Methods for handovers

Abstract

A method, apparatus, and computer program are described comprising: obtaining at a user equipment, UE, information from a first network node of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the first network node and one or more UEs of at least a first cell of the mobile communication system, and wherein the information indicates: a service area, the RIS being configured to support communications between the first network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the first network node and UEs of the first cell; and indicating, by the UE, the information to a second network node, the second network node serving the UE's current cell

Description

[0001] METHODS FOR HANDOVERS

[0002] Field

[0003] Example embodiments may relate to devices, access nodes, and methods for handovers and / or cell selection.

[0004] Background

[0005] Reconfigurable intelligent surfaces may be controlled by a mobile communication system to provide improved communication capabilities. There remains an interest in providing methods for controlling mobile communication systems and user equipment to take advantage of the capabilities of reconfigurable intelligent surfaces.

[0006] Summary

[0007] The scope of protection sought for various embodiments of the invention is set out by the independent claims. The 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] A first aspect provides a user equipment (UE) comprising: means for obtaining information from a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between a first network node and user equipment of at least a first cell of the mobile communication system, and wherein the information is indicative of the RIS being configured to provide said support; and means for determining during a cell selection or reselection procedure to camp on the first cell based at least in part on the obtained information.

[0009] In some examples, the means for determining during a cell selection or reselection procedure to camp on the first cell based on the obtained information is configured to prioritise, in the cell selection or reselection procedure, the first cell or the operating frequency of the first cell based at least in part on the information. In some examples, the obtained information comprises information indicative of a service area of the RIS; the UE further comprises means for determining that the UE is within the indicated service area of the RIS; and the means for determining to camp on the first cell is configured to prioritise, in the cell selection or reselection procedure, the first cell or the operating frequency of the first cell based at least in part on the determination that the UE is within the service area of the RIS.

[0010] In some examples, the obtained information comprises information indicative of a gain; and the means for determining during a cell selection or reselection procedure to camp on the first cell based on the obtained information are configured to apply the gain to at least one measurement of at least one cellspecific reference signal associated with the first cell. In some examples the obtained information comprises information indicative of a service area of the RIS; the UE further comprises means for determining that the UE is within the indicated service area of the RIS; and the means for determining to camp on the first cell is configured to apply the indicated gain to at least one measurement of at least one cell specific reference signal associated with the first cell based at least in part on the determination that the UE is within the service area of the RIS.

[0011] In some examples, the information indicative of a service area is indicative of a geographical area, and wherein determining that the UE is within the indicated service area of the RIS comprises determining that the UE is within the indicated geographical area.

[0012] In some examples, the UE comprises means for selecting, for at least one respective cell, a respective cell-specific reference signal to obtain cell-specific signalling from, wherein the information indicative of a service area is indicative of one or more cell specific reference signals, and wherein the means for determining that the UE is within the indicated service area is configured to determine that the UE is within the indicated service area based at least in part on one or more of the one or more indicated cell-specific reference signals being a selected cell-specific reference signal to obtain cell-specific signalling from. In some examples, the means for determining to camp on the first cell is configured to prioritise the first cell based at least in part on determining that the UE meets a mobility condition.

[0013] In some examples, the means for obtaining the information is configured to derive the information from the manner in which a cell-specific reference signal of the first cell is encoded.

[0014] In some examples, the means for obtaining the information are configured to obtain the information from system information broadcast by the first network node.

[0015] In some examples, the means for obtaining the information are configured to obtain the information from system information broadcast by a second network node, wherein the second network node does not serve the first cell.

[0016] A second aspect provides a method comprising: obtaining information from a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between a network node and user equipment of at least a first cell of the mobile communication system, and wherein the information is indicative of the RIS being configured to provide said support; and determining during a cell selection or reselection procedure to camp on the first cell based at least in part on the obtained information.

[0017] In some examples, determining during a cell selection or reselection procedure to camp on the first cell based on the obtained information comprises prioritising, in the cell selection or reselection procedure, the first cell or the operating frequency of the first cell based at least in part on the information. In some examples, the obtained information comprises information indicative of a service area of the RIS; the method further comprises determining that the UE is within the indicated service area of the RIS; and determining to camp on the first cell comprises prioritizing, in the cell selection or reselection procedure, the first cell or the operating frequency of the first cell based at least in part on the determination that the UE is within the service area of the RIS.

[0018] In some examples, the obtained information comprises information indicative of a gain; and determining during a cell selection or reselection procedure to camp on the first cell based on the obtained information comprises applying the gain to at least one measurement of at least one cell-specific reference signal associated with the first cell. In some examples, the obtained information comprises information indicative of a service area of the RIS; the method further comprises determining that the UE is within the indicated service area of the RIS; and determining to camp on the first cell comprises applying the indicated gain to at least one measurement of at least one cell specific reference signal associated with the first cell based at least in part on the determination that the UE is within the service area of the RIS.

[0019] In some examples, the information indicative of a service area is indicative of a geographical area, and determining that the UE is within the indicated service area of the RIS comprises determining that the UE is within the indicated geographical area.

[0020] In some examples, the method further comprises selecting, for at least one respective cell, a respective cell-specific reference signal to obtain cell-specific signalling from, wherein the information indicative of a service area is indicative of one or more cell specific reference signals, and wherein determining that the UE is within the indicated service area comprises determining that the UE is within the indicated service area based at least in part on one or more of the one or more indicated cell-specific reference signals being a selected cell-specific reference signal to obtain cell-specific signalling from.

[0021] In some examples, determining to camp on the first cell is comprises prioritising the first cell based at least in part on determining that the UE meets a mobility condition. In some examples, obtaining the information comprises deriving the information from the manner in which a cell-specific reference signal of the first cell is encoded.

[0022] In some examples, obtaining the information comprises obtaining the information from system information broadcast by the first network node.

[0023] In some examples, obtaining the information comprises obtaining the information from system information broadcast by a second network node, wherein the second network node does not serve the first cell.

[0024] A third aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: obtaining information from a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between a network node and user equipment of at least a first cell of the mobile communication system, and wherein the information is indicative of the RIS being configured to provide said support; and determining during a cell selection or reselection procedure to camp on the first cell based at least in part on the obtained information.

[0025] In some example embodiments, the third aspect may include any other feature mentioned with respect to the method of the second aspect.

[0026] A fourth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: obtaining information from a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between a network node and user equipment of at least a first cell of the mobile communication system, and wherein the information is indicative of the RIS being configured to provide said support; and determining during a cell selection or reselection procedure to camp on the first cell based at least in part on the obtained information.

[0027] The fourth aspect may include any other feature mentioned with respect to the method of the second aspect.

[0028] A fifth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising: obtaining information from a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between a network node and user equipment of at least a first cell of the mobile communication system, and wherein the information is indicative of the RIS being configured to provide said support; and determining during a cell selection or reselection procedure to camp on the first cell based at least in part on the obtained information.

[0029] The fifth aspect may include any other feature mentioned with respect to the method of the second aspect.

[0030] A sixth aspect provides a network node of a mobile communication system, the network node comprising: means for providing information to a user equipment, UE, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS.

[0031] In some examples, the means for providing information to a UE comprises means for selecting an encoding of broadcasts of cell-specific system information of the first cell based on the RIS being configured to support communications between the network node and UEs of the first cell. A seventh aspect provides a method comprising: providing, by a network node of a mobile communication system, to a user equipment, UE, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS.

[0032] In some examples, providing information to a UE comprises selecting an encoding of broadcasts of cell-specific system information of the first cell based on the RIS being configured to support communications between the network node and UEs of the first cell.

[0033] An eighth aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: providing, by a network node of a mobile communication system, to a user equipment, UE, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS.

[0034] In some example embodiments, the eighth aspect may include any other feature mentioned with respect to the method of the seventh aspect.

[0035] A ninth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: providing, by a network node of a mobile communication system, to a user equipment, UE, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS.

[0036] The ninth aspect may include any other feature mentioned with respect to the method of the seventh aspect.

[0037] A tenth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising: providing, by a network node of a mobile communication system, to a user equipment, UE, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS.

[0038] The tenth aspect may include any other feature mentioned with respect to the method of the seventh aspect.

[0039] An eleventh aspect provides a first network node of a mobile communication system, the first network node comprising: means for obtaining information from a second network node of the mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the second network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS; and means for providing the information to a user equipment, UE.

[0040] In some examples, the means for providing information to a UE is configured to provide the information as part of a system information broadcast by the network node.

[0041] A twelfth aspect provides a method comprising: obtaining, at a first network node of a mobile communication system, from a second network node of the mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the second network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS; and providing the information to a user equipment, UE.

[0042] In some examples, providing information to a UE comprises providing the information as part of a system information broadcast by the network node.

[0043] A thirteenth aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: obtaining, at a first network node of a mobile communication system, from a second network node of the mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the second network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS; and providing the information to a user equipment, UE.

[0044] In some example embodiments, the thirteenth aspect may include any other feature mentioned with respect to the method of the twelfth aspect.

[0045] A fourteenth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: obtaining, at a first network node of a mobile communication system, from a second network node of the mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the second network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS; and providing the information to a user equipment, UE.

[0046] The fourteenth aspect may include any other feature mentioned with respect to the method of the twelfth aspect.

[0047] A fifteenth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising: obtaining, at a first network node of a mobile communication system, from a second network node of the mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the second network node and user equipment of at least a first cell of the mobile communication system, wherein the information is indicative of the RIS being configured to provide said support, and wherein the information is further indicative of one or more of: a service area of the RIS, and a gain of the RIS; and providing the information to a user equipment, UE.

[0048] The fifteenth aspect may include any other feature mentioned with respect to the method of the twelfth aspect. A sixteenth aspect provides a user equipment, UE, comprising: means for obtaining information from a first network node of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the first network node and one or more UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the first network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the first network node and UEs of the first cell; and means for indicating the information to a second network node, the second network node serving a cell to which the UE is currently connected.

[0049] In some examples, the UE further comprises: means for making one or more measurements of cell-specific reference signals of one or more cells served by the first network node; and means for indicating the one or more measurements to the second network node. In some examples, indicating the one or more measurements to the second network node comprises sending an LI or L3 measurement report and wherein indicating the information to the second network node comprises sending the information with or as part of the LI or L3 measurement report. In some examples, the UE further comprises means for, based on measurements of at least one cell-specific reference signal of at least one cell served by the first network node, detecting the presence of the RIS associated with the first network node. In some examples, the means for obtaining information is configured to, responsive to the UE detecting the presence of a RIS associated with the first network node, obtain the information by reading system information of the first network node.

[0050] In some examples, the UE further comprises means for receiving an instruction to read a system information broadcast of the first network node associated with one or more cells served by the first network node, wherein the means for obtaining information from the first network node is configured to, responsive to the UE receiving the instruction to read system information broadcast by the first network node, obtain the information by reading the information from said system information. In some examples, the means for receiving an instruction to read system information broadcast by the first network node is configured to receive the instruction from the second network node. In some examples, the means for receiving an instruction to read system information broadcast by the first network node is configured to receive the instruction from the first network node. In some examples, the means for receiving an instruction to read system information broadcast by the first network node is configured to receive the instruction with or as part of a configuration for use by the UE when being served by a respective cell served by the first network node. In some examples, the means for receiving an instruction to read system information broadcast by the first network node is configured to receive the instruction with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the first network node. In some examples, the means for making one or more measurements of cell-specific reference signals is configured to prioritise measurements of cellspecific reference signals associated with cells for which the UE has received an instruction to read an associated system information broadcast.

[0051] In some examples, the means for obtaining the information from the first network node is configured to obtain the information by reading the information from a configuration for use by the UE when being served by a respective cell served by the first network node.

[0052] In some examples, the means for obtaining the information from the first network node is configured to obtain the information by reading the information from a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the first network node.

[0053] In some examples, the means for making one or more measurements of cellspecific reference signals is configured to prioritise measurements of cell-specific reference signals of the first cell, based at least in part on the UE having obtained the information.

[0054] In some examples, the UE further comprises means for indicating to the second network node that the UE is capable of reporting at least one of a RIS service area and a RIS gain of a RIS associated with a first network node.

