80results about How to "Precise time synchronization" patented technology

Devices and methods for synchronizing devices over a switched fabric. A switch receives a request packet from a device, transmits a completion packet to the device, determines an in-switch delay, and stores the in-switch delay. Another switch receives a packet from a first device, forwards the packet to a second device, determines an in-switch delay of the packet, and stores the in-switch delay. Storing of in-switch delays may include adding an in-switch delay to values in one or more transaction delay fields of a packet. Storing of in-switch delays may include storing the delays in a storage element of a switch. In-switch delay may be determined as a difference between a receiving time corresponding to reception of a packet and a forwarding or transmittal time corresponding to forwarding or transmitting of a packet.

In a communication system using a PON, time synchronization of a slave device such as a base station is realized with respect to a master device such as an L2SW or the base station. Time information acquired by a GPS satellite is corrected by ranging information of a discovery function of an OLT so as to be reflected on time information of each ONU. A propagation delay from the L2SW to the OLT is obtained with the use of a delay estimation mechanism, a propagation delay from the OLT to the ONU which is obtained by ranging is added to obtain a propagation delay from the L2SW to the ONU. The obtained propagation delay from the L2SW to the ONU is added to the transmitted time stamp value whereby a time stamp value received at a base station or femtocell side becomes a time into which the propagation delay to the ONU is incorporated, and absolute values of clock timers can be synchronized with each other. The addition process can be realized by rewriting the time stamp value of the packet within the OLT or the ONU.

The position of a node is identified. There is provided a module for identifying the position of a node using a locator node that sniffs communication of the node in a sensor network system capable of continuously tracking a situational change in the state, position or the like of people or an object.

A novel method and apparatus for preamble detection and time synchronization estimation in OFDM communication systems is described. The present invention can be easily implemented to provide preamble detection and highly accurate time synchronization estimations. The inventive method and apparatus utilizes phase and magnitude information obtained from a received signal to detect a preamble and to calculate a time synchronization estimation for the received signal.

A burst signal receiver comprises a correlation computation unit configured to compute a correlation value between a received known signal and a generated known signal, a moving average calculator to moving-average the correlation value to obtain a moving average value, a peak detector to detect a peak value of the moving average value and a peak position thereof for each of the constant periods; and a synchronization determination unit configured to determine a synchronization position according to a given condition using the peak value and the peak position.

A time synchronization method includes: after sending a synchronization message to the opposite end, sending a following message where an ending time for sending the synchronization message is recorded; receiving a delay request message sent by the opposite end, and sending a delay response message where the initial time for receiving the delay request message is recorded; receiving the synchronization message and the following message, and recording the initial time for receiving the synchronization message and the ending time recorded in the following message for sending the synchronization message; sending a delay request message, and recording an ending time for sending the delay request message; receiving a delay response message, and recording an initial time recorded in the delay response message for the opposite end to receive the delay request message; calculating the time offset value between the two ends, and completing time synchronization.

Devices and methods for synchronizing devices over a switched fabric. A master device maintains a global time, determines a mapping between the global time and a counter of a switch over a memory-mapped fabric, and sends the mapping to a slave device. A slave device maintains a local time, determines a first mapping between the local time and a counter of a switch, receives a second mapping between the counter and a global time of the master device, and synchronizes its local time to the global time based on the first and second mappings. The master and slave device may map their times to the counter by sending respective request packets to the switch and receiving respective completion packets including respective counter values from the switch. The master and slave device may determine respective time values corresponding to the respective counter values based on in-switch delays of the packets.

A parallel processing-based time synchronization apparatus is disclosed. The time synchronization apparatus employs a double-filter structure based on parallel processing, thereby providing more precise and reliable time synchronization between a master device and a slave device.

Provided are a time synchronization method and a frequency offset estimation method using the same in an OFDM system. The time synchronization method using a preamble transmitted from a transmitter to a receiver in the OFDM communication network includes the steps of: a) calculating a moving sum of a first sequence and a second sequence obtained by a product of neighboring elements in a received signal when the received signal containing a preamble is received from the transmitter; b) estimating a location of the received signal corresponding to the moving sum having a maximum value; and c) acquiring a time synchronization with respect to the received signal, based on the estimated location, wherein the first sequence is obtained from a product of neighboring elements in the preamble and a correlation value obtained by correlating another sequence with the first sequence is smaller than a predetermined value.

A method synchronizes assemblies in a base station to a reference clock signal. A local clock signal and a frame are formed in a first assembly. The clock signal and the frame are transmitted, using a synchronous transmission with a predictable propagation time, to a second assembly. A reference clock signal is received in the second assembly, and a phase difference and a time difference between the transmitted clock signal on the one hand and the reference clock signal on the other hand are determined. The phase difference and the time difference are transmitted from the second assembly to the first assembly via a link without a predictable propagation time. The phase difference and the time difference are used in the first assembly to determine a manipulated variable which controls the formation of the local clock signal, such that the first and the second assemblies are synchronized in time.

