Re: [Discuss-gnuradio] Synchronisation

[John Shields]

Thanks both,
All good now - I get a roughly constant phase delta 
and when I re-run the FG, I get a different phase delta ( I don't need 
to power cycle the USRPs). Now I will put in the synchronisation code 
and the phase offset should be close to zero.


  Kind Regards,

 John

On 12/09/17 21:12, mle...@ripnet.com wrote:


Use "unknown PPS" on both of them.  The MIMO cable shares both 
REFCLOCK and 1PPS signals, so they will both be synchronized to the 
same time.


On 2017-09-12 16:13, John Shields wrote:


Thanks Derek,
   No, I hadn't been power cycling between the 
runs - good point, obviously, I should have.


   In terms of the 10 MHz and 1 pps references, 
in the configuration I was testing, I don't believe so in that I had 
the MIMO cable disconnected. My strategy was to have 2 USRPs with no 
MIMO - expecting little synchonisation. Then I was going to add the 
devices into the same container and connect the MIMO cable and 
expected things to improve and lastly, I was going to hand-code the 
SBX phase synch code.


   In terms of the version of UHD, the fg shows: 
<<< Welcome to GNU Radio Companion 3.7.11.1 >>>


Thanks Marcus,
   I will implement your way of measuring the 
running phase offset and also thanks for correcting my understanding 
of O/B GPS .



   In terms of getting the devices in the 
container to be the best synch they can be, I presume for the device 
which has the GPS, for the clock source and time source, I would put 
O/B GPS for the device which has it and for the other, I would put 
MIMO cable for both but in terms of the 'Sync' field, where the 
options are PC Clock, Unknown PPS and Don't Sync, which option should 
I select?


   Thanks again for your help.

Kind Regards,

 John


On 11/09/17 09:00, Derek Kozel wrote:

Hi John,

Are you power cycling the USRPs between tests or just rerunning the 
GRC flowgraph? Do you have shared 10 MHz and 1 PPS references? What 
version of UHD is printed in the output?

Thanks,
Derek

On Mon, Sep 11, 2017 at 1:50 AM, John Shields > wrote:


Thanks for the feedback but I am not sure that I understand it.
What I was hoping to do was step through the configurations with
increasing levels of synchronisation and expecting to see same.

Marcus' comment is correct and I have not, yet, put in the code
which synchronises SBXs.

I guess my basic point, from looking at previous post from
others Marcus L included, was that UHD would somehow improve the
synchronisation between two USRPs in the same container versus
those two separately.

When I executed the FG shown (separately) with the USRPs
individually and then within a UHD container the results in
terms of phase variation was the same. I had expected that,
based on my understanding, the containerised USRPs would have
behaved better.

So, either my FG does not measure what I thought it should or
there is little UHD-related benefit to having USRPs individually
or in the 'domain' as MarcusL has mentioned previously. From my
situation it doesn't hence the first question in the post:


   Does my FG not measure what I claim to be wishing
to measure?


Kind Regards,

John



On 11/09/17 01:03, Marcus D. Leech wrote:

On 09/10/2017 08:58 PM, Dan CaJacob wrote:


I could be wrong, but I thought the SBX was one of the few
daughter cards that starts with s known phase offset?


Only if you ask it to do so, and only if it's sharing clock
with its buddies...



On Sun, Sep 10, 2017, 2:49 PM Fulcrum Associates
> wrote:

Dear All,

  I have a couple of USRPs connected, through 
a strong

attenuator to a signal generator (NWT4001). While the
units have a MIMO
option, I don't have that cable. (Option A) When I run the
GRC as
attached, I see too good a result to the extent that the
differential
Phi seems to range over +/- 5 degrees.


  What I had hoped to prove to myself that two
N200 with SBX
would have a varying offset without MIMO cable, then I
would connect the
MIMO cable and move the USRPs into a multi-unit and enable
GPSD O/B on
the unit which has the feature and MIMO for one without
(Option B) and
that the phase differential would improve noticeably and
be a variable
constant, but it didn't.