[0055] A seventeenth aspect provides a method comprising: obtaining at a user equipment, UE, information from a first network node of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the first network node and one or more UEs of at least a first cell of the mobile communication system, and wherein the information indicates: a service area, the RIS being configured to support communications between the first network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the first network node and UEs of the first cell; and indicating, by the UE, the information to a second network node, the second network node serving the UE's current cell.

[0056] In some examples, the method further comprises: making one or more measurements of cell-specific reference signals of one or more cells served by the first network node; and indicating the one or more measurements to the second network node. In some examples, indicating the one or more measurements to the second network node comprises sending an LI or L3 measurement report, and indicating the information to the second network node comprises sending the information with or as part of the LI or L3 measurement report. In some examples, the method further comprises, based on measurements of at least one cell-specific reference signal of at least one cell served by the first network node, detecting the presence of the RIS associated with the first network node.

[0057] In some examples, obtaining the information comprises, responsive to the UE detecting the presence of a RIS associated with the first network node, obtaining the information by reading system information of the first network node. In some examples, the method further comprises receiving an instruction to read a system information broadcast of the first network node associated with one or more cells served by the first network node, wherein obtaining information from the first network node comprises, responsive to the UE receiving the instruction to read system information broadcast by the first network node, obtaining the information by reading the information from said system information. In some examples, receiving an instruction to read system information broadcast by the first network node comprises receiving the instruction from the second network node. In some examples, receiving an instruction to read system information broadcast by the first network node comprises receiving the instruction from the first network node. In some examples, receiving an instruction to read system information broadcast by the first network node comprises receiving the instruction with or as part of a configuration for use by the UE when being served by a respective cell served by the first network node. In some examples, receiving an instruction to read system information broadcast by the first network node comprises receiving the instruction with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the first network node. In some examples, making one or more measurements of cell-specific reference signals comprises prioritising measurements of cell-specific reference signals associated with cells for which the UE has received an instruction to read an associated system information broadcast.

[0058] In some examples, obtaining the information from the first network node comprises obtaining the information by reading the information from a configuration for use by the UE when being served by a respective cell served by the first network node.

[0059] In some examples, obtaining the information from the first network node comprises obtaining the information by reading the information from a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the first network node. In some examples, making one or more measurements of cell-specific reference signals comprises prioritizing measurements of cell-specific reference signals of the first cell, based at least in part on the UE having obtained the information.

[0060] In some examples, the method further comprises indicating to the second network node that the UE is capable of reporting at least one of a RIS service area and a RIS gain of a RIS associated with a first network node.

[0061] An eighteenth aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: obtaining at a user equipment, UE, information from a first network node of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the first network node and one or more UEs of at least a first cell of the mobile communication system, and wherein the information indicates: a service area, the RIS being configured to support communications between the first network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the first network node and UEs of the first cell; and indicating, by the UE, the information to a second network node, the second network node serving the UE's current cell.

[0062] In some example embodiments, the eighteenth aspect may include any other feature mentioned with respect to the method of the seventeenth aspect.

[0063] A nineteenth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: obtaining at a user equipment, UE, information from a first network node of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the first network node and one or more UEs of at least a first cell of the mobile communication system, and wherein the information indicates: a service area, the RIS being configured to support communications between the first network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the first network node and UEs of the first cell; and indicating, by the UE, the information to a second network node, the second network node serving the UE's current cell.

[0064] The nineteenth aspect may include any other feature mentioned with respect to the method of the seventeenth aspect.

[0065] A twentieth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising: obtaining at a user equipment, UE, information from a first network node of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the first network node and one or more UEs of at least a first cell of the mobile communication system, and wherein the information indicates: a service area, the RIS being configured to support communications between the first network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the first network node and UEs of the first cell; and indicating, by the UE, the information to a second network node, the second network node serving the UE's current cell.

[0066] The twentieth aspect may include any other feature mentioned with respect to the method of the seventeenth aspect.

[0067] A twenty-first aspect provides a network node comprising: means for sending information to a user equipment, UE, of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the network node and UEs of the first cell.

[0068] In some examples, the network node further comprises means for generating a first cell-specific reference signal indicative of the RIS being configured to support communications between the network node and UEs of the first cell.

[0069] In some examples, the means for sending information to the UE is configured to broadcast the information. In some examples, the network node further comprises means for instructing the UE to read the information from the broadcast. In some examples, the network node further comprises means for receiving an indication that the UE has a target cell RIS reporting capability, and wherein the means for instructing the UE to read the information from the broadcast are configured to do so responsive, at least in part, to receiving the indication that the UE has a target cell RIS reporting capability. In some examples, the means for instructing the UE to read the information from a broadcast is configured to send the instruction with or as part of a configuration for use by the UE when being served by a respective cell served by the network node. In some examples, the means for instructing the UE to read the information from a broadcast is configured to send the instruction with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the network node.

[0070] In some examples, the means for sending information to the UE is configured send the information with or as part of a configuration for use by the UE when being served by a respective cell served by the first network node.

[0071] In some examples, the means for sending information to the UE is configured to send the information with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the network node. In some examples, the network node further comprises: means for receiving a handover request from a serving node, the serving node serving the UE; means for determining a handover condition based at least in part on the information; and means for sending a conditional handover command to the UE comprising the handover condition.

[0072] A twenty-second aspect provides a method comprising: sending, from a network node, to a user equipment, UE, of a mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the network node and UEs of the first cell.

[0073] In some examples, the method further comprises generating a first cell-specific reference signal indicative of the RIS being configured to support communications between the network node and UEs of the first cell.

[0074] In some examples, sending information to the UE comprises broadcasting the information. In some examples, the method further comprises instructing the UE to read the information from the broadcast. In some examples, the method further comprises receiving an indication that the UE has a target cell RIS reporting capability, and wherein instructing the UE to read the information from the broadcast is performed responsive, at least in part, to receiving the indication that the UE has a target cell RIS reporting capability. In some examples instructing the UE to read the information from a broadcast comprises sending the instruction with or as part of a configuration for use by the UE when being served by a respective cell served by the network node. In some examples, instructing the UE to read the information from a broadcast comprises sending the instruction with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the network node.

[0075] In some examples, sending information to the UE comprises sending the information with or as part of a configuration for use by the UE when being served by a respective cell served by the first network node.

[0076] In some examples sending information to the UE comprises sending the information with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the network node.

[0077] In some examples, the method further comprises: receiving a handover request from a serving node, the serving node serving the UE; determining a handover condition based at least in part on the information; and sending a conditional handover command to the UE comprising the handover condition.

[0078] A twenty-third aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: sending, from a network node, to a user equipment, UE, of a mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the network node and UEs of the first cell.

[0079] In some example embodiments, the twenty-third aspect may include any other feature mentioned with respect to the method of the twenty-second aspect.

[0080] A twenty-fourth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: sending, from a network node, to a user equipment, UE, of a mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the network node and UEs of the first cell.

[0081] The twenty-fourth aspect may include any other feature mentioned with respect to the method of the twenty-second aspect.

[0082] A twenty-fifth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising: sending, from a network node, to a user equipment, UE, of a mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the network node and UEs of the first cell.

[0083] The twenty-fifth aspect may include any other feature mentioned with respect to the method of the twenty-second aspect.

[0084] A twenty-sixth aspect provides a network node comprising: means for receiving information associated with a reconfigurable intelligent surface, RIS, the RIS being configured to support communications between a target network node and user equipments, UEs, of at least a first cell of a mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the target network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the target network node and UEs of the first cell; and means for making a handover decision regarding a UE of the mobile communication system based at least in part on the received information, the UE being in communication with the mobile communication system via a cell served by the network node.

[0085] In some examples, the means for receiving the information is configured to receive the information from the UE. In some examples, the network node further comprises means for sending an instruction to the UE to read a system information broadcast of the target network node associated with one or more cells served by the target network node. In some examples, the network node further comprises means for receiving an indication from the UE that the UE is capable of sending the information.

[0086] In some examples, the means for receiving the information is configured to receive the information from the target network node.

[0087] In some examples, the network node further comprises: means for receiving from the UE one or more measurements of cell-specific reference signals of one or more cells served by the target network node, wherein the means for making a handover decision is configured to determine to perform a handover of the UE from a cell served by the network node to the first cell based at in part on the received information and the received measurements.

[0088] In some examples, the network node further comprises: means for receiving from the UE one or more measurements of cell-specific reference signals of one or more cells served by the target network node, wherein the means for making a handover decision is configured to set up a conditional handover of the UE from a cell served by the network node to the first cell based at in part on the received information and the received measurements.

[0089] In some examples, receiving the one or more measurements comprises receiving an LI or L3 measurement report, wherein receiving the service area and / or gain comprises receiving the indication with or as part of the LI or L3 measurement report.

[0090] A twenty-seventh aspect provides a method comprising: receiving, at a network node, information associated with a reconfigurable intelligent surface, RIS, the RIS being configured to support communications between a target network node and user equipments, UEs, of at least a first cell of a mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the target network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the target network node and UEs of the first cell; and making, a handover decision regarding a UE of the mobile communication system based at least in part on the received information, the UE being in communication with the mobile communication system via a cell served by the network node.

[0091] In some examples, receiving the information comprises receiving the information from the UE. In some examples, the method further comprises sending an instruction to the UE to read a system information broadcast of the target network node associated with one or more cells served by the target network node. In some examples, the method further comprises receiving an indication from the UE that the UE is capable of sending the information.

[0092] In some examples, receiving the information comprises receiving the information from the target network node.

[0093] In some examples, the method further comprises: receiving from the UE one or more measurements of cell-specific reference signals of one or more cells served by the target network node, wherein making a handover decision comprises determining to perform a handover of the UE from a cell served by the network node to the first cell based at in part on the received information and the received measurements.

[0094] In some examples, the method further comprises: receiving from the UE one or more measurements of cell-specific reference signals of one or more cells served by the target network node, wherein making a handover decision comprises setting up a conditional handover of the UE from a cell served by the network node to the first cell based at in part on the received information and the received measurements.

[0095] In some examples, receiving the one or more measurements comprises receiving an LI or L3 measurement report and receiving the service area and / or gain comprises receiving the indication with or as part of the LI or L3 measurement report.

[0096] A twenty-eighth aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: receiving, at a network node, information associated with a reconfigurable intelligent surface, RIS, the RIS being configured to support communications between a target network node and user equipments, UEs, of at least a first cell of a mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the target network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the target network node and UEs of the first cell; and making, a handover decision regarding a UE of the mobile communication system based at least in part on the received information, the UE being in communication with the mobile communication system via a cell served by the network node.

[0097] In some example embodiments, the twenty-eighth aspect may include any other feature mentioned with respect to the method of the twenty-seventh aspect.

[0098] A twenty-ninth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: receiving, at a network node, information associated with a reconfigurable intelligent surface, RIS, the RIS being configured to support communications between a target network node and user equipments, UEs, of at least a first cell of a mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the target network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the target network node and UEs of the first cell; and making, a handover decision regarding a UE of the mobile communication system based at least in part on the received information, the UE being in communication with the mobile communication system via a cell served by the network node.

[0099] The twenty-ninth aspect may include any other feature mentioned with respect to the method of the twenty-seventh aspect.

[0100] A thirtieth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising: receiving, at a network node, information associated with a reconfigurable intelligent surface, RIS, the RIS being configured to support communications between a target network node and user equipments, UEs, of at least a first cell of a mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the target network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the target network node and UEs of the first cell; and making, a handover decision regarding a UE of the mobile communication system based at least in part on the received information, the UE being in communication with the mobile communication system via a cell served by the network node.

[0101] The thirtieth aspect may include any other feature mentioned with respect to the method of the twenty-seventh aspect.

