Compliance checks for lower layered triggered mobility

Abstract

According to various, but not necessarily all, examples there is provided an apparatus comprising, means for receiving a plurality of lower layer triggered mobility (LTM) configurations; means for performing compliance checks on at least two LTM configurations of the plurality of LTM configurations; means for proceeding with at least one LTM configuration of the plurality of LTM configurations which passes a compliance check; and means for discarding at least one LTM configuration of the plurality of LTM configurations which fails a compliance check.

Description

[0001] TITLE

[0002] Compliance checks for lower layered triggered mobility

[0003] TECHNOLOGICAL FIELD

[0004] Examples of the disclosure relate to lower layered triggered mobility (LTM), and in particular to multiple compliance checks for LTM.

[0005] BACKGROUND

[0006] In a wireless networks, a user equipment (UE) can undergo a handover from one serving cell to another. Lower layered triggered mobility (LTM) can be used for the handover.

[0007] LTM configurations can undergo compliance checks so it can be determined if the cells, group of cells, central units (CUs) or distributed units (DUs) are compliant and suitable for LTM.

[0008] BRIEF SUMMARY

[0009] According to various, but not necessarily all, examples there is provided an apparatus comprising, means for receiving a plurality of lower layer triggered mobility (LTM) configurations; means for performing compliance checks on at least two LTM configurations of the plurality of LTM configurations; means for proceeding with at least one LTM configuration of the plurality of LTM configurations which passes a compliance check; and means for discarding at least one LTM configuration of the plurality of LTM configurations which fails a compliance check.

[0010] The plurality of LTM configurations may be associated with respective cells. The LTM configurations may be for switching from the serving cell.

[0011] Proceeding with the at least one LTM configuration may comprise using the at least one LTM configuration which passes a compliance check for LTM measurements.

[0012] The apparatus may further comprise means for transmitting, to a network node, an indication that at least one LTM configuration, which fails a compliance check, has failed the compliance check. Receiving the plurality of LTM configurations may comprise receiving a radio resource control (RRC) reconfiguration message comprising at least one of the plurality of LTM configurations.

[0013] The apparatus may further comprise: means for transmitting an indication that the apparatus has the capability to perform multiple compliance checks, and means for receiving instructions to perform multiple compliance checks.

[0014] An LTM configuration may comprise a reference configuration and a delta configuration, wherein the reference configuration is associated with a CU, the delta configuration is associated with a cell, and the delta configuration is defined based at least in part on the reference configuration.

[0015] The apparatus may further comprise means for discarding at least one LTM configuration of the plurality of LTM configurations associated with the same CU, DU and / or group of cells as the LTM configuration which fails a compliance check.

[0016] The apparatus may further comprise means for storing results of the at least two compliance checks.

[0017] According to various, but not necessarily all, examples there is provided an apparatus comprising: means for receiving, from a first network node, a first indication that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check; and means for transmitting, to a second network node, a second indication that the at least one LTM configuration has failed the compliance check, wherein transmitting the second indication is based at least in part on receiving the first indication.

[0018] The apparatus may further comprise means for determining which network node to transmit the second indication to.

[0019] The apparatus may further comprise means for transmitting a plurality of LTM configurations prior to receiving the first indication, wherein the at least one LTM configuration is of the plurality of LTM configurations, and wherein the plurality of LTM configurations are associated with respective cells. The apparatus may further comprise means for receiving the at least one LTM configuration prior to transmitting the plurality of LTM configurations

[0020] Transmitting the second indication may comprise transmitting the second indication to a network node associated with the LTM configuration which has failed a compliance check.

[0021] The apparatus may further comprise means for receiving from a first network node, an indication that at least one LTM configuration has passed a compliance check.

[0022] The apparatus may further comprise means for initiating a LTM cell switch for the at least one LTM configuration that has passed a compliance check.

[0023] The apparatus may further comprise means for initiating release of resources for a network node associated with the at least one LTM configuration that has failed a compliance check.

[0024] According to various, but not necessarily all, examples there is provided a method comprising: receiving a plurality of lower layer triggered mobility (LTM) configurations; performing compliance checks on at least two LTM configurations of the plurality of LTM configurations; proceeding with at least one LTM configuration of the plurality of LTM configurations which passes a compliance check; and discarding at least one LTM configuration of the plurality of LTM configurations which fails a compliance check.

[0025] According to various, but not necessarily all, examples there is provided a computer program comprising program instructions, which when executed by an apparatus cause the apparatus to perform at least the following: receiving a plurality of lower layer triggered mobility (LTM) configurations; performing compliance checks on at least two LTM configurations of the plurality of LTM configurations; proceeding with at least one LTM configuration of the plurality of LTM configurations which passes a compliance check; and discarding at least one LTM configuration of the plurality of LTM configurations which fails a compliance check.

[0026] According to various, but not necessarily all, examples there is provided a method comprising: receiving, from a first network node, a first indication that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check; and transmitting, to a second network node, a second indication that the at least one LTM configuration has failed the compliance check, wherein transmitting the second indication is based at least in part on receiving the first indication.

[0027] According to various, but not necessarily all, examples there is provided a computer program comprising program instructions, which when executed by an apparatus cause the apparatus to perform at least the following: receiving, from a first network node, a first indication that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check; and transmitting, to a second network node, a second indication that the at least one LTM configuration has failed the compliance check, wherein transmitting the second indication is based at least in part on receiving the first indication.

