Uplink inter-distributed unit low layer mobility

Abstract

In accordance with an example embodiment of the present invention, at least one method and apparatus may be used to perform establishing, by a user equipment, a connection to a serving cell supported by a first network node supporting at least one of a distributed unit function or a layer 2 protocol of a radio access network, and receiving data from the serving cell, the user equipment is configured to support parallel reception of data from two cells belonging to different network nodes of a radio access network; sending, to the serving cell, a Layer 1 measurement report comprising an indication of a second cell supported by a second network node supporting at least one of a distributed unit function or Layer 2 protocol of the radio access network, and related measurement information, to enable the first network node to monitor a low layer mobility condition; and receiving a Layer 2 message comprising an instruction for a cell change to the second cell, where the Layer 2 message further comprises an instruction to perform parallel reception from both the serving cell and the second cell at least during the cell change, and to perform parallel reception from both the serving cell and the second cell after success of the cell change to the second cell. At least one configuration of at least one of data transmission or reception with the serving cell is reserved.

Description

Technical Field

[0001] Teachings according to example embodiments of the present invention relate generally to reducing disruption of cell change operations, and more particularly, to reducing disruption of low-layer mobility between distributed units through ping-pong operations. Background Art

[0002] This section is intended to provide a background or context to the inventions described in the claims. The description herein may include concepts that could be pursued, but not necessarily concepts that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.

[0003] Certain abbreviations that may appear in the specification and / or drawings are defined as follows:

[0004] CE: Control Element

[0005] CU: Central Unit

[0006] CU-CP: Central Unit Control Panel

[0007] CU-UP: Centralized Unit User Plane

[0008] DAPS: Dual Active Protocol Stack

[0009] DU: Distributed Unit

[0010] gNB: Base Station

[0011] HO: Handover

[0012] L1: Layer 1

[0013] L2: Layer 2

[0014] LLM: Low Layer Mobility

[0015] MAC: Media Access Control

[0016] MAC CE: Media Access Control Element

[0017] mTRP: Multiple Send / Receive Points

[0018] NR: New Radio

[0019] NR-CGI: New Radio Cell Global Identity

[0020] PDCP: Packet Data Convergence Protocol

[0021] PDU: Protocol Data Unit

[0022] RACH: Random Access Channel

[0023] RAN: Random Access Network

[0024] RRC: Radio Resource Control

[0025] RRM: Radio Resource Management

[0026] SCC: Serving Cell Change

[0027] TAC: Tracking Area Code

[0028] PS: Protocol Stack

[0029] UE: User Equipment

[0030] UP: User plane

[0031] At the time of this application, 3GPP defines Figure 1 The decomposed architecture shown in the specification breaks down the gNB into multiple logical entities. Similarly, a single DU can host multiple cells (up to 512 in the specification). The gNB-CU-CP hosts the PDCP and RRC layers, while the gNB-DU hosts the RLC / , MAC, and PHY layers. Scheduling operations are performed at the gNB-DU.

[0032] At the time of this application (hereinafter referred to as "current"), the standard version is limited to intra-DU mTRP operation to support transmission and reception of multiple beams from different cells, and operators and vendors strongly request that more extensive work continue in future standard versions, and may reach an agreement. This will also expand support for changing the serving cell via L1 / L2-based mechanisms in both intra-DU scenarios and inter-DU scenarios. Figure 2 An inter-cell mobility scenario centered around L1 / L2 is shown.

[0033] To support L1 / L2 centric inter-cell changes (i.e., change of serving cell) in a decomposed gNB architecture, a new mechanism is required where the configuration will be done at the gNB-CU-CP but performed autonomously by the gNB-DU without further interaction with upper layers.

[0034] Example embodiments of the invention disclosed herein address at least these needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and other aspects, features, and benefits of various embodiments of the present disclosure will become more apparent through the following detailed description with reference to the accompanying drawings, in which the same reference numerals are used to represent the same or equivalent elements. The accompanying drawings are illustrated to facilitate a better understanding of the embodiments of the present disclosure and are not necessarily drawn to scale. In the accompanying drawings:

[0036] Figure 1The decomposed gNB architecture is shown;

[0037] Figure 2 An inter-cell mobility scenario centered around L1 / L2 is shown;

[0038] Figure 3 An LLM inter-DU scenario is shown;

[0039] Figure 4 shows low-layer mobility capture data forwarding;

[0040] Figure 5A and Figure 5B shows message exchanges with reduced UP outages and DAPS / mTRP interworking according to an example embodiment of the present invention;

[0041] Figure 6 shows high-level block diagrams of various devices used to implement various aspects of the invention; and

[0042] Fig. 7A , Figure 7B , Figure 7C , Fig.7D ,as well as Fig. 7E Each of which illustrates a method according to an example embodiment of the present invention, which method may be performed by an apparatus;

[0043] Figure 8 Message exchanges with reduced UP outages and without DAPS / mTRP configured are shown according to an example embodiment of the present invention. DETAILED DESCRIPTION

[0044] In the exemplary embodiments of the present invention disclosed herein, operations and apparatus are proposed for reducing the disruption of low-layer mobility between distributed units through ping-pong operations.

[0045] As mentioned above, in order to support L1 / L2 centric inter-cell changes (i.e., change of serving cell) in a decomposed gNB architecture, a new mechanism is required where the configuration will be done at the gNB-CU-CP but performed autonomously by the gNB-DU without further interaction with upper layers.

[0046] This includes two aspects:

[0047] a. Multi-TRP operation involving serving and secondary cells, including both intra-DU and inter-DU scenarios; and

[0048] b. Inter-cell changes centered on L1 / L2, including intra-DU scenarios and inter-DU scenarios.

[0049] Some definitions used in this article are as follows:

[0050] mTRP operation: simultaneous DL / UL transmission in serving and supplementary cell TRPs;

[0051] · Secondary cell: A non-serving cell used to assist the UE in multi-TRP operation. It can belong to the same DU or a different DU of the hosting serving cell, but must belong to the same gNB-CU; and

[0052] DAPS: Dual Active Protocol Stack, defined as part of the current standard.

[0053] Some of the goals of the current standard include:

[0054] 1. To specify mechanisms and procedures for L1 / L2 based inter-cell mobility for mobility delay reduction:

[0055] ○ Configure and maintain multiple candidate cells to allow for quick application of the configuration of the candidate cells [RAN2, RAN3],

[0056] ○ Dynamic switching mechanism between candidate serving cells (including SC cells) for potential applicable scenarios based on L1 / L2 signaling [RAN2, RAN1],

[0057] ○ L1 enhancements for inter-cell beam management, including L1 measurements and reporting, and beam indication [RAN1, RAN2]:

[0058] - NOTE 1: Early engagement of RAN2 is necessary, including further clarification of the potential for interaction between this point and previous points,

[0059] ○Timing advance management [RAN1, RAN2],

[0060] o CU-DU interface signalling, if required, to support L1 / L2 mobility [RAN3]:

[0061] NOTE 2: FR2 specific enhancements are not excluded (if any).

[0062] Note 3: The L1 / L2-based inter-cell mobility process is applicable to the following scenarios:

[0063] ■Standalone, CA, and NR-DC situations of serving cell changes within a CG,

[0064] ■ Intra-DU case and intra-CU inter-DU case (applicable to both standalone and CA: no new RAN interface is expected),

[0065] ■Both intra-frequency and inter-frequency,

[0066] ■Both FR1 and FR2, and

[0067] ■The source cell and the target cell can be synchronized or not

[0068] Further explanation:

[0069] Low layer mobility is a mobility feature and can be considered as a basic UE capability (starting from R18),

[0070] DAPS and mTRP operations are two other different functions and therefore they have different UE capabilities, and

[0071] It is very likely that a UE is capable of LLM but not mTRP or DAPS.

[0072] Some objectives of example embodiments of the present invention may include:

[0073] Provide uninterrupted data transmission during inter-DU LLM, and / or

[0074] Enabling low-layer mobility procedures to meet stringent requirements for low outage times in certain use cases (e.g., AR / XR, URLLC), where outage times of 5-10ms are expected.

[0075] Figure 3 The DU scenario in LLM is shown. Figure 3 In the scenario shown, there are:

[0076] DL transmission at the source DU (controlling serving cell 1),

[0077] a target cell (non-serving cell) (cell 3), which is configured as one of the LLM preparation cells at both the DU(s) and the UE,

[0078] The UE reports L1 measurements to the serving DU, and

[0079] • Based on the conditions configured for LLM, the serving DU sends a MAC CE to the UE to perform a serving cell change (SCC) and random access to the target cell (if required in an unsynchronized scenario).

[0080] Figure 4 The low layer mobility capture data forwarding according to current standards is shown.

[0081] Figure 4 A signaling diagram of the inter-DU low layer mobility procedure is shown, including data forwarding to the UE from both the source cell (before the cell change in step 14) and the target cell (after the cell change).

[0082] Problems with the current standards include:

[0083] During the SCC from the source cell (cell 1) to the target cell (cell 3), i.e. Figure 4 In step 14 to step 22 of the above, there is a UP interruption, and such a delay may be unacceptable for some of the above services, and

[0084] • After performing LLM HO, the CU needs to perform bearer modification to enable data transmission from the target (now serving) DU to the UE.

[0085] Example embodiments of the invention disclosed herein aim to at least reduce user plane interruptions during LLM execution.

[0086] There are some L3-based mechanisms that can be suitable for reducing user plane disruptions, but require a lot of additional signaling, some of which are as follows.

[0087] 1: LTE is established first and then interrupted.

[0088] 2: No RACH HO,

[0089] 3: DAPS switching (and early data forwarding),

[0090] 4: Single active protocol stack handover (UE performs random access to the target cell while receiving from the source cell, and when it receives a RACH response, the UE detaches from the source cell and sends an RRC completion to the target cell),

[0091] 5: DC-based HO, and

[0092] 6: Add the target gNB as a SN, swap roles later, and then release the SN (i.e., the old source gNB).

[0093] Note, however, that there appears to be no known prior art that can reduce user plane outages during L1 mobility. It is also important to note that the above mechanism cannot be used like LLM.

[0094] In addition, in 5G (e.g., due to the network topology that enables support / provides multiple different services, and a large number of overlapping 5G cells / small cells / millimeter wave beams, etc.), more and more ping-ponging may occur. Ping-pong can be based on inadvertently switching to cells in multiple cells in succession over a period of time. In 5G technology, the use of millimeter waves is a major factor affecting mobility. This is due to the high path loss when using millimeter wave bands, which reduces cell coverage. The result is a significant increase in the probability of switching, which leads to an increase in mobility issues such as high switching failures, switching ping-pong effects, and radio link failures.

[0095] Example embodiments of the present invention relate to, for example:

[0096] Resolving user plane outage issues through early detection of low layer mobility at the source DU and early data transfer to the target DU, and / or

[0097] Ping-Pong problem (continuous handovers to and fro the same cell or any other cell within a certain time limit (e.g. 3 seconds)) can be solved by creating and storing a mapping table at the CU-UP to identify the UE and its configuration in a given DU / cell, as long as ping-pong is possible. During this period, the user configuration can also be retained at the DU:

[0098] The mapping table at the CU-UP is created based on the input from the CU-CP. It associates the UE with its configuration in the gNB. For example: a UE configured for multi-TRP operation may include the UE ID, configured service (mTRP), serving and secondary cells in each DU served by the CU-UP, etc., and

[0099] • This enables the CU-UP to decide whether a connection to the old source cell is available when starting data transmission.

[0100] Before describing in detail exemplary embodiments of the present invention, please refer to Figure 6 , Figure 6 Simplified block diagrams are provided to illustrate various electronic devices that are suitable for practicing the example embodiments of this invention.

