Adaptive power efficient radio environment measurements

1. A method of operating user equipment (UE) in a cellular telecommunications system, the method comprising:

causing the UE to begin operating in a power saving state by determining that a first set of predefined criteria have been satisfied; and

causing the UE to leave the power saving state by determining that a second set of predefined criteria have been satisfied,

wherein determining that the second set of predefined criteria have been satisfied includes:

making a plurality of signal quality measurements of a signal received from a serving cell during power saving state;

determining which of the plurality of signal quality measurements represents a best one of the signal quality measurements;

determining a threshold value as a function of the best one of the signal quality measurements; and

determining that the second set of predefined criteria have been satisfied if a current signal quality measurement satisfies a predefined relationship with respect to the threshold value.

2. The method of claim 1 , wherein determining the threshold value as a function of the best one of the signal quality measurements comprises:

subtracting a signal quality measurement of a neighboring cell's signal from the best one of the signal quality measurements.

3. The method of claim 1 , comprising:

receiving a serving cell offset value from a serving cell of the UE; and

wherein determining the threshold value as a function of the best one of the signal quality measurements comprises:

adjusting the best one of the signal quality measurements by subtracting a signal quality measurement of a neighboring cell's signal from the best one of the signal quality measurements and by adding the serving cell offset value.

4. The method of claim 3 , wherein determining the threshold value as a function of the best one of the signal quality measurements comprises:

selecting the adjusted best one of the signal quality measurements if the adjusted best one of the signal quality measurement does not indicate a lower quality than a predetermined low limit value.

5. The method of claim 1 , comprising:

determining that the second set of predefined criteria have been satisfied if the current signal quality measurement satisfies a predetermined relationship with respect to a term derived from one or more telecommunication network-supplied parameters.

6. The method of claim 5 , wherein the telecommunications system is a Wideband Code Division Multiple Access (WCDMA) telecommunications system, and the term derived from the one or more telecommunication network-supplied parameters is S intrasearch +QqualMin,

wherein S intrasearch is a parameter that specifies a threshold for intra-frequency measurements, and QqualMin defines a minimum required quality level within the serving cell.

7. The method of claim 1 , wherein the plurality of signal quality measurements are a plurality of signal-to-noise ratio measurements.

8. The method of claim 1 , wherein the plurality of signal quality measurements are a plurality of received signal code power measurements.

9. The method of claim 1 , comprising:

upon entering a full measurement state from the power saving state, remaining in the full measurement state for a predefined period of time regardless of a determination that the first set of predefined criteria have been satisfied during the predefined period of time.

10. The method of claim 1 , wherein:

the power saving state comprises a first power saving state and a second power saving state, wherein fewer measurements are made during the second power saving state than in the first power saving state; and

the method comprises:

entering the first power saving state from a full measurement state; and

detecting that the first set of predefined criteria have been satisfied for a predefined period of time, and in response to said detection, causing the UE to begin operating in the second power saving state.

11. The method of claim 1 , wherein determining that the first set of predefined criteria have been satisfied includes:

making a current signal quality measurement of a signal received from the serving cell during a non-power saving state;

determining a threshold value as a function of a constant stored in the UE; and

determining that the first set of predefined criteria have been satisfied if the current signal quality measurement satisfies a predefined relationship with respect to the threshold value.

12. The method of claim 11 , wherein determining the threshold value as a function of the constant stored in the UE comprises combining the constant stored in the UE with a value supplied by the telecommunications network.

13. An apparatus for operating user equipment (UE) in a cellular telecommunications system, the apparatus comprising:

logic configured to cause the UE to begin operating in a power saving state by determining that a first set of predefined criteria have been satisfied; and

logic configured to cause the UE to leave the power saving state by determining that a second set of predefined criteria have been satisfied,

wherein determining that the second set of predefined criteria have been satisfied includes:

making a plurality of signal quality measurements of a signal received from a serving cell during power saving state;

determining which of the plurality of signal quality measurements represents a best one of the signal quality measurements;

determining a threshold value as a function of the best one of the signal quality measurements; and

determining that the second set of predefined criteria have been satisfied if a current signal quality measurement satisfies a predefined relationship with respect to the threshold value.

14. The apparatus of claim 13 , wherein determining the threshold value as a function of the best one of the signal quality measurements comprises:

subtracting a signal quality measurement of a neighboring cell's signal from the best one of the signal quality measurements.

15. The apparatus of claim 13 , comprising:

receiving a serving cell offset value from a serving cell of the UE; and

wherein determining the threshold value as a function of the best one of the signal quality measurements comprises:

adjusting the best one of the signal quality measurements by subtracting a signal quality measurement of a neighboring cell's signal from the best one of the signal quality measurements and by adding the serving cell offset value.

16. The apparatus of claim 15 , wherein determining the threshold value as a function of the best one of the signal quality measurements comprises:

selecting the adjusted best one of the signal quality measurements if the adjusted best one of the signal quality measurement does not indicate a lower quality than a predetermined low limit value.

17. The apparatus of claim 13 , wherein determining that the second set of predefined criteria have been satisfied includes:

determining that the second set of predefined criteria have been satisfied if the current signal quality measurement satisfies a predetermined relationship with respect to a term derived from one or more telecommunication network-supplied parameters.

18. The apparatus of claim 17 , wherein the telecommunications system is a Wideband Code Division Multiple Access (WCDMA) telecommunications system, and the term derived from the one or more telecommunication network-supplied parameters is S intrasearch +QqualMin,

wherein S intrasearch is a parameter that specifies a threshold for intra-frequency measurements, and QqualMin defines a minimum required quality level within the serving cell.

19. The apparatus of claim 13 , wherein the plurality of signal quality measurements are a plurality of signal-to-noise ratio measurements.

20. The apparatus of claim 13 , wherein the plurality of signal quality measurements are a plurality of received signal code power measurements.

21. The apparatus of claim 13 , comprising:

logic that, upon entering a full measurement state from the power saving state, causes the UE to remain in the full measurement state for a predefined period of time regardless of a determination that the first set of predefined criteria have been satisfied during the predefined period of time.

22. The apparatus of claim 13 , wherein:

the power saving state comprises a first power saving state and a second power saving state, wherein fewer measurements are made during the second power saving state than in the first power saving state; and

the apparatus comprises:

logic that, after entering the first power saving state from a full measurement state, detects that the first set of predefined criteria have been satisfied for a predefined period of time, and in response to said detection, causes the UE to begin operating in the second power saving state.

23. The apparatus of claim 13 , wherein determining that the first set of predefined criteria have been satisfied includes:

making a current signal quality measurement of a signal received from the serving cell during a non-power saving state;

determining a threshold value as a function of a constant stored in the UE; and

determining that the first set of predefined criteria have been satisfied if the current signal quality measurement satisfies a predefined relationship with respect to the threshold value.

24. The apparatus of claim 23 , wherein determining the threshold value as a function of the constant stored in the UE comprises combining the constant stored in the UE with a value supplied by the telecommunications network.