WO2024208510A1

WO2024208510A1 - Lower layer triggered mobility in a wireless communication network

Info

Publication number: WO2024208510A1
Application number: PCT/EP2024/055596
Authority: WO
Inventors: Umur KARABULUT; Panagiotis SPAPIS; Jedrzej STANCZAK; Chitradeep MAJUMDAR; Srinivasan Selvaganapathy; Sanjay Goyal
Original assignee: Nokia Technologies Oy
Priority date: 2023-04-06
Filing date: 2024-03-04
Publication date: 2024-10-10

Abstract

A user equipment for connecting towards a Radio Access Network, comprising: at least one processor; and at least one memory storing instruction which, when executed by the at least one processor, cause the user equipment at least to: establish a connection with a first network node that supports at least one of the distributed unit functionality or a Layer (2) protocol of the Radio Access Network via a first cell supported by the first network node; receive, from the Radio Access Network, a configuration message to perform Layer (1) measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer (1) measurement shall be performed and an associated first signal threshold level criterion; perform the configured Layer (1) measurements and evaluate for which candidate target cell a respective Layer (1) measurement is to be included in a respective Layer (1) measurement report based a respective measurement for on the at least one specific candidate target cell achieving the first signal threshold level criterion, and generate and transmit the respective Layer (1) measurement report towards the first network node.

