Abstract: A road usage charge system tracks and reports the distance travelled by a vehicle. The accuracy of the distance driven versus competing considerations such as battery drain of the mobile device doing the reporting is augmented by defining a speed threshold. When the vehicle is travelling faster than the speed threshold, location sampling is performed less frequently, over larger distance intervals. However, when the vehicle is travelling at a speed less than the speed threshold, the location sampling rate is increased such that location sampling is performed at shorter distance intervals.

Abstract: A jamming signal detection control method includes: receiving, at a satellite positioning signal receiver, one or more satellite positioning signals; determining, at the satellite positioning signal receiver, one or more quality metric values based on the one or more satellite positioning signals; determining, at the satellite positioning signal receiver, whether the one or more quality metric values are indicative of jamming; and activating, at the satellite positioning signal receiver and in response to the one or more quality metric values being indicative of jamming, a jammer detection technique to determine whether a jamming signal is received by the satellite positioning signal receiver.

Abstract: An example device for filtering decoded video data includes a memory configured to store video data; and one or more processors implemented in circuitry and configured to: decode a block of video data to form a decoded block; apply a filter to the decoded block to form a filtered block; multiply samples of the filtered block by a scaling factor to form a refined filtered block; and combine samples of the refined filtered block with corresponding samples of the decoded block. The one or more processors may further encode the block prior to decoding the block. The one or more processors may encode or decode a value of a syntax element representing the scaling factor, e.g., in a picture header of a picture including the block.

Abstract: A precise point position and real-time kinematic (PPP-RTK) positioning method, including: when direct emission signals broadcast by a multi-system navigation satellite and a low-earth-orbit constellation are detected, determining raw observation data (S11); receiving navigation satellite augmentation information broadcast by the low-earth-orbit constellation, and a low-earth-orbit satellite precise orbit and precise clock difference (S12); using the navigation satellite augmentation information, the low-earth-orbit satellite precise orbit and precise clock difference and the raw observation data for precise point positioning (S13); or when comprehensive ground-based augmentation error correction information is received, using the navigation satellite augmentation information, the low-earth-orbit satellite precise orbit and precise clock difference, the raw observation data and the comprehensive ground-based augmentation error correction information for precise point positioning of ground-based augmentation (S

Abstract: A wireless receiver receives location pilots embedded in received symbols and uses the location pilots to detect the first path for every base station the network has designated for the receiver to use in time of arrival estimation. The receiver preferably applies matching pursuit strategies to offer a robust and reliable identification of a channel impulse response's first path. The receiver may also receive and use estimation pilots as a supplement to the location pilot information in determining time of arrival. The receiver can use metrics characteristic of the channel to improve the robustness and reliability of the identification of a CIR's first path. With the first path identified, the receiver measures the time of arrival for signals from that path and the receiver determines the observed time difference of arrival (OTDOA) to respond to network requests for OTDOA and position determination measurements.

Abstract: A first positioning portion, a calculator, and a second positioning portion are provided in an electronic device targeted for positioning. The first positioning portion obtains, by Doppler positioning, a candidate position which is a candidate for an initial position of the electronic device in code phase positioning from radio waves received from each of GPS satellites. The calculator calculates an index value indicating the magnitude of variation in code phase from a difference between a code phase obtained from the radio waves received from each of the GPS satellites and a code phase obtained based on a candidate position and a position of each GPS satellite. The second positioning portion performs the code phase positioning using ZCount or a candidate position according to the index value.

Abstract: The disclosed technology for preparing digital samples for synthesis of RF to simulate channels and GNSS satellites using GPUs includes receiving simulated position and velocity of an antenna, dividing the cycle into points to be converted into the synthesized signal, and computing the points. A first LUT includes pseudo random sequences combinable to produce a code that varies over time for encoding the channel, and a second LUT specifies linear combinations of the pseudo random sequences in the first LUT that produce channel codes to produce the digital sample points. Also included is using GPUs to generate the channel code for a point by mapping the channel code and time position, combining the code with data to be encoded, repeatedly applying the using and combining to produce points, using multiple GPU cores to encode sample points concurrently in the cycle, and sending an ordered sequence of points to a converter.

Abstract: A system for tracking a state of a GNSS receiver uses a subset of the measurements of satellite signals selected to minimize a loss of information with respect to the set of measurements available to the GNSS receiver. The system uses a probabilistic state estimator that tracks the state of the GNSS receiver using a probabilistic motion model subject to noise and a probabilistic measurement model relating the selected subset of the measurements of satellite signals to the current state of the receiver.

