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The application of LPC in a communication system such as GSM is shown in Figure 16.54. The speech input is first digitized by a 16-bit ADC at a sampling frequency of 8 kSPS. This produces output data at 128 Kbps, which is much too high to be transmitted directly. The transmitting DSP uses the LPC algorithm to break the speech signal into digital filter coefficients and pitch. This is done in 20 ms windows, which have been found to be optimum for most speech applications. The actual transmitted data is only 2.4 Kbps, which represents a 53.3 compression factor. The receiving DSP uses the LPC model to reconstruct the speech from the coefficients and the excitat...


Cover of Circuit Design: Know It All


Amazing how compressed voice data is over GSM!