Description

LOWER LAYER TRIGGERED MOBILITY IN A WIRELESS COMMUNICATION NETWORK TECHNOLOGICAL FIELD Various example embodiments relate to wireless telecommunication networks, and more particularly, to facilitating mobility within such wireless telecommunication networks. BACKGROUND As user equipment (UE) moves through a wireless telecommunication network, it may move through cells that comprise regions of radio coverage that are supported by one or more network access node. Maintaining an ability for a UE to communicate effectively with the wireless communication system as it moves through regions of radio coverage is typically referred to as mobility. Layer 1 (L1) or Layer 2 (L2), sometimes termed lower layer, triggered mobility is being increasingly considered to reduce the latency, overhead and interruption time associated with a UE moving between the different cells. BRIEF SUMMARY The scope of protection sought for various example embodiments of the invention is set out by the independent claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention. According to various, but not necessarily all, example embodiments of the invention there is provided a user equipment for connecting towards a Radio Access Network, comprising: at least one processor; and at least one memory storing instruction which, when executed by the at least one processor, cause the user equipment at least to: establish a connection with a first network node that supports at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell supported by the first network node; receive, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; perform the configured Layer 1 measurements and evaluate for which candidate target cell a respective Layer 1 measurement is to be included in a respective Layer 1 measurement report based on a respective measurement for the at least one specific candidate target cell achieving the first signal threshold level criterion; and generate and transmit the respective Layer 1 measurement report towards the first network node. The configuration message may further include an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements. The configuration message may further include an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements for a first group of cells, and at least one different evaluating and/or reporting criterion for the performed measurements for a second group of cells. The configuration message may include an indication to enable identification of the at least one specific candidate target cell of a second group of specific candidate target cells achieving a second signal threshold level for which a Layer 1 measurement shall be performed and an associated second signal threshold level. The indication may identify an offset between the first signal threshold level and the second signal threshold level The first signal threshold level may be equal to or lower than the second signal threshold level. The configuration message may include an indication to enable identification of evaluating criteria for the Layer 1 measurement to be included in a respective Layer 1 measurement report. The configuration message may include an indication specifying a number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying a number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The Layer 1 measurements reports may carry N measurement values and the configuration message may include an indication specifying measurement values to be included when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level is less than N. The Layer 1 measurements reports may carry N measurement values and the configuration message may include an indication specifying measurement values to be included when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level is less than N. The indication specifying measurement values to be included may specify that measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports. The indication specifying measurement values to be included may specify that strongest measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying a maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. When the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level exceeds the maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level, the instruction, when executed by the at least one processor, may cause the user equipment at least to: generate and transmit the respective Layer 1 measurement report towards the first network node with strongest measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the first group. The configuration message may include an indication specifying a maximum number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. When the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level exceeds the maximum number measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level, the instruction, when executed by the at least one processor, may cause the user equipment at least to: generate and transmit the respective Layer 1 measurement report towards the first network node with strongest measurement values of beams of the second group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the second group. The maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group may be set to equal N. The maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group may be set to exceed N. When the maximum number measurement values of beams of the first group added to the maximum number measurement values of beams of the second group is set to exceed N, the configuration message may include an indication specifying which measurement values to prioritise including when the number of measurement values of beams of the first group fails to exceed the maximum number measurement values of beams of the first group and/or when the number of measurement values of beams of the second group fails to exceed the maximum number measurement values of beams of the second group but the summed number of measurement values exceed N. The configuration message may include an indication specifying prioritising measurement values of beams of the first group over measurement values of beams of the second group. The configuration message may include an indication specifying prioritising strongest measurement values of beams of the first group over measurement values of beams of the second group. The first group of cells may include at least one candidate target cell for which Timing Advance information at the user equipment is available and the second group of cells may include at least one candidate target cell for which Timing Advance information at the user equipment is not available. The first group of cells may include at least one candidate target synchronised cell for which Timing Advance for a potential connection between the user equipment and the candidate target synchronised cell is available and the second group of cells may include at least one candidate target non-synchronised cell for which Timing Advance information for a potential connection between the user equipment and the candidate target synchronised cell is not available. The measurement values may comprise beam Reference Signal Received Power values and strongest measurement values may comprise those highest measured beam Reference Signal Received Power values. The configuration message may include at least one evaluation criteria to select, as the at least one indicated specific candidate cell, a candidate target cell for which a Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available. The instructions, when executed by the at least one processor, may cause the user equipment at least to: receive, from the Radio Access Network, a message to trigger an acquisition of a Timing Advance information for at least one candidate target cell with which the user equipment may connect. The instructions, when executed by the at least one processor, may cause the user equipment at least to: determine, for at least one of the candidate target cells, whether Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available. The Timing Advance information may be based on information received from the first network node and/or from a target network node in response to the triggered Timing Advance acquisition. The instructions, when executed by the at least one processor, may cause the user equipment at least to: classify a candidate targets cell for which Timing Advance information is available as a synchronised cell in the first group and a candidate targets cell for which Timing Advance information is not available as a non-synchronised cell in the second group. The network node may comprise at least one of or supports functionality of at least one of: a base station, a 5G gNB, a Centralised Unit, a Distributed Unit, a secondary node, a source node or a source secondary node. The configuration message may comprise a Radio Resource Configuration message. According to various, but not necessarily all, example embodiments of the invention there is provided a user equipment for connecting towards a Radio Access Network, comprising: means for establishing a connection with a first network node that supports at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell supported by the first network node; means for receiving, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; means for performing the configured Layer 1 measurements and evaluating for which candidate target cell a respective Layer 1 measurement is to be included in a respective Layer 1 measurement report based on a respective measurement for the at least one specific candidate target cell achieving the first signal threshold level criterion; and means for generating and transmitting the respective Layer 1 measurement report towards the first network node. The means may perform the optional features set out in relation to the apparatus mentioned above. According to various, but not necessarily all, example embodiments of the invention there is provided a user equipment for connecting towards a Radio Access Network, comprising: circuitry configured to establish a connection with a first network node that supports at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell supported by the first network node; circuitry configured to receive, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; circuitry configured to perform the configured Layer 1 measurements and evaluate for which candidate target cell a respective Layer 1 measurement is to be included in a respective Layer 1 measurement report based on a respective measurement for the at least one specific candidate target cell achieving the first signal threshold level criterion; and circuitry configured to generate and transmit the respective Layer 1 measurement report towards the first network node. The circuitry may be configured perform the optional features set out in relation to the apparatus mentioned above. According to various, but not necessarily all, example embodiments of the invention there is provided a method for connecting towards a Radio Access Network, comprising: establishing a connection with a first network node that supports at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell supported by the first network node; receiving, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; performing the configured Layer 1 measurements and evaluating for which candidate target cell a respective Layer 1 measurement is to be included in a respective Layer 1 measurement report based on a respective measurement for the at least one specific candidate target cell achieving the first signal threshold level criterion; and generating and transmitting the respective Layer 1 measurement report towards the first network node. The configuration message may further include an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements. The configuration message may further include an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements