Method and apparatus for performing handoff in a high speed communication system

• US 7,206,580 B2
• Filed: 11/04/1999
• Issued: 04/17/2007
• Est. Priority Date: 11/04/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Black, Peter J.
• Primary Examiner(s): Urban; Edward F.
• Assistant Examiner(s): Lee; John J.
• Application Number:
  US09/434,314
• Publication Number:
  US 20030153311A1
• Time in Patent Office: 2,721 Days
• Field of Search: 455/436, 455/435, 455/437, 455/439, 455/442, 455/438, 455/522, 455/515, 455/443, 455/435.1, 455/69, 455/517, 455/67.13, 370/2.52, 370/335, 370/411, 370/331, 370/332, 370/333
• US Class Current: 455/437
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

A communication system including a closed loop power control system. Prior to allowing a handoff to a new base station, the subscriber station verifies that its reverse link signal is being received by the destination base station with sufficient energy. The determination is made based on the received reverse link power control commands from the base station. Moreover, a handoff may be forced when the base station providing the best forward link signal is not receiving the reverse link signal from the subscriber station with sufficient energy.

Claims

1. A method for performing handoff in a communication system, the method comprising:

receiving, by a subscriber station, pilot signals and reverse link power control commands from one or more base stations;

selecting a first base station for transmission of forward link data to the subscriber station based, at least in part, on energy of the pilot signals received from the one or more base stations; and

performing a handoff to the first base station if signals transmitted by the subscriber station are received by the first base station with sufficient energy based in part on history of the reverse link power control commands received from the first base station.

2. The method of claim 1 further comprising:

storing information corresponding to the reverse link power control commands received from the one or more base stations.

3. The method of claim 1 further comprising:

determining whether it is necessary to perform the handoff to the first base station; and

if it is necessary to perform the handoff and if the signals transmitted by the subscriber station are received by the first base station with sufficient energy, permitting the handoff to the first base station.

4. The method of claim 3 further comprising:

if the signals transmit by the subscriber station are not received by the first base station with sufficient energy, inhibiting the handoff to the first base station.

5. The method of claim 4 wherein the inhibiting comprises:

selecting an alternative base station for transmission of forward link data to the subscriber station.

6. The method of claim 3 further comprising:

if it is not necessary to perform the handoff, determining whether a base station currently being used for transmission of forward link data to the subscriber station receives signals from the subscriber station with sufficient energy; and

if the base station currently being used does not receive signals from the subscriber station with sufficient energy, performing a handoff to an alternative base station.

7. The method of claim 6 wherein the performing the handoff to the alternative base station comprises:

selecting the alternative base station based on reverse link power control commands received from the alternative base station indicating that signals transmitted by the subscriber station are received by the alternative base station with sufficient energy.

8. The method of claim 3 wherein the permitting the handoff to the first base station comprises:

transmitting, by the subscriber station, a message indicating identity of the first base station.

9. The method of claim 8 wherein the message further indicates a requested rate to transmit to the subscriber station.

10. An apparatus comprising:

a receiver to receive pilot signals and reverse link power control commands from one or more base stations; and

a processor to select a first base station for transmission of forward link data to a subscriber station based, at least in part, on energy of the pilot signals received from the one or more base stations and to perform a handoff to the first base station if signals transmitted by the subscriber station are received by the first base station with sufficient energy based in part on history of the reverse link power control commands received from the first base station.

11. The apparatus of claim 10 further comprising:

a memory to store information corresponding to the reverse link power control commands received from the one or more base stations.

12. The apparatus of claim 11 wherein the processor determines whether it is necessary to perform handoff to the first base station and, if it is necessary to perform handoff to the first base station, permits handoff to the first base station if the signals transmitted by the subscriber station are received by the first base station with sufficient energy.

13. The apparatus of claim 12 wherein, if the signals transmit by the subscriber station are not received by the first base station with sufficient energy, the processor inhibits the handoff to the first base station.

14. The apparatus of claim 13 wherein the processor selects an alternative base station for transmission of forward link data to the subscriber station.

15. The apparatus of claim 12 wherein, if it is not necessary to perform the handoff to the first base station, the processor determines whether a base station currently being used for transmission of forward link data to the subscriber station receives signals from the subscriber station with sufficient energy and performs a handoff to an alternative base station if the base station currently being used does not receive signals from the subscriber station with sufficient energy.

16. The apparatus of claim 15 wherein the processor selects the alternative base station based on reverse link power control commands received from the alternative base station indicating that signals transmitted by the subscriber station are received by the alternative base station with sufficient energy.

17. The apparatus of claim 12 wherein the processor transmits a message indicating identity of the first base station.

18. The apparatus of claim 17 wherein the message further indicates a requested rate to transmit to the subscriber station.

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

means for receiving, at a subscriber station, pilot signals and reverse link power control commands from one or more base stations;

means for selecting a first base station for transmission of forward link data to the subscriber station based, at least in part, on energy of the pilot signals received from the one or more base stations; and

means for performing a handoff to the first base station if signals transmitted by the subscriber station are received by the first base station with sufficient energy based in part on history of the reverse link power control commands received from the first base station.

20. The apparatus of claim 19 further comprising:

means for storing information corresponding to the reverse link power control commands received from the one or more base stations.

21. The apparatus of claim 19 further comprising:

means for determining whether it is necessary to perform the handoff to the first base station; and

means for permitting the handoff to the first base station, if it is necessary to perform the handoff and if the signals transmitted by the subscriber station are received by the first base station with sufficient energy.

22. The apparatus of claim 21 further comprising:

means for inhibiting the handoff to the first base station, if the signals transmit by the subscriber station are not received by the first base station with sufficient energy.

23. The apparatus of claim 21 further comprising:

means for determining, if it is not necessary to perform the handoff to the first base station, whether a base station currently being used for transmission of forward link data to the subscriber station receives signals from the subscriber station with sufficient energy; and

means for performing a handoff to an alternative base station, if the base station currently being used does not receive signals from the subscriber station with sufficient energy.

24. The apparatus of claim 21 wherein the means for permitting the handoff to the first base station comprises:

means for transmitting a message indicating identity of the first base station.

25. The apparatus of claim 24 wherein the message further indicates a requested rate to transmit to the subscriber station.