Distributed unit, central unit and method thereof

Abstract

A central unit (1) of a base station sends a message requesting to add a secondary cell for carrier aggregation to a distributed unit (2) of the base station. The message includes a first information element indicating that the secondary cell needs to be initially activated or dormant. Therefore, for example, it can help to improve the direct configuration of the secondary cell state in an architecture where the base station is divided into a central unit and a distributed unit.

Description

Technical Field

[0001] The present invention relates to radio communication systems and, in particular, to enhancements to carrier aggregation. Background Art

[0002] The 3rd Generation Partnership Project (3GPP) Release 15 will introduce enhancements to Carrier Aggregation (CA). These enhancements are intended to rapidly (or quickly) set up and activate Secondary Cells (SCells) (see Non-Patent Documents 1-4).

[0003] One of these enhancements is the introduction of a new SCell state called the "dormant state". When the SCell is in the dormant state, the radio terminal (i.e., the user equipment (UE)) measures and reports channel state information (CSI), but does not decode the physical downlink control channel (PDCCH). That is, the dormant SCell state (or the SCell in the dormant state) differs from the activated SCell state (or the SCell in the activated state) at least in that the UE does not monitor or decode the PDCCH. In addition, the dormant SCell state differs from the deactivated SCell state (or the SCell in the deactivated state) at least in that the UE measures and reports CSI.

[0004] Another of the enhancements is direct SCell state configuration via radio resource control (RRC). In existing CA, when a SCell is added, the SCell is initially deactivated. In contrast, direct SCell state configuration allows the SCell to be initially activated or dormant via RRC during SCell addition or switching. In the case where the eNB configures the SCell, it can set the initial state of the SCell to "activated" or "dormant".

[0005] In addition, it is also known that 3GPP is committed to the standardization of the fifth generation mobile communication system (5G) to make 5G a commercial reality in or after 2020. In this specification, the fifth generation mobile communication system is referred to as a 5G system or a next generation (NextGen) system (NG system). The new radio access technology (RAT) for the 5G system is referred to as a new air interface, NR, 5G RAT or NGRAT. The new radio access network (RAN) for the 5G system is referred to as NextGen RAN, NG RAN or 5G-RAN. The new base station in NG-RAN is referred to as gNodeB or gNB. The new core network for the 5G system is referred to as a 5G core network (5GC) or NextGen core (NG core). A radio terminal (ie, user equipment (UE)) that can be connected to a 5G system is referred to as a 5G UE or NextGen UE (NG UE), or simply UE.

[0006] The main components of 5GC include access and mobility management function (AMF), session management function (SMF) and user plane function (UPF). AMF performs, for example, connection and mobility management of UE, and provides termination of the control plane (CP) of NG-RAN (e.g., exchanging CP information with NG-RAN node) and termination of NAS layer (e.g., exchanging NAS messages with UE). SMF performs, for example, session management (SM) and provides termination of the session management part of NAS messages. UPF is the anchor point for intra-RAT and inter-RAT mobility (e.g., handover), and performs, for example, management of QoS flows (e.g., DL reflective QoS marking).

[0007] Unless otherwise specified, the term "LTE" used in this specification includes enhancements / evolutions of LTE and advanced LTE to provide intercommunication with 5G systems. The enhancement / evolution of LTE and advanced LTE for intercommunication with 5G systems is referred to as advanced LTE Pro, LTE + or enhanced LTE (eLTE). For example, an eLTE eNB used as a NG-RAN node is referred to as ng-eNB. In addition, unless otherwise specified, the terms related to LTE networks and logical entities used in this specification (such as "evolved packet core (EPC)", "mobility management entity (MME)", "serving gateway (S-GW)" and "packet data network (PDN) gateway (P-GW)", etc.) include their enhancements / evolutions to provide intercommunication with 5G systems. Enhanced EPC, enhanced MME, enhanced S-GW and enhanced P-GW are, for example, respectively referred to as enhanced EPC (eEPC), enhanced MME (eMME), enhanced S-GW (eS-GW) and enhanced P-GW (eP-GW).

[0008] NR supports the use of different radio parameter sets in multiple frequency bands. Each radio parameter set is called a "numerology". The OFDM numerology used by the Orthogonal Frequency Division Multiplexing (OFDM) system includes, for example, subcarrier spacing, system bandwidth, Transmit Time Interval (TTI) length, subframe duration, cyclic prefix length, and symbol duration. The 5G system supports various types of services with different service requirements, including, for example, enhanced mobile broadband (eMBB), highly reliable and low latency communications (URLLC), and M2M communications with a large number of connections (e.g., massive machine type communications (mMTC)). The selection of the numerology depends on the service requirements.

[0009] NR supports a wider channel bandwidth than LTE (e.g., 100 MHz). One channel bandwidth (i.e., BW_Channel) is the radio frequency (RF) bandwidth that supports one NR carrier. Channel bandwidth is also called system bandwidth. While LTE supports channel bandwidths up to 20 MHz, 5G NR supports, for example, channel bandwidths up to 800 MHz.

[0010] In order to effectively support multiple 5G services, such as broadband services like eMBB and narrow bandwidth services like the Internet of Things (IoT), it is preferred to multiplex these services onto a single channel bandwidth. In addition, if each 5G UE needs to support transmission and reception in a transmission bandwidth corresponding to the entire channel bandwidth, this may hinder the realization of lower cost and lower power consumption of UEs for narrow bandwidth IoT services. Therefore, 3GPP allows one or more bandwidth parts (BWPs) to be configured in the carrier bandwidth (i.e., channel bandwidth or system bandwidth) of each NR component carrier. A bandwidth part is also referred to as a carrier bandwidth part. Multiple BWPs can be used for frequency division multiplexing (FDM) schemes using different digital schemes, such as subcarrier spacing (SCS). For example, multiple BWPs can have different SCSs and different bandwidths.

[0011] In one example, the channel bandwidth of one component carrier is divided into BWP#1 and BWP#2, and the two BWPs are used for FDM schemes using different digital schemes (e.g., different subcarrier spacings). In another example, a narrowband BWP#1 is set in the channel bandwidth of one component carrier, and a narrowband BWP#2 narrower than BWP#1 is further set within BWP#1. In the case where BWP#1 or BWP#2 is activated for a UE, the UE can reduce its power consumption by suppressing reception and transmission within the channel bandwidth other than the active BWP.

[0012] A bandwidth part (BWP) is frequency contiguous and consists of contiguous physical resource blocks (PRBs). The bandwidth of a BWP is at least as large as a synchronization signal (SS) / physical broadcast channel (PBCH) block. A BWP may or may not include SS / PBCH blocks (SSBs).

