585 results about "Clock error" patented technology

A system and method for synchronizing a local clock to a reference clock using a linear model of the clock error between the local clock and the reference clock is disclosed. In one embodiment, a double-exponential smoothing process is used in conjunction with the linear model to estimate a frequency offset by which the frequency of an oscillator of the local clock is adjusted. Also disclosed herein is a phased-lock loop (PLL) adapted to synchronize a local clock with a reference clock using the double-exponential smoothing process, as well as a system implementing the PLL for timing the playout of data received from a transmitter.

A method and apparatus for time synchronization in a communications system such as a system including cable modems is provided. The synchronization method comprises the steps of receiving a first timestamp from a headend unit with the cable modem, and generating a first cable modem time reference with the cable modem in response to the receipt of the first timestamp. The cable modem then receives a second timestamp from the headend unit and generates a second cable modem time reference in response to the receipt of the second timestamp. A headend difference time comprising the difference of the first and second timestamps is then generated as is a cable modem difference time comprising the difference of the first and second cable modem time references. A clock error time that comprises the difference of the headend difference time and the cable modem difference time is then generated as well as a correction factor in response to the clock error time. The local clock of the cable modem is then synchronized with the master clock of the headend unit through the adjusting of the output of the local clock output in response to the correction factor. The correction factor in one instance comprises an offset value representative of the amount of clock error per local clock pulse. This offset value is added to an accumulator on each local clock pulse, and the local clock output is adjusted when the accumulator rolls over. The synchronized clock signal can then be utilized to determine a time slot in which the cable modem can transmit an upstream signal to the headend without colliding the upstream signal with upstream signals from other modems in the system.

The invention discloses a real-time precise orbit determining method of a short orbit arc low earth orbit (LEO) navigation satellite. The method is characterized in that four or more ground receivers are used for tracking navigation signals of a plurality of GNSS (Global Navigation Satellite System) navigation satellites and LEO navigation satellites, and transmitting the navigation signals to a data center in real time. The method comprises the following steps: I, acquiring and preprocessing observing data; II, performing precise time synchronization on the receivers; III, calculating tropospheric delay in an LEO gazing direction by using tropospheric delay in a vertical direction and a projection function; IV, correcting hardware delay of the receivers to build an LEO determining geometric observing equation; V, solving an LEO precise orbit and a precise clock error through a dynamical model and the geometric equation of the LEO; VI, distributing the LEO precise orbit and the precise clock error in real time. By adopting the method, the problem of need of post-processing due to incapability of calculating the precise orbit of a low earth orbit satellite can be solved.

A satellite clock error is determined for each navigation satellite based on the pseudo-range code measurements, the carrier phase measurements, and broadcast satellite clock errors provided by a receiver network. Differences are determined between the computed satellite clock errors and the broadcast clock errors for each satellite. For each constellation, a clock reference satellite is selected from among the navigation satellites, where the clock reference satellite has the median value of clock error difference for that satellite constellation. A correction is determined for the broadcast clock error by applying a function of the reference satellite's clock error to the broadcast clock error for each satellite in the one or more constellations.

A system and method are provided for adaptive synchronization of timing information provided in communications messages transmitted between independently clocked communication nodes of a wireless communications network. The system and method include measures for collecting timestamps of messages generated by a plurality of the nodes, each timestamp being generated by one of the nodes relative to a local time reference thereof. A pairwise clock error is computed for at least one pair of nodes based upon a plurality of network messages passed therebetween. A global time reference is adaptively established for the timestamps responsive to the pairwise clock error. A plurality of mapping factors are defined each for translating from one local time reference to the global time reference. The mapping factors are selectively applied to corresponding ones of the timestamps.

The invention discloses a clock synchronization method in a transmission network. The method comprises the steps of obtaining the arrival time t2 and the sending time t1 of first message through the interaction of a slave clock and a master clock; adopting external clock source to detect the time delay of the master clock and the salve clock; seeking clock error Offset according to the time delay between the master clock and the slave clock, t1 and t2; and adjusting the clock of the slave clock according to Offset. The invention further discloses a clock synchronization method in other two transmission networks, and also discloses a clock synchronization system of three transmission networks. The clock synchronization method of the invention can accurately calculate clock error Offset, thereby ensuring the synchronization of the slave clock and the master clock.

