Re: [Discuss-gnuradio] parallel and time/frequency-synchronized TX/RX with large number of USRPs ?

[hanwen]

Thanks for you reply Rahlph.

I our cases, the off-line measurement is enough which is not sensitve to jitter issue.

What we want to make sure is that at TX side, the waveform to different antenna can be transmitted at the same time; and at the RX side, some time stamp is on the waveform so we kown exactly at which time point the multiple waveform streams is synchronized.

The other requirement is no sample loss over the ethernet connections is allowed, especially for large amount of USRPs that packet collision might be quite often. I guess if UHD support TCP, this could be solved.

2013/4/3 Ralph A. Schmid, dk5ras <address@hidden>

Just keep in mind, on one ethernet network there is no real parallel transfer, everything is sequential, at least on the shared parts like the cable from the switch to the PC. Can you live with this latency? Of course you can try to force a given sequence, with known timing, and jitter should be small when the network is separated from other networks and has the pure purpose to serve your USRPs...

 

I have to do with industrial test/measurement equipment where those latency/jitter effects _are_ a real PITA, and I am amazed how easily in many RF applications those problems are “workarounded”.

  

Ralph.

 

 

From: discuss-gnuradio-bounces+ralph=address@hidden [mailto:discuss-gnuradio-bounces+ralph=address@hidden] On Behalf Of hanwen
Sent: Wednesday, 03 April, 2013 14:35
To: address@hidden
Subject: [Discuss-gnuradio] parallel and time/frequency-synchronized TX/RX with large number of USRPs ?

 

Dear *,

 

Is it possible to syncronize large number of USRPs (e.g. N210) in time and frequency for building an large MIMO array.

My imagination would be using an Ethernet switch hubbing all the USRPs and connect to a host PC vial 10Gbps ethernet. All the USRPs share a common 10MHz/1PPS input.

The communications between all the USRPs with the host PC is via TCP (I'm not sure if UHD support TCP now) so that there is no packet loss.

 

We previously build a 2x2 MIMO using USRP2s with two ethernet adapters on host PC, which is quite successful.

 

Bests,

Hanwen

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