User equipment and base station participating in mobility procedure

Abstract

The present disclosure relates to a Base Station Central Unit (BS-CU) including the following. A transmitter transmits a mobility request to a distributed unit-mobility candidate BS-DU of the base station, the mobility candidate BS-DU being a candidate participating in mobility of a user equipment (UE). A receiver of the BS-CU receives, from a mobility candidate BS-DU, a reference signal, RS, resource configuration of the mobility candidate BS-DU related to a candidate cell of the mobility candidate BS-DU. The processing circuitry of the BS-CU generates an updated list having information on the RS resource configurations of the received mobility candidate BS-DUs and information on the RS resource configurations of at least a serving BS-DU serving the UE. The transmitter transmits the content of the updated list to the serving BS-DU for further forwarding to the UE.

Description

Technical Field

[0001] The present disclosure relates to methods, apparatus and articles in a communication system, such as a 3GPP communication system. Background Art

[0002] Currently, the 3rd Generation Partnership Project (3GPP) is developing technical specifications for a new radio access technology, 5G NR (New Radio), which is also referred to as fifth generation (5G) or NR and is used interchangeably in this article.

[0003] One goal is to provide a single technical framework to address all use cases, requirements, and deployment scenarios (see, for example, Section 6 of 3GPP TR 38.913, e.g., Release 16.0.0 or Release 17.0.0), including at least enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC). For example, eMBB deployment scenarios may include indoor hotspots, dense urban, rural, urban macro base stations, and high-speed scenarios; URLLC deployment scenarios may include industrial control systems, mobile healthcare (remote monitoring, diagnosis, and treatment), real-time control of vehicles, and wide-area monitoring and control systems for smart grids; and mMTC deployment scenarios may include scenarios with a large number of devices transmitting non-time-critical data, such as smart wearables and sensor networks. eMBB and URLLC services are similar in that they both require very wide bandwidth, but different in that URLLC services may require even more ultra-low latency.

[0004] The second goal is to achieve forward compatibility, which facilitates completely new system designs and / or the introduction of new features. Summary of the Invention

[0005] One non-limiting exemplary embodiment facilitates a base station central unit to perform improved mobility procedures.

[0006] In an embodiment, the technology disclosed herein is characterized by a base station central unit BS-CU and includes the following contents. A transmitter sends a mobility request to a distributed unit of a base station (a mobility candidate BS-DU that is a candidate for mobility participation of a user equipment (UE)). A receiver of the BS-CU receives a reference signal (RS) resource configuration related to a candidate cell of the mobility candidate BS-DU from the mobility candidate BS-DU. The processing circuit of the BS-CU generates an updated list, and the updated RS resource configuration list contains the RS resource configuration information of the received mobility candidate BS-DU and the RS resource configuration information of at least one serving BS-DU serving the UE. The transmitter sends the contents of the updated RS resource configuration list to the serving BS-DU for further forwarding to the UE.

[0007] A non-limiting exemplary embodiment facilitates a UE to perform an improved mobility procedure. In one embodiment, the technology disclosed herein is characterized in that a user equipment (UE) includes the following parts. A receiver receives a communication configuration of a BS-DU that is a candidate for UE mobility participation from a base station distributed unit (serving BS-DU) serving the UE. A processing circuit of the UE decodes the received communication configuration of the mobility candidate BS-DU to obtain a reference signal (RS) resource configuration associated with a candidate cell of the mobility candidate BS-DU. The processing circuit updates a current list containing RS resource configuration information of at least the serving BS-DU based on the decoded RS resource configuration of the mobility candidate BS-DU.

[0008] Additional benefits and advantages of the disclosed embodiments and various implementations will be apparent from the description and drawings. These benefits and / or advantages may be achieved individually by various embodiments and features of the description and drawings, and not all of these embodiments and features need be provided in order to achieve one or more such benefits and / or advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Hereinafter, exemplary embodiments will be described in more detail with reference to the accompanying drawings.

[0010] Figure 1 An exemplary architecture of a 3GPP NR system is shown, to which the improved procedures of the present disclosure may be applied;

[0011] Figure 2 is a schematic diagram illustrating the functional split between the NG Radio Access Network (NG-RAN) and the 5G Core Network (5GC), to which the improved procedures of the present disclosure are applicable,

[0012] Figure 3 is a sequence diagram of a radio resource control (RRC) connection establishment / reconfiguration process, to which the improved process of the present disclosure can be applied,

[0013] Figure 4 is a schematic drawing showing a usage scenario of eMBB, mMTC and URLLC, to which the improved process of the present disclosure is applicable,

[0014] Figure 5 is a block diagram illustrating an exemplary 3GPP NR system architecture for a non-roaming scenario,

[0015] Figure 6 Describes a split gNB architecture where the gNB is split into a gNB central unit and one or more gNB distributed units,

[0016] Figure 7A simplified and exemplary embodiment of a set of synchronization signal blocks distributed in half a frame is described,

[0017] Figure 8 It describes multiple beams and their corresponding SSB indices SSB1-SSB8, and how the gNB transmits these beams in a beam scanning manner.

[0018] Figure 9 illustrates a simplified signaling diagram for intra-DU low-layer cell handover,

[0019] Figure 10 illustrates an exemplary and simplified structure of a UE and a gNB,

[0020] Figure 11 An example of basic mobility procedures and cell handover preparation is described, to which various solutions and variants are applied.

[0021] Figure 12 illustrates the structure of a base station central unit according to an exemplary embodiment of a first solution for an improved mobility procedure,

[0022] Figure 13 A flowchart illustrating the behavior of the BS-CU according to an exemplary embodiment of the first solution of the improved mobility procedure,

[0023] Figure 14 a signalling diagram illustrating an exemplary and simplified implementation of an improved mobility procedure according to a first solution,

[0024] Figure 15 A further signalling diagram illustrating a first variant of the first solution for the improved mobility procedure,

[0025] Figure 16 Further signalling diagram illustrating a first variant of the first solution of the improved mobility procedure, for a scenario including a second candidate gNB-DU-2,

[0026] Figure 17 A further signalling diagram illustrating a second variant of the first solution for the improved mobility procedure,

[0027] Figure 18 illustrates the structure of a UE according to an exemplary embodiment of the second solution of the improved mobility procedure,

[0028] Figure 19 a flow chart illustrating UE behavior according to an exemplary embodiment of the second solution of the improved mobility procedure,

[0029] Figure 20 a signalling diagram illustrating an exemplary and simplified implementation of a second solution for an improved mobility procedure, and

[0030] Figure 21 A more detailed signalling diagram illustrating an exemplary and simplified implementation of the second solution for the improved mobility procedure. DETAILED DESCRIPTION

[0031] 5G NR system architecture and protocol stack

[0032] 3GPP has been working on the next version of 5th generation cellular technology, or 5G for short, including the development of new radio access technologies operating in the frequency range up to 100 GHz. The first version of the 5G standard was completed at the end of 2017, allowing for the continuation of trials and commercial deployment of smartphones compliant with the 5G NR standard.

[0033] Among other things, the overall system architecture assumes an NG-RAN (Next Generation Radio Access Network) consisting of gNBs, which provides NG radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocol termination towards the UE. The gNBs are interconnected via the Xn interface. The gNBs are also connected to the 5GC via the Next Generation (NG) interface, more specifically, to the AMF (Access and Mobility Management Function) (e.g., a specific core entity implementing the AMF) via the NG-C interface, and to the UPF (User Plane Function) (e.g., a specific core entity implementing the UPF) via the NG-U interface. Figure 1 The NG-RAN architecture is described in (see e.g. 3GPP TS 38.300 e.g. v17.2.0 Section 4).

[0034] The user plane protocol stack for NR (see, for example, 3GPP TS 38.300, Section 4.4.1) consists of the PDCP (Packet Data Convergence Protocol, see TS 38.300, Section 6.4), the RLC (Radio Link Control, see TS 38.300, Section 6.3), and the MAC (Medium Access Control, see TS 38.300, Section 6.2) sublayers, which terminate in the gNB on the network side. Furthermore, a new Access Stratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) is introduced above PDCP (see, for example, TS 38.300, Section 6.5). A control plane protocol stack is also defined for NR (see, for example, TS 38.300, Section 4.4.2). An overview of Layer 2 functionality is provided in TS 38.300, Section 6. The RRC layer functionality is outlined in TS 38.300, Section 7.

[0035] For example, the medium access control layer handles logical channel multiplexing as well as scheduling and scheduling-related functions, including the handling of different parameter sets.

[0036] The physical layer (PHY) is responsible for, for example, coding, PHY HARQ processing, modulation, multi-antenna processing, and mapping signals to appropriate physical time-frequency resources. It also handles the mapping of transport channels to physical channels. The physical layer provides services to the MAC layer in the form of transport channels. A physical channel corresponds to a set of time-frequency resources used for the transmission of a specific transport channel, and each transport channel is mapped to a corresponding physical channel. For example, physical channels are PRACH (Physical Random Access Channel), PUSCH (Physical Uplink Shared Channel), and PUCCH (Physical Uplink Control Channel) for uplink, and PDSCH (Physical Downlink Shared Channel), PDCCH (Physical Downlink Control Channel), and PBCH (Physical Broadcast Channel) for downlink.

[0037] NR use cases / deployment scenarios may include enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), massive machine-type communications (mMTC), which have different requirements in terms of data rate, latency, and coverage. For example, eMBB is expected to support data rates and peak data rates that are three times higher than those provided by advanced IMT (20Gbps for downlink and 10Gbps for uplink). On the other hand, in the case of URLLC, the requirements for ultra-low latency (0.5ms for user plane latency, UL and DL each) and high reliability (1-10 times within 1ms) are also high. -5 ) puts forward more stringent requirements. Finally, mMTC may preferably require high connection density (1000000 devices / km in urban environments) 2 ), large coverage in harsh environments and extremely long battery life (15 years) for low-cost devices.

[0038] Therefore, an OFDM parameter set (e.g., subcarrier spacing, OFDM symbol duration, cyclic prefix (CP) duration, number of symbols per scheduling interval) that is suitable for one use case may not be well suited for another use case. For example, low latency services may preferably require shorter symbol duration (and therefore larger subcarrier spacing) and / or fewer symbols per scheduling interval (also known as TTI) than mMTC services. In addition, deployment scenarios with large channel delay spread may preferably require longer CP duration than scenarios with short delay spread. The subcarrier spacing should be optimized accordingly to maintain similar CP overhead. NR can support more than one subcarrier spacing value. Accordingly, subcarrier spacings of 15kHz, 30kHz, 60kHz, ... are currently under consideration. Symbol duration T u And the subcarrier spacing Δf is calculated by the formula Δf=1 / T uIn a similar manner as in the LTE system, the term "resource element" may be used to denote a minimum resource unit consisting of one subcarrier of the length of one OFDM / SC-FDMA symbol.

[0039] In the new radio system 5G-NR, for each parameter set and carrier, a resource grid of subcarriers and OFDM symbols is defined for uplink and downlink, respectively. Each element in the resource grid is called a resource element and is identified based on a frequency index in the frequency domain and a symbol position in the time domain (see 3GPP TS 38.211, e.g., v17.4.0, e.g., Section 4). For example, downlink transmissions and uplink transmissions are organized into frames with a duration of 10 ms, each frame comprising ten subframes each having a duration of 1 ms. In a 5g NR implementation, the number of consecutive OFDM symbols per subframe depends on the subcarrier spacing configuration. For example, for a 15-kHz subcarrier spacing, a subframe has 14 OFDM symbols (similar to an LTE-compliant implementation, assuming a normal cyclic prefix). On the other hand, for a 30-kHz subcarrier spacing, a subframe has two slots, each of which includes 14 OFDM symbols.

[0040] 5G NR functional split between NG-RAN and 5GC

[0041] Figure 2 The functional split between NG-RAN and 5GC is shown. The NG-RAN logical node is the gNB or ng-eNB. The 5GC has the logical nodes AMF, UPF, and SMF.

[0042] Specifically, gNB and ng-eNB host the following key functions:

[0043] - Functions for radio resource management, such as radio bearer control, radio admission control, connection mobility control, dynamic allocation of resources to UEs in uplink and downlink (scheduling);

[0044] -IP header compression, data encryption and integrity protection;

[0045] - selection of the AMF at UE attach when the route to the AMF cannot be determined from the information provided by the UE;

[0046] - Routing user plane data towards (one or more) UPFs;

[0047] - Routing control plane information to the AMF;

[0048] -Connection establishment and release;

[0049] - Scheduling and transmission of paging messages;

[0050] - Scheduling and transmission of system broadcast information (derived from AMF or OAM);

[0051] - Measurement and measurement reporting configuration for mobility and scheduling;

[0052] - Transport level packet marking in uplink;

[0053] -Session management;

[0054] -Support network slicing;

[0055] -QoS flow management and mapping to data radio bearers;

[0056] -Support UE in RRC_INACTIVE state;

[0057] -Distribution function for NAS messages;

[0058] - Radio access network sharing;

[0059] -Dual connectivity;

[0060] - Tight interworking between NR and E-UTRA.

[0061] The Access and Mobility Management Function (AMF) hosts the following key functions:

[0062] - Non-access stratum NAS signaling termination;

[0063] -NAS signaling security;

[0064] -Access layer AS security control;

[0065] - Core Network (CN) inter-node signalling for mobility between 3GPP access networks;

[0066] - Idle mode UE reachability (including control and execution of paging retransmissions);

[0067] -Registration area management;

[0068] -Support intra-system mobility and inter-system mobility;

[0069] -Access authentication;

[0070] -Access authorization, including roaming permission checks;

[0071] - Mobility management control (subscription and policy);

[0072] -Support network slicing;

[0073] -Session Management Function SMF selection.

[0074] In addition, the user plane function UPF hosts the following main functions:

[0075] - Anchor point for intra-RAT / inter-RAT mobility (when applicable);

[0076] - External PDU session points for interconnection to data networks;

[0077] -Packet routing & forwarding;

[0078] -Packet inspection and user plane part enforced by policy rules;

[0079] -Business usage reports;

[0080] - Uplink classifier to support routing of traffic flows to the data network;

[0081] -Support branch points for multi-homed PDU sessions;

[0082] -QoS processing for user plane, such as packet filtering, gating, UL / DL rate enforcement;

[0083] - Uplink service verification (SDF to QoS flow mapping);

[0084] - Downlink packet buffering and downlink data notification triggering.

[0085] Finally, the session management function SMF hosts the following main functions:

[0086] -Session management;

[0087] -UE IP address allocation and management;

[0088] -Selection and control of UP function;

[0089] -Configure traffic steering at the user plane function (UPF) to route traffic to the correct destination;

[0090] -Control some policy implementation and QoS;

[0091] - Downlink data notification.

[0092] RRC connection establishment and reconfiguration process

[0093] Figure 3 Describes some interactions between the UE, gNB and AMF (5GC entity) in the context of the UE transitioning from RRC_IDLE to RRC_CONNECTED for the NAS part (see 3GPP TS 38.300).

[0094] RRC is the higher-layer signaling (protocol) used for UE and gNB configuration. Specifically, the transition involves the AMF preparing UE context data (including, for example, PDU session context, security keys, UE radio capabilities, and UE security capabilities) and transmitting it to the gNB along with an INITIAL CONTEXT SETUP REQUEST. The gNB then activates AS security with the UE, which is performed by the gNB sending a SecurityModeCommand message to the UE, to which the UE responds with a SecurityModeComplete message. The gNB then performs reconfiguration to establish Signaling Radio Bearer 2 (SRB2) and (one or more) Data Radio Bearers (DRBs) by sending an RRCReconfiguration message to the UE, and in response, the gNB receives an RRCReconfigurationComplete message from the UE. For signaling-only connections, steps related to RRCReconfiguration are skipped because SRB2 and DRBs are not established. Finally, the gNB notifies the AMF that the setup procedure is complete with the INITIAL CONTEXTSETUP RESPONSE.

[0095] Therefore, the present disclosure provides a 5GC entity (e.g., AMF, SMF, etc.), which includes a circuit and a transmitter. The circuit establishes a next generation (NG) connection with a gNodeB, and the transmitter sends an initial context setup message to the gNodeB via the NG connection to cause a signaling radio bearer to be established between the gNodeB and a user equipment (UE). Specifically, the gNodeB sends RRC signaling containing a resource allocation configuration information element (IE) to the UE via the signaling radio bearer. The UE then performs uplink transmission or downlink reception based on the resource allocation configuration.

