Distributed unit, central unit and method used by base station

Abstract

The present invention provides a distributed unit, a central unit and a method used by a base station. The distributed unit (2) of the base station sends at least one terminal list to the central unit (1) of the base station. The at least one terminal list represents at least one of the following items: radio terminals that do not configure a common search space (CSS) in their active downlink bandwidth part (BWP); radio terminals that do not configure at least a search space for receiving system information in their active downlink BWP; radio terminals that need to receive updated system information via dedicated signaling of each radio terminal; radio terminals whose active downlink BWP is a non-initial downlink BWP; and radio terminals that are receiving on each downlink BWP.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application date of July 25, 2019, application number 201980052740.0, and invention name “Distributed Unit, Central Unit and Method Thereof”. Technical Field

[0002] The present invention relates to radio communication systems, and in particular to the use of one or more bandwidth portions allocated within a carrier bandwidth. Background Art

[0003] The 3rd Generation Partnership Project (3GPP) has been working on the standardization of the fifth generation mobile communication system (5G) to make 5G a commercial reality in or after 2020. 5G is achieved through the continuous enhancement / evolution of LTE and LTE-Advanced and the innovative enhancement / evolution through the introduction of new 5G air interfaces (i.e., new radio access technologies (RATs)). The new RAT, for example, supports frequency bands higher than those supported by LTE / LTE-Advanced and its continuous evolution (e.g., 6 GHz or lower). For example, the new RAT supports centimeter wave bands (10 GHz or higher) and millimeter wave bands (30 GHz or higher).

[0004] 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 RAT of the 5G system is referred to as a new air interface (NR), 5G RAT or NG RAT. The new radio access network (RAN) used by the 5G system is called NextGen RAN (NG RAN) or 5G-RAN. The new base station in the NG-RAN is called gNodeB (gNB). The new core network used by the 5G system is called the 5G core network (5GC) or NextGen core (NG core). A radio terminal (ie, user equipment (UE)) that can be connected to the 5G system is called a 5G UE or NextGen UE (NG UE), or simply UE.

[0005] Unless otherwise specified, the term "LTE" used in this specification includes enhancements / evolutions of LTE and LTE-Advanced to provide intercommunication with 5G systems. The enhancements / evolutions of LTE and LTE-Advanced for intercommunication with 5G systems are referred to as LTE-Advanced Pro, LTE+, or enhanced LTE (eLTE). In addition, unless otherwise specified, terms related to the LTE network and logical entities used in this specification (such as "Evolved Packet Core (EPC)", "Mobile 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 respectively referred to as, for example, enhanced EPC (eEPC), enhanced MME (eMME), enhanced S-GW (eS-GW), and enhanced P-GW (eP-GW).

[0006] In LTE and LTE-Advanced, in order to achieve Quality of Service (QoS) and packet routing, bearers for each QoS level and each PDN connection are used in both the RAN (i.e., Evolved Universal Terrestrial RAN (E-UTRAN)) and the core network (i.e., EPC). That is, in the bearer-based QoS (or per-bearer QoS) concept, one or more Evolved Packet System (EPS) bearers are configured between the UE and the P-GW in the EPC, and multiple service data flows (SDFs) with the same QoS level are transmitted through one EPS bearer that meets the QoS.

[0007] In contrast, with respect to the 5G system, although radio bearers can be used in the NG RAN, bearers are not used in the 5GC or in the interface between the 5GC and the NG-RAN. Specifically, QoS flows are defined instead of EPS bearers, and one or more SDFs are mapped to one or more QoS flows. The QoS flow between the 5G UE and the user plane terminal entity in the NG core (i.e., the entity corresponding to the P-GW in the EPC) corresponds to the EPS bearer in the EPS bearer-based QoS concept. The QoS flow corresponds to the finest granularity of packet forwarding and processing in the 5G system. That is, the 5G system adopts a flow-based QoS (or QoS per flow) concept instead of a bearer-based QoS concept. In the flow-based QoS concept, QoS is processed for each QoS flow. The association between the 5GUE and the data network is called a "PDU session". The term "PDU session" corresponds to the term "PDN connection" in LTE and LTE-Advanced. Multiple QoS flows can be configured in one PDU session. The 3GPP specification defines a 5G QoS indicator (5QI) corresponding to the QCI of LTE for the 5G system.

[0008] Figure 1 Shows the basic architecture of the 5G system. Figure 1 The architecture shown is referred to as "Standalone NR (in NextGen systems)" or "Option 2". The UE establishes one or more signaling radio bearers (SRBs) and one or more data radio bearers (DRBs) with the gNB. The 5GC and the gNB establish a control plane interface and a user plane interface used by the UE. The control plane interface between the 5GC and the gNB (i.e., RAN) is called the NG-c interface and is used to transfer non-access stratum (NAS) information and to transfer control information (e.g., N2AP information elements) between the 5GC and the gNB. The user plane interface between the 5GC and the gNB (i.e., RAN) is called the NG-u interface and is used to transfer packets of one or more QoS flows in a PDU session of the UE.

[0009] NR supports the use of different radio parameter sets in multiple frequency bands. Each radio parameter set is called a "numerology". The OFDM numerology of an 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, such as enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and M2M communications with a large number of connections (e.g., massive machine type communications (mMTC)). The numerology selection depends on the service requirements.

[0010] NR supports a channel bandwidth wider than that of LTE (e.g., 100 MHz). 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 500 MHz.

[0011] In order to efficiently support multiple 5G services (e.g., broadband services such as eMBB, and narrowband services such as the Internet of Things (IoT)), it is preferred to be able to multiplex these services onto a single channel bandwidth. In addition, if each 5G UE must support transmission and reception in a transmission bandwidth corresponding to the entire channel bandwidth, it may not be possible to reduce the cost of UEs for narrowband IoT services and the power consumption of the UEs. 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 different frequency division multiplexing (FDM) schemes using different digital schemes (e.g., subcarrier spacing (SCS)). For example, multiple BWPs can have different SCSs and different bandwidths.

[0012] Figure 2 and 3 An example of using BWP is shown. Figure 2 In the example shown, the channel bandwidth of one component carrier is divided into BWP#1 and BWP#2, and the two BWPs are used for different FDM schemes using different digital schemes (e.g., different subcarrier spacing). Figure 3 In the example shown, 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 in BWP#1. When BWP#1 or BWP#2 is activated for a UE, the UE can reduce its power consumption by suppressing reception and transmission in the channel bandwidth other than the active BWP.

[0013] A bandwidth part (BWP) is frequency continuous 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 contain a SS / PBCH block (SSB).

[0014] The BWP configuration includes, for example, a digital scheme, a frequency location, and a bandwidth (e.g., the number of PRBs). To specify the frequency location, a common PRB indexing 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 SSB to be accessed by the UE is configured by upper layer signaling. The reference point "PRB0" is common to all UEs sharing the same broadband component carrier.

