User equipment for communication over a cellular network and method of operating a user equipment for communication over a cellular network - Patents.com

Abstract

The present disclosure relates to user equipment for communication over a cellular network, the user equipment configured to simultaneously 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, and to methods for operating such user equipment for communication over the cellular network. Furthermore, the present disclosure relates to a user equipment for communication over a cellular network, the cellular network including a plurality of base stations connected to a core network of the cellular network via a 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, and to a method for operating such user equipment for communication over the cellular network.

Description

[Technical field]

[0001] The present disclosure relates to user equipment for communication over a cellular network and a method of operating user equipment for communication over a cellular network. Summary of the Invention [Problem to be solved by the invention]

[0002] [Means for solving the problem]

[0003] In one aspect, the present disclosure provides a user equipment for communication over a cellular network, comprising: the user equipment is configured to communicate simultaneously 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; The user equipment comprises a monitoring unit for monitoring a quality of a first communication link between the user equipment and a first one of the cells of the first node and / or for monitoring a quality of a second communication link between the user equipment and a first one of the cells of the second node, The user equipment a first replacement request to replace the first cell of the first node with a first replacement cell, the first replacement cell being the second cell of the first node or a cell of a third node, if the monitoring unit detects a first change condition of the first communication link; and / or a second replacement request to replace the first cell of the second node with a second replacement cell, the second cell of the second node or a cell of a fourth node, when the monitoring unit detects a second change condition of the second communication link. The present invention relates to a user equipment (UE) configured to transmit

[0004] In a further aspect, the present disclosure provides a method of operating a user equipment for communication over a cellular network, the method comprising: using a user equipment 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; using a monitoring unit of the user equipment for monitoring a quality of a first communication link between the user equipment and a first one of the cells of the first node and / or for monitoring a quality of a second communication link between the user equipment and a first one of the cells of the second node; a first replacement request to replace the first cell of the first node with a first replacement cell, the first replacement cell being the second cell of the first node or a cell of a third node, if the monitoring unit detects a first change condition of the first communication link; and / or a second replacement request to replace the first cell of the second node with a second replacement cell, the second cell of the second node or a cell of a fourth node, when the monitoring unit detects a second change condition of the second communication link. using the user equipment for transmitting The present invention relates to a method comprising the steps of:

[0005] In a further aspect, the present disclosure provides a user equipment for communication over a cellular network, comprising: the user equipment is configured to communicate simultaneously 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; The user equipment is configured to receive a first reconfiguration request including an indication that a first cell of a 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 to receive a second reconfiguration request including an indication that a first cell of a 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 the first change condition and / or the second change condition; The user equipment is configured to replace a first cell of a first node with a first replacement cell if the monitoring unit detects that a first change condition is met, and / or to replace a first cell of a second node with a second replacement cell if the monitoring unit detects that a second change condition is met.

[0006] In a further aspect, the present disclosure provides a method of operating a user equipment for communication over a cellular network, the method comprising: using a user equipment 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; using a user equipment for receiving a first reconfiguration request including an indication that a first cell of a first node communicating with the user equipment should 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 should be executed, and / or a user equipment for receiving a second reconfiguration request including an indication that a first cell of a second node communicating with the user equipment should 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 should be executed; using a monitoring unit of the user equipment for monitoring the first change condition and / or the second change condition; using the user equipment to replace the first cell of the first node with a first replacement cell if the monitoring unit detects that a first change condition is met, and / or to replace the first cell of the second node with a second replacement cell if the monitoring unit detects that a second change condition is met; The present invention relates to a method comprising the steps of:

[0007] In a further aspect, the present disclosure provides a user equipment for communication over a cellular network, the cellular network comprising a plurality of base stations connected to a core network of the cellular network via a xhaul network of the cellular network; The user equipment is 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 respectively used as serving base stations, The user equipment is configured to transmit to one of the serving base stations a list of candidate base stations eligible to replace at least one of the serving base stations; The user equipment is configured to receive, from at least one of the serving base stations, quality information regarding a quality of a communication link between one of the candidate base stations and a core network for the plurality of candidate base stations; The user equipment is 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 provides a method of operating a user equipment for communication over a cellular network, the cellular network comprising a plurality of base stations connected to a core network of the cellular network via a xhaul network of the cellular network, the method comprising: using a user equipment to communicate with one of the base stations of the cellular network used as a serving base station or for simultaneously communicating with more of the base stations of the cellular network respectively used as serving base stations; using a user equipment for transmitting a list of candidate base stations eligible to replace at least one of the serving base stations to one of more other base stations of the cellular network, which will become the new serving base station; using a user equipment for receiving, from at least one of the serving base stations, quality information regarding a quality of a communication link between one of the candidate base stations and a core network for the plurality of candidate base stations; using the user equipment to select one or more of the candidate base stations for replacing one or more of the base stations currently being used as serving base stations based on the quality information; The present invention relates to a method comprising the steps of: Preferred embodiments of the present invention are described below with reference to the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1] 1 illustrates a schematic diagram of an embodiment of a user equipment and its interaction with a cellular network according to the present disclosure. [Diagram 2] 2 illustrates a schematic diagram of a further embodiment of a user equipment and its interaction with a cellular network according to the present disclosure; [Diagram 3] 2 illustrates a schematic diagram of a further embodiment of a user equipment and its interaction with a cellular network according to the present disclosure; [Figure 4] FIG. 2 illustrates a dual connected user equipment. [Diagram 5] A diagram showing the control plane architecture of EN-DC (left) and MR-DC (right) with 5GC (TS37.340). [Figure 6] A diagram showing the radio protocol architecture of MCG, SCG and split bearer from the UE perspective in MR-DC according to EPC (EN-DC) (TS37.340). [Figure 7] A diagram showing MCG, SCG and split bearers from the perspective of user equipment in MR-DC by 5GC (NGEN-DC, NE-DC and NR-DC). [Figure 8] This illustrates the addition of SN in EN-DC (TS37.340). [Figure 9] Indicates SN addition by 5GC (TS37.340). [Figure 10] FIG. 10.5.2-1 showing MN initiated in MRDC with SN change - 5GC according to (TS37.340). [Figure 11] FIG. 10.5.12-2 showing SN change of MRDC when 5GC - SN is initiated according to (TS37.340). [Figure 12] FIG. showing MN handover in EN - DC with SgNb change according to (TS37.340). [Figure 13] FIG. showing PSCell failure. [Figure 14] FIG. showing SN change after RLF on SCG. [Figure 15] FIG. showing SgNb correction after RLF on SCG. [Figure 16] FIG. showing PSCell / SCG change within SN. [Figure 17] Schematic diagram showing the implementation of a user equipment and its interaction with a cellular network according to FIG. 1 of 5G. [Figure 18] Schematic diagram showing the implementation of a user equipment and its interaction with a cellular network according to FIG. 2 of 5G. [Figure 19] FIG. showing PSCell change between SNs. [Figure 20] Schematic diagram showing the implementation of a user equipment and its interaction with a cellular network according to FIG. 1 of 5G. [Figure 21] Schematic diagram showing the implementation of a user equipment and its interaction with a cellular network according to FIG. 2 of 5G. [Figure 22] FIG. showing the basic CHO procedure (Ericsson "R2 - 1900404 Conditional Handover"). [Figure 23] FIG. showing a situation where the backhaul between a central unit (CU) and a distributed unit (DU) affects the quality of the path from the UE to the core network. [Figure 24]A diagram showing the impact of backhaul on the quality of the path from the UE to the core network in the IAB case. [Diagram 25] FIG. 1 is a diagram showing a basic procedure (procedure 0) for taking the backhaul situation into consideration when selecting a base station. [Figure 26] 5 shows a schematic diagram of a user equipment implementation according to FIG. 3 for 5G and its interaction with a cellular network. [Figure 27] A schematic diagram shows a further implementation of a user equipment according to FIG. 3 for 5G and its interaction with a cellular network. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Elements that are equal or equivalent or have equal or equivalent functions are indicated in the following description with equal or equivalent reference numbers. It should be noted that any information given in the context of an embodiment of one of the figures is also valid in the context of the embodiment of the other figures. This is particularly true for the definitions and features contained in the following description.

