Method, apparatus and computer program product for replacement of secondary cells

Abstract

The present disclosure relates to a user equipment for communicating on a cellular network, wherein the user equipment is configured to simultaneously communicate with one or more cells of a first node of the cellular network and with one or more cells of a second node of the cellular network, and a method for operating such a user equipment for communicating on a cellular network. In addition, the present disclosure relates to a user equipment for communicating on a cellular network, wherein the cellular network includes a plurality of base stations connected to a core network of the cellular network via an xhaul network of the cellular network, wherein the user equipment is configured to communicate with one of the base stations of the cellular network as a serving base station, or to simultaneously communicate with a plurality of base stations of the cellular network each serving as a serving base station, and a method for operating such a user equipment for communicating on a cellular network.

Description

Technical Field

[0001] The present disclosure relates to user equipment for communicating on a cellular network and methods for operating user equipment for communicating on a cellular network. Summary of the invention

[0002] In one aspect, the present disclosure relates to a user equipment for communicating on a cellular network;

[0003] wherein the user equipment is configured to simultaneously communicate 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;

[0004] The user equipment includes a monitoring unit, which is used to monitor the quality of a first communication link between the user equipment and a first cell in a cell of the first node and / or to monitor the quality of a second communication link between the user equipment and a first cell in a cell of the second node;

[0005] The user equipment is configured to send

[0006] A first replacement request, when the monitoring unit detects a first change condition of the first communication link, is used 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 the cell of the third node; and / or

[0007] The second replacement request is used to replace the first cell of the second node with a second replacement cell when the monitoring unit detects a second change condition of the second communication link. The second replacement cell is the second cell of the second node or the cell of the fourth node.

[0008] In a further aspect, the present disclosure relates to a method for operating a user equipment to communicate on a cellular network; the method comprising the steps of:

[0009] communicating 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 using a user equipment;

[0010] Using a monitoring unit of the user equipment to monitor the quality of a first communication link between the user equipment and a first cell in the cells of the first node and / or to monitor the quality of a second communication link between the user equipment and a first cell in the cells of the second node;

[0011] Send using user device

[0012] A first replacement request, when the monitoring unit detects a first change condition of the first communication link, is used 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 the cell of the third node; and / or

[0013] The second replacement request is used to replace the first cell of the second node with a second replacement cell when the monitoring unit detects a second change condition of the second communication link. The second replacement cell is the second cell of the second node or the cell of the fourth node.

[0014] In a further aspect, the present disclosure relates to a user equipment for communicating on a cellular network;

[0015] wherein the user equipment is configured to simultaneously communicate 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;

[0016] The user equipment is configured to receive a first reconfiguration request, which includes an indication that a first cell of a first node communicating with the user equipment must be replaced by a first replacement cell of the cellular network, wherein the first reconfiguration request includes a first change condition, under which the first change condition the first reconfiguration request must be executed, and / or is configured to receive a second reconfiguration request, which includes an indication that a first cell of a second node communicating with the user equipment must be replaced by a second replacement cell of the cellular network, wherein the second reconfiguration request includes a second change condition, under which the second change condition the second reconfiguration request must be executed;

[0017] Wherein, the user equipment comprises a monitoring unit for monitoring the first change condition and / or the second change condition; and

[0018] 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 / or is configured 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.

[0019] In a further aspect, the present disclosure relates to a method for operating a user equipment to communicate on a cellular network; the method comprising the steps of:

[0020] communicating 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 using a user equipment;

[0021] receiving, with the user equipment, a first reconfiguration request, the request comprising an indication that a first cell of a first node in communication with the user equipment must be replaced by a first replacement cell of the cellular network, wherein the first reconfiguration request comprises a first change condition under which the first reconfiguration request must be performed, and / or receiving, with the user equipment, a second reconfiguration request, the request comprising an indication that a first cell of a second node in communication with the user equipment must be replaced by a second replacement cell of the cellular network, wherein the second reconfiguration request comprises a second change condition under which the second reconfiguration request must be performed;

[0022] monitoring the first change condition and / or the second change condition using a monitoring unit of the user equipment; and

[0023] Using the user equipment, when the monitoring unit detects that a first change condition is met, the first cell of the first node is replaced with a first replacement cell, and / or when the monitoring unit detects that a second change condition is met, the first cell of the second node is replaced with a second replacement cell.

[0024] In a further aspect, the present disclosure relates to a user equipment for communicating on a cellular network, wherein the cellular network comprises a plurality of base stations connected to a core network of the cellular network via an xhaul network of the cellular network;

[0025] The user equipment is configured to communicate with one of the base stations of the cellular network used as a serving base station, or is configured to communicate simultaneously with a plurality of base stations of the cellular network respectively used as serving base stations;

[0026] wherein the user equipment is configured to send a list of candidate base stations to one of the serving base stations, the candidate base stations being eligible to replace at least one of the serving base stations;

[0027] wherein the user equipment is configured to receive, from at least one serving base station, quality information about a quality of a communication link between one of the candidate base stations and a core network for a plurality of candidate base stations;

[0028] The user equipment is configured to select one or more candidate base stations based on the quality information to replace one or more base stations currently used as serving base stations.

[0029] In a further aspect, the present disclosure relates to a method for operating a user equipment to communicate on a cellular network, wherein the cellular network includes a plurality of base stations connected to a core network of the cellular network via an xhaul network of the cellular network; the method comprising the steps of:

[0030] Using the user equipment to communicate with one of the base stations of the cellular network used as a serving base station, or to communicate simultaneously with a plurality of base stations of the cellular network each used as a serving base station;

[0031] sending, using a user equipment, a list of candidate base stations to one of more other base stations in the cellular network to become a new serving base station, the candidate base stations being eligible to replace at least one of the serving base stations;

[0032] receiving, using a user equipment, from at least one serving base station, quality information regarding a quality of a communication link between one of the candidate base stations and a core network for a plurality of candidate base stations;

[0033] One or more candidate base stations are selected using the user equipment based on the quality information to replace one or more base stations currently serving as a serving base station. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Preferred embodiments of the present invention are discussed below with reference to the accompanying drawings, in which:

[0035] Figure 1 An embodiment of a user equipment according to the present disclosure and its interaction with a cellular network are schematically shown;

[0036] Figure 2 A further embodiment of a user equipment according to the present disclosure and its interaction with a cellular network is schematically shown;

[0037] Figure 3 A further embodiment of a user equipment according to the present disclosure and its interaction with a cellular network is schematically shown;

[0038] Figure 4 A dual connected user equipment is shown;

[0039] Figure 5 Shown is the control plane architecture of EN-DC (left) and MR-DC with 5GC (right) - (TS37.340);

[0040] Figure 6 shows the radio protocol architecture of MCG, SCG and split bearers in MR-DC with EPC (EN-DC) (TS37.340) from the UE perspective;

[0041] Figure 7 shows MCG, SCG and split bearers in MR-DC with 5GC (NGEN-DC, NE-DC and NR-DC) from the perspective of user equipment;

[0042] Figure 8 The addition of SN in EN-DC (TS37.340.) is shown;

[0043] Fig. 9 SN addition with 5GC (TS37.340.) is shown;

[0044] Fig.10 It is shown that according to (TS37.340.), Fig.10 .5.2-1 SN changes - MN starts with 5GC in MRDC;

[0045] Fig.11 It is shown that according to (TS37.340.), Fig.10 .5.12-2 SN changes in 5GC–SN-initiated MRDC;

[0046] Fig.12 MN switching in EN-DC with SgNb change according to (TS37.340.) is shown;

[0047] Figure 13 shows a PSCell failure;

[0048] Figure 14 shows the SN changes after RLF on SCG;

[0049] Figure 15 shows the SgNb correction after RLF on SCG;

[0050] Fig.16 PSCell / SCG changes within SN are shown;

[0051] Fig.17 The schematic diagram shows the Figure 1 implementation of user equipment in 5G and its interaction with cellular networks;

[0052] FIG. 18 schematically shows a Figure 2 implementation of user equipment in 5G and its interaction with cellular networks;

[0053] Fig.19 Inter-SN PSCell changes are shown;

[0054] FIG. 20 schematically shows a Figure 1 implementation of user equipment in 5G and its interaction with cellular networks;

[0055] Fig.21 The schematic diagram shows the Figure 2 implementation of user equipment in 5G and its interaction with cellular networks;

[0056] Fig. 22 The basic CHO procedure (Ericsson "R2-1900404 Conditional Handover) is shown;

[0057] Fig.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;

[0058] Fig.24 shows the impact of backhaul on the quality of the path from UE to the core network in the case of IAB;

[0059] Fig.25 The basic process of considering backhaul status in base station selection is shown (process 0);

[0060] Fig.26 The schematic diagram shows the Figure 3 implementation of user equipment in 5G and its interaction with cellular networks; and

[0061] Fig. 27 The schematic diagram shows the Figure 3 Further implementation of user equipment in 5G and its interaction with cellular networks. DETAILED DESCRIPTION

[0062] Identical or equivalent elements or elements having the same or equivalent functions are denoted by identical or equivalent reference numerals in the following description. It must 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 embodiments of the other figures. This applies in particular to the definitions and features contained in the following description.

[0063] In the following description, a number of details are set forth to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other examples, well-known structures and devices are shown in block diagram form rather than in detail to avoid confusing embodiments of the present invention. In addition, unless otherwise specifically stated, the features of the different embodiments described below may be combined with each other.

[0064] Figures 1 to 3 The embodiments of the present disclosure are shown in a general manner. In contrast, Figures 4 to 27 An embodiment of the present disclosure in multi-radio dual connectivity in 5G is shown. However, those skilled in the art will appreciate that the present disclosure is not limited to the latter. In addition, those skilled in the art will appreciate that the features explained in the context of 5G are also possible in other cellular networks.

[0065] Figure 1 An embodiment of a user equipment 1 according to the present disclosure and its interaction with a cellular network CN is shown in a schematic diagram.

[0066] According to some embodiments, the user equipment 1 for communicating via the cellular network CN is configured to simultaneously communicate 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;

[0067] The user equipment 1 includes a monitoring unit 2, which is used to monitor the quality of a first communication link CL1 between the user equipment 1 and a first cell CE in a cell CE of a first node NO1 and / or to monitor the quality of a second communication link CL2 between the user equipment 1 and a first cell CE in a cell CE of a second node NO2;

[0068] The user equipment 1 is configured to send

[0069] A first replacement request REP1, in case the monitoring unit 2 detects a first change condition of the first communication link CL1, is used 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; and / or

[0070] The second replacement request REP2 is used to replace the first cell CE of the second node NO2 with a second replacement cell RCE2 when the monitoring unit 2 detects a second change condition of the second communication link CL2. The second replacement cell RCE2 is the second cell CE of the second node NO2 or the cell of the fourth node NO4.