[0013] The BWP configuration includes, for example, a digital scheme, a frequency position, and a bandwidth (e.g., the number of PRBs). To indicate the frequency position, a common PRB index is used at least for the downlink (DL) BWP configuration in the radio resource control (RRC) connected state. Specifically, the offset from PRB 0 to the lowest PRB of the SS / PBCH block to be accessed by the UE is configured by upper layer signaling. The reference point "PRB 0" is common to all UEs sharing the same wideband component.

[0014] One or more BWP configurations for each component carrier are semi-statically signaled to the UE. Specifically, for each UE-specific serving cell, one or more DL BWPs (e.g., up to four DL BWPs) and one or more UL BWPs (e.g., up to four UL BWPs) may be configured for the UE via a dedicated RRC message. The one or more DL BWPs and one or more UL BWPs configured for the UE are referred to as a DL BWP set and a UL BWP set, respectively.

[0015] Each BWP in one or more BWPs (i.e., BWP sets) configured for a UE can be activated and deactivated. An activated BWP is referred to as an active BWP. Specifically, the UE receives signals on one or more active DL BWPs in the configured DL BWP set at a given time. Similarly, the UE sends signals on one or more active UL BWPs in the configured UL BWP set at a given time. In the current specification, only one DL BWP and only one UL BWP are activated at a given time.

[0016] Next, the cloud RAN (C-RAN) deployment of NG-RAN is described. NG-RAN consists of a set of gNBs connected to 5GC via corresponding NG interfaces. gNBs can be connected to each other via Xn interfaces. gNBs can consist of a gNB central unit (gNB-CU) and one or more gNB distributed units (gNB-DU). gNB-CU and gNB-DU are connected to each other via F1 interface. gNB-CU is the logical node that hosts the radio resource control (RRC), service data adaptation protocol (SDAP) and packet data convergence protocol (PDCP) protocols of gNB (or hosts the RRC and PDCP protocols of gNB). gNB-DU is the logical node that hosts the radio link control (RLC), MAC and PHY layers of gNB.

[0017] In addition, 3GPP has studied the CU-DU split architecture of LTE eNB. This aims to introduce eNB-CU and eNB-DU.

[0018] Citation List

[0019] Non-patent literature

[0020] [Non-Patent Document 1] Nokia, Nokia Shanghai Bell, “Stage-2 description of euCA”, 3GPP R2-1809245, 3GPP TSG-RAN WG2 Meeting #102, Busan, South Korea, 21-25 May 2018

[0021] [Non-patent document 2] Nokia, Nokia Shanghai Bell, “UE capability definitions for eUCA”, 3GPP R2-1809246, 3GPP TSG-RAN WG2 Meeting #102, Busan, South Korea, 21-25 May 2018

[0022] [Non-Patent Document 3] Nokia, Nokia Shanghai Bell, “MAC functionality for euCA”, 3GPP R2-1809269, 3GPP TSG-RAN WG2 Meeting #102, Busan, South Korea, 21-25 May 2018

[0023] [Non-Patent Document 4] Nokia, Nokia Shanghai Bell, “Signalling for euCA (Enhancing LTE CA Utilization)”, 3GPP RP-182006, 3GPP TSG RAN Meeting #81, Gold Coast, Australia, 10-13 September 2018 Summary of the invention

[0024] Problem that the invention aims to solve

[0025] The inventors have studied the above enhancements to carrier aggregation and found various problems. For example, when the direct SCell state configuration is applied to the gNB CU-DU split architecture or the eNB CU-DU split architecture, it is unclear whether the node that determines the direct SCell state is the CU or the DU, and it is also unclear how the CU (or DU) notifies the DU (or CU) of the direct SCell state.

[0026] One of the purposes of the embodiments disclosed herein is to provide improved devices, methods and programs that facilitate direct SCell state configuration in a CU-DU split architecture. It should be noted that this purpose is only one of the purposes of the embodiments disclosed herein. Other purposes or problems and novel features will become apparent from the following description and drawings.

[0027] Solutions for solving problems

[0028] In a first aspect, a central unit of a base station includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to send a first message to a distributed unit of the base station requesting to add a secondary cell for carrier aggregation. The first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0029] In a second aspect, a distributed unit of a base station includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first message from a central unit of the base station requesting to add a secondary cell for carrier aggregation. The first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0030] In a third aspect, a method performed by a central unit of a base station includes sending a first message to a distributed unit of the base station requesting to add a secondary cell for carrier aggregation. The first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0031] In a fourth aspect, a method performed by a distributed unit of a base station includes receiving a first message from a central unit of the base station requesting to add a secondary cell for carrier aggregation. The first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0032] In a fifth aspect, the program includes instructions (software codes) which, when loaded into a computer, cause the computer to perform the method according to the third aspect or the fourth aspect described above.

[0033] Effects of the Invention

[0034] According to the above aspects, it is possible to provide an improved device, method, and program for implementing direct SCell state configuration in a CU-DU split architecture. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a diagram showing a configuration example of a radio communication network according to an embodiment;

[0036] Figure 2 is a diagram showing a configuration example of a radio communication network according to an embodiment;

[0037] Figure 3 is a sequence diagram showing an example of signaling between a central node and distributed nodes according to the first embodiment;

[0038] Figure 4 is a diagram showing a specific example of the format of a UE CONTEXT SETUP REQUEST message;

[0039] Figure 5 is a flowchart showing an example of the operation of the central node according to the first embodiment;

[0040] Figure 6 is a flowchart showing an example of the operation of a distributed node according to the first embodiment;

[0041] Figure 7 is a sequence diagram showing an example of signaling between a central node and distributed nodes according to the second embodiment;

[0042] Figure 8 is a flowchart showing an example of the operation of the central node according to the second embodiment;

[0043] Fig. 9 is a flowchart showing an example of the operation of a distributed node according to the second embodiment;

[0044] Fig.10 is a sequence diagram showing an example of signaling between a central node and distributed nodes according to the third embodiment;

[0045] Fig.11 is a diagram showing a specific example of the format of a UE context setting request message according to the third embodiment;

[0046] Fig.12 is a diagram showing a specific example of the format of a UE CONTEXT MODIFICATION REQUEST message according to the third embodiment;

[0047] Fig.13 is a diagram showing a specific example of the format of a UE INACTIVITY NOTIFICATION message according to the third embodiment;

[0048] Fig.14 is a sequence diagram showing an example of signaling between a central node and distributed nodes according to a fourth embodiment;

[0049] Fig.15 is a sequence diagram showing an example of signaling between a central node and distributed nodes according to the fifth embodiment;

[0050] Fig.16 is a block diagram showing a configuration example of a central node (e.g., gNB-CU) according to an embodiment; and

[0051] Fig.17 is a block diagram showing a configuration example of a distributed node (e.g., gNB-DU) according to an embodiment. DETAILED DESCRIPTION

[0052] Hereinafter, specific embodiments will be described in detail with reference to the accompanying drawings. In all the drawings, the same or corresponding elements are represented by the same reference numerals, and for the sake of clarity, repeated descriptions are omitted when necessary.