[0011] In the following description, a number of details are set forth 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 may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the embodiments of the present invention. In addition, the features of different embodiments described below can be combined with each other unless otherwise specified.

[0012] 1-3 show schematic implementations of the present disclosure. In contrast, FIGs. 4-27 show implementations 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. Moreover, those skilled in the art will understand that the features described in the 5G context are also possible in other cellular networks. FIG. 1 illustrates in a schematic diagram an embodiment of a user equipment 1 and its interaction with a cellular network CN according to the present disclosure.

[0013] According to some embodiments, a user equipment 1 for communication via a cellular network CN is configured to communicate simultaneously with one or more cells CE of a first node NO1 of the cellular network and with one or more cells CE of a second node NO2 of the cellular network CN, The user equipment 1 comprises a monitoring unit 2 for monitoring the 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 the 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 device 1 is 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 RCE1 being the second cell CE of the first node NO1 or the cell CE of the 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 the fourth node NO4, if the monitoring unit 2 detects a second change condition of the second communication link CL2; is configured to transmit

[0014] The user equipment 1 may comprise one or more of a mobile terminal, or a fixed terminal, or a cellular IoT user equipment, or a vehicular 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 any other item or device with network connectivity that enables an item / device to communicate using a wireless communication network, e.g., a sensor or actuator, or any other item or device with network connectivity that enables an item / device to communicate using a sidelink wireless communication network, e.g., a sensor or actuator, or any sidelink-capable network entity. The user equipment may also be part of an integrated access and backhaul (IAB) node, e.g., a mobile terminal (MT) portion 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 the cellular network.

[0016] The cellular network may comprise a number of base stations, which may comprise one or more of a macro cell base station, or a small cell base station, or a central unit of a base station, or a base station acting as a Cloud RAN (CRAN), or a distributed unit of a base station, or a roadside unit (RSU), or a cell, or a node, or a specific cell (SpCell), a further user equipment, or a group leader (GL) user equipment, or a relay, or a remote radio head, or an access and mobility management function (AMF), or a session management function (SMF), or a core network entity, or a mobile edge computing (MEC) entity, or a network slice such as in an NR or 5G core context, or any transmission / reception point TRP that enables an item or device to communicate using a wireless communication network, where the item or device has network connectivity to communicate using a 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) / spatial coding (beam and / or precoding) resources.

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

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

[0020] According to some embodiments, the user equipment 1 is configured to communicate over the cellular network CN using dual connectivity or multi-connectivity, where dual connectivity means simultaneous communication to two base stations and multi-connectivity means simultaneous communication to more than two base stations, e.g.

[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 and / or second change conditions include: 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; a specified number of retransmissions from the RLC layer that 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 each replacement cell RCE1, RCE2 is better than the corresponding adopted metric of the respective first cell CE during at least one specified period, where one of the adopted metrics of each replacement cell RCE1, RCE2 is better than a threshold during at least one specified period, or where one of the adopted metrics of each first cell CE is worse than a first threshold during at least one specified period and the corresponding adopted metric of each replacement cell RCE1, RCE2 is better than a second threshold during at least one specified period, 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; Either or a combination of the above.

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

[0025] The first modified condition and / or the second modified condition may include one or more of the following conditions: - coded / uncoded BER measurements, -Packet loss, packet error rate (PER), - data rate requirements, - supported bandwidth (e.g., the UE may want to use less bandwidth to reduce power consumption, or may want to have a higher bandwidth and then enter a power saving mode to have a faster data transfer); Based on an event, e.g. a multi-cell event, a trigger from the base station or the network, or a trigger configured in the UE, see (TS36.331 and TS38.331), e.g. Event A3 (neighborhood is offset better than SpCell), Event A4 (neighborhood becomes better than threshold), · Event A5 (SpCell becomes worse than threshold 1 and its neighbors become better than threshold 2).

