Apparatus, and associated method, for adaptively selecting a handoff threshold in a radio communication system

• US 6,745,034 B2
• Filed: 12/22/2000
• Issued: 06/01/2004
• Est. Priority Date: 12/22/2000
• Status: Expired due to Fees

• Current Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Green, Marilynn, Wang, Shu-Shaw
• Primary Examiner(s): Gary, Erika
• Assistant Examiner(s): BEAMER, TEMICA M
• Application Number:
  US09/746,129
• Publication Number:
  US 20020082012A1
• Time in Patent Office: 1,257 Days
• Field of Search: 455/436, 455/437, 455/438, 455/439, 455/440, 455/441, 455/456.1, 455/67.11, 455/226.1, 455/226.2, 370/331, 370/332, 370/333, 370/334
• US Class Current: 455/441
• CPC Class Codes: H04W 36/32 by location or mobility data, e.g. speed data
• CPC Class Codes: H04W 36/322 by location data

Abstract

Apparatus, and an associated method, dynamically selects values of thresholds to be used in a determination of whether to request a handoff of communications between serving and target base stations of a cellular, or other, radio communication system. Because the thresholds are dynamically determined, the thresholds are selectable responsive to communication characteristics about the mobile stations with which communications are to be handed off.

Claims

1. In a radio communication system in which a mobile station is operable to communicate with a serving fixed-site communication station and to communicate with a target fixed-site communication station subsequent to effectuation of a communication hand-off thereto, an improvement of apparatus for facilitating selection of when to initiate the effectuation of the communication hand-off, said apparatus comprising:

a movement determiner coupled to receive indications of differences between signal indicia associated with signals generated by the serving fixed-site communication station, signal indicia associated with signals generated by the target fixed-site communication station, said movement determiner selectably operable at least when the indications of the differences are beyond a first threshold set to determine movement indicia associated with the mobile station, the first threshold set formed of a first upper bound value and a first lower bound value;

a second threshold set calculator coupled to receive indications of the movement indicia determined by said movement determiner, the movement indicia determined by said movement determiner when the indications of the differences are beyond the first threshold set, said second threshold set calculator for calculating second threshold set values when the movement indicia indicates selected movement of the mobile station, the second threshold set values formed of a second upper bound value and a second lower bound value;

a second-threshold-set comparator coupled to receive indications of the second threshold set values and indications of the differences between the signal indicia associated with the signals generated by the serving and the target fixed-site transceivers, respectively, said second-threshold-set comparator for comparing the differences between the signal indicia and the second threshold set values, said second-threshold-set comparator selectably operable at least when the indications of the differences are beyond the first threshold set; and

a handoff request selector coupled to said second-threshold set comparator, said handoff request selector for selectably requesting handoff of communications to the target fixed-site communication station responsive to comparisons made by said second-threshold-set comparator.

2. The apparatus of claim 1 further comprising a first-threshold-set comparator coupled to receive indications of the signal indicia associated with the signals generated by the serving fixed-site communication station and the signal indicia associated with the signals generated by the target fixed-site communication station, said first-threshold-set comparator for comparing values of the signals generated by the serving and target fixed-site communication stations and for indicating results of comparisons made thereat, at least when the comparison indicates differences beyond the first threshold set.

3. The apparatus of claim 2 wherein the indication of the differences between the signal indicia to which said movement determiner is coupled to receive are generated by said first-threshold-set comparator.

4. The apparatus of claim 1 wherein the signal indicia, associated with the signals generated by the serving and the target fixed-site communication stations, comprise signal strengths measured at the mobile station.

5. The apparatus of claim 1 wherein said movement determiner is operable only responsive to when the indications of the differences between the signal indicia associated with the signals generated by the serving and by the target fixed-site communication stations, respectively, are beyond the first threshold set.

6. The apparatus of claim 1 wherein, said movement determiner is operable to determine the movement indicia when the indication of the differences are above the first upper bound value and when the indications of the differences are beneath the first lower bound value.

7. The apparatus of claim 1 wherein the movement indicia determined by said movement determiner comprises a velocity, formed of a speed component and of a direction component.

8. The apparatus of claim 7 wherein said handoff request selector is further coupled to said movement determiner, said handoff request selector further requesting handoff of communications to the target fixed-site communication station when the velocity is less than a minimum level and the indications of the differences between the signal indicia associated with the signals generated by the serving and by the target fixed-site communication stations, respectively, are beyond the first threshold set.

9. The apparatus of claim 1 wherein said second threshold set calculator is further coupled to receive indications of propagation characteristics in an area at which the mobile station is positioned and wherein the second threshold set calculated thereat is further calculated responsive to values of the propagation characteristics.

10. The apparatus of claim 9 wherein the propagation characteristics to which said second threshold set calculator is coupled to receive comprises average signal strength values of the signals generated by the serving and by the target fixed-site communication stations, respectively.

11. The apparatus of claim 10 wherein the propagation characteristics to which said second threshold set calculator is coupled to receive comprises a standard deviation of the average signal strength.

12. The apparatus of claim 11 wherein said second threshold set calculator further calculates a time constant responsive to the movement indicia determined by said movement determiner and by the propagation characteristics to which said second threshold set calculator is coupled to receive.

13. The apparatus of claim 12 wherein the request for handoff of communications by said handoff request selector is further responsive to the time constant calculated by said second threshold set calculator.

14. The apparatus of claim 1 further comprising a memory device at which data forming a look-up table is stored, the look-up table having values representative at least of movement indicia, calculations made by said second threshold set calculator comprising accessing the look-up table.

15. In a method for communicating with a mobile station in a radio communication system, the mobile station operable to communicate with a serving fixed-site communication station and to communicate with a target fixed-site communication station subsequent to effectuation of a communication hand-off thereto, an improvement of a method for facilitating selection of when to initiate the effectuation of the communication hand-off, said method comprising:

selectably determining movement indicia associated with the mobile station when differences between signals generated by the serving fixed-site communication station and signals generated by the target fixed-site communication station are beyond a first threshold set, the first threshold set formed of a first upper bound value and a first lower bound value;

calculating second threshold set values when the movement indicia determined during said operation of determining indicates selected movement of the mobile station and the differences between the signals generated by the serving fixed-site communication station and the signals generated by the target fixed-site communication station are beyond the first threshold set, the second threshold set values formed of a second upper bound value;

comparing values of indications of the differences between the signal indicia associated with signals generated by the serving and the target fixed-site transceivers, respectively, and the second threshold set values calculated during said operation of calculating at least when the differences between the signals generated by the serving and the target fixed-site stations are beyond the first threshold set; and

selectably requesting handoff of communications to the target fixed-site communication station responsive to comparisons made during said operation of comparing.

16. The method of claim 15 wherein the movement indicia determined during said operation of selectably determining comprises a velocity indicia, formed of a speed component and a direction component, and a position indicia indicating a position at which the mobile station is located.

17. The method of claim 16 wherein handoff of communication is further requested during said operating of selectably requesting handoff of communications when the velocity indicia is less than a minimum level and the indications of the differences between the signal indicia associated with the signals generated by the serving and by the target fixed-site communication stations are beyond a first threshold set.

18. The method of claim 16 wherein the second threshold set values calculated during said operation of calculating the second threshold set values are calculated further responsive to indications of propagation characteristics in an area at which the mobile station is positioned, indicated by the position indicia.

19. The method of claim 18 wherein the propagation characteristics comprise average signal strength values of the signals generated by the serving and by the target fixed-site communication stations, respectively.