User equipment for communication over cellular network, and method for operating user equipment for communication over cellular network

Abstract

To improve robustness of the MRDC function and provide seamless experience in the MRDC mode.SOLUTION: User equipment for communication over a cellular network is configured for simultaneously communicating with one or more cells of a first node of the cellular network and with one or more cells of a second node of the cellular network, and such user equipment is operated for communication over the cellular network. User equipment is configured for communicating with one of base stations of the cellular network which is used as a serving base station, or for communicating simultaneously with more of the base stations of the cellular network which respectively are used as serving base stations, and such user equipment is operated for communication over the cellular network.SELECTED DRAWING: Figure 18(1)

Description

Technical Field

[0001] The present disclosure relates to a user equipment for communication via a cellular network and a method for operating a user equipment for communication via a cellular network.

Summary of the Invention

Problems to be Solved by the Invention

[0002]

Means for Solving the Problems

[0003] In one aspect, the present disclosure is a user equipment for communication via a cellular network, the user equipment is configured to communicate simultaneously with one or more cells of a first node of the cellular network and one or more cells of a second node of the cellular network, the user equipment includes a monitoring unit for monitoring the quality of a first communication link between the user equipment and a first cell among the cells of the first node and / or for monitoring the quality of a second communication link between the user equipment and a first cell among the cells of the second node, the user equipment, when the monitoring unit detects a first change condition of the first communication link, a first replacement request for replacing the first cell of the first node with a first replacement cell that is a second cell of the first node or a cell of a third node, and / or when the monitoring unit detects a second change condition of the second communication link, a second replacement request for replacing the first cell of the second node with a second replacement cell that is a second cell of the second node or a cell of a fourth node is configured to transmit, relating to the user equipment.

[0004] In a further aspect, the present disclosure is a method for operating a user equipment for communication via a cellular network, the method comprising Using a user equipment for communicating with one or more cells of a first node of a cellular network and one or more cells of a second node of the cellular network simultaneously, Using a monitoring unit of the user equipment for monitoring the quality of a first communication link between the user equipment and a first cell among the cells of the first node and / or for monitoring the quality of a second communication link between the user equipment and a first cell among the cells of the second node, When the monitoring unit detects a first change condition of the first communication link, a first replacement request for replacing the first cell of the first node with a first replacement cell which is a second cell of the first node or a cell of a third node, and / or When the monitoring unit detects a second change condition of the second communication link, a second replacement request for replacing the first cell of the second node with a second replacement cell which is a second cell of the second node or a cell of a fourth node Using the user equipment for transmitting relating to a method comprising

[0005] In a further aspect, the present disclosure relates to a user equipment for communication via a cellular network, The user equipment is configured to communicate with one or more cells of a first node of the cellular network and one or more cells of a second node of the cellular network simultaneously, The user equipment is configured to receive a first reconfiguration request including an indication that a first cell of the first node communicating with the user equipment has to be replaced by a first replacement cell of the cellular network, the first reconfiguration request including a first change condition under which the first reconfiguration request has to be executed, and / or is configured to receive a second reconfiguration request including an indication that a first cell of the second node communicating with the user equipment has to be replaced by a second replacement cell of the cellular network, the second reconfiguration request including a second change condition under which the second reconfiguration request has to be executed, The user equipment comprises a monitoring unit for monitoring a first change condition and / or a second change condition. The user equipment is configured to replace the first cell of the first node with a first replacement cell when the monitoring unit detects that the first change condition is satisfied, and / or to replace the first cell of the second node with a second replacement cell when the monitoring unit detects that the second change condition is satisfied.

[0006] In a further aspect, the present disclosure is a method of operating a user equipment for communication via a cellular network, the method comprising: using the user equipment to communicate simultaneously with one or more cells of a first node of the cellular network and one or more cells of a second node of the cellular network; using the user equipment to receive a first reconfiguration request including an indication that the first cell of the first node communicating with the user equipment has to be replaced by a first replacement cell of the cellular network, the first reconfiguration request including a first change condition under which the first reconfiguration request has to be executed, and / or using the user equipment to receive a second reconfiguration request including an indication that the first cell of the second node communicating with the user equipment has to be replaced by a second replacement cell of the cellular network, the second reconfiguration request including a second change condition under which the second reconfiguration request has to be executed; using a monitoring unit of the user equipment to monitor the first change condition and / or the second change condition; using the user equipment to replace the first cell of the first node with the first replacement cell when the monitoring unit detects that the first change condition is satisfied, and / or to replace the first cell of the second node with the second replacement cell when the monitoring unit detects that the second change condition is satisfied. Including, regarding the method.

[0007] In a further aspect, the present disclosure is a user equipment for communication via a cellular network, the cellular network comprising a plurality of base stations connected to the core network of the cellular network via the xhaul network of the cellular network, the user equipment being configured to communicate with one of the base stations of the cellular network used as a serving base station or to communicate simultaneously with more of the base stations of the cellular network each used as a serving base station, the user equipment being configured to transmit a list of candidate base stations eligible to replace at least one of the serving base stations to one of the serving base stations, the user equipment being configured to receive quality information regarding the quality of a communication link between one of the candidate base stations and the core network for the plurality of candidate base stations from at least one of the serving base stations, relating to the user equipment, the user equipment being configured to select, based on the quality information, one or more of the candidate base stations for replacing one or more of the base stations currently used as serving base stations.

[0008] In a further aspect, the present disclosure is a method of operating a user equipment for communication via a cellular network, the cellular network comprising a plurality of base stations connected to the core network of the cellular network via the xhaul network of the cellular network, the method comprising: using the user equipment to communicate with one of the base stations of the cellular network used as a serving base station or to communicate simultaneously with more of the base stations of the cellular network each used as a serving base station; and using the user equipment to transmit a list of candidate base stations eligible to replace at least one of the serving base stations to one of the other more base stations of the cellular network to become a new serving base station. Using a user equipment to receive quality information regarding the quality of a communication link between one of a plurality of candidate base stations and a core network for the plurality of candidate base stations from at least one of serving base stations; Using a user equipment to select one or more of the candidate base stations for replacing one or more of the base stations currently used as serving base stations based on the quality information; relates to a method comprising the above. Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Elements that are equal or equivalent or elements having equal or equivalent functions are denoted by equal or equivalent reference numerals in the following description. Note that any information given in the context of one embodiment of the figures is also valid in the context of the embodiments of other figures. This is particularly valid for the definitions and features included in the following description.

[0011] In the following description, a plurality of details are shown to provide a more complete description of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other instances, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments of the present invention. Also, the features of the different embodiments described below can be combined with each other unless otherwise specified.

[0012] FIGS. 1 to 3 schematically show the implementation forms of the present disclosure. In contrast, FIGS. 4 to 27 show the implementation forms of the present disclosure in 5G multi-radio dual connectivity. However, those skilled in the art will understand that the present disclosure is not limited to the latter. Furthermore, those skilled in the art will understand that the features described in the context of 5G are also possible in other cellular networks. FIG. 1 schematically shows an embodiment of the interaction between the user equipment 1 and the cellular network CN according to the present disclosure.

[0013] According to some embodiments, the user equipment 1 for communication via the cellular network CN is configured to communicate simultaneously with one or more cells CE of a first node NO1 of the cellular network and one or more cells CE of a second node NO2 of the cellular network CN. The user equipment 1 includes a monitoring unit 2 for monitoring the quality of a first communication link CL1 between the user equipment 1 and a first cell CE among the cells CE of the first node NO1, and / or for monitoring the quality of a second communication link CL2 between the user equipment 1 and a first cell CE among the cells CE of the second node NO2. The user equipment 1 When the monitoring unit 2 detects a first change condition of the first communication link CL1, a first replacement request REP1 for replacing the first cell CE of the first node NO1 with a first replacement cell RCE1 which is a second cell CE of the first node NO1 or a cell CE of a third node NO3, and / or When the monitoring unit 2 detects a second change condition of the second communication link CL2, a second replacement request REP2 for replacing the first cell CE of the second node NO2 with a second replacement cell RCE2 which is a second cell CE of the second node NO2 or a cell of a fourth node NO4 is configured to be transmitted.

[0014] User equipment 1 may comprise one or more of a mobile terminal, or a fixed terminal, or a cellular IoT user equipment, or a vehicle user equipment, or a vehicle group leader (GL) user equipment, or an IoT or narrowband IoT, NB-IoT, device, or a ground-based vehicle, or an aircraft, or a drone, or a mobile base station, or a roadside unit (RSU), or a building, or a wireless communication network, for example, any other item or device with network connectivity enabling an item / device to communicate using a sensor or an actuator, or a sidelink wireless communication network, for example, any other item or device with network connectivity enabling an item / device to communicate using a sensor or an actuator, or any sidelink-capable network entity. The user equipment may also be part of an integrated access and backhaul (IAB) node, for example, the mobile terminal (MT) part of an IAB node.

[0015] User equipment 1 may be configured for downlink / uplink / sidelink communication, for example, using resources from a set of downlink / uplink / sidelink resources of a cellular network.

[0016] The cellular network may comprise a plurality of base stations, which may operate as macrocell base stations, or small cell base stations, or central units of the base stations, or base stations operating as cloud RAN (CRAN), or distributed units of the base stations, or roadside units (RSUs), or cells, or nodes, or specific cells (SpCells), further user equipment, or group leader (GL) user equipment, or relays, or remote radio heads, or access and mobility management functions (AMF), or session management functions (SMF), or core network entities, or mobile edge computing (MEC) entities, or network slices such as in an NR or 5G core context, or any transmission and reception point (TRP) that enables an item or device to communicate using a wireless communication network, and may comprise one or more of any of the transmission and reception points that have network connectivity for the item or device to communicate using the wireless communication network.

[0017] A cell CE is a device that uses a set of time / frequency / code (e.g., like CDM) / space (e.g., sector) / space coding (beam and / or precoding) resources.

[0018] In some embodiments, the user equipment 1 is configured to communicate simultaneously with one or more cell CEs of a plurality of first nodes NO1 and one or more cell CEs of a plurality of second nodes NO2.

[0019] The term "first cell CE" refers to a specific cell CE within a cell to distinguish it from other cell CEs of each node NO. In other words, this term does not refer to the order of the cell CEs. The monitoring unit 2 may comprise a software module configured to operate on the processor of the user equipment 1.

[0020] According to some embodiments, the user equipment 1 is configured to communicate via a cellular network CN using dual connectivity or multi-connectivity. Dual connectivity means simultaneous communication with two base stations, and multi-connectivity means simultaneous communication with three or more base stations, for example three or more base stations.