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

[0027] According to some embodiments, 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 the 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 the first replacement cell RCE1 from the first node NO1 or the second node NO2.

[0029] According to some embodiments, the user equipment 1 is 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.

[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 the 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 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.

[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 to the third node NO3.

[0034] According to some embodiments, the user equipment 1 is configured to receive a second reconfiguration request REC2 comprising 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 the 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 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.

[0037] According to some embodiments, 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. Further disclosed is an embodiment of a method of operating a user equipment 1 for communication over a cellular network CN, the method comprising: - using a user equipment 1 for simultaneously communicating with one or more cells CE of a first node NO1 of a cellular network CN and with 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 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 CL1 between the user equipment 1 and a first one of the cells CE of the 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 RCE1 being the second cell CE of the first node NO1 or the cell CE of the 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 the fourth node NO4, if the monitoring unit 2 detects a second change condition of the second communication link CL2; using a user equipment 1 for transmitting Includes.

[0038] Further disclosed are embodiments of a computer program for performing the above-mentioned method when executed on a processor. FIG. 2 shows in a schematic diagram a further embodiment of a user equipment 1′ and its interaction with a cellular network CN according to the present disclosure.

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

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

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

[0042] According to some embodiments, the user equipment 1' is configured to communicate over 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 and / or second change conditions include: 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; a specified number of retransmissions from the RLC layer that 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 each replacement cell RCE1, RCE2 is better than the corresponding adopted metric of the respective first cell CE during at least one specified period, where one of the adopted metrics of each replacement cell RCE1, RCE2 is better than a threshold during at least one specified period, or where one of the adopted metrics of each first cell CE is worse than a first threshold during at least one specified period and the corresponding adopted metric of each replacement cell RCE1, RCE2 is better than a second threshold during at least one specified period, 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; Either or a combination of the above.

[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 a first modification condition is met.

[0048] According to some embodiments, the user equipment 1' is configured to perform a random access procedure towards the first replacement cell RCE1 after the first change condition is met, 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, the user equipment 1′ is configured to stop the random access procedure towards the first replacement cell RCE1 and maintain the connection with the first cell CE of the first node NO1 if a maximum number of attempts or a maximum delay of the random access procedure towards the first replacement cell RCE1 is reached. According to some embodiments, the user equipment 1' is configured to communicate with the second replacement cell RCE2 after a second modification condition is met.

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

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

[0052] 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 after a first condition is met, where 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 send a second message ME2' to the first node NO1 or the second node NO2 after a second condition is met, the second message ME2' indicating 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 a first node NO1 of the cellular network CN or to a 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 a second node NO2 of the cellular network CN or to a fourth node NO4 of the cellular network CN.

[0055] Further disclosed is an embodiment of a method of operating a user equipment 1' for communication over a cellular network CN, the method comprising: - using a user equipment 1' for simultaneously communicating with one or more cells CE of a first node NO1 of the cellular network CN and with one or more cells CE of a second node NO2 of the cellular network CN; using the user equipment 1' for receiving a first reconfiguration request REC1' comprising an indication that a first cell CE of a first node NO1 communicating with the user equipment 1' has to be replaced by a first replacement cell RCE1 of the cellular network CN, the first reconfiguration request REC1' comprising a first modification condition under which the first reconfiguration request REC1' has to be executed, and / or the user equipment 1' for receiving a second reconfiguration request REC2' comprising an indication that a first cell CE of a second node NO2 communicating with the user equipment 1' has to be replaced by a second replacement cell RCE2' of the cellular network CN, the second reconfiguration request REC2' comprising a second modification condition under which the second reconfiguration request REC2' has to be executed; - using a monitoring unit 2' of the user equipment 1' for monitoring the first changed condition and / or the second changed condition; using the user equipment 1' for replacing the first cell CE of the first node NO1 with a first replacement cell RCE1 if the monitoring unit 2' detects that a first change condition is met and / or for replacing the first cell CE of the second node NO2 with a second replacement cell RCE2 if the monitoring unit 2' detects that a second change condition is met; Includes.

[0056] Further disclosed are embodiments of a computer program for performing the methods according to the present disclosure when executed on a processor. FIG. 3 shows in a schematic diagram a further embodiment of a user equipment 1'' and its interaction with a cellular network CN according to the present disclosure.

[0057] According to some embodiments, the cellular network CN comprises a number of base stations BS connected to a core network COR of the cellular network CN via a xhaul network XN of the cellular network, the user equipment 1 ″ is adapted 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 used respectively as serving base stations SBS, The user equipment 1 ″ is configured 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 adapted to receive, from at least one of the serving base stations SBS, quality information QI on a quality of a communication link CL′ between one of the candidate base stations CBS and a core network COR for the plurality of candidate base stations CBS, The user equipment 1'' is configured to select, based on the quality information QI, 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.

[0058] The xhaul network XN may be a fronthaul network or a backhaul network. It may be wireless or wired. It may also be a different RAT technology than the access technology, 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. In addition, the xhaul network may also include proprietary wired technologies, such as data transmitted over 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, the quality information request QIR requesting the at least one of the serving base stations SBS to transmit a quality information QI.

[0060] In other embodiments, one of the serving base stations SBS may 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 adapted to receive the quality information QI as an unsorted list comprising quality indications of a number 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, based on the sorted list, 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.

[0062] In some embodiments, the sorted list is an indexed list where the index corresponds to an ordering, for example by a network entity, or where the index corresponds to a quality indication value or a criterion that depends on the quality indication value.

[0063] According to some embodiments, the user equipment 1 ″ may transmit the quality information QI as: as a sorted list of multiple candidate base stations CBS, or As an indexed list, where the index corresponds to the ordering, or an indexed list, the index corresponding to a quality indication value; is configured to receive, The user equipment 1'' is configured to select, based on the sorted list, 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.