[0101] Figure 6 A block diagram of one possible and non-limiting exemplary system in which an exemplary embodiment of the present invention may be practiced is shown. Figure 6 In the embodiment, the user equipment (UE) 10 and the Figure 6 The wireless network 1 or network 1 shown performs wireless communication. Figure 6 The wireless network 1 or network 1 shown in the figure may include a communication network, such as a mobile network, for example, the mobile network 1 or the first mobile network disclosed herein. Figure 6 Any reference to wireless network 1 in the specification may be considered a reference to any wireless network disclosed herein. Figure 6 The wireless network 1 shown in the figure may also include hard-wired features that may be required by the communication network. UE is a wireless device that can access a wireless network, usually a mobile device. For example, UE can be a mobile phone (or "cellular" phone), and / or a computer with mobile terminal functions. For example, UE or mobile terminal can also be a portable, pocket-sized, handheld, computer-embedded, or vehicle-mounted mobile device, and performs voice signaling and / or data exchange with RAN.

[0102] UE 10 comprises: one or more processors DP 10A, one or more memories MEM 10B, and one or more transceivers TRANS 10D interconnected by one or more buses. Each transceiver TRANS 10D in the one or more transceivers TRANS 10D comprises a receiver and a transmitter. One or more buses may be address, data or control buses, and may comprise any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, optical fiber, or other optical communication devices, etc. One or more transceivers TRANS 10D may optionally be connected to one or more antennas for communicating with NN 12 and NN 13, respectively. One or more memories MEM 10B comprise computer program code PROG 10C. UE 10 communicates with NN 12 and / or NN 13 via wireless link 11 or 14.

[0103] NN 12 (NR / 5G NodeB, Evolved NB or LTE equipment) is connected to the Figure 6 The NN 12 is a network node for communicating with devices such as NN 13 and UE 10, such as a master node or a secondary node base station (for example, for NR or LTE long term evolution). NN 12 provides access to wireless devices (such as UE 10) of the wireless network 1. NN 12 includes one or more processors DP 12A, one or more memories MEM 12B, and one or more transceivers TRANS 12D interconnected by one or more buses. According to an example embodiment, these TRANS 12D may include X2 and / or Xn interfaces for performing example embodiments of the present invention. Each transceiver TRANS 12D in the one or more transceivers TRANS 12D includes a receiver and a transmitter. One or more transceivers TRANS 12D may optionally be connected to one or more antennas for communicating with UE 10 via at least link 11. One or more memories MEM 12B and computer program code PROG 12C are configured to, together with one or more processors DP 12A, cause NN 12 to perform one or more of the operations described herein. NN 12 may communicate with another gNB or eNB or a device such as NN 13, such as via link 14. In addition, link 11, link 14, and / or any other link may be wired or wireless or both, and may implement, for example, an X2 or Xn interface. In addition, link 11 and / or link 14 may pass through other network devices, such as, but not limited to, Figure 6 The NCE / MME / SGW / UDM / PCF / AMF / SMF / LMF 14 devices are shown. The NN 12 may perform MME (Mobility Management Entity) or SGW (Serving Gateway) functions, such as user plane functions and / or access management functions of LTE and similar functions of 5G.

[0104] NN 13 may be associated with a mobility function device such as AMF or SMF, and may include: NR / 5G NodeB, or possibly an evolved NB, i.e. a base station such as a master node or a slave node base station (e.g., for NR or LTE long term evolution) that communicates with devices such as NN 12 and / or UE 10 and / or wireless network 1. NN 13 includes: one or more processors DP 13A, one or more memories MEM 13B, one or more network interfaces, and one or more transceivers TRANS 13D interconnected by one or more buses. According to an exemplary embodiment, these network interfaces of NN 13 may include X2 and / or Xn interfaces for performing exemplary embodiments of the present invention. Each of the one or more transceivers TRANS 13D includes a receiver and a transmitter that may be optionally connected to one or more antennas. The one or more memories MEM 13B include computer program code PROG 13C. For example, one or more memories MEM 13B and computer program code PROG 13C are configured to, together with one or more processors DP 13A, cause NN 13 to perform one or more of the operations described herein. NN 13 may communicate with another mobility function device and / or eNB (such as NN 12 and UE 10) or any other device using, for example, link 11 or link 14 or another link. Figure 6 The link 14 shown may be used for communication between NN 12 and NN 13. These links may be wired or wireless or both, and may implement, for example, an X2 or Xn interface. In addition, as described above, link 11 and / or link 14 may pass through other network devices, such as but not limited to NCE / MME / SGW devices, such as Figure 6 NCE / MME / SSGW / UDM / PCF / AMF / SMF / LMF 14.

[0105] Figure 6 The one or more buses of the devices may be address, data, or control buses and may include any interconnection mechanism, such as a series of wires on a motherboard or integrated circuit, optical fiber or other optical communication devices, wireless channels, etc. For example, one or more transceivers TRANS 12D, TRANS 13D, and / or TRANS 10D may be implemented as a remote radio head (RRH) where the other elements of the NN 12 are physically located at a different location from the RRH, and the devices may include one or more buses that may be implemented in part as fiber optic cables for connecting the other elements of the NN 12 to the RRH.

[0106] It should be noted that although Figure 6Network nodes such as NN 12 and NN 13 are shown, but any of these nodes may be incorporated or merged into an eNodeB, eNB, or gNB, such as for LTE and NR, and may still be configured to perform example embodiments of the present invention.

[0107] It should also be noted that the description herein indicates that a "cell" performs functions, but it should be clear that the gNB and / or user equipment and / or mobility management function device forming the cell will perform these functions. In addition, a cell constitutes part of a gNB, and each gNB can have multiple cells.

[0108] The wireless network 1 or any network it may represent may or may not include NCE / MME / SGW / UDM / PCF / AMF / SMF / LMF 14, which may include: (NCE) network control element function, MME (mobility management entity) / SGW (serving gateway) function, and / or serving gateway (SGW), and / or MME (mobility management entity), and / or SGW (serving gateway) function, and / or user data management function (UDM), and / or PCF (policy control) function, and / or access and mobility management function (AMF) function and, and / or session management (SMF) function, and / or location management function (LMF), and / or authentication server (AUSF) function, and provide connection to another network (such as a telephone network and / or a data communication network (e.g., the Internet)), and it is configured to perform any 5G and / or NR operations as a supplement or alternative to other standard operations at the time of this application. NCE / MME / SGW / UDM / PCF / AMF / SMF / LMF 14 may be configured to perform operations according to an exemplary embodiment of the present invention in any of LTE, NR, 5G, and / or any standard-based communication technologies implemented or discussed at the time of this application. In addition, it should be noted that operations according to an exemplary embodiment of the present invention (such as performed by NN 12 and / or NN 13) may also be performed at NCE / MME / SGW / UDM / PCF / AMF / SMF / LMF 14.

[0109] The NCE / MME / SGW / UDM / PCF / AMF / SMF / LMF 14 includes: one or more processors DP 14A, one or more memories MEM 14B, and one or more network interfaces (N / WI / F) interconnected by one or more buses coupled to the link 13 and / or the link 14. According to an exemplary embodiment, these network interfaces may include X2 and / or Xn interfaces for performing exemplary embodiments of the present invention. The one or more memories MEM 14B include computer program code PROG 14C. The one or more memories MEM 14B and the computer program code PROG 14C are configured to, together with the one or more processors DP 14A, enable the NCE / MME / SGW / UDM / PCF / AMF / SMF / LMF 14 to perform one or more operations that may be required to support operations according to exemplary embodiments of the present invention.

[0110] It should be noted that the NN 12 and / or the NN 13 and / or the UE 10 may be configured (e.g., based on standard implementations, etc.) to perform location management functions (LMF). The LMF function may be embodied in content consumer A, content consumer B, a cache server, and / or a content provider, or may be part of these network devices or other devices associated with these devices. In addition, the LMF (such as Figure 6 The LMF of the MME / SGW / UDM / PCF / AMF / SMF / LMF 14, at least as described below) can be co-located with the UE 10 so as to communicate with the UE 10. Figure 6 NN 12 and / or NN 13 are separate for performing operations according to the example embodiments of the present invention disclosed herein.

[0111] The wireless network 1 can implement network virtualization, which is a process of combining hardware and software network resources and network functions into a single software-based management entity (i.e., a virtual network). Network virtualization involves platform virtualization, which is usually combined with resource virtualization. Network virtualization is divided into two categories: one is external, which combines many networks or network parts into virtual units; the other is internal, which provides network-like functions for software containers on a single system. Note that the virtualized entities generated by network virtualization are still implemented to some extent using hardware such as processors DP10, DP12A, DP13A, and / or DP14A, and memories MEM 10B, MEM 12B, MEM 13B, and / or MEM 14B, and such virtualized entities also produce technical effects.

[0112] The computer readable memory MEM 12B, MEM 13B, and MEM 14B may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The computer readable memory MEM 12B, MEM 13B, and MEM 14B may be a component for performing storage functions. The processor DP10, DP12A, DP13A, and DP14A may be of any type suitable for the local technical environment and, as a non-limiting example, may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. The processor DP10, DP12A, DP13A, and DP14A may be a component for performing functions, such as controlling UE 10, NN 12, NN 13, and other functions described herein.

[0113] As described above, example embodiments of the present invention relate to, for example:

[0114] addressing user plane outage issues by supplementing early detection of low-layer mobility at the source DU and early data transmission to the target DU, and / or

[0115] By creating and storing a mapping table at the CU-UP to identify the UEs and their configurations in a given DU / cell, the ping-pong problem (continuous switching back and forth to the same cell within a certain time limit, such as 3 seconds) can be solved as long as ping-pong is possible. The user configuration can also be retained at the DU during this duration.

[0116] The mapping table at the CU-UP is created based on the input from the CU-CP. It associates the UE with its configuration in the gNB. For example: a UE configured for multi-TRP operation may include the UE ID, configured service (mTRP), serving and secondary cells in each DU served by the CU-UP, etc., and

[0117] This enables the CU-UP to decide whether a connection to the old source cell is available when starting data transmission.

[0118] While this may be an implementation detail, one principle is that both the forward and reverse paths can be covered (e.g. cell change ping-pong back and forth), in which case the CU-UP stores the mapping of the source and target paths and can replicate in both branches based on instructions from the CU-CP. Figure 5B After step 39 in ), use Figure 5AThe cell ID index configured in step 9 is used to address the CU-UP, and similarly follows Figure 5B Follow steps 29 to 37 in the documentation. Figure 5A and Figure 5B Message exchanges with reduced UP outages and parallel data paths (eg, based on UE's DAPS / mTRP support) according to example embodiments of the present invention are shown.

[0119] More specifically, elements of an exemplary embodiment of the present invention may include at least one of the following:

[0120] • The UE is configured to keep the source cell configuration after receiving the LLM handover (step 13), and is also able to receive packets via the source configuration until the source configuration is released (and / or if the ping-pong timer expires).

[0121] Before or after sending the MAC CE command for the LLM SCC, the serving DU sends a control PDU to the CU-UP to initiate repeated transmission of packets at the serving DU and the target DU (e.g., steps 13 and 14, or steps 31 and 36). This is decided based on the RRM defined thresholds configured by the CU-CP or DU. The control PDU may also indicate (via an index) the exact target DU and cell to which data transmission is to be initiated,

[0122] Indication of SCC switching from DU to CU-UP:

[0123] After or before sending the MAC CE for the LLM SCC, the service DU sends a control PDU to indicate that the UE serving cell change is initiated. The CU-UP may also initiate the duplication of the PDCP PDU at this time (e.g., step 15 or step 33),

[0124] After sending the MAC command for LLM switching, the serving DU shall keep the low layer configuration. If the UE indicates that the switching requires RACH access, the source DU can continue to be scheduled using the current TCI, because the TCI switching is only valid after RACH. When the switching notification is received from the CU-CP, the PDCCH using the old TCI will stop, and

[0125] The target DU can be determined based on RACH,

[0126] • After a successful RACH, the target DU sends a control PDU to the CU-UP to indicate that the serving cell change is complete (eg, step 22).

