USRP2 with a Switch

Dear all,
We have 12 USRP2 boards which we would like to synchronise and run in a
phase array system as an expansion of the 4 element system we currently
have
running using the VRT branch of GNURadio.

Currently we use a 4 port PCIe Gb Ethernet Card to connect the USRP2
boards
to the host computer. Our Communications group suggested that we could
use
an Ethernet switch to support 12 boards instead of trying to find a
computer
we can stuff that many Ethernet cards in to.

Data from all 4 boards should get streamed into a data buffer on the
switch
and then be accessed sequentially by the host computer at a rate to
avoid
the over-run of the buffers. Switches work on the ethernet layer and
hence
the protocol should be compatible.

We have read about some problems on the forums regarding using a switch
for
the USRP2’s. Does anybody know if it is a realistic task to be able to
use a
switch to stream data in from multiple boards in this manner and how one
might start in creating a system which can do this? Does a new protocol
for
sending packets to the computer need to be created. If so then where is
the
current protocol specified?

Best regards,
Marc.

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I don’t know that much about this, but I am also interested in getting
a lot of USRP2s working coherently. I currently have approximately the
same setup as you do, but I am also curious about how to expand it.
Please let us know how you advance on this front.

The solution that I am playing with right now is to just make a
cluster of PCs with up to four USRP2s per PC. This way I also get a
compute cluster as a by-product. I need a lot of computing power for
processing my data anyway, and it is nice to have that power close to
the data. Once the data is in the cluster, the data can then be
channeled through standard gigabit ethernet switches (e.g., using MPI)
without problems.

However, I would welcome a feature that would allow USRP2s to be
hooked up into a switch.

juha

On 03/23/2010 05:47 PM, Juha V. wrote:

channeled through standard gigabit ethernet switches (e.g., using MPI)
without problems.

However, I would welcome a feature that would allow USRP2s to be
hooked up into a switch.

I ran across this board the other day and started wondering what you
could do with it and four USRP2’s:

http://www.netfpga.org/

It appears to be four gig-e interfaces connected to a Virtex-4 FPGA on a
PCI card.

I am way over my head now :slight_smile: but it seems like you should be able to
configure the FPGA on the netFPGA board to communicate with four USRP’s
and crunch the data from the USRP’s before feeding it to the PC. Not an
easy task, but might be really useful for people looking for low latency
links to four USRP2’s.

Philip

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