[0028] According to various, but not necessarily all, embodiments there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform at least a part of one or more methods described herein.

[0029] According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for performing at least part of one or more methods described herein. The description of a function and / or action should additionally be considered to also disclose any means suitable for performing that function and / or action. Functions and / or actions described herein can be performed in any suitable way using any suitable method.

[0030] According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims.

[0031] While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate. The description of a function should additionally be considered to also disclose any means suitable for performing that function

[0032] BRIEF DESCRIPTION

[0033] Some examples will now be described with reference to the accompanying drawings in which:

[0034] FIG. 1 shows an example of the subject matter described herein;

[0035] FIG. 2 shows another example of the subject matter described herein;

[0036] FIG. 3 shows another example of the subject matter described herein;

[0037] FIG. 4 shows another example of the subject matter described herein;

[0038] FIG. 5 shows another example of the subject matter described herein;

[0039] FIG. 6 shows another example of the subject matter described herein;

[0040] FIG. 7 shows another example of the subject matter described herein;

[0041] FIG. 8 shows another example of the subject matter described herein;

[0042] FIG. 9 shows another example of the subject matter described herein;

[0043] FIG. 10 shows another example of the subject matter described herein; and FIG. 11 shows another example of the subject matter described herein.

[0044] The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

[0045] DETAILED DESCRIPTION

[0046] FIG. 1 illustrates an example of a network 100 comprising a plurality of network nodes including terminal nodes 110, access nodes 120 and one or more core nodes 129. The terminal nodes 110 and access nodes 120 communicate with each other. The one or more core nodes 129 communicate with the access nodes 120.

[0047] The network 100 is in this example a radio telecommunications network, in which at least some of the terminal nodes 110 and access nodes 120 communicate with each other using transmission / reception of radio waves / signals. The one or more core nodes 129 may, in some examples, communicate with each other. The one or more access nodes 120 may, in some examples, communicate with each other.

[0048] The network 100 may be a cellular network comprising a plurality of cells 122 each served by an access node 120. In this example, the interface between the terminal nodes 110 and an access node 120 defining a cell 122 is a wireless interface 124.

[0049] The access node 120 is a cellular radio transceiver. The terminal nodes 110 are cellular radio transceivers.

[0050] In the example illustrated the cellular network 100 is a third generation Partnership Project (3GPP) network in which the terminal nodes 110 are user equipment (UE) and the access nodes 120 are base stations.

[0051] In examples the network 100 is an Evolved Universal Terrestrial Radio Access network (E- UTRAN). The E-UTRAN consists of E-UTRAN NodeBs (eNBs) 120, providing the E-UTRA user plane and control plane (RRC) protocol terminations towards the UE. The eNBs 120 are interconnected with each other by means of an X2 interface 126. The eNBs are also connected by means of the S1 interface 128 to the Mobility Management Entity (MME) 129.

[0052] In other examples the network 100 is a Next Generation (or New Radio, NR) Radio Access network (NG-RAN). The NG-RAN consists of gNodeBs (gNBs) 120, providing the user plane and control plane (RRC) protocol terminations towards the UE 110. The gNBs 120 are interconnected with each other by means of an Xn interface 126. The gNBs are also connected by means of the N2 interface 128 to the Access and Mobility management Function (AMF).

[0053] In some examples, the access nodes 120 can comprise at least one wireless edge computing server.

[0054] A user equipment (UE) can comprise a mobile equipment. Where reference is made to user equipment that reference includes and encompasses, wherever possible, a reference to mobile equipment.

[0055] The network 100 can comprise a combination of E-UTRAN and NG-RAN. The network 100 can comprise a 6thgeneration radio access network, 6GRAN.

[0056] A terminal node 110, such as a UE, can be configured to perform lower layer triggered mobility (LTM). LTM results in a decision to perform handover being made at a lower layer. The decision is made at layer 2 or layer 1 (for example, using Medium Access Control) rather than layer 3 (Radio Resource Control RRC). LTM is sometimes known as layer 1 , L1 , 1 layer 2, L2, triggered mobility.

[0057] FIG. 2 illustrates an example of signaling between entities. FIG. 2 illustrates methods performed by a system comprising interaction between different system entities. FIG. 2 also illustrates a collection of separate methods performed separately by the different system entities.

[0058] One or more of the features discussed in relation to FIG. 2 can be found in one or more of the other FIGs.

[0059] In the example of FIG. 2, a plurality of apparatuses transmit and / or receive one or more signals and / or messages across and / or via and / or using a network. In examples, any suitable form of communication in any suitable network can be used. For example, at least a portion of the network 100 of FIG. 1 can be used.

[0060] One of the apparatuses of FIG. 2 may be a UE 152 which may be a terminal node 110 of FIG. 1. One of the apparatuses of FIG. 2 may be a network node 154 such as a base station 154, which may be an access node 120 of FIG. 1. In some examples the base station 154 is a gNB.

[0061] At block 202, the base station 154 transmits a plurality of lower layer triggered mobility (LTM) configurations 211 .