[0102] Brief Description of the Drawings

[0103] Example embodiments will now be described by way of non-limiting example, with reference to the accompanying drawings, in which:

[0104] Figs. 1 - 3 are block diagrams of example systems;

[0105] Fig. 4 is a schematic diagram of an example RIS architecture;

[0106] Fig. 5 is a schematic diagram of an example system;

[0107] Figs. 6 and 7 are block diagram of example systems;

[0108] Fig 8 is a message flow sequence chart in accordance with an example;

[0109] Figs. 9 and 10 are flow diagrams in accordance with examples;

[0110] Figs. 11 and 12 are message flow sequence charts in accordance with examples;

[0111] Fig. 13 is a flow diagram in accordance with an examples;

[0112] Figs. 14 and 15 are message flow sequence charts in accordance with examples;

[0113] Fig. 16 is a block diagram of components of a system in accordance with an example embodiment; and

[0114] Fig. 17 shows an example of tangible media for storing computer-readable code which when run by a computer may perform methods according to example embodiments described above.

[0115] Detailed Description

[0116] The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Further, when a particular feature, structure, or characteristic is described in connection of an embodiment, it is within the knowledge of one skilled in the art to apply such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that although the terms "first," "second" and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0117] For the purposes of the present disclosure, the phrases "at least one of A or B", "at least one of A and B", and "A and / or B" means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase "A, B, and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0118] Embodiments described may be implemented in a communication system, such as any of the following radio access technologies (RATs): World-wide Interoperability for Micro-wave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced, and enhanced LTE (eLTE), 5G (also called NR), or any future RAT such as 6G. Moreover, communication within the communication system may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), and / or Discrete Fourier Transform spread OFDM (DFT-s-OFDM).

[0119] As used herein, the term "network device" or "network node" refers to a node in a communication system via which user equipment may access the network and / or which is capable of controlling radio communication and managing radio resources within a cell. The network node or network device may be referred to as a base station (BS), an access point (AP) or an access node. The network device may be, depending on the applied technology, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node, a nonterrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, or an aircraft network device.

[0120] Moreover, in connection of split radio access network (RAN), the network device may refer to a centralised unit (CU) of a base station and / or a distributed unit (DU) of a base station. An interface between CU and DU may be referred to as an Fl interface in NR. In the split RAN architecture, node operations may be carried out, at least partly, in the central / centralized unit, CU, (e.g. server, host or node) operationally coupled to the DU, (e.g. a radio head / node). One CU may control one or more DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some embodiments, the DUs may comprise e.g. a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the CU may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layers. Other functional splits are possible too. In practice, any processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may depend on the applied implementation.

[0121] The term "terminal device" refers to any end device that may be capable of wireless communication. By way of example, a terminal device may be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), or a Mobile Station (MS). The terminal device may include a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and play-back appliances, vehicle-mounted wireless terminal devices, USB dongles, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. A term "resource", as used herein, may refer to radio resources in time domain, in frequency domain, in space domain, and / or in code domain. Some examples of resources include e.g. a physical resource block (PRB), a radio frame, a subframe, a time slot, a subband, a frequency region, a sub-carrier, a beam, etc. The term "transmission" and / or "reception" may refer to wirelessly transmitting and / or receiving via a wireless propagation channel on radio resources.

[0122] Reconfigurable intelligent surfaces (RISs) are being investigated in industry and academia as a technology for cellular communication systems that could complement existing radio infrastructures. Reconfigurable intelligent surfaces comprise antenna elements (typically cheap antenna elements) that can be configured according to different use cases. RIS offers a programmable antenna array solution for controlling the propagation of signals, for example by changing electrical and magnetic properties of the reflective surface of RIS depending on the use case. RIS may be able to provide a cost-effective alternative to deploying new gNBs / acquiring new spectrum in some circumstances. For example, the properties of the RIS may be changed to direct incident radio waves. This may allow for a beam to be redirected in a controlled direction (e.g., by controlling the properties of the RIS to direct the beam through reflection and / or refraction). This may also allow for a beam to be focused by the RIS (e.g., also by controlling the properties of the RIS to direct the beam through reflection or refraction). These properties of RISs mean that RISs may be suitable for offsetting some of the drawbacks of higher frequencies (e.g. greater sensitivity to line-of-sight blockages).

[0123] FIG. 1 is a block diagram of an example system indicated generally by the reference numeral 10. The system 10 comprises a network node 12 (such as a transmission-reception point, TRP, a base station or a gNB), a user equipment, UE, 14 (or some other mobile communication device or terminal device) and a reconfigurable intelligent surface, RIS, 16. As shown in FIG. 1, the system 10 also includes an obstacle 18 between the network node 12 and the UE 14 such that there is no direct communication possible between the node 12 and the UE 14. The RIS 16 may comprise a plurality of antenna elements that can be configured according to a desired use case. One configuration corresponds to one or multiple beams (e.g. a narrow beam) pointing in a given direction.

[0124] In the system 10, the RIS 16 is configured to redirect signals from the network node 12 towards the UE 14 and vice-versa, such that the network node 12 and the UE 14 can still communicate despite the presence of the obstacle 18. Thus, the system 10 provides a simple coverage enhancement use case of a RIS.

[0125] FIG. 2 is a block diagram of an example system, indicated generally by the reference numeral 20. The system 20 includes a network node 22, a UE 24 and a RIS 26 (similar to the network node 12, UE 14 and RIS 16 of the system 10, but omitting the obstacle 18). A line-of-sight (LOS) connection can be made between the network node 22 and the UE 24. However, a second communication link is also available via the RIS 26. Providing an additional physical path can, for example, provide capacity improvement in the event of a dominant LOS channel.

[0126] In the system 20, the RIS 26 can be exploited to increase channel rank, and therefore increase spectral efficiency for applications requiring large throughputs in the downlink. More specifically, there are scenarios where the link between the network node 22 and the UE 24 exhibits a strong line-of- sight (LOS) component, and as a result, only rank one MIMO transmission is possible. This is especially true in higher frequency bands, where RISs may be deployed (a smaller wavelength facilitates RIS deployment due to the RIS antenna spacing being a fraction of the wavelength, resulting in smaller RIS array size). The RIS 26 provides an additional propagation path and could increase the channel rank to two by proper configuration. Note also that there are cases where the channel rank is greater than one without RIS (e.g., equal to two with cross polarized antennas), in which case providing a RIS can be exploited to increase the rank to, e.g., three.

[0127] FIG. 3 is a block diagram of an example system, indicated generally by the reference numeral 30. The system 30 includes a network node 32, a UE 34 and RIS 36 (similar to the network nodes, UEs and RISs of the systems 10 and 20 described above). In the system 30, the RIS 36 can be used as a positioning anchor in order to enhance positioning accuracy. The RIS 36 is typically a cheaper alternative to deploying additional network nodes, e.g., transmit / receive points (TRPs) for positioning purposes.

[0128] FIG. 4 shows an example RIS architecture, indicated generally by the reference numeral 40. The RIS architecture 40 may be used to implement the RISs 16, 26 and 36 described above, for example. The RIS 40 includes a number of passive elements (shown in white in FIG. 4) and active elements (shown in grey in FIG. 4).

[0129] The passive elements of the RIS 40 provide a planar array of passive reflecting elements that can reflect incoming rays with adjustable phase shifts and gains. The passive nature of the reflecting elements results in low hardware costs, low energy consumption, and the ability to naturally operate in full-duplex (FD) mode. Phases of the passive elements may be configured to reflect the incoming signal in the desired direction. In some examples, active elements of the RIS 40 may also serve a similar purpose, possibly by providing further amplification to the signals.

[0130] Passive and active elements of the RIS 40 may be controlled by a RIS controller. The active elements may be used for functions such as communicating control messages between a RIS and a network node (such as any of the network nodes 12, 22 and 32 described above) and / or for channel sensing by measuring reference signals. In some examples, passive elements may additionally or alternatively be used for functions such as communicating control messages and / or for channel sensing by measuring reference signals.

[0131] FIG. 5 is a schematic diagram of a system, indicated generally by the reference numeral 50. The system 50 comprising a network node 52, a plurality of UEs 54 (UE1 to UE4), and a RIS 56. The system 50 shows a predefined grid of beams at both the network node and the RIS. Here, the RIS can be configured to optimize communication within the cell in which UEs 54 are located.

[0132] The system 50 shows the use of a RIS in a single-cell scenario. However, a RIS presents additional spatial degrees of freedom and can be used to optimise the performance of multicell networks by directed RIS beams to selected cells in a dynamic manner according to cell radio conditions.

[0133] Network-controlled Repeaters (NCRs) and RISs

[0134] RIS and NCR act as signal boosters aiming to extend coverage / capacity. Both may need similar control mechanisms, for example, to control beamforming, on-off control, and time division duplexing (TDD). Depending on the RIS implementation, both RIS and NCR forward signals without decoding.

[0135] FIG. 6 is a block diagram of a system, indicated generally by the reference numeral 60. System 60 is a model of the architecture of an NCR 62. The NCR comprises a Mobile Termination (MT) part 67 and a Forwarding (Fwd) part 68. The forwarding part amplifies and forwards signals towards a UE 66 and / or from a UE 66 based on control information provided by gNB 64 via the control link using NCR-MT. The NCR-MT can have functionality of a UE (for connecting to a gNB), with additional functionality for exchanging messages for the NCR-Fwd part.

[0136] FIG. 7 is a block diagram of a system, indicated generally by the reference numeral 70. System 70 is a model of an architecture of RIS 72. Similar to NCRs, RISs may be controlled by a gNB 74, via similar control mechanisms (although in some examples a RIS may also be UE controlled, e.g. via sidelink signals).

[0137] Similar to NCRs, gNB 74 may exchange control information with a control unit 77 of RIS 72, which we will call RIS-MT from now on. Similar to NCR-Fwd, RIS panel 78 with a plurality of antenna elements may similarly serve to enhance the signals to and / or from UE 76. Information used to control the RIS panel 78 may correspond to information used to control NCR-Fwd 68. Three options for the activation of RIS configurations are set out below. These correspond to mechanisms defined for NCRs.

[0138] Aperiodic Activation

[0139] Under aperiodic activation, the RIS-MT can receive a configuration via RRC signalling, and the activation of the configuration can be prompted by downlink control information (DCI) dynamically sent by the gNB. This means that beam directing / focusing by the RIS in a given symbol and / or time slot may be controlled dynamically by DCIs sent from the gNB.

[0140] Periodic Activation

[0141] Under periodic activation, the RIS-MT can receive a configuration via RRC signalling and apply the configuration immediately based on the periodicity provided in the configuration. This means that by obtaining the configuration, RIS- MT starts to periodically enhance signals based on the configuration.

[0142] Semi-static Activation

[0143] Under semi-static activation, the RIS-MT can be given a configuration via RRC signalling and the activation of the configuration can be prompted by a medium access control (MAC) control element (MAC-CE). When receiving the MAC-CE, the RIS-MT applies the configuration based on the periodicity provided in the RRC configuration (e.g., for a configured or indicated number of repetitions, with a configured period).

[0144] Lower layer triggered mobility

[0145] When a UE moves from the coverage area of one cell to another cell, a serving cell change needs to be performed at some point. In "baseline" handover procedures, the serving cell change is triggered by Layer 3 (L3) measurements (e.g., an RRC Measurement Report from the UE) and is performed through downlink RRC signalling, i.e., via an RRC Reconfiguration message with Synchronization for a change of Primary Cell (PCell) and / or Primary Secondary Cell (PSCell). The RRC Reconfiguration may release and add Secondary Cells (SCell)s when applicable. These cases may involve complete L2 (and LI) resets, leading to longer latency, larger overhead, and longer interruption time than beam switch mobility.

[0146] The goal of L1 / L2 mobility enhancements is to enable a serving cell change via L1 / L2 signalling, to reduce the latency, overhead and interruption time.

[0147] Fig. 8 shows an exemplary message sequence chart (MSC), designated generally by the reference numeral 100, for L1 / L2, or lower-layer, triggered mobility (LTM).

[0148] The method starts at step 110 of the message sequence, in an LTM preparation phase 140, with UE 102 in RRC_CONNECTED mode.

[0149] At step 112 of the message sequence, UE 102 sends a MeasurementReport (i.e., a Layer 3 measurement report) message to gNB 104.

[0150] At step 114, gNB 104 decides to configure LTM and initiates LTM candidate preparation. For an intra-gNB handover, this may comprise gNB 104 preparing configurations for use by UE 102 when connected to one or more respective candidate cells served by gNB 104. For an inter-gNB handover, this may comprise gNB 104 sending a handover request to a neighbouring gNB, whereas the neighbouring gNB prepares configurations for use by UE 102 when connected to one or more respective candidate cells served by the neighbouring gNB.

