Abstract: The femtocell network allows connecting to cellular network through broadband connection. In femtocell, time with network synchronization becomes a critical issue at present. Synchronization is a process which is required in the femtocell network due to the shortcomings of centralized coordination between a number of femtocell Base Station (fBS) and clock synchronization server. Time synchronization procedure allows exchanging message that contains timestamp and delay measurement. There are several time synchronization protocols and algorithms based on precision which are Network Time Protocol (NTP), Simple Network Time Protocol (SNTP), IEEE 1588 Timing Protocol, enhancement of IEEE 1588 timing and receiverreceiver synchronization scheme. In this study, we investigated some of the time synchronization protocols and schemes for femtocell network. In addition, we proposed intra-cluster synchronization scheme to minimize the clock offset and skew for better synchronization accuracy. The proposed scheme is able to perform precise synchronization for clock offset and clock skew than the existing receiver-receiver synchronization scheme.

Abstract: Many substation applications require accurate time-stamping. The performance of systems such as Network Time Protocol (NTP), IRIG-B and one pulse per second (1-PPS) have been sufficient to date. However, new applications, including IEC 61850-9-2 process bus and phasor measurement, require accuracy of one microsecond or better. Furthermore, process bus applications are taking time synchronisation out into high voltage switchyards where cable lengths may have an impact on timing accuracy. IEEE Std 1588, Precision Time Protocol (PTP), is the means preferred by the smart grid standardisation roadmaps (from both the IEC and US National Institute of Standards and Technology) of achieving this higher level of performance, and integrates well into Ethernet based substation automation systems. Significant benefits of PTP include automatic path length compensation, support for redundant time sources and the cabling efficiency of a shared network. This paper benchmarks the performance of established IRIG-B and 1-PPS synchronisation methods over a range of path lengths representative of a transmission substation. The performance of PTP using the same distribution system is then evaluated and compared to the existing methods to determine if the performance justifies the additional complexity. Experimental results show that a PTP timing system maintains the synchronising performance of 1-PPS and IRIG-B timing systems, when using the same fibre optic cables, and further meets the needs of process buses in large substations.

Abstract: The invention discloses a self-adaptive clock synchronous system which comprises a main service layer, a secondary service layer and a client layer, wherein the main service layer comprises one or more main time servers; the main time servers are externally connected with an atomic clock; the secondary service layer comprises a plurality of secondary time servers; one part of secondary time servers and the main time servers are subjected to time synchronization; the other part of secondary time servers are mutually subjected to time synchronization; the client layer comprises a plurality of terminals; and the terminals are used for sending time synchronization requests to the secondary time servers to carry out time synchronization. According to the invention, when a reference time source goes wrong, a suitable time source can be automatically searched, so that the system automatically completes the configuration of a synchronization network and the time synchronization network has sufficient stability and robustness and has strong self-adaptive capacity; and meanwhile, a self-adaptive clock synchronous system has higher safety. The self-adaptive clock synchronous system adopts a hierarchical system structure, has clear layers and clear layout as well as strong expandability and is suitable for growth of services.

Abstract: Accurate and reliable time is necessary for financial and legal transactions, transportation, distribution systems, and many other applications. Time synchronization protocols such as NTP (the Network Time Protocol) have kept clocks of such applications synchronized to each other for many years. Nowadays there are many commercial GPS based NTP time server products at the market but they almost have a high price. In this paper we are going to use a Low Cost GPS engine to build a time server to provide time synchronization with accuracy of a few milliseconds. This time server is relatively very cheap and it can be used in almost all typical applications. We also proposed a software based NTP time server implemented in MATLAB as well.

Abstract: A method for improving accuracy in the computation of a one-way transfer time between two networked devices. In one aspect, variability in time transfer latency that is caused by cache loading, data structure setup time, and scheduling variability in software is reduced by initiating a first sequence of loading data structures into cache and priming scheduling, and then initiating a second sequence of calibrating the timing of a subsequent synchronization message so that the completion of the first sequence occurs just in time for the reception of the synchronization message. The method is applicable for any network time synchronization protocol, including Network Time Protocol (NTP) and Precision Time Protocol (PTP).