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

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

[0066] According to some embodiments, the user equipment 1 ″ is configured to communicate over the cellular network CN using dual or multi-connectivity, The user equipment 1 ″ is configured to simultaneously communicate with one of the serving base stations SBS as a master node and one of the serving base stations SBS as a secondary node; The user equipment 1'' may 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 multiple candidate base stations CBS eligible to replace the master node as one of the serving base stations SBS and / or multiple candidate base stations CBS 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, from at least one of the serving base stations SBS, quality information QI on the quality of a communication link CL' between one of the candidate base stations CBS and the core network CN for a plurality of candidate base stations CBS eligible to replace the master node as one of the serving base stations SBS; and / or The user equipment 1'' is configured to receive, from at least one of the serving base stations SBS, quality information regarding the quality of a communication link CL' between one of the candidate base stations CBS and the 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.

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

[0069] Further disclosed is an embodiment of a method of operating a user equipment 1'' for communication via a cellular network CN, the cellular network CN comprising a number 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 a 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 for simultaneously communicating with more of the base stations BS of the cellular network CN used respectively as serving base stations SBS; using a user equipment 1″ for transmitting 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; using a user equipment 1″ for receiving, from at least one of the serving base stations SBS, quality information QI relating to a quality of a communication link CL′ between one of the candidate base stations CBS and a core network COR for the plurality of candidate base stations CBS; using the user equipment 1 ″ for selecting, based on the quality information QI, 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; Includes.

[0070] Further disclosed are embodiments of a computer program for performing the methods 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 also include aspects related to (wireless or wired) backhaul networks, which currently feature nodes with integrated access and backhaul (IAB) functionality. IAB nodes can use a special IAB routing protocol to communicate between different IAB nodes.

[0072] Figure 4 illustrates a dual connected user equipment 1. MR-DC is a feature that allows a multi-Rx / Tx capable UE to be configured 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 acts as a MN and the other node acts as a SN. The MN and SN are connected via a network interface, where at least the MN is connected to the core network (TS37.340).

[0073] As part of the MR-DC configuration, each user equipment (UE) is assigned to two separate scheduled cell groups, namely: >Master Cell Group (MCG) >It is composed of Secondary Cell Groups (SCGs).

[0074] A Master Cell Group (MCG) belongs to a Master Node (MN), and a Secondary Cell Group (MSG) belongs to a Secondary Node (SN). Based on the MR-DC architecture, the MCG and SCG can be either LTE or NR cells, or cells using any other RAT, such as WiFi or technologies of future cellular standards beyond 5G (B5G). The network configures a UE with an MCG and zero or one SCG.

[0075] When a UE is dual-attached to an MN and an 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, the PSCell is the SpCell for the SCG, and the SpCell is the primary cell of the master or secondary cell group. The other cells in the MCG or SCG are secondary cells (SCells).

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

[0077] Below 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 operating on a primary frequency and on which a UE performs an initial connection establishment procedure or initiates a connection re-establishment procedure, or which is indicated as the primary cell in a handover procedure.

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

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

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

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

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

[0083] MR-DC with 5G Core: E-UTRA-NR dual connectivity (NGEN-DC) NG-RAN E-UTRA-NR Dual Connectivity with 5G Core (NGEN-DC): The UE is connected to one ng-eNB acting as MN and one gNB acting as 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), where a UE is connected to one gNB acting as a MN and one ng-eNB acting as a 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), where a UE is connected to one gNB acting as a MN and another gNB acting as a SN. The master gNB is connected to the 5GC via an NG interface and to a secondary gNB via an Xn interface. The secondary gNB may also be connected to the 5GC via an NG-U interface. Furthermore, NR-DC can also be used when a UE is connected to two gNB-DUs, one serving an MCG and the other serving an SCG, connected to the same gNB-CU and acting as both an MN and an SN.

[0086] In the EN-DC, the MCG is configured as specified in TS 36.331. The network provides the configuration parameters of the cell group in the CellGroupConfig IE (TS 38.331-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 (right) with 5GC (TS37.340). In MR-DC, the UE has a single RRC state based on a single C-plane connection to the MN RRC and core network. Each radio node has its own RRC entity that can generate RRC PDUs to be sent to the UE. RRC PDUs generated by the SN can be transmitted to the UE via the MN. The MN always transmits 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 handled using SRBs, which 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) as well as for NAS messages prior to the establishment of SRB2, all using the DCCH logical channel; SRB2 is for NAS messages and all use the DCCH logical channel. 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 all use the DCCH logical channel.

[0089] In the downlink, NAS message piggybacking is used only for one dependent (i.e., with joint success / failure) procedure: bearer establishment / modification / release. In the uplink piggybacking, NAS messages are used only to transport initial NAS messages during connection setup and connection resumption. NOTE 1: NAS messages transferred via SRB2 are also included in the 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 ciphered by PDCP. The NAS applies integrity protection and ciphering to NAS messages independently (see TS 24.501).

[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. The NAS independently applies integrity protection and ciphering to NAS messages (see TS 24.501

[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] FIG. 6 is a diagram showing the radio protocol architecture of MCG, SCG and split bearer from the UE perspective in MR-DC according to EPC (EN-DC) (TS37.340).

[0095] Figure 7 is a diagram showing MCG, SCG and split bearers from the perspective of 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. Split Bearer - In the split bearer option, the second bearer is provided by two nodes. The secondary node does not implement PDCP but implements the RLC layer below.

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

[0098] Figure 8 illustrates the SN addition in EN-DC (TS 37.340). One of the most important steps of the MR-DC procedure is the Secondary Node (SN) addition. The SN addition is done according to (TS 37.340), section 10.2. Some of the most relevant aspects of the procedure are given 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 allowed bearers. The NR RRC configuration message is included in the message. Figure 9 shows SN addition by 5GC (TS37.340).

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

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

[0102] RRC related aspects (measurements): measurement: Measurements can be configured independently by MN and SN (intra-RAT measurements on 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 UE capabilities are not exceeded.

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

[0104] If SRB3 is not configured, the reports of measurements configured by the SN are sent on SRB1. If SRB3 is configured, the reports of measurements configured by the SN are sent on SRB3.