[0021] According to some embodiments, the first node NO1 is a base station and a master node for dual connectivity or multi-connectivity, and the second node NO2 is a base station and a secondary node for dual connectivity or multi-connectivity.

[0022] According to some embodiments, the first cell CE of the first node NO1 is a specific cell or a secondary cell of a master cell group for dual connectivity or multi-connectivity, and / or the first cell CE of the second node NO2 is a specific cell or a secondary cell of a secondary cell group for dual connectivity or multi-connectivity.

[0023] According to some embodiments, the first change condition and / or the second change condition are a specified number of instances where the timer of the radio link failure timer has been started but has not expired within a specified period, and a specified number of HARQ retransmissions from the PHY layer, and a specified number of retransmissions from the RLC layer that is less than the maximum number at which the user equipment 1 detects a radio link failure, and a weighted average or a moving average or any other specified statistical method using an adopted metric indicating degradation of signal quality, and an encoded or non-encoded bit error rate, and a packet loss rate or a packet error rate, and a data rate requirement, and a supported bandwidth, and One of the metrics employed for each of the replacement cells RCE1, RCE2 is a multi-cell event that becomes good during at least one specified period compared to the corresponding metric employed for each of the first cells CE, one of the metrics employed for each of the replacement cells RCE1, RCE2 is a multi-cell event that becomes good during at least one specified period compared to a threshold, or one of the metrics employed for each of the first cells CE becomes bad during at least one specified period compared to a first threshold, and the corresponding metrics employed for each of the replacement cells RCE1, RCE2 become good during at least one specified period compared to a second threshold, such as a multi-cell event, and the multi-cell event is triggered by one of the user equipment 1, nodes NO1, NO2, or another device of the cellular network CN. Any one or a combination thereof.

[0024] The term "employed metric" can refer to a channel quality indicator (CQI), reference signal received power (RSRP), received signal strength indicator (RSSI), signal reference signal received quality (RSRQ), signal-to-noise and interference ratio (SINR), any metric for evaluating the quality of channel state information (CSI), or any other suitable metric.

[0025] The first change condition and / or the second change condition can include one or more of the following conditions: - Encoded / uncoded BER measurement, - Packet loss, packet error rate (PER), - Data rate requirement, - Supported bandwidth (e.g., the UE may desire to use less bandwidth to reduce power consumption, or may have a higher bandwidth for faster data transfer and then desire to enter a power-saving mode), - Events, e.g., multi-cell events, triggers from the base station or network, or triggers configured within the UE (refer to TS36.331 and TS38.331), e.g., · Event A3 (neighbor is offset better than the SpCell), · Event A4 (neighbor is better than the threshold), · Event A5 (SpCell becomes worse than threshold 1 and neighbor becomes better than threshold 2).

[0026] According to some embodiments, the user equipment 1 is configured to transmit a first replacement request REP1 to a first node NO1 or a second node NO2. According to some embodiments, the user equipment 1 is configured to transmit a second replacement request REP2 to a first node NO1 or a second node NO2.

[0027] According to some embodiments, the user equipment 1 is configured to identify a candidate cell CE of a first replacement cell RCE1 or a second replacement cell RCE2 by measuring signals of possible candidate cells.

[0028] According to some embodiments, the user equipment 1 is configured to receive a first list LI1 of candidate cells CE of a first replacement cell RCE1 from a first node NO1 or a second node NO2.

[0029] According to some embodiments, the user equipment 1 is configured to receive a second list LI2 of candidate cells CE of a second replacement cell RCE2 from a first node NO1 or a second node NO2.

[0030] According to some embodiments, the user equipment 1 is configured to receive a first reconfiguration request REC1 including an indication of which of the cells CE of the cellular network CN is the first replacement cell RCE1 and an indication that the first reconfiguration request REC1 is a response to the first replacement request REP1. According to some embodiments, the user equipment 1 is configured to receive a first reconfiguration request REC1 from the first node NO1 or the second node NO2.

[0031] According to some embodiments, the user equipment is configured to communicate with a first replacement cell RC1 after the first reconfiguration request REC1 is received by the user equipment 1.

[0032] According to some embodiments, the user equipment 1 is configured to send a first message ME1 to the first node NO1 or the second node NO2, and after the first reconfiguration request REC1 is received by the user equipment 1, the first message ME1 indicates that the first cell CE of the first node NO1 has been released.

[0033] According to some embodiments, the user equipment 1 is configured to indicate in the first replacement request REC1 whether the first replacement cell RCE1 belongs to the first node NO1 or the third node NO3.

[0034] According to some embodiments, the user equipment 1 is configured to receive a second reconfiguration request REC2 including an indication of which of the cells CE of the cellular network CN is the second replacement cell RCE2 and an indication that the second reconfiguration request REC2 is a response to the second replacement request REP2. According to some embodiments, the user equipment 1 is configured to receive a second reconfiguration request REC2 from the first node NO1 or the second node NO2.

[0035] According to some embodiments, the user equipment 1 is configured to communicate with a second replacement cell RCE2 after the second reconfiguration request REC2 is received by the user equipment 1.

[0036] According to some embodiments, the user equipment 1 is configured to transmit a second message ME2 to the first node NO1 or the second node NO2, and after a second reconfiguration request REC is received by the user equipment 1, the second message ME2 indicates that the first cell CE of the second node NO2 has been released.

[0037] According to some embodiments, the user equipment 1 is configured to indicate, within a second replacement request REC2, whether the second replacement cell RCE2 belongs to the second node NO2 or the fourth node NO4. A further disclosure is an embodiment of a method of operating a user equipment 1 for communication via a cellular network CN, the method comprising: using the user equipment 1 to communicate simultaneously with one or more cells CE of a first node NO1 of the cellular network CN and one or more cells CE of a second node NO2 of the cellular network CN; using a monitoring unit 2 of the user equipment 1 to monitor the quality of a first communication link CL1 between the user equipment 1 and a first cell CE among the cells CE of the first node NO1, and / or to monitor the quality of a second communication link CL1 between the user equipment 1 and a first cell CE among the cells CE of the second node NO2; when the monitoring unit 2 detects a first change condition of the first communication link CL1, a first replacement request REP1 for replacing the first cell CE of the first node NO1 with a first replacement cell RCE1 which is a second cell CE of the first node NO1 or a cell CE of a third node NO3, and / or when the monitoring unit 2 detects a second change condition of the second communication link CL2, a second replacement request REP2 for replacing the first cell CE of the second node NO2 with a second replacement cell REC2 which is a second cell CE of the second node NO2 or a cell of a fourth node NO4 using the user equipment 1 to transmit; and includes.

[0038] A further disclosure is an embodiment of a computer program for performing the above-described method when executed on a processor. FIG. 2 schematically shows a further embodiment of the interaction of the user equipment 1' according to the present disclosure with the cellular network CN.

[0039] According to some embodiments, the user equipment 1' for communication via the cellular network CN is configured to communicate simultaneously with one or more cells CE of a first node NO1 of the cellular network CN and one or more cells CE of a second node NO2 of the cellular network CN. The user equipment 1' is configured to receive a first reconfiguration request REC1' including an indication that the first cell CE of the first node NO1 communicating with the user equipment 1' must be replaced by a first replacement cell RCE1 of the cellular network CN, the first reconfiguration request REC1' including a first change condition that the first reconfiguration request REC1' must be executed, and / or a second reconfiguration request REC2' including an indication that the first cell CE of the second node NO2 communicating with the user equipment 1' must be replaced by a second replacement cell RCE2' of the cellular network CN, the second reconfiguration request RCE2' including a second change condition that the second reconfiguration request RCE2' must be executed. The user equipment 1' comprises a monitoring unit 2' for monitoring the first change condition and / or the second change condition. The user equipment 1' is configured to replace the first cell CE of the first node NO1 with the first replacement cell RCE1 when the monitoring unit 2' detects that the first change condition is satisfied and / or to replace the first cell CE of the second node NO2 with the second replacement cell RCE2 when the monitoring unit 2' detects that the second change condition is satisfied.

[0040] According to some embodiments, the user equipment 1' is configured such that, before the user equipment 1' connects to the first replacement cell RCE1, the first cell CE of the first node NO1 is replaced by the first replacement cell RCE1 so that the first cell CE of the first node NO1 is released by the user equipment 1', and / or before the user equipment 1' connects to the second replacement cell RCE2, the first cell CE of the second node NO2 is replaced by the second replacement cell RCE2 so that the first cell CE of the second node NO2 is released by the user equipment 1'.

[0041] According to some embodiments, the user equipment 1' is configured such that, before the first cell CE of the first node NO1 is released by the user equipment 1, the first cell CE of the first node NO1 is replaced by the first replacement cell RCE1 so that the user equipment 1 connects to the first replacement cell RCE1, and / or before the first cell CE of the second node NO2 is released by the user equipment 1', the first cell CE of the second node NO2 is replaced by the second replacement cell RCE2 so that the user equipment 1' connects to the second replacement cell RCE2.

[0042] According to some embodiments, the user equipment 1' is configured to communicate via the cellular network CN using dual connectivity or multi-connectivity.

[0043] According to some embodiments, the first node NO1 is a base station and a master node for dual connectivity or multi-connectivity, and the second node NO2 is a base station and a secondary node for dual connectivity or multi-connectivity.

[0044] According to some embodiments, the first cell CE of the first node NO1 is a specific cell or a secondary cell of a master cell group for dual connectivity or multi - connectivity, and / or the first cell CE of the second node NO2 is a specific cell or a secondary cell of a secondary cell group for dual connectivity or multi - connectivity.

[0045] According to some embodiments, the first change condition and / or the second change condition are a specified number of instances where the timer of the radio link failure timer has been started but has not expired within the specified period, and a specified number of HARQ re - transmissions from the PHY layer, and a specified number of re - transmissions from the RLC layer that is less than the maximum number of times the user equipment 1 detects a radio link failure, and a weighted average or a moving average or any other specified statistical method using an adopted metric indicating degradation of signal quality, and an encoded or non - encoded bit error rate, and a packet loss rate or a packet error rate, and a data rate requirement, and a supported bandwidth, and One of the metrics adopted by each of the replacement cells RCE1 and RCE2 is a multi-cell event that becomes better during at least one specified period than the corresponding adopted metric of each of the first cells CE, one of the metrics adopted by each of the replacement cells RCE1 and RCE2 is a multi-cell event that becomes better than a threshold during at least one specified period, or one of the metrics adopted by each of the first cells CE becomes worse during at least one specified period than a first threshold, and the corresponding adopted metrics of each of the replacement cells RCE1 and RCE2 are multi-cell events such as a multi-cell event that becomes better than a second threshold during at least one specified period, where the multi-cell event is triggered by one of the user equipment 1, nodes NO1, NO2 or another device of the cellular network CN, a multi-cell event is any one or a combination thereof.