Abstract: The discriminability of an RF fingerprint is increased by “abstracting,” “enhancing,” and “reconstructing” a digital signal before it is transmitted, where the abstraction is a reversible nonlinear compression, the enhancement is a modification of the abstracted data, and the reconstruction is a mapping-back of the abstraction. During a training phase, for each individual RF transmitter, RF fingerprints are analyzed and candidate enhancements are modified until a successful enhancement is identified that provides satisfactory discriminability improvement with minimal signal degradation. The successful enhancement is implemented in the RF transmitter, and the RF fingerprint is communicated to receivers for subsequent detection and verification. Reinforcement learning can direct modifications to the candidate enhancements. The abstraction can implement a deep generative model such as an auto-encoder.

Abstract: An illustrated embodiment disclosed herein is a method including receiving, by a gateway, a first physical data unit (PDU) of a plurality of PDUs from an endpoint via a first satellite, receiving, by the gateway, a second PDU of the plurality of PDUs from the endpoint via a second satellite, and decoding, by the gateway, a payload from the first PDU and the second PDU.

Abstract: Techniques and a system are provided for generating correlations based on inferred behavior by an inferred event detection system executing on a mobile computing device. Inferred events are events that are detected without an explicit input to the mobile computing device. The inferred events are further classified by the inferred event detection system.

Abstract: A global navigation satellite system (GNSS) receiver including a sequential chip mixed frequency correlator array system (SCMFCAS) is provided. The SCMFCAS includes P signal generators, each receiving N samples of intermediate frequency (IF) data of a GNSS signal. Each signal generator includes a primary mixer, a pseudo random noise code generator, and Q mixed frequency correlators (MFCs). Each MFC generates accumulated correlation components of the N samples of the IF data by processing the N samples of the IF data. Adders and subtractors operably connected to the SCMFCAS are time division multiplexed for generating correlation values of a positive frequency and a negative frequency of the N samples of the IF data by combining the accumulated correlation components. Time division multiplexing the adders and the subtractors across the SCMFCAS and generation of the correlation values reduce logic area of the SCMFCAS, thereby reducing power consumption of the GNSS receiver.

Abstract: A portable electronic device includes a processor configured to determine a first scan interval, and a transceiver configured to receive a first beacon signal using the first scan interval as an interval. The processor is further configured to obtain a first positioning result according to received signal strength of beacon signals received by a transceiver—in m continuous first scan intervals, and determine an average quantity of scans according to the first positioning result, the transceiver is further configured to receive a second beacon signal using an increased second scan interval as an interval when the average quantity of scans is greater than a preset value, and the processor is further configured to obtain a second positioning result according to received signal strength of beacon signals received in p continuous second scan intervals, where m and p are integers greater than one.

Abstract: Relaxation of mobile device features restrictions leveraging embedded auditing systems is presented. One or more managed applications are designated on the mobile device via a software plug-in to an application management adapter running on the mobile device, each of the one or more managed applications being associated with at least one mobile device feature that generates data related to a local environment of the mobile device. A front-end auditing component captures the data generated by the at least one mobile device feature, which transmits the data to a backend auditing component. The backend auditing component logs the data, and a notification of an event associated with the data is generated for one or more designated recipients.

Abstract: A method of predictive targeting of a directional antenna is provided. The method includes receiving a plurality of state information at a directional antenna control system from a mobile communication node, where the state information includes a position and a trajectory of the mobile communication node. The directional antenna control system logs the state information as a last known position and a last known trajectory of the mobile communication node. An estimated future position of the mobile communication node is determined based on the last known position, the last known trajectory, and a time period. Based on a loss of communication between the directional antenna and the mobile communication node, the directional antenna control system positions the directional antenna to establish a line-of-sight between the directional antenna and the estimated future position of the mobile communication node.

Abstract: Systems and methods to transition between viewpoints in a three-dimensional environment are provided. One example method includes obtaining data indicative of an origin position and a destination position of a virtual camera. The method includes determining a distance between the origin position and the destination position of the virtual camera. The method includes determining a peak visible distance based at least in part on the distance between the origin position and the destination position of the virtual camera. The method includes identifying a peak position at which the viewpoint of the virtual camera corresponds to the peak visible distance. The method includes determining a parabolic camera trajectory that traverses the origin position, the peak position, and the destination position. The method includes transitioning the virtual camera from the origin position to the destination position along the parabolic camera trajectory.

