keywords={IEEE standards;access protocols;local area networks;metropolitan area networks;IEEE standard;MAC service;VLAN bridges;bridged networks;local area networks;media access control service;metropolitan area networks;Bridged circuits;IEEE standards;Local area networks;Media Access Protocol;Metropolitan area networks;Protofcols;Virtual environments;Bridged Network;IEEE 802.1Q(TM);LAN;MAC Bridge;MSTP;Multiple Spanning Tree Protocol;PBN;Provider Bridged Network;RSTP;Rapid Spanning Tree Protocol;SPB Protocol;Shortest Path Bridging Protocol;VLAN Bridge;Virtual Bridged Network;local area network;metropolitan area networks;virtual LAN},
doi={10.1109/IEEESTD.2014.6991462},}
@online{biblio:allan90,
author = {D.B. Sullivan and D.W. Allan and D.A. Howe and F.L. Walls},
title = {{Characterization of Clocks and Oscillators}},
url = {tf.nist.gov/general/pdf/868.pdf},
note = "{NIST Technical Note 1337}",
urldate = {1990},
}
@article{biblio:IEEE802.3,
journal="{IEEE 802.3-2012}",
title = {{IEEE Standard for Ethernet}},
doi = {10.1109/IEEESTD.2012.6419735},
abstract = {Ethernet local area network operation is specified for selected speeds of operation from 1 Mb/s to 100 Gb/s using a common media access control ({MAC}) specification and management information base ({MIB}). The Carrier Sense Multiple Access with Collision Detection ({CSMA}/{CD}) {MAC} protocol specifies shared medium (half duplex) operation, as well as full duplex operation. Speed specific Media Independent Interfaces ({MIIs}) allow use of selected Physical Layer devices ({PHY}) for operation over coaxial, twisted-pair or fiber optic cables. System considerations for multisegment shared access networks describe the use of Repeaters that are defined for operational speeds up to 1000 Mb/s. Local Area Network ({LAN}) operation is supported at all speeds. Other specified capabilities include various {PHY} types for access networks, {PHYs} suitable for metropolitan area network applications, and the provision of power over selected twisted-pair {PHY} types.},
date = {2012-12},
keywords = {1000BASE, 100BASE, 100GBASE, 100 Gigabit Ethernet, 10BASE, 10GBASE, 10 Gigabit Ethernet, 40GBASE, 40 Gigabit Ethernet, attachment unit interface, {AUI}, Auto Negotiation, Backplane Ethernet, bit rate 1 Mbit/s to 100 Gbit/s, carrier sense multiple access, carrier sense multiple access with collision detection, coaxial cable, coaxial cables, computer network management, {CSMA}-{CD}, data processing, {DTE} Power via the {MDI}, {EPON}, Ethernet, Ethernet in the First Mile, Ethernet networks, Ethernet passive optical network, Fast Ethernet, formal specification, full duplex operation, Gigabit Ethernet, {GMII}, {IEEE} standards, {IEEE} Std 802.3-2008 Revision, {IEEE} Std 802.3-2012, information exchange, local area network, {MAC} protocol specification, management, management information base, {MDI}, media access control, media independent interface, medium dependent interface, metropolitan area network, Metropolitan area networks, {MIB}, {MII}, multisegment shared access network, network interfaces,
optical fibre {LAN}, optical repeaters, Passive optical networks, {PHY}, physical coding sublayer, Physical layer, physical layer device, physical medium attachment, {PMA}, Power over Ethernet, repeater, twisted pair cable, twisted pair cables, type field, {VLAN} {TAG}, {XGMII}}
}
@article{biblio:IEEE1588,
journal = "{IEEE 1588-2008}",
title = "{IEEE} {Standard} for {PTP}",
organization = "IEEE",
address = "New York",
}
@Misc{biblio:WRPTP,
author = "E.G. Cota and M. Lipi\'{n}ski et al.",
title = "{White Rabbit Specification: Draft for Comments}",
title = "{White Rabbit: a PTP application for robust sub-nanosecond synchronization}",
booktitle = "ISPCS",
year = "2011",
}
@Inproceedings{biblio:WRproject,
author = "J. Serrano and et al.",
title = "{The White Rabbit Project}",
booktitle = "ICALEPCS",
year = "2015",
}
@mastersthesis{biblio:TomekMSc,
author = "T. W\l{}ostowski",
title = "Precise time and frequency transfer in a {White} {Rabbit} network",
year = "2011",
school = "Warsaw University of Technology",
note = {\url{www.ohwr.org/documents/80}},
}