[0046] According to some embodiments, the user equipment 1' is configured to receive a first reconfiguration request REC1' from the first node NO1 or the second node NO2.

[0047] According to some embodiments, the user equipment 1' is configured to receive a second reconfiguration request REC2' from the first node NO1 or the second node NO2. According to some embodiments, the user equipment 1' is configured to communicate with the first replacement cell RCE1 after the first change condition is satisfied.

[0048] According to some embodiments, the user equipment 1' is configured to execute a random access procedure towards the first replacement cell RCE1 after the first change condition is satisfied, and the user equipment 1' is configured to release the first cell CE of the first node NO1 after the random access procedure towards the first replacement cell RCE1 is successfully completed.

[0049] According to some embodiments, when the maximum number of attempts or the maximum delay of the random access procedure directed to the first replacement cell RCE1 is reached, the user equipment 1' is configured to stop the random access procedure directed to the first replacement cell RCE1 and maintain the connection with the first cell CE of the first node NO1. According to some embodiments, the user equipment 1' is configured to communicate with the second replacement cell RCE2 after the second change condition is satisfied.

[0050] According to some embodiments, the user equipment 1' is configured to execute a random access procedure directed to the second replacement cell RCE2 after the second change condition is satisfied, and the user equipment 1' is configured to release the first cell CE of the second node NO2 after the random access procedure directed to the second replacement cell RCE2 is successfully completed.

[0051] According to some embodiments, when the maximum number of attempts or the maximum delay of the random access procedure directed to the second replacement cell RCE2 is reached, the user equipment 1' is configured to stop the random access procedure directed to the second replacement cell RCE2 and maintain the connection with the second cell CE of the second node NO2.

[0052] According to some embodiments, the user equipment 1' is configured to transmit a first message ME1' to the first node NO1 or the second node NO2 after the first condition is satisfied, and the first message M1' indicates that the first cell CE of the first node NO1 has been released.

[0053] According to some embodiments, the user equipment 1' is configured to transmit a second message ME2' to the first node NO1 or the second node NO2 after the second condition is satisfied, and the second message ME2' indicates that the first cell CE of the second node NO2 has been released.

[0054] According to some embodiments, the user equipment 1’ is configured to derive from the first reconfiguration request REC1’ whether the first replacement cell RCE1 belongs to the first node NO1 of the cellular network CN or to the third node NO3 of the cellular network CN, and / or to derive from the second reconfiguration request REC2’ whether the second replacement cell RCE2’ belongs to the second node NO2 of the cellular network CN or to the fourth node NO4 of the cellular network CN.

[0055] A further disclosure is an embodiment of a method for operating a user equipment 1’ for communication via a cellular network CN, the method comprising: using the user equipment 1’ for simultaneously communicating with one or more cells CE of the first node NO1 of the cellular network CN and one or more cells CE of the second node NO2 of the cellular network CN; using the user equipment 1’ for receiving a first reconfiguration request REC1’ including an indication that the first cell CE of the first node NO1 communicating with the user equipment 1’ must be replaced by the first replacement cell RCE1 of the cellular network CN, the first reconfiguration request REC1’ including a first change condition that the first reconfiguration request REC1’ must be executed, and / or using the user equipment 1’ for receiving a second reconfiguration request REC2’ including an indication that the first cell CE of the second node NO2 communicating with the user equipment 1’ must be replaced by the second replacement cell RCE2’ of the cellular network CN, the second reconfiguration request REC2’ including a second change condition that the second reconfiguration request REC2’ must be executed; using a monitoring unit 2’ of the user equipment 1’ for monitoring the first change condition and / or the second change condition; When the monitoring unit 2’ detects that the first change condition is satisfied, replacing the first cell CE of the first node NO1 with the first replacement cell RCE1, and / or when the monitoring unit 2’ detects that the second change condition is satisfied, using the user equipment 1’ to replace the first cell CE of the second node NO2 with the second replacement cell RCE2 including.

[0056] A further disclosure is an embodiment of a computer program for executing the method according to the present disclosure when executed on a processor. FIG. 3 schematically shows a further embodiment of the interaction between the user equipment 1’’ and the cellular network CN according to the present disclosure.

[0057] According to some embodiments, the cellular network CN includes a plurality of base stations BS connected to the core network COR of the cellular network CN via the xhaul network XN of the cellular network, The user equipment 1’’ is configured to communicate with one of the base stations BS of the cellular network CN used as the serving base station SBS, or to communicate with more of the base stations BS of the cellular network CN used as the serving base station SBS simultaneously, The user equipment 1’’ is configured to transmit a list LI’ of candidate base stations CBS eligible to replace at least one of the serving base stations SBS to one of the serving base stations SBS, The user equipment 1’’ is configured to receive quality information QI regarding the quality of the communication link CL’ between one of the candidate base stations CBS and the core network COR for the plurality of candidate base stations CBS from at least one of the serving base stations SBS, The user equipment 1’’ is configured to select one or more of the candidate base stations CBS for replacing one or more of the base stations BS currently used as the serving base station SBS based on the quality information QI.

[0058] The xhaul network XN may be a fronthaul network or a backhaul network, and may be wireless or wired. It may also be a RAT technology different from access technologies such as Wi-Fi, LTE, LTE-Advanced, LTE-Advanced Pro, 5G, or direct D2D link. The xhaul network XN may also be an IAB network. Furthermore, the xhaul network may also include its own wired technology such as data transmitted via optical fiber using the common public radio interface CPRI.

[0059] According to some embodiments, the user equipment 1’’ is configured to transmit a quality information request QIR to at least one of the serving base stations SBS, and the quality information request QIR requests at least one of the serving base stations SBS to transmit quality information QI.

[0060] In other embodiments, one of the serving base stations SBS can provide the quality information QI to the user equipment 1 via direct signaling or via broadcast or multicast.

[0061] According to some embodiments, the user equipment 1’’ is configured to receive the quality information QI as an unsorted list including the quality indication values of a plurality of candidate base stations CBS, the user equipment 1’’ is configured to sort the unsorted list to create a sorted list, the user equipment 1’’ is configured to select one or more of the candidate base stations CBS for replacing one or more of the base stations BS currently used as the serving base station SBS based on the sorted list.

[0062] In some embodiments, the sorted list is a list with indices corresponding to, for example, an ordering by network entities, or the indices are a list with indices corresponding to quality indication values, or criteria depending on quality indication values.

[0063] According to some embodiments, user equipment 1’’ is configured to receive quality information QI as a sorted list for a plurality of candidate base stations CBS, or as a list with indices where the indices correspond to an ordering, or as a list with indices where the indices correspond to quality indication values. User equipment 1’’ is configured to select one or more of the candidate base stations CBS for replacing one or more of the base stations BS currently used as the serving base station SBS based on the sorted list. User equipment 1’’ is configured to select one or more of the candidate base stations CBS for replacing one or more of the base stations BS currently used as the serving base station SBS based on the sorted list.

[0064] In some embodiments, user equipment 1’’ is configured to select one or more candidate base stations CBS for replacing one or more of the base stations BS currently used as the serving base station SBS based on the ranking included in the sorted list or based on criteria, such as a cost function.

[0065] According to some embodiments, user equipment 1’’ is configured to transmit a signal SI indicating which one or more of the candidate base stations CBS have been selected to one of the base stations BS currently used as the serving base station SBS and / or to one of the selected candidate base stations CBS.

[0066] According to some embodiments, user equipment 1’’ is configured to communicate via a cellular network CN using dual or multi-connectivity. The user equipment 1’’ is configured to communicate with a master node which is one of the serving base stations SBS and a secondary node which is one of the serving base stations SBS simultaneously. The user equipment 1’’ can create a list LI’ of candidate base stations CBS such that the candidate base stations CBS in the list LI’ of candidate base stations CBS include a plurality of candidate base stations CBS that are eligible to replace the master node as one of the serving base stations SBS, and / or a plurality of candidate base stations CBS that are eligible to replace the secondary node as one of the serving base stations SBS.

[0067] According to some embodiments, the user equipment 1’’ is configured to receive quality information QI regarding the quality of a communication link CL’ between one of the candidate base stations CBS and a core network CN for a plurality of candidate base stations CBS that are eligible to replace the master node as one of the serving base stations SBS from at least one of the serving base stations SBS, and / or The user equipment 1’’ is configured to receive quality information regarding the quality of a communication link CL’ between one of the candidate base stations CBS and a core network CN for a plurality of candidate base stations CBS that are eligible to replace the secondary node as one of the serving base stations SBS from at least one of the serving base stations SBS.

[0068] According to some embodiments, the user equipment 1’’ is configured to select one or more of the candidate base stations CBS for replacing one of the master nodes currently used as one of the serving base stations CBS, and / or The user equipment 1’’ is configured to select one or more of the candidate base stations CBS for replacing one of the secondary nodes currently used as one of the serving base stations SBS.

[0069] A further disclosure is an embodiment of a method for operating a user equipment 1'' for communication via a cellular network CN, the cellular network CN comprising a plurality of base stations BS connected to a core network COR of the cellular network CN via an xhaul network XN of the cellular network CN, the method comprising: using the user equipment 1'' to communicate with one of the base stations BS of the cellular network CN used as a serving base station SBS or to communicate simultaneously with more of the base stations BS of the cellular network CN each used as a serving base station SBS; using the user equipment 1'' to send a list LI' of candidate base stations CBS eligible to replace at least one of the serving base stations SBS to one of the serving base stations SBS; using the user equipment 1'' to receive quality information QI regarding the quality of a communication link CL' between one of the candidate base stations CBS and the core network COR for the plurality of candidate base stations CBS from at least one of the serving base stations SBS; using the user equipment 1'' to select one or more of the candidate base stations CBS for replacing one or more of the base stations BS currently used as serving base stations SBS based on the quality information QI and including.

[0070] A further disclosure is an embodiment of a computer program for executing the method according to the present disclosure when executed on a processor.

[0071] The purpose of the following description is to present the ideas of the present disclosure related to multi-radio dual connectivity (MR-DC) in 5G. The proposed enhancements may, in some cases, also include aspects related to the (radio or wired) backhaul network, and currently feature nodes with integrated access and backhaul (IAB) functionality. The IAB nodes can use a special IAB routing protocol to communicate between different IAB nodes.

