218 results about "Network time synchronization" patented technology

Techniques for removing delay fluctuations from network time synchronization so that timing packets that experience an inordinate network delay to not cause unneeded adjustments to a local clock. Time synchronization according to the present techniques includes measuring a network delay associated with a timing packet and discarding the timing packet if the network delay exceeds an adjustable threshold. The adjustable threshold enables balancing the quality of delay measurements in terms of delay fluctuation against the number of delay measurements that are sufficient to maintain time synchronization.

The invention discloses a time synchronization method for a wireless sensor network. The method comprises the following steps of: generating a synchronous data packet, and marking a transmission timestamp in the synchronous data packet; transmitting the synchronous data packet to a child node; receiving the synchronous data packet, and marking a receiving timestamp in the synchronous data packet; and compensating for the clock drift of the child node according to the transmission timestamp and the receiving timestamp in the synchronous data packet. By the time synchronization method and the time synchronization system for the wireless sensor network, clock drift compensation between a parent node and the child node is realized only by transmitting the synchronous data packet to the child node to realize regional time synchronization in a region formed by the parent node and the child node, and compared with conventional all-network time synchronization, the regional time synchronization reduces network energy consumption and also can avoid the energy consumption caused by crosstalk interference as much as possible.

A node with local GPS time in an ad-hoc wireless network synchronizes with the network time immediately and slowly pulls the network time to GPS time. However, network nodes may immediately transition to the common GPS time after an island or group head node determines that the transition in network time does not disturb the communication links.

The invention discloses a time synchronization method which comprises the steps: a client sends synchronous doubleaction frame delay measurement (SDMM) messages which carry the sending time of the client; the client receives synchronous doubleaction frame delay measurement response (SDMR) messages ( SDMR) returned from a server, records the client receiving time of the SDMR messages, and extracts the client sending time of the SDMM messages from the SDMR messages, the server receiving time of the SDMM messages, and the server sending time of the SDMR messages; therefore, the client calculates nonsynchronous time difference, and adjusts the personal clock value according to the difference so as to be synchronous with the server. The invention also discloses a time synchronization system and a client, can be realized without depending on external network time synchronization protocol (NTP), has high synchronization precision, and also enhances the independence and the robustness of transporting multi-protocol label switching (T-MPLS) network functions.

Network timing synchronization for virtual machine (VM) host systems and related methods are disclosed that provide synchronization of master/slave clocks within VM host hardware systems. Master timing messages are sent from the master clocks to slave clocks within VM guest platforms hosted by the VM host hardware system within a virtualization layer, and return slave timing messages are communicated from the VM guest platforms to the master clock. Virtual switches within the virtualization layer use virtual transparent clocks to determine intra-switch delay times for the timing packets traversing the virtual switch. These intra-switch delay times are then communicated to target destinations and used to account for variations in packet transit times through the virtual switch. The VM guest platforms synchronize their timing using the timing messages. The master/slave timing messages can be PTP (Precision Time Protocol) timing messages and/or timing messages based upon some other timing protocol.

A time synchronization system comprises a GPS (Global Positioning System) receiver for receiving a time signal from a Global Positioning System (GPS), and outputting a UTC (Universal Time Coordinated) synchronization reference signal synchronizing with UTC and a UTC synchronization absolute time signal, and a time signal distributor for generating a reference time signal synchronizing with UTC from the synchronization reference signal and the absolute time signal, and transmits this reference time signal in distribution to a plurality of distributed control oriented terminal devices. The time synchronization between the plurality of distributed control oriented terminal devices can be thereby taken.

The invention relates to a method and a system for synchronously inserting network time. The method comprises the following steps: S1, a client generating an NTP (Network Time Protocol) timestamp query information packet and sending the NTP timestamp query information packet to an optimal time server, wherein the optimal time server is a time server selected by the client according to an optimal time server algorithm; S2, the client receiving an NTP timestamp answer information packet generated by the optimal time server according to the NTP timestamp query information packet; S3, repeating S1 and S2, and executing S4 when the repeated times is N, wherein N is more than or equal to 5 and less than or equal to 10, the repeated time interval is t, and t is more than or equal to 10s and less than or equal to 30s; S4, the client calculating a time difference data mean by adopting an information packet filter algorithm; S5, the client calibrating the client time according to the time difference data mean; and S6,the client displaying the calibrated client time. By adopting the method and the system, the calibrating precision is high, the system is small, the scheme is easy to realize, and the hardware cost is relatively low.