[0053] Each embodiment described below can be used alone, or two or more embodiments can be appropriately combined with each other. These embodiments include novel features that are different from each other. Therefore, these embodiments help to achieve different goals or solve different problems from each other, and also help to obtain different advantages from each other.

[0054] The embodiments are described below mainly for the 3GPP 5G system. However, these embodiments can be applied to other radio communication systems.

[0055] First embodiment

[0056] Figure 1 An example of a configuration of a radio communication network according to a plurality of embodiments including the present embodiment is shown. Figure 1 In the example shown, the radio communication network includes a gNB central unit (gNB-CU) 1, a gNB distributed unit (gNB-DU) 2, and a radio terminal (i.e., UE) 3. The gNB-CU 1 and the gNB-DU 2 are located in the radio access network (RAN). The gNB-CU 1 and the gNB-DU 2 are connected to each other via an interface 101. The interface 101 is an F1 interface. The gNB-CU 1 can be connected to two or more gNB-DU 2. The gNB-CU 1 can be a logical node that hosts the RRC, SDAP, and PDCP protocols of the gNB (or hosts the RRC and PDCP protocols of the gNB). The gNB-DU 2 can be a logical node that hosts the RLC, MAC, and PHY layers of the gNB.

[0057] gNB-CU 1 and gNB-DU 2 provide a primary cell (PCell) 10 and a secondary cell (SCell) 20 for UE 3. UE 3 communicates with gNB-CU 1 and gNB-DU 2 using carrier aggregation (CA) between the primary cell (PCell) 10 and the secondary cell (SCell) 20. UE 3 can be simultaneously connected to multiple base stations (i.e., a primary gNB (MgNB) and a secondary gNB (SgNB) or a primary node (MN) and a secondary node (SN)) for dual connectivity. In this case, Figure 1 The gNB-CU 1 and gNB-DU 2 shown in the figure may be the CU and DU of a MgNB, or may be the CU and DU of a SgNB. Figure 1The PCell 10 and SCell 20 shown in the figure may be the PCell and SCell included in the main cell group (MCG), or may be the primary SCG cell (PSCell) and SCell included in the secondary cell group (SCG). The PCell of the MCG and the PSCell of the SCG are each called a special cell (SpCell).

[0058] like Figure 2 As shown, the gNB-CU 1 may include a control plane (CP) unit (i.e., gNB-CU-CP) 11 and one or more user plane (UP) units (i.e., gNB-CU-UP) 12. In this case, the gNB-CU-CP 11 is connected to the gNB-CU-UP 12 via a control plane interface 201 (i.e., E1 interface). The gNB-CU-CP 11 is also connected to the gNB-DU 2 via a control plane interface 202 (i.e., F1-C interface). The gNB-CU-UP 12 is connected to the gNB-DU 2 via a user plane interface 203 (i.e., F1-U interface).

[0059] Figure 3 An example of the operation of gNB-CU 1 and gNB-DU 2 according to an embodiment is shown. In step 301, gNB-CU1 sends a control message (i.e., F1 Application Protocol (F1AP) message) to gNB-DU 2 requesting the addition of SCell 20. The control message may be a UE Context Setup Request message or a UE Context Modification Request message. The control message contains an information element (IE) indicating that SCell 20 needs to be initially activated or dormant. In other words, in the case of requesting gNB-DU 2 to add SCell 20, gNB-CU 1 indicates to gNB-DU 2 that the SCell 20 to be added should be initially activated or dormant. The control message causes gNB-DU 2 to activate or dormant the added SCell 20 instead of deactivating it. This operation implements direct SCell state configuration in the gNB CU-DU split architecture.

[0060] The information element indicating the initial state of SCell 20 may be, for example, an SCell state IE. This information element may be included in the SCell item to be set IE included in the UE context setup request message or the UE context modification request message. The gNB-CU 1 may send this information element to the gNB-DU 2 only if the initial state of the SCell 20 is an active state or a dormant state. If the F1AP message requesting the addition of the SCell 20 does not include this information element, the gNB-DU 2 may consider that the initial state of the SCell 20 is not specified or that the SCell 20 is initially deactivated. Figure 4A specific example of the format of the UE context setup request message improved to include an information element indicating the initial state of the SCell 20 (ie, the SCell state IE) is shown.

[0061] Figure 5 An example of the operation of the gNB-CU 1 according to the embodiment is shown. In step 501, the gNB-CU 1 determines to add an SCell 20 for the UE 3, and further determines the initial state (i.e., activated, dormant, or deactivated) of the SCell 20 to be added. In step 502, the gNB-CU 1 sends a F1AP message (e.g., a UE context setup request message or a UE context modification request message) to the gNB-DU 2, the F1AP message requesting to add the SCell 20 and indicating the initial state of the SCell 20. The F1AP message may indicate that the initial state of the SCell 20 is an activated state or a dormant state. In other words, the F1AP message may indicate that the SCell 20 should not be initially deactivated.

[0062] Figure 6 An example of the operation of the gNB-DU 2 according to the embodiment is shown. In step 601, the gNB-DU 2 receives an F1AP message from the gNB-CU1 requesting the addition of the SCell 20 and indicating the initial state (activated state or dormant state) of the SCell 20. In step 602, the gNB-DU 2 configures the SCell 20 in response to receiving the message. In addition, the gNB-DU 2 activates or dormants the added SCell 20 instead of deactivating it.

[0063] In some implementations, gNB-DU 2 may send a response message to gNB-CU 1. The response message may be a F1AP: UE CONTEXT SETUP RESPONSE message or a F1AP: UE CONTEXT MODIFICATION RESPONSE message. gNB-DU 2 may include an information element indicating the initial state of the added SCell 20 in the response message. The information element may be an sCellState IE and may be included in the CellGroupConfig IE. The CellGroupConfig IE is included in the DU to CU RRC Information IE carried from gNB-DU 2 to gNB-CU 1 via the UE CONTEXT SETUP RESPONSE (or UE CONTEXT MODIFICATION RESPONSE) message.

[0064] In some implementations, gNB-CU 1 may receive an F1AP message including auxiliary information from gNB-DU 2, and then determine based on the auxiliary information that SCell 20 should be initially activated or dormant. In other words, gNB-CU 1 may determine that SCell 20 should not be initially deactivated. That is, the auxiliary information enables gNB-CU 1 to determine that SCell 20 should be activated or dormant. The F1AP message carrying the auxiliary information may be a UE context modification request message.