[0105] Measurement results related to the target SN may be provided by the MN to the target SN at the MN that initiated the SN change procedure. Measurement results related to the target SN may be forwarded 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 may be provided by the source MN to the target MN in an inter-MN handover with or without an SN change procedure (see below).

[0106] Detailed description of the configuration of (secondary) cell groups: The main function of the RRC reconfiguration is to configure radio bearers, measurements and Scells or cell groups. The information elements of CGConfig are given in TS 36.331-f60 and TS 38.331-f60.

[0107] SCG Failure Handling: RLF is declared separately for MCG and SCG. If a radio link failure is detected for MCG, the UE initiates the RRC connection re-establishment procedure (TS 37.340). Note that RAN2 includes a new procedure - Fast MCG Recovery in Release 16 (3GPP RAN2, 2019) to address the delays associated with the RRC connection re-establishment procedure. Please note that MCG disorders will not be discussed further herein.

[0108] Instead, we will discuss SCG disorders. The following SCG failure cases are supported: -SCG RLF, -SN change disorder, - For EN-DC, NGEN-DC and NR-DC, SCG configuration failure (messages on SRB3 only), -For EN-DC, NGEN-DC and NR-DC, SCG RRC integrity check failure (on SRB3). When the SCG fails, the UE suspends SCG transmission for all radio bearers and reports SCG failure information to the MN instead of triggering re-establishment.

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

[0110] NOTE: The UE may not continue configuration-based measurements from the SN after an SCG failure in certain cases (e.g., the UE is unable to maintain the timing of the PSCell).

[0111] The UE includes in the SCG Fault Information message the available measurement results according to the current measurement configuration of both the MN and the SN. The MN can process the SCG Fault Information message and decide to keep, modify or release the SN / SCG. In all cases, the measurement results according to the SN configuration and the SCG failure type may be forwarded to the old SN and / or the new SN.

[0112] More detailed explanation of SCG failure: Failure definition: The failure in the specification is called SCG failure in both LTE and NR. As mentioned before, an SCG is a group of cells configured for a UE belonging to an SN. Within an SCG, there exists a Primary Secondary Cell (PSCell). In LTE, this is the cell where the UE is instructed to perform random access or initial PUSCH transmission if the random access procedure is skipped when performing an SCG modification procedure (TS36.331-f60). In NR, the PSCell is the cell where random access is performed when the UE performs a reconfiguration using the Sync procedure (TS38.331-f60).

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

[0114] Actions on failure: When initiating the procedure, the UE: - Abort all SCG DRBs, abort SCG transmission of split DRBs, Reset the SCG-MAC, Stop the T307 timer, The T307 timer is started upon reception of an RRCConnectionReconfiguration message containing MobilityControlInfoSCG. It is stopped upon successful completion of random access on the PSCell, upon initiation of re-establishment, and upon SCG release. · Start sending SCGFailureInformation messages.

[0115] NR specifications: The purpose of this procedure is to inform an LTE or NR MN about an SCG failure encountered by the UE. An SCG failure is reported by the UE (TS 38.331-f60) in the following cases: When detecting a radio link failure of the SCG (section 5.3.10.3), During reconfiguration with SCG sync failure (section 5.3.5.8.3), SCG configuration failure, i.e. inability to comply with a reconfiguration request (section 5.3.5.8.2), Upon integrity check failure indication from SCG lower layers for SRB3. Actions on failure: When initiating the procedure, the UE: Suspends the SCG transmission of all SRBs and DRBs, Reset the SCG MAC, - Stop the T304 timer if it is running Timer T304 is started upon reception of an RRCReconfiguration message containing reconfigurationWithSync. It is stopped upon successful completion of random access on the corresponding SpCell. For SCG T304, the timer is stopped upon SCG release.

[0116] If the UE is in EN-DC, · Initiate transmission of the SCGFailureInformationNR message as specified in TS36.331 clause 5.6.13a.

[0117] All of the above, and according to the current specifications - TS36.331-f60 and TS38.331-f60, only the PCell on the MN and the SpCell on the SN are reported RLF.

[0118] FIG. 13 is a diagram illustrating a PSCell failure. The objective of the present invention is to improve robustness and provide a seamless experience for UEs in a Multi-Radio Dual Connectivity (MR-DC) mode. As mentioned above, MR-DC refers to a system in dual connectivity between an 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) degrades, which may lead to a PSCell failure.

[0119] The robustness of the MR-DC functionality depends on the stability of the links on the PCell and the PSCell. That is, as explained in Section 0, an SCG failure occurs, among other things, when there is a Radio Link Failure (RLF) on a specific cell (SpCell) on a SN (PSCell). In that case, the SCG data radio bearers are released, the MAC is reset, and the appropriate timers are stopped. Considering that the possible deployment of MR-DC is a heterogeneous deployment with small cells and / or SNs using cmWave / mmWave spectrum (e.g., FR2 in 5G), the PSCell radio link may be particularly subject to fluctuations and disturbances, making the multi-connectivity functionality unstable. In particular, operation in the mmWave frequency band, which is 28 GHz as specified by 3GPP, but above 52 GHz, e.g., 60 GHz, leads to a significant increase in path loss and deterioration of signal penetration, which in particular affects the stability and quality of the link.

[0120] Figure 13 shows the potential impact of a radio link failure in a PSCell. A PSCell failure can result in large variations in QoS for the UE, since in this case a larger pipe is not available.

[0121] In case of an SCG failure 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), Fig. 5.7.3.1.1. Currently, the standard does not specify what action the MN shall take after receiving an SCG RLF notification. According to (TS37.340), the MN shall: Hold a SN / SCG, or Change your SN / SCG, or · You may decide to release the SN / SCG.

[0122] When an SCG data radio bearer is released, even if the MN decides to retain the SN / SCG and re-establish the radio bearer or to change the SN / SCG, there may be interruptions in the UE service since there may be large gaps in the data rates due to unavailability of all SCG cells.