[0096] IMT usage scenarios in 2020 and beyond

[0097] Figure 4 Some use cases for 5G NR are described. Within the 3rd Generation Partnership Project New Radio (3GPP NR), three use cases are being considered that envision a wide range of services and applications supported by IMT-2020. Phase 1 specifications for enhanced mobile broadband (eMBB) have been completed. In addition to further expanding eMBB support, current and future work will also address the standardization of ultra-reliable low-latency communications (URLLC) and massive machine-type communications. Figure 4Some examples of envisaged usage scenarios for IMT for 2020 and beyond are described (see for example ITU-R M.20183 Figure 2 ).

[0098] URLLC use cases have stringent requirements on capabilities such as throughput, latency, and availability, and have been envisioned as one of the enablers of future vertical applications such as wireless control of industrial manufacturing or production processes, remote medical surgery, distribution automation in smart grids, transportation safety, etc. The ultra-reliability of URLLC will be supported by identifying technologies that meet the requirements set by 3GPP TR38.913. For NR URLLC in Release 15, the key requirements include a target user plane latency of 0.5ms for UL (uplink) and a target user plane latency of 0.5ms for DL ​​(downlink). For a packet size of 32 bytes with a user plane latency of 1ms, the general URLLC requirement for one transmission of a packet is a BLER (block error rate) of 1E-5.

[0099] From a physical layer perspective, reliability can be improved in a number of possible ways. The current scope for improving reliability involves defining a separate CQI table for URLLC, more compact DCI formats, repetition of PDCCH, etc. However, as NR becomes more stable and developed (a key requirement for NR URLLC), the scope for achieving ultra-reliability may widen. Specific use cases for NR URLLC in Release 15 include augmented reality / virtual reality (AR / VR), e-health, e-safety, and mission-critical applications.

[0100] In addition, the technical enhancements targeted by NR URLLC are aimed at latency improvement and reliability improvement. The technical enhancements for latency improvement include configurable parameter sets, non-slot-based scheduling with flexible mapping, grant-free (configured grant) uplink, slot-level repetition for data channels, and downlink preemption. Preemption means stopping the transmission for which resources have been allocated, and the allocated resources are used for another transmission that has been requested later but has lower latency / higher priority requirements. Accordingly, the authorized transmission is preempted by the later transmission. Preemption can be applied independently of the specific service type. For example, a transmission for service type A (URLLC) can be used to preempt a transmission for service type B (such as eMBB). Technical enhancements for reliability improvement include a dedicated CQI / MCS table for a target BLER of 1E-5.

[0101] The mMTC (Massive Machine Type Communication) use case is characterized by a very large number of connected devices, typically sending relatively small amounts of non-delay-sensitive data. Devices are required to be low-cost and have very long battery life. From an NR perspective, utilizing very narrow bandwidth segments is a possible solution to save power from the UE's perspective and achieve long battery life.

[0102] As mentioned above, the scope of reliability in NR is expected to become wider. A key requirement for all cases, especially necessary for URLLC and mMTC, is high reliability or ultra-reliability. From a radio perspective and a network perspective, several mechanisms can be considered to improve reliability. Overall, there are several key potential areas that can help improve reliability. These areas include compact control channel information, data / control channel repetition, and diversity in the frequency, time, and / or spatial domains. These areas apply to reliability in general, regardless of the specific communication scenario.

[0103] For NR URLLC, other use cases with more stringent requirements have been identified, such as factory automation, transportation industry, and power distribution. The more stringent requirements are higher reliability (up to 10 -6 level), higher availability, packet sizes up to 256 bytes, time synchronization down to a few μs (where this value can be one or a few μs, depending on the frequency range), and short latency on the order of 0.5 to 1 ms (specifically a target user plane latency of 0.5 ms, depending on the use case).

[0104] In addition, for NR URLLC, several technical enhancements from the physical layer perspective have been identified. These technologies include PDCCH (Physical Downlink Control Channel) enhancements related to compact DCI, PDCCH repetition, and increased PDCCH monitoring. In addition, UCI (Uplink Control Information) enhancements are related to enhanced HARQ (Hybrid Automatic Repeat Request) and CSI feedback enhancements. PUSCH enhancements related to mini-slot level hopping and retransmission / repetition enhancements are also identified. The term "mini-slot" refers to a transmission time interval (TTI) that includes a smaller number of symbols than a slot (a slot including fourteen symbols).

[0105] QoS control

[0106] The 5G QoS (Quality of Service) model is based on QoS flows and supports both QoS flows that require a guaranteed stream bit rate (GBR QoS flows) and QoS flows that do not require a guaranteed stream bit rate (non-GBR QoS flows). At the NAS level, a QoS flow is the finest granularity for QoS differentiation within a PDU session. A QoS flow is identified within a PDU session by a QoS Flow ID (QFI) carried in the encapsulation header on the NG-U interface.

[0107] For each UE, the 5GC establishes one or more PDU Sessions. For each UE, the NG-RAN establishes at least one Data Radio Bearer (DRB) together with the PDU Session and may subsequently configure (one or more) additional DRBs for the QoS Flow(s) of that PDU Session (when to do so depends on the NG-RAN), e.g. as described above with reference to Figure 3 As shown in the figure, NG-RAN maps packets belonging to different PDU sessions to different DRBs. NAS-level packet filters in the UE and 5GC associate UL and DL packets with QoS flows, while AS-level mapping rules in the UE and NG-RAN associate UL and DL QoS flows with DRBs.

[0108] Figure 5 The 5G NR non-roaming reference architecture is described (see, e.g., 3GPP TS 23.501, e.g., v16.9.0, Section 4.2.3, also see v17.5.0 or v18.0.0). Application Function (AF) (e.g., in Figure 4 The external application server hosting 5G services exemplarily described in

[15] interacts with the 3GPP core network to provide services, for example, to support the application's impact on service routing, access to the Network Exposure Function (NEF), or interaction with the policy framework for policy control (see Policy Control Function (PCF), such as QoS control). Based on operator deployment, application functions that are considered to be trusted by the operator may be allowed to interact directly with relevant network functions. Application functions that are not allowed by the operator to directly access network functions use the external exposure framework to interact with relevant network functions via the NEF.

[0109] Figure 5 Other functional units of the 5G architecture are shown, namely the Network Slice Selection Function (NSSF), Network Repository Function (NRF), Unified Data Management (UDM), Authentication Server Function (AUSF), Access and Mobility Management Function (AMF), Session Management Function (SMF) and Data Network (DN), such as operator services, Internet access or third-party services. All or part of the core network functions and application services can be deployed and run on a cloud computing environment.

[0110] Therefore, in the present disclosure, an application server (e.g., AF of a 5G architecture) is provided, which includes a transmitter and a circuit, which sends a request containing QoS requirements of at least one of URLLC, eMMB and mMTC services to at least one function of 5GC (e.g., NEF, AMF, SMF, PCF, UPF, etc.) to establish a PDU session including a radio bearer between a gNodeB and a UE according to the QoS requirements, and the circuit performs the service using the established PDU session.

[0111] Transmission Configuration Indicator Status and Quasi Co-location

[0112] According to 3GPP TS 38.214: "Physical layer procedures for data (Release 17)", v.17.3.0, September 2022, two reference signals can have a quasi-co-located QCL relationship. Two antenna ports are said to be quasi-co-located if the characteristics of the channel over which symbols are transmitted on one antenna port can be inferred from the channel over which symbols are transmitted on the other antenna port.

[0113] In the 5G NR system, the Transmission Configuration Indicator (TCI) state is used to establish a Quasi Co-location (QCL) connection between the target Reference Signal (RS) and the source RS. The antenna port QCL type is defined as follows:

[0114]

[0115] The TCI state is configured for PDCCH, PDSCH, and channel state information reference signal (CSI-RS) to transmit QCL indications for the corresponding RS. QCL type AC applies in frequency range 1 (FR1, below 7.125GHz), and QCL type AD applies in frequency range 2 (FR2, above 24.250GHz). QCL type D in FR2 indicates that the PDCCH / PDSCH / CSI-RS is transmitted with the same spatial filter as the reference signal associated with the TCI. In FR2, the network can indicate a change in the transmit beam of PDSCH or PDCCH by switching the TCI state.

[0116] Each TCI state may include a TCI state identifier (TCI state ID) and a set of RSs, or one or more individual RSs, for QCL reference. Each RS within a TCI state may be associated with a set of one or more Tx (transmit) and / or Rx (receive) beams.

[0117] Split gNB architecture

[0118] In the 3GPP standard, a gNB can be split into a gNB-CU (central unit) and one or more gNB-DUs (distributed units). Figure 6Shown in.

[0119] The gNB-CU is a logical node that provides support for the higher layers of the protocol stack, such as SDAP, PDCP, and RRC. The gNB-DU, on the other hand, is a logical node that provides support for the lower layers of the protocol stack, such as the RLC layer, MAC layer, and physical layer. Also, note that if the CU is connected to a 4G core network, the SDAP layer will not be present, as a 5G core network is required to support SDAP.

[0120] Therefore, the PHY and MAC layers terminate at the gNB-DU, while Layer 3 (RRC) terminates at the gNB-CU.

[0121] Each gNB has a single CU; that is, a gNB-DU is connected to only one gNB-CU. Alternatively, for resiliency, a gNB-DU can be connected to multiple gNB-CUs. A gNB-CU can control multiple gNB-DUs; for example, more than 100 gNB-DUs can be connected to a single gNB-CU. Each gNB-DU can support one or more cells. Unlike a 4G BTS, where a single gNB can control hundreds of cells, a cell is supported by only one gNB-DU.

[0122] Also, note that the interface between the CU and DU is called F1, and according to 3GPP regulations, it should be an open interface. For NG-RAN, the NG and Xn-C interfaces of the gNB, consisting of the gNB-CU and gNB-DU, terminate at the gNB-CU. For EN-DC, the S1-U and X2-C interfaces of the gNB, consisting of the gNB-CU and gNB-DU, terminate at the gNB-CU. The gNB-CU and the connected gNB-DU are visible only as gNBs to other gNBs and the 5GC.

[0123] The gNB-CU / DU architecture is specified in more detail in, for example, 3GPP TS 38.401 v17.3.0, e.g., Section 6.1. The F1 interface is specified in more detail in, for example, 3GPP TS 38.473 v17.3.0.

[0124] Synchronization signal block measurement timing configuration—SMTC—PSS / SSS, PBCH

[0125] NR introduces the so-called synchronization signal block (SS block, SSB), which includes the primary synchronization signal (PSS), the secondary synchronization signal (SSS), and the physical broadcast channel (PBCH) (actually PBCH DMRS and PBCH data). The UE can use the PSS and SSS to find, synchronize to, and identify the network. The PBCH carries a minimum amount of system information, including an indication of where the remaining broadcast system information is sent.

[0126] In LTE, these three signals—PSS, SSS, and PBCH—are also used, but they are not part of a single SSB. In NR, the three SSB components are always transmitted together, i.e., with the same period. A given SSB can repeat within an SS burst set, potentially enabling gNB beam sweeping transmissions. SS burst sets can be restricted to a specific time period, such as a 5ms window (half a frame). For initial cell selection, the UE can assume a default SS burst set period of 20ms.

[0127] 5G NR PSS is a physical layer-specific signal used to identify radio frame boundaries and is an m-sequence. 5G NR SSS is also a physical layer-specific signal used to identify subframe boundaries and is also an m-sequence. The PSS / SSS sequence consists of a complex value used for each element / sample of the sequence. Information on current example 5G implementations of PSS and SSS can be found in 3GPP TS 38.211 v17.4.0, Sections 7.4.2.2 and 7.4.2.3, including their respective sequence generation and mapping to physical resources.

[0128] The time-frequency structure of the SS / PBCH block carrying the SSS is described in TS 38.211, Section 7.4.3.1. In this exemplary 5G implementation, in the time domain, the SS / PBCH block consists of four OFDM symbols, numbered sequentially from 0 to 3. The distribution of the PSS, SSS, and PBCH signals within the SS / PBCH block is defined in Table 7.4.3.1-1.

[0129] In the frequency domain, an SS / PBCH block consists of 240 consecutive subcarriers, indexed from 0 to 239. The exact subcarriers used by each PSS, SSS, and PBCH signal within an SS / PBCH block are also defined in Table 7.4.3.1-1.

[0130] A simplified and exemplary description of SSB according to the above definition is given in Figure 7 As shown in FIG, the bottom of the figure shows PSS, SSS and PBCH in the time domain and frequency domain.

[0131] SS blocks sent by gNB (see Figure 7 ) can be defined differently. Specifically, the first symbol index (within each half-frame containing an SSB) where the candidate SSB starts is determined according to 3GPP 38.213 v17.4.0 Section 4.1 "Cell Search". Figure 7Examples of SSB sets are described, assuming starting OFDM symbols are 2, 8, 16, 22, 30, 36, 44, and 50 (for SCS = 30 kHz and frequency > 3 GHz), where the related OFDM symbols within a half-frame are numbered starting at 0. The number of SSBs in an SSB set can also be limited to a maximum of Lmax. In one example, an SSB set can include 4, 8, or 64 SSBs.

[0132] The candidate SS / PBCH blocks within a half-frame (e.g., referred to as an SSB set) are indexed in ascending time order from 0 to Lmax – 1. Accordingly, each SSB within the SSB set is assigned a unique number (starting from 0 and increasing by 1 each time).

[0133] Figure 7 The illustrated SSB set illustrates the case where the base station actually transmits all possible candidate SSBs. However, transmission of all SSBs is not required. Instead, the gNB can select and transmit only a subset of SSBs from the SSB set based on certain requirements. The SSBs actually transmitted by the gNB are referred to as SSB patterns. SSB patterns have essentially the same characteristics as the corresponding SSB set, including periodicity.

[0134] The gNB informs the UE about the SSB pattern, i.e., which SSBs are actually transmitted and which are not. This can be achieved, for example, by the gNB sending an SSB bitmap that defines the SSB pattern, where each bit in the SSB bitmap is associated with an SSB and identifies whether the SSB is transmitted. The length of the SSB bitmap depends on the applicable SSB set, e.g., 4 bits, 8 bits, or 64 bits.

[0135] In short, a set of candidate SSBs is configured for use by the gNB in ​​a cell. Furthermore, within this set of candidate SSBs, the gNB can select all or some of the candidate SSBs for actual transmission, which is called the SSB mode.

[0136] All SSBs can be transmitted using all beams in the system. Alternatively, when SSB beamforming is enabled, SSBs can be transmitted in different beams. In this case, each SSB is transmitted on a different spatial beam, such as Figure 8 As shown. Figure 7 Similar to the example of assuming that there are 8 SSBs (0-7), they can be sent in different beams, each beam sending in a different beam direction. Therefore, beam scanning transmission of SSBs is achieved; in other words, the scanning transmission of beams (and SSBs) is time-division multiplexed and occurs at different times. Two UEs, namely UE1 and UE2, will receive different SSBs at different times. Each beam has a beam index, for example, the beam index corresponds to the index of the SSB sent via the beam.

[0137] The UE uses SSB, and specifically SSB signals (eg, PSS, SSS, PBCH), in different mechanisms, such as for serving cell measurements, time / frequency synchronization, etc.

[0138] Beam management

[0139] Beam management is a collection of Layer 1 (PHY) and Layer 2 (MAC) procedures used to establish and maintain optimal beam pairs for good connectivity. For example, a beam pair consists of a transmit beam in one link direction and a corresponding receive beam.

[0140] Before a UE can communicate with the network, it must perform a cell search and selection process and obtain initial cell synchronization and system information. The first step in this process is to obtain frame synchronization, determine the cell identity, and decode the MIB and SIB1.

[0141] In the case of a multi-antenna system that transmits multiple beams, detecting the beams from the gNB is also part of the initialization process (e.g., the UE will typically detect all beams in the search space).

[0142] Beam management can be divided into three main processes:

[0143] Initial beam establishment,

[0144] Beam steering (also known as beam tracking and refinement), and

[0145] Beam failure recovery, the details of which are described below.

[0146] Layer 1-Layer 2 Triggered Mobility (LTM)

[0147] When a UE moves from the coverage area of ​​one cell to another, it may need to perform a serving cell handover at some point. According to one possibility, the serving cell handover is triggered by L3 measurements and is accomplished through RRC signaling-triggered reconfiguration of the primary cell (PCell) and primary secondary cell (PSCell) handover with synchronization, as well as the release and addition of secondary cells (SCells) when applicable. Such a process may involve a complete L2 (and L1) reset, resulting in longer latency, greater overhead, and longer interruption time compared to beam switching mobility.

[0148] One of the topics in the ongoing work on 3GPP Release 18 mobility enhancements is support for Layer 1-Layer 2 (also known as low layer) triggered mobility (LTM). The UE is first configured with a set of candidate cells by RRC (L3). Then, L1 or L2 signaling (e.g., MAC CE (and / or possible DCI)) is used to trigger the UE to switch serving cells between candidate cells without the need for RRC reconfiguration. In other words, to facilitate sequential cell switching, cell switching should be prepared so that after the cell switch, no matter which candidate cell becomes the new serving cell, the UE does not need to perform RRC reconfiguration. The goal is to reduce the latency, overhead and interruption time of serving cell switching. Both intra-DU and intra-CU-inter-DU cell switching are within this scope. Figure 6 The intra-DU handover between two cells of the same gNB-DU and the inter-DU handover between two cells of different gNB-DUs are demonstrated.