[0015] One SS / PBCH block includes the main signals required by idle UEs, such as NR synchronization signal (NR-SS) and NR physical broadcast channel (NR-PBCH). UE uses NR-SS for DL ​​synchronization. Reference signals (RS) are sent in SS / PBCH blocks to enable idle UEs to perform radio resource management (RRM) measurements (e.g., RSRP measurements). The RS can be the NR-SS itself, or it can be an additional RS. NR-PBCH broadcasts part of the minimum system information (SI), such as the master information block (MIB). The remaining minimum SI (RMSI) is sent on the physical downlink shared channel (PDSCH).

[0016] The network may transmit multiple SS / PBCH blocks within the channel bandwidth of one wideband component carrier. In other words, the SS / PBCH blocks may be transmitted in multiple BWPs within the channel bandwidth. In a first scheme, all SS / PBCH blocks within one wideband carrier are based on NR-SS corresponding to the same physical layer cell identity (e.g., primary SS (PSS) and secondary SS (SSS)). In a second scheme, different SS / PBCH blocks within one wideband carrier may be based on NR-SS corresponding to different physical layer cell identities.

[0017] From the perspective of the UE, a cell is associated with one SS / PBCH block. Therefore, for the UE, each serving cell has a single associated SS / PBCH block in the frequency domain. Note that each serving cell is a primary cell (PCell) in carrier aggregation (CA) and dual connectivity (DC), a primary secondary cell (PSCell) in DC, or a secondary cell (SCell) in CA and DC. Such an SSB is called a cell-defined SS / PBCH block. The cell-defined SS / PBCH block has an associated RMSI. The cell-defined SS / PBCH block is used as a time reference or timing reference for the serving cell. In addition, the cell-defined SS / PBCH block is used for RRM measurements based on SS / PBCH blocks (SSBs). The cell-defined SS / PBCH block can be changed for PCell / PSCell by "synchronous reconfiguration" (e.g., reconfiguration of radio resource configuration information using the RRC reconfiguration process and not involving switching), while the cell-defined SS / PBCH block can be changed for SCell by "SCell release / addition".

[0018] The one or more BWP configurations of 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 4 DL BWPs) and one or more UL BWPs (e.g., up to 4 UL BWPs) can 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 "DL BWP set" and "UL BWP set", respectively.

[0019] Each BWP in one or more BWPs (i.e., BWP set) configured for the 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 transmits signals on one or more active UL BWPs in the configured UL BWP set at a given time. Note that in the current specification, at most one DL BWP and at most UL BWP are activated at a given time.

[0020] The activation / deactivation of the BWP is determined by the lower layer (e.g., the physical (PHY) layer or the medium access control (MAC) layer), not by the RRC layer. The switching of the active BWP is performed by, for example, downlink control information (DCI) (e.g., scheduling DCI) sent on the NR physical downlink control channel (PDCCH). In other words, the deactivation of the currently active BWP and the activation of the new active BWP can be performed by the DCI in the NR PDCCH. The network can activate / deactivate the BWP, for example, according to the data rate or the digital scheme required for the service, and the active BWP of the UE can be dynamically switched thereby.

[0021] The BWP that the UE initially resides on when it accesses the serving cell (i.e., when the UE transitions from idle mode to connected mode) (i.e., the initial active BWP) is called the "initial BWP". The initial BWP includes at least the DL BWP and (when uplink is configured for the serving cell) may include the UL BWP. The initial BWP may also be referred to as the default BWP, reference BWP, primary BWP, anchor BWP, or primary BWP. The set of BWPs configured for a UE always includes the initial BWP.

[0022] The initial BWP always configures a common search space. On the other hand, BWPs other than the initial BWP may or may not be configured with a common search space. Note that the common search space is a subset of resources (i.e., PDCCH search space) on which the UE performs blind decoding to find PDCCH data (i.e., DCI). Similar to LTE, in the 5G system, the PDCCH search space includes a common search space and a UE-specific search space. The UE-specific search space is configured separately for each UE through RRC signaling. On the other hand, all UEs accessing the serving cell know the extent or scope of the common search space. The NR common search space is used to broadcast, for example, system information, paging, and random access channel (RACH) responses. The NR common search space includes a "Type0-PDCCH common search space". In the Type0-PDCCH common search space, a PDCCH (i.e., DCI) scrambled with a system information radio network temporary identifier (SI-RNTI) is sent to enable the UE to receive system information block type 1 (SIB1).

[0023] It is discussed in 3GPP that if the UE's active DL BWP is not configured with a common search space, the UE does not need to receive system information updates (SI updates) by broadcast (see, for example, non-patent document 1). In this case, the network (ie, NG-RAN) can send updated SI to the UE residing in the active DL BWP that is not configured with any common search space via dedicated signaling (e.g., RRC reconfiguration message).

[0024] Next, the deployment of NG-RAN’s cloud RAN (C-RAN) is described. Figure 4 The overall architecture of NG-RAN is shown in FIG. 2 (see non-patent document 2). 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. Figure 4 As shown. Each gNB can consist of a gNB Central Unit (gNB-CU) and one or more gNB Distributed Units (gNB-DU). The gNB-CU and gNB-DU are connected to each other through the F1 interface. The gNB-CU is the logical node that hosts the RRC, Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) protocols of the gNB (or the RRC and PDCP protocols of the gNB). The gNB-DU is the logical node that hosts the Radio Link Control (RLC) layer, MAC layer and PHY layer of the gNB.

[0025] Reference List

[0026] Non-patent literature

[0027] Non-patent document 1: CATT, "CSS configuration for SI acquisition in non-initialBWP[C077]", R2-1810493, 3GPP TSG-RAN WG2 Meeting #AH-1807, Montreal, Canada, July 2nd-July 6th 2018

[0028] Non-patent document 2: 3GPP TS 38.401V15.2.0 (2018-06), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Architecture description (Release 15)", June 2018 Summary of the invention

[0029] Problem that the invention aims to solve

[0030] The inventors considered the problem when the gNB-CU sends SI updates to the UE via dedicated signaling. The gNB-CU sends updated SI to the UE residing in the corresponding active DLBWP that is not configured with any common search space via dedicated signaling. Therefore, the gNB-CU is preferably able to know the UE residing in the active DL BWP that is not configured with any common search space.

[0031] However, as described above, the active BWP is changed, for example, by DCI on the NR PDCCH. Therefore, in some implementations, the gNB-DU may determine the change of the active BWP of the UE and send a DCI to the UE to change the active BWP. In this case, the gNB-CU may not know which DL BWP in the set of DL BWPs configured for the UE is the active DL BWP. In other words, the gNB-CU may not have knowledge about the active DL BWP of each UE. In addition, in some implementations, the gNB-DU may determine whether to configure a common search space in a non-initial BWP. In this case, the gNB-CU may not know whether a common search space is configured in each non-initial BWP included in the UE's DL BWP set.