[0065] The assistance information may include, for example, but not limited to, the following information. The assistance information may include information related to the load status of a cell used as a serving cell for UE 3 (e.g., cell load, radio resource usage, or the number of active UEs). Additionally or alternatively, the assistance information may include a utilization status indicating how UE 3 uses each serving cell (e.g., cell usage or cell utilization status). Additionally or alternatively, the assistance information may include information related to the QoS satisfaction of UE 3 (e.g., QoS performance, QoS satisfaction, or gap to required / expected QoS). Additionally or alternatively, the assistance information may include information related to characteristics desired by UE 3 (e.g., expected / target data rate or throughput).

[0066] Second embodiment

[0067] The configuration example of the radio communication network according to the present embodiment is Figure 1 and Figure 2 This embodiment provides an example in which gNB-DU 2 determines the initial state of SCell 20 to be added.

[0068] Figure 7 An example of the operation of gNB-CU 1 and gNB-DU 2 according to the embodiment is shown. In step 701, gNB-CU1 sends a control message (i.e., F1 Application Protocol (F1AP) message) to gNB-DU 2 requesting to add SCell 20. The control message may be a UE context setup request message or a UE context modification request message.

[0069] In step 702, in response to receiving the message in step 701, gNB-DU 2 adds SCell 20 and determines the initial state (i.e., activated, dormant, or deactivated) of SCell 20. For example, gNB-DU 2 determines that SCell 20 to be added will be immediately activated or dormant instead of deactivated. Then, gNB-DU 2 sends a response message including an information element indicating the initial state of SCell 20 to gNB-CU 1. gNB-DU 2 may send the information element to gNB-CU 1 only in the case where the initial state of SCell 20 is an activated state or a dormant state. In this case, if the message from gNB-DU 2 does not include the information element, gNB-CU 1 may assume that the initial state of SCell 20 is initially deactivated.

[0070] This information element may be, for example, the SCellState IE. This information element may be contained in the CellGroupConfig IE. The CellGroupConfig IE is contained in the DU to CU RRC Information IE carried from gNB-DU 2 to gNB-CU 1 via the UE Context Setup Response (or UE Context Modification Response) message.

[0071] If the gNB-DU 2 operates a plurality of SCells 20, the gNB-DU 2 may transmit a response message including an information element (e.g., sCellState IE) indicating the initial state of each SCell 20 for each SCell to the gNB-CU 1. That is, the above-mentioned information element indicating the initial state of the SCell 20 may be a list of sCellState IEs (sCellStateList IE).

[0072] Figure 7 The operations shown in enable direct SCell state configuration in the gNB CU-DU split architecture.

[0073] In some implementations, in order to assist the gNB-DU 2 in determining the initial state of the SCell 20, the gNB-CU 1 may include assistance information in the message of step 701. The gNB-DU 2 may consider the assistance information when determining the initial state of the SCell 20 to be added. For example, the assistance information may indicate whether the addition of the SCell 20 is urgent. If the assistance information indicates the urgency of adding the SCell 20, the gNB-DU 2 may configure the SCell 20 so that the initial state of the SCell 20 is activated or dormant.

[0074] Additionally or alternatively, the assistance information may indicate an intended use or necessity (eg, emergency, load balancing, or normal) of the SCell 20. Additionally or alternatively, the assistance information may indicate a purpose for adding the SCell 20 (eg, load balancing or throughput (improvement)).

[0075] Additionally or alternatively, the assistance information may include information related to the PDCP buffer of gNB-CU 1 (e.g., PDCP buffer status or PDCP buffer usage radio). The information may indicate a utilization status (or load) of the PDCP buffer of gNB-CU 1. In other words, the information may indicate that the addition of SCell 20 is required due to high utilization (or load) of the PDCP buffer of gNB-CU 1.

[0076] Figure 8 An example of the operation of gNB-CU 1 according to the embodiment is shown. In step 801, gNB-CU 1 determines to add SCell 20 for UE 3, and sends a F1AP message requesting to add SCell 20 to gNB-DU 2. The F1AP message may be, for example, a UE context setup request message or a UE context modification request message. In step 802, gNB-CU 1 receives a F1AP message indicating the initial state of SCell 20 from gNB-DU 2. The F1AP message may be, for example, a UE context setup response message or a UE context modification response message.

[0077] Fig. 9 An example of the operation of gNB-DU 2 according to an embodiment is shown. In step 901, gNB-DU 2 receives an F1AP message requesting the addition of SCell 20 from gNB-CU1. In step 902, gNB-DU 2 configures SCell 20 in response to the reception of the message. In addition, gNB-DU 2 determines the initial state of the SCell 20 to be added. For example, gNB-DU 2 causes the added SCell 20 to be activated or dormant instead of deactivated. In step 903, gNB-DU 2 sends an F1AP message (e.g., a UE context setup response message or a UE context modification response message) indicating the initial state of SCell 20 to gNB-CU 1.

[0078] Third embodiment

[0079] The configuration example of the radio communication network according to the present embodiment is Figure 1 and Figure 2In this embodiment, after adding SCell 20 for UE 3, gNB-CU 1 instructs gNB-DU 2 or proposes to gNB-DU 2 to switch the state of SCell 20 between the activated state, the dormant state, and the deactivated state. This operation allows gNB-CU 1 to control the current state of SCell 20.

[0080] Fig.10 An example of the operation of gNB-CU 1 and gNB-DU 2 according to the embodiment is shown. In step 1001, gNB-CU 1 sends an F1AP message to gNB-DU 2, which instructs gNB-DU 2 or proposes to gNB-DU 2 to change the state of SCell 20. The F1AP message may be, for example, a UE context modification request message.

[0081] In some implementations, the gNB-CU 1 may include an information element in the UE context modification request message to cause the gNB-DU 2 to change the state of the SCell 20. The information element may be an SCell state IE. The information element may be newly defined and included in the SCell item to be modified IE included in the UE context modification request message.

[0082] In some implementations, in order for the gNB-DU 2 to change the state of the SCell 20, the gNB-CU 1 may include both an information element indicating the removal of the SCell 20 and an information element indicating the setting of the SCell 20 in a single UE context modification request message. The information element indicating the removal of the SCell 20 may be an SCell item to be removed IE, and the information element indicating the setting of the SCell 20 may be an SCell item to be set IE. In this case, the SCell item to be set IE may include an information element indicating the state change of the SCell 20 (e.g., the SCell state IE).