[0127] Notice:

[0128] If mTRP or DAPS is configured for the UE during this serving cell change duration, or if the UE supports DAPS and / or mTRP operation, the UE may receive from both the serving cell and the target cell, resulting in almost zero user interruption time (e.g., steps 16 and 17), or

[0129] If the UE is not configured with mTRP or DAPS due to UE capability limitations, in case of ping-pong, user service interruption will be reduced and SCC will be faster because the F1-U tunnel to the serving DU is not released during this period.

[0130] As long as ping-pong is possible, the source cell connection is retained (at CU-UP, DU and UE). This is determined, for example, based on UE measurements:

[0131] CU-UP stores the UE’s configuration in a given target cell,

[0132] If there is a ping-pong, the new SRC (old target) sends a control PDU to indicate that the UE serving cell change is initiated (e.g., step 31),

[0133] The CU-UP may start copying the PDCP PDUs to the new TRC (old source) by activating the old source connection that was deactivated after stopping before the copying of the data (e.g., steps 33 and 34),

[0134] The target cell ID index is indicated in the control PDU so that the CU-UP can determine whether it can start replication for a given UE in a given cell (based on the stored mapping),

[0135] If, after the serving cell change from the source cell to the target cell, the UE does not return to the source cell within a timer (required for ping-pong detection, e.g., 1 s or 3 s), the old serving DU may notify the CU-UP to release the UE context of the source cell from the mapping table (e.g., step 26).

[0136] · Figure 5A Step 5 is to prepare the target cell in the target DU according to an exemplary embodiment of the present invention. Therefore, it is from the CU-CP to the target DU. Figure 5A In step 5, the UE context establishment request message may include at least one of the following:

[0137] - Cell ID index (used to enable triggering of PDU duplication, pausing source cell transmission, etc.), and

[0138] -UE configuration information (with information / flag: "Preserve source connection configuration after SCC (serving cell change, handover)" (-> in case of handover to target DU, it will be forwarded to UE). It should be noted that the information / flag "Preserve source connection configuration after SCC (serving cell change, handover)" can be forwarded to the UE in step 10 included in the RRC reconfiguration message, or in step 13 included in the MAC CE message. It should be noted that the information / flag: "Preserve target connection configuration after SCC (serving cell change, handover)" can be forwarded to the UE in step 10 in step 37 included in the MAC CE message.

[0139] It should be noted that Figure 5B In the example embodiment, steps 23-28 and steps 29-44 may be alternative or optional steps, i.e., based on different scenarios when ping-pong processing is no longer needed or activated. At least for this reason, options according to example embodiments of the present invention may include: Figure 5B Option 1 with steps 23 to 28, or Figure 5B Option 2 with steps 29 to 44.

[0140] Release the old source cell and stop data transmission (CU-UP, old source DU):

[0141] DL transmission to the previous source cell is advantageously not stopped upon receipt of an indication from the target DU, but after the source buffer transmission is complete. This is particularly beneficial for avoiding PDCP duplicate detection and reordering,

[0142] A control PDU-based indication from the source DU to the CU-UP indicating that the remaining PDUs were successfully sent (based on timer or packet status). The CU-UP can indicate to the CU-CP that the source connection can be released based on this indication,

[0143] The target DU also reports its request to release the source protocol stack (PS) when the source cell condition deteriorates. The CU-CP decides on the release of the source PS based on the indications from the CU-UP and the target DU, and

[0144] When there is a ping-pong, the source connection can be restored.

[0145] Cell index:

[0146] CU-CP recommends indexing all LLM target cell configurations for a UE for easy identification. It is also recommended to signal CU-UP and DU (both serving DU and target DU). This ensures that when sending a control PDU from a DU to a CU-UP or vice versa, the cell index can be used to identify the DU and the cell, and determine the NR-CGI of the cell.

[0147] Note that the cell index can be used to enable the CU-UP to provide data to the target DU without providing the entire NR-CGI.

[0148] None of the above steps can overturn the CU-CP decision. If the CU-CP initiates a release, it can override the CU-UP decision.

[0149] According to an exemplary embodiment of the present invention, Figure 5A In step 7, the bearer establishment request message may include at least one of the following:

[0150] - Cell ID index (used to enable duplication of PDUs, suspension of source cell transmissions, etc.), and

[0151] -UE configuration information (UE supports simultaneous / parallel data transmission / reception, e.g. indicated by supporting DAPS and / or mTRP), to enable duplication of PDUs and parallel transmission of data to different DUs).

[0152] This index identifies one of the 8 potential target cells. The selection of 8 (maximum possible) potential target cells is a matter of the RRM algorithm at the CU-CP. The CU-CP selects the target cell based on L3 measurements. This may be affected by the cell size, UE mobility, RSRP reported by the UE, etc. The index can be seen from the UE's perspective. It is unique to the UE. Each UE can have 8 LLM targets, and instead of using their NR-CGI (36-bit identifier) ​​to indicate these 8 cells, we recommend using an index that only requires 3 bits to represent the 8 values. When the target cell is configured for the UE, the CU-CP will send a mapping between the NR-CGI of the LLM target cell and the index. It may be overwritten when needed.

[0153] If the UE does not return to the source cell within a timer (required for ping-pong detection, such as 1 s or 3 s) after a cell change from the source cell to the target cell, the DU may notify the CU-UP to release the UE context of the source cell.

[0154] It should be noted that at step 20, a ping-pong timer is started, and then if the timer expires, a different procedure may still be followed to switch.

[0155] It should be noted that in an exemplary implementation, the source DU and the target DU share the same CU-UP (same TEID). This is beneficial because no PDCP relocation is required and no security aspects need to be considered.

[0156] According to an exemplary embodiment of the present invention, the value of the timer can correspond to a specific local requirement of the network, for example, the network can monitor the number of ping-pongs occurring locally, for example, the CU collects the number of ping-pongs in the controlled cells, and then the CU can determine a configurable value of the timer to reduce the negative impact of ping-ponging, for example, in areas with a large number of ping-pongs, for example, many cells overlap due to the local environment, such as many cells in some areas such as the central station and the constant movement of users, a higher number of ping-pons may occur, so a higher value (e.g., a longer duration of the timer, such as 3 seconds instead of 1 second) can be beneficial. For example, in areas where a low number of ping-pongs is expected and / or measured and / or actually occurs, for example, there are few cell overlaps due to the local environment, such as few cells in some areas such as rural areas, alleys, and / or the amount of user movement is low (e.g., pedestrians only), a lower number of ping-pongs may occur, so a lower value (e.g., a shorter duration of the timer, such as 1 second instead of 3 seconds) can be beneficial. The CU can even decide to set the timer to zero, and / or not use the special process of ping-ponging at all, but follow the traditional process. In the conventional process, the source connection will not be retained after the SCC, so after a successful handover, the source configuration will be released. This usually occurs within milliseconds, such as 10 to 60ms. In contrast, when using the new process with the process of retaining the source connection after the SCC, a ping-pong timer will be started so that the retention time can be extended to 3 seconds. The ping-pong timer can be configured to have any value between 1 and 3 seconds, for example, to cover the range of time periods where potential ping-pong may occur, thereby simplifying the handover to the source cell.

[0157] Therefore, after determining that a target cell needs to be prepared in a DU different from the DU serving the UE, the CU checks the situation related to the ping-pong probability from / to the target cell, and according to the result (and according to whether the UE supports the SCC post-retention source connection process), sets the value of the timer to a lower or higher value, or decides not to use the SCC post-retention source connection, but simply cancels the source configuration after a successful handover. In this way, fast handover can be enabled if necessary and adapted to the local environment, network, and UE capabilities.

[0158] Furthermore, if resources reserved in the CU-UP (reserved for copy / ping-pong but not used after a successful handover to the target DU but without potential ping-pong, e.g. during 3 seconds, these resources will be reserved but no physical transmission will occur, so these resources will be reserved in the network for (potential) ping-pong. According to an example embodiment of the present invention, the resources should be released after ping-pong is no longer possible.

[0159] There are at least two purposes for the timer in the DU: to check whether the UE has indeed returned to the source cell, and to release the source cell after all remaining PDUs have been sent. Figure 5B As shown in FIG, the timer expires in step 29, which results in the release of the source cell. Figure 5B As shown, it starts immediately after step 21.

[0160] exist Figure 5B In step 22 of , the CU-UP is notified of the successful handover to the target DU, but the copying of data continues (even after a successful handover, the UE continues to receive data from the source and target DUs, for example, until a certain data buffer is empty, such as for the successful transmission of an ongoing video sequence, etc., and / or to avoid a ping-pong effect (as can be determined based on L1 measurements). Then, as Figure 5B As shown in , the copying will continue to step 26.

[0161] RRC configuration completion is not processed at the DU but at the CU, and the trigger indicated here is to send a notification immediately after the RA step is completed.

[0162] Notice, Figure 5B It may be adapted to optionally include a new step 21a (not shown) - sending RRC reconfiguration complete, and a new step 20b (not shown) - sending a notification to trigger stopping replication. As an alternative, if RACH is performed, the UE sending a MACCE in the UL may be an indication of the DU, but this is not necessary because the target DU may simply rely on the RACH success.

[0163] like Figure 5B As shown in , the control PDU is used for copying in step 26. In addition, according to an exemplary embodiment of the present invention, the old service DU may be allowed to indicate to the CU-UP to stop providing data, such as after the buffer is completed (to avoid a sudden stop).

[0164] In addition, if Figure 5A and Figure 5B As shown in , in the case where a control PDU can be used, a second option can be applied, for example, "pause source" stops copying and thereby releases resources in the CU-UP. In addition, in an alternative embodiment ( Figure 5A or Figure 5B (not shown), an additional timer is required in the CU-UP, which will release the resources after expiration. This timer can be triggered so that the timer in the CU-UP is synchronized with the timer in the target DU. Then, there is no need for Figure 5B 26 in the above example, but CU-UP will execute the following steps independently: Figure 5B 27 and 28 as shown in FIG.

[0165] According to an exemplary embodiment of the present invention, if the resources are released based on a timer, no control PDU is needed (implicit release). If it is based on source cell radio conditions, a control PDU may be used.

[0166] Furthermore, according to an example embodiment of the present invention, from the UE side, based on an indication from the DU, parallel reception from the source cell and the target cell is performed. Subsequently, it is also new that the source cell resources are reserved for data transmission / reception until an explicit indication from the DU (avoiding ping-pong). It should be noted that although there are similarities between this and mTRP, the key difference is that the source cell in LLM is / is not a secondary cell (as in mTRP). This is purely from a HO perspective, unlike mTRP, the data in the source cell and the target cell cannot be different, they must be duplicated.

[0167] According to an exemplary embodiment of the present invention, there is a UE that can support receiving data from two different DUs in parallel, wherein the UE is configured to: connect to a first cell of a source DU, receive data from the source cell, send a measurement report, receive a message including a cell change command to a second cell of a target DU, the message also including instructions for performing parallel reception from the source and target cells, and after the cell change to the second cell, retaining source cell resources / configuration for data transmission / reception, receiving data from the second cell, and retaining source cell resources and / or configuration.