[0151] At step 116, gNB 104 transmits an RRCReconfiguration message to UE 102 including LTM candidate configurations.

[0152] At step 118, UE 102 stores the LTM candidate configurations and transmits an RRCReconfigurationComplete message to gNB 104. In some examples, UE 102 performs early synchronisation before receiving the cell switch command. At step 120, in an early synchronisation phase 142, UE 102 performs downlink (DL) synchronization with the LTM candidate cell(s). UE 102 may activate and deactivate transmission configuration indicator (TCI) states of LTM candidate cell(s), as triggered by gNB 104. An active TCI state may indicate a relationship between one or more properties of a signal and corresponding properties of a reference signal (e.g., by indicating a similarity in doppler shift). An active TCI state may therefore allow a UE to predict one or more properties of a signal based on properties of a reference signal.

[0153] At step 122, UE 102 may perform uplink (UL) synchronization with LTM candidate cell(s) before receiving the cell switch command, by using UE-based timing advance (TA) measurement, if configured, and / or by transmitting a preamble towards the candidate cell, as triggered by gNB 104. When UE-based TA measurement is configured, UE 102 acquires the TA value(s) of the candidate cell(s) by measurement. Also, UE 102 may perform early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command. This is done via contention-free random access (CFRA) triggered by a physical downlink control channel (PDCCH) order from the source cell, following which UE 102 sends the preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), UE 102 does not receive a random access response from the network for the purpose of TA value acquisition and the TA value of the candidate cell is indicated in the cell switch command. UE 102 does not maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.

[0154] In an LTM cell switch execution phase 144, at step 124, UE 102 performs LI measurements on the configured LTM candidate cell(s) and transmits LI measurement reports to gNB 104. LI measurements should be performed as long as the RRC reconfiguration (of step 116) is applicable.

[0155] At step 126, gNB 104 decides to execute a cell switch to a target cell and transmits, at step 128, an LTM cell switch command MAC CE triggering the cell switch by including: a target configuration ID, which indicates the index of the candidate configuration of the target cell; a beam, indicated with a TCI state, or beams, indicated with DL and UL TCI states; and a timing advance command for the target cell, if available. At step 130, UE 102 switches to the target cell and applies the candidate configuration indicated by the target configuration ID.

[0156] At step 132, UE 102 performs the random-access procedure towards the target cell, if UE does not have valid TA of the target cell.

[0157] At step 134, UE 102 completes the LTM cell switch procedure by sending an RRCReconfigurationComplete message to the target cell. If UE 102 has performed a random access procedure at step 128, UE 102 considers that the LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For random access channel (RACH)-less LTM, UE 102 considers that the LTM cell switch execution is successfully completed when UE 102 determines that the network has successfully received its first UL data.

[0158] Steps 120 - 134 can be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in step 116.

[0159] The procedure over the air interface described above is applicable to both intra- gNB-distributed unit (DU) LTM and inter-gNB-DU LTM. It can also apply to inter- gNB LTM (e.g., inter gNB-CU LTM).

[0160] Both LTM (L1 / L2) and baseline / conditional (L3) handover procedures rely on the UE measuring cell specific reference signals, typically synchronisation signal blocks (SSBs), and the measurements of these cell specific reference signals are used in handover decisions (e.g., the measurements of step 124 are used at step 126 in the LTM procedure).

[0161] For both RISs and NCRs, there is a need to consider how cell-specific reference signals and measurement reports will be handled in the context of LTM and baseli ne / conditional handover procedures.

[0162] A typical procedure for performing a handover (HO) is the following: A UE in RRC_CONNECTED state performs reference signal (RS) measurements by measuring (typically, and in most scenarios) SSBs. SSBs measurements are distinct from measurements of channel state information (CSI)-RSs. The SSB measurements are then provided to the source gNB for handover decisions.

[0163] For example, in LTM, a UE performs L3 measurements and reports them to a source gNB. Based on these measurements, source gNB prepares a target gNB with LTM configurations, which are then provided to the UE. Afterwards, UE performs LI measurements and provides them to the source gNB, which may prompt a cell switch command.

[0164] At least in some scenarios, a RIS (or NCR) is expected to be used for enhancing UE-specific signal, such as CSI-RS transmissions and data transmissions, more than the cell-specific signals such as SSBs.

[0165] One reason for this is that, when a RIS / NCR is used to enhance the SSB signals, it may be required that those enhancements of the SSB signals are always "on". This would mean that even when there is no UE in the system, the RIS / NCR would be enhancing the SSBs transmitted periodically over the air. This may be inefficient in terms of energy consumption, and, this may cause unnecessary interference to neighbouring cells.

[0166] One explanation for requiring that SSBs (and other cell-specific reference signals) are always enhanced (if they are enhanced at all) can be understood by considering the UE data reception procedure. A UE expects similar physical channel properties (e.g., in terms of signal quality, Doppler shift, average delay, or / and spatial receive parameters) when receiving data Quasi-collocated (QCL- ed) with an SSB. This means that if the gNB desires to transmit data QCL-ed with SSBs, it should ensure that the UE has the proper SSB measurements (e.g., if the UE had received the SSB enhanced with RIS / NCR, the data should also be enhanced with it). Otherwise, problems may occur when decoding the data by the UE (e.g., because of incorrect assumptions based on the enhanced SSB measurements). Therefore, by enhancing some SSB signals, a RIS may effectively be committed to enhancing every signal QCL-ed with those SSB signals, which may be impractical.

[0167] Data can be QCL-ed with an SSB or a CSI-RS signal. In the case of CSI-RS signals, CSI-RS signals are typically UE-specific (e.g., per UE configured) and they are not mandatorily transmitted over the air even if there is no UE, so enhancing these signals would not require any signal enhancement in the absence of UEs, and the signals enhanced could be based on the UEs that are present in the cell.

[0168] Therefore, it is expected that in some RIS / NCR deployments, SSB signals will not be enhanced by the RIS / NCR. We consider this scenario.

[0169] However, for UE that is in RRC_CONNECTED and using SSBs for candidate cell measurements, this would mean that handover decisions may be made (e.g., the selection of the best candidate cell or frequency by the source gNB), without considering RIS / NCR-enhanced signals. This may therefore result in a UE being handed over to a cell that does not have an NCR / RIS even though an NCR / RIS- enhanced neighbouring cell (with lower measured SSB RSRP than the non- NCR / RIS-enhanced cell) may provide a better reception.

[0170] It would be desirable to guide RRC_CONNECTED UEs to the best possible cells in RIS / NCR-aided systems. It would be desirable to guide UEs to the best possible cell for different handover procedures (LTM / L1 / L2, "baseline" / L3, and "conditional" / L3).

[0171] Two scenarios are considered below.

[0172] In a first scenario, a "source" gNB (i.e., the gNB currently serving the UE in question) learns RIS properties in a neighbour gNB prior to making a HO or during HO preparation. A gNB served by a RIS (i.e., a gNB that is configured to utilise a RIS to enhance communications) informs its neighbour gNBs of presence of the RIS. The gNB may provide more information on, e.g., the service area of RIS (which could be defined in terms of SSB IDs or a geographical area) and possible RIS gains, such as a delta value indicating how much gain the UE can expect when a RIS is used (e.g., a decibel difference in expected signal strength).

[0173] In other embodiments, this information may be configured by operations, administration and maintenance (OAM) in neighbour gNBs (i.e., rather than being exchanged over the Xn interface between gNBs).

[0174] The serving or "source" gNB can utilize this information in cell switch decisions. For example, the serving gNB may assume that the UE will have the indicated RIS gains when the UE connects to the target cell, and it may therefore add the delta value to the provided measurements (e.g., layer 1 measurements or layer 3 measurements) in case the UE provides measurements within the service area of the RIS (e.g., if the SSBs that the UE is reporting correspond to the ones indicated as the service area of the RIS by the target gNB). Both initial HO preparation decisions, early downlink and uplink synchronization decisions (e.g., beam / cell selection for early downlink and uplink synchronization), and actual cell-switch decisions can be influenced similarly.

[0175] This solution could also be applied if we consider intra-CU LTM (or intra-CU handovers more generally), although we considered inter-CU (i.e., inter gNB) LTM throughout the invention. The source DU may be informed by the CU of the existence of the RIS in a neighbour intra-CU DU, and more information may be provided as discussed above. The source DU may take the information into account when making LTM decisions such as cell switch decisions.

[0176] Fig. 9 is a flow diagram illustrating a method designated generally by the reference numeral 200. Method 200 may be carried out by a network node (such as a gNB) serving a UE. At step 210, the network node receives information associated with a RIS. The RIS is configured to support communications between a target network node (e.g., a neighbouring node and potential candidate cell for UEs served by the network node) and UEs, of at least a first cell of a mobile communication system. The information indicates at least one of: a service area, the RIS being configured to support communications between the target network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the target network node and UEs of the first cell.

[0177] At step 212, the network node makes a handover decision regarding a UE of the mobile communication system served by the network node (i.e., the UE is in communication with the mobile communication system via a cell served by the network node). The network node makes this handover decision based at least in part on the information received at step 210.

[0178] By using RIS service area or gain information in making handover decisions, the RIS may be accounted for in handover decisions, which may avoid suboptimal handover decisions based on incomplete information. This could also be applied to corresponding NCR information.

[0179] In the first scenario, the information is received from the target network node (e.g., via the Xn interface). In other examples, the information may be received from the UE that the handover decision relates to. For example, the network node may instruct the UE to read the information from a system information broadcast of the target network node. The network node may be configured to receive capability information from the UE, indicating that the UE is capable of reporting the RIS information. An advantage of receiving the information from the UE is that, if the target node is a suitable candidate for a handover, then the UE is likely to be able to retrieve the information from the target node (e.g., from an SSB of the target node).

[0180] In some examples, the network node may receive measurements (e.g., LI, L2, or L3) of cell-specific reference signals (e.g., SSBs) of the target network node from the UE, and the handover decision may be based on the measurements and the information received.

[0181] In some examples, the network node may decide to set up a conditional handover of the UE from a cell served by the network node to a cell served by the target node based on the information and measurements. The network node may then send a conditional handover request to the target network node, which may then determine conditions for a conditional handover. The condition prepared by the target gNB can take the RIS into account. For example, if a signal strength measurement condition is defined, the signal strength threshold above which the handover is executed may be lowered (e.g., for RIS supported cells), to take RIS gains into account.

[0182] In some examples, in which the network node receives the information from the UE, this information is received with or as part of an LI or L3 measurement report.

[0183] In a second scenario, a serving gNB does not know that there is a RIS supporting communications in target cell(s) before or during HO preparation.

[0184] In this scenario, there are several options for providing RIS related information to the serving gNB via the UE. An LTM scenario is considered here, but aspects below are applicable to baseline and conditional handovers, as will be apparent from examples presented later in the specification.

[0185] According to a first option, the target gNB provides the LTM configuration to the UE (i.e., the configuration of a prepared cell), along with a request for the UE to read a SIB of the prepared cell. The target gNB may prepare multiple cells, and send respective configurations, and the target gNB may request that the UE read a SIB of some or all of these cells (e.g., based on whether the RIS supports communications between UEs of those cells and the target gNB).

[0186] According to a second option, the target gNB provides the LTM configuration to the UE with RIS related information, which could include an indication of RIS presence (e.g., an indication of whether a RIS supports communications between UEs of a cell and the target gNB), an indication of a RIS service area (e.g., within which a UE may have communications with the target gNB enhanced by the RIS) and / or an indication of a RIS gain (e.g., a signal strength gain in decibels) associated with enhancement of communications between a UE and the target node by the RIS. The gain may be cell dependent (e.g., an expected gain when communications between a UE in a particular cell and the target node are enhanced by the RIS), and / or area dependent (e.g., an expected gain when communications between a UE in a particular area and the target node are enhanced by the RIS). A RIS service area may be indicated as a geographical area (e.g., which may be compared to positioning measurements, such as GNSS derived location measurements, etc.). A RIS service area may additionally or alternatively be indicated by a list of one or more SSBs. For example at a location within a given cell, a particular SSB of that cell will typically be received more strongly than others, and the locations at which that SSB is received more strongly can be considered to define an area associated with that SSB. Relatedly, a UE may select a particular SSB of a given cell to receive cell specific signalling (e.g., SIBs) from. This selection may be based at least in part on how strongly an SSB is received, and the locations at which a UE would select a particular SSB to receive cell-specific signalling from could be considered to define an area associated with that SSB.

