Declaring radio link failure based on target-specific threshold

Patent metadata

Field	Value
Publication number	US-9521565-B2
Application number	US-61810509-A
Country	US
Kind code	B2
Filing date	Nov 13, 2009
Priority date	Nov 17, 2008
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

Abstract

The number of handover-related failures that occur in a communication system may be reduced by taking target access point conditions into account when declaring radio link failure and/or by delaying certain handover operations. In some aspects, criteria for radio link failure detection and access terminal-controlled mobility may take into account access point parameters related to neighboring cells that may be available as mobility targets. For example, filtering mechanisms for detecting radio link failure based on radio layer problem reports may also take into account the availability of various neighbor access points and their measured signal strengths. In addition, a handover command may be sent earlier than in conventional systems (e.g., the handover command may be sent even though the target access point is weaker than the source access point) and include an indication that instructs the access terminal to delay handover until a specified condition is met. For example, handover may be delayed until the target access point becomes stronger than the source access point.

First claim

What is claimed is:

1. A method of communication, comprising:
receiving, at an access terminal, a non-serving access point signal condition threshold for declaring, based on a measured quantity of at least one signal of at least one non-serving access point, radio link failure of a first radio link between the access terminal and a serving access point;
receiving the at least one signal from the at least one non-serving access point; and
initiating, by the access terminal, a radio link failure based mobility procedure based on the non-serving access point signal condition threshold and the received at least one signal, wherein the radio link failure based mobility procedure comprises declaring radio link failure of the first radio link and transmitting a radio resource control (RRC) connection reestablishment request to one of the at least one non-serving access points.

2. The method of claim 1 , wherein the initiating the radio link failure based mobility procedure comprises initiating the radio link failure based mobility procedure based on the non-serving access point signal condition threshold and the received at least one signal irrespective of a signal condition of the serving access point.

3. The method of claim 2 , wherein the radio link failure based mobility procedure is autonomously initiated by the access terminal such that the radio link failure based mobility procedure is not triggered by a command from a serving access point of the access terminal.

4. The method of claim 1 , wherein the initiating a radio link failure based mobility procedure comprises using the non-serving access point signal condition threshold and the received at least one signal in conjunction with filtering of at least one radio layer problem indication to determine whether to declare radio link failure.

5. The method of claim 1 , wherein:
the non-serving access point signal condition threshold comprises a signal strength threshold; and
the initiating a radio link failure based mobility procedure comprises comparing a received signal strength of the received at least one signal with the non-serving access point signal condition threshold.

6. The method of claim 1 , wherein:
the non-serving access point signal condition threshold comprises a relative measured quantity threshold; and
the initiating a radio link failure based mobility procedure comprises determining a relative measured quantity based on a measured quantity associated with the received at least one signal and a measured quantity associated with the first radio link, and comparing the relative measured quantity with the non-serving access point signal condition threshold.

7. The method of claim 1 , wherein:
the non-serving access point signal condition threshold comprises a relative received signal strength threshold; and
the initiating a radio link failure based mobility procedure comprises determining a relative received signal strength value based on a received signal strength of the received at least one signal and a received signal strength of the first radio link, and comparing the relative received signal strength value with the non-serving access point signal condition threshold.

8. The method of claim 1 , wherein:
the non-serving access point signal condition threshold comprises a time threshold; and
the initiating a radio link failure based mobility procedure comprises determining a duration of time that a signal received from a serving access point satisfies a condition, and comparing the duration of time with the non-serving access point signal condition threshold.

9. The method of claim 1 , wherein the non-serving access point signal condition threshold is based on whether the at least one non-serving access point has been prepared for mobility of the access terminal.

10. The method of claim 1 , further comprising sending a message to the serving access point, wherein the message is indicative of the radio link failure condition being declared.

11. The method of claim 1 , further comprising:
receiving other signal condition thresholds for declaring radio link failure, wherein the other signal condition thresholds are associated with other access points;
receiving other signals from the other access points; and
determining whether to declare radio link failure based on the other signal condition thresholds and the received other signals.

12. The method of claim 1 , wherein the at least one non-serving access point comprises one or more of a femto cell or a pico cell.

13. The method of claim 1 , wherein the non-serving access point signal condition threshold is based on whether the at least one non-serving access point is able to fetch context information associated with the access terminal from the serving access point.

14. An apparatus for communication, comprising:
a radio link failure controller configured to receive a non-serving access point signal condition threshold for declaring, based on a measured quantity of at least one signal of at least one non-serving access point, radio link failure of a first radio link between an access terminal and a serving access point; and
a communication controller configured to receive the at least one signal from the at least one non-serving access point, wherein the radio link failure controller is further configured to initiate a radio link failure based mobility procedure based on the non-serving access point signal condition threshold and the received at least one signal, wherein the radio link failure based mobility procedure comprises declaring radio link failure of the first radio link and transmitting a radio resource control (RRC) connection reestablishment request to one of the at least one non-serving access points.

15. The apparatus of claim 14 , wherein the communication controller is configured to initiate the radio link failure based mobility procedure based on the non-serving access point signal condition threshold and the received at least one signal irrespective of a signal condition of the serving access point.

16. The apparatus of claim 14 , wherein the radio link failure controller is configured to use the non-serving access point signal condition threshold and the received at least one signal in conjunction with filtering of at least one radio layer problem indication to determine whether to initiate the radio link failure based mobility procedure.

17. The apparatus of claim 14 , wherein:
the non-serving access point signal condition threshold comprises a signal strength threshold; and
the radio link failure controller is further configured to initiate the radio link failure based mobility procedure based on comparing a received signal strength of the received at least one signal with the non-serving access point signal condition threshold.

18. The apparatus of claim 14 , wherein:
the non-serving access point signal condition threshold comprises a relative received signal strength threshold; and
the radio link failure controller is configured to determine the relative received signal strength value based on a received signal strength of the received at least one signal and a received signal strength of the first radio link, and comparing the relative received signal strength value with the non-serving access point signal condition threshold.

19. The apparatus of claim 14 , wherein the non-serving access point signal condition threshold is based on at least whether the at least one non-serving access point has been prepared for mobility of the access terminal.

20. The apparat

Assignees

• Tenny Nathan E
• Agashe Parag A
• Prakash Rajat
• Qualcomm Inc

Inventors

• Tenny Nathan E
• Agashe Parag A
• Prakash Rajat

Classifications

• H04W36/0085

  Hand-off measurements · CPC title

• H04W36/362

  Conditional handover · CPC title

• H04W36/305 Primary

  Handover due to radio link failure (control signalling for hand-off failure H04W36/0079) · CPC title

• H04W36/36

  by user or terminal equipment · CPC title

• H04W24/08 Primary

  Testing, {supervising or monitoring} using real traffic · CPC title