Method and Apparatus for Cell Reselection for a Wireless Communication Device

Abstract

A method and apparatus for cell reselection for a wireless communication device are disclosed.

1 . A method for cell reselection in a user equipment UE for use in a mobile telecommunications system, in which the UE is arranged to receive a plurality of system information blocks, SIBs, including a primary SIB and a secondary SIB of the same type, and in which the UE is camped on a first cell, and in which the cells listed comprise a second cell for reselection; the method comprising:
 conditional on receipt of the secondary SIB before receipt of the primary SIB:
 starting measurements, and cell reselection evaluation, of cells listed in the secondary SIB; 
 reselecting to the second cell conditional upon satisfying a predetermined criteria; 
 and in which the predetermined criteria relates to a quality of the first cell, 
 and in which the predetermined criteria comprises at least one of: 
 a received signal strength of the first cell or a signal-to-interference ratio of the first cell is below a threshold; 
 the UE has attempted to receive the primary SIB for more than a predetermined period of time; and 
 for a communications channel carrying the SIBs, an indication of errors on the channel is above a threshold. 
   
     
     
         2 . The method as claimed in  claim 1 , in which the predetermined criteria relates to a quality of the first cell and the quality of the second cell. 
     
     
         3 . The method as claimed in  claim 1 , in which the predetermined criteria comprises:
 Srxlev ServingCell <=S SIB11-threshP  or Squal ServingCell <=S SIB11-threshQ .   
     
     
         4 . The method as claimed in  claim 1 , further comprising:
 initiating a secondary SIB treselection timer for a cell listed in the secondary SIB; and   
       when the secondary SIB treselection timer expires:
   reselecting to a cell listed in the primary SIB or the secondary SIB dependent at least in part upon whether there is a running primary SIB treselection timer for a cell listed in the primary SIB.   
 
     
     
         5 . The method as claimed in  claim 1 , further comprising:
 initiating a secondary SIB treselection timer for a cell listed in the secondary SIB; and   when the secondary SIB treselection timer expires:
 reselecting to a cell listed in the primary SIB or the secondary SIB dependent at least in part upon whether there is a running primary SIB treselection timer for a cell listed in the primary SIB; 
   
       and further comprising:
 conditional on there being no primary SIB treselection timer running:
 reselecting to a cell listed in the secondary SIB. 
 
 
     
     
         6 . The method as claimed in  claim 1 , further comprising:
 initiating a secondary SIB treselection timer for a cell listed in the secondary SIB; and when the secondary SIB treselection timer expires:
 reselecting to a cell listed in the primary SIB or the secondary SIB dependent at least in part upon whether there is a running primary SIB treselection timer for a cell listed in the primary SIB; and 
   conditional on there being a primary SIB treselection timer running:
 reselecting to a cell listed in the primary SIB if the primary SIB treselection timer expires and the cell in the primary SIB satisfies a reselection criteria, and 
 assessing whether there is a further primary SIB treselection timer running if the primary SIB treselection timer stops. 
   
     
     
         7 . The method as claimed in  claim 1 , further comprising:
 conditional on receiving no indication that a previously received primary SIB is no longer valid:
 starting measurements, and cell reselection evaluation, of cells listed in the previously received primary SIB. 
   
     
     
         8 . The method as claimed in  claim 1 , in which the UE is camped on a primary cell prior to camping on the first cell, the method further comprising:
 conditional on receiving no information that a previously received primary SIB is no longer valid:
 starting measurements, and cell reselection evaluation, of cells listed in the previously received primary SIB; 
   the previously received primary SIB received when the UE is camped on the previous cell.   
     
     
         9 . The method as claimed in  claim 1 , in which the secondary SIB comprises the information elements IEs “Intra-frequency cell info list”, “Inter-frequency cell info list” and “Inter-RAT cell info list”, one or more of the IEs comprising the listed cells. 
     
     
         10 . The method as claimed in  claim 1 , in which the secondary SIB comprises the information IE “Inter-RAT info list”, in which the Inter-RAT cell info list comprises cells associated with a radio access technology (RAT) different to a RAT associated with the first cell. 
     
     
         11 . The method as claimed in  claim 1 , in which receipt of the primary SIB comprises the UE successfully receiving system information from the primary SIB. 
     
     
         12 . The method as claimed in  claim 1 , in which the type of SIB is type 11, the primary SIB comprises SIB 11, and the secondary SIB comprises SIB11bis. 
     
     
         13 . The method as claimed in  claim 1 , in which at least one or more of the first cell, second cell and cells listed, is associated with either frequency division duplex, FFD, or time division duplex, TDD. 
     
     
         14 . A user equipment device, UE, comprising:
 a processor; and a memory; the UE adapted for cell reselection and arranged to receive a plurality of system information blocks SIBs including a primary SIB and a secondary SIB of the same type; the UE operable so that:   conditional on receipt of the secondary SIB before the primary SIB:
 start measurements and call reselection evaluation, of cells listed in the secondary SIB; 
 reselect to the second cell conditional upon satisfying a predetermined criteria; 
 and in which predetermined criteria relates to a quality of the first cell, and in which the predetermined criteria comprises at least one of: 
 a received signal strength of the first cell or a signal-to-interference ratio of the first cell is below a threshold; 
 the UE has attempted to receive the primary SIB for more than a predetermined period of time; and 
 for a communications channel carrying the SIBs, an indication of errors on the channel is above a threshold. 
   
