# Does data rate depends on Frequency not on BW?

If we have two RF signals of 900Mhz and 1800Mhz both of equal Bandwidth 20Mhz which one has higher data rate?

• Do they use the same modulation scheme? – Andy aka May 14 at 16:40
• Everything same – Shashank May 14 at 16:41
• @Shashank what of you have a 20 MHz bandwidth between 0 Hz and 20 MHz, is it any different than having a 20 MHz bandwidth anywhere else? – Justme May 14 at 16:55
• You sure have been asking a LOT of trivial questions with no hint of having made any prior research effort. – Chris Stratton May 16 at 14:37

The value 900MHz and 1800MHz refer only to the carrier frequency. A pure perfect sine wave doesn't transmit / carry any information. Only when some parameter of the carrier changes, is data transmitted. This process is called modulation. The parameter could be something like frequency, phase, amplitude etc. More frequently you change the parameter, more data gets transmitted. The frequency with which you modulate the chosen parameter determines the bandwidth. So a signal with higher bandwidth transmits data at a higher rate. Two signals with same bandwidth and modulation scheme at two different carrier frequencies transport data at the same rate.

• Does that frequency of changing parameters remains at a constant rate or oscillates b/w more frequent changing to less frequent changing giving us a BW; is that right? – Shashank May 14 at 17:05
• The frequency with which the parameter changes is determined by the frequency of the original message signal you are trying to transmit. Say, it is a human voice signal, its frequency will be within 20kHz. – AJN May 14 at 17:12
• Let's say two message signals with BW 2k-20khz and other with 4k-10khz now the first signal has more BW ,does it mean it can accommodate more symbols than second one? So more sample rate and a better data rate? Is this correct? – Shashank May 15 at 7:14

## The Shannon–Hartley theorem. If the signal to noise ratio is identical for both systems and they are both presumed to use the same modulation method, the data rate (C) is proportional to B, bandwidth and nothing to do with the carrier frequency.

• @Shashank - if you are finished with this question now please select one answer for formal acceptance. If you still have questions then leave a comment. – Andy aka Jun 1 at 8:34

If, as you say, everything about the two systems is the same (modulation, etc.), and the only difference is in the carrier frequency (one at 900 MHz, the other at 1800 MHz), then the data rate would be the same, ideally.

In practice, if there's more interference in one band than other, if the performance of RF components varies from one band to the other, etc., you may observe differences. But I don't think that's what you asking about in this question? So, then the answer would be that they are the same.