A communication station needs to autonomously and synchronously operate by maintaining an equal frame interval. A clock error is measured from a received packet in a wireless communication system where a beacon is transmitted periodically. This clock error is used to synchronize a counter to count the beacon's transmission / reception time and adjust a clock cycle deviation for synchronization. The synchronization is possible even in the case of restoration from a sleep state when the reference clock accuracy is poor. A period to maintain the sleep state can be extended irrespectively of the clock accuracy. It is possible to prevent desynchronization due to incorrect synchronization with an abnormal value.

The invention provides a method for determining a whole-cycle ambiguity of a three-frequency carrier phase of a BeiDou navigation system. The method comprises the steps of by utilizing the advantage of high determination accuracy rate of a whole-cycle ambiguity of a BeiDou ultra-wide lane carrier phase combination, firstly determining whole-cycle ambiguities of two groups of ultra-wide lane carrier phase combinations, and correcting a pseudo-range initial value through the whole-cycle ambiguities of the ultra-wide lane carrier phase combinations; meanwhile, removing influences from an orbit error, a clock error and an ionized layer error in original observed quantity by combining with carrier phase observation quantity of geometry-free de-ionized layer composed of a narrow lane carrier phase combination, so as to enable the resolution of the whole-cycle ambiguity of the narrow lane carrier phase combination to be only affected by random measurement noise; taking an average value of combined observation quantity of multiple epochs to remove random noise error and determine the whole-cycle ambiguity of the narrow lane carrier phase combination; finally, determining the whole-cycle ambiguity of the carrier phases of three frequencies B1, B2 and B3 by resolving a system of linear equations which is composed of the whole-cycle ambiguities of the two ultra-wide lane carrier phase combinations and the whole-cycle ambiguity of the narrow lane carrier phase combination.

Methods and apparatus are provided for processing a set of GNSS signal data derived from observations of GNSS signals of multiple transmitters over multiple epochs, the GNSS signals having a first signal and a second signal in a first band which can be tracked as a single wide-band signal and each of which can be tracked separately, comprising: obtaining carrier-phase observations of the first signal, obtaining carrier-phase observations of the second signal, obtaining code observations of the wide-band signal, and estimating from a set of observables comprising the carrier-phase observations of the first signal, the carrier-phase observations of the second signal and the code observations of the wide-band signal values for a set of parameters comprising: position of a receiver of the GNSS signals, clock error of a receiver of the GNSS signals, and an array of ambiguities comprising an ambiguity for each transmitter from which carrier-phase observations of the first signal are obtained and an ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained.

The invention relates to a precise orbit determination method of a navigation satellite for assisting a clock error between stations, which is characterized by comprising the following steps: configuring an atomic clock and a nanosecond stage time synchronization system at each station of an area network, receiving a distance measurement signal of a navigation satellite by each station of the area network to obtain the carrier phase data of each station, detecting the periodic trip generation moment of the carrier phase data by a Blewitt method and carrying out time synchronization between the stations by a two-way satellite time frequency transmission method TWSTFT to obtain a clock error between the stations; resolving a differential equation under an inertial coordinate system to obtain an orbit of the navigation satellite. Before orbit determination data are processed, the method firstly realizes the time synchronization between the stations with high accuracy (i.e.: obtaining the clock error between the stations). During the processing of the orbit determination data, an improved non-error method is adopted, only the orbit needs to be resolved, and the clock error between the stations does not need to be resolved, which not only can improve geometrical factors but also is beneficial to separating a system error (the clock error between the stations). Thus, the orbit determination accuracy can be enhanced.

The invention discloses a method for determining the satellite differentia pseudo-range deviation based on single-frequency navigation satellite data, and relates to a satellite differential pseudo-range deviation determination and correction technology in satellite navigation applications. The method comprises the steps of A, acquiring single-frequency GNSS original observation data and obtaining precision satellite orbit and clock error products; B, building single-frequency GNSS non-combination pseudo-range and phase observation equations; C, building a single-frequency non-combination precision single-point positioning function model; D, solving single-frequency non-combination precision single-point positioning Kalman filtering; and E, performing ionospheric delay modeling and determining the navigation satellite differential pseudo-range deviation. Determination for navigation satellite differential pseudo-range deviation parameters is realized by using a single-frequency receiver, and the hardware cost of an existing navigation satellite differential pseudo-range deviation estimation method can be reduced by more than 90%. Meanwhile, the method is reasonable and simple in design and improves the efficiency. The design is not only low in cost, but also high in efficiency.

