Mobility in wireless communication systems

Abstract

A communication network supporting mobility of a user equipment moving through cells supported by different network node. During a period where the user equipment is applying lower layer triggered mobility and is periodically performing measurements related to candidate cells or beams, the user equipment may receive a deactivation message indicating at least one of said candidate cells or beams is deactivated; and in response the user equipment may at least temporarily stop at least one of the following: performing or reporting at least one of the measurements related to the at least one deactivated cell or beam; or selecting the deactivated cell for handover.

Description

[0001] MOBILITY IN WIRELESS COMMUNICATION SYSTEMS

[0002] TECHNOLOGICAL FIELD

[0003] Various example embodiments relate to wireless communication systems, and more particularly, to mobility within such wireless communication systems.

[0004] BACKGROUND

[0005] As a user equipment (UE) moves through a wireless communication system, it may move through cells that comprise regions of radio coverage that are supported by one or more network nodes. This requires the UE to switch between cells and there is latency, measurement signalling overhead and interruption time associated with such cell switches. Although layer 1 or layer 2, sometimes termed lower layer triggered mobility is being increasingly considered to reduce the latency, overhead and interruption time associated with a UE moving between the different cells, there are still reconfiguration overheads associated with such mobility, particularly where the availability of cells change.

[0006] BRIEF SUMMARY

[0007] The scope of protection sought for various example embodiments of the invention is set out by the independent claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0008] According to various, but not necessarily all, example embodiments of the disclosure there is provided according to one aspect a user equipment comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the user equipment at least to perform: during a period where said user equipment is applying lower layer, that is layer 1 or layer 2, triggered mobility and is periodically performing measurements related to candidate cells or beams; receiving a deactivation message indicating at least one of said candidate cells or beams is deactivated; and in response at least temporarily stopping at least one of the following : performing or reporting at least one of said measurements related to said at least one deactivated cell or beam; or selecting said deactivated cell for handover.

[0009] There may be reasons such as current overloading of a cell or beam, that make a cell or beam unsuitable or unavailable for a user equipment to swich to. Providing a mechanism to inform the user equipment of this allows the user equipment to discount this cell when selecting a cell for a handover. Thus, the user equipment may in response to a message indicating one or more cells or beams are deactivated, stop performing and / or reporting measurements relating to the cell or beam and / or where the user equipment is configured to perform user equipment triggered mobility it may inhibit selection of the deactivated cell / beam by the user equipment. In this way without requiring reconfiguration the UE can be kept up to date with changes in the availability of cells / beams and can reduce power overheads involved in measuring and reporting measurements related to an unsuitable cell or involved in attempting to switch to such a cell.

[0010] In some example embodiments, said at least one of said measurements comprises at least one of: layer 1 measurements; layer 3 measurements; path loss or received time difference RTD measurements.

[0011] The layer 1 and layer 3 measurements may be RSRP received signal to received power measurements. They may be performed and reported at layer 1 - the physical layer such as when sending Channel state information CSI or at the RRC radio resource control layer - layer 3 when sending an RRC measurement report. Layer 1 may be unfiltered or L1 filtered RSRP measurements and L3 measurement may be L3 filtered RSRP measurements.

[0012] In some example embodiments, said at least temporarily stopping comprises one of: performing said at least one measurement less often; or not performing said at least one measurement for a predetermined duration; or not performing said at least one measurement until receipt of a further message indicating said candidate cell or beam is to be reactivated.

[0013] In some example embodiments, where said at least temporarily stopping comprises not performing said at least one measurement for a predetermined duration, said user equipment is caused to activate a deactivation timer for a time indicative of said predetermined duration in response to receipt of said deactivation message.

[0014] The timer may be set for a time that is equal to the predetermined duration, or it may be set for a shorter duration, such that the UE recommences the measurements before the cell is reactivated. The predetermined duration may be predefined in the specification or it may be configured by the network.

[0015] In some example embodiments, where said at least temporarily stopping comprises not performing said at least one measurement for a predetermined duration, said user equipment is caused to initiate performing said at least one measurement a certain time before expiry of said predetermined duration.

[0016] The certain time can be determined by the UE or configured by the network.

[0017] In some example embodiments, said deactivation message comprises an indication of resources of said at least one deactivated cell or beam for which measurements are to be at least temporarily stopped, said user equipment being configured to at least temporarily stop performing said indicated measurements.

[0018] The resources may be reference signals that the cell is no longer transmitting.

[0019] In some example embodiments, wherein said deactivation message comprises an indication of a reason for deactivation of said cell. The reason may be related to the loading of the cell.

[0020] In some example embodiments, said deactivation message comprises an indication of a start time and a duration of deactivation of said cell or beam.

[0021] In some example embodiments, said deactivation message comprises an identifier indicating at least one of the following: a cell; or beam; or related cell / beam configuration of the cell or beam to be deactivated.

[0022] In some example embodiments, in response to receipt of said deactivation message, said user equipment is caused to perform: discarding stored measurements relating to said deactivated cell or beam.

[0023] In some example embodiments, in response to receipt of said deactivation message said user equipment is caused to perform at least one of the following: retaining stored measurements relating to said deactivated cell or beam that were measured within a predetermined time before said deactivation message was received and discarding those measured prior to said predetermined time; retaining stored measurements relating to said deactivated cell or beam that were measured within a predetermined time before reactivation of said cell or beam and discarding those measured prior to said predetermined time; and retaining received stored measurements relating to said deactivated cell or beam for a predetermined time and discarding older measurements received more than said predetermined time ago.

[0024] In some example embodiments, in response to receipt of said deactivation message stopping timing advance TA acquisition, update, maintenance or estimation of said deactivated cell or beam and triggering TA acquisition and / or estimation for an alternative candidate cell or beam.

[0025] The user equipment may be configured to perform certain processes for a certain number of candidate cells or beams, and thus, where one is marked as deactivated the UE may commence the certain processes for a further cell or beam.

[0026] In some example embodiments, said user equipment is caused to perform at least one of the following: measuring and reporting of a predetermined number of cells or beams, and in response to receipt of said deactivation message to initiate at least one of the following: measuring and reporting other cells or beams to replace said deactivated cells or beams.

[0027] In some example embodiments, said user equipment may be caused to perform at least one of the following in response to receipt of said deactivation message: monitoring other target candidate cells for handover, or performing handover related procedure such TA estimation or acquisition for other candidate cells.

[0028] In some example embodiments, said user equipment is configured to signal to a network node a capability to support deactivated cells and / or a predetermined number of supported deactivated cells. The UE may signal this information during RRC connection setup or resume.

[0029] In some example embodiments, in response to receipt of said deactivation message, marking said cell or beam as currently not available for handover in a list of candidate target cells or beams. In some example embodiments, said user equipment is caused to perform: receiving a cell or beam reactivation message; and in response to receipt of said reactivation message reinitiating at least one of the following: performing or reporting of at least one of said measurements or including said deactivated cell as a target candidate cell for a handover.

[0030] Where there is a deactivation timer, then in response to the reactivation message the deactivation timer may be stopped.

[0031] In some example embodiments, said user equipment is further caused to perform in response to receipt of said reactivation message at least one of the following: starting TA acquisition, update maintenance or estimation for said activated cell or beam; initiating synchronisation steps; initiating pathloss estimation; initiating received time difference RTD measurements; and marking said activated cell or beam as available for handover in a list of candidate cells or beams.

