[time-nuts] febo.com mailing lists are back!
Thanks to quick work by our new mailing list hosting company, emwd.com, the febo.com mailing lists are back up ahead of schedule. The list posting addresses remain @lists.febo.com The web interface to manage your subscription info, and the archives, do require slightly different URLs. To access the web interface, use this format: lists.febo.com/mailman/listinfo/_lists.febo.com For example, lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com Similarly, the archives are reached at lists.febo.com/pipermail/_lists.febo.com For example, lists.febo.com/pipermail/time-nuts_lists.febo.com (This change may make Google searches of the archives unreliable for a while, but they should catch up fairly quickly.) Best wishes, John ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] febo.com mailing lists are back!
Hurray! Good work! Now we can focus on time-nuttery again. I held a crash-coarse for a friend (and silent casual reader of time-nuts) this weekend, and he learned a lot. :) Doing it oneself is fun, sharing it is even more fun. Cheers, Magnus On 07/02/2018 05:01 PM, John Ackermann N8UR wrote: > Thanks to quick work by our new mailing list hosting company, emwd.com, > the febo.com mailing lists are back up ahead of schedule. > > The list posting addresses remain @lists.febo.com > > The web interface to manage your subscription info, and the archives, do > require slightly different URLs. To access the web interface, use this > format: lists.febo.com/mailman/listinfo/_lists.febo.com > > For example, lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > Similarly, the archives are reached at > lists.febo.com/pipermail/_lists.febo.com > > For example, lists.febo.com/pipermail/time-nuts_lists.febo.com > > (This change may make Google searches of the archives unreliable for a > while, but they should catch up fairly quickly.) > > Best wishes, > John > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] once again timenuts in the news
https://news.slashdot.org/story/18/07/01/2022232/google-and-nasdaq-pursuing-nano-second-precision-in-network-time-protocol https://www.nytimes.com/2018/06/29/technology/computer-networks-speed-nasdaq.html 100 ns... Doesn't seem particularly challenging if you have something like PTP. But there's this:"The new synchronization system will make it possible for Nasdaq to offer “pop-up” electronic markets on short notice anywhere in the world, Mr. Prabhakar said" OK, 100ns world wide is a trickier proposition. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] once again timenuts in the news
On 7/2/18 10:42 AM, jimlux wrote: https://news.slashdot.org/story/18/07/01/2022232/google-and-nasdaq-pursuing-nano-second-precision-in-network-time-protocol https://www.nytimes.com/2018/06/29/technology/computer-networks-speed-nasdaq.html 100 ns... Doesn't seem particularly challenging if you have something like PTP. But there's this:"The new synchronization system will make it possible for Nasdaq to offer “pop-up” electronic markets on short notice anywhere in the world, Mr. Prabhakar said" OK, 100ns world wide is a trickier proposition. hhh I see what's new and different - the authors of the paper https://www.usenix.org/conference/nsdi18/presentation/geng https://www.usenix.org/system/files/conference/nsdi18/nsdi18-geng.pdf they're using Support Vector Machines and Machine Learning (how sexy! how fashionable!) and "Because HUYGENS is implemented in software running on standard hardware, it can be readily deployed in current data centers." And, more troubling - in terms of the desire to do fast transactions.. They do the processing in batches ( on page 82 of the paper) A crucial feature of HUYGENS is that it processes the transmit (Tx) and receive (Rx) timestamps of probe packets exchanged by a pair of clocks in bulk: over a 2 second interval and simultaneously from multiple servers. SO they're actually not really "synchronizing the systems" (in the sense that I can schedule an event on System A to occur tomorrow at 12:34:56.000,000,000 and an event on System B tomorrow at 12:34:56.000,000,001 and record the events on System C by starting my recorder at 12:34:55.999,999,999 and stopping the recorder at 12:34:56.000,000,002 They're "adjusting the time of events recorded by multiple different clocks to a common time scale, post hoc" We do this now in spacecraft work - it's generically called "time correlation" where you relate the onboard spacecraft clock (generally some sort of free running counter) to external measured events (i.e. the Earth Received Time of a message, or GPS 1pps ticks, or ...) and then create a suitable model of the clock behavior so that you can schedule future events (thruster burns, camera actions), etc. Sometimes the results are quite