# QPSK over air **URL:** \ **Category:** GNU Radio\ **Created:** [February 25, 2014, 7:13pm UTC](https://www.ruby-forum.com/t/qpsk-over-air/239425 "2014-02-25T19:13:28Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [February 25, 2014, 7:13pm UTC](https://www.ruby-forum.com/t/qpsk-over-air/239425/1 "2014-02-25T19:13:28Z")
I’m looking for an example of a higher-order modulation implemented successfully in GNU Radio with an SDR frontend. I’ve seen bpsk, GMSK, etc. implemented over a wireless channel, but I’ve only seen simulations of higher-order modulations. Could someone point me towards one or confirm that there’s no examples? Mark ---
**Author:** ![SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/dec6dc/32.png) [@SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/u/SOUTHCOTTS_MARK_A_C)\ **Post date:** [February 25, 2014, 7:19pm UTC](https://www.ruby-forum.com/t/qpsk-over-air/239425/2 "2014-02-25T19:19:21Z")
Hi Mark, The problem is that GNU Radio does not have equalizers that can perform sufficiently well for constellations such as 64-QAM. As far as I know, the only one present is a simple decision feedback equalizer. I’m working on implementing a few equalizers: a) 2D Triangulation, and b) Whittaker-Shannon Sinc interpolator, and c) one of my own. These aren’t yet ready to share, but once they are, I will send out an email to the list. Best, Aditya On Tue, Feb 25, 2014 at 1:11 PM, SOUTHCOTT, MARK A CIV USAF AFMC AFRL/RITC \< ---
**Author:** ![SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/dec6dc/32.png) [@SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/u/SOUTHCOTTS_MARK_A_C)\ **Post date:** [February 25, 2014, 9:05pm UTC](https://www.ruby-forum.com/t/qpsk-over-air/239425/3 "2014-02-25T21:05:53Z")
On 02/25/2014 07:17 PM, Aditya D. wrote: > email to the list. > Yeah, that’s a good point 🙂 > What we have in stock GR should work up to 8-PSK, but higher than that, > they will probably be the limiting factor. M ---
**Author:** ![SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/dec6dc/32.png) [@SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/u/SOUTHCOTTS_MARK_A_C)\ **Post date:** [February 25, 2014, 9:03pm UTC](https://www.ruby-forum.com/t/qpsk-over-air/239425/4 "2014-02-25T21:03:31Z")
On 02/25/2014 07:11 PM, SOUTHCOTT, MARK A CIV USAF AFMC AFRL/RITC wrote: > Im looking for an example of a higher-order modulation implemented > successfully in GNU Radio with an SDR frontend. Ive seen bpsk, GMSK, > etc. implemented over a wireless channel, but Ive only seen simulations > of higher-order modulations. Could someone point me towards one or > confirm that theres no examples? Mark, check out files in gr-digital/examples/narrowband and -demod. QPSK and 8-PSK will work out-of-the-box, people have done that ota, too (I’ve done it inside the OFDM code, for example). M ---
**Author:** ![SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/dec6dc/32.png) [@SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/u/SOUTHCOTTS_MARK_A_C)\ **Post date:** [February 25, 2014, 10:01pm UTC](https://www.ruby-forum.com/t/qpsk-over-air/239425/5 "2014-02-25T22:01:13Z")
On Tue, Feb 25, 2014 at 3:04 PM, Martin B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > These aren’t yet ready to share, but once they are, I will send out an > > email to the list. > > Yeah, that’s a good point 🙂 > What we have in stock GR should work up to 8-PSK, but higher than that, > they will probably be the limiting factor. > > M The lms\_dd\_equalizer should work fine for any constellation, for some definition of ‘fine’. Tom ---
**Author:** ![SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/dec6dc/32.png) [@SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/u/SOUTHCOTTS_MARK_A_C)\ **Post date:** [February 26, 2014, 9:59am UTC](https://www.ruby-forum.com/t/qpsk-over-air/239425/6 "2014-02-26T09:59:04Z")
Hi Mark, the gr-dvbt has a QPSK, QAM-16 and QAM-64 implementation of constellation for both Tx/Rx. The standard it implements is ETSI 300 744 which is OFDM based in which each subcarier is modulated using the modulations above. Regards, Bogdan On Tuesday, February 25, 2014 8:12 PM, “SOUTHCOTT, MARK A CIV USAF AFMC AFRL/RITC” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: I’m looking for an example of a higher-order modulation implemented successfully in GNU Radio with an SDR frontend. I’ve seen bpsk, GMSK, etc. implemented over a wireless channel, but I’ve only seen simulations of higher-order modulations. Could someone point me towards one or confirm that there’s no examples? Mark ---
**Author:** ![SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/dec6dc/32.png) [@SOUTHCOTTS\_MARK\_A\_C](https://www.ruby-forum.com/u/SOUTHCOTTS_MARK_A_C)\ **Post date:** [February 26, 2014, 1:24am UTC](https://www.ruby-forum.com/t/qpsk-over-air/239425/7 "2014-02-26T01:24:45Z")
Only half of the solution, but there’s a fully functional 64-QAM transmitter for bladeRF here: > **[GitHub - argilo/gr-qam: A QAM-64 transmitter for GNU Radio. This project was...](https://github.com/argilo/gr-qam)** > > A QAM-64 transmitter for GNU Radio. This project was merged into GNU Radio in version 3.7.10. - GitHub - argilo/gr-qam: A QAM-64 transmitter for GNU Radio. This project was merged into GNU Radio in... It implements the North American CATV standard ANSI/SCTE07 also known as ITU-T J.83 Annex B. We’re just using cable ready TV’s as receivers. Ron