[0083] In some implementations, in order for the gNB-DU 2 to change the state of the SCell 20, the gNB-CU 1 may send a reason indicating the purpose or context of the change of state to the gNB-DU 2. The reason may be, for example, information indicating that the UE 3 is in an overheat state (i.e., the UE 3 is overheated) or information indicating that it is intended to solve the overheating problem. For example, the gNB-CU 1 may send the reason to the gNB-DU 2 together with an indication or proposal to put the SCell 20 to sleep or deactivate. Alternatively, the gNB-CU 1 may determine to remove the SCell 20 from the settings for the UE 3 in response to receiving a report about overheating (e.g., overheat assistance information) from the UE 3, and then send the reason to the gNB-DU 2 together with an information element indicating the removal of the SCell 20.

[0084] In some implementations, gNB-DU 2 may send information about the activity of UE 3 associated with SCell 20 to gNB-CU 1. Specifically, gNB-CU 1 may send an F1AP message to gNB-DU 2, the F1AP message including an information element indicating permission to monitor (or desire to monitor) the activity of UE 3. The F1AP message may be a UE Context Setup Request message (see Fig.11 ) or UE context modification request message (see Fig.12 ). Fig.11 and Fig.12 The message shown in includes an Inactivity Monitoring Request IE indicating whether monitoring of the activity of UE 3 is permitted (or required). If gNB-CU 1 permits (or requests) gNB-DU 2 to monitor the activity of UE 3, gNB-CU 1 sets the Inactivity Monitoring Request IE to a "true" value. gNB-DU 2 may send an F1AP: UE INACTIVITY NOTIFICATION message to gNB-CU 1. The activity information indicates whether the communication state of UE 3 in SCell 20 (or the state of the data radio bearer (DRB) of UE 3, or the data communication state linked to a logical channel identifier (LCID)) is active. The activity information may be referred to as inactivity information.

[0085] For example, in an implementation in which DRB data is sent or received only through a specific serving cell, the use of UE activity based on the data communication state linked to the LCID is effective. More specifically, in some implementations, UE 3 allows uplink data of certain DRBs to be sent only through a specific serving cell (allowed serving cell) pre-permitted by RRC signaling of the gNB (e.g., gNB-CU 1). Similarly, UE 3 allows downlink data to be received only through a specific serving cell according to the determination of the gNB (e.g., gNB-DU 2). This is an indispensable technology for sending or receiving data on an original logical channel (e.g., LCID#1) and data on an additional logical channel (e.g., LCID#2) for packet duplication via corresponding serving cells different from each other in packet duplication (or CA-type PDCP duplication), in which one PDCP packet (i.e., PDCP SDU) is redundantly sent during the execution of carrier aggregation (CA). In addition, this technology can be used regardless of whether packet duplication exists. When the LCID is linked to a specific serving cell in this way, it is effective in managing the SCell state to monitor the activity of the LCID by gNB-DU 2 and provide the resulting information from gNB-DU2 to gNB-CU 1.

[0086] The gNB-CU 1 may determine to change the state of the SCell 20 based on the received activity information. Specifically, if the activity information indicates that the UE 3 (or the DRB of the UE 3, or the logical channel) is inactive, the gNB-CU 1 may determine to change the state of the SCell 20 from active to dormant, or from active to deactivated. Fig.13 A specific example of a UE inactivity notification message is shown. Fig.13 In the example of , the SCell Activity List IE indicates the activity of UE 3 for each SCell (SCell Activity IE).

[0087] Fourth embodiment

[0088] The configuration example of the radio communication network according to the present embodiment is Figure 1 and Figure 2 In this embodiment, after adding SCell 20 for UE 3, gNB-DU 2 switches the state of SCell 20 between an activated state, a dormant state, and a deactivated state. gNB-DU 2 can determine the state of SCell 20 based on the auxiliary information from gNB-CU 1. This operation allows gNB-DU 2 to control the current state of SCell 20.

[0089] Fig.14 An example of the operation of gNB-CU 1 and gNB-DU 2 according to the embodiment is shown. In step 1401, gNB-CU 1 sends a F1AP message including auxiliary information related to the change of the state of SCell 20 to gNB-DU 2. The F1AP message may be, for example, a UE context modification request message.

[0090] In some implementations, the gNB-CU 1 may include in the UE Context Modification Request message auxiliary information related to the change in the state of the SCell 20. The auxiliary information may relate to the load or situation of the UE 3. The auxiliary information may be an Overheat Assistance IE. The Overheat Assistance IE may be equivalent to or related to information related to an overheating problem reported by the UE 3 to the gNB (e.g., gNB-CU) via RRC signaling (e.g., Overheat Assistance Information). The Overheat Assistance IE may contain information related to settings recommended to resolve the heating problem (e.g., reduced UE categories, reduced maximum CCs, reduced maximum MIMO layers, or reduced maximum active BWP).

[0091] The auxiliary information may be included in the SCell item to be modified IE that is newly defined and included in the UE context modification request message. gNB-DU 2 may determine to change the state of SCell 20 based on the auxiliary information. For example, gNB-DU 2 may determine to change the SCell 20 in an activated state to a dormant state or a deactivated state, and then give an indication of the change to UE 3. Alternatively, gNB-DU 2 may determine the removal of SCell 20 and request gNB-CU 1 or propose to gNB-CU1 to remove SCell 20. This allows gNB-DU 2 to manage the state of SCell 20 while taking into account the load or situation of UE 3.

[0092] Fifth embodiment

[0093] The configuration example of the radio communication network according to the present embodiment is Figure 1 and Figure 2 The example shown is the same. In this embodiment, gNB-CU 1 instructs gNB-DU 2 or proposes to gNB-DU 2 to activate two or more downlink BWPs among multiple BWPs configured for SCell 20. The multiple BWPs (i.e., BWP sets) configured for SCell 20 can be DL BWPs or ULBWPs. Based on the instruction or proposal from gNB-CU 1, gNB-DU 2 can activate two or more downlink BWPs for SCell 20. This operation allows gNB-CU 1 to control the number of active BWPs for SCell 20.

[0094] Fig.15 An example of the operation of gNB-CU 1 and gNB-DU 2 according to an embodiment is shown. In step 1501, gNB-CU 1 sends a F1AP message to gNB-DU 2, which indicates gNB-DU 2 or proposes to gNB-DU 2 to activate two or more downlink BWPs of SCell 20. In some implementations, gNB-CU 1 may include an information element indicating the number of BWPs to be activated in a F1AP message (e.g., a UE context setup request message or a UE context modification request message) requesting to add SCell 20. Additionally or alternatively, gNB-CU 1 may include an information element indicating the number of BWPs to be activated in a F1AP message (e.g., a UE context modification request message) requesting to modify a UE context.