Abstract: This acquisition method is provided for acquiring a satellite signal emitted by a radio navigation satellite, the satellite signal containing a cyclic pseudo-random identification code specific to the satellite. The acquisition method includes the generation of a local code producing a replica of the identification code, and the production of a combined correlation (EDDC) of a received signal with the local code, the combined correlation corresponding to the linear combination of a first double delta correlation and of a second narrow correlation.

Abstract: A system mounted to an object for detecting repetitive motion of the object. The system includes a GPS receiver for receiving GPS signals while being maneuvered in a repetitive motion by the object, and a processor for detecting repetitive phase shifts in the received GPS signals. In general, the system computes the repetitive motion of the GPS receiver based on the repetitive phase shifts.

Abstract: A GNSS receiver includes at least one buffer and at least one correlator block. The at least one buffer stores a plurality of samples corresponding to a received signal. The at least one correlator block includes a Doppler derotation block configured to perform Doppler derotation corresponding to at least one Doppler frequency on the plurality of samples, a register array configured to be loaded with the plurality of samples on Doppler derotation corresponding to a Doppler frequency of the at least one Doppler frequency, and a correlator engine configured to generate correlation results by correlating the plurality of samples in the register array with a plurality of code phases for at least one GNSS satellite. A presence of at least one GNSS satellite signal may be detected based on coherent accumulation and a non-coherent accumulation of the correlation results.

Abstract: A satellite positioning subsystem includes a frequency converter that applies a downshift in frequency to a received signal that should contain a satellite signal that has been spread and modulated on a carrier signal. A non-crystal oscillator produces an output signal whose frequency acts as a controlling reference for the frequency converter. A crystal oscillator is coupled to a controller that develops a control signal for controlling the frequency of the output signal of the non-crystal oscillator. A processor intermittently corrects the crystal oscillator such that its output frequency experiences jumps. A filter filters the control signal to limit the rate of change of frequency that the control signal demands of the output signal of the non-crystal oscillator such that a phase rotation of ? cannot occur in the output signal of the non-crystal oscillator in the time that would be taken to despread a sample of the satellite signal.

Abstract: Asynchronous Global Positioning System (GPS) baseband processor architectures with a focus on minimizing power consumption. All subsystems run at their natural frequency without clocking and all signal processing is done on-the-fly.

Abstract: A navigation receiver operably coupled to an antenna can determine location by receiving and processing radiofrequency navigation signals from global navigation satellites. The navigation receiver includes a quartz crystal oscillator that serves as a reference frequency source for a local oscillator signal that is mixed with the radiofrequency navigation signals to generate intermediate signals at intermediate frequencies lower than the radiofrequencies. In particular applications, the quartz crystal oscillator and the antenna are subjected to vibration and shock. A shift in the frequency or phase of the intermediate signals can result, and performance of phase-lock loops can degrade. Performance is improved with a phase-lock loop that processes a combination of individual channel control signals and common control signals.

Abstract: A pseudo range is corrected with high accuracy using a pseudo range correction method that incorporates carrier smoothing. A code pseudo range correction unit (19) performs carrier smoothing of an L1 code pseudo range (PRL1(i)) by the temporal change (?ADRL1(i)) in an L1 carrier phase, and performs carrier correction of a code ionosphere delay (IPRL1(i)) by the temporal change (?IADRL1(i)) in a carrier ionosphere delay. The code pseudo range correction unit (19) performs ionosphere delay correction by subtracting the corrected ionosphere delay (I?L1sm(i)) from the L1 code pseudo range (PRL1sm(i)) after smoothing processing. At this time, a direction of the delay in the temporal change (?IADRL1(i)) in the carrier ionosphere delay included in the temporal change (?ADRL1(i)) in the L1 carrier phase is matched with a direction of the delay in the temporal change (?IADRL1(i)) in the carrier ionosphere delay used to calculate the corrected ionosphere delay (I?L1sm(i)).

Abstract: A telematics unit incorporating an antenna for receiving Global Navigation Satellite System (GNSS) signals from GNSS signal sources, and a GNSS receiver supporting over-the-air configuration is described herein. The telematics unit is configured with a processor and a non-transitory computer-readable medium including computer-executable instructions for facilitating the over-the-air configuration of the GNSS receiver by acquiring GNSS status information relating to multiple supported GNSS signal sources. Thereafter, the telematics unit forwards GNSS selection information, including at least GNSS requirements information and the GNSS status information, to a GNSS control center. In response, the GNSS receiver receives a GNSS type selection notification message from the GNSS control center. The GNSS receiver applies information contained within the GNSS type selection notification to configure GNSS type-specific components to operate according to a GNSS type-specific mode.