The invention discloses a satellite group network time synchronization method based on a cross-layer design. A spread spectrum signal mechanism is employed in a physical layer. A clock difference between a son node and a father node is calculated in a semi-two-way inter-satellite distance measurement mode, thereby finishing high-precision time synchronization between the nodes. Network synchronization management is employed in an MAC layer, synchronization state information is broadcasted in a network and synchronization topology management is carried out. A time synchronization father node selection result is provided for the physical layer for inter-node synchronization, thereby finishing time synchronization among the nodes of the whole network. The method provided by the invention is applicable to inter-satellite time synchronization demands of various satellite groups; there is no special demand for a satellite system; the universality is high; the application range is wide; on-satellite processing is simple; and the method has good application prospect.

The present invention belongs to the field of the whole network time synchronization, and especially relates to a multi-mode high-precision timing system and method. The system provided by the invention comprises a Beidou timing unit, a GPS timing unit, an IRIG-B timing unit, a taming timekeeping unit and a timing algorithm unit. The Beidou timing unit, the GPS timing unit and the IRIG-B timing unit are in both-way communication connection with the timing algorithm unit, and the timing algorithm unit is in both-way communication connection with the taming timekeeping unit; and the taming timekeeping unit includes a taming timing circuit, in the condition of Beidou pulse signals, GPS pulse per second signals and IRIG-B pulse per second signals are all lost, the taming timing circuit enters a timekeeping state, and the timing algorithm unit outputs timing time and timing pulse per second. Through adoption of Beidou satellite time, GPS satellite time and IRIG-B code time as external clock source of a timing system, the multi-mode high-precision timing system and method is able to avoid the problem caused by unstable time performance of a PGS satellite, and is high in precision, good in reliability and stable in performance.

The invention discloses a mobile sensor network routing method based on regional gradient updating. The method is helpful for the application and development of wireless sensor network technology in China, and will take important roles in environmental monitoring and forecasting, emergency treatment of natural disaster, scientific expedition and exploration, intelligent family, urban traffic, management of large-scale garage and warehouse, safety monitoring of large-scale industry park and other fields. The invention mainly solves the problems of the protocol in prior art, including large energy expenditure and large storage space. The method comprises a base station constructs regional gradient and performs periodical regional gradient updating, so as to synchronizing the time of the entire network. When a source node transmits data to a merge mode, the source node constructs a link going through the merge node, so as to conduct data transmission. The invention is based on wireless sensor network, increases the service life of wireless sensor network, and saves storage space of a sensor.

The invention discloses a network time synchronization device, system and method, the method includes following steps: step A: the business device sends the time request to at least one time sever at intervals of time; step B: compares the time samples returned by the time sever, choose the time sample to calculate the time difference between the local time and the time sever; step C: according to obtained time difference data to adjust the frequency regulator in the business device, and locks the time of superior time sever. Using the invention, it can obtain the time information of superior time sever via the transmission network, and according to the time information obtained in different time it can calculate the shift of local oscillator, and it can eliminate the local time shift by adjusting the frequency regulator to satisfy the requirement for the time of business device.

The invention relates to the field of the Internet of things, and particularly relates to the industrial Internet of things, such as an industrial control service time synchronization scheme design of a smart power grid. In an application environment of the industrial Internet of things, the invention provides a service message time synchronization scheme, for overcoming the defect that a service terminal has no time synchronization function with an information master station. It can be seen from analysis that, the scheme can be used for guaranteeing the time synchronization of a service message between a terminal device and the information master station in the case of no congestion of the network, and can be used for guaranteeing the service message to meet the time sequence logic requirements of the terminal device in the case of congestion of the network, so the scheme is a weak synchronization technology. Meanwhile, the invention provides a three-level time synchronization structure suitable for the construction of the smart power grid by combining the time synchronization scheme with the current situation of the power grid. The three-level time synchronization structure can support whole network time synchronization of a power system, guarantee the time synchronization and time sequence requirements of a power service message and meet the demands of multi-service access and multi-service protocol type conversion of a master station of the power system.

