Method and apparatus for performing mobile assisted hard handoff between communication systems

• US 6,810,254 B2
• Filed: 09/04/2001
• Issued: 10/26/2004
• Est. Priority Date: 01/15/1997
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr., Wheatley, Charles E. III, Chen, Tao
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US09/946,910
• Publication Number:
  US 20020032034A1
• Time in Patent Office: 1,148 Days
• Field of Search: 455/436, 455/437, 455/438, 455/439, 455/442, 455/525, 455/552.1, 455/553.1
• US Class Current: 455/437
• CPC Class Codes: H04W 36/0061 of neighbour cell information
• CPC Class Codes: H04W 36/0066 of control information between different types of networks in order to establish a new radio link in the target network
• CPC Class Codes: H04W 36/0079 in case of hand-off failure or rejection
• CPC Class Codes: H04W 36/0094 Definition of hand-off measurement parameters
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method and apparatus for performing inter-system hard handoff between communication systems or inter-frequency hard handoff within a CDMA communication system is disclosed. The purpose is to reduce the probability of dropped calls during inter-system hard handoff. In the event that a hard handoff attempt is unsuccessful, the mobile station will return to the original system with information which the communication system of the present invention uses to assist in the performance of future handoff attempts. Alternatively, with no handoff attempt made, the mobile station monitors the destination system then returns to the original system with information used to assist in subsequent handoff attempts. The information returned from monitoring a CDMA system consists of results of a search for one or more pilots given at offsets in a specific list provided to the mobile station by the base station or a set of offsets based upon a predetermined search algorithm.

Claims

1. A method of providing handoff of a mobile station from an origination system operating at a first frequency to a destination system operating at a second frequency, the method comprising:

receiving from the origination system a first message directing the mobile station to perform a hard handoff to the destination system;

tuning, at the mobile station, to the second frequency;

measuring, at the mobile station, a total received pilot energy received at said second frequency; and

sending at said first frequency from the mobile station to the origination system a second message based on the total received pilot energy.

2. The method of claim 1 further comprising receiving from the origination system a set of parameters comprising instructions to the mobile station in the event of a failed hard handoff attempt.

3. The method of claim 1 wherein said second message further comprises measurements from a search performed at the second frequency.

4. A method of providing handoff of a mobile station from an origination system operating at a first frequency to a destination system operating at a second frequency, the method comprising:

receiving from the origination system a first message directing the mobile station to perform a hard handoff to the destination system;

tuning, at the mobile station, to the second frequency;

measuring, at the mobile station, a total received power received at said second frequency; and

sending at said first frequency from the mobile station to the origination system a second message based on the total received power.

5. The method of claim 4 further comprising receiving from the origination system a set of additional parameters comprising instructions to the mobile station in the event of a failed hard handoff attempt.

6. The method of claim 4 wherein said second message further comprises measurements from a search performed at the second frequency.

7. A computer readable medium containing computer-executable instructions embodying a method of providing handoff of a mobile station from an origination system operating at a first frequency to a destination system operating at a second frequency, comprising:

receiving from the origination system at least one PN offset associated with the destination system and a minimum total received pilot value;

tuning, at the mobile station, to the second frequency;

determining a pilot energy associated with the at least one PN offset received at the mobile station;

comparing the determined pilot energy with the minimum total received pilot value; and

sending, from the mobile station to the origination system, a message based on said comparing.

8. The computer readable medium of claim 7 wherein said message comprises said determined pilot energy.

9. The computer readable medium of claim 7 wherein said receiving further comprises receiving from the origination system a set of parameters comprising instructions to the mobile station following a failed hard handoff attempt.

10. The computer readable medium of claim 9 wherein said sending is based on said instructions.

11. The computer readable medium of claim 7 further comprising performing a search at the second frequency based on said comparing.

12. The computer readable medium of claim 11 wherein said performing a search is based on said instructions.

13. A computer readable medium containing computer-executable instructions embodying a method of providing handoff of a mobile station from an origination system operating at a first frequency to a destination system operating at a second frequency, comprising:

receiving from the origination system at least one PN offset associated with the destination system and a received power threshold;

tuning, at the mobile station, to the second frequency;

determining a pilot energy associated with the at least one PN offset received at the mobile station;

measuring in-band energy received by the mobile station at the second frequency;

comparing the measured in-band energy with the received power threshold; and

sending, from the mobile station to the origination system, a message based on said comparing.

14. The computer readable medium of claim 13 wherein said message comprises said measured in-band energy.

15. The computer readable medium of claim 13 wherein said receiving further comprises receiving from the origination system a set of additional parameters comprising instructions to the mobile station following a failed hard handoff attempt.

16. The computer readable medium of claim 15 wherein said sending is based on said instructions.

17. The computer readable medium of claim 13 further comprising performing a search at the second frequency based on said comparing.

