Re: [Discuss-gnuradio] Clock Recovery MM documentation

[Iluta V]

Thanks for your explanation! That's worth while looking into!

On Fri, Jul 31, 2015 at 1:17 AM, Francisco Albani <address@hidden> wrote:

From Matlab MM documentation [1]:

"[...] Typically, the input signal is the output of a receive filter that is matched to the transmitting pulse shape. [...]"

Assuming the MM Gnuradio implementation has the same hypothesis on the input signal (anybody can confirm this?), I deduced this block is usually misused when feed with a square signal, because it will take only one sample per symbol discarding the rest (with useful energy). You can put a Moving Average before for better results.

This is one of the reason why the pfb_clock_recovery block is better, but unfortunately unfit for square signals [2]. I found even better results using a gaussian filter inside pfb_clock_recovery as the pseudo-matched filter to square pulses (with a proper bt value). (Obviously I can only guarantee this for the specific signal I worked with)

[1] http://www.mathworks.com/help/comm/ref/muellermullertimingrecovery.html

[2] See discussion: http://gnuradio.org/redmine/issues/812

2015-07-30 16:03 GMT-03:00 Iluta V <address@hidden>:

Hi, Tom,

Could you be more specific where exactly it is not "the right algorithm"? We'd appreciate that and would correct that in own work as well, if Security Research Assessment made a mistake here.

I will be looking forward to your response,

Iluta

On Thu, Jul 30, 2015 at 9:55 PM, Tom Rondeau <address@hidden> wrote:

On Thu, Jul 30, 2015 at 2:38 PM, Iluta V <address@hidden> wrote:

Research paper CONVERTING RADIO SIGNALS TO DATA PACKETS (Examination of Using GNU Radio Companion for Security Research and Assessment) deals with Clock Recovery MM, I attached the paper, have a look at:

6.Section 6.Counting the Bits
7.Analyzing Demodulated Data

Both deal with Clock Recovery MM usage and has flowgraphs.

Best regards,

Iluta

That's great, and I'm glad they got it to work for their application. Looks like they provide a good explanation of its use, too. Still, it's not the right algorithm.

 

Tom

 

On Thu, Jul 30, 2015 at 9:23 PM, Tom Rondeau <address@hidden> wrote:

Another point to keep in mind is that the M&M block isn't great in fading environments. It's really suboptimal in general. Look at the pfb_clock_recovery block, instead.

Tom

On Thu, Jul 30, 2015 at 2:18 PM, Daniel Camara <address@hidden> wrote:

Hi Klauss,

You could also take a look at https://www.tablix.org/~avian/blog/archives/2015/03/notes_on_m_m_clock_recovery/, it helped me quite a bit!

 Best regards...

   Daniel

On Thu, Jul 30, 2015 at 7:17 PM, Martin Braun <address@hidden> wrote:

Klaus,

the manual page for this block has a paper reference in it:
http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1clock__recovery__mm__ff.html#details

M

On 30.07.2015 10:16, Klauss Wolfeinstein wrote:
> Hello,
>
> I would like to find a proper documentation on MM algorithm block (paper
> for example). Any ideas ?
>
> Thank you.
>
> Regards.
>

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    Best regards...
           
                     Daniel

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