[0032] Therefore, there is a possibility that the gNB-CU may not be aware of UEs that each reside in an active DL BWP for which a common search space is not configured. In addition, for other purposes or uses, in addition to or in lieu of sending SI updates, the gNB-CU preferably is able to be aware of UEs that each reside in an active DL BWP for which a common search space is not configured.

[0033] One of the purposes to be achieved by the embodiments disclosed herein is to provide an apparatus, method and program that helps enable a central unit (e.g., gNB-CU) of a base station (e.g., gNB) to know each radio terminal (e.g., UE) residing in an active bandwidth portion for which a common search space is not configured. It should be noted that the above purpose is only one of the purposes to be achieved by the embodiments disclosed herein. Other purposes or problems and novel features will become apparent from the following description and drawings.

[0034] Solutions for solving problems

[0035] In a first 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 send at least one terminal list to a central unit of the base station. The at least one terminal list represents at least one of the following:

[0036] (a) a plurality of radio terminals each having no common search space configured in an active downlink bandwidth portion, i.e., an active downlink BWP;

[0037] (b) a plurality of radio terminals each of which has at least no search space, i.e., SS, configured in an active downlink BWP for receiving system information;

[0038] (c) A plurality of radio terminals need to receive updated system information via dedicated signaling for each radio terminal;

[0039] (d) a plurality of radio terminals whose respective active downlink BWP is a non-initial downlink BWP; and

[0040] (e) A plurality of radio terminals receiving on each downlink BWP.

[0041] In a second 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 receive at least one terminal list from a distributed unit of the base station. The at least one terminal list is the same as in the first aspect.

[0042] In a third aspect, a method used by a distributed unit of a base station comprises sending at least one terminal list to a central unit of the base station. The at least one terminal list is the same as in the first aspect.

[0043] In a fourth aspect, a method used by a central unit of a base station comprises receiving at least one terminal list from a distributed unit of the base station. The at least one terminal list is the same as in the first aspect.

[0044] In a fifth aspect, a distributed unit of a base station comprises 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 message containing an information element indicating a change of an active downlink bandwidth part, i.e., an active downlink BWP, of a radio terminal to a central unit of the base station.

[0045] In a sixth aspect, a central unit of a base station comprises 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 message containing an information element indicating a change of an active downlink BWP of a radio terminal from a distributed unit of the base station.

[0046] In a seventh aspect, a method for a distributed unit of a base station comprises sending a message containing an information element indicating a change of an active downlink BWP of a radio terminal to a central unit of the base station.

[0047] In an eighth aspect, a method for use by a central unit of a base station comprises receiving, from a distributed unit of the base station, a message containing an information element indicative of a change of an active downlink BWP of a radio terminal.

[0048] In a ninth aspect, the program comprises an instruction set (software code), wherein the instruction set, when loaded into a computer, causes the computer to perform the method according to the third aspect, fourth aspect, seventh aspect or eighth aspect described above.

[0049] Effects of the Invention

[0050] According to the above aspects, devices, methods and programs can be provided to help enable a central unit (e.g., gNB-CU) of a base station (e.g., gNB) to be aware of radio terminals (e.g., UEs) each residing in an active bandwidth portion for which a common search space is not configured. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Show the basic architecture of the 5G system;

[0052] Figure 2 shows an example of the use of bandwidth part (BWP);

[0053] Figure 3 shows an example of the use of bandwidth part (BWP);

[0054] Figure 4 Shows the overall architecture of NG-RAN;

[0055] Figure 5 An example of the structure of a radio communication network according to the first embodiment is shown;

[0056] Figure 6An example of the structure of a radio communication network according to the first embodiment is shown;

[0057] Figure 7 is a sequence diagram showing an example of signaling between a CU and a DU according to the first embodiment;

[0058] Figure 8 is a sequence diagram showing an example of signaling between a CU and a DU according to the second embodiment;

[0059] Fig. 9 is a sequence diagram showing an example of signaling for sending updated SI according to the third embodiment;

[0060] Fig.10 An example of the format of an F1AP message (eg, a BWP INFORMATION message) according to the third embodiment is shown;

[0061] Fig.11 is a sequence diagram showing an example of signaling between a CU and a DU according to the fourth embodiment;

[0062] Fig.12 An example of the format of an F1AP message (eg, UE CONTEXTMODIFICATION REQUIRED message) according to a fourth embodiment is shown;

[0063] Fig.13 is a block diagram showing a structural example of a central node (e.g., gNB-CU) according to some embodiments; and

[0064] Fig.14 is a block diagram showing a structural example of a distributed node (e.g., gNB-DU) according to some embodiments. DETAILED DESCRIPTION

[0065] The specific embodiments will be described in detail below with reference to the accompanying drawings. In the entire drawings, the same or corresponding elements are represented by the same symbols, and for the sake of clarity, repeated descriptions are omitted as needed.

[0066] Each embodiment in the embodiments described below can be used alone, or two or more embodiments in these 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 purposes or solve different problems from each other, and also help to obtain different advantages from each other.

[0067] The following description of the embodiments mainly focuses on the 3GPP 5G system. However, these embodiments can be applied to other radio communication systems.

[0068] First embodiment

[0069] Figure 5 An example of the structure of a radio communication network according to the present embodiment is shown. The radio communication network according to the present embodiment includes a gNB central unit (gNB-CU) 1 and one or more gNB distributed units (gNB-DU) 2. Each gNB-DU 2 is connected to the gNB-CU 1 via an interface 501. The interface 501 is an F1 interface. The UE 3 is connected to at least one gNB-DU 2 via at least one air interface 502.

[0070] like Figure 6 As shown, the gNB-CU 1 may include a control plane (CP) unit (gNB-CU-CP) 11 and one or more user plane (UP) units (gNB-CU-UP) 12. In this case, the gNB-CU-CP 11 is connected to the gNB-CU-UP 12 through a control plane interface 601 (i.e., E1 interface). In addition, the gNB-CU-CP 11 is connected to the gNB-DU 2 through a control plane interface 602 (i.e., F1-C interface). On the other hand, the gNB-CU-UP 12 is connected to the gNB-DU 2 through a user plane interface 603 (i.e., F1-U interface).

[0071] gNB-CU 1 may be a logical node that hosts the RRC, SDAP, and PDCP protocols of the gNB (or the RRC and PDCP protocols of the gNB). gNB-DU 2 may be a logical node that hosts the RLC layer, MAC layer, and PHY layer of the gNB. In such a functional configuration, gNB-DU 2 may determine the gNB set to be configured for UE 3 and notify the associated gNB-CU 1 of the configuration of the BWP set for UE 3. In addition, gNB-DU 2 may determine one or more (initial) active BWPs for UE 3 and notify the associated gNB-CU 1 of the active BWPs. Alternatively, gNB-CU 1 may determine the BWP set to be configured for UE 3 and notify the associated gNB-DU 2 of the configuration of the BWP set for UE 3. Additionally or alternatively, gNB-CU 1 may determine one or more (initial) active BWPs for UE 3 and notify the associated gNB-DU 2 of the active BWPs. Note that in any of these cases, gNB-DU 2 may change the active BWP of UE 3. That is, gNB-DU 2 may determine activation / deactivation of BWP. In addition, gNB-DU 2 may notify gNB-CU1 of information related to the changed BWP. The information related to the changed BWP may be, for example, information indicating whether each BWP is activated or deactivated or information indicating the difference between the BWP before the change and the BWP after the change.

