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

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.

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 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 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 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.

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 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.

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.