The present invention relates to a time synchronization method in a wireless sensor network. In the present invention, if an upper node requests a lower reference node to start time synchronization, the lower reference node broadcasts a first sync reference packet. The upper node receives the first sync reference packet and transmits the first sync reference packet reception time to the lower reference node. The lower reference node broadcasts the first sync reference packet reception time, such that the other nodes perform time synchronization on the basis of the first sync reference packet reception time. Meanwhile, the lower reference node estimates the first sync reference packet reception time of the upper node to calculate the reception estimation time, and transmits the reception estimation time to a determination node that is two hops anterior to the lower reference node. Therefore, the determination node compares the reception time received from the upper node and the reception estimation time received from the lower reference node and determines whether a capture attack on the upper node has occurred.

The invention relates to a method of synchronizing first and second digital signals presenting digital elements to be put into correspondence, on the basis of time references. The method implementing: a) preliminary synchronization of the two digital signals using time references, by putting time references recognized as having the same value in the first and second digital signals into correspondence; and b) fine synchronization on the basis of a characteristic parameter obtained from the binary streams of said digital elements, and computed for each of said first and second digital signals.

The invention relates to a method for acquiring accurate line transmission delay during time synchronization. The method comprises the following steps: a subsystem is selected as a main subsystem; an auxiliary subsystem is selected; the main subsystem sends a pulse per second at t1 time, and the pulse per second reaches the auxiliary subsystem after line transmission delay tpdBA; after the auxiliary subsystem receives the pulse per second, the auxiliary subsystem starts a timing register; the auxiliary subsystem computes that the time of the auxiliary subsystem is delayed for tpdAB compared with the main subsystem by combining with a counting time value Delta t' from a current time value; the auxiliary subsystem sends the pulse per second to the main subsystem at t2 time, and when the pulse per second reaches the main subsystem after the line transmission delay tpdBA, the time value t3 of the main subsystem is recorded at the time; and the one-way delay tpd of the main subsystem and the auxiliary subsystem is computed through tpd=(tpdBA+tpdAB) / 2=(t3-t2). According to the method disclosed by the invention, the one-way or two-way accurate line transmission delay of a system can be accurately obtained, and therefore delay is convenient to subsequentially compensate.

The invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) time synchronization algorithm based on a conjugate symmetric sequence. The OFDM time synchronization algorithm comprises the steps of constructing a sequence with conjugate symmetry; carrying out symmetric related calculation at a receiving end by using the conjugate symmetry of the sequence so as to obtain a related peak value of a timing measurement function; and determining a beginning position of an OFDM signal by using the position of the related peak value so as to finish time synchronization. By using the invention, the adverse effect on the time synchronization, caused by a cyclic prefix and the conjugate symmetry of the sequence, is overcome, and higher timing accuracy is obtained; and the OFDM time synchronization algorithm based on the conjugate symmetric sequence, provided by the invention, can be effectively used for the time synchronization of the OFDM system under a multipath channel.

Provided are a method and apparatus for transmitting and receiving media data, which can provide D-layer timing information, which is transmitted from a media transmission service based on an MMT system and required for timely synchronization playout time of the media and media. The apparatus for transmitting the media data comprises a packetizer for generating a delivery layer packet (D-layer packet), which packetizes encapsulation layer data (E-layer data) to include timing information, wherein the timing information comprises sampling time information and transmission process delay information.

The invention discloses a droplet target control system guided by a laser beam. The droplet target control system comprises a droplet nozzle, a high-power pump laser, a third focusing lens and a time delay pulse generator, and further comprises a laser source, a first reflector, a half valve plate, a Brewster angle polarizing film, a quarter wave plate, a second reflector, a first focusing lens, a vacuum tube, a second focusing lens, an annular plane reflector and an annular focusing lens. A dropping track of metal droplets in 20 micron dimension can be precisely controlled by the droplet target control system, and the dropping speed of the droplets can be regulated. The system is capable of stably working for a long time, the time synchronization and the space coincidence of the droplets and the high-power pump laser are guaranteed.

