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Detection and selection of a reference signal for network-based wireless location

  • US 8,204,510 B2
  • Filed: 10/08/2010
  • Issued: 06/19/2012
  • Est. Priority Date: 10/08/2010
  • Status: Expired due to Fees
First Claim
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1. A method for use in a wireless location system (WLS) associated with a wireless communications network (WCN), wherein the WCN is configured to serve mobile devices using a cellular arrangement of base stations, a frequency reuse pattern, and frequency hopping patterns, comprising:

  • at a serving mobile location center (SMLC) associated with the WLS, receiving a position request concerning a mobile-of-interest (MOI), wherein the MOI is operating in a discontinuous transmission (DTX) mode in the WCN;

    in response to the position request, tasking the WLS to locate the MOI, wherein said tasking includes communicating commands from the SMLC to a plurality of location measurement units (LMUs) at sites surrounding the MOI, wherein said commands instruct said LMUs to receive and digitize radio frequency (RF) energy, and to store signal data representing said RF energy;

    at said plurality of LMUs, receiving a signal of interest (SOI) and cross-correlating a known midamble, pre-amble or post-amble with the received signal of interest to produce a received detection metric;

    weighting the detection metric produced by each of said plurality of LMUs so as to favor the MOI even in the presence of interference from other mobile devices operating in the WCN;

    at the SMLC, selecting the LMU with the best weighted detection metric as a reference site and selecting two or more LMUs with lesser weighted detection metrics above a threshold as co-operating sites;

    at the reference site, sampling the received SOI and communicating sample data to the SMLC;

    at the SMLC, distributing the sample data to the co-operating sites;

    at the co-operating sites, producing a reference waveform from the sample data, and cross-correlating the reference waveform with stored signal data to produce a time-difference-of-arrival (TDOA) measurement at each of said co-operating sites;

    communicating the TDOA measurements from the co-operating sites to the SMLC; and

    at the SMLC, computing position, velocity, and error estimates for the MOI.

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