DATEREMOTE CDS-9020, Manual

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combined and modulated onto a carrier frequency in the 800 MHz range.
At the receiving side, the received signals are quantized (tur ned into bits) and
run through the Walsh code and PN sequence correlation receiver to recover
the transmitted bits of the original signal. When 20ms of voice data is
received, a Viterbi decoder corrects the errors using the convolutional code,
and that all goes to the vocoder which turns the bits back into waveforms
(sound).
The following illustration shows how bits move from base station to cellphone
and a single bit example takes you through the Boolean math. The example
bit is a 1, and the Walsh and PN codes are 0.