Cell selection and inter-frequency handover

• US 7,430,420 B2
• Filed: 12/23/2004
• Issued: 09/30/2008
• Est. Priority Date: 12/23/2004
• Status: Expired due to Fees

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Schacht, Mirko, Jugl, Enrico, Derakhshan, Fariborz
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Ewart, James D
• Application Number:
  US11/021,554
• Publication Number:
  US 20060142032A1
• Time in Patent Office: 1,377 Days
• Field of Search: 455/436, 455/437, 455/438, 455/439, 455/442, 455/443, 455/444, 455/450, 455/452.1, 455/452.2, 455/464, 455/509, 455/525, 455/10, 455/62, 455/63.1, 455/67.11, 455/67.12, 455/115.4, 455/161.1, 455/176.1, 455/180.1, 455/188.1, 455/266, 370/331, 370/332, 370/395.14, 370/431, 370/468
• US Class Current: 455/452.2
• 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 for transferring said mobile wireless device from a first frequency band to a second frequency band having a transmit power level lower than that of said first frequency band, 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, wherein selecting said target cell comprises selecting said target cell that provides the lowest path loss from a set of cells that guarantee a desired value of a ratio of a received pilot power from a sector to a total interference so that emission of radio transmit power from said first and second base station is reduced upon an initial access of said target cell by said mobile wireless device;

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;

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 cell reselection criterion;

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

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; and

calculating the path loss of each cell of said at least two cells based on the corresponding pilot powers.

2. 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 for transferring said mobile wireless device from a first frequency band to a second frequency band having a transmit power level lower than that of said first frequency band;

triggering the inter-frequency handover if a sum of a predetermined power and a second expected power difference remains less than a first expected power difference to ensure that the power consumption in a target system is less than the power consumption in the current system, the first expected power difference representing a power difference if said mobile wireless device leaves a cell of said at least two cells in a current system and the second expected power difference representing a power difference if said mobile wireless device enters said target cell; and

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

3. A method, as set forth in claim 2, 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 the first expected power difference in said multi-layer access network if said mobile wireless device leaves the cell of said at least two cells in the current system; and

calculating the second expected power difference in said multi-layer access network if said mobile wireless device enters said target cell.