Patents by Inventor Anant Sahai

Anant Sahai has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 8218766
    Abstract: Systems and methods are provided to facilitate transactions or limit operations. According to one embodiment, region information is determined in accordance with information received by a user device from a local location device. A region requirement is also determined, and it is arranged for the user device to operate in accordance with the region information and the region requirement.
    Type: Grant
    Filed: October 16, 2002
    Date of Patent: July 10, 2012
    Assignee: Sirf Technology, Inc.
    Inventor: Anant Sahai
  • Patent number: 7280626
    Abstract: Techniques are provided for synthesizing a long coherent I and Q correlation integral at a particular frequency by synthetically combining a sequence of shorter correlation integrals at the same or different frequency. Techniques are also provided for acquiring a carrier-modulated signal with an unknown shift of the carrier frequency, and possibly some additional unknown signal parameters. These techniques involve synthesizing coherent correlation sums at a fine frequency resolution, using coherent correlation sums that are calculated at a coarse frequency resolution. This approach allows for coherent processing of the received signal over an arbitrarily long time interval, while avoiding the excessive computational requirements of traditional methods.
    Type: Grant
    Filed: September 6, 2006
    Date of Patent: October 9, 2007
    Assignee: SiRF Technology, Inc.
    Inventors: Anant Sahai, John Tsitsiklis
  • Publication number: 20070105502
    Abstract: System and method for mitigating the effects of narrowband noise in a location-determining signal are provided, wherein the location-determining signal is associated with a periodic reference signal, the embodiments include identifying a set of noisy frequencies in the signal, determining a set of frequencies to be removed, and removing the set of frequencies from either the location-determining signal or the reference signal, thereby removing the effects of narrowband noise from the location-determining signal.
    Type: Application
    Filed: January 2, 2007
    Publication date: May 10, 2007
    Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
  • Patent number: 7177614
    Abstract: System and method for mitigating the effects of narrowband noise in a location-determining signal are provided, wherein the location-determining signal is associated with a periodic reference signal, the embodiments include identifying a set of noisy frequencies in the signal, determining a set of frequencies to be removed, and removing the set of frequencies from either the location-determining signal or the reference signal, thereby removing the effects of narrowband noise from the location-determining signal.
    Type: Grant
    Filed: December 31, 2002
    Date of Patent: February 13, 2007
    Assignee: SiRF Technology, Inc.
    Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
  • Patent number: 7164736
    Abstract: Techniques are provided for synthesizing a long coherent I and Q correlation integral at a particular frequency by synthetically combining a sequence of shorter correlation integrals at the same or different frequency. Techniques are also provided for acquiring a carrier-modulated signal with an unknown shift of the carrier frequency, and possibly some additional unknown signal parameters. These techniques involve synthesizing coherent correlation sums at a fine frequency resolution, using coherent correlation sums that are calculated at a coarse frequency resolution. This approach allows for coherent processing of the received signal over an arbitrarily long time interval, while avoiding the excessive computational requirements of traditional methods.
    Type: Grant
    Filed: June 22, 2001
    Date of Patent: January 16, 2007
    Assignee: SiRF Technology, Inc.
    Inventors: Anant Sahai, John Tsitsiklis
  • Publication number: 20070002978
    Abstract: Techniques are provided for synthesizing a long coherent I and Q correlation integral at a particular frequency by synthetically combining a sequence of shorter correlation integrals at the same or different frequency. Techniques are also provided for acquiring a carrier-modulated signal with an unknown shift of the carrier frequency, and possibly some additional unknown signal parameters. These techniques involve synthesizing coherent correlation sums at a fine frequency resolution, using coherent correlation sums that are calculated at a coarse frequency resolution. This approach allows for coherent processing of the received signal over an arbitrarily long time interval, while avoiding the excessive computational requirements of traditional methods.
    Type: Application
    Filed: September 6, 2006
    Publication date: January 4, 2007
    Inventors: Anant Sahai, John Tsitsklis
  • Patent number: 7069019
    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.
    Type: Grant
    Filed: September 6, 2002
    Date of Patent: June 27, 2006
    Assignee: SiRF Technology, Inc.
    Inventors: Anant Sahai, Andrew Chou
  • Patent number: 7027534
    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.
    Type: Grant
    Filed: June 22, 2001
    Date of Patent: April 11, 2006
    Assignee: SiRF Technology, Inc.