[0072] Figure 4 is a diagram showing a dual-connected user equipment 1. MR-DC is a function that enables a multi-Rx / Tx capable UE to utilize resources provided by two different nodes connected via a non-ideal backhaul, one providing NR access and the other providing either E-UTRA or NR access. One node functions as the MN and the other as the SN. The MN and the SN are connected via a network interface, and at least the MN is connected to the core network (TS37.340).

[0073] As part of the MR-DC configuration, each user equipment (UE) consists of two separate scheduled cell groups, namely, > a master cell group (MCG) > a secondary cell group (SCG).

[0074] The master cell group (MCG) belongs to the master node (MN), and the secondary cell group (MSG) belongs to the secondary node (SN). Based on the MR-DC architecture, the MCG and SCG can be either LTE cells or NR cells, or cells using any other RAT, such as WiFi or future cellular standards technologies beyond 5G (B5G). The network configures the UE using the MCG and 0 or 1 SCG.

[0075] When the UE is dual-connected to the MN and the SN, there are two important cells. One is the PCell (Primary Cell), and the other is the PSCell (Primary Secondary Cell). The PCell is the SpCell (Specific Cell) of the MCG, and the PSCell is the SpCell for the SCG. The SpCell is the primary cell of the master or secondary cell group. The other cells within the MCG or SCG are the secondary cells (SCells).

[0076] The SCell is applicable for each MCG or SCG and is in a carrier aggregation (CA) configuration with the PCell, i.e., the PSCell.

[0077] The following are some of the applicable terms used in this document as defined in the relevant specifications. LTE specification (TS36.331-f60): Primary Cell (PCell): A cell that operates on the primary frequency and is the cell on which the UE performs the initial connection establishment procedure, or starts the connection re-establishment procedure, or is indicated as the primary cell in a handover procedure.

[0078] Primary Secondary Cell (PSCell): The SCG cell on which the UE is instructed to perform a random access or an initial PUSCH transmission when the random access procedure is skipped when performing an SCG change procedure.

[0079] Secondary Cell (SCell): A cell that operates on a secondary frequency and is configured when the RRC connection is established and can be used to provide additional radio resources. Except for the case of (NG)EN-DC, the PSCell is considered to be an SCell. NR specification (TS38.331-f60): Primary Cell: A cell that operates on the primary frequency and is the MCG cell on which the UE performs the initial connection establishment procedure, or starts the connection re-establishment procedure.

[0080] Primary SCG Cell: The SCG cell that performs random access when the UE executes reconfiguration using the Sync procedure for dual connectivity operation. Secondary Cell: For a UE configured with CA, the cell that provides additional radio resources on top of a specific cell (SC).

[0081] Specific Cell (SC): In the case of dual connectivity (DC) operation, the term specific cell refers to the PCell of the MCG or the PSCell of the SCG; otherwise, the term specific cell refers to the PCell. Combination of LTE and NR, and corresponding abbreviations (TS37.340): · En-gNB: The node that provides NR user plane and control plane protocol termination to the UE and operates as a secondary node in EN-DC. · ng-eNB: An eNodeB that can be connected to the 5G core. MR-DC with LTE core: · E-UTRA-NR Dual Connectivity (EN-DC).

[0082] E-UTRA-NR Dual Connectivity (EN-DC) is with the LTE core. The UE is connected to one eNB operating as the MN and one en-gNB operating as the SN. The eNB is connected to the EPC via the S1 interface and to the en-gNB via the X2 interface. The en-gNB may also be connected to the EPC via the S1-U interface and to other en-gNBs via the X2-U interface.

[0083] MR-DC with 5G core: · E-UTRA-NR Dual Connectivity (NGEN-DC) 5G Core - associated NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC): The UE is connected to one ng-eNB functioning as the MN and one gNB functioning as the SN. The ng-eNB is connected to the 5GC, and the gNB is connected to the ng-eNB via the Xn interface.

[0084] ·NR-E-UTRA Dual Connectivity (NE-DC) The NG-RAN supports NR-E-UTRA Dual Connectivity (NE-DC), and the UE is connected to one gNB functioning as the MN and one ng-eNB functioning as the SN. The gNB is connected to the 5GC, and the ng-eNB is connected to the gNB via the Xn interface.

[0085] ·NR-NR Dual Connectivity (NR-DC) The NG-RAN supports NR-NR Dual Connectivity (NR-DC), and the UE is connected to one gNB functioning as the MN and another gNB functioning as the SN. The master gNB is connected to the 5GC via the NG interface and to the secondary gNB via the Xn interface. The secondary gNB may also be connected to the 5GC via the NG-U interface. Furthermore, NR-DC can also be used when the UE is connected to two gNB-DUs, where one serves the MCG and the other serves the SCG, and both are connected to the same gNB-CU and function as both the MN and the SN.

[0086] In EN-DC, the MCG is configured as defined in TS36.331. The network provides the cell group configuration parameters in the CellGroupConfig IE (TS38.331-f60), Sec. 5.3.5.5 (see 0 of this document).

[0087] Figure 5 shows the control plane architecture of EN-DC (left) and MR-DC with 5GC (TS37.340) (right). In MR-DC, the UE has a single RRC state based on a single C-plane connection to the MN RRC and the core network. Each radio node has its own RRC entity that can generate RRC PDUs to be sent to the UE. The RRC PDUs generated by the SN can be transmitted to the UE via the MN. The MN always sends the initial SN RRC configuration via the MCG signaling radio bearer 1 (SRB1), but subsequent reconfigurations may be transmitted via the MN or the SN. When transmitting RRC PDUs from the SN, the MN does not change the UE configuration provided by the SN (TS37.340).

[0088] Therefore, the control plane is processed using SRBs. SRBs are used for the transmission of RRC messages and non-access stratum (NAS) messages. More specifically, the following SRBs are defined: - SRB0 is for RRC messages using the CCCH logical channel SRB1 is for RRC messages (which may include piggybacked NAS messages) and for NAS messages before the establishment of SRB2, and uses all DCCH logical channels SRB2 is for NAS messages and uses all DCCH logical channels. SRB2 has a lower priority than SRB1 and can be configured by the network after AS security activation. SRB3 is for specific RRC messages when the UE is in (NG) EN-DC or NR-DC and uses all DCCH logical channels.

[0089] In the downlink, piggybacking of NAS messages is used only for one dependent (i.e., with common success / failure) procedure of bearer establishment / modification / release. In the uplink piggybacking, NAS messages are used only for transferring initial NAS messages during connection setup and connection re-establishment. Note 1: NAS messages transferred via SRB2 are also included in RRC messages, but do not include RRC protocol control information.

[0090] When AS security is activated, all RRC messages on SRB1, SRB2, and SRB3, including those containing NAS messages, are integrity protected and encrypted by PDCP. NAS applies integrity protection and encryption independently to NAS messages (see TS24.501).

[0091] Split SRB is supported for all MR-DC options in both SRB1 and SRB2 (Split SRB is not supported for SRB0 and SRB3).

[0092] When AS security is activated, all RRC messages on SRB1, SRB2, and SRB3, including those containing NAS messages, are integrity protected and encrypted by PDCP. NAS applies integrity protection and encryption independently to NAS messages (see TS24.501

[23] ).

[0093] Split SRB is supported for all MR-DC options in both SRB1 and SRB2 (Split SRB is not supported for SRB0 and SRB3).

[0094] Figure 6 is a diagram showing the radio protocol architecture of MCG, SCG, and split bearers from the perspective of the UE in MR-DC by EPC (EN-DC) (TS37.340).

[0095] Figure 7 is a diagram showing MCG, SCG, and split bearers from the perspective of the user equipment in MR-DC by 5GC (NGEN-DC, NE-DC, and NR-DC). Two different user plane options can enable multi-connectivity.

[0096] 1. In the split bearer - split bearer option, the second bearer is provided by two nodes. The secondary node does not implement PDCP, but implements below the RLC layer.

[0097] 2. Separate bearer - In the separate bearer option, each bearer terminates at a different node. The bearers are separated at the S - GW / User Plane Function (UPF) and the Access and Mobility Management Function (AMF), and each node implements the protocol stack from the following PDCP.

[0098] Figure 8 illustrates SN addition in EN - DC (TS37.340). One of the most important procedures in the MR - DC procedure is secondary node (SN) addition. The addition of the SN is carried out according to (TS37.340), section 10.2. Some of the most relevant aspects of the procedure are shown below (at the end of the document, there are information elements applicable to the signaling procedures specified below).

[0099] SgNB addition request: The MN decides to add an SN. The MN sends a secondary node addition request to the SN. The message carries the RRC and radio bearer configuration. UE capabilities and security information are also included in the message. SgNB addition request response: The SN responds with information about radio resources and the permitted bearers. The NR RRC configuration message is included in the message. Figure 9 shows SN addition by 5GC (TS37.340).

[0100] Figure 10 shows an MN initiated in an MRDC with SN change - 5GC according to (TS37.340) of Figure 10.5.2 - 1. The SN change procedure is initiated either by the MN or the SN, transfers the UE context from the source SN to the target SN, and changes the SCG configuration in the UE from one SN to another (TS37.340). Figures 10 and 11 show the MN initiation and SN - initiated node change in MR - DC with 5GC. The case of EN - DC is shown in Figures 4 and 5. Figure 11 shows the SN change in an MRDC when 5GC - SN is initiated, according to (TS37.340) of Figure 10.5.12 - 2.

[0101] Figure 12 shows the MN handover in EN - DC with SgNb change according to (TS37.340). Master - node handover with / without secondary - node change: Figure 12 shows the MN handover with / without secondary - node change in the case of EN - DC. The specification (TS37.340) also includes the case of 5GC - see Figure 10.7.2 - 1 of (TS37.340).

[0102] RRC - related aspects (measurements): Measurements: · Measurements can be configured independently by the MN and the SN (intra - RAT measurements in serving and non - serving frequencies). The MN indicates the maximum number of frequency layers and measurement identities that can be used by the SN to ensure that it does not exceed the UE capabilities.

[0103] · The secondary - node change procedure can be triggered by both the MN and the SN (only for inter - frequency secondary - node change). In the case of a secondary - node change triggered by the SN, the RRM measurement configuration is maintained by the SN that also processes the measurement reports without providing the measurement results to the MN.

[0104] · When SRB3 is not configured, the measurement report configured by the SN is sent on SRB1. When SRB3 is configured, the measurement report set by the SN is sent on SRB3.