[0168] It should be noted that some key differences from L3-based DAPS can be summarized as follows. (The details of these methods involving new inter-node messages between CU / S-DU / T-DU are specific new methods):

[0169] -DU triggers dual-cell transmission / reception between / to UEs, with "minimum capabilities / features of DAPS, but not all the complexity". For example, PDCP at CU-UP can remain unchanged, as the CU is fixed here for LLM. The goal is hitless LLM, which is not achievable using DAPS, and

[0170] -Switch to multiple target cells or ping-pong is possible. Keeping the source PS part of DAPS inactive instead of releasing the source PS is a new aspect. This is also an important way to reduce LLM interrupts, which are expected to switch frequently between multiple cells. (In DAPS, by default, the source PS is released after the RACH to the target is successfully completed. This should not happen with LLM).

[0171] 1. Potential problems:

[0172] During the SCC, from the source cell (cell 1) to the target cell (cell 3), that is, from step 14 to step 22, as shown in FIG. Figure 4 As shown in , there is a UP interruption; for some services as described above, this delay may be unacceptable.

[0173] In fact, if there is DAPS, the UP outage can be eliminated. But DAPS requires dual receiver chains at the UE and has heavy resource requirements on the network side. It is preferable to have supplementary features to overcome the UP outage problem of basic UE capabilities (e.g., Layer 2 capabilities). Example embodiments of the present invention propose a solution to reduce UP outages using LLM.

[0174] 2. Potential problems:

[0175] After performing LLM HO, the CU needs to perform bearer modification to enable data transmission from the target (now serving) DU to the UE.

[0176] As mentioned above, DAPS is not a mandatory capability of the UE. But UP interruption reduction also applies to non-DAPS UEs. For example, it can be a UE without any enhanced features or an mTRP UE. In addition, LLM allows up to 8 cells, and the present invention proposes to remember the UE configuration of these cells at the CU-UP so that in the case of ping-pong, the configuration can be activated immediately.

[0177] DAPS is a high-level feature (L3 preparation and execution). Even if we consider UE and network that support DAPS, it is reasonable to prepare DAPS in 1 target cell. It is very complicated to prepare and configure DAPS among 8 cells. This becomes an overhead when intercommunication between DAPS and LLM is performed. DAPS must be configured before LLM can be performed, which also slows down LLM.

[0178] A suggestion according to an example embodiment of the present invention may include that whenever a target cell is prepared, the CU-CP notifies the CU-UP of the association between the LLM target cell and the index.

[0179] Furthermore, it can be assumed that ping-pong refers to switching back and forth between one source cell and one target cell, or it can be ping-pong between 8 cells. It should be noted that ping-pong by definition is usually only between two cells, but the concept can be extended to more than 2 cells if the vendor implementation requires it.

[0180] 3. Potential Problems

[0181] To the best of the inventors' knowledge, there is no known prior art for reducing user plane outages during L1 mobility. The example embodiments of the present invention address this problem. This is because DAPS is considered an expensive feature in terms of overhead and resource consumption. Therefore, it is not part of the basic feature set in the UE or the network. Therefore, it cannot be assumed to be a basic solution to prevent UP outages.

[0182] 4. Example embodiments of the present invention include:

[0183] Example embodiments of the present invention address the user plane outage problem by supplementing early detection of low-layer mobility at the source DU and by early data transmission to the target DU. (Features such as DAPS and mTRP can also be optionally configured for capable UEs)

[0184] As discussed in this article, some other differences in DAPS include:

[0185] - In case of DAPS, packet duplication occurs at L3 where PDCP is reconfigured as PDCP-DAPS. In lower layer mobility scenarios, PDCP remains unaffected,

[0186] - In DAPS, the CU decides on the DAPS activation as well as the handover command (L3 message) itself. In case of LLM, the DU only knows when the handover occurs (L2 message), the packet replication will be initiated based on the trigger from the DU to the CU, and the execution is at the DU, and

[0187] - LLM is different from L3 handover from the perspective of delayed execution based on decisions at the DU. In this case, PDCP duplication for hitless operation at the CU would be redundant, also affecting reordering after execution. Moreover, the CU does not even know where to start packet duplication. Therefore, the initiation of hitless LLM dual-cell transmission triggered by the DU is a new aspect compared to the basic L3-based DAPS operation.

[0188] Example embodiments of the present invention include:

[0189] By creating and storing a mapping table at the CU-UP to identify the UEs and their configurations in a given DU / cell, the ping-pong problem (continuous switching back and forth to the same cell within a certain time limit, such as 3 seconds) can be solved as long as ping-pong is possible. The user configuration can also be retained at the DU during this duration.

[0190] If a required cell change occurs after a successful DAPS handover, a new RRC configuration is needed to prepare the UE for the handover (if the cell does not belong to the same DU as the serving cell), which requires time and additional signaling messages. A method is being sought to reduce the workload of such new handovers.

[0191] In a ping-pong case, e.g. a first DAPS handover from cell 1 of DU1 to cell 2 of DU2, and after a successful DAPS handover, a second handover back to cell 1 (and back to cell 2, ...):

[0192] An example embodiment of the present invention proposes to store the cell 1 configuration for a period of time, for example 3 seconds, even after a successful first handover. It is assumed that a ping-pong situation may occur over a period of time. Therefore, it is advantageous to keep the source configuration even after a successful handover in order to be prepared for a potential ping-pong handover situation, thereby enabling fast handover in a ping-pong handover situation. This reduces processing time and improves mobility robustness.

[0193] According to an exemplary embodiment of the present invention, the number of ping-pongs is reduced. However, if a ping-pong must be triggered (eg, TTT is in the range of 20 to 100 ms. The lower the TTT value, the higher the number of required handovers and ping-pongs), then a solution is sought to perform fast handovers.

[0194] Fig. 7A , Figure 7B , Figure 7C , Fig.7D ,as well as Fig. 7E Each of illustrates a method according to an example embodiment of the present invention, which method may be performed by an apparatus.

[0195] Fig. 7A Operations that may be performed by a device are illustrated, such as, but not limited to, a device (e.g., Figure 6 UE 10 in FIG. Fig. 7A As shown in step 705 of , the user equipment establishes a connection to a serving cell supported by a first network node supporting at least one of a distributed unit function of a radio access network or a layer 2 protocol, and receives data from the serving cell, and the user equipment is configured to support parallel reception of data from two cells belonging to different network nodes of the radio access network. Fig. 7A As shown in step 710 of , a layer 1 measurement report including an indication of a second cell supported by a second network node and related measurement information is sent to the serving cell to enable the first network node to monitor low-layer mobility conditions, wherein the second network node supports at least one of a distributed unit function of a radio access network or a layer 2 protocol. Fig. 7A As shown in step 715 of , a layer 2 message including an instruction for a cell change to a second cell is received. Then, as Fig. 7AAs shown in step 720, the layer 2 message also includes instructions to perform parallel reception from both the serving cell and the second cell at least during the cell change, and to retain at least one configuration of at least one of data transmission or reception with the serving cell after the success of the cell change to the second cell.

[0196] According to the example embodiment described in the above paragraphs, the indication includes: a cell identity or a cell identity index identifying the second cell.

[0197] According to the example embodiment described in the above paragraphs, the layer 1 measurement report is sent using a layer 2 medium access control message.

[0198] According to the example embodiment described in the above paragraphs, the layer 1 measurement report includes: at least one reference signal received power measurement of the second cell.

[0199] According to the example embodiments described in the above paragraphs, the low-layer mobility refers to layer 2 mobility.

[0200] According to the example embodiment described in the above paragraphs, the layer 2 message is sent using a layer 2 medium access control message.

[0201] According to the example embodiment described in the above paragraphs, monitoring the low layer mobility condition comprises: at the first network node, detecting a serving cell change requirement based on a received layer 1 measurement report.

[0202] According to the example embodiments described in the above paragraphs, the connection with the second cell is established by performing a random access procedure to the second cell.

[0203] According to the example embodiments described in the above paragraphs, a ping-pong timer is started after a successful cell change to a second cell, and as long as the ping-pong timer is running, at least one configuration of at least one of data transmission or reception with the serving cell is retained after the successful cell change to the second cell.

[0204] According to the example embodiments described in the above paragraphs, the value of the ping-pong timer is configurable and is received via the radio access network.

[0205] According to the example embodiment described in the above paragraphs, before sending the Layer 1 measurement report, a Layer 3 measurement report including a physical cell ID or index of a second cell supported by the second network node, and related measurement information is sent to a third network node, wherein the third network node supports at least one of a central unit control plane function or a Layer 3 protocol of a radio access network; and a Layer 3 radio resource control message for configuring a user equipment to perform Layer 1 measurements related to the second cell is received from the third network node.

[0206] According to the example embodiment described in the above paragraphs, after a successful cell change to a second cell, another layer 1 measurement report including an indication of a serving cell and an indication of the second cell, and related measurement information is sent to the second cell to enable the second network node to monitor low-layer mobility conditions; and a layer 2 message including an instruction to suspend at least one of transmission or reception of the serving cell is received.

[0207] According to the example embodiment described in the above paragraphs, after a successful cell change to a second cell, another layer 1 measurement report including an indication of the serving cell and an indication of the second cell, and related measurement information is sent to the second cell to enable the second network node to monitor low-layer mobility conditions; and a layer 2 message including an instruction for a cell change back to the serving cell is received, wherein the layer 2 message also includes instructions to perform parallel reception from both the serving cell and the second cell at least during the cell change, and after a successful cell change back to the serving cell, retain at least one configuration of at least one of data transmission or reception with the second cell.

[0208] According to the example embodiments described in the above paragraphs, a connection is established with a serving cell by performing a random access procedure to the serving cell.

[0209] According to the example embodiment described in the above paragraphs, after a successful cell change to a serving cell, a timer is started and as long as the timer is running, at least one configuration of at least one of data transmission or reception with the second cell is retained after the successful cell change to the serving cell.

[0210] According to the example embodiments described in the above paragraphs, the user equipment is configured to support at least one of multiple transmission and reception points and dual active protocol stack capabilities.

[0211] A non-transitory computer readable medium (such as Figure 6 MEM 10B in the storage device stores program code (such as Figure 6 PROG10C in, the program code is executed by at least one processor (such as Figure 6 DP 10A and / or DP 10F) in the process is executed to perform at least the operations described in the above paragraphs.

[0212] According to an exemplary embodiment of the present invention as described above, there is an apparatus comprising means for: comprising a device configured to support a slave to a radio access network (such as Figure 6 A user equipment (such as a user equipment) receiving data in parallel from two cells of different network nodes in the network 1) Figure 6 UE 10 in the establishment (such as Figure 6TRANS 10D, MEM 10B, PROG 10C and DP 10A) in the wireless access network to a first network node (such as a wireless access network) that supports at least one of the distributed unit functions or layer 2 protocols of the wireless access network. Figure 6 12 or NN 13) in the NN 12 or NN 13) and receiving data from the serving cell; and receiving data from the serving cell (such as Figure 6 TRANS 10D, MEM 10B, PROG 10C and DP 10A) data in the serving cell (such as Figure 6 TRANS 10D, MEM 10B, PROG 10C and DP 10A in the first embodiment) including an indication of a second cell supported by a second network node, and a layer 1 measurement report of related measurement information to enable the first network node to monitor low layer mobility conditions, wherein the second network node supports at least one of a distributed unit function or a layer 2 protocol of a radio access network; receiving (such as Figure 6 The method further comprises: providing a layer 2 message for instructing a cell change to a second cell by means of TRANS 10D, MEM 10B, PROG 10C and DP 10A in the cell change protocol, wherein the layer 2 message further comprises instructions to perform concurrent reception from both the serving cell and the second cell at least during the cell change, and to retain at least one configuration (such as the configuration of ... Figure 6 TRANS 10D, MEM 10B, PROG 10C and DP 10A).

[0213] In an exemplary aspect of the invention according to the above paragraphs, wherein at least the means for establishing, receiving, sending, and indicating comprises a non-transitory computer readable medium [such as Figure 6 MEM 10B], the medium is used with a computer program [such as Figure 6 PROG 10C] in, the computer program is executed by at least one processor [such as Figure 6 DP 10A] in is executable.

