Mobile communications system

• US 6,556,829 B1
• Filed: 06/29/1998
• Issued: 04/29/2003
• Est. Priority Date: 06/30/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Persson, Gunnar
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): CRAVER, CHARLES R
• Application Number:
  US09/106,362
• Time in Patent Office: 1,765 Days
• Field of Search: 455/13.3, 455/447, 455/63, 455/428, 455/446, 455/67.1, 455/524, 455/436, 455/437, 455/438, 455/439, 455/442, 455/434, 455/423, 370/252, 370/331-334, 370/337
• US Class Current: 455/437
• CPC Class Codes: H04W 16/18 Network planning tools
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 36/00835 Determination of neighbour cell lists
• CPC Class Codes: H04W 36/302 due to low signal strength

Abstract

A base station, as is conventional, directs mobile stations within its cell to make measurements on channels used by neighbouring cells. The base station also directs the mobile stations to make measurements on an additional channel not used by a neighbouring cell. The additional channel is changed regularly. Measurements made on the additional channel are useful when assessing the potential impact of changes to the frequency reuse plan.

Claims

1. A method of operation of a mobile communications network for communication with a plurality of mobile stations, the network comprising a plurality of base stations, each base station being associated with a particular cell, each cell being identified within the network by a colour code signal transmitted by a base station within the cell, and each base station within a cell communicating with the respective mobile stations on an operating frequency chosen from a preselected number of available frequencies, the number of cells in the network being greater than the number of available frequencies, the method comprising:

sending control signals to each respective mobile station, instructing it to make signal quality measurements on a plurality of frequencies, the plurality of frequencies remaining generally the same over time, and being the operating frequencies of neighbouring cells said neighbouring cells being the cells to which the mobile station may execute a handover if required;

sending control signals to each respective mobile station, instructing it to make signal quality measurements on at least one additional frequency in use within the network, the additional frequency not being associated with any neighbouring cells, the additional frequency being changed frequently;

receiving detected signal quality measurements made by each respective mobile station on the additional frequency;

receiving a detected colour code associated with any signal detected on the additional frequency, the colour code being detected by one of the mobile stations;

determining, on the basis of the detected colour code, the cell from which the signal detected on the additional frequency originated; and

determining on the basis of the signal quality measurements whether said cell, from which the signal detected on the additional frequency originated, can be designated as a neighbouring cell to which a mobile station may execute a handover.

2. A method as claimed in claim 1, wherein the additional frequency is selected from all of the frequencies available within the network other than the plurality of frequencies of neighbouring cells.

3. A method as claimed in claim 1, wherein the additional frequency is selected from a subset of the available frequencies within the network other than the plurality of frequencies of neighbouring cells.

4. A method as claimed in claim 1, wherein the additional frequency is changed in each cycle of signal quality measurements.

5. A mobile communications network for communication with a plurality of mobile stations, the network comprising a plurality of base stations, each base station being associated with a particular cell, each base station within a cell communicating with each respective mobile station on an operating frequency chosen from a preselected number of frequencies available to the network operator, the number of cells in the network being greater than the number of available frequencies, each base station within the network comprising:

means for transmitting a colour code signal, said colour code signal identifying the cell in which the base station resides;

means for sending first control signals to each respective mobile station, instructing the mobile station to attempt to detect signals on frequencies within a first group of frequencies selected from the plurality of frequencies available within the network, the first group of frequencies being the operating frequencies of neighbouring cells to which a mobile station may execute a handover;

means for sending second control signals to each respective mobile station, instructing the mobile station to attempt to detect a signal on at least one additional frequency in use within the network, the additional frequency not being associated with any neighbouring cells, the additional frequency being altered regularly;

means for receiving the results of said attempts to detect a signal made by each respective mobile station on the additional frequency;

means for receiving a detected colour code associated with any signal detected on the additional frequency, the colour code being detected by one of the mobile stations;

the network further comprising;

means for determining, on the basis of the detected colour code, the cell from which the signal detected on the additional frequency originated; and

means for determining, on the basis of said results, whether said cell, from which the signal originated, can be designated as a neighbouring cell to which a mobile station may execute handover.

6. A mobile communications network as claimed in claim 5, further comprising means for selecting the additional frequency from all of the frequencies available within the network other than the plurality of frequencies of neighbouring cells.

7. A mobile communications network as claimed in claim 5, further comprising means for selecting the additional frequency from a subset of the frequencies available within the network other than the plurality of frequencies of neighbouring cells.

8. A mobile communications network as claimed in claim 5, further comprising means for changing the additional frequency in each cycle of signal quality measurements.

9. A mobile communications network as claimed in claim 5, wherein the means for determining the cell from which the signal detected on the additional frequency originated and the means for determining whether said cell can be designated as a neighbouring cell is within the base station.

10. A mobile communications network as claimed in claim 5, wherein the means for determining the cell from which the signal detected on the additional frequency originated and the means for determining whether said cell can be designated as a neighbouring cell is within a Mobile Switching Centre (MSC).