     
     
         15 . The device as claimed in  claim 14 , further operable to:
 reselect to the second cell conditional upon satisfying a predetermined criteria;   and in which the predetermined criteria relates to a quality of the first cell and the quality of the second cell.   
     
     
         16 . The device as claimed in  claim 14 , further operable to:
 reselect to the second cell conditional upon satisfying a predetermined criteria; in which the predetermined criteria comprises:   Srxlev ServingCell <=S SIB11-threshP  or Squal ServingCell <=S SIB11-threshQ .   
     
     
         17 . The device as claimed in  claim 14 , further operable to:
 initiate a secondary SIB treselection timer for a cell listed in the secondary SIB; and when the secondary SIB treselection timer expires:
 reselect to a cell listed in the primary SIB or the secondary SIB dependent at least in part upon whether there is a running primary SIB treselection timer for a cell listed in the primary SIB. 
   
     
     
         18 . The device as claimed in  claim 14 , further operable to:
 initiate a secondary SIB treselection timer for a cell listed in the secondary SIB; and when the secondary SIB treselection timer expires:
 reselect to a cell listed in the primary SIB or the secondary SIB dependent at least in part upon whether there is a running primary SIB treselection timer for a cell listed in the primary SIB; and further conditional on there being no primary SIB treselection timer running: 
 reselect to a cell listed in the secondary SIB. 
   
     
     
         19 . The device as claimed in  claim 14 , further operable to:
 initiate a secondary SIB treselection timer for a cell listed in the secondary SIB; and when the secondary SIB treselection timer expires:   reselect to a cell listed in the primary SIB or the secondary SIB dependent at least in part upon whether there is a running primary SIB treselection timer for a cell listed in the primary SIB; and   conditional on there being a primary SIB treselection timer running:   reselect to a cell listed in the primary SIB if the primary SIB treselection timer expires and the cell in the primary SIB satisfies a reselection criteria, and   assess whether there is a further primary SIB treselection timer running if the primary SIB treselection timer stops.   
     
     
         20 . The device as claimed in  claim 14 , further operable to:
 conditional on receiving no indication that a previously received primary SIB is no longer valid:
 start measurements, and cell reselection evaluation, of cells listed in the previously received primary SIB. 
   
     
     
         21 . The device as claimed in  claim 14 , in which the UE is camped on a primary cell prior to camping on the first cell, the UE further operable to:
 conditional on receiving no information that a previously received primary SIB is no longer valid:   start measurements, and all reselection evaluation, of cells listed in the previously received primary SIB;   the previously received primary SIB received when the UE is camped on the previous cell.   
     
     
         22 . The device as claimed in  claim 14 , in which the secondary SIB comprises the information elements IEs “Intra-frequency cell info list”, “Inter-frequency cell info list” and “Inter-RAT cell info list”, one or more of the IEs comprising the listed cells. 
     
     
         23 . The device as claimed in  claim 14 , in which receipt of the primary SIB comprises the UE successfully receiving system information from the primary SIB; or in which the type of SIB is type 11, the primary SIB comprises SIB 11, and the secondary SIB comprises SIB11bis. 
     
     
         24 . A non-transitory computer readable medium having computer executable instructions stored thereon, the computer executable instructions arranged, in use, to cause a device, that comprises a processor; and a memory; where the device is adapted for cell reselection and arranged to receive a plurality of system information blocks SIBs including a primary SIB and a secondary SIB of the same type; to be operable to:
 conditional on receipt of the secondary SIB before the primary SIB:
 start measurements and call reselection evaluation, of cells listed in the secondary SIB; 
 reselect to the second cell conditional upon satisfying a predetermined criteria; 
 and in which predetermined criteria relates to a quality of the first cell, and in which the predetermined criteria comprises at least one of: 
 a received signal strength of the first cell or a signal-to-interference ratio of the first cell is below a threshold; 
 the UE has attempted to receive the primary SIB for more than a predetermined period of time; and 
 for a communications channel carrying the SIBs, an indication of errors on the channel is above a threshold. 
   
     
     
         25 . A non-transitory computer program comprising computer executable instructions arranged, in use in a device, that comprises a processor; and a memory; where the device is adapted for cell reselection and arranged to receive a plurality of system information blocks SIBs including a primary SIB and a secondary SIB of the same type; to cause the device to be operable to:
 conditional on receipt of the secondary SIB before the primary SIB:
 start measurements and call reselection evaluation, of cells listed in the secondary SIB; 
 reselect to the second cell conditional upon satisfying a predetermined criteria; 
 and in which predetermined criteria relates to a quality of the first cell, and in which the predetermined criteria comprises at least one of: 
 a received signal strength of the first cell or a signal-to-interference ratio of the first cell is below a threshold; 
 the UE has attempted to receive the primary SIB for more than a predetermined period of time; and 
 for a communications channel carrying the SIBs, an indication of errors on the channel is above a threshold.