Apparatus and corresponding method relating to cell reselection

Abstract

A method and related apparatus are disclosed, the method comprising: receiving, at user equipment (UE), uplink (UL) wake up signal (WUS), configuration information for requesting an on-demand (OD) system information block (SIB) from candidate cell; and determining whether to include the candidate cell in a candidate list for reselection based on public land mobile network (PLMN) related information associated with the candidate cell and a PLMN ID of the UE, wherein the WUS configuration information includes the PLMN related information associated with the candidate cell.

Description

[0001] DESCRIPTION

[0002] Title of the Invention

[0003] APPARATUS AND CORRESPONDING METHOD RELATING TO CELL RESELECTION

[0004] Field of the Invention

[0005] Various example embodiments relate to apparatus and a corresponding methods relating to cell reselection.

[0006] Background to the Invention

[0007] As referred to in 3GPP, a Network Energy Saving (NES) cell when operating in an On-Demand System Information Block Type 1 (OD-SIB1) mode will not periodically broadcast the SIB1. Instead, the SIB1 of the cell will be provided on-demand. That is, when UE is operating in RRC idle or RRC inactive mode, that UE must request its transmission. Such a UE will trigger the transmission of an OD-SIB1 by sending a wake-up signal (WUS).

[0008] Summary of the Invention

[0009] In accordance with the present invention, there is provided methods of networking devices and corresponding network devices, computer programs and non-transitory computer readable media as claimed in the accompanying claims.

[0010] According to a first example embodiment, a method is provided comprising: receiving, at user equipment (UE), uplink (UL) wake up signal (WUS), configuration information for requesting an on-demand (OD) system information block (SIB) from candidate cell; and determining whether to include the candidate cell in a candidate list for reselection based on public land mobile network (PLMN) related information associated with the candidate cell and a PLMN ID of the UE, wherein the WUS configuration information includes the PLMN related information associated with the candidate cell. The candidate cell may be a network energy saving cell

[0011] According to a second embodiment, a method is provided comprising: transmitting UL WUS configuration information for requesting an OD-SIB from candidate cell, wherein the WUS configuration information includes PLMN related information associated with the candidate cell .

[0012] The UL WUS configuration information may be transmitted by the candidate cell to anchor cell.

[0013] Alternatively, the UL WUS configuration information may be transmitted by anchor cell to UE. Where this is the case, the PLMN related information may include a flag which indicates that the candidate cell will serve UE if such UE is served by the anchor cell .The PLMN related information may include PLMN ID(s) associated with the candidate cell which indicate whether and / or to what extent the candidate cell will serve UE. For example, the PLMN ID(s) associated with the candidate cell may be used to indicate that the candidate cell will serve UEs of those PLMN ID(s). Alternatively, the PLMN ID(s) associated with the candidate cell may be used to indicate that the candidate cell will not serve UEs of those PLMN ID(s).

[0014] According to a third example embodiment, apparatus may be provided comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform a method as previously described.

[0015] According to a fourth example embodiment, a computer program may be provided comprising instructions which, when executed by an apparatus, cause the apparatus to perform a method as previously described.

[0016] According to a fifth example embodiment, a non-transitory computer readable medium may be provided comprising program instructions that, when executed by an apparatus, cause the apparatus to perform a method a method as previously described.

[0017] According to a sixth example embodiment, apparatus is provided comprising: means for receiving, at user equipment (UE), uplink (UL) wake up signal (WUS), configuration information for requesting an on-demand (OD) system information block (SIB) from candidate cell; and means for determining whether to include the candidate cell in a candidate list for reselection based on public land mobile network (PLMN) related information associated with the candidate cell and a PLMN ID of the UE, wherein the WUS configuration information includes the PLMN related information associated with the candidate cell. The candidate cell may be a network energy saving cell

[0018] According to a seventh embodiment, apparatus is provided comprising: means for transmitting UL WUS configuration information for requesting an OD-SIB from candidate cell, wherein the WUS configuration information includes PLMN related information associated with the candidate cell.