[0072] Figure 7 Process 700 is shown as an example of signaling between gNB-CU 1 and gNB-DU 2. In step 701, gNB-DU 2 sends an F1 application protocol message. The name of the message may be, but is not limited to, a BWP INFORMATION message. The message contains at least one terminal list (i.e., UE list). The at least one UE list represents at least one of the following:

[0073] (a) UEs that do not have a common search space (CSS) configured in their active downlink bandwidth part (BWP);

[0074] (b) UEs each of which has at least no search space (SS) configured in an active downlink BWP for receiving SI;

[0075] (c) UEs that need to receive updated SI via dedicated signaling of each UE (or UEs to which updated SI needs to be sent via dedicated signaling of each UE, or UEs to which gNB-CU 1 needs to send updated SI via dedicated signaling of each UE);

[0076] (d) UEs whose respective active DL BWP is a non-initial downlink BWP; and

[0077] (e) UE receiving on each downlink BWP.

[0078] By receiving from the gNB-DU 2 a UE list representing UEs that do not have CSS configured in their respective active DL BWPs (i.e., UEs whose active DL BWPs do not have CSS configured), the gNB-CU 1 may know the UEs residing in its respective active DL BWPs that do not have CSS configured. This therefore allows, for example, the gNB-CU 1 to determine the UEs to which the updated SI needs to be sent via dedicated signaling (e.g., RRC reconfiguration message). In other words, this allows the gNB-DU 2 to inform the gNB-CU 1 of the UEs to which the updated SI needs to be sent via dedicated signaling. The UE list is useful, for example, for the implementation of the gNB-DU 2 determining whether to configure CSS to a non-initial BWP. The UE list may be a list of UEs residing in an active DL BWP that does not have CSS configured. The gNB-DU 2 may select a UE that is receiving on an active DL BWP that does not have CSS configured from the UEs in its cell that are in RRC_Connected, and then send the list of selected UEs to the gNB-CU 1.

[0079] Additionally or alternatively, the gNB-DU 2 may send a list of UEs for which at least a search space (SS) for receiving SI (i.e., SI-SS) is not configured in the active DL BWP to the gNB-CU 1. By doing so, the gNB-CU 1 may be aware of the UEs residing in the active DL BWP for which the SI-SS is not configured. Note that the SI-SS may be included in the CSS or may be included in the UE-specific search space (USS).

[0080] By receiving from the gNB-DU 2 a list of UEs indicating the UEs that need to receive updated SI via dedicated signaling for each UE (per UE), the gNB-CU 1 can directly obtain knowledge about these UEs. This therefore allows, for example, the gNB-CU 1 to determine the UEs to which the updated SI needs to be sent via dedicated signaling. This UE list is useful, for example, for the implementation of the gNB-DU 2 to determine whether to configure CSS to a non-initial BWP. The gNB-DU 2 can select UEs that are receiving on an active DL BWP that is not configured with CSS from the UEs in its cell that are in RRC_Connected, and then send the list of selected UEs to the gNB-CU 1.

[0081] By receiving from gNB-DU 2 a UE list indicating UEs whose respective active DL BWP is a non-initial downlink BWP, gNB-CU 1 can know the UEs residing in the non-initial DL BWP. This thus allows gNB-CU 1 to determine, for example, the UEs to which the updated SI needs to be sent via dedicated signaling. The UE list is useful, for example, for implementations in which gNB-CU 1 determines whether to configure CSS to a non-initial BWP and instructs gNB-DU 2 to configure CSS to the non-initial BWP. In addition, the UE list is also useful for implementations in which gNB-DU 2 determines whether to configure CSS to a non-initial BWP. In these implementations, gNB-CU 1 may also refer to other information (e.g., cell group configuration (CG-Config or CellGroupConfig)) to know whether each non-initial BWP is configured with CSS. gNB-DU 2 may select a UE that is receiving on a non-active DL BWP from the UEs in its cell that are in RRC_Connected, and then send a list of the selected UEs to gNB-CU 1.

[0082] By receiving a UE list representing UEs that are receiving on each downlink BWP (i.e., a list of UEs per BWP) from the gNB-DU 2, the gNB-CU 1 can know the UEs residing in each DL BWP (i.e., the UEs that use each DL BWP as their active DL BWP). This therefore allows, for example, the gNB-CU1 to determine the UEs to which the updated SI needs to be sent via dedicated signaling. This UE list is useful, for example, for implementations in which the gNB-DU2 determines whether to configure CSS to a non-initial BWP. In these implementations, the gNB-CU 1 may also refer to other information (e.g., CG-Config or CellGroupConfig) to know whether each non-initial BWP is configured with CSS.

[0083] Specifically, during the UE context setup procedure, gNB-CU 1 may check the content of the CellGroupConfig IE included in the "DU-CU RRC Information" information element (IE) included in the F1AP:UE context setup response message received from gNB-DU 2. gNB-DU 2 may merge the information related to the common search space into the "CellGroupConfig" IE. Therefore, by checking the CellGroupConfig IE, gNB-CU 1 may know whether each non-initial BWP is configured with a CSS by gNB-DU 2.

[0084] In addition, the UE list is also useful for gNB-CU 1 to determine whether to configure CSS for a non-initial BWP and to instruct gNB-DU 2 to configure CSS for the non-initial BWP.

[0085] Each of the above UE lists may use any identifier to distinguish UEs from each other. For example, the identifier used to distinguish UEs in the UE list may be a cell RNTI (C-RNTI), a gNB-CU UE F1AP ID, a gNB-DU UE F1AP ID, or a gNB-CU UE F1AP ID and a gNB-DU UE F1AP ID pair. The C-RNTI uniquely identifies the UE (or the RRC connection of the UE) within the cell for scheduling. The gNB-CU UE F1AP ID uniquely identifies the UE association on the F1 interface within gNB-CU 1. The gNB-DU UE F1AP ID uniquely identifies the UE association on the F1 interface within gNB-DU 2.

