Abstract: Discriminative methods for multipath fingerprinting, enabling single-site localization in rich multipath environments, are provided herein. In contrast to the existing descriptive method that uses only the data of each location for its fingerprint extraction, these methods use also the data of the other locations in the database, and leverage it to make the fingerprint as different as possible from the other fingerprints in the database. The performance of these methods, validated with both simulated and real data, is superior to the existing method, demonstrating localization accuracy of about 1 m in typical indoor environments.

Abstract: Single-site localization of wireless emitters in a rich multipath environment is presented. The localization method is based on exploiting the spatio-temporal characteristics of the multipath signals, referred to as the multipath fingerprint, as captured by the base station antenna array. The method is applicable to all modern communication techniques such as WiFi and LTE and to any rich multipath environment in indoors and outdoors.

Abstract: Discriminative methods for multipath fingerprinting, enabling single-site localization in rich multipath environments, are provided herein. In contrast to the existing descriptive method that uses only the data of each location for its fingerprint extraction, these methods use also the data of the other locations in the database, and leverage it to make the fingerprint as different as possible from the other fingerprints in the database. The performance of these methods, validated with both simulated and real data, is superior to the existing method, demonstrating localization accuracy of about 1 m in typical indoor environments.

Abstract: A wireless access point coherently receives signals transmitted from client devices and from interfering devices, measures noise and interference capture samples from the received signals, and computes a characterization of noise plus interference. Receive gains and threshold levels are adjusted based on the computed noise plus interference characterization. A set of weights for an interference suppression spatial filter are calculated from the measured noise and interference capture samples and used to produce a filtered signal by spatially filtering the received signals such that interference is spatially nulled in the filtered signal. The method may also include setting PHY parameters at the wireless access point based on the computed noise plus interference characterization. In some embodiments, a protection transmission is transmitted from the wireless access point, requesting connected client devices to suspend transmissions during a specified time period.

Abstract: A method for communication over a wireless local area network (WLAN) includes receiving uplink signals from a plurality of stations in the WLAN. Responsively to the uplink signals, a set of the stations is selected for inclusion in a spatial multiplexing group. Downlink signals are transmitted simultaneously to the stations in the set using spatial division multiplexing (SDM).

Abstract: A wireless access point coherently receives signals transmitted from client devices and from interfering devices, measures noise and interference capture samples from the received signals, and computes a characterization of noise plus interference. Receive gains and threshold levels are adjusted based on the computed noise plus interference characterization. A set of weights for an interference suppression spatial filter are calculated from the measured noise and interference capture samples and used to produce a filtered signal by spatially filtering the received signals such that interference is spatially nulled in the filtered signal. The method may also include setting PHY parameters at the wireless access point based on the computed noise plus interference characterization. In some embodiments, a protection transmission is transmitted from the wireless access point, requesting connected client devices to suspend transmissions during a specified time period.

Abstract: A method for communication includes receiving signals transmitted over the air by first and second mobile stations on a common frequency channel in a wireless packet network, the signals carrying first and second data packets transmitted by the first and second mobile stations, respectively, the first and second data packets comprising respective, first and second headers. The received signals are processed so as to identify the first header. Responsively to the identified first header, signal values corresponding to at least a portion of the first data packet are reconstructed, and the reconstructed signal values are subtracted from the received signals so as to produce a modified signal. The modified signal is processed in order to identify the second header. The first and second data packets are demodulated using the identified first and second headers.

Abstract: A method for communication includes receiving signals transmitted over the air by first and second mobile stations on a common frequency channel in a wireless packet network, the signals carrying first and second data packets transmitted by the first and second mobile stations, respectively, the first and second data packets comprising respective, first and second headers. The received signals are processed so as to identify the first header. Responsively to the identified first header, signal values corresponding to at least a portion of the first data packet are reconstructed, and the reconstructed signal values are subtracted from the received signals so as to produce a modified signal. The modified signal is processed in order to identify the second header. The first and second data packets are demodulated using the identified first and second headers.

Abstract: A method for communication over a wireless local area network (WLAN) includes receiving uplink signals from a plurality of stations in the WLAN. Responsively to the uplink signals, a set of the stations is selected for inclusion in a spatial multiplexing group. Downlink signals are transmitted simultaneously to the stations in the set using spatial division multiplexing (SDM).

Abstract: A CDMA receiver for measuring spatial signal information corresponding to several user transmitters comprises a bank of coherent receivers coupled to an antenna array, a bank of signal buffers for recording samples of the received signal data, and a bank of I/Q despreaders for despreading selected signal samples. The receiver also comprises a buffer control circuit for selecting active power control groups in the recorded signal samples for despreading, and a despreader control circuit for selecting PN despreading sequences required to despread the selected power groups. Selected data samples from the signal buffers are fed into the despreaders. The output of the despreaders is a set of spatially correlated I/Q data streams divided into temporal frames, where each frame contains active power control groups from different user transmitters.

Abstract: A system for easily and inexpensively distributing real time location information of cellular telephone users to various third party information subscribers comprises an HTTP server machine which maintains a dynamic database of current cellular users. The database has a list of caller entries, where each entry typically comprises a user ID number, such as a phone number, mobile ID number, and/or handset serial ID. The entry also includes, for each user ID number, a user location identifier such as a latitude and longitude, a sector number, a caller or called phone number and/or a street address. The HTTP server is connected to the internet so that registered third party information subscribers have access to the database by means of standard HTTP protocols that ensure authentication and provide encryption for security.

