Re: USRP X300 Synchronization

[Marcus Müller]

No, that's the opposite of what I said. (also, why would you need a GPSDO when these USRPs are colocated?)

You *always* have time offset at a receiver – due to the finiteness of the speed of light.

So, *any* working receiver you have has to have timing recovery, there's no way around it. So, getting better hardware-level synchronization *does not help you at all*. Not if you do it badly, not if you do it really really well.

Best,

Marcus

On 18.05.23 18:21, Hamed Al-Zubi wrote:

So, I have to get GPS modules and use GPSDO synchronization. 

On Thursday, May 18, 2023 at 11:20:02 AM CDT, Marcus Müller <marcus.mueller@ettus.com> wrote:

On 18.05.23 18:10, Hamed Al-Zubi wrote:

Actually, I don't know. I thought that by using PC clock in UHD sink and source block in gnuradio allows synchronization.

Not in a way meaningful for synchronizing transceivers, no.

Also, I thought that Schmidl and Cox algorithm used for timing recovery in OFDM receivers.

Exactly, that's why your PC clock synchronization would contribute nothing, even if it was more accurate. You just don't benefit from synchronization.

On Thursday, May 18, 2023 at 10:46:38 AM CDT, Marcus Müller <mmueller@gnuradio.org> wrote:

Any OFDM receiver needs a timing recovery method anyways, so that has nothing to do with

how well your PC is suitable for synchronizing two devices.

On 18.05.23 17:43, Hamed Al-Zubi wrote:

> Thanks for your response, Marcus!

> I have observed a constellation rotation for OFDM subcarriers when I use the PC clock for

> synchronization. However, by using the channel model, I am able to see the QPSK

> constellation.

>

> Thanks!

> HZ

>

> On Thursday, May 18, 2023 at 10:35:01 AM CDT, Marcus Müller <marcus.mueller@ettus.com> wrote:

>

>

> No, it's several orders of magnitude worse and generally insufficient for anything where

> you need synchronization.

>

> Best,

> Marcus

>

> On 18.05.23 17:12, Hamed Al-Zubi wrote:

> Hello Dears,

>

> I would like to inquire about the synchronization of two USRPs X300, one acting as a

> transmitter (Tx) and the other as a receiver (Rx). If both USRPs are connected to the same

> laptop, I'm wondering if the accuracy provided by PC clock synchronization is similar (or

> close) to that achieved through GPSDO synchronization?

>

> Regards,

> HZ