for a first group of cells, and at least one different evaluating and/or reporting criterion for the performed measurements for a second group of cells. The configuration message may include an indication to enable identification of the at least one specific candidate target cell of a second group of specific candidate target cells achieving a second signal threshold level for which a Layer 1 measurement shall be performed and an associated second signal threshold level. The indication may identify an offset between the first signal threshold level and the second signal threshold level The first signal threshold level may be equal to or lower than the second signal threshold level. The configuration message may include an indication to enable identification of evaluating criteria for the Layer 1 measurement to be included in a respective Layer 1 measurement report. The configuration message may include an indication specifying a number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying a number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The Layer 1 measurements reports may carry N measurement values and the configuration message may include an indication specifying measurement values to be included when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level is less than N. The Layer 1 measurements reports may carry N measurement values and the configuration message may include an indication specifying measurement values to be included when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level is less than N. The indication specifying measurement values to be included may specify that measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports. The indication specifying measurement values to be included may specify that strongest measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying a maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying that, when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level exceeds the maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level, the respective Layer 1 measurement report towards the first network node shall include the strongest measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the first group. The configuration message may include an indication specifying a maximum number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying that, when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level exceeds the maximum number measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level, the respective Layer 1 measurement report towards the first network node shall include the strongest measurement values of beams of the second group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the second group. The maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group may be set to equal N. The maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group may be set to exceed N. When the maximum number measurement values of beams of the first group added to the maximum number measurement values of beams of the second group is set to exceed N, the configuration message may include an indication specifying which measurement values to prioritise including when the number of measurement values of beams of the first group fails to exceed the maximum number measurement values of beams of the first group and/or when the number of measurement values of beams of the second group fails to exceed the maximum number measurement values of beams of the second group but the summed number of measurement values exceed N. The configuration message may include an indication specifying prioritising measurement values of beams of the first group over measurement values of beams of the second group. The configuration message may include an indication specifying prioritising strongest measurement values of beams of the first group over measurement values of beams of the second group. The first group of cells may include at least one candidate target cell for which Timing Advance information at the user equipment is available and the second group of cells may include at least one candidate target cell for which Timing Advance information at the user equipment is not available. The first group of cells may include at least one candidate target synchronised cell for which Timing Advance for a potential connection between the user equipment and the candidate target synchronised cell is available and the second group of cells may include at least one candidate target non-synchronised cell for which Timing Advance information for a potential connection between the user equipment and the candidate target synchronised cell is not available. The measurement values may comprise beam Reference Signal Received Power values and strongest measurement values comprise those highest measured beam Reference Signal Received Power values. The configuration message may include at least one evaluation criteria to select, as the at least one indicated specific candidate cell, a candidate target cell for which a Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available. The method may comprise: receiving, from the Radio Access Network, a message to trigger an acquisition of a Timing Advance information for at least one candidate target cell with which the user equipment may connect. The method may comprise: determining, for at least one of the candidate target cells, whether Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available. The Timing Advance information may be based on information received from the first network node and/or from a target network node in response to the triggered Timing Advance acquisition. The method may comprise: classifying a candidate targets cell for which Timing Advance information is available as a synchronised cell in the first group and a candidate targets cell for which Timing Advance information is not available as a non- synchronised cell in the second group. The network node may comprise at least one of or supports functionality of at least one of: a base station, a 5G gNB, a Centralised Unit, a Distributed Unit, a secondary node, a source node or a source secondary node. The configuration message may comprise a Radio Resource Configuration message. According to various, but not necessarily all, example embodiments of the invention there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: establishing a connection with a first network node that supports at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell supported by the first network node; receiving, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; performing the configured Layer 1 measurements and evaluating for which candidate target cell a respective Layer 1 measurement is to be included in a respective Layer 1 measurement report based on a respective measurement for the at least one specific candidate target cell achieving the first signal threshold level criterion; and generating and transmitting the respective Layer 1 measurement report towards the first network node. The instructions may be for performing the optional features set out in relation to the method mentioned above. According to various, but not necessarily all, example embodiments of the invention there is provided a network node of a Radio Access Network, comprising: at least one processor; and at least one memory storing instruction which, when executed by the at least one processor, cause the network node at least to: support at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell to establish a connection with a user equipment; transmit, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; and receive the respective Layer 1 measurement report from the user equipment. The configuration message may further include an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements. The configuration message may further include an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements for a first group of cells, and at least one different evaluating and/or reporting criterion for the performed measurements for a second group of cells. The configuration message may include an indication to enable identification of the at least one specific candidate target cell of a second group of specific candidate target cells achieving a second signal threshold level for which a Layer 1 measurement shall be performed and an associated second signal threshold level. The indication may identify an offset between the first signal threshold level and the second signal threshold level The first signal threshold level may be equal to or lower than the second signal threshold level. The configuration message may include an indication to enable identification of evaluating criteria for the Layer 1 measurement to be included in a respective Layer 1 measurement report. The configuration message may include an indication specifying a number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying a number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The Layer 1 measurements reports may carry N measurement values and the configuration message may include an indication specifying measurement values to be included when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level is less than N. The Layer 1 measurements reports may carry N measurement values and the configuration message may include an indication specifying measurement values to be included when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level is less than N. The indication specifying measurement values to be included may specify that measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports. The indication specifying measurement values to be included may specify that strongest measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying a maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying, when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level exceeds the maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level, the respective Layer 1 measurement report shall include the strongest measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the first group. The configuration message may include an indication specifying a maximum number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying, when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level exceeds the maximum number measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level, the respective Layer 1 measurement report shall include the strongest measurement values of beams of the second group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the second group. The maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group may be set to equal N. The maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group may be set to exceed N. When the maximum number measurement values of beams of the first group added to the maximum number measurement values of beams of the second group is set to exceed N, the configuration message may include an indication specifying which measurement values to prioritise including when the number of measurement values of beams of the first group fails to exceed the maximum number measurement values of beams of the first group and/or when the number of measurement values of beams of the second group fails to exceed the maximum number measurement values of beams of the second group but the summed number of measurement values exceed N. The configuration message may include an indication specifying prioritising measurement values of beams of the first group over measurement values of beams of the second group. The configuration message may include an indication specifying prioritising strongest measurement values of beams of the first group over measurement values of beams of the second group. The first group of cells may include at least one candidate target cell for which Timing Advance information at the user equipment is available and the second group of cells may include at least one candidate target cell for