# Re g : spectrum sensing code **URL:** \ **Category:** GNU Radio\ **Created:** [August 27, 2012, 2:01pm UTC](https://www.ruby-forum.com/t/re-g-spectrum-sensing-code/222392 "2012-08-27T14:01:44Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\ **Post date:** [August 27, 2012, 2:01pm UTC](https://www.ruby-forum.com/t/re-g-spectrum-sensing-code/222392/1 "2012-08-27T14:01:44Z")
Hi Community, Question - 1 I was working with the UHD version of spectrum sensing code. I have USRP2 with me. I learnt that USRP2 can achieve 50MHz of RF bandwidth with 8 bit samples and 25MHz of RF bandwidth with 16 bit samples. I wanted to know how does this information translates while passing min\_freq ans max\_freq parameters to the spectrum sensing code. Does it mean (max\_freq - min\_freq) = 25MHz. Please correct me if I am wrong :teeth: Question - 2 Why the minimum center frequency is set as follows : self.min\_center\_freq = self.min\_freq + self.freq\_step/2 Why it simply doesn’t take the minimum frequency as we provided. Setting the max\_center\_freq I understood somehow. Question - 3 In non UHD version of spectrum sensing code the adc\_rate was fixed fro USRP-1 i.e. 64M and that was used to calculate usrp\_rate while in UHD version of the same code usrp\_rate is calculated by the sampling rate we give. I was wondering how does the code manages to work with devices of different sampling rates i.e. USRP-1 with 64M USRP2 with 100M Context : I am trying to scan WLAN channels 1, 6, 11 continuously. So I have to keep working with a total bandwidth of 76 MHz * * * ## Sumit Kr. Research Assistant Communication Research center IIIT Hyderabad India View this message in context: [http://old.nabble.com/Reg-%3A-spectrum-sensing-code-tp34330101p34330101.html](http://old.nabble.com/Reg-%3A-spectrum-sensing-code-tp34330101p34330101.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![sumitstop](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/97f17d/32.png) [@sumitstop](https://www.ruby-forum.com/u/sumitstop)\ **Post date:** [August 27, 2012, 2:05pm UTC](https://www.ruby-forum.com/t/re-g-spectrum-sensing-code/222392/2 "2012-08-27T14:05:10Z")
> Please correct me if I am wrong :teeth: As far as I understand spectrum sensing code is used for wideband spectrum analysis, that is to scan across wide RF bands which USRP is not able to analyze at a time. So obviously max\_freq - min\_freq \> 25 MHz . e.g Conider you have to analyze the spectrum from 400 MHz to 500 MHz. You can keep min\_freq = 400 MHz and max\_freq = 500MHz. If you have configured USRP sample rate to get 25 MHz bandwidth, ideally one round of scan will be complete by 4 tuning steps. (practically 6 steps as the code is using 25% overlap to reduce non-linearity in DDC response). Firas posted a detailed explanation of the code in the mailing list long back. You can find it here [Some usrp\_spectrum\_sense.py code Explanation - GNU Radio - Ruby-Forum](http://www.ruby-forum.com/topic/174437). > Question - 2 > Why the minimum center frequency is set as follows : > > self.min\_center\_freq = self.min\_freq + self.freq\_step/2 > Why it simply doesn’t take the minimum frequency as we provided. Setting the > max\_center\_freq I understood somehow. e.g. Scan range 10MHz to 40 MHz USRP1 B/W = 8MHz First tuning step is with centre freq 14Mhz (10+8/2 ideally) which will cover the bandwidth from 10 to 18 Mhz > Question - 3 > In non UHD version of spectrum sensing code the adc\_rate was fixed fro > USRP-1 i.e. 64M and that was used to calculate usrp\_rate while in UHD > version of the same code usrp\_rate is calculated by the sampling rate we > give. > I was wondering how does the code manages to work with devices of different > sampling rates i.e. USRP-1 with 64M USRP2 with 100M sampling rate ----\> Bandwidth ----\> feq\_step > Context : I am trying to scan WLAN channels 1, 6, 11 continuously. So I have > to keep working with a total bandwidth of 76 MHz Check the tuning delay of the device you are using and make sure that you are not losing any data during the sweeping process.I may be wrong somewhere. Please go through Firas’s explanation which will make things clear. regards Sreeraj Rajendran ---
**Author:** ![sumitstop](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/97f17d/32.png) [@sumitstop](https://www.ruby-forum.com/u/sumitstop)\ **Post date:** [August 27, 2012, 2:05pm UTC](https://www.ruby-forum.com/t/re-g-spectrum-sensing-code/222392/3 "2012-08-27T14:05:53Z")
Hi Sreeraj, Thanks for the reply. sreeraj r wrote: > > Question - 1 > > > > I was working with the UHD version of spectrum sensing code. > > > > I have USRP2 with me. I learnt that USRP2 can achieve 50MHz of RF > > bandwidth > > with 8 bit samples and 25MHz of RF bandwidth with 16 bit samples. > > > > I wanted to know how does this information translates while passing > > min\_freq > > ans max\_freq parameters to the spectrum sensing code. Does it mean > > (max\_freq > > e.g Conider you have to analyze the spectrum from 400 MHz to 500 MHz. You > > here [Some usrp\_spectrum\_sense.py code Explanation - GNU Radio - Ruby-Forum](http://www.ruby-forum.com/topic/174437). > > so shall I pass sampling rate = 2_bandwidth i.e. for this case 2_25Mhz = > > 50MSPS (Pl correct if I am wrong) > > Question - 2 > > > Why the minimum center frequency is set as follows : > > > > self.min\_center\_freq = self.min\_freq + self.freq\_step/2 > > > Why it simply doesn’t take the minimum frequency as we provided. Setting > > the > > > In non UHD version of spectrum sensing code the adc\_rate was fixed fro > > USRP-1 i.e. 64M and that was used to calculate usrp\_rate while in UHD > > version of the same code usrp\_rate is calculated by the sampling rate we > > give. > > > I was wondering how does the code manages to work with devices of > > different > > sampling rates i.e. USRP-1 with 64M USRP2 with 100M > > sampling rate ----\> Bandwidth ----\> feq\_step > > > Context : I am trying to scan WLAN channels 1, 6, 11 continuously. So I > > have > > regards > > Sreeraj Rajendran > > * * * > > 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) * * * ## Sumit Kr. Research Assistant Communication Research center IIIT Hyderabad India View this message in context: [http://old.nabble.com/Reg-%3A-spectrum-sensing-code-tp34330101p34335158.html](http://old.nabble.com/Reg-%3A-spectrum-sensing-code-tp34330101p34335158.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com).