[0187] According to a third option, the target gNB is not required to provide additional information in the LTM configuration.

[0188] When using the first or second option a new UE capability may be introduced, the UE capability indicating that a UE is capable of obtaining RIS-related information from a cell / LTM configuration. This capability could be transferred or indicated to the target cell gNB during the LTM context setup. Then, based on the capability, the target cell could provide the relevant RIS-related information with the LTM configuration (e.g., the request to read the SIB of the first option, or the RIS related information of the second option may be provided by the target gNB in the LTM configuration based on the capability).

[0189] When using the first or third options, measurement reports (e.g., LI measurement reports or L3 measurement reports with beam specific information) from the UE to the source gNB could provide RIS related information to the source gNB / serving gNB. For example, the presence of a RIS in prepared cells , the RIS service area, and / or the RIS gain could be provided. Additionally, or alternatively, the UE could modify the measurement report based on the information, e.g., by applying the RIS gain to a measurement.

[0190] RIS presence information can be included in an indication from a target cell (e.g., in a SIB). In an example, a one bit indication may be provided along with the SSB (or beam) ID of a candidate cell being reported (e.g., in the SIB) to indicate whether that beam can be enhanced with the RIS or not.

[0191] In another example, RIS existence information for a candidate cell for which one or more measurements are being reported may be provided in the measurement report along with RIS service area and possible RIS gains. The UE may learn such information by reading the SIB of the prepared cell. In the first option, the UE may be requested to read the SIB, while in the third option the UE may determine to read the SIB without receiving an explicit request from the target gNB. Under the third option the UE may read the SIB of the target node by default, or based on some other indication from the target node, such as the manner in which the SSB of the target node are encoded.

[0192] The serving gNB can utilize measurement report information in cell switch decisions. For example, the serving gNB may assume that the UE will have the indicated RIS gains when the UE connects to the target cell, and may therefore, add the "delta" value or gain to the provided measurements. This addition of the gain to the provided measurements may be performed for measurements within the service area of RIS (for example, if an SSBs that the UE is reporting corresponds to an SSB indicated as being part of the service area of the RIS by the target gNB, the gain may be applied to measurements of that SSB). In some examples, the initial HO preparation decisions (e.g., the decision based on L3 measurements to prepare the LTM configuration) are not influenced, rather, the early downlink and uplink synchronization decisions (e.g., beam / cell selection for early downlink and uplink synchronization) and actual cell-switch decisions (based on LI measurements or L3 measurement reports with beam specific information) can be influenced.

[0193] Furthermore, in some examples the UE prioritizes making and providing to the source gNB measurements associated with cells with a RIS presence, based on the received LTM configuration (e.g., of the first and second options) including RIS related information. The UE may be provided with a set of resources for measurement reporting, and may select measurements to report based on the prioritisation (e.g., the UE may be capable of performing more measurements than it is allocated the resources to report, and the UE may determine to perform and / or report measurements related to a cell with RIS presence based on the RIS presence).

[0194] This solution could also be applied if we consider intra-CU LTM (or intra-CU handovers more generally), although we considered inter-CU (i.e., inter gNB) LTM throughout the invention. The source DU may be informed by the CU of the existence of the RIS in a neighbour intra-CU DU, and more information may be provided as discussed above. The source DU may take the information into account when making LTM decisions such as cell switch decisions.

[0195] Aspects of the above options may be applied to baseline and conditional handover procedures.

[0196] For example, in the first scenario, baseline handover decisions, rather than LTM decisions may be based on RIS information received over the Xn interface. Similarly, the decision by a serving gNB to prepare a conditional handover may be based on received RIS information. Additionally, conditions prepared by the target gNB may take the RIS into account. For example, if the condition includes a signal strength measurement threshold (of a cell-specific reference signal) above which a conditional handover will be triggered, the signal strength measurement threshold may be set lower to account for gains from the RIS once the handover takes place.

[0197] For example, in the second scenario, a UE's L3 measurement reports (e.g., in the baseline or conditional handover procedure) to the source gNB can be enhanced, in a similar way to the above discussed enhancements of LI measurement reports, to inform the source gNB of RIS presence / properties at a possible target gNB.

[0198] Similar to the LTM case, a new UE capability can be introduced for a UE capable of obtaining RIS-related information from a conditional handover (CHO) configuration. This capability could be transferred to the target cell gNB during the handover preparation stage. Then, based on the capability, the target cell gNB would know to provide the relevant RIS-related information with the CHO configuration.

[0199] Fig. 10 is a flow diagram illustrating a method designated generally by the reference numeral 300. Method 300 may be carried out by a user equipment being served by a network node (such as a gNB).

[0200] At step 310, the UE obtains information from a target network node. The information indicates at least one of: a RIS service area and a RIS gain. The RIS is configured to support communications between the first network node and one or more UEs of a first cell (or a first set of cells) of a mobile communication system. The RIS is configured to support communications between the target network node and UEs of the first cell or set of cells within the service area. The RIS gain is a gain associated with RIS enhancement of communications between the target network node and UEs of a first cell or set of cells.

[0201] At step 312, the UE indicates the information to the serving network node (i.e. the network node serving the cell to which the UE is currently connected). By obtaining the information from the target network node, and indicating the information to the serving network node, the UE may facilitate handover decision making by the serving node that accounts for the RIS in the target network node.

[0202] In some examples, the method further comprises making one or more measurements of cell-specific reference signals of one or more cells served by the target network node; and indicating the one or more measurements to the serving network node. Indicating the one or more measurements to the serving network node may comprise sending an LI or L3 measurement report, and indicating the information to the serving network node may comprise sending the information with or as part of the LI or L3 measurement report. Sending the information at this stage allows it to be used alongside measurement information in handover decision making.

[0203] In some examples, the method further comprises detecting the presence of the RIS associated with the target network node based on measurements of at least one cell-specific reference signal of at least one cell served by the target network node. For example, the presence of the RIS may be indicated in the SSB encoding used, or in the content of the SIB. In some examples, obtaining the information comprises, responsive to detecting the presence of a RIS associated with the target network node (e.g., from the encoding of the SSBs), obtaining the information by reading system information (e.g., from a SIB) of the target network node. In examples in which the UE detects the presence of the RIS without explicit instruction to do so (e.g., in an LTM configuration), the UE may more flexibly provide the serving network node with information for making a more suitable handover decision.

[0204] In some examples the method further comprises receiving an instruction to read a system information broadcast associated with one or more cells served by the target network node. Obtaining information from the target network node may comprise obtaining the information by reading the information from said system information broadcast, responsive to the UE receiving the instruction to read system information broadcast. In some examples the serving node provides the instruction to read the system information broadcast, while in other examples the target node provides the instruction. In some examples the target node provides the instruction with or as part of a configuration for use by the UE when being served by a respective cell served by the target network node (e.g., in an LTM configuration comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the target network node). By providing the instruction in such a configuration, it is not necessary to rely on UE detection of the RIS in the LTM procedure (e.g., even if the UE does not, or is not able to detect the RIS on its own).

[0205] In some examples measurements of cell-specific reference signals associated with cells for which the UE has received an instruction to read an associated system information broadcast are prioritised when making measurements of cell-specific reference signals. This may allow for the efficient allocation of measurement and measurement reporting resources to a cell even when a cell-specific reference signal does not convey the gains from a RIS.

[0206] In some examples the information is obtained from the target network node by reading the information from a configuration for use by the UE when being served by a respective cell served by the target network node (e.g., in an LTM configuration comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the target network node). By providing the information in such a configuration, it can be made available for later stages of the LTM procedure (e.g., even if the UE does not, or is not able to detect the RIS on its own).

[0207] In some examples measurements of cell-specific reference signals of the first cell are prioritised based at least in part on the UE having obtained the information.

[0208] In some examples the UE indicates to the serving network node that the UE is capable of reporting at least one of a RIS service area and a RIS gain of a RIS associated with a target network node. This may allow the serving node to request that the UE reads neighbour cell SIBs for RIS information, and / or this may allow the serving node to indicate this capability to neighbour / potential target nodes, so that RIS information may be included in an LTM configuration.

[0209] Fig. 11 shows an exemplary message sequence chart (MSC), designated generally by the reference numeral 400. This message flow sequence shows aspects of the present disclosure applied to the LTM procedure.

[0210] At step 410, a RIS 404 establishes a connection with gNB 2 408, so that the RIS may be used for enhancing signals between gNB 2 and UEs of a cell or a set of cells served by gNB 2.

[0211] At step 412, gNB 2 408 determines to use RIS 404 to enhance data and CSI-RS signals (and not SSBs). This could be to enhance energy efficiency, reduce unnecessary interference with other cells, etc.

[0212] Steps 414 - 432 correspond to the first scenario, in which RIS information is indicated to gNB 1 406 by gNB 2 408.

[0213] At step 414, a connection is established between UE 402 and gNB 1 406.

[0214] At step 416, gNBl 406 and gNB2 408 perform an Xn setup / configuration update. This may happen before or after RIS 404 connection to gNB2 408, or UE 402 connects to gNBl 406. Along with Xn setup messages, gNB2 408 sends an information element indicating the presence of RIS 404 in a cell served by gNB2 408, a service area for the RIS and possible RIS gains.

[0215] In another embodiment (not shown in the figures), OAM configures gNBl 406 with RIS information for RIS 404 (for example, based on gNBl 406 being a neighbour to gNB2 408). No Xn information exchange is required in that embodiment.

[0216] At step 418, gNBl 406 acknowledges the Xn Setup / configuration update request.

[0217] At step 420, a measurement report is sent by UE 402 (e.g. an L3 measurement report) to gNBl 406. The measurement report may include measurements of neighbouring cells, such as cells served by gNB2 408, including cells in which UE communications with gNB2 408 are supported by RIS 404.

[0218] At step 422, gNBl 406 decides to perform a handover of the UE. The handover decision may take into account (e.g., be based at least in part on) the possibility of RIS enhancement, based on gNB2's information. For example, gNBl 406 can decide to perform handover preparation earlier, based on information indicating that there is a RIS covering the UE's location, and that the RIS will provide gains to the UE (based on the information provided by gNB2).

[0219] At step 424, gNBl 406 sends an LTM handover request to gNB2 408.

[0220] At step 426, gNB2 408 prepares at least one candidate cell (e.g., Cell 2 and Cell 3) for LTM.

[0221] At step 428, the LTM configuration (e.g., comprising configurations for use by the UE when connecting to the candidate cells) is sent to UE 402.

[0222] In other examples (not illustrated), the information provided at step 416 can instead be provided to gNBl 406 at this stage. In such examples, later stages of the LTM procedure could proceed based on this information (e.g., a decision to send the cell switch command), but the earlier stages, such as the handover decision at step 422, would not take this information into account.

[0223] At step 430, UE 402 makes measurements of the cells of the LTM configuration (e.g. Cell 2 and Cell 3).

[0224] At step 432, UE 402 sends an LI measurement report (e.g., a periodic measurement report), which may be based on the measurements performed at step 430.

[0225] Steps 434 - 450 correspond to the second scenario, in which RIS information is indicated to gNB 1 406 by UE 402.

[0226] At step 434, UE 402 connects to gNBl 406 and sends an indication of its capabilities. In some examples, this includes a target Cell RIS reporting capability (e.g., for LTM or for handovers in general).

[0227] At step 436, UE 402 sends a measurement report to gNBl 406.

[0228] At step 438, based on the measurement report, gNBl 406 decides to perform LTM.

[0229] At step 440, gNBl 406 sends an LTM handover request to gNB2 408. If the UE 402 indicated a target cell RIS reporting capability (e.g., at step 434), gNBl 406 may also indicate this UE capability.

