170results about How to "Synchronization speed is fast" patented technology

The invention discloses a security cloud storage system based on increment synchronization. A three-tier architecture of client-intermediate server-private cloud terminal is adopted, and data security is guaranteed by multiple security protection technology. After being blocked and encrypted, a user file is transmitted to a cloud terminal through an SSL (security socket layer) security transmission protocol; after finishing the work of user management and key management, the intermediate server terminal adopts a mutual authentication mechanism and an access control mechanism to realize the safe data share so as to completely prevent original data from leaking from the server terminal; the binding of the file and a mobile device is realized at a client, the specific file can be only opened on a specific device, and even though the file is leaked by an insider, a leaking device can be traced; moreover, the unique increment synchronization technology is realized, and the file can be synchronized by only synchronizing modified file blocks, so that the flow consumption in the file transmission process is reduced, the transmission efficiency is improved, the system usability is enhanced, and user experience is promoted.

Orders of the block link exchange are signed by users, the quantities are generally not totally matched, and according to regulations, when prices with signatures meet transaction requirements, the transacted quantity is cumulatively no more than the signature quantity, the matching order for the same price on the same server is ordered according to a time order of entering the server. If to-be-matched users are respectively located in multiple areas with certain network time delay, apart from a unique whole network matching center, multiple area matching centers can also be added, the users can assign an area matching center for being matched, each user can only assign (requiring a signature) a certain server in a certain area for matching the transaction, and if a matching server needs to be replaced, the order needs to be canceled and then the order is posted again. The transaction records transacted in the area matching centers are sent to the whole network matching center, and the transaction records can be directly written to a new block in the block chain without matching by the whole network matching center.

The invention discloses a block synchronization method and system, wherein the method is applied to a block chain network; furthermore, according to block mark numbers of block chains, snapshot blocksand snapshot intervals formed by separation of the snapshot blocks are pre-defined; a miner node judges whether a current block to be packaged is a snapshot block or not according to the block mark number of the current block to be packaged; if the current block to be packaged is the snapshot block, the snapshot block, the block head of which includes snapshot field information, is generated; a conventional node verifies the snapshot block and the snapshot field information; the snapshot block passing verification is added into a block chain copy of the node itself; a newly increased node downloads a pre-set number of blocks from the conventional node, wherein the snapshot block is included in the pre-set number of blocks; the snapshot field information in the block head of the snapshot block is utilized for verifying trade information in the downloaded blocks; therefore, the check time of transaction signature in the existing technical scheme is reduced; and furthermore, the block synchronization speed of the newly increased node is also greatly increased.

The invention discloses a method for synchronizing multi-region data of a comprehensive monitoring system. The method is characterized by comprising the following steps: 1) synchronization region definition, in which, basic information of data servers of a control center, a spare center, a station and a rolling stock depot is defined; 2) cross-linking of ring queue and data service thread, in which, a thread corresponding to the data server is established, and is simultaneously cross linked with the ring queue so as to manage global state information; 3) data extraction and generation and encapsulation of identification information, in which, data to be synchronized is extracted, data description information is established, and the description information and the extracted data are encapsulated; 4) detection and management of server state, in which, the data synchronizing thread detects the state of the server, and updates state information corresponding to the data server in the global state information; 5) data submission and server failure processing; and 6) data submission result identification and data cleaning. The method for synchronizing data of the comprehensive monitoring system can realize high usability, high synchronization speed and high security of data synchronization.

The invention provides a class synchronization system based on the wireless network. The class synchronization system based on the wireless network comprises a wireless router, an all-in-one computer, a mobile terminal and a server side. The method adopted in the class synchronization system comprises the monitoring step, the judging step and the outputting step. In the monitoring step, the picture information of a brush panel of the mobile terminal is monitored in real time, and a picture synchronization order is sent to the server side to request for the synchronous displaying. In the judging step, whether the picture of the brush panel changes or not is judged, wherein if yes, a screen synchronization processor packages the coordinate pixel points and the corresponding color values of the changing parts in real time and transmits the coordinate pixel points and the corresponding color values of the changing parts to the server side to be processed, and synchronization picture information is generated. In the outputting step, the synchronization picture information is output to the all-in-one computer to be displayed. The screen picture of the mobile terminal can be synchronized to the all-in-one computer to be displayed in real time, the consumption on the CPU, the internal storage and the wireless network flow is reduced, the speed and running efficiency are high, and the synchronization picture is fluent.