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

[0124] Figure 16 shows the intra-SN PSCell / SCG modification. The proposed enhancement aims to improve the robustness of the MR-DC functionality and provide a seamless experience for UEs in MR-DC mode by enabling preemptive actions as the link on the PSCell degrades.

[0125] The cases of inter-SN and intra-SN changes are described separately. Intra-SN PSCell / SCG change is shown in Figure 16. The new SCG may also include the previous SCell and / or the new SCell. Conditions related to quality degradation of the PSCell trigger a decision to change the PSCell / SCG within the same SN.

[0126] Figure 17 shows in a schematic diagram the implementation of a user equipment according to Figure 1 of 5G and its interaction with the cellular network. Intra-SN PSCell / SCG change is shown. The UE decides to change the PSCell and therefore the SCG based on a trigger condition that takes into account the quality of the existing PSCell.

[0127] This enhancement aims to give the UE the right to request a PSCell change due to a degradation in the quality of the PSCell. To that end, the UE may have a built-in trigger condition to initiate a PSCell change. For example, the trigger condition may be configured as x instances where timer T310 (RLF timer) has started but has not expired within y seconds. The trigger condition may also be based on the number of retransmissions from the RLC layer on the PSCell being less than the maximum number for which the UE detects a radio link failure. Based on the trigger condition, the UE decides to change the PSCell and SCG accordingly. This enhancement also assumes that the UE creates a pool of candidate PSCells. It then has to provide the SN with a PSCell preference from this pre-configured pool by transmitting an ordered list of PSCells. The pool of candidate cells may be created by one or more of the following: The UE monitors potential candidates by measurements such as correlation of synchronization signals with reference signals (e.g., channel state information reference signal, beamstream 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 that evaluates the quality of the Channel State Information (CSI) to create the pool (3GPP, 2019).

[0128] The MN and / or the SN, and / or one of the SCells and / or SpCells in the MN or SN, may provide the list of candidates directly to the UE; A combination of the above.

[0129] In addition to the PSCell pool, the UE may also provide the network with an ordered list of SCells 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 SCells. PSCells and SCells may be swapped between pools.

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

[0131] 1) Upon deciding to change the PSCell, the UE sends a PSCell / SCG reconfiguration request to the SN. The request can be sent 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 message containing the new PSCell / SCG radio resource configuration, where the RRCReconfigurationRequest message contains an indicator that the message is a response to a PSCellChangeRequest.

[0133] 3) The UE performs a Random Access (RA) procedure to the new cell. The UE may be configured with a maximum number of attempts or maximum delay for the RA procedure (less than that specified for detection of SCG RLF failure), in which case the UE reports 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 now piggybacked 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 inform the MN of the new PSCell / SCG configuration. It is also possible to have a procedure that is mainly handled between the UE and the MN (RRC reconfiguration), 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 or not, according to the existing specifications of the SN modifications.

[0136] NOTE 1: Steps 3) and 4) are interchangeable. As explained above, if a Random Access (RA) is performed in step 3), a potential problem with the RA procedure means that the old cell is not released and the UE reports an RRCReconfigurationFailure via the MN or directly to the SN.

[0137] FIG. 18 shows in a schematic diagram the implementation of a user equipment according to FIG. 2 in 5G and its interaction with the cellular network. An intra-SN PSCell change is shown. The SN can decide to pre-configure its resources (as shown in FIG. 18). When the conditions are met, the UE performs a change of the PSCell, and therefore the SCG, based on a trigger condition that takes into account the quality of the existing PSCell.

[0138] This enhancement is based on the Conditional Handover (CHO) feature currently being discussed for inclusion in Release 16 (3GPP RAN2, 2019), where the network is responsible for the PSCell / SCG change. The UE only acts after the triggering conditions are met. So-called conditional PSCell addition and SCG change are also proposed in (MediaTek, 2019) and (NEC, 2019). The triggering conditions can be the same as those mentioned above.

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

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

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

[0142] Figure 19 illustrates an inter-SN PSCell change. A condition related to a degradation in the quality of the PSCell triggers a decision to switch to a new SN and change the PSCell and SCG accordingly. In inter-SN PSCell / SCG change enhancement, the PSCell and the new SCG belong to different SNs. This enhancement is described below.

[0143] Figure 20 shows in a schematic diagram the implementation of a user equipment according to Figure 1 in 5G and its interaction with the cellular network. The figure shows an inter-SN PSCell change where the procedure is mainly handled between the UE and the SN. The UE decides to change the SN, and therefore the PSCell / SCG, based on a trigger condition that takes into account the quality of the existing PSCell.

[0144] This enhancement aims to give the UE the right to request a SN change, and thus a PSCell / SCG change, e.g. due to mobility and generally due to 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. It then has to provide the current SN with SN / PSCell preferences from these pre-configured pools, e.g. by sending an ordered list of SNs and PSCells. The pool of candidate SNs and PSCells can be created similarly to above.

[0145] In addition to the SN and PSCell pool, the UE may also provide the network with an ordered list of SCells on the new SN for the new SCG. The SCell pool may be created similarly to the PSCell pool. The PSCells and SCells may be swapped between pools. The following steps are proposed, as shown in FIG.

[0146] 1) Upon deciding to change SN / PSCell, 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 the SN-S (using SRB3). The changePSCellRequest message includes an indicator that it is an SN change request. If the MN is not involved, the SN-S informs the MN of the request.

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

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

[0149] 4) An RRCReconfigurationRequest message is sent from the SN-S (directly or via the MN) to the UE with 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 to the SN-T and the new PSCell. The UE may be configured with a maximum number of attempts or maximum delay for the RA procedure (less than that specified for detection of SCG RLF failure), in which case the UE reports RRCReconfigurationFailure and does not release the SN-S and existing PSCell / SCG configuration.

[0151] 6) The UE sends an RRCReconfigurationComplete message again via the MN or directly to the SN-S. An indication to release the SN-S is now piggybacked 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 inform the MN of the new PSCell / SCG configuration.