[0062] In some but not necessarily all examples, the plurality of LTM configurations 211 are associated with respective cells. In some examples the respective cells belong to same central unit (CUs) or distributed units (DU) or are directly related to a cell or group of cells. In some examples, an LTM configuration is the candidate cell configurations belonging to a CU or the candidate cell configurations belonging to a DU. The plurality of LTM configurations 211 can be any suitable LTM candidate cell configurations. For example, the an LTM configuration 211 can be any suitable LTM candidate cell configuration to configure the UE 152 for LTM towards at least one candidate cell. In some, but not necessarily all, examples, the LTM configurations are for switching the UE 152 from the serving cell to a candidate cell.

[0063] In some examples, the plurality of LTM configurations 211 may be LTM candidate cell radio resource control (RRC) configurations.

[0064] At block 204, the UE 152 receives the plurality of LTM configurations 211 .

[0065] In some examples receiving the plurality of LTM configurations 211 comprises receiving a radio resource control (RRC) reconfiguration message comprising at least one of the plurality of LTM configurations 211. In some examples receiving the plurality of LTM configurations 211 comprises receiving one or more LTM candidate information elements (lEs) comprising the plurality of LTM configurations 211.

[0066] In some, but not necessarily all, examples, an LTM configuration comprises a reference configuration and a delta configuration. The reference configuration can be associated with a CU, the delta configuration can be associated with a cell, and the delta configuration can be defined based at least in part on the reference configuration.

[0067] In some examples, receiving a plurality of LTM configurations 211 comprises receiving at least one reference configuration and a plurality of delta configurations. In some examples, receiving a plurality of LTM configurations 211 comprises receiving a plurality of reference configurations, and a plurality of delta configurations.

[0068] In some examples, a reference configuration corresponds to more than one delta configurations. In some examples a reference configuration corresponds to more than one LTM configuration.

[0069] At block 206, the UE 152 performs compliance checks on at least two LTM configurations of the plurality of LTM configurations 211 . A compliance check, checks that the LTM configuration is compliant for an LTM cell switch for the UE 152. The compliance checks can be any suitable compliance checks. A compliance check can be passed or failed.

[0070] In some examples, performing compliance checks on at least two LTM configurations of the plurality of LTM configurations 211 comprises performing a first compliance check on a first LTM configuration and a second compliance check on a second LTM configuration. In some examples, performing compliance checks on at least two LTM configurations of the plurality of LTM configurations 211 comprises performing a compliance check on each of the at least two LTM configurations of the plurality of LTM configurations 211.

[0071] In some examples, performing compliance checks on at least two LTM configurations comprises performing a compliance check on all of the of the plurality of LTM configurations 211. In other examples, performing compliance checks on at least two LTM configurations comprises performing compliance checks on a subset of the plurality of LTM configurations 211.

[0072] In some, but not necessarily all, examples, the compliance checks for the at least two LTM configurations are performed at or close to the same time. In some examples the compliance checks for the at least two LTM configurations are performed within 100 seconds of each other. In some examples the compliance checks for the at least two LTM configurations are performed for the same LTM cell switch.

[0073] In some examples the UE 152 stores results of the at least two compliance checks. In some examples the UE 152 stores ACK (acknowledgement), NACK (negative acknowledgement) and / or DID_NOT_CHECK flags for the results of the at least two compliance checks. In some examples an ACK flag indicates that the respective LTM configuration passed the compliance check, a NACK flag indicates that the respective LTM configuration failed the compliance check and a DID_NOT_CHECK flag indicates that a compliance check was not performed for the respective LTM configuration. In some examples the UE 152 stores that status of the at least two compliance checks.

[0074] At block 208, the UE 152 proceeds with at least one LTM configuration of the plurality of LTM configurations 211 which passes a compliance check. In some, but not necessarily all, examples proceeding with the at least one LTM configuration comprises using the at least one LTM configuration for LTM measurements. The results of the LTM measurements can later be used for an LTM cell switch. In some examples proceeding with the at least one LTM configuration comprises initiating LTM measurements and / or performing LTM measurements.

[0075] At block 210, the UE 152 discards at least one LTM configuration of the plurality of LTM configurations 211 which fails a compliance check. This has an advantage that a UE can perform compliance checks and continue even if one LTM configuration fails.

[0076] In some but not necessarily all examples discarding at least one LTM configuration of the plurality of LTM configurations 211 which fails a compliance check comprises not proceeding with the at least one LTM configuration. For example, not using the at least one LTM configuration for LTM measurements.

[0077] In some but not necessarily all examples the UE 152 discards at least one LTM configuration of the plurality of LTM configurations 211 associated with the same CU, DU and / or group of cells as the LTM configuration which fails a compliance check. This can involve discarding LTM configurations of the same CU, DU and / or group of cells as the LTM configuration which fails a compliance check.

[0078] FIG. 3 illustrates an example of signaling between entities. FIG. 3 illustrates methods performed by a system comprising interaction between different system entities. FIG. 3 also illustrates a collection of separate methods performed separately by the different system entities.

[0079] One or more of the features discussed in relation to FIG. 3 can be found in one or more of the other FIGs. FIG. 3 comprises the blocks of FIG. 2 as well as some additional blocks. For brevity only the new blocks will be described.

[0080] As well as the UE 152 and the first base station I network node 154 that are present in FIG. 2, one of the apparatuses of FIG. 3 is a second base station I network node 156 which may be an access node 120 of FIG. 1 . At block 312, the UE 152 transmits an indication 313 that at least one LTM configuration, which fails a compliance check, has failed the compliance check. The indication 313 may be considered to be a failure indication 313.