[0019] The UL WUS configuration information may be transmitted by the candidate cell to anchor cell.

[0020] Alternatively, the UL WUS configuration information may be transmitted by anchor cell to UE. Where this is the case, the PLMN related information may include a flag which indicates that the candidate cell will serve UE if such UE is served by the anchor cell .

[0021] The PLMN related information may include PLMN ID(s) associated with the candidate cell which indicate whether and / or to what extent the candidate cell will serve UE. For example, the PLMN ID(s) associated with the candidate cell may be used to indicate that the candidate cell will serve UEs of those PLMN ID(s). Alternatively, the PLMN ID(s) associated with the candidate cell may be used to indicate that the candidate cell will not serve UEs of those PLMN ID(s).Brief Description of the Drawings.

[0022] Example embodiments will now be described with reference to the accompanying figures in which:

[0023] Figs. 1 and 2 are message sequence diagram illustrating problems that arises when on-demand SIB1 with support of an anchor cell is implemented in cell border areas where cells belonging to multiple PLMNs are present as neighbours;

[0024] Figs. 3 and 4 are message sequence diagram illustrating solutions to the problems illustrated in figs. 1 and 2;

[0025] Fig. 5 illustrates an example embodiment of a UE method;

[0026] Fig. 6 illustrates an example embodiment of a cell method;

[0027] Fig. 7 is a simplified block diagram illustrating a device that is suitable for implementing example embodiments of the present disclosure.

[0028] Detailed Description of Embodiments

[0029] The principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these example embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

[0030] The terminology used herein to describe embodiments is not intended to limit the scope. The articles "a," "an," and "the" are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and / or "including," when used herein, specify the presence of stated features, items, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and / or groups thereof.

[0031] Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealized or overly formal sense unless expressly so defined herein.

[0032] As mentioned above, as referred to in 3GPP, a Network Energy Saving (NES) cell when operating in an On-Demand System Information Block Type 1 (OD-SIB1) mode will not periodically broadcast the SIB1. Instead, the SIB1 of the cell will be provided on-demand. That is, when UE is operating in RRC idle or RRC inactive mode, that UE must request its transmission. Such a UE will trigger the transmission of an OD-SIB1 by sending a wake-up signal (WUS) which could, for example, be a Physical Random-Access Channel (PRACH); i.e. a preamble. This requires that the UE is configured with resources and information to transmit the WUS.On-demand SIB1 can be implemented with the support of an Anchor Cell as follows:

[0033] ■ A UE can obtain WUS configuration from an Anchor Cell

[0034] ■ The UE can send uplink, UL, WUS (e.g. RACH / Msgl) to a NES cell operating in an On-Demand System Information Block Type 1 (OD-SIB1) mode.

[0035] ■ The UE can monitor / receive a Random Access Response (RAR) response from the cell that receives the WUS.

[0036] ■ The UE can then receive OD-SIB1 from the NES cell.

[0037] The inventors have appreciated that a problem (problem 1) can arise where OD-SIB1 is implemented in cell border areas where cells belonging to multiple public land mobile network (PLMNs) are present as neighbours. A scenario demonstrating this problem is illustrated in fig. 1 and, in particular, where a NES cell operates an Equivalent PLMN (EPLMN) which is not valid for the UE:

[0038] ■ Anchor Cell A belongs to a first PLMN, PLMN-1, of a first Mobile Network Operator, MNO-1. ■ In this scenario, PLMN-1 is a Home PLMN (HPLMN) and provides services only for UEs of MNO- 1. UEs of MNO-1 may be configured with EPLMNs of other MNOs to operate on those EPLMNs in areas where PLMN-1 is not available. For example, MNO-1 can be an operator with reduced coverage that expands its coverage in those areas using UE roaming to the equivalent EPLMNs.

[0039] ■ A NES Cell offers service for PLMN-2, which is not a valid EPLMN for the UE.

