QPSK over air

GNU Radio
1

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

2

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 <

3

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

4

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

5

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

6

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

7

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

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