The invention discloses a real-time GNSS / INS (global navigation satellite system / inertial navigation system) combined navigation signal simulator based on a PXI (PCI extensions for instrumentation) bus and relates to a real-time GNSS / INS combined navigation signal simulator in the navigation field. The simulator comprises a time-frequency signal processing unit, a user signal generating unit, the PXI bus, a PXI slot-0 controller, a rubidium clock and the like; the user signal generating unit is composed of multiple frequency-point signal generating modules, a radiofrequency signal combiner, a power divider, a power attenuator and the like. The PXI bus technique is used in system structuring, configurability and extensibility are excellent, the simulator is imparted multi-navigation system multi-frequency GNSS / INS navigation signal simulation capacity by selecting parts, especially the multi-user GNSS / INS combined negation signal simulation output capacity, and the need of the navigation field for real-time testing of GNSS, INS and GNSS / INS combined navigation signals is fully met.

A method and apparatus for time synchronization and an OFDMA receiver thereof are provided. A preamble timing is obtained by a two-stage correlation in a time domain between a sequence of a received symbol and a reference preamble. The two-stage correlation is further simplified to perform a conjugate multiplication between a one-stage correlation and its correspondingly delayed result. A preamble boundary is adaptively determined by a peak value based on a result of the two-stage correlation. In this way, the time synchronization is achieved with a robust performance in a low SNR, high frequency offset or large delay spread fading channel.

The invention discloses a distributed ultra-high-definition video synchronous processing method, which comprises the following steps of step 1, collecting video data in real time by a camera, converting the collection time into a uniform timestamp, and pushing a video stream to a client; step 2, the client reads and analyzes the video stream of each path of camera to obtain video frame data; step 3, decoding the video frame data by using a GPU (Graphic Processing Unit), and storing the decoded video frame data into a decoding cache queue; step 4, reading and processing the image from the corresponding decoding cache queue by each thread, and storing the image into a corresponding rendering cache queue; and step 5, reading the image data from each rendering buffer queue, synchronizing multiple paths of image data through uniform timestamp comparison, and merging the synchronized image sequences on the same canvas for rendering display. According to the method, video decoding and processing are carried out by using a GPU parallel calculation framework, the time delay and jitter of video processing are reduced, timestamp synchronization is integrated, and synchronous, real-time and smooth processing of distributed multi-channel ultra-high-definition videos is realized.

The present invention provides are a method and an apparatus for processing time synchronization. The method comprises: extending an instruction set of an OpenFlow protocol, the extended instruction set of the OpenFlow protocol being used for implementing time synchronization of a 1588 protocol; and sending a flow table configuration message to a time synchronization device, the flow table configuration message comprising the extended instruction set, and the time synchronization device implementing time synchronization according to the extended instruction set. By using the present invention, the problem in the related art is solved that time cannot be precisely synchronized by means of an OpenFlow protocol, so as to achieve the effect that the OpenFlow can support precise time synchronization and the OpenFlow application field is expanded.

A method for the detection of an object by the TDOA principle is provided. The object transmits a signal, which is received by a plurality of stations having known positions. The stations' clocks can have different unknown time delays in relation to each other. An additional stationary reference station having a known position relative to the stations and transmitting a signal that is received by the stations is provided. An unknown transmission delay can be generated between the emission of the signal from the object and the emission of the signal from the reference station. For each station the difference in travel time between receipt of the signal from the object and the signal from the reference station and the difference of the travel time differences between the stations are determined. Mathematical algorithms for determining the location are performed.

The invention discloses a special network switching method with a synchronous digital hierarchy (SDH) network accurate clock synchronization function. A master clock in a master substation of a power grid transmits a network clock synchronization message consistent with an institute of electrical and electronic engineers (IEEE)-1588 protocol, and the network clock synchronization message is transmitted to each satellite substation through an Ethernet over SDH (EOS) switch. In each satellite substation, an SDH over Ethernet switch converts the network clock synchronization message into a transmission message consistent with an Ethernet protocol, wherein the switch comprises an internal central processing unit (CPU) and a layer-3 network switching chip, and realizes the data exchange of the Ethernet, and the configuration (selection of adoption of an EOS chip) of each data exchange interface of the Ethernet realizes EOS switching. A data interface of the network switching chip is a reduced gigabit media independent interface (RGMII), and an output interface of the EOS chip is a serializer / deserializer (Serees) interface. A field programmable gate array (FPGA) receives data from the RGMII and the Serdes interface to realize the 1-microsecond accurate clock synchronization.

The system is composed of the laser oscillator in femtosecond level, the pulse stretcher of grating pair, the pulse shortener of grating pair, the beam splitter, the first stage OPA amplifier, the back stage OPA amplifier, the prime amplifier of pump source system, the first double frequency crystal, the dichroism spectroscopic plate etc. the characters of the invention are that the signal light and the pump light source are come from the same laser oscillator. The accurate time synchronization between the signal light pulse and the pump light pulse can be realized and the time jitted is reduced without need of the additional collimation light source. That is to say the signal light of each optical parameter amplification stage and the pump light can be collimated and synchronous adjusted.