The invention belongs to the time synchronization technical field and discloses a distributed network time synchronization method. The method includes following steps that: the difference of the clock of a center node and the clock of terminal nodes is determined; after receiving time synchronization request signals sent by different terminal nodes through different carrier frequencies, the center node captures, tracks and demodulates the request signals by using a local spread spectrum sequence database so as to obtain terminal node serial numbers, request sign information and terminal node clock information contained in the request signals, and center node clock information is compared with the local clock of the center node, time difference is measured; and offset correction is performed on the local clock of the terminal nodes according to the difference of the clock of the center node and the clock of the terminal nodes. Through synchronization, accuracy can reach a level of several hundreds of nanoseconds or even a level of dozens of nanoseconds.

The invention relates to a wireless network communication technology, and in particular relates to a time synchronization error compensation method for a multi-hop wireless backhaul network based on a PTP protocol. According to the method, based on the PTP protocol, timestamps for transmitting and receiving a PTP synchronous message Sync and a delay request message Delay_Req is counted by using an intermediate node, and local forwarding time of the synchronous message Sync and the delay request message Delay_Req and link delay of transmitting the same between nodes are detected and compensated based on a linear regression technology, and finally wireless link asymmetrical delay correction of the main and slave nodes is achieved, and time synchronization error compensation is completed. According to the method provided by the invention, message overhead is reduced by using additional time information such as header transmission compensation time of a PTP message, message transmitting and reaching time and time modification value without modifying an existing PTP protocol, requirements on real-time and high precision of time synchronization error compensation are met, existing time synchronization precision is improved and strong practicability is provided.

A method for time synchronization of a computer network by a main computer, in which case, for synchronization with an N-th interrupt, a time signal corresponding to the instant of the interrupt plus a time interval between the interrupts is transmitted on an ATM bus and the secondary computers to be synchronized set their clock to this transmitted time signal with the next interrupt.

The invention provides a mobile terminal positioning method, an acoustic positioning transmitter-receiver, a mobile terminal and a mobile terminal positioning system. At least three acoustic positioning transmitter-receivers with synchronized networks and different frequencies are arranged at a certain positioning region, and acoustic signals are synchronously transmitted to the mobile terminal by all the acoustic positioning transmitter-receivers through network time synchronization; after the mobile terminal enters the positioning region, the acoustic signals of the at least three acoustic positioning transmitter-receivers are received, and each acoustic positioning transmitter-receiver is identified from the received acoustic signals and corresponding data flows are acquired; a signal transmission time difference between each two acoustic positioning transmitter-receivers is acquired from the data flows; and TDOA (Time Difference of Arrival) calculation is carried out according the position of each acoustic positioning transmitter-receiver and the transmission time difference between each two acoustic positioning transmitter-receivers so as to determine the position of the mobile terminal in the positioning region. According to the technical scheme provided by the invention, the positioning cost of the positioning region is reduced and the positioning precision and reliability of the mobile terminal are improved.

A time regulation algorithm of network time synchronization in telecommunication field includes utilizing network time approximation algorithm and applying time convergence-approximation method to make time of device be converged and approximated to time of server step by step, finally controlling deflection of standard time between time of device and time server to be at a small range.

The invention discloses a method for improving time synchronization precision under a complex network environment. The method mainly solves the problems that synchronization precision of an existing network time synchronization method can not meet requirements of engineering projects and in a serious case, master equipment and slave equipment can not be synchronized normally. The method includes the first step that that a master clock and a slave clock extract timestamps of multiple moments respectively; the second step that unlink delay and downlink delay are measured, and an uplink time delay threshold value and a downlink time delay threshold value are obtained through a time delay detection algorithm; the third step that the timestamps corresponding to the moments beyond the time delay threshold values are removed; the fourth step that precise network time delay is figured out through a time synchronization algorithm and an asymmetrical time delay compensation algorithm; the fifth step that the time of the master clock and the time of the slave clock are synchronized by the utilization of the time synchronization algorithm. The method is suitable for any network time synchronization algorithm, and by the adoption of the method, the time synchronization precision and stability can be greatly improved.