@phdthesis{biblio:MaciekPhD,
author = "Lipinski, Maciej",
title = "{Methods to Increase Reliability and Ensure
Determinism in a White Rabbit Network}",
year = "2016",
school = "Warsaw University of Technology",
note = {\url{cds.cern.ch/record/2261452}},
}
@phdthesis{biblio:CesarPhD,
author = "Prados, Cesar",
title = "{Rock Solid WR Network for GSI/FAIR Control System}",
year = "Unpublished",
school = "Technische Universität Darmstadt",
address = "Darmstadt, Germany"
}
@ARTICLE{biblio:JosePhD,
author={F. Ramos and et al.},
journal={IEEE Transactions on Industrial Informatics},
title={Accurate Timing Networks for Dependable Smart Grid Applications},
year={2018},
}
@online{biblio:CERN,
title = {{European Organization for Nuclear Research (CERN)}},
url = {www.cern.ch/},
howpublished = {\url{www.cern.ch/}},
abstract = {{CERN}, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works.},
keywords={IEEE standards;access protocols;local area networks;metropolitan area networks;IEEE standard;MAC service;VLAN bridges;bridged networks;local area networks;media access control service;metropolitan area networks;Bridged circuits;IEEE standards;Local area networks;Media Access Protocol;Metropolitan area networks;Protofcols;Virtual environments;Bridged Network;IEEE 802.1Q(TM);LAN;MAC Bridge;MSTP;Multiple Spanning Tree Protocol;PBN;Provider Bridged Network;RSTP;Rapid Spanning Tree Protocol;SPB Protocol;Shortest Path Bridging Protocol;VLAN Bridge;Virtual Bridged Network;local area network;metropolitan area networks;virtual LAN},
doi={10.1109/IEEESTD.2014.6991462},}
@online{biblio:allan90,
author = {D.B. Sullivan and D.W. Allan and D.A. Howe and F.L. Walls},
title = {{Characterization of Clocks and Oscillators}},
url = {tf.nist.gov/general/pdf/868.pdf},
note = "{NIST Technical Note 1337}",
urldate = {1990},
}
@article{biblio:IEEE802.3,
journal="{IEEE 802.3-2012}",
title = {{IEEE Standard for Ethernet}},
doi = {10.1109/IEEESTD.2012.6419735},
abstract = {Ethernet local area network operation is specified for selected speeds of operation from 1 Mb/s to 100 Gb/s using a common media access control ({MAC}) specification and management information base ({MIB}). The Carrier Sense Multiple Access with Collision Detection ({CSMA}/{CD}) {MAC} protocol specifies shared medium (half duplex) operation, as well as full duplex operation. Speed specific Media Independent Interfaces ({MIIs}) allow use of selected Physical Layer devices ({PHY}) for operation over coaxial, twisted-pair or fiber optic cables. System considerations for multisegment shared access networks describe the use of Repeaters that are defined for operational speeds up to 1000 Mb/s. Local Area Network ({LAN}) operation is supported at all speeds. Other specified capabilities include various {PHY} types for access networks, {PHYs} suitable for metropolitan area network applications, and the provision of power over selected twisted-pair {PHY} types.},
date = {2012-12},
keywords = {1000BASE, 100BASE, 100GBASE, 100 Gigabit Ethernet, 10BASE, 10GBASE, 10 Gigabit Ethernet, 40GBASE, 40 Gigabit Ethernet, attachment unit interface, {AUI}, Auto Negotiation, Backplane Ethernet, bit rate 1 Mbit/s to 100 Gbit/s, carrier sense multiple access, carrier sense multiple access with collision detection, coaxial cable, coaxial cables, computer network management, {CSMA}-{CD}, data processing, {DTE} Power via the {MDI}, {EPON}, Ethernet, Ethernet in the First Mile, Ethernet networks, Ethernet passive optical network, Fast Ethernet, formal specification, full duplex operation, Gigabit Ethernet, {GMII}, {IEEE} standards, {IEEE} Std 802.3-2008 Revision, {IEEE} Std 802.3-2012, information exchange, local area network, {MAC} protocol specification, management, management information base, {MDI}, media access control, media independent interface, medium dependent interface, metropolitan area network, Metropolitan area networks, {MIB}, {MII}, multisegment shared access network, network interfaces,
optical fibre {LAN}, optical repeaters, Passive optical networks, {PHY}, physical coding sublayer, Physical layer, physical layer device, physical medium attachment, {PMA}, Power over Ethernet, repeater, twisted pair cable, twisted pair cables, type field, {VLAN} {TAG}, {XGMII}}