The invention discloses a walking hydraulic control system comprising a reversible pump, a first left walking motor and a first right walking motor; the walking hydraulic control system further comprises a first flow split and flow collection valve, wherein a confluence oil opening of the first flow split and flow collection valve is communicated with a first working oil opening of the reversible pump, and two flow split oil openings of the first flow split and flow collection valve are respectively communicated with first working oil openings of the first left walking motor and the first right walking motor; and second working oil openings of the first left walking motor and the first right walking motor are communicated with a second working oil opening of the reversible pump. Compared with the prior art, the walking hydraulic control system is provided with the first flow split and flow collection valve to realize the equivalent flow split and equivalent flow collection of the walking motors on the left and right sides so as to improve the speed synchronism of the walking hydraulic motors and provide reliable guarantee for controlling the non-uniform friction of wheels. On the basis, the invention further provides self-walking type engineering machinery provided with the walking hydraulic control system.

A method and apparatus for synchronizing to a frame structure associated with base station transmissions in a radiocommunication system are described. A broadcast control channel can contain synchronization symbols within each of a plurality of timeslots. The symbols are organized in a sequence that is repeated each frame. Within each sequence are plurality of subsets of symbols which can be used to uniquely identify the phase of the frame.

The present invention relates to a single planetary gear hybrid power transmission system which comprises a single planetary row, wherein the single planetary row comprises three rotatable parts, namely, an outer gear ring, a sun gear and a planetary gear respectively meshed with the outer gear ring and the sun gear, and the planetary gear is connected to a planetary frame; a power supply, whereinthe power supply comprises an engine, a first motor and a second motor respectively connected to the single planetary row in a transmission manner, and a power storage battery for charging and powerutilization is mounted on the first motor and the second motor; a gear shift component, wherein the gear shift component comprises a gear shift element and a single-phase clutch or a brake for lockingthe transmission of the engine and the single planetary row; and an output shaft, wherein the output shaft is connected to the single planetary row in a transmission manner, and a main reducer is mounted on the output shaft. Compared with the prior art, the invention has the advantages of low mechanical complexity, low control difficulty, multiple modes and so on.

The invention discloses a method for transmitting real time parallel data flow, which comprises: sealing the parallel data bits into a data frame with frame head, transferring the parallel data bits of the data frame into the serial data flow and output it on the sending side; orienting the frame head of each data frame from the received serial data flow, transferring the serial data flow into the data frame with frame head which is formed by the parallel data bits, at last opening each obtained data frame and recovering the initial parallel data flow to achieve the TDM data flow cross transmission.

The invention discloses a method for synchronizing photos. The method includes the steps of uploading thumbnails of the photos to a cloud photo album server, synchronizing the thumbnails of the photos to a second terminal through the cloud photo album server, and uploading the photos to the cloud photo album server for saving. By means of the method, the shot high-quality photos are rapidly and synchronously displayed to other terminal devices through the cloud photo album server, and the downloading requirement of a user for the photos is met. The invention further discloses a device for achieving the method.

The invention discloses a ring network distributed bus protection synchronization method. The ring network distributed bus protection synchronization method includes the steps of sampling synchronization, constant value pressing plate synchronization and time synchronization. According to the sampling synchronization, fixed delay and measurement delay are adopted; the delay correction domain of sampling messages is corrected real time; and after obtaining sampling messages of all interval units, a ring network bus protection unit performs software interpolation synchronization through analyzing sampling delay in the delay correction domain. According to the constant value pressing plate synchronization, a source-end synchronous method is adopted; and a constant value pressing plate can be synchronized at any intervals of ring network bus protection. According to the time synchronization, a time synchronization method based on minimum addresses is adopted; and each interval of the ring network bus protection can still have very high timing precision under the situation in which an external time source is lost at an extreme end. The ring network distributed bus protection synchronization method of the invention is advantageous in easiness in implementation, no need for external synchronization sources and high synchronization precision.

