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Old 11-09-2011, 11:32 PM
JWT Kottekoe JWT Kottekoe is offline
Join Date: Apr 2003
Location: California
Posts: 937
Originally Posted by Francis Vaughan View Post
The information rate is dependant upon two things, the bandwidth and the signal to noise ratio. It is the product of the two that determines the information transfer rate.
No, it is the product of bandwidth and the logarithm of the signal to noise ratio (SNR)* that determines the maximum bit rate. This is Shannon's theorem, one of the most important results from information theory. The logarithm means that you reach a point of diminishing returns when increasing the SNR, but doubling the bandwidth doubles the bit rate (all else being equal).

* Actually, it is logarithmic in (1+SNR): Bit Rate = Bandwidth*log2(1+SNR)

Edit: I suppose it is OK to say the product, if you are expressing (1+SNR) in dB's as engineers are wont to do.

Last edited by JWT Kottekoe; 11-09-2011 at 11:35 PM. Reason: Clarification