[0040] ■ A problem arises if UE is provided with a list of EPLMNs of the HPLMN (PLMN-1) and the UE is further provided by Anchor Cell A of HPLMN with a WUS configuration of NES-Cells including a subset of NES-cells not operating on HPLMN and out of which at least one NES Cell serves a PLMN-2 which is not included in the list of EPLMNs of PLMN-1 (step 2).

[0041] ■ The UE can attempt reselection to the NES Cell (step 3) but as it cannot be served by the NES Cell, this inevitably leads to reselection failure (step 7). However, this only arises after a UE has made an OB-SIB1 request (step 5) and the NES Cell has responded with SIB1 (step 6), wasting resources.

[0042] A further problem scenario (problem 1) is illustrated in fig. 2:

[0043] ■ Anchor Cell A uses network sharing of PLMN-1 and 2 but NES Cell is for PLMN-1 only

[0044] ■ Anchor Cell A broadcasts PLMN-1 of MNO-1 and PLMN-2 of MNO-2, meaning that it provides services for both PLMNs. For example, MNO-2 can be for example a virtual operator entirely relying on the Base Transceiver Station (BTS) network infrastructure of MNO-1, or an operator with reduced coverage that expands its coverage in certain areas by using network sharing with MNO-1. In both cases, MNO-2 may operate on fewer frequency layers than MNO-1. ■ NES Cell offers services only for PLMN-1 (and not PLMN-2).

[0045] ■ A problem arises because the UE of PLMN-2 can be served by Cell A (which broadcasts both PLMN-1 and 2), and receives the WUS Config of NES-Cells from Cell A, but cannot be served by that NES Cell, which operates only PLMN-1.■ The UE can atempt reselection to the NES Cell (step 3) but as it cannot be served by the NES Cell, this inevitably leads to reselection failure (step 7), wasting resources.

[0046] In both problem scenarios, it is observe that the UE atempts reselection to a cell that it shouldn't have tried to reselect to (based on the PLMN rules to be used in cell reselection) - and this results in reselection failure. Analogously similar problem may arise with tracking areas (TA) where UE may reselect to cell and request OD-SIB1 even though the cell is part of forbidden TA list for the UE. This also results in delayed discovery of service in NES cells, additional UE processing (and energy consumption) and overall user experience degradation. Furthermore, it will also consume energy in the NES cell to broadcast the SIB1 to a UE that will eventually not camp on that cell.

[0047] In accordance with the present invention, UL WUS provides configuration information for requesting OD-SIB1 from candidate cell apparatus which includes network related information indicating whether and / or to what extent the candidate cell will serve a UE. For example, this may include PLMN or TA related information associated with the candidate cell which can be compared to that of the UE to determine whether is worthwhile a UE requesting an OD-SIB1 from a candidate cell. If reselection to a cell will inevitably result in reselection failure, that UE can refrain from making an unnecessary atempt at reselection.

[0048] In one embodiment, a UE may receive an UL WUS Configuration from Anchor Cell A which includes PLMN IDs and / or TA Identity (TAI) of the NES Cells. Before atempting to reselect from Anchor Cell A to a NES Cell, the UE can consider the associated TAIs / PLMN ID(s) of the NES Cell and discard the NES Cells in the WUS configuration that are associated with TAs / PLMNs which are not valid for the UE. For example, if the NES-Cells-PLMNs are not included in the list of valid HPLMN / EPLMNs of the UE as stored in the USIM or TA being part of forbidden TA list.

[0049] PLMN-related information may comprise the PLMN ID(s) associated to each NES Cell included in the WUS Configuration. Such PLMN might also include EPLMN or Equivalent Home PLMN (EHPLMN) IDs. Similarly, TA-related information may comprise the TAI(s) associated to each NES Cell included in the WUS Configuration.

