Method for reselecting a cell and detecting whether a terminal is stationary in mobile telecommunications system

• US 8,320,918 B2
• Filed: 09/27/2008
• Issued: 11/27/2012
• Est. Priority Date: 09/28/2007
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Chun, Sung-Duck, Yi, Seung-June, Lee, Young-Dae, Park, Sung-Jun, Lee, Seon-Don
• Primary Examiner(s): Ajibade Akonai, Olumide T
• Assistant Examiner(s): HOLLIDAY, JAIME MICHELE
• Application Number:
  US12/680,422
• Publication Number:
  US 20100240356A1
• Time in Patent Office: 1,522 Days
• Field of Search: 455436-441
• US Class Current: 455/441
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination

Abstract

Disclosed is a method for determining, by a terminal, its mobility and deciding a time to select another cell in a mobile communication system, in which the terminal determines the mobility by using variation information in signal characteristic values of measurable specific cells, thereby appropriately controlling a size of a time restriction (e.g., Treselection) for a cell re-selection and preventing frequent occurrence of cell selection such as a ping-pong situation, thus to reduce an unnecessary service delay due to the cell re-selection and maximize a service quality for a user.

Claims

1. A method for selecting a cell by a mobile terminal in a mobile communication system comprised of a plurality of cells, the method comprising:

determining that the mobile terminal is in a high mobility state;

upon determining that the mobile terminal is in the high mobility state, determining that a predetermined event has occurred or that a timer has expired; and

upon determining that the predetermined event has occurred or that the timer has expired, performing a cell re-selection process, the cell re-selection process including

performing a first measurement at a first time period to identify a first set of cells having signal strengths over a predetermined threshold;

performing a second measurement at a second time period to identify a second set of cells having signal strengths over the predetermined threshold;

determining a variation between the first and second measurements, the determined variation being equal to a number of cells that are present in one but not both of the first and second sets divided by a total number of cells in both of the first and second sets;

using the determined variation to determine that the mobile terminal has transitioned from the high mobility state to a substantially stationary state within the first and second sets of cells;

if the mobile terminal is determined to have transitioned from the high mobility state to the substantially stationary state within the first and second sets of cells, determining a final cell re-selection time restriction by applying a first predetermined scale factor to a cell re-selection time restriction previously provided to the mobile terminal by a base station; and

delaying an initiation of a subsequent cell re-selection process based on the final cell re-selection time restriction.

2. The method of claim 1, wherein the step of using the determined variation to determine that the mobile terminal has transitioned from the high mobility state to the substantially stationary state within the first and second sets of cells comprises:

determining that the number of cells that are present in one but not both of the first and second sets is greater than a predetermined stationary count number.

3. The method of claim 1, further comprising:

using the determined variation to determine that the mobile terminal has not transitioned from the high mobility state to the substantially stationary state within the first and second sets of cells but that the mobile terminal is in one of the high mobility state, a medium mobility state and a low mobility state within the first and second sets of cells;

if the mobile terminal is determined to be in the one of the high mobility state, the medium mobility state and the low mobility state within the first and second sets of cells, determining another final cell re-selection time restriction by applying a second predetermined scale factor to the cell re-selection time restriction previously provided to the mobile terminal by the base station; and

delaying the initiation of the subsequent cell re-selection process based on the another final cell re-selection time restriction.

4. The method of claim 3, wherein the predetermined threshold is one of a first threshold corresponding to the high mobility state and a second threshold corresponding to the medium mobility state.

5. A mobile terminal configured to select a cell in a mobile communication system comprised of a plurality of cells, comprising:

a processor configured to

determine that the mobile terminal is in a high mobility state,

upon determining that the mobile terminal is in the high mobility state, determine that a predetermined event has occurred or that a timer has expired, and

upon determining that the predetermined event has occurred or that the timer has expired, perform a cell re-selection process, the cell re-selection process including

performing a first measurement at a first time period to identify a first set of cells having signal strengths over a predetermined threshold,

performing a second measurement at a second time period to identify a second set of cells having signal strengths over the predetermined threshold,

determining a variation between the first and second measurements, the determined variation being equal to a number of cells that are present in one but not both of the first and second sets divided by a total number of cells in both of the first and second sets,

using the determined variation to determine that the mobile terminal has transitioned from the high mobility state to a substantially stationary state within the first and second sets of cells,

if the mobile terminal is determined to have transitioned from the high mobility state to the substantially stationary state within the first and second sets of cells, determining a final cell re-selection time restriction by applying a first predetermined scale factor to a cell re-selection time restriction previously provided to the mobile terminal by a base station, and

delaying an initiation of a subsequent cell re-selection process based on the final cell re-selection time restriction.

6. The mobile terminal of claim 5, wherein the processor is configured to use the determined variation to determine that the mobile terminal has transitioned from the high mobility state to the substantially stationary state within the first and second sets of by determining that the number of cells that are present in one but not both of the first and second sets is greater than a predetermined stationary count number.

7. The mobile terminal of claim 5, wherein the processor is further configured to

use the determined variation to determine that the mobile terminal has not transitioned from the high mobility state to the substantially stationary state within the first and second sets of cells but that the mobile terminal is in one of the high mobility state, a medium mobility state and a low mobility state within the first and second sets of cells,

if the mobile terminal is determined to be in the one of the high mobility state, the medium mobility state and the low mobility state within the first and second sets of cells, determine another final cell re-selection time restriction by applying a second predetermined scale factor to the cell re-selection time restriction previously provided to the mobile terminal by the base station, and

delay the initiation of the subsequent cell re-selection process based on the another final cell re-selection time restriction.

8. The mobile terminal of claim 7, wherein the predetermined threshold is one of a first threshold corresponding to the high mobility state and a second threshold corresponding to the medium mobility state.