}
@article{biblio:IEEE1588,
journal = "{IEEE 1588-2008}",
title = "{IEEE} {Standard} for {PTP}",
organization = "IEEE",
address = "New York",
}
@Misc{biblio:WRPTP,
author = "E.G. Cota and M. Lipi\'{n}ski et al.",
title = "{White Rabbit Specification: Draft for Comments}",
title = "{White Rabbit: a PTP application for robust sub-nanosecond synchronization}",
booktitle = "ISPCS",
year = "2011",
}
@Inproceedings{biblio:WRproject,
author = "J. Serrano and et al.",
title = "{The White Rabbit Project}",
booktitle = "ICALEPCS",
year = "2015",
}
@mastersthesis{biblio:TomekMSc,
author = "T. W\l{}ostowski",
title = "Precise time and frequency transfer in a {White} {Rabbit} network",
year = "2011",
school = "Warsaw University of Technology",
note = {\url{www.ohwr.org/documents/80}},
}
@phdthesis{biblio:MaciekPhD,
author = "Lipinski, Maciej",
title = "{Methods to Increase Reliability and Ensure
Determinism in a White Rabbit Network}",
year = "2016",
school = "Warsaw University of Technology",
note = {\url{cds.cern.ch/record/2261452}},
}
@phdthesis{biblio:CesarPhD,
author = "Prados, Cesar",
title = "{Rock Solid WR Network for GSI/FAIR Control System}",
year = "Unpublished",
school = "Technische Universität Darmstadt",
address = "Darmstadt, Germany"
}
@ARTICLE{biblio:JosePhD,
author={F. Ramos and et al.},
journal={IEEE Transactions on Industrial Informatics},
title={Accurate Timing Networks for Dependable Smart Grid Applications},
year={2018},
}
@online{biblio:CERN,
title = {{European Organization for Nuclear Research (CERN)}},
url = {www.cern.ch/},
howpublished = {\url{www.cern.ch/}},
abstract = {{CERN}, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works.},
abstract = {We present a new measurement principle to determine the absolute time delay of a waveform from an optical reference plane to an electrical reference plane and vice versa. We demonstrate a method based on this principle with 2 ps uncertainty. This method can be used to perform accurate time delay determinations of optical transceivers used in fiber-optic time-dissemination equipment. As a result the time scales in optical and electrical domain can be related to each other with the same uncertainty. We expect this method will be a new breakthrough in high-accuracy time transfer and absolute calibration of time-transfer equipment.},
@@ -55,7 +55,7 @@ enhancements to the White Rabbit (WR) extension of the IEEE 1588 Precision Time
Initially developed to serve accelerators at the European Organization for
Nuclear Research (CERN), WR has become a widely-used synchronization solution
in scientific installations. This article classifies WR applications
into five types, briefly explains each and describes its example
into five types, briefly explains each and describes example
installations. The article then summarizes WR enhancements that have been triggered by
different applications and outlines WR's integration into the PTP standard.
Based on the presented variety of WR applications and enhancements, it concludes
...
...
@@ -95,10 +95,11 @@ implement WR enhancements:
% \textcolor{red}{(802.1Q end stations)} that implement WR enhancements:
\begin{enumerate}
\item\textbf{Synchronization with sub-nanosecond accuracy and tens of picoseconds precision} among all
WR switches/nodes. Such synchronization is provided by the WR extension to PTP (WR-PTP,
WR switches/nodes. %\footnote{The accuracy is the mean offset between the times of two synchronized WR switches/nodes while precision is the standard deviation of this offset.}.
Such synchronization is provided by the WR extension to PTP (WR-PTP
\cite{biblio:WRPTP}) and its supporting hardware \cite{biblio:ISPCS2011}\cite{biblio:TomekMSc}\cite{biblio:WRproject}.
\item\textbf{Deterministic and low-latency communication} between WR nodes provided by
a purposely customized and open design of the WR switch, described in
a purposely-made and open design of the WR switch, described in
\cite{biblio:MaciekPhD}.
\end{enumerate}
Studies \cite{biblio:MaciekPhD}\cite{biblio:CesarPhD}\cite{biblio:JosePhD} have shown
...
...
