Time-to-Trigger Handling Methods and Apparatus

• US 20090059871A1
• Filed: 09/04/2007
• Published: 03/05/2009
• Est. Priority Date: 09/04/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Nader, Ali G., Junno, Tobias
• Granted Patent: US 8,681,736 B2
• Time in Patent Office: Days
• US Class Current: 370/337
• CPC Class Codes: H04W 36/00837 Determination of triggering parameters for hand-off
• CPC Class Codes: H04W 36/0085 Hand-off measurements
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/304 due to measured or perceived resources with higher communication quality

Abstract

Time-to-trigger (TtT) time periods are usually fixed. A better TtT parameter is adapted based on the signal quality that a receiver perceives from its surrounding area. For example, the lower the value of a first signal quality at the same time that the value of a second signal quality is greater than a trigger threshold, the shorter the TtT parameter becomes.

Claims

1. A method in a communication system of adapting a time period based on signal measurements, comprising:

obtaining a first measurement of a signal quality;

comparing the first measurement to a trigger threshold;

if the first measurement passes the trigger threshold, initiating measurement of a time period; and

adapting a length of the time period based on the first measurement of the signal quality.

2. The method of claim 1, wherein the trigger threshold comprises a plurality of different thresholds that respectively correspond to a plurality of quality scaling factors, and the adapting step comprises scaling the time period according to one of the quality scaling factors based on a comparison of the first measurement to the plurality of different thresholds.

3. The method of claim 2, wherein the length of the time period is adapted based on an amount that the first measurement passes a trigger threshold.

4. The method of claim 3, wherein the length of the time period is adapted according to:

Adapted TtT=QSF(Quality)×

(1−

TCP)×

TtT

in which Adapted TtT is an adapted length of the time period, QSF(Quality) indicates a functional dependence of a value of the quality scaling factor on signal quality, TCP is a threshold condition penetration level, and TtT is a length of the time period before adaptation.

5. The method of claim 4, wherein the TCP is normalized.

6. The method of claim 3, further comprising the step of obtaining at least one subsequent measurement of the signal quality, wherein the length of the time period is successively adapted based on an amount that the at least one subsequent measurement passes a trigger threshold.

7. The method of claim 6, wherein the length of the time period is adapted a plurality of times.

8. The method of claim 7, wherein adapting the length of the time period a plurality of time includes:

determining whether a current adapted length of the time period is the same as a previous adapted length of the time period;

if the current adapted length is not the same as the previous adapted length and if the previous adapted time period has not yet elapsed, deducting a time period that has already elapsed from the current adapted time period; and

if the current adapted length is not the same as the previous adapted length and if the previous adapted time period has elapsed, triggering an event corresponding to the time period.

9. An apparatus in a receiver for adapting a time period based on received signal measurements, comprising:

a processor for obtaining a first measurement of a signal quality;

for comparing the first measurement to a trigger threshold;

if the first measurement passes the trigger threshold, for initiating measurement of a time period; and

for adapting a length of the time period based on the first measurement of the signal quality.

10. The apparatus of claim 9, wherein the first measurement is a measurement of signal to interference ratio, received signal code power, or block error rate.

11. The apparatus of claim 9, wherein the trigger threshold comprises a plurality of different thresholds that respectively correspond to a plurality of quality scaling factors, and the adapting step comprises scaling the time period according to one of the quality scaling factors based on a comparison of the first measurement to the plurality of different thresholds.

12. The apparatus of claim 11, wherein the processor adapts the length of the time period based on an amount that the first measurement passes a trigger threshold.

13. The apparatus of claim 12, wherein the processor adapts the length of the time period according to:

Adapted TtT=QSF(Quality)×

(1−

TCP)×

TtT

in which Adapted TtT is an adapted length of the time period, QSF(Quality) indicates a functional dependence of a value of the quality scaling factor on signal quality, TCP is a threshold condition penetration level, and TtT is a length of the time period before adaptation.

14. The apparatus of claim 12, wherein the processor obtains at least one subsequent measurement of the signal quality, and successively adapts the length of the time period based on an amount that the at least one subsequent measurement passes a trigger threshold.

15. The apparatus of claim 14, wherein the processor adapts the length of the time period a plurality of times.

16. The apparatus of claim 15, wherein the processor adapts the length of the time period a plurality of time by at least determining whether a current adapted length of the time period is the same as a previous adapted length of the time period;

if the current adapted length is not the same as the previous adapted length and if the previous adapted time period has not yet elapsed, deducting a time period that has already elapsed from the current adapted time period; and

if the current adapted length is not the same as the previous adapted length and if the previous adapted time period has elapsed, triggering an event corresponding to the time period.

17. A computer-readable medium encoded with a computer program for adapting a time period based on signal measurements by a receiver, wherein the computer program when executed causes the computer to perform at least the steps of:

obtaining a first measurement of a signal quality;

comparing the first measurement to a trigger threshold;

if the first measurement passes the trigger threshold, initiating measurement of a time period; and

adapting a length of the time period based on the first measurement of the signal quality.

18. The computer-readable medium of claim 17, wherein the trigger threshold comprises a plurality of different thresholds that respectively correspond to a plurality of quality scaling factors, and the adapting step comprises scaling the time period according to one of the quality scaling factors based on a comparison of the first measurement to the plurality of different thresholds.

19. The computer-readable medium of claim 18, wherein the length of the time period is adapted based on an amount that the first measurement passes a trigger threshold.

20. The computer-readable medium of claim 19, wherein the length of the time period is adapted according to:

Adapted TtT=QSF(Quality)×

(1−

TCP)×

TtT

in which Adapted TtT is an adapted length of the time period, QSF(Quality) indicates a functional dependence of a value of the quality scaling factor on signal quality, TCP is a threshold condition penetration level, and TtT is a length of the time period before adaptation.

21. The computer-readable medium of claim 20, wherein the computer program when executed causes the computer to perform at least the further step of obtaining a plurality of subsequent measurements of the signal quality;

the length of the time period is successively adapted a plurality of times based on respective amounts that the subsequent measurements pass a trigger threshold; and

adapting the length of the time period a plurality of time includes;

determining whether a current adapted length of the time period is the same as a previous adapted length of the time period;

if the current adapted length is not the same as the previous adapted length and if the previous adapted time period has not yet elapsed, deducting a time period that has already elapsed from the current adapted time period; and

if the current adapted length is not the same as the previous adapted length and if the previous adapted time period has elapsed, triggering an event corresponding to the time period.