[0214] Figure 7B The diagram illustrates operations that may be performed by a network device, such as but not limited to Figure 6 The network node NN 12, or NN 13, or eNB in Figure 7B As shown in step 750 of , a user equipment context establishment request is received by a second network node from a third network node supporting at least one of a central unit control plane function of a radio access network or a layer 3 protocol, the second network node supporting at least one of a distributed unit function of a radio access network or a layer 2 protocol. Figure 7BAs shown in step 755 of , the user equipment is configured to support parallel reception of data from two cells of different network nodes belonging to a radio access network, and is connected to a serving cell supported by a first network node supporting at least one of a distributed unit function or a layer 2 protocol of the radio access network. Figure 7B As shown in step 760 of , the user equipment context establishment request includes: information for preparing for a low-layer mobility cell change from a serving cell to a second cell supported by a second network node. Figure 7B As shown in step 765 of , a random access request is received from the user equipment, and a connection is established with the user equipment. Figure 7B As shown in step 770 of , the ping-pong timer is started. Then, as Figure 7B As shown in step 775 of , a cell change complete notification is sent to a fourth network node supporting a central unit user plane function.

[0215] According to the example embodiment described in the above paragraphs, a second network node receives a layer 1 measurement report from a user equipment, the layer 1 measurement report including: an indication of a first cell and a second cell, and related measurement information, so that the second network node can monitor low-layer mobility conditions; monitor whether a ping-pong timer is still running; if the low-layer mobility conditions are met and the ping-pong timer is still running, a layer 2 message including instructions for cell change is sent to the user equipment, the layer 2 message including: instructions for cell change back to the serving cell, wherein the layer 2 message also includes instructions to perform parallel reception from both the serving cell and the second cell at least during the cell change, and after a successful cell change back to the serving cell, retain at least one configuration of at least one of data transmission or reception with the second cell; and a cell change trigger notification is sent to a fourth network node to trigger the duplication of data so that data can be sent to both the first cell and the second cell in parallel in a timely manner.

[0216] According to the example embodiment described in the above paragraphs, the indication includes: a cell identity or a cell identity index identifying the second cell.

[0217] According to the example embodiments described in the above paragraphs, at least one configuration of at least one of data transmission or reception with the serving cell is retained after a successful cell change to a second cell as long as the ping-pong timer is running.

[0218] According to the example embodiment described in the above paragraphs, a second network node receives a layer 1 measurement report from a user equipment, the layer 1 measurement report including: an indication of a first cell and a second cell, and related measurement information, so that the second network node can monitor low-layer mobility conditions and whether a ping-pong timer is still running; if the low-layer mobility conditions are not met and the ping-pong timer is still running or if the ping-pong timer expires, a layer 2 message including an instruction to suspend serving cell transmission is sent; and a suspend cell trigger notification is sent to a fourth network node to trigger stopping of replication of data, so as to suspend sending data to both the first cell and the second cell in parallel in a timely manner.

[0219] According to the example embodiment described in the above paragraphs, it is monitored whether the ping-pong timer is still running; and if the ping-pong timer expires, a suspend serving cell trigger notification is sent to the fourth network node to trigger the stopping of the copying of data, so as to suspend the timely and parallel sending of data to both the first cell and the second cell.

[0220] According to the example embodiments described in the above paragraphs, an indication comprising a measurement report is received from the user equipment; and based on the indication, repeated transmission of the packet is initiated at the fourth network node.

[0221] According to the example embodiments described in the above paragraphs, the initiating of radio resource management based on measurement reports defines a threshold.

[0222] According to the example embodiment described in the above paragraphs, a layer 1 measurement report is received from a user equipment; and based on the reception, a medium access control control element indicating a cell change is sent to the user equipment.

[0223] A non-transitory computer readable medium (such as Figure 6 MEM 12B and / or MEM 13B) in the storage device stores program code (such as Figure 6 PROG 12C and / or PROG 13C in the processor), the program code is executed by at least one processor (such as Figure 6 DP 12A and / or DP 13A) in the process is executed to perform at least the operations described in the above paragraphs.

[0224] According to an exemplary embodiment of the present invention as described above, there is an apparatus comprising means for: supporting a radio access network (such as Figure 6 A second network node (such as a distributed unit function in a network 1) or at least one of the layer 2 protocols Figure 6 NN 12 and / or NN 13 in the radio access network) receives from a third network node supporting at least one of a central unit control plane function or a layer 3 protocol of the radio access network (such as Figure 6TRANS 12D and / or TRANS 13D, MEM 12B and / or MEM 13B, PROG 12C and / or PROG 13C, and DP 12A and / or DP 13A) user equipment (such as Figure 6 10) context establishment request in the UE 10, wherein the user equipment is configured to support parallel reception of data from two cells of different network nodes belonging to a radio access network, and is connected to a serving cell supported by a first network node supporting at least one of a distributed unit function or a layer 2 protocol of the radio access network, wherein the user equipment context establishment request (such as Figure 6 TRANS 12D and / or TRANS 13D, MEM 12B and / or MEM 13B, PROG 12C and / or PROG 13C, and DP 12A and / or DP 13A) in the second network node include information for preparing a low-layer mobility cell change from a serving cell to a second cell supported by a second network node; receiving from a user equipment (e.g. Figure 6 TRANS 12D and / or TRANS 13D, MEM 12B and / or MEM 13B, PROG 12C and / or PROG 13C, and DP 12A and / or DP 13A) in the random access request and establish a connection with the user equipment; start (such as Figure 6 TRANS 12D and / or TRANS 13D, MEM 12B and / or MEM13B, PROG 12C and / or PROG 13C, and DP 12A and / or DP 13A) ping-pong timer; and sending to a fourth network node supporting the user plane function of the central unit (such as Figure 6 TRANS 12D and / or TRANS 13D, MEM 12B and / or MEM13B, PROG 12C and / or PROG 13C, and DP 12A and / or DP 13A) cell change completion notification.

[0225] In an exemplary aspect of the invention according to the above paragraphs, wherein at least the means for establishing, receiving, requesting, initiating, and sending comprises a non-transitory computer readable medium [such as Figure 6 MEM 12B and / or MEM 13B], the medium encoding at least one processor [such as Figure 6 DP 12A and / or DP 13A] executable computer program [such as Figure 6 PROG 12C and / or PROG 13C in ].

[0226] Figure 7C The diagram illustrates operations that may be performed by a network device, such as but not limited to the central unit control plane described herein. Figure 7CAs shown in step 780 of the method, a user context establishment request is sent to a second network node by a central unit control plane supporting at least one of a distributed unit function of a radio access network or a layer 2 protocol, wherein the central unit control plane supports at least one of a central unit control plane function of a radio access network or a layer 3 protocol. Figure 7C As shown in step 782 of , the user context establishment request includes: information for preparing a low-layer mobility cell change of a user equipment, the user equipment being configured to: support parallel reception of data from two cells belonging to different network nodes of a radio access network and controlled by a first network node supporting at least one of a distributed unit function of the radio access network or a layer 2 protocol, and from a serving cell controlled by the first network node supporting at least one of a distributed unit function of the radio access network or a layer 2 protocol. Then, as Figure 7C As shown in step 784 of , a layer 1 measurement report including an indication of a second cell controlled by a second network node and related measurement information is sent to a serving cell to enable monitoring of low-layer mobility conditions of a low-layer mobility cell change of a user equipment, wherein the indication includes: a cell identifier or a cell identifier index identifying at least one of the second cell, a serving distributed unit, a target distributed unit, and a central unit control plane.

[0227] Fig.7D The diagram illustrates operations that may be performed by a central unit control plane as described herein. Fig.7D As shown in step 788 of , a bearer context establishment request for a user equipment to change a serving cell to a second cell is received by a centralized unit user plane from a central unit control plane function of a radio access network or a central unit control plane supporting a layer 3 protocol, and the centralized unit user plane supports at least one of a distributed unit function of the radio access network or a layer 2 protocol. Fig.7D As shown in step 789 of , in order to solve the ping-pong problem, a mapping table is created and stored to identify the user equipment and its configuration in a given distributed unit or cell, as long as ping-pong is possible. Fig.7D As shown in step 790 of , where the mapping table is created based on input from the centralized unit control plane. Fig.7D As shown in step 791 of , where the mapping table indicates: a distributed unit, cell, index, or cell configuration for each user equipment associated with the radio access network. Fig.7D As shown in step 792 of , the mapping is used to determine whether a user equipment configuration exists and whether parallel transmission can be started before the serving cell is changed. Fig.7D As shown in step 790 of , a control protocol data unit message is received from a serving cell controlled by a first network node supporting at least one of a distributed unit function of a radio access network or a layer 2 protocol. Then, as Fig.7D As shown in step 794 of , wherein the layer 2 message also includes instructions to perform parallel reception from both the serving cell and the second cell at least during the serving cell change, and to retain at least one configuration of at least one of data transmission or reception with the serving cell after a successful serving cell change to the second cell.

[0228] Fig. 7E The diagram illustrates operations that may be performed by a service distribution unit as described herein. Fig. 7E As shown in step 795 of , in order to solve the ping-pong problem, as long as ping-pong is possible, a mapping table is created and stored to identify the user equipment and its configuration in a given distributed unit or cell, wherein the mapping table is created based on input from the centralized unit control plane. Fig. 7E As shown in step 796 of , a layer 3 radio resource control message is received from a third network node, the layer 3 radio resource control message configuring the user equipment to perform layer 1 measurements related to a second cell controlled by a second network node supporting at least one of a distributed unit function of a radio access network or a layer 2 protocol, and a bearer context establishment request for the user equipment to change to a serving cell of the second cell if a low layer mobility condition is met and the ping-pong timer is still running. Fig. 7E As shown in step 797 of , wherein the third network node supports at least one of a central unit control plane function or a layer 3 protocol of the radio access network. Then, as Fig. 7E As shown in step 798 of , a cell change trigger notification is sent to the fourth network node to trigger the duplication of data, thereby enabling the data to be sent to both the first cell and the second cell in parallel in a timely manner.

[0229] advantage:

[0230] If the source connection is maintained for the serving cell change duration, the UE can receive from both the serving cell and the target cell simultaneously, resulting in almost no user interruption time.Some features of mTRP or DAPS can be reused here.

[0231] Figure 8Another embodiment is related, which shows the signaling flow of inter-DU LLM through ping-pong by the UE without configuring mRTP / DAPS. Note that even in the case where the UE does not have simultaneous reception capability (e.g., as in mTRP), or does not activate or use simultaneous reception capability (e.g., does not use simultaneous reception, although it may be due to load conditions, contractual reasons, or the source DU and / or target DU does not support or activate mTRP, or other reasons), user plane interruption is reduced because the mapping and configuration of the previous serving cell ( / DU) are stored in the CU-UP (expected to be ping-pong), so data transmission starts earlier compared to the prior art. Since the CU-UP remembers the previous serving cell and its configuration at least when the ping-pong timer is running, there is no resource reservation issue that can be associated with the target LLM cell.

[0232] exist Figure 5B In step 24, ping-pong is avoided and the expiration of the timer causes the data transmission to the source cell to be suspended. Figure 8 In step 26, ping pong is detected before the timer expires. Therefore, transmission to the old serving cell (source cell) is initiated: step 30 activates the old source cell, step 32 receives data at the source cell, step 33 buffers / stores the received data before the UE starts sending random access, step 37 accepts the random access at the source cell, step 38 sends a random access response, and step 41 sends the buffered data and new data to the UE.

