PENALTY OF CELL RESELECTION FOR A WIRELESS DEVICE

• US 20040162074A1
• Filed: 02/13/2003
• Published: 08/19/2004
• Est. Priority Date: 02/13/2003
• Status: Active Grant

• Current Assignee: Innovative Sonic Limited
• Original Assignee: Innovative Sonic Limited
• Inventors: Chen, Rex Huan-Yueh
• Granted Patent: US 7,127,253 B2
• Time in Patent Office: Days
• US Class Current: 455/437
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells
• CPC Class Codes: H04W 36/302 due to low signal strength

Abstract

An improved device and method for determining when to start a timer that applies a temporary offset to a signal quality measurement of a cell that is a candidate for reselection in a 3GPP Hierarchical Cell Structured wireless communications system. For a cell ranking criterion R, the timer is started to apply the temporary offset according to present invention rules that insure that the temporary offset is not applied until a candidate is eligible for reselection, preventing premature expiration of the timer and unintended cell reselection. A present invention mobile unit that uses the improved method includes a housing, a central processor, a timer for applying the temporary offset, and a memory. The memory includes computer code that applies the claimed invention rules for starting the timer.

Claims

1. An improved method for serving cell reselection by a mobile unit in a Hierarchical Cell Structure (HCS) wireless communications system, each cell in the HCS wireless communications system having an assigned HCS priority, the mobile unit comprising a Radio Resource Control (RRC) used to establish at least a radio bearer for receiving system information transmitted from the serving cell to the mobile unit when the mobile unit is within a service area of the serving cell, the method comprising:

if the HCS priority of the serving cell equals the HCS priority of a candidate cell and the measured signal quality of the candidate cell is greater than the sum of a measured signal quality of the serving cell plus a system information supplied offset between the serving and the candidate cell plus a system information specified hysteresis value for the serving cell, starting a timer to apply a temporary offset to signal quality measurements of the candidate cell, the adjusted signal quality measurements used for ranking that candidate cell for reselection.

2. The method of claim 1 wherein the serving cell and the candidate cell are both Frequency Division Duplex cells, the quality value of the received signal for FDD cells is derived from Received Signal Code Power (RSCP) of Common Pilot Channel (CPICH)in the serving cell, and the system information supplied offset equals a first value.

3. The method of claim 1 wherein the serving cell and the candidate cell are both Frequency Division Duplex cells, the quality value of the received signal for FDD cells is derived from received energy per chip divided by the power density (Ec/N₀) of Common Pilot Channel (CPICH)in the serving cell, and the system information supplied offset equals a second value.

4. A mobile unit for use in a Hierarchical Cell Structure (HCS) wireless communications system, each cell in the HCS wireless communications system having an assigned HCS priority, the mobile unit in radio contact with a serving cell and capable of reselecting to a candidate cell, the serving cell broadcasting system information to be used by the mobile unit in a cell reselection process, the mobile unit comprising:

a housing;

a timer for applying a temporary offset to a signal quality measurement of the candidate cell for a predetermined time interval;

a central processing unit for executing computer code; and

a memory comprising;

computer code for determining a quality measure for cell reselection setting in the serving cell; and

improved computer code for starting a timer to apply a temporary offset to signal quality measurements of the candidate cell when the candidate cell qualifies for reselection, the adjusted signal quality measurements used for ranking that candidate cell for reselection.

5. The mobile unit of claim 4 wherein the improved computer code starts the timer if the HCS priority of the serving cell equals the HCS priority of the candidate cell and the measured signal quality of the candidate cell is greater than the sum of a measured signal quality of the serving cell plus a system information supplied offset between the serving and the candidate cell plus a system information specified hysteresis value for the serving cell.

6. The mobile unit of claim 5 wherein when the serving cell and the candidate cell are both Frequency Division Duplex cells, the computer code indicates the quality value of the received signal for FDD cells is derived from Received Signal Code Power (RSCP) of Common Pilot Channel (CPICH)in the serving cell, the improved computer code utilizes a system information supplied offset equal to a first value.

7. The mobile unit of claim 5 wherein the serving cell and the candidate cell are both Frequency Division Duplex cells, the computer code indicates the quality value of the received signal for FDD cells is derived from received energy per chip divided by the power density (Ec/N₀) of Common Pilot Channel (CPICH)in the serving cell, the improved computer code utilizes a system information supplied offset equal to a second value.

8. A method of ranking candidate cells during a cell reselection procedure in a Hierarchical Cell Structure (HCS) wireless communications system, each cell in the HCS wireless communications system having an assigned HCS priority, the wireless communications system comprising a mobile unit and a serving cell, the mobile unit having a Radio Resource Control (RRC) for establishing at least a radio bearer for receiving system information transmitted from the serving cell to the mobile unit when the mobile unit is within a service area of the serving cell, the method comprising:

selecting candidate neighboring cells according to predetermined measurement rules using system information supplied thresholds;

starting a timer in the mobile unit for application of a temporary offset adjusting signal quality measurements of a candidate cell when that candidate cell qualifies for reselection; and

ranking candidate cells according to the adjusted signal quality measurements for each candidate cell.

9. The method of claim 8 wherein the candidate cell qualifies for reselection when the ranking of the candidate cell is greater than the ranking of the serving cell.

10. The method of claim 8 wherein the candidate cell qualifies for reselection if the HCS priority of the serving cell equals the HCS priority of a candidate cell and the measured signal quality of the candidate cell is greater than the sum of a measured signal quality of the serving cell plus a system information supplied offset between the serving and the candidate cell plus a system information specified hysteresis value for the serving cell.

11. The method of claim 10 wherein the serving cell and the candidate cell are both Frequency Division Duplex cells, the quality value of the received signal for FDD cells is derived from Received Signal Code Power (RSCP) of Common Pilot Channel (CPICH) in the serving cell, and the system information supplied offset equals a first value.

12. The method of claim 10 wherein the serving cell and the candidate cell are both Frequency Division Duplex cells, the quality value of the received signal for FDD cells is derived from received energy per chip divided by the power density (Ec/N₀) of Common Pilot Channel (CPICH)in the serving cell, and the system information supplied offset equals a second value.

13. The method of claim 10 further comprises reselecting to the highest ranked cell if all criteria for that highest ranked time are fulfilled during a predetermined time interval.