Cell identification based on distance

• US 6,285,874 B1
• Filed: 11/20/1998
• Issued: 09/04/2001
• Est. Priority Date: 11/21/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Isaksson, Katarina, Trzeciak, Stephan, Olofsson, Håkan, Magnusson, Sverker
• Primary Examiner(s): Le, Thanh Cong
• Assistant Examiner(s): LE, LANA N
• Application Number:
  US09/196,167
• Time in Patent Office: 1,019 Days
• Field of Search: 455/422, 455/423, 455/517, 455/426, 455/436, 455/458, 455/445, 455/424, 455/67.1, 455/450, 455/452, 455/446, 455/524
• US Class Current: 455/456.1
• CPC Class Codes: H04W 16/00 Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00

Abstract

The present invention relates generally to the problem of determining the identity of a cell for e.g. cell handoff or automatic frequency planning, and more particularly to the problem of determining the true identity of a cell when only the transmission frequency and a non-unique identity code is known. A candidate list is created for each cell. This candidate list is created based on a function of various elements e.g. distance, transmission power, cell type, and antenna placement. The cells are then ranked on the candidate list based on this function. When a particular frequency/code combination is detected, the candidate list is then consulted, and the highest ranking cell with the same frequency/code combination is chosen as being the signal source. In an alternative embodiment the neighbor cell list is used to create the candidate list. If there are no matches on this list for the detected frequency/code combination, then the neighbors of the cells on the candidate list are also added to the candidate list which is then checked for a match.

Claims

1. A method for determining the identity of a cell from which a signal is transmitted in a cellular mobile communications system having a plurality of cells, said cells having base stations for receiving and transmitting radio signals to and from at least one mobile station, said mobile station being situated in a first cell, said first cell having a candidate list and a non-unique identification of a second cell, said method comprising the steps of:

defining a virtual distance from said first cell to said second cell;

detecting, in said first cell, a non-unique identification transmitted from a cell other than said first cell;

checking said candidate list for said first cell for a matching, non-unique identification; and

concluding that the cell identity on said candidate list, for which the non-unique identification matches the non-unique identification transmitted from said other cell, and for which said virtual distance is shortest, is the identity of the cell from which the signal was transmitted.

2. The method of claim 1 wherein said virtual distance is a function of the geographical distance between said first cell and said second cell.

3. The method of claim 1 wherein said virtual distance is a function of the transmitted power from said second cell and received in said first cell.

4. The method of claim 1 wherein said virtual distance is a function of the placement of the antenna for the base station in said second cell.

5. The method of claim 1 wherein said virtual distance is a function of the cell type of said second cell.

6. The method of claim 5 wherein said cell type is a macrocell.

7. The method of claim 5 wherein said cell type is a microcell.

8. The method of claim 5 wherein said cell type is a picocell.

9. The method of claim 1 wherein said virtual distance is a function of the factors relating to radio propagation of the signal from said second cell.

10. The method of claim 1 wherein said virtual distance is a functionf=A*Distance+B*Power+C*Placement+D*Cell-Type+E*Signal-Propagation, where A, B, C, D and E are constants determined by the operator of said system.

11. The method of claim 10 wherein said variables of said function f are placed in a coverage planning tool, resulting in a virtual distance based on the predicted attenuation between any cell in said system and any other cell in said system.

12. The method of claim 1 wherein said non-unique transmitted identification is a combination of the transmission signal frequency and a transmitted identification code.

13. The method of claim 1 wherein said non-unique transmitted identification is the transmission signal frequency.

14. The method of claim 1 wherein said non-unique transmitted identification is a transmitted code.

15. The method of claim 1 wherein said origin of said signal is used for planning the frequencies broadcast by the cells in said system.

16. The method of claim 1 wherein said origin of said signal is used for deciding which cell to handover to from said first cell.

17. The method of claim 1 wherein said origin of said signal is used for automatically producing a neighbor cell list for said first cell.

18. A method for determining the identity of a cell from which a signal is transmitted in a cellular mobile communications system having a plurality of cells, said cells having base stations for receiving and transmitting radio signals to and from at least one mobile station, said mobile station being situated in a first cell, said first cell having a neighbor cell list including a plurality of fields corresponding to neighbor cells of said first cell and fields for non-unique identification of a neighbor cells, said first cell also having a candidate list and a non-unique identification of said second cell, said method comprising the steps of:

a first step of detecting, in said first cell, a non-unique identification transmitted from a cell other than said first cell;

a second step of adding said plurality of fields for said cells in said neighbor cell list to said candidate list;

a third step of checking said candidtate list for a matching non-unique identification;

if there is no match then checking the neighbor cell lists for each cell on said candidate list and modifying said candidate list by repeating said second step and adding fields for each cell on each neighbor cell list for each cell on said candidate list and then repeating said third step and checking the modified candidate list for a matching non-unique identification.

19. The method of claim 18 wherein if there is only one match in said third step then conclude that the match is the origin of said signal.

20. The method of claim 18 wherein if there is more than one match in said third step then conclude that the method fails to find the origin of said signal.

21. The method of claim 20 wherein said neighbor cell list has a field for a virtual distance from said first cell to said neighbor cells, said candidate list has a field for a virtual distance from said first cell to said second cell, and further concluding that the cell identity on said candidate list for which the non-unique identification matches the non-unique identification transmitted.

22. The method of claim 21 wherein said virtual distance is a function of the geographical distance between said first cell and said second cell.

23. The method of claim 21 wherein said virtual distance is a function of the transmitted power from said second cell and received in said first cell.

24. The method of claim 21 wherein in that said virtual distance is a function of the placement of the antenna for the base station in said second cell.

25. The method of claim 21 wherein said virtual distance is a function of the cell type of said second cell.

26. The method of claim 25 wherein said cell type is a macrocell.

27. The method of claim 25 wherein said cell type is a microcell.

28. The method of claim 25 said cell type is a picocell.

29. The method of claim 21 wherein said virtual distance is a function of the factors relating to radio propagation of the signal from said second cell.

30. The method of claim 21 wherein said virtual distance is a function f=A*Distance+B*Power+C*Placement+D*CellType+E*Signal-Propagation, where A, B, C, D and E are constants determined by the operator of said system.

31. The method of claim 30 wherein said variables of said function f are placed in a coverage planning tool, resulting in a virtual distance based on the predicted attenuation between any cell in said system and any other cell in said system.

32. In a cellular communications system, a method for determining the identity of a cell from which a signal is transmitted comprising the steps of:

creating, in a first cell, a candidate list, wherein said candidate list includes a plurality of cells in said communication system;

sorting said plurality of cells in said candidate list by a distance from said first cell;

detecting, in said first cell, said signal, wherein said signal includes a non-unique identification;

checking said sorted candidate list for entries which match said transmitted non-unique identification; and

determining the identity of said cell from which said signal is transmitted as the cell which corresponds to a first entry which matches said transmitted non-unique identification in said sorted candidate list.