[0233] Figure 8 A user equipment may be configured in the following manner: A UE, comprising:

[0234] at least one processor; and

[0235] at least one non-transitory memory including computer program code, wherein the at least one non-transitory memory and the computer program code are configured to, together with the at least one processor, cause the user device to at least:

[0236] establishing, by a user equipment, a connection to a serving (source) cell controlled by a first network node supporting at least one of a distributed unit function of a radio access network, or a layer 2 protocol, and receiving data from the serving cell, the user equipment being configured to support reception of data from a network node of the radio access network;

[0237] sending a layer 1 measurement report including an indication of a second cell controlled by a second network node and related measurement information to a serving cell to enable the first network node to monitor low layer mobility conditions, wherein the second network node supports at least one of a distributed unit function of a radio access network or a layer 2 protocol; and

[0238] receiving a layer 2 message including an instruction for a cell change to a second cell,

[0239] The layer 2 message further includes an instruction to retain at least one configuration of at least one of data transmission or reception with the serving cell after the success of the cell change to the second cell.

[0240] The UE is configured to start a ping-pong timer after a successful cell change to the second cell and retain at least one configuration of at least one of data transmission or reception with the serving cell after the successful cell change to the second cell as long as the ping-pong timer is running.

[0241] The user equipment advantageously receives the value of the ping-pong timer via the radio access network, for example together with a layer 2 message (or in a separate message), wherein the value of the ping-pong timer is configurable.

[0242] In case ping-pong occurs, for example after provision of an L1 measurement report to a second cell, the UE receives a layer 2 message including instructions for a cell change back to the source cell,

[0243] The layer 2 message further includes an instruction to retain at least one configuration of at least one of data transmission or reception with the serving (target, second) cell after success of the cell change back to the source cell.

[0244] The UE is configured to start a ping-pong timer after a successful cell change to the source cell and retain at least one configuration of at least one of data transmission or reception with the target cell after the successful cell change to the source cell as long as the ping-pong timer is running.

[0245] Figure 5A , Figure 5B and Figure 8 The parts (e.g., single or multiple messages, reports, instructions, etc.) can be combined together to enrich the corresponding other diagrams and their operations and message flows, and / or generate new embodiments.

[0246] The following description may provide further details of alternatives, modifications, and variations: The gNB includes, for example, a node that provides NR user plane and control plane protocol termination to the UE and is connected to the 5GC via an NG interface (e.g., in accordance with Section 3.2 of 3GPP TS 38.300 V16.6.0 (2021-06) incorporated by reference).

[0247] The gNB Central Unit (gNB-CU) includes, for example, a logical node that hosts, for example, the RRC, SDAP, and PDCP protocols of the gNB, or the RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU.

[0248] The gNB distributed unit (gNB-DU) includes, for example, a logical node that hosts, for example, the RLC, MAC, and PHY layers of a gNB or en-gNB, and whose operation is partially controlled by the gNB-CU. One gNB-DU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0249] The gNB-CU control plane (gNB-CU-CP) comprises, for example, a logical node that hosts the control plane portion of the protocols such as RRC and PDCP for an en-gNB or gNB-CU of a gNB. The gNB-CU-CP terminates the E1 interface with the gNB-CU-UP and the F1-C interface with the gNB-DU.

[0250] The gNB-CU user plane (gNB-CU-UP) includes, for example, a logical node that hosts, for example, the user plane portion of the PDCP protocol for the gNB-CU of the en-gNB, and the user plane portions of the PDCP protocol and the SDAP protocol for the gNB-CU of the gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU, for example, according to Section 3.1 of 3GPP TS 38.401 V16.6.0 (2021-07) incorporated by reference.

[0251] There can be different functional splits between central and distributed units, called options for example:

[0252] Option 1 (Class 1A Split):

[0253] - The functional split in this option is similar to the 1A architecture in DC. RRC is in the central unit. PDCP, RLC, MAC, physical layer, and RF are all in the distributed unit.

[0254] Option 2 (Class 3C Split):

[0255] - The functional split in this option is similar to the 3C architecture in DC. RRC and PDCP are in the central unit. RLC, MAC, physical layer, and RF are all in the distributed unit.

[0256] Option 3 (split within RLC):

[0257] - Low RLC (part of the RLC function), MAC, physical layer, and RF are all in the distributed unit. PDCP and high RLC (another part of the RLC function) are in the central unit.

[0258] Option 4 (RLC-MAC split):

[0259] -MAC, physical layer, and RF are in the distributed unit. PDCP and RLC are in the central unit.

[0260] Or, for example according to section 11 of 3GPP TR 38.801 V14.0.0 (2017-03), incorporated by reference.

[0261] gNB supports different protocol layers, such as Layer 1 (L1) - the physical layer.

[0262] NR's Layer 2 (L2) is split into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Service Data Adaptation Protocol (SDAP), where for example:

[0263] The physical layer provides transport channels to the MAC sublayer;

[0264] -The MAC sublayer provides logical channels to the RLC sublayer;

[0265] -The RLC sublayer provides RLC channels to the PDCP sublayer;

[0266] -The PDCP sublayer provides radio bearers to the SDAP sublayer;

[0267] -The SDAP sublayer provides 5GC QoS flow;

[0268] -Comp. refers to header compression and Segm. segmentation;

[0269] -Control channels include (BCCH, PCCH).

[0270] Layer 3 (L3) includes, for example, Radio Resource Control (RRC) in accordance with 3GPP TS 38.300 V16.6.0 (2021-06) Section 6 (incorporated herein by reference).

[0271] A RAN (Radio Access Network) node or a network node (such as a gNB, a base station, a gNB CU or a gNB DU or a part thereof) can be implemented using, for example, a device having at least one processor and / or at least one memory (having computer-readable instructions (computer program)), which is configured to: support and / or supply and / or process CU and / or DU related functions and / or features, and / or at least one protocol (sub) layer of the RAN (Radio Access Network), such as Layer 2 and / or Layer 3.

[0272] The gNB CU and gNB DU parts may be collocated or physically separated. The gNB DU may be split even further, for example into two parts, for example one part including processing equipment and the other part including antennas. The Central Unit (CU) may also be referred to as BBU / REC / RCC / C-RAN / V-RAN, O-RAN or a part thereof. The Distributed Unit (DU) may also be referred to as RRH / RRU / RE / RU or a part thereof.

[0273] The gNB-DU supports one or more cells and can thus serve as, for example, a serving cell for a user equipment (UE).

[0274] User equipment (UE) may include a wireless or mobile device, a device having a radio interface that interacts with a RAN (Radio Access Network), a smartphone, an in-vehicle device, an IoT device, an M2M device, or other device. Such a UE or device may include: at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured to, together with the at least one processor, enable the device to perform at least certain operations, such as an RRC connection with the RAN. The UE is, for example, configured to generate a message (e.g., including a cell ID) to send to the RAN via radio (e.g., to reach a serving cell and communicate with it). The UE can generate, send, and receive RRC messages containing one or more RRC PDUs (packet data units).

[0275] The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0 (2021-06) Sections 42.1 and 4.4, incorporated herein by reference).

[0276] When the RRC connection has been established, the UE is in, for example, an RRC_CONNECTED state or an RRC_INACTIVE state.

[0277] In the RRC_CONNECTED state, the UE may:

[0278] Store AS context;

[0279] -Transmission of unicast data to / from UE;

[0280] - Monitor the control channel associated with the shared data channel to determine if it is a data signal

[0281] Road scheduling data;

[0282] -Provide channel quality and feedback information;

[0283] -Perform neighbor cell measurements and measurement reporting;

[0284] The RRC protocol includes the following main functions:

[0285] -RRC connection control;

[0286] - Measurement configuration and reporting;

[0287] - Establishment / modification / release of measurement configurations (e.g., intra-frequency, inter-frequency, and inter-RAT

[0288] Measurement);

[0289] -Measurement of gap creation and release;

[0290] - Measurement report.

[0291] According to 3GPP TS23.501 v17.4.0 (2022-03), the 5G system architecture is defined to support data connectivity and services, enabling deployments to use technologies such as network function virtualization and software-defined networking. The 5G system architecture should leverage service-based interactions between control plane (CP) network functions. Some key principles and concepts are: a) separation of user plane (UP) functions (UPF) from control plane (CP) functions to allow independent scalability, evolution, and flexible deployment, such as centralized locations or distributed (remote) locations, b) modular functional design, such as enabling flexible and efficient network slicing, c) where applicable, defining processes (i.e., sets of interactions between network functions) as services so that they can be reused, d) enabling each network function (NF) and its network function services to interact directly or indirectly with another NF and its network function services via a service communication agent, if necessary. The architecture does not exclude the use of another intermediate function to help route control plane messages (e.g., DRA).

[0292] The user plane in this patent specification can, for example, support one or more UPFs and / or user plane connections listed in the above-mentioned TS23.501 (and / or its future versions) in one or more architectures, and can be implemented using, for example, one or more processors, and / or one or more memories, and / or (multiple) routers, and / or (multiple) software modules and / or firmware, and / or (multiple) switches, and / or using plane components and / or (multiple) using plane nodes.

[0293] The UPF provides encapsulation and decapsulation of the GPRS tunneling protocol of the user plane (GTP U), for example, the interconnection point between the mobile infrastructure and the data network (DN).

[0294] A Protocol Data Unit (PDU) session is the anchor point for providing mobility within and between Radio Access Technologies (RATs), including sending one or more end marker packets to the gNB.

[0295] (Multiple) User Plane Functions handle the user plane path of a PDU Session. 3GPP specifications support the deployment of a single UPF or multiple UPFs for a given PDU Session. UPF selection is performed by the SMF. Details of UPF selection are given in clause 6.3.3. The number of UPFs supported for a PDU Session is not restricted.

[0296] about Figure 5A and Figure 5B , different messages currently defined in the 3GPP standards may require some modifications to include the above-mentioned inventive features, for example regarding step 5 TS 38.473 v17.0.0 (2022-04, e.g. Sections 8.3.1 and 9.2.2.1) (included by reference) may require some (some) modifications to implement handover operations supported by ping-pong, e.g. Figure 5A Step 5):

[0297] The UE context establishment request message may include at least one of the following:

[0298] - Cell ID index (enables triggering PDU duplication, pausing source cell transmission, etc.),

[0299] -UE Configuration Information (with information / flag: "Preserve source connection configuration after SCC (serving cell change, handover) (-> will be forwarded to UE in case of handover to target DU)"

[0300] Step 5 is to prepare the target cell in the target DU. Therefore, it is necessary to go from CU-CP to the target DU.

[0301] It is assumed that UE context establishment with the source DU has already occurred in step 1.

[0302] Regarding step 7 messages and fields that may need to be modified (CU-CP to CU-UP interface E1): TS37.483v17.0.0 (2022-04), such as Section 8.3.1 and Section 9.2.2.1 (included by reference). The above sections may require some (some) modification to enable handover operations supported by ping-pong, for example.

[0303] Figure 5A In step 7, the bearer establishment request message may include at least one of the following:

[0304] - Cell ID index (used for duplicating PDUs, suspending source cell transmission, etc.).

[0305] -UE configuration information (UE supports simultaneous / parallel data transmission / reception, e.g. indicated by supporting DAPS and / or mTRP), to enable duplication of PDUs and parallel transmission of data to different DUs).

[0306] Step 15 Messages and fields that may need to be modified (CU-UP and DU interface F1-U): TS38.470 and TS38.475. Other Layer 2 (e.g., MAC CE) and Layer 3 (e.g., RRC) messages may require some modifications, such as including information related to at least one of the following: cell ID, flag: SCC post-retention source configuration, etc.). This may involve TS38.331, TS38.300, and / or TS38.321, if, for example, 5G is involved, and if, for example, LTE corresponding TS36.xxx specifications are involved.

