Method and apparatus for performing handoff in a spread-spectrum communication system

• US 6,449,305 B1
• Filed: 05/10/1996
• Issued: 09/10/2002
• Est. Priority Date: 05/10/1996
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Menich, Barry J., Fernandez, Samuel D., Aldrich, James P.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US08/644,465
• Time in Patent Office: 2,314 Days
• Field of Search: 375/200, 375/205, 375/371, 375/316, 375/130, 375/141, 375/146, 375/147, 379/60, 455/33.2, 455/51.1, 455/67.6, 455/456, 455/436-444, 370/331, 370/332, 370/335
• US Class Current: 375/141
• CPC Class Codes: H04W 36/0085 Hand-off measurements
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others

Abstract

Handoff from a Code-Division, Multiple Access (CDMA) protocol to an Advanced Mobile Phone Service (AMPS) protocol occurs by comparing a remote unit'"'"'s (405) phase shift measurement to a threshold (503) and determining a reference CDMA base station (401) from an active set of CDMA base stations (515). Next, corrected phase shifts are calculated for each CDMA base station in the active set (521) and the remote unit (405) is handed off to an AMPS base station (109) underlying the CDMA coverage area (126) having the smallest corrected phase shift (525).

Claims

1. A method for performing handoff in a spread-spectrum communication system, the method comprising the steps of:

measuring a time between a base station'"'"'s transmitted signal and a corresponding received signal transmitted from a remote unit to produce a measured phase shift;

comparing the measured phase shift to a threshold to produce a comparison;

correcting the measured phase shift to produce a corrected phase shift, wherein the step of correcting comprises adjusting the measured phase shift based on a time between a second base station'"'"'s transmitted signal and a corresponding signal received at the second base station; and

handing off the remote unit based on the corrected phase shift and the comparison.

2. The method of claim 1 wherein the step of correcting the measured phase shift comprises the steps of:

determining a reference base station to produce a determined reference base station; and

determining a corrected phase shift based on the measured phase shift and the determined reference base station.

3. The method of claim 1 wherein the step of handing off the remote unit comprises the steps of:

determining a smallest corrected phase shift measurement; and

handing off the remote unit to a first base station having a first coverage area, said first coverage area related to a second coverage area of a second base station, said second base station having the smallest corrected phase shift measurement.

4. The method of claim 1 further comprising the steps of:

determining if a non-border base station is part of an active set to produce a determination; and

handing off a remote unit based on the determination, the corrected phase shift, and the comparison.

5. The method of claim 1 wherein the spread-spectrum communication system is a code-division, multiple-access (CDMA) communication system.

6. The method of claim 1 wherein the step of handing off the remote unit comprises the step of handing off the remote unit from a Code-Division, Multiple-Access (CDMA) protocol to an Advanced Mobile Phone Service (AMPS) protocol.

7. A method for handoff in a spread-spectrum communication system, the method comprising the steps of:

communicating between a first base station and a remote unit on a first frequency;

measuring a time between a base station'"'"'s transmitted signal and a corresponding received signal transmitted from a remote unit to produce a measured phase shift;

comparing the phase shift to a threshold to produce a comparison; and

communicating between the first base station and the remote unit on a second frequency said step of communicating based on the comparison.

8. The method of claim 7 wherein the step of measuring a phase shift comprises the step of measuring a corrected phase shift.

9. The method of claim 8 wherein the step of measuring a corrected phase shift comprises the steps of:

determining a reference base station to produce a determined reference base station; and

determining a corrected phase shift based on the measured phase shift and the determined reference base station.

10. The method of claim 7 wherein the spread-spectrum communication system is a code-division, multiple-access (CDMA) communication system.

11. A method of handoff in a Code-Division, Multiple-Access (CDMA) communication system, the method comprising the steps of:

communicating with a plurality of base stations;

measuring a plurality of times between the plurality of base station'"'"'s transmitted signals and corresponding received signals transmitted from a remote unit to produce a plurality of phase shift measurements;

determining if a base station existing within the plurality of base stations is a non-border base station, to produce a base station determination;

comparing the plurality of phase shift measurements to a plurality of thresholds to produce a comparison;

correcting the plurality of phase shift measurements to produce a plurality of corrected phase shift measurements wherein the step of correcting comprises adjusting the plurality of phase shift measurements based on a time between a second base station'"'"'s transmitted signal and a corresponding signal received at the second base station; and

handing off a remote unit based on the plurality of corrected phase shift measurements, the comparison, and the base station determination.

12. The method of claim 11 wherein the step of correcting the plurality of phase shift measurements comprises the steps of:

determining a reference base station to produce a determined reference base station; and

determining a plurality of corrected phase shifts based on the determined reference base station and the plurality of phase shift measurements.

13. The method of claim 11 wherein the step of handing off the remote unit comprises the step of handing off the remote unit from a Code-Division, Multiple-Access (CDMA) protocol to an Advanced Mobile Phone Service (AMPS) protocol.

14. An apparatus performing handoff in a communication system, the apparatus comprising:

means for measuring an uncorrected phase shift of a remote unit to produce a measured phase shift, wherein the uncorrected phase shift is based on a time between a base station'"'"'s transmitted signal and a corresponding signal received at the base station;

means, coupled to means for measuring, for comparing the measured phase shift to a threshold to produce a comparison;

means, coupled to means for comparing, for correcting the measured phase shift to produce a corrected phase shift, wherein the corrected phase shift is based on adjusting the uncorrected phase shift based on a time between a second base station'"'"'s transmitted signal and a corresponding signal received at the second base station; and

means, coupled to means for correcting, for handing off the remote unit based on the corrected phase shift and the comparison.

15. The apparatus of claim 14 wherein the spread-spectrum communication system is a code-division, multiple-access (CDMA) communication system.

16. The apparatus of claim 14 wherein the means for handing off the remote unit comprises means for of handing off the remote unit from a Code-Division, Multiple-Access (CDMA) protocol to an Advanced Mobile Phone Service (AMPS) protocol.