Abstract: The invention relates to a time synchronization method of a femto base station route (BSR) The method comprises the following steps: extracting line clock information in a core network; comparing the core network line clock information with internal clock information and external clock information and determining the clock information with a highest synchronization quality grade; carrying out time synchronization of the femto BSR according to the clock information with the highest synchronization quality grade A time synchronization system of the femto BSR comprises: an apparatus used to extract the line clock information in the core network, the apparatus used to comparing the core network line clock information with the internal clock information and the external clock information and determine the clock information with the highest synchronization quality grade and the apparatus used to carry out the time synchronization of the femto BSR according to the clock information with the highest synchronization quality grade By using the method and the system of the invention, the clock synchronization between a femto BSR clock and a network time protocol (NTP) server can be stable and accurate

Abstract: The invention provides a time synchronizing device with a safe isolation function, which comprises an NTP (Network Time Protocol) client module (1), a window filter failure compensation module (2), a high reconstruction clock module (5), a voice transformation module (6), an in/out log module (7), a voice player (8), a panel display module (9), a press key (10), two NTP server modules (13, 14), a TOD time and date follower (15) and a driving module (18). The time synchronizing device provided by the invention can safely isolate a service to an Intranet, which is provided by an external network, and provides a safe, convenient and high-precision time synchronizing method for servers; and the time synchronizing device can synchronize with NTP website timing, and also can synchronize with a TOD series signal, and outputs series TOD and net opening signals to allow the plurality of device of a system formed by multiple servers to achieve time synchronizing.

Abstract: The invention discloses a clock synchronizing method for an NTP (Network Time Protocol) network and a PTP (Precision Time Protocol) network, which comprises the following steps: a PTP network side is configured as a master clock, an NTP network side is configured as a slave clock, and a message processing server is arranged between the master and slave clocks; a clock synchronizing message sent from the PTP network side is received by the message processing server, converted into message with an NTP message format, and finally transmitted to the NTP network side; and after response message sent from the NTP network and for the clock synchronizing message, the response message is converted into delay request message with a PTP message format, and the delay request message is transmitted to the PTP network side. The method achieves the clock synchronizing of the NTP network and the PTP network, enables the most conventional NTP network can be communicated with the PTP network, and obtains technical effects including cost conversation and precision improvement.

Abstract: The invention discloses a method and a device for time synchronization, a time stamping device and a trusted time server. The method for time synchronization comprises: protecting integrity of time synchronization request to be sent to the trusted time server; sending the integrity protected time synchronization request to the time synchronization request; receiving a time synchronization response returned by the trusted time server; verifying the integrity of the time synchronization response; verifying consistency of the time synchronization response according to consistency validated information respectively included in the time synchronization request and the time synchronization response; and adjusting a local time of the time stamping device based on the time synchronization response to make the local time of the time stamping device and a time of the trusted time server synchronized. With the method and the device, the local time of the time stamping device and a trusted time source can be easily synchronized to ensure the local time of the time stamping device accurate and reliable.

Abstract: This paper reports a study and practical evaluation of two different clock synchronization methods for distributed measurement and control nodes based on Linux Single Board Computers (SBCs) with ARM processors and communicating through a TCP/IP wide area network. First the Network Time Protocol (NTP) is configured and evaluated in different network scenarios. The second solution is a specific development for Global Positioning System (GPS) clock synchronization. After a description of the hardware and software implementation of this solution the experimental results are reported and commented.

Abstract: Advanced optimization of Smart Micro Grids (SMGs) requires precise electrical measurements in amplitude and phase, the latter requiring precise clock synchronization between devices. In this context, the paper presents some field test results for SMG synchronization using the powerline communication standard PRIME. The performance of PRIME is first tested in a realistic scenario corrupted by impulsive noise, showing that robust non-standard coding method are required. Then, a synchronization protocol based upon a NTP (network time protocol) like algorithm with a further frequency offset correction is proposed and tested. The protocol is implemented at the MAC layer. By use of a very light message exchange every 10 s, it assures a synchronization error below 10 µs, making it adequate for the SMG scenario.