@@ -113,57 +114,55 @@ manner ensuring at most a single failure per year for a network of 2000 WR nodes
% \end{figure}
Since its conception in 2008, the number of WR applications has grown beyond
any expectations. The WR Users website \cite{biblio:WRusers} attempts to keep
track of WR applications. Apart from the suitable synchronization performance, the reasons for such a proliferation of WR applications
any expectation. The WR Users website \cite{biblio:WRusers} attempts to keep
track of WR applications and the newsletter in \cite{biblio:WR-APPLICATIONS-SNAPSHOT}
provides a status of a number of WR application in June 2018. Apart from the suitable synchronization performance, the reasons for such a proliferation of WR applications
are the open nature of the WR project and the fact that the WR technology is based
on standards. The former encourages collaboration,
reuse of work and adaptations that also prevent vendor lock-in. The latter allows using
off-the-shelf solutions with WR networks and catalyzes
collaboration with companies.
What started as a project to renovate one of the most critical systems at CERN,
GMT \cite{biblio:GMT}\cite{biblio:GMTJavierPres}, is now a multilaboratory,
the General Machine Timing (GMT \cite{biblio:GMT}\cite{biblio:GMTJavierPres}), is now a multilaboratory,
multicompany and multinational collaboration developing a technology that is
commercially available, used all over the world, and being incorporated into
the original PTP standard \cite{biblio:P1588}\cite{P1588-HA-enhancements}.
commercially available, used worldwide, and incorporated into
the original PTP \cite{biblio:P1588}\cite{P1588-HA-enhancements}.
% This article attempts at providing a snapshot of the various WR applications,
% the ongoing work on enhancing WR and evolution of WR into IEEE 1588.
The article briefly describes in Section~\ref{sec:wrElements} the portfolio of
This article briefly describes in Section~\ref{sec:wrElements} the portfolio of
readily available WR network elements. It then explains in
Sections~\ref{sec:time-and-freq}-\ref{sec:RFoverWR} different types of
WR applications, their concept and use examples,
summarized in Table~\ref{tab:applications}. Application-triggered enhancements are described in
Section~\ref{sec:WRenhancements}. Finally, in Section~\ref{sec:WRin1588} we
briefly describe the integration of WR into the
IEEE 1588 standard and we conclude in Section~\ref{sec:conclusions}.
summarized in Table~\ref{tab:applications}.
\begin{table}[!t]
\caption{Non-exhaustive list of White Rabbit applications}
\multicolumn{7}{|l|}{TF= time and frequency transfer, TC= time-triggered control, TS= timestamping,}\\
\multicolumn{7}{|l|}{TD= trigger distribution, FL= Fixed-latency data transfer, RF= Radio-Freq. transfer}\\
\multicolumn{7}{|l|}{N= number of WR nodes, S= number of WR switches, L= number of layers}\\\hline
% \multicolumn{7}{|l|}{A: accuracy, P: precision, Link len. - it is the lenght of link between devices in the network, Tot. distance = the total distance that the networks spans } \\
% \multicolumn{7}{|l|}{} \\ \hline
\end{tabular}
\label{tab:applications}
\end{table}
Application-triggered enhancements are described in
Section~\ref{sec:WRenhancements}. Finally, in Section~\ref{sec:WRin1588} we
briefly describe the integration of WR into the
IEEE 1588 standard and we conclude in Section~\ref{sec:conclusions}.
\section{WR Network Elements}
\label{sec:wrElements}
...
...
@@ -224,9 +227,9 @@ WR network elements, WR nodes and WR switches, are openly available on the Open
While all of the WR networks use the same design of
the WR switch \cite{biblio:wr-switch},
the design of WR nodes depends on the application. Therefore the WR node design is made available
as an open-source intellectual property (IP) Core \cite{biblio:wr-node} that can be easily used in one of
as an open-source intellectual property (IP) core \cite{biblio:wr-node} that can be easily used in one of
the supported boards or integrated into a custom design. WR-compatible boards
are available on OHWR in various form factors, including:
are available on OHWR in various form factors, including
Cherenkov Telescope Array to be built in Chile and Spain \cite{biblio:CTA-WR-timestamps},
the Extreme Light Infrastructures in Hungary \cite{biblio:ELI-ALP-WR} and Czech Republic
\cite{biblio:ELI-BEAMS-WR}, Satellite Laser Ranging at German Aerospace Center,
High Precision Timestamps Daily File Service at German Stock Exchange (Deutsche Boerse) \cite{biblio:WR-EUREXCHANGE}
or Power Industry and Smart Grid studied at Swiss Federal
Cherenkov Telescope Array (CTA) to be built in Chile and Spain \cite{biblio:CTA-WR-timestamps},
the Extreme Light Infrastructures (ELI) in Hungary \cite{biblio:ELI-ALP-WR} and Czech Republic
\cite{biblio:ELI-BEAMS-WR}, Satellite Laser Ranging at German Aerospace Center (DLR),
High Precision Timestamps Daily File Service at German Stock Exchange (Deutsche B{\"o}rse) \cite{biblio:WR-EUREXCHANGE}
or Phasor Measurement Units synchronization for Power Industry and Smart Grid studied at Swiss Federal
Institute of Technology Lausanne (EPFL) \cite{biblio:EPFL-WR-PMU}.
