Abstract: A systematic method for acquiring positioning signals, such as global positioning system (GPS) signals, uses different signal detection algorithms at different stages of signal detection. For example, a method for detecting multiple positioning signals may include first detecting a first positioning signal using a robust but less sensitive signal detection method, such as non-coherent integration. Based on the signal parameter values that allow detection of the first positional signal, detecting a second positioning signal using a more sensitive method, such as coherent integration. In this manner, by capturing the strongest signal first using a robust method, signal detection parameter values common to positioning signals can be narrowed to allow subsequent signal acquisitions using a more sensitive—but computationally more intensive—method.

Abstract: A multi-function device with a positioning function and a real time positioning engine is disclosed. The device contains also a shared processor used by the positioning function and other functions of the device, such as a mobile radio-communication function. The positioning engine performs in real time the most computational intensive calculations of the positioning function, such as downsampling, Doppler mixing and correlation calculations. Since the received signal need not be stored, the memory requirements of the positioning function are significantly reduced if aiding data is available.

Abstract: A multi-function device with a positioning function and a real time positioning engine is disclosed. The device contains also a shared processor used by the positioning function and other functions of the device, such as a mobile radio-communication function. The positioning engine performs in real time the most computational intensive calculations of the positioning function, such as downsampling, Doppler mixing and correlation calculations. Since the received signal need not be stored, the memory requirements of the positioning function are significantly reduced if aiding data is available.

Abstract: Techniques are provided for aiding in acquiring a signal using the data bit information that is associated with each signal source. One aspect of the invention is to use the data bit information that is associated with each signal source when calculating the In Phase and Quadrature correlation integrals by using the sampled data associated with the received signal. By using the data bit information that is associated with each signal source, coherent correlation may be performed by breaking the signal into data blocks and performing calculations on a block-by-block basis. Coherent correlation is the calculation of In Phase and Quadrature correlation integrals for sampled data that is associated with the received signal.

Abstract: A method in a Global Positioning System (GPS) receiver achieves enhanced performance by scheduling searches in the Doppler search space according to a cost function. The cost function relates to both the cost of building a 3-dimensional correlation grid and the cost of searching satellite, code phase, Doppler and integration time interval spaces for values that provide a maximum in the correlation grid. In one embodiment, after the clock Doppler is determined upon acquiring one satellite, the Doppler search range associated with a cell in the grid is dominated by the receiver's own motion. The scheduler schedules searching of the Doppler search space using search ranges determined empirically by the expected receiver velocity. In one embodiment, the scheduler increases integration times before changing Doppler search ranges, which require a recalculation of the grid.

Abstract: System and method to determine the location of a receiver are provided. The received signal is decomposed into signal chunks that are then correlated with the reference signals of the transmitting sources. In some embodiments, the signal chunks may be shorter than the period of the reference signals. For each signal source, a grid of correlation values is constructed containing one column of correlation values for each signal chunk. Each column contains correlation values for several code-phases. Probes are executed in the grid to acquire the location-determining signals. In some embodiments, a probe includes calculating the fourier transform of a row in the grid, yielding correlation values associated with a refined set of frequency values. Potential acquisitions are verified by processing increasing portions of the received signal. Confirmed acquisition may be used to aid further acquisitions.

Abstract: A systematic method for acquiring positioning signals, such as global positioning system (GPS) signals, uses different signal detection algorithms at different stages of signal detection. For example, a method for detecting multiple positioning signals may include first detecting a first positioning signal using a robust but less sensitive signal detection method, such as non-coherent integration. Based on the signal parameter values that allow detection of the first positional signal, detecting a second positioning signal using a more sensitive method, such as coherent integration. In this manner, by capturing the strongest signal first using a robust method, signal detection parameter values common to positioning signals can be narrowed to allow subsequent signal acquisitions using a more sensitive—but computationally more intensive—method.

Abstract: A method for detecting a positioning signal includes (a) correlating a segment of a received positioning signal with a reference signal of a selected code phase and frequency to obtain a correlation value, (b) if the correlation value is less than a predetermined minimum, assigning the correlation value to the predetermined minimum, and (c) accumulating the correlation value in a sum of correlation values obtained using other segments of the received positioning signal. In addition, the correlation value may be reduced by a predetermined value, which is preferably an expected mean value for a noise component in the segment of the received positioning signal.

Abstract: A multi-function device with a positioning function and a real time positioning engine is disclosed. The device contains also a shared processor used by the positioning function and other functions of the device, such as a mobile radio-communication function. The positioning engine performs in real time the most computational intensive calculations of the positioning function, such as downsampling, Doppler mixing and correlation calculations. Since the received signal need not be stored, the memory requirements of the positioning function are significantly reduced if aiding data is available.

Abstract: A method in a Global Positioning System (GPS) receiver achieves enhanced performance by scheduling searches in the Doppler search space according to a cost function. The cost function relates to both the cost of building a 3-dimensional correlation grid and the cost of searching satellite, code phase, Doppler and integration time interval spaces for values that provide a maximum in the correlation grid. In one embodiment, after the clock Doppler is determined upon acquiring one satellite, the Doppler search range associated with a cell in the grid is dominated by the receiver's own motion. The scheduler schedules searching of the Doppler search space using search ranges determined empirically by the expected receiver velocity. In one embodiment, the scheduler increases integration times before changing Doppler search ranges, which require a recalculation of the grid.