Abstract: By introducing the requirements of time synchronization(TS),the technical characteristics,operation principle and the networking methods of network time protocol in smart substations,the advantages and shortages of the network TS system are analyzed.To solve the potential security risks of system management,product design and network architecture caused by IEC 61588 network TS system,a security evaluation method based on the simulation technique under network traffic for smart substation is proposed.The proposed method has been used to analyze a case,and the safe and reliable operation of the IEC 61588 TS system is ensured.

Abstract: The invention discloses a method for testing network time service precision, which comprises the following steps: (1) generating a standard time mark signal and a standard frequency mark signal; (2) generating standard time source information by using the generated standard time mark signal and the standard frequency mark signal; and (3) measuring the time service precision of a tested device by using the generated standard time source information. The invention provides a device and a method for measuring the time service precision of a network time server with high precision, which use external input high-precision time mark and frequency mark signals to generate a standard time source for measuring; in addition, the device and the method use the generated standard time source information to measure the time service precision of the tested device during calibrating a time tag at an MAC layer, remove the prior network processing delay introduced by calibrating the time at an application layer, and reduce the measurement error introduced by a time service measuring device. The method uses a PC machine to output the primary measuring data and calculate the time service result, and provides data support for analyzing the time service result and improving the time service precision of a time service server.

Abstract: This paper describes a use case study on a novel Intelligent Electronics Device (IED) network for wide-area power system monitoring, protection and control (WAMPAC), featuring wide-area Ethernet and IEEE 1588-based time synchronization associated with decentralized modular devices. Use cases include configurable WAMPAC system architecture accommodating various applications and enabling redundant configurations, wide-area integrated primary and backup protection with a current differential scheme, and special protection with centralized synchronous cyclic and data-driven communication and processing. Preliminary evaluations and experiments indicate that the wide-area current differential protection requires a bandwidth of several tens or hundreds of Mbps for its Ethernet network, and that IEEE 1588-embedded IEDs associated with an off-the-shelf IEEE 1588 time server achieve time synchronization accuracy to within a few microseconds. The need for wide-area network engineering guides is also discussed.

Abstract: The invention discloses a vehicle-mounted time synchronization serving method and system; and the vehicle-mounted time synchronization serving system corrects and adjusts the time of a client of a vehicle-mounted device to be in a more accurate state through a time synchronization function. The technical scheme of the invention is as follows: the vehicle-mounted time synchronization serving system comprises a time synchronization client, a vehicle full-time online system and a time server, wherein the time synchronization client establishes real-time connection with the vehicle full-time online system and transmits network events establishing connection with the vehicle full-time online system to the time server of a cloud terminal; the vehicle full-time online system establishes communication link with the time server; and the timer server synchronizes time information to the time synchronization client after receiving the network events establishing connection and transmitted by the time synchronization client.

Abstract: The embodiment of the invention discloses a method and a device capable of allowing an internal network to obtain time information. The method comprises the following steps: sending an NTP (Network Time Protocol) request to a time providing server in the internet through an intranet interface so as to obtain the time information; and sending the obtained time information to equipment in the internal network in an appointed format through an internal network interface, wherein the internal network interface is a unidirectional interface and is used for providing the time information in the appointed format, but not used for information exchanging. Due to the adoption of the method provided by the invention, the safety of the internal network is greatly improved, when the intranet NTP time information is obtained; and the internal network is protected from being attacked by the intranet.

Abstract: Network time service system is constructed in NIM based on network time protocol (NTP). The synchronization software programm based on NTP is run at the client side. The mathematical uncertainty model of time offset is established. The uncertainty is analyzed and evaluated. The uncertainty of time server and client are evaluated particularly by the synchronizing experiments using a time and frequency solutions TimeAcc-007. The data processing algorithms are proposed for improving synchronization precision based on the result of uncertainty evaluation.