18. The computer readable medium of claim 17 wherein said performing a search is based on said instructions.

19. A computer readable medium containing computer-executable instructions embodying a method of providing handoff of a mobile station from an origination system operating at a first frequency to a destination system operating at a second frequency, comprising:

sending from the origination system to the mobile station at least one PN offset associated with the destination system and a minimum total received pilot value;

sending from the origination system to the mobile station a message directing the mobile station to perform a hard handoff to the destination system;

receiving at the origination system from the mobile station a message based on a total received pilot value measured by the mobile station at the second frequency; and

sending to the mobile station at least one adjusted PN offset having a different value than said at least one PN offset based on said message.

20. The computer readable medium of claim 19 wherein said sending to the mobile station further comprises sending to the mobile station a set of additional parameters comprising instructions to the mobile station following a failed hard handoff attempt.

21. The computer readable medium of claim 19 wherein said message further comprises measurements from a search performed at the second frequency.

22. A computer readable medium containing computer-executable instructions embodying a method of providing handoff of a mobile station from an origination system operating at a first frequency to a destination system operating at a second frequency, comprising:

sending from the origination system to the mobile station at least one PN offset associated with the destination system and a received power threshold;

sending from the origination system to the mobile station a message directing the mobile station to perform a hard handoff to the destination system;

receiving at the origination system from the mobile station a message based on a received power measured by the mobile station at the second frequency; and

sending to the mobile station at least one adjusted PN offset having a different value than said at least one PN offset based on said message.

23. The computer readable medium of claim 22 wherein said sending to the mobile station further comprises sending to the mobile station a set of additional parameters comprising instructions to the mobile station following a failed hard handoff attempt.

24. The computer readable medium of claim 22 wherein said message further comprises measurements from a search performed at the second frequency.

25. A digital signal processing apparatus for performing handoff from an origination system operating at a first frequency to a destination system operating at a second frequency, comprising:

memory; and

a digital signal processing unit communicatively coupled to said memory, the digital signal processor capable of executing instructions and data to perform the handoff by;

receiving from the origination system a first message directing the mobile station to perform a hard handoff to the destination system;

tuning, at the mobile station, to the second frequency;

measuring, at the mobile station, a total received power received at said second frequency; and

sending at said first frequency from the mobile station to the origination system a second message based on the total received power.

26. A digital signal processing apparatus for performing handoff from an origination system operating at a first frequency to a destination system operating at a second frequency, comprising:

memory; and

a digital signal processing unit communicatively coupled to said memory, the digital signal processor capable of executing instructions and data to perform the handoff by;

receiving from the origination system at least one PN offset associated with the destination system and a minimum total received pilot value;

tuning, at the mobile station, to the second frequency;

determining a pilot energy associated with the at least one PN offset received at the mobile station;

comparing the determined pilot energy with the minimum total received pilot value; and

sending, from the mobile station to the origination system, a message based on said comparing.

27. A mobile station apparatus for performing handoff from an origination system operating at a first frequency to a destination system operating at a second frequency, the mobile station apparatus comprising:

means for receiving from the origination system at least one PN offset associated with the destination system and a minimum total received pilot value;

means for tuning, at the mobile station, to the second frequency;

means for determining a pilot energy associated with the at least one PN offset received at the mobile station;

means for comparing the determined pilot energy with the minimum total received pilot value; and

means for sending a message to the origination system based on said comparing.

28. A mobile station apparatus for performing handoff from an origination system operating at a first frequency to a destination system operating at a second frequency, the mobile station apparatus comprising:

means for receiving from the origination system at least one PN offset associated with the destination system and a received power threshold;

means for tuning, at the mobile station, to the second frequency;

means for determining a pilot energy associated with the at least one PN offset received at the mobile station;

means for measuring in-band energy received by the mobile station at the second frequency;

means for comparing the measured in-band energy with the received power threshold; and

means for sending a message based on said comparing to the origination system at the first frequency.

29. A communication system apparatus comprising:

means for sending at a first frequency to a mobile station a minimum total received pilot value and at least one PN offset associated with a destination system operating at a second frequency;

means for receiving from the mobile station a message based on a total received pilot value measured by the mobile station at the second frequency; and

means for sending to the mobile station at least one adjusted PN offset having a different value than said at least one PN offset based on said message.

30. A communication system apparatus comprising:

method of providing handoff of a mobile station from an origination system operating at a first frequency to a destination system operating at a second frequency, comprising;

means for sending at a first frequency to a mobile station a received power threshold and at least one PN offset associated with a destination system operating at a second frequency;

means for receiving from the mobile station a message based on a received power measured by the mobile station at the second frequency; and

means for sending to the mobile station at least one adjusted PN offset having a different value than said at least one PN offset based on said message.