[0071] The user equipment 1 may include a mobile terminal, or a fixed terminal, or a cellular IoT user equipment, or a vehicle-mounted user equipment, or a vehicle-mounted 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 having network connectivity that enables an item or device to communicate using a wireless communication network, such as a sensor or actuator, or any other item or device having network connectivity that enables an item or device to communicate using a sidelink wireless communication network, such as a sensor or actuator, or any network entity with sidelink capabilities. The user equipment may also be part of an integrated access and backhaul (IAB) node, such as the mobile terminal (MT) part of the IAB node.

[0072] The user equipment 1 may be configured for downlink / uplink / sidelink communications using resources, for example, from a set of downlink / uplink / sidelink resources of a cellular network.

[0073] A cellular network may include multiple base stations, wherein the base station may include a macrocell base station, or a small cell base station, or a central unit of a base station, or a base station operating as a cloud-RAN (CRAN), or a distributed unit of a base station, or a road side unit (RSU), or a cell, or a node, or a special 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 in the context of NR or 5G core, or any one or more of the sending / receiving points TRPs that enable an item or device to communicate using a wireless communication system, wherein a network connection is provided for the item or device to communicate using the wireless communication network.

[0074] A cell CE is a device that uses a set of time / frequency / code (eg, as in CDM) / space (eg, partitioning) / spatial coding (beams and / or precoding) resources.

[0075] In some embodiments, the user equipment 1 is configured to simultaneously communicate 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 .

[0076] The term "first cell CE" refers to any specific cell CE among the cells so as to distinguish it from other cell CEs of the corresponding node NO. In other words, the term does not refer to any order of the cell CEs.

[0077] The monitoring unit 2 may include a software module configured to run on a processor of the user equipment 1 .

[0078] According to some embodiments, the user equipment 1 is configured to communicate via the cellular network CN using dual connectivity or multi-connectivity. Dual connectivity means communicating with two base stations simultaneously, while multi-connectivity means communicating with more than two base stations simultaneously, for example three or more base stations.

[0079] According to some embodiments, the first node NO1 is a base station and a master node for dual connectivity or multiple connectivity; and wherein the second node NO2 is a base station and a secondary node for dual connectivity or multiple connectivity.

[0080] According to some embodiments, the first cell CE of the first node NO1 is a special cell or a secondary cell of a primary cell group for dual connectivity or multiple connectivity; and / or the first cell CE of the second node NO2 is a special cell or a secondary cell of a secondary cell group for dual connectivity or multiple connectivity.

[0081] According to some embodiments, the first change condition and / or the second change condition is any one or a combination of the following:

[0082] a specified number of instances in which the timer for the radio link failure timer was started but did not expire within a specified period of time;

[0083] A specified number of HARQ retransmissions from the PHY layer;

[0084] The number of designated retransmissions from the RLC layer is less than the maximum number of radio link failures detected by the user equipment (1);

[0085] Use a weighted average or moving average or any other specified statistical method of the metrics employed that indicate degradation of signal quality;

[0086] Coded or uncoded bit error rate;

[0087] Packet loss rate or packet error rate;

[0088] Data rate requirements;

[0089] Supported bandwidth;

[0090] A multi-cell event, such as a multi-cell event in which one of the metrics adopted by the corresponding replacement cells RCE1, RCE2 becomes better than the corresponding metric adopted by the corresponding first cell CE within at least one specified period, a multi-cell event in which one of the metrics adopted by the corresponding replacement cells RCE1, RCE2 becomes better than a threshold within at least one specified period, or a multi-cell event in which one of the metrics adopted by the corresponding first cell CE becomes worse than a first threshold within at least one specified time period and the corresponding metric adopted by the corresponding replacement cells RCE1, RCE2 becomes better than a second threshold within at least one specified time period, wherein the multi-cell event is triggered by user equipment 1, one of nodes NO1, NO2 or another device of the cellular network CN.

[0091] The term "employed metric" may refer to a channel quality indicator (CQI), reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), signal-to-noise and interference ratio (SINR), any metric for assessing the quality of channel state information (CSI), or any other suitable metric.

[0092] The first change condition and / or the second change condition may include one or more of the following:

[0093] - Coded / uncoded BER measurements,

[0094] -Packet loss, packet error rate (PER),

[0095] - Data rate requirements,

[0096] - supported bandwidth (e.g., the UE may wish to use less bandwidth to reduce power consumption, or it may wish to have a higher bandwidth to transfer data faster and then enter a power saving mode),

[0097] - Event-based, such as multi-cell events, triggered from the base station or network or configured in the UE - see (TS 36.331 and TS 38.331), for example:

[0098] o Event A3 (neighbor becomes better than SpCell at offset),

[0099] o Event A4 (neighbor becomes better than threshold),

[0100] o Event A5 (SpCell becomes worse than Threshold 1, while the neighbor becomes better than Threshold 2).

[0101] According to some embodiments, the user equipment 1 is configured to send a first replacement request REP1 to the first node NO1 or the second node NO2.

[0102] According to some embodiments, the user equipment 1 is configured to send a second replacement request REP2 to the first node NO1 or the second node NO2.

[0103] According to some embodiments, the user equipment 1 is configured to identify a candidate cell CE for the first replacement cell RCE1 or the second replacement cell RCE2 by measuring signals of possible candidate cells.

[0104] According to some embodiments, the user equipment 1 is configured to receive a first list LI1 of candidate cells CE for the first replacement cell RCE1 from the first node NO1 or from the second node NO2.

[0105] 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 from the second node NO2.

[0106] According to some embodiments, the user equipment 1 is configured to receive a first reconfiguration request REC1 comprising an indication indicating which cell CE of the cellular network CN is the first replacement cell RCE1 and an indication indicating that the first reconfiguration request REC1 is a response to the first replacement request REP1.

[0107] According to some embodiments, the user equipment 1 is configured to receive a first reconfiguration request REC1 from the first node NO1 or from the second node NO2.

[0108] According to some embodiments, the user equipment is configured to communicate with the first replacement cell RC1 after receiving the first reconfiguration request REC1 by the user equipment 1 .

[0109] 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 , wherein the first message ME1 indicates that the first cell CE of the first node NO1 has been released after receiving the first reconfiguration request REC1 by the user equipment 1 .

[0110] According to some embodiments, the user equipment 1 is configured to indicate within the first replacement request REC1 whether the first replacement cell RCE1 belongs to the first node NO1 or to the third node NO3.

[0111] According to some embodiments, the user equipment 1 is configured to receive a second reconfiguration request REC2 comprising an indication indicating which cell CE of the cellular network CN is the second replacement cell RCE2 and an indication indicating that the second reconfiguration request REC2 is a response to the second replacement request RCE2.

[0112] According to some embodiments, the user equipment 1 is configured to receive a second reconfiguration request REC2 from the first node NO1 or from the second node NO2.

[0113] According to some embodiments, the user equipment 1 is configured to communicate with the second replacement cell RCE2 after receiving the second reconfiguration request REC2 by the user equipment 1 .

[0114] 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, wherein the second message ME2 indicates that after receiving the second reconfiguration request REC by the user equipment 1, the first cell CE of the second node NO2 has been released.

[0115] According to some embodiments, the user equipment 1 is configured to indicate within the second replacement request REC2 whether the second replacement cell RCE2 belongs to the second node NO2 or the fourth node NO4.

[0116] Further disclosed is an embodiment of a method for operating a user equipment 1 for communicating over a cellular network CN; the method comprising the following steps:

[0117] using the user equipment 1 to simultaneously communicate 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;

[0118] Using the monitoring unit 2 of the user equipment 1, for monitoring the quality of the first communication link CL1 between the user equipment 1 and a first cell CE in the cell CE of the first node NO1 and / or for monitoring the quality of the second communication link CL1 between the user equipment 1 and a first cell CE in the cell CE of the second node NO2;

[0119] Use user device 1 to send

[0120] A first replacement request REP1, in case the monitoring unit 2 detects a first change condition of the first communication link CL1, is used 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; and / or

[0121] The second replacement request REP2 is used to replace the first cell CE of the second node NO2 with a second replacement cell RCE2 when the monitoring unit 2 detects a second change condition of the second communication link CL2. The second replacement cell RCE2 is the second cell CE of the second node NO2 or the cell of the fourth node NO4.

[0122] Further disclosed are embodiments of a computer program for performing the above method when run on a processor.

[0123] Figure 2 A further embodiment of a user equipment 1 ′ according to the present disclosure and its interaction with a cellular network CN is schematically shown.

[0124] According to some embodiments, the user equipment 1 ′ for communicating through the cellular network CN is configured to simultaneously communicate 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;

[0125] The user equipment 1' is configured to receive a first reconfiguration request REC1', which includes an indication that a first cell CE of a first node NO1 communicating with the user equipment 1' must be replaced by a first replacement cell RCE1 of the cellular network CN, wherein the first reconfiguration request REC1' includes a first change condition, under which the first change condition the first reconfiguration request REC1' must be executed, and / or is configured to receive a second reconfiguration request REC2', which includes an indication that a first cell CE of a second node NO2 communicating with the user equipment 1' must be replaced by a second replacement cell RCE2' of the cellular network CN, wherein the second reconfiguration request RCE2' includes a second change condition, under which the second reconfiguration request RCE2' must be executed;

[0126] The user equipment 1' comprises a monitoring unit 2' for monitoring the first change condition and / or the second change condition; and

[0127] In which, the user equipment 1' is configured to replace the first cell CE of the first node NO1 with the first replacement cell RCE1 when the monitoring unit 2' detects that the first change condition is met, and / or is configured to replace the first cell CE of the second node NO2 with the second replacement cell RCE2 when the monitoring unit 2' detects that the second change condition is met.

[0128] According to some embodiments, the user equipment 1' is configured to replace the first cell CE of the first node NO1 with the first replacement cell RCE1, so that the first cell CE of the first node NO1 is released by the user equipment 1' before the user equipment 1' is connected to the first replacement cell RCE1, and / or is configured to replace the first cell CE of the second node NO2 with the second replacement cell RCE2, so that the first cell CE of the second node NO2 is released by the user equipment 1' before the user equipment 1' is connected to the second replacement cell RCE2.

[0129] 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, so that the user equipment 1 is connected 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 is configured to replace the first cell CE of the second node NO2 by the second replacement cell RCE2, so that the user equipment 1' is connected to the second replacement cell RCE2 before the first cell CE of the second node NO2 is released by the user equipment 1'.

[0130] According to some embodiments, the user equipment 1 ′ is configured to communicate over the cellular network CN using dual connectivity or multiple connectivity.

[0131] According to some embodiments, the first node NO1 is a base station and a master node for dual connectivity or multiple connectivity; wherein the second node NO2 is a base station and a secondary node for dual connectivity or multiple connectivity.