impressive (https://www.nasa.gov/mission_pages/msl/news/msl20120806b.html) But I will readily concede that the current spacecraft approach is not scalable to dozens, much less, thousands of entities. So Huygens meets the "reconcile transaction time stamps at the end of the day" kind of need, but does NOT meet the "schedule future events independently" need. I find that "knowing the time of an event in the past precisely" is interesting and useful, but "scheduling the time of an event in the future precisely" is, in the long term, a more useful thing. Here's a practical example.. You have a constellation of N satellites, all independent (in the sense that they do not communicate with each other) and observing an astronomical object for a sporadic phenomenon (a coronal mass ejection, as it happens). You don't have enough storage or communication bandwidth to record everything all the time, so you record some at a duty cycle of 1% - record a millisecond's data every 100 milliseconds. The phenomenon of interest lasts minutes or hours, so you'll get plenty of data. However, the 1 millisecond recording times must be synchronized across all satellites, because you're going to combine the data later, and it needs to be coherent - (they're radio interferometers). So what you need is "good clocks" that are predictable in the future - if satellite 1 is at 10.000,01 MHz and satellite 2 is at 9.999,997, you can adjust the sampling rate generator accordingly (in terms of rate and offset) to ensure that every 100 ms, the sampling gate opens for 1 ms - and they're all the same millisecond. http://adsabs.harvard.edu/abs/2018AAS...23221102K http://www.ursi.org/proceedings/procGA17/papers/Paper_HJ26-3(1332).pdf https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3662&context=smallsat (Full Disclosure - I'm the project manager for SunRISE) ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] once again timenuts in the news
In message <1e83f1bb-8688-687b-6840-e6d2cfd31...@earthlink.net>, jimlux writes: Jim, The more you tell us about this stuff, the more we'll have to pester you to write a book, or at least a long article titled "Clocks in Spaace!" :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] White Rabbit time distribution performance
Hello! I published a paper on WR time distribution performance that you might consider interesting. It's available at IEEExplorer: https://ieeexplore.ieee.org/document/8400550/ Abstract: This article investigates the ultimate limits of White Rabbit (WR), an high-accuracy time distribution system based on FPGA. The knowledge of such limits is essential for new emerging applications that are evaluating WR. In this article, we identify and study the key elements in the WR synchronization: the Digital Dual Mixer Time Difference phase detector and the Gigabit Ethernet transceiver. The benchmarks and experimental analysis of these key elements allow us to determine the WR Switch performance limits and evaluate their evolution with newer FPGAs. The identified performance limits are achievable by the present-day generation of WR Switch. The ultimate limits of short-term synchronization performance due to FPGA implementation have been derived through analysis and then demonstrated using the existing WR Switch enhanced with an additional daughter-board. This combination (WR Switch and daughter-board) achieves a tenfold improvement in terms of phase noise, jitter and shortterm stability with respect to the current WR performance. Both phase detectors and Gigabit transceivers have a similar phase noise contribution equal to a short-term stability of MDEV 4E-13 at τ=1 s (dominated by flicker PM noise). cheers Mattia ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] once again timenuts in the news
On 7/2/18 12:35 PM, Poul-Henning Kamp wrote: In message <1e83f1bb-8688-687b-6840-e6d2cfd31...@earthlink.net>, jimlux writes: Jim, The more you tell us about this stuff, the more we'll have to pester you to write a book, or at least a long article titled "Clocks in Spaace!" :-) I have been thinking about just that... There are others who are *much* better at some of the details - the literature on Ultra Stable Oscillators, for instance. I'm more of a "now that we have it, what do we do with it, and why do we care about ADEV and PN" ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] White Rabbit time distribution performance