[0105] · Measurement results related to the target SN can be provided to the target SN by the MN at the MN that initiated the SN change procedure. The measurement results of the target SN can be transferred from the source SN to the target SN via the MN at the SN that initiated the SN change procedure. Measurement results related to the target SN can be provided to the target MN by the source MN in an MN - to - MN handover regardless of the presence or absence of the SN change procedure (see below).

[0106] (Secondary) Cell group configuration details: The main functions of RRC re - configuration are to configure radio bearers, measurements, and Scell or cell groups. The information element of CGConfig is given in TS36.331 - f60 and TS38.331 - f60.

[0107] SCG failure handling: RLF is declared separately for the MCG and the SCG. When a radio link failure is detected for the MCG, the UE starts the RRC connection re - establishment procedure (TS37.340). Note that RAN2 includes a new procedure - Release 16 fast MCG recovery (3GPP RAN2, 2019) to address the delay associated with the RRC connection re - establishment procedure. Note that MCG failures are not described further in this document.

[0108] Instead, SCG failures are described. The following cases of SCG failures are supported. - SCG RLF, - SN change failure, - For EN - DC, NGEN - DC, and NR - DC, SCG configuration failure (only messages on SRB3), - For EN - DC, NGEN - DC, and NR - DC, SCG RRC integrity check failure (on SRB3). If the SCG fails, instead of interrupting the SCG transmission of all radio bearers and triggering re-establishment, the UE reports the SCG failure information to the MN.

[0109] In all cases of SCG failure, the UE maintains the current measurement configuration from both the MN and the SN, and the UE continues to make measurements based on the configurations from the MN and the SN if possible. SN measurements configured to be routed through the MN continue to be reported after the SCG failure.

[0110] Note: In certain cases (e.g., the UE is unable to maintain the timing of the PSCell), the UE may not continue to make measurements based on the configuration from the SN after the SCG failure.

[0111] The UE includes available measurement results in the SCG failure information message according to the current measurement configurations of both the MN and the SN. The MN can process the SCG failure information message and decide to hold, change, or release the SN / SCG. In all cases, the measurement results according to the SN configuration and SCG failure type may be transferred to the old SN and / or the new SN.

[0112] More detailed description of SCG failure: Definition of failure: A failure in the specification is called an SCG failure in both LTE and NR. As described above, the SCG is a cell group configured for the UE belonging to the SN. Inside the SCG, there is a Primary Secondary Cell (PSCell). In LTE, this is the cell where the UE is instructed to perform a random access or an initial PUSCH transmission when the random access procedure is skipped when performing the SCG change procedure (TS36.331-f60). In NR, the PSCell is the cell where the UE performs a random access when performing reconfiguration using the Sync procedure. (TS38.331-f60).

[0113] LTE specification: An SCG failure is reported by the UE in the following cases (TS36.331-f60). · When detecting a radio link failure of the SCG, · During an SCG change failure (due to the mobility of the SCG), · When, according to TS36.133, the powerControlMode is configured to 1 and the uplink transmission timing difference exceeds the maximum, stopping the uplink transmission towards the PSCell.

[0114] Actions during failure: When starting the procedure, the UE · Interrupts all SCG DRBs, interrupts the SCG transmission of split DRBs, · Resets the SCG-MAC, · Stops the T307 timer, · The T307 timer is started upon receiving an RRCConnectionReconfiguration message containing MobilityControlInfoSCG. It is stopped upon successful completion of random access on the PSCell, at the start of re-establishment, and at the release of the SCG. · Starts transmitting the SCGFailureInformation message.

[0115] NR specification: The purpose of this procedure is for the UE to notify the LTE or NR MN about the SCG failure it has encountered. The SCG failure is reported by the UE in the following cases (TS38.331-f60). · When detecting a radio link failure of the SCG (Section 5.3.10.3), · During reconfiguration with an SCG sync failure (Section 5.3.5.8.3), · SCG configuration failure, i.e., when unable to comply with the reconfiguration request (Section 5.3.5.8.2), · When receiving an integrity check failure indication from the SCG lower layer regarding SRB3. Actions during failure: When starting the procedure, the UE · Interrupts the SCG transmission of all SRBs and DRBs, ·Reset the SCG MAC, ·If running, stop the T304 timer ·The timer T304 is started when an RRCReconfiguration message containing reconfigurationWithSync is received. It is stopped upon successful completion of random access on the corresponding SpCell. For the SCG's T304, the timer is stopped upon SCG release.

[0116] ·If the UE is in EN-DC, ·Start transmitting the SCGFailureInformationNR message as specified in Section 5.6.13a of TS36.331.

[0117] All of the above, and in accordance with the current specifications - TS36.331-f60 and TS38.331-f60, only the PCell on the MN and the SpCell on the SN report RLF.

[0118] Figure 13 is a diagram showing a PSCell failure. The object of the present invention is to improve robustness and provide a seamless experience to a UE in a multi-radio dual connectivity (MR-DC) mode. As described above, MR-DC means a system in dual connectivity between E-UTRA and an NR node, or between two NR nodes. The present invention addresses the case where the quality of the PSCell link of a secondary node (SN) deteriorates and may lead to a PSCell failure.

[0119] The robustness of the MR-DC function depends on the stability of the links on the PCell and PSCell. That is, as explained in Section 0, an SCG failure occurs especially when there is a Radio Link Failure (RLF) on a specific cell (SpCell) on the SN(PSCell). In that case, the SCG data radio bearer is released, the MAC is reset, and the appropriate timer is stopped. Considering that a possible deployment of MR-DC is a heterogeneous deployment with an SN using small cells and / or the cmWave / mmWave spectrum (e.g., FR2 in 5G), the PSCell radio link is particularly subject to variations and failures, which may destabilize the multi-connectivity function. In particular, operation in mmWave frequency bands above 28 GHz, but 52 GHz, for example 60 GHz, as specified by 3GPP, results in a significant increase in path loss and degradation of signal penetration, which particularly affects the stability and quality of the link.

[0120] Figure 13 shows the potential impact of a radio link failure in the PSCell. A PSCell failure may cause significant QoS variations for the UE as, in this case, the larger pipe becomes unavailable.

[0121] When an SCG failure occurs due to a radio link failure (RLF) of the PSCell, the network, specifically the MN, processes the SCG failure information message (scgFailureInformation / scgFailureInformationEUTRA). This message is sent from the UE to the MN-EUTRA or NR (TS38.331-f60), Figure 5.7.3.1.1. Currently, the standard does not specify the action that the MN should take after receiving an SCG RLF notification. According to (TS37.340), the MN may · retain the SN / SCG, or · change the SN / SCG, or · release the SN / SCG.

[0122] When the SCG data radio bearer is released, even if the MN decides to re - establish the radio bearer while retaining the SN / SCG or change the SN / SCG, there may be an interruption in the UE service because all SCG cells are not available, which can lead to a large data rate gap.

[0123] Figures 14 and 15 show the case of SN change, i.e., SCG modification by the MN. Figure 14 shows the SN change after RLF on the SCG. Figure 15 shows the SgNb modification after RLF on the SCG.

[0124] Figure 16 shows the PSCell / SCG change within the SN. The proposed enhancement aims to improve the robustness of the MR - DC function and provide a seamless experience for UE in MR - DC mode by enabling proactive actions as the link on the PSCell degrades.

[0125] The cases of changes between SNs and within SNs are described separately. The PSCell / SCG change within the SN is shown in Figure 16. The new SCG can also include the previous SCell and / or a new SCell. The conditions related to the quality degradation of the PSCell trigger the decision to change the PSCell / SCG within the same SN.

[0126] Figure 17 schematically shows the implementation of a user equipment according to Figure 1 of 5G and its interaction with a cellular network. It shows the PSCell / SCG change within the SN. The UE decides to change the PSCell, and thus the SCG, based on trigger conditions taking into account the quality of the existing PSCell.

[0127] This enhancement aims to give the UE the right to request PSCell changes due to PSCell quality degradation. To that end, the UE can have built-in trigger conditions to initiate PSCell changes. For example, the trigger condition can be configured as x instances where the timer T310 (RLF timer) has started but not expired within y seconds. The trigger condition can also be based on the number of retransmissions from the RLC layer on the PSCell, which is less than the maximum number of radio link failures detected by the UE. Based on the trigger condition, the UE decides to change the PSCell and SCG accordingly. This enhancement also assumes that the UE can create a pool of candidate PSCs. Then, it is necessary to provide the SN with the PSCell preference from this pre-configured pool by transmitting an ordered list of PSCs. The pool of candidate cells can be created by one or more of the following: · The UE monitors potential candidates by measurements such as the correlation between the synchronization signal and the reference signal (e.g., channel state information reference signal, beam stream reference signal, and demodulation reference signal). The UE may use defined metrics such as reference signal received power (RSRP), received signal strength indicator (RSSI), signal reference signal received quality (RSRQ), or signal-to-noise and interference ratio (SINR), or any metric for evaluating the quality of channel state information (CSI) for creating the pool (3GPP, 2019).

[0128] · One of the MN and / or SN, and / or one of the SCell and / or SpCell within the MN or SN can directly provide the UE with a list of candidates, · The above combination.

[0129] In addition to the PSCell pool, the UE can also provide the network with an ordered list of SCell for the new SCG. The SCell pool may be created in the same way as the PSCell pool and may include existing and / or new SCell. The PSCell and SCell may be exchanged between the pools.

[0130] The following steps shown in Fig. 17 are proposed. This figure shows the case where the procedure is mainly processed between the UE and the SN.

[0131] 1) When the UE determines a PSCell change, it sends a PSCell / SCG reconfiguration request to the SN. The request can be sent to the SN via the MN (using SRB1) or directly to the SN (using SRB3).

[0132] 2) The SN checks the available radio resources on the proposed cell and sends an RRCReconfigurationRequest including the new PSCell / SCG radio resource configuration. Here, the RRCReconfigurationRequest message includes an indicator that the message is a response to the PSCellChangeRequest.

[0133] 3) The UE performs a random access (RA) procedure for the new cell. a. The UE can be configured with a maximum number of attempts or maximum delay for the RA procedure (smaller than that specified for the detection of SCG RLF failures). In that case, the UE reports an RRCReconfigurationFailure and does not release the existing PSCell / SCG configuration.

[0134] 4) The UE sends a modified RRCReconfigurationComplete message, again via the MN or directly to the SN. An indication to release the old PSCell is piggybacked here in the RRCReconfigurationComplete message. The SN releases the old cell.

[0135] 5) If the signaling from 4) is not transmitted via the MN, the SN needs to notify the MN of the new PSCell / SCG configuration. It is also possible to have a procedure (RRC reconfiguration) that is mainly processed between the UE and the MN, which can be sent directly or via the SN. In either case, the existing procedures for the core network can be preserved, which also depends on whether the MN is involved according to the existing specifications for SN modification.