which Timing Advance information at the user equipment is not available. The first group of cells may include at least one candidate target synchronised cell for which Timing Advance for a potential connection between the user equipment and the candidate target synchronised cell is available and the second group of cells may include at least one candidate target non-synchronised cell for which Timing Advance information for a potential connection between the user equipment and the candidate target synchronised cell is not available. The measurement values may comprise beam Reference Signal Received Power values and strongest measurement values comprise those highest measured beam Reference Signal Received Power values. The configuration message may include at least one evaluation criteria to select, as the at least one indicated specific candidate cell, a candidate target cell for which a Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available. The instructions, when executed by the at least one processor, may cause the network node at least to: send, from the Radio Access Network, a message to trigger an acquisition of a Timing Advance information for at least one candidate target cell with which the user equipment may connect. The instructions, when executed by the at least one processor, may cause the network node at least to: determine, for at least one of the candidate target cells, whether Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available. The instructions, when executed by the at least one processor, may cause the network node at least to: send information relating to the Timing Advance the first network node and/or from a target network node in response to the triggered Timing Advance acquisition. The instructions, when executed by the at least one processor, may cause the network node at least to: classify a candidate targets cell for which Timing Advance information is available as a synchronised cell in the first group and a candidate targets cell for which Timing Advance information is not available as a non-synchronised cell in the second group. The network node may comprise at least one of or supports functionality of at least one of: a base station, a 5G gNB, a Centralised Unit, a Distributed Unit, a secondary node, a source node or a source secondary node. The configuration message may comprise a Radio Resource Configuration message. According to various, but not necessarily all, example embodiments of the invention there is provided a network node of a Radio Access Network, comprising: means for supporting at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell to establish a connection with a user equipment; means for transmitting, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; and means for receiving the respective Layer 1 measurement report from the user equipment. The means may perform the optional features set out in relation to the apparatus mentioned above. According to various, but not necessarily all, example embodiments of the invention there is provided a network node of a Radio Access Network, comprising: circuitry configured to support at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell to establish a connection with a user equipment; circuitry configured to transmit, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; and circuitry configured to receive the respective Layer 1 measurement report from the user equipment. The circuitry may be configured perform the optional features set out in relation to the apparatus mentioned above. According to various, but not necessarily all, example embodiments of the invention there is provided a method for connecting towards a Radio Access Network, comprising: supporting at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell to establish a connection with a user equipment; transmitting, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; and receiving the respective Layer 1 measurement report from the user equipment. The configuration message may further include an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements. The configuration message may further include an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements for a first group of cells, and at least one different evaluating and/or reporting criterion for the performed measurements for a second group of cells. The configuration message may include an indication to enable identification of the at least one specific candidate target cell of a second group of specific candidate target cells achieving a second signal threshold level for which a Layer 1 measurement shall be performed and an associated second signal threshold level. The indication may identify an offset between the first signal threshold level and the second signal threshold level The first signal threshold level may be equal to or lower than the second signal threshold level. The configuration message may include an indication to enable identification of evaluating criteria for the Layer 1 measurement to be included in a respective Layer 1 measurement report. The configuration message may include an indication specifying a number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying a number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The Layer 1 measurements reports may carry N measurement values and the configuration message may include an indication specifying measurement values to be included when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level is less than N. The Layer 1 measurements reports may carry N measurement values and the configuration message may include an indication specifying measurement values to be included when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level is less than N. The indication specifying measurement values to be included may specify that measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports. The indication specifying measurement values to be included may specify that strongest measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying a maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying that, when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level exceeds the maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level, the respective Layer 1 measurement report shall include the strongest measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the first group. The configuration message may include an indication specifying a maximum number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports. The configuration message may include an indication specifying that, when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level exceeds the maximum number measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level, the respective Layer 1 measurement report shall include the strongest measurement values of beams of the second group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the second group. The maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group may be set to equal N. The maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group may be set to exceed N. When the maximum number measurement values of beams of the first group added to the maximum number measurement values of beams of the second group is set to exceed N, the configuration message may include an indication specifying which measurement values to prioritise including when the number of measurement values of beams of the first group fails to exceed the maximum number measurement values of beams of the first group and/or when the number of measurement values of beams of the second group fails to exceed the maximum number measurement values of beams of the second group but the summed number of measurement values exceed N. The configuration message may include an indication specifying prioritising measurement values of beams of the first group over measurement values of beams of the second group. The configuration message may include an indication specifying prioritising strongest measurement values of beams of the first group over measurement values of beams of the second group. The first group of cells may include at least one candidate target cell for which Timing Advance information at the user equipment is available and the second group of cells may include at least one candidate target cell for which Timing Advance information at the user equipment is not available. The first group of cells may include at least one candidate target synchronised cell for which Timing Advance for a potential connection between the user equipment and the candidate target synchronised cell is available and the second group of cells may include at least one candidate target non-synchronised cell for which Timing Advance information for a potential connection between the user equipment and the candidate target synchronised cell is not available. The measurement values may comprise beam Reference Signal Received Power values and strongest measurement values may comprise those highest measured beam Reference Signal Received Power values. The configuration message may include at least one evaluation criteria to select, as the at least one indicated specific candidate cell, a candidate target cell for which a Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available. The method may comprise: sending, from the Radio Access Network, a message to trigger an acquisition of a Timing Advance information for at least one candidate target cell with which the user equipment may connect. The method may comprise: determining, for at least one of the candidate target cells, whether Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available. The method may comprise: sending information relating to the Timing Advance information from the first network node and/or from a target network node in response to the triggered Timing Advance acquisition. The method may comprise: classifying a candidate targets cell for which Timing Advance information is available as a synchronised cell in the first group and a candidate targets cell for which Timing Advance information is not available as a non- synchronised cell in the second group. The network node may comprise at least one of or supports functionality of at least one of: a base station, a 5G gNB, a Centralised Unit, a Distributed Unit, a secondary node, a source node or a source secondary node. The configuration message may comprise a Radio Resource Configuration message. According to various, but not necessarily all, example embodiments of the invention there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: supporting at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell to establish a connection with a user equipment; transmitting, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; and receiving the respective Layer 1 measurement report from the user equipment. The instructions may be for performing the optional features set out in relation to the method mentioned above. Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims. Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function. BRIEF DESCRIPTION Some example embodiments will now be described with reference to the accompanying drawings in which: FIG.1 illustrates a messaging sequence chart for L1/L2 Triggered Mobility (LTM); FIG.2 illustrates a messaging sequence chart for L1/L2 Triggered Mobility Framework for a Central Unit (CU)-Distributed Unit (DU) split architecture; FIG.3 illustrates a L1 Beam Measurement and Reporting configuration structure (extended for LTM Beam Management); FIG.4 illustrates L1 RSRP measurements performed by the UE for serving cell and target cells; and FIG.5 illustrates a messaging sequence chart according to one example embodiment. DETAILED DESCRIPTION Before discussing the example embodiments in any more detail, first an overview will be provided. Some example embodiments provide an arrangement for providing measurement reports of candidate target cells which reduce interruption when connecting to those candidate target cells. Unlike in current Layer 1 measurement reports where only the strongest (those with the highest received power) beams are reported, the user equipment is instead configured to provide measurements of (beams of) other candidate target cells, even if those are not the strongest. In particular, the user equipment is configured to provide measurements of (beams of) a first group of target candidate cells (such as, for example, those which have a valid timing advance (so-called sync cells)) even when those are not the strongest. The user equipment is also configured to provide measurements of (beams of) a second group of target candidate cells (such as, for example, those which have a no valid timing advance (so- called non-sync cells)). It will be appreciated that timing advance information for a potential connection between the user equipment and the candidate target cell can be considered as being valid or available if that timing advance information is available at the user equipment, at the distributed unit (and not at the user equipment), or elsewhere in the network. The user equipment, even without the timing advance information (or knowledge of the acquired timing advance information), could be instructed to use different criteria for different groups such as, for example, evaluation criteria 1 for (beam) measurements related to cells of the first group, and evaluation criteria 2 for (beam) measurements related to cells of the second group. Typically, the allocation of measurements between the first group (such as sync cells which are used as an example below) and the second group (such as non-sync cells which are used as an example below) that can be carried by the measurement report(s) is configured in the user equipment. In order that measurements of suitable sync cells are provided, a threshold (or offset from a non-sync cell threshold) is configured above which a sync cell can be considered a potential candidate. This removes sync cells which are unlikely to be suitable and helps to ensure that only potentially suitable sync cells are reported. The non-sync cell threshold also helps to ensure that only potentially suitable non-sync cells are reported. The user equipment can be configured with an indication of the number of measurements to be reported in the measurement report(s) sync cells and/or non-sync cells. The user equipment can also be configured with an indication of the maximum number of measurements to be reported in the measurement report(s) for sync cells and/or non-sync cells, together with an indication of which measurements should be included if the maximum numbers are not achieved (for example, when the maximum number is not exceeded, then measurements from the other group may be included) or exceeded (for example, when the maximum number is exceeded, then the strongest measurements from that group may be included). This gives the option of connecting to those sync cells where suitable to do so which can help to reduce interruption that would otherwise occur when connecting to other than a sync cell. L1/L2 Triggered Mobility (LTM) Framework (38.300 CR) [R2-2300375] FIG.1 shows an exemplary message sequence chart (MSC) for Layer 1 (L1)/Layer 2 (L2) triggered mobility (LTM) based on the change request (CR) [R2-2300375] on the LTM framework. In steps S1 to S3: the Central Unit (CU) prepares target cells for LTM; the CU provides the LTM configuration for the prepared target cells; the CU also configures the UE with L1 measurement reporting needed for LTM execution. In step S4, the UE performs early Uplink (UL)/Downlink (DL) synchronization with the candidate target cells to minimize the interruption during LTM execution. In steps S5 to S6, the UE sends the L1 beam measurements of the target cells and the source DU decides on which cell the UE should handover (HO). In case the Timing Advance (TA) of the target cell is still valid (from step S4), the UE skips the RACH procedure (step S7) during HO. L1/L2 Triggered Mobility Framework The LTM framework defined in the running Change Request (CR) (38.300) does not elaborate the details of the split architecture as the technical specification of TS 38.300 only covers the RAN Overall descriptions. The internal view on the LTM framework for split architecture will now be explained. FIG.2 shows an exemplary MSC for L1/L2 triggered mobility (LTM). In steps S1 to S12: the CU prepares the target cells for LTM; the CU provides the LTM configuration for prepared cells; the CU also configures UE with L1 measurement reporting needed for LTM execution. In step S13, the UE performs early UL/DL sync with candidate cells to minimize the interruption during LTM execution. In steps S14 to S16, the UE sends the L1 beam measurements of the target cells and the source DU decides on which cell the UE should handover. In case the TA of the target cell is still valid (from step S13), the UE skips the RACH procedure (steps S17 and S18) during HO. Periodic L1 Beam Measurements Channel State Information (CSI-ReportConfig) CSI-ReportConfig and CSI-MeasConfig A maximum of 48 CSI reporting configurations can be provided to the UE (as per maxNrofCSI-ReportConfigurations) and the UE can be configured to measure up to 192 CSI individual Reference Signals (RSs). In LTM it is assumed that the UE can be configured to measure on multiple candidate cells (e.g. up to 8, the number is not yet decided – Stage-3 detail). The UE can be configured to report periodically, aperiodically or according to semi-persistent configuration. The UE can report up to 4 RS measurements in one L1 beam measurement (and expected to be 8). FIG.3 shows the existing L1 CSI MeasConfig structure that is used for intra-cell beam management (serving cell beams) and inter-cell beam management (non-serving cell beams) which are already in the Standard. The configuration may be extended for the LTM beam management procedure (the two right-most columns) to acquire the L1 beam measurements of the candidate cells. However, since the L1 measurements are reported in lower layers (from UE to DU), the amount of the measurements need to be configured economically (the number of RS measurements will be limited to 4, for each Report Config). Early TA Acquisition for a candidate cell in LTM Early TA acquisition (before the cell switch command is received by the UE) is possible in Release-18 LTM: Physical Downlink Control Channel (PDCCH) ordered Random Access Channel (RACH) is agreed to be supported: The PDCCH order is triggered by source cell (serving cell) which contains the indication of the candidate cell. The reserved bit(s) in Downlink Control Information (DCI) format 1_0 for PDCCH order can be used for indication of cell identity. Other parameters such as Random Access Preamble indices and indication of RACH occasions with the associated SSB indices are configured for each candidate target cell. For PDCCH ordered-RACH for a candidate target cell, Re-Authorization Request (RAR) reception can be configured by RRC. If reception of RAR is not configured/indicated (without RAR), the TA value of the candidate target cell is indicated in the cell switch command. If reception of RAR is configured/indicated (with RAR), it still needs to finalized whether RAR is received from the serving cell or the candidate target cell. if RAR is received from a candidate target cell, it needs to be finalized whether Type1-PDCCH CSS of the candidate target cell is configured to the UE. If reception of RAR is configured/indicated, RAR contains at least TA of candidate target cell, other values such as UE ID, candidate cell ID, etc. need to be discussed and finalized later. Other techniques are agreed as working assumptions in RAN1 for now: UE-based TA measurement where UE derives TA based on reception (Rx) timing difference between current serving cell and candidate target cell as well as TA value for the current serving cell. Corresponding UE capability is to be introduced to support UE-based TA measurement. For a UE reports support of this capability, network configuration of UE-based TA measurement is supported. In the above mentioned approaches, in some options, the UE could receive and maintain the TA value of the candidate cells before the UE receives the cell switch command, e.g., for which the RAR reception is configured or UE based TA measurement is used. As mentioned above, the UE can send a limited number of L1 Reference Signal Received Power (RSRP) beam measurements in the L1 measurement report. The reported measurements may not include the measurements of a target cell for which the UE has a valid TA (sync-cell). This is because the content of the L1 measurement report can be dominated by beam measurements of another target cell for which the UE does not have a valid TA (non-sync-cell) even if the sync-cell measurements are good enough for handover. The issue is illustrated in FIG.4 and in that case, the serving DU will typically perform one of the following: trigger the TA acquisition for the non-sync-cell – this leads interruption on both UL and DL and the risk of failure due to delayed HO procedure (TA acquisition takes time); trigger cell change to the non-sync- cell without TA acquisition – this leads interruption on UE side during cell change due to random access procedure; wait for one of the sync-cells to be reported in the L1 measurement report – this risks failure due to delayed HO procedure (the sync-cell may never be strongest but good enough to handover). In the current L1 measurement reporting configuration and UE behaviour, when the UE is configured to report the L1 measurements, the UE reports the N strongest beam measurements that are measured at the UE side. The UE does not consider any criteria except the strength of the measurements. As explained below, due to the nature of L1 measurement fluctuations, this straightforward reporting criteria leads the network to miss the L1 measurement reports of some cells that are required on the network side for better cell switch decision (that considers the TA acquisition). Prioritising Measurements In some example embodiments, a technique is proposed that configures UE to prioritize the reported L1 measurements of the cells against each other before reporting the L1 measurements. An aim of this prioritization technique is to prioritize the L1 reporting of the cell(s) with a valid TA (sync-cells) over reporting of the cell(s) without a valid TA (non-sync-cells). Hence, even if the L1 measurements of the non-sync cell(s) are strongest, the UE will report the L1 measurements of the sync-cell(s) with high priority. However, the prioritisation and reporting is not performed blindly, a reasonable threshold configuration and comparison method is provided so that the L1 reporting and filtering criteria considers the amount of difference between the sync and non-sync cell measurements and prioritizes the sync-cells only if they are slightly weaker than the non-sync cells. In particular, L1 measurement reports for the cells where the UE has obtained the sync are prioritized: • Assume the UE can report ^ number of L1 beam RSRPs in each L1 Measurement report. • Define two RSRP thresholds for beams that are reported in the L1 measurements • One threshold is for non-sync cell measurements (^_^^^^^^^^) • One threshold is for sync cell measurements (^_^^^^) • ^_^^^^ ≤ ^_^^^^^^^^ so that the threshold for synced cells is lower to prioritize the reporting for sync cells • Alternatively, the UE will receive an offset to be applied to sync cell measurements and UE sorts all beam measurements typically in one place. • The UE will compare the L1 RSRPs of the “sync cells” against the ^_^^^^ threshold and mark them as the beams to be reported. Assume that there are ^_^^^^ beams detected above the ^_^^^^ threshold. • Then, the UE will compare the L1 RSRPs of the “non-sync cells” against the ^_^^^^^^^^ threshold and mark them as well. Assume