[0132] According to some embodiments, the first cell CE of the first node NO1 is a special cell or a secondary cell of a primary cell group for dual connectivity or multiple connectivity; and / or the first cell CE of the second node NO2 is a special cell or a secondary cell of a secondary cell group for dual connectivity or multiple connectivity.

[0133] According to some embodiments, the first change condition and / or the second change condition is any one or a combination of the following:

[0134] a specified number of instances in which the timer for the radio link failure timer was started but did not expire within a specified period of time;

[0135] A specified number of HARQ retransmissions from the PHY layer;

[0136] The number of designated retransmissions from the RLC layer is less than the maximum number of radio link failures detected by the user equipment 1;

[0137] Use a weighted average or moving average or any other specified statistical method of the metrics employed that indicate degradation of signal quality;

[0138] Coded or uncoded bit error rate;

[0139] Packet loss rate or packet error rate;

[0140] Data rate requirements;

[0141] Supported bandwidth;

[0142] A multi-cell event, such as a multi-cell event in which one of the metrics adopted by the corresponding replacement cells RCE1, RCE2 becomes better than the corresponding metric adopted by the corresponding first cell CE within at least one specified period, a multi-cell event in which one of the metrics adopted by the corresponding replacement cells RCE1, RCE2 becomes better than a threshold within at least one specified period, or a multi-cell event in which one of the metrics adopted by the corresponding first cell CE becomes worse than a first threshold within at least one specified time period and the corresponding metric adopted by the corresponding replacement cells RCE1, RCE2 becomes better than a second threshold within at least one specified time period, wherein the multi-cell event is triggered by user equipment 1', one of the nodes NO1, NO2 or another device of the cellular network CN.

[0143] 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 .

[0144] 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 .

[0145] According to some embodiments, the user equipment 1 ′ is configured to communicate with the first replacement cell RCE1 after a first change condition is met.

[0146] According to some embodiments, the user equipment 1' is configured to perform a random access procedure to the first replacement cell RCE1 after satisfying the first change condition, wherein the user equipment 1' is configured to release the first cell CE of the first node NO1 after the random access procedure to the first replacement cell RCE1 has been successfully completed.

[0147] According to some embodiments, the user equipment 1 ′ is configured to stop the random access procedure towards the first replacement cell RCE1 and to maintain the connection with the first cell CE of the first node NO1 in case a maximum number of attempts or a maximum delay of the random access procedure for the first replacement cell RCE1 is reached.

[0148] According to some embodiments, the user equipment 1 ′ is configured to communicate with the second replacement cell RCE2 after the second change condition is met.

[0149] According to some embodiments, the user equipment 1' is configured to perform a random access procedure to the second replacement cell RCE2 after satisfying the second change condition, wherein the user equipment 1' is configured to release the first cell CE of the second node NO2 after the random access procedure to the second replacement cell RCE2 has been successfully completed.

[0150] According to some embodiments, the user equipment 1 ′ is configured to stop the random access procedure to the second replacement cell RCE2 and to maintain the connection with the second cell CE of the second node NO2 in case a maximum number of attempts or a maximum delay for the random access procedure to the second replacement cell RCE2 is reached.

[0151] 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 satisfied, wherein the first message ME1 ′ indicates that the first cell CE of the first node NO1 has been released.

[0152] 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 the second condition is satisfied, wherein the second message ME2 ′ indicates that the first cell CE of the second node NO2 has been released.

[0153] According to some embodiments, the user equipment 1' is configured to derive from the first reconfiguration request REC1' whether the first replacement cell RCE1 belongs to the first node NO1 of the cellular network CN or the third node NO3 of the cellular network CN, and / or is configured to derive from the second reconfiguration request REC2' whether the second replacement cell RCE2' belongs to the second node NO2 of the cellular network CN or the fourth node NO4 of the cellular network CN.

[0154] Further disclosed is an embodiment of a method for operating a user equipment 1' for communicating over a cellular network CN; the method comprising the following steps:

[0155] using the user equipment 1' to simultaneously communicate 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;

[0156] receiving, using the user equipment 1', a first reconfiguration request REC1', the request comprising an indication that a first cell CE of a first node NO1 in communication with the user equipment 1' must be replaced by a first replacement cell RCE1 of the cellular network CN, wherein the first reconfiguration request REC1' comprises a first change condition under which the first reconfiguration request REC1' must be performed, and / or receiving, using the user equipment 1', a second reconfiguration request REC2', the request comprising an indication that a first cell CE of a second node NO2 in communication with the user equipment 1' must be replaced by a second replacement cell RCE2' of the cellular network CN, wherein the second reconfiguration request REC2' comprises a second change condition under which the second reconfiguration request REC2' must be performed;

[0157] monitoring the first change condition and / or the second change condition using the monitoring unit 2' of the user device 1'; and

[0158] Using user equipment 1', when monitoring unit 2' detects that a first change condition is met, the first cell CE of the first node NO1 is replaced by a first replacement cell RCE1, and / or when monitoring unit 2' detects that a second change condition is met, the first cell CE of the second node NO2 is replaced by a second replacement cell RCE2.

[0159] Further disclosed is an embodiment of a computer program for performing a method according to the present disclosure when run on a processor.

[0160] Figure 3 A further embodiment of a user equipment 1 ″ according to the present disclosure and its interaction with a cellular network CN is schematically shown.

[0161] According to some embodiments, the cellular network CN comprises a plurality of base stations BS connected to a core network COR of the cellular network CN via an xhaul network XN of the cellular network;

[0162] The user equipment 1" is configured to communicate with one of the base stations BS of the cellular network CN serving as a serving base station SBS, or is configured to communicate simultaneously with a plurality of base stations BS of the cellular network CN serving as serving base stations SBS respectively;

[0163] Wherein, the user equipment 1″ is configured to send a list LI′ of candidate base stations CBS to one of the serving base stations SBS, the candidate base stations CBS being eligible to replace at least one of the serving base stations SBS;

[0164] Therein, the user equipment 1″ is configured to receive, from at least one serving base station SBS, quality information QI about the quality of a communication link CL′ between one of the candidate base stations CBS and a core network COR for a plurality of candidate base stations CBS;

[0165] The user equipment 1" is configured to select one or more candidate base stations CBS based on the quality information QI to replace one or more base stations BS currently used as serving base stations SBS.

[0166] The xhaul network XN may be a fronthaul network or a backhaul network. It may be wireless or wired. It may also be a RAT technology different from the access technology, such as Wi-Fi, LTE, LTE Advanced, LT Advanced Professional, 5G, or a 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 using a Common Public Radio Interface (CPRI) to transmit data over optical fiber.

[0167] According to some embodiments, the user equipment 1″ is configured to send a quality information request QIR to at least one of the serving base stations SBS, wherein the quality information request QIR requests at least one of the serving base stations SBS to send quality information QI.

[0168] 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.

[0169] According to some embodiments, the user equipment 1″ is configured to receive the quality information QI as an unordered list comprising quality indication values ​​for a plurality of candidate base stations CBS;

[0170] wherein the user device 1″ is configured to sort the unsorted list to create a sorted list;

[0171] Therein, the user equipment 1″ is configured to select one or more candidate base stations CBS based on the sorted list to replace one or more base stations BS currently used as serving base stations SBS.

[0172] In some embodiments, the ordered list is an indexed list, wherein the index corresponds to an ordering, eg ordered by a network entity or an indexed list, wherein the index corresponds to a quality indication value or a criterion dependent on a quality indication value.

[0173] According to some embodiments, the user equipment 1″ is configured to receive quality information QI:

[0174] as a sorted list of a plurality of candidate base stations CBS, or

[0175] as a list of indices, where the indices correspond to the orderings, or

[0176] as a list of indices, where the indices correspond to the quality indicator values;

[0177] Therein, the user equipment 1″ is configured to select one or more candidate base stations CBS based on the sorted list to replace one or more base stations BS currently used as serving base stations SBS.

[0178] In some embodiments, the user equipment 1" is configured to select one or more candidate base stations CBS to replace one or more base stations BS currently serving as serving base station SBS based on the ranks contained in the sorted list or based on a criterion, such as a cost function.

[0179] According to some embodiments, the user equipment 1" is configured to send a signal SI indicating which of the one or more candidate base stations CBS has been selected; to one of the base stations BS currently serving as a serving base station SBS and / or to one of the selected candidate base stations CBS.

[0180] According to some embodiments, the user equipment 1″ is configured to communicate via the cellular network CN using dual connectivity or multiple connectivity;

[0181] The user equipment 1" is configured to simultaneously communicate with a master node that is one of the serving base stations SBS and a secondary node that is one of the serving base stations SBS;

[0182] Therein, the user equipment 1" is capable of creating a list LI' of candidate base stations CBS in such a way that the candidate base stations CBS in the list LI' of candidate base stations CBS include multiple candidate base stations CBS that are eligible to replace the main node as one of the serving base stations SBS, and / or multiple candidate base stations CBS that are eligible to replace the auxiliary node as one of the serving base stations SBS.

[0183] According to some embodiments, the user equipment 1″ is configured to receive quality information QI about the quality of a communication link CL′ between one of the candidate base stations CBS and a core network CN for a plurality of candidate base stations CBS, the candidate base station CBS being eligible to replace the master node as one of the serving base stations SBS from at least one serving base station SBS; and / or

[0184] Therein, the user equipment 1" is configured to receive quality information about the quality of the communication link CL' between one of the candidate base stations CBS and the core network CN for multiple candidate base stations CBS, and the candidate base station CBS is eligible to replace the auxiliary node from at least one serving base station SBS as one of the serving base stations SBS.

[0185] According to some embodiments, the user equipment 1″ is configured to select one or more candidate base stations CBS to replace the master node currently serving as one of the serving base stations CBS; and / or

[0186] Therein, the user equipment 1" is configured to select one or more candidate base stations CBS to replace the auxiliary node currently used as one of the serving base stations SBS.

[0187] Further disclosed is an embodiment of a method for operating a user equipment 1″ for communicating via a cellular network CN, wherein the cellular network CN comprises a plurality of base stations BS connected to a core network COR of the cellular network CN via an xhaul network XN of the cellular network CN; the method comprising the following steps:

[0188] using the user equipment 1″ for communicating with one of the base stations BS of the cellular network CN acting as a serving base station SBS, or for communicating simultaneously with a plurality of base stations BS of the cellular network CN acting as respective serving base stations SBS;

[0189] using the user equipment 1″ to send a list LI′ of candidate base stations CBS to one of the serving base stations SBS, the candidate base stations CBS being eligible to replace at least one of the serving base stations SBS;

[0190] receiving, using a user equipment 1″, from at least one serving base station SBS, quality information QI about the quality of a communication link CL′ between one of the candidate base stations CBS and a core network COR for a plurality of candidate base stations CBS;

[0191] The user equipment 1" selects one or more candidate base stations CBS based on the quality information QI to replace one or more base stations BS currently serving as a serving base station SBS.