[0081] In some examples, the indication 313 comprises an identifier, such as CU_ID, a DLIJD and / or a CELLJD of a CU, DU or cell associated with the at least one LTM configuration that has failed the compliance check. The identifier may be a network node identifier.

[0082] In some examples the indication 313 that at least one LTM configuration has failed the compliance check comprises at least one NACK flag for the at least one LTM configuration. In some examples the indication 313 that the at least one LTM configuration has failed the compliance check comprises ACK, NACK and / or DID_NOT_CHECK flags for the at least one LTM configuration.

[0083] In some examples the indication 313 comprises an information element indicating the non- compliant LTM configurations. The indication 313 can comprise the status of each LTM configuration per CU / DU / cell / cell group. For example, statuses could be NOT_CHECKED, COMPLIANT, and NOT_COMPLIANT.

[0084] In some examples transmitting the indication 313 that at least one LTM configuration has failed the compliance check comprises transmitting an RRC reconfiguration complete message. The RRC reconfiguration complete message may comprise the indication 313 that the at least one LTM configuration has failed the compliance check.

[0085] In other examples an RRC reconfiguration complete message is transmitted which is separate to the indication 313 that the at least one LTM configuration has failed the compliance check.

[0086] At block 314, the first base station 154 receives the indication 313 that at least one LTM configuration has failed a compliance check.

[0087] At block 316, the first base station 154 transmits an indication 317 that the at least one LTM configuration has failed the compliance check.

[0088] The first base station 154 receives a first indication 313 from a first network node 152, the UE 152, and transmits a second indication 317 to a second network node 156, the second base station 156. Transmitting the second indication 317 is based at least in part on receiving the first indication 313. The second indication 317 may be considered to be a failure indication 317.

[0089] In some examples, the second indication 317 is the same as the first indication 313. In other examples the first and second indications 313, 317 are different.

[0090] In some examples the second indication 317 comprises an information element indicating the non-compliant configurations.

[0091] In some, but not necessarily all, examples transmitting the second indication 317 comprises transmitting the second indication 317 to a network node associated with the LTM configuration which has failed a compliance check. Transmitting the second indication 317 may comprises transmitting the indication 317 to a CU or a DU associated with the LTM configuration which has failed a compliance check.

[0092] In some examples the first base station 154 initiates release of resources for a network node associated with the at least one LTM configuration that has failed a compliance check. In some examples transmitting the second indication 317 comprises initiating the release of resources. The release of network resources improves the performance and efficiency of the network.

[0093] In some examples the first base station 154 initiates correction of the at least one LTM configuration that has failed a compliance check. In some examples the first base station 154 initiates correction for the LTM configurations associated with same CU, DU, or group of cells as the at least one LTM configuration that has failed a compliance check.

[0094] In some examples the first bases station 154 determines which network node to transmit the second indication to 317. In some examples determining which network node to transmit the second indication 317 to is based at least in part on an identifier, such as a CU_ID, a DU_ID and / or a CELLJD.

[0095] At block 318, the second base station 156 receives the indication 317 that at least one LTM configuration, which fails a compliance check, has failed the compliance check. In some examples the second base station 156 releases resources associated with the at least one LTM configuration that has failed a compliance check. These resources might be those reserved for a potential LTM cell switch for the UE 152.

[0096] FIG. 4 illustrates an example of signaling between entities. FIG. 4 illustrates methods performed by a system comprising interaction between different system entities. FIG. 4 also illustrates a collection of separate methods performed separately by the different system entities.

[0097] One or more of the features discussed in relation to FIG. 4 can be found in one or more of the other FIGs. FIG. 4 comprises blocks of FIGs 2 and 3 as well as some additional blocks.

[0098] One of the apparatuses of FIG. 4 is a third base station I network node 158. The second and third base stations I network nodes 156, 158 may be different potential target base stations. One of the apparatuses of FIG. 4 is an access and mobility management function (AMF) node. Finally, one of the apparatuses of FIG. 4 is one or more user plane functions (UPFs).

[0099] At block 402, user data can be transmitted between the system entities.

[0100] At block 404, the UE 152 transmits an indication 421 that the UE 152 has the capability to perform multiple compliance checks.

[0101] At block 406, mobility control information is provided by the AMF.

[0102] At block 408, the UE 152 provides L3 measurement reports to the source base station 154.

[0103] At block 410, the source base station 154 makes a decision on LTM. This may comprise determining to perform a LTM cell switch I handover.

[0104] At block 412, the source base station 154 transmits handover requests 423 to the target base stations 156, 158.

[0105] In some examples, at least one handover request 423 comprises a request for at least one LTM configuration. In some examples the at least one handover request 423 comprises a flag indicating a request for at least one LTM configuration such as a request for a reference plus delta configuration. At block 414, the target base stations 156, 158 perform admission control.

[0106] At block 416, handover request acknowledgements 425 are transmitted by the target base stations 156, 158 and received by the source base station 154.

[0107] In some examples the handover request acknowledgements 425 comprises at least one LTM configuration of the plurality of LTM configurations 211. In some examples the handover request acknowledgements 425 comprises reference and delta configurations.

[0108] In some the source base station 154 receives at least one LTM configuration and can receive the plurality of LTM configurations 211. This can be part of or sperate to the handover request acknowledgements 425.