[0032] According to various, but not necessarily all, example embodiments of the disclosure there is provided a network node for supporting providing radio coverage within one or more cells of a communication network, said network node comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the network node at least to perform: receiving an indication that at least one cell or beam of a target network node is at least temporarily not available to at least some user equipment; in response to receipt of said indication generating deactivation information for said at least one cell or beam.

[0033] The network node may be a source or serving network node for the user equipment according to one aspect. Where the network node is a NR new radio node providing user plane and control plane protocol terminations towards the UE, then the network node may be a central unit CU or a distributed unit DU. The indication may be received from a target network node, the target network node may be a DU if target and source DU are supported by a same CU or if not it may be received from a different CU supporting the target DU.

[0034] In some example embodiments, said indication comprises at least one of the following: a reason for said at least one cell or beam being temporarily unavailable; a capability, a service requirement, a status condition, bearer type or identifiers of said at least some user equipment for which said cell or beam is not currently available and said network node is caused to: determine from at least one of capabilities, service requirements, status condition, bearer type and identifier of user equipment being served by said one or more cells whether said cell or beam is to be deactivated for said user equipment.

[0035] The reason may be the load at cell or DU level. The service requirements may relate to uplink, downlink or bearer type requirements. The UE status may be related to whether there is an alternative cell for the UE to connect to and whether if not there is a risk of radio link failure.

[0036] In some example embodiments, said network node is configured to transmit an indication of said user equipment for which said at least one cell or beam is deactivated to said target network node or to a further target network node. Where it is sent to more than one target network node, then if one of the target network nodes becomes the serving node it is already aware of other deactivated cells for the UE.

[0037] The indication may indicate a UE by its capabilities, status or service requirements or it may do so by an identifier. In this regard during the initial HO preparation the UE ID is provided to the target-cell or node as part of UE context. It may also be provided to a potential further target network node.

[0038] In some example embodiments, said network node comprising a central network node supporting at least one distributed network node providing said radio coverage to said one or more cells, said central network node receiving said indication from said target network node; and being caused to transmit said deactivation information to at least one of the following: said at least one distributed network node and a further central network node.

[0039] In some example embodiments, said network node comprises a distributed network node providing said radio coverage within said one or more cells, said distributed network node being caused to perform: receiving said indication that at least one cell or beam of a target network node is at least temporarily not available for at least some user equipment from a central network node; and in response to receipt of said indication generating said deactivation information as a cell or beam deactivation message; and transmitting said deactivation message to said at least some user equipment. In some example embodiments, said distributed network node is caused to transmit said deactivation message to said user equipment for which said cell or beam is determined to be deactivated.

[0040] In some example embodiments, said distributed network node is caused to inhibit any cell or beam handover to a cell or beam which has been deactivated.

[0041] In some example embodiments, said deactivation information comprises at least one of the following: an indication of resources of said at least one deactivated cell or beam for which measurements are to be at least temporarily stopped; an indication of a reason for deactivation of said cell; and an indication of a time period during which said cell or beam is to be deactivated.

[0042] The reason for deactivation may be current overloading of said cell or beam.

[0043] The deactivation message may comprise an identifier indicating at least one of the following: a cell; or beam; or related cell / beam configuration.

[0044] The deactivation message may be transmitted via MAC-CE medium access control control element when transmitted by a DU or RRC signalling when transmitted by a CU.

[0045] In some example embodiments, the source network node may generate new meas-config or meas-report config for the UE, and / or new HO config and / or may mark the cell as deactivated in LTM cell config.

[0046] In some example embodiments, said network node is caused to perform: receiving an indication that said at least one cell or beam of a target network node that was temporarily not available for a user equipment is available again; and in response to receipt of said indication generating reactivation information for said at least one cell or beam.

[0047] In some example embodiments, said central network node is caused to transmit said reactivation information to at least one of the following: said at least one distributed network node and a further central network node.

[0048] In some example embodiments, said distributed network node is caused to perform: in response to receipt of said available indication generating said reactivation information as a cell or beam reactivation message; and transmitting said reactivation message to said at least some user equipment.

[0049] According to various, but not necessarily all, example embodiments of the disclosure there is provided a second network node for supporting providing radio coverage within one or more cells of a communication network, said network node comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the network node at least to perform: determining that at least one of said one or more cells or at least one beam within said one or more cells is currently unavailable to at least some user equipment; generating an indication that said at least one beam or cell is deactivated for said at least some user equipment; transmitting said indication to one of: a serving network node or a central unit supporting said second network node.

[0050] A network node that supports multiple cells may determine that one or more cells or beams are not currently available, perhaps due to overloading, for a cell switch in a handover, particularly in a LTM, but also perhaps for other handovers. Providing an indication of this to a network node that is serving a user equipment that is moving through a network allows this cell to be discounted in the handover procedure.

[0051] In some example embodiments, said indication comprises an indication that that said at least one beam or cell is deactivated for all user equipment.

[0052] In some example embodiments, said indication comprises an indication of at least one of the following: a reason, a capability, a service requirement, status condition, bearer type or identifier of said at some user equipment for which said cell or beam is not currently available.

[0053] In some example embodiments, said indication comprises an indication of at least one of the following: a start time and duration for which said cell is to be deactivated.

[0054] In some example embodiments, said indication comprises an indication that said deactivation is relevant for LTM handovers. In other embodiments, said indication may indicate that the deactivation is relevant for all types of handovers. In some example embodiments, said indication comprises an indication of UE dedicated reference signal resources that are to be maintained or deactivated by said network node while said cell or beam is deactivated.

[0055] In some example embodiments, said dedicated reference signal resources are those used by a UE for LTM handover.

[0056] Where a cell or beam is to be deactivated for all UEs, then it may be sensible to pause the broadcast of reference signals thereby saving power and reducing signalling.

[0057] In some example embodiments, said network node is configured to stop transmission of said deactivated UE dedicated reference signal resources for a period of time that is equal to said duration during which said cell is to be deactivated or is less than said duration by a certain time.

[0058] The reference signals may be stopped during the whole time the cell is deactivated or for a part of the time, such that they start transmitting again before the cell is reactivated for handover purposes, allowing a UE to perform and report measurements ready for the cell reactivation.

[0059] In some example embodiments, said indication comprises at least one of the following: an indication of a type of handover for which said cell is deactivated; an indication of one or more beams for which said deactivation applies; a reason for said deactivation, information about activation or deactivation of one or more of said other cells or beams supported by said network node; an indication of allocated resources used for handover purposes that are to be maintained or deactivated by said network node while said cell or beam is deactivated

[0060] Example of the allocated resources include RA resources provided to the UE for TA acquisition / estimation, RA resources for handover, or uplink UL resources provided for UL transmission of the UE after HO to the target cell.

[0061] In some example embodiments, said network node is further caused to receive an indication of user equipment for which said at least one cell or beam has been deactivated. In some example embodiments, said network node is further caused at least to perform: determining that said at least one cell or beam that is currently unavailable to at least some user equipment is to become available again; generating an indication that said at least one cell or beam is to be activated for said at least some user equipment; transmitting said reactivation indication to one of: a serving network node or a central unit supporting said second network node.

[0062] In some example embodiments, said reactivation indication comprises an indication of UE dedicated reference signal resources that are to be reactivated by said network node.

[0063] In some example embodiments, said network node is further caused at least to perform: determining that said at least one cell or beam that is currently unavailable to at least some user equipment is to become available again; reactivating said UE dedicated reference signal resources.

[0064] The second network node described above may also be configured with the functionality of the network node described earlier, that is it may be a source network node for some user equipment and a target network node for others.

