US 6,185,429 B2Granted

Method and apparatus for performing a time synchronization of a base site

AssigneeMotorola, Inc.

InventorsJames K. Gehrke, Timothy J. Groch, Steven P. Shipton, Mark G. Spiotta

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Abstract

An unsynchronized base site (104) transmits a time synchronization request to a communication unit (110). A time synchronization error, or a timing offset, for the unsynchronized base site (104) is then determined and transmitted back to the unsynchronized base site (104) to enable the unsynchronized base site to synchronize itself. The time synchronization error is determined for the unsynchronized base site (104) based on the time difference of arrival of the signals received by the communication unit (110) from the base site (104) and at least one synchronized base site (101), the location of the communication unit (110), the location of the base site (104), and the location of the at least one synchronized base site (101).

Claims13

Dependent claims

A communication system comprising:

a base site that transmits a time synchronization calibration request;
a communication unit including:
a receiver to receive the time synchronization calibration request;
and
a transmitter to transmit time difference of arrival information to a controller;
at least a second base site to transmit a radio frequency signal to the communication unit and to receive a radio frequency signal from the communication unit;
a location-determining device to determine a location of the base site and a location of the at least a second base site;
and
a controller to determine the location of the communication unit and to calculate time synchronization error for the base site, wherein the controller calculates the time synchronization error according to the following equations:
Expected TDOA12−(D1−D2)/(speed of light)
Time synchronization error=Expected TDOA12−TDOA12
wherein:
D1 is a distance from the location of the communication unit to the location of the at least a second base site;
D2 is a distance from the location of the communication unit to the location of the base site;
Expected TDOA12 is an expected time difference of arrival for signals received by the communication unit from the base site and the at least a second base site;
TDOA12 is a measured time difference of arrival for signals transmitted to the communication unit by the base site and by the at cast a second base site;
and
Time synchronization error is an amount of time by which a timing reference of the base site is offset from a timing reference of the at least a second base site.

15 more elements

A method for time synchronization of a base site comprising the steps of:

receiving, by a communication unit, a time synchronization request for the base site;
receiving, by the communication unit, signals transmitted by the base site and by at least a second base site;
determining a location of the base site and a location of the at least a second base site;
determining a location of the communication unit;
determining a time difference of arrival of a signal transmitted from the base site to the communication unit and a signal transmitted from the at least a second base site to the communication unit;
determining a time synchronization error for the base site based on the time difference of arrival of the signals from the base site and the at least a second base site, the location of the communication unit, and the location of the base site, and the location of the at least a second base site;
and
providing the time synchronization error to the base site, wherein the step of determining the time synchronization error for the base site comprises the step of calculating the time synchronization error according to the following equations:
Expected TDOA12=(D1−D2)/(speed of light)
Time synchronization error=Expected TDOA12−TDOA12
wherein:
D1 is a distance from the location of the communication unit to thc location of the at least a second base site;
D2 is a distance from the location of the communication unit to the location of the base site;
Expected TDOA12 is an expected time difference of arrival for signals received by the communication unit from the base site and the at least a second base site;
TDOA12 is a measured time difference of arrival for signals transmitted to the communication unit by the base site and by the at least a second base site;
and
Time synchronization error is an amount of time by which a timing reference of the base site is offset from a timing reference of the at least a second base site.

14 more elements

Dependencies are inferred from the claim text.