that there are ^_^^^^^^^^ beams detected above the (^_^^^^^^^^) threshold. Alternatives on the reported content decision: In a first alternative (Alternative 1), the UE will report the sync-cell measurements and if ^_^^^^ < ^ (the maximum number of L1 beam RSRPs in each L1 Measurement report is not reached), then the UE will report the strongest non-sync L1 RSRPs - as much as the maximum number of L1 beam RSRPs in each L1 Measurement report allows. In other words, the UE incorporate into the L1 Measurement report all the L1 beam RSRPs for the sync cells exceeding the threshold for sync cell measurements (^_^^^^), with any unoccupied space in the L1 Measurement report being used for the strongest L1 beam RSRPs for the non-sync cells exceeding the threshold for non-sync cell measurements (^_^^^^^^^^). In a second alternative (Alternative 2), the UE is configured with a maximum number of L1 beam RSRPs for the sync cells ^_^^^^,^^^ exceeding the threshold (^_^^^^) for sync cell measurements that can be selected for incorporation into the L1 Measurement report. The UE is also configured with a maximum number of L1 beam RSRPs for the non-sync cells ^_^^^^^^^^,^^^ exceeding the threshold (^_^^^^^^^^) for non-sync cell measurements that can be selected for incorporation into the L1 Measurement report. The UE will report the strongest ^_^^^^,^^^ measurements if the ^_^^^^ is above ^_^^^^,^^^. Similarly, the UE will report the strongest ^_^^^^^^^^,^^^ measurements if the ^_^^^^^^^^ is above ^_^^^^^^^^,^^^. ^_^^^^^^^^,^^^ + ^_^^^^,^^^ = ^ can be configured in order to facilitate the maximum number of beams can be reported. ^_^^^^^^^^,^^^ + ^_^^^^,^^^ > ^ can also be configured and the network can configure which of the measurements to be prioritized if the max number of reported beam is still not reached (in case some of the beams above the threshold are not reported due to initial criteria). FIG.5 is a message sequence chart illustrating the approach of an example embodiment. In step S32, the CU 40 configures the UE L1 Measurement configuration to report the L1 beam RSRPs for sync and non-sync cells. In particular, the RSRP thresholds for both sync (^_^^^^) and non-sync (^_^^^^^^^^) cells are configured using a RRC configuration message. These thresholds can be selected to facilitate the selection of sync and non-sync cells that are suited for connection by the UE 10. In a first alternative (Alt1), the number of reported RSRPs for sync cells ^_^^^^ and condition for reporting both sync and non-sync cells are configured. The UE 10 will report the sync-cell measurements and if ^_^^^^ < ^ (max number is not reached), then the UE 10 will report the strongest non-sync L1 RSRPs. In a second alternative (Alt2), the number of reported RSRPs for both sync and non- sync cells, ^_^^^^ and ^_^^^^^^^^ , respectively are configured. Also configured is the condition for reporting both sync and non-sync cells. The UE 10 will report the strongest ^_^^^^,^^^ measurements if the ^_^^^^ is above ^_^^^^,^^^. Similarly, the UE 10 will report the strongest ^_^^^^^^^^,^^^ measurements if the ^_^^^^^^^^ is above ^_^^^^^^^^,^^^. ^_^^^^^^^^,^^^ + ^_^^^^,^^^ = ^ can be configured to facilitate the maximum number of beams can be reported. ^_^^^^^^^^,^^^ + ^_^^^^,^^^ > ^ can be configured and the network can configure which of the measurements to be prioritized if the maximum number of reported beams is still not reached (in case some of the beams above the threshold are not reported due to initial criteria). The configuration is forwarded to the UE 10 in steps S33 and S44. In an alternative arrangement, the DU 20 configures the UE L1 Measurement configuration to report the L1 beam RSRPs for sync and non-sync cells and this is forwarded to the UE 10 in step S38. In the case that the UE 10 is not aware of the TA (the TA is maintained at the network), the serving DU/cell 20 configures the UE 10 with cell specific report threshold after early TA acquisition(s). In step S39 onwards, the UE 10 reports the L1 RSRPs of the sync cells although they are below the non-sync threshold, ^_^^^^^^^^ if they are above the sync-cell threshold ^_^^^^. This reporting can be either periodic or aperiodic (depending on configuration of the UE 10 by the serving cell 20). In the case of “per cell” reporting, the UE 10 decides to report sync and non-sync cells based on the different thresholds described above (instead of applying quota in one report, “per cell” reporting will be sent or skipped). The source DU 20 can monitor the sync-cell RSRPs and trigger the cell change to the sync-cell without interruption due to skipped random access. Through this approach, the UE 10 can handover to a cell that the UE 10 has a valid TA without any random access procedure. The UE 10 measures the cells which are most likely to become the next serving cells (assuming TA is acquired for such cells), instead of measuring for all cells with equal priority. The reporting overhead can be reduced (by configuring ^_^^^^ and ^_^^^^^^^^ values). Considering the dynamic cell change in LTM, it gives the network more flexibility on deciding the triggered cell change without concerning about cost of a handover This is because, even in the case of ping-pong or short stay, the handover will be cost-free, as the handover to a cell with valid TA has close-to-zero interruption time. The following description may provide further details of alternatives, modifications and variances: a gNB comprises e.g., a node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC, e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 3.2 incorporated by reference. A gNB Central Unit (gNB-CU) comprises e.g., a logical node hosting e.g., RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en- gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected with the gNB-DU. A gNB Distributed Unit (gNB-DU) comprises e.g., a logical node hosting e.g., RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected with the gNB-CU. A gNB-CU-Control Plane (gNB-CU-CP) comprises e.g., a logical node hosting e.g., the RRC and the control plane part of the PDCP protocol of the gNB-CU for an en-gNB or a gNB. The gNB-CU-CP terminates the E1 interface connected with the gNB-CU-UP and the F1-C interface connected with the gNB-DU. A gNB-CU-User Plane (gNB-CU-UP) comprises e.g., a logical node hosting e.g., the user plane part of the PDCP protocol of the gNB-CU for an en-gNB, and the user plane part of the PDCP protocol and the SDAP protocol of the gNB-CU for a gNB. The gNB-CU-UP terminates the E1 interface connected with the gNB-CU-CP and the F1-U interface connected with the gNB-DU, e.g., according to 3GPP TS 38.401 V16.6.0 (2021-07) section 3.1 incorporated by reference. Different functional splits between the central and distributed unit are possible, e.g., called options: Option 1 (1A-like split): The function split in this option is similar to the 1A architecture in DC. RRC is in the central unit. PDCP, RLC, MAC, physical layer and RF are in the distributed unit. Option 2 (3C-like split): The function split in this option is similar to the 3C architecture in DC. RRC and PDCP are in the central unit. RLC, MAC, physical layer and RF are in the distributed unit. Option 3 (intra RLC split): Low RLC (partial function of RLC), MAC, physical layer and RF are in the distributed unit. PDCP and high RLC (the other partial function of RLC) are in the central unit. Option 4 (RLC- MAC split): MAC, physical layer and RF are in the distributed unit. PDCP and RLC are in the central unit. Or else, e.g., according to 3GPP TR 38.801 V14.0.0 (2017-03) section 11 incorporated by reference. A gNB supports different protocol layers, e.g., Layer 1 (L1) – physical layer. The layer 2 (L2) of NR is split into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP) and Service Data Adaptation Protocol (SDAP), where e.g.: The physical layer offers to the MAC sublayer transport channels; The MAC sublayer offers to the RLC sublayer logical channels; The RLC sublayer offers to the PDCP sublayer RLC channels; The PDCP sublayer offers to the SDAP sublayer radio bearers; The SDAP sublayer offers to 5GC QoS flows; Comp. refers to header compression and Segm. To segmentation; Control channels include (BCCH, PCCH). Layer 3 (L3) includes e.g., Radio Resource Control (RRC), e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 6 incorporated by reference. A RAN (Radio Access Network) node or network node like e.g. a gNB, base station, gNB CU or gNB DU or parts thereof may be implemented using e.g. an apparatus with at least one processor and/or at least one memory (with computer-readable instructions (computer program)) configured to support and/or provision and/or process CU and/or DU related functionality and/or features, and/or at least one protocol (sub- )layer of a RAN (Radio Access Network), e.g. layer 2 and/or layer 3. The gNB CU and gNB DU parts may e.g., be co-located or physically separated. The gNB DU may even be split further, e.g., into two parts, e.g., one including processing equipment and one including an antenna. A Central Unit (CU) may also be called BBU/REC/RCC/C-RAN/V-RAN, O-RAN, or part thereof. A Distributed Unit (DU) may also be called RRH/RRU/RE/RU, or part thereof. Hereinafter, in various example embodiments of the present disclosure, the CU-CP (or more generically, the CU) may also be referred to as a (first) network node that supports at least one of central unit control plane functionality or a layer 3 protocol of a radio access network; and similarly, the DU may be referred to as a (second) network node that supports at least one of distributed unit functionality or the layer 2 protocol of the radio access network. A gNB-DU supports one or multiple cells, and could thus serve as e.g., a serving cell for a user equipment (UE). A user equipment (UE) may include a wireless or mobile device, an apparatus with a radio interface to interact with a RAN (Radio Access Network), a smartphone, an in- vehicle apparatus, an IoT device, a M2M device, or else. Such UE or apparatus may comprise: at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform certain operations, like e.g. RRC connection to the RAN. A UE is e.g., configured to generate a message (e.g., including a cell ID) to be transmitted via radio towards a RAN (e.g., to reach and communicate with a serving cell). A UE may generate and transmit and receive RRC messages containing one or more RRC PDUs (Packet Data Units). The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0 (2021-06) sections 42.1 and 4.4, incorporated by reference). A UE is e.g., either in RRC_CONNECTED state or in RRC_INACTIVE state when an RRC connection has been established. In RRC_CONNECTED state a UE may: store the AS context; transfer unicast data to/from the UE; monitor control channels associated with the shared data channel to determine if data is scheduled for the data channel; provide channel quality and feedback information; perform neighboring cell measurements and measurement reporting. The RRC protocol includes e.g. the following main functions: RRC connection control; measurement configuration and reporting; establishment/modification/release of measurement configuration (e.g. intra-frequency, inter-frequency and inter-RAT measurements); setup and release of measurement gaps; measurement reporting. A person of skill in the art would readily recognize that steps of various above- described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine- executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods. The tern non-transitory as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. RAM vs ROM). As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device. Although example embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. Features described in the preceding description may be used in combinations other than the combinations explicitly described. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