[0065] According to various, but not necessarily all, example embodiments of the disclosure there is provided a central unit supporting said second network node, said central unit being caused to receive said deactivation indication and to transmit said deactivation indication to a serving network node.

[0066] In some example embodiments, said central unit is configured to receive from said serving network node an indication of user equipment for which said cell or beam is deactivated and to generate a message indicative of said user equipment and to transmit said message to said second network node.

[0067] In some example embodiments, said central unit is caused to receive said reactivation indication and to transmit said reactivation indication to a serving network node.

[0068] According to various, but not necessarily all, example embodiments of the disclosure there is provided a method performed at a user equipment, said method comprising: during a period where said user equipment is applying lower layer, that is layer 1 or layer 2, triggered mobility and is periodically performing measurements related to candidate cells or beams; receiving a deactivation message indicating at least one of said candidate cells or beams is deactivated; and in response, at least temporarily stopping at least one of the following : performing or reporting at least one of said measurements related to said at least one deactivated cell or beam; or selecting said deactivated cell for handover.

[0069] In some example embodiments, said at least one of said measurements comprises at least one of: layer 1 measurements; layer 3 measurements; path loss or received time difference RTD measurements.

[0070] In some example embodiments said at least temporarily stopping comprises one of: performing said at least one measurement less often; or not performing said at least one measurement for a predetermined duration; or not performing said at least one measurement until receipt of a further message indicating said candidate cell or beam is to be reactivated.

[0071] In some example embodiments, where said at least temporarily stopping comprises not performing said at least one measurement for a predetermined duration, said method comprises activating a deactivation timer for a time indicative of said predetermined duration in response to receipt of said deactivation message.

[0072] In some example embodiments, where said at least temporarily stopping comprises not performing said at least one measurement for a predetermined duration, said method comprises performing said at least one measurement a certain time before expiry of said predetermined duration.

[0073] In some example embodiments, said deactivation message comprises an indication of resources of said at least one deactivated cell or beam for which measurements are to be at least temporarily stopped, said method comprises at least temporarily stopping performing said indicated measurements.

[0074] In some example embodiments, in response to receipt of said deactivation message, said method comprises discarding stored measurements relating to said deactivated cell or beam.

[0075] In some example embodiments, in response to receipt of said deactivation message said method comprises: at least one of the following: retaining stored measurements relating to said deactivated cell or beam that were measured within a predetermined time before said deactivation message was received and discarding those measured prior to said predetermined time; retaining stored measurements relating to said deactivated cell or beam that were measured within a predetermined time before reactivation of said cell or beam and discarding those measured prior to said predetermined time; and retaining received stored measurements relating to said deactivated cell or beam for a predetermined time and discarding older measurements received more than said predetermined time ago.

[0076] In some example embodiments, in response to receipt of said deactivation message stopping timing advance TA acquisition, update, maintenance or estimation of said deactivated cell or beam and triggering TA acquisition and / or estimation for an alternative candidate cell or beam.

[0077] In some example embodiments, in response to receipt of said deactivation message, marking said cell or beam as currently not available for handover in a list of candidate target cells or beams.

[0078] In some example embodiments, said method comprises signalling to a network node a capability to support deactivated cells and / or a predetermined number of supported deactivated cells.

[0079] In some example embodiments, said method comprises performing at least one of the following: measuring and reporting of a predetermined number of cells or beams, and in response to receipt of said deactivation message initiating at least one of the following: measuring and reporting other cells or beams to replace said deactivated cells or beams.

[0080] In some example embodiments, said method comprises receiving a cell or beam reactivation message; and in response to receipt of said reactivation message reinitiating at least one of the following: performing or reporting of at least one of said measurements or including said deactivated cell as a target candidate cell for a handover.

[0081] In some example embodiments, said method comprises in response to receipt of said reactivation message performing at least one of the following: starting TA acquisition, updating maintenance or estimation for said activated cell or beam; initiating synchronisation steps; initiating pathloss estimation; initiating received time difference RTD measurements; and marking said activated cell or beam as available for handover in a list of candidate cells or beams.

[0082] According to various, but not necessarily all, example embodiments of the disclosure there is provided a computer program comprising computer readable instructions which when executed by at least one processor on a user equipment is operable to control said user equipment to perform a method described above.

[0083] According to various, but not necessarily all, example embodiments of the disclosure there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: during a period where a user equipment is applying lower layer, that is layer 1 or layer 2, triggered mobility and is periodically performing measurements related to candidate cells or beams; in response to the user equipment receiving a deactivation message indicating at least one of said candidate cells or beams is deactivated; at least temporarily controlling the user equipment to stop at least one of the following : performing or reporting at least one of said measurements related to said at least one deactivated cell or beam; or

[0084] The instructions may be for performing the optional features set out in relation to the method mentioned above.

[0085] According to various, but not necessarily all, example embodiments of the disclosure there is provided a method performed at a network node, said method comprising: receiving an indication that at least one cell or beam of a target network node is at least temporarily not available to at least some user equipment; in response to receipt of said indication generating deactivation information for said at least one cell or beam.

[0086] In some example embodiments, said indication comprises at least one of the following: a reason for said at least one cell or beam being temporarily unavailable; a capability, a service requirement, a status condition, bearer type or identifiers of said at least some user equipment for which said cell or beam is not currently available and said method comprises: determining from at least one of capabilities, service requirements, status condition, bearer type and identifier of user equipment being served by said one or more cells whether said cell or beam is to be deactivated for said user equipment. In some example embodiments, said method comprises transmitting an indication of said user equipment for which said at least one cell or beam is deactivated to said target network node.

[0087] In some example embodiments, said method is performed at a central network node and comprises receiving said indication from said target network node; and transmitting said deactivation information to at least one of the following: said at least one distributed network node and a further central network node.

[0088] In some example embodiments, said method is performed at a distributed network node providing said radio coverage within said one or more cells, and comprises: receiving said indication that at least one cell or beam of a target network node is at least temporarily not available for at least some user equipment from a central network node; and in response to receipt of said indication generating said deactivation information as a cell or beam deactivation message; and transmitting said deactivation message to said at least some user equipment.

[0089] In some example embodiments, said method comprises transmitting said deactivation message to said user equipment for which said cell or beam is determined to be deactivated.

[0090] In some example embodiments, said method comprises inhibiting any cell or beam handover to a cell or beam which has been deactivated.

[0091] In some example embodiments, said method comprises receiving an indication that said at least one cell or beam of a target network node that was temporarily not available for a user equipment is available again; and in response to receipt of said indication generating reactivation information for said at least one cell or beam.

[0092] In some example embodiments, said method comprises transmitting said reactivation information to at least one of the following: said at least one distributed network node and a further central network node.

[0093] In some example embodiments, said method comprises in response to receipt of said available indication generating said reactivation information as a cell or beam reactivation message; and transmitting said reactivation message to said at least some user equipment.

[0094] According to various, but not necessarily all, example embodiments of the disclosure there is provided a computer program comprising computer readable instructions which when executed by at least one processor on a network node is operable to control said network node to perform a method described above.

[0095] According to various, but not necessarily all, example embodiments of the disclosure there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: controlling receiving an indication that at least one cell or beam of a target network node is at least temporarily not available to at least some user equipment; in response to receipt of said indication generating deactivation information for said at least one cell or beam.

[0096] The instructions may be for performing the optional features set out in relation to the method mentioned above.