   If it had, but there still was a fixed
phase offset which
varied each time it was setup 

Re: [Discuss-gnuradio] Synchronisation

[mleech]

Use "unknown PPS" on both of them.  The MIMO cable shares both REFCLOCK
and 1PPS signals, so they will both be synchronized to the same time. 

On 2017-09-12 16:13, John Shields wrote:

> Thanks Derek,
> No, I hadn't been power cycling between the runs - good point, obviously, I 
> should have.
> 
> In terms of the 10 MHz and 1 pps references, in the configuration I was 
> testing, I don't believe so in that I had the MIMO cable disconnected. My 
> strategy was to have 2 USRPs with no MIMO - expecting little synchonisation. 
> Then I was going to add the devices into the same container and connect the 
> MIMO cable and expected things to improve and lastly, I was going to 
> hand-code the SBX phase synch code.
> 
> In terms of the version of UHD, the fg shows: <<< Welcome to GNU Radio 
> Companion 3.7.11.1 >>>
> 
> Thanks Marcus,
> I will implement your way of measuring the running phase offset and also 
> thanks for correcting my understanding of O/B GPS .
> 
> In terms of getting the devices in the container to be the best synch they 
> can be, I presume for the device which has the GPS, for the clock source and 
> time source, I would put O/B GPS for the device which has it and for the 
> other, I would put MIMO cable for both but in terms of the 'Sync' field, 
> where the options are PC Clock, Unknown PPS and Don't Sync, which option 
> should I select?
> 
> Thanks again for your help.
> 
> Kind Regards,
> 
> John
> 
> On 11/09/17 09:00, Derek Kozel wrote: 
> 
> Hi John,
> 
> Are you power cycling the USRPs between tests or just rerunning the GRC 
> flowgraph? Do you have shared 10 MHz and 1 PPS references? What version of 
> UHD is printed in the output? Thanks, Derek 
> 
> On Mon, Sep 11, 2017 at 1:50 AM, John Shields  wrote:
> 
> Thanks for the feedback but I am not sure that I understand it. What I was 
> hoping to do was step through the configurations with increasing levels of 
> synchronisation and expecting to see same.
> 
> Marcus' comment is correct and I have not, yet, put in the code which 
> synchronises SBXs.
> 
> I guess my basic point, from looking at previous post from others Marcus L 
> included, was that UHD would somehow improve the synchronisation between two 
> USRPs in the same container versus those two separately. 
> 
> When I executed the FG shown (separately) with the USRPs individually and 
> then within a UHD container the results in terms of phase variation was the 
> same. I had expected that, based on my understanding, the containerised USRPs 
> would have behaved better.
> 
> So, either my FG does not measure what I thought it should or there is little 
> UHD-related benefit to having USRPs individually or in the 'domain' as 
> MarcusL has mentioned previously. From my situation it doesn't hence the 
> first question in the post: 
> 
> Does my FG not measure what I claim to be wishing to measure?
> 
> Kind Regards,
> 
> John 
> 
> On 11/09/17 01:03, Marcus D. Leech wrote: 
> 
> On 09/10/2017 08:58 PM, Dan CaJacob wrote: 
> 
> I could be wrong, but I thought the SBX was one of the few daughter cards 
> that starts with s known phase offset? Only if you ask it to do so, and only 
> if it's sharing clock with its buddies...
> 
> On Sun, Sep 10, 2017, 2:49 PM Fulcrum Associates  
> wrote: Dear All,
> 
> I have a couple of USRPs connected, through  a strong
> attenuator to a signal generator (NWT4001). While the units have a MIMO
> option, I don't have that cable. (Option A) When I run the GRC as
> attached, I see too good a result to the extent that the differential
> Phi seems to range over +/- 5 degrees.
> 
> What I had hoped to prove to myself that two N200 with SBX
> would have a varying offset without MIMO cable, then I would connect the
> MIMO cable and move the USRPs into a multi-unit and enable GPSD O/B on
> the unit which has the feature and MIMO for one without (Option B) and
> that the phase differential would improve noticeably and be a variable
> constant, but it didn't.
> 
> If it had, but there still was a fixed phase offset which
> varied each time it was setup (which is what I would expect under B)
> then I would hand-code the SBX stream initialisation code to remove the
> offset.
> 
> Does my FG not measure what I claim to be wishing to
> measure?
> 
> If it does measure it correctly, why do my expectations
> of options A and B leading to a different (though improved) situation
> not eventuate?
> 
> Kind Regards,
> 
> John
> 
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> -- 
> 
> Very Respectfully, 
> 
> Dan CaJacob 
> 
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Re: [Discuss-gnuradio] Synchronisation