[0149] Figure 9 This section provides a simplified and example message exchange for intra-DU low-layer cell handover according to ongoing 3GPP Release 18 work. Accordingly, it is assumed that the gNB-DU controls multiple cells, including the UE's current serving cell. The gNB-DU is connected to the gNB-CU.

[0150] As can be seen, cell handover decisions are based on low-layer (e.g., Layer 1 RSRP) measurements performed at the UE and reported to the gNB-DU (see "Low-Layer Measurement Reporting"). More specifically, the UE measures the reference signal of one or more candidate cells from the gNB-DU and reports the results to the gNB-DU. The gNB-DU can use the received measurement results to determine whether to perform LTM on the candidate target cell. A low-layer cell handover trigger signal is sent to the UE, enabling it to perform a handover from its current cell to another cell of the gNB-DU.

[0151] The benefit gained from measuring and reporting via Layer 1 is low latency.

[0152] As described above, the low-layer mobility procedures are based on the UE performing measurements and reporting the measurement results to the UE's serving gNB (serving gNB-DU and / or serving gNB-CU). To this end, the UE may be configured with the necessary parameters and information by its serving gNB. For example, the configuration of the UE for performing measurements and reporting measurement results conceptually involves:

[0153] The quantity or collection of quantities to be reported.

[0154] • The downlink resources on each cell that should be measured in order to arrive at the quantity or set of quantities to report.

[0155] • How the actual reporting should be done, such as reporting timing and uplink channel used for reporting.

[0156] According to an example, the measurement and reporting may be based on a CSI reporting framework, which may generally be considered to involve two parts, one for configuration and another for triggering CSI reporting.

[0157] The CSI-MeasConfig IE is the highest-level IE for CSI configuration. It configures not only L1-RSRP-related measurements / reports for beam management, but also traditional CSI-related measurements / reports (such as CQI) for determining appropriate multi-MIMO precoding, modulation, and coding.

[0158] The CSI-MeasConfig IE mainly configures three types of lists:

[0159] 1) RS resource set list

[0160] Each RS resource set in the list contains one or more RS resources. For example, multiple CSI-RS resources can be configured via the NZP-CSI-RS-Resource IE and then grouped into RS resource sets via the NZP-CSI-RS-ResourceSet IE. Other possible RS resources are defined by the IEs CSI-IM-Resource (CSI-IM resource) and SSB-Index (SSB index).

[0161] 2) CSI-ResourceConfig IE list (CSI resource configuration IE list)

[0162] The different CSI-ResourceConfigs in the list may contain one or more different RS resource sets, which are selected from list element 1. This may include an NZP-CSI-RS resource set, a CSI-IM resource set, and / or a CSI-SSB resource set, respectively, each identified by an appropriate ID (see, for example, NZP-CSI-RS-ResourceSetId, CSI-IM-ResourceSetId, and / or CSI-SSB-ResourceSetId).

[0163] 3) CSI-ReportConfig IE list.

[0164] Different CSI-ReportConfigs in the list configure different CSI reporting instances. This is an information element that associates the reporting configuration of this CSI-ReportConfig (such as via PUCCH or PUSCH) with a measurement resource set (i.e., a CSI resource configuration in element 2 of the list above). The CSI resource configuration ID contained in the CSI report configuration information element identifies the CSI resource configuration information element to be used.

[0165] Measurements and reporting can be performed periodically, semi-periodically, or aperiodically. The measurement results are reported by the UE to the gNB, for example as uplink control information on the PUCCH or PUSCH. In a 5G-compliant example, the UE performs CSI reporting based on the definition in 3GPP TS 38.212 v17.4.0, Section 6.3.

[0166] In the current 3GPP 5G system, there are two types of reference signals that can be used for measurement, namely SSB (see SSB-Index above) and CSI-RS (Channel State Information Reference Signal; see NZP-CSI-RS-Resource IE and CSI-IM Resource Information Element above). SSB is always sent by the network and is not specific to a certain UE, so it is less flexible. For example, SSB can be used with relatively wide beams. On the other hand, CSI-RS can be configured specifically for a certain UE and has great flexibility in terms of transmission time (time domain) and frequency domain resources. CSI-RS can be used with relatively narrow beams because it can be configured for only one or a few UEs.

[0167] In 5G NR there are several reporting components of CSI (i.e. several different types of CSI), for example, based on 3GPP TS38.214 - Section 5.2.1:

[0168] CQI (channel quality information)

[0169] PMI (Precoding Matrix Indicator)

[0170] CRI (CSI-RS Resource Indicator)

[0171] SSBRI (SS / PBCH Resource Block Indicator)

[0172] LI (Layer Indicator)

[0173] RI (Rank Indicator)

[0174] L1-RSRP, and / or

[0175] Capability indicators

[0176] The UE may report one or more or a combination of different indicators. Generally speaking, these indicators can be divided into two categories:

[0177] - Quantities related to L1-RSRP (e.g., cri-RSRP and ssb-Index-RSRP, see the subsequent IE CSI-Report Config for details)

[0178] - CSI-related quantities (e.g., the rest of the IE CSI-Report Config)

[0179] L1-RSRP-related quantities are new quantities first introduced in NR (Release 15), one of the purposes of which is to facilitate beam management. In contrast, CSI-related quantities (such as CQI) are traditional quantities that already exist in LTE. Base stations can use these traditional CSI-related quantities to select appropriate MIMO precoding, modulation, and coding size to match channel conditions.

[0180] An exemplary implementation follows the current definition of the 5G 3GPP standard, such as defined in 3GPP TS 38.331, and may involve the following information elements (IEs):

[0181] CellGroupConfig, CSI-MeasConfig, CSI-ReportConfig, CSI-ResourceConfig, NZP-CSI-RS-Resource and NZP-CSI-RS-ResourceSet.

[0182] In short, LTM measurement and reporting can be based on the 5G CSI reporting framework. Specifically, the information element (IE) CSI-MeasConfig and the information element CSI-ReportConfig indicate the parameters of the CSI reporting framework that the UE can use to measure and then report the measurement results.

[0183] A possible IE sequence for defining measurements and reporting according to the CSI framework is given below:

[0184]

[0185] The following exemplary definition of IE CellGroupConfig is obtained from Section 6.3.2 of 3GPP TS 38.331:

[0186] -CellGroupConfig

[0187] The CellGroupConfig IE is used to configure a primary cell group (MCG) or a secondary cell group (SCG). A cell group includes a MAC entity, a set of logical channels with associated RLC entities, a primary cell (SpCell), and one or more secondary cells (SCells).

[0188] CellGroupConfig information element

[0189]

[0190]

[0191]

[0192]

[0193]

[0194] The fields and parameters of the CellGroupConfig IE are defined in 3GPP TS 38.331. The relevant ones include ServingCellConfig and ServingCellConfigCommon:

[0195]

[0196] The following example definition of IE CSI-MeasConfig is taken from 3GPP TS 38.331 section 6.3.2:

[0197] -CSI-MeasConfig

[0198] The IE CSI-MeasConfig is used to configure the CSI-RS (reference signal) belonging to the serving cell containing the CSI-MeasConfig, the channel state information reports to be sent on the PUCCH on the serving cell containing the CSI-MeasConfig, and the channel state information reports on the PUSCH triggered by the DCI received on the serving cell containing the CSI-MeasConfig. See also TS 38.214

[19] , clause 5.2.

[0199] CSI-MeasConfig information element

[0200]

[0201]

[0202] The above fields and parameters of the CSI-MeasConfig IE are defined in 3GPP TS 38.331. The relevant contents include the following:

[0203]

[0204] The following exemplary definition of the IE CSI-ReportConfig is extracted from 3GPP TS 38.331:

[0205] –CSI-ReportConfig

[0206] The IE CSI-ReportConfig is used to configure periodic or semi-persistent reporting sent on the PUCCH on the cell containing this CSI-ReportConfig, or to configure semi-persistent or aperiodic reporting sent on the PUSCH triggered by DCI received on the cell containing this CSI-ReportConfig (in this case, the cell sending the report is determined by the received DCI). See TS 38.214

[19] , section 5.2.1.

[0207] CSI-ReportConfig Information Element

[0208]

[0209]

[0210]

[0211]

[0212] The above fields and parameters of the CSI-ReportConfig IE are defined in 3GPP TS 38.331. The relevant definitions include the following:

[0213]

[0214]

[0215] The following exemplary definition of the IE CSI-ResourceConfig is obtained from 3GPP TS 38.331 Section 6.3.2:

[0216] –CSI-ResourceConfig

[0217] The IE CSI-ResourceConfig defines a set of one or more NZP-CSI-RS-ResourceSet, CSI-IM-ResourceSet and / or CSI-SSB-ResourceSet.

[0218] CSI-ResourceConfig information element

[0219]

[0220] The fields and parameters of the CSI-ResourceConfig IE are defined in 3GPP TS 38.331. The relevant definitions include the following:

[0221]

[0222]

[0223] Further improvements

[0224] In Release 15 / 16, the UE performs Layer 1 (L1) measurements on the reference signals of the serving cell. In Release 17, to support Inter-Cell Beam Management (ICBM), a new mechanism is introduced to enable the UE to perform L1 measurements on the reference signals of neighboring cells, which will be explained below.

[0225] This mechanism mainly includes the RS of neighboring cells into the measurement resource set configured by the serving cell. However, the implementation methods for SSB and CSI-RS are different.

[0226] For SSB, the IE CSI-SSB-ResourceSet has a parameter “ServingAdditionalPCIIndex-r17” that provides the non-serving cell ID for SSB. Detailed information can be found in TS 38.331.

[0227] For CSI-RS, it is necessary to configure the UE with a CSI-RS that has a QCL relationship with the SSB of the neighboring cell under its serving cell. This is achieved by using TCI-State to provide the QCL source. In more detail, in the IE NZP-CSI-RS-Resource, there is a field TCI-StateId, which points to additionalPCI-r17, in which the non-serving cell ID can be indicated for the SSB used as the QCL source for the related CSI-RS. For details, see TS 38.331.

[0228] However, for Release 17-ICBM, there is an important condition that the neighboring cell and the serving cell are served by the same gNB-DU. Specifically, the gNB-DU must be aware of the resource signal configuration of the neighboring cell. The gNB-DU can include the resource signal configuration of any of its neighboring cells in the measurement resource set configuration for the UE. Accordingly, the UE has the necessary information about the resource signals of the neighboring cells required to perform L1 measurements for Release 17-ICBM. This condition can be met by the gNB-DU for intra-DU cell handovers, such as Figure 9 shown.

[0229] On the other hand, for L1-L2 triggered mobility (LTM) between different gNB-DUs, i.e., for inter-DU LTM, it is unclear how to configure the UE to measure the reference signals of the cell of another gNB-DU, because the source gNB-DU of the UE's serving cell is unaware of the resource signal configuration of the other gNB-DU.

[0230] The inventors have therefore realised that it is possible to define an improved mobility procedure for facilitating avoiding one or more of the above-mentioned disadvantages.The present invention relates to different solutions and variants for such an improved mobility procedure.

[0231] Example

[0232] The following describes a UE, base station, and corresponding processes that meet these requirements for the new radio access technology envisioned for 5G mobile communication systems. However, these processes are also applicable to previous LTE-based mobile communication systems and future (e.g., 6G) mobile communication systems. Various implementations and variations are also described. The following disclosure benefits from, and may be based at least in part on, the above discussions and findings.

[0233] In general, it should be noted that many assumptions have been and are being made herein in order to explain the underlying principles of this disclosure in a clear, concise, and understandable manner. However, these assumptions should be understood as examples provided herein for illustrative purposes only and are not necessarily required by the present invention and, therefore, should not limit the scope of this disclosure. Those skilled in the art will appreciate that the principles of the following disclosure and the principles set forth in the claims can be applied to different scenarios and in ways not explicitly described herein.

[0234] In addition, some of the terms used below, such as processes, entities, and layers, are closely related to those used in LTE / LTE-A systems or the current 3GPP 5G standardization, although the specific terminology for the new wireless access technology used for the next-generation communication system has not yet been fully determined or may eventually change. Therefore, the terminology may change in the future without affecting the functionality of the corresponding features and solutions. Therefore, those skilled in the art will appreciate that the solution and its scope of protection should not be limited to the specific terms used exemplarily herein due to the lack of updated or ultimately agreed-upon terminology, but should be understood more broadly from the perspective of the functionality and concepts of the solution explained in this disclosure.

[0235] For example, a mobile station or mobile node or user terminal or user equipment (UE) is a physical entity (physical node) within a communication network. A node may have multiple functional entities. A functional entity refers to a software or hardware module that implements and / or provides a predetermined set of functions for the same node, other nodes or other functional entities of the network. A node may have one or more interfaces that connect the node to a communication facility or medium through which the node can communicate. Similarly, a network entity may have a logical interface that attaches the functional entity to a communication facility or medium through which the functional entity can communicate with other functional entities or corresponding nodes.

[0236] The term "base station" or "radio base station" here refers to a physical entity within a communication network. Like a mobile station, a base station may have multiple functional entities. A functional entity is a software or hardware module that implements and / or provides a predetermined set of functions for the same node, other nodes, or other functional entities of the network. This physical entity performs some control tasks for the communication equipment, including one or more of scheduling and configuration. It should be noted that the base station functionality and the communication equipment functionality can also be integrated into a single device. For example, a mobile terminal can also implement the functionality of a base station for other terminals. The term used in LTE is eNB (or eNodeB), while the term currently used in 5G NR is gNB. In addition, in non-terrestrial network (NTN) NR systems, the base station can also be a gNB.

[0237] The communication between the UE and the base station is generally standardized and may be defined by different layers, such as PHY, MAC, RRC, etc. (see the above background discussion).

[0238] Figure 10 This diagram illustrates a simplified, generalized block diagram of a user equipment (also called a communication device) and a scheduling device (here, illustratively assumed to be located in a base station, such as an LTE eNB (also called ng-eNB) or a gNB in ​​5G NR). The UE and eNB / gNB each communicate with each other using a transceiver via a (radio) physical channel.

[0239] A communications device may include a transceiver and processing circuitry. A transceiver may include a receiver and a transmitter, and / or function as both a receiver and a transmitter. The processing circuitry may be one or more hardware components, such as one or more processors or LSIs. An input / output point (or node) exists between the transceiver and the processing circuitry, through which the processing circuitry can control the transceiver, i.e., control the receiver and / or transmitter and exchange received / transmitted data. A transceiver, acting as both a transmitter and a receiver, may include an RF (radio frequency) front end, which includes one or more antennas, amplifiers, and RF modulators / demodulators. The processing circuitry may perform control tasks, such as controlling the transceiver to transmit user data and control data provided by the processing circuitry, and / or receiving user data and control data, which will be further processed by the processing circuitry. The processing circuitry may also be responsible for executing other processes, such as determination, decision, calculation, and measurement. The transmitter may be responsible for executing the transmission process and other related processes. The receiver may be responsible for executing the reception process and other related processes, such as monitoring a channel.

[0240] The present invention relates to different solutions and variants for an improved mobility process. Figure 11 An example of a simplified mobility process is given.

[0241] Specifically, for example, a split gNB architecture is assumed, with one gNB-CU and multiple gNB-DUs. A UE is located in the cell of its serving gNB-DU and exchanges user data with the gNB-CU via its serving gNB-DU. Furthermore, the UE may be configured to perform measurements on the cell of its serving gNB-DU and report the measurement results to the gNB-DU (and potentially further to the gNB-CU). For example, the UE may already have configuration information for its serving gNB-DU, including measurement configuration for the serving gNB-DU. This gNB-DU communication configuration may also include, for example, low-layer configuration parameters for the gNB-DU, such as information about downlink and uplink channels. The UE may also be provided with higher-layer parameters, such as RRC-related parameters, necessary for its operation and connection to the gNB-CU.

[0242] Assuming the gNB-CU identifies a new cell for a new gNB-DU (i.e., different from the currently serving gNB-DU), the UE may eventually be handed over to that cell. In one example, the gNB-CU maintains a list of candidate cells (and their corresponding gNB(-DUs)) for the UE. For example, the candidate cell list indicates candidate cells, each associated with the communication configuration of the cell and its gNB(-DU).

[0243] To prepare for this cell handover, the gNB-CU requests (see Mobility Request) whether the new gNB-DU will participate in the UE's mobility. Therefore, the new gNB-DU and its cell become candidates for the UE's subsequent cell handover.

