Neighbor cell list creation and verification in a telecommunications system

• US 5,915,221 A
• Filed: 08/08/1995
• Issued: 06/22/1999
• Est. Priority Date: 08/08/1995
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Beliveau, Andre, Sawyer, Francois
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US08/512,449
• Time in Patent Office: 1,414 Days
• Field of Search: 455/33.1, 455/33.2, 455/54.1, 455/56.1, 455/63, 455/67.1, 455/67.3, 455/422, 455/436, 455/437, 455/438, 455/450, 455/524, 455/525, 379/59, 379/60
• US Class Current: 455/437
• CPC Class Codes: H04W 36/00835 Determination of neighbour cell lists
• CPC Class Codes: H04W 36/0085 Hand-off measurements

Abstract

A method and system for neighbor cell list creation and verification in a telecommunications system is provided. Over a period of time measurements are performed on signals transmitted and received on measurement channels of cells neighboring the cell for which a neighbor cell list is being created. The results of the signal measurements are used to create an ordered list of the measurement channels on which the measurements were done. A neighbor cell list containing a desired number of cells is then created by placing a certain number of cells having the most interfered measurement channels in the neighbor cell list. The invention also presents a method and system for verifying an existing neighbor cell list. In the method and system measurements are performed on measurement channels of neighbor cells over a period of time. Periodically the measurement results are checked to determine if cells should be added to or deleted from the existing neighbor cell list.

Claims

1. In a cellular telecommunications system comprising a plurality of mobile stations, a first cell, and a plurality of neighbor cells, said neighbor cells each comprising at least one base station transmitting and receiving on one or more measurement channels, a method of creating a neighbor cell list for said first cell, said neighbor cell list used for transmission to mobile stations thereby enabling mobile stations to select candidate cells for handoff from said first cell, said method comprising the steps of:

establishing a first neighbor cell list for said first cell;

over the course of a plurality of calls by mobile stations within said first cell;

measuring by those mobile stations in said first cell of signal strength on measurement channels of a group of neighbor cells including cells not in the first neighbor list; and

sending the signal strength measurements by those mobile stations to the cellular telecommunications system; and

processing by the cellular telecommunications system after the plurality of calls of the mobile station sent signal strength measurements, said step of processing including the steps of;

creating an ordered list of said measurement channels, said list ordered according to said signal strength measurements obtained by the mobile stations over the course of the plurality of calls;

determining one or more of the measurement channels from said ordered list having highest signal strength; and

modifying said first neighbor cell list for said first cell to include the neighbor cells associated with said determined one or more measurement channels having highest signal strength.

2. The method of claim 1 in which said step of creating an ordered list comprises the steps of:

averaging said signal strength measurements to obtain an averaged signal strength measurement for each of said selected measurement channels; and

creating said ordered list of said measurement channels, said list ordered according to said averaged signal strength measurements.

3. The method of claim 1 in which said step of determining comprises the steps of:

identifying one or more measurement channels of said ordered list having a signal strength measurement level above a certain signal strength level threshold.

4. In a cellular telecommunications system comprising a plurality of mobile stations, a first cell and a plurality of neighbor cells, each of said neighbor cells comprising a base station transmitting and receiving on one or more measurement channels, a method of verifying a neighbor cell list for said first cell, said neighbor cell list used for transmission to mobile stations thereby enabling mobile stations to select candidate cells for handoff from said first cell, said method comprising the steps of:

assigning a first group of said neighbor cells to said neighbor cell list;

over the course of a plurality of calls by mobile stations within said first cell;

measuring by those mobile stations in said first cell of signal strength on a measurement channel of each of said neighbor cells including cells not in the first group; and

sending the signal strength measurements by those mobile stations to the cellular telecommunications system; and

processing by the cellular telecommunications system after the plurality of calls of the mobile station sent signal strength measurements, said step of processing including the steps of;

creating an ordered list of said neighbor cells, said list ordered according to said signal strength measurements obtained by the mobile stations over the course of the plurality of calls; and

reconfiguring said neighbor cell list according to said created ordered list, said step of reconfiguring comprising the steps of;

determining if any of said neighbor cells on the created ordered list have a signal strength measurement above a threshold value; and

assigning those neighbor cells from the created ordered list having a signal strength measurement above said threshold value to said neighbor cell list.

5. The method of claim 4 in which said step of creating an ordered list comprises the steps of:

averaging said signal strength measurements to obtain an averaged signal strength measurement for each of said neighbor cells measurement channels of said neighbor cells; and

creating said ordered list of said neighbor cells, said list ordered according to said averaged signal strength measurements for each of said neighbor cells.