[John Shields]

Thanks Derek,
   No, I hadn't been power cycling between the runs 
- good point, obviously, I should have.


   In terms of the 10 MHz and 1 pps references, in 
the configuration I was testing, I don't believe so in that I had the 
MIMO cable disconnected. My strategy was to have 2 USRPs with no MIMO - 
expecting little synchonisation. Then I was going to add the devices 
into the same container and connect the MIMO cable and expected things 
to improve and lastly, I was going to hand-code the SBX phase synch code.


   In terms of the version of UHD, the fg shows: 
<<< Welcome to GNU Radio Companion 3.7.11.1 >>>


Thanks Marcus,
   I will implement your way of measuring the 
running phase offset and also thanks for correcting my understanding of 
O/B GPS .



   In terms of getting the devices in the container 
to be the best synch they can be, I presume for the device which has the 
GPS, for the clock source and time source, I would put O/B GPS for the 
device which has it and for the other, I would put MIMO cable for both 
but in terms of the 'Sync' field, where the options are PC Clock, 
Unknown PPS and Don't Sync, which option should I select?


   Thanks again for your help.

Kind Regards,

 John


On 11/09/17 09:00, Derek Kozel wrote:

Hi John,

Are you power cycling the USRPs between tests or just rerunning the 
GRC flowgraph? Do you have shared 10 MHz and 1 PPS references? What 
version of UHD is printed in the output?


Thanks,
Derek

On Mon, Sep 11, 2017 at 1:50 AM, John Shields > wrote:


Thanks for the feedback but I am not sure that I understand it.
What I was hoping to do was step through the configurations with
increasing levels of synchronisation and expecting to see same.

Marcus' comment is correct and I have not, yet, put in the code
which synchronises SBXs.

I guess my basic point, from looking at previous post from others
Marcus L included, was that UHD would somehow improve the
synchronisation between two USRPs in the same container versus
those two separately.

When I executed the FG shown (separately) with the USRPs
individually and then within a UHD container the results in terms
of phase variation was the same. I had expected that, based on my
understanding, the containerised USRPs would have behaved better.

So, either my FG does not measure what I thought it should or
there is little UHD-related benefit to having USRPs individually
or in the 'domain' as MarcusL has mentioned previously. From my
situation it doesn't hence the first question in the post:


   Does my FG not measure what I claim to be wishing
to measure?


Kind Regards,

John



On 11/09/17 01:03, Marcus D. Leech wrote:

On 09/10/2017 08:58 PM, Dan CaJacob wrote:


I could be wrong, but I thought the SBX was one of the few
daughter cards that starts with s known phase offset?


Only if you ask it to do so, and only if it's sharing clock with
its buddies...



On Sun, Sep 10, 2017, 2:49 PM Fulcrum Associates
> wrote:

Dear All,

  I have a couple of USRPs connected, through  a
strong
attenuator to a signal generator (NWT4001). While the units
have a MIMO
option, I don't have that cable. (Option A) When I run the
GRC as
attached, I see too good a result to the extent that the
differential
Phi seems to range over +/- 5 degrees.


  What I had hoped to prove to myself that two
N200 with SBX
would have a varying offset without MIMO cable, then I would
connect the
MIMO cable and move the USRPs into a multi-unit and enable
GPSD O/B on
the unit which has the feature and MIMO for one without
(Option B) and
that the phase differential would improve noticeably and be
a variable
constant, but it didn't.


