Method of and apparatus for estimating a characteristic of a signal

• US 6,256,494 B1
• Filed: 11/18/1999
• Issued: 07/03/2001
• Est. Priority Date: 05/08/1999
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Lopes, Luis, Ludden, Brendan, Villier, Eric
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): CHOW, CHARLES CHIANG
• Application Number:
  US09/442,792
• Time in Patent Office: 593 Days
• Field of Search: 455/423, 455/67.4, 455/226.1, 455/500, 455/575, 455/115, 375/340, 370/335, 342/457
• US Class Current: 455/423
• CPC Class Codes: G01S 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

This invention relates to a method of estimating a characteristic of a signal such as a time of arrival or a transmitter identity in particular in a cellular communication system. Most known techniques have limited performance as they rely on limited amounts of known data. The method of the invention comprise a first step (201) of receiving the signal at a subscriber unit. In a second step (203) the subscriber unit receives assistance data from the fixed network and in a third step (205) an expected signal is derived in response to this assistance data. For GSM the assistance data can be a frame number and a BSIC permitting an entire expected SCH burst to be derived. In a fourth (207) step the signal characteristic is determined by correlation of the received signal and the expected signal. The invention is particularly applicable to location determination in a GSM communication system.

Claims

1. A method of estimating a characteristic of a first signal having at least partly a varying information content, the method comprising the steps of, in a receiver:

receiving, from a first transmitter, the first signal;

receiving, from a second transmitter remote from the first transmitter, a second signal comprising assistance data comprising compressed data having a known relationship to the information content of the first signal;

in response to the second signal, deriving an expected third signal in which said expected third signal is a replica of at least a part of the first signal;

and correlating the first signal with the expected third signal to estimate the characteristic of the first signal.

2. A method of estimating a characteristic of a signal as claimed in claim 1 wherein the characteristic estimated is a time of arrival of the signal.

3. A method of estimating a characteristic of a signal as claimed in claim 1 wherein the characteristic estimated is an identity of a transmitter transmitting the signal.

4. A method of estimating a characteristic of a signal as claimed in claim 1 used in cellular communication system.

5. A method of estimating a characteristic of a signal as claimed in claim 1 wherein the signal is transmitted from a non-serving base station and the assistance data is transmitted from a serving base station and comprise information related to the information content of the signal transmitted from the non-serving base station.

6. A method of estimating a characteristic of a signal as claimed in claim 5 wherein the cellular communication system is a GSM cellular communication system.

7. A method of estimating a characteristic of the signal as claimed in claim 6 wherein the assistance data is a frame number of a non-serving base station transmitting the signal, and the expected signal is derived in response to this frame number.

8. A method of estimating a characteristic of a signal as claimed in claim 6 wherein the assistance data includes a frame number offset between the serving base station and the non-serving base station transmitting the signal, and the frame number offset is used to derive an expected time of arrival window of the signal.

9. A method of estimating a characteristic of a signal as claimed in claim 1 wherein the signal comprises an SCH burst.

10. A method of estimating a characteristic of a signal as claimed in claim 8 further comprising the step of tracking the frame numbers of transmissions from the non-serving base station.

11. A method of estimating a characteristic of the signal as claimed in claim 6 wherein the assistance data is a Base Station Identity Code of a non-serving base station transmitting the signal and the expected signal is derived in response to this Base Station Identity Code.

12. A communication system operable to use a method of determining a characteristic of a signal in accordance with claim 1.

13. A base station operable to use a method of determining a characteristic of a signal in accordance claim 1.

14. A subscriber unit operable to use a method of determining a characteristic of a signal in accordance with claim 1.