...
...
@@ -564,7 +573,7 @@ Institute of Technology Lausanne (EPFL) \cite{biblio:EPFL-WR-PMU}.
\subsection{Basic Concept}
Trigger distribution combines, to some extend, the time-triggered control and precise timestamping
Trigger distribution combines, to some extent, the time-triggered control and precise timestamping
described before. In this application, an input trigger signal is timestamped by a WR node and sent over the
WR network to many WR nodes that act upon the received message simultaneously, at
a precise delay with respect to the input signal.
...
...
@@ -610,8 +619,8 @@ their actions.
The concept that has been proven to work in WRTD is now being generalized to
provide trigger distribution for CERN's Open Analog Signals Information System
(OASIS) \cite{biblio:OASIS}. OASIS is a gigantic distributed oscilloscope that
provides $\approx$6000 input channels and spans all CERN's accelerators except LHC.
Triggers in this system are currently distributed via coax cables that may be 1~km long without
provides over 6000 input channels and spans all CERN's accelerators except LHC.
Triggers in this system are currently distributed via coax cables that may be one kilometer long without
delay compensation and multiplexed using analogue multiplexers. In order to use
OASIS to diagnose LHC and to improve its performance, the distribution of triggers
is being upgraded to use WR. The WR-based trigger distribution in OASIS is meant
...
...
@@ -640,7 +649,7 @@ The time of data transmission is timestamped and this timestamp
is sent in the Ethernet frame with the data. When the data is received, a programmable
delay is added to the transmission timestamp and the associated data is provided
to an application precisely at the delayed time. Such a functionality is implemented
by the so-called "WR Streamers" IP Core \cite{biblio:wr-streamers} which adds a
by the so-called "WR Streamers" IP core \cite{biblio:wr-streamers} which adds a
data transmission layer on top of WR and acts as a fixed-latency FIFO over Ethernet.
By providing such functionality to the application, the application does not need
to be aware of time but rather processes data as it comes, knowing that all the
...
...
@@ -662,7 +671,7 @@ While the RF cavities
simply follow the ramp of the magnetic field, the power converters adjust the current
of the magnets such that the intended B-value is obtained, closing a control
loop. BTrain is essential to the operation of most of CERN accelerators, i.e.
Booster, PS, SPS, LEIR, AD, and ELENA.
Booster, PS, SPS, LEIR, AD and ELENA.
% \begin{figure}[!ht]
% \centering
% \vspace{0.5cm}
...
...
@@ -678,7 +687,7 @@ WR-based distribution of the absolute B-value and additional information
at 250~kHz (every $4\mu$s) from the measurement WR node to all the other WR nodes
that are integrated with RF cavities, power converters and beam instrumentation. In the most
demanding accelerator, SPS, the data must be delivered over 2 hops (WR switches)
with latency of $10\mu s\pm8ns$.
with a latency of $10\mu s\pm8ns$.
The WR-BTtrain has been successfully evaluated in the PS accelerator where it has
been running operationally since 2017 \cite{biblio:WR-BTrain-RF}. By 2021, all
...
...
@@ -688,7 +697,7 @@ the CERN accelerators, except LHC, should be running WR-BTrain operationally \ci
% WR switches and 2-5 WR nodes.
% }
Fixed-latency data transfer is considered for the operation of the
Fixed-latency data transfer is also considered for the operation of the
Nuclotron-based Ion Collider Facility (NICE) at the Joint Institute for Nuclear
Research (JINR) \cite{biblio:JINR} that already uses WR as the main clock
and time distribution system \cite{biblio:JINR-WR}.
...
...
