QPSK over air

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

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 <

On 02/25/2014 07:17 PM, Aditya D. wrote:

email to the list.
Yeah, that’s a good point :slight_smile:
What we have in stock GR should work up to 8-PSK, but higher than that,
they will probably be the limiting factor.

M

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

On Tue, Feb 25, 2014 at 3:04 PM, Martin B. [email protected]
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 :slight_smile:
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

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” [email protected] 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

Only half of the solution, but there’s a fully functional
64-QAM transmitter for bladeRF here:

https://github.com/argilo/gr-qam

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

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