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How does the total transmit power affects the number of subcarriers?

For example, if we have 624 subcarrier, can we use the same maximum power (for example the budget is 64 watts) as we will when we have 128 subcarriers?

Specifically how does the available power impacts the subcarrier in ofdm?

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The power does not impact the number of subcarriers, at all.

Of course, if you have some fixed power $P$ to spend on all subcarriers, then each subcarrier will get less power when you increase the number of subcarriers. While that might reduce the SNR per subcarrier, it does not directly limit the number of subcarriers.

More subcarriers also increases PAPR. But that just means you need an amplifier with more dynamic range, not more transmit power (which is an average measure).

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  • $\begingroup$ Actually i am simulating a system with a max power P. whenever i increase the number of subcarriers than the maximum power limit some subcarriers gets 0 power although the the sum of power allocated still have the margin. for example if my power is 15 watt and subcarriers are 16 4 subcarriers will get zero while the sum allocated power is just 6 does this means i am making a mistake somewhere $\endgroup$ Apr 4, 2022 at 13:46
  • $\begingroup$ that's a result of some system constraints that you're not mentioning. Maybe you have fixed modulation, a specific type of receiver, an acceptable bit error rate and use water-filling. That would be one type of system that would lead to unused carriers. But there's infinitely many possible rules according to which your simulation calculates subcarrier power allocation, and we can't possibly know! $\endgroup$ Apr 4, 2022 at 15:17

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