A frame synchronization method of a GPS receiver comprises the following steps: (1) after the GPS receiver is turned on and is fixed firstly, the local clock is adjusted periodically to ensure that the times and variation periods of the local clock and the GPS clock are consistent, the current position of the GPS receiver is recorded; (2) after the channel of the GPS receiver is unlocked and recaptured, the local time and ephemeris are read, the preliminary position of the satellite is calculated according to the ephemeris and the approximate launch time of satellite signals; (3) the uncorrected approximate distance of the GPS receiver and the satellite is calculated according to the recorded initial position of the GPS receiver and the preliminary position of the satellite so as to obtain pseudorange; (4) the local time is corrected according to the time used for executing the step (2) and the step (3) to obtain the satellite launch time of the current teletext; and (5) the frame count, bit count and millisecond count of the current teletext are calculated according to the result of the step (4), and frame synchronization is performed to extract the teletext.

The invention discloses a data synchronization method, a server and a storage medium, which are suitable for terminal data synchronization. The method provided by the invention comprises the followingsteps: receiving an update request of a client; comparing a timestamp of the local data of the client with the timestamp of server data; when the timestamp of the local data of the client is different from the timestamp of the server data, obtaining fields of the to-be-updated data of the client according to the difference of the local data of the client and the server data, and splicing a SQL statement; and sending a set of the SQL statements to the client. In the data synchronization method, the o-be-updated data are spliced into the SQL statements on the server and are sent to the client,so that the client can directly execute the SQL statements and execute the data update operation in the server, thereby greatly improving the data synchronization speed of the client, and reducing thetraffic occupation.

The invention relates to a signal transmission method used in a broadband wireless mobile communication system, belonging to the technical field of digital information transmission. Firstly, source coding, channel coding and digital modulation are subsequently implemented on information which is generated by a sending terminal, and the modulated information is obtained; TFU-OFDM modulation is implemented on the modulated information, and a plurality of modulated symbols are combined into frame signals to be sent out; the received frame signals are separated into TFU-OFDM modulated symbols according to the corresponding combining mode; the TFU-OFDM demodulation is implemented on the modulated symbols to obtain serial data, and digital demodulation, channel decoding and source decoding are successively implemented on the serial data to obtain initial information. The advantage of fast synchronous speed of TDS-OFDM technology is maintained. And the estimation of the receiving terminal on the channel response is more accurate. Synchronization and channel estimation are separated, which is convenient for the modularization of the system. The processing efficiency of the system is improved. And the method is especially applied to the broadband wireless mobile communication system.

The invention provides a method for synchronizing a radio navigation system of a direct sequence spread-spectrum and frequency hopping system, which comprises the steps that: an antenna (1) receives a radio signal and transmits the radio signal to a low-noise amplifier (2); the low-noise amplifier (2) performs low-noise amplification on the signal and transmits the amplified signal to a radio frequency processing module (3), the radio frequency processing module (3) performs filtering and automatic gain control (AGC) on the signal and then transmits the processed signal to a direct sequence spread-spectrum and frequency hopping synchronizing module (4); the direct sequence spread-spectrum and frequency hopping synchronizing module (4) realizes the synchronization of a frequency hopping sequence and a direct sequence spread-spectrum sequence; and a subsequent processing module (5) performs subsequent operations which are observed vector extraction, information demodulation and position resolution respectively according to synchronization information provided by the direct sequence spread-spectrum and frequency hopping module (4). The method effectively improves performance of capturing and tracking direct sequence spread-spectrum and frequency hopping signals, can quickly capture and stably track the direct sequence spread-spectrum sequence and the frequency hopping sequence which are relatively longer, and compared with the conventional method for synchronizing frequency hopping first and then synchronizing direct sequence spread-spectrum, is higher in synchronization speed, higher in synchronization accuracy and more ensured in privacy.

The invention relates to a network operating on a time triggered protocol using time slots, wherein at least two clusters are included in the network, each cluster includes at least a node. Further, it relates to a method for clock synchronization within a time triggered network. To provide a network and a method reducing the amount of time needed for aligning multiple communication clusters as much as possible it is proposed to provide a network operating on a time triggered protocol using time slots, wherein at least two clusters (A, B, X) are included in the network, each cluster (A, B, X) includes at least a node (11), wherein the node (11) includes a communication controller (15) having a node clock source (18) for determining a timing for the node (11), wherein the clusters (A, B, X) are connected to a coupling unit (10) having a clock alignment control logic (20) comprising a coupling unit clock source (21) which is more accurate than the node clock source (18), wherein the coupling unit clock source (21) is used for aligning the timing between the at least two clusters (A, B, X). Further it is proposed to provide a method for clock synchronization within a time triggered network using time slots, having at least two clusters (A, B, X), wherein each cluster includes at least one node (11), each node (11) comprises a node clock source (18) and a communication controller (15) and the clusters (A, B, X) are connected to a coupling unit (10) having a clock alignment control logic (20) comprising a coupling unit clock source (21) which is more accurate than the node clock source (18), the method comprising the steps of: monitoring the timing of the connected clusters (A, B, X) within the coupling unit (10); increasing or decreasing a cycle length of the timing within the clusters by use of the coupling unit clock source (21).