[0230] At step 442, gNB2 408 performs LTM candidate preparation (preparing candidate cells and configurations for LTM). gNB2 408 may take the indicated UE capability into account.

[0231] At step 444, gNB2 408 sends the LTM configuration to UE 402. The LTM configuration may include an instruction to read a SIB of a candidate cell to obtain RIS related information (e.g., this request may be included based on the indicated UE capability and the presence of a RIS in the candidate cell). Additionally or alternatively, the LTM configuration may include RIS related information, related to a RIS of a candidate cell.

[0232] At step 446, UE 402 may determine to prioritise making (and / or reporting) measurements of a cell or cells associated with a RIS or RISs (e.g., based on the instruction to read a SIB of the cell, or based on receiving RIS information related to the cell). Additionally or alternatively, measurements of particular SSBs may be prioritised, based on an indication that the RIS is associated with particular SSBs. At step 448, UE 402 performs measurements of at least a cell associated with a RIS. The UE may read the SIB of a cell associated with a RIS responsive to an instruction (if received) from gNB2 408, or responsive to detecting the presence of a RIS associated with the cell (e.g., based on an SSB pattern associated with the presence of a RIS).

[0233] At step 450, UE 402 sends a periodic LI measurement report to gNBl 406. Included in the measurement report is the RIS related information (which may include a RIS presence indication, a RIS service area, a RIS gain, etc. associated with one or more cells of the LTM configuration).

[0234] Regardless of whether the RIS related information was provided by gNB2 408 (e.g., in the case of steps 414 - 432) or by the UE (e.g., in the case of steps 434 - 450), the method may then proceed to step 452, at which point gNBl 406 has received a measurement report and has obtained the RIS related information.

[0235] At step 452, gNBl 406 uses this information in making a cell switch decision. For example, gNBl 406 may assume that UE 402 will have indicated RIS gains when the UE connects to the target cell (associated with the gNB), therefore, it may add a delta value to the provided measurements in case the UE provides measurements within the service area of RIS (e.g., SSBs UE is reporting correspond to the ones indicated as service area of RIS by the target gNB). gNBl may therefore select a cell with worse measurements over a cell with better measurements based on a RIS gain associated with the cell with worse measurements.

[0236] At step 454, UE 402 receives a cell switch command (via MAC-CE), instructing the UE to use the prepared configuration associated with the selected cell, and connect to the selected cell.

[0237] At step 456, UE 402 performs an LTM cell switch as instructed.

[0238] At step 458, UE 402 is connected to gNB2 408. It's communications with gNB2 408 are enhanced by a RIS associated with the cell in which it is present.

[0239] Fig. 12 shows an exemplary message sequence chart (MSC), designated generally by the reference numeral 500. This message flow sequence shows aspects of the present disclosure applied to the baseline / conditional handover procedure.

[0240] Steps 510 and 512 correspond to steps 410 and 412 of method 400.

[0241] Steps 514 - 534 correspond to the first scenario, in which RIS information is indicated to gNB 1 406 by gNB 2 408.

[0242] Steps 514 - 518 correspond to steps 416 - 420 of method 400.

[0243] Steps 520 - 526 correspond to a baseline handover version of the first scenario.

[0244] At step 520, similar to step 422 of method 400, gNBl 406 decides to perform a handover of the UE 402, taking into account to the RIS information received at step 514.

[0245] At step 522, gNBl 406 sends a handover request to gNB2 408. Unlike step 424, this handover request is a baseline handover request (i.e., not a request to prepare an LTM configuration).

[0246] At step 524, gNB2 408 prepares a cell for handover. A handover reply (from gNB2 to gNBl) may follow, but this is not shown in method 500.

[0247] At step 526, gNB2 sends a handover command to UE 402.

[0248] Steps 528 - 534 correspond to a conditional handover version of the first scenario.

[0249] At step 528, similar to step 422 of method 400, gNBl 406 decides to perform a conditional handover of the UE 402, taking into account to the RIS information received at step 514. For example, gNBl can decide to perform earlier handover preparation based on a RIS service area covering the location of the UE and the RIS providing gains to the UE (as indicated by gNB2).

[0250] At step 530, gNBl 406 sends a handover request to gNB2 408. Unlike step 424, this handover request is a conditional handover request (i.e., not a request to prepare an LTM configuration).

[0251] At step 532, gNB2 408 prepares a cell for conditional handover. In creating the handover condition for the conditional handover, gNB2 may take the RIS presence into account. For example, if the UE is in the service area of the RIS, a SSB signal strength condition may be adjusted (e.g., downwards by an indicated RIS gain).

[0252] At step 534, gNB2 408 sends the conditional handover command to UE 402.

[0253] Steps 536 - 550 correspond to the second scenario, in which RIS information is indicated to gNB 1 406 by UE 402.

[0254] At step 536, UE 402 connects to gNBl 406 and sends UE capability information. As part of the capability information, UE 402 informs gNBl 406 that UE 402 is capable of target Cell RIS reporting (e.g., for baseline handover, conditional handover or for handovers in general).

[0255] At step 538, gNBl 406 sends a measurement report configuration to UE 402, along with a request to explore a neighbour frequency or cell (or a plurality of neighbour frequencies or cells) to determine whether a RIS is present, or to determine other RIS information such as service area or gain.

[0256] At step 540, UE 402 makes cell measurements. UE 402 reads the SIB of the cell (or a plurality of cells) based on an instruction received at step 538, to obtain the RIS information. In some examples UE 402 detects RIS presence based on an SSB pattern.

[0257] At step 542, UE 402 sends a measurement report to gNBl 406. The measurement is an L3 measurement report, and includes the RIS information (e.g., RIS presence, RIS service area, and / or RIS gain information).

[0258] At step 544, based on the measurement report, gNBl 406 decides to perform a handover or conditional handover. The decision is made accounting for the possibility of RIS enhancement based on the RIS information received from UE 402. For example, gNBl can decide to perform handover preparation earlier when taking into account that there is a RIS serving the UE's location, and that the RIS will provide gains to the UE.

[0259] At step 546, the handover request or conditional handover request is sent to gNB2 408.

[0260] At step 548, gNB2 508 creates a handover command in response to the handover request. If the request is a conditional handover request, gNB2 considers the RIS presence in an area where gains can be observed based on the reported measurements from the UE, while creating the condition.

[0261] At step 550, the baseline or conditional handover command is sent to UE 402.

[0262] At step 552, in response to the handover command of step 526, 534, or 550, UE 402 connects to a cell served by gNB2 408 according to the command.

[0263] At step 554, UE 402's communications with gNB2 408 are enhanced using the RIS.

[0264] Idle mode cell reselection

[0265] A UE in RRC_INACTIVE / IDLE state performs reference signal (RS) measurements using synchronization signal blocks (SSBs). SSBs are cell-specific reference signals, so SSB measurements are distinct from reference signal measurements that measure channel state information (CSI)-RSs (which can be considered UE specific reference signals, as these are generated based on UE presence). The SSB measurements are then used to pick a cell to camp in RRC_INACTIVE / IDLE state. In above portions of the detailed description, it is explained that in at least some deployments, it is expected that SSBs will not be enhanced by RISs or NCRs (e.g., for energy efficiency and / or interference reasons).

[0266] However, for UE is in RRC_IDLE / IN ACTIVE, this would mean cell reselection decisions may be made (i.e., the best cell / frequency on which to camp may be picked), without considering the improvements possible through the use of RIS / NCR-enhanced signals.

[0267] Cell selection / reselection decisions by a UE are based on SSB signals, so a UE may initially select a cell that doesn't have an NCR / RIS even though a neighbouring cell (with lower SSB RSRP) that has an NCR / RIS may provide a better reception in practice (i.e. as a result of RIS / NCR enhancement.

[0268] As discussed above, basing cell selection / reselection decisions on SSB signals that are not enhanced by an NCR / RIS may not guide an RRC_IDLE / IN ACTIVE UE to the best possible cell in a RIS / NCR-aided system.

[0269] To assist in UE cell reselection decisions, a gNB may signal at least one of the following RIS information elements, which may be used by UEs to determine a cell to camp in.

[0270] RIS presence information

[0271] A gNB may include information indicating the presence of a RIS in a cell in a SIB of that cell. Additionally or alternatively, a gNB may encode the SSBs of cells in which a RIS is present differently from the SSBs of cells in which a RIS is not, so the encoding may implicitly indicate whether a RIS is present in a cell (e.g., a different set of sequences for the primary synchronisation signal (PSS) and / or the secondary synchronisation signal (SSS) may be selected, or a different demodulation-reference signal (DM-RS) may be used for the physical broadcast channel (PBCH). RIS presence in a cell does not necessarily mean physical presence. Rather, presence in a cell may mean the ability to support communications between UEs of that cell and the gNB serving those UEs. For example, a RIS may be positioned between a TRP and a cell, without being within the geographical area of the cell, and support communications between UEs of that cell and a gNB (e.g., via the TRP).

[0272] When a UE sees the indication of RIS presence (whether this is indicated explicitly or implicitly), it may inherently assume there is a RIS deployed and prioritize the cell to camp on.

[0273] Additionally or alternatively, a gNB can provide a RIS presence indication about neighbour gNBs. For example, it can provide the UE with an indication of RIS presence in a neighbour frequency / cell. This may involve information exchange among neighbour gNBs (e.g., using Xn, Fl, or / and NG interface), indicating the presence of a RIS. If a UE is able to determine RIS / NCR presence in neighbour cells in signals from the cell on which it is camped, it may not need to decode signals (such as the SIB) from other cells to obtain this information.

[0274] In some embodiments, RIS presence information may be configured by the OAM in neighbour gNBs. An Xn interface information exchange may not be required in such cases.

[0275] RIS service area information

[0276] In addition to, or instead of, the RIS presence information, the UE may receive RIS service area information. This corresponds to the area in which a RIS (or NCR) can amplify / modify a signal. The service area information may include positioning information, an indication of SSB IDs in the coverage of the area of the RIS, and / or a set of intra / inter-frequency cells (e.g. PCIs) served by the same NCR / RIS.

[0277] Based on this information, a UE can determine whether the RIS / NCR can be used at the UE's location, and prioritize camping on a cell based on knowledge that the UE is within the service area of the RIS. The UE may also use additional information when determining whether to camp or prioritise camping on a cell based on RIS information. For example, a high mobility UE may not remain in the RIS service area for a sufficient duration to justify taking the RIS into account. The UE may therefore take the size of the geographical area into account when determining whether to prioritise a cell based on the UE being within the service area of a RIS. If the service area is small, and the UE is moving fast (e.g., the UE is a high mobility UE), the RIS or NCR may not be used for a significant duration (e.g., not for long enough to justify basing a cell selection or reselection decision on the presence of the RIS or NCR).

[0278] An SSB may be beamformed in both azimuthal and elevation / inclination domains, so an SSB index can give an indication of a geographical area in which the UE is present. For example, the area in which a particular SSB of a cell is received more strongly than the other SSBs may be considered an area defined by that SSB. There may therefore be no need for the UE to perform additional measurements / calculate its exact location (if this is not known) if a service area is expressed in terms of an SSB index (or a set of SSB indices).

[0279] As discussed above, this information may be provided in system information of the cell at which the RIS is present, or the information may be provided by neighbouring cells. In the case that the neighbouring cell is served by a different gNB, the gNBs may exchange information over the Xn interface, or the other possibilities discussed above in connection with RIS presence information sharing may be used.

[0280] In some embodiments, this information may be configured by the OAM in neighbour gNBs. An Xn interface information exchange may not be required in such cases.

[0281] RIS gain information

[0282] In some examples RIS information comprises RIS gain information. RIS gain information may comprise a delta value indicating how much gain the UE can expect when a RIS / NCR is used. The UE may use this information when selecting a cell to camp on. For example, the UE may "assume" that it will benefit from the gain when being served by a cell supported by a RIS (or when in the service area of a RIS, while served by a cell supported by the RIS). The UE may therefore add the gain to a cell measurement (e.g. an SSB measurement) when selecting a cell to camp on.