[0050] To reduce the signalling overhead, the PLMN-related information may comprise only the PLMN ID(s) associated to those NES Cells that broadcast PLMN ID(s) which differ at least partially from the PLMN ID(s) broadcast by Anchor Cell A. This requires that the gNB of a NES Cell is made aware of the PLMN ID(s) of Anchor Cell A to decide whether to include or not the PLMN information in the WUS Configuration.

[0051] Alternatively, the gNB of the NES Cell can always include the PLMN ID(s) and the gNB of Anchor Cell A can remove the PLMN ID(s) from the WUS Configuration if those are not needed (i.e. the same as for the Anchor Cell).

[0052] In another embodiment, a flag is used and is set to indicate "NES cell has same PLMN as cell A". This is relevant in case the PLMN information is not mandatory to be signalled, because the UE will then not know whether the absence of PLMN information for a NES cell is due to the NES cell sharing PLMN with the cell A or because the cell A decided not to provide the information.In another embodiment, to reduce the signalling overhead, TA-related information may comprise only the TAI(s) associated to those NES Cells that broadcast TAI(s) which differ at least partially from the TA(s) broadcast by the Cell A.

[0053] In another embodiment, the gNB serving Anchor Cell A may provide (e.g. broadcast) the UL WUS Configuration to its UEs including PLMN-related information.

[0054] In another embodiment, the gNB of the NES Cell(s) may include PLMN related information of at least one NES Cell in the UL WUS Configuration Information IE in a transmission over XnAP to the gNB of the serving Anchor Cell.

[0055] In another embodiment, the gNB-DU may host the NES Cell shall include the PLMN related information in the UL WUS Configuration to the gNB-CU over F1AP.

[0056] Figs. 3 and 4 are message sequence diagram illustrating solutions to problems 1 and 2 described above.

[0057] Referring to figure 3 in respect of problem 1:

[0058] Steps 1 & 2: The WUS Configuration includes the PLMN ID(s) 'PLMN-2' associated with the NES Cell. This is stored in Anchor Cell A and broadcast to its served UEs. The UE stores the PLMN IDs and uses them during the reselection process later.

[0059] Step 3: At the time of reselection, the UE checks if the PLMN-2 is part of its EPLMN list. If not, then it does not attempt reselect to this NES cell.

[0060] Step 4: The UE doesn't include any NES cell with PLMNs that are not in the Equivalent PLMN of its HPLMN (this is as per reselection rules). The UE is able to make this decision only because it has the knowledge of the PLMN IDs associated with the NES Cell (currently, it is completely blind to this critical information). This prevents a wasted OD-SIB1 procedure on that particular NES Cell.

[0061] Step 5: The UE may then reselect to a different cell not belonging to PLMN-2.

[0062] The same logic could be applied at the time of reselection based on UE checking NES Cell's TA list that is sent in the WUS Configuration.

[0063] Referring to figure 4 in respect of problem 2:

[0064] Steps 1 & 2: The WUS Configuration now includes also the PLMN ID(s) associated with the NES Cell. This is stored in the Cell A and then broadcast to its served UEs. The UE stores the PLMN IDs and uses them during the reselection process later.

[0065] Step 3: When the UE attempts to reselect, it doesn't include the NES cell associated with only PLMN-1 (since that is not a HPLMN for this UE - this is as per reselection rules). The UE is able to make this decision only because it has the knowledge of the PLMN IDs associated with the NES Cell (currently, it is completely blind to this critical information). This prevents a wasted OD-SIB1 procedure on that particular NES Cell.

[0066] Step 4: The UE may then reselect to a different cell that could be associated with PLMN-2.Again, the same logic could be applied at the time of reselection based on UE checking NES Cell's TA List that is sent in the WUS Configuration.

[0067] The principles described above can be extended to slice-based cell reselection.

[0068] A Network Slice AS Group is an identifier of a group of network slices which are associated with it. A Network Slice AS Group association with a group of network slices may be valid in one or more Tracking Areas. An Single Network Slice Selection Assistance Information (S-NSSAI) identifier can be associated with at most one NSAG values for Random Access and at most one NSAG value for Cell Reselection within a Tracking Area. An S-NSSAI can be associated with different NSAG values in different Tracking Areas.