[0192] Further disclosed is an embodiment of a computer program for performing a method according to the present disclosure when run on a processor.

[0193] 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. In some cases, the proposed enhancements also include aspects related to the (wireless or wired) backhaul network, which now has nodes with integrated access and backhaul (IAB) functionality. IAB nodes can use special IAB routing protocols to communicate between different IAB nodes.

[0194] Figure 4 A dual connected user equipment 1 is shown. MR-DC is a feature that enables multiple Rx / Tx capable UEs 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 E-UTRA or NR access. One node acts as a MN and the other acts as a SN. The MN and SN are connected via a network interface, at least the MN is connected to the core network (TS37.340).

[0195] As part of the MR-DC configuration, each user equipment (UE) is configured with two separate scheduling cell groups, namely:

[0196] >Master Cell Group (MCG)

[0197] >Secondary Cell Group (SCG).

[0198] The Master Cell Group (MCG) belongs to the Master Node (MN), and the Secondary Cell Group (MSG) belongs to the Secondary Node (SN). Based on the MR-DC architecture, the MCG and SCG can be LTE cells or NR cells or cells using any other RAT, such as WiFi or future cellular standard technologies beyond 5G (B5G). The network configures the MCG for the UE, and zero or one SCG.

[0199] There are two important cells when the UE is dual-connected to the MN and SN. One is the PCell (primary cell) and the other is the PSCell (primary secondary cell). The PCell is the SpCell (special cell) of the MCG and the PSCell is the SpCell of the SCG, where the SpCell is the primary cell of the primary cell group or the secondary cell group. Other cells in the MCG or SCG are secondary cells (SCells).

[0200] SCells are applicable to each MCG or SCG, and they are in a carrier aggregation (CA) configuration with the PCell, ie, PSCell.

[0201] The following are some applicable terms used in the document and defined in the relevant specifications:

[0202] LTE specification (TS 36.331-f60):

[0203] Primary cell (PCell): A cell operating on a primary frequency, in which the UE performs an initial connection establishment procedure or initiates a connection reestablishment procedure, or is indicated as a primary cell during a handover procedure.

[0204] Primary Secondary Cell (PSCell): indicates the SCG cell in which the UE performs random access or initial PUSCH transmission if the random access procedure is skipped when performing the SCG change procedure.

[0205] Secondary Cell (SCell): A cell operating on a secondary frequency, which can be configured once an RRC connection is established and can be used to provide additional radio resources. Except in the case of (NG) EN-DC, the PSCell is considered to be a SCell.

[0206] NR specification (TS 38.331-f60):

[0207] Primary cell: An MCG cell operating on a primary frequency, in which the UE performs an initial connection establishment procedure or initiates a connection re-establishment procedure.

[0208] Primary SCG cell: For dual connectivity operation, the SCG cell in which the UE performs random access when reconfiguration is performed using the Sync procedure.

[0209] Secondary cell: A cell that provides additional radio resources on top of a special cell (SC) for UEs configured with CA.

[0210] Special Cell (SC): For dual connectivity (DC) operation, the term special cell refers to the PCell of the MCG or the PSCell of the SCG, otherwise the term special cell refers to the PCell.

[0211] The combination of LTE & NR, and the corresponding abbreviations (TS37.340):

[0212] En-gNB: The node provides NR user plane and control plane protocol terminations to the UE and acts as a secondary node in EN-DC.

[0213] ng-eNB – eNodeB that can connect to the 5G core.

[0214] MR-DC with LTE Core:

[0215] E-UTRA-NR Dual Connectivity (EN-DC).

[0216] E-UTRA-NR Dual Connectivity (EN-DC) with LTE Core. The UE is connected to one eNB acting as MN and one en-gNB acting as SN. The eNB is connected to the EPC via the S1 interface and to the en-gNB via the X2 interface. The en-gNB can also be connected to the EPC via the S1-U interface and to other en-gNBs via the X2-U interface.

[0217] MR-DC with 5G core.

[0218] E-UTRA-NR Dual Connectivity (NGEN-DC)

[0219] NG-RANE-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.

[0220] NR-E-UTRAD Dual Connectivity (NE-DC)

[0221] NG-RAN supports NR-E-UTRA Dual Connectivity (NE-DC), where the UE is connected to a gNB acting as a MN and an 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.

[0222] NR-NR Dual Connectivity (NR-DC)

[0223] NG-RAN supports NR-NR Dual Connectivity (NR-DC), where the UE is connected to one gNB acting as a MN and another gNB acting as a SN. The primary gNB is connected to the 5GC via the NG interface and to the secondary gNB via the Xn interface. The secondary gNB may also be connected to the 5GC via the NG-U interface. In addition, NR-DC can also be used when the UE is connected to two gNB-DUs, one serving the MCG and the other serving the SCG, connected to the same gNB-CU, acting as both a MN and a SN.

[0224] In EN-DC, the MCG is configured as specified in TS 36.331. The network provides configuration parameters for the cell group in Section 5.3.5.5 of the CellGroupConfig IE (TS 38.331-f60), see 0 of this document.

[0225] Figure 5 The control plane architecture of EN-DC (left) and MR-DC with 5GC (right) (TS37.340.) is shown. In MR-DC, the UE has a single RRC state based on the MN RRC and a single C-plane connection to the core network. Each radio node has its own RRC entity and can generate RRC PDUs to send to the UE. The RRC PDUs generated by the SN can be transmitted to the UE via the MN. The MN always sends the initial SN RRC configuration via MCG Signaling Radio Bearer 1 (SRB1), but subsequent reconfigurations can be transmitted via the MN or the SN. When transmitting RRC PDUs from the SN, the MN does not modify the UE configuration provided by the SN. (TS37.340).

[0226] Therefore, the control plane uses SRB processing. SRBs are used to transport RRC and non-access stratum (NAS) messages. More specifically, the following SRBs are defined:

[0227] -SRB0 is used for RRC messages using CCCH logical channel;

[0228] -SRB1 is used for RRC messages (possibly including piggybacked NAS messages) and for NAS messages before establishing SRB2, both using the DCCH logical channel;

[0229] -SRB2 is used for NAS messages, all using the DCCH logical channel. SRB2 has a lower priority than SRB1 and can be configured by the network after AS security activation;

[0230] -SRB3 is used for specific RRC messages when the UE is in (NG)EN-DC or NR-DC, both using the DCCH logical channel.

[0231] In the downlink, piggybacking of NAS messages is used only for one related (i.e. joint success / failure) procedure: bearer establishment / modification / release. In the uplink, piggybacking of NAS messages is used only for the delivery of initial NAS messages during connection establishment and connection recovery.

[0232] NOTE 1: NAS messages transmitted via SRB2 are also included in RRC messages, but do not include any RRC protocol control information.

[0233] Once AS security is activated, all RRC messages on SRB1, SRB2 and SRB3, including those containing NAS messages, are integrity protected and ciphered by PDCP. NAS independently applies integrity protection and ciphering to NAS messages, see TS 24.501.

[0234] All MR-DC options in SRB1 and SRB2 support split SRB (split SRB is not supported for SRB0 and SRB3).

[0235] Once AS security is activated, all RRC messages on SRB1, SRB2 and SRB3, including those containing NAS messages, are integrity protected and ciphered by PDCP. NAS independently applies integrity protection and ciphering to NAS messages, see TS 24.501

[23] .

[0236] All MR-DC options in SRB1 and SRB2 support split SRB (split SRB is not supported for SRB0 and SRB3).

[0237] Figure 6 The radio protocol architecture for MCG, SCG and split bearers in MR-DC with EPC (EN-DC) (TS37.340.) is shown from the perspective of the UE.

[0238] Figure 7 The MCG, SCG and split bearers in MR-DC with 5GC (NGEN-DC, NE-DC and NR-DC) are shown from the perspective of the user equipment.

[0239] Two different user plane options enable multi-connectivity:

[0240] 1. Split bearer - In the split bearer option, the secondary bearer is provided by two nodes. The secondary node does not implement PDCP but RLC layer and below.

[0241] 2. Split bearer - In the split bearer option, each bearer terminates at a different node. The bearers are separated in the S-GW / User Plane Function (UPF) and Access and Mobility Management Function (AMF), each node implements the protocol stack from the PDCP below.

[0242] Figure 8 SN addition in EN-DC (TS37.340.) is shown. One of the most important procedures of the MR-DC procedure is the Secondary Node (SN) addition. SN addition is done according to section 10.2 of (TS37.340). Some of the most relevant aspects of the procedure are shown below (at the end of the document are the information elements applicable to the signaling procedures specified below).

[0243] SgNB Add Request: MN decides to add SN. MN sends a Secondary Node Add Request to SN. This message carries RRC and radio bearer configuration. UE capability and security information are also included in the message.

[0244] SgNB Add Request Confirm: The SN responds with information about radio resources and allowed bearers. The NR RRC Configuration message is included in the message.

[0245] Fig. 9 SN addition with 5GC (TS37.340.) is shown.

[0246] Fig.10 According to (TS37.340.), Fig.10 .5.2-1, shows SN change - MN initiated in MRDC with 5GC. The SN change procedure is initiated by the MN or SN and transfers the UE context from the source SN to the target SN and changes the SCG configuration in the UE from one SN to another (TS37.340). Fig.10 and Fig.11 Depicted are the MN- and SN-initiated nodal changes of MR-DC with 5GC. Figure 4 and Figure 5 The case of EN-DC is described in .

[0247] Fig.11 According to (TS37.340.), Fig.10 .5.12-2, shows the SN changes in 5GC–SN initiated MRDC.

[0248] Fig.12MN handover in EN-DC with SgNb change is shown according to (TS37.340.) Inter-primary node handover with / without secondary node change: Fig.12 Describes MN handover with / without secondary node change in case of EN-DC. The specification (TS37.340) also includes cases for 5GC - see (TS37.340) Fig.10 .7.2-1.

[0249] RRC related aspects (measurements):

[0250] Measurement:

[0251] • Measurements can be configured independently by the MN and the 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 in the SN to ensure that the UE capabilities are not exceeded.

[0252] · Both MN (only for inter-frequency secondary node change) and SN can trigger the secondary node change process. For secondary node change triggered by SN, the RRM measurement configuration is maintained by SN, and SN also processes the measurement report without providing measurement results to MN.

[0253] When SRB3 is not configured, the measurement reports configured by the SN are sent on SRB1. When SRB3 is configured, the measurement reports configured by the SN are sent on SRB3.

[0254] The measurement results related to the target SN may be provided by the MN to the target SN at the MN initiating the SN change procedure. The measurement results of the target SN may be forwarded from the source SN to the target SN via the MN at the SN initiating the SN change procedure. The measurement results related to the target SN may be provided by the source MN to the target MN in an inter-MN handover with / without the SN change procedure (see below).

[0255] In more detail, the configuration of the (secondary) cell group is described as follows: The main function of 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.