[0244] To facilitate a subsequent possible handover to the cell of the new gNB-DU, the gNB-CU provides the UE with appropriate configuration information for the new candidate gNB-DU, which it retrieves from the Mobility Confirm message received from the new gNB-DU. The configuration information for the new candidate gNB-DU may include the necessary information required by the UE to connect to the gNB-DU, such as information about downlink and uplink channels. The UE continues to perform measurements to support low-layer mobility (e.g., see 5G LTM described above), including measurements on the new candidate cell of the new gNB-DU. At this point, the UE should have been provided with information about the reference signals transmitted in the new candidate cell of the new candidate gNB-DU. The UE can therefore measure reference signals on the cell serving the gNB-DU, as well as on the candidate cells of the new candidate gNB-DU (and potentially any other candidate cells of other gNB-DUs that were previously present). The low layer measurement reports are sent to the serving gNB-DU, which may then decide at some point to perform a cell handover for the UE from the serving gNB-DU's current serving cell to the cell of the candidate gNB-DU; i.e., perform an inter-DU cell handover. This process may also include, for example, the serving gNB-DU notifying the new gNB-DU and possibly the gNB-CU of the cell handover.

[0245] Regardless, the serving gNB-DU sends a lower-layer cell handover trigger to the UE, which indicates the determined candidate cell of the new candidate gNB-DU as the target for cell handover. The UE then performs a cell handover to the indicated candidate cell. As a result, user data is now exchanged between the UE and the gNB-CU via the new serving gNB-DU (the previous candidate gNB-DU).

[0246] like Figure 11 As part of the cell handover preparation shown and as a goal, the UE also needs to be provided with appropriate information about the reference signals of the candidate cells of the new candidate gNB-DU, so that low-layer measurements can be made to support low-layer mobility. Furthermore, to facilitate sequential cell handover, the cell handover should be prepared in such a way that no higher-layer (e.g., RRC) reconfiguration is required by the UE after the cell handover, regardless of which candidate cell becomes the new serving cell.

[0247] The present invention provides several solutions and their respective variations to improve cell handover preparation and thereby improve the overall mobility procedure.

[0248] In summary, the first solution is that the gNB-CU is primarily responsible for obtaining the required RS information for any candidate gNB-DU and then maintaining an updated list of the RS resource configurations for the UE's current serving gNB-DU and all candidate gNB-DUs that may support cell handover. The first solution also distinguishes two variants. The first variant involves each gNB-DU (including the serving gNB-DU and all candidate gNB-DUs) including a measurement configuration with an up-to-date and complete list of RS resource configurations (e.g., including the configurations for the UE's current serving gNB-DU and all candidate gNB-DUs that may be used for cell handover). The second variant of the first solution, on the other hand, uses a new measurement configuration that does not necessarily include the RS resource configuration for the corresponding gNB-DU. The RS resource configuration for a gNB-DU is provided separately from the measurement configuration for that gNB-DU. Furthermore, the up-to-date and complete list of RS resource configurations is also separate from the gNB-DU's measurement configuration, allowing them to be used together.

[0249] The second solution is based on the UE being primarily responsible for maintaining an updated and complete list of RS resource configurations, such as the current serving gNB-DU for the UE and all candidate gNB-DUs that could be used for a possible cell handover.

[0250] Regarding the first and second solutions, an improved UE, an improved base station (e.g., a distributed unit and a central unit of a base station), and an improved integrated circuit are presented, which individually or collectively participate in an improved mobility process. Corresponding methods for UE behavior and base station behavior are also provided. The integrated circuit can correspond to the UE and the base station, and their corresponding behaviors.

[0251] The following first and second solutions may be based on some or a combination of the different mechanisms described above in the context of the exemplary 3GPP 5G-NR implementation, including, for example, the use of signaling mechanisms (e.g., a new F1 interface for split gNB architecture, the use of information elements for measurement configuration and reporting), or how to define L1-L2 triggered mobility (LTM), as currently discussed in 3GPP.

[0252] According to an exemplary implementation, an improved mobility procedure according to the following first and second solutions may be provided according to the 3GPP standard. In this case, the communication configuration mentioned for the improved mobility procedure may be implemented identically or similarly to the information IECellGroupConfig, and the measurement configuration may be implemented identically or similarly to the IE CSI-MeasConfig.

[0253] According to an example implementation, the candidate list of the UE may have the following structure:

[0254] LTM candidate cell list: {

[0255] Candidate Cell Configuration ID 1: octet string of cell 1 (including CellGroupConfig)

[0256] Candidate Cell Configuration ID 2: octet string of cell 2 (including CellGroupConfig)

[0257] …

[0258] }

[0259] Then, the LTM cell handover command may indicate one of the configuration IDs. Once the UE receives such an LTM cell handover command, the corresponding CellGroupConfig IE becomes the new serving cell.

[0260] Solution 1: gNB-CU maintains updated RS resource configuration list

[0261] As mentioned above, the first solution involves the gNB-CU being primarily responsible for obtaining the required RS information for any candidate gNB-DU, and then maintaining an updated RS resource configuration list for the UE's current serving gNB-DU and all candidate gNB-DUs to support possible cell handovers.

[0262] In more detail, the first solution to improve the mobility procedure provides at least an improved Base Station Central Unit (BS-CU), as will be discussed below.

[0263] Figure 12 A simplified example structure of a base station central unit is illustrated for an example implementation of an improved mobility procedure according to a first solution, which can be based on a combination of Figure 10 The general base station structure explained is implemented. Figure 12 The various structural elements of the base station central unit shown in FIG can be interconnected via corresponding input / output nodes (not shown), for example, to exchange control and user data and other signals. For ease of illustration, although not shown, the base station central unit may include more structural elements.

[0264] It can be seen that the base station central unit includes a mobility request transmitter, a reference signal resource configuration receiver, a reference signal resource configuration update circuit and a reference signal resource configuration transmitter.

[0265] As will be apparent from the following disclosure, in the present case, the receiver of the base station central unit may be exemplarily configured to at least partially perform one or more of the following operations, such as receiving reference signal resource configuration and receiving communication configuration.

[0266] As will be apparent from the following disclosure, in the present case, the processing circuit of the central unit of the base station may be exemplarily configured to at least partially perform operations such as generating an updated reference signal (RS) resource configuration list.

[0267] As will be apparent from the following disclosure, in the present case, the transmitter of the base station central unit may be exemplarily configured to at least partially perform one or more of the following operations, such as sending a mobility request and sending the contents of an updated RS resource configuration list.

[0268] An exemplary process, which will be disclosed in more detail below, is implemented by a base station central unit, which includes the following parts. A transmitter sends a mobility request to a distributed unit of a base station, namely a candidate mobility candidate base station distributed unit (BS-DU) participating in the mobility of a user equipment (UE). A receiver of a base station central unit (BS-CU) receives a reference signal (RS) resource configuration related to a candidate cell of the mobility candidate BS-DU from the mobility candidate BS-DU. The processing circuit of the BS-CU generates an updated list, which contains information about the RS resource configuration of the received mobility candidate BS-DU and the RS resource configuration of at least one serving BS-DU serving the UE. The transmitter sends the content of the updated RS resource configuration list to the serving BS-DU for further forwarding to the UE.

[0269] A corresponding method comprises the following steps performed by a base station central unit:

[0270] Sending a mobility request to the distributed unit of the base station (i.e., the candidate mobility candidate BS-DU participating in the UE mobility),

[0271] receiving, from a mobility candidate BS-DU, a reference signal (RS) resource configuration associated with a candidate cell of the mobility candidate BS-DU,

[0272] generating an updated list containing information about the received RS resource configurations of the mobility candidate BS-DUs and the RS resource configurations of at least one serving BS-DU serving the UE, and

[0273] The content of the updated RS resource configuration list is sent to the serving BS-DU for further forwarding to the UE.

[0274] The corresponding timing diagram of the exemplary behavior of the base station central unit consistent with the above-discussed base station central unit and corresponding method is shown in FIG. Figure 13 This timing diagram shows an exemplary simplified implementation of the above method.

[0275] Figure 14 is a signaling diagram of an exemplary simplified implementation of the Improved Mobility procedure according to the first solution, illustrating the message exchanges between the different participating entities (here UE, gNB-DU and gNB-CU) and the steps performed by these entities. Figure 14 It can be clearly seen that the content of the updated RS resource configuration list updated by the gNB-CU is finally forwarded from the gNB-CU to the UE via the serving gNB-DU.

[0276] According to the above implementation of the first solution, it is possible to maintain an up-to-date list of RS resource configurations associated with different gNB-DUs to support cell handover to a cell controlled by a gNB-DU different from the currently serving gNB-DU. The contents of such an up-to-date RS resource configuration list, including the necessary information regarding the RS resources used by the serving gNB-DU and at least one other different gNB-DU, can then be easily provided to the UE. The UE can thus perform measurements on cells of gNB-DUs different from its serving gNB-DU. This facilitates inter-gNB-DU cell handover.

[0277] Two different variations of the first solution are described below.

[0278] First variant-

[0279] As described above, the first variant involves each gNB-DU (including the serving gNB-DU and all candidate gNB-DUs) generating a measurement configuration that contains the latest and complete list of RS resource configurations (e.g., including the configuration of the UE's current serving gNB-DU and the configurations of all candidate gNB-DUs that may be used for cell handover).

[0280] Will combine Figure 15 A more detailed implementation of the first solution for the improved mobility procedure is described for the first variant, the figure can be seen as illustrating how the initial combination is performed. Figure 11 This section discusses cell handover preparation. More specifically, it describes how to extend the UE's lower layer mobility to cover new candidate gNB-DUs and their cells. The cells to be added to the UE's candidate cell list belong to a different candidate gNB-DU than the serving gNB-DU. One goal of cell handover preparation is to provide the UE with appropriate information about the reference signals of the candidate cells of the new candidate gNB-DU.

[0281] For simplicity, we assume that the new candidate gNB-DU has only one cell for which preparation is required. However, the first variant of the first solution is also applicable to scenarios where the new candidate gNB-DU has multiple cells for which preparation is required. In this case, cell handover preparation covers multiple candidate cells of the candidate gNB-DU (either a subset or the entire set of cells of the candidate gNB-DU).

[0282] To enable the new candidate gNB-DU to participate in the UE’s lower layer mobility, the gNB-CU sends a Mobility Request message to the new candidate gNB-DU (step 1).

[0283] In this example, it is assumed that the mobility request may have included a list of current RS resource configurations, which includes the RS resource configuration of the serving gNB-DU. To achieve this, the gNB-CU may have previously obtained the RS resource configuration of the serving gNB-DU.

[0284] As yet another example, the current RS resource configuration list may also be provided to the candidate gNB-DU via another message other than the mobility request.

[0285] It is assumed that the candidate gNB-DU confirms its participation in UE lower layer mobility.

[0286] In step 2, the candidate gNB-DU generates a communication configuration for the candidate gNB-DU related to the candidate cell. This communication configuration may include the RS resource configuration related to its own candidate cell and the RS resource configuration related to the serving gNB-DU (if received from the gNB-CU). These two RS resource configurations may, for example, be included in the measurement configuration of the communication configuration and thus mapped (also referred to as "associated") to the measurement configuration of the candidate gNB-DU.

[0287] In addition, the candidate gNB-DU generates the RS resource configuration for the candidate gNB-DU (and its candidate cell) separately and sends it to the gNB-CU. Separating the RS resource configuration from the communication configuration allows the gNB-CU to decode only the RS resource configuration without decoding the communication configuration of the candidate gNB-DU. As explained below, the gNB-CU can simply forward the communication configuration to the UE via the serving gNB-DU without interpreting it.

[0288] In step 3, the candidate gNB-DU sends an appropriate mobility confirmation message to the gNB-CU, including the items thus generated: the candidate gNB-DU communication configuration and the RS resource configuration of the individual candidate gNB-DU.

[0289] In step 4, the gNB-CU obtains the RS resource configuration of the candidate gNB-DU. Then, in step 5, the gNB-CU updates the current RS resource configuration list to also include the received RS resource configuration of the candidate gNB-DU. The resulting updated and now complete list will therefore include the RS resource configurations of the cells associated with the serving gNB-DU and the candidate gNB-DU.

[0290] According to the first variant of the first solution, the serving gNB-DU is required to generate a communication configuration, specifically a measurement configuration as part of the communication configuration, which includes the latest RS resource configuration list. This updated communication configuration of the serving gNB-DU will be provided to the UE, and the UE should adhere to it while still connected to the serving gNB-DU. Therefore, the communication configuration needs to include the latest RS resource configuration. To this end, the gNB-CU requests the serving gNB-DU to modify the communication configuration and provide the serving gNB-DU with the updated RS resource configuration list (step 6).

[0291] In response to this request, the serving gNB-DU updates its measurement configuration to include the updated RS resource configuration list (step 7). The serving gNB-DU then updates its communication configuration based on the updated measurement configuration (step 8). The resulting updated communication configuration maps (also referred to as "associates") the contents of the updated RS resource configuration list to the serving gNB-DU's measurement configuration. This updated communication configuration of the serving gNB-DU (updated to include the latest RS resource configuration list) is then sent to the gNB-CU as part of a Modify Confirm message (step 9).

[0292] The gNB-CU can now transmit the received updated communication configuration of the serving gNB-DU and the communication configuration of the candidate gNB-DU to the serving gNB-DU (step 10). The serving gNB-DU forwards the received information to the UE (step 11).

[0293] Therefore, the communication configurations of both the serving gNB-DU and the candidate gNB-DU contain the updated RS resource configurations, respectively providing the UE with complete information about the RS resources to be measured. While the UE remains connected to the serving gNB-DU, it follows the measurement configuration in the communication configuration of the serving gNB-DU, specifically the RS resource configuration, which contains RS resource configuration information for all mobility candidate cells.

[0294] Accordingly, in step 12, the UE may measure the cells as configured, for example, the cells of the serving gNB-DU and the new candidate gNB-DU (and possibly the cells of all other candidate gNB-DUs if other candidate gNB-DUs were added previously).

[0295] Furthermore, when the UE eventually performs a cell handover to a cell of a candidate gNB-DU, it will follow the measurement configuration in the candidate gNB-DU communication configuration, in particular the RS resource configuration therein, which also contains the RS resource configuration information of all mobility candidate cells.

[0296] As described above, steps 6, 7, 8, and 9 of the first variant are provided so that the gNB-CU can obtain the updated communication configuration of the serving gNB, which should typically be generated by the serving gNB-DU. This updated communication configuration of the serving gNB carries the contents of the updated RS resource configuration list. In steps 10 and 11, the RS resource configurations for the cells of the serving gNB-DU and candidate gNB-DUs can be provided to the UE. This facilitates mobility procedures because the UE is aware of the reference signal information for all candidate cells in both the serving gNB-DU and candidate gNB-DUs.

[0297] On the other hand, steps 10 and 11 are also provided to convey the communication configuration of the new candidate gNB-DU to the UE. This also facilitates the mobility process because when the UE eventually switches to a candidate cell of the candidate gNB-DU, it already has all the information required to connect to that candidate cell and candidate gNB-DU without involving higher layers terminating at the gNB-CU.

[0298] In the improved mobility procedure described above according to the first variant of the first solution, it is described how, in steps 7 and 8, the serving gNB-DU updates its measurement configuration and communication configuration to include the RS resource configurations of itself and the candidate gNB-DUs. In an example implementation that can be combined with other described embodiments, these update procedures can be implemented in the same or similar manner as is known from Inter-Cell Beam Management (ICBM) in 3GPP Rel. 17.

[0299] According to an example of Rel.17 ICBM, the serving cell includes the neighboring cell's reference signal in the measurement resource set configuration. There are different approaches, such as the distinction between reference signals SSB and CSI-RS.

[0300] For SSB, the information element CSI-SSB-ResourceSet has a parameter "ServingAdditionalPCIIndex-r17" that provides the non-serving cell ID to the SSB. Here is an example taken from 3GPP TS 38.331 Section 6.3.2:

[0301] CSI-SSB-ResourceSet

[0302] IE CSI-SSB-ResourceSet is used to configure an SS / PBCH block resource set, which refers to the SS / PBCH indicated in ServingCellConfigCommon and ServingCellConfig.

[0303] CSI-SSB-ResourceSet information element

[0304]

[0305]

[0306] For the channel state information reference signal (CSI-RS), the user equipment (UE) can configure a CSI-RS under its serving cell, which has a quasi-co-location (QCL) relationship with a synchronization signal block (SSB) beam of a neighboring cell. This can be achieved by using the parameter "Transmission Configuration Indication (TCI) State" to provide a QCL resource. In one example, in the information element (IE) non-zero power (NZP)-CSI-RS resource, there is a TCI state identifier (TCI-StateID) field that points to an additional PCI-r17, in which the non-serving cell ID of an SSB can be indicated to be used as the QCL source of the relevant CSI-RS.