[0069] Slice-based cell reselection information can be included in SIB16 and in RRCRelease messages. The slice-based cell reselection information may include reselection priorities per NSAG (Network Slice AS Group) per frequency and corresponding list(s) of cells where the slices of the NSAG are supported or not supported. The UE determines the NSAG(s) and their priorities to be considered during cell reselection. When a UE supports slice-based cell reselection, and when slice-based cell reselection information is provided to the UE, then the UE uses the slice-based cell reselection information. For example, slice based reselection can be expressed as follows, with each carrier frequency is associated with a slice info list which in turn has the NSAG ID + cell reselection priority value:

[0070] FreqPriorityListSlicing-rl7 :: = SEQUENCE (SIZE (l..maxFreqPlusl)) OF FreqPrioritySlicing-rl7 FreqPrioritySlicing-rl7 ::= SEQUENCE {

[0071] dl-ImplicitCarrierFreq-rl7 INTEGER (O..maxFreq),

[0072] sliceInfoList-rl7 SliceInfoList-rl7 OPTIONAL - Cond Mandatory

[0073] }

[0074] SliceInfoList-rl7 ::= SEQUENCE (SIZE (l..maxSliceInfo-rl7)) OF Slicelnfo-rl7

[0075] Slicelnfo-rl7 :: = SEQUENCE {

[0076] nsag-ldentitylnfo-rl7 NSAG-IdentityInfo-rl7,

[0077] nsag-CellReselectionPriority-rl7 CellReselectionPriority OPTIONAL, - Need R

[0078] nsag-CellReselectionSubPriority-rl7 CellReselectionSubPriority OPTIONAL, - Need R sliceCellListNR-rl7 CHOICE {

[0079] sliceAllowedCellListNR-rl7 SliceCellListNR-rl7,

[0080] sliceExcludedCellListNR-rl7 SliceCellListNR-rl7

[0081] } OPTIONAL - Need R

[0082] }

[0083] In addition to problem 1 and 2 identified above, a further problem (problem 3) can be identified in respect of network slices. The reselection priorities are given to the UE in a list of frequencies with associated NSAG IDs and reselection priorities. These are used by the UE in making a service-awaredecision of reselection. In case of Anchor Cell A to NES cell reselection, if the UE is not aware of this slice-based reselection priority - it could lead to the following issues:

[0084] ■ If there are certain services that the NES cell doesn't offer, then it may lead to the termination of those services post-reselection. This could lead to a bad user experience.

[0085] ■ On the other hand, if the UE has to request and get the slice based reselection priorities in the Cell A (as part of SIB16), then it could lead to additional UE power consumption since the UE has to already request and get the SIB-X that has the WUS Configuration.

[0086] In a further embodiment of the present invention, the WUS Configuration may include a Slice Information List of the NES Cell(s). This can be shared by the NES Cell to the Anchor A over Fl / Xn and then added to the WUS Configuration shared to the UE in the SIB-X. The UE could then make use of the same in its cell reselection decision.

[0087] For example, with reference to figure 3 above, in steps 1-2, the WUS Configuration includes the PLMN ID(s) (specifically PLMN-2) associated with the NES Cell. The WUS configuration may also include the Slice Info List of NES Cells. Thus, at the time of reselection in step 3 where the UE checks if the PLMN-2 is part of its EPLMN list, the UE could similarly use the prioritization provided by the Slice Information IE and decide to reselect or not the NES cell. Also, in respect of step 4, in addition to preventing a wasted OD-SIB1 procedure on that particular NES Cell, if the NES cell has a low priority for a given slice that the UE is interested in, the UE may not choose to reselect to that NES cell.

[0088] Fig. 5 illustrates a further example embodiment of method performed by UE comprising receiving (step 501) UL WUS configuration information for requesting an OD-SIB1 including PLMN, TA or network slice related information, and determining (step 502) whether to include the candidate cell in a candidate list for reselection based on the PLMN, TA or network slice information.