According to an aspect, a wireless station uses a low-frequency clock during sleep intervals and a high-frequency clock during awake intervals. Drift between the low-frequency clock and the high-frequency clock are corrected to enable aligning a wake time instant of the wireless receiver with start of beacon transmissions from an access point, and thereby to reduce power wastage. According to another aspect, errors between the clock of an access point and that of a wireless station are corrected. The wireless station computes an error between the clocks, and extrapolates the error for a sleep interval to compute a wake-up time instant. The correction and extrapolation are performed in every awake interval. Again, undesired power consumption in the wireless station is thereby reduced.

The disclosure generally relates to techniques for time acquisition, synchronization and location estimation when the GPS signal condition deteriorate or when the signal is unavailable. In one embodiment, the disclosure relates to a processor for detecting clock error of a wireless location sensor (WLS) in a communication network having several wireless sensors, the processor programmed with instructions for determining clock error of an asynchronous WLS. The instructions include identifying a first WLS having asynchronous clock and a second WLS having synchronous clock; directing each of the first and the second WLS to detect a broadcast transmitted from a transmission station of known location and report an actual time of arrival at each of the first and the second WLS; computing an expected time of arrival of the broadcast at the first WLS as a function of the distance between the first WLS and the second WLS; and determining a clock error at the first WLS as a function of the expected time of arrival and the actual time of arrival of the broadcast at the first WLS.

The present invention provides a unified model-based Beidou undifferenced and uncombined PPP (precise point positioning)-RTK (real-time kinematic) positioning method. According to the method, as for users on the globe, real-time orbits and clock error corrections are received, so that undifferenced and uncombined PPP calculation is performed; initialization is performed, so that decimeter-centimeter-level precision positioning is realized; for users in regions, integrated error corrections of the regions are received, undifferenced network RTK calculation is performed; and initialization is performed, so that centimeter-level precision positioning is realized. With the method of the invention adopted, the seamless linking of undifferenced PPP data processing and undifferenced network RTK data processing can be realized, fast and high-precision positioning services can be provided, and the total electron content of an ionized layer and the differential code deviation information of a receiver can be obtained.

A long baseline satellite formation GNSS relative positioning method based on ambiguity fixing is provided in order to improve the success rate of ambiguity fixing and the accuracy of relative positioning results. According to the technical scheme, the method comprises the following steps: first, collecting and pre-processing input data, and determining the absolute general orbit of a formation satellite; then, eliminating the geometric distance and clock error in differential observation data, estimating a single-difference phase ambiguity float solution and a single-difference ionosphere delay parameter, carrying out double-difference transform to get a double-difference wide-lane ambiguity float solution and a covariance matrix, and fixing the double-difference wide-lane integer ambiguity and the double-difference narrow-lane integer ambiguity; and finally, outputting the relative positioning result of ambiguity fixing. By adopting the method of the invention, the problem that ambiguity fixing strongly depends on a pseudo code with low observation precision due to equally-weighted pseudo code and phase processing in M-W combination in the traditional method is avoided, the success rate of long baseline satellite formation GNSS relative positioning ambiguity fixing and the accuracy of final relative positioning results are improved, calculation is stable, and the reliability of relative positioning results is improved.

A communication station needs to autonomously and synchronously operate by maintaining an equal frame interval. A clock error is measured from a received packet in a wireless communication system where a beacon is transmitted periodically. This clock error is used to synchronize a counter to count the beacon's transmission / reception time and adjust a clock cycle deviation for synchronization. The synchronization is possible even in the case of restoration from a sleep state when the reference clock accuracy is poor. A period to maintain the sleep state can be extended irrespectively of the clock accuracy. It is possible to prevent desynchronization due to incorrect synchronization with an abnormal value.

