[USRP-users] Sync two USRP devices to sense 100MHz of spectrum

Derek Kozel derek.kozel at ettus.com
Thu Nov 9 10:30:45 EST 2017


Hello Wahhab,

I do not know about using the MIMO cable between a USRP2 and a N2x0, the
USRP2 became end of life before I started at Ettus. I think it would work,
but cannot test it myself. Others at Ettus may know the answer.

You will need at least two 1 Gigabit connections to your host computer. The
other option would be a Gigabit Switch with a 10 Gigabit Ethernet
connection to the host, but it is usually less expensive and easier to get
an extra Ethernet Card for your host computer. It is simply not possible to
carry 100 MS/s, even at 8 bits, over a 1 GigE connection. (100
Megasamples/second * (2 * 8) bits / complex sample = 1.6 Gigabits per
second).

Yes, you can use two B210s to monitor 100 MHz of bandwidth. USB 3 can carry
over 50 MS/s in 16 bit samples in theory but some computers cannot handle
it. The benchmark_rate program included with the USRP driver is good tool
for testing if your computer can handle the data rate. In order to
frequency and time synchronize them you would have to supply 10 MHz and 1
PPS references from an external source. Ettus sells the Octoclock which can
synchronize up to 8 devices. It comes with or without a GPS reference
inside to supply the signals. There are other hardware options available if
you look around, the requirements for the reference signals are on the
knowledge base. There are app notes about doing synchronization as well on
there.
https://kb.ettus.com/B200/B210/B200mini/B205mini#Timing_Reference_Input

Regards,
Derek

On Thu, Nov 9, 2017 at 2:46 PM, Wahhab Albazrqaoe <albazrqa at msu.edu> wrote:

> Thank you Derek for the comments.
> I just want to clarify this point about connecting two USRP devices;
> first, it seems to be fine to connect a USRPN200 with USRP2 (via a MIMO
> cable), right?
> Second, by connecting two devices via MIMO cable, I need to connect their
> GigaBit Ethenet cables to a GigaBit switch, which feeds the host, right? Is
> there an example (i.e. code) on how to do such configuration? What
> parameters to send to each device?
> I also don't have an external source, like 10MHz and 1 PPS references; my
> plan is just to use MIMO cable; it seems from your reply it is doable.
>
> Another question, I have two USRPB210 devices, is it possible to use these
> devices instead of USRPN/2? Is there an extra hardware/software that we
> need to use with USRPB210 to get the two devices sync in time and freq?
>
> Best,
> Wahhab
>
> On Thu, Nov 9, 2017 at 9:34 AM, Derek Kozel <derek.kozel at ettus.com> wrote:
>
>> Hello Wahhab Albazrqaoe,
>>
>> It is certainly possible to configure each USRP to be tuned to a
>> different frequency and to be synchronized closely in time. A 1 Gigabit
>> Ethernet connection can carry approximately 25 MS/s of 16 bit samples and
>> 50 MS/s of 8 bit samples. We do not support sending 4 bit samples so it is
>> not possible to carry 100 MHz worth of spectrum over the 1 GigE cable of an
>> N2x0 or USRP2. You should operate in Dual Ethernet mode using the MIMO
>> cable to share clock and time references. If you already have external 10
>> MHz and 1 PPS references that you can send to both then the MIMO cable
>> gives you little benefit in this situation.
>> http://files.ettus.com/manual/page_usrp2.html#usrp2_mimocable
>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__files.ettus.com_manual_page-5Fusrp2.html-23usrp2-5Fmimocable&d=DwMFaQ&c=nE__W8dFE-shTxStwXtp0A&r=Tlms1z6tKiruwUlcy5dGsCCn_nZvNYIamSz8XsFHSRs&m=VGOSWfv9tGkGmMnimSB1CdXINqvkCsEy9vnk0K6qq0M&s=u0ke8LMqaemeiYKZA49AdF5DAzQavZgSuReDgT8yQx8&e=>
>>
>> You will be limited to 8 bit samples so you should check that you
>> application will be ok with that limitation. Newer USRPs use faster
>> connections such as USB 3 and 10 Gigabit Ethernet to pass higher resolution
>> samples at higher rates.
>>
>> Regards,
>> Derek
>>
>>
>> On Thu, Nov 9, 2017 at 2:07 PM, Wahhab Albazrqaoe via USRP-users <
>> usrp-users at lists.ettus.com> wrote:
>>
>>> Dear All,
>>> We would like to sense (i.e. sample) 100 MHz of 2.4GHz spectrum. My idea
>>> is to connect 2 USRPs (USRPN200 and USRP2) via a MIMO cable (available at
>>> ettus.com
>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__ettus.com&d=DwMFaQ&c=nE__W8dFE-shTxStwXtp0A&r=Tlms1z6tKiruwUlcy5dGsCCn_nZvNYIamSz8XsFHSRs&m=VGOSWfv9tGkGmMnimSB1CdXINqvkCsEy9vnk0K6qq0M&s=PSyPhuuc6w7iP77pKr2zZ4IPIUy5TJxL8odqr6wBua8&e=>).
>>> Then, we configure each USRP separately to monitor 50MHz of bandwidth (8bit
>>> per sample).
>>>
>>> My question:
>>> 1- is it possible to configure each USRP separately to monitor different
>>> spectrum segment? Example, USRPN200 senses 2400MHz to 2450MHz and USRP2
>>> sense 2450MHz up to 2500MHz.
>>> If this is possible, is it possible to get the samples over one GigaBit
>>> Ethernet cable (i.e. connected to one USRP device)? Or we may need to take
>>> a cable out of each device and connect them to a switch, which feeds the
>>> host ?
>>>
>>> 2- is it possible to connect USRPN200 with USRP2 via a MIMO cable? Or we
>>> need to use two USRP devices of the same type? like two of USRPN200 or two
>>> of USRP2.
>>>
>>> Thanks
>>> Wahhab Albazrqaoe
>>>
>>> _______________________________________________
>>> USRP-users mailing list
>>> USRP-users at lists.ettus.com
>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.ettus.com_mailman_listinfo_usrp-2Dusers-5Flists.ettus.com&d=DwMFaQ&c=nE__W8dFE-shTxStwXtp0A&r=Tlms1z6tKiruwUlcy5dGsCCn_nZvNYIamSz8XsFHSRs&m=VGOSWfv9tGkGmMnimSB1CdXINqvkCsEy9vnk0K6qq0M&s=UDrnn2_SdXQRAou4zuu0Q6u5SVQBZwepHogZ0taR6Xw&e=>
>>>
>>>
>>
>
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