay systems good quality voice. In addition, also echo cancellation needs to be done in voice over IP systems. | 
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