[0256] SCG failure handling: RLF is declared for MCG and SCG separately. If radio link failure to MCG is detected, the UE initiates the RRC connection reestablishment procedure (TS37.340). Note that RAN 2 included a new procedure - Fast MCG Recovery in Release 16 (3GPP RAN2, 2019) to address the delays associated with the RRC connection reestablishment procedure.

[0257] Note that MCG failures are not discussed further in this document.

[0258] Rather, it describes SCG failure.

[0259] The following SCG failure cases are supported:

[0260] -SCGRLF;

[0261] -SN change failed;

[0262] - SCG configuration fails for EN-DC, NGEN-DC and NR-DC (only for messages on SRB3);

[0263] - SCG RRC integrity check fails (on SRB3) for EN-DC, NGEN-DC and NR-DC.

[0264] When SCG fails, the UE suspends SCG transmission of all radio bearers and reports SCG failure information to the MN instead of triggering reestablishment.

[0265] In case of all SCG failures, the UE keeps the current measurement configuration from the MN and SN, and if possible, the UE continues measurements based on the configuration from the MN and SN. SN measurements configured to be routed via the MN will continue to be reported after SCG failure.

[0266] NOTE: In some cases (e.g., the UE cannot maintain timing of the PSCell), the UE may not continue measurements based on the configuration from the SN after SCG failure.

[0267] The UE includes in the SCG Failure Information message the measurement results available according to the current measurement configuration of the MN and SN. The MN processes the SCG Failure Information message and may decide to keep, change or release the SN / SCG. In all cases, the measurement results may be forwarded to the old SN and / or the new SN depending on the SN configuration and the type of SCG failure.

[0268] Let’s look at SCG failure in more detail: Failure definition: Failures in the specification are referred to as SCG failures in both LTE and NR.

[0269] As mentioned before, the SCG is a group of cells configured in a UE belonging to a SN. Within the SCG, there is a Primary Secondary Cell (PSCell). In LTE, this is the cell in which the UE is instructed to perform a random access or initial PUSCH transmission if the random access procedure is skipped when performing the SCG Change procedure (TS 36.331-f60). In NR, the PSCell is the cell in which the UE performs a random access when performing a reconfiguration with the Sync procedure (TS 38.331-f60).

[0270] LTE specifications:

[0271] SCG failure (TS 36.331-f60) is reported by the UE in the following cases:

[0272] Upon detecting a failure of the radio link for the SCG,

[0273] When the SCG change fails (due to the mobility of the SCG),

[0274] According to TS 36.133, when the power control mode is configured as 1, uplink transmission to the PSCell is stopped due to exceeding the maximum uplink transmission timing difference.

[0275] Actions in case of failure:

[0276] When initiating the process, the UE:

[0277] Suspend all SCG DRBs and suspend SCG transmission for split DRBs,

[0278] Reset SCG-MAC,

[0279] Stop T307 timer,

[0280] The T307 timer is started when the RRC connection reconfiguration message including MobilityControlInfoSCG is received. It is stopped when random access, reestablishment and SCG release on the PSCell are successfully completed.

[0281] Initiate the transmission of SCG failure information messages.

[0282] NR Specifications:

[0283] The purpose of this procedure is to inform the LTE or NR MN about the SCG failure that the UE has experienced. The UE reports SCG failure (TS 38.331-f60) in the following cases:

[0284] Upon detection of radio link failure for the SCG (subclause 5.3.10.3),

[0285] · Reconfiguration in case of SCG synchronization failure (subclause 5.3.5.8.3),

[0286] When the SCG configuration fails, i.e. cannot comply with the reconfiguration request (subclause 5.3.5.8.2),

[0287] • Integrity check failure indication on SRB3 from SCG lower layers.

[0288] Actions in case of failure:

[0289] When initiating the process, the UE:

[0290] Suspend SCG transmission of all SRBs and DRBs,

[0291] Reset SCG MAC,

[0292] Stop the T304 timer if it is running

[0293] oTimer T304 is started when an RRC reconfiguration message including reconfigurationWithSync is received. It is stopped after a random access to the corresponding SpCell is successfully completed. For T304 of SCG, the timer is stopped when the SCG is released.

[0294] If the UE is in EN-DC:

[0295] o Initiate the transmission of the SCGFailureInformationNR message as specified in clause 5.6.13a of TS 36.331.

[0296] Following all of the above and the current specifications TS 36.331-f60 and TS 38.331-f60, only the PCell on the MN and the SpCell on the SN will report RLF.

[0297] Figure 13 shows a PSCell failure. The purpose of the present invention is to improve robustness and provide a seamless experience for UEs in Multi-Radio Dual Connectivity (MR-DC) mode. As mentioned above, MR-DC means a system with dual connectivity between E-UTRA and NR nodes or between two NR nodes. The present invention addresses the situation where the PSCell link of the secondary node (SN) experiences quality degradation, which may lead to PSCell failure.

[0298] The robustness of the MR-DC feature depends on the stability of the links on the PCell and PSCell. That is, as explained in Section 0, an SCG failure occurs, among other cases, when there is a radio link failure (RLF) on a special cell (SpCell) on the SN (PSCell). In this case, the SCG data radio bearer is released, the MAC is reset and the appropriate timers are stopped. Considering that the possible deployments of MR-DC are heterogeneous deployments, with SNs using small cells and / or cmWave / mmWave spectrum (e.g. FR2 in 5G), the PSCell radio link may be particularly susceptible to fluctuations and failures, making the multi-connectivity functionality unstable. In particular, operation in mmWave frequencies of 28 GHz, but also above 52 GHz, such as 60 GHz specified by 3GPP, leads to a significant increase in path loss and deterioration of signal penetration, which will particularly affect the stability and quality of the link.

[0299] The potential impact of radio link failure on the PSCell is shown in Figure 13. PSCell failure may cause the UE to experience large fluctuations in QoS, in which case larger pipes become unavailable.

[0300] When SCG failure occurs due to radio link failure (RLF) on PSCell, the network, especially MN, processes SCG failure information message (scgFailureInformation / scgFailureInformationEUTRA). This message is sent from UE to MN-EUTRA or NR (TS 38.331-f60), Figure 5 .7.3.1.1. The current standard does not specify the actions to be taken by the MN after receiving the SCGRLF notification. According to (TS37.340), the MN can decide:

[0301] Keep SN / SCG, or

[0302] Change SN / SCG, or

[0303] Release SN / SCG.

[0304] With the release of the SCG data radio bearer, even if the MN decides to retain the SN / SCG and re-establish the radio bearer, or change the SN / SCG, the service to the UE may be interrupted because the data rate gap may be large due to the unavailability of all SCG cells.

[0305] Figures 14 and 15 depict the case of SN change, i.e., SCG is modified by MN. Figure 14 shows SN change after RLF on SCG. Figure 15 shows SgNb modification after RLF on SCG.

[0306] Fig.16 Intra-SN PSCell / SCG changes are shown. The proposed enhancements aim to improve the robustness of the MR-DC feature and provide a seamless experience for the UE in MR-DC mode by enabling preemptive actions when the link on the PSCell degrades.

[0307] Inter-SN and intra-SN changes are described separately.

[0308] Fig.16 Intra-SN PSCell / SCG change is depicted. The new SCG may also include previous and / or new SCells. Conditions related to quality degradation of the PSCell trigger the decision to change the PSCell / SCG within the same SN.

[0309] Fig.17 The schematic diagram shows the Figure 1Implementation of user equipment in 5G and its interaction with the cellular network. Here, intra-SN PSCell / SCG change is shown. The UE decides to change the PSCell and thereby the SCG based on a trigger condition taking into account the quality of the existing PSCell.

[0310] 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 this end, the UE may have a built-in trigger condition that will initiate a change in the PSCell. For example, the trigger condition may be configured as x instances where the timer T310 (RLF timer) has been 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, which is less than the maximum number of radio link failures detected by the UE. Based on the trigger condition, the UE decides to change the PSCell and SCG accordingly. The enhancement also envisions that the UE creates a candidate PSCell pool. It should then provide the SN with a PSCell preference from this pre-configured pool by sending an ordered list of PSCells. The candidate cell pool may be created by one or more of the following:

[0311] The UE monitors potential candidates by measuring, for example, the correlation of synchronization signals and reference signals (e.g., channel state information reference signal, beam spreading reference signal, and demodulation reference signal). The UE may use defined metrics such as reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), or signal-to-noise and interference ratio (SINR), or any metric for evaluating the quality of channel state information (CSI) (3GPP, 2019) to create a pool.

[0312] The MN and / or the SN and / or one of the SCells and / or SpCells within the MN or SN may directly provide the candidate list to the UE,

[0313] A combination of the above.

[0314] 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 like the PSCell pool, and it may include existing and / or new SCells. PSCells and SCells may be interchanged between pools.

[0315] The following steps are proposed, such as Fig.17 This figure depicts the situation where the process is mainly handled between UE and SN:

[0316] 1) After the UE makes a decision to change the PSCell, it 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).

[0317] 2) The SN checks the available radio resources of the proposed cell and sends an RRC Reconfiguration Request including the new PSCell / SCG radio resource configuration. The RRC Reconfiguration Request message now includes an indicator indicating that the message is a response to a PSCell change request.

[0318] 3) The UE performs a random access (RA) procedure for the new cell.

[0319] a. The UE may be configured with a maximum number of attempts or a maximum delay for the RA procedure (less than the delay specified for detecting SCG RLF failure). In this case, the UE will report an RRC reconfiguration failure and will not release the existing PSCell / SCG configuration.

[0320] 4) The UE sends a modified RRC Reconfiguration Complete message - again via the MN or directly to the SN. An indication to release the old PSCell is now appended to the RRC Reconfiguration Complete message. The SN releases the old cell.

[0321] 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.

[0322] It is also possible to have the procedure handled primarily between the UE and the MN (RRC reconfiguration), which can be sent directly or via the SN. In either case, existing procedures towards the core network can be retained, also depending on whether the MN is involved - according to existing specifications for SN amendments.

[0323] Note 1: Steps 3) and 4) can be interchanged. As described above, in the case where 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 RRC Reconfiguration-Failure via the MN or directly to the SN.

[0324] FIG. 18 schematically shows a Figure 2 Implementation of user equipment in 5G and its interaction with the cellular network. Intra-SN PSCell change is shown here. The SN can decide the preconfiguration of its resources (as depicted in Figure 18). Once the conditions are met, the UE performs the change of PSCell and corresponding SCG based on the trigger conditions taking into account the quality of the existing PSCell.

[0325] This enhancement is based on the Conditional Handover (CHO) feature, which is currently being discussed for inclusion in Release 16 (3GPP RAN2, 2019), where the network is responsible for the PSCell / SCG change. The UE only operates when the triggering conditions are met. In (MediaTek, 2019) and (NEC, 2019), so-called conditional PSCell addition and SCG change are also proposed. The triggering conditions can be the same as discussed above.

