Method and apparatus for providing reference frequency aiding among peers operating in a direct communication mode

• US 20070026792A1
• Filed: 07/29/2005
• Published: 02/01/2007
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Korneluk, Jose, Segerson, Charles, Haverkamp, Kristi, Klug, Keith, Anderson, Bobby
• Granted Patent: US 7,620,403 B2
• Time in Patent Office: Days
• US Class Current: 455/10
• CPC Class Codes: G01S 19/03 Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: H04B 17/403 generated by local oscillators
• 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 92/18 between terminal devices

Abstract

A mobile communication device (202) and peer mobile communication devices (204, 206) are capable of direct voice and data communication. The mobile communication device has a reference oscillator (104) which is used for generating operating frequencies, and is subject to frequency errors resulting from manufacturing tolerances, heat, and other error sources. The mobile communication device receives a frequency correction message (506) from a peer mobile communication device that has calibrated its reference oscillator. The frequency correction message contain offset information which is used by the mobile communication device to determine its offset (316) from a nominal frequency (302).

Claims

1. A method of acquiring a positioning signal from a global positioning satellite at a positioning receiver of an uncorrected mobile communication device, comprising:

detecting a signal transmitted by a corrected mobile communication device, the signal being at an uncorrected nominal frequency of the corrected mobile communication device, the uncorrected nominal frequency being offset from a nominal frequency due to a frequency error of the corrected mobile communication device, the detecting performed by the uncorrected mobile communication device;

tuning a communications transceiver of the uncorrected mobile communication device to the uncorrected nominal frequency of the corrected mobile communication device from an uncorrected nominal frequency of the uncorrected mobile communication device;

determining a tuning offset between the uncorrected nominal frequency of the uncorrected mobile communication device and the uncorrected nominal frequency of the corrected mobile communication device, determining the tuning offset performed at the uncorrected mobile communication device;

receiving a frequency correction message at the uncorrected mobile communication device from the corrected mobile communication device at the uncorrected nominal frequency of the corrected mobile communication device, the frequency correction message including reference oscillator offset information of the corrected mobile communication device;

extracting the reference oscillator offset information of the corrected mobile communication device from the frequency correction message at the uncorrected mobile communication device;

comparing the reference oscillator offset information of the corrected mobile communication device and the tuning offset to determine a reference offset of a reference oscillator of the uncorrected mobile communication device from the nominal frequency;

providing the reference offset of the reference oscillator of the uncorrected mobile communication device to the positioning receiver of the uncorrected mobile communication device, the positioning receiver sharing the reference oscillator with the communication receiver; and

adjusting a positioning receiver tuning in response to the reference offset to receive the positioning signal.

2. The method of claim 1, further comprising, prior to detecting the frequency correction message transmitted by the corrected mobile communication device, broadcasting a frequency assistance message from the communication transceiver of the uncorrected mobile communication device.

3. The method of claim 1, wherein tuning the communications transceiver of the uncorrected mobile communication device to the uncorrected nominal frequency of the corrected mobile communication device comprises adjusting a frequency synthesizer of the communication transceiver so that an output frequency of the frequency synthesizer used to down-mix a signal received at the communications transceiver is equal to the uncorrected nominal frequency of the corrected mobile communication device.

4. The method of claim 3, wherein adjusting the frequency synthesizer of the communication receiver comprises adjusting the value of a digital control word latched by the frequency synthesizer, wherein the digital control word is used to control the output frequency of the frequency synthesizer.

5. The method of claim 4, wherein determining the tuning offset comprises determining the difference between the digital control word latched by the frequency synthesizer when the output frequency is equal to the uncorrected nominal frequency of the corrected mobile communication device and a nominal control word corresponding to the uncorrected nominal frequency of the uncorrected mobile communication device.

6. The method of claim 1, wherein detecting the signal transmitted by a corrected mobile communication device comprises:

tuning the communications transceiver to the uncorrected nominal frequency of the uncorrected mobile communication device;

sweeping the tuning of the communication transceiver in a band around the uncorrected nominal frequency of the uncorrected mobile communication device; and

detecting an initial signal at the uncorrected nominal frequency of the corrected mobile communication device.

7. A mobile communication device, comprising;

a communications transceiver operable in a direct communication mode to communicate with a peer mobile communication device, and including a frequency synthesizer;

a positioning receiver for receiving satellite positioning signals and determining a position of the mobile communication device;

a reference oscillator for providing a reference frequency to the communications transceiver and the positioning receiver;

wherein the mobile communication device receives a frequency correction message from the peer mobile communication device which allows the mobile communication device to determine a reference frequency offset of the reference oscillator; and

wherein the reference frequency offset is used by the positioning receiver to compensate for the reference frequency offset in performing a location fix.

8. A mobile communication device as defined in claim 7, wherein the communications transceiver is further operable in a network communication mode to communicate with a fixed equipment network of a communication system.

9. A mobile communication device as defined in claim 8, wherein the communications transceiver is further operable in network mode.

10. A method of determining a frequency offset of a reference oscillator of a mobile communication device, comprising:

tuning a communications transceiver of the mobile communication device to an uncorrected nominal frequency;

searching for a signal from a peer mobile communication device in a frequency band around the uncorrected nominal frequency;

detecting the signal at an offset frequency receiving a frequency correction message from the peer mobile communication device at the offset frequency, the offset frequency being offset from a nominal frequency, frequency correction message including offset information quantifying the offset from the nominal frequency to the first frequency; and

determining a difference between the uncorrected nominal frequency and the nominal frequency using the offset information of the frequency correction message.

11. A method of determining a frequency offset as defined in claim 10, further comprising broadcasting a frequency correction request message from the mobile communication device prior to receiving the frequency correction message from the peer mobile communication device.

12. A method of determining a frequency offset as defined in claim 10, wherein tuning the communications transceiver to the offset frequency comprises adjusting a frequency synthesizer of the communication transceiver so that an output frequency of the frequency synthesizer used to down-mix a signal received at the communications transceiver is equal to the offset frequency of the corrected mobile communication device.

13. A method of determining a frequency offset as defined in claim 12, wherein adjusting the frequency synthesizer of the communication receiver comprises adjusting the value of a digital control word latched by the frequency synthesizer, wherein the digital control word is used to control the output frequency of the frequency synthesizer.

14. A method of determining a frequency offset as defined in claim 13, wherein determining the difference between the uncorrected nominal frequency and the nominal frequency comprises determining the difference between the digital control word latched by the frequency synthesizer when the output frequency is equal to the offset frequency and a nominal control word corresponding to the uncorrected nominal frequency of the mobile communication device.

15. A method of determining a frequency offset as defined in claim 10, wherein searching for the signal comprises:

tuning the communications transceiver to the uncorrected nominal frequency;

sweeping the tuning of the communication transceiver in a band around the uncorrected nominal frequency; and

detecting an initial signal at the offset frequency of the corrected mobile communication device.