Re: [Discuss-gnuradio] Synchronizing N210 TX and RX channels

[Daniele Nicolodi]

Hello Marcus,

I'm aware of that, what I want to achieve at the moment is simply to
have a predictable phase delay between the tx and rx channels. This is
prerequisite to measure the round-trip time and account for it.

Cheers,
Daniele


On 22/07/2014 22:14, Marcus Müller wrote:
> Hi Daniele,
> 
> your problem is actually harder: The latency of digital signal
> processing depends on your desired decimation, and analog signal latency
> depends on a ton of factors like target RF frequency, adjustable filters
> (if your daughterboard has something like this), antenna and cabling
> delay, and so on.
> The only real way to know is to *measure* the roundtrip for each
> configuration, and that's exactly what echotimer is for.
> 
> With best regards,
> Marcus
> 
> On 22.07.2014 19:25, Daniele Nicolodi wrote:
>> Hello Stephan,
>>
>> thank for your reply.  What I would like to do is more simple than that:
>> I need to synchronize tx and rx of the same USRP, not of two different
>> devices.  But I need continuous streaming and not burst.
>>
>> Any help in this direction is much appreciated.
>>
>> Thanks. Best,
>> Daniele
>>
>>
>> On 22/07/2014 19:14, Stefan Wunsch wrote:
>>> Hey Daniele,
>>>
>>> I have done the radar toolbox and implemented a synced USRP interface
>>> (USRP Echotimer).
>>>
>>> You are right, the USRP Echotimer does align the timestamps of the TX/RX
>>> commands on both USRPs. But if you connect them by MIMO, the time and
>>> clock are pretty good in sync. Therefore I think the Echotimer can
>>> provide a sync with an accuracy of at least +- 1 sample. Check out [0]
>>> for a video of the sync. There is also a sync setup for testing
>>> (gr-radar/examples/usrp). Unfortunately the documentation is not
>>> finished yet.
>>>
>>> But care: The Echotimer bursts only a packet in sync, it does not stream
>>> the whole time! The packet is defined by a tagged stream.
>>>
>>> Greetings,
>>> Stefan
>>>
>>> [0]
>>> https://grradar.wordpress.com/2014/06/17/synchronisation-echotimer-usrp-interface/
>>>
>>> Am 22.07.2014 18:40, schrieb Daniele Nicolodi:
>>>> On 22/07/2014 18:18, Martin Braun wrote:
>>>>> On top of what Marcus' has said,
>>>>>
>>>>> the gr-radar toolbox might be helpful. It has a block that takes a
>>>>> tagged stream, and outputs a signal it acquired synchronously to the
>>>>> transmitted one.
>>>> Thanks Martin.  This seems to imply that there is no way to actually
>>>> synchronize the hardware, and that the synchronization can only be done
>>>> in software aligning the timestamps of the two streams. Is that the case?
>>>>
>>>> Thanks. Cheers,
>>>> Daniele
>>>>
>>>>
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