[0326] The network (MN or SN) already has a mechanism to create a pool of candidate PSCells and SCells, which will be sent to the UE.

[0327] This is depicted in Figure 18 and described below.

[0328] 1) The SN decides, for example based on measurement results, to initiate a PSCell / SCG change of pre-configured radio resources, which may also include the old or new SCell. It sends an RRC reconfiguration request including the new PSCell / SCG radio resource configuration and triggering conditions.

[0329] 2) Once the conditions are met, the UE changes the PSCell, reconfigures the SCG and performs the RA process to the new PSCell.

[0330] 3) The UE sends a modified RRC Reconfiguration Complete message - again via the MN or directly to the SN. The indication of the release of the old PSCell and / or SCell is now piggybacked on the RRC Reconfiguration Complete message. The SN releases the old cell.

[0331] 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.

[0332] Fig.19 An inter-SN PSCell change is shown. Conditions related to degradation of the quality of the PSCell trigger the decision to switch to a new SN, and change the PSCell and SCG accordingly.

[0333] In the inter-SN PSCell / SCG change enhancement, the PSCell and the new SCG belong to different SNs. This enhancement is described below.

[0334] FIG. 20 schematically shows a Figure 1 Implementation of user equipment in 5G and its interaction with the cellular network. Here, inter-SN PSCell change is shown when the process is mainly handled between UE and SN. UE decides to change SN based on trigger conditions considering the quality of the existing PSCell and changes PSCell / SCG accordingly.

[0335] This enhancement aims to give the UE the right to request a SN change and accordingly a PSCell / SCG change due to, for example, mobility, and typically a reduction 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 envisages that in addition to the PSCell and SCell pools, the UE creates a pool of candidate SNs. It should then provide SN / PSCell preferences to the current SN from these pre-configured pools by sending, for example, an ordered list of SNs and PSCells. The candidate SN and PSCell pools can be created in the same way as above.

[0336] In addition to the SN and PSCell pools, the UE may also provide the network with an ordered list of SCells on new SNs for the new SCG. SCell pools may be created in the same way as PSCell pools. PSCells and SCells may be interchanged between pools.

[0337] The following steps are recommended, as shown in Figure 20:

[0338] 1) When the UE decides to change the SN / PSCell, it sends a PSCell / SCG reconfiguration request to the source SN (SN-S). The request can be sent via the MN (using SRB1) or directly to the SN-S (using SRB3). The PSCell change request message contains an indicator indicating that this is an SN change request. In the case where the MN is not involved, the SN-S informs the MN of the request.

[0339] 2) The MN or 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 envisaged that the SN-S can now also send a request to the SN-T. The figure depicts a MN-initiated add.

[0340] 3) SN-T checks available radio resources and sends SN Add Request Acknowledgement including an indication of full or incremental RRC configuration. Add Request Notification is sent to SN-S.

[0341] 4) An RRC Reconfiguration Request 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 PSCell Change Request (including SN change).

[0342] 5) The UE performs a random access (RA) procedure for the SN-T and the new PSCell.

[0343] a. The UE may configure a maximum number of attempts or a maximum delay for the RA procedure (less than the delay specified for detecting SCG RLF failure). In this case, the UE shall report an RRC reconfiguration failure and shall not release the SN-S and the existing PSCell / SCG configuration.

[0344] 6) UE sends RRC Reconfiguration Complete message - again via MN or directly to SN-S. Now the indication to release SN-S is piggybacked on the RRC Reconfiguration Complete message. SN-S releases its resources.

[0345] 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.

[0346] It is also possible to have the procedure handled primarily between the UE and the MN (RRC reconfiguration), which can be sent directly or via the SN. In either case, the existing procedures towards the core network can be retained, also depending on whether the MN is involved - according to existing specifications for SN amendments.

[0347] Note that steps 5) and 6) are interchangeable. As described above, in the case where 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 the RRC reconfiguration failure to the SN-S directly or via the MN.

[0348] Fig.21 The schematic diagram shows the Figure 2 Implementation of user equipment in 5G and its interaction with the cellular network. Here, an inter-SN PSCell change is shown. The network decides to pre-configure a new SN and corresponding PSCell / SCG based on a trigger condition that takes into account the quality of the existing PSCell. Fig.21 Inter-SN changes using CHO as a basis are depicted.

[0349] Note that it is also possible to let the MN decide on the change of SN and PSCell / SCG. Fig.21 Depicted in.

[0350] The network (MN or SN) already has a mechanism to create a pool of candidate SNs, PSCells and SCells, which will be sent to the UE.

[0351] The following steps are recommended, such as Fig.21 As shown:

[0352] 1) Based on the measurement results from the UE, the network (MN or SN-S) makes a decision on the SN / PSCell change. This figure depicts the situation where the SN-S sends a pre-configuration request for resources to the SN-T.

[0353] 2) The SN-T sends an acknowledgement of the pre-configured resources, indicating either full availability or a delta between requested and available resources.

[0354] 3) If the MN has not started pre-configuration, the SN-S informs the MN about the resources pre-configured by the SN-T.

[0355] 4) The RRC Reconfiguration Request message is sent from the SN-S to the UE with the new configuration, including the triggering conditions. Once the conditions are met, the UE performs the change of SN and PSCell.

[0356] 5) The UE performs a random access (RA) procedure for the SN-T and the new PSCell.

[0357] a. The UE may configure a maximum number of attempts or a maximum delay for the RA procedure (less than the delay specified for detecting SCG RLF failure). In this case, the UE shall report an RRC reconfiguration failure and shall not release the SN-S and the existing PSCell / SCG configuration.

[0358] 6) UE sends RRC Reconfiguration Complete message - either via MN or directly to SN-S. The indication to release SN-S is now piggybacked on the RRC Reconfiguration Complete message. SN-S releases its resources.

[0359] 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.

[0360] Existing procedures towards the core network may be retained, also depending on whether a MN is involved - according to existing specifications for SN amendments.

[0361] Note that steps 5) and 6) can be interchanged. As described above, in the case where 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 the RRC reconfiguration failure to the SN-S directly or via the MN.

[0362] During handover (HO), the backhaul scenario is not considered. A target base station for HO is selected based on the signal strength and / or quality of the link between the UE and one or more base stations or access points.

[0363] Fig. 22A basic conditional HO (CHO) process is shown. A similar situation exists in conditional HO (CHO). In CHO, the target base station is selected taking into account the link of the UE. The quality of the backhaul links of different base stations is not compared and not considered in this selection. The UE is then configured with the configuration required to connect to the selected target base station. Based on a threshold agreed between the base station and the UE with reduced signaling, in CHO, the selection of the target base station takes into account the link quality on the Uu link. If the UE reaches a certain link quality threshold, the UE can automatically perform a HO to its target base station without sending measurement reports to its source base station. In addition, the UE can directly perform a HO without waiting for a HO command from its source base station, which may fail due to fluctuations on the Uu link. The quality of the backhaul links of different base stations is not compared or exchanged and not considered in this selection.

[0364] In SN selection in dual / multiple connectivity, the master node (MN) selects the SN in consideration of its link with the UE. The quality of the backhaul links of different base stations is not compared and is not considered when selecting the SN.

[0365] The SN change or modification can be initiated by the MN or the SN. The quality of the backhaul links of different base stations is not compared and is not considered in the change or modification of the SN.

[0366] Fig.23 The case 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 is shown. When there are two or more candidate base stations, one base station is selected taking into account the available resources and the signal strength (to the UE). The quality of the backhaul is ignored in this selection. For example, in Fig.23 In the example, the UE is within the coverage of DU2 and DU3. If one of them is to be selected to serve the UE (eg, handover or as a SN), the backhaul link between each of the two base stations and the core network (CN) is not considered or compared.

[0367] Fig.24 The impact of backhaul on the quality of the path from the UE to the core network in the case of IAB is shown. An example of how IAB can be used to implement backhaul. Fig.24 In Figure 1, consider the case where the UE obtains a stronger signal from IAB Node 1 than from IAB Node 1', even though both powers are above the acceptable threshold for communicating with the UE. On the other hand, the signal from / to IAB Node 1 experiences a greater delay when reaching the core network. However, the backhaul link from the IAB Access Node to the IAB-Donor-CU is transparent to the UE. This means that the serving node is also transparent to the UE, whether it is an IAB node or not.

[0368] HO scenario: Fig.24In FIG. 1 , node 1 and node 1 ′ are candidates for HO. In the prior art, neither the serving base station nor the UE has any information about the backhaul links of these two candidates.

[0369] Dual / multiple connection scenarios: Fig.24 In the example, node 1 and node 1' are candidates for becoming SNs. In the prior art, neither the MN nor the UE has any information about the backhaul links of these two candidates.

[0370] However, in both scenarios, if the UE and / or the serving base station / MN know 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.

[0371] The solution consists of two possible enhancements that can be applied together or separately.

[0372] Recommended enhancement 1: Consider the backhaul status (quality of the backhaul link)

[0373] Information about the quality of the backhaul is transmitted between base stations, for example, via X2 or Xn. In the prior art, the grant confirmation is transmitted via X2 / Xn.

[0374] Two enhancements are proposed in this invention: One enhancement is to transmit an indication of the quality of the backhaul (from BS to CN). Another proposed enhancement is to enable UE initiated base station selection in dual / multi connectivity, for example in HO.

[0375] Fig.25 The basic process of considering backhaul status in base station selection is shown (process 0).

[0376] Process 0:

[0377] 1. The UE provides a list of candidate base stations to the current serving base station / MN. The serving base station / MN transmits this list from the UE to a specific entity in the network. The serving base station / MN itself may be that specific entity.

[0378] NOTE 1—Some candidates may be IAB nodes.

[0379] NOTE 2 - The currently serving base station / MN may be an IAB node.

[0380] 2. The so-called specific entity estimates or measures or obtains the quality of the backhaul link from each candidate base station to the core network.

[0381] If a backhaul link does not exist, the entity may estimate the quality of the link, if possible.

[0382] If there is an IAB node in the candidate list, the IAB-Donor-CU can be an entity that estimates or measures the quality of the backhaul link. In particular, when two (or all) IAB nodes are connected to the same IAB-Donor-CU, the IAB-Donor-CU compares the quality of the backhaul link from the core network to each IAB node. For example, the number of hops of the path can estimate the delay of the path.

[0383] 3. In case the so-called specific network entity is different from the serving base station / MN, the quality of the backhaul link is sent from the network entity to the serving base station / MN.

[0384] 4. The serving base station / MN considers the link measurements from the UE and the backhaul information it obtains from the network (step 3) and sorts the list of candidate base stations.

[0385] 5. The serving base station / MN selects a base station and decides on an action and / or initiates that action, such as HO / CHO to the selected base station, initiating an auxiliary link with the selected base station, exchanging MN and SN.