The invention discloses an area enhanced precision positioning service method suitable for large-scale users. According to the technical scheme, the method includes the steps that after the users effectively fix wide-lane ambiguity and L1 ambiguity of at least four satellites in a zero difference network RTK processing mode, area enhanced information of surrounding base stations does not need to be acquired, at this moment ambiguity fixed results and zenith troposphere delay residual errors acquired by interpolation are used as known truth values, received satellite UPD information is combined, and an ambiguity fixed solution in a PP-RTK mode can be immediately acquired without initialization. Due to the fact that satellite UPD, real-time satellite orbits and real-time satellite clock errors are only related to the satellites, and short-term forecast lasting tens of seconds to a few minutes can be conducted, the information can be broadcasted to the users through the communication satellites in a broadcast mode, and then real-time data communication burdens among the users and the base stations can be greatly reduced. Once user ambiguity is firstly fixed, the number of the users simultaneously serviced by an area enhanced system is no longer restricted at this moment.

The invention relates to a self-capacitance change measuring circuit with high precision and high stability. A filter capacitor in a system discharges through a switch circuit of a measured capacitor and is charged through a switch circuit of a coupling capacitor so as to change the voltage of the filter capacitor at the vicinity of a reference voltage. As discharging current generated by the switch circuits of different measured capacitors is different, the time that the voltage of the filter capacitor is lower than the reference voltage and the time that the voltage of the filter capacitor is higher than the reference voltage change; and the change of the measured capacitor can be measured by measuring the time change or the change of a ratio of the time. By an error elimination method, the voltage fluctuation and the metering clock error do not influence the measuring result; and the entire measuring result is only related to the error of the coupling capacitor. As the coupling capacitor built in a chip has high stability and high precision, the measurement method has excellent measuring precision and stability.

The invention provides a GNSS / MINS (global navigation satellite system / micro-electro-mechanical systems inertial navigation system) super-deep combination navigation method, aiming to realize super-deep combination of a GNSS and an MINS. The GNSS uses a direct location estimation method to estimate location errors, speed error and clock errors according to location and speed auxiliary information provided by an INS (inertial navigation system) to close loops; a system takes an MIMU (MINS inertial measurement unit) and a base band correlator as sensors to realize all the navigation functions in a top combinational algorithm, in other words, the algorithm takes the GNSS base band correlator as the sensor of sensitive space-time locating fields and takes the MIMU as the sensor of sensitive inertance fields to realize integral combination of the GNSS and the MINS; and by the aid of the INS, the GNSS combines multichannel information to perform vector phase discrimination and vector locating. The invention further provides super-deep combination system and device applied to the method. The method, the system and the device have the advantages of high navigation accuracy, good dynamic property, high GNSS tracking sensitivity, high GNSS anti-interference performance, wide GNSS dynamic pulling range and the like; and in theory, the dynamic range is limited by trends of the MINS, and -160dBM (decibels above one milliwatt in 600 ohms) signal tracking can be realized by the GNSS by the aid of the MINS.

The invention discloses a high-precision relative distance measurement and time synchronization method based on an inter-satellite link, aiming to provide a distance measurement and time synchronization with high measurement accuracy. The present invention is realized through the following technical solutions: the inter-satellite link is established based on the respective satellite carrier frequency standards of two satellites A and B respectively, and the speed measurement information and clock error are incorporated into the dynamic error model; In the receiving time slot, capture, track, and demodulate the received signal of the other party, recover the information frame, and calculate the local pseudorange when the epoch is sent in conjunction with the other party's measurement time slot; finally, the A star and the B star will respectively correct The subsequent pseudorange is embedded in the local baseband data and sent to the other party. The two satellites independently use the locally measured corrected pseudorange and the other party’s corrected pseudorange demodulated from the received information frame to obtain the inter-satellite relative distance value and time difference, adjust the clocks of the two satellites, and correct the satellite ephemeris and clock parameters.

