Method and Apparatus for Cell Reselection for a Wireless Communication Device

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.