[0386] In case the second proposed enhancement is available and the UE is able to initiate HO and / or SN establishment, two possible procedures are suggested.

[0387] Fig.26 The schematic diagram shows the Figure 3 The implementation of user equipment in 5G and its interaction with cellular networks.

[0388] Process 1:

[0389] 1 to 3: Same as process 0 ( Fig.25 ).

[0390] 4. The serving base station / MN sends the quality of the backhaul link to the UE.

[0391] 5. The UE considers the UE's own measurements and the backhaul information obtained from the network, and sorts the list of candidate base stations.

[0392] 6. The UE selects a base station and decides on an action, and triggers the action, such as HOing to the selected base station and starting an auxiliary link with the selected base station.

[0393] In process 1, backhaul information is transmitted to the UE (step 4), the UE ranks the base stations (step 5) and makes a decision (step 6).

[0394] Fig. 27 The schematic diagram shows the Figure 3 Further implementation of user equipment in 5G and its interaction with cellular networks.

[0395] An alternative procedure is to not send the backhaul information to the UE. Instead, the serving base station or MN uses this information in addition to the measurements collected from the UE and ranks the candidate base stations / nodes. This alternative procedure is as follows Fig. 27 , and described below.

[0396] Process 2:

[0397] 1 to 4: Same as process 0 ( Fig.25 ).

[0398] 5. The serving base station / MN sends the sorted list of candidate base stations to the UE.

[0399] 6. The UE selects a base station and decides on an action, and triggers the action, such as HOing to the selected base station and starting an auxiliary link with the selected base station.

[0400] According to certain implementation requirements, embodiments of the apparatus of the present invention may be implemented in hardware and / or software. The implementation may be performed using a digital storage medium with electronically readable control signals stored thereon, such as a floppy disk, DVD, Blu-ray disc, CD, ROM, PROM, EPROM, EEPROM or flash memory, which cooperates (or is capable of cooperating) with a programmable computer system to perform one or more or all functions of the apparatus or system of the present invention.

[0401] In some embodiments, a programmable logic device (e.g., a field programmable gate array) may be used to perform one or more or all functions of the devices and systems described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor to perform one or more or all functions of the devices and systems described herein.

[0402] Although some aspects have been described in the context of an apparatus, it is clear that these aspects also represent a description of a corresponding method, where a block or device corresponds to a method step or a 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.

[0403] According to certain implementation requirements, embodiments of the method of the present invention may be implemented using a device including hardware and / or software. The implementation may be performed using a digital storage medium with electronically readable control signals stored thereon, such as a floppy disk, DVD, Blu-ray disc, CD, ROM, PROM, EPROM, EEPROM or flash memory, which cooperates (or is capable of cooperating) with a programmable computer system to perform the corresponding method.

[0404] Depending on certain implementation requirements, embodiments of the method according to the invention can be implemented using a device comprising hardware and / or software.

[0405] Some or all of the method steps may be performed by (or using) hardware devices, such as microprocessors, programmable computers or electronic circuits. Some or more of the most important method steps may be performed by such devices.

[0406] Some embodiments according to the invention comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed.

[0407] Generally, embodiments of the present invention can be implemented as a computer program product with a program code, the program code being operative for performing 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.

[0408] 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.

[0409] 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.

[0410] A further embodiment comprises a computer having installed thereon the computer program for performing one of the methods described herein.

[0411] In general, these methods are advantageously performed by any apparatus including hardware and / or software.

[0412] Although the present invention has been described according to several embodiments, there are still some changes, permutations and equivalents that may fall within the scope of the present invention. It should also be noted that there are many alternatives for implementing the method and composition of the present invention. Therefore, it is intended that the following appended claims be interpreted as including all such changes, permutations and equivalents that fall within the true spirit and scope of the present invention.

[0413] Reference numerals:

[0414] 1 User equipment

[0415] 2 Monitoring unit

[0416] CN Cellular Network

[0417] CE Community

[0418] NO Node

[0419] CL Communication Link

[0420] REP Replacement Request

[0421] RCE Replacement Cell

[0422] LI List

[0423] REC Reconfiguration Request

[0424] ME Message

[0425] BS Base Station

[0426] XN xhaul Network

[0427] COR Core Network

[0428] SBS Service Base Station

[0429] CBS candidate base stations

[0430] QI Quality Information

[0431] QIR Quality Information Request

[0432] SI signal

[0433] References:

[0434] (ETRI), Lee. 2015. "A Study of the Radio Resource Control Connection." 38.401, 3GPP. "Architecture description NG RAN 38.401."

[0435] 3GPP RAN2.2019. "RAN 2-107-Chairmains Notes." Prague.

[0436] 3GPP.2019.TS 38.215NR; Physical layer measurements.3GPP.

[0437] Ahmadi. 2019. “5G NR.” Elsevier.

[0438] Ericsson. "R2-1900404Conditional Handover."

[0439] MediaTek.2019. "Conditional PSCell addition."

[0440] NEC.2019. "R2-1904069Reuse of conditional handover for SCG change inNR-DC."

[0441] Rao,Jaya,and Sophie Vrzic.2018.“Packet Duplication for URLLC in 5G:Architectural Enhancements and Performance Analysis.”IEEE Network.

[0442] Rosa,Claudio.2016.Dual Connectivity forLTE Small Cell Evolution:Functionality and Performance Aspects.IEEE Communications Magazine.

[0443] 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 andBackhaul.”

[0444] TS 36.331-f60.“LTE Radio Resource Specification.”

[0445] TS 38.331-f60.“Radio Resource Control(RRC)protocol specification.”

[0446] TS37.340,TS-f60.Multi-Radio Dual Connectivity.

Claims

1. A user equipment for communicating on a cellular network (CN); in, The user equipment (1') is configured to communicate simultaneously 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); wherein the user equipment (1') is configured to receive a first reconfiguration request (REC1'), the request comprising an indication that a first cell (CE) of a first node (NO1) in communication with the user equipment (1') must be replaced by a first replacement cell (RCE1) of a cellular network (CN), wherein the first reconfiguration request (REC1') comprises a first change condition under which the first reconfiguration request (REC1') must be executed, and / or the user equipment (1') is configured to receive a second reconfiguration request (REC2'), the request comprising an indication that a first cell (CE) of a second node (NO2) in communication with the user equipment (1') must be replaced by a second replacement cell (RCE2') of the cellular network (CN), wherein the second reconfiguration request (RCE2') comprises a second change condition under which the second reconfiguration request (RCE2') must be executed, wherein the first change condition and / or the second change condition comprises: a specified number of instances in which a timer of a radio link failure timer has been started but has not expired within a specified time period; Wherein, the user equipment (1') comprises a monitoring unit (2') for monitoring the first change condition and / or the second change condition; and The user equipment (1') is configured to replace the first cell (CE) of the first node (NO1) with the first replacement cell (RCE1) when the monitoring unit (2') detects that the first change condition included in the first reconfiguration request (REC1') is met, and / or is configured to replace the first cell (CE) of the second node (NO2) with the second replacement cell (RCE2) when the monitoring unit (2') detects that the second change condition included in the second reconfiguration request (RCE2') is met.

2. The user equipment according to claim 1, wherein: The user equipment (1') is configured to replace the first cell (CE) of the first node (NO1) by the first replacement cell (RCE1), so that the first cell (CE) of the first node (NO1) is released by the user equipment (1') before the user equipment (1') is connected to the first replacement cell (RCE1), and / or the user equipment (1') is configured to replace the first cell (CE) of the second node (NO2) by the second replacement cell (RCE2), so that the first cell (CE) of the second node (NO2) is released by the user equipment (1') before the user equipment (1') is connected to the second replacement cell (RCE2).

3. The user equipment according to claim 1, wherein: The user equipment (1') is configured to replace the first cell (CE) of the first node (NO1) by the first replacement cell (RCE1), so that the user equipment (1) is connected 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 the user equipment (1') is configured to replace the first cell (CE) of the second node (NO2) by the second replacement cell (RCE2), so that the user equipment (1') is connected to the second replacement cell (RCE2) before the first cell (CE) of the second node (NO2) is released by the user equipment (1').

4. The user equipment according to claim 1, wherein: The user equipment (1') is configured to communicate on a cellular network (CN) using dual connectivity or multiple connectivity.

5. The user equipment according to claim 1, wherein: The first node (NO1) is a base station and a master node for dual connectivity or multiple connectivity; and wherein the second node (NO2) is a base station and a secondary node for dual connectivity or multiple connectivity.

6. The user equipment according to claim 4, wherein: The first cell (CE) of the first node (NO1) is a special cell or a secondary cell of a primary cell group for dual connectivity or multiple connectivity; and / or the first cell (CE) of the second node (NO2) is a special cell or a secondary cell of a secondary cell group for dual connectivity or multiple connectivity.

7. The user equipment according to claim 1, wherein: The first change condition and / or the second change condition further include any one of the following or a combination thereof: A specified number of HARQ retransmissions from the PHY layer; The number of designated retransmissions from the RLC layer is less than the maximum number of radio link failures detected by the user equipment (1); Use a weighted average or moving average or any other specified statistical method of the metrics employed that indicate degradation of signal quality; Coded or uncoded bit error rate; Packet loss rate or packet error rate; Data rate requirements; Supported bandwidth; A multi-cell event, comprising: a multi-cell event in which one of the metrics adopted by the corresponding replacement cell (RCE1, RCE2) becomes better than the corresponding metric adopted by the corresponding first cell (CE) within at least one specified period, a multi-cell event in which one of the metrics adopted by the corresponding replacement cell (RCE1, RCE2) becomes better than a threshold within at least one specified period, or a multi-cell event in which one of the metrics adopted by the corresponding first cell (CE) becomes worse than a first threshold within at least one specified time period and the corresponding metric adopted by the corresponding replacement cell (RCE1, RCE2) becomes better than a second threshold within at least one specified time period, wherein the multi-cell event is triggered by a user equipment (1'), one of the nodes (NO1, NO2) or another device of a cellular network (CN).

8. The user equipment according to claim 1, wherein: The user equipment (1') is configured to receive a first reconfiguration request (REC1') from the first node (NO1) or the second node (NO2).

9. The user equipment according to claim 1, wherein: The user equipment (1') is configured to receive a second reconfiguration request (REC2') from the first node (NO1) or from the second node (NO2).

10. The user equipment according to claim 1, wherein: The user equipment (1') is configured to communicate with the first replacement cell (RCE1) after the first change condition is met.

11. The user equipment according to claim 1, wherein: The user equipment (1') is configured to perform a random access procedure to the first replacement cell (RCE1) after the first change condition is met, wherein the user equipment (1') is configured to release the first cell (CE) of the first node (NO1) after the random access procedure to the first replacement cell (RCE1) has been successfully completed.