WE CLAIM: 1. A user equipment for connecting towards a Radio Access Network, comprising: at least one processor; and at least one memory storing instruction which, when executed by the at least one processor, cause the user equipment at least to: establish a connection with a first network node that supports at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell supported by the first network node; receive, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; perform the configured Layer 1 measurements and evaluate for which candidate target cell a respective Layer 1 measurement is to be included in a respective Layer 1 measurement report based on a respective measurement for the at least one specific candidate target cell achieving the first signal threshold level criterion, and generate and transmit the respective Layer 1 measurement report towards the first network node.

2. The user equipment of claim 1, wherein the configuration message further includes: an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements; and/or an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements for a first group of cells, and at least one different evaluating and/or reporting criterion for the performed measurements for a second group of cells; and/or an indication to enable identification of the at least one specific candidate target cell of a second group of specific candidate target cells achieving a second signal threshold level for which a Layer 1 measurement shall be performed and an associated second signal threshold level.

3. The user equipment of claim 2, wherein the indication identifies an offset between the first signal threshold level and the second signal threshold level

4. The user equipment of claim 2 or 3, wherein the first signal threshold level is equal to or lower than the second signal threshold level.

5. The user equipment of any preceding claim, wherein the configuration message includes an indication to enable identification of evaluating criteria for the Layer 1 measurement to be included in a respective Layer 1 measurement report.

6. The user equipment of any preceding claim, wherein the configuration message includes an indication specifying a number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports.

7. The user equipment of any one of claims 2 to 6, wherein the configuration message includes an indication specifying a number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports.

8. The user equipment of any preceding claim, wherein the Layer 1 measurements reports carry N measurement values and the configuration message includes an indication specifying measurement values to be included when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level is less than N.

9. The user equipment of any one of claims 2 to 8, wherein the Layer 1 measurements reports carry N measurement values and the configuration message includes an indication specifying measurement values to be included when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level is less than N.

10. The user equipment of any one of claims 2 to 9, wherein the indication specifying measurement values to be included specifies that measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports.

11. The user equipment of any one of claims 2 to 10, wherein the indication specifying measurement values to be included specifies that strongest measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports.

12. The user equipment of any preceding claim, wherein the configuration message includes an indication specifying a maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports.

13. The user equipment of claim 12, wherein, when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level exceeds the maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level, the instruction, when executed by the at least one processor, cause the user equipment at least to: generate and transmit the respective Layer 1 measurement report towards the first network node with strongest measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the first group.

14. The user equipment of any one of claims 2 to 13, wherein the configuration message includes an indication specifying a maximum number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports.

15. The user equipment claim 14, wherein, when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level exceeds the maximum number measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level, the instruction, when executed by the at least one processor, cause the user equipment at least to: generate and transmit the respective Layer 1 measurement report towards the first network node with strongest measurement values of beams of the second group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the second group.

16. The user equipment of claim 14, wherein the maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group is set to equal N.

17. The user equipment of claim 14, wherein the maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group is set to exceed N.

18. The user equipment of claim 17, wherein when the maximum number measurement values of beams of the first group added to the maximum number measurement values of beams of the second group is set to exceed N, the configuration message includes an indication specifying which measurement values to prioritise including when the number of measurement values of beams of the first group fails to exceed the maximum number measurement values of beams of the first group and/or when the number of measurement values of beams of the second group fails to exceed the maximum number measurement values of beams of the second group but the summed number of measurement values exceed N.

19. The user equipment of any one of claims 2 to 18, wherein the configuration message includes: an indication specifying prioritising measurement values of beams of the first group over measurement values of beams of the second group; and/or an indication specifying prioritising strongest measurement values of beams of the first group over measurement values of beams of the second group.

20. The user equipment of any one of claims 2 to 19, wherein the first group of cells includes at least one candidate target cell for which Timing Advance information at the user equipment is available and the second group of cells includes at least one candidate target cell for which Timing Advance information at the UE is not available.

21. The user equipment of any preceding claim, wherein the measurement values comprise beam Reference Signal Received Power values and strongest measurement values comprise those highest measured beam Reference Signal Received Power values.

22. The user equipment of any preceding claim, wherein the configuration message includes at least one evaluation criteria to select, as the at least one indicated specific candidate cell, a candidate target cell for which a Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available.

23. The user equipment of any preceding claim, wherein the instructions, when executed by the at least one processor, cause the user equipment at least to: receive, from the Radio Access Network, a message to trigger an acquisition of a Timing Advance information for at least one candidate target cell with which the user equipment may connect.

24. The user equipment of any preceding claim, wherein the instructions, when executed by the at least one processor, cause the user equipment at least to: determine, for at least one of the candidate target cells, whether Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available.

25. The user equipment claim 23 or 24, wherein the Timing Advance information is based on information received from the first network node and/or from a target network node in response to the triggered Timing Advance acquisition.

26. The user equipment of any one of claims 22 to 25, wherein the instructions, when executed by the at least one processor, cause the user equipment at least to: classify a candidate targets cell for which Timing Advance information is available as a synchronised cell in the first group and a candidate targets cell for which Timing Advance information is not available as a non-synchronised cell in the second group.

27. The user equipment of any preceding claim, wherein the network node comprises at least one of or supports functionality of at least one of: a base station, a 5G gNB, a Centralised Unit, a Distributed Unit, a secondary node, a source node or a source secondary node.

