channel capacity

[SONET]

Hi

I've got a question driving me crazy
All of us know that for a signal with a bandwidth B, we can send 2B bps via a channel and not more
This came from the sampling theory; reconstructing the signal from its minimum sampling rate, which is 2B
The question is: What if we sampled the signal more than 2B, let's say 3B, will that affect the functionality of the channel? in other words, will the same channel be able to transmit the same bit rate which is 3B??

 

[pstuckey]

Channel capacity is NOT limited to 2*B, see Shannon's theorem:

Channel capacity = B * log_base2(1+SNR)

Higher SNR leads to higher channel capacity, although not linearly.

Peter

 

[zappedagain]

Don't forget that 3B lets in 3/2 as much Johnson noise as 2B sampling if you don't filter accordingly, so you will degrade your signal to noise ratio.

You can also undersample, and digitize frequency bands above your sampling frequency. Google will give you a lot of good links; Analog Devices has a few articles.

Z

 

[benta]

Think about 56 kbps modems on a telephone line with 3.2 kHz bandwidth...

Benta.