@@ -704,9 +713,10 @@ Radio-frequency (RF) transfer over WR network allows the digitization of periodi
the sending of
their digital form over a WR network, and the subsequent regeneration of the signal coherently with a fixed delay in many
WR slave nodes. Such a digital RF transfer provides a number of advantages over an analogue transmission of RF signals. For example, it is
scalable and allows transmission of multiple RF signals from multiple sources over a single WR network
whereas analogue transmission typically requires dedicated network per source and signal. It also allows easy and automatic phase-alignment of the output
RF signals with compensation for temperature changes of transmission cables whereas such alignment and compensation in analogue transmission is very challenging.
scalable and allows the transmission of multiple RF signals from multiple sources over a single WR network,
whereas analogue transmission typically requires a dedicated network per source and signal. It also allows easy and automatic phase-alignment of the output
RF signals with compensation for temperature changes of transmission cables, whereas such alignment and compensation in analogue transmission is very challenging.
% Lastly, the digital RF transfer over WR network minimizes bandwidth of transmitted data allowing to use WR network also for other purposes.
In the RF transfer over WR Network schema, depicted in Figure~\ref{fig:RFoverWR} and detailed in \cite{biblio:WR-LIST},
...
...
@@ -723,7 +733,7 @@ input RF signal. The error measured by the phase detector is an input to a
loop filter (e.g. Integral-Proportional controller) that steers the DDS to produce a signal identical to the RF input -
effectively locking the DDS to the input signal.
The tuning words of the DDS are the digital form of the RF input
that is sent over WR network. Each of the receiving WR slave nodes recreates the RF input signal
that is sent over the WR network. Each of the receiving WR slave nodes recreates the RF input signal
by using the received tuning words to control the local DDS with a fixed delay.
In such way, the WR slave nodes produce RF outputs that are syntonized with
the RF input, phase-aligned among each other, and delayed with respect to the RF input --
...
...
@@ -738,16 +748,16 @@ of the digital RF signal transmission, thus negligible.
The WR-based radio-frequency transfer is being implemented in the European Synchrotron Radiation
Facility (ESRF) \cite{biblio:ESRF}\cite{biblio:ESRF-WR}. The operation of the ESRF accelerator facility
is controlled by a "Bunch Clock" system\footnote{
Bunch Clock is a clock signal that is synchronous with particle bunches
circulating in a synchrotron or an accelerator. The "Bunch Clock" system generates such a clock signal.}
A "Bunch Clock" system generates a clock signal that is synchronous with particle bunches
circulating in a synchrotron or an accelerator.}
that delivers to accelerator subsystems a
$\approx$352 MHz RF signal and triggers initiating sequential actions synchronous
to the RF signal, such as
"gun trigger", "injection trigger" or "extraction trigger"\footnote{
"Gun trigger" initiates generation of an electron bunch at the LINAC input,
"injection trigger" initiates transfer of the bunch from the LINAC into the Booster,
"extraction trigger" initiates extraction of the bunch from the Booster into the
Storage Ring at the end of acceleration, see \cite{biblio:ESRF-WR} for details.
"injection trigger" initiates the transfer of the bunch from the LINAC into the Booster,
"extraction trigger" initiates the extraction of the bunch from the Booster into the
Storage Ring at the end of acceleration\cite{biblio:ESRF-WR}.
}.
The jitter of the output RF signal is required to be below 50~ps. The RF signal is continuously
trimmed around the 352~MHz value as the tuning parameter in the "fast orbit feedback"
...
...
@@ -755,7 +765,7 @@ process. Apart from the 352~MHz signal, other frequencies are distributed, such
355~kHz Storage Ring revolution frequency or the 10~Hz Injection sequence.
The current ESRF "Bunch Clock" system is being refurbished to use WR \cite{biblio:ESRF-WR}.
The solution has passed a 6-months validation tests in 2015. In 2016, a prototype system
The solution has passed a 6-months validation test in 2015. In 2016, a prototype system
successfully injected
bunches in the storage ring providing $<$10ps jitter. A system consisting
of a WR switch and eight WR nodes is expected to be operational in July 2018. It
...
...
@@ -1175,15 +1185,15 @@ of WR performance that are summarized in this section.
The applications of WR for time and frequency transfer in National Time Laboratories
as well as for RF transfer in CERN's SPS require improvement of jitter and clock
stability.
The frequency transfer over WR network was characterized in
\cite{biblio:WR-characteristics} and its ultimate performance limits
The frequency transfer over a WR network was characterized in
\cite{biblio:WR-characteristics} and its ultimate performance limits were
studied in \cite{biblio:WR-ultimate-limits}. The studies
