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

Vladimir www2008_2 at mail.ru
Thu Jul 23 16:31:18 EDT 2015

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)

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!

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