Cell selection and inter-frequency handover

• US 20060142032A1
• Filed: 12/23/2004
• Published: 06/29/2006
• Est. Priority Date: 12/23/2004
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Derakhshan, Fariborz, Jugl, Enrico, Schacht, Mirko
• Granted Patent: US 7,430,420 B2
• Time in Patent Office: Days
• US Class Current: 455/509
• CPC Class Codes: H04W 16/32 Hierarchical cell structures
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 36/302 due to low signal strength
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention provides a method and an apparatus for controlling a communications system that includes a mobile wireless device, a first and a second base station and a radio network controller. The communications system may allocate frequency bands to users on a multiplicity of channels associated with a multi-layer access network across at least two cells communicatively coupled to a first and a second base station, respectively. The method comprises monitoring a radio emission parameter associated with the first and second base stations that communicate with the mobile wireless device. A radio emission parameter associated with the first and second base stations, such as signal strength or quality, is monitored, to select a target cell among a set of candidate cells for the mobile wireless device and to transfer the mobile wireless device from a first frequency band to a second frequency band. For example, radio resource management algorithms may cause emission-controlled cell selection and inter-frequency handover from a first frequency band to a second frequency band with a transmit power level lower than that of the first frequency band. In accordance with one aspect of the instant application, electromagnetic exposure to a user of the mobile wireless device is substantially decreased, resulting in lower energy costs and reduced environmental impacts.

Claims

1. A method for allocating frequency bands to users on a multiplicity of channels associated with a multi-layer access network across at least two cells communicatively coupled to a first and a second base station, respectively, the method comprising:

monitoring a radio emission parameter associated with said first and second base stations; and

based on the radio emission parameter of said first and second base stations, selecting a target cell among said at least two cells for a mobile wireless device and transferring said mobile wireless device from a first frequency band to a second frequency band.

2. A method, as set forth in claim 1, wherein selecting a target cell further comprising:

maintaining a desired level of radio transmit power from said first and second base stations based on the selection of said target cell when transferring said mobile wireless device from said first frequency band to said second frequency band with a transmit power level lower than that of said first frequency band.

3. A method, as set forth in claim 1, wherein transferring said mobile wireless device further comprising:

monitoring a radio propagation condition of at least two channels of said multiplicity of channels associated with said multi-layer access network; and

causing an inter-frequency handover for a user of said mobile wireless device based on the radio propagation condition of said at least two channels.

4. A method, as set forth in claim 1, further comprising:

selecting said target cell among said at least two cells based on the radio emission parameter of said first and second base stations and a radio propagation condition of at least two channels of said multiplicity of channels associated with said multi-layer access network.

5. A method, as set forth in claim 4, wherein selecting a target cell further comprising:

selecting said target cell as a cell with a lowest path loss and a cell that fulfils at least one of a cell selection criterion and a cell reselection criterion.

6. A method, as set forth in claim 5, further comprising:

causing reduction in emission of radio transmit power from said first and second base stations upon an initial access of said target cell by said mobile wireless device.

7. A method, as set forth in claim 6, further comprising:

executing instructions at said mobile wireless device to reduce the emission of radio transmit power from said first and second base stations.

8. A method, as set forth in claim 6, wherein executing instructions at said mobile wireless device further comprising:

measuring a ratio of a received pilot power from a sector to a total interference defined as the sum of received power from one or more other sectors and a thermal noise of said at least two cells;

measuring received signal code power of a common pilot channel of said at least two cells;

determining a pilot power for said common pilot channel of said at least two cells;

calculating the path loss of each cell of said at least two cells; and

selecting said target cell that provides the lowest path loss from a set of cells that guarantee a desired value of the said ratio of a received pilot power from a sector to a total interference.

9. A method, as set forth in claim 3, further comprising:

executing instructions at a radio network controller to cause the inter-frequency handover for said user of said mobile wireless device.

10. A method, as set forth in claim 9, wherein executing instructions at said radio network controller further comprising:

initiating one or more inter-frequency measurements at said mobile wireless device at a call setup;

reporting to said radio network controller one or more inter-frequency neighbor candidate cells of said at least two cells based on values of a ratio of a received pilot power from a sector to a total interference defined as the sum of received power from one or more other sectors and a thermal noise of said at least two cells relative to a threshold value;

determining a load in each of said monitored at least two cells;

estimating a downlink resource consumption of a service for said mobile wireless device in said one or more inter-frequency neighbor candidate cells of said at least two cells;

calculating a first expected power difference in said multi-layer access network if said mobile wireless device leaves a cell of said at least two cells in a current system;

calculating a second expected power difference in said multi-layer access network if said mobile wireless device enters said target cell; and

triggering the inter-frequency handover if a sum of a predetermined power and said second expected power difference remains less than said first expected power difference to ensure that the power consumption in a target system is less than the power consumption in the current system.

11. A method for controlling a communications system including a first and second base station and a radio network controller, the method comprising:

monitoring a radio emission parameter associated with said first and second base stations;

executing instructions at a mobile wireless device to reduce the emission of radio transmit power from said first and second base stations;

executing instructions at said radio network controller to cause an inter-frequency handover for a user of said mobile wireless device; and

allocating a lower frequency band to said user on a multiplicity of channels associated with a multi-layer access network across at least two cells communicatively coupled to said first and second base stations, respectively.

