[time-nuts] Re: What everyday uses are there for accurate clocks?

[adrien.demarez at free.fr]

I didn't read the whole thread so I may have missed some past answers. However one example I may give for " What everyday uses are there for accurate clocks" is the one about TDD phase/time synchronization for TDD 4G/5G base stations: equipments on the same channel (same operator, or different operators across a border) or on adjacent channels within the same band all need to transmit at the same time and receive at the same time (otherwise the cross-link BS-BS interference vastly outscales what 3GPP RAN4 has specified, and specific measures need to be taken - but 5G base stations no longer enable the possibility to add custom operator-specific cavity filters...). You may have a look at https://docdb.cept.org/download/1160 



In order to transmit/receive at the same time, all equipments from all operators must use on a common clock (typically traceable to UTC), with an accuracy of +/-1.5 µs (as specified by 3GPP). This is often done with GPS, but all the standards from ITU-T Q13 (PTP, SyncE...) enable to transfer time across a network which alleviates the need for a GPS receiver at each site (or the need to shutdown the site if its GPS receiver gets jammed. Unfortunately more and more GPS jamming events are observed despite it is highly illegal... :-/ ). Having a high quality local oscillator in base stations enables to keep it in free-run for a longer holdover time in the case of such a GPS jamming event (since it will take longer until the +/-1.5µs budget is exceeded). 


-- 
Adrien 

----- Mail original -----

De: "Clint Jay via time-nuts" <time-nuts at lists.febo.com> 
À: "Discussion of precise time and frequency measurement" <time-nuts at lists.febo.com> 
Cc: "Dr. David Kirkby" <drkirkby at kirkbymicrowave.co.uk>, "Clint Jay" <cjaysharp at gmail.com> 
Envoyé: Mardi 29 Novembre 2022 10:50:28 
Objet: [time-nuts] Re: What everyday uses are there for accurate clocks? 

I believe radio and television broadcasting makes use of accurate time in 
studio and the wider transmission network. 

I've worked in quite a few data centres where there's been a local NTP 
server that was synced to GPS or, prior to the availability of GPS, the 
"local" broadcast time signal. 

On Tue, 29 Nov 2022, 09:29 Dr. David Kirkby via time-nuts, < 
time-nuts at lists.febo.com> wrote: 

> I mentioned to someone the other day that I owned an HP GPS time and 
> frequency standard. He asked me a simple question, but one I didn’t know 
> the answer to. 
> 
> 
> Apart from GPS, what in the daily lives of the general public need the sort 
> of accuracy one can get from time-nut grade clocks? I believe some 
> financial transactions is one application, and the cellular phone system 
> another. Are there others? 
> 
> I found a few links 
> 
> “The importance of time measurement” 
> 
> 
> https://www.nsai.ie/national-metrology/calibration-services/time-and-frequency-calibration/the-importance-of-time-measurement/ 
> 
> 
> “The importance of measuring time” 
> 
> 
> https://www.cranfield.ac.uk/alumni/communications/alumni-news/2021/0108-the-importance-of-measuring-time 
> 
> but have not seen any reference to anything much on the topic. 
> -- 
> Dr. David Kirkby, 
> Kirkby Microwave Ltd, 
> drkirkby at kirkbymicrowave.co.uk 
> https://www.kirkbymicrowave.co.uk/ 
> Telephone 01621-680100./ +44 1621 680100 
> 
> Registered in England & Wales, company number 08914892. 
> Registered office: 
> Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United 
> Kingdom 
> _______________________________________________ 
> time-nuts mailing list -- time-nuts at lists.febo.com 
> To unsubscribe send an email to time-nuts-leave at lists.febo.com 
_______________________________________________ 
time-nuts mailing list -- time-nuts at lists.febo.com 
To unsubscribe send an email to time-nuts-leave at lists.febo.com