[USRP-users] Hardware selection for X310-based system

Rob Kossler rkossler at nd.edu
Thu Jul 23 17:24:09 EDT 2015


Hi Vladimir,
I won't address all of your questions, but I will mention a few things
about our experience using X310s.
1) We use the 10Gb interface using a X520-DA2 board and SFP+ direct attach
cable (5m cable from CablesOnDemand for $78).  This works quite well.  We
rarely have any "communication issues".  We also use the same X520-DA2
board with Intel E10GSFPSR SFP+ optical transceivers and LC/LC (OM3) fiber
(~35m).  This also works quite well.
2) We use HP Workstations (Z230 SFF or Z440).  The Z230 has an i7-4770 cpu
while the Z440 has a Xeon E5-1620 v3 cpu.  For both PCs, we have 32GB RAM
installed.  This has been crucial for us because it allows us to set up a
large RAM file system for streaming the RX data to "files" in RAM.
3) We can run the benchmark_rate utility and achieve 200 MS/s
simultaneously on TX and RX.  Occasionally we will get a couple of
underruns on the TX but it is not all that common.
4) When we try to stream data to files, we never have issues for RAM-based
files.  But, on our Z440, we also have 4 SSDs (Samsung EVO 840) in a SW
RAID 0 config which should be able to handle very large write speeds (~500
MB/s per SSD), but we experience Overruns if we try to stream at rates
higher than 100 MS/s.  (Note, all the rates I'm giving here are for single
channel with the understanding that the rate should be divided by the
number of channels).  We're still not sure how to fix this (via buffering
or other).
5) We often use two X310s in a synchronized 4 channel RX configuration
using the 2 SFP+ ports of the X520-DA2.  In this case if we try to record
data to even RAM-based files, we cannot run at 200 MS/s on both X310s
simultaneously.  This produces overruns indicating the PC is not keeping
up.
6) Regarding PCIe, we haven't used this via UHD, but we have used it from
LabVIEW.  We have the 8371 card, but we haven't tested it for high data
rates.  I do know that the X310 PCIe interface is a Gen1 interface so it is
only necessary to have a Gen1 host adapter card.  We have also successfully
run the NI USRP RIO (i.e., X310) via a PCIe-over-fiber product from Samtec
allowing us to use this interface with a remote device (again ~ 35m).
7) Regarding PCIe vs 10Gb ethernet, the latter is much more convenient with
regard to being able to connect & disconnect without powering up/down the
computer every time you want to change a cable or a device.  I have found
both to be very reliable.  10Gb is also _MUCH_ more convenient for running
the device remotely over fiber.

Rob


On Thu, Jul 23, 2015 at 4:31 PM, Vladimir via USRP-users <
usrp-users at lists.ettus.com> wrote:

> Hello everybody,
>
> Primarily this post is addressed to Ettus personnel, but I'd be glad to
> hear from everyone who has/had experience doing something like described
> below.
>
> We are planning to order an X310 with UBX-160 and need some
> clarification/proofcheck on the input into PC (using powerfull but still
> consumer level, not specialized Windows & Unix desktop PCs). Since we plan
> to get some kind of experimental system to be able to play with pretty
> wideband signals/modulations and which will hopefully serve us for some
> time (taking into accont its cost), we want to have the hw configuration
> that would not limit the maximum bandwidth that X310+UBX160 can give - it
> should be 120 MHz if I'm correct. At least we are speaking about streaming
> the signal to disk for offline processing or smth like this. Guys at
> Fairwaves could not consult us in detail on this, so I'm asking here to do
> some proofcheck to be shure we don't end up with some limitations.
> Currently we have in mind the following config:
>
> 783145-01 USRP X310 KIT
> 783775-01 UBX-160
> 783343-01 (10 Gb SFP+ ETHERNET CABLE, 1M)
> 783346-01 PCIE INTERFACE KIT
>
> 1. We already have an Intel X520-DA2 board which Ettus recommends for
> 10GBE input. Would it suffice to order just 783343-01 (10 Gb SFP+ ETHERNET
> CABLE, 1M) to X310 kit to get complete setup to be able to stream data
> into/from PC?
>
> 2. From what I read earlier here and saw at Ettus website, I understand
> that PCI-Express Connectivity Kit (PCIe – Desktop) is NI PCIe-8371 board
> with the cord. NI states its speed to be 798 MB/s. But to stream 100 MS/s
> we need 800 MB/s. Is their number - 798 - approximate (which would look
> kind of strange for me given its precision :)) and this won't in practice
> lead to speed problems, or do they actually mean 798 MiB/s, or some other
> explanation? Could anyone shed some light on this?
>
> 3. Would it make sense to look at the NI-recommended alternative - 8381
> board? Given that the price difference on NI site for 8371 and 8381 is just
> $50, is it a good idea to go with 8381 to be sure it definitely won't be a
> bottleneck? Or it was not tested with X310 and we might encounter some
> compatibility issues, or any other reasons against it? If it was tested,
> can we order it from Ettus instead of 8371 at comparable price?
>
> 4. Do I get it right that if we encounter problems on 100 MS/s, the next
> sampling rate we can use would be 50 MS/s, as we must use integer
> decimation values from the max one? And in this case we'll get 100 MHz
> bandwidth and limit X310 potential of 120 MHz. Am I correct here?
>
> 5. Am I coerrect that the frequency accuracy of stock X310 oscillator is
> much better than that of previous models, so we don't need external clock
> if we don't plan to sync several devices, work at large distance, etc? It
> won't be used for any 'real-world' cases like network deployment etc, -
> still, speaking about GSM/UMTS lab experiments (like connecting one-two MS
> in the room), may we need additional clock source?
>
> Am I missing any critical parts to build up the working SDR set?
>
> I would also like to hear from people who tried to get about 100-120 MHz
> RX-TX bandwidth from X3X0, e.g. just simply streaming at 100 MS/s to/from
> disk and doing processing offline later  - which is the most stable and
> reliable way to do it - 10GBE or PCIe?
>
> Thank you!
> Vladimir
> _______________________________________________
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> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
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