12. A method, as set forth in claim 11, further comprising:

managing radio resources in said first and second base stations, wherein the managed radio resources are associated with communicating between at least one of said first and second base stations and said mobile wireless device.

13. A method, as set forth in claim 11, further comprising:

based on the radio emission parameter of said first and second base stations, selecting a target cell among said at least two cells for said mobile wireless device.

14. A method, as set forth in claim 11, further comprising:

based on the radio emission parameter of said first and second base stations, transferring said mobile wireless device from a higher frequency band to said lower frequency band with a transmit power level lower than that of said higher frequency band.

15. A method, as set forth in claim 11, further comprising:

monitoring a radio propagation condition of at least two channels of said multiplicity of channels associated with said multi-layer access network; and

causing an inter-frequency handover for a user of said mobile wireless device based on the radio propagation condition of said at least two channels.

16. A communications system comprising:

a first and a second base station;

a radio network controller coupled to said first and second base stations; and

a storage coupled to said radio network controller, said storage storing instructions to cause an inter-frequency handover for a user of a mobile wireless device that monitors a radio emission parameter associated with said first and second base stations to enable allocation of a lower frequency band to said user on a multiplicity of channels associated with a multi-layer access network across at least two cells communicatively coupled to said first and second base stations, respectively, for reducing the emission of radio transmit power from said first and second base stations.

17. A telecommunication system, as set forth in claim 16, wherein said multi-layer access network, said first and second base stations and said radio network controller are being defined at least in part by a Universal Mobile Telecommunication System (UMTS) protocol.

18. An article comprising a computer readable storage medium storing instructions that, when executed cause a system to:

monitor a radio emission parameter associated with a first and a second base station for allocating frequency bands to users on a multiplicity of channels associated with a multi-layer access network across at least two cells communicatively coupled to said first and second base stations, respectively; and

based on the radio emission parameter of said first and second base stations, select a target cell among said at least two cells for a mobile wireless device and transfer said mobile wireless device from a first frequency band to a second frequency band.

19. An article, as set forth in claim 18, comprising a medium storing instructions that, when executed cause a system to:

maintain a desired level of radio transmit power from said first and second base stations based on the selection of said target cell when transferring said mobile wireless device from said first frequency band to said second frequency band with a transmit power level lower than that of said first frequency band.

20. An article, as set forth in claim 18, comprising a medium storing instructions that, when executed cause a system to:

monitor a radio propagation condition of at least two channels of said multiplicity of channels associated with said multi-layer access network; and

cause an inter-frequency handover for a user of said mobile wireless device based on the radio propagation condition of said at least two channels.

21. An article, as set forth in claim 18, comprising a medium storing instructions that, when executed cause a system to:

select said target cell among said at least two cells based on the radio emission parameter of said first and second base stations and a radio propagation condition of at least two channels of said multiplicity of channels associated with said multi-layer access network.

22. An article comprising a computer readable storage medium storing instructions that, when executed cause a system to:

monitor a radio emission parameter associated with said first and second base stations;

execute instructions at a mobile wireless device to reduce the emission of radio transmit power from said first and second base stations;

execute instructions at said radio network controller to cause an inter-frequency handover for a user of said mobile wireless device; and

allocate a lower frequency band to said user on a multiplicity of channels associated with a multi-layer access network across at least two cells communicatively coupled to said first and second base stations, respectively.

23. An article, as set forth in claim 22, comprising a medium storing instructions that, when executed cause a system to:

manage radio resources in said first and second base stations, wherein the managed radio resources are associated with communicating between at least one of said first and second base stations and said mobile wireless device.

24. An article, as set forth in claim 22, comprising a medium storing instructions that, when executed cause a system to:

based on the radio emission parameter of said first and second base stations, select a target cell among said at least two cells for said mobile wireless device.

25. An article, as set forth in claim 22, comprising a medium storing instructions that, when executed cause a system to:

based on the radio emission parameter of said first and second base stations, transfer said mobile wireless device from a higher frequency band to said lower frequency band with a transmit power level lower than that of said higher frequency band.

26. An apparatus for allocating frequency bands to users on a multiplicity of channels associated with a multi-layer access network across at least two cells communicatively coupled to a first and a second base station, respectively, the apparatus comprising:

means for monitoring a radio emission parameter associated with said first and second base stations; and

means for selecting a target cell among said at least two cells for a mobile wireless device and transferring said mobile wireless device from a first frequency band to a second frequency band based on the radio emission parameter of said first and second base stations.

27. An apparatus for controlling a communications system including a first and second base station and a radio network controller, the apparatus comprising:

means for monitoring a radio emission parameter associated with said first and second base stations when transferring said mobile wireless device from said first frequency band to said second frequency band with a transmit power level lower than that of said first frequency band;

means for executing instructions at a mobile wireless device to reduce the emission of radio transmit power from said first and second base stations;

means for executing instructions at said radio network controller to cause an inter-frequency handover for a user of said mobile wireless device; and

means for allocating a lower frequency band to said user on a multiplicity of channels associated with a multi-layer access network across at least two cells communicatively coupled to said first and second base stations, respectively.