[0307] In addition, according to an exemplary embodiment of the present invention, there is a circuit system for performing operations according to an exemplary embodiment of the present invention as disclosed herein. The circuit system may include any type of circuit system, including a content encoding circuit system, a content decoding circuit system, a processing circuit system, an image generation circuit system, a data analysis circuit system, etc.). In addition, the circuit system may include a discrete circuit system, an application-specific integrated circuit system (ASIC), and / or a field programmable gate array circuit system (FPGA), etc., as well as a processor specially configured by software to perform corresponding functions, or a dual-core processor with software and a corresponding digital signal processor, etc.). In addition, the necessary inputs and outputs of the circuit system, the functions performed by the circuit system, and the interconnection of the circuit system with other components that may include other circuit systems (possibly via inputs and outputs) are provided to perform the exemplary embodiments of the present invention described herein.

[0308] According to an exemplary embodiment of the present invention disclosed in this application, the provided “circuitry system” may include at least one or more or all of the following:

[0309] (a) Hardware circuit implementation only (such as implementation in analog and / or digital circuit systems only)

[0310] now);

[0311] (b) a combination of hardware circuitry and software such as (where applicable):

[0312] (i) a combination of analog and / or digital hardware circuits and software / firmware;

[0313] as well as

[0314] (ii) any portion of hardware processor(s) with software (including digital signal processor(s), software, and memory(s) that work together to enable a device such as a mobile phone or server to perform various functions, such as functions or operations according to the example embodiments of the present invention disclosed herein); and

[0315] (c) Hardware circuit(s) and / or processor(s), such as microprocessor(s) or portion(s) of microprocessor(s), that require software (e.g., firmware) for operation, but in which the software may not be present when not required for operation.”

[0316] According to an example embodiment of the present invention, there is sufficient circuitry for performing at least the novel operations disclosed in this application, and "circuitry" as used herein refers to at least the following:

[0317] (a) Hardware circuit implementation only (such as implementation in analog and / or digital circuit systems only)

[0318] now); and

[0319] (b) a combination of circuitry and software (and / or firmware) such as (as applicable):

[0320] (i) a combination of processors, or

[0321] (ii) Processor / software components (including digital signal processor(s), software, and memory(s) that work together to enable

[0322] devices such as mobile phones or servers to perform various functions); and

[0323] (c) Circuitry that requires software or firmware to operate (even if the software or firmware is not physically present), such as microprocessor(s) or portion(s) of microprocessor(s).

[0324] This definition of “circuitry” applies to all uses of this term in this application, including in any claims. As another example, as used in this application, the term “circuitry” would also cover an implementation of only a processor (or multiple processors), or a portion of a processor and its accompanying software and / or firmware. For example, the term “circuitry” would also cover a baseband integrated circuit or an application processor integrated circuit for a mobile phone, or a similar integrated circuit in a server, cellular network device, or other network device, if applicable to a particular claim element.

[0325] In general, various embodiments may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device, but the invention is not limited thereto. Although various aspects of the invention may be illustrated and described with block diagrams, flow charts, or using some other graphical representation, it is well understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0326] Embodiments of the present invention may be implemented in various components such as integrated circuit modules. The design of integrated circuits is generally a highly automated process. Complex and powerful software tools are available to convert logic level designs into semiconductor circuit designs for etching and formation on semiconductor substrates.

[0327] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred over other embodiments. All embodiments described in this detailed description are exemplary embodiments intended to enable persons skilled in the art to make or use the invention, rather than to limit the scope of the invention which is defined by the claims.

[0328] The foregoing description has provided by way of exemplary and non-limiting examples a complete and informative description of the best method and apparatus presently contemplated by the inventors for carrying out the invention. However, various modifications and adaptations will become apparent to those skilled in the relevant art in view of the foregoing description when read in conjunction with the accompanying drawings and the appended claims. Nevertheless, all such and similar modifications of the teachings of the present invention will still fall within the scope of the present invention.

[0329] It should be noted that the terms "connected", "coupled", or any variations thereof refer to any direct or indirect connection or coupling between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between elements may be physical, logical, or a combination thereof. As used herein, as several non-limiting and non-exhaustive examples, two elements may be considered to be "connected" or "coupled" together by using one or more wires, cables, and / or printed electrical connections, and by using electromagnetic energy (such as electromagnetic energy having wavelengths in the radio frequency region, microwave region, and optical (visible and invisible) region).

[0330] Furthermore, some of the features of the preferred embodiments of this invention may be used to advantage without the corresponding use of other features.Accordingly, the above description should be regarded as merely illustrative of the principles of the present invention, and not in limitation thereof.

Claims

1. A method comprising: establishing, by a user equipment, a connection to a serving cell controlled by a first network node supporting at least one of a distributed unit function or a layer 2 protocol of a radio access network, and receiving data from the serving cell, the user equipment being configured to support parallel transmission and / or reception of data from two different cells belonging to different network nodes of the radio access network; sending a layer 1 measurement report including an indication of a second cell controlled by a second network node and related measurement information to the serving cell to enable the first network node to monitor low layer mobility conditions, wherein the second network node supports at least one of a distributed unit function or a layer 2 protocol of the radio access network; as well as receiving a layer 2 message including an instruction to change to a serving cell of said second cell, The layer 2 message also includes instructions to perform at least one of parallel reception or transmission from both the serving cell and the second cell at least during the serving cell change, and to retain at least one of a connection or configuration for at least one of data transmission or reception with the serving cell after a successful serving cell change to the second cell.

2. The method according to claim 1, wherein the indication comprises: A cell identifier or a cell identifier index identifying the second cell.

3. The method of claim 1, wherein the layer 1 measurement report is sent using a layer 2 medium access control message.

4. The method of claim 1 , wherein the layer 1 measurement report comprises: At least one reference signal received power measurement of the second cell. The method according to claim 1 , wherein the low-layer mobility refers to layer 1 / layer 2 mobility.

6. The method of claim 1, wherein the layer 2 message is sent using a layer 2 medium access control message.

7. The method of claim 1 , wherein monitoring low-level mobility conditions comprises: At the first network node, a serving cell change requirement is detected based on the layer 1 measurement report.

8. The method according to claim 1, wherein the method further comprises: A connection is established with the second cell by performing a random access procedure to the second cell.

9. The method according to claim 1, wherein the method further comprises: After the successful serving cell change to the second cell, a ping-pong timer is started, and as long as the ping-pong timer is running, at least one connection and / or configuration of at least one of data transmission or reception with the serving cell is retained after the successful cell change to the second cell.

10. The method of claim 9, wherein the value of the ping-pong timer is configurable and is received via the radio access network air interface.

11. The method according to claim 1, wherein the method further comprises: before sending the layer 1 measurement report, sending a layer 3 measurement report including a physical cell ID or index of the second cell controlled by the second network node and related measurement information to a third network node, wherein the third network node supports at least one of a central unit control plane function or a layer 3 protocol of the radio access network; as well as A layer 3 radio resource control message is received from the third network node for configuring the user equipment to perform layer 1 measurements related to the second cell.

12. The method according to claim 1, wherein the method further comprises: after the successful cell change to the second cell, sending another layer 1 measurement report including an indication of the serving cell and an indication of the second cell, and related measurement information to the second cell to enable the second network node to monitor low-layer mobility conditions, and receiving a layer 2 message including an instruction to suspend at least one of transmission or reception of the serving cell.

13. The method according to claim 1, wherein the method further comprises: after the successful cell change to the second cell, sending to the second cell another layer 1 measurement report including an indication of the serving cell and an indication of the second cell, and related measurement information, to enable the second network node to monitor low layer mobility conditions, and Receiving a layer 2 message including instructions for a cell change back to the serving cell, wherein the layer 2 message also includes instructions to perform parallel reception from both the serving cell and the second cell at least during the cell change, and to retain at least one configuration of at least one of data transmission or reception with the second cell after the successful cell change back to the serving cell.

14. The method according to claim 13, wherein the method further comprises: A connection is established with the serving cell by performing the random access procedure on the serving cell.

15. The method according to claim 1, wherein the method further comprises: After the successful cell change to the serving cell, a timer is started to monitor ping-pong, and as long as the timer is running, at least one configuration of at least one of data transmission or reception with the second cell is retained after the successful cell change to the serving cell.

16. The method of claim 1, wherein the user equipment is configured to support at least one of multiple transmission reception points and dual active protocol stack capabilities.

17. A user equipment, comprising: at least one processor; as well as at least one non-transitory memory including computer program code, wherein the at least one non-transitory memory and the computer program code are configured to, together with the at least one processor, cause the user device to at least: establishing, by the user equipment, a connection to a serving cell controlled by a first network node supporting at least one of a distributed unit function or a layer 2 protocol of the radio access network, and receiving data from the serving cell, the user equipment being configured to support parallel reception of data from two different cells belonging to different network nodes of the radio access network; sending a layer 1 measurement report including an indication of a second cell controlled by a second network node and related measurement information to the serving cell to enable the first network node to monitor low layer mobility conditions, wherein the second network node supports at least one of a distributed unit function or a layer 2 protocol of the radio access network; as well as receiving a layer 2 message comprising an instruction for a cell change to said second cell, The layer 2 message further includes instructions to perform parallel reception from both the serving cell and the second cell at least during the cell change, and to retain at least one configuration of at least one of data transmission or reception with the serving cell after success of the cell change to the second cell.

18. The user equipment according to claim 17, wherein the indication comprises: A cell identifier or a cell identifier index identifying the second cell.

19. The user equipment of claim 17, wherein the layer 1 measurement report is sent using a layer 2 medium access control message.

20. The user equipment of claim 17, wherein the layer 1 measurement report comprises: At least one reference signal received power measurement of the second cell.

21. The user equipment according to claim 17, wherein the low layer mobility refers to layer 2 mobility.

22. The user equipment of claim 17, wherein the layer 2 message is sent using a layer 2 medium access control message.

23. The user equipment of claim 17, wherein the monitoring of low-layer mobility conditions comprises: At the first network node, a serving cell change requirement is detected based on the received layer 1 measurement report.

24. The user device of claim 17, wherein the at least one non-transitory memory including the computer program code is configured to, together with the at least one processor, cause the user device to: A connection is established with the second cell by performing a random access procedure to the second cell.

25. The user device of claim 17, wherein the at least one non-transitory memory including the computer program code is configured to, together with the at least one processor, cause the user device to: After the successful cell change to the second cell, a ping pong timer is started, and as long as the ping pong timer is running, at least one configuration of at least one of data transmission or reception with the serving cell is retained after the successful cell change to the second cell.

26. The user equipment of claim 25, wherein the value of the ping-pong timer is configurable and is received via the radio access network.

27. The user device of claim 17, wherein the at least one non-transitory memory including the computer program code is configured to, together with the at least one processor, cause the user device to: before sending the layer 1 measurement report, sending a layer 3 measurement report including a physical cell ID or index of the second cell controlled by the second network node and related measurement information to a third network node, wherein the third network node supports at least one of a central unit control plane function or a layer 3 protocol of the radio access network; and A layer 3 radio resource control message is received from the third network node for configuring the user equipment to perform layer 1 measurements related to the second cell.

28. The user device of claim 17, wherein the at least one non-transitory memory including the computer program code is configured to, together with the at least one processor, cause the user device to: after the successful cell change to the second cell, sending to the second cell another layer 1 measurement report including an indication of the serving cell and an indication of the second cell, and related measurement information, to enable the second network node to monitor low layer mobility conditions, and A layer 2 message including an instruction to suspend at least one of transmission or reception of the serving cell is received.