[0136] Note 1: Steps 3) and 4) can be swapped. As explained above, when random access (RA) is performed in step 3), the potential problem associated with the RA procedure means that the old cell is not released and the UE reports RRC Reconfiguration Failure to the SN via the MN or directly.

[0137] Figure 18 schematically shows the implementation of a user equipment according to FIG. 2 of 5G and its interaction with the cellular network. The PSCell change within the SN is shown. The SN can determine the pre-configuration of its resources (as shown in FIG. 18). When the conditions are met, the UE performs a change of the PSCell, and thus the SCG, based on trigger conditions taking into account the quality of the existing PSCell.

[0138] This enhancement is based on the conditional handover (CHO) function currently being discussed as included in Release 16 (3GPP RAN2, 2019), where the network is responsible for PSCell / SCG changes. The UE operates only after the trigger conditions are met. Also, (MediaTek, 2019) and (NEC, 2019) have proposed so-called conditional PSCell addition and SCG changes. The trigger conditions can be the same as those described above.

[0139] The network (MN or SN) already has a mechanism to create a pool of candidate PSCells and SCells to be sent to the UE. This is shown in FIG. 18 and will be explained below.

[0140] 1) The SN decides to initiate a PSCell / SCG change, for example, based on measurement results, and the radio resources may include the old or new SCell. It sends an RRCReconfigurationRequest including the new PSCell / SCG radio resource configuration and trigger conditions. 2) When the conditions are met, the UE changes the PSCell, reconfigures the SCG, and performs a RA procedure for the new PSCell.

[0141] 3) The UE sends a modified RRCReconfigurationComplete message to the SN, either via the MN again or directly. An indication of the release of the old PSCell and / or SCell is piggybacked on the RRCReconfigurationComplete message here. The SN releases the old cell. 4) If the signaling from 4) is not transmitted via the MN, the SN needs to notify the MN of the new PSCell / SCG configuration.

[0142] Figure 19 shows the PSCell change between SNs. Conditions related to the quality degradation of the PSCell trigger a decision to switch to a new SN and accordingly change the PSCell and SCG. In the PSCell / SCG change enhancement between SNs, the PSCell and the new SCG belong to different SNs. This enhancement is described below.

[0143] Figure 20 schematically shows the implementation of a user equipment according to FIG. 1 of 5G and its interaction with a cellular network. This figure shows the PSCell change between SNs when the procedure is mainly processed between the UE and the SN. The UE decides to change the SN, and thus the PSCell / SCG, based on trigger conditions taking into account the quality of the existing PSCell.

[0144] This enhancement aims to give the UE the right to request an SN change, and thus a PSCell / SCG change, for example due to mobility and generally a degradation in the quality of the PSCell. The same trigger conditions as above can be defined. Based on the trigger conditions, the UE decides to change the SN and PSCell / SCG accordingly. The enhancement also assumes that the UE creates a pool of candidate SNs in addition to the PSCell and SCell pools. Then, for example, it is necessary to provide the SN / PSCell preference from these pre-configured pools to the current SN by sending an ordered list of SNs and PSCells. The pools of candidate SNs and PSCs can be created in the same way as above.

[0145] In addition to the SN and PSCell pools, the UE can also provide the network with an ordered list of SCells on a new SN for a new SCG. The SCell pool may be created in the same way as the PSCell pool. The PSCell and SCell may be exchanged between the pools. The following steps shown in Figure 20 are proposed.

[0146] 1) When deciding on an SN / PSCell change, the UE sends a PSCell / SCG reconfiguration request to the source SN (SN-S). This request can be sent via the MN (using SRB1) or directly to SN-S (using SRB3). The changePSCellRequest message contains an indicator that it is an SN change request. If the MN is not involved, SN-S notifies the MN of the request.

[0147] 2) Either the MN or SN-S sends an addition request to the target SN (SN-T. This is the same message as the existing specification (TS37.340), except that it is assumed that currently SN-S can also send the request to SN-T. This figure shows the addition initiated by the MN.

[0148] 3) The SN-T checks the available radio resources and transmits a SN addition request response including an indication of full or delta RRC configuration. The addition request notification is sent to the SN-S.

[0149] 4) The RRCReconfigurationRequest message is sent from the SN-S to the UE (either directly or via the MN) in the new configuration, including an indicator that the message is a response to a PSCellChangeRequest (including SN change).

[0150] 5) The UE performs a random access (RA) procedure for the SN-T and the new PSCell. a. The UE may be configured with a maximum number of attempts or a maximum delay for the RA procedure (smaller than that specified for the detection of SCG RLF failures). In that case, the UE reports an RRCReconfigurationFailure and does not release the SN-S and the existing PSCell / SCG configuration.

[0151] 6) The UE sends an RRCReconfigurationComplete message to the SN-S again, either via the MN or directly. An indication to release the SN-S is piggybacked here in the RRCReconfigurationComplete message. The SN-S releases its resources. 7) If the signaling from 4) is not transmitted via the MN, the SN needs to notify the MN of the new PSCell / SCG configuration.

[0152] It is also possible to have procedures (RRCreconfiguration) mainly processed between the UE and the MN, which can be sent either directly or via the SN. In either case, the existing procedures for the core network can be preserved, which also depends on whether the MN is involved according to the existing specifications for SN modification.

[0153] Note that steps 5) and 6) can be swapped. As described above, when RA is executed in step 5), the potential problem associated with the RA procedure means that SN-S is not released and the UE reports RRCReconfigurationFailure to SN-S directly or via MN.

[0154] Figure 21 schematically shows the implementation of a user equipment according to FIG. 2 of 5G and its interaction with a cellular network. The change of the PSCell between SNs is shown. The network decides to pre-configure a new SN, and thus the PSCell / SCG, based on trigger conditions taking into account the quality of the existing PSCell. Figure 21 is a diagram showing the change between SNs using CHO as a basis. Note that it is also possible to let MN decide on the change of SN and PSCell / SCG. This is not shown in Figure 21.

[0155] The network (MN or SN) already has a mechanism for creating a pool of candidate SNs, PSCs, and SCells to be sent to the UE. As shown in Figure 21, the following steps are proposed.

[0156] 1) Based on the measurement results from the UE, the network (MN or SN-S) makes a decision regarding the SN / PSCell change. This figure shows the case where SN-S sends a request for pre-configuration of resources to SN-T. 2) SN-T sends a confirmation of the pre-configured resources indicating full availability or the difference between the requested resources and the available resources. 3) If MN does not start the pre-configuration, SN-S notifies MN about the resources pre-configured by SN-T.

[0157] 4) The RRCReconfigurationRequest message is sent from SN-S to the UE with a new configuration including the trigger conditions. When the conditions are met, the UE performs the change of SN and PSCell.

[0158] 5) The UE performs a random access (RA) procedure for the SN-T and the new PSCell. a. The UE may be configured with a maximum number of attempts or a maximum delay for the RA procedure (smaller than that specified for the detection of SCG RLF failures). In that case, the UE reports RRCReconfigurationFailure and does not release the SN-S and the existing PSCell / SCG configuration.

[0159] 6) The UE sends an RRCReconfigurationComplete message to the SN-S either via the MN or directly. An indication to release the SN-S is piggybacked here in the RRCReconfigurationComplete message. The SN-S releases its resources.

[0160] 7) If the signaling from 4) is not transmitted via the MN, the SN needs to notify the MN of the new SN / PSCell / SCG configuration. The existing procedures for the core network can be preserved, which also depends on whether the MN is involved according to the existing specifications for SN correction.

[0161] Note that steps 5) and 6) can be interchanged. As explained above, if RA is performed in step 5), the potential problem associated with the RA procedure means that the SN-S is not released and the UE reports RRCReconfigurationFailure to the SN-S either directly or via the MN.

[0162] During handover (HO), the backhaul situation is not considered. The target base station for HO is selected based on the signal strength and / or quality of the link between the UE and one or several base stations or access points.

[0163] Figure 22 shows the basic conditional HO(CHO) procedure. Similar situations also exist for conditional HO(CHO). In CHO to the target base station, it is selected considering the link to the UE. The quality of the backhaul links of different base stations is not compared and not considered in this selection. Then, the UE is configured with the configuration necessary to connect to its selected target base station. In CHO, the target base station is selected considering the link quality on the Uu link based on an agreed threshold between the base station and the UE with reduced signaling. If a specific link quality threshold is met by the UE, the UE can automatically perform HO to its target base station without transmitting a measurement report to its source base station. Further, the UE can directly perform HO without waiting for an HO command from its source base station, which may fail due to fluctuations in the Uu link. The quality of the backhaul links of different base stations is neither compared nor exchanged and not considered in this selection.

[0164] In SN selection in dual / multi-connectivity, the master node (MN) selects the SN considering its link to the UE. The quality of the backhaul links of different base stations is not compared and not considered in the selection of the SN.

[0165] The change or modification of the SN can be initiated by the MN or the SN. The quality of the backhaul links of different base stations is not compared and not considered in the change or modification of the SN.

[0166] Figure 23 shows a situation where the backhaul between the central unit (CU) and the distributed unit (DU) affects the quality of the path from the UE to the core network. When there are two or more candidate base stations, one base station is selected considering the available resources and the signal strength (to the UE). In this selection, the quality of the backhaul is ignored. For example, in Figure 23, the UE is under the coverage of both DU2 and DU3. If one of them is to be selected to serve the UE (e.g., for handover or as the SN), the backhaul links between each of these two base stations and the core network (CN) are neither considered nor compared.

[0167] Figure 24 shows the impact of the backhaul on the quality of the path from the UE to the core network in the case of IAB. IAB is an example of how the backhaul can be implemented. For example, in Figure 24, consider the case where the signal the UE receives from IAB node 1 is stronger than the signal from IAB node 1’, but both powers exceed the acceptable threshold for communication to the UE. On the other hand, the signal from / to IAB node 1 experiences a greater delay to reach the core network. However, the backhaul link from the IAB access node to the IAB - Donor - CU is transparent to the UE. This also means it is transparent to the UE regardless of whether the serving node is an IAB node or not.

[0168] HO scenario: In Figure 24, nodes 1 and 1’ are candidates for HO. In the state of the art, neither the serving base station nor the UE has information about the backhaul links of these two candidates.

[0169] Dual connectivity scenario / Multi - connectivity scenario: In Figure 24, nodes 1 and 1’ are candidates to become the SN. In the state of the art, neither the MN nor the UE has any information about the backhaul links of these two candidates.