[0097] According to various, but not necessarily all, example embodiments of the disclosure there is provided a method performed at a second network node, said method comprising: determining that at least one of said one or more cells or at least one beam within said one or more cells is currently unavailable to at least some user equipment; generating an indication that said at least one beam or cell is deactivated for said at least some user equipment; transmitting said indication to one of: a serving network node or a central unit supporting said second network node.

[0098] In some example embodiments, said method comprises stopping transmitting said deactivated UE dedicated reference signal resources for a period of time that is equal to said duration during which said cell is to be deactivated or is less than said duration by a certain time.

[0099] In some example embodiments, said method comprises receiving an indication of user equipment for which said at least one cell or beam has been deactivated.

[0100] In some example embodiments, said method comprises: determining that said at least one cell or beam that is currently unavailable to at least some user equipment is to become available again; generating an indication that said at least one cell or beam is to be activated for said at least some user equipment; transmitting said reactivation indication to one of: a serving network node or a central unit supporting said second network node.

[0101] In some example embodiments, said method comprises determining that said at least one cell or beam that is currently unavailable to at least some user equipment is to become available again; reactivating said UE dedicated reference signal resources.

[0102] According to various, but not necessarily all, example embodiments of the disclosure there is provided a computer program comprising computer readable instructions which when executed by at least one processor on a second network node is operable to control said second network node to perform a method described above.

[0103] According to various, but not necessarily all, example embodiments of the disclosure there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: determining that at least one of said one or more cells or at least one beam within said one or more cells is currently unavailable to at least some user equipment; generating an indication that said at least one beam or cell is deactivated for said at least some user equipment; controlling transmitting said indication to one of: a serving network node or a central unit supporting said second network node.

[0104] The instructions may be for performing the optional features set out in relation to the method mentioned above.

[0105] According to various, but not necessarily all, example embodiments of the disclosure there is provided a method performed at a central unit supporting said second network node, said method comprising receiving said deactivation indication and transmitting said deactivation indication to a serving network node.

[0106] In some example embodiments, said method comprises receiving from said serving network node an indication of user equipment for which said cell or beam is deactivated and generating a message indicative of said user equipment and to transmit said message to said second network node. In some example embodiments, said method comprises receiving said reactivation indication and transmitting said reactivation indication to a serving network node.

[0107] According to various, but not necessarily all, example embodiments of the disclosure there is provided a method performed at a central network node, said method comprising: receiving a cell deactivation indication and transmitting said cell deactivation indication to a serving network node.

[0108] According to various, but not necessarily all, example embodiments of the disclosure there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: controlling receiving a cell deactivation indication and controlling transmitting said cell deactivation indication to a serving network node.

[0109] The instructions may be for performing the optional features set out in relation to the method mentioned above.

[0110] According to various, but not necessarily all, example embodiments of the disclosure there is provided a user equipment comprising: means for controlling handover; means for performing measurements related to candidate cells or beams; and means for receiving messages; wherein during a period where said user equipment is applying lower layer, that is layer 1 or layer 2, triggered mobility and said means for performing measurements is periodically performing said measurements, in response to said means for receiving, receiving a deactivation message indicating at least one of said candidate cells or beams is deactivated; said user equipment is configured to at least temporarily stop at least one of the following: said means for performing measurements performing or reporting at least one of said measurements related to said at least one deactivated cell or beam; and said means for controlling handover selecting said deactivated cell for handover.

[0111] According to various, but not necessarily all, example embodiments of the disclosure there is provided a network node comprising: a means for receiving an indication that at least one cell or beam of a target network node is at least temporarily not available to at least some user equipment; and means for generating deactivation information, said means for generating said deactivation information generating said deactivation information in response to receipt of said indication for said at least one cell or beam. According to various, but not necessarily all, example embodiments of the disclosure there is provided a second network node comprising: means for determining that at least one of said one or more cells or at least one beam within said one or more cells is currently unavailable to at least some user equipment; means for generating an indication that said at least one beam or cell is deactivated for said at least some user equipment; and means for transmitting said indication to one of: a serving network node or a central unit supporting said second network node.

[0112] According to various, but not necessarily all, example embodiments of the disclosure there is provided a central network node comprising: means for receiving a cell deactivation indication and transmitting said cell deactivation indication to a serving network node.

[0113] The means may perform the optional features set out in relation to the apparatus mentioned above.

[0114] According to various, but not necessarily all, example embodiments of the disclosure there is provided a user equipment comprising: circuitry configured to control handover; circuitry configured to perform measurements related to candidate cells or beams; and circuitry configured to receive messages; wherein during a period where said user equipment is applying lower layer, that is layer 1 or layer 2, triggered mobility and said circuitry configured to perform measurements is periodically performing said measurements, in response to said circuitry configured to receive receiving a deactivation message indicating at least one of said candidate cells or beams is deactivated; said user equipment is configured to at least temporarily stop at least one of the following: said circuitry configured to perform measurements performing or reporting at least one of said measurements related to said at least one deactivated cell or beam; and said circuitry configured to control handover selecting said deactivated cell for handover.

[0115] According to various, but not necessarily all, example embodiments of the disclosure there is provided a network node comprising: circuitry configured to receive an indication that at least one cell or beam of a target network node is at least temporarily not available to at least some user equipment; and circuitry configured to generate deactivation information, said circuitry configured to generate said deactivation information generating said deactivation information in response to receipt of said indication for said at least one cell or beam. According to various, but not necessarily all, example embodiments of the disclosure there is provided a second network node comprising: circuitry configured to determine that at least one of said one or more cells or at least one beam within said one or more cells is currently unavailable to at least some user equipment; circuitry configured to generate an indication that said at least one beam or cell is deactivated for said at least some user equipment; and circuitry configured to transmit said indication to one of: a serving network node or a central unit supporting said second network node.

[0116] According to various, but not necessarily all, example embodiments of the disclosure there is provided a central network node comprising: circuitry configured to receive a cell deactivation indication and transmit said cell deactivation indication to a serving network node.

[0117] The circuitry may be configured perform the optional features set out in relation to the apparatus mentioned above.

[0118] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

[0119] Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

[0120] BRIEF DESCRIPTION

[0121] Some example embodiments will now be described with reference to the accompanying drawings in which:

[0122] FIG. 1 illustrates signalling during L1 / L2 centric mobility;

[0123] Fig. 2 shows inter-DU LTM signalling flow;

[0124] Fig. 3 shows LTM signalling flow, including the signalling of cell deactivation according to an embodiment; and

[0125] Fig. 4 shows a communication network comprising network nodes and user equipment according to an embodiment. DETAILED DESCRIPTION

[0126] Before discussing the example embodiments in any more detail, first an overview will be provided.

[0127] Embodiments are concerned with mobility within a wireless network. Particular embodiments are concerned with lower layer triggered mobility LTM or L1 / L2- Triggered Mobility. This is a PCell (or PSCell) primary or primary secondary cell switch procedure that the network triggers via MAC CE based on L1 measurements. In effect the decision about the cell change is based on L1 measurements and is made in the MAC layer in the Distributed Unit (DU).

[0128] Embodiments relate to target candidate cells or beams that may become unavailable to at least some user equipment and to how such information may be supplied to the relevant entities to inhibit them from selecting the cell or beam for a cell switch during a handover procedure. Information regarding the non-availability of a cell may be transmitted in a cell deactivation message that may be sent from a target network node via a serving or source network node to a user equipment. The deactivation of a cell may imply one or more of the following: that the cell is not available for a handover, in some cases just a LTM handover, for all or some UEs; and that the candidate target cell will no longer be transmitting reference signals that are relevant to the handover process.