Abstract: A technique for reducing the dwell time in acquiring a satellite signal is provided. The technique minimizes the dwell time in searching for a satellite signal in cells of a search space by comparing the peak-power-to-average ratio (PAPR) to one or more thresholds at one or more intermediate points during the search in a code phase/Doppler frequency bin. The comparison is then used to determine whether to continue the search in a current code phase/Doppler frequency bin or to continue to the next code phase/Doppler frequency bin.

Abstract: Satellite positioning system (SATPS) receiver that has a plurality of modes and channels, where a timeline module configures the channels based on the mode of operation of the SATPS receiver and reconfigures the channels if the mode of operation of the SATPS changes.

Abstract: To realize a GNSS receiver that can perform further optimal correlation processing on a positioning signal phase-modulated by a CBOC signal. A correlation processing module 32 performs correlation processing between a baseband signal and a BOC(1, 1) replica code to output a BOC(1, 1) correlation data, and also performs correlation processing between the baseband signal and a BOC(6, 1) replica code to output a BOC(6, 1) correlation data. A synthesis module 33 uses a BOC(1, 1) synthesizing ratio coefficient G11 and a BOC(6, 1) synthesizing ratio coefficient G61 to synthesize the BOC(1, 1) correlation data with the BOC(6, 1) correlation data, and outputs the synthesized correlation data to a calculation module 30. The calculation module 30 detects a reception environment based on the synthesized correlation data, sets a BOC(1, 1) synthesizing ratio coefficient and a BOC(6, 1) synthesizing ratio coefficient based on the reception environment, and supplies them to the synthesis module 33.

Abstract: A Global Positioning System (GPS) commercial receiver includes programmable logic that utilizes P-code modulated L1 and L2 GPS signals to derive estimates of in-phase and quadrature-phase components of both L1 and L2 signals, a programmable processor that calculates pseudoranges and pseudo-Doppler phases, and derives navigation solutions. A resulting complex accumulated L2 signal comprises near-ML estimates of desired L2 amplitude and pseudo-Doppler phase.

Abstract: A GPS receiver for tracking a GPS signal. The receiver generates a mixed GPS signal by mixing the GPS signal with an oscillator signal, generates a first correlation signal by correlating the mixed GPS signal with a reference signal, and generates a filtered GPS signal from the GPS signal. The receiver also generates a filtered reference signal from the reference signal, generates a second correlation signal by correlating the filtered GPS signal with the filtered reference signal, and a generates a combined correlation signal by combining the first correlation signal with the second correlation signal. The receiver tracks the GPS signal by adjusting the phase of the oscillator signal based on the combined correlation signal.

Abstract: The effects of shock and vibration on a navigation receiver processing satellite signals received from global navigation satellites are reduced by controlling the frequency and the phase of the individual numerically controlled oscillator in each individual satellite channel. The frequency is controlled by an individual frequency control signal based on individual correlation signals generated in an individual satellite channel. The phase is controlled by a common phase control signal or a combination of a common phase control signal and an individual phase control signal. The common phase control signal is based on all the correlation signals generated in all the satellite channels processed by a separate common broadband quartz loop (SCBQL). An individual phase control signal is based on the individual correlation signals generated in an individual satellite channel.

Abstract: A global navigation satellite system (GNSS) receiver may be operable to quantize two-dimensional GNSS sample data with an in-phase (I) and quadrature (Q) pair to two-dimensional quantized data with a magnitude and angle pair using the polar quantization, for example, an unrestricted polar quantization. The GNSS receiver may be operable to reduce a size of the two-dimensional quantized data for storage by representing the two-dimensional quantized data by the one-dimensional symbol data. The one-dimensional symbol data may be stored in a random access memory (RAM) for further processing. The I and Q pair associated with the one-dimensional symbol data stored in the RAM may be retrieved and processed by the GNSS receiver using a correlation such as a fast Fourier transform (FFT) correlation.

Abstract: A GNSS receiver includes a RF front end for receiving GNSS ranging signals, a navigation processor for calculating location from the ranging signals, and a repository of static data. The navigation processor includes the static data in the location calculation. Examples of static data include a digital elevation map, coordinates of tunnel entrances for use when the receiver resumes reception of the signals upon exiting a tunnel, and descriptions of structures in sufficient detail to enable multipath mitigation.

