Trueposition, Inc.

Other

Massachusetts Institute of Technology

Joseph W Sheehan

Robert J Anderson

Louis A Stilp

Alan E E Rogers

Vineet Sachdev

Andrew F Harbison

Jeffrey Francis Bull

Thomas S Ginter

Edwin E McCook

John Solley

Anthony Richard Brigidi

Michael John Kovach, Jr

Tim J Harris

Alan E Rogers

An Applications Processor () including a centralized database system is used in a wireless location system (WLS). The APsmay be used to manage resources in the WLS, including signal collection systems (SCSs) and TDOA location processors (TLPs). Each APcontains a database containing triggers for the WLS. The WLS can be programmed to locate only certain pre-determined types of transmissions. When a transmission of a pre-determined type occurs, then the WLS is triggered to begin location processing. Each APalso contains applications interfaces that permit a variety of applications to securely access the WLS. These applications may access location records in real time or non-real time, create or delete certain types of triggers, or cause the WLS to take other actions. Each APis also capable of certain post-processing functions.

Applications processor including a database system, for use in a wireless location system

In a network overlay Location Services solution for a GSM communications network, the LMU monitors the uplink and/or downlink control channels and determines which call originations are for E911 emergencies and which call setup (Stand-alone Dedicated Control Channel, or SDCCH), assigned traffic (TCH) and associated (Slow Associated Control Channel, or SACCH) channels are subsequently assigned. Capturing the energy on the call setup channel, SDCCH, and its associated SACCH will typically provide a sub-100 meter level of accuracy. If not, the SMLC can redirect the LMU to the assigned traffic channel, TCH, to capture additional RF energy and improve the location accuracy as required. This approach takes advantage of the fact that Channel Request messages on the RACH include an information element that indicates the purpose for the access request. One of the values of this information element identifies that the Channel Request is for an emergency call. By monitoring the Access Grant channels (downlink), e.g., the AGCH, the primary (serving) LMU (LMUA in FIG.) can capture the Immediate Assignment Message (IMM ASS) for emergency calls. The Immediate Assignment Message contains the Channel Request message (with the emergency call indication) and the SDCCH channel to be used by the MS for subsequent call setup messaging. The primary LMU will forward the Immediate Assignment Message to the SMLC, which will task the cooperating LMUs to collect the RF energy from the associated SDCCH, SACCH and TCH channels and provide TDOA, AoA, and FDOA determinations.

E911 overlay solution for GSM, for use in a wireless location system

An antenna selection method is used in a wireless location system that determines the geographic location of a mobile wireless transmitter. The wireless location system includes signal collection systems connected to multiple antennas at a plurality of cell sites and a location processor for processing digital data provided by the signal collection systems. The antenna selection method comprises evaluating segments of data collected from a plurality of antennas at a signal collection system, selecting a subset of the segments of data, and using only the selected segments of data in location processing.

Antenna selection method for a wireless location system

A collision recovery method for use in a Wireless Location System includes receiving a transmission from a wireless transmitter at multiple signal collection systems and multiple antenna ports of each of the multiple signal collection systems. At each of the multiple signal collection systems, the transmission received at each antenna port is converted into a digital format, and digital data representative of the received transmission is stored. The transmission is then demodulated, and TDOA analysis is performed on the digital data from pairs of signal collection systems. The location of the wireless transmitter is determined using the TDOA data. The method further involves verifying that the RF data from each antenna port is from the wireless transmitter to be located, e.g., by demodulating a segment of the transmission received at each antenna port and verifying that at least a combination of the following fields is correct: MIN, MSID, TMSI, IMSI, and ESN.

Collision recovery in a wireless location system

The accuracy of the location estimate of a Wireless Location System is dependent, in part, upon both the transmitted power of the wireless transmitter and the length in time of the transmission from the wireless transmitter. In general, higher power transmissions and transmissions of greater transmission length can be located with better accuracy by the Wireless Location System than lower power and shorter transmissions. Wireless communications systems generally limit the transmit power and transmission length of wireless transmitters in order to minimize interference within the communications system and to maximize the potential capacity of the system. The inventive method disclosed herein meets the conflicting needs of both systems by enabling the wireless communications system to minimize transmit power and length while enabling improved location accuracy for certain types of calls, such as wireless 9-1-1 calls. The method comprises the following steps: a wireless transmitter receives normal transmission parameters from a base station; the user of the wireless transmitter initiates a call on the wireless transmitter by dialing a sequence of digits and pressing &ldquo;SEND&rdquo; or &ldquo;YES&rdquo;; a processor within the wireless transmitter compares the dialed sequence of digits with one or more trigger events stored within the wireless transmitter; if the dialed sequence of digits does not match the trigger event, then the wireless transmitter uses the normal transmission parameters in making the call; and if the dialed sequence of digits matches the trigger event, then the wireless transmitter uses a modified transmission sequence.