[0307] The following is an example of the NZP-CSI-RS Resource IE and TCI Status IE obtained from Section 6.3.2 of the 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 38.331:

[0308] –NZP-CSI-RS-Resource

[0309] The NZP-CSI-RS Resource IE is used to configure the non-zero power (NZP) CSI-RS transmitted in the cell containing this IE, and the UE can be configured to measure it (see TS 38.214

[19] section 5.2.2.3.1). Changes to the periodic, semi-persistent, or aperiodic configuration of the NZP-CSI-RS resource are not supported without a release and add operation.

[0310] NZP-CSI-RS-Resource information element

[0311]

[0312] –TCI-State

[0313] The IE TCI-State associates one or two downlink reference signals with the corresponding Quasi Co-location (QCL) type.

[0314] TCI-State information element

[0315]

[0316] In the improved mobility procedure described above according to the first variant of the first solution, step 9 describes how the updated communication configuration of the serving gNB-DU is sent back to the gNB-CU. In an example implementation that can be combined with any of the other described embodiments, this transmission can be achieved by sending a Cell Group Configuration IE generated by the serving gNB-DU and known from 3GPP. The updated Cell Group Configuration IE of the serving gNB-DU is then signaled to the UE transparently (transparent to the gNB-CU, meaning the gNB-CU does not need to interpret the Cell Group Configuration IE) via steps 10 and 11. For example, in step 10, a message is sent based on higher layers (e.g., RRC) terminating between the gNB-CU and the UE. In step 11, a higher layer message with the updated Cell Group Configuration IE is forwarded directly from the serving gNB-DU to the UE. For example, the RRC message can be an RRC reconfiguration message.

[0317] As described above, steps 10 and 11 are also used to convey the communication configuration of the new candidate gNB-DU to the UE. Similarly, the communication configuration can be implemented using the IE cell group configuration, which is obtained from the new candidate gNB-DU in step 3. The advantage of this implementation is that the gNB-CU can directly forward such a container without interpreting the contents of the cell group configuration.

[0318] Note that in the above Figure 15 In the relevant description, it is assumed that the RS resource configuration serving the gNB-DU is already available at the gNB-CU. Such information can be found in Figure 15 Obtained before step 1 of , for example, when communication is established between the serving gNB-DU and the gNB-CU.

[0319] Alternatively, such information on RS resource configuration for the serving gNB-DU can be found in Figure 15 This means that the serving gNB-DU generates the RS resource configuration for its own cell independently and uses the same Figure 15This information is sent back to the gNB-CU in a similar manner to step 3 of the previous example. In the latter case, the currently available RS resource configuration list (if included) in step 1 will not include the RS configuration of the serving gNB-DU. Furthermore, the updated RS resource configuration list sent from the gNB-CU to the serving gNB-DU in step 6 will also not include the RS configuration of the serving gNB-DU. This does not pose a problem for the serving gNB-DU when updating the serving gNB-DU communication configuration in step 8, as the serving gNB-DU is responsible for the RS configuration of its own cell and therefore has all the necessary information for its own cell's RS configuration.

[0320] Figure 16 The first variant of the first solution is described, namely the case when another cell (e.g., the cell of another candidate gNB-DU-2) is to be added to the candidate cell list of the UE. In more detail, a cell of another candidate gNB-DU-2 is detected as a potential candidate cell for cell handover, and this gNB-DU-2 is different from the previous gNB-DU (see Figure 15 , such as gNB-DU-1), and is also different from the serving gNB-DU. Figure 16 Based on the previous Figure 15 Expanded to showcase the new candidate gNB-DU-2.

[0321] Figure 16 This section illustrates how steps 1 to 5 are now performed again in conjunction with the new candidate gNB-DU-2, as explained in detail above. Steps 1, 2, and 3 are used to obtain the communication configuration of the new candidate gNB-DU-2, which is then forwarded to the UE (its contents) in step 10. This facilitates mobility procedures because when the UE eventually switches to the candidate cell of the new candidate gNB-DU-2, it already has all the information to connect to that candidate cell and the candidate gNB-DU-2.

[0322] Figure 16 It also explains how, after the RS resource configuration list is updated at the gNB-CU, the updated RS resource configuration list must be further propagated to the remaining two gNB-DUs, in this case the serving gNB-DU and the candidate gNB-DU-1. Specifically, steps 6-1 to 9-1 are provided to update the communication configuration of the serving gNB-DU again, as Figure 15 Similarly, steps 6-2 to 9-2 are additionally provided to update the communication configuration of gNB-DU-1.

[0323] The reason for this is that each gNB-DU participating in low-layer mobility according to the first variant of the first solution needs to generate a communication configuration, specifically a measurement configuration as part of the communication configuration, which includes the latest RS resource configuration list. The communication configuration received from the new candidate gNB-DU-2 can be prepared by gNB-DU-2 to include the latest RS resource configuration list, as gNB-DU-2 receives this list when generating its communication configuration.

[0324] All of these updated communication configurations are then provided to the UE (see steps 10 and 11).

[0325] Therefore, every time the RS resource configuration list changes (e.g., due to the addition of a new candidate cell), the updated RS resource configuration list must be propagated to any remaining gNB-DUs as described above. Steps 6 through 9 must be repeated frequently, resulting in significant signaling overhead on the interfaces between gNB-DUs, gNB-CUs, and towards the UE. This drawback is exacerbated as the number of gNB-DUs participating in the UE's low-layer mobility increases.

[0326] As explained above for the first variant of the first solution, each gNB-DU (including the serving gNB-DU and all candidate gNB-DUs) has the functionality to receive the RS resource configuration list from the gNB-CU and then create an up-to-date and complete RS resource configuration list by adding its own RS resource configurations for new candidate cells participating in mobility. This complete RS resource configuration list is then used to create the measurement configuration and, in turn, the communication configuration for the gNB-DU.

[0327] Furthermore, the gNB-DU according to the first variant of the first solution has the capability to participate in cell handover preparation by transmitting its own RS resource configuration to the gNB-CU, which is responsible for maintaining an up-to-date and complete RS resource configuration list. Alternatively, instead of transmitting only its own RS resource configuration, the gNB-DU can transmit an updated RS resource configuration list prepared for generating its own measurement configuration to the gNB-CU. In this alternative scenario, the gNB-CU may not need to perform the update procedure itself but instead adopt the received updated RS resource configuration list.

[0328] Thus, a first variation of the improved mobility procedure provides at least an improved base station distributed unit (eg, serving BS-DU or candidate BS-DU), which will be discussed below.

[0329] An exemplary base station distributed unit (BS-DU) includes the following parts. A receiver of the BS-DU receives a mobility request for a user equipment (UE) to participate in mobility from a central unit of a base station. The mobility request or another message received by the receiver contains a list having reference signal (RS) resource configuration information of at least one BS-DU serving the UE, wherein the RS resource configuration of the serving BS-DU is associated with a candidate cell of the serving BS-DU. The processing circuit of the BS-DU updates the received RS resource configuration list with the RS resource configuration of the BS-DU associated with the candidate cell of the BS-DU. The transmitter of the BS-DU sends the RS resource configuration of the BS-DU or the updated RS resource configuration list to the base station central unit (BS-CU).

[0330] Furthermore, each gNB-DU has the capability to regenerate its measurement configuration and, accordingly, its communication configuration, using the latest and complete RS resource configuration list even after initial configuration. Accordingly, an improved BS-DU is provided, whereby a receiver of the BS-DU receives a modification request from a BS-CU, the modification request including an updated list of RS resource configurations, which includes, in addition to the RS resource configurations of the serving BS-DU and the BS-DU, the RS resource configurations of another mobility candidate BS-DU. The BS-DU's processing circuitry generates an updated communication configuration for the BS-DU based on the updated RS resource configuration list received from the BS-CU in the modification request. The BS-DU's transmitter transmits the generated updated BS-DU communication configuration to the BS-CU.

[0331] Second variant-

[0332] As mentioned above, the second variant of the first solution uses a new type of measurement configuration that does not necessarily include the RS resource configuration for the corresponding gNB-DU. The RS resource configuration for the gNB-DU is provided separately from the measurement configuration for that gNB-DU. Similarly, the latest and complete list of RS resource configurations is also separate from the gNB-DU's measurement configuration so that they can be used together. According to one example of the second variant, the gNB-DU's communication configuration (in one example, the measurement configuration) contains a pointer to another external RS resource configuration. This pointer facilitates mapping the gNB-DU's measurement configuration (included in the gNB-DU's communication configuration) to a separate RS resource configuration or list of RS resource configurations.

[0333] This new type of measurement configuration, and therefore the new type of communication configuration (including the measurement configuration), is available to all gNBs participating in the UE's mobility. Therefore, the communication configuration of the serving gNB-DU, and in particular its measurement configuration, also does not include the RS resource configuration of its cell. Instead, the RS resource configuration of the serving gNB-DU is provided separately, which the UE can then use together with the measurement configuration, for example, when measuring the serving gNB-DU's cell and reporting the measurement results to the serving gNB-DU. Accordingly, in conjunction with Figure 17 The following discussion assumes for example that the UE has been configured for operation with the serving gNB-DU, thus including the new measurement configuration, but does not itself include the available RS resource configuration. Instead, the UE has independent access to the RS resource configuration of the cell serving the gNB-DU.

[0334] Combine Figure 17 A more detailed embodiment of the first solution for improving the mobility process will be described for the second variant, the figure being considered as an illustration of how to perform the initial combination of Figure 11 The cell handover preparation discussed. In more detail, it shows how the UE's low-layer mobility is extended to cover new candidate gNB-DUs and their cells. The cells to be added to the UE's candidate cell list belong to a different candidate gNB-DU than the serving gNB-DU. One goal of the cell handover preparation is to provide the UE with appropriate information about the candidate cell reference signals of the new candidate gNB-DU.

[0335] For simplicity, we again assume that the new candidate gNB-DU has a single cell for which preparation is required. However, the second variant of the first solution also applies to scenarios where the new candidate gNB-DU has multiple cells for which preparation is required. In this case, cell handover preparation covers multiple candidate cells of the candidate gNB-DU (either a subset or the entire set of cells of the candidate gNB-DU).

[0336] In step 1, the gNB-CU sends a Mobility Request message to the new candidate gNB-DU, requesting it to participate in the UE's low-layer mobility. Compared to the first variant, there is no need to provide the new candidate gNB-DU with the current RS resource configuration list, as the communication configuration to be prepared by the new candidate gNB-DU does not include RS resource configuration anyway.

[0337] In step 2, the candidate gNB-DU generates a communication configuration for itself. This communication configuration differs from the first variant in that it does not include the RS resource configuration of the candidate gNB-DU (e.g., the configuration associated with one of its cells). However, the candidate gNB-DU generates RS resource configurations for its candidate cells separately, e.g., in addition to the communication configuration.

[0338] In step 3, the candidate gNB-DU sends an appropriate confirmation message to the gNB-CU, including the generated items: the new candidate gNB-DU communication configuration and the RS resource configuration of the individual candidate gNB-DU.

[0339] In step 4, the gNB-CU obtains the RS resource configuration of the candidate gNB-DU. Then, in step 5, the gNB-CU updates the current RS resource configuration list to also include the received RS resource configuration of the candidate gNB-DU. The resulting updated and complete list will therefore contain the RS resource configuration of the cells associated with the serving gNB-DU and the candidate gNB-DU.

[0340] In step 6, the gNB-CU now transmits the received communication configuration of the candidate gNB-DU and the generated updated RS resource configuration list to the serving gNB-DU. The serving gNB-DU forwards the received information to the UE (step 7).

[0341] Therefore, the UE receives the RS resource configuration list in step 8, thereby obtaining the necessary information about the reference signals transmitted on the new candidate cell of the candidate gNB-DU. For example, the UE's previous RS resource configuration list may only contain information about the reference signals of the serving gNB-DU. The UE then associates the received updated RS resource configuration with the measurement configuration of the serving gNB-DU.

[0342] Therefore, this updated RS resource configuration list can be used together with the measurement configuration of the serving gNB-DU to perform measurements on the configured cells (e.g., the cells of the serving gNB-DU and the new candidate gNB-DU) (steps 9 and 10).

[0343] although Figure 17 Not shown, but as above combined Figure 11 As discussed, as part of low-layer mobility, the UE may report measurement results to the serving BS-DU.

[0344] As described in the example implementation above, to use the updated RS resource configuration list with the measurement configuration of the serving gNB-DU, the UE associates the measurement configuration of the serving gNB-DU with the updated RS resource configuration list. This can be achieved, for example, by ignoring the previous RS resource configuration list and then using the updated RS resource configuration list instead. In other words, the previous RS resource configuration in the serving gNB-DU measurement configuration is overwritten by the newly updated RS resource configuration list generated by the UE.

[0345] In one example, the measurement configuration of the serving gNB-DU contains a pointer to an external RS resource configuration. In this case, the external RS resource configuration is the RS resource configuration list maintained by the gNB-CU (the gNB-CU is also responsible for sending the updated RS resource configuration list to the UE).

[0346] As described above, steps 3, 4, and 5 of the second variant are provided so that the gNB-CU generates an updated RS resource configuration list for the UE. In steps 6 and 7, the RS resource configurations for the cells of the serving gNB-DU and candidate gNB-DUs can be provided to the UE. This facilitates mobility procedures because the UE is aware of the reference signals of all candidate cells in the serving gNB-DU and candidate gNB-DUs.

[0347] Steps 6 and 7 are also provided to communicate the communication configuration of the new candidate gNB-DU to the UE. This also facilitates the mobility process because when the UE eventually switches to a candidate cell of the candidate gNB-DU, it will follow the communication configuration of the candidate gNB-DU and therefore have all the information required to connect to that candidate cell and candidate gNB-DU without involving higher layers terminating at the gNB-CU.

[0348] By separating the reference signal (RS) resource configuration of a gNB-DU from the measurement configuration of said gNB-DU, the second variant has the advantage over the first variant that the gNB-CU can continuously update the RS resource configuration without requiring each gNB-DU to regenerate its own measurement configuration and communication configuration.

[0349] Compared to the first variant of the first solution, the advantage of the second variant is that the above-mentioned propagation problem does not occur. Specifically, according to the second variant, when another cell (e.g., the cell of another candidate gNB-DU-2) is to be added to the candidate cell list of the UE, the same steps 1 to 9 are theoretically performed. More specifically, a cell of another candidate gNB-DU-2 is detected as a potential candidate cell for cell handover, and the gNB-DU-2 is different from the previous candidate gNB-DU (e.g., see Figure 17 The gNB-DU-2 candidate cell is also different from the serving gNB-DU. Steps 1 through 5 are performed again to provide the gNB-CU with the independent RS resource configuration for the new candidate cell of gNB-DU-2 and to update the current RS resource configuration list to include the RS resource configuration for the new candidate cell of gNB-DU-2. This updated RS resource configuration list is then sent to the UE's serving gNB-DU and then to the UE, following steps 6 and 7.

[0350] In addition, in parallel, the communication configuration of the new candidate gNB-DU-2 cell is provided to the gNB-CU and then also to the UE, executing steps 2 to 7.

[0351] According to step 10, the UE obtains the updated RS resource configuration list and uses this list (instead of the previous RS resource configuration list) for mobility procedures, in particular for measurements on the cells of the serving gNB-DU, candidate gNB-DU-1, and candidate gNB-DU-2.

[0352] As mentioned above, the second variant is based on the use of a gNB-DU communication configuration, where the measurement configuration itself does not contain the (available) RS resource configurations for the corresponding gNB-DU (and its associated cells). Instead, an external, independent list of RS resource configurations is maintained and updated, which the UE can then flexibly use in conjunction with this modified measurement configuration.

[0353] Therefore, the corresponding new candidate gNB-DU-1 and gNB-DU-2 generate their communication configuration using the modified measurement configuration (excluding the available RS resource configuration), making the communication configuration independent of the (updated) content of the RS resource configuration list.

[0354] Compared to the first variant of the first solution, therefore, each time a new cell is added to the RS resource configuration list, there is no need to propagate the latest RS resource configuration list to the existing gNB-DUs that are already participating in UE mobility. Specifically, according to the second solution, there is no need to perform the same Figure 16 Steps corresponding to steps 6, 7, 8 and 9 of the first variant of the first solution in .

[0355] As described above for the second variant of the first solution, each gNB-DU (including the serving gNB-DU and all candidate gNB-DUs) has the function of creating a new measurement configuration that does not necessarily include the RS resource configuration of the corresponding gNB-DU.