The invention discloses a database data synchronization method and device and a computer storage medium. Time stamps and version hash values are set for version information of databases of the Internet of Things terminal device and the cloud server. Only when the timestamps and the version hash values of the respective version information of the databases are consistent, synchronization of database is performed. The cloud server only sends different data between the data of the database corresponding to the latest update record of the cloud server and the data of the database of the version corresponding to the successful consistency check to the Internet of Things terminal device for synchronization. Through the scheme, data synchronization of the cloud server and the database of the Internet of Things terminal device can be ensured, and after consistency verification is successful, the cloud server only sends the difference data between the latest version of the database and the database when consistency verification is successful, so that the resource occupancy rate can be reduced, and the synchronization speed can be increased.

A multi-motor motion synchronization improved adjacent coupling control method based on active disturbance rejection comprises the steps of establishing a model of a permanent magnet synchronous motor system and initializing the system state and control parameters, designing an improved adjacent coupling control strategy, designing a multi-motor speed controller based on an active disturbance rejection technology, and designing a multi-motor synchronization controller by combining the improved adjacent coupling control strategy and an integral sliding mode technology. The speed consistency problem of a multi-motor synchronization system is solved effectively, the tracking performance and robustness of the system are improved, and stable operation of the multi-motor synchronization system is realized.

The invention provides a master-secondary synchronization method and device. The method comprises steps that data synchronization commands sent by a master node are received the first thread of secondary nodes, and log files are sequentially recorded according to the order of the data synchronization commands; the data synchronization commands are distributed by the first thread to multiple secondthreads of the secondary nodes and are simultaneously performed by the multiple second threads; if the data synchronization commands are successfully performed by the second threads, the confirmationinformation is sent to third threads of the secondary nodes; the offset amount of the log files is updated by the third threads according to the confirmation information. The master-secondary synchronization method is advantaged in that on the condition that the synchronization command input order of the secondary nodes and the command sending order of the master node are guaranteed to be consistent, the multiple second threads are opened and the data synchronization commands are simultaneously performed, the data synchronization speed is accelerated, master-secondary synchronization delay isshortened, and master-secondary data synchronization is efficiently accomplished.

The invention discloses a method for directly operating a file stored at a cloud end. The method comprises the following steps that a terminal device periodically obtains file structure indexing information of a file stored at a cloud end by a network and locally establishes a directory structure which is the same as the directory structure at the cloud end; when the file stored at the cloud end is to be operated locally at the terminal device according to the established directory structure, a file content request is sent to the cloud end, the file content sent by the cloud end is received and cached locally for operation; after operation, the terminal device records change of the file structure indexing information, caused by local operation, and sends the changed file structure indexing information to the cloud end; and the cloud end receives the changed file structure indexing information and synchronizes the file and the directory structure at the cloud end according to the information. The method disclosed by the invention provides convenience for operation of files stored at the cloud end and is high in synchronizing efficiency.

The invention discloses a high-reliability clock synchronization system and method for a time sensitive network, and relates to the technical field of communication. The network is divided into two levels according to a clock synchronization function, a master-slave synchronization method is adopted for a top-layer network to achieve time and frequency offset correction, the time and frequency offset is compared with a bottom-layer network clock reference in order that the network reliability is guaranteed; and the bottom-layer network adopts a distributed structure to realize calculation release and frequency release of the time reference. According to the invention, the dependence of the network clock reference on the GM is reduced, and the fault tolerance and reliability are improved; roles of all devices in the network are dynamically distributed so that the agglomeration phenomenon is avoided, and clock synchronization of all network devices is achieved; time and frequency offsetcorrection is considered at the same time, synchronization of a network system clock and UTC in time and frequency is achieved, the problems that in a traditional clock synchronization method, time offset correction precision is not high, and frequency offset correction is slow are effectively solved, namely synchronization precision is improved, and synchronization speed is increased.