[0089] Fig. 6 illustrates a further example embodiment of method performed by a cell (including an anchor cell to a candidate cell and a candidate cell to UE) comprising transmitting (step 601) UL WUS configuration information for requesting an OD-SIB1 including PLMN, TA or network slice related information...

[0090] FIG. 7 is a simplified block diagram of a device 700 that is suitable for implementing example embodiments of the present disclosure. The device 700 can be implemented at or as a part of either UE apparatus or cell providing apparatus.

[0091] As shown, the device 700 includes a processor 710, a memory 720 coupled to the processor 710, a communication module 730 coupled to the processor 710, and a communication interface (not shown) coupled to the communication module 730. The memory 720 stores at least a program 740. The communication module 730 is for bidirectional communications, for example, via multiple antennas. The communication interface may represent any interface that is necessary for communication.

[0092] The program 740 is assumed to include program instructions that, when executed by the associated processor 710, enable the device 700 to operate in accordance with the example embodiments of the present disclosure, as discussed herein with reference to FIGS. 1-7. The example embodiments herein may be implemented by computer software executable by the processor 710 of the device 700, or byhardware, or by a combination of software and hardware. The processor 710 may be configured to implement various example embodiments of the present disclosure.

[0093] The memory 720 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 720 is shown in the device 700, there may be several physically distinct memory modules in the device 700. The processor 710 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 700 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0094] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0095] (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and

[0096] (b) combinations of hardware circuits and software, such as (as applicable):

[0097] (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and

[0098] (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation."

[0099] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0100] Generally, various example embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of example embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computerexecutable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the methods of figures 5 and 6. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various example embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0101] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server. In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable media. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), Digital Versatile Disc (DVD), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0102] The present invention is described primarily in the context of 5G, however, it will be appreciated that the same principles might apply to other cellular architectures including as yet unspecified, future architectures including 6G. Other variations to the present invention will suggest themselves to those skilled in the art.Abbreviations

[0103] EPLMN Equivalent PLMN

[0104] HPLMN Home PLMN

[0105] NAS Non-access stratum

[0106] NES Network energy saving OD On-demand

[0107] PLMN Public Land Mobile Network SIB1 System information block UE User equipment

[0108] WUS wake-up signal

Claims

WE CLAIM:

1. A method comprising:receiving, at user equipment (UE), uplink (UL) wake up signal (WUS), configuration information for requesting an on-demand (OD) system information block (SIB) from candidate cell; anddetermining whether to include the candidate cell in a candidate list for reselection based on public land mobile network (PLMN) related information associated with the candidate cell and a PLMN ID of the UE,wherein the WUS configuration information includes the PLMN related information associated with the candidate cell.

2. The method of claim 1, wherein the candidate cell is a network energy saving cell.

3. A method comprising:transmitting UL WUS configuration information for requesting an OD-SIB from candidate cell,wherein the WUS configuration information includes PLMN related information associated with the candidate cell .

4. The method of claim 3, wherein the UL WUS configuration information is transmitted by the candidate cell to anchor cell .

5. The method of claim 3, wherein the UL WUS configuration information is transmitted by anchor cell to UE .

6. The method of claim 5, wherein the PLMN related information includes a flag which indicates that the candidate cell will serve UE if such UE is served by the anchor cell .

7. The method of any preceding claim, wherein the PLMN related information includes PLMN ID(s) associated with the candidate cell which indicate whether and / or to what extent the candidate cell will serve UE .

8. The method of claim 7, wherein the PLMN ID(s) associated with the candidate cell are used to indicate that the candidate cell will serve UEs of those PLMN ID(s).

9. The method of claim 7, wherein the PLMN ID(s) associated with the candidate cell are used to indicate that the candidate cell will not serve UEs of those PLMN ID(s).

10. An apparatus comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the method of the preceding claims.

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