[0129] Conventionally, in order for a UE to be made aware that a cell is no longer available, the UE’s LTM cell configurations is reconfigured. And further, when the overloaded candidate cell becomes available again, the UE’s LTM candidate configuration is reconfigured a second time to activate the candidate cell that was formerly released.

[0130] This results in signalling overhead both at the air and F1 interfaces and an increase of UE processing. In the worst-case, a failure might happen at the UE side if the re-preparation is delayed after the candidate cell is available.

[0131] Embodiments provide a method of deactivating an LTM candidate cell in case the cell is temporary overloaded or unavailable and a method of reactivating it again without requiring the UE’s LTM cell configurations to be reconfigured. In effect a candidate cell that is overloaded is deactivated and then reactivated without causing any significant signalling overhead and heavy RRC processing at the UE side. Fig. 1 shows steps performed in a conventional LTM handover between a UE 50, a source or serving distributed unit DU 20 and a target DU 30, the source and target DU both being controlled by the same central unit CU 40. The handover process is triggered using L3 measurements during a preparation phase, then the final decision on a cell to handover to is performed in response to L1 measurement reports during the execution phase.

[0132] In this example, the UE 50 provides the L3 measurements to the source DU 20, which are forwarded to the CU 40 (steps 1-2). Based on these measurements the CU 40 decides about the cell preparation (HO Decision - step 3) and proceeds in setting up the UE context in the target DU 30 (steps 4-5). CU 40 communicates with the source DU 20 for the modification of the UE 50 context if needed and the provision of the target cell 30 information (i.e., target cell CSI resource configuration, TCI states, etc.) (steps 6-7).

[0133] In step 8, the CU 40 creates and forwards the RRC Reconfiguration message to the source DU 30 using a DL RRC Message Transfer and the latter forwards it to the UE 50 (steps 9-10). UE 50 responds with an RRC Reconfiguration Complete to the CU 40 (steps 11 -12).

[0134] Based on its configuration, the UE provides the periodic L1 measurement reports to the source DU (step 13).

[0135] Based on the received L1 measurement report, the source DU 20 may trigger the UE 50 to acquire TA for the set of candidate cells (i.e., candidate cells for the handover target cell) (step 14-15). The UE 50 continues L1 measurement reporting. Once the source DU decides that the UE should be handed over to a cell (i.e., target cell) of another DU (i.e., target DU) it triggers the cell switch, using a cell switch command (e.g., a MAC CE) (step 16-18). the cell switch command may also contain the TA of the target cell.

[0136] Then the UE applies the RRC configuration for the target cell of target DU- indicated by the cell switch command (via MAC CE) and switches to the target DU.

[0137] The UE may be configured to perform Random Access (RA) to the target cell if TA is not available at the UE side or MAC CE command did not include the TA value of the target cell (this is one option which is not shown in the figure). To initiate the communication with the target DU, the UE transmits an RRC Reconfiguration Complete using already configured UL resources to the target cell of target DU, which is forwarded to the CU (steps 19-20).

[0138] The CU releases the UE context from the source DU with a UE Context Release Request and performs Path Switch to the new DU (steps 21 -22).

[0139] It has been considered that the UE 50 can maintain the LTM configuration for subsequent cell switch(es). In this case, it is possible for the UE 50 to perform cell switch without the need for RRC reconfiguration .

[0140] Fig. 2 shows inter DU LTM signalling flow, where LTM configuration is provided for several cells and these are maintained for a period of time and the UE can perform measurements and switch between them. This is sometimes termed dynamic switching, where reconfiguration between cell switches is not required and it is in this context, that embodiments are applicable.

[0141] Fig. 2 provides a signalling diagram showing such switching and step 7-8 are to enable LTM subsequent cell switches without reconfiguration by providing the LTM configuration to all the candidate DUs 30a-n. This has allowed LTM dynamic switching to proceed for these cells, if one of the cells is deemed to be unavailable and it is desirable to inhibit a switch to the cell, then conventionally, it has been required to reconfigure completely, that is recommence the configuration stage.

[0142] Now it may happen that one of the candidate cells temporarily may not be able to accept a UE handover e.g., due to increased traffic of the served UEs of the candidate cell which may cause overloading at that cell. Conventionally, the network addresses this by providing the UE with RRC-configuration to modify (release) the UE LTM cell configurations which comes with RRC-reconfiguration message overhead (both at the air interface and F1 interfaces) as well as processing at the UE side. When the overloaded candidate cell becomes available, the UE needs to be re-configured with LTM candidate configuration that were formerly released. This leads to further signalling overhead and UE processing. In the worst-case, it leads to failure at the UE side if the UE needs to handover to that candidate cell but if the re-preparation is delayed after the candidate cell is available. The problem that is addressed by embodiments is how to avoid or at least inhibit LTM to the candidate cell that is overloaded without causing undue additional signalling overhead and RRC processing at the UE side. In addition, it is discussed, how to enable the LTM handover to the candidate cell if it becomes available after it was overloaded without undue preparation delay, signalling overhead and heavy RRC processing at the UE side.

[0143] In effect LTM subsequent cell switch, where unavailable cells are identified and a switch to these cells is inhibited without requiring reconfiguration is sought.

[0144] A mechanism is proposed that enables the LTM candidate cell activation / deactivation to address the issue of temporary LTM candidate cell overload / unavailability without a reconfiguration requirement.

[0145] Some of these cell activation / deactivation techniques may be used in other handovers. In other words the deactivation and reactivation of the cell or beam may be applicable to other types of handover in addition to LTM. The type of handover may be signalled in the reactivation / deactivation messages.

[0146] Embodiments propose;

[0147] 1 . Target-DU / CU informs the source DU / CU about the temporary unavailability of the LTM candidate cell or beam for LTM so that the candidate cell preparations can be deactivated: a. UEs that are subjected to LTM candidate cell activation / deactivation can be selected through the following options; i. In one embodiment, the target-DU / CU informs deactivations for all the UEs (or all UEs served by a certain DU / cell / or beam). ii. In another embodiment, the deactivation can be announced for one or more specific UE. iii. In another embodiment, this can be conditioned based on or limited to UEs with specific service requirements (e.g., UEs with high UL traffic demand) and / or bearer type. iv. In another embodiment, this can be conditioned based on the UE status. For example, if there is alternative cell for the UE to connect (or handover to), then the target-cell is deactivated. Otherwise, if there is no other target-cell(s) available and there is a risk of radio link failure RLE, then the UE is allowed to HO (i.e., the target cell remains activated for the UE). v. This can be also based on the UE capability. As an example, FR1 LTM cell deactivation may be subjected to the UEs which support both FR1 and FR2 frequencies. In this example, the affected UEs are be able to connect to a cell in FR2. b. Activation / deactivation duration; i. In one case deactivation duration can be limited by time duration and an indication can be sent from the target DU (e.g., time the deactivation starts and the deactivation duration). ii. In another case, the deactivation continues until further indication from the network. c. Additional information that can be implicitly / explicitly provided with a deactivation message; i. In one case, deactivation message implicitly implies the invalidity of UE dedicated assigned (part of or all of) allocated resources for measurement (e.g., CSI-RS, Tracking Reference Signal TRS). Therefore, the UE does not perform measurement on the deactivated resources. ii. In another case, deactivation message may imply the availability (i.e., transmission) of UE dedicated reference signal RS resources for UE to continue the measurement. So, the UE can continue the measurement on these resources. iii. In case of deactivation with a pre-defined deactivation duration, the RS (e.g., CSI-RS) may also be deactivated for a same or different duration compared to the target-cell deactivation time (e.g., shorter than target-cell deactivation, so the UE can trigger measurement ahead of time to have measurement results available when the target-cell is reactivated again) iv. Additional information can provide indications about the validity (or activation / deactivation) of the other already provided resources such as resources for UL transmission, or resources for RA / TA acquisition. v. It can also provide explicit implicit information about the UE acquired / provided TA value. vi. Activation / indication may also provide information on which type of handover are affected (e.g., only LTM or all other types such as legacy HO, CHO). vii. Activation / deactivation may apply only to a set of beams (SSBs or TCI-state IDs) for example, in case of Multiple Transmission Reception Point multi- TRP scenario (e.g., non-collocated radio resource heads RRHs with the same physical cell ID PCI) where one of the RRH becomes overloaded. viii. The activation / deactivation indications may also provide explicit / implicit information about activation / deactivation of the other cells (e.g., in case of co-located carrier aggregation) ix. The reason of LTM deactivation can be included in the message.