[0109] At block 204, the UE 152 receives the plurality of LTM configurations 211. In some examples the UE 152 also receives instructions to perform multiple compliance checks. In some examples the UE 152 receives an indication that multiple compliance checks are possible

[0110] FIG. 5 illustrates an example of signaling between entities. FIG. 5 illustrates methods performed by a system comprising interaction between different system entities. FIG. 5 also illustrates a collection of separate methods performed separately by the different system entities.

[0111] One or more of the features discussed in relation to FIG. 5 can be found in one or more of the other FIGs. FIG. 5 comprises blocks of FIGs 2, 3 and 4 as well as some additional blocks.

[0112] At block 520, the source base station 154 can re-prepare the target(s) for LTM cell switch. The source base station 154 can release resources of base stations, such as target base stations 156, 158, for which an associated LTM configuration was non-compliant.

[0113] In some examples, the source base station 154 receives from a first network node, an indication that at least one LTM configuration has passed a compliance check. This may be received from the UE 152. In some examples the indication that at least one LTM configuration has passed a compliance check comprises an ACK message. In some examples the indication that at least one LTM configuration has passed a compliance check is received as part of the same message as the failure indication 313. In other examples the indication that at least one LTM configuration has passed a compliance check is received separately to the failure indication 313.

[0114] In some examples but not necessarily all examples the source base station 154 initiates a LTM cell switch for the at least one LTM configuration that has passed a compliance check. This may be based at least in part on receiving the indication that at least one LTM configuration has passed a compliance check.

[0115] An example of an RRC Configuration provided to a UE 152 for LTM, such as may occur in blocks 202 and 204, is captured schematically in FIG. 6. As shown, it contains the serving cell configuration information elements (IE), measurements’ config IE, radio bearer configuration IE and LTM Configuration IE (LTMConfig) which may contain target cell(s) LTM configurations.

[0116] In this example, the LTM Configuration IE contains: a reference configuration which is common for target cells; a list of delta configurations (one for a target cell), which contains the delta (cell-specific) configuration of target cells; and a channel state information (CSI) resource config IE which contains the target cells beam configuration.

[0117] In some examples, when the UE 152 receives a medium access control control element (MAC CE) to trigger cell change, it applies the target cell delta configuration on top of the reference configuration, and it will create a complete configuration for the LTM candidate cell.

[0118] LTM can offer improvements in handover latency and interruption time compared to Layer 3 based mobility.

[0119] In some but not necessarily all examples RRC structure for Inter-CU LTM designed is in a modular fashion (for example an LTM Config per CU). That may involve that there are multiple “Reference Configuration”. The UE 152 may form independently the “complete configuration = Reference Configuration + Delta Configuration” on a per CU basis. FIG. 7 illustrates a hierarchical structure of LTM configurations. In this illustrated example LTM Config = LTM ConfigGroup 1 (Ref 1 + candidate cells, DU 1.1 , DU 1.2) + LTM ConfigGroup 2 (Ref2 + candidate cells, DU 2.1 , DU 2.2) + LTM ConfigGroup 3 (Ref3 + candidate cells, DU 3.1 , DU 3.2).

[0120] In case of CU specific RRC configuration, such as in FIG. 7, it might not be clear how to perform compliance checks. Two issues are:

[0121] 1 : What should be the UE 152 behavior if compliance checks are allowed for RRC configuration per CU / DU / Cell?

[0122] According to 38.331 , 5.3.5.8 Reconfiguration failure, after a compliance check failure the UE 152 goes back to the previous valid configuration and initiates re-establishment upon which the connection reconfiguration ends. This means that UE 152 keeps using the serving cell configuration and does not perform a handover. There is no optimization on network side which has already reserved the resources in candidate target cells and eventually UE 152 will face radio link failure.

[0123] 2: How can signaling and fast recovery be optimized in case of compliance check and configuration failure per CU / DU / Cell?

[0124] If the network, in particular the source base station 164, does not get to know about compliance failure at the UE 152 side this results in unnecessarily reservation of resources in candidate target cells and higher interruption time due to no fast recovery mechanism.

[0125] According to some examples the UE 152 performs multiple compliance checks on LTM configurations provided by the network. The UE 152 may indicate the ability to perform multiple compliance checks to the UE 152. Besides the UE 152 may internally retain the status of the compliance check results for the configurations.

[0126] In one example, a compliance check is performed per CU level. A compliance check can be performed on at least one LTM configuration comprising reference configuration plus delta configurations for the candidate target cells per CU.

[0127] In a second example, a compliance check is performed per DU level. A compliance check can be performed on at least one LTM configuration comprising reference configuration plus delta configurations for the candidate target cells per DU. In a third example, a compliance check is performed per cell level. A compliance check can be performed on at least one LTM configuration comprising reference configuration plus delta configuration of the cell.

[0128] In a fourth alternative, a compliance check is performed per group of cells (belonging to different Dlls). A compliance check can be performed on at least one LTM configuration comprising reference configuration plus delta configuration of those cells.

[0129] Example 1 : UE 152 behavior in case of multiple compliance checks:

[0130] According to an example,

[0131] In case of multiple compliance checks per CU / DU / cell(s), if the UE 152 is unable to comply with one complete LTM configuration (which may be the combination of reference plus delta of one of the LTM candidates), the UE 152 continues using the other complete LTM configuration(s) (the combination of reference plus delta of one of the LTM candidates) which have not failed. Compliancy of configuration can mean that the LTM configuration is according to UE 152 capabilities.