[0086] In some implementations, in response to receiving a first control message (i.e., F1AP message) containing a system information update notification from gNB-CU 1, gNB-DU 2 may send a second control message (i.e., F1AP message) containing the above-mentioned UE list to gNB-CU 1. The system information update notification indicates that the system information will be updated in the next modification time period. This helps to enable gNB-DU 2 to promptly notify gNB-CU 1 of the UEs to which the updated SI needs to be sent via dedicated signaling when gNB-CU 1 updates any SI. Note that the system information may be, for example, an alert notification message of a public warning system (PWS) or an alert notification message of an earthquake and tsunami warning system (ETWS) (e.g., an ETWS primary notification or an ETWS secondary notification or both).

[0087] The first control message may be a SYSTEM INFORMATION DELIVERY COMMAND message. Upon receiving the SYSTEM INFORMATION DELIVERY COMMAND message, gNB-DU 2 broadcasts the requested system information via the CSS. In addition, in this embodiment, gNB-DU 2 sends a second control message including the above UE list to gNB-CU 1. The name of the second control message may be, for example, but not limited to, a SYSTEM INFORMATION DELIVERY CONFIRM message.

[0088] Figure 8 Process 800 is shown as an example of signaling between gNB-CU 1 and gNB-DU 2. In step 801, gNB-CU 1 sends a SYSTEM INFORMATION DELIVERY COMMAND message containing a system information update notification to gNB-DU 2. In step 802, upon receiving the SYSTEM INFORMATION DELIVERY COMMAND message, gNB-DU 2 sends a SYSTEM INFORMATION DELIVERY CONFIRM message containing the above-mentioned UE list to gNB-CU 1.

[0089] Additionally or alternatively, gNB-DU 2 may send the above UE list to gNB-CU 1 when it determines the update of system information. This helps to enable gNB-DU 2 to promptly notify gNB-CU 1 of the existence of UEs to which the updated SI needs to be sent via dedicated signaling when gNB-DU 2 updates the SI.

[0090] Additionally or alternatively, the gNB-DU 2 may send the above UE list to the gNB-CU 1 in response to receiving a request for the UE list from the gNB-CU 1. This thus allows the gNB-CU 1 to know the UEs to which the updated SI needs to be sent via dedicated signaling at a given time.

[0091] It can be understood from the above description that in this embodiment, gNB-DU 2 is configured to send at least one UE list to gNB-CU 1. The at least one UE list represents at least one of the following items:

[0092] (a) UEs that do not have a common search space (CSS) configured in their active downlink BWP;

[0093] (b) UEs each of which has at least no search space (SS) configured in an active downlink BWP for receiving SI;

[0094] (c) UEs that need to receive updated SI via dedicated signaling of each UE (UEs to which updated SI needs to be sent via dedicated signaling of each UE, or UEs to which gNB-CU 1 needs to send updated SI via dedicated signaling of each UE);

[0095] (d) UEs whose respective active DL BWP is a non-initial downlink BWP; and

[0096] (e) UE receiving on each downlink BWP.

[0097] This helps gNB-CU 1 to gain knowledge about the UEs residing in the active DL BWP that are not configured with any CSS. For example, by referring to this UE list, gNB-CU 1 can determine the UEs to which the updated SI needs to be sent via dedicated signaling (e.g., gNB reconfiguration message).

[0098] Second embodiment

[0099] This embodiment provides details of the signaling for sending the updated SI. Figure 5 and 6 The structural example of the radio communication network shown in is the same.

[0100] Fig. 9A process 900 is shown as an example of signaling for sending updated SI. In step 901, gNB-DU 2 instructs UE 3 to change the active DL BWP to a non-initial DL BWP that is not configured with a common search space (CSS) via PDCCH (i.e., DCI). In step 902, UE 3 resides in the non-initial DL BWP that is not configured with CSS and operates to receive signals on the non-initial DL BWP.

[0101] Steps 903 and 904 are the same as Figure 8 Steps 801 and 802 are the same. Specifically, in step 903, gNB-CU 1 sends a SYSTEMINFORMATION DELIVERY COMMAND message containing a system information update notification to gNB-DU 2. In step 904, upon receiving the SYSTEM INFORMATION DELIVERY COMMAND message, gNB-DU 2 sends a SYSTEMINFORMATION DELIVERY CONFIRM message containing the UE list described in the first embodiment to gNB-CU 1.

[0102] In step 905, after receiving the UE list, gNB-CU 1 sends the updated SI to one or more UEs 3 via dedicated signaling (e.g., gNB reconfiguration message) for each UE. Specifically, by referring to the received UE list, gNB-CU1 obtains knowledge about the UEs residing in the active DLBWP that is not configured with any CSS, and determines the UEs to which the updated SI needs to be sent via dedicated signaling. The RRC Reconfiguration message containing the updated SI is delivered from gNB-CU 1 to gNB-DU 2 via a DL RRC MESSAGETRANSFER message on the F1 interface, and then sent by gNB-DU 2 to UE 3.

[0103] In step 906, UE 3 sends an RRC Reconfiguration Complete message to gNB-CU 1. The RRC Reconfiguration Complete message is delivered from gNB-DU 2 to gNB-CU 1 via a UL RRC MESSAGE TRANSFER message on the F1 interface.

[0104] according to Fig. 9 According to the process shown, gNB-CU 1 can determine the UEs residing in active DLBWPs without CSS configured and send updated SI to these UEs via dedicated signaling.

[0105] Third embodiment

[0106] This embodiment provides details of the F1AP message for delivering the UE list described in the first embodiment. Figure 5 and 6 The structural examples of the radio communication networks shown are the same.

[0107] Fig.10 An example of the format of an F1AP message (eg, BWPINFORMATION message) for delivering the UE list explained in the first embodiment is shown. Fig.10 The message shown is sent by gNB-DU 2 to gNB-CU 1. Fig.10 The F1AP message (e.g., BWP INFORMATION message) shown includes a BWP list representing all (DL) BWPs. The BWP list includes a UE list (or UE ID list) for each (DL) BWP. Fig.10 In the example shown, the UE list (or UE ID list) uses C-RNTI to distinguish UEs from each other. The UE list (or UE ID list) can use other identifiers (e.g., gNB-CU UE F1AP ID or gNB-DU UE F1AP ID) instead of C-RNTI.

[0108] Fig.10 The F1AP message shown enables the gNB-DU 2 to provide the gNB-CU 1 with a UE list representing the UEs that are receiving on each DLBWP (i.e., a list of UEs per DL BWP).

[0109] Fourth embodiment

[0110] The configuration example of the radio communication network according to the present embodiment is Figure 5 and 6 The structural examples of the radio communication networks shown are the same. The first to third embodiments provide examples in which gNB-DU 2 provides a UE list to gNB-CU1. The examples described in the first to third embodiments use a procedure or signaling that is not associated with any UE (i.e., a non-UE-associated procedure or signaling) to send the UE list from gNB-DU 2 to gNB-CU 1. Therefore, the first to third embodiments have the following advantages over other technologies that use UE-associated procedures or signaling: it can reduce the number of signaling messages between gNB-CU 1 and gNB-DU2.