Abstract: A positioning apparatus calculates an offset frequency of a local oscillator based on position information which is positioned, satellite position information acquired from a satellite signal of a GPS satellite, and a velocity vector of a GPS satellite. A GLONASS function is operated based on the offset frequency; then, positioning is carried out by the GPS function and the GLONASS function.

Abstract: A receiver for receiving both GPS signals and GLONASS signals is provided. This receiver includes an analog front end (AFE), a GPS digital front end (DFE) and a GLONASS DFE for receiving an output of the AFE, and a dual mode interface (DMI) for receiving outputs of the GPS and GLONASS DFEs. Search engines are provided for receiving outputs of the DMI. Notably, certain front-end components of the AFE are configured to process both the GPS signals and the GLONASS signals.

Abstract: A GNSS navigation system and navigation method for determining user position, user velocity, and improved uncertainty metrics for position and velocity. A measurement engine in an applications processor of the system determines pseudorange and delta range values over each time period for each received satellite signal, and also determines measurement noise variances for both pseudorange and delta range for the individual signals. The satellite-specific pseudorange and delta range measurement variances are used to determine the position and velocity uncertainties by a position engine, either by way of a least-squares linearization or by way of an enhanced Kalman filter. The uncertainties may be communicated to the system user, or used in generating an integrated position and velocity result from both the GNSS navigation function and an inertial navigation system result.

Abstract: An electronic circuit for a satellite receiver. The electronic circuit includes a correlator circuit operable to supply a data signal including ephemeris data and a subsequent satellite time datum, and a data processor operable to infer satellite time TS from as few as one of the ephemeris data prior to the satellite time datum. Other circuits, devices, receivers, systems, processes of operation and processes of manufacture are also disclosed.

Abstract: A radio communications device comprising location finding means for determining the device's location based on satellite signals, a crystal oscillator whose output frequency acts as a controlling reference for the location finding means and processing means for intermittently correcting the crystal oscillator such that the output frequency experiences jumps. The location finding means is arranged to take account of the jumps in the determination of the device's location.

Abstract: Methods and apparatuses are provided that may be implemented various electronic devices to affect application of a filtering model used for obtaining a navigation solution. In particular, signal characteristics of one or more received signals are used for selecting application of a particular filtering model from a plurality of filtering models.

Abstract: A GNSS platform architecture with advanced tracking and search engines. The tracking and search functions are separated into 2 independent engines each highly optimized for their targeted functions.

Abstract: In a hot start mode of a navigation device, the process of obtaining pseudo-range measurements can be synchronized with the processes of tracking navigation satellites and initializing a positioning unit to compute a position, velocity, and time (PVT) solution of the navigation device. This can influence a time instant at which the pseudo-range measurements are determined and a time to first fix, depending on whether the navigation device is in a strong or weak signal environment. A measurement unit can receive a first indication that a predetermined number of navigation satellites have been acquired and that navigation signals transmitted by the acquired navigation satellites have been locked. The measurement unit can receive a second indication that the positioning unit has been initialized to compute the PVT solution. In response to receiving both indications, the measurement unit can obtain the pseudo-range measurements. Accordingly, the positioning unit can compute the PVT solution.

Abstract: A satellite navigation receiver receives a combination of radio frequency signals from satellites in satellite navigation systems and process the radio frequency signals to calculate an approximate current location of the satellite navigation receiver. Satellite acquisition plays an important part in identifying the current location of the satellite navigation receiver. Acquisition involves identifying the satellites in the satellite navigation that can be used to provide navigation information. Fast Fourier transform based acquisition involves using FFT and subsequently inverse FFT (IFFT) to correlate a coarse acquisition (C/A) code transmitted by a satellite with a C/A code locally generated on the GPS receiver to identify and acquire a transmitting satellite.

Abstract: A GPS receiver for tracking a GPS signal. The receiver generates a mixed GPS signal by mixing the GPS signal with an oscillator signal, generates a first correlation signal by correlating the mixed GPS signal with a reference signal, and generates a filtered GPS signal from the GPS signal. The receiver also generates a filtered reference signal from the reference signal, generates a second correlation signal by correlating the filtered GPS signal with the filtered reference signal, and a generates a combined correlation signal by combining the first correlation signal with the second correlation signal. The receiver tracks the GPS signal by adjusting the phase of the oscillator signal based on the combined correlation signal.