Abstract: The embodiment of the invention provides a method for selecting network time protocol (NTP) servers. According to the method, the NTP servers are screened through two fields such as a Stratum layer and Precision local clock precision in a response message of each NTP server. Compared with the conventional NTP server selection method, the method has the advantages that the design is relatively simple; in an allowed computing capacity range of the hardware of network element equipment, the most reliable NTP server can be selected to the greatest extent for time synchronization, and time precision is ensured; and after the NTP server is set, the network element equipment automatically performs time synchronization, and manual intervention is not required. An NTP server selection scheme provided by the invention is simple, practical and easy to implement on the network element equipment. By adoption of the scheme provided by the embodiment of the invention, the quantity of the NTP servers is 3 to 5 preferably. If the quantity of the NTP servers exceeds 5, the computing capacity of the hardware of the network element equipment can be influenced, and efficiency is influenced.

Abstract: PROBLEM TO BE SOLVED: To solve the problem that in the communication network of a distribution automation system, a communication speed is slow and a response time from packet transmission to reception, therefore, is long and fluctuates greatly, which, in a time synchronization procedure as network time protocol (NTP), significantly affects monitoring control and degrades time accuracy.SOLUTION: In a distribution automation system, an operation status is inquired of each piece of equipment individually from a control unit and the equipment which received the inquiry notifies the control unit of their status information. A response time from inquiry until when status information is received is measured for every equipment, and the response time is notified to the equipment side by making use of a broadcast. A communication unit on the equipment side receives the response time and a timestamp by a timer synchronized to a radio clock, compares them with the time of day of its own timer, and, if a difference is greater than a given value, corrects the time of day of the timer. According to the present invention, a communication traffic volume needed for time synchronization control can be reduced to eliminate effects of delay time in a communication network, making it possible to realize highly accurate time synchronization.

Abstract: This paper introduces the Construction of the Clock Synchronization System in Management Information Domain of Power Grid. Along with the development of the SMART GRID, Clock synchronization system plays a more and more important roles for information system. The Synchronous accuracy needed by management information domain is lower than 1 second. The network time protocol (NTP) satisfies the needs of the management information domain with less investment, and it is easily carried out. The Synchronization system is verified at Shanghai Disaster Preparedness Center.

Abstract: The invention discloses a method for realizing a clock synchronization subsystem in a passenger special line comprehensive monitoring system. The method comprises a time synchronization step for a scheduling end and a controlled end, wherein an NTP (Network Time Protocol) clock server is arranged at the scheduling end, and is used for acquiring Universal Time Coordinated (UTC) through a GPS (Global Positioning System) antenna and performing gradual time service for an entire scheduling end computer system; and a controlled end provided with the GPS antenna is used for directly acquiring the UTC, and a controlled end without any GPS antenna performs system clock comparison with a communication server of the scheduling end through a communication machine, so that time synchronization is realized. According to the method, certain characteristics of the system are fully utilized, functions of different modules are integrated, possibly existing conflicts are solved, and the accuracy and unity of system time in the entire system are realized through simple configuration.

Abstract: A system and method for providing data such as text, graphics or sound to a portable user device, in synchronisation with a service broadcast received by separate receivers, includes a broadcast time server. The broadcast time server receives a broadcast audio-video transmission from which it derives a time signal (e.g. a broadcast clock) and provides the time signal to a user device in the serverâ s locality. At the user device, such as a mobile telephone, laptop or PDA, the data can be asserted in synchronization with a broadcast, such as a television programme simultaneously viewed by the user. Thus, additional, supplementary data accessed by a user mobile device is synchronized with broadcast (e.g. DVB) data. Transmission delays between user device and broadcast time server may be determined. The user device does not require any connection to the user's television receiver and so no modification to the broadcast transmitter or receiver is required.

Abstract: The invention provides an IP-Based implement television system and the synchronization playing stream service method thereof. wherein, when each implement terminal receives a stream service, the network time protocol timestamp sequence corresponding to the stream service and a synchronized clock from the network equipment, the implement terminal restores the network time protocol reference clock used for presenting the received stream service according to the synchronized clock and synchronous time difference value, and plays the received stream service according to the restored network time protocol reference clock and the received network time protocol timestamp. Therefore, a plurality of implement terminals in the IP-Based implement television system can play the received stream services in a synchronous mode.