[0111] However, in some implementations, the gNB-DU 2 may notify the gNB-CU 1 of the change of the active DL BWP of the UE by using a procedure or signaling associated with the UE 3 (i.e., UE-associated procedure or signaling). In this embodiment, the gNB-DU 2 sends a message indicating the change of the active DL BWP of the UE 3 to the gNB-CU 1. The gNB-DU 2 may send a message indicating the change of the active DL BWP of the UE 3 to the gNB-CU 1 in response to the change of the active DL BWP of the UE 3. The gNB-DU 2 may send a message indicating the change of the active DL BWP of the UE 3 to the gNB-CU 1 after the change of the active DL BWP of the UE 3. Specifically, the gNB-DU 2 may notify the gNB-CU 1 that the active DL BWP of the UE 3 has changed from the initial BWP to the non-initial DL BWP (particularly, to the non-initial DL BWP without CSS). In this way, the gNB-CU 1 may know the UEs residing in the active DL BWP without CSS configured. This therefore allows, for example, gNB-CU 1 to determine the UEs to which updated SI needs to be sent via dedicated signaling.

[0112] In some implementations, in the case where the gNB-DU 2 has changed or switched the active DL BWP of the UE 3, the gNB-DU 2 may send a message including an information element indicating the change or switch of the active DL BWP of the UE 3 to the gNB-CU 1 during a UE CONTEXT MODIFICATION REQUIRED procedure initiated by the gNB-DU 2. Specifically, in response to the active DL BWP of the UE 3 being changed from an initial BWP to a non-initial DL BWP (particularly, to a non-initial DL BWP without CSS), the gNB-DU 2 may send a message including the information element to the gNB-CU 1. The gNB-DU 2 may incorporate the information element into a F1AP:UECONTEXTMODIFICATION REQUIRED message.

[0113] The information element may be a BOOLEAN data type variable indicating whether the active DL BWP of UE 3 has changed from the initial DL BWP to the non-initial DL BWP. Alternatively, the information element may be an ENUMERATED type variable indicating that the active DL BWP of UE 3 does not have a CSS. Alternatively, the information element may be an INTEGER type variable indicating an identifier (e.g., BWP ID) of the active DL BWP of UE 3.

[0114] Fig.11A process 1100 is shown as an example of signaling according to the present embodiment. In step 1101, gNB-DU 2 sends a UE CONTEXT MODIFICATION REQUIRED message. The message includes the information elements described in the present embodiment.

[0115] Fig.12 An example of the format of the F1 message including the information elements described in this embodiment is shown. Fig.12 The UE CONTEXT MODIFICATION REQUIRED message shown is sent by gNB-DU 2 to gNB-CU 1 to request modification of the UE context. Fig.12 The UE CONTEXTMODIFICATION REQUIRED message shown includes a "UE switches to BWP" information element (IE). As described above, the "UE switches to BWP" IE can be a BOOLEAN data type variable indicating whether the active DL BWP of UE 3 has changed from the initial DL BWP to the non-initial DL BWP. Alternatively, the "UE switches to BWP" IE can be an ENUMERATED type variable indicating that the active DL BWP of UE 3 does not have a CSS.

[0116] Fig.12 The UE CONTEXT MODIFICATION REQUIRED message may include a "BWP-ID" information element (IE) instead of the "UE HANDOVER TO BWP" IE. The "BWP-ID" IE may be an INTEGER type variable representing an identifier (eg, BWP ID) of the active DL BWP of UE 3.

[0117] The following provides a structural example of gNB-CU 1 and gNB-DU 2 according to the above embodiment. Fig.13 1 is a block diagram showing a structural example of the gNB-CU 1 according to the above embodiment. Note that the structural examples of the gNB-CU-CP 11 and the gNB-CU-UP 12 may be the same as those of the gNB-CU-CP 11 and the gNB-CU-UP 12. Fig.13 The structure examples shown are the same. Fig.13 As shown, gNB-CU 1 includes a network interface 1301, a processor 1302, and a memory 1303. The network interface 1301 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 1301 may include multiple interfaces. The network interface 1301 may include an optical fiber interface for CU-DU communication and a network interface compliant with the IEEE 802.3 series.

[0118] The processor 1302 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for radio communication. The processor 1302 may include multiple processors. The processor 1302 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.

[0119] The memory 1303 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 1303 may include a memory located separately from the processor 1302. In this case, the processor 1302 may access the memory 1303 through the network interface 1301 or an I / O interface (not shown).

[0120] The memory 1303 may store one or more software modules (computer programs) 1304, which include instructions and data for performing the processing of the gNB-CU 1 described in the above embodiments. In some implementations, the processor 1302 may load one or more software modules 1304 from the memory 1303 and execute the loaded software modules to perform the processing of the gNB-CU 1 described in the above embodiments.

[0121] Fig.14 2 is a block diagram showing a structural example of the gNB-DU 2 according to the above embodiment. Fig.14 As shown, the gNB-DU2 includes a radio frequency transceiver 1401, a network interface 1403, a processor 1404, and a memory 1405. The RF transceiver 1401 performs analog RF signal processing to communicate with the NG UE. The RF transceiver 1401 may include multiple transceivers. The RF transceiver 1401 is connected to the antenna array 1402 and the processor 1404. The RF transceiver 1401 receives modulation symbol data from the processor 1404, generates a transmit RF signal, and supplies the generated transmit RF signal to the antenna 1402. In addition, the RF transceiver 1401 generates a baseband receive signal based on the receive RF signal received by the antenna 1402, and supplies the signal to the processor 1404. The RF transceiver 1401 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, multiple phase shifters and multiple power amplifiers.

[0122] The network interface 1403 is used to communicate with network nodes (e.g., gNB-CU 1, gNB-CU-CP 11, and gNB-CU-UP 12). The network interface 1403 may include multiple interfaces. The network interface 1403 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.

[0123] The processor 1404 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for radio communication. The processor 1404 may include multiple processors. The processor 1404 may include a modem processor (e.g., DSP) for digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) for control plane processing. The processor 1404 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.

[0124] The memory 1405 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 1405 may include a memory located separately from the processor 1404. In this case, the processor 1404 may access the memory 1405 through the network interface 1403 or an I / O interface (not shown).

[0125] The memory 1405 may store one or more software modules (computer programs) 1406, which include instructions and data for performing the processing of the gNB-DU 2 described in the above embodiments. In some implementations, the processor 1404 may load one or more software modules 1406 from the memory 1405 and execute the loaded software modules to perform the processing of the gNB-DU 2 described in the above embodiments.

[0126] As mentioned above Figures 13 to 14As described, 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 a 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 ROMs, and random access memories (RAMs). These programs can be supplied to a 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., wires and optical fibers) or a wireless communication line.

[0127] Other embodiments

[0128] The above embodiment provides an example in which gNB-CU 1 uses the UE list received from gNB-DU 2 to determine the UEs to which the updated SI needs to be sent via dedicated signaling. However, gNB-CU 1 may use the UE list received from gNB-DU 2 for other purposes.