Abstract: A system for easily and inexpensively distributing real time location information of cellular telephone users to various third party information subscribers comprises an HTTP server machine which maintains a dynamic database of current cellular users. The database has a list of caller entries, where each entry typically comprises a user ID number, such as a phone number, mobile ID number, and/or handset serial ID. The entry also includes, for each user ID number, a user location identifier such as a latitude and longitude, a sector number, a caller or called phone number and/or a street address. The HTTP server is connected to the internet so that registered third party information subscribers have access to the database by means of standard HTTP protocols that ensure authentication and provide encryption for security.

Abstract: A method and apparatus for location finding in a CDMA wireless communication system uses multipath signals in order to accurately determine a transmitter—s location. Direct path and multipath signals from a mobile transmitter arrive at an array of p antennas belonging to a cellular network base station. A location finding apparatus connected to the base station contains a multichannel receiver that uses PN sequence information provided by the base station receiver to despread the p signals and to separate each of the p signals into temporally distinct multipath parts. A signal processor calculates a signal signature for each active mobile. The signature is comprises a code correlation function, a set of temporal delays corresponding to the multipath parts and a set of signal subspaces.

Abstract: A method and apparatus are provided for easily and accurately calibrating an antenna array in a multipath environment. A calibration table containing spatial signature data together with corresponding location data is used to calibrate the antenna array, i.e. to determine the array response in various directions. The calibration table includes a set of calibrated signal covariances R1, . . . , RN together with a set of N corresponding geographical locations. From this data, a set of array calibration vectors {a(&thgr;)} is determined, where each vector a(&thgr;) characterizes the complex signal response of the antenna array in the direction &thgr;. Once the array calibration vectors are determined, this information can be used for direction finding, beamforming, and other enhancements to the performance of the communication system.

Abstract: A method and apparatus for wireless location finding determines a set of likely locations from a signal covariance matrix R, a set of array calibration vectors {a(.theta.)}, and a set of calibrated signal covariance matrices {R.sub.k } corresponding to calibrated locations. From these quantities, an angular energy distribution function B(.theta.) is calculated from R and a(.theta.), and compared to a set of calibrated angular energy distribution functions B.sub.1 (.theta.), . . . , B.sub.N (.theta.) corresponding to the set of calibrated signal covariance matrices R.sub.1, . . . , R.sub.N. The function B(.theta.) is then compared with each of the calibrated functions B.sub.1 (.theta.), . . . , B.sub.N (.theta.) to determine those calibrated functions that most closely match the calculated function B(.theta.). From these calculations a set of likely locations is then determined.

Abstract: A method and apparatus improves the accuracy of a wireless location finding system based on the use of multipath signal signatures. A location finding apparatus measures an array covariance matrix R of a signal. The covariance matrix is compared to a database of signatures comprising calibrated signal subspaces. The comparison is based on calculating the projection of R onto each calibrated subspace. From these calculations a set of likely locations is then determined.

Abstract: A method for determining a geographical location from a measured wireless signal signature comprises calculating from the measured wireless signal signature a multi-dimensional signature vector, wherein each component of the vector measures a degree of coincidence between the measured wireless signal signature and a calibrated signal signature stored in a calibration table. The method also includes matching the signature vector with vectors in a set of multi-dimensional calibrated vectors. The matching uses a procedure comprising searching a hierarchical tree structure and eliminating nodes that cannot contain the best match vector. Within the remaining nodes, the search eliminates individual vectors that cannot be the best match vector, and selects one or more vectors in the set of multi-dimensional calibrated vectors, where the matched vectors correspond to calibrated geographical locations.

Abstract: A method is provided for the direction of arrival (DOA) tracking of at least one source, along a single azimuth axis or along both azimuth and elevation axes. The method includes the steps of selecting all the high peaks from a DOA function as potential track points, converting the potential track points into a plurality of tracks and selecting a true track from the plurality of tracks.

Abstract: A system and method is provided for processing a calibration table used in a wireless location finding system. The initial calibration table data comprises points partitioned into routes followed by moving vehicles, where each point comprises a wireless signal signature and corresponding geographical location. The method comprises calculating, for each point, a list of neighboring points; and generating, for each route, a plurality of geographical bins covering all points in the route. Each bin has a bin location and a bin signature derived from those of the points within the bin. The resulting calibration table, which contains fewer redundant data points than the original calibration table data, may be used in a location finding system for quickly identifying the location of wireless transmitters in real time.

Abstract: A method for improving the accuracy of signal signature determinations in wireless location finding systems advantageously uses transmitter velocity estimates to accurately and reliably determine in real time a present signal covariance matrix for a transmitter. In a preferred embodiment of the invention, a method for determining a likely location of a transmitter in a wireless transmitter location finding system comprises coherently measuring transmitter signals received at an antenna array, and calculating a current signal covariance matrix from the measured transmitter signals. The method further comprises calculating an average covariance matrix by forming a linear combination of the current signal covariance matrix with past average covariance matrices.