Abstract: In an embodiment, provided is a communication device connected to time servers via a network with transfer devices. In the communication device: a network controller receives a message containing time information counted by the time server and containing a network identifier, and obtains a receiving timing of the message; a network processing unit, when the network identifier in the message does not match with any network identifier, destroys the message; a protocol processing unit, when the network identifier has a match, calculates a time error by the time information in the message and the receiving timing, detects whether a first time server is malfunctioning, and when detected the first time server malfunctioning, outputs the time error calculated by a network identifier assigned to a second time server; a servo calculates an operation amount by the time error; and a clock varies a clock rate according to the operation amount.

Abstract: This paper reports on the synchronization performance of a hardware implemented network time protocol (HwNTP) module for digitized radio over fiber (DROF) system. In the experiments, the HwNTP client is synchronized with the HwNTP server via an asynchronous packet network, and provides highly accurate time and frequency references compared to software based NTP. The achieved accuracy over a commercial Ethernet service is sufficient to satisfy the DROF requirements.

Abstract: Military radio networks such as mobile ad hoc networks (MANETs) usually rely on global satellite navigation systems (GNSSs) for network time synchronization. However, in reality all nodes may not have a GNSS timing device or they do not have a direct link to a GNSS timed node. In addition, in some situations GNSSs may fail. Therefore, additional supporting mechanisms are needed for synchronization. This paper provides a hybrid algorithm that uses GNSS timed nodes as master time servers if they are available but automatically turns to a distributed mode if GNSS time is not available providing robustness and survivability. Furthermore, the distributed mode can be used also as a stand-alone synchronization mechanism, i.e., a GNSS time reference is not necessarily needed at all. Simulations show the behavior of the algorithm in different scenarios but as main conclusions it can be said that the availability of GNSS timed nodes speeds up the initial convergence, the convergence rate depends on the number of nodes and the number of hops and that if GNSS time is lost, the network still maintains synchronism but time is not necessarily GNSS time.

Abstract: According to an embodiment, an information processing apparatus includes a selector. The selector is configured to acquire a first time obtained by converting a measurement time of a first piece of measurement data based on a clock of a first time server, a second time obtained by converting the measurement time of the first piece of measurement data based on a clock of a second time server, a third time obtained by converting a measurement time of a second piece of measurement data based on the clock of the first time server, and a fourth time obtained by converting the measurement time of the second piece of measurement data based on the clock of the second time server. The selector is also configured to select a time server with the largest number of combinations of the converted times resulting in no error among pieces of measurement data and time servers.

Abstract: The embodiment of the invention provides a multilevel time synchronizing system and an implementing method The system mainly comprises a secondary time server and a tertiary time server, wherein the secondary time server is used for receiving peer to peer (PTP) signals transmitted by a main clock to synchronize the time and continuously transmitting the PTP signals to the tertiary time server; the tertiary time server is used for receiving the PTP signals transmitted by the secondary time server to synchronize the time; the secondary time server comprises a boundary clock, a synchronizing digital system algorithm module and a PTP output port; the synchronizing digital system algorithm module is used for accurately and stably tracking and synchronizing the PTP signals from a synchronizing digital system network; the boundary clock is used for correcting the PTP signals received from the main clock by the synchronizing digital system algorithm module by using second pulse generated when the inner part of the secondary time server synchronizes upstream signals to the main clock, and transmitting new PTP signals generated after correcting to the PTP output port; and the PTP output port is used for transmitting the PTP signals to the tertiary time server

Abstract: The utility model discloses a clock synchronization device for acquiring a synchronous clock stamp. The clock synchronization device comprises a GPS (global positioning system) clock module, a Bits clock module, an NTP (network time protocol) network clock module, a singlechip module, an FPGA (field-programmable gate array) module, and an output module, wherein the singlechip module is connected with the FPGA module for self-adaptively processing time information of the singlechip module; and the GPS clock module, the Bits clock module and the NTP network clock module are connected with the singlechip module. The clock synchronization device can select a plurality of clock sources as clock synchronous signals, and can achieve time synchronization of data acquired by equipment at different locations in the distributed acquisition mode.