[0129] The signaling between gNB-CU 1 and gNB-DU 2 described in the above embodiment can be carried out between gNB-CU-CP 11 and gNB-DU 2.

[0130] In addition, the above-described embodiments are merely examples of application of the technical ideas obtained by the inventors. These technical ideas are not limited to the above-described embodiments, and various modifications can be made thereto.

[0131] For example, all or part of the embodiments disclosed above may be described as, but not limited to, the following supplementary notes.

[0132] (Supplementary Note 1)

[0133] A distributed unit of a base station, the distributed unit comprising:

[0134] at least one memory; and

[0135] At least one processor coupled to the at least one memory and configured to send to a central unit of the base station at least one terminal list representing at least one of the following:

[0136] a plurality of radio terminals each having no common search space configured in an active downlink bandwidth portion, i.e., an active downlink BWP;

[0137] a plurality of radio terminals each of which has at least no search space, SS, configured in an active downlink BWP for receiving system information;

[0138] A plurality of radio terminals needing to receive updated system information via dedicated signaling for each radio terminal;

[0139] a plurality of radio terminals whose respective active downlink BWPs are non-initial downlink BWPs; and

[0140] A number of radio terminals are receiving on each downlink BWP.

[0141] (Supplementary Note 2)

[0142] The distributed unit according to Supplementary Note 1, wherein the at least one processor is configured to send the at least one terminal list to the central unit in response to receiving a first control message including a system information update notification from the central unit.

[0143] (Supplementary Note 3)

[0144] The distributed unit according to Supplementary Note 2, wherein the first control message is a SYSTEMINFORMATION DELIVERY COMMAND message.

[0145] (Supplementary Note 4)

[0146] The distributed unit according to any one of Supplementary Notes 1 to 3, wherein the at least one processor is configured to send the at least one terminal list to the central unit in response to determining an update of system information.

[0147] (Supplementary Note 5)

[0148] The distributed unit according to any one of Supplementary Notes 1 to 4, wherein the at least one processor is configured to send the at least one terminal list to the central unit in response to receiving a request from the central unit.

[0149] (Supplementary Note 6)

[0150] The distributed unit according to any one of Supplementary Notes 1 to 5, wherein the at least one terminal list represents a plurality of radio terminals whose respective active downlink BWPs are not configured with a common search space.

[0151] (Supplementary Note 7)

[0152] The distributed unit according to any one of Supplementary Notes 1 to 5, wherein the at least one terminal list represents a plurality of radio terminals whose respective active downlink BWPs are at least not configured with a search space (SS) for receiving system information.

[0153] (Supplementary Note 8)

[0154] The distributed unit according to any one of Supplementary Notes 1 to 5, wherein the at least one terminal list represents a plurality of radio terminals whose respective active downlink BWPs are non-initial downlink BWPs.

[0155] (Supplementary Note 9)

[0156] The distributed unit according to any one of Supplementary Notes 1 to 5, wherein the at least one terminal list includes a terminal list for each BWP representing a plurality of radio terminals receiving on each downlink BWP.

[0157] (Supplementary Note 10)

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

[0159] at least one memory; and

[0160] At least one processor coupled to the at least one memory and configured to receive, from a distributed unit of the base station, at least one terminal list representing at least one of the following:

[0161] a plurality of radio terminals each not configured with a common search space, CSS, in an active downlink bandwidth part, ie, an active downlink BWP;

[0162] a plurality of radio terminals each of which has at least no search space, SS, configured in an active downlink BWP for receiving system information;

[0163] A plurality of radio terminals needing to receive updated system information via dedicated signaling for each radio terminal;

[0164] a plurality of radio terminals whose respective active downlink BWPs are non-initial downlink BWPs; and

[0165] A number of radio terminals are receiving on each downlink BWP.

[0166] (Supplementary Note 11)

[0167] The central unit according to Supplementary Note 10, wherein:

[0168] The at least one processor is configured to send a first control message including a system information update notification to the distributed unit, and

[0169] The first control message causes the distributed unit to send the at least one terminal list to the central unit.

[0170] (Supplementary Note 12)

[0171] The central unit according to Supplementary Note 11, wherein the first control message is a SYSTEM INFORMATION DELIVERY COMMAND message.

[0172] (Supplementary Note 13)

[0173] The central unit according to any one of Supplementary Notes 10 to 12, wherein the at least one processor is configured to send a request for the at least one terminal list to the distributed unit.

[0174] (Supplementary Note 14)

[0175] The central unit according to any one of Supplementary Notes 10 to 13, wherein the at least one processor is configured to send update system information to one or more radio terminals via dedicated signaling for each radio terminal after receiving the at least one terminal list.

[0176] (Supplementary Note 15)

[0177] The central unit according to any one of Supplementary Notes 10 to 14, wherein the at least one terminal list represents a plurality of radio terminals whose respective active downlink BWPs are not configured with a common search space (CSS).

[0178] (Supplementary Note 16)

[0179] The central unit according to any one of Supplementary Notes 10 to 14, wherein the at least one terminal list represents a plurality of radio terminals whose respective active downlink BWPs are not configured with at least a search space (SS) for receiving system information.

[0180] (Supplementary Note 17)

[0181] The central unit according to any one of Supplementary Notes 10 to 14, wherein the at least one terminal list represents a plurality of radio terminals whose respective active downlink BWPs are non-initial downlink BWPs.

[0182] (Supplementary Note 18)

[0183] The central unit according to any one of Supplementary Notes 10 to 14, wherein the at least one terminal list includes a terminal list for each BWP representing a plurality of radio terminals receiving on each downlink BWP.

[0184] (Supplementary Note 19)

[0185] A method for a distributed unit of a base station, the method comprising sending to a central unit of the base station at least one terminal list representing at least one of the following:

[0186] a plurality of radio terminals each having no common search space configured in an active downlink bandwidth portion, i.e., an active downlink BWP;

[0187] a plurality of radio terminals each of which has at least no search space, SS, configured in an active downlink BWP for receiving system information;

[0188] A plurality of radio terminals needing to receive updated system information via dedicated signaling for each radio terminal;

[0189] a plurality of radio terminals whose respective active downlink BWPs are non-initial downlink BWPs; and

[0190] A number of radio terminals are receiving on each downlink BWP.

[0191] (Supplementary Note 20)

[0192] A method for a central unit of a base station, the method comprising receiving from a distributed unit of the base station at least one terminal list representing at least one of the following:

[0193] a plurality of radio terminals each not configured with a common search space, CSS, in an active downlink bandwidth part, ie, an active downlink BWP;

[0194] a plurality of radio terminals each of which has at least no search space, SS, configured in an active downlink BWP for receiving system information;

[0195] A plurality of radio terminals needing to receive updated system information via dedicated signaling for each radio terminal;

[0196] a plurality of radio terminals whose respective active downlink BWPs are non-initial downlink BWPs; and

[0197] A number of radio terminals are receiving on each downlink BWP.