[0170] However, in both scenarios, if the UE and / or the serving base station / MN have knowledge of the quality of the two possible backhaul paths, they can determine which is more suitable for the required QoS of the service being used by the UE. This solution includes two possible enhancements that can be applied together or separately. Enhancement 1: Consider the backhaul situation (quality of the backhaul link) For example, information on the quality of the backhaul transferred between base stations via X2 or Xn. In the state of the art, the acknowledgement is transferred via X2 / Xn.

[0171] In the present invention, two enhancements are proposed. One enhancement is to transfer an indication of the quality of the backhaul (from the BS to the CN). The other proposed enhancement is to enable UE-initiated base station selection, for example in handover, in dual / multi-connectivity. FIG. 25 shows the basic procedure (procedure 0) for considering the backhaul situation in base station selection.

[0172] Procedure 0: 1. The UE provides a list of candidate base stations to the current serving base station / MN. The serving base station / MN transfers this list from the UE to a specific entity within the network. The serving base station / MN itself may be that specific entity. Note 1 - Some candidates may be IAB nodes. Note 2 - The current serving base station / MN may be an IAB node.

[0173] 2. The so-called specific entity estimates or measures or obtains the quality of the backhaul link from each candidate base station to the core network. If there is no backhaul link, the entity may estimate the quality of that link if possible. If there is an IAB node in the candidate list, the IAB-Donor-CU can be an entity that estimates or measures the quality of the backhaul link. In particular, if both (or all) of the IAB nodes are connected to the same IAB-Donor-CU, that IAB-Donor-CU compares the quality of the backhaul link from the core network to each IAB node. For example, the number of hops in a path can provide an estimate of the delay of the path.

[0174] 3. When a so-called specific network entity is different from the serving base station / MN, the quality of the backhaul link is transmitted from that network entity to the serving base station / MN.

[0175] 4. The serving base station / MN considers the link measurement values from the UE and the backhaul information obtained from the network (step 3) and sorts the list of candidate base stations.

[0176] 5. The serving base station / MN selects a base station, determines an action, and / or initiates that action, for example, initiates a HO / CHO to the selected base station, initiates a secondary link with the selected base station, and exchanges MN and SN. A second proposed enhancement is available, and if the UE can initiate HO and / or SN establishment, two possible procedures are proposed. FIG. 26 schematically shows the implementation of a user equipment according to FIG. 3 of 5G and its interaction with a cellular network.

[0177] Procedure 1: 1 to 3: The same as procedure 0 (FIG. 25). 4. The serving base station / MN transmits the quality of the backhaul link to the UE. 5. The UE considers the measurement values it has and the backhaul information obtained from the network and sorts the list of candidate base stations. 6. The UE selects a base station, determines an action, and triggers an action, e.g., an HO to the selected base station, and initiates a secondary link with the selected base station. In procedure 1, backhaul information is transferred to the UE (step 4), the UE sorts the base stations (step 5), and makes a decision (step 6). Figure 27 schematically shows a further implementation of a user equipment according to FIG. 3 of 5G and its interaction with a cellular network.

[0178] An alternative procedure is that the backhaul information is not sent to the UE. Instead, the serving base station or MN uses this information in addition to the measurements collected from the UE to sort the candidate base stations / nodes. This alternative procedure is shown in Figure 27 and will be described below.

[0179] Procedure 2: 1 to 4: The same as procedure 0 (Figure 25). 5. The serving base station / MN sends the sorted list of candidate base stations to the UE. 6. The UE selects a base station, determines an action, and triggers an action, e.g., an HO to the selected base station, and initiates a secondary link with the selected base station.

[0180] Depending on specific implementation requirements, embodiments of the apparatus of the present invention can be implemented in hardware and / or software. The embodiments have electronically readable control signals stored therein and cooperate (or are capable of cooperating) with a programmable computer system such that one or more or all of the functions of the apparatus or system of the present invention are performed, and can be executed using a digital storage medium such as a floppy disk, DVD, Blu-ray disk, CD, ROM, PROM, EPROM, EEPROM, or flash memory.

[0181] In some embodiments, a programmable logic device (e.g., a field programmable gate array) can be used to perform one or more or all of the functions of the devices or systems described herein. In some embodiments, a field programmable gate array can cooperate with a microprocessor to perform one or more or all of the functions of the devices and systems described herein.

[0182] Although some aspects are described in the context of devices, these aspects also represent corresponding method descriptions, and it is clear that a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of method steps also represent descriptions of corresponding blocks or corresponding items or features of a device.

[0183] Depending on specific implementation requirements, embodiments of the method of the present invention can be implemented using a device comprising hardware and / or software. Embodiments can be implemented using a digital storage medium, such as a floppy disk, DVD, Blu-ray disk, CD, ROM, PROM, EPROM, EEPROM, or flash memory, which has electronically readable control signals stored therein and can cooperate (or be capable of cooperating) with a programmable computer system such that each method is executed. Depending on specific implementation requirements, embodiments of the method of the present invention can be implemented using a device comprising hardware and / or software.

[0184] Some or all of the method steps may be executed by (or using) a hardware device such as a microprocessing unit, a programmable computer, or an electronic circuit. Some of the most important method steps may be executed by such a device.

[0185] Some embodiments in accordance with the present invention include a data carrier having electronically readable control signals that, in cooperation with a programmable computer system, cause one of the methods described herein to be executed.

[0186] In general, embodiments of the present invention can be implemented as a computer program product having program code that, when the computer program product is run on a computer, causes one of the methods to be executed. The program code can be stored, for example, on a machine-readable carrier.

[0187] Other embodiments include a computer program for executing one of the methods described herein, stored on a machine-readable carrier or a non-transitory storage medium.

[0188] Further embodiments include a processing means, such as a computer, or a programmable logic device, in particular a processor comprising hardware configured or adapted to execute one of the methods described herein. Further embodiments include a computer having installed thereon a computer program for executing one of the methods described herein. In general, the method is advantageously executed by any device comprising hardware and / or software.

[0189] Although the invention has been described with respect to some embodiments, there are changes, substitutions, and equivalents that fall within the scope of the invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. Accordingly, the following appended claims are intended to be construed to include all such changes, substitutions, and equivalents that fall within the true spirit and scope of the invention.

Description of the Reference Numerals

[0190] 1 User equipment 2 Monitoring unit CN Cellular network CE Cell NO Node CL Communication Link REP Replacement Request RCE Replacement Cell LI List REC Reconfiguration Request ME Message BS Base Station XN xhaul Network COR Core Network SBS Serving Base Station CBS Candidate Base Station QI Quality Information QIR Quality Information Request SI Signal

[0191] References : (ETRI),Lee.2015.’’A Study of the Radio Resource Control Connection.’’ 38.401,3GPP.’’Architecture description NG RAN 38.401.’’

[0192] 3GPP RAN2.2019.’’RAN 2-107-Chairmains Notes.’’ Prague. 3GPP.2019.TS 38.215 NR;Physical layer measurements.3GPP.

[0193] Ahmadi.2019.’’5G NR.’’ Elsevier. Ericsson.’’R2-1900404 Conditional Handover.’’ MediaTek.2019.’’Conditional PSCell addition.’’

[0194] NEC. 2019. “R2-1904069 Reuse of conditional handover for SCG change in NR-DC.”

[0195] Rao, Jaya, and Sophie Vrzic. 2018. “Packet Duplication for URLLC in 5G: Architectural Enhancements and Performance Analysis.” IEEE Network.

[0196] Rosa, Claudio. 2016. Dual Connectivity for LTE Small Cell Evolution: Functionality and Performance Aspects. IEEE Communications Magazine.

[0197] Sauter, Martin. https: / / blog.wirelessmoves.com / 2017 / 09 / 5g-part-3-dual-connectivity-en-dc.html. SI 38.874, 3GPP. 2018. “Study on Integrated Access and Backhaul.”

[0198] TS 36.331-f60. “LTE Radio Resource Specification.” TS 38.331-f60. “Radio Resource Control (RRC) protocol specification.” TS37.340, TS-f60. Multi-Radio Dual Connectivity.

Claims

1. A user equipment for communication over a cellular network (CN), comprising: said user equipment (1) being adapted to communicate simultaneously with one or more cells (CE) of a first node (NO1) of said cellular network and with one or more cells (CE) of a second node (NO2) of said cellular network (CN); The user equipment (1) comprises a monitoring unit (2) for monitoring a quality of a first communication link (CL1) between the user equipment (1) and a first one of the cells (CE) of the first node (NO1) and / or for monitoring a quality of a second communication link (CL2) between the user equipment (1) and a first one of the cells (CE) of the second node (NO2), The user equipment (1) a first replacement request (REP1) to replace the first cell (CE) of the first node (NO1) with a first replacement cell (RCE1), the first replacement cell being a second cell (CE) of the first node (NO1) or a cell (CE) of a third node (NO3), if the monitoring unit (2) detects a first change condition of the first communication link (CL1); and / or a second replacement request (REP2) to replace the first cell (CE) of the second node (NO2) with a second replacement cell (RCE2), the second cell (CE) of the second node (NO2) or a cell of a fourth node (NO4), if the monitoring unit (2) detects a second change condition of the second communication link (CL2); The user equipment is configured to transmit.

2. The user equipment (1') of claim 1, wherein the user equipment (1') is configured to communicate over the cellular network (CN) using dual connectivity or multi-connectivity.

3. 3. The user equipment of claim 2, wherein the first node (NO1) is a base station and a master node for dual connectivity or multi-connectivity, and the second node (NO2) is a base station and a secondary node for dual connectivity or multi-connectivity.

4. 4. The user equipment according to claim 2 or 3, wherein the first cell (CE) of the first node (NO1) is a specific cell or a secondary cell of a master cell group for dual connectivity or multi-connectivity, and / or the first cell (CE) of the second node (NO2) is a specific cell or a secondary cell of a secondary cell group for dual connectivity or multi-connectivity.

5. The first change condition and / or the second change condition are a specified number of instances in which a radio link failure timer has been started but has not expired within a specified period of time; a specified number of HARQ retransmissions from the PHY layer; and a specified number of retransmissions from the RLC layer, which is less than the maximum number of times that the user equipment (1) detects a radio link failure; a weighted or moving average or any other specified statistical method using an adopted metric indicative of degradation of signal quality; Coded or uncoded bit error rate; A packet loss rate or a packet error rate; A data rate requirement; The supported bandwidth and a multi-cell event such as a multi-cell event where one of the adopted metrics of the respective replacement cells (RCE1, RCE2) becomes better than the corresponding adopted metric of the respective first cell (CE) during at least one designated period of time, a multi-cell event where one of the adopted metrics of the respective replacement cells (RCE1, RCE2) becomes better than a threshold during at least one designated period of time, or a multi-cell event where one of the adopted metrics of the respective first cell (CE) becomes worse than a first threshold during at least one designated period of time and the corresponding adopted metric of the respective replacement cell (RCE1, RCE2) becomes better than a second threshold during at least one designated period of time, the multi-cell event being triggered by the user equipment (1), one of the nodes (NO1, NO2) or another device of the cellular network (CN).