[0095] A configuration example of gNB-CU 1 and gNB-DU 2 according to the above embodiment is provided below. Fig.16 1 is a block diagram showing a configuration example of the gNB-CU 1 according to the above embodiment. The gNB-CU-CP 11 and the gNB-CU-UP 12 may have Fig.16 The configuration shown is the same as the configuration shown. Fig.16 , gNB-CU 1 includes a network interface 1601, a processor 1602, and a memory 1603. The network interface 1601 is used to communicate with network nodes (e.g., gNB-DU 2 and a control plane (CP) node and a user plane (UP) node in 5GC). The network interface 1601 may include multiple interfaces. The network interface 1601 may include an optical fiber interface for CU-DU communication and a network interface compliant with the IEEE 802.3 series.

[0096] The processor 1602 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for radio communication. The processor 1602 may include a plurality of processors. The processor 1602 may include a modem processor (e.g., a digital signal processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a central processing unit (CPU) or a microprocessing unit (MPU)) that performs control plane processing.

[0097] The memory 1603 is a volatile memory, a non-volatile memory, or a combination thereof. The volatile memory is, for example, a static random access memory (SRAM), a dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, a mask read-only memory (MROM), an electrically erasable programmable ROM (EEPROM), a flash memory, a hard disk drive, or any combination thereof. The memory 1603 may include a storage device located separately from the processor 1602. In this case, the processor 1602 may access the memory 1603 through the network interface 1601 or an I / O interface (not shown).

[0098] The memory 1603 may store one or more software modules (computer programs) 1604, which include instructions and data for performing the processing of the gNB-CU 1 described in the above embodiments. In some implementations, the processor 1602 may load one or more software modules 1604 from the memory 1603 and execute the loaded software modules to perform the processing of the gNB-CU 1 described in the above embodiments.

[0099] Fig.17 2 is a block diagram showing a configuration example of the gNB-DU 2 according to the above-described embodiment. Fig.17 , the gNB-DU 2 includes a radio frequency transceiver (RF transceiver) 1701, a network interface 1703, a processor 1704, and a memory 1705. The RF transceiver 1701 performs analog RF signal processing to communicate with the NG UE. The RF transceiver 1701 may include a plurality of transceivers. The RF transceiver 1701 is connected to an antenna array 1702 and a processor 1704. The RF transceiver 1701 receives modulated symbol data from the processor 1704, generates a transmit RF signal, and supplies the generated transmit RF signal to the antenna 1702. In addition, the RF transceiver 1701 generates a baseband receive signal based on the receive RF signal received by the antenna 1702 and supplies the signal to the processor 1704. The RF transceiver 1701 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, a plurality of phase shifters and a plurality of power amplifiers.

[0100] The network interface 1703 is used to communicate with network nodes (e.g., gNB-CU 1, gNB-CU-CP 11, and gNB-CU-UP 12). The network interface 1703 may include multiple interfaces. The network interface 1703 may include either or both of an optical fiber interface for CU-DU communication and a network interface compliant with the IEEE 802.3 series.

[0101] The processor 1704 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for radio communication. The processor 1704 may include multiple processors. The processor 1704 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing. The processor 1704 may include a digital beamformer module for beamforming. The digital beamformer module may include a multiple-input multiple-output (MIMO) encoder and a MIMO precoder.

[0102] The memory 1705 is a volatile memory, a non-volatile memory, or a combination thereof. The volatile memory is, for example, an SRAM, a DRAM, or a combination thereof. The non-volatile memory is, for example, an MROM, an EEPROM, a flash memory, a hard disk drive, or any combination thereof. The memory 1705 may include a storage device located separately from the processor 1704. In this case, the processor 1704 may access the memory 1705 through the network interface 1703 or an I / O interface (not shown).

[0103] The memory 1705 may store one or more software modules (computer programs) 1706, which include instructions and data for performing the processing of the gNB-DU 2 described in the above embodiments. In some implementations, the processor 1704 may load one or more software modules 1706 from the memory 1705 and execute the loaded software modules to perform the processing of the gNB-DU 2 described in the above embodiments.

[0104] As mentioned above Fig.16 and Fig.17As described above, each processor included in the gNB-CU 1 and gNB-DU 2 in the above embodiment executes one or more programs including an instruction set for causing a computer to perform the algorithm described above with reference to the accompanying drawings. These programs can be stored in various types of non-transitory computer-readable media and thus supplied to the computer. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (such as floppy disks, magnetic tapes, and hard disk drives), magneto-optical recording media (such as magneto-optical disks), compact disk read-only memories (CD-ROMs), CD-Rs, CD-R / Ws, and semiconductor memories (such as mask ROMs, programmable ROMs (PROMs), erasable PROMs (EPROMs), flash memory ROMs, and random access memories (RAMs). These programs can be supplied to the computer by using various types of transient computer-readable media. Examples of transient computer-readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable media can be used to supply programs to a computer through a wired communication line (e.g., electric wires and optical fibers) or a wireless communication line.

[0105] Other embodiments

[0106] The signaling between gNB-CU 1 and gNB-DU 2 described in the above embodiments can be completed between gNB-CU-CP 11 and gNB-DU 2.

[0107] The above embodiments have been described by assuming gNB-CU 1 and gNB-DU 2 in a 5G system, but the embodiments are also applicable to other network configurations. For example, an LTE eNB connected to a 5GC is also referred to as an ng-eNB (or eLTE eNB), and it is assumed that the functions of the ng-eNB are distributed to the CU (i.e., ng-eNB-CU) and the DU (i.e., ng-eNB-DU) as with the gNB. Signaling equivalent to or the same as the signaling through the F1 interface between gNB-CU 1 and gNB-DU 2 described in the above embodiments can be accomplished through an interface (e.g., W1 interface) between the ng-eNB-CU and the ng-eNB-DU.

[0108] In addition, the above embodiments are merely examples of applications of the technical concepts obtained by the inventors. These technical concepts are not limited to the above embodiments, and various modifications may be made thereto.

[0109] For example, all or part of the embodiments disclosed above may be described as, but not limited to, the following supplementary notes.

[0110] (Supplementary Note 1)

[0111] A distributed unit of a base station, the distributed unit comprising:

[0112] at least one memory; and

[0113] at least one processor coupled to the at least one memory and configured to:

[0114] receiving, from a central unit of the base station, a first message requesting to add a secondary cell for carrier aggregation;

[0115] In response to the first message, determining that the secondary cell is to be initially activated or dormant; and

[0116] A second message is sent to the central unit indicating that the secondary cell is to be initially activated or dormant.

[0117] (Supplementary Note 2)

[0118] The distributed unit according to Supplementary Note 1, wherein the first message includes auxiliary information indicating whether adding of the secondary cell is urgent.

[0119] (Supplementary Note 3)

[0120] The distributed unit according to Supplementary Note 1, wherein the first message contains auxiliary information related to a purpose of adding the secondary cell.

