300 results about "Clock drift" patented technology

A system and method for estimating the range between two devices performs two or more ranging estimates with subsequent estimates performed using a clock that is offset in phase with respect to a prior estimate. The subsequent estimate allows estimate uncertainties due to a finite clock resolution to be reduced and can yield a range estimate with a higher degree of confidence. In one embodiment, these additional ranging estimates are performed at n / N (for n=1, . . . N−1, with N>1 and a positive integer) clock-period offset introduced in the device. The clock-period offset can be implemented using a number of approaches, and the effect of clock drift in the devices due to relative clock-frequency offset can also be determined. To eliminate the bias due to clock-frequency offset, a system and method to estimate the clock-frequency offset is also presented.

A system and method for providing a digital In-Flight Entertainment (IFE) system in a vehicle, such as an aircraft, that is capable of presenting a video program and associated audio in a synchronized manner to a large number of individual video monitors and speakers. The system and method employ processing operations in at least one decoder of the IFE system, to perform operations such as adjusting a local clock based on a master clock, setting a delay time in relation to a master clock, and adjusting video and audio playback based on the delay, to substantially synchronize playback of the audio and video data by the audio and video players, to thus eliminate or at least minimize the negative effects of source and load based jitter, network delays, clock drifts, network errors and decoder buffering differences, on synchronizing video and audio playback.

Position determination at a rover station on the basis of positioning signals from a plurality of positioning satellites. During normal operation a position of the rover station is determined on the basis of the positioning signal from the positioning satellites and reference data received via a separate connection from a reference station. Upon detecting an outage of the reference data from the reference station, error data at least including satellite clock drifts is obtained from error data transmitter and applied in the determination process in order to eliminate positioning errors introduced by satellite clock drifts that cannot be compensated on the basis of the reference data due to the outage.

A system and method for adaptive estimation and compensation of clock drift in echo cancellers is provided. The invention includes an acoustic echo cancellation system with a built in adaptive clock drift compensation system. The acoustic echo cancellation system has an AEC component that performs acoustic echo cancellation on data from a capture buffer, by also using information derived from a render buffer. The clock drift compensation system has access to this capture buffer and render buffer. The clock drift compensation system includes a clock drift compensator that calculates, based on the current location of the capture data being processed by the AEC component as well as additional information, the ideal location in the render buffer from which the AEC component should process data. The clock drift compensator further adjusts the current location in the render buffer from which the AEC component processes data based, at least in part, upon this ideal location. The clock drift compensator can further detect and correct for glitches in the hardware positions received from the render and capture devices.

The invention relates to technologies for industrial wireless networks, in particular to a method for precisely synchronizing time of an industrial wireless network on the basis of prediction and compensation. The method includes constructing the factory-automation-oriented industrial wireless network into a star network on the basis of an IEEE (institute of electrical and electronics engineers) 802.11 single-hop basic service set (BBS) structure; setting a master clock and slave clocks according to types and functions of nodes in the industrial wireless network; enabling a master clock side and slave clock sides to interact with one another via two-way timestamp information and computing a time deviation value of a current synchronizing cycle; predicting a time deviation value of a next synchronizing cycle by the aid of the time deviation value of the current synchronizing cycle; compensating clock drift by the aid of the predicted time deviation value of the next synchronizing cycle and correcting the clocks. The method has the advantages that the method is implemented on the premise that application requirements of factory automation are sufficiently considered, so that high time synchronization precision can be realized by the aid of few wireless communication resources, and purposes of high precision, high efficiency, low expenditure and easiness in implementation can be achieved.

A free-running secure clock in a computing device that is adjustable by a user of the device so long as cumulative adjustments do not exceed a predicted clock drift. The clock may be initially set by the user or by a trusted time authority or the like. Such a clock may be required in a trust-based system that measures a temporal requirement against the clock.

The clocks of remote computing devices are synchronized within a range of certainty through the determination of an upper bound and a lower bound around a reference time. A message from a computing device is propagated up a network tree of devices to a device having a reference time, which encodes the reference time and returns the message down the tree. Each receiving device can determine that the reference time could not have occurred before their transmission of the message, nor could it have occurred after their receipt of the return message. Cryptographic hashes can be used to guard against malicious computing devices. Alternate paths and scheduling of messages can be used to provide a narrower spread between the upper and lower bounds, and clock drift can be accounted for by increasing the spread over time.

A loop carrier system includes a home local area network having plural telephone modules and a hub coupled to in-home telephone wiring. The telephone modules and the hub communicate voice signals over the in-home wiring in a dedicated frequency band above baseband POTS. The hub converts between voice signals and voice packets and is connected to a network access device for transferring the voice packets from the home local area network to a telecommunications network which routes the voice packets to a gateway. The gateway converts between the voice packets and a circuit format compatible with a local digital voice switch. The home local area network includes a timing recovery mechanism which in the absence of a clock that is traceable to the Primary Reference Clock on the public network is robust to clock drift, cell delay variation and cell impairments.

A system and method for providing precision locations for sensors which make up an array of sensors in a gunshot detection system. In a preferred embodiment sensors employ a commercial GPS which reports a sensor position or a group of pseudoranges to GPS satellites. A server collects differential information from a differential node and, in one preferred embodiment, calculates a precision position for each sensor by adjusting the reported position or pseudoranges with the differential information. In another preferred embodiment differential information is sent from the host to individual sensors which calculate their own precision positions. Differential information may be latitude and longitude corrections, pseudorange corrections, ionospheric delay, GPS satellite clock drift, or other corrective term which will improve the accuracy of a sensor position.

The present invention permits RMS traveltime error in a seismic data acquisition to be minimized. Field measurements of source and receiver coordinates, speed of sound in water as a function of depth and time, receiver timing, and clock drift are first collected. The seismic data is then examined to measure travel time from each source to each reciever. A model travel time can then be computed based on the field measurements. By iteratively perturbing at least one of the field measured data using a look-up table and calculating the travel time after each perturbation until an acceptable RMS error has been achieved, conditioned seismic data that takes into account the dynamic nature of the water column will provide the basis for creating an accurate seismic map that is unaffected by the changing water conditions.

Disclosed is a layered time comparative clock synchronized method in the wireless sensor network, which belongs to the wireless network technology field. The method comprises the following steps: step one, the network initialization is started, and the network is layered from a basic station / a coordinator according to the signal intensity and the device category; step two, the whole network is divided into outer clock source synchronization and inner clock source synchronization, the nodes are synchronized by adopting the timestamp comparative method, and the upper-level nodes and the lower-level nodes respectively take the outer clock source synchronization and the inner clock source synchronization; step three, the synchronizing cycle and the clock drift parameter are regulated according to previous synchronization effects; step four, the old timestamp is automatically discarded. Compared with prior art, the method can better correspond with the accuracy of the wireless sensor network time synchronization method, and has the advantages of low cost and solidity.