Japan Standard Time Group

Labo（Internet Time-Transfer Technique）

■Experiment equipments

■NTP Experimental Servers using FPGA

Upper: A SNTP server using our PCI-X hardware server card which was developed in 2004.
This server uses the clock signal directly from the Japan standarad time which is maintained in NICT.

Middle: The same hardware as above.
This PC is used for measuring other NTP/SNTP servers using our FPGA hardware card.
The Japan standarad time is also supplied to this server.

Lower: 10GbE and GbE L2/L3 switches.
10Gbase-LR port on the left side is connected to the NICT Otemachi via the WDM line.

■SNTP servers using smaller server cards.


Upper: Ordinary software NTP server using ntpd version 4.

Middle: A SNTP server using smaller server card which was developed in 2005.

Lower: The same hardware as above. This is for cold stand-by.

■Hardware of Time Stamper and hardware of SNTP server

In order:
Machine for 10GbE(development in 2004)
Machine for GbE(development in 2004)
Small size machine for GbE(development in 2005)

All of these three kinds of cards operate as pass-type Time-stamper (original packet format).
The delay time between each main base can be independently measured by one packet by inserting it in the main base on the network.

There is the memory of 1GB on two upper kind of large-scale card. It is possible to capture packet header at the wire speed and to send an arbitrary Ethernet frame at accurate intervals of time.

There is on two lower kinds of cards the SNTP server and the miscellaneous function (for composing a precise NTP client).
Though thinks that installing these functions in the machine for 10GbE of is possible, but not carry into effect yet.

The small size machine for GbE was miniaturized. (Some functions were omitted from a large-scale card developed in 2004 and the mounting density was raised upper by reexamining parts and the substrate composition.)
At the same time, a detailed point (like the part relations to convenience on the programming, and the Falesafe function when the SNTP server is really operated)
is improved. Installed OCXO (crystal oscillator with the temperature controlled bath) is stably though small, and the frequency fine-tuning by the register value rewriting became possible.

■Machine parts related to supply of signal of time

In order:
Notebook computer for data collection
Counter of time interval(2)
10MHz signal: Distribute machine of five outputs
1PPS signal: Distribution machine of five outputs
Rubidium clock for comparison
1PPS signal: Distribution machine of ten outputs
10MHz signal: Distribution machine of ten outputs

The signal is received in the Japan Standard Time Group at NICT of the maintenance at a Japanese standard with machine parts here, and it distributes it to the experiment machine parts of our group.

■Feedback control algorithm performance evaluation experiment to rubidium clock

Upper row: Rubidium Clock made in Stanford Research Company
The lower: Cesium Clock made in Agerent Company


In the device here, the difference of time with the cesium clock is measured, and the performance evaluation experiment of the algorithm that feeds back the result to the rubidium clock is done.
If the machine parts developed in our group is used, the difference measurement of time in the error margin of the micro seconds or less becomes possible by way of the high-speed Internet line.
This develops the control algorithm for that at the level that can be used enough for the rubidium clock in the remote place to synchronize.

■GPS common view device

Though a usual GPS receiver receives information on the position and time from the GPS satellite, The GPS Common View method receives the signal in two or more bases from GPS, and requests the relative time　difference of clock set up in these bases.
The time difference with a Japanese standard can be requested in other bases if there is the one based on a Japanese standard in these bases.
The GPS Common View method is used for the comparison with the time between international and the decision of the world agreement (UTC), etc.