The invention provides a high precision single point positioning system of a single frequency global positioning system (GPS) and a method, which belong to the technical field of GPS positioning. The positioning system is provided with a single frequency GPS receiver which finishes the processing of a GPS baseband signal, tracing of a GPS signal and pressure-volume-temperature (PVT) resolving and provides required GPS observation data and various error correcting information for a precision single point positioning solving module. The receiving of various correction data and loading of information of international GPS service (IGS) precise ephemeris, clock error, ionospheric delay and the like are finished by wireless communication module general packet radio service (GPRS) through wireless networks. The wireless communication module GPRS performs ionospheric delay error correction, satellite clock error correction and satellite track error correction, and utilizes IGS network data to finish precision single point positioning processing. An ARM core plate receives various observation data, satellite-based augmentation system (SBAS) observation data and various correction data of the wireless communication module and performs automatic processing computing of precision single point positioning algorithm. The single frequency GPS high precision single point positioning system and the method have the advantages of being simple in data collection and high in precision, and the feasibility and flexibility of the precision positioning are improved.

The invention provides a real-time precision single-point positioning based satellite navigation device and method. A satellite navigation receiver receives satellite signals, performs down-conversionand sends into an intermediate-frequency signal preprocessing unit to complete A / D conversion, and the digital intermediate-frequency signals subjected to interference suppression are sent into a baseband signal processing unit for signal capturing and tracking to complete original observation data extraction and original navigation message demodulation. A master control unit comprehensively processes original observation data and navigation messages to obtain observation data and broadcast ephemeris through analysis; in addition, IGS center satellite orbit parameters and satellite clock errors are acquired in real time through the network, performing data preprocessing, space-time datum unifying and positioning model establishment, adopting a Kalman filter method for real-time precisionpositioning, storing a positioning result, and transmitting to a display control unit to display. The device and the method have advantages that cost saving is realized, operating efficiency can be improved, distance restraining is avoided, and independent completeness and precision of a positioning system can be remarkably improved.

The invention relates to the field of related clock error compensation technology, and in particular relates to a clock-temperature-error compensation method and a system thereof. The clock-temperature-error compensation method comprises the following steps of: measuring the temperature at initial time, obtaining and storing a first temperature value, and storing the first temperature value; after measuring time T, measuring the temperature again and obtaining a second temperature value; adopting the first temperature value or the second temperature value as the measuring temperature, and according to the relation between the measuring temperature and the clock crystal-oscillator error, calculating and obtaining an error value of a clock; calculating a clock error of the measuring time T; repeatedly executing the steps from step 2 to step 4, till the clock error accumulated value is larger than a preset clock adjusting threshold, adding the value same as the clock adjusting threshold for the clock, and executing the steps from step 2 to step 4 again. The clock-temperature-error compensation method has the advantages that the clock compensation can be realized only by using the common circuit and algorithm without needing to use GPS or a function clock chip with expensive price and adjustable oscillating circuit frequency, so that the production cost is greatly reduced.

The invention discloses a high-frequency clock error estimation method of a satellite navigation system. The method includes acquiring observed data of a tracking station; testing the reliability of the observed data; rejecting outliers from the observed data after reliability test by using linear combination of the observation quantity, determining an initial ambiguity, detecting and repairing the cycle slip, and obtaining codes and phase observed values; acquiring a satellite obit parameter, an earth polar motion parameter, a troposphere parameter and a station coordinate parameter; obtaining clock error estimated values of a satellite and a receiver according to original observed data, the satellite obit parameter, the earth polar motion parameter, the troposphere parameter and the station coordinate parameter; and interpolating the obtained clock error estimation by using the code and the phase observed value to obtain the high-frequency clock error estimation of the satellite navigation system. The method has the advantages of high reliability and accuracy and capability of improving the high-frequency clock error estimation accuracy of the satellite navigation system.

The invention provides a navigation satellite autonomous time synchronization method based on synthetic aperture observation. The method comprises the following steps: all the cooperative observation satellites and a reference satellite perform timing observation on the same millisecond pulsar at the same time; the reference satellite completes time delay correction between each cooperative observation satellite and the reference satellite by the relative position measurement data between satellites at different times, and stacks each group of observation data completing the time delay correction to obtain the observation waveform of a synthetic aperture timing observation system; the clock error of an onboard clock of the reference satellite is measured; and the clock error between each satellite of a navigation constellation and a standard time TCB is measured and the clock error correction value is broadcast in the broadcast ephemeris of each satellite so as to complete the autonomous time synchronization of the navigation satellite. The method achieves the technical effects of reducing the X-ray detector load of the navigation satellite, shortening the observation time, and improving the autonomous time synchronization precision and real-time property of the navigation satellite.