[0148] 2. The source CU provides such LTM cell activation / deactivation to the source-DU (and other DUs if applicable).

[0149] The steps above inhibit triggering the cell change towards the candidate cells that are temporarily unavailable as the S-DU will not trigger the cell change after receiving the indication from Target CU / DU.

[0150] In the case of UE triggered mobility the UE may also respond to the deactivation message by not triggering the cell or beam change after receiving the message.

[0151] As one or more optional features: the source DU / CU may inform the target-DU / CU about the affected UEs (UEs for which the LTM cell is considered as deactivated). This is applicable for potential cases that such information is not already available at the target- DU / CU. It may also inform other potential target-DU / CUs, which for consecutive LTM, may allow a target node that becomes a serving node to be informed in advance of deactivated cells for the UE.

[0152] 3. S-DU / CU then (optional and mainly for cases with one configured target-cell) a. Generate new meas config or meas-report config for the UE b. May generate new HO config (if only one cell prepared) c. The cell is marked as de-activated in LTM cell config d. It may also stop early data forwarding (if has been triggered)

[0153] Where UE capabilities on the number of supported deactivated cells indicate that it cannot support a further deactivated cell and it’s supported performance has been already indicated to the network (i.e., during RRC connection setup / resume)., then it may simply not select this cell, but may not trigger UE to not measure, and / or may restart procedure.

[0154] 4. The source DU / CU provides such LTM cell (de-)activation / indications to the UE a. In the simplest format (preferred) information can be transmitted to the UE via MAC-CE (from the source-DU) b. As another alternative option, a short RRC-LTM cell activation / deactivation message is provided to the UE.

[0155] 5. The UE may be configured to perform one or multiple of the following actions upon the reception of LTM cell deactivation message a. The UE may stop L1 measurement / reporting of the deactivated cells (or beams) b. The UE may also stop / continue performing L3 related measurement and reporting. c. The UE may stop measuring reporting other potential configured objects (e.g., pathloss, RTD, etc). d. If the UE has been configured to measure and report a set of e,g, K best cells (beams), the UE may initiate searching / measuring other cells (beams) and reporting them when one of the k cells is deactivated. e. The UE may be configured to erase the previous measured samples (measurement results). Or in an alternative case the UE may be configured to store / use samples which have been measured within the last X sec. f. The UE may stop TA acquisition / tracking / updating of the deactivated cells and may trigger TA acquisition / estimation for an alternative candidate target cell. g. In case of deactivation within the certain period (i.e., with certain duration), the UE may start measurement before the re-activation to have timely measurement results available, or trigger TA estimation, acquisition. h. If configured, the UE triggers an LTM deactivation timer and perform the required actions after timer expiry. i. The UE marks the cell as deactivated in its maintained list of (de)activated LTM cells. j. The UE can be configured to measure the deactivated cell less frequently (e.g., L3 measurement) and if the measurement exceeds a certain threshold (e.g., with respect to the serving cell or other potential target cells) then initiate legacy (e.g.., L1) measurement once the target-cell is re-activated (or sometimes before reactivation to have the measurement ready).

[0156] 6. Target-DU / CU informs the source DU / CU about the availability of the already deactivated LTM candidate cell for LTM. 7. The UE may be configured to perform one or multiple of the following actions upon the reception of LTM cell reactivation message a. Trigger measurement and reporting b. T riger TA acquisition / update or maintenance c. If the UE is configured to perform autonomous HO, then the UE may trigger cell change (i.e., HO) if the required conditions meet. d. The UE marks the cell as activated in the maintained list of activated LTM cells.

[0157] Fig. 3 shows a signalling diagram showing signalling between a user equipment 50, a distributed unit of the source or serving network node 20, a target or candidate network node 30 and the central unit of the serving network node 40 which may also be the central unit of the candidate or network node 30. The first 15 steps are the same as those of Fig. 2 and show the preparations for setting up LTM mobility ready for handover decisions to be made. For some reasons, e.g., overloading the target-gNB may decides to trigger LTM configuration deactivation for some cells or beams. In this example, the candidate network node 30 at step 16.1 makes the deactivation decision for cells, or beams within the target cells, where these cells or beams are deemed to be not currently available or suitable for connection of one or more user equipment 50. The cell / beam may be unavailable to all user equipment or it may be to particular user equipment. These particular user equipments may be ones with particular service requirements, thus, they may be ones that have a particular high uplink or downlink load or require particular bearer types, and it may be that particular cells or beams within the target node 30 have no capacity for a high uplink load, say but have sufficient capacity for a high downlink load. It may alternatively be that the user equipment may have a particular current status such that there may be an alternative cell for the UE to connect or handover to and in which case the target cell may be deactivated, whereas if there were no alternative target cell and there was perhaps an associated risk of radial link failure RLF, then the cell may not be deactivated for that UE. The deactivation decision may also be based on UE capability, for example frequency range 1 FR1 LTM cell deactivation may be subjected to particular UEs which support both FR1 and frequency range 2 FR2 frequencies as in this case the affected UEs are able to connect to a cell in FR2 frequency.

[0158] Having made the deactivation decision, the target node 30 may then transmit a deactivation notification at step 16.2 to the source central CU 40 , this indication may indicate the reason for the deactivation and may identify user equipment concerned. The deactivation notification may also comprise deactivation configuration if required. The deactivation notification may also include information such as the start time and / or duration of the deactivation and / or whether it requires a signal to reactivate it, whether the cell will continue to transmit reference signals or whether they will be deactivated.

[0159] The source central unit 40 then communicates with the distributed unit 20 at step 16.3 providing it with the deactivation information. If needed, they coordinate to generate a new LTM (HO) config and the source DU 20 provides a LTM deactivation command to the UE. In one alternative the message contains a list of deactivated cells. In this case RRC (re)configurations or MAC-CE will contain a list of configured cells that can be deactivated.

[0160] The source DU 20 will then send a deactivation command or message at signalling step 16.4 to the UE 50. The UE 50 will react to this information and perform an action based on this command. In this regard, it may no longer measure or report signals for the deactivated cells or beams. The CU 40 may also as an optional step inform the target node 30 of the affected UEs for which the LTM cells are considered as deactivated. This is applicable for potential cases that such information is not already available at the target- DU / CU. It can be also informed to the other target-DU / CUs.

[0161] Once the issue is solved, target-gNB may decides to trigger LTM reactivation at step 16.7 and it will notify the source CU 40 of its reactivation decision with reactivation configuration if necessary at signal 16.8 and this information will be forwarded to the DU 20 with signal 16.9. This information is then transmitted to the UE at signal 16.10.