   If it had, but there still was a fixed phase
offset which
varied each time it was setup (which is what I would expect
under B)
then I would hand-code the SBX stream initialisation code to
remove the
offset.


   Does my FG not measure what I claim to be
wishing to
measure?

   If it does measure it correctly, why do my
expectations
of options A and B leading to a different (though improved)
situation
not eventuate?


   Kind Regards,


  John

___

Re: [Discuss-gnuradio] Synchronisation

[Marcus D. Leech]

On 09/11/2017 04:50 AM, John Shields wrote:
Thanks for the feedback but I am not sure that I understand it. What I 
was hoping to do was step through the configurations with increasing 
levels of synchronisation and expecting to see same.


Marcus' comment is correct and I have not, yet, put in the code which 
synchronises SBXs.


I guess my basic point, from looking at previous post from others 
Marcus L included, was that UHD would somehow improve the 
synchronisation between two USRPs in the same container versus those 
two separately.
What the multi_usrp object will do is to *align timestamps* among all 
the devices within the "container".   That is distinct from arranging for
  synchronization in time and phase.   For that, you must have a shared 
10MHz reference and 1PPS source, and you must ask the

  UHD source to use them.

What I do for testing ongoing phase coherence is to conjugate multiply 
the two halves, then low-pass filter and decimate.  This allows me to
  observe any phase-drift between the two sides over time.  This 
assumes that both sides are tuned to some common test signal.


In the case where two devices aren't sharing a reference clock, one can 
expect the above to produce a noise-like output, since there will be random
  mutual phase noise.   In the case where the two sides have a slow 
phase-drift with respect to one another, one can expect a slow 
sinusoidal output.
  In the case where both sides are in constant phase coherence, one can 
expect an essentially-constant output.





When I executed the FG shown (separately) with the USRPs individually 
and then within a UHD container the results in terms of phase 
variation was the same. I had expected that, based on my 
understanding, the containerised USRPs would have behaved better.


So, either my FG does not measure what I thought it should or there is 
little UHD-related benefit to having USRPs individually or in the 
'domain' as MarcusL has mentioned previously. From my situation it 
doesn't hence the first question in the post:



   Does my FG not measure what I claim to be wishing to 
measure?



Kind Regards,

John


On 11/09/17 01:03, Marcus D. Leech wrote:

On 09/10/2017 08:58 PM, Dan CaJacob wrote:


I could be wrong, but I thought the SBX was one of the few daughter 
cards that starts with s known phase offset?


Only if you ask it to do so, and only if it's sharing clock with its 
buddies...




On Sun, Sep 10, 2017, 2:49 PM Fulcrum Associates 
> wrote:


Dear All,

  I have a couple of USRPs connected, through a strong
attenuator to a signal generator (NWT4001). While the units have
a MIMO
option, I don't have that cable. (Option A) When I run the GRC as
attached, I see too good a result to the extent that the
differential
Phi seems to range over +/- 5 degrees.


  What I had hoped to prove to myself that two N200
with SBX
would have a varying offset without MIMO cable, then I would
connect the
MIMO cable and move the USRPs into a multi-unit and enable GPSD
O/B on
the unit which has the feature and MIMO for one without (Option
B) and
that the phase differential would improve noticeably and be a
variable
constant, but it didn't.


   If it had, but there still was a fixed phase
offset which
varied each time it was setup (which is what I would expect under B)
then I would hand-code the SBX stream initialisation code to
remove the
offset.


   Does my FG not measure what I claim to be wishing to
measure?

   If it does measure it correctly, why do my
expectations
of options A and B leading to a different (though improved)
situation
not eventuate?


   Kind Regards,


  John

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Re: [Discuss-gnuradio] Synchronisation

[Derek Kozel]

Hi John,

Are you power cycling the USRPs between tests or just rerunning the GRC
flowgraph? Do you have shared 10 MHz and 1 PPS references? What version of
UHD is printed in the output?