[0283] As discussed above, RIS information is in some examples provided by a cell supported by the RIS (e.g., indicated in the SIB). In some examples, the RIS information is provided by neighbouring cells (e.g., the RIS information may be exchanged via the Xn, Fl, and / or NG interface, so that neighbour cells can provide the RIS information in their SIBs).

[0284] The RIS gain (e.g., a power gain, such as a signal strength gain) can be area / SSB specific, with the determination / definition of areas being as discussed above. The gain can indicate the effect of RIS / NCR enhancement on signal strength.

[0285] This gain can be calculated based on measurements made when an NCR / RIS operates for the first time, for example, using the minimisation of drive test (MDT) mechanism.

[0286] The gain can be an average value over a service area or a minimum value over a service area. The gain may correspond to multiple SSBs to reduce overhead (e.g., compared to recording, storing, and sending a separate gain for each SSB). In the latter case, a minimum gain value over the multiple SSBs may be signalled.

[0287] In some examples, the RIS gain may be seen as an offset value to be applied to a cell selection / reselection criterion (e.g., for cell ranking criterion) based on RIS / NCR support indication. This may allow the RIS enhancements to be accounted for during cell selection / reselection.

[0288] Fig. 13 is a flow diagram illustrating a method designated generally by the reference numeral 600. Method 600 may be carried out by a user equipment in an RRC state in which it carries out cell selection or cell reselection, such as RRC_IDLE or RRC_INACTIVE.

[0289] At step 610, the user equipment obtains information from a mobile communication system. The mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between a network node and user equipment of at least a first cell of the mobile communication system. The information is indicative of the RIS being configured to provide said support.

[0290] At step 612, the user equipment determines during a cell selection or reselection procedure to camp on the first cell based at least in part on the obtained information.

[0291] By basing cell reselection decisions (at least partly) in information indicative of RIS support, cell reselection decisions may take RIS presence into account, even when cell-specific reference signals are not enhanced by the RIS. This may allow a UE to select a more suitable cell (e.g., a cell that will provide a better connection between the UE and the network after transitioning to the RRC_CONNECTED state).

[0292] In some examples determining a cell to camp on during cell selection or reselection comprises prioritising the first cell or the operating frequency of the first cell based at least in part on the information. For example, if a plurality of cells or frequencies satisfy a cell reselection condition, then the cell(s), or the frequency or frequencies of the cell(s), supported by the RIS may be prioritised over other cells (e.g., by selecting the prioritised cell or cells in preference to the other cells). In some examples, the obtained information comprises information indicative of a service area of the RIS. Method 600 may further comprise determining that the UE is within the indicated service area of the RIS, and the prioritising may be performed based on determining that the UE is within the service area of the RIS. The enhancements provided by a RIS may be available in a particular area, or the enhancements may be large enough to take into account during the cell selection or reselection procedure in a particular area, so taking an indicated service area into account may reduce instances of overestimating RIS support resulting in unsuitable cell selection or reselection decisions. For example, this may avoid RIS support being taken into account in cell selection or reselection when the support would not be available (or significant).

[0293] In some examples, the obtained RIS information comprises information indicative of a gain (e.g., a signal power gain, such as a decibel value). In such examples determining during a cell selection or reselection procedure to camp on the first cell based on the obtained information may comprise applying the gain to at least one measurement of at least one cell-specific reference signal associated with the first cell (e.g., for a measurement of a received power of a cell specific reference signal expressed on a logarithmic scale, the gain may be added to the measurement). By applying the gain to the cell-specific reference signal, the effect of RIS enhancements (e.g., on UE specific signalling) can be estimated without enhancing the cell-specific reference signal, allowing the UE to take the effect or RIS enhancements into account.

[0294] In some examples, the obtained RIS information is indicative of a service area and gain, and the gain is applied to measurements of the cell-specific reference signal based on the UE determining that it is within the indicated service area. By applying the RIS gain based on the UE being within the RIS service area, instances of the UE taking RIS gains into account in cell reselection when they are not available may be reduced. In some examples the RIS gain is a minimum gain within the RIS service area. In some examples, the RIS gain is an average gain within the RIS service area. In some examples, a RIS may provide different gains within different areas, and the RIS information may provide different gains for different service areas of the same RIS, to provide more granular information, and facilitate improved decision making.

[0295] In some examples, RIS service area information is indicative of a geographical area, and determining that the UE is within the service area comprises determining that the UE is within the indicated geographical area (for example, using global navigation satellite system, GNSS, based positioning, or network assisted positioning using the network's location management function, LMF). In some examples, the service area information is indicative of one or more cell specific reference signals. A UE's selection of a cell-specific reference signal to receive cell specific signalling from may depend at least in part on the location of the UE (e.g., because the selection is based at least in part on a signal strength of the cellspecific reference signal, which may be location dependent, for example due to beamforming). The selected cell-specific reference signal may therefore correspond to a location, and a set of at least one cell-specific reference signals may therefore define an area, corresponding to UE locations within which those cell-specific reference signals may be selected by the UE to receive cell-specific signalling. Determining that the UE is within the service area may therefore comprise determining whether a cell specific reference signal that the UE receives cell-specific signalling from is in a list (of at least one) cell-specific reference signals defining the RIS service area. Defining a RIS service area may provide precision in the definition of the service area, but require additional information for the UE determine whether it is within the service area (e.g., GNSS positioning information). Defining a service area in terms of a set of SSBs may allow a UE to compare it's position to a service area using already available information (e.g., the identity of the cell-specific reference signal selected for receiving cell-specific signalling from a given cell.

[0296] In some examples, determining to camp on the first cell comprises prioritising the first cell based at least in part on determining that the UE meets a mobility condition. For example, highly mobile UEs may not be able to benefit from RIS enhancement for enough time to justify basing cell-selection or reselection decisions on RIS enhancement, so it may be decided that highly mobile UEs should not take the RIS into account.

[0297] In some examples, obtaining the RIS information comprises deriving the information from the manner in which a cell-specific reference signal of the first cell is encoded. This may allow for RIS information to be determined even without decoding system information.

[0298] In some examples, obtaining the RIS information comprises obtaining the information from system information broadcast by the first network node (i.e., the network node serving the first cell, wherein communications between UEs of the first cell and the network node are supported by the RIS.

[0299] In some examples, obtaining the information comprises obtaining the information from system information broadcast by a second network node, wherein the second network node does not serve the first cell.

[0300] Fig. 14 shows an exemplary message sequence chart (MSC), designated generally by the reference numeral 700. This message flow sequence shows aspects of the present disclosure applied to the cell reselection procedure.

[0301] In method 700 a RIS has established a connection with gNBl cell 1, so that the RIS may be used for enhancing signals between gNBl and UEs of cell 1 (or a set of cells served by gNBl including cell 1). gNBl has determined to use the RIS to enhance data and CSI-RS signals (and not SSBs). This could be to enhance energy efficiency, reduce unnecessary interference with other cells, etc.

[0302] At step 710, a UE comes into the vicinity of cell 1, while the UE is camping in the RRC_IDLE / IN ACTIVE state in a different cell (e.g., cell 2, not shown in the figure).

[0303] At step 712, the UE performs cell reselection. The UE reads neighbour cells SIBs, for example, to find cells on the best frequency (e.g., based on SSB measurements).

[0304] According to a first option, in steps 714 - 716 the UE uses RIS presence information in the cell reselection procedure.

[0305] At step 714, the UE receives the RIS presence information from gNBl. The RIS presence information could be included in the SIB of cell 1, and / or the RIS presence information could be indicated by the encoding of the SSBs of cell 1 (e.g., by using different encodings for SSBs of cells with a deployed RIS and cells without a deployed RIS).

[0306] At step 716, the UE prioritises camping on cell 1 due to the RIS presence information (e.g., over other cells). For example, a plurality of cells may meet a cell selection or reselection requirement and the UE may prioritise camping on cell 1 over other cells that meet that requirement based on the RIS presence information.

[0307] According to a second option, which may be combined with aspects of the first option (e.g., by making the prioritising contingent on the location of a UE being within a RIS service area), in steps 718 - 720, the UE uses RIS service area information in the cell reselection procedure.

[0308] At step 718, the UE receives RIS service area information from gNBl. For example, this information may be included in the SIB of cell 1. The RIS service area information may comprise a list of SSBs, and / or a geographical area. The geographical area may be used when positioning information is available.

[0309] At step 720, the UE compares its current location with the service area. If the UE falls within the service area, it prioritises cell 1 in the cell reselection procedure. The UE may also use further information, such as current velocity, when determining whether to prioritise cell 1. For example, if the UE has a very high velocity (e.g., higher than a threshold), the UE may refrain from prioritising the cell.

[0310] According to a third option, which may be combined with aspects of the first and / or second options (e.g., by making consideration of the RIS gain contingent on the UE being within the RIS service area), in steps 722 - 724, the UE uses RIS gain information in the cell reselection procedure.

[0311] At step 722, the UE receives RIS gain information from gNBl. For example, this information may be included in the SIB of cell 1. This may be an average gain, or a minimum gain, expected when using the to support communications. The UE may receive RIS gain information that is associated with a particular service area.

[0312] At step 724, the UE applies the RIS gain to measurements of cell 1 (e.g., of SSBs of cell 1) when comparing measurements of SSBs in the cell reselection procedure.

[0313] Steps 714, 718, and 722, may be combined in some embodiments. For example, if the information is included in the SIB of cell 1, this may be retrieved from one broadcast of the SIB.

[0314] At step 726, based on performing steps according to one, some, or all of the three options, the UE selects cell 1 to camp on.

[0315] At step 728, the UE connects to cell 1.

[0316] At step 730, the UE receives data from gNBl via RIS-enhanced signals.

[0317] Fig. 15 shows an exemplary message sequence chart (MSC), designated generally by the reference numeral 800. This message flow sequence shows aspects of the present disclosure applied to the cell reselection procedure.

[0318] In method 800, as with method 700, a RIS has established a connection with gNBl cell 1, so that the RIS may be used for enhancing signals between gNBl and UEs of cell 1 (or a set of cells served by gNBl including cell 1). gNBl has determined to use the RIS to enhance data and CSI-RS signals (and not SSBs). This could be to enhance energy efficiency, reduce unnecessary interference with other cells, etc.

[0319] At step 810, gNBl exchanges information with gNB2. gNBl sends gnB2 RIS related information that may be relayed to the UE by gNB2 at a later step of method 800. This may involve gNBl and gNB2 performing an Xn setup / configuration update (note that this can happen even before RIS connection or any UE connects to gNBl). Along with Xn setup / configuration update messages, gNBl sends an information element indicating the presence of the RIS in Cell 1, service area for the RIS and possible RIS gains to gNB2.

[0320] In another embodiment (not shown in this figure), the OAM configures neighbour gNBs with this information. Therefore, No Xn information exchange is required in that embodiment.

[0321] Steps 812 - 826 are similar to steps 710 - 724, except that it is gNB2, rather than gNBl that sends RIS related information to the UE regarding RIS connected to gNBl. In this example, the RIS presence in cell 1 of gNBl is not indicated by the encoding of the SSBs of cell 2 of gNB2, but RIS presence information may be included in the SIB of cell 2 of gNB2.

[0322] Indicating this information in the SIB of cell 2 of gNB2 means that this information can be indicated in the SIB of a cell that the UE monitors (i.e., there may be no requirement for the UE to read the SIBs of neighbouring cells to obtain RIS presence information of neighbours).

[0323] Steps 828 - 832 correspond to steps 726 - 730.

[0324] If a UE camps in a cell that has been prioritised due to the presence of a RIS, and that RIS ceases to serve that cell, the UE may re-evaluate best frequency / cell to camp on. For example, the UE could perform another cell reselection without using the above-described prioritisation methods.

[0325] This re-evaluation could be based on current cell-reselection mechanisms (e.g., without requiring a new trigger), or the RIS ceasing to serve the cell may trigger re-evaluation (e.g., may trigger another cell reselection procedure).

[0326] For completeness, FIG. 15 is a schematic diagram of components of one or more of the example embodiments described previously, which hereafter are referred to generically as a processing system 1800. The processing system 1800 may, for example, be comprised by the device referred to in the claims below.