[0198] (Supplementary Note 21)

[0199] A program for causing a computer to perform a method used by a distributed unit of a base station, wherein the method comprises sending to a central unit of the base station at least one terminal list representing at least one of the following:

[0200] a plurality of radio terminals each having no common search space configured in an active downlink bandwidth portion, i.e., an active downlink BWP;

[0201] a plurality of radio terminals each of which has at least no search space, SS, configured in an active downlink BWP for receiving system information;

[0202] A plurality of radio terminals needing to receive updated system information via dedicated signaling for each radio terminal;

[0203] a plurality of radio terminals whose respective active downlink BWPs are non-initial downlink BWPs; and

[0204] A number of radio terminals are receiving on each downlink BWP.

[0205] (Supplementary Note 22)

[0206] A program for causing a computer to perform a method used by a central unit of a base station, wherein the method comprises receiving from a distributed unit of the base station at least one terminal list representing at least one of the following:

[0207] a plurality of radio terminals each having no common search space configured in an active downlink bandwidth portion, i.e., an active downlink BWP;

[0208] a plurality of radio terminals each of which has at least no search space, SS, configured in an active downlink BWP for receiving system information;

[0209] A plurality of radio terminals needing to receive updated system information via dedicated signaling for each radio terminal;

[0210] a plurality of radio terminals whose respective active downlink BWPs are non-initial downlink BWPs; and

[0211] A number of radio terminals are receiving on each downlink BWP.

[0212] (Supplementary Note 23)

[0213] A distributed unit of a base station, the distributed unit comprising:

[0214] at least one memory; and

[0215] At least one processor is coupled to the at least one memory and is configured to send a message containing an information element indicating a change of an active downlink bandwidth part, active downlink BWP, of a radio terminal to a central unit of the base station.

[0216] (Supplementary Note 24)

[0217] The distributed unit according to Supplementary Note 23, wherein the at least one processor is configured to send the message to the central unit of the base station in response to a change in an active downlink BWP of the radio terminal.

[0218] (Supplementary Note 25)

[0219] The distributed unit according to supplementary note 23 or 24, wherein the information element indicates whether an active downlink BWP of the radio terminal has been changed from an initial downlink BWP to a non-initial downlink BWP.

[0220] (Supplementary Note 26)

[0221] The distributed unit according to supplementary note 23 or 24, wherein the information element indicates that the active downlink BWP of the radio terminal does not include a common search space.

[0222] (Supplementary Note 27)

[0223] The distributed unit according to supplementary note 23 or 24, wherein the information element represents an identifier of a changed active downlink BWP of the radio terminal.

[0224] (Supplementary Note 28)

[0225] A central unit of a base station, the central unit comprising:

[0226] at least one memory; and

[0227] At least one processor is coupled to the at least one memory and is configured to receive a message from a distributed unit of the base station containing an information element indicating a change of an active downlink BWP of a radio terminal.

[0228] (Supplementary Note 29)

[0229] The central unit according to Supplementary Note 28, wherein the information element indicates whether an active downlink BWP of the radio terminal has been changed from an initial downlink BWP to a non-initial downlink BWP.

[0230] (Supplementary Note 30)

[0231] The central unit according to Supplementary Note 28, wherein the information element indicates that the active downlink BWP of the radio terminal does not include a common search space.

[0232] (Supplementary Note 31)

[0233] The central unit according to Supplementary Note 28, wherein the information element represents an identifier of a changed active downlink BWP of the radio terminal.

[0234] (Supplementary Note 32)

[0235] The central unit according to any of Supplementary Notes 28 to 31, wherein the at least one processor is configured to send updated system information to the radio terminals via dedicated signaling for each radio terminal after receiving the information element.

[0236] (Supplementary Note 33)

[0237] A method for a distributed unit of a base station, the method comprising sending a message containing an information element indicating a change of an active downlink bandwidth part, active downlink BWP, of a radio terminal to a central unit of the base station.

[0238] (Supplementary Note 34)

[0239] A method for use by a central unit of a base station, the method comprising receiving from a distributed unit of the base station a message containing an information element indicating a change of an active downlink BWP of a radio terminal.

[0240] This application is based upon and claims the benefit of priority from Japanese patent application No. 2018-150709, filed on August 9, 2018, the disclosure of which is incorporated herein in its entirety by reference.

[0241] Reference numerals list

[0242] 1 gNB-CU

[0243] 2 gNB-DU

[0244] 3 UE

[0245] 11 gNB-CU-CP

[0246] 12 gNB-CU-UP

[0247] 1302 Processor

[0248] 1303 Memory

[0249] 1304 Module

[0250] 1404 Processor

[0251] 1405 Memory

[0252] 1406 Module

Claims

1. A method used by a distributed unit, namely, DU (2), the method comprising: Receiving (801) a first message from a central unit, i.e. CU (1), the first message indicating system information to be broadcast; as well as In response to the first message, a second message including a list is sent (802) to the CU (1), the list indicating at least one user equipment, i.e., at least one UE, to which the system information needs to be sent via dedicated signaling.

2. The method according to claim 1, wherein: The system information is updated system information.

3. The method according to claim 1 or 2, wherein: The DU is a gNB distributed unit, i.e., gNB-DU, and The CU is the gNB central unit, namely gNB-CU.

4. The method according to claim 1 or 2, further comprising: receiving, from the CU (1), the system information included in an RRC reconfiguration message, the RRC reconfiguration message being included in a DL RRC messaging message; as well as The system information included in the RRC reconfiguration message is sent to a UE that is one of the at least one UE in the list.

5. The method according to claim 1 or 2, wherein: The list includes gNB-CU UE F1AP ID.

6. The method according to claim 1 or 2, wherein: The first message and the second message are each an F1AP message.

7. The method according to claim 1 or 2, wherein: The system information includes an alarm message of an alarm system.

8. The method according to claim 1 or 2, wherein: The at least one UE indicated in the list is at least one UE each of which has no common search space, CSS, configured in an active downlink bandwidth part, ie, active DL BWP.

9. A method for use by a central unit (CU) (1), the method comprising: Sending (801) a first message to a distributed unit, namely DU (2), the first message indicating system information to be broadcast; as well as In response to the first message, a second message is received (802) from the DU (2) including a list indicating at least one user equipment (UE) to which the system information needs to be sent via dedicated signaling.

10. A method for a base station, the base station comprising a distributed unit (DU) (2) and a central unit (CU) (1), the method comprising: The CU (1) sends (801) a first message to the DU (2), wherein the first message indicates system information to be broadcast; as well as In response to the first message, the DU (2) sends (802) a second message to the CU (1) including a list, wherein the list indicates at least one UE to which the system information needs to be sent via dedicated signaling for each user equipment, i.e., each UE.

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