Hi LoyCurtis,
there's no general resource; this is just time synchronization for wireless networks;
you'd need to implement it within the bounds of the wireless system you're building. GPS
does it differently than GSM than LTE than distributed radar systems than…
I don't know whether and if so, how, OAI implements such things. This is a question for
the OAI documentation, I guess.
Typically, cellular base stations tend to have a shared clock and time – either via
GPS-disciplined oscillators (such as the GPSDOs for the USRPs!) or via explicit
distribution (via coax) or implicit distribution (recovered from the clock of the
networking link). So, in larger networks, this is something that's solved with hardware
making a shared clock available. However, there's in principle no mathematical obstacle
that a base station that's able to receive other base stations could not derive its own
version of time – just as a handset/UE does in a cellular network. It is, though, a bit
dangerous, since of course everything you recover from a noisy, variable-group-delay
channel, has its own variance, and so would the recovered clock and time (i.e., you get
offset, jitter); and seeing that this is then used by many UEs to coordinate access, again
incurring additional error, this can seriously limit performance.
Also, a hardware solution comes as no additional computational cost to the signal
calculation; doing a resampling by 1.00001 and a delay by 0.3376 sample periods is
relatively expensive in terms of CPU cycles.
Best regards,
Marcus
DISCLAIMER: Any attached Code is provided As Is. It has not been tested or
validated as a product, for use in a deployed application or system, or for use
in hazardous environments. You assume all risks for use of the Code. Use of the
Code is subject to terms of the licenses to the UHD or RFNoC code with which
the Code is used. Standard licenses to UHD and RFNoC can be found at
https://www.ettus.com/sdr-software/licenses/.
NI will only perform services based on its understanding and condition that the
goods or services (i) are not for the use in the production or development of
any item produced, purchased, or ordered by any entity with a footnote 1
designation in the license requirement column of Supplement No. 4 to Part 744,
U.S. Export Administration Regulations and (ii) such a company is not a party
to the transaction. If our understanding is incorrect, please notify us
immediately because a specific authorization may be required from the U.S.
Commerce Department before the transaction may proceed further.
On 26.01.22 09:30, LoyCurtis Smith via USRP-users wrote:
Is there a resource for synchronizing multiple USRP x310s without an external reference
clock?
Also, would SBX-120 daughterboards perform better when using multiple USRPs because of
its phase sync feature?
V/r
LoyCurtis Smith
*From: *Marcus D. Leech <mailto:patchvonbr...@gmail.com>
*Sent: *Tuesday, January 25, 2022 11:14
*To: *LoyCurtis Smith <mailto:ljsmi...@ncsu.edu>
*Cc: *usrp-users@lists.ettus.com
*Subject: *Re: [USRP-users] Re: Synchronization of two USRP x310s
On 2022-01-25 11:12, LoyCurtis Smith wrote:
Would their mechanism included UHD based code?
Since UHD is the way ANY application talks to the radios, yes. But I have no idea if
OAI, as one of dozens and dozens of different appilcations
"out there" has any way to support that functionality.
Also, I assume that the only other option would be to purchase an Octoclock
or some
other clock distribution module?
Yes, you'd need some kind of shared 10MHz reference clock and 1PPS source, AND your
application needs to be able to configure the radios to
use it.
On Tue, Jan 25, 2022 at 10:40 Marcus D. Leech <patchvonbr...@gmail.com>
wrote:
On 2022-01-24 20:53, LoyCurtis Smith via USRP-users wrote:
My system setup is as follows:
·2 x USRP x310 with CBX-120 daughterboard
·2 x Ubuntu 18.04 workstation
·2 x Taoglas 45.8113 antenna
·2 x Internal Reference Clock (Master Clock set at 184.32 MHz)
·2 x Internal Time source
·2 x Connected via 1 Gig-E interfaces
·2 x Using UHD 4.1
The devices have been in two setups: stacked and a few inches apart.
I am attempting to deploy a 5G network using the openairinterface
(OAI)
software system. Both devices synchronize initially, then they
fail. With
openairinterface, I am using frequency offset compensation at the
UE. Its a
useful parameter when running over the air and/or without an
external
clock/time source
(https://gitlab.eurecom.fr/oai/openairinterface5g/blob/develop/doc/RUNMODEM.md)
Is there a way to synchronize the reference clock/timing of both
USRP x310s
over the air? In the future, I will be attempting to connect a
third USRP
x310. My setup will include one base station and two user devices.
V/r
LoyCurtis Smith
Unless OAI provides some mechanism for that, the answer would be no.
You need a
shared reference clock.
_______________________________________________
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-le...@lists.ettus.com
--
V/r
LoyCurtis Smith
_______________________________________________
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-le...@lists.ettus.com
_______________________________________________
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-le...@lists.ettus.com
