0
$\begingroup$

The maximum bit rate that can be transmitted over a channel with bandwidth B is determined by Shannon C=B log(1+S/N)

Are there any techniques that could break this limit?

$\endgroup$
1
  • 2
    $\begingroup$ It's sorta like asking if there is a technique that can break the Conservation of Energy principle. $\endgroup$ Mar 19 at 20:18

1 Answer 1

3
$\begingroup$

No, but the capacity formula you mentioned assumes a very specific channel. Other channels may have larger capacities (see "faster than Nyquist signaling", for example in this question).

Also, nitpicking but this is important: the bit rate over a given channel is unbounded; you can transmit as fast as you want. The capacity is the limit at which you can transmit with vanishing probability of error.

$\endgroup$
2
  • $\begingroup$ Some of the faster than nyquist (FTN) papers seem to imply that since the shannon capacity assumes the use of orthogonal sinc pulses, that FTN signaling will actually have a higher capacity. Perhaps this is just a misunderstanding on my part, but it seems to me the shannon capacity will always hold (for the AWGN channel w/ bandwidth B) and that FTN 'gains' are actually the result of re-gaining the BW thrown away in typical communication systems that use for example RRC filtering w/ excess BW. In other words - IF we could use nyquist pulses in the real world easily then we wouldn't need FTN. $\endgroup$
    – user67081
    Mar 19 at 23:19
  • 1
    $\begingroup$ It is correct to say that FTN exploits the excess bandwidth; FTN is impossible with sinc pulses. However, note that the formula C = B log(1+SNR) is not the Shannon capacity -- it's the capacity of a very specific channel. It is possible to calculate the Shannon capacity of other channels, for example a channel with excess bandwidth when using a given pulse shape. There's a paper by Anderson that shows this. $\endgroup$
    – MBaz
    Mar 19 at 23:50

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.