GPS synchronization for wireless communications stations

• US 7,593,738 B2
• Filed: 12/29/2005
• Issued: 09/22/2009
• Est. Priority Date: 12/29/2005
• Status: Expired due to Fees

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: TruePosition Incorporated
• Inventors: Anderson, Robert J.
• Primary Examiner(s): Pérez-Gutiérrez; Rafael
• Assistant Examiner(s): Kasraian; Allahyar
• Application Number:
  US11/321,893
• Publication Number:
  US 20070161385A1
• Time in Patent Office: 1,363 Days
• Field of Search: 455/456.1, 455/456.5, 455/502, 455/67.11, 370/509, 370/510, 370/321, 370/324, 370/350, 370/503, 342/357.12
• US Class Current: 455/456.1
• CPC Class Codes: G01S 19/03 Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers

Abstract

A method and system are specified to determine, provide, and exploit the precise time base relations between the distinct signal timings of the Global Positioning System (GPS) and a wireless communications system (WCS) for which the internal WCS downlink time base standards are not inherently synchronized to GPS timing. These downlink signal synchronization facilities are particularly beneficial for a wireless location system (WLS) and related methods and subsystems that provide mobile-station location determination through the exploitation of the time base synchronization information, e.g., to assist a GPS-equipped mobile station in determining its GPS-derived measurements with enhanced efficiency and accuracy.

Claims

1. A signal processing method for use in processing a base transceiver station (BTS) downlink signal, comprising:

acquiring a candidate time series from a received BTS downlink burst signal;

correlating a frequency correction channel (FCCH) replica with a candidate broadcast control channel (BCCH) beacon signal to determine a nominal frame time alignment and time of arrival (TOA) for an FCCH burst signal;

correlating a synchronization channel (SCH) extended training sequence to determine a time alignment and TOA for an SCH burst signal;

attempting to demodulate the SCH burst signal;

determining that the SCH demodulation is not acceptable, and in response thereto performing the following steps;

obtaining A-bis monitoring system (AMS)-derived possible partial/modulo frame and associated BSIC information for the candidate BCCH signal;

calibrating the AMS-derived timings to GPS-based times for possible partial/modulo frames, and using the candidate AMS-derived partial/modulo frame information to form the possible complete frame numbers (FNs) with associated reduced frame numbers (RFNs) for the SCH;

applying selected BSIC and FN/RFN to form a complete SCH replica;

correlating the SCH replica with a candidate BCCH signal to refine the TOA measurement for the SCH burst signal;

integrating the SCH correlation with an associated FCCH correlation for a refined measurement of TOA;

determining that the correlation results are acceptable and propagating a measured GPS-timebased TOA to a frame boundary, thereby determining a measured GPS-timebased TOA corresponding to a frame boundary; and

forming a record of correlated BCCH carrier identification, BSIC, FN, and GPS-timebased TOA.

2. A signal processing system for use in processing a base transceiver station (BTS) downlink signal, comprising a processor and executable instructions for configuring the processor to perform a sequence of predefined steps, said steps including:

acquiring a candidate time series from a received BTS downlink burst signal;

correlating a frequency correction channel (FCCH) replica with a candidate broadcast control channel (BCCH) beacon signal to determine a nominal frame time alignment and time of arrival (TOA) for an FCCH burst signal;

correlating a synchronization channel (SCH) extended training sequence to determine a time alignment and TOA for an SCH burst signal;

attempting to demodulate the SCH burst signal;

determining that the SCH demodulation is not acceptable, and in response thereto performing the following steps;

obtaining A-bis monitoring system (AMS)-derived possible partial/modulo frame and associated BSIC information for the candidate BCCH signal;

calibrating the AMS-derived timings to GPS-based times for possible partial/modulo frames, and using the candidate AMS-derived partial/modulo frame information to form the possible complete frame numbers (FNs) with associated reduced frame numbers (RFNs) for the SCH;

applying selected BSIC and FN/RFN to form a complete SCH replica;

correlating the SCH replica with a candidate BCCH signal to refine the TOA measurement for the SCH burst signal;

integrating the SCH correlation with an associated FCCH correlation for a refined measurement of TOA;

determining that the correlation results are acceptable and propagating a measured GPS-timebased TOA to a frame boundary, thereby determining a measured GPS-timebased TOA corresponding to a frame boundary; and

forming a record of correlated BCCH carrier identification, BSIC, FN, and GPS-timebased TOA.