DAB receiver

GNU Radio
1

Hello,

I am an electrical engineering student, and I would like to implement a
DAB receiver as a semester thesis (about 1/3 the size of a Master
thesis).

I intend to implement each part first in Matlab and then in GNU Radio.
Ideally, I hope to use the existing OFDM code in gnuradio-core and some
external MP2 library for the audio decoding.

However, I am wondering if this is feasible as a semester thesis. Any
comment about the rough amount of work that would be needed would be
greatly appreciated.

In the mailing lists, there are some references to an existing DAB
implementation from ([1],[2]). Can anyone tell me how far this got? The
referenced website (http://www.1c3.de/gr-dab.tar.bz2) is empty.

Regards, Andreas

[1]
http://lists.gnu.org/archive/html/discuss-gnuradio/2006-08/msg00205.html
[2]
http://lists.gnu.org/archive/html/discuss-gnuradio/2006-03/msg00397.html

2

Hallo Andreas,

with the current status of OFDM PHY code in GNU Radio I think it is
definately
worth a try.

The work I did on DAB was basically OFDM synchronization in one GNU
Radio block. The code was more or less a hack, but it deepened my
understanding of digital signal processing. Not as easy as in text
books. :slight_smile: I’ll email the report to you separately.

I wouldn’t underestimate the complexities of the higher DAB layers,
it has quite a protocol stack. But you should give it a try. If you
need captured Mode I/II samples I can make them available for download.

Gruesse,
Jens

On Wed, Feb 20, 2008 at 07:14:24PM +0100, Andreas Müller wrote:

comment about the rough amount of work that would be needed would be
[2]
[Discuss-gnuradio] OFDM / DAB demodulation

3

Jens E. wrote:

Hallo Andreas,

with the current status of OFDM PHY code in GNU Radio I think it is definately
worth a try.

The work I did on DAB was basically OFDM synchronization in one GNU
Radio block. The code was more or less a hack, but it deepened my
understanding of digital signal processing.
Jens, I have downloaded your gr-dab code in 2007.
Is it OK if I put up a mirror of it on my website.
Maybe it could deepen the understanding of others about OFDM too.
Greetings,
Martin
Not as easy as in text
books. :slight_smile: I’ll email the report to you separately.

I wouldn’t underestimate the complexities of the higher DAB layers,
it has quite a protocol stack. But you should give it a try. If you
need captured Mode I/II samples I can make them available for download.

Gruesse,
Jens

4

Hello Jens

The work I did on DAB was basically OFDM synchronization in one GNU
Radio block. The code was more or less a hack, but it deepened my
understanding of digital signal processing. Not as easy as in text
books. :slight_smile: I’ll email the report to you separately.

Thanks …

I wouldn’t underestimate the complexities of the higher DAB layers,
it has quite a protocol stack. But you should give it a try. If you

I actually did get a bit scared when I first looked at the 200 page
standard, but I hope that if I go for the “simplest possible” approach
for a start, a lot can be omitted (like service information). As DAB+
isn’t available here, I also intend to just go for DAB.

need captured Mode I/II samples I can make them available for download.

Thanks, but I can get quite a nice Mode I signal with the TVRX, so no
need…

Regards, Andreas

5

Hello Ravi

Ravi Trivedi wrote:

Hello all,

I am trying to implement synchronization of DAB receiver in matlab. I
have been facing some problems when I test the matlab receiver code for
real time streams.
First issue is sampling rate estimation problem. I see that real time
frame has shortage of samples when compared to values given in
specification. I do frame detection first followed by joint estimation

What is your sampling rate, and how many samples are you missing? It’s
likely that your sampling rate is not exactly what you expect, when you
use real-world data, and maybe you have to do sampling rate correction
as well.

of fine timing and coarse frequency offset. After compensation, I
perform fine frequency offset estimation and compensation. I see that
for real time streams FIC decoder doesn’t pass the CRC. If I use
simulated data CRC check gets passed.
Does anyone have receiver matlab code working for real time data which
I can use for comparison with my code? Thanks in advance.

I did an implementation for GNU Radio a while ago. You can find it at
[1] and a description in [2]. Although it’s not complete, it does
everything on the lower levels, up to (and including) FIC CRC
verification (which works, also with real-world data).

Regards, Andreas

[1] http://people.ee.ethz.ch/~andrmuel/files/gnuradio/gr-dab.tgz
[2] http://people.ee.ethz.ch/~andrmuel/files/gnuradio/dab-doc/thesis.pdf

6

Hello Andreas,

Sampling rate is 2.048Msps. When I analyze every DAB frame captured, I
see
that in total the whole frame has shortage of 9 to 10 samples. There
could
be a very high possibility due to ADC clock drift when we capture the
data
from DAB generator and digitize it.

Thanks for the references. I have developed the receiver side matlab
code
which works for simulated data. But I face issues in getting it working
for
real time streams. I need to add sampling rate converter in the code
which I
will be doing. You have mentioned in your thesis.pdf that you did refer
to a
matlab code for DAB receiver. If possible and if it’s not copyrighted
can
you share the same to me?

Best Regards
Ravi

7

Hello all,

I am trying to implement synchronization of DAB receiver in matlab. I
have been facing some problems when I test the matlab receiver code for
real time streams.
First issue is sampling rate estimation problem. I see that real time
frame has shortage of samples when compared to values given in
specification. I do frame detection first followed by joint estimation
of fine timing and coarse frequency offset. After compensation, I
perform fine frequency offset estimation and compensation. I see that
for real time streams FIC decoder doesn’t pass the CRC. If I use
simulated data CRC check gets passed.
Does anyone have receiver matlab code working for real time data which
I can use for comparison with my code? Thanks in advance.

8

Hello Andreas,

Sampling rate is 2.048Msps. When I analyze every DAB frame captured, I
see
that in total the whole frame has shortage of 9 to 10 samples. There
could
be a very high possibility due to ADC clock drift when we capture the
data
from DAB generator and digitize it.

Thanks for the references. I have developed the receiver side matlab
code
which works for simulated data. But I face issues in getting it working
for
real time streams. I need to add sampling rate converter in the code
which I
will be doing. You have mentioned in your thesis.pdf that you did refer
to a
matlab code for DAB receiver. If possible and if it’s not copyrighted
can
you share the same to me?

Best Regards
Ravi

9

Hello Ravi

Sampling rate is 2.048Msps. When I analyze every DAB frame captured, I see
that in total the whole frame has shortage of 9 to 10 samples. There could
be a very high possibility due to ADC clock drift when we capture the data
from DAB generator and digitize it.

Sounds reasonable - and afaik, 9 to 10 samples drift per frame could
corrupt
the signal enough to invalidate the CRC.

Thanks for the references. I have developed the receiver side matlab code
which works for simulated data. But I face issues in getting it working for
real time streams. I need to add sampling rate converter in the code which I
will be doing. You have mentioned in your thesis.pdf that you did refer to a
matlab code for DAB receiver. If possible and if it’s not copyrighted can
you share the same to me?

Unfortunately it is copyrighted, and I don’t have the permission of the
author to distribute it - but I’ll forward his email to you, you can try
asking him directly.

Regards, Andreas