5. The user equipment of claim 1 , wherein the first and second inputs are connected to the first and second inputs, or a combination of the first and second inputs.

6. 6. The user equipment (1) according to claim 1, configured to transmit the first replacement request (REP1) to the first node (NO1) or to the second node (NO2).

7. 7. The user equipment (1) according to claim 1, wherein the user equipment (1) is configured to transmit the second replacement request (REP2) to the first node (NO1) or to the second node (NO2).

8. 8. The user equipment according to claim 1, wherein the user equipment (1) is configured to identify candidate cells (CE) for the first replacement cell (RCE1) or the second replacement cell (RCE2) by measuring signals of possible candidate cells.

9. 9. The user equipment (1) according to claim 1, configured to receive a first list (LI1) of candidate cells (CE) for the first replacement cell (RCE1) from the first node (NO1) or the second node (NO2).

10. 10. The user equipment (1) according to claim 1, configured to receive a second list (LI2) of candidate cells (CE) for the second replacement cell (RCE2) from the first node (NO1) or the second node (NO2).

11. 11. The user equipment (1) according to claim 1, configured to receive a first reconfiguration request (REC1) including an indication of which of the cells (CE) of the cellular network (CN) is the first replacement cell (RCE1) and an indication that the first reconfiguration request (REC1) is a response to the first replacement request (REP1).

12. 12. The user equipment (1) of claim 11, configured to receive the first reconfiguration request (REC1) from the first node (NO1) or the second node (NO2).

13. 13. The user equipment according to claim 11 or 12, wherein the user equipment is configured to communicate with the first replacement cell (RC1) after the first reconfiguration request (REC1) is received by the user equipment (1).

14. 13. The user equipment according to claim 11 or 12, wherein the user equipment (1) is configured to transmit a first message (ME1) to the first node (NO1) or the second node (NO2), and after the first reconfiguration request (REC1) is received by the user equipment (1), the first message (ME1) indicates that the first cell (CE) of the first node (NO1) has been released.

15. 15. The user equipment according to claim 11, wherein the user equipment (1) is configured to indicate in the first replacement request (REC1) whether the first replacement cell (RCE1) belongs to the first node (NO1) or to the third node (NO3).

16. 16. The user equipment (1) according to claim 1, configured to receive a second reconfiguration request (REC2) including an indication of which of the cells (CE) of the cellular network (CN) is the second replacement cell (RCE2) and an indication that the second reconfiguration request (REC2) is a response to the second replacement request (REP2).

17. 17. The user equipment (1) of claim 16, wherein the user equipment (1) is configured to receive the second reconfiguration request (REC2) from the first node (NO1) or the second node (NO2).

18. 18. The user equipment according to claim 16 or 17, wherein the user equipment (1) is configured to communicate with the second replacement cell (RCE2) after the second reconfiguration request (REC2) is received by the user equipment (1).

19. 19. The user equipment (1) according to any one of claims 16 to 18, wherein the user equipment (1) is configured to transmit a second message (ME2) to the first node (NO1) or the second node (NO2), and after the second reconfiguration request (REC) is received by the user equipment (1), the second message (ME2) indicates that the first cell (CE) of the second node (NO2) has been released.

20. 20. The user equipment (1) according to any one of claims 16 to 19, wherein the user equipment (1) is configured to indicate in the second replacement request (REC2) whether the second replacement cell (RCE2) belongs to the second node (NO2) or to the fourth node (NO4).

21. A method of operating a user equipment (1) for communication over a cellular network (CN), the method comprising the steps of: using said user equipment (1) for simultaneously communicating with one or more cells (CE) of a first node (NO1) of said cellular network (CN) and with one or more cells (CE) of a second node (NO2) of said cellular network (CN); using a monitoring unit (2) of said user equipment (1) for monitoring the quality of a first communication link (CL1) between said user equipment (1) and a first one of said cells (CE) of said first node (NO1) and / or for monitoring the quality of a second communication link (CL1) between said user equipment (1) and a first one of said cells (CE) of said second node (NO2); a first replacement request (REP1) to replace the first cell (CE) of the first node (NO1) with a first replacement cell (RCE1), the first replacement cell being a second cell (CE) of the first node (NO1) or a cell (CE) of a third node (NO3), if the monitoring unit (2) detects a first change condition of the first communication link (CL1); and / or a second replacement request (REP2) to replace the first cell (CE) of the second node (NO2) with a second replacement cell (REC2), the second cell (CE) of the second node (NO2) or a cell of a fourth node (NO4), if the monitoring unit (2) detects a second change condition of the second communication link (CL2); and using the user equipment (1) for transmitting.

22. 22. A computer program for performing the method of claim 21 when the computer program is run on a processor.

23. A user equipment for communication over a cellular network (CN), the cellular network (CN) comprising a plurality of base stations (BS) connected to a core network (COR) of the cellular network (CN) via a xhaul network (XN) of the cellular network, said user equipment (1'') is adapted to communicate with one of said base stations (BS) of said cellular network (CN) used as a serving base station (SBS) or to communicate simultaneously with more of said base stations (BS) of said cellular network (CN) respectively used as serving base stations (SBS), The user equipment (1'') is adapted to transmit to one of the serving base stations (SBS) a list (LI') of candidate base stations (CBS) eligible to replace at least one of the serving base stations (SBS), The user equipment (1'') is configured to receive quality information (QI) from at least one of the serving base stations (SBS) on a quality of a communication link (CL') between one of the candidate base stations (CBS) and the core network (COR) for a plurality of the candidate base stations (CBS), The user equipment (1'') is configured to select one or more of the candidate base stations (CBSs) for replacing one or more of the base stations (BSs) currently used as serving base stations (SBSs) based on the quality information (QI).

24. 24. The user equipment (1'') of claim 23, wherein the user equipment (1'') is configured to transmit a quality information request (QIR) to the at least one of the serving base stations (SBS), the quality information request (QIR) requesting the at least one of the serving base stations (SBS) to transmit the quality information (QI).

25. said user equipment (1'') being adapted to receive said quality information (QI) as an unsorted list comprising quality indications of said plurality of candidate base stations (CBSs), said user equipment (1'') being configured to sort said unsorted list to create a sorted list; 25. The user equipment (1'') according to claim 23 or 24, wherein the user equipment (1'') is configured to select, based on the sorted list, the one or more of the candidate base stations (CBS) for replacing the one or more of the base stations (BS) currently used as serving base stations (SBS).

26. The user equipment (1 '') transmits the quality information (QI) as as a sorted list of the plurality of candidate base stations (CBSs); or As an indexed list, the index corresponding to an ordering; or an indexed list, the index corresponding to the quality indication value; is configured to receive, 26. The user equipment (1'') according to any one of claims 23 to 25, wherein the user equipment (1'') is configured to select, based on the sorted list, the one or more of the candidate base stations (CBS) for replacing the one or more of the base stations (BS) currently used as serving base stations (SBS).

27. 27. A user equipment according to any one of claims 23 to 26, wherein the user equipment (1'') is configured to transmit a signal (SI) indicating which of the one or more of the candidate base stations (CBS) has been selected to one of the base stations (BS) currently being used as a serving base station (SBS) and / or to one of the selected candidate base stations (CBS).

28. said user equipment (1 ″) being configured to communicate over said cellular network (CN) using dual connectivity or multi-connectivity; The user equipment (1'') is configured to simultaneously communicate with a master node, which is one of the serving base stations (SBS), and with a secondary node, which is one of the serving base stations (SBS), 28. The user equipment (1'') according to any one of claims 23 to 27, wherein the user equipment (1'') is capable of creating a list (LI') of candidate base stations (CBSs) such that the candidate base stations (CBSs) in the list (LI') of candidate base stations (CBSs) include a plurality of candidate base stations (CBSs) eligible to replace the master node as one of the serving base stations (SBSs) and / or a plurality of candidate base stations (CBSs) eligible to replace the secondary node as one of the serving base stations (SBSs).

29. The user equipment (1'') is configured to receive, from at least one of the serving base stations (SBS), the quality information (QI) regarding the quality of the communication link (CL') between one of the candidate base stations (CBS) and the core network (CN) for a plurality of the candidate base stations (CBS) eligible to replace the master node as one of the serving base stations (SBS); and / or 29. The user equipment (1'') of claim 28, configured to receive, from at least one of the serving base stations (SBS), the quality information regarding the quality of the communication link (CL') between one of the candidate base stations (CBS) and the core network (CN) for a plurality of the candidate base stations (CBS) eligible to replace the secondary node as one of the serving base stations (SBS).

30. The user equipment (1'') is configured to select one or more of the candidate base stations (CBS) to replace the master node currently used as one of the serving base stations (CBS); and / or 30. The user equipment (1'') of claim 28 or 29, wherein the user equipment (1'') is configured to select one or more of the candidate base stations (CBS) for replacing the secondary node currently used as one of the serving base stations (SBS).

31. A method of operating a user equipment (1'') for communication over a cellular network (CN), the cellular network (CN) comprising a plurality of base stations (BS) connected to a core network (COR) of the cellular network (CN) via a xhaul network (XN) of the cellular network (CN), the method comprising the steps of: using said user equipment (1'') to communicate with one of said base stations (BS) of said cellular network (CN) used as a serving base station (SBS) or for simultaneously communicating with more of said base stations (BS) of said cellular network (CN) respectively used as serving base stations (SBS); using said user equipment (1'') for transmitting to one of said serving base stations (SBSs) a list (LI') of candidate base stations (CBSs) eligible to replace at least one of said serving base stations (SBSs); using said user equipment (1'') for receiving quality information (QI) from at least one of said serving base stations (SBS) on the quality of a communication link (CL') between one of said candidate base stations (CBS) and said core network (COR) for a plurality of said candidate base stations (CBS); using said user equipment (1'') for selecting one or more of said candidate base stations (CBS) for replacing one or more of said base stations (BS) currently used as serving base stations (SBS) based on said quality information (QI); A method comprising:

32. 32. A computer program for performing the method of claim 31 when the computer program is run on a processor.

Images