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Re: [Discuss-gnuradio] DBSRX tune delay

From: Sylvain Munaut
Subject: Re: [Discuss-gnuradio] DBSRX tune delay
Date: Tue, 08 Dec 2009 21:24:48 +0100
User-agent: Thunderbird (X11/20091028)

Vadim Uvin wrote:
> Thanks for the suggestion, Sylvian. But it is not the case, since the
> GSM does not use inband signalling.

? I'm taking about inband signalling for the USRP where the USRP marks
each sample received with a timestamp.

> Buying the second DBSRX is not very
> convenient since I in the future I want to try to implement channel
> hopping. That is why I'm wondering is it feasible at all to change USRP
> frequency fast enough to keep up with the GSM. By the way, the delay
> should be comparable to about 1 ms.
> Also, the downlink and uplink channel separation is at least 45 MHz, so
> I cannot cover it with USRP's 8 MHz.
> 2009/12/8 Sylvain Munaut <address@hidden <mailto:address@hidden>>
>     Vadim Uvin wrote:
>     > I have USRP+DBSRX. I'm trying to listen to uplink channel (MS->BTS) of
>     > GSM. To do that, I first need to be synced with the BS (i.e. listen to
>     > synchronization channel of BTS). Then I have to change the center
>     > frequency to uplink channel, but I need to know how long it takes
>     before
>     > USRP gets stable or I can lost the synchronization. Unfortunately, I
>     > can't find what the tune delay of DBSRX is. Maybe someone knows?
>     You should use inband signalling, this way you have a 'sample' counter
>     and you know precisely 'where' you are in time.
>     Or you use two dbsrx, following both up & downlink ....
>       Sylvain

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