[0356] Accordingly, the second variation of the first solution of the improved mobility procedure provides at least an improved base station distributed unit (eg, serving BS-DU or candidate BS-DU), as will be discussed below.

[0357] An exemplary BS-DU includes the following components: a receiver of the BS-DU receives a mobility request from a central unit of a base station to participate in user equipment (UE) mobility; a processing circuit of the BS-DU generates a communication configuration for the BS-DU, wherein the BS-DU communication configuration does not include a reference signal (RS) resource configuration for the BS-DU; and a transmitter of the BS-DU transmits the BS-DU communication configuration to a BS-CU.

[0358] As explained above for the second variant of the first solution, the user equipment (UE) is equipped with the capability to repeatedly receive updated lists of reference signal (RS) resource configurations and then use the most recently received RS resource configuration list, rather than outdated RS resource configuration lists, in conjunction with measurement configurations to perform measurements on different cells. Furthermore, according to this second variant, the UE is able to handle new measurement configurations that do not necessarily include RS resource configurations for each gNB-DU.

[0359] Accordingly, the second variant of the first solution of the improved mobility procedure provides at least an improved UE, as described below.

[0360] An exemplary UE includes the following parts. The processing circuit of the UE can access the communication configuration of the base station (serving BS-DU) serving the UE. The serving BS-DU communication configuration includes the measurement configuration of the serving BS-DU, which does not include the reference signal (RS) resource configuration of the serving BS-DU. The processing circuit of the UE can access a list of one or more RS resource configurations, which list includes at least the RS resource configuration of the serving BS-DU, wherein the RS resource configuration is related to the candidate cell of the serving BS-DU. The receiver of the UE receives an updated list of one or more RS resource configurations from the serving BS-DU. The updated RS resource configuration list includes the RS resource configuration of the serving BS-DU and the BS-DU that is a candidate for participation in the mobility of the UE. The processing circuit of the UE uses the updated RS resource configuration list in conjunction with the measurement configuration of the serving BS-DU.

[0361] The improved UE according to the second variant is also capable of processing a pointer included in the gNB-DU communication configuration (in one example, included in the measurement configuration of the communication configuration), where the pointer points to an external RS resource configuration, such as the above-mentioned updated RS resource configuration list.

[0362] In the above implementation descriptions of the improved mobility procedure according to the first and second variants of the first solution, how the gNB-CU maintains the RS resource configuration list is described. Other implementations of the improved mobility procedure can be combined with any other described implementations, which describe exemplary implementations of the RS resource configuration list.

[0363] The RS resource configuration list can be implemented as an information element, for example, denoted as "LTM-L1-MeasResourceSetList", which may contain at least the set of SSBs (and optionally a set of CSI-RS) for L1 measurement of each candidate cell of the gNB-DU. The LTM-L1-MeasResourceSetList information element can be defined as follows:

[0364]

[0365] The above IELTM-L1 measurement resource set list can be transmitted as an RS resource configuration list represented in other ways, specifically

[0366] For the first variant of the first solution:

[0367] oIn Figure 15 In step 6

[0368] For the second variant of the first solution:

[0369] oIn Figure 17 In steps 6 and 7

[0370] In the second variant of the first solution above, the updated RS resource configuration list is transmitted from the gNB-CU to the UE’s serving gNB-DU and further to the UE (see Figure 17 In one example, the updated RS resource configuration list may be included in a higher layer message, such as an RRCReconfiguration message.

[0371] According to the following example, the updated RS resource configuration can be defined as follows:

[0372]

[0373] Therefore, LTM-L1-MeasResourceSetList may point to one or more LTM-L1-ResourceSets identified by LTM-L1-ResourceSetID, wherein each LTM-L1-ResourceSet may be defined as follows, for example:

[0374]

[0375] In a second variation of the first solution described above, the measurement configuration itself does not include RS resource configuration, but may include, for example, a pointer to a separate RS resource configuration list (see, for example, the above-mentioned LTE-L1-MeasResourceSetList). For this purpose, a new IE "CSI-ResourceConfig-r18" may be used, which is defined as follows:

[0376] CSI-ResourceConfig-r18::= SEQUENCE{

[0377] csi-ResourceConfigld CSl-ResourceConfigld

[0378] Itm-L1-MeasResourceSetList LTM-L1-MeasResourceSetList

[0379] Apparently, it defines a resource configuration for the CSI, has an ID (here “CSI-ResourceConfigID”) and has a pointer that allows establishing a link with a separate RS-resource-configuration list, LTE-L1-MeasResourceSetList.

[0380] Second solution - UE maintains updated RS-resource-configuration list

[0381] As mentioned above, the second solution is based on the following: the UE is primarily responsible for maintaining an updated and complete list of RS resource configurations, i.e., its current serving gNB-DU and all candidate gNB-DUs that could be used for a possible cell handover. Thus, the UE has all necessary information related to the RS resource configuration to perform low-layer mobility operations, including, in particular, measurements on the cell of its current serving gNB-DU and other (candidate gNB-DUs).

[0382] In more detail, the second solution of the improved mobility procedure provides an improved UE, which will be discussed below.

[0383] Figure 18 A simplified exemplary UE structure according to an exemplary embodiment of the second solution of the improved mobility procedure is illustrated, which may be based on a combination of Figure 10 The explained general UE structure is implemented. Figure 18 The various structural elements of the UE shown in the figure can be interconnected with each other, for example, through corresponding input / output nodes (not shown) to exchange control data, user data and other signals. For ease of illustration, although not shown, the UE may also include other structural elements.

[0384] from Figure 18 As can be clearly seen in FIG, the UE may include a communication configuration receiver, a communication configuration decoder and a reference signal resource configuration update circuit.

[0385] In the present case, the receiver of the UE may therefore exemplarily be configured to at least partially perform the operation of receiving a communication configuration from a base station BS-DU or the like.

[0386] In this case, it can be clearly seen from the following disclosure that the processing circuit of the UE can be exemplarily configured to at least partially perform one or more of the following operations: decoding the received communication configuration, updating the reference signal resource configuration list, etc.

[0387] In this case, it will be apparent from the following disclosure that the transmitter of the UE may be exemplarily configured to at least partially perform one or more operations, such as measurement reporting.

[0388] An exemplary process, disclosed in greater detail below, is implemented by a UE comprising the following components. A receiver receives, from a distributed unit (a serving BS-DU) of a base station serving the UE, a communication configuration of a BS-DU that is a participating UE mobility candidate. Processing circuitry in the UE decodes the received communication configuration of the mobility candidate BS-DU to obtain a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU. The processing circuitry updates a list currently containing at least RS resource configuration information of the serving BS-DU based on the decoded RS resource configuration of the mobility candidate BS-DU.

[0389] A corresponding exemplary method includes the following steps performed by the UE:

[0390] receiving, from a base station distributed unit (serving BS-DU) serving the UE, a communication configuration of a BS-DU that is a candidate for participating in the UE's mobility,

[0391] decoding the received mobility candidate BS-DU communication configuration to obtain a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU, and

[0392] According to the decoded RS resource configuration of the mobility candidate BS-DU, the list currently including at least the RS resource configuration information of the serving BS-DU is updated.

[0393] The corresponding sequence diagram of exemplary UE behavior consistent with the UE and UE method discussed above is as follows: Figure 19 shown.

[0394] Figure 20 is a signaling diagram of an exemplary simplified implementation of the Improved Mobility procedure according to the second solution, illustrating the message exchanges between the different participating entities (here, the UE and its serving gNB-DU) and the steps performed by these entities.

[0395] The above mobility procedure thus achieves the goal and overcomes some of the above disadvantages.The second solution is simple and can provide the UE with the necessary information about the cell reference signal of another BS-DU.

[0396] Will combine Figure 21 Describing a more detailed implementation of the second solution for improving the mobility procedure, the figure can be seen as illustrating how the initial combination Figure 11 This discussion discusses cell handover preparation. More specifically, it shows how to extend the UE's lower layer mobility to include new candidate gNB-DUs and their cells. The cells to be added to the UE's candidate cell list belong to a different candidate gNB-DU than the serving gNB-DU. One goal of cell handover preparation is to provide the UE with appropriate information about the candidate cell reference signals of the new candidate gNB-DU.

[0397] For simplicity, it is assumed that the new candidate gNB-DU has one cell that needs to be prepared.

[0398] However, the second solution also applies to scenarios where the new candidate gNB-DU has multiple cells for which preparation is required. In this case, the cell handover preparation covers multiple candidate cells of the candidate gNB-DU (either a subset or the entire set of cells of the candidate gNB-DU).

[0399] To enable the new candidate gNB-DU to participate in the UE's lower layer mobility, the gNB-CU sends a Mobility Request message to the new candidate gNB-DU (step 1). Assuming the candidate gNB-DU confirms its participation in the UE's lower layer mobility, the new candidate gNB-DU generates (step 2) a communication configuration that the UE can use to connect to the cell of the candidate gNB-DU. This candidate gNB-DU communication configuration includes the candidate gNB-DU's measurement configuration, which in turn includes the reference signal resource configuration that the candidate gNB-DU uses to transmit reference signals in its cell.

[0400] The candidate gNB-DU communication configuration thus generated and its contents are sent back to the gNB-CU as part of the appropriate Mobility Confirmation message (step 3).

[0401] Furthermore, the gNB-CU sends the received communication configuration of the candidate gNB-DU to the UE's serving gNB-DU (step 4). The UE's serving gNB-DU then forwards the received communication configuration of the candidate gNB-DU to the UE (step 5).

[0402] The UE is responsible for maintaining an up-to-date list of RS resource configurations for the cell of the serving gNB-DU and the new candidate gNB-DU, as well as a list of other candidate gNB-DUs that may have been added previously.

[0403] The UE then decodes the received communication configuration of the new candidate gNB-DU (step 6) and obtains the RS resource configuration of the new candidate gNB-DU (particularly its cell). The UE updates (step 7) its current RS resource configuration list to also include the RS resource configuration of the new candidate gNB-DU thus decoded.

[0404] This updated RS resource configuration list can then be used together with the measurement configuration of the serving gNB-DU to perform measurements on the cells (e.g., the cells of the serving gNB-DU and the new candidate gNB-DU) as configured (steps 8 and 9).

[0405] although Figure 21 Not shown, but as above combined Figure 11 As discussed, as part of low layer mobility, the UE may report measurement results to the serving BS-DU.

[0406] According to an exemplary embodiment, to use the updated RS resource configuration list with the measurement configuration of the serving gNB-DU, the UE associates the measurement configuration of the serving gNB-DU with the updated RS resource configuration list. This can be achieved, for example, by ignoring the previous RS resource configuration list and then using the updated RS resource configuration list instead. In other words, the previous RS resource configuration in the serving gNB-DU measurement configuration is overwritten by the newly updated RS resource configuration list generated by the UE.

[0407] The advantage of the second solution is that it simplifies mobility procedures. Furthermore, the second solution relies on already defined signaling and mechanisms for mobility procedures, such as obtaining the BS-DU's communication configuration and forwarding it to the UE. Therefore, there is no need to define new signaling and mechanisms for the gNB-DUs, gNB-CUs, and the interfaces between them (e.g., the F1 interface in 3GPP).

[0408] Compared to the first variant of the first solution, the second solution described above also has the advantage that the above-mentioned propagation problem does not occur. Specifically, according to the second solution, when more cells (e.g., cells of another candidate gNB-DU-2) are to be added to the candidate cell list of the UE, conceptually the same steps 1 to 8 are performed. More specifically, a cell of another candidate gNB-DU-2 is detected as a potential candidate for cell handover, and the gNB-DU-2 is different from the previous candidate gNB-DU (e.g., see Figure 21The UE decodes the corresponding RS resource configuration associated with the new candidate cell for candidate gNB-DU-2 and updates the current RS resource configuration list accordingly to include the RS resource configuration associated with the new candidate cell for candidate gNB-DU-2, in addition to the existing RS resource configuration for the serving gNB-DU and the cell of the previous candidate gNB-DU-1.

[0409] Finally, the UE continues with the measurements as in step 9, but in this case, using the latest and complete RS resource configuration list maintained by the UE, and measures the cells of the serving gNB-DU, candidate gNB-DU-1, and candidate gNB-DU-2.

[0410] Therefore, the respective new candidate gNB-DU-1 and gNB-DU-2 generate their communication configurations so as to include only the RS resource configuration of their own cell (unlike the first variant of the first solution), making the communication configuration independent of the (updated) content of the RS resource configuration list.

[0411] Compared to the first variant of the first solution, each time a new cell is added to the Reference Signal (RS) resource configuration list, there is no need to propagate the latest RS resource configuration list to the existing gNB-Distributed Unit (DU) participating in the User Equipment (UE) mobility. Specifically, according to the second solution, Figure 16 The steps corresponding to steps 6, 7, 8 and 9 of the first variant of the first solution are unnecessary.

[0412] On the other hand, the second solution requires the UE to perform steps to maintain an up-to-date list of RS resource configurations, which increases the UE's computational complexity. For example, the UE must decode the communication configurations of all candidate cells (gNB-DUs) to obtain complete information about the RS resource configurations. With the first solution, the UE only needs to decode a single communication configuration to obtain the up-to-date list of RS resource configurations (prepared by the gNB-centralized unit (CU)).

[0413] Further aspects

[0414] According to a first aspect, a base station central unit is provided, comprising the following parts. A transmitter sends a mobility request to a distributed unit of a base station (a mobility candidate base station distributed unit, i.e., a candidate unit participating in the mobility of a user equipment (UE)). A receiver of a base station central unit (BS-CU) receives a reference signal (RS) resource configuration related to a candidate cell of the mobility candidate base station distributed unit from the mobility candidate base station distributed unit. The processing circuit of the BS-CU generates an updated list, i.e., an updated RS resource configuration list, which contains the received RS resource configuration information of the mobility candidate base station distributed unit and the RS resource configuration information of at least one serving base station distributed unit serving the UE. The transmitter sends the content of the updated RS resource configuration list to the serving base station distributed unit for further forwarding to the UE.

[0415] According to a second aspect provided in addition to the first aspect, a transmitter transmits an updated RS resource configuration list to a serving base station distributed unit of a UE. A receiver receives an updated communication configuration of the serving base station distributed unit from the serving base station distributed unit. The updated serving base station distributed unit communication configuration includes content of the updated RS resource configuration list mapped to the serving base station distributed unit measurement configuration. Transmitting the content of the updated RS resource configuration list includes forwarding the updated serving base station distributed unit communication configuration to the serving base station distributed unit.

[0416] According to a third aspect provided in addition to the second aspect, a mobility request or other message sent to a mobility candidate base station distributed unit includes a list of at least RS resource configuration information of a serving base station distributed unit. A receiver receives the communication configuration of the mobility candidate base station distributed unit from the mobility candidate base station distributed unit. A transmitter forwards the received communication configuration of the mobility candidate base station distributed unit to the serving base station distributed unit for further forwarding to the UE. In an optional embodiment, the communication configuration of the mobility candidate base station distributed unit includes the content of an RS resource configuration list mapped to a measurement configuration of the mobility candidate base station distributed unit. The mapped RS resource configuration list includes the RS resource configurations of the serving base station distributed unit and the mobility candidate base station distributed unit.

[0417] According to a fourth aspect provided in addition to the second or third aspect, a transmitter sends another mobility request to another mobility candidate base station distributed unit to participate in the mobility of the UE; optionally, the another mobility request or further message includes an RS resource configuration list for at least the serving base station distributed unit and the mobility candidate base station distributed unit. A receiver receives RS resource configuration related to the candidate cell of the other mobility candidate base station distributed unit from the other mobility candidate base station distributed unit. The processing circuit updates the RS resource configuration list based on the received RS resource configuration of the other mobility candidate base station distributed unit. The transmitter sends the updated RS resource configuration list to the serving base station distributed unit. The receiver receives an updated communication configuration of the serving base station distributed unit from the serving base station distributed unit. The updated serving base station distributed unit communication configuration includes the contents of the updated RS resource configuration list mapped to the serving base station distributed unit measurement configuration. The transmitter forwards the received serving base station distributed unit communication configuration to the serving base station distributed unit for forwarding to the UE. In an optional embodiment, the transmitter sends the updated RS resource configuration list to the mobility candidate base station distributed unit. The receiver receives an updated communication configuration of the mobility candidate base station distributed unit from the mobility candidate base station distributed unit at runtime, and the transmitter forwards the received updated communication configuration of the mobility candidate base station distributed unit to the serving base station distributed unit at runtime for forwarding to the UE. In an optional embodiment, the receiver receives the communication configuration of another mobility candidate base station distributed unit from another mobility candidate base station distributed unit. The transmitter sends the received communication configuration of the other mobility candidate base station distributed unit to the serving base station distributed unit for further forwarding to the UE.

