# Is there any correlation between bandwidth and subcarriers-tounes in ofdm? **URL:** \ **Category:** GNU Radio\ **Created:** [March 27, 2013, 10:55am UTC](https://www.ruby-forum.com/t/is-there-any-correlation-between-bandwidth-and-subcarriers-tounes-in-ofdm/227743 "2013-03-27T10:55:55Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Yingjie\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/f14d63/32.png) [@Yingjie\_C](https://www.ruby-forum.com/u/Yingjie_C)\ **Post date:** [March 27, 2013, 10:55am UTC](https://www.ruby-forum.com/t/is-there-any-correlation-between-bandwidth-and-subcarriers-tounes-in-ofdm/227743/1 "2013-03-27T10:55:55Z")
Hi guys, I wonder if there is any correlation between baseband bandwidth of receiver side and fft-subcarriers-tounes of sender sider in OFDM? When I set the bandwidth to 20Mhz in sender side, the spectrum analyzer of receiver side shows only half of bandwidth（10Mhz). Does the reason that I use 128fft and 64 subcarriers account for this phenomenon? Sent from my iPhone ---
**Author:** ![Yingjie\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/f14d63/32.png) [@Yingjie\_C](https://www.ruby-forum.com/u/Yingjie_C)\ **Post date:** [March 27, 2013, 11:04am UTC](https://www.ruby-forum.com/t/is-there-any-correlation-between-bandwidth-and-subcarriers-tounes-in-ofdm/227743/2 "2013-03-27T11:04:41Z")
The fraction of the Nyquist zone occupied is equal to the number of active tones divided by the FFT length. The actual bandwidth then depends on your sampling rate. MB On Wed, Mar 27, 2013 at 05:54:46PM +0800, Yingjie C. wrote: > * * * > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) – Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin B. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT – University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association ---
**Author:** ![Yingjie\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/f14d63/32.png) [@Yingjie\_C](https://www.ruby-forum.com/u/Yingjie_C)\ **Post date:** [March 27, 2013, 12:47pm UTC](https://www.ruby-forum.com/t/is-there-any-correlation-between-bandwidth-and-subcarriers-tounes-in-ofdm/227743/3 "2013-03-27T12:47:35Z")
Thanks for your reply. You mean the bandwidth in receiver side(spectrum analyser) is only half of that of sender side if the active tones is half of the FFT length, is that right? Can you provide the explicit formula for helping me better understand. 2013/3/27 Martin B. (CEL) [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)