Signal collection system for a wireless location system

• US 6,388,618 B1
• Filed: 03/31/2000
• Issued: 05/14/2002
• Est. Priority Date: 01/08/1999
• Status: Expired due to Term

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: TruePosition Incorporated
• Inventors: Bull, Jeffrey F., Anderson, Robert J., Sheehan, Joseph W., Stilp, Louis A.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US09/539,370
• Time in Patent Office: 774 Days
• Field of Search: 342/357.01, 342/357.06, 342/385, 342/457
• US Class Current: 342/457
• CPC Class Codes: G01S 1/026 of associated receivers
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 5/011 Identifying the radio environment
• CPC Class Codes: G01S 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• 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 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.

Claims

1. A wireless location system comprising a plurality of signal collection systems (SCSs) each including a narrowband receiver module wherein the narrowband receiver module comprises a narrowband receiver that receives at most a few RF channels at a time, wherein the wireless location system performs the following steps:

a) determining the cell site, sector, RF channel, timeslot, long code mask, and encryption key currently in use by the first wireless transmitter;

b) tuning a first narrowband receiver at a first SCS to the RF channel and timeslot at a designated cell site and sector;

c) based on a time segment of RF data from the first narrowband receiver, evaluating the transmission'"'"'s power, SNR, and modulation characteristics;

d) if the transmission'"'"'s power or SNR is below a predetermined threshold, waiting a predetermined length of time and then returning to the above step (a).

2. A wireless location system as recited in claim 1, wherein the wireless location system performs the additional steps of

e) if the transmission is an AMPS voice channel transmission and the modulation is below a threshold, then causing the first wireless transmitter to transmit a blank and burst;

f) preventing a hand-off of the wireless transmitter to another RF channel for a predetermined length of time.

3. A wireless location system as recited in claim 1 or 2, wherein the wireless location system performs the additional steps of

g) determining a list of antennas that will be used in location processing;

h) determining the earliest wireless location system timestamp at which the narrowband receivers connected to the selected antennas are available to begin simultaneously collecting RF data from the RF channel currently in use by the first wireless transmitter;

i) based at least in part upon the earliest wireless location system timestamp, causing the narrowband receivers connected to the antennas that will be used in location processing to tune to the cell site, sector, and RF channel currently in use by the first wireless transmitter and to receive RF data for a predetermined dwell time;

j) writing RF data received by the narrowband receivers into a memory; and

k) commencing location processing on the received RF data.

4. A wireless location system as recited in claim 3, wherein the wireless location system performs the additional steps of:

l) again determining the cell site, sector, RF channel, timeslot, mask, and encryption key currently in use by the first wireless transmitter;

m) if the cell site, sector, RF channel, timeslot, mask, and encryption key currently in use by the first wireless transmitter has changed, ceasing location processing, and re-triggering this entire process; and

n) completing location processing on the received RF data.

6. A wireless location system as recited in claim 1, wherein each SCS comprises:

a first receiver module;

a first digital signal processing (DSP) module coupled to said first receiver module;

a control and communications module;

a timing signal generator, including an enhanced GPS receiver, coupled to said communications and control module; and

a bus coupling said DSP module to said communications and control module;

wherein said receiver module receives RF signals from said mobile transmitters via a plurality of antennas and digitizes said RF signals, and provides digitized RF data to the first DSP module.

5. A signal collection system (SCS) for use in a wireless location system that determines the geographical locations of mobile wireless transmitters, comprising:

a first receiver module;

a first digital signal processing (DSP) module coupled to said first receiver module;

a control and communications module;

a timing signal generator, including an enhanced GPS receiver, coupled to said communications and control module; and

a bus coupling said DSP module to said communications and control module;

wherein said receiver module receives RF signals from said mobile transmitters via a plurality of antennas and digitizes said RF signals, and provides digitized RF data to the first DSP module;

wherein the digital receiver module outputs a digitized data stream having a specified bandwidth and bit resolution, and the DSP module receives the digitized data stream and extract individual RF channels by digital mixing and filtering; and

wherein the DSP module performs the following steps in automatic detection;

a) for each possible control and/or voice channel which may be used in the coverage area of the SCS, peg counters are established;

b) at the start of a detection period, all peg counters are reset to zero;

c) each time that a transmission occurs in a specified RF channel, and the received power level is above a particular pre-set threshold, the peg counter for that channel is incremented;

d) each time that a transmission occurs in a specified RF channel, and the received power level is above a second particular pre-set threshold, the DSP module attempts demodulation of a portion of the transmission using a first preferred protocol;

e) if the demodulation is successful, a second peg counter for that channel is incremented;

f) if the demodulation is unsuccessful, the DSP module attempts demodulation of a portion of the transmission using a second preferred protocol;

g) if the demodulation is successful, a third peg counter for that channel is incremented;

h) at the end of a detection period, the wireless location system reads all peg counters; and

i) the wireless location system automatically assigns primary channels based upon the peg counters.