Prioritization of neighboring cells

• US 5,509,051 A
• Filed: 09/09/1993
• Issued: 04/16/1996
• Est. Priority Date: 09/09/1993
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: King, Lou, Barnett, Charles A., Mehta, Ashok D.
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Stoll, Thomas L.
• Application Number:
  US08/118,710
• Time in Patent Office: 950 Days
• Field of Search: 379/58, 379/59, 379/60, 379/63, 455/33.2, 455/33.1, 455/54.1, 455/56.1
• US Class Current: 455/443
• CPC Class Codes: H04W 36/0061 of neighbour cell information
• CPC Class Codes: H04W 36/00835 Determination of neighbour cell lists
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data

Abstract

Each cell has an assigned classification that determines its inclusion in a measurement list for handing off. The candidate cells, which are selected from the measurement list are given priority level assignments. The priority levels are implemented by the candidate neighboring cells measured RF signal strength; and the order of handing off is arranged in accordance with the adjusted RF signal strength.

Claims

1. A method of prioritizing cells in a cellular communication system including a plurality of serving cells and a plurality of neighboring cells, the method comprising:

assigning to the plurality of neighboring cells for each of a plurality of serving cells a measurement classification designation;

assigning a priority level to each of the classified neighboring Cells, said priority level being assigned without regard to the RF signal strength of the neighboring cells relative to the signal strength of the plurality of serving cells;

generating a measurement list of neighboring cells in accordance with the measurement class of the cells;

selecting candidate cells for handoff from the measurement list;

determining the difference between a maximum priority level and the assigned priority level of each of the neighboring cells;

normalizing the RF signal strength of each selected neighboring cell in accordance with attenuation parameters of the mobile unit; and

adjusting the normalized RF signal strength of each normalized cell in accordance with the determined difference multiplied by a number of decibels for each priority level difference.

2. The method of claim 1 wherein the step of assigning the measurement classification designations comprises the substeps of assigning the neighboring cells to one of not less than three different measurement classifications.

3. The method of claim 1 wherein the step of assigning the priority level comprises assigning a priority to one of not less than eight priority levels.

4. The method of claim 1 wherein the step of generating a measurement list comprises including in the measurement list a neighboring cell having an assigned first designated class without regard to an RF signal strength of the serving cell, and including in the measurement list at least one cell of a second designated class at times when a measurement threshold of the designated cell is greater than the RF signal strength of the serving cell.

5. The method of claim 1 wherein the step of generating a measurement list comprises including in the measurement list a cell of one of the plurality of designated measurement classes at times when the cell has a measurement threshold greater than the RF signal strength of the serving cell, and including in the measurement list a cell of another of the plurality of designated classes at times when the RF signal strength of the serving cell is less than the critical threshold of the designated cell.

6. The method of claim 1 wherein the step of generating the measurement list comprises including cells of one of the assigned measurement classes to the list in response to activation of a communication channel in the serving cell.

7. The method of claim 1 wherein the neighboring cells are selected for the measurement list from scanning receivers;

and the scanning receiver scans neighboring cells in descending order of importance.

8. A cellular communication system having a serving cell for communicating with a mobile unit and a plurality of neighboring cells capable of communicating with the mobile unit as it leaves the serving cell, the system comprising:

a plurality of individual overlapping cells, each of said plurality of cells constituting one of a plurality of neighboring cells to another cell, each of said plurality of neighboring cells having one of a plurality of measurement classes;

each of said plurality of neighboring cells having an assigned priority level independent of the RF signal strength of the cell;

means for generating a measurement list of the neighboring cells in accordance with the corresponding measurement class;

means for selecting candidate cells for handoff from the generated measurement list;

means for determining the difference between a maximum priority level and the assigned priority level of each of the neighboring cells;

means for normalizing the RF signal strength of each selected neighboring cell in accordance with attenuation parameters of the mobile unit; and

means for adjusting the normalized RF signal strength of each cell in accordance with the determined difference multiplied by a number of decibels for each priority level difference.

9. The system of claim 8 wherein the neighboring cells have one of not less than three different measurement classes.

10. The system of claim 8 wherein each of said plurality of neighboring cells has one of not less than eight priority levels.

11. The system of claim 8 wherein the means for generating a measurement list includes means for including cells in the measurement list of the plurality of neighboring cells having a first of the plurality of measurement classes without regard to an RF signal strength of the serving cell, and including means for including in the measurement list one of the plurality of neighboring cells having another of the plurality of measurement classes at times when a measurement threshold of the neighboring cell is greater than the RF signals strength of the serving cell.

12. The system of claim 8 wherein the means for generating a measurement list includes means for including in the measurement list a neighboring cell of one of the plurality of measurement classes at times when the neighboring cell has a measurement threshold greater than the RF signal strength of the serving cell, and including means for including in the measurement list a neighboring cell of another of the plurality of measurement classes at times when the RF signal strength of the serving cell is less than the critical threshold of the neighboring cell.

13. The system of claim 8 wherein the means for generating a measurement list includes means for commencing the generation of the list upon activation of a channel in the serving cell.