The invention provides a GNSS data signal quality monitor method. The GNSS data signal quality monitor method includes the steps that every observation station receives original satellite data and transmits the original satellite data to a data processing center via a communication network; the data processing center calculates the satellite clock error of n satellite clocks and other (m-1) receiver clocks relative to a reference receiver clock; the maximum error point of a satellite is calculated within the visible range of the satellite; the signal error of the maximum error point position is analyzed according to the satellite clock error, and then the GNSS data signal quality is monitored. According to the GNSS data signal quality monitor method, when the GNSS data signal quality is monitored, the satellite clock error accuracy, space signal forecast accuracy and space data signal quality monitor accuracy are monitored in real time, and as the accuracy is compared with a threshold value and is monitored and issued in real time, the GNSS data signal quality can be monitored in real time.

The invention relates to a satellite clock error real-time prediction method based on a phase jump. The satellite clock error real-time prediction method comprises steps of: acquiring an original satellite clock error data sequence, preprocessing the original satellite clock error data sequence, performing polynomial fitting on a processed satellite clock error phase sequence, removing a periodicterm of the phase sequence, and calculating fitting precision; and predicting a satellite clock error and ending the operations if the fitting precision is less than a threshold value, detecting a frequency abnormal values from back to front if the fitting precision is greater than the threshold value to obtain a plurality of pieces of front and back data, predicting a satellite clock error and ending the operations if no anomaly occurs in frequency and the data is stable, and predicting a satellite clock error and ending the operations by adopting clock error data after the jump if the frequency is abnormal and / or the jump exists in the data. The satellite clock error real-time prediction method fully considers the frequency stability and frequency drift features of an atomic clock, performs order selection on GPS, GLONASS, BDS and Galileo, is applied to real-time clock error prediction of a satellite-based augmentation system, is stable and reliable in clock error prediction, improves clock difference error precision in SSR correction information, and improves the precision of the terminal positioning service.

In an OFDM receiver with a diversity configuration having a plurality of demodulation modules, to perform FFT window position recovery and clock recovery, the gain values calculated by the AGC units (16, 26) provided in the demodulation modules for adjusting the level of the received signal are supplied to a correlation combiner (35); the correlation combiner (35) multiplies the correlation signals supplied from the correlation detectors (17, 27) in the demodulation modules by coefficients calculated from the gain values, then adds the products to generate a combined correlation signal and supplies it to an FFT window position recovery unit (32) and a clock error detector (33). FFT window position recovery and clock recovery can thus be performed properly without depending on any one demodulation module.

A linear regression equation is comprised of the objective variables and the explanatory variables. The objective variables are comprised of the L1 carrier phases, the L2 carrier phases, the C / A code pseudorange, the P(Y) code pseudorange, the clock error data, the delay data of the ionosphere, and the delay data of the troposphere that related with every satellite respectively. The explanatory variables are comprised of at least the integer ambiguity and a receiver's position.The receiver's position has been linear-approximated by using the estimation results of the passed receiver's positions. Applying a least square method to the regression equation, the integer ambiguity and the receiver's position is estimated.

The invention provides a GNSS multimode single-frequency RTK cycle slip detection method and apparatus. The method comprises the following steps: communicating with a GPS satellite, a GLONASS satellite, a Galileo satellite and a Beidou satellite and obtaining corresponding data; according to a formula, carrying out calculation so as to obtain a residual error vector of a station epoch secondary difference carrier wave observation value of each satellite; according to the residual error vector, calculating an RMS value, and if the RMS value is greater than or equal to a threshold EPS, determining that a satellite generates a cycle slip; according to a formula (2), calculating a standard residual error V<->; comparing |error V<->| with u<alpha / 2>, and carrying out corresponding operation; and fusing the determined cycle slip with a cycle slip detected by use of a Doppler integration method. The invention brings forward a novel method for detecting a cycle slip by combining a multimode station epoch secondary difference method and a Doppler integration method. The multimode station epoch secondary difference method detecting the cycle slip based on a residual error domain only sets one station epoch relative clock error parameter, such that even if a single system has only one satellite, effective utilization and cycle slip detection can still be realized.