Thank you very much Mattia - I am interested to read and to learn - but I see: "Sign in or purchase", not loved by everybody, and I have no membership, a pity, sorry. My best wishes, Arnold, DK2WT Am 02.07.2018 um 21:37 schrieb Mattia Rizzi: Hello! I published a paper on WR time distribution performance that you might consider interesting. It's available at IEEExplorer: https://ieeexplore.ieee.org/document/8400550/ Abstract: This article investigates the ultimate limits of White Rabbit (WR), an high-accuracy time distribution system based on FPGA. The knowledge of such limits is essential for new emerging applications that are evaluating WR. In this article, we identify and study the key elements in the WR synchronization: the Digital Dual Mixer Time Difference phase detector and the Gigabit Ethernet transceiver. The benchmarks and experimental analysis of these key elements allow us to determine the WR Switch performance limits and evaluate their evolution with newer FPGAs. The identified performance limits are achievable by the present-day generation of WR Switch. The ultimate limits of short-term synchronization performance due to FPGA implementation have been derived through analysis and then demonstrated using the existing WR Switch enhanced with an additional daughter-board. This combination (WR Switch and daughter-board) achieves a tenfold improvement in terms of phase noise, jitter and shortterm stability with respect to the current WR performance. Both phase detectors and Gigabit transceivers have a similar phase noise contribution equal to a short-term stability of MDEV 4E-13 at τ=1 s (dominated by flicker PM noise). cheers Mattia ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] OCXO Support board
In a moment of weakness and impulse, for no particular reason I bought a Morion MV80 on the auction site. Now I'd like to power it up and am looking for an easy way to do that. So, rather than reinventing the wheel, I'm looking for something similar to this: https://www.tindie.com/products/AnalysIR/10mhz-ocxo-frequency-standard-module-or-kit/?pt=ac_prod_search with a footprint that will accept the MV80. Does anyone know of such a source? Thanks, Wes ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] once again timenuts in the news
Usenix paper: https://www.usenix.org/system/files/conference/nsdi18/nsdi18-geng.pdf Usenix talk: https://www.usenix.org/conference/nsdi18/presentation/geng At the end of the talk the presenter mentions WAN sync between labs at Utah, Wisconsin and Clemson "under 10 microseconds" I'd like to see an error analysis and a complete list of prerequisites. How does RTT/2 disappear? On Mon, Jul 2, 2018 at 12:42 PM, jimlux wrote: > https://news.slashdot.org/story/18/07/01/2022232/google-and- > nasdaq-pursuing-nano-second-precision-in-network-time-protocol > > https://www.nytimes.com/2018/06/29/technology/computer-netwo > rks-speed-nasdaq.html > > 100 ns... Doesn't seem particularly challenging if you have something like > PTP. > > But there's this:"The new synchronization system will make it possible for > Nasdaq to offer “pop-up” electronic markets on short notice anywhere in the > world, Mr. Prabhakar said" > > > OK, 100ns world wide is a trickier proposition. > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/ > listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Lady Heather V6.0 and RINEX files...
Time Nutters-- Mark Sims said of the latest release of Lady Heather: There are several cosmetic tweaks. A major new feature is the ability to write RINEX files for receivers that can output satellite RAW observation data. RINEX files can be processed to produce very accurate positions (typically 150-250mm for L1 only receivers, 10mm for L1/L2 receivers). The recommended online processor is CSRS-PPP from Natural Resources of Canada (NARCAN)... they seem to be the only service that supports L1 only data. In layman's terms, what does this mean with regard to being able to set an *AFFORDABLE* GPS RX out in the field and use it to do site surveys and process the recorded RINEX data later to establish the geo-position of each of the sites within a precision of +/- a few centimeters? I presume this may not be a simple as setting up my Trimble Thunderbolt and Lady Heather V6.0 in the field and gathering RINEX files for a few minutes?? Mike Baker Micanopy, FL * ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] once again timenuts in the news
On Tue, Jul 3, 2018 at 2:18 AM, jimlux wrote: > they're using Support Vector Machines and Machine Learning (how sexy! how > fashionable!) > This approach has been done before, I wonder why it's not mentioned in their literature survey. The papers below have more details. [1] Sirdey, R. & Maurice, F. "A linear programming approach to highly precise clock synchronization over a packet network" F. 4OR (2008) 6: 393. https://doi.org/10.1007/s10288-007-0060-6 [2] D. E. Pinkovich and N. Shimkin, "Clock synchronization using maximal margin estimation" 2011 19th Mediterranean Conference on Control & Automation (MED), Corfu, 2011, pp. 1182-1187. https://doi.org/10.1109/MED.2011.5983128 ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