[0132] In one alternative, if compliance check is performed per CU and one CU LTM configuration has failed to comply:

[0133] UE 152 continues using the LTM configuration for other CUs which have passed the compliance check.

[0134] In second alternative, if compliance check is performed per DU and one DU LTM configuration has failed to comply:

[0135] UE 152 continues using the LTM configurations of other DUs which have passed the compliance check.

[0136] In third alternative, if compliance check is performed per candidate target cell and one candidate target cell LTM configuration has failed to comply:

[0137] UE 152 continues using the LTM configurations of other candidate target cells which have passed the compliance check.

[0138] In fourth alternative, if compliance check is performed per group of candidate target cells (belonging to different DUs) and one group of candidate target cells LTM configuration has failed to comply: UE 152 continues using the LTM configurations of other groups of candidate target cells which have passed the compliance check .

[0139] In some examples, the UE 152 releases the LTM candidate cell configuration which has failed the compliance check. In some examples, the UE 152 stops performing L1 or L3 measurements for the LTM candidate cell configuration which has failed the compliance check. In some examples, the UE 152 does not execute LTM recovery for the LTM candidate cell configuration which has failed the compliance check. In some examples, the UE 152 internally keeps record of the checked compliance checks for the different LTM configurations.

[0140] Example 2: Indication to network in case of multiple compliance checks: According to an example,

[0141] In case of multiple compliance checks per CU / DU / cell(s), if one LTM configuration is failed the UE 152 continues using the other LTM configurations which have not failed and indicates to the network, such as to the source base station 154, which LTM configuration has failed.

[0142] In one alternative, if compliance check is performed per CU and one CU LTM configuration has failed to comply:

[0143] UE 152 indicates to the network the CU LTM configuration that has failed to comply.

[0144] In second alternative, if compliance check is performed per DU and one DU LTM configuration has failed to comply:

[0145] UE 152 indicates to the network the DU LTM configuration that has failed to comply.

[0146] In third alternative, if compliance check is performed per candidate target cell and one candidate target cell LTM configuration has failed to comply:

[0147] UE 152 indicates to the network the candidate target cell LTM configuration that has failed to comply.

[0148] According to some examples, an association of configurations with an identity (ID) is established.

[0149] In one alternative of per CU configuration, an ID may be the gNB ID. In second alternative of per DU configuration, an ID may be a combination of gNB ID and DU ID.

[0150] In third alternative per cell configuration, an ID may be a global cell ID or a LTM candidate ID.

[0151] Network (source base station 154) behavior on receiving indication 313 of configuration failure:

[0152] According to an example,

[0153] In case of multiple compliance checks per CU / DU / cell(s), if one LTM configuration is failed, the UE 152 continues using the other LTM configuration which have not failed and indicates to the network which LTM configuration has failed.

[0154] On receiving the indication 313, the source base station 154 releases the LTM configuration which has failed.

[0155] In one alternative, the source CU indicates to candidate target CU whose LTM configuration has failed to comply.

[0156] In second alternative, the source CU indicates to candidate target DUs (within same or different CUs) whose LTM configuration has failed to comply.

[0157] In third alternative, the source CU indicates to candidate target DUs (within same or different CUs) whose LTM configuration of a cell has failed to comply.

[0158] UE 152 behavior on compliancy check failure:

[0159] In some examples, the UE 152 releases the LTM candidate cell configuration which has failed the compliance check. In some examples, the UE 152 stops performing L1 or L3 measurements for the LTM candidate cell configuration which has failed the compliance check. In some examples, the UE 152 does not execute LTM recovery for the LTM candidate cell configuration which has failed the compliance checks. In some examples, the UE 152 internally keeps a record of the checked compliance checks for the different LTM configurations.

[0160] FIG. 8 illustrates an example of a method 800. The method 800 may be performed by an apparatus. For example, the UE 152. At block 802, the method 800 comprises receiving a plurality of lower layer triggered mobility (LTM) configurations 211.

[0161] At block 804, the method 800 comprises performing compliance checks on at least two LTM configurations of the plurality of LTM configurations 211 ;

[0162] At block 806, the method 800 comprises proceeding with at least one LTM configuration of the plurality of LTM configurations 211 which passes a compliance check.

[0163] At block 808, the method 800 comprises discarding at least one LTM configuration of the plurality of LTM configurations 211 which fails a compliance check.

[0164] In some examples a method comprises: receiving a plurality LTM configurations 211 ; and transmitting an indication 313 that at least one LTM configuration of the plurality of LTM configurations 211 has failed a compliance check.

[0165] FIG. 9 illustrates an example of a method 900. The method 900 may be performed by an apparatus. For example, the source base station 154 or another network node.

[0166] At block 902, the method 900 comprises receiving, from a first network node, a first indication 313 that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check.

[0167] At block 904, the method 900 comprises transmitting, to a second network node, a second indication 317 that the at least one LTM configuration has failed the compliance check. Transmitting the second indication 317 is based at least in part on receiving the first indication 313.

[0168] FIG. 10 illustrates an example of a controller 1000 suitable for use in an apparatus, such a UE 152 or a base station 154. Implementation of a controller 1000 may be as controller circuitry. The controller 1000 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

[0169] As illustrated in FIG. 10 the controller 1000 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions 1006 in a general-purpose or special-purpose processor 1002 that may be stored on a machine readable storage medium (disk, memory etc.) to be executed by such a processor 1002.