28. The user equipment of any preceding claim, wherein the configuration message comprises a Radio Resource Configuration message.

29. A method for connecting towards a Radio Access Network, comprising: establishing a connection with a first network node that supports at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell supported by the first network node; receiving, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; performing the configured Layer 1 measurements and evaluating for which candidate target cell a respective Layer 1 measurement is to be included in a respective Layer 1 measurement report based on a respective measurement for the at least one specific candidate target cell achieving the first signal threshold level criterion, and generating and transmitting the respective Layer 1 measurement report towards the first network node.

30. A network node of a Radio Access Network, comprising: at least one processor; and at least one memory storing instruction which, when executed by the at least one processor, cause the network node at least to: support at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell to establish a connection with a user equipment; transmit, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; and receive the respective Layer 1 measurement report from the user equipment.

31. The network node of claim 30, wherein the configuration message further includes: an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements; and/or an indication to enable identification of at least one evaluating and/or reporting criterion for the performed measurements for a first group of cells, and at least one different evaluating and/or reporting criterion for the performed measurements for a second group of cells; and/or an indication to enable identification of the at least one specific candidate target cell of a second group of specific candidate target cells achieving a second signal threshold level for which a Layer 1 measurement shall be performed and an associated second signal threshold level.

32. The network node of claim 31, wherein the indication identifies an offset between the first signal threshold level and the second signal threshold level

33. The network node of claim 31 or 32, wherein the first signal threshold level is equal to or lower than the second signal threshold level.

34. The network node of any one of claims 30 to 33, wherein the configuration message includes an indication to enable identification of evaluating criteria for the Layer 1 measurement to be included in a respective Layer 1 measurement report.

35. The network node of any one of claims 30 to 34, wherein the configuration message includes an indication specifying a number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports.

36. The network node of any one of claims 31 to 35, wherein the configuration message includes an indication specifying a number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports.

37. The network node of any one of claims 30 to 36, wherein the Layer 1 measurements reports carry N measurement values and the configuration message includes an indication specifying measurement values to be included when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level is less than N.

38. The network node of any one of claims 31 to 37, wherein the Layer 1 measurements reports carry N measurement values and the configuration message includes an indication specifying measurement values to be included when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level is less than N.

39. The network node of any one of claims 31 to 38, wherein the indication specifying measurement values to be included specifies that measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports.

40. The network node of any one of claims 31 to 39, wherein the indication specifying measurement values to be included specifies that strongest measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level shall be included in at least one of the associated Layer 1 measurements reports.

41. The network node of any one of claims 30 to 40, wherein the configuration message includes an indication specifying a maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports.

42. The network node of claim 41, wherein the configuration message includes an indication specifying, when the number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level exceeds the maximum number of measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level, the respective Layer 1 measurement report shall include the strongest measurement values of beams of the first group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the first group.

43. The network node of any one of claims 31 to 42, wherein the configuration message includes an indication specifying a maximum number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level for which a Layer 1 measurement shall be included in at least one of the associated Layer 1 measurements reports.

44. The network node of claim 43, wherein the configuration message includes an indication specifying, when the number of measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level exceeds the maximum number measurement values of beams of the second group of specific candidate target cells achieving the second signal threshold level, the respective Layer 1 measurement report shall include the strongest measurement values of beams of the second group of specific candidate target cells achieving the first signal threshold level up to the maximum number of measurement values of the second group.

45. The network node of any one of claims 41 to 44, wherein the maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group is set to equal N.

46. The network node of any one of claims 41 to 44, wherein the maximum number measurement values of beams of the first group added to the maximum number measurement values of the second group is set to exceed N.

47. The network node of claim 46, wherein when the maximum number measurement values of beams of the first group added to the maximum number measurement values of beams of the second group is set to exceed N, the configuration message includes an indication specifying which measurement values to prioritise including when the number of measurement values of beams of the first group fails to exceed the maximum number measurement values of beams of the first group and/or when the number of measurement values of beams of the second group fails to exceed the maximum number measurement values of beams of the second group but the summed number of measurement values exceed N.

48. The network node of any one of claims 31 to 47, wherein the configuration message includes: an indication specifying prioritising measurement values of beams of the first group over measurement values of beams of the second group; and/or an indication specifying prioritising strongest measurement values of beams of the first group over measurement values of beams of the second group.

49. The network node of any one of claims 31 to 48, wherein the first group of cells includes at least one candidate target cell for which Timing Advance information at the user equipment is available and the second group of cells includes at least one candidate target cell for which Timing Advance information at the UE is not available.

50. The network node of any one of claims 30 to 49, wherein the measurement values comprise beam Reference Signal Received Power values and strongest measurement values comprise those highest measured beam Reference Signal Received Power values.

51. The network node of any one of claims 30 to 50, wherein the configuration message includes at least one evaluation criteria to select, as the at least one indicated specific candidate cell, a candidate target cell for which a Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available.

52. The network node of any one of claims 30 to 51, wherein the instructions, when executed by the at least one processor, cause the network node at least to: send, from the Radio Access Network, a message to trigger an acquisition of a Timing Advance information for at least one candidate target cell with which the user equipment may connect.

53. The network node of any one of claims 30 to 52, wherein the instructions, when executed by the at least one processor, cause the network node at least to: determine, for at least one of the candidate target cells, whether Timing Advance information for a potential connection between the user equipment and the determined candidate target cell is available.

54. The network node of any one of claims 51 to 53, wherein the instructions, when executed by the at least one processor, cause the network node at least to: send information relating to the Timing Advance the first network node and/or from a target network node in response to the triggered Timing Advance acquisition.

55. The network node of any one of claims 30 to 54, wherein the instructions, when executed by the at least one processor, cause the network node at least to: classify a candidate targets cell for which Timing Advance information is available as a synchronised cell in the first group and a candidate targets cell for which Timing Advance information is not available as a non-synchronised cell in the second group.

56. The network node of any one of claims 30 to 55, wherein the network node comprises at least one of or supports functionality of at least one of: a base station, a 5G gNB, a Centralised Unit, a Distributed Unit, a secondary node, a source node or a source secondary node.

57. The network node of any one of claims 30 to 56, wherein the configuration message comprises a Radio Resource Configuration message.

58. A method for connecting towards a Radio Access Network, comprising: supporting at least one of the distributed unit functionality or a Layer 2 protocol of the Radio Access Network via a first cell to establish a connection with a user equipment; transmitting, from the Radio Access Network, a configuration message to perform Layer 1 measurements for at least one candidate target cell with which the user equipment may connect, and an indication to enable identification of at least one specific candidate target cell of a first group of specific candidate target cells for which a Layer 1 measurement shall be performed and an associated first signal threshold level criterion; and receiving the respective Layer 1 measurement report from the user equipment.