Method for measuring the time of arrival of radio signals

• US 8,130,146 B2
• Filed: 07/29/2008
• Issued: 03/06/2012
• Est. Priority Date: 07/29/2008
• Status: Active Grant

• Current Assignee: Bison Patent Licensing, LLC
• Original Assignee: Motorola Solutions, Inc.
• Inventors: Alapuranen, Pertti O., Belcea, John M.
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): Nguyen, Nga X
• Application Number:
  US12/181,727
• Publication Number:
  US 20100026576A1
• Time in Patent Office: 1,316 Days
• Field of Search: 342387-394, 342/385, 455/509
• US Class Current: 342/387
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 13/76 wherein pulse-type signals are transmitted
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/02213 Receivers arranged in a network for determining the position of a transmitter

Abstract

A method for measuring the time of arrival of radio signals within a network comprises receiving the received signals including at least a first pseudorandom code and a second pseudorandom code from at least one other node; identifying a frequency difference between the node and the other node using a phase difference between each of a maximum value of a cross-correlation provided by the first pseudorandom code and the second pseudorandom code; applying the frequency difference to the reception of the received signal; and calculating the time of arrival of the received signal comprising a time, measured with a local clock, when the cross-correlation has achieved the maximum value.

Claims

1. A method for measuring the time of arrival of one or more signals comprising:

receiving, at a receiving node, at least one signal including a first pseudorandom code and a second pseudorandom code from a transmitting node;

identifying, at the receiving node, an approximated frequency difference between the receiving node and the transmitting node using a phase difference between each of a maximum value of a cross-correlation provided by the first pseudorandom code and the second pseudorandom code;

applying, at the receiving node, the approximated frequency difference to the reception of the received signal; and

calculating, at the receiving node, the approximated time of arrival of the received signal comprising a time, measured with a local clock, when the cross-correlation has achieved the maximum value.

2. The method of claim 1, wherein the transmitting node sends the at least one signal as one or more RANGE messages each including a pseudorandom code repeatedly for a plurality of times.

3. The method of claim 1, further comprising prior to receiving the signal:

broadcasting, by the receiving node, a LOCATION message including a “

Request for Coordinates”

flag set to TRUE to notify the transmitting node that the receiving node requires references for computing its own position.

4. The method of claim 3, further comprising:

receiving, by the receiving node, data associated with reception of RANGE messages from one or more neighbor nodes.

5. The method of claim 4, wherein the received data comprises, for each neighbor:

a neighbor identification, a time of arrival of a last RANGE message received from that neighbor node, an apparent difference of frequencies between the receiving node and the neighbor node, and a one bit COORDINATE DATA flag.

6. The method of claim 5, wherein the COORDINATE DATA flag value is selected from a group of values comprising:

no coordinates, Geocentric, Geographic, Local, and Relative.

7. The method of claim 2, wherein the received RANGE signals comprise a sequence of received quadrature (I, Q) samples, the method further comprising operating the receiving node to:

de-rotate each received sample thereby resulting in a vector of components;

compute a phase shift correction from at least one de-rotation angle of the de-rotated samples;

correlate the de-rotated samples with a pseudorandom code sequence;

structure the result of correlation as a matrix comprising a plurality of matrix elements arranged with a plurality of rows and a plurality of columns;

average at least some of the matrix elements on each of the columns into a vector of elements;

process the averaged vector of elements for identifying a best correction of time of arrival of a direct path in relation with the approximated time of arrival measured by the node;

compute the frequency difference from the phase shift correction and the approximated frequency difference; and

compute the Doppler frequency shift between at least two neighboring nodes.

8. The method of claim 7, wherein a shift considers a second half of the vector first, and further wherein a first half of the vector is considered during the processing the shifted average vector step.

9. The method of claim 7, further comprising operating the receiving node to:

compute a relative speed between the at least two neighboring nodes from the Doppler frequency shift.