Thanks,
Derek

On Mon, Sep 11, 2017 at 1:50 AM, John Shields  wrote:

> Thanks for the feedback but I am not sure that I understand it. What I was
> hoping to do was step through the configurations with increasing levels of
> synchronisation and expecting to see same.
>
> Marcus' comment is correct and I have not, yet, put in the code which
> synchronises SBXs.
>
> I guess my basic point, from looking at previous post from others Marcus L
> included, was that UHD would somehow improve the synchronisation between
> two USRPs in the same container versus those two separately.
>
> When I executed the FG shown (separately) with the USRPs individually and
> then within a UHD container the results in terms of phase variation was the
> same. I had expected that, based on my understanding, the containerised
> USRPs would have behaved better.
>
> So, either my FG does not measure what I thought it should or there is
> little UHD-related benefit to having USRPs individually or in the 'domain'
> as MarcusL has mentioned previously. From my situation it doesn't hence the
> first question in the post:
>
>
>Does my FG not measure what I claim to be wishing to
> measure?
>
>
> Kind Regards,
>
> John
>
>
>
> On 11/09/17 01:03, Marcus D. Leech wrote:
>
> On 09/10/2017 08:58 PM, Dan CaJacob wrote:
>
> I could be wrong, but I thought the SBX was one of the few daughter cards
> that starts with s known phase offset?
>
> Only if you ask it to do so, and only if it's sharing clock with its
> buddies...
>
>
> On Sun, Sep 10, 2017, 2:49 PM Fulcrum Associates 
> wrote:
>
>> Dear All,
>>
>>   I have a couple of USRPs connected, through  a strong
>> attenuator to a signal generator (NWT4001). While the units have a MIMO
>> option, I don't have that cable. (Option A) When I run the GRC as
>> attached, I see too good a result to the extent that the differential
>> Phi seems to range over +/- 5 degrees.
>>
>>
>>   What I had hoped to prove to myself that two N200 with SBX
>> would have a varying offset without MIMO cable, then I would connect the
>> MIMO cable and move the USRPs into a multi-unit and enable GPSD O/B on
>> the unit which has the feature and MIMO for one without (Option B) and
>> that the phase differential would improve noticeably and be a variable
>> constant, but it didn't.
>>
>>
>>If it had, but there still was a fixed phase offset which
>> varied each time it was setup (which is what I would expect under B)
>> then I would hand-code the SBX stream initialisation code to remove the
>> offset.
>>
>>
>>Does my FG not measure what I claim to be wishing to
>> measure?
>>
>>If it does measure it correctly, why do my expectations
>> of options A and B leading to a different (though improved) situation
>> not eventuate?
>>
>>
>>Kind Regards,
>>
>>
>>   John
>>
>> ___
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> --
> Very Respectfully,
>
> Dan CaJacob
>
>
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>
>
>
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Re: [Discuss-gnuradio] Synchronisation

[John Shields]

Thanks for the feedback but I am not sure that I understand it. What I 
was hoping to do was step through the configurations with increasing 
levels of synchronisation and expecting to see same.


Marcus' comment is correct and I have not, yet, put in the code which 
synchronises SBXs.


I guess my basic point, from looking at previous post from others Marcus 
L included, was that UHD would somehow improve the synchronisation 
between two USRPs in the same container versus those two separately.


When I executed the FG shown (separately) with the USRPs individually 
and then within a UHD container the results in terms of phase variation 
was the same. I had expected that, based on my understanding, the 
containerised USRPs would have behaved better.


So, either my FG does not measure what I thought it should or there is 
little UHD-related benefit to having USRPs individually or in the 
'domain' as MarcusL has mentioned previously. From my situation it 
doesn't hence the first question in the post:



   Does my FG not measure what I claim to be wishing to 
measure?



Kind Regards,

John


On 11/09/17 01:03, Marcus D. Leech wrote:

On 09/10/2017 08:58 PM, Dan CaJacob wrote:


I could be wrong, but I thought the SBX was one of the few daughter 
cards that starts with s known phase offset?