12. User equipment according to claim 1, wherein the user equipment (1') is configured to stop the random access procedure towards the first replacement cell (RCE1) and is configured to maintain a connection with the first cell (CE) of the first node (NO1) in case a maximum number of attempts or a maximum delay for the random access procedure towards the first replacement cell (RCE1) is reached.

13. The user equipment according to claim 1, wherein: The user equipment (1') is configured to communicate with the second replacement cell (RCE2) after the second change condition is met.

14. The user equipment according to claim 1, wherein: 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, wherein 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) has been successfully completed.

15. User equipment according to claim 1, wherein the user equipment (1') is configured to stop the random access procedure towards the second replacement cell (RCE2) and is configured to maintain a connection with the second cell (CE) of the second node (NO2) in case a maximum number of attempts or a maximum delay for the random access procedure towards the second replacement cell (RCE2) is reached.

16. The user equipment according to claim 1, wherein: The user equipment (1') is configured to send a first message (ME1') to the first node (NO1) or the second node (NO2) after the first condition is met, wherein the first message (M1') indicates that the first cell (CE) of the first node (NO1) has been released.

17. The user equipment according to claim 1, wherein: The user equipment (1') is configured to send a second message (ME2') to the first node (NO1) or the second node (NO2) after the second condition is met, wherein the second message (ME2') indicates that the first cell (CE) of the second node (NO2) has been released.

18. The user equipment according to claim 1, wherein: The user equipment (1') is configured to derive from the first reconfiguration request (REC1') whether the first replacement cell (RCE1) belongs to the first node (NO1) of the cellular network (CN) or the third node (NO3) of the cellular network (CN), and / or the user equipment (1') is configured to derive from the second reconfiguration request (REC2') whether the second replacement cell (RCE2') belongs to the second node (NO2) of the cellular network (CN) or the fourth node (NO4) of the cellular network (CN).

19. A method for operating a user equipment (1') for communicating on a cellular network (CN); the method comprising the following steps: Using a user equipment (1') to simultaneously communicate 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); receiving, with the user equipment (1'), a first reconfiguration request (REC1'), the request comprising an indication that a first cell (CE) of a first node (NO1) in communication with the user equipment (1') must be replaced by a first replacement cell (RCE1) of a cellular network (CN), wherein the first reconfiguration request (REC1') comprises a first change condition under which the first reconfiguration request (REC1') must be performed, and / or receiving, with the user equipment (1'), a second reconfiguration request (REC2'), the request comprising an indication that a first cell (CE) of a second node (NO2) in communication with the user equipment (1') must be replaced by a second replacement cell (RCE2') of the cellular network (CN), wherein the second reconfiguration request (REC2') comprises a second change condition under which the second reconfiguration request (REC2') must be performed, wherein the first change condition and / or the second change condition comprises: a specified number of instances in which a timer of a radio link failure timer has been started but has not expired within a specified time period; monitoring the first change condition and / or the second change condition using a monitoring unit (2') of the user device (1'); and A user equipment (1') is used to replace a first cell (CE) of a first node (NO1) by a first replacement cell (RCE1) when a monitoring unit (2') detects that a first change condition included in a first reconfiguration request (REC1') is met, and / or to replace a first cell (CE) of a second node (NO2) by a second replacement cell (RCE2) when the monitoring unit (2') detects that a second change condition included in a second reconfiguration request (REC2') is met.

20. A computer program product comprising a computer program which, when run on a processor, performs the method according to claim 19.

21. A user equipment for communicating on a cellular network (CN); wherein the user equipment (1) is configured to simultaneously communicate with one or more cells (CE) of a first node (NO1) of a cellular network and with one or more cells (CE) of a second node (NO2) of a cellular network (CN); in, 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 cell (CE) in a cell (CE) of a first node (NO1) and / or for monitoring the quality of a second communication link (CL2) between the user equipment (1) and a first cell (CE) in a cell (CE) of a second node (NO2); The user equipment (1) is configured to sending a first replacement request (REP1) for replacing a first cell (CE) of a first node (NO1) by a first replacement cell (RCE1) when the monitoring unit (2) detects a first change condition of the first communication link (CL1), the first replacement cell (RCE1) being a second cell (CE) of the first node (NO1) or a cell (CE) of a third node (NO3); and / or In the case where the monitoring unit (2) detects a second change condition of the second communication link (CL2), a second replacement request (REP2) is sent to replace the first cell (CE) of the second node (NO2) by a second replacement cell (RCE2), the second replacement cell (RCE2) being the second cell (CE) of the second node (NO2) or the cell of the fourth node (NO4), wherein the first change condition and / or the second change condition include: a specified number of instances in which the timer of the radio link failure timer has been started but has not expired within a specified time period.

22. The user equipment according to claim 21, wherein: The user equipment (1) is configured to communicate on a cellular network (CN) using dual connectivity or multiple connectivity.

23. The user equipment according to claim 21, wherein: The first node (NO1) is a base station and a master node for dual connectivity or multiple connectivity; and wherein the second node (NO2) is a base station and a secondary node for dual connectivity or multiple connectivity.

24. The user equipment according to claim 22, wherein: The first cell (CE) of the first node (NO1) is a special cell or a secondary cell of a primary cell group for dual connectivity or multiple connectivity; and / or the first cell (CE) of the second node (NO2) is a special cell or a secondary cell of a secondary cell group for dual connectivity or multiple connectivity.

25. The user equipment according to claim 21, wherein the first change condition and / or the second change condition further comprises any one of the following items or a combination thereof: A specified number of HARQ retransmissions from the PHY layer; The number of designated retransmissions from the RLC layer is less than the maximum number of radio link failures detected by the user equipment (1); Use of a weighted average or moving average or any other specified statistical method of the metrics employed that indicates degradation of signal quality; Coded or uncoded bit error rate; Packet loss rate or packet error rate; Data rate requirements; Supported bandwidth; A multi-cell event, comprising: a multi-cell event in which one of the metrics adopted by the corresponding replacement cell (RCE1, RCE2) becomes better than the corresponding metric adopted by the corresponding first cell (CE) within at least one specified period, a multi-cell event in which one of the metrics adopted by the corresponding replacement cell (RCE1, RCE2) becomes better than a threshold within at least one specified period, or a multi-cell event in which one of the metrics adopted by the corresponding first cell (CE) becomes worse than a first threshold within at least one specified time period and the corresponding metric adopted by the corresponding replacement cell (RCE1, RCE2) becomes better than a second threshold within at least one specified time period, wherein the multi-cell event is triggered by a user equipment (1'), one of the nodes (NO1, NO2) or another device of a cellular network (CN).

26. The user equipment according to claim 21, wherein: The user equipment (1) is configured to send the first replacement request (REP1) to the first node (NO1) or to the second node (NO2).

27. The user equipment according to claim 21, wherein: The user equipment (1) is configured to send the second replacement request (REP2) to the first node (NO1) or to the second node (NO2).

28. The user equipment according to claim 21, wherein: The user equipment (1) is configured to identify a candidate cell (CE) for the first replacement cell (RCE1) or the second replacement cell (RCE2) by measuring signals of possible candidate cells.

29. The user equipment according to claim 21, wherein: The user equipment (1) is configured to receive a first list (LI1) of candidate cells (CE) for the first replacement cell (RCE1) from the first node (NO1) or from a second node (NO2).

30. The user equipment according to claim 21, wherein: 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 from a second node (NO2).

31. The user equipment according to claim 21, wherein: The user equipment (1) is configured to receive a first reconfiguration request (REC1) comprising an indication of which of the cells (CE) of the cellular network (CN) is a first replacement cell (RCE1) and an indication that the first reconfiguration request (REC1) is a response to the first replacement request (REP1).

32. The user equipment according to claim 21, wherein the user equipment (1) is configured to receive the first reconfiguration request (REC1) from the first node (NO1) or from the second node (NO2).

33. The user equipment according to claim 31, wherein the user equipment is configured to communicate with the first replacement cell (RC1) after the first reconfiguration request (REC1) has been received by the user equipment (1).

34. The user equipment according to claim 31, wherein: The user equipment (1) is configured to send a first message (ME1) to the first node (NO1) or to the second node (NO2), wherein the first message (ME1) indicates that a first cell (CE) of the first node (NO1) has been released after a first reconfiguration request (REC1) has been received by the user equipment (1).

35. The user equipment according to claim 31, wherein: The user equipment (1) is configured to indicate in the first replacement request (REC1) whether the first replacement cell (RCE1) belongs to the first node (NO1) or to a third node (NO3).

36. The user equipment according to claim 21, wherein: The user equipment (1) is configured to receive a second reconfiguration request (REC2), the request comprising an indication of which of the cells (CE) of the cellular network (CN) is a second replacement cell (RCE2) and an indication that the second reconfiguration request (REC2) is a response to the second replacement request (REP2).

37. The user equipment according to claim 21, wherein the user equipment (1) is configured to receive the second reconfiguration request (REC2) from the first node (NO1) or from the second node (NO2).

38. The user equipment according to claim 36, wherein: The user equipment (1) is configured to communicate with the second replacement cell (RCE2) after receiving the second reconfiguration request (REC2) by the user equipment (1).

39. The user equipment according to claim 36, wherein: The user equipment (1) is configured to send a second message (ME2) to the first node (NO1) or to the second node (NO2), wherein the second message (ME2) indicates that the first cell (CE) of the second node (NO2) has been released after the user equipment (1) has received a second reconfiguration request (REC).

40. The user equipment according to claim 36, wherein: The user equipment (1) is configured to indicate in the second replacement request (REC2) whether the second replacement cell (RCE2) belongs to the second node (NO2) or to a fourth node (NO4).

41. A method for operating a user equipment (1) for communicating on a cellular network (CN); the method comprising the following steps: Using a user equipment (1) to simultaneously communicate 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 a user equipment (1) to monitor the quality of a first communication link (CL1) between the user equipment (1) and a first cell (CE) in a cell (CE) of a first node (NO1) and / or to monitor the quality of a second communication link (CL1) between the user equipment (1) and a first cell (CE) in a cell (CE) of a second node (NO2); Using User Equipment(1) sending a first replacement request (REP1) for replacing a first cell (CE) of a first node (NO1) by a first replacement cell (RCE1) when the monitoring unit (2) detects a first change condition of the first communication link (CL1), the first replacement cell (RCE1) being a second cell (CE) of the first node (NO1) or a cell (CE) of a third node (NO3); and / or In the case where the monitoring unit (2) detects a second change condition of the second communication link (CL2), a second replacement request (REP2) is sent to replace the first cell (CE) of the second node (NO2) by a second replacement cell (RCE2), the second replacement cell (RCE2) being the second cell (CE) of the second node (NO2) or the cell of the fourth node (NO4), wherein the first change condition and / or the second change condition include: a specified number of instances in which the timer of the radio link failure timer has been started but has not expired within a specified time period.

42. A computer program product comprising a computer program which, when run on a processor, performs the method according to claim 41.

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