[0121] (Supplementary Note 4)

[0122] A central unit of a base station, the central unit comprising:

[0123] at least one memory; and

[0124] at least one processor coupled to the at least one memory and configured to:

[0125] Sending a first message requesting to add a secondary cell for carrier aggregation to a distributed unit of the base station; and

[0126] A second message is received from the distributed unit indicating that the secondary cell is to be initially activated or dormant.

[0127] (Supplementary Note 5)

[0128] The central unit according to supplementary note 4, wherein the first message contains auxiliary information indicating whether adding of the secondary cell is urgent.

[0129] (Supplementary Note 6)

[0130] The central unit according to Supplementary Note 4, wherein the first message contains auxiliary information related to a purpose of adding the secondary cell.

[0131] (Supplementary Note 7)

[0132] A central unit of a base station, the central unit comprising:

[0133] at least one memory; and

[0134] At least one processor is coupled to the at least one memory and is configured to send a first message to a distributed unit of the base station, wherein the first message indicates the distributed unit or proposes to the distributed unit to change the state of a secondary cell used for carrier aggregation or remove the secondary cell.

[0135] (Supplementary Note 8)

[0136] The central unit according to supplementary note 7, wherein the first message contains cause information indicating a purpose of changing a state of the secondary cell or removing the secondary cell.

[0137] (Supplementary Note 9)

[0138] The central unit according to Supplementary Note 8, wherein the cause information indicates that a radio terminal associated with the secondary cell is overheated or indicates that it is intended to resolve an overheated state of the radio terminal.

[0139] (Supplementary Note 10)

[0140] The central unit according to any one of supplementary notes 7 to 9, wherein the at least one processor is configured to receive activity information related to a radio terminal associated with the secondary cell from the distributed unit.

[0141] (Supplementary Note 11)

[0142] The central unit according to Supplementary Note 10, wherein the activity information indicates an activity of the radio terminal in each of a plurality of secondary cells activated for the radio terminal.

[0143] (Supplementary Note 12)

[0144] The central unit according to supplementary note 10 or 11, wherein the at least one processor is configured to determine to change a state of the secondary cell or to remove the secondary cell based on the activity information.

[0145] (Supplementary Note 13)

[0146] A distributed unit of a base station, the distributed unit comprising:

[0147] at least one memory; and

[0148] At least one processor is coupled to the at least one memory and is configured to receive a first message from a central unit of the base station instructing the distributed unit or proposing to the distributed unit to change a state of a secondary cell for carrier aggregation or to remove the secondary cell.

[0149] (Supplementary Note 14)

[0150] A distributed unit of a base station, the distributed unit comprising:

[0151] at least one memory; and

[0152] At least one processor is coupled to the at least one memory and is configured to receive auxiliary information related to a change in a state of a secondary cell for carrier aggregation or removal of the secondary cell from a central unit of the base station.

[0153] (Supplementary Note 15)

[0154] The distributed unit according to Supplementary Note 14, wherein the at least one processor is configured to determine to change a state of the secondary cell or to remove the secondary cell based on the auxiliary information.

[0155] (Supplementary Note 16)

[0156] The distributed unit according to supplementary note 14 or 15, wherein the auxiliary information indicates a load or situation of a radio terminal associated with the secondary cell.

[0157] (Supplementary Note 17)

[0158] A central unit of a base station, the central unit comprising:

[0159] at least one memory; and

[0160] At least one processor is coupled to the at least one memory and configured to send auxiliary information related to a change in a state of a secondary cell for carrier aggregation or removal of the secondary cell to a distributed unit of the base station.

[0161] (Supplementary Note 18)

[0162] A central unit of a base station, the central unit comprising:

[0163] at least one memory; and

[0164] At least one processor is coupled to the at least one memory and is configured to send a message to a distributed unit of the base station, the message instructing the distributed unit or proposing to the distributed unit to activate two or more downlink BWPs among multiple downlink bandwidth parts, i.e., downlink BWPs, configured for the secondary cell of carrier aggregation.

[0165] (Supplementary Note 19)

[0166] A distributed unit of a base station, the distributed unit comprising:

[0167] at least one memory; and

[0168] At least one processor is coupled to the at least one memory and is configured to receive a message from a central unit of the base station, the message instructing the distributed unit or proposing to the distributed unit to activate two or more downlink BWPs among multiple downlink bandwidth parts, i.e., downlink BWPs, configured for the secondary cell of carrier aggregation.

[0169] (Supplementary Note B1)

[0170] A central unit of a base station, the central unit comprising:

[0171] at least one memory; and

[0172] At least one processor is coupled to the at least one memory and is configured to send a first message requesting to add a secondary cell for carrier aggregation to a distributed unit of the base station, wherein:

[0173] The first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0174] (Supplementary Note B2)

[0175] The central unit according to Supplementary Note B1, wherein the first information element enables the distributed unit to activate or sleep the added secondary cell instead of deactivating it.

[0176] (Supplementary Note B3)

[0177] The central unit according to supplementary note B1 or B2, wherein the at least one processor is configured to receive a second message including auxiliary information from the distributed unit, and determine that the secondary cell is to be activated or dormant based on the auxiliary information.

[0178] (Supplementary Note B4)

[0179] A central unit according to any one of supplementary notes B1 to B3, wherein the at least one processor is further configured to send a third message to the distributed unit after adding the secondary cell, wherein the third message instructs the distributed unit or proposes to the distributed unit to switch the state of the secondary cell between an activated state, a dormant state, and a deactivated state.

[0180] (Supplementary Note B5)

[0181] The central unit according to supplementary note B4, wherein the at least one processor is further configured to receive activity information about radio terminals associated with the secondary cell from the distributed unit, and determine to change the state of the secondary cell based on the activity information.

[0182] (Supplementary Note B6)

[0183] A central unit according to any one of the supplementary opinions B1 to B5, wherein the first message further comprises a second information element, wherein the second information element indicates or proposes to the distributed unit to activate two or more downlink BWPs of the multiple downlink bandwidth parts, i.e., downlink BWPs, of the secondary cell.

[0184] (Supplementary Note B7)

[0185] A central unit according to any one of Supplementary Notes B1 to B5, wherein the at least one processor is further configured to send a fourth message to the distributed unit, wherein the fourth message instructs the distributed unit or proposes to the distributed unit to activate two or more downlink BWPs of the multiple downlink bandwidth parts, i.e., downlink BWPs, of the secondary cell.

[0186] (Supplementary Note B8)

[0187] A distributed unit of a base station, the distributed unit comprising:

[0188] at least one memory; and

[0189] at least one processor coupled to the at least one memory and configured to receive a first message requesting to add a secondary cell for carrier aggregation from a central unit of the base station, wherein:

[0190] The first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0191] (Supplementary Note B9)

[0192] The distributed unit according to supplementary note B8, wherein the at least one processor is further configured to cause the added secondary cell to be activated or dormant instead of being deactivated.