The embodiment of the invention provides a method, equipment and a system for layer network structure-based precise time synchronization. The method comprises the following steps of: receiving a PTP message sent by a PTP message sending node by a first precise time protocol (PTP) end node, and encapsulating the PTP message according to the requirement of a layer network; and forwarding the encapsulated PTP message to a second PTP end node, sending the PTP message to a PTP message receiving node through the second PTP end node, and performing the precise time synchronization through the PTP message receiving node. Through the method, the equipment and the system of the embodiment of the invention, the PTP message is subjected to layering according to a layer network structure, so that the load of processing the PTP message by a PTP port is relieved, and the layer network structure is favorable for realizing the precise time synchronization.

Method, system and node for providing time synchronisation between local clocks located in nodes within a network and a central clock. The central clock and the nodes exchange messages. The messages transmitted contain a time stamp indicating the time of transmission. When messages are received, the time of reception is also determined. Based upon the calculation of the elapsed time taken by messages to be transmitted and received, a time difference can be estimated which indicates how much the clock on a node lags behind the central clock. Once this lag is known, the clock on the node can be updated. The proposed invention allows for a more precise time synchronisation to take place between nodes and a central clock without having to perform modifications on the transport circuitry of the system. The invention also allows for any changes in the network topology to be detected via any changes in the Round Trip Time, and a management centre to be notified in turn. Additionally, the invention allows for statistical information to be gathered in order to determine the quality of the synchronisation procedure.

The invention discloses a dispersion compensation device and method for a high-accuracy optical fiber timing system. The method comprises a step of measuring a sum deltaT1 of forward and backward transmission delays of two different wavelengths between a timing master station and a timing slave station receiving end. The step comprises the following sub-steps that: a pulse signal output by a cesium atomic clock is modulated into a radio frequency signal through a first encoding modulator on the timing master station; a first wavelength division multiplexer converts the radio frequency signal into an optical signal of which the wavelength is lambda1, and couples the optical signal into an optical fiber; after reception of the optical signal of which the wavelength is lambda1, a second photoelectric converter transmits the radio frequency signal to a second laser and a second demodulation decoder respectively; after reception of the radio frequency signal, the second laser converts the radio frequency signal into an optical signal of which the wavelength is lambda2; and lastly, a returned pulse signal and the pulse signal output by the cesium atomic clock are transmitted to a delay measurement module simultaneously in order to perform delay measurement, wherein a measurement result is the sum of the forward and backward transmission delays between the timing master station and the timing slave station receiving end. Through adoption of the device and method, all-optical network synchronization can be realized, and the timing accuracy is increased.

In a communication system using a PON, time synchronization of a slave device such as a base station is realized with respect to a master device such as an L2SW or the base station. Time information acquired by a GPS satellite is corrected by ranging information of a discovery function of an OLT so as to be reflected on time information of each ONU. A propagation delay from the L2SW to the OLT is obtained with the use of a delay estimation mechanism, a propagation delay from the OLT to the ONU which is obtained by ranging is added to obtain a propagation delay from the L2SW to the ONU. The obtained propagation delay from the L2SW to the ONU is added to the transmitted time stamp value whereby a time stamp value received at a base station or femtocell side becomes a time into which the propagation delay to the ONU is incorporated, and absolute values of clock timers can be synchronized with each other. The addition process can be realized by rewriting the time stamp value of the packet within the OLT or the ONU.

A circuit device includes a phase comparator that performs phase comparison between an input signal based on an oscillation signal and a reference signal, a processor that performs a signal process, and an oscillation signal generation circuit that generates the oscillation signal having an oscillation frequency which is set on the basis of frequency control data from the processor. The circuit device also includes at least one of a first register that stores phase comparison result data, a second register in which one of offset adjustment data for GPS and offset adjustment data for UTC is set, and a third register in which offset adjustment data for adjusting a phase difference is set.

The present invention relates to a time synchronization method in a wireless sensor network. In the present invention, if an upper node requests a lower reference node to start time synchronization, the lower reference node broadcasts a first sync reference packet. The upper node receives the first sync reference packet and transmits the first sync reference packet reception time to the lower reference node. The lower reference node broadcasts the first sync reference packet reception time, such that the other nodes perform time synchronization on the basis of the first sync reference packet reception time. Meanwhile, the lower reference node estimates the first sync reference packet reception time of the upper node to calculate the reception estimation time, and transmits the reception estimation time to a determination node that is two hops anterior to the lower reference node. Therefore, the determination node compares the reception time received from the upper node and the reception estimation time received from the lower reference node and determines whether a capture attack on the upper node has occurred.