The invention provides a high frequency domain energy concentration synchronization method based on fractional Fourier transform. Three chirp signals are connected in series as a synchronization signal, and the synchronization signal is transmitted at a transmitting terminal; the transmitted synchronization signal is received at a receiving terminal, and the fractional Fourier transform in performed on the received synchronization signal to produce a fractional domain magnitude spectrum; three peak value positions of the fractional domain magnitude spectrum are detected, and the three peak value positions are compared with peak value positions in the case of without time offset and without frequency offset to produce an offset deviation; calculating time offset and frequency offset of the system according to the offset deviation; and adjusting a time window position of the system and the frequency of local carrier waves according to the time offset and the frequency offset of the system to realize synchronization. Aiming at low synchronization signal frequency domain energy concentration and susceptible system synchronization accuracy problems in synchronization methods adopted in modern frequency modulation communication systems, a synchronization method based on the fractional Fourier transform is provided. The method is applicable for synchronization of communication signals.

The invention relates to a multiple access signal transmission method for a broadband wireless communication system, belonging to the technical field of digital information transmission. The method comprises the following steps of: respectively carrying out channel coding and digital modulation on transmission block data of a user on each path to obtain digitally modulated information; mapping the information and the pilot frequency of the user to corresponding data subcarrier and pilot frequency subcarrier, dividing all the data subcarriers into a plurality of subchannels to ensure that the information of each user corresponds to one or more than one subchannel, and setting protection subcarriers and DC subcarriers to be 0; carrying out inverse discrete Fourier transform on all the subcarriers to obtain time domain signals; and combining a generated protection interval sequence and the time domain signals, converting into a serial data stream, and sending the serial data stream. The invention has the advantages of high synchronization speed, accurate channel estimation and the like; more users can be supported by using smaller access time delay, wireless resources can be distributed freely, depth fading and narrow-band interference can be effectively resisted, and multiple-user diversity gain can be realized conveniently.

The invention discloses a time frequency combined synchronizing method based on fractional Fourier transform, relating to synchronization technology in wireless communication, and solving the problems that the existing time frequency synchronizing method has poor time frequency synchronization and high system complexity. The method is realized by the following steps: connecting two chip signals in series as a synchronization signal and emitting the synchronization signal; receiving the synchronization signal by a receiving terminal, carrying out fraction Fourier transform to the synchronization signal, detecting the positions of two peak values of fractional domain amplitude spectrum, calculating difference values with the positions at the peak values of a synchronization signal fractional domain without time deviation or frequency deviation, carrying out calculation to two difference values through a formula so as to obtain the correct time deviation and frequency deviation of the system, thus adjusting time window position of the system and the frequency of a local carrier wave, and realizing time frequency combined synchronization. The method is applicable to the processes of signal transmission in the wireless communication.

The invention relates to a cluster-based distributed antenna time frequency synchronizing method in wireless communication, and belongs to the technical field of wireless communication. The method comprises the following steps of: dividing mass distributed antennas into clusters, selecting cluster representative antennas, and performing distributed bidirectional coordinated synchronization on the cluster representative antennas; and then, initiating intra-cluster distributed bidirectional coordinated synchronization by the cluster representative antennas so as to finally realize time frequency synchronization of all distributed antennas in a system. The method has the following advantages that: through cluster division, a plurality of clusters are simultaneously synchronized, the total synchronization time is reduced and the synchronization speed is quickened; the synchronization between the cluster representative antennas is performed first and then the intra-cluster distributed bidirectional coordinated synchronization is performed so as to obtain higher synchronization precision and meet the requirement of a distributed wireless communication system for synchronization precision; and the synchronization between the distributed antennas is finished in advance so as to avoid multiple times of synchronization between a terminal user and a plurality of distributed antennas. The method reduces the system resource overhead of the terminal user, and improves the communication reliability.

