# BER and OFDM **URL:** \ **Category:** GNU Radio\ **Created:** [April 7, 2014, 6:10pm UTC](https://www.ruby-forum.com/t/ber-and-ofdm/240307 "2014-04-07T18:10:34Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\ **Post date:** [April 7, 2014, 6:10pm UTC](https://www.ruby-forum.com/t/ber-and-ofdm/240307/1 "2014-04-07T18:10:34Z")
Hello guys, I’m getting some problems to use the error rate on a ofdm system, i used the example ofdm\_loopback as base and add the error rate and number sink but there’s not any response, it doesn’t bring me any error but the results are clearly wrong… There’s a picture of the circuit Sorry about the bad English, not my main language [http://gnuradio.4.n7.nabble.com/file/n47428/ofdm2.png](http://gnuradio.4.n7.nabble.com/file/n47428/ofdm2.png) – View this message in context: [http://gnuradio.4.n7.nabble.com/BER-and-OFDM-tp47428.html](http://gnuradio.4.n7.nabble.com/BER-and-OFDM-tp47428.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![MegaDuzera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e47c2d/32.png) [@MegaDuzera](https://www.ruby-forum.com/u/MegaDuzera)\ **Post date:** [April 8, 2014, 8:46am UTC](https://www.ruby-forum.com/t/ber-and-ofdm/240307/2 "2014-04-08T08:46:39Z")
On 04/07/2014 06:09 PM, MegaDuzera wrote: > Hello guys, > > I’m getting some problems to use the error rate on a ofdm system, i used the > example ofdm\_loopback as base and add the error rate and number sink but > there’s not any response, it doesn’t bring me any error but the results are > clearly wrong… MegaDuzera, what exactly is wrong? Also, you could try the new OFDM blocks (OFDM Transmitter / Receiver). Martin ---
**Author:** ![MegaDuzera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e47c2d/32.png) [@MegaDuzera](https://www.ruby-forum.com/u/MegaDuzera)\ **Post date:** [April 9, 2014, 5:44am UTC](https://www.ruby-forum.com/t/ber-and-ofdm/240307/3 "2014-04-09T05:44:54Z")
Dear user, I think this is not the way to implement OFDM simulation. It requires multiply const block before channel model. You may get variation in BER value when you use USRP boards. I will execute the same flow-graph and let me inform you results in soon. – View this message in context: [http://gnuradio.4.n7.nabble.com/BER-and-OFDM-tp47428p47464.html](http://gnuradio.4.n7.nabble.com/BER-and-OFDM-tp47428p47464.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![MegaDuzera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e47c2d/32.png) [@MegaDuzera](https://www.ruby-forum.com/u/MegaDuzera)\ **Post date:** [April 9, 2014, 9:53am UTC](https://www.ruby-forum.com/t/ber-and-ofdm/240307/4 "2014-04-09T09:53:07Z")
On 04/09/2014 05:43 AM, bsivakumar wrote: > Dear user, > I think this is not the way to implement OFDM simulation. It requires > multiply const block before channel model. You may get variation in BER > value when you use USRP boards. I will execute the same flow-graph and let > me inform you results in soon. Not in this case: I assume the EbN0 drives the SNR of the channel model. A noise voltage above 2 will definitely cause dropped packets. M ---
**Author:** ![MegaDuzera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e47c2d/32.png) [@MegaDuzera](https://www.ruby-forum.com/u/MegaDuzera)\ **Post date:** [April 9, 2014, 9:54am UTC](https://www.ruby-forum.com/t/ber-and-ofdm/240307/5 "2014-04-09T09:54:17Z")
On 04/08/2014 02:43 PM, MegaDuzera wrote: > I already tried the new blocks… > > The BER results are wrong, it gives me a value of “0.00000 Units” always With an Eb/N0 of 30 dB, that’s what I’d expect. For other cases, I don’t think your setup works, because of the packet-based nature of the OFDM transceiver (what happens if the demod doesn’t find a packet?). Martin ---
**Author:** ![MegaDuzera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e47c2d/32.png) [@MegaDuzera](https://www.ruby-forum.com/u/MegaDuzera)\ **Post date:** [April 10, 2014, 12:41pm UTC](https://www.ruby-forum.com/t/ber-and-ofdm/240307/6 "2014-04-10T12:41:19Z")
Hi, Some time ago I also tested this ofdm\_loopback file and i figure out that is good to use additional noise source (simulate the channel but also add AWGN). I don’t know if this is a proper way of simulating OFDM Tx/Rx but it can be some hint. Best regards, Piotr Potocki 2014-04-09 9:52 GMT+02:00 Martin B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): ---
**Author:** ![MegaDuzera](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e47c2d/32.png) [@MegaDuzera](https://www.ruby-forum.com/u/MegaDuzera)\ **Post date:** [April 8, 2014, 2:44pm UTC](https://www.ruby-forum.com/t/ber-and-ofdm/240307/7 "2014-04-08T14:44:41Z")
I already tried the new blocks… The BER results are wrong, it gives me a value of “0.00000 Units” always – View this message in context: [http://gnuradio.4.n7.nabble.com/BER-and-OFDM-tp47428p47449.html](http://gnuradio.4.n7.nabble.com/BER-and-OFDM-tp47428p47449.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com).