The PDH hierarchy
The PDH hierarchy
The PDH hierarchy
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© ICT electronics<br />
Nyquist Sampling theorem<br />
“In order to convert an analog signal to digital it is necessary to use a sampling<br />
frequency (f s ) at least two times the highest frequency”<br />
• f s ≥ 2BW (in Hertzs)<br />
i.e. to digitalize a phone channel BW c = 4000 Hz in 8 bits each sample it<br />
would be necessary:<br />
• f s =2*4000=8000 Hz<br />
T= 125μs: this is the base period for all digital networks<br />
codifying:<br />
• 8000 samples/seg* 8 bits/sample = 64.000 bits/seg<br />
this is the basic speed for digital channels<br />
Plesiochronous Digital Hierarchy<br />
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