[0170] The processor 1002 is configured to read from and write to the memory 1004. The processor 1002 may also comprise an output interface via which data and / or commands are output by the processor 1002 and an input interface via which data and / or commands are input to the processor 1002.

[0171] The memory 1004 stores instructions, program, or code 1006 that controls the operation of the apparatus 152, 154 when loaded into the processor 1002. The computer program instructions, program or code 1006, provide the logic and routines that enables the apparatus 152, 154 to perform the methods illustrated in the accompanying FIGs. The processor 1002 by reading the memory 1004 is configured to load and execute the instructions, program, or code 1006.

[0172] The apparatus 152 comprises: at least one processor 1002; and at least one memory 1004 storing instructions that, when executed by the at least one processor 1002, cause the apparatus at least to: receive a plurality of lower layer triggered mobility (LTM) configurations; perform compliance checks on at least two LTM configurations of the plurality of LTM configurations 211 ; proceed with at least one LTM configuration of the plurality of LTM configurations 211 which passes a compliance check; and_ discard at least one LTM configuration of the plurality of LTM configurations 211 which fails a compliance check.

[0173] The apparatus 154 comprises: at least one processor 1002; and at least one memory 1004 storing instructions that, when executed by the at least one processor 1002, cause the apparatus at least to: receive, from a first network node, a first indication 313 that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check; and transmit, to a second network node, a second indication 317 that the at least one LTM configuration has failed the compliance check, wherein transmitting the second indication 317 is based at least in part on receiving the first indication 313. As illustrated in FIG. 11 , the instructions, program, or code 1006 may arrive at the apparatus 152, 154 via any suitable delivery mechanism 1008. The delivery mechanism 1008 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD-ROM) or a Digital Versatile Disc (DVD) or a solid-state memory, an article of manufacture that comprises or tangibly embodies the computer program 1006. The delivery mechanism may be a signal configured to reliably transfer the computer program 1006. The apparatus 152, 154 may propagate or transmit the computer program 1006 as a computer data signal.

[0174] The term “non-transitory” as used herein, is a limitation of the medium itself (i.e. , tangible, not a signal ) as opposed to a limitation on data storage persistency (for example, RAM vs. ROM).

[0175] Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: receive a plurality of lower layer triggered mobility (LTM) configurations; perform compliance checks on at least two LTM configurations of the plurality of LTM configurations 211 ; proceed with at least one LTM configuration of the plurality of LTM configurations 211 which passes a compliance check; and_ discard at least one LTM configuration of the plurality of LTM configurations 211 which fails a compliance check.

[0176] Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: receive, from a first network node, a first indication 313 that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check; and transmit, to a second network node, a second indication 317 that the at least one LTM configuration has failed the compliance check, wherein transmitting the second indication 317 is based at least in part on receiving the first indication 313.

[0177] The computer program instructions may be comprised in a computer program, a non- transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program.

[0178] Although the memory 1004 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable and / or may provide permanent / semi-permanent / dynamic / cached storage.

[0179] Although the processor 1002 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable. The processor 1002 may be a single core or multi-core processor.

[0180] References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

[0181] As used in this application, the term ‘circuitry’ may refer to one or more or all the following:

[0182] (a) hardware-only circuitry implementations (such as implementations in only analog and / or digital circuitry) and

[0183] (b) combinations of hardware circuits and software, such as (as applicable): i. a combination of analog and / or digital hardware circuit(s) with software / firmware and ii. any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory or memories that work together to cause an apparatus, such as a mobile phone or server, to perform various functions and

[0184] (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (for example, firmware) for operation, but the software may not be present when it is not needed for operation. 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 and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0185] The blocks illustrated in the accompanying Figs may represent steps in a method and / or sections of code in the computer program 1006. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

[0186] As used here ‘module’ refers to a unit or apparatus that excludes certain parts / components that would be added by an end manufacturer or a user. The apparatus 152, 154 can, for example be a module. A controller 1000 of the apparatus 152, 154 can, for example be a module.

[0187] Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

[0188] Elements may be operationally coupled and any number or combination of intervening elements can exist (including no intervening elements).

[0189] The above-described examples find application as enabling components of: automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and / or augmented reality; personal systems including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things; virtualized networks; and related software and services. The apparatus can be provided in an electronic device, for example, a mobile terminal, according to an example of the present disclosure. It should be understood, however, that a mobile terminal is merely illustrative of an electronic device that would benefit from examples of implementations of the present disclosure and, therefore, should not be taken to limit the scope of the present disclosure to the same. While in certain implementation examples, the apparatus can be provided in a mobile terminal, other types of electronic devices, such as, but not limited to: mobile communication devices, hand portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of electronic systems, can readily employ examples of the present disclosure. Furthermore, devices can readily employ examples of the present disclosure regardless of their intent to provide mobility.

[0190] The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to ‘comprising only one...’ or by using ‘consisting.’

[0191] In this description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e., to provide direct or indirect connection / coupling / communication. Any such intervening components can include hardware and / or software components.

[0192] As used herein, the term "determine / determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database, or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also, " determine / determining" can include resolving, selecting, choosing, establishing, and the like.