[0418] According to a fifth aspect, in addition to the first aspect, as a response to a mobility request, a receiver receives a communication configuration of a mobility candidate base station distributed unit (BS-DU) from the mobility candidate BS-DU. A transmitter forwards the received mobility candidate BS-DU communication configuration to a serving BS-DU for further forwarding to a user equipment (UE). The mobility candidate BS-DU communication configuration does not include a reference signal (RS) resource configuration of the mobility candidate BS-DU. In an optional embodiment, the mobility candidate BS-DU communication configuration includes a pointer to an updated RS resource configuration list, which is sent to the serving BS-DU so as to map the updated RS resource configuration list to the measurement configuration of the mobility candidate BS-DU included in the mobility candidate BS-DU communication configuration.

[0419] According to a sixth aspect, in addition to the fifth aspect, a transmitter transmits another mobility request to another BS-DU, making the other BS-DU a candidate for participating in UE mobility. In response to the another mobility request, a receiver receives from the other mobility candidate BS-DU the RS resource configuration of the other mobility candidate BS-DU associated with the candidate cell of the other mobility candidate BS-DU. The processing circuit updates the current RS resource configuration list based on the received RS resource configuration of the other mobility candidate BS-DU. The transmitter transmits the updated RS resource configuration list to the serving BS-DU for further forwarding to the UE. In an optional embodiment, the receiver receives, in response to the another mobility request, a communication configuration of the other mobility candidate BS-DU. The transmitter forwards the received communication configuration of the other mobility candidate BS-DU to the serving BS-DU for further forwarding to the UE. The communication configuration of the other mobility candidate BS-DU does not include the RS resource configuration of the other mobility candidate BS-DU.

[0420] According to a seventh aspect, there is provided a method comprising the following steps performed by a central unit of a base station:

[0421] Sending a mobility request to a distributed unit of a base station (mobility candidate BS-DU) that is a candidate for participating in the mobility of a user equipment (UE),

[0422] receiving, from a mobility candidate BS-DU, a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU,

[0423] generating an updated list containing information about the received RS resource configurations of the mobility candidate BS-DUs and the RS resource configurations of at least one serving BS-DU serving the UE, and

[0424] The contents of the updated RS resource configuration list are sent to the serving BS-DU for further forwarding to the UE.

[0425] According to an eighth aspect, there is provided an integrated circuit which, when in operation, controls a process of a Base Station Central Unit (BS-CU), the process comprising the following steps performed by the BS-CU:

[0426] Sending a mobility request to a distributed unit of a base station (mobility candidate BS-DU) that is a candidate for participating in the mobility of a user equipment (UE),

[0427] receiving, from a mobility candidate BS-DU, a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU,

[0428] generating an updated list of reference signal (RS) resource configurations, the updated list including RS resource configuration information about the received mobility candidate base station distributed units (BS-DUs) and RS resource configuration information of at least one serving BS-DU serving a user equipment (UE), and

[0429] The content of the updated RS resource configuration list is sent to the serving BS-DU for further forwarding to the UE.

[0430] According to a ninth aspect, a base station distributed unit (BS-DU) is provided, comprising the following parts. A receiver of the BS-DU receives a mobility request to participate in the mobility of a user equipment (UE) from a central unit of a base station. The mobility request or another message received by the receiver includes a list containing RS resource configuration information of at least one BS-DU serving the UE, wherein the RS resource configuration of the serving BS-DU is associated with a candidate cell of the serving BS-DU. The processing circuit of the BS-DU updates the received RS resource configuration list with the RS resource configuration of the BS-DU associated with the candidate cell of the BS-DU. The transmitter of the BS-DU sends the RS resource configuration of the BS-DU or the updated RS resource configuration list to the base station central unit (BS-CU).

[0431] According to a tenth aspect provided in addition to the ninth aspect, a receiver receives a modification request from a BS-CU, the request including an updated RS resource configuration list containing, in addition to the RS resource configuration of a serving BS-DU and the BS-DU, the RS resource configuration of another mobility candidate BS-DU. A processing circuit generates an updated communication configuration for the BS-DU based on the updated RS resource configuration list received from the BS-CU in the modification request. A transmitter transmits the generated updated BS-DU communication configuration to the BS-CU.

[0432] According to an eleventh aspect, a base station distributed unit (BS-DU) is provided, comprising the following components. A receiver of the BS-DU receives a mobility request from a central unit of a base station to participate in user equipment (UE) mobility. A processing circuit generates a communication configuration for the BS-DU, wherein the BS-DU communication configuration does not include a reference signal (RS) resource configuration for the BS-DU. A transmitter transmits the BS-DU communication configuration to a BS-CU.

[0433] According to the twelfth aspect provided in addition to the eleventh aspect, the BS-DU communication configuration includes a pointer to one or more current RS resource configuration lists, which is used to map the current RS resource configuration list to the measurement configuration of the BS-DU contained in the BS-DU communication configuration.

[0434] According to a thirteenth aspect provided in addition to the eleventh aspect or the twelfth aspect, the transmitter transmits the RS resource configuration of the BS-DU related to the candidate cells of the BS-DU to the BS-CU.

[0435] According to the fourteenth aspect, a UE is provided, comprising the following parts. A processing circuit of the UE may access a communication configuration of a base station (serving BS-DU) serving the UE. The serving BS-DU communication configuration includes a measurement configuration of the serving BS-DU, which does not include a reference signal (RS) resource configuration of the serving BS-DU. The processing circuit may access one or more RS resource configuration lists, which include at least the RS resource configuration of the serving BS-DU and RS resource configurations related to candidate cells of the serving BS-DU. The receiver of the UE receives one or more updated RS resource configuration lists from the serving BS-DU. The updated RS resource configuration list includes the RS resource configuration of the serving BS-DU and the BS-DU that is a candidate for participating in the mobility of the UE. The processing circuit uses the updated RS resource configuration list together with the measurement configuration of the serving BS-DU.

[0436] According to a fifteenth aspect provided in addition to the fourteenth aspect, the measurement configuration of the serving BS-DU includes a pointer to an updated RS resource configuration list. In an optional embodiment, a receiver receives a communication configuration of a mobility candidate BS-DU from the serving BS-DU. In an optional embodiment, the processing circuit performs measurements based on the updated RS resource configuration list and the measurement configuration of the serving BS-DU. In a further optional embodiment, the UE includes a transmitter that transmits a measurement report containing measurement results to the serving BS-DU.

[0437] According to a sixteenth aspect, there is provided a method performed by a user equipment (UE), comprising the following steps:

[0438] Accessing a communication configuration of a base station (serving BS-DU) serving the UE, wherein the serving BS-DU communication configuration includes a measurement configuration of the serving BS-DU, and the measurement configuration does not include a reference signal (RS) resource configuration of the serving BS-DU.

[0439] A list of one or more RS resource configurations is accessed, the list including at least the RS resource configuration of the serving BS-DU, the RS resource configuration being associated with a candidate cell of the serving BS-DU.

[0440] An updated list of one or more RS resource configurations is received from a serving BS-DU, where the updated RS resource configuration list includes RS resource configurations of the serving BS-DU and BS-DUs that are candidates for participation in the UE's mobility.

[0441] The updated RS resource configuration list is used together with the measurement configuration of the serving BS-DU.

[0442] According to a seventeenth aspect, there is provided an integrated circuit that, when in operation, controls a process of a user equipment, the process comprising the following steps performed by the user equipment (UE):

[0443] Access a communication configuration of a base station distributed unit (serving BS-DU) serving the UE, wherein the communication configuration of the serving BS-DU includes a measurement configuration of the serving BS-DU, and the measurement configuration does not include a reference signal (RS) resource configuration of the serving BS-DU.

[0444] A list of one or more RS resource configurations is accessed, the list including at least the RS resource configuration of the serving BS-DU, the RS resource configuration being associated with a candidate cell of the serving BS-DU.

[0445] An updated list of one or more RS resource configurations is received from a serving BS-DU, where the updated RS resource configuration list includes RS resource configurations of the serving BS-DU and BS-DUs that are candidates for participation in the UE's mobility.

[0446] The updated RS resource configuration list is used together with the measurement configuration of the serving BS-DU.

[0447] According to the eighteenth aspect, a UE is provided, comprising the following parts. A receiver receives a communication configuration of a BS-DU that is a mobility participation candidate of the UE from a distributed unit (serving BS-DU) of a base station serving the UE. A processing circuit of the UE decodes the received mobility candidate BS-DU communication configuration to obtain a reference signal (RS) resource configuration of the mobility candidate BS-DU related to a candidate cell of the mobility candidate BS-DU. The processing circuit updates a current list having at least RS resource configuration information of the serving BS-DU based on the decoded RS resource configuration of the mobility candidate BS-DU.

[0448] According to the nineteenth aspect, in addition to the eighteenth aspect, the processing circuit maps the updated RS resource configuration list to the measurement configuration of the serving BS-DU. In an optional embodiment, the mapping includes ignoring the current RS resource configuration list and instead combining the updated RS resource configuration list with the measurement configuration of the serving BS-DU.

[0449] According to the twentieth aspect, in addition to the eighteenth or nineteenth aspect, a receiver receives a communication configuration of another mobility candidate BS-DU from a serving BS-DU. The processing circuit decodes the received communication configuration of the other mobility candidate BS-DU to obtain an RS resource configuration of the other mobility candidate BS-DU associated with a candidate cell of the other mobility candidate BS-DU. The processing circuit updates a current RS resource configuration list based on the decoded RS resource configuration of the other mobility candidate BS-DU. In an optional embodiment, the processing circuit maps the updated RS resource configuration list to the measurement configuration of the serving BS-DU.

[0450] According to the twenty-first aspect, in addition to any one of the eighteenth to twentieth aspects, the processing circuit performs measurement based on the updated RS resource configuration list. In an optional embodiment, the UE includes a transmitter that sends a measurement report including the measurement result to the serving BS-DU.

[0451] According to the twenty-second aspect, in addition to any one of the fourteenth, fifteenth, and eighteenth to twenty-first aspects, the receiver receives a cell switching trigger signal from the serving BS-DU, which indicates a cell of the mobility candidate BS-DU as a target for cell switching. The processing circuit controls switching from the current cell of the serving BS-DU to the cell of the indicated mobility candidate BS-DU. In an optional embodiment, the communication configuration of the mobility candidate BS-DU also includes low-layer configuration parameters of the BS-DU related to facilitating communication between the UE and the cell of the mobility candidate BS-DU. In a further optional embodiment, one RS resource configuration of a BS-DU is associated with one cell of the BS-DU, and another RS ​​resource configuration of the BS-DU is associated with another cell of the BS-DU.

[0452] According to a twenty-third aspect, there is provided a method comprising the following steps performed by a user equipment (UE):

[0453] receiving, from a base station distributed unit (BS-DU) serving a user equipment (UE), a communication configuration of a candidate BS-DU that may participate in the mobility of the UE, decoding the received communication configuration of the mobility candidate BS-DU to obtain a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU, and

[0454] Based on the decoded RS resource configuration of the mobility candidate BS-DU, the list currently including at least the RS resource configuration information of the serving BS-DU is updated.

[0455] According to a 24th aspect, there is provided an integrated circuit which, when in operation, controls a process of a user equipment (UE), the process comprising the following steps performed by the UE:

[0456] A communication configuration of a base station-distributed unit that may participate in the mobility of a user equipment (UE) is received from a base station distributed unit (ie, a serving base station-distributed unit (BS-DU)).

[0457] The received base station-distributed unit communication configuration that may participate in the mobility is decoded to obtain a reference signal (RS) resource configuration related to a candidate cell of the base station-distributed unit that may participate in the mobility.

[0458] Based on the decoded reference signal resource configuration of the base station-distributed unit that may participate in the mobility, the list currently including at least the reference signal resource configuration information of the serving base station-distributed unit is updated.

[0459] Other variations of the present disclosure, including hardware and software implementations

[0460] The present disclosure can be implemented by software, hardware, or software and hardware collaboration. Each functional block used in the description of the above embodiments can be partially or entirely implemented by a large-scale integrated circuit (LSI) such as an integrated circuit, and each process described in each embodiment can be partially or entirely controlled by the same large-scale integrated circuit or a combination of large-scale integrated circuits. The large-scale integrated circuit can be made into a chip alone, or can be made into a chip containing some or all of the functional blocks. The large-scale integrated circuit can include data inputs and outputs connected thereto. The large-scale integrated circuit here can be referred to as an integrated circuit (IC), a system large-scale integrated circuit, a super large-scale integrated circuit, or an ultra-large-scale integrated circuit, depending on the degree of integration. However, the technology for implementing integrated circuits is not limited to large-scale integrated circuits, and can also be implemented using dedicated circuits, general-purpose processors, or dedicated processors. In addition, a field programmable gate array (FPGA) that can be programmed after the large-scale integrated circuit is manufactured can also be used, or a reconfigurable processor that can reconfigure the connections and settings of the circuit units set inside the large-scale integrated circuit can be used. The present disclosure can be implemented as digital processing or analog processing. If the development of future semiconductor technology or other derivative technologies causes future integrated circuit technology to replace large-scale integrated circuits, these functional blocks can be integrated using future integrated circuit technology. Biotechnology can also be applied.

[0461] The present disclosure may be implemented by any device, equipment, or system having a communication function, and such a device, equipment, or system is referred to as a communication device.

[0462] The communication device may include a transceiver and processing / control circuitry. The transceiver may include a receiver and a transmitter and / or function as both a receiver and a transmitter. The transceiver functioning as both a transmitter and a receiver may include a radio frequency (RF) module including an amplifier, a radio frequency modulator / demodulator, etc., and one or more antennas.

[0463] Some non-limiting examples of such communication devices include phones (e.g., cellular phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), game consoles, digital book readers, telemedicine devices, and vehicles providing communication capabilities (e.g., cars, airplanes, ships), and various combinations thereof.

[0464] Communication devices are not limited to portable or movable, but can also include any non-portable or fixed device, equipment or system, such as smart home devices (e.g., appliances, lighting devices, smart meters, control panels), vending machines, and any other "things" in the "Internet of Things (IoT)" network.

[0465] Communications may include, for example, data exchange via cellular systems, wireless local area network systems, satellite systems, etc., and various combinations thereof.

[0466] A communication device may include a device, such as a controller or a sensor, that is connected to a communication device that performs the communication functions described in this disclosure. For example, a communication device may include a controller or a sensor that generates control signals or data signals that are used by the communication device that performs the communication functions of the communication device.

[0467] The communication device may also include infrastructure facilities, such as base stations, access points, and any other devices, equipment, or systems that communicate with or control the devices in the above non-limiting examples.

[0468] (Control Signal)

[0469] In the present disclosure, downlink control signals (information) related to the present disclosure may be signals (information) transmitted via a physical downlink control channel (PDCCH) of the physical layer, or signals (information) transmitted via a medium access control (MAC) control element (CE) or radio resource control (RRC) of a higher layer. The downlink control signal may be a predefined signal (information).

[0470] The uplink control signal (information) involved in the present disclosure may be a signal (information) transmitted via the physical uplink control channel (PUCCH) of the physical layer, or a signal (information) transmitted via the medium access control layer control element (MAC CE) or radio resource control (RRC) of the higher layer. In addition, the uplink control signal may be a predefined signal (information). The uplink control signal may be replaced by uplink control information (UCI), first-stage sidelink control information (SCI), or second-stage SCI.

[0471] (Base Station)

[0472] In this disclosure, a base station may be, for example, a transmit / receive point (TRP), a cluster head, an access point, a remote radio head (RRH), an evolved Node B (eNB), a 5G base station (gNB), a base station (BS), a base transceiver station (BTS), a base station unit, or a gateway. Furthermore, in sidelink communications, a terminal may be used instead of a base station. A base station may be a relay device that relays communications between higher-level nodes and a terminal. A base station may also be a roadside unit (ROU).

[0473] (Uplink / Downlink / Sidelink)

[0474] The present disclosure can be applied to any of uplink, downlink, and sidelink.

[0475] The present disclosure can be applied to, for example, uplink channels such as the physical uplink shared channel (PUSCH), the physical uplink control channel (PUCCH) and the physical random access channel (PRACH); downlink channels such as the physical downlink shared channel (PDSCH), the physical downlink control channel (PDCCH) and the physical broadcast channel (PBCH); and sidelink channels such as the physical sidelink shared channel (PSSCH), the physical sidelink control channel (PSCCH) and the physical sidelink broadcast channel (PSBCH).

[0476] PDCCH, PDSCH, PUSCH, and PUCCH are examples of downlink control channels, downlink data channels, uplink data channels, and uplink control channels, respectively. PSCCH and PSSCH are examples of sidelink control channels and sidelink data channels, respectively. PBCH and PSBCH are examples of broadcast channels, respectively, and PRACH is an example of a random access channel.