29. The user device of claim 17, wherein the at least one non-transitory memory including the computer program code is configured to, together with the at least one processor, cause the user device to: after the successful cell change to the second cell, sending to the second cell another layer 1 measurement report including an indication of the serving cell and an indication of the second cell, and related measurement information, to enable the second network node to monitor low layer mobility conditions; and Receiving a layer 2 message including instructions for a cell change back to the serving cell, wherein the layer 2 message also includes instructions to perform parallel reception from both the serving cell and the second cell at least during the cell change, and to retain at least one configuration of at least one of data transmission or reception with the second cell after the successful cell change back to the serving cell.

30. The user equipment of claim 29, wherein the at least one non-transitory memory including the computer program code is configured to, with the at least one processor, cause the user equipment to: A connection is established with the serving cell by performing the random access procedure on the serving cell.

31. The user device of claim 17, wherein the at least one non-transitory memory including the computer program code is configured to, with the at least one processor, cause the user device to: After the successful cell change to the serving cell, a timer is started, and as long as the timer is running, at least one configuration of at least one of data transmission or reception with the second cell is retained after the successful cell change to the serving cell.

32. The user equipment of claim 17, wherein the user equipment is configurable to support at least one of multiple transmission reception points and dual active protocol stack capabilities.

33. A method comprising: receiving, by a second network node, a user equipment context establishment request from a third network node supporting at least one of a central unit control plane function or a layer 3 protocol of a radio access network, the second network node supporting at least one of a distributed unit function or a layer 2 protocol of the radio access network, wherein the user equipment is configured to support parallel transmission and / or reception of data from two different cells belonging to different network nodes of the radio access network, and is connected to a serving cell controlled by a first network node supporting at least one of a distributed unit function or a layer 2 protocol of the radio access network, and wherein the user equipment context establishment request comprises: information for preparing a target cell for a low layer mobility serving cell change from the serving cell to a second cell controlled by the second network node, wherein the information comprises a target cell identification index; receiving a random access request from the user equipment and establishing a connection with the user equipment; Starting a ping-pong timer; and A serving cell change complete notification is sent to a fourth network node supporting a central unit user plane function.

34. The method of claim 33, further comprising: receiving, by the second network node from the user equipment, a layer 1 measurement report comprising: an indication of the first cell and the second cell, and related measurement information, to enable the second network node to monitor low layer mobility conditions; Monitor whether the ping-pong timer is still running; If the low layer mobility condition is met and the ping pong timer is still running, sending a layer 2 message including an instruction for a cell change to the user equipment, the layer 2 message including an instruction for a cell change back to the serving cell, wherein the layer 2 message further comprises instructions to perform concurrent reception from both the serving cell and the second cell at least during the cell change, and to retain at least one configuration of at least one of data transmission or reception with the second cell after a successful cell change back to the serving cell; and A cell change trigger notification is sent to the fourth network node to trigger the duplication of data so that the data can be sent to both the first cell and the second cell in parallel in a timely manner.

35. The method of claim 34, wherein the indication comprises: A cell identifier or a cell identifier index identifying the second cell.

36. The method of claim 33, further comprising: As long as the ping-pong timer is running, at least one configuration of at least one of data transmission or reception with the serving cell is retained after the successful cell change to the second cell.

37. The method of claim 33, further comprising: receiving, by the second network node, a layer 1 measurement report from the user equipment, the layer 1 measurement report comprising: an indication of the first cell and the second cell, and related measurement information, so as to enable the second network node to monitor low layer mobility conditions, Monitor whether the ping-pong timer is still running; If the lower layer mobility condition is not met and the ping-pong timer is still running, or if the ping-pong timer expires, sending a layer 2 message including an instruction to suspend serving cell transmissions; and A suspend cell trigger notification is sent to the fourth network node to trigger stopping of the copying of data, so as to suspend sending data to both the first cell and the second cell in parallel in time.

38. The method of claim 33, further comprising: Monitor whether the ping-pong timer is still running; as well as If the ping-pong timer expires, a suspend serving cell trigger notification is sent to the fourth network node to trigger the stopping of the copying of data, so as to suspend timely and parallel sending of data to both the first cell and the second cell.

39. The method of claim 33, comprising: receiving, from the user equipment, an indication comprising a measurement report; as well as Based on the indication, initiation of repeated transmission of packets at the fourth network node is triggered if a serving cell change to an old serving cell is expected.

40. The method of claim 39, wherein the initiating defines a threshold for radio resource management based on the measurement report.

41. The method of claim 33, comprising: receiving a layer 1 measurement report from the user equipment; as well as Based on the receiving, a media access control element indicating the cell change is sent to the user equipment.

42. A second network node, comprising: at least one processor; as well as at least one non-transitory memory comprising computer program code, wherein the at least one non-transitory memory and the computer program code are configured to, with the at least one processor, cause the second network node to at least: receiving, by the second network node, a user equipment context establishment request from a third network node supporting at least one of a central unit control plane function or a layer 3 protocol of a radio access network, the second network node supporting at least one of a distributed unit function or a layer 2 protocol of the radio access network, wherein the user equipment is configured to support parallel reception of data from two cells belonging to different network nodes of the radio access network, and is connected to a serving cell controlled by a first network node supporting at least one of a distributed unit function or a layer 2 protocol of the radio access network, and wherein the user equipment context establishment request comprises: information for preparing a low layer mobility cell change from the serving cell to a second cell controlled by the second network node; receiving a random access request from the user equipment and establishing a connection with the user equipment; Starting a ping-pong timer; and A cell change complete notification is sent to a fourth network node supporting a user plane function of the central unit.

43. The second network node of claim 42, wherein the at least one non-transitory memory comprising the computer program code is configured to, with the at least one processor, cause the second network node to: The second network node receives a layer 1 measurement report from the user equipment, where the layer 1 measurement report includes: an indication of the first cell and the second cell, and related measurement information to enable the second network node to monitor low layer mobility conditions; Monitor whether the ping-pong timer is still running; If the low layer mobility condition is met and the ping pong timer is still running, sending a layer 2 message including an instruction for a cell change to the user equipment, the layer 2 message including an instruction for a cell change back to the serving cell, wherein the layer 2 message further comprises instructions to perform concurrent reception from both the serving cell and the second cell at least during the cell change, and to retain at least one configuration of at least one of data transmission or reception with the second cell after the successful cell change back to the serving cell, and A cell change trigger notification is sent to the fourth network node to trigger the duplication of data so that the data can be sent to both the first cell and the second cell in parallel in a timely manner.

44. The second network node according to claim 43, wherein the indication comprises: A cell identifier or a cell identifier index identifying the second cell.

45. The second network node of claim 42, wherein the at least one non-transitory memory comprising the computer program code is configured to, with the at least one processor, cause the second network node to: As long as the ping-pong timer is running, at least one configuration of at least one of data transmission or reception with the serving cell is retained after the successful cell change to the second cell.

46. ​​The second network node of claim 43, wherein the at least one non-transitory memory comprising the computer program code is configured to, with the at least one processor, cause the second network node to: The second network node receives a layer 1 measurement report from the user equipment, where the layer 1 measurement report includes: an indication of the first cell and the second cell, and related measurement information to enable the second network node to monitor low layer mobility conditions; Monitor whether the ping-pong timer is still running; If the lower layer mobility condition is not met and the ping-pong timer is still running, or if the ping-pong timer expires, sending a layer 2 message including an instruction to suspend serving cell transmissions, and A suspend cell trigger notification is sent to the fourth network node to trigger stopping of the copying of data, so as to suspend sending data to both the first cell and the second cell in parallel in time.

47. The second network node of claim 42, wherein the at least one non-transitory memory comprising the computer program code is configured to, with the at least one processor, cause the second network node to: Monitor whether the ping-pong timer is still running; and If the ping-pong timer expires, a suspend serving cell trigger notification is sent to the fourth network node to trigger the stopping of the copying of data, so as to suspend timely and parallel sending of data to both the first cell and the second cell.

48. The second network node of claim 42, wherein the at least one non-transitory memory comprising the computer program code is configured to, with the at least one processor, cause the second network node to: receiving an indication including a measurement report from the user equipment; and Based on the indication, repeated transmission of the packet is initiated at the fourth network node.

49. The second network node according to claim 48, wherein the initiating is based on a radio resource management definition threshold of the measurement report.

50. The second network node of claim 42, wherein the at least one non-transitory memory comprising the computer program code is configured to, with the at least one processor, cause the second network node to: receiving a layer 1 measurement report from the user equipment; and Based on the receiving, a media access control element indicating the cell change is sent to the user equipment.

51. A central unit control plane, comprising: at least one processor; as well as at least one non-transitory memory including computer program code, wherein the at least one non-transitory memory and the computer program code are configured to, together with the at least one processor, cause the central unit control plane to at least: sending, by the central unit control plane supporting at least one of a distributed unit function of a radio access network or a layer 2 protocol, a user context establishment request to a second network node, the central unit control plane supporting at least one of a central unit control plane function of the radio access network or a layer 3 protocol, wherein the user context establishment request comprises: information for preparing a low layer mobility cell change of a user equipment, the user equipment being configured to: support parallel reception of data from two cells belonging to different network nodes of the radio access network and controlled by a first network node supporting at least one of a distributed unit function of the radio access network or the layer 2 protocol, from a serving cell controlled by a first network node supporting at least one of a distributed unit function of the radio access network or the layer 2 protocol; and sending a layer 1 measurement report including an indication of a second cell controlled by the second network node and related measurement information to the serving cell to enable monitoring of a low layer mobility condition of a change of the low layer mobility cell of a user equipment, wherein the indication includes: a cell identifier or a cell identifier index identifying at least one of the second cell, a serving distributed unit, a target distributed unit, and a central unit control plane.

52. A centralized unit user plane, comprising: at least one processor; as well as at least one non-transitory memory including computer program code, wherein the at least one non-transitory memory and the computer program code are configured to, together with the at least one processor, cause the centralized unit user plane to at least: receiving, by the centralized unit user plane, a bearer context establishment request for a user equipment to change a serving cell of a second cell from a central unit control plane function of a radio access network or a central unit control plane supporting a layer 3 protocol, the centralized unit user plane supporting at least one of a distributed unit function of the radio access network or a layer 2 protocol; To solve the ping-pong problem, a mapping table is created and stored to identify the user equipment and its configuration in a given distributed unit or cell, as long as ping-pong is possible. wherein the mapping table is created based on input from a centralized unit control plane, wherein the mapping table indicates: a distributed unit, a cell, an index, or a cell configuration for each user equipment associated with the radio access network, and wherein the mapping is used to determine whether a user equipment configuration exists and whether parallel transmission can be started before the serving cell is changed; receiving a control protocol data unit message from a serving cell controlled by a first network node supporting at least one of a distributed unit function of the radio access network or the layer 2 protocol, and The layer 2 message further includes instructions to perform parallel reception from both the serving cell and the second cell at least during the serving cell change, and to retain at least one configuration of at least one of data transmission or reception with the serving cell after success of the serving cell change to the second cell.

53. A service distribution unit, comprising: at least one processor; as well as at least one non-transitory memory including computer program code, wherein the at least one non-transitory memory and the computer program code are configured to, together with the at least one processor, cause the service distribution unit to at least: To solve the ping-pong problem, a mapping table is created and stored to identify the user equipment and its configuration in a given distributed unit or cell, as long as ping-pong is possible, wherein the mapping table is created based on input from a centralized unit control plane; receiving a layer 3 radio resource control message from a third network node, the layer 3 radio resource control message configuring a user equipment to perform layer 1 measurements related to a second cell controlled by a second network node supporting at least one of a distributed unit function or a layer 2 protocol of the radio access network, a bearer context establishment request for a serving cell change of the user equipment to the second cell if a low layer mobility condition is met and a ping pong timer is still running, wherein the third network node supports at least one of a central unit control plane function or a layer 3 protocol of the radio access network; as well as A cell change trigger notification is sent to a fourth network node to trigger duplication of data to enable timely and parallel transmission of data to both the first cell and the second cell.

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