[0193] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’, or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

[0194] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0195] Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

[0196] Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

[0197] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0198] The description of a feature, such as an apparatus or a component of an apparatus, configured to perform a function, or for performing a function, should additionally be considered to also disclose a method of performing that function. For example, description of an apparatus configured to perform one or more actions, or for performing one or more actions, should additionally be considered to disclose a method of performing those one or more actions with or without the apparatus.

[0199] Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not. The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

[0200] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

[0201] In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

[0202] The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

[0203] Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon. l / we claim:

Claims

28CLAIMS1. An apparatus comprising: means for receiving a plurality of lower layer triggered mobility (LTM) configurations; means for performing compliance checks on at least two LTM configurations of the plurality of LTM configurations; means for proceeding with at least one LTM configuration of the plurality of LTM configurations which passes a compliance check; and means for discarding at least one LTM configuration of the plurality of LTM configurations which fails a compliance check.

2. The apparatus of claim 1, wherein the plurality of LTM configurations are associated with respective cells.

3. The apparatus of claim 1 or 2, wherein proceeding with the at least one LTM configuration comprises using the at least one LTM configuration which passes a compliance check for LTM measurements.

4. The apparatus of claim 1 , 2 or 3, further comprising means for transmitting, to a network node, an indication that at least one LTM configuration, which fails a compliance check, has failed the compliance check.

5. The apparatus of any of the preceding claims, wherein receiving the plurality of LTM configurations comprises receiving a radio resource control (RRC) reconfiguration message comprising at least one of the plurality of LTM configurations.

6. The apparatus of any of the preceding claims, further comprising means for transmitting an indication that the apparatus has the capability to perform multiple compliance checks, and means for receiving instructions to perform multiple compliance checks.

7. The apparatus of any of the preceding claims, wherein an LTM configuration comprises a reference configuration and a delta configuration, wherein the reference configuration is associated with a CU, the delta configuration is associated with a cell, and the delta configuration is defined based at least in part on the reference configuration.

8. The apparatus of any of the preceding claims, further comprising means for discarding at least one LTM configuration of the plurality of LTM configurations associated with the same CU, DU and / or group of cells as the LTM configuration which fails a compliance check.

9. The apparatus of any of the preceding claims, wherein the LTM configurations are for switching from the serving cell.

10. The apparatus of any of the preceding claims, further comprising means for storing results of the at least two compliance checks.

11. An apparatus comprising: means for receiving, from a first network node, a first indication that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check; and means for transmitting, to a second network node, a second indication that the at least one LTM configuration has failed the compliance check, wherein transmitting the second indication is based at least in part on receiving the first indication.

12. The apparatus of claim 11 , further comprising means for determining which network node to transmit the second indication to.

13. The apparatus of claim 11 or 12, further comprising means for transmitting a plurality of LTM configurations prior to receiving the first indication, wherein the at least one LTM configuration is of the plurality of LTM configurations, and wherein the plurality of LTM configurations are associated with respective cells.

14. The apparatus of claim 13, further comprising means for receiving the at least one LTM configuration prior to transmitting the plurality of LTM configurations15. The apparatus of any of claims 11 to 14, wherein transmitting the second indication comprises transmitting the second indication to a network node associated with the LTM configuration which has failed a compliance check.

16. The apparatus of any of claims 11 to 15, further comprising means for receiving from a first network node, an indication that at least one LTM configuration has passed a compliance check.

17. The apparatus of claim 16, further comprising means for initiating a LTM cell switch for the at least one LTM configuration that has passed a compliance check.

18. The apparatus of any of claims 11 to 17, further comprising means for initiating release of resources for a network node associated with the at least one LTM configuration that has failed a compliance check.

19. The apparatus of any of claims 11 to 18, wherein an LTM configuration comprises a reference configuration and a delta configuration, wherein the reference configuration is associated with a CU, the delta configuration is associated with a cell, and the delta configuration is defined based at least in part on the reference configuration.

20. A method comprising: receiving a plurality of lower layer triggered mobility (LTM) configurations; performing compliance checks on at least two LTM configurations of the plurality of LTM configurations; proceeding with at least one LTM configuration of the plurality of LTM configurations which passes a compliance check; and discarding at least one LTM configuration of the plurality of LTM configurations which fails a compliance check.

21. The method of claim 20, further comprising transmitting, to a network node, an indication that at least one LTM configuration, which fails a compliance check, has failed the compliance check22. A computer program comprising program instructions, which when executed by an apparatus cause the apparatus to perform at least the following: receiving a plurality of lower layer triggered mobility (LTM) configurations; performing compliance checks on at least two LTM configurations of the plurality of LTM configurations; proceeding with at least one LTM configuration of the plurality of LTM configurations which passes a compliance check; anddiscarding at least one LTM configuration of the plurality of LTM configurations which fails a compliance check.

23. A method comprising: receiving, from a first network node, a first indication that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check; and transmitting, to a second network node, a second indication that the at least one LTM configuration has failed the compliance check, wherein transmitting the second indication is based at least in part on receiving the first indication.

24. The method of claim 23, further comprising: initiating release of resources for a network node associated with the at least one LTM configuration that has failed a compliance check.

25. A computer program comprising program instructions, which when executed by an apparatus cause the apparatus to perform at least the following: receiving, from a first network node, a first indication that at least one lower layer triggered mobility (LTM) configuration has failed a compliance check; and transmitting, to a second network node, a second indication that the at least one LTM configuration has failed the compliance check, wherein transmitting the second indication is based at least in part on receiving the first indication.

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