[0193] (Supplementary Note B10)

[0194] The distributed unit according to supplementary note B8 or B9, wherein the at least one processor is configured to send a second message containing auxiliary information to the central unit.

[0195] (Supplementary Note B11)

[0196] A distributed unit according to any one of Supplementary Notes B8 to B10, wherein the at least one processor is further configured to receive a third message from the central unit after adding the secondary cell, the third message instructing the distributed unit or proposing to the distributed unit to switch the state of the secondary cell between an activated state, a dormant state, and a deactivated state.

[0197] (Supplementary Note B12)

[0198] The distributed unit according to supplementary note B11, wherein the at least one processor is configured to change the state of the secondary cell according to the third message.

[0199] (Supplementary Note B13)

[0200] A distributed unit according to any one of Supplementary Notes B8 to B12, wherein the first message further includes a second information element, wherein the second information element indicates the distributed unit or proposes to the distributed unit to activate two or more downlink BWPs of the multiple downlink bandwidth parts, i.e., downlink BWPs, of the secondary cell.

[0201] (Supplementary Note B14)

[0202] A distributed unit according to any one of Supplementary Notes B8 to B13, wherein the at least one processor is further configured to receive a fourth message from the central unit, the fourth message instructing the distributed unit or proposing to the distributed unit to activate two or more downlink BWPs of the multiple downlink bandwidth parts of the secondary cell, i.e., the downlink BWPs.

[0203] (Supplementary Note B15)

[0204] A method performed by a central unit of a base station, the method comprising:

[0205] A first message requesting to add a secondary cell for carrier aggregation is sent to a distributed unit of the base station, wherein the first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0206] (Supplementary Note B16)

[0207] A method performed by a distributed unit of a base station, the method comprising:

[0208] A first message requesting to add a secondary cell for carrier aggregation is received from a central unit of the base station, wherein the first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0209] (Supplementary Note B17)

[0210] A program for causing a computer to perform a method of a central unit of a base station, wherein the method comprises:

[0211] A first message requesting to add a secondary cell for carrier aggregation is sent to a distributed unit of the base station, wherein the first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0212] (Supplementary Note B18)

[0213] A program for causing a computer to perform a method of a distributed unit of a base station, wherein the method comprises:

[0214] A first message requesting to add a secondary cell for carrier aggregation is received from a central unit of the base station, wherein the first message includes a first information element indicating that the secondary cell needs to be initially activated or dormant.

[0215] This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-207415, filed on November 2, 2018, the disclosure of which is incorporated herein by reference in its entirety.

[0216] Reference numerals

[0217] 1 gNB-CU

[0218] 2 gNB-DU

[0219] 3 UE

[0220] 11 gNB-CU-CP

[0221] 12 gNB-CU-UP

[0222] 1602 processor

[0223] 1603 Memory

[0224] 1604 Module

[0225] 1704 processor

[0226] 1705 Memory

[0227] 1706 Module

Claims

1. A method performed by a gNB distributed unit (gNB-DU), the method comprising: Receiving a UE context modification request message from the gNB central unit, i.e., the gNB-CU, requesting to add a secondary cell, i.e., the SCell; as well as In response to receiving the UE context modification request message, sending a UE context modification response message to the gNB-CU, The UE context modification response message includes a first information element indicating whether the initial state of the SCell is to be an activated state.

2. The method according to claim 1, wherein: The UE context modification response message includes a DU to CU RRC information information element including a cell group configuration IE, namely, a DU to CU RRC information IE, and The first information element is included in the cell group configuration IE.

3. The method according to claim 2, wherein: When the cell group configuration IE does not include the first information element, the gNB-CU considers that the initial state of the SCell is to be a deactivated state.

4. A method performed by a gNB central unit (gNB-CU), the method comprising: Send a UE context modification request message to the gNB distributed unit, i.e. gNB-DU, requesting to add a secondary cell, i.e. SCell; as well as After sending the UE CONTEXT MODIFICATION REQUEST message, receiving a UE CONTEXT MODIFICATION RESPONSE message from the gNB-DU, The UE context modification response message includes a first information element indicating whether the initial state of the SCell is to be an activated state.

5. The method according to claim 4, wherein: The UE context modification response message includes a DU to CU RRC information information element including a cell group configuration IE, namely, a DU to CU RRC information IE, and The first information element is included in the cell group configuration IE.

6. The method according to claim 5, further comprising: When the cell group configuration IE does not include the first information element, it is considered that the initial state of the SCell is to be a deactivated state.

7. A method performed by a gNB, the gNB comprising a gNB central unit (gNB-CU) and a gNB distributed unit (gNB-DU), the method comprising: Sending a UE context modification request message requesting to add a secondary cell, i.e., a SCell, to the gNB-DU through the gNB-CU; as well as Sending, by the gNB-DU, a UE Context Modification Response message to the gNB-CU in response to receiving the UE Context Modification Request message, The UE context modification response message includes a first information element indicating whether the initial state of the SCell is to be an activated state.

8. A gNB distributed unit, i.e., a gNB-DU, comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to: Receiving a UE Context Modification Request message from the gNB Central Unit (gNB-CU) requesting to add a secondary cell (SCell); and In response to receiving the UE context modification request message, sending a UE context modification response message to the gNB-CU, The UE context modification response message includes a first information element indicating whether the initial state of the SCell is to be an activated state.

9. The gNB-DU according to claim 8, wherein: The UE context modification response message includes a DU to CU RRC information information element including a cell group configuration IE, namely, a DU to CU RRC information IE, and The first information element is included in the cell group configuration IE.

10. The gNB-DU according to claim 9, wherein: The gNB-CU is configured to: when the cell group configuration IE does not include the first information element, consider that the initial state of the SCell is to be a deactivated state.

11. A gNB central unit, i.e., a gNB-CU, comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to: Sending a UE context modification request message to the gNB distributed unit, i.e., gNB-DU, requesting the addition of a secondary cell, i.e., SCell; and After sending the UE CONTEXT MODIFICATION REQUEST message, receiving a UE CONTEXT MODIFICATION RESPONSE message from the gNB-DU, The UE context modification response message includes a first information element indicating whether the initial state of the SCell is to be an activated state.

12. The gNB-CU according to claim 11, wherein: The UE context modification response message includes a DU to CU RRC information information element including a cell group configuration IE, namely, a DU to CU RRC information IE, and The first information element is included in the cell group configuration IE.

13. The gNB-CU according to claim 12, wherein: The at least one processor is configured to: when the cell group configuration IE does not include the first information element, consider that the initial state of the SCell is to be a deactivated state.

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