    Inventors: Anant Sahai, John Tsitsiklis, Stefano Casadei, Andrew Chou, Benjamin Van Roy, Jesse Robert Stone
  • Patent number: 6933886
    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.
    Type: Grant
    Filed: December 11, 2002
    Date of Patent: August 23, 2005
    Assignee: SiRF Technology, Inc.
    Inventors: Anant Sahai, Wallace Mann, Andrew Chou, Benjamin Van Roy
  • Patent number: 6900758
    Abstract: A server provides GPS aiding data to mobile GPS receivers are provided with an enclosed environment (e.g., within a large building) where the received GPS signal is likely to be weak or suffer multipath signal interference. The server receives GPS signals from one or more antennas within the enclosed environment and measures the multipath error in the vicinity of each antenna. Using the multipath error data for various satellite positions at various times, the server creates a delay model for the enclosed environment to generate GPS aiding data for the mobile GPS receivers. A generic delay model can be created that is applicable to similarly constructed buildings.
    Type: Grant
    Filed: October 16, 2002
    Date of Patent: May 31, 2005
    Assignee: SiRF Technology, Inc.
    Inventors: Wallace Mann, Anant Sahai
  • Publication number: 20040205194
    Abstract: Systems and methods are provided to facilitate transactions or limit operations. According to one embodiment, region information is determined in accordance with information received by a user device from a local location device. A region requirement is also determined, and it is arranged for the user device to operate in accordance with the region information and the region requirement.
    Type: Application
    Filed: October 16, 2002
    Publication date: October 14, 2004
    Inventor: Anant Sahai
  • Publication number: 20040174943
    Abstract: System and method for mitigating the effects of narrowband noise in a location-determining signal are provided, wherein the location-determining signal is associated with a periodic reference signal, the embodiments include identifying a set of noisy frequencies in the signal, determining a set of frequencies to be removed, and removing the set of frequencies from either the location-determining signal or the reference signal, thereby removing the effects of narrowband noise from the location-determining signal.
    Type: Application
    Filed: December 31, 2002
    Publication date: September 9, 2004
    Applicant: SiRF Technology, Inc.
    Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
  • Publication number: 20040176099
    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.
    Type: Application
    Filed: September 6, 2002
    Publication date: September 9, 2004
    Applicant: SiRF Technology, Inc.
    Inventors: Anant Sahai, Andrew Chou
  • Publication number: 20030156664
    Abstract: Techniques are provided for synthesizing a long coherent I and Q correlation integral at a particular frequency by synthetically combining a sequence of shorter correlation integrals at the same or different frequency. Techniques are also provided for acquiring a carrier-modulated signal with an unknown shift of the carrier frequency, and possibly some additional unknown signal parameters. These techniques involve synthesizing coherent correlation sums at a fine frequency resolution, using coherent correlation sums that are calculated at a coarse frequency resolution. This approach allows for coherent processing of the received signal over an arbitrarily long time interval, while avoiding the excessive computational requirements of traditional methods.
    Type: Application
    Filed: June 22, 2001
    Publication date: August 21, 2003
    Inventors: Anant Sahai, John Tsitsiklis
  • Publication number: 20030156665
    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.
    Type: Application
    Filed: June 22, 2001
    Publication date: August 21, 2003
    Inventors: Anant Sahai, John Tsitsiklis, Stefano Casadei, Andrew Chou, Benjamin Van Roy, Jesse Robert Stone
  • Patent number: 6542116
    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.
    Type: Grant
    Filed: June 22, 2001
    Date of Patent: April 1, 2003
    Assignee: Enuvis, Inc.
    Inventors: Anant Sahai, Andrew Chou, Wallace Mann, Stefano Casadei
  • Patent number: 6535163
    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.
    Type: Grant
    Filed: June 22, 2001
    Date of Patent: March 18, 2003
    Assignee: Enuvis, Inc.
    Inventors: Anant Sahai, John Tsitsiklis, Benjamin Van Roy, Andrew Chou, Wallace Mann, Jesse Robert Stone, Wungkum Fong
  • Patent number: 6512479
    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.
    Type: Grant
    Filed: June 22, 2001
    Date of Patent: January 28, 2003
    Assignee: Enuvis, Inc.
    Inventors: Anant Sahai, Wallace Mann, Andrew Chou, Benjamin Van Roy