Only if you ask it to do so, and only if it's sharing clock with its 
buddies...




On Sun, Sep 10, 2017, 2:49 PM Fulcrum Associates 
> wrote:


Dear All,

  I have a couple of USRPs connected, through  a strong
attenuator to a signal generator (NWT4001). While the units have
a MIMO
option, I don't have that cable. (Option A) When I run the GRC as
attached, I see too good a result to the extent that the differential
Phi seems to range over +/- 5 degrees.


  What I had hoped to prove to myself that two N200
with SBX
would have a varying offset without MIMO cable, then I would
connect the
MIMO cable and move the USRPs into a multi-unit and enable GPSD
O/B on
the unit which has the feature and MIMO for one without (Option
B) and
that the phase differential would improve noticeably and be a
variable
constant, but it didn't.


   If it had, but there still was a fixed phase
offset which
varied each time it was setup (which is what I would expect under B)
then I would hand-code the SBX stream initialisation code to
remove the
offset.


   Does my FG not measure what I claim to be wishing to
measure?

   If it does measure it correctly, why do my
expectations
of options A and B leading to a different (though improved) situation
not eventuate?


   Kind Regards,


  John

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Re: [Discuss-gnuradio] Synchronisation

[Marcus D. Leech]

On 09/10/2017 08:58 PM, Dan CaJacob wrote:


I could be wrong, but I thought the SBX was one of the few daughter 
cards that starts with s known phase offset?


Only if you ask it to do so, and only if it's sharing clock with its 
buddies...




On Sun, Sep 10, 2017, 2:49 PM Fulcrum Associates 
> wrote:


Dear All,

  I have a couple of USRPs connected, through  a strong
attenuator to a signal generator (NWT4001). While the units have a
MIMO
option, I don't have that cable. (Option A) When I run the GRC as
attached, I see too good a result to the extent that the differential
Phi seems to range over +/- 5 degrees.


  What I had hoped to prove to myself that two N200
with SBX
would have a varying offset without MIMO cable, then I would
connect the
MIMO cable and move the USRPs into a multi-unit and enable GPSD O/B on
the unit which has the feature and MIMO for one without (Option B) and
that the phase differential would improve noticeably and be a variable
constant, but it didn't.


   If it had, but there still was a fixed phase offset
which
varied each time it was setup (which is what I would expect under B)
then I would hand-code the SBX stream initialisation code to
remove the
offset.


   Does my FG not measure what I claim to be wishing to
measure?

   If it does measure it correctly, why do my expectations
of options A and B leading to a different (though improved) situation
not eventuate?


   Kind Regards,


  John

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Re: [Discuss-gnuradio] Synchronisation

[Dan CaJacob]

I could be wrong, but I thought the SBX was one of the few daughter cards
that starts with s known phase offset?

On Sun, Sep 10, 2017, 2:49 PM Fulcrum Associates 
wrote:

> Dear All,
>
>   I have a couple of USRPs connected, through  a strong
> attenuator to a signal generator (NWT4001). While the units have a MIMO
> option, I don't have that cable. (Option A) When I run the GRC as
> attached, I see too good a result to the extent that the differential
> Phi seems to range over +/- 5 degrees.
>
>
>   What I had hoped to prove to myself that two N200 with SBX
> would have a varying offset without MIMO cable, then I would connect the
> MIMO cable and move the USRPs into a multi-unit and enable GPSD O/B on
> the unit which has the feature and MIMO for one without (Option B) and
> that the phase differential would improve noticeably and be a variable
> constant, but it didn't.
>
>
>If it had, but there still was a fixed phase offset which
> varied each time it was setup (which is what I would expect under B)
> then I would hand-code the SBX stream initialisation code to remove the
> offset.
>
>
>Does my FG not measure what I claim to be wishing to
> measure?
>
>If it does measure it correctly, why do my expectations
> of options A and B leading to a different (though improved) situation
> not eventuate?
>
>
>Kind Regards,
>
>
>   John
>
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-- 
Very Respectfully,

Dan CaJacob
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