[0162] As an optional feature: the source DU / CU may inform the target-DU / CU about the affected UEs (UEs for which the LTM cell is considered as reactivated). This is applicable for potential cases that such information is not already available at the target-DU / CU. It can be also informed to the other target-DU / CUs (this signalling is not present in the signalling chart).

[0163] Following receipt of the reactivation command or message the user equipment 50 will reinstate that cell in its list of candidate cells and may commence starting measurements and reporting the measurements of reference signals for that candidate cell. A lower layer measurement report will then be transmitted to the source CU 40 and the source CU 40 may determine that a cell change should occur and will issue a LTM command signal 17 and will notify the CU 40 which in this embodiment is also the CU for the target cell 30 of the change. Where it is not the CU for the target cell then the CU 40 will notify the CU of the target cell. In this way, lower layered triggered mobility may occur and its cells or beams of a target node are not currently available for a particular reason then these may be deactivated without requiring any RRC messaging reconfiguration and the measuring and reporting of the reference signals for these cells may also be paused in some cases leading to reduced power and signalling.

[0164] Fig. 4 schematically shows a user equipment 50, source DU 20, target DU 30 and source / target CU 40 according to an embodiment. The UE 50 comprises a memory 52 storing computer program instructions, a processor 54 for executing the instructions and a transceiver 56 for transmitting and receiving signals. The UE 50 further comprises a data store 58 for storing data such as a target candidate cell list.

[0165] In the embodiment shown the UE 50 is being served by cell 23 that is provided by DU 20 and supported by CU 40. CU 40 in this embodiment also supports DU 30 which supports candidate target cells 32, 33 and 34 which the UE is moving towards.

[0166] The UE 50 may be set up for LTM and may periodically perform lower layer measurements of reference signals from various candidate target cells such as cells 32, 33 and 34. Target node 30 may determine that one or more of the cells that it supports is currently overloaded and may generate an indication that that cell is to be deactivated for handover purposes. These may be just LTM handovers or it may be for other types of handover too. The determination and indication generation may be performed by processor 36 executing computer program instructions stored within memory 37 and this information may be sent to the CU 40 using transceiver 38.

[0167] CU 40 may receive the information at transceiver 46 and may itself generate a deactivation message for transmission to serving DU 20 using processor 44 executing code stored in memory 42. The deactivation message is transmitted using transceiver 46.

[0168] The message is received at transceiver 26 of DU 20 and processor 25 generates a deactivation command or message in response to receipt of the deactivation message by executing computer code stored in memory 24. The deactivation command is transmitted by transceiver 26 to UE 50. UE 50 will receive the message at transceiver 56 and will mark the cell as unavailable or deactivated in a candidate cell list stored in data store 58. Processor 54 will then control UE 50 not to monitor for reference signals relating to the deactivated cell. In some embodiments the deactivation message or command may comprise a time duration during which the cell is to be deactivated and in some embodiments the UE will set a timer 57 in response to receiving the message. The timer may be set for the deactivation time duration or for a certain time less than the time duration. When the timer has expired the UE 50 may recommence monitoring reference signals for the cell that was deactivated, the list in data store 58 may also be updated to reflect the reactivation of the cell.

[0169] The user equipment refers to any mobile end or terminal device that may be capable of wireless communication. By way of example rather than limitation, user equipment UE may also be referred to as a communication device, a terminal device, a Mobile Station (MS). The user equipment may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a tablet, a wearable terminal device, a personal digital assistant (PDA) , vehicle-mounted wireless terminal devices, smart devices etc.

[0170] A person of skill in the art would readily recognize that steps of various above-described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computerexecutable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods. The tern 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 (e.g. RAM vs ROM).

[0171] As used in this application, the term “circuitry” may refer to one or more or all of the following:

[0172] (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and

[0173] (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / fi rmware and

[0174] (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

[0175] (c) 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.

[0176] 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.

[0177] Although example embodiments of the present invention 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 invention as claimed.

[0178] Features described in the preceding description may be used in combinations other than the combinations explicitly described.

[0179] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0180] Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

[0181] Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A user equipment, comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the user equipment at least to perform: during a period where said user equipment is applying lower layer, that is layer 1 or layer 2, triggered mobility and is periodically performing measurements related to candidate cells or beams; receiving a deactivation message indicating at least one of said candidate cells or beams is deactivated; and in response at least temporarily stopping at least one of the following : performing or reporting at least one of said measurements related to said at least one deactivated cell or beam; or selecting said deactivated cell for handover.

2. A user equipment according to claim 1 , wherein said at least one of said measurements comprises at least one of: layer 1 measurements; layer 3 measurements; path loss or received time difference RTD measurements.

3. A user equipment according to any preceding claim, wherein said at least temporarily stopping comprises one of: performing said at least one measurement less often; or not performing said at least one measurement for a predetermined duration; or not performing said at least one measurement until receipt of a further message indicating said candidate cell or beam is to be reactivated.

4. A user equipment according to claim 3, wherein, where said at least temporarily stopping comprises not performing said at least one measurement for a predetermined duration, said user equipment is caused to activate a deactivation timer for a time indicative of said predetermined duration in response to receipt of said deactivation message.

5. A user equipment according to claim 3 or 4, wherein where said at least temporarily stopping comprises not performing said at least one measurement for a predetermined duration, said user equipment is caused to initiate performing said at least one measurement a certain time before expiry of said predetermined duration.

6. A user equipment according to any preceding claim, wherein said deactivation message comprises an indication of resources of said at least one deactivated cell or beam for which measurements are to be at least temporarily stopped, said user equipment being configured to at least temporarily stop performing said indicated measurements.

7. A user equipment according to any preceding claim, wherein in response to receipt of said deactivation message, said user equipment is caused to perform: discarding stored measurements relating to said deactivated cell or beam.

8. A user equipment according to any one of claims 1 to 6, wherein in response to receipt of said deactivation message said user equipment is caused to perform at least one of the following: retaining stored measurements relating to said deactivated cell or beam that were measured within a predetermined time before said deactivation message was received and discarding those measured prior to said predetermined time; retaining stored measurements relating to said deactivated cell or beam that were measured within a predetermined time before reactivation of said cell or beam and discarding those measured prior to said predetermined time; and retaining received stored measurements relating to said deactivated cell or beam for a predetermined time and discarding older measurements received more than said predetermined time ago.

9. A user equipment according to any preceding claim, wherein in response to receipt of said deactivation message said user equipment is caused to perform stopping timing advance TA acquisition, update, maintenance or estimation of said deactivated cell or beam and triggering TA acquisition and / or estimation for an alternative candidate cell or beam.

10. A user equipment according to any preceding claim, wherein in response to receipt of said deactivation message, said user equipment is caused to perform marking said cell or beam as currently not available for handover in a list of candidate target cells or beams.

11. A user equipment according to any preceding claim, said user equipment being configured to signal to a network node a capability to support deactivated cells and / or a predetermined number of supported deactivated cells.

12. A user equipment according to any preceding claim, wherein said user equipment is caused to perform at least one of the following: measuring and reporting of a predetermined number of cells or beams, and in response to receipt of said deactivation message to initiate at least one of the following: measuring and reporting other cells or beams to replace said deactivated cells or beams.

13. A user equipment according to any preceding claim, said user equipment being caused to perform: receiving a cell or beam reactivation message; and in response to receipt of said reactivation message reinitiating at least one of the following: performing or reporting of at least one of said measurements or including said deactivated cell as a target candidate cell for a handover.

