Station based processing method for a wireless location system

• US 6,285,321 B1
• Filed: 08/24/2000
• Issued: 09/04/2001
• Est. Priority Date: 01/08/1999
• Status: Expired due to Term

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.), Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology, TruePosition Incorporated
• Inventors: Anderson, Robert J., Sheehan, Joseph W., Stilp, Louis A., Rogers, Alan E. E.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US09/645,802
• Time in Patent Office: 376 Days
• Field of Search: 342/450, 342/465, 342/457, 342/357.02, 701/207, 701/214
• US Class Current: 342/465
• CPC Class Codes: G01S 1/026 of associated receivers
• CPC Class Codes: G01S 2205/006 for emergency situations
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 2205/06 Emergency
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/02216 Timing or synchronisation of the receivers
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0246 involving frequency difference of arrival or Doppler measurements G01S5/02685 takes precedence
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: G01S 5/0268 by deriving positions from different combinations of signals or of estimated positions in a single positioning system
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 76/50 for emergency connections
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

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.

Claims

1. A station-based method for use in a wireless location system to determine the geographic location of a mobile wireless transmitter, the wireless location system including signal collection systems and location processors for processing digital data provided by the signal collection systems, the method comprising:

a) receiving a transmission from a wireless transmitter at multiple antennas and at multiple signal collection systems;

b) converting the transmission into a digital format in a receiver connected to each antenna at the multiple signal collection systems;

c) at each signal collection system, storing digital data representative of the received transmissions in a memory in the signal collection system;

d) demodulating the transmission at a first signal collection system and determining appropriate phase correction intervals;

e) at the first signal collection system, for each such phase correction interval calculating appropriate phase correction parameters, and encoding the phase correction parameters along with the demodulated data;

f) sending the demodulated data and phase correction parameters from the first signal collection system to a location processor;

g) at the location processor, determining the signal collection systems and receiving antennas to use in location processing;

h) sending the demodulated data and any needed phase correction parameters from the location processor to a plurality of signal collection systems that will be used in location processing;

i) at each signal collection system to be used in location processing, creating a first re-modulated signal based upon the demodulated data and any needed phase correction parameters;

j) at each signal collection system to be used in location processing, performing a time difference of arrival (TDOA) determination using the digital data stored in memory and the first re-modulated signal;

k) sending the TDOA and multipath mitigation data from the signal collection systems to the location processor; and

l) at the location processor, determining the location of the wireless transmitter using the TDOA data.

2. A method as recited in claim 1, further comprising performing FDOA analysis in step j) using the digital data stored in memory and the first re-modulated signal to provide FDOA data.

3. A method as recited in claim 2, further comprising determining the speed of the wireless transmitter using the FDOA data from each signal collection system.

4. A method as recited in claim 1, further comprising performing multipath mitigation in step j) using the digital data stored in memory and the first re-modulated signal.

5. A method as recited in claim 4, further comprising correcting the TDOA data using the multipath mitigation results.

6. A method as recited in claim 1, wherein, if the phase correction parameters are calculated to be zero, or are not needed, then these parameters are not sent to the location processor, whereby the number of bits transmitted on the communications link between each signal collection system and location processor is conserved.

7. A method as recited in claim 1, wherein a fixed phase correction interval is used for a particular type of transmission.

8. A method as recited in claim 1, wherein a fixed phase correction interval is used for all transmissions of a particular air interface protocol.

9. A method as recited in claim 1, wherein a fixed phase correction interval is used for all transmissions made by a particular type of wireless transmitter.

10. A method for determining whether to use a predefined central-based or a predefined station-based method to determine the geographic location of a mobile wireless transmitter using a wireless location system including signal collection systems and location processors, the method comprising:

a) at a first signal collection system, receiving a transmission from the wireless transmitter;

b) at the first signal collection system, converting the received transmission into a digital format;

c) demodulating the transmission at a first signal collection system and estimating an appropriate phase correction interval and number of bits required to encode phase correction parameters;

d) estimating the number of bits required for supporting station- and central-based processing methods; and

c) based upon the estimated number of bits required for each of central-based and station-based processing methods, determining the most efficient method to perform location processing for the transmission.