[0477] (Data channel / Control channel)

[0478] The present disclosure can be applied to any one of data channels and control channels. The channels in the present disclosure can be replaced by data channels including PDSCH, PUSCH and PSSCH and / or control channels including PDCCH, PUCCH, PBCH, PSCCH and PSBCH.

[0479] (Reference signal)

[0480] In the present disclosure, a reference signal is a signal known to both a base station and a mobile station. Each reference signal may be referred to as a reference signal (RS), and sometimes also referred to as a pilot signal. A reference signal may be any of a demodulation reference signal (DMRS), a channel state information reference signal (CSI-RS), a tracking reference signal (TRS), a phase tracking reference signal (PTRS), a cell-specific reference signal (CRS), and a sounding reference signal (SRS).

[0481] (Time interval)

[0482] In the present disclosure, the time resource unit is not limited to one or a combination of a time slot and a symbol, and may be a time resource unit such as a frame, a superframe, a subframe, a time slot, a time slot subslot, a mini-time slot, or a time resource unit such as a symbol, an orthogonal frequency division multiplexing (OFDM) symbol, a single carrier frequency division multiple access (SC-FDMA) symbol, or other time resource units. The number of symbols included in a time slot is not limited to any number of symbols exemplified in the above embodiments, and may be other numbers of symbols.

[0483] (Frequency band)

[0484] The present disclosure can be applied to any one of the licensed frequency bands and the unlicensed frequency bands.

[0485] (communication)

[0486] The present disclosure can be applied to any of the following: communication between a base station and a terminal (Uu link communication), communication between terminals (side link communication), and vehicle-to-everything (V2X) communication. The channels in the present disclosure can be replaced by physical sidelink control channel (PSCCH), physical sidelink shared channel (PSSCH), physical sidelink feedback channel (PSFCH), physical sidelink broadcast channel (PSBCH), physical downlink control channel (PDCCH), physical uplink control channel (PUCCH), physical downlink shared channel (PDSCH), physical uplink shared channel (PUSCH), and physical broadcast channel (PBCH).

[0487] Furthermore, the present disclosure is applicable to any terrestrial network or a non-terrestrial network (NTN) using satellites or high-altitude pseudo-satellites (HAPS). Furthermore, the present disclosure is applicable to networks with large cell sizes and terrestrial networks with large delays compared to symbol lengths or slot lengths, such as ultra-wideband transmission networks.

[0488] (Antenna port)

[0489] An antenna port refers to a logical antenna (antenna group) formed by one or more physical antennas. This means that an antenna port does not necessarily refer to a single physical antenna; it can sometimes refer to an array antenna formed by multiple antennas. For example, the number of physical antennas forming an antenna port is not defined; rather, an antenna port is defined as the minimum unit that allows a terminal to transmit a reference signal. An antenna port can also be defined as the minimum unit for weighted multiplication of precoding vectors.

[0490] Furthermore, various embodiments may also be implemented via software modules that are executed by a processor or implemented directly in hardware. Combinations of software modules and hardware implementations are also possible. Software modules may be stored on any type of computer-readable storage medium, such as random access memory (RAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, registers, hard disks, compact disk read-only memory (CD-ROM), digital versatile disks (DVD), etc. It should also be noted that individual features of different embodiments may be the subject of another embodiment, alone or in any combination.

[0491] Those skilled in the art will appreciate that numerous changes and / or modifications may be made to the disclosure shown in the specific embodiments. Therefore, the present embodiments should be considered in all aspects as illustrative and not restrictive.

Claims

1. A base station central unit (BS-CU), comprising: a transmitter that sends a mobility request to a distributed unit of the base station, a mobility candidate BS-DU, the mobility candidate BS-DU being a candidate for participating in the mobility of the user equipment UE, a receiver that receives, from the mobility candidate BS-DU, a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU, a processing circuit that generates an updated list having information about the received RS resource configuration of the mobility candidate BS-DU and information about the RS resource configuration of at least a serving BS-DU serving the UE, and The transmitter sends the content of the updated list to the serving BS-DU for further forwarding to the UE.

2. The BS-CU according to claim 1, wherein The transmitter sends the updated list to the serving BS-DU of the UE, The receiver receives an updated communication configuration of the serving BS-DU from the serving BS-DU, wherein: The updated serving BS-DU communication configuration has contents mapped to an updated list of measurement configurations of the serving BS-DU, and The sending of the content on the updated list includes forwarding the updated serving BS-DU communication configuration to the serving BS-DU.

3. The BS-CU according to claim 2, wherein the mobility request or another message sent to the mobility candidate BS-DU includes a list with information about RS resource configuration of at least the serving BS-DU, The receiver receives a communication configuration of the mobility candidate BS-DU from the mobility candidate BS-DU, The transmitter forwards the received mobility candidate BS-DU communication configuration to the serving BS-DU for further forwarding to the UE, and Optionally, the mobility candidate BS-DU communication configuration has the contents of an RS resource configuration list mapped to the measurement configuration of the mobility candidate BS-DU, wherein, The mapped RS resource configuration list content includes the RS resource configuration of the serving BS-DU and the RS resource configuration of the mobility candidate BS-DU.

4. The BS-CU according to claim 2 or 3, wherein: The transmitter sends another mobility request to another mobility candidate BS-DU for participating in the mobility of the UE, optionally wherein the another mobility request or another message includes at least an RS resource configuration list for the serving BS-DU and the mobility candidate BS-DU, The receiver receives, from the another mobility candidate BS-DU, an RS resource configuration of the another mobility candidate BS-DU associated with a candidate cell of the another mobility candidate BS-DU, The processing circuit updates the RS resource configuration list based on the received RS resource configuration of the another mobility candidate BS-DU, The transmitter sends the updated RS resource configuration list to the serving BS-DU, the receiver receiving an updated communication configuration of the serving BS-DU from the serving BS-DU, wherein the updated serving BS-DU communication configuration has contents of an updated RS resource configuration list mapped to a measurement configuration of the serving BS-DU, The transmitter forwards the received serving BS-DU communication configuration to the serving BS-DU for forwarding to the UE, Optionally, the transmitter sends the updated RS resource configuration list to the mobility candidate BS-DU, and the receiver receives the updated communication configuration of the mobility candidate BS-DU from the mobility candidate BS-DU, and the transmitter forwards the received updated mobility candidate BS-DU communication configuration to the serving BS-DU for forwarding to the UE, Optionally, the receiver receives the communication configuration of another mobility candidate BS-DU from the another mobility candidate BS-DU, and the transmitter sends the received communication configuration of the another mobility candidate BS-DU to the serving BS-DU for further forwarding to the UE.

5. The BS-CU according to claim 1, wherein In response to the mobility request, the receiver receives a communication configuration of the mobility candidate BS-DU from the mobility candidate BS-DU, The transmitter forwards the received mobility candidate BS-DU communication configuration to the serving BS-DU for further forwarding to the real-time UE, in, The mobility candidate BS-DU communication configuration does not include RS resource configuration of the mobility candidate BS-DU, Optionally, the mobility candidate BS-DU communication configuration includes a pointer to the updated list sent to the serving BS-DU, so as to map the updated list to the measurement configuration of the mobility candidate BS-DU contained in the mobility candidate BS-DU communication configuration.

6. The BS-CU according to claim 5, wherein The transmitter transmits another mobility request to another BS-DU to make the another BS-DU a candidate for participating in the mobility of the UE, In response to the another mobility request, the receiver receives, from the another mobility candidate BS-DU, an RS resource configuration of the another mobility candidate BS-DU associated with a candidate cell of the another mobility candidate BS-DU, The processing circuit updates the current RS resource configuration list based on the received RS resource configuration of the another mobility candidate BS-DU, The transmitter sends the updated RS resource configuration list to the serving BS-DU for further forwarding to the UE, Optionally, wherein In response to the another mobility request, the receiver receives a communication configuration of the another mobility candidate BS-DU, and the transmitter forwards the received communication configuration of the another mobility candidate BS-DU to the serving BS-DU for further forwarding to the UE, wherein the communication configuration of the another mobility candidate BS-DU does not include the RS resource configuration of the another mobility candidate BS-DU.

7. A method comprising the following steps performed by a central unit of a base station: sending a mobility request to a distributed unit of the base station, wherein the distributed unit of the base station is called a mobility candidate BS-DU and is a candidate for participating in the mobility of the user equipment UE, receiving, from the mobility candidate BS-DU, a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU, generating an updated list having information on the received RS resource configuration of the mobility candidate BS-DU and information on the RS resource configuration of at least a serving BS-DU serving the UE, and The contents of the updated list are sent to the serving BS-DU for further forwarding to the UE.

8. An integrated circuit controlling a process of a central unit (BS-CU) of a base station, said process comprising the following steps performed by said BS-CU: sending a mobility request to a distributed unit of the base station, wherein the distributed unit of the base station is called a mobility candidate BS-DU and is a candidate for participating in the mobility of the user equipment UE, receiving, from the mobility candidate BS-DU, a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU, generating an updated list having information on the received RS resource configuration of the mobility candidate BS-DU and information on the RS resource configuration of at least a serving BS-DU serving the UE, and The contents of the updated list are sent to the serving BS-DU for further forwarding to the UE.

9. A distributed unit (BS-DU) of a base station, comprising: a receiver that receives, from a central unit of the base station, a mobility request for participating in mobility of a user equipment UE, wherein the mobility request or another message received by the receiver includes a list having RS resource configuration information about at least a BS-DU serving the UE, wherein the serving BS-DU RS resource configuration is related to a candidate cell of the serving BS-DU, a processing circuit that updates the received list with the RS resource configuration of the BS-DU associated with the candidate cell of the BS-DU, and A transmitter that sends the RS resource configuration of the BS-DU or, alternatively, an updated list to the BS-CU.

10. The BS-DU according to claim 9, wherein: The receiver receives a modification request from a BS-CU, the modification request including an updated list of RS resource configurations, the updated list having an RS resource configuration of another mobility candidate BS-DU in addition to the RS resource configuration of the serving BS-DU and the RS resource configuration of the BS-DU, the processing circuitry generating an updated communication configuration for the BS-DU based on the updated list of RS resource configurations received from the BS-CU in the modification request, The transmitter transmits the generated updated BS-DU communication configuration to the BS-CU.

11. A distributed unit (BS-DU) of a base station, comprising: a receiver that receives a mobility request for participating in the mobility of a user equipment UE from a central unit of said base station, a processing circuit that generates a communication configuration of the BS-DU, wherein the BS-DU communication configuration does not include a reference signal (RS) resource configuration of the BS-DU, and A transmitter transmits the BS-DU communication configuration to the BS-CU.

12. The BS-DU of claim 11 , wherein the BS-DU communication configuration includes a pointer to a current list of one or more RS resource configurations, capable of mapping the current list to a measurement configuration of the BS-DU included in the BS-DU communication configuration. 13 . The BS-DU according to claim 11 , wherein the transmitter transmits an RS resource configuration of the BS-DU related to a candidate cell of the BS-DU to the BS-CU.

14. A user equipment (UE), comprising: a processing circuit capable of accessing a communication configuration of a base station serving the UE, namely a serving BS-DU, wherein the serving BS-DU communication configuration includes a measurement configuration of the serving BS-DU, and the measurement configuration does not include a reference signal (RS) resource configuration of the serving BS-DU; the processing circuit being capable of accessing a list of one or more RS resource configurations, the list including at least the RS resource configuration of the serving BS-DU, the RS resource configuration being associated with a candidate cell of the serving BS-DU, a receiver that receives an updated list of one or more RS resource configurations from the serving BS-DU, the updated list including the RS resource configuration of the serving BS-DU and RS resource configurations of BS-DUs that are candidates for participating in the mobility of the UE, and The processing circuit uses the updated list together with the measurement configuration of the serving BS-DU.

15. The UE according to claim 14, wherein the measurement configuration of the serving BS-DU comprises a pointer to the updated list, Optionally, wherein the receiver receives the communication configuration of the mobility candidate BS-DU from the serving BS-DU, Optionally, the processing circuit performs measurements based on the updated list and the measurement configuration of the serving BS-DU, and Optionally, the UE includes a transmitter, and the transmitter sends a measurement report with the measurement result to the serving BS-DU.

16. A method comprising the following steps performed by a user equipment (UE): Accessing a communication configuration of a serving BS-DU serving the UE, wherein the serving BS-DU communication configuration includes a measurement configuration of the serving BS-DU, and the measurement configuration does not include a reference signal (RS) resource configuration of the serving BS-DU. accessing a list of one or more RS resource configurations, the list including at least the RS resource configuration of the serving BS-DU, the RS resource configuration being associated with a candidate cell for the serving BS-DU, receiving an updated list of one or more RS resource configurations from the serving BS-DU, the updated list including the RS resource configuration of the serving BS-DU and RS resource configurations of BS-DUs that are candidates for participating in the mobility of the UE, and The updated list is used together with the measurement configuration of the serving BS-DU.

17. An integrated circuit controlling a process of a user equipment (UE), the process comprising the following steps performed by the UE: Accessing a communication configuration of a base station (serving BS-DU) serving the UE, wherein the serving BS-DU communication configuration includes a measurement configuration of the serving BS-DU, and the measurement configuration does not include a reference signal (RS) resource configuration of the serving BS-DU. accessing a list of one or more RS resource configurations, the list including at least the RS resource configuration of the serving BS-DU, the RS resource configuration being associated with a candidate cell for the serving BS-DU, receiving an updated list of one or more RS resource configurations from the serving BS-DU, the updated list including the RS resource configuration of the serving BS-DU and RS resource configurations of BS-DUs that are candidates for participating in the mobility of the UE, and The updated list is used together with the measurement configuration of the serving BS-DU.

18. A user equipment (UE), comprising: a receiver that receives, from a distributed unit-serving BS-DU of a base station serving the UE, a communication configuration of a BS-DU that is a candidate for participating in the mobility of the UE, a processing circuit that decodes the received mobility candidate BS-DU communication configuration to obtain a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU, and The processing circuit updates a current list with information about at least the RS resource configuration of the serving BS-DU based on the decoded RS resource configuration of the mobility candidate BS-DU.

19. The UE of claim 18, wherein the processing circuit maps the updated list to the measurement configuration of the serving BS-DU, and Optionally, the mapping comprises ignoring the current list and instead using an updated list in conjunction with the serving BS-DU measurement configuration.

20. The UE according to claim 18 or 19, wherein the receiver receives a communication configuration of another mobility candidate BS-DU from the serving BS-DU, the processing circuit decoding the received another mobility candidate BS-DU communication configuration to obtain the RS resource configuration of the another mobility candidate BS-DU associated with the candidate cell of the another mobility candidate BS-DU, The processing circuit updates the current list based on the decoded RS resource configuration of the another mobility candidate BS-DU, and Optionally, the processing circuit maps the updated list to the measurement configuration of the serving BS-DU.

21. The UE according to any one of claims 18 to 20, wherein the processing circuit performs measurements based on the updated list, and Optionally, the UE includes a transmitter, and the transmitter sends a measurement report with the measurement result to the serving BS-DU.

22. The UE according to any one of claims 14, 15, and 18 to 21, wherein the receiver receives a cell handover trigger from the serving BS-DU, the cell handover trigger indicating a cell of the mobility candidate BS-DU as a target of the cell handover, wherein the processing circuit controls handover from a current cell of the serving BS-DU to an indicated cell of the mobility candidate BS-DU, Optionally, the communication configuration of the mobility candidate BS-DU further includes lower layer configuration parameters of the BS-DU related to facilitating communication between the UE and the cell of the mobility candidate BS-DU, and Optionally, the RS resource configuration of the BS-DU is related to one cell of the BS-DU, and another RS ​​resource configuration of the BS-DU is related to another cell of the BS-DU.

23. A method comprising the following steps performed by a user equipment (UE): receiving, from a distributed unit (serving BS-DU) of a base station serving the UE, a communication configuration of a BS-DU that is a candidate for participating in the mobility of the UE, decoding the received communication configuration of the mobility candidate BS-DU to obtain a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU, and Based on the decoded RS resource configuration of the mobility candidate BS-DU, a current list having information on at least the RS resource configuration of the serving BS-DU is updated.

24. An integrated circuit controlling a process of a user equipment (UE), the process comprising the following steps performed by the UE: receiving, from a distributed unit-serving BS-DU of a base station serving the UE, a communication configuration of a BS-DU that is a candidate for participating in the mobility of the UE, decoding the received mobility candidate BS-DU communication configuration to obtain a reference signal (RS) resource configuration of the mobility candidate BS-DU associated with a candidate cell of the mobility candidate BS-DU, and Based on the decoded RS resource configuration of the mobility candidate BS-DU, a current list having information on at least the RS resource configuration of the serving BS-DU is updated.

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