11. A base station for use in a radio communications network comprising a plurality of base stations and a plurality of available operating frequencies, the base station comprising:

means for sending first messages to respective mobile devices, each first message instructing the mobile device to attempt to detect signals on frequencies within a first group of frequencies selected from the plurality of available operating frequencies, the first group of frequencies being the operating frequencies of base stations defined as neighbours of the base station;

means for comparing identifying codes of signals detected in response to the first message with identifying codes associated with the base stations defined as neighbours;

means for reporting if the detected identifying codes of signals detected in response to the first message differ from the identifying codes associated with the base stations defined as neighbours;

means for sending second messages to respective mobile devices, each second message instructing the mobile device to attempt to detect a signal on at least one second frequency not within the first group of frequencies; and

means for reporting the identifying codes of any signals detected in response to the second message.

12. A base station as claimed in claim 11, further comprising means for selecting the second frequency from all of the available frequencies other than the first group of frequencies.

13. A base station as claimed in claim 11, further comprising means for selecting the second frequency from a subset of the available frequencies other than the first group of frequencies.

14. A base station as claimed in claim 11, further comprising means for changing the second frequency in each cycle of signal quality measurements.

15. A mobile communications network as claimed in claim 11, wherein the means for comparing colour codes of signals detected in response to a first control signal, the means for reporting if the colour codes differ from the colour codes associated with neighbouring cells in response to a first control signal, the means for determining the cell from which the signal detected on the additional frequency originated and the means for determining whether said cell can be designated as a neighbouring cell is within the base station.

16. A mobile communications network as claimed in claim 11, wherein the means for comparing colour codes of signals detected in response to a first control signal, the means for reporting if the colour codes differ from the colour codes associated with neighbouring cells in response to a first control signal, the means for determining the cell from which the signal detected on the additional frequency originated and the means for determining whether said cell can be designated as a neighbouring cell is within a Mobile Switching Centre (MSC).

17. A mobile communications network for communication with a plurality of mobile stations, the network comprising a plurality of base stations, each base station being associated with a particular cell, each base station within a cell communicating with each respective mobile station on an operating frequency chosen from a preselected number of frequencies available to the network operator, the number of cells in the network being greater than the number of available frequencies, each base station within the network comprising:

means for transmitting a colour code signal, said colour code signal identifying the cell in which the base station resides;

means for sending first control signals to each respective mobile station, instructing the mobile station to attempt to detect signals on frequencies within a first group of frequencies selected from the plurality of frequencies available within the network, the first group of frequencies being the operating frequencies of neighbouring cells to which a mobile station may execute a handover;

means for receiving the results to said attempts to detect a signal made by each respective mobile station on the first group of frequencies;

means for sending second control signals to each respective mobile station, instructing the mobile station to attempt to detect a signal on at least one additional frequency in use within the network, the additional frequency not being associated with any neighbouring cells, the additional frequency being altered regularly;

means for receiving the results of said attempts to detect a signal made by each respective mobile station on the additional frequency;

means for receiving the colour codes of any signals detected in response to the second control signal;

means for comparing colour codes of signals detected in response to the first control signal with colour codes associated with the neighbouring cells;

means for reporting if the colour codes of signals detected in response to the first control signal differ from the colour codes associated with the neighbouring cells;

means for determining, on the basis of the detected colour code, the cell from which the signal detected on the additional frequency originated; and

means for determining, on the basis of said results, whether said cell, from which the signal originated, can be designated as a neighbouring cell to which a mobile station may execute a handover.

18. In a mobile communications network for communication with a plurality of mobile stations, the network comprising a plurality of base stations each base station being associated with a particular cell, each cell being identified within the network by a colour code signal transmitted by a base station within the cell, and each base station within a cell communicating with the respective mobile stations on an operating frequency chosen from a preselected number of available frequencies, the number of cells in the network being greater than the number of available frequencies, a method for assessing the performance of the network comprising the steps of:

sending first control signals instructing each respective mobile station to measure signals on a first group of frequencies selected from the plurality of frequencies available within the network, the first group of frequencies being associated with cells which are neighbouring cells to the cell in which the mobile station is currently located;

receiving the results of said attempts to detect a signal made by each respective mobile station on the first group of frequencies;

comparing a colour code of signals detected in response to the first control signal with colour codes associated with the neighbouring cells;

reporting the results of the comparing step, if any of the colour codes detected in response to the first control signal are different to the colour codes associated with the neighbouring cells;

sending second control signals to each respective mobile station, instructing the mobile station to attempt to detect a signal on at least one additional frequency in use within the network, the additional frequency not being associated with any neighbouring cells and the additional frequency being altered regularly;

receiving the results of said attempts to detect a signal made by each respective mobile station on the additional frequency;

receiving the colour codes of any signals detected in response to the second control signal;

determining, on the basis of the detected colour code, the cell from which the signal detected on the additional frequency originated; and

determining, on the basis of said results, whether said cell, from which the signal originated, can be designated as a neighbouring cell to which a mobile station may execute a handover.