Shannon Capacity and DSSS

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Patrick

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May 10, 2005, 10:32:08 AM5/10/05
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Hi everybody,

You know that Claude Elwood Shannon defined the maximum data rate that
can be transmit over a channel bandwidth W and says that this capacity
is W.log2(1+S/N).

So in the Wi-Fi (802.11) the modulation is DSSS (Direct Sequence
Spread Spectrum) with 11 Mchips/s in 22 MHz of bandwith...

So with the above equation we can find that the mimimum S/N for this
chip rate is - 3.8 dB ? Is it correct ?

Like the noise floor for this bandwith is -174dBm + 10.log(W) = -100
dBm

Then the minimum sensitivity becomes : -103.8 dBm

If we assume that the noise figure of the radio frequency stage is 3
dB (better case, I think)

Then the minimum sensitivity is -100.8 dBm

It's the lower limit for the 802.11 ?

What do you think about this reflexion ?

Perhaps I have made mistakes...

Best regards...

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