Abstract: Techniques are provided for fine-tuning estimates of a delay value for a sampled signal. One aspect of the invention is to perform, for the sampled signal, coarse-grained calculations of the In Phase and Quadrature (I and Q) correlation integrals at a limited number of points, wherein the calculations are performed over a range of hypothesized delay values. A range of delay values of interest are then determined from the coarse-grained calculations of the I and Q correlation integrals. A subset of I and Q values based on the coarse granularity calculations of the I and Q correlation functions is used to perform a time-domain interpolation to obtain fine-grained values of the I and Q integrals in the range of the delay values of interest. Magnitude calculations are performed based on the fine-grained values of the I and Q integrals. Fine-tuned estimates of delay value are based on the magnitude calculations. Alternatively, fine-tuned estimates of delay value are based on the template-matching approach.

Abstract: To determine the clock doppler of a signal receiver, sampled data received from a receiver into are divided into data segments of incremental length. The clock doppler is estimated based on correlating each data segment with the expected signal from each satellite, from a set of satellites, that is overhead the receiver. For each data segment, the correlated result of each satellite is used to refine subsequent calculations of the clock doppler of the next overhead satellite. When the clock doppler calculations for a data segment have been performed using all overhead satellites from the set of satellites, then the results for that data segment are used to refine the calculations for the next data segment.

Abstract: To determine the location of a signal receiver, sampled data received from a receiver is divided into data segments of increasing length. Current ranges for a delay value and for a modulation frequency value are calculated relative to each satellite signal source that is overhead the signal receiver. Using the data segments of increasing length, the current ranges, estimates for the delay value and for the modulation frequency value are then iteratively calculated and updated. For each signal source, I and Q correlation integrals and their magnitude values are calculated using the modulation frequency value estimate and each of a range of delay values centered around the delay value estimate. The resulting magnitude-curve is interpolated using the calculated magnitude values. The location of the receiver is calculated using the shape of the magnitude-curve to represent the I and Q correlation integrals for each signal source.

Abstract: Some embodiments of the invention provide a location-determination system that includes a number of transmitters and at least one receiver. Based on a reference signal received by the receiver, this location-determination system identifies an estimated location of the receiver within a region. In some embodiments, the system selects one or more locations within the region. For each particular selected location, the system calculates a metric value that quantifies the similarity between the received signal and the signal that the receiver could expect to receive at the particular location, in the absence or presence of interference. Based on the calculated metric value or values, the system identifies the estimated location of the receiver.

Abstract: Some embodiments of the invention provide a location-determination system that includes several transmitters and at least one receiver. Each transmitter transmits a signal that includes a unique periodically-repeating component, and the receiver receives a reference signal. Based on the received reference signal, the location-determination system identifies an estimated location of the receiver as follows. For each transmitter in a set of transmitters, the system computes a phase offset between the received reference signal and a replica of the transmitter's periodically-repeating component. The system also identifies an approximate location of the receiver and an approximate receive time for the received signal. The system then uses the identified approximate location and time, and the computed phase offsets, to compute pseudoranges for the set of transmitters. Finally, the system identifies the estimated location of the receiver by using the computed pseudoranges.

Abstract: Techniques are provided for aiding in acquiring a signal using the data bit information that is associated with each signal source. One aspect of the invention is to use the data bit information that is associated with each signal source when calculating the In Phase and Quadrature correlation integrals by using the sampled data associated with the received signal. By using the data bit information that is associated with each signal source, coherent correlation may be performed by breaking the signal into data blocks and performing calculations on a block-by-block basis. Coherent correlation is the calculation of In Phase and Quadrature correlation integrals for sampled data that is associated with the received signal.

Abstract: Some embodiments of the invention provide a location-determination system that includes a number of transmitters and at least one receiver. Based on a reference signal received by the receiver, this location-determination system identifies an estimated location of the receiver within a region. In some embodiments, the system selects one or more locations within the region. For each particular selected location, the system calculates a metric value that quantifies the similarity between the received signal and the signal that the receiver could expect to receive at the particular location, in the absence or presence of interference. Based on the calculated metric value or values, the system identifies the estimated location of the receiver.

Abstract: Some embodiments of the invention provide a location-determination system that includes several transmitters and at least one receiver. Each transmitter transmits a signal that includes a unique periodically-repeating component, and the receiver receives a reference signal. Based on the received reference signal, the location-determination system identifies an estimated location of the receiver as follows. For each transmitter in a set of transmitters, the system computes a phase offset between the received reference signal and a replica of the transmitter's periodically-repeating component. The system also identifies an approximate location of the receiver and an approximate receive time for the received signal. The system then uses the identified approximate location and time, and the computed phase offsets, to compute pseudoranges for the set of transmitters. Finally, the system identifies the estimated location of the receiver by using the computed pseudoranges.

Abstract: A method for operating a machine to perform unsupervised training of a set of character templates uses as the source of training samples an image source of character images, called glyphs, that need not be manually or automatically segmented or isolated prior to training. A recognition operation performed on the image source of character images produces a labeled glyph position data structure that includes, for each glyph in the image source, a glyph image position in the image source associating an estimated image location of the glyph in the image source with a character label paired with the glyph image position that indicates the character in the character set being trained. The labeled glyph position data and the image source are then used to determine sample image regions in the image source; each sample image region is large enough to contain at least a single glyph but need not be restricted in size to only contain a single glyph.

Abstract: A method for producing, or training, a set of character templates uses as the source of training samples an image source of character images, called glyphs, that are not previously segmented or isolated for training. Also used is a labeled glyph position data structure that includes, for each glyph in the image source, a glyph image position in the image source associating an image location of the glyph with a character label paired with the glyph image position that indicates the character in the character set being trained. The labeled glyph position data is used to identify a collection of glyph sample image regions in the image source for each character in the character set; each glyph sample image region is large enough to contain a glyph and typically contains adjacent glyphs for other characters.