What is the relation between symbol duration and subcarrier frequency spacing in OFDM?

Question

What is the exact relation between symbol duration and frequency spacing?

You may know in WiFi6, about 11ax band, there are more sub-carriers compared to WiFi5 because of using shorter frequency spacing, but also uses a longer symbol duration. I guess there is some relation between them.

score 1 · Accepted Answer · answered Jul 30 '21 at 17:28

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Subcarrier spacing is equal to the reciprocal of the symbol time.

Equalizing narrower channels flattens group delay error and improves noise margin at the expense of added DSP processing.

answered Jul 30 '21 at 17:28

Tony Stewart EE75

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Thank you for your answer. you mean that added DSP processing needs more time to process, and it extends the symbol time? – ssabassaba Jul 30 '21 at 18:51
It does everything – Tony Stewart EE75 Jul 30 '21 at 20:01
What do you mean everything? – ssabassaba Aug 01 '21 at 05:39
More processing does not cause extended symbol time, it is caused by narrower BW – Tony Stewart EE75 Aug 01 '21 at 10:09
Thank you! my point is how are those two parameters reciprocal? – ssabassaba Aug 01 '21 at 12:34
BW /symbol rate must be maintained by definition of deviation ratio and SNR improvement. – Tony Stewart EE75 Aug 01 '21 at 12:44

What is the relation between symbol duration and subcarrier frequency spacing in OFDM?

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