Modified transmission method for improving accuracy for E-911 calls

A Wireless Location System includes signal collection systems and location processors for processing digital data provided by the signal collection systems. To determine the geographic location of a mobile wireless transmitter, time difference of arrival, or TDOA, data is determined with respect to a plurality of first signal collection system/antenna second signal collection system/antenna baselines. A method for selecting baselines for use in location processing comprises calculating a number of parameters for each of the plurality of baselines, and including in a final location solution only those baselines meeting or exceeding predefined threshold criteria for each of the parameters.

Baseline selection method for use in a wireless location system

The accuracy of the location estimate of a Wireless Location System is dependent, in part, upon both the transmitted power of the wireless transmitter and the length in time of the transmission from the wireless transmitter. In general, higher power transmissions and transmissions of greater transmission length can be located with better accuracy by the Wireless Location System than lower power and shorter transmissions. Wireless communications systems generally limit the transmit power and transmission length of wireless transmitters in order to minimize interference within the communications system and to maximize the potential capacity of the system. Several methods meet the conflicting needs of both systems by enabling the wireless communications system to minimize transmit power and length while enabling improved location accuracy for certain types of calls, such as wireless 9-1-1 (emergency) calls. Such methods include mobile-assisted techniques in which the mobile unit includes functionality to assist in improving location accuracy. The WLS locates the transmitter (mobile unit) while the latter is using a modified transmission sequence comprising a message sent from the wireless transmitter using transmission parameters different from the normal transmission parameters broadcast on the forward control channel by the base stations in the associated wireless communications system. A trigger event, such as the user dialing 9-1-1, causes the mobile unit to operate in the mode in which the modified transmission sequence is used.

Mobile-assisted network based techniques for improving accuracy of wireless location system

A signal collection system (SCS) is used in a wireless location system that determines the geographical locations of mobile wireless transmitters. The SCS includes a first receiver module, a first digital signal processing (DSP) module, a control and communications module, a timing signal generator including an enhanced GPS receiver, and a bus coupling the DSP module to the communications and control module. The receiver module receives RF signals from the mobile transmitters via a plurality of antennas and digitizes said RF signals, and provides digitized RF data to the first DSP module.

Signal collection system for a wireless location system

Modified transmission method for improving accuracy for e-911 calls

A centralized database system is used in a wireless location system that determines the geographical locations of mobile wireless transmitters, the wireless location system including signal collection systems, location processors for processing digitized RF data provided by the signal collection systems, and a centralized database system for managing resources in the wireless location system. The centralized database system includes a computer, a database, and a plurality of software processes for managing the wireless location system, providing interfaces to external users and applications, and storing location records and configuration information.

Centralized database system for a wireless location system

A station-based method for use in a wireless location system determines the geographic location of a mobile wireless transmitter. The wireless location system includes signal collection systems and location processors for processing digital data provided by the signal collection systems. The station-based method comprises receiving a transmission from a wireless transmitter at multiple antennas and at multiple signal collection systems. The transmission is converted into a digital format in a receiver connected to each antenna at the multiple signal collection systems. At each signal collection system, digital data representative of the received transmissions are stored in a memory. The transmission is then demodulated at a first signal collection system, and appropriate phase correction intervals are determined. At the first signal collection system, for each such phase correction interval, appropriate phase correction parameters are calculated, and the phase correction parameters are encoded along with the demodulated data. The demodulated data and phase correction parameters are sent from the first signal collection system to a location processor. At the location processor, the signal collection systems and receiving antennas to use in location processing are determined. The demodulated data and any needed phase correction parameters are then sent from the location processor to a plurality of signal collection systems that will be used in location processing. At each signal collection system to be used in location processing, a first re-modulated signal based upon the demodulated data and any needed phase correction parameters is created; and a time difference of arrival (TDOA) determination is performed using the digital data stored in memory and the first re-modulated signal. The TDOA and multipath mitigation data are sent from the signal collection systems to the location processor. Finally, the location of the wireless transmitter is determined at the location processor using the TDOA data.

Station based processing method for a wireless location system

A signal collection system (SCS) for use in a Wireless Location System is disclosed. The SCS performs wideband energy detection and reporting at the front end of the SCS receiver. Other aspects of the SCS include a protocol for efficiently setting levels for wideband energy detection, DSP sharing within an SCS, and recursive location processing using progressively greater bandwidth from temporarily stored wideband data. The disclosed SCS includes antennas, a wideband receiver, a DSP for wideband energy detection, a memory for temporarily storing digital samples of received signals, a digital drop receiver, demodulation and normalization processors, and a communications processor. The wideband energy detection and the demodulation and normalization processors are implemented with DSP's that detect energy in a particular band, demodulate selected signals, and extract signals of interest for forwarding. The wideband energy detection unit determines the presence of a transmitted signal in the control channels monitored by the SCS. The wideband energy detection involves forming a map of the channel spectrum, and the map is used to determine when to demodulate signals within selected channels.

Growing community of inventors

Newtown Square, PA, United States of America

Joseph W Sheehan