14. A user equipment according to claim 13, said user equipment being further caused to perform in response to receipt of said reactivation message at least one of the following: starting TA acquisition, update maintenance or estimation for said activated cell or beam; initiating synchronisation steps; initiating pathloss estimation; initiating received time difference RTD measurements; and marking said activated cell or beam as available for handover in a list of candidate cells or beams.

15. A network node for supporting providing radio coverage within one or more cells of a communication network, said network node comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the network node at least to perform: receiving an indication that at least one cell or beam of a target network node is at least temporarily not available to at least some user equipment;in response to receipt of said indication generating deactivation information for said at least one cell or beam.

16. A network node according to claim 15, wherein said indication comprises at least one of the following: a reason for said at least one cell or beam being temporarily unavailable; a capability, a service requirement, a status condition, bearer type or identifiers of said at least some user equipment for which said cell or beam is not currently available and said network node is caused to: determine from at least one of capabilities, service requirements, status condition, bearer type and identifier of user equipment being served by said one or more cells whether said cell or beam is to be deactivated for said user equipment.

17. A network node according to claim 16, said network node being configured to transmit an indication of said user equipment for which said at least one cell or beam is deactivated to said target network node or to a further target network node.

18. A network node according to any one of claims 15 to 17, said network node comprising a central network node supporting at least one distributed network node providing said radio coverage to said one or more cells, said central network node receiving said indication from said target network node; and being caused to transmit said deactivation information to at least one of the following: said at least one distributed network node and a further central network node.

19. A network node according to any one of claims 15 to 17, said network node comprising a distributed network node providing said radio coverage within said one or more cells, said distributed network node being caused at least to perform: receiving said indication that at least one cell or beam of a target network node is at least temporarily not available for at least some user equipment from a central network node; and in response to receipt of said indication generating said deactivation information as a cell or beam deactivation message; and transmitting said deactivation message to said at least some user equipment.

20. A distributed network node according to claim 19 when dependent upon claim 16 or 17, wherein said distributed network node is caused to transmit said deactivation message to said user equipment for which said cell or beam is determined to be deactivated.21 . A distributed network node according to claim 19 or 20, said distributed network node being caused to inhibit any cell or beam handover to a cell or beam which has been deactivated.

22. A network node according to any one of claims 15 to 21 , wherein said deactivation information comprises at least one of the following: an indication of resources of said at least one deactivated cell or beam for which measurements are to be at least temporarily stopped; an indication of a reason for deactivation of said cell; and an indication of a time period during which said cell or beam is to be deactivated.

23. A network node according to any one of claims 15 to 22, said network node being caused to perform: receiving an indication that said at least one cell or beam of a target network node that was temporarily not available for a user equipment is available again; and in response to receipt of said indication generating reactivation information for said at least one cell or beam.

24. A network node according to claim 23 when dependent upon claim 18, said central network node being caused to transmit said reactivation information to at least one of the following: said at least one distributed network node and a further central network node.

25. A network node according to claim 23 when dependent upon any one of claim 19 to 21 , said distributed network node being caused to perform: in response to receipt of said available indication generating said reactivation information as a cell or beam reactivation message; and transmitting said reactivation message to said at least some user equipment.

26. A second network node for supporting providing radio coverage within one or more cells of a communication network, said network node comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the network node at least to perform: determining that at least one of said one or more cells or at least one beam within said one or more cells is currently unavailable to at least some user equipment; generating an indication that said at least one beam or cell is deactivated for said at least some user equipment; transmitting said indication to one of: a serving network node or a central unit supporting said second network node.

27. A second network node according to claim 26, wherein said indication comprises an indication that that said at least one beam or cell is deactivated for all user equipment.

28. A second network node according to claim 26 or 27, wherein said indication comprises an indication of at least one of the following: a reason, a capability, a service requirement, status condition, bearer type or identifier of said at some user equipment for which said cell or beam is not currently available.

29. A second network node according to any one of claims 26 to 28, wherein said indication comprises an indication of at least one of the following: a start time and duration for which said cell is to be deactivated.

30. A second network node according to any one of claims 26 to 29, wherein said indication comprises an indication of UE dedicated reference signal resources that are to be maintained or deactivated by said network node while said cell or beam is deactivated.31 . A second network node according to claim 30 when dependent on claim 29, wherein said network node is configured to stop transmission of said deactivated UE dedicated reference signal resources for a period of time that is equal to said duration during which said cell is to be deactivated or is less than said duration by a certain time.

32. A second network node according to any one of claims 26 to 31 , wherein said indication comprises at least one of the following: an indication of a type of handover for which said cell is deactivated; an indication of one or more beams for which saiddeactivation applies; a reason for said deactivation, information about activation or deactivation of one or more of said other cells or beams supported by said network node; an indication of allocated resources used for handover purposes that are to be maintained or deactivated by said network node while said cell or beam is deactivated.

33. A second network node according to any one of claims 26 to 32, said network node being further caused to receive an indication of user equipment for which said at least one cell or beam has been deactivated.

34. A second network node according to any one of claims 26 to 33, said network node being further caused at least to perform: determining that said at least one cell or beam that is currently unavailable to at least some user equipment is to become available again; generating an indication that said at least one cell or beam is to be activated for said at least some user equipment; transmitting said reactivation indication to one of: a serving network node or a central unit supporting said second network node.

35. A second network node according to any one of claims 26 to 33 when dependent on claim 30, said network node being further caused at least to perform: determining that said at least one cell or beam that is currently unavailable to at least some user equipment is to become available again; reactivating said UE dedicated reference signal resources.

36. A central unit supporting said second network node according to any one of claims 26 to 35, said central unit being caused to receive said deactivation indication and to transmit said deactivation indication to a serving network node.

37. A central unit according to claim 36, said central unit being configured to receive from said serving network node an indication of user equipment for which said cell or beam is deactivated and to generate a message indicative of said user equipment and to transmit said message to said second network node.

38. A central unit according to claim 36 or 37 when dependent upon claim 34 or 35, said central unit being caused to receive said reactivation indication and to transmit said reactivation indication to a serving network node.

39. A method performed at a user equipment, said method comprising: during a period where said user equipment is applying lower layer, that is layer 1 or layer 2, triggered mobility and is periodically performing measurements related to candidate cells or beams; receiving a deactivation message indicating at least one of said candidate cells or beams is deactivated; and in response, at least temporarily stopping at least one of the following : performing or reporting at least one of said measurements related to said at least one deactivated cell or beam; or selecting said deactivated cell for handover.

40. A method performed at a network node, said method comprising: receiving an indication that at least one cell or beam of a target network node is at least temporarily not available to at least some user equipment; in response to receipt of said indication generating deactivation information for said at least one cell or beam.41 . A method performed at a second network node, said method comprising: determining that at least one of said one or more cells or at least one beam within said one or more cells is currently unavailable to at least some user equipment; generating an indication that said at least one beam or cell is deactivated for said at least some user equipment; transmitting said indication to one of: a serving network node or a central unit supporting said second network node.

42. A method performed at a central network node, said method comprising: receiving a cell deactivation indication and transmitting said cell deactivation indication to a serving network node.

43. A computer program comprising computer readable instructions which when executed by at least one processor on a user equipment is operable to control said user equipment to perform a method according to claim 39.

44. A computer program comprising computer readable instructions which when executed by at least one processor on a network node is operable to control said network node to perform a method according to any one of claims 40 to 42.

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