6. The method of claim 5 in which said step of reconfiguring further comprises the steps of:

determining a second group of neighbor cells having highest averaged signal strength measurements;

deleting neighbor cells within said first group from said neighbor cell list; and

assigning neighbor cells of said second group to said neighbor cell list.

7. The method of claim 5 in which said step of reconfiguring further comprises the step of:

adding neighbor cells associated with one or more measurement channels having highest signal strength of said ordered list to said neighbor cell list.

8. The method of claim 4 in which said step of reconfiguring further comprises the steps of:

determining if any of said neighbor cells contained in said first group have an averaged signal strength measurement below said threshold value; and

removing neighbor cells contained in said first group having a signal strength measurement below said threshold from said neighbor cell list.

9. In a cellular telecommunications system comprising a plurality of mobile stations, a first cell, and a plurality of neighbor cells, said neighbor cells each comprising at least one base station transmitting and receiving on one or more measurement channels, a method for creating a neighbor cell list for said first cell, said neighbor list for transmission to mobile stations thereby enabling mobile stations to select candidate cells for handoff from said first cell, said method comprising the steps of:

establishing a first neighbor cell list for said first cell;

over the course of a plurality of calls by mobile stations within said first cell;

measuring by a base station for the first cell of signal strength on measurement channels of a group of neighbor cells including cells not in the first neighbor list; and

sending the signal strength measurements by the base station to the cellular telecommunications system; and

processing by the cellular telecommunications system after the plurality of calls of the base station sent signal strength measurements, said step of processing including the steps of;

creating an ordered list of said measurement channels, said list ordered according to said signal strength measurements obtained by the base station over the course of the plurality of calls;

determining one or more of the measurement channels from said ordered list having highest signal strength; and

modifying said first neighbor cell list for said first cell to include the neighbor cells associated with said determined one or more measurement channels having highest signal strength.

10. The method claim 9 in which said step of creating an ordered list comprises the steps of:

averaging said signal strength measurements to obtain an averaged signal strength measurement for each of said selected measurement channels; and

a creating said ordered list of said measurement channels, said list ordered according to said averaged signal strength measurements.

11. The method of claim 9 in which said step of determining comprises the step of:

identifying one or more measurement channels of said ordered list having a signal strength measurement level above a certain signal strength level threshold.

12. In a cellular telecommunications system comprising a plurality of mobile stations, a first cell and a plurality of neighbor cells, each of said neighbor cells comprising a base station transmitting and receiving on one or more measurement channels, a method for verifying a neighbor cell list for said first cell, said neighbor cell list used for transmission to mobile stations thereby enabling mobile stations to select candidate cells for handoff from said first cell, said method comprising the steps of:

assigning a first group of said neighbor cells to said neighbor cell list;

over the course of a plurality of calls by mobile stations within said first cell;

measuring signal strength by a base station for said first cell on measurement channels of each of said neighbor cells including cells not in the first group; and

sending the signal strength measurements by the base station to the cellular telecommunications system; and

processing by the cellular telecommunications system after the plurality of calls of the base station sent signal strength measurements, said step of processing including the steps of;

creating an ordered list of said neighbor cells, said list ordered according to said signal strength measurements obtained by the base station over the course of the plurality of calls; and

reconfiguring said neighbor cell list according to said created ordered list, said step of reconfiguring comprising the steps of;

determining if any of said neighbor cells on the created ordered list have a signal strength measurement above a threshold value; and

assigning those neighbor cells on the created ordered list having a signal strength measurement above said threshold value to said neighbor cell list.

13. The method of claim 12 in which said step of creating an ordered list comprises the steps of:

averaging said signal strength measurements to obtain an averaged signal strength measurement for each of said neighbor cells measurement channels of said neighbor cells; and

creating said ordered list of said neighbor cells, said list ordered according to said averaged signal strength measurements for each of said neighbor cells.

14. The method of claim 13 in which said step of reconfiguring further comprises the steps of:

determining a second group of neighbor cells having highest averaged signal strength measurements;

deleting neighbor cells within said first group from said neighbor cell list; and

assigning neighbor cells of said second group to said neighbor cell list.

15. The method of claim 13 in which said step of reconfiguring further comprises the step of:

adding neighborhood cells associated with one or more measurement channels having highest signal strength of said ordered list to said neighbor cell list.

16. The method of claim 12 in which said step of reconfiguring further comprises the steps of:

determining if any of said neighbor cells contained in said first group have an averaged signal strength measurement below said threshold value; and

removing neighbor cells contained in said first group having a measurement signal strength below said threshold from said neighbor cell list.