Abstract: An arrangement of M signal generators in a global navigation satellite signal baseband chip for obtaining a sequential chip correlation array is provided. The sequential chip correlation array generates M×N code bit sequences, M in-phase and M quadrature-phase carrier mixed signals. The M signal generators are arranged consecutively. A programmable parameter is created for providing a spacing of TC between each N code bit sequences. A first carrier and code generator is provided within each signal generator for generating an in-phase and a quadrature-phase component of a first carrier signal, and N code bit sequences. The first carrier and code generators within adjacently arranged signal generators are programmed with same code chip offset, different carrier signal frequency, different code frequency, and different code phase offset. M in-phase and M quadrature-phase carrier mixed signals, and N code bit sequences are generated by the M signal generators based on the programmable parameter.

Abstract: Radiolocalization receiver with a massively parallel array of correlators, comprising a data compression module (199) to compress the incoherent integration values accumulated into the incoherent integration memories (176). By compressing incoherent integration values, relevant memory saving can be obtained or, in alternative, loss of data by excessive prescaling can be avoided or attenuated. The invention proposes a simple compression scheme based on offset subtraction which allows save memory size.

Abstract: An acquisition unit of a GNSS receiver base band circuit includes an integrator with a number of preprocessors where an incoming digital signal is mixed with different frequency signals to compensate at least in part for clock drift and Doppler shifts. The resulting digital signals are, after an accumulation step reducing sample frequency, integrated over an integration period extending over several basic intervals of the length of a basic sequence characteristic for a GNSS satellite, so that samples separated by a multiple of the basic interval are superposed. The resulting data sequence of 1,023 digital values is stored in one of two memories and then, in mixers, sequentially shifted by post-integration frequencies which are multiples of the inverse of the length of the basic interval. The pre-integration frequencies employed in the preprocessors deviate, with one possible exception, from the post-integration frequencies and are usually smaller.

Abstract: We describe a device that is able to compute its range and time offset relative to another similar device, and thereby also a three-dimensional position, speed and time relative to other similar devices provided that at least four are present and within range. It does so by transmitting at least two signals at different frequencies and by receiving similar signals transmitted by the other devices. The signals are constructed so that they are independent of the radio band used and so that they lead to cancellation of common-mode effects in the transmitter and receiver circuits. No fixed infrastructure of transmitters, receivers or local measurement units is required and the devices do not need to be synchronized. The system scales to very large networks of devices in which they work collectively each solving a part of the problem that describes the relative positions of all interconnected devices.

Abstract: The present invention relates to navigation data bit synchronization for a GNSS receiver and more specifically to a software-based GNSS receiver that is operable to rapidly achieve accurate navigation data bit synchronization. It provides a system, method and computer program for navigation data bit synchronization for a GNSS receiver. The system comprises a navigation bit synchronization engine operable to detect one or more indicators in one or more data samples received from a GNSS satellite. The location of the navigation bit is derivable from the one or more indicators. The bit synchronization engine may include one or more of (i) a coarse search utility, (ii) a regular search utility, (iii) a fine search utility and (iv) a bit-edge prediction utility.

Abstract: A system and method capable of mitigating the migration from the current GPS system to the Galileo system and allow a single satellite system positioning receiver to process both GPS signals and Galileo signals.

Abstract: A method of processing received satellite radio signals is disclosed in which signals are received the signals from plural satellites through a common antenna. The received signals are digitised to produce a time-series of digitised signal samples and a plurality of replicas representing the signals of each of the plurality of satellites are obtained. At least one sample is selected from each of the replicas and the elements of a register are set equal to the selected replica samples. Thereafter, in turn, for each one of said digitised signal samples, the value of the digitised signal sample is combined with each of the values of the elements of the register to produce corresponding modified values; and the modified values corresponding to each of said register elements are accumulated.

Abstract: A system that provides GPS-based navigation/orbit determination capabilities for high-altitude spacecraft. The system uses an existing spacecraft processor and an easy-to-space-qualify minimum-hardware front end to minimize the need for new space-qualified hardware. The system also uses coherent integration to acquire and track the very weak GPS signals at high altitudes. The system also uses diurnal thermal modeling of a spacecraft clock and precision orbit propagation to enable longer coherent integration, a special Kalman filter to allow weak signal tracking by integrated operation of orbit determination and GPS signal tracking, and a segment-by-segment, post-processing, delayed-time approach to allow a low-speed spacecraft processor to provide the software GPS capability.