OFDM system capacity if we double the subcarriers

Suppose we have two OFDM based systems A & B.

• System A has $$N$$ subcarriers and bandwidth $$W$$, and the number of samples in the CP is 10% of $$N$$.
• System B has $$2N$$ subcarriers, $$2W$$ bandwidth and the number of samples in the CP is 5% of $$2N$$.

Which system has higher capacity?

• Guessing this is some sort of homework question, have you tried answering it yourself first? If so, you should post where you are in your reasoning at least.
– Jdip
Commented Aug 14, 2022 at 15:22
• Does this answer your question? Does the data rate of ofdm depends on number of subcarriers Commented Aug 15, 2022 at 14:06
• (my answer there addresses all the aspects in your homework/exam problem: changing number of subcarriers, changing procentual length of CP, bandwidth) Commented Aug 15, 2022 at 14:08
• Can be solved the above questions by using data rate= bandwidth * spectral efficiency ? Commented Aug 16, 2022 at 5:06
• The question is actually from an interview. Commented Aug 16, 2022 at 5:11

The capacity of $$A$$ is $$W\log_2(1+\text{snr})/1.1/NW$$
The capacity of $$B$$ is $$2W\log_2(1+\text{snr}/2)/1.05/NW$$
So the capacity of $$B$$ is larger than that of $$A$$.