[0152] It is also possible to have a procedure that is mainly handled between the UE and the MN (RRC reconfiguration), 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 or not, according to the existing specifications of the SN modifications.

[0153] Note that steps 5) and 6) can be interchanged. As explained above, if RA is performed in step 5), a potential problem with the RA procedure means that the SN-S is not released and the UE reports RRCReconfigurationFailure to the SN-S directly or via the MN.

[0154] Figure 21 shows in a schematic diagram the implementation of a user equipment according to Figure 2 of 5G and its interaction with the cellular network. An inter-SN PSCell change is shown. The network decides to pre-configure a new SN, and therefore a PSCell / SCG, based on a trigger condition that takes into account the quality of the existing PSCell. Figure 21 shows an inter-SN change using CHO as a basis. It is also possible to let the MN decide to change the SN and PSCell / SCG, which is not shown in FIG.

[0155] The network (MN or SN) already has a mechanism to create a pool of candidate SNs, PSCells, and SCells that are sent to the UE. As shown in FIG. 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 SN / PSCell change. This figure shows the case where the SN-S sends a request for resource pre-configuration to the SN-T. 2) The SN-T sends a confirmation of pre-configured resources indicating full availability or the difference between requested and available resources. 3) If the MN does not initiate pre-configuration, the SN-S informs the MN about the SN-T pre-configured resources.

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

[0158] 5) The UE performs a random access (RA) procedure to the SN-T and the new PSCell. The UE may be configured with a maximum number of attempts or maximum delay for the RA procedure (less than that specified for detection of SCG RLF failure), in which case the UE reports RRCReconfigurationFailure and does not release the SN-S and 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 now piggybacked 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 inform the MN of the new SN / PSCell / SCG configuration. Existing procedures for the core network can be preserved, which also depend on whether the MN is involved or not, according to the existing specifications of the SN modification.

[0161] Note that steps 5) and 6) can be interchanged. As explained above, if RA is performed in step 5), a potential problem with the RA procedure means that the SN-S is not released and the UE reports RRCReconfigurationFailure to the SN-S 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. A similar situation exists for conditional HO (CHO). In CHO to a 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 is not considered in this selection. The UE is then configured with the necessary configuration to connect to its selected target base station. In CHO, a 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 certain link quality threshold is met by the UE, the UE can automatically perform HO to its target base station without sending a measurement report to its source base station. Furthermore, the UE can directly perform HO without waiting for a 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 not compared or exchanged and is not considered in this selection.

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

[0165] The change or modification of the SN may be initiated by the MN or the SN. The quality of the backhaul links of different base stations is not compared and is not taken into account 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. If 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 should be selected to serve the UE (e.g., to handover or as a SN), the backhaul links between each of these two base stations and the core network (CN) are not considered or compared.

[0167] Figure 24 shows the impact of 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 backhaul can be implemented. For example, in Figure 24, consider the case where the signal the UE gets from IAB node 1 is stronger than the signal from IAB node 1', but the power of both is above the acceptable threshold for communication to the UE. Meanwhile, the signal from / to IAB node 1 experiences a larger 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 that it is transparent to the UE whether the serving node is an IAB node or not.

[0168] HO Scenario: In Fig. 24, Node 1 and Node 1' are candidates for HO. In the state of the art, neither the serving base station nor the UE has information of the backhaul links of these two candidates.

[0169] Dual Connectivity Scenario / Multi-Connectivity Scenario: In Fig. 24, Node 1 and Node 1' are candidates to become SN. In the state of the art, neither the MN nor the UE has any information of 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 decide which one is more suitable for the required QoS of the service the UE is using. The solution includes two possible reinforcements that can be applied together or separately. Strengthening Option 1: Consider the backhaul conditions (quality of the backhaul link) Information on the quality of the backhaul is transferred between base stations, for example via X2 or Xn. In the state of the art, acknowledgements are transferred via X2 / Xn.

[0171] In this invention, two enhancements are proposed, one is to transfer the indication of the quality of the backhaul (from BS to CN), the other proposed enhancement is to enable UE-initiated base station selection in dual / multi-connectivity, e.g., HO. FIG. 25 shows a basic procedure (procedure 0) for taking the backhaul situation into consideration in base station selection.

[0172] Step 0: 1. The UE provides a list of candidate base stations to the current serving base station / MN, which forwards this list from the UE to a specific entity in the network, which may be the serving base station / MN itself. NOTE 1 – Some candidates may be IAB nodes. NOTE 2 – The current serving base station / MN may be an IAB node.

[0173] 2. A 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 a backhaul link does not exist, 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 may be the entity that estimates or measures the quality of the backhaul links. 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 links from the core network to each IAB node. For example, the number of hops in the path can give an estimate of the delay of the path.

[0174] 3. If 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 measurements 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 the action, e.g., initiates HO / CHO to the selected base station, initiates a secondary link with the selected base station, exchanges MN and SN. When the second proposed enhancement is available and the UE is able to initiate HO and / or SN establishment, two possible procedures are proposed. FIG. 26 shows a schematic diagram of a 5G implementation of a user equipment according to FIG. 3 and its interaction with a cellular network.

[0177] Step 1: 1 to 3: Same as step 0 (Figure 25). 4. The serving base station / MN transmits the quality of the backhaul link to the UE. 5. The UE sorts the list of candidate base stations taking into account its own measurements and backhaul information obtained from the network. 6. The UE selects a base station, decides on an action, triggers the action, e.g., 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), and the UE sorts base stations (step 5) and makes a decision (step 6). Figure 27 shows in a schematic diagram a further implementation of the user equipment according to Figure 3 in 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 measurements collected from the UE to sort the candidate base stations / nodes. This alternative procedure is shown in Figure 27 and described below.

[0179] Step 2: 1 to 4: Same as step 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, decides on an action, triggers the action, e.g., HO to the selected base station, and initiates a secondary link with the selected base station.