The invention relates to an intelligent power unit for a high-power converter device and a control method, used for a high-voltage frequency converter and a photovoltaic inverter. The frequency converter is formed by a plurality of power units, each phase of which is arranged in multiple layers, in series; each power unit is provided with a unit field programmable logic array FPGA and a single chip microcomputer unit STM32; the unit field programmable logic array FPGA and the single chip microcomputer unit STM32 are connected through a serial interface SPI; bus over-voltage detection, temperature measurement, bridge arm open-circuit and short-circuit state detection having flash lamp indication, pulse wide measurement and the like are connected to the inlet of the FPGA; the outlet is connected to a driving circuit; a main control system comprises a central data controller and a layer controller on the same mainboard; bidirectional transmission between the main control system and the FPGA is realized through two optical fibres; the two have communication state detection; transmission is carried out according to a specified time sequence; therefore, the anti-interference performance is high; the real-time performance of fault response is ensured; dead-time compensation in pulse width measurement is carried out according to the real waveform; the compensation precision is the highest; a variable-frequency motor is constant in waveform and steady in torque; a test result shows that: the communication speed is high; the synchronization performance is good; the reliability is high; performances are comprehensively optimized and intelligentized; the cost is low; and the intelligent power unit is used for the driving power supply of the variable-frequency motor and the power supply of the photovoltaic inverter.

The invention discloses a conference room management system and method. The conference room management system comprises a server, a database and at least one smart terminal; B / S architecture and a WebSocket protocol are adopted between the server and the smart terminal to perform two-way communication; the smart terminal generates a conference room reservation request including user information and conference information according to an input on a Web browser by a user and sending the conference room reservation request to the server; the server calls the conference room information in the database, screens out the conference room information of an available conference room according to the user information and the conference information included in the conference room reservation request,and sends the screened conference room information of the available conference room to the smart terminal; the smart terminal displays the conference room information of the available conference room, generates a reservation determination information according to the input of the user and sends the reservation determination information to the server; and the server updates the conference room information in the database according to the user information and the reservation determination information. Through the conference room management system and method disclosed by the invention, the conference room reservation is conveniently realized, and the information interaction between the server and the smart terminal is optimized.

The invention belongs to the technical field of intelligent control, and discloses an event-driven time-varying coupled complex dynamic network synchronization method. The cooperative directed spanning tree topology gives a sufficient condition for realizing time-varying complex dynamic network index synchronization and a strict positive lower bound of event-driven interval time so as to eliminatethe Zeno behavior. The cooperative directed spanning tree topology allows that the nodes in the network are not connected any time, and only the integration of the Laplacian matrix of the network topology requires to include a directed spanning tree within a period T so that the requirement of network communication for the network topology can be reduced. A theoretical basis can be laid for application of time-varying coupled complex dynamic network synchronization and the range of application can be extended; and the communication traffic between the network nodes can be reduced, the networkbandwidth can be saved and the communication cost can be saved.

The present invention relates to a wireless remote control technique. The present invention solves the problem of long synchronization time or high complexity of frequency hopping method in existing radio-frequency remote control system and provides a frequency hopping method based on radio-frequency remote control system, the technical solution of the method is summarized as follows: the difference from prior art is primarily in that: scanning all channels respectively by a radio-frequency receiving end and a radio-frequency remote controller and conducting sequencing according to qualities of the channels in a sequence from good ones to poor ones, selecting a certain number of channels from the top of the sequence for marking, correspondingly conducting frequency hopping according to the marking and sequence in subsequent frequency hopping operations, and if the radio-frequency receiving end receives frequency hopping information sent from the radio-frequency remote controller, correspondingly conducting frequency hopping according to the frequency hopping information, and sending the frequency hopping information for the next frequency hopping to the radio-frequency receiving end by the radio-frequency remote controller after synchronization. The beneficial effects of the present invention are that the method meets the real time needs for the remote controller while meeting the demand of interference resistance and is suitable for a radio-frequency remote control system.

The invention relates to a caller identification method and device. The method comprises the steps of submitting a local version number of a local address list to a background server by a mobile terminal, comparing the local version number with a latest remote version number of a remote address list by the background server; analyzing to obtain all operation records between a remote version number corresponding to the local version number and the latest remote version number and forming operation data by the background server; updating the data and the local version number of the local address list according to the operation data and the latest remote version number by the mobile terminal; monitoring communication state by the mobile terminal. According to the method and the device, a version number comparing mode is adopted, comparing all contact information in the address list is not needed each time, and the loads of the mobile terminal and the background server are reduced; only updated contact information is synchronized into the local address list, and incremental updating is realized, so that the synchronizing speed is improved.