[0327] The processing system 1800 may have a processor 1802, a memory 1804 closely coupled to the processor and comprised of a Random Access Memory (RAM) 1814 and a Read Only Memory (ROM) 1812, and, optionally, a user input 1810 and a display 1818. The processing system 1800 may comprise one or more network / apparatus interfaces 1808 for connection to a network / apparatus, e.g., a modem which may be wired or wireless. The network / apparatus interface 1808 may also operate as a connection to other apparatus such as device / apparatus which is not network side apparatus. Thus, direct connection between devices / apparatus without network participation is possible.

[0328] The processor 1802 is connected to each of the other components in order to control operation thereof.

[0329] The memory 1804 may comprise a non-volatile memory, such as a hard disk drive (HDD) or a solid-state drive (SSD). The ROM 1812 of the memory 1804 stores, amongst other things, an operating system 1815 and may store software applications 1816. The RAM 1814 of the memory 1804 is used by the processor 1802 for the temporary storage of data. The operating system 1815 may contain code which, when executed by the processor implements aspects of the methods 100, 200, 300, 400, 500, 600, 700, and 800 described above, along with aspects of the message flow sequence 100. Note that in the case of small device / apparatus the memory can be most suitable for small size usage i.e., not always a hard disk drive (HDD) or a solid state drive (SSD) is used.

[0330] The processor 1802 may take any suitable form. For instance, it may be a microcontroller, a plurality of microcontrollers, a processor, or a plurality of processors.

[0331] The processing system 1800 may be a standalone computer, a server, a console, or a network thereof. The processing system 1800 and needed structural parts may be all inside device / apparatus such as loT device / apparatus i.e., embedded to very small size.

[0332] In some example embodiments, the processing system 1800 may also be associated with external software applications. These may be applications stored on a remote server device / apparatus and may run partly or exclusively on the remote server device / apparatus. These applications may be termed cloud-hosted applications. The processing system 1800 may be in communication with the remote server device / apparatus in order to utilize the software application stored there.

[0333] FIG. 16 shows a tangible media, in the form of a removable memory unit 1910, storing computer-readable code which when run by a computer may perform methods according to example embodiments described above. The removable memory unit 1910 may be a memory stick, e.g., a Universal Serial Bus (USB) memory stick, having internal memory 1930 storing the computer-readable code. The internal memory 1930 may be accessed by a computer system via a connector 1920. Of course, other forms of tangible storage media may be used, as will be readily apparent to those of ordinary skilled in the art. Tangible media can be any device / apparatus capable of storing data / information which data / information can be exchanged between devices / apparatus / network.

[0334] Embodiments of the present invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and / or hardware may reside on memory, or any computer media. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "memory" or "computer-readable medium" may be any non-transitory media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. Reference to, where relevant, "computer-readable medium", "computer program product", "tangibly embodied computer program" etc., or a "processor" or "processing circuitry" etc. should be understood to encompass not only computers having differing architectures such as single / multi-processor architectures and sequencers / parallel architectures, but also specialised circuits such as field programmable gate arrays (FPGA), application specific integrated circuits (ASIC), signal processing devices / apparatus and other devices / apparatus. References to computer program, instructions, code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device / apparatus as instructions for a processor or configured or configuration settings for a fixed function device / apparatus, gate array, programmable logic device / apparatus, etc.

[0335] If desired, the different functions discussed herein may be performed in a different order and / or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined. Similarly, it will also be appreciated that the flow and signalling diagrams of Figures 8 - 15 are examples only and that various operations depicted therein may be omitted, reordered and / or combined.

[0336] It will be appreciated that the above-described example embodiments are purely illustrative and are not limiting on the scope of the invention. Other variations and modifications will be apparent to persons skilled in the art upon reading the present specification.

[0337] Moreover, the disclosure of the present application should be understood to include any novel features or any novel combination of features either explicitly or implicitly disclosed herein or any generalization thereof and during the prosecution of the present application or of any application derived therefrom, new claims may be formulated to cover any such features and / or combination of such features. Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described example embodiments and / or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

[0338] It is also noted herein that while the above describes various examples, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.

[0339] List of abbreviations

[0340] 3GPP 3rd Generation Partnership Project

[0341] CHO Conditional Handover

[0342] CU Control Unit

[0343] DU Distributed Unit

[0344] HO Handover

[0345] LTM Layer 1 / Layer 2 Triggered Mobility

[0346] NCR Network-controlled Repeater

[0347] NR New Radio

[0348] QoS Quality of Service

[0349] RAN Radio Access Network

[0350] RRC Radio Resource Configuration

[0351] RIS Reconfigurable intelligent surface

[0352] SI System Information

[0353] SIB System Information Block

[0354] NAS Non-Access Stratum

[0355] S-NSSAI Single Network Slice Selection Assistance Information

[0356] UE User Equipment

Claims

ClaimsWhat is claimed is:

1. A user equipment, UE, comprising: means for obtaining information from a first network node of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the first network node and one or more UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the first network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the first network node and UEs of the first cell; and means for indicating the information to a second network node, the second network node serving a cell to which the UE is currently connected.

2. The UE of claim 1, further comprising: means for making one or more measurements of cell-specific reference signals of one or more cells served by the first network node; and means for indicating the one or more measurements to the second network node.

3. The UE of claim 2, wherein indicating the one or more measurements to the second network node comprises sending an LI or L3 measurement report and wherein indicating the information to the second network node comprises sending the information with or as part of the LI or L3 measurement report.

4. The UE of claim 2 or claim 3, further comprising means for, based on measurements of at least one cell-specific reference signal of at least one cell served by the first network node, detecting the presence of the RIS associated with the first network node.

5. The UE of claim 4, wherein the means for obtaining information is69configured to, responsive to the UE detecting the presence of a R.IS associated with the first network node, obtain the information by reading system information of the first network node.

6. The UE of any preceding claim, further comprising means for receiving an instruction to read a system information broadcast of the first network node associated with one or more cells served by the first network node, wherein the means for obtaining information from the first network node is configured to, responsive to the UE receiving the instruction to read system information broadcast by the first network node, obtain the information by reading the information from said system information.

7. The UE of claim 6, wherein the means for receiving an instruction to read system information broadcast by the first network node is configured to receive the instruction from the second network node.

8. The UE of claim 6, wherein the means for receiving an instruction to read system information broadcast by the first network node is configured to receive the instruction from the first network node.

9. The UE of claim 6, wherein the means for receiving an instruction to read system information broadcast by the first network node is configured to receive the instruction with or as part of a configuration for use by the UE when being served by a respective cell served by the first network node.

10. The UE of claim 6, wherein the means for receiving an instruction to read system information broadcast by the first network node is configured to receive the instruction with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the first network node.

11. The UE of any of claims 6 - 10 when dependent on claim 2, wherein the means for making one or more measurements of cell-specific reference signals is70configured to prioritise measurements of cell-specific reference signals associated with cells for which the UE has received an instruction to read an associated system information broadcast.

12. The UE of any preceding claim, wherein the means for obtaining the information from the first network node is configured to obtain the information by reading the information from a configuration for use by the UE when being served by a respective cell served by the first network node.

13. The UE of any preceding claim, wherein the means for obtaining the information from the first network node is configured to obtain the information by reading the information from a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the first network node.

14. The UE of any preceding claim, wherein the means for making one or more measurements of cell-specific reference signals is configured to prioritise measurements of cell-specific reference signals of the first cell, based at least in part on the UE having obtained the information.

15. The UE of any preceding claim, further comprising means for indicating to the second network node that the UE is capable of reporting at least one of a RIS service area and a RIS gain of a RIS associated with a first network node.

16. A network node comprising: means for sending information to a user equipment, UE, of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the network node71and UEs of the first cell.

17. The network node of claim 16, further comprising means for generating a first cell-specific reference signal indicative of the RIS being configured to support communications between the network node and UEs of the first cell.

18. The network node of claim 16 or 17, wherein the means for sending information to the UE is configured to broadcast the information.

19. The network node of claim 18, further comprising means for instructing the UE to read the information from the broadcast.

20. The network node of claim 19, further comprising means for receiving an indication that the UE has a target cell RIS reporting capability, and wherein the means for instructing the UE to read the information from the broadcast are configured to do so responsive, at least in part, to receiving the indication that the UE has a target cell RIS reporting capability.

21. The network node of claim 19 or 20, wherein the means for instructing the UE to read the information from a broadcast is configured to send the instruction with or as part of a configuration for use by the UE when being served by a respective cell served by the network node.

22. The network node of claim 19 or 20, wherein the means for instructing the UE to read the information from a broadcast is configured to send the instruction with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the network node.

23. The network node of any of claims 16 - 22, wherein the means for sending information to the UE is configured send the information with or as part of a configuration for use by the UE when being served by a respective cell served by the first network node.

24. The network node of any of claims 16 - 22, wherein the means for sending information to the UE is configured to send the information with or as part of a lower layer triggered mobility, LTM, configuration, comprising at least one configuration for use by the UE when the UE is being served by a respective cell served by the network node.

25. The network node of any of claims 16 - 24, further comprising: means for receiving a handover request from a serving node, the serving node serving the UE; means for determining a handover condition based at least in part on the information; and means for sending a conditional handover command to the UE comprising the handover condition.

26. A network node comprising: means for receiving information associated with a reconfigurable intelligent surface, RIS, the RIS being configured to support communications between a target network node and user equipments, UEs, of at least a first cell of a mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the target network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the target network node and UEs of the first cell; and means for making a handover decision regarding a UE of the mobile communication system based at least in part on the received information, the UE being in communication with the mobile communication system via a cell served by the network node.

27. The network node of claim 26, wherein the means for receiving the information is configured to receive the information from the UE.

28. The network of any claim 27, further comprising means for sending an73instruction to the UE to read a system information broadcast of the target network node associated with one or more cells served by the target network node.

29. The network node of claim 27 or claim 28, further comprising means for receiving an indication from the UE that the UE is capable of sending the information.

30. The network node of claim 26, wherein the means for receiving the information is configured to receive the information from the target network node.

31. The network node of any of claims 26 - 30, further comprising: means for receiving from the UE one or more measurements of cellspecific reference signals of one or more cells served by the target network node, wherein the means for making a handover decision is configured to determine to perform a handover of the UE from a cell served by the network node to the first cell based at in part on the received information and the received measurements.

32. The network node of claim 26 - 30, further comprising: means for receiving from the UE one or more measurements of cellspecific reference signals of one or more cells served by the target network node, wherein the means for making a handover decision is configured to set up a conditional handover of the UE from a cell served by the network node to the first cell based at in part on the received information and the received measurements.

33. The network node of claim 31 or claim 32, when dependent on claim 27, wherein receiving the one or more measurements comprises receiving an LI or L3 measurement report and wherein receiving the service area and / or gaincomprises receiving the indication with or as part of the LI or L3 measurement report.

34. A method comprising: obtaining at a user equipment, UE, information from a first network node of a mobile communication system, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the first network node and one or more UEs of at least a first cell of the mobile communication system, and wherein the information indicates: a service area, the RIS being configured to support communications between the first network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the first network node and UEs of the first cell; and indicating, by the UE, the information to a second network node, the second network node serving the UE's current cell.

35. A method comprising: sending, from a network node, to a user equipment, UE, of a mobile communication system, information, wherein the mobile communication system comprises a reconfigurable intelligent surface, RIS, that is configured to support communications between the network node and UEs of at least a first cell of the mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the network node and UEs within the service area; and a gain associated with RIS enhancement of communications between the network node and UEs of the first cell.

36. A method comprising: receiving, at a network node, information associated with a reconfigurable intelligent surface, RIS, the RIS being configured to support communications between a target network node and user equipments, UEs, of at least a first cell of a mobile communication system, and wherein the information indicates at least one of: a service area, the RIS being configured to support communications between the target network node and UEs within the service area; and a gainassociated with RIS enhancement of communications between the target network node and UEs of the first cell; and making, a handover decision regarding a UE of the mobile communication system based at least in part on the received information, the UE being in communication with the mobile communication system via a cell served by the network node.

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