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

[0181] In some embodiments, a programmable logic device (e.g., a field programmable gate array) may 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 may 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 an apparatus, it will be apparent that these aspects also represent a description of a corresponding method, and that a block or apparatus corresponds to a method step or feature of a method step. Similarly, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus.

[0183] Depending on specific implementation requirements, the method embodiments of the present invention can be implemented using an apparatus comprising hardware and / or software. The 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, having electronically readable control signals stored therein and cooperating (or capable of cooperating) with a programmable computer system such that the methods are performed. Depending on certain implementation requirements, embodiments of the inventive method may be implemented using apparatus comprising hardware and / or software.

[0184] Some or all of the method steps may be performed by (or using) hardware apparatus such as a microprocessor, a programmable computer or electronic circuitry. Some of the most important method steps may be performed by such apparatus.

[0185] Some embodiments according to the invention comprise a data carrier having electronically readable control signals which cooperate with a programmable computer system to perform one of the methods described herein.

[0186] Generally, embodiments of the present invention may be implemented as a computer program product having a program code operative to perform one of the methods when the computer program product runs on a computer. The program code may for example be stored on a machine readable carrier.

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

[0188] A further embodiment comprises a processing means, for example a computer, or a programmable logic device, in particular a processor, comprising hardware configured or adapted to perform one of the methods described herein. A further embodiment comprises a computer having installed thereon the computer program for performing one of the methods described herein. In general, the methods are advantageously performed by any apparatus comprising hardware and / or software.

[0189] Although the present invention has been described with respect to several embodiments, there are modifications, permutations, and equivalents that fall within the scope of the present invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. Therefore, it is intended that the following appended claims be interpreted to include all such modifications, permutations, and equivalents that fall within the true spirit and scope of the present invention. [Explanation of symbols]

[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 Messages 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 forLTE 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. 1. A user equipment for communication over a cellular network, comprising: the user equipment is configured to communicate simultaneously with one or more cells of a first node that is a master node for dual connectivity or multi-connectivity of the cellular network and with one or more cells of a second node that is a secondary node for dual connectivity or multi-connectivity of the cellular network; 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 must 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 must be executed, and a second reconfiguration request including an indication that a first cell of the second node communicating with the user equipment must 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 must be executed; the user equipment comprises a monitoring unit for monitoring the first change condition and the second change condition; The user equipment is configured 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 met, and 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 met.

2. 2. The user equipment of claim 1, configured to replace the first cell of the first node by the first replacement cell such that the first cell of the first node is released by the user equipment before the user equipment connects to the first replacement cell, and to replace the first cell of the second node by the second replacement cell such that the first cell of the second node is released by the user equipment before the user equipment connects to the second replacement cell.

3. 2. The user equipment of claim 1, wherein the user equipment is configured to replace the first cell of the first node by the first replacement cell such that the user equipment connects to the first replacement cell before the first cell of the first node is released by the user equipment, and to replace the first cell of the second node by the second replacement cell such that the user equipment connects to the second replacement cell before the first cell of the second node is released by the user equipment.

4. 2. The user equipment of claim 1, wherein the first cell of the first node is a specific cell or a secondary cell of a master cell group for dual connectivity or multi-connectivity, and the first cell of the second node 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 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 that is less than a maximum number of times that the user equipment 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 becomes better than the corresponding adopted metric of the respective first cell during at least one designated period of time, a multi-cell event where one of the adopted metrics of the respective replacement cells 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 becomes worse than a first threshold during at least one designated period of time and the corresponding adopted metric of the respective replacement cell becomes better than a second threshold during the at least one designated period of time, the multi-cell event being triggered by the user equipment, one of the nodes or another device of the cellular network.

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 of claim 1, wherein the user equipment is configured to receive the second reconfiguration request from the first node or the second node.

7. 7. The user equipment of claim 1, wherein the user equipment is configured to communicate with the first replacement cell after the first change condition is met.

8. 8. The user equipment of claim 1, wherein the user equipment is configured to perform a random access procedure towards the first replacement cell after the first change condition is met, and wherein the user equipment is configured to release the first cell of the first node after the random access procedure towards the first replacement cell is successfully completed.

9. 9. The user equipment of claim 1, wherein the user equipment is configured to communicate with the second replacement cell after the second change condition is met.

10. 10. The user equipment of claim 1, wherein the user equipment is configured to perform a random access procedure towards the second replacement cell after the second change condition is met, and wherein the user equipment is configured to release the first cell of the second node after the random access procedure towards the second replacement cell is successfully completed.

11. 11. The user equipment of claim 1, wherein the user equipment is configured to transmit a first message to the first node or the second node after the first change condition is met, the first message indicating that the first cell of the first node has been released.

12. 12. The user equipment of claim 1, wherein the user equipment is configured to transmit a second message to the first node or the second node after the second change condition is met, the second message indicating that the first cell of the second node has been released.

13. 13. The user equipment according to claim 1, wherein the user equipment is configured to derive from the first reconfiguration request whether the first replacement cell belongs to the first node of the cellular network or to a third node of the cellular network, and to derive from the second reconfiguration request whether the second replacement cell belongs to the second node of the cellular network or to a fourth node of the cellular network.

14. 1. A method of operating a user equipment for communication over a cellular network, the method comprising: using the user equipment to communicate simultaneously with one or more cells of a first node that is a master node for dual connectivity or multi-connectivity of the cellular network and with one or more cells of a second node that is a secondary node for dual connectivity or multi-connectivity of the cellular network; using the user equipment for receiving a first reconfiguration request including an indication that a first cell of the first node communicating with the user equipment should 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 should be executed, and the user equipment for receiving a second reconfiguration request including an indication that a first cell of the second node communicating with the user equipment should 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 should be executed; using a monitoring unit of said user equipment for monitoring said first change condition and said second change condition; using the user equipment to replace the first cell of the first node with the first replacement cell if the monitoring unit detects that the first change condition is met, and to replace the first cell of the second node with the second replacement cell if the monitoring unit detects that the second change condition is met. A method comprising:

15. A computer program for performing the method according to claim 14 when the computer program is run on a processor.

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