Wireless access network node, wireless terminal, method thereof, and computer readable medium

Abstract

The present invention relates to a radio access network node, a wireless terminal, and a method and a computer-readable medium thereof. A second RAN node (2) sends an indication of on-demand system information available in a cell of the second RAN node (2) to a wireless terminal (3) via a first RAN node (1). Thus, for example, a UE can be notified of an indication related to on-demand system information available in a cell served by a secondary gNB for inter-RAT dual connectivity between E-UTRA and NR, or available in a cell served by a target gNB for an inter-RAT handover from E-UTRA to NR.

Description

[0001] (This application is a divisional application of an application filed on November 21, 2017, with application number 201780088061.X, and invention name “Wireless access network node, wireless terminal, method thereof, and non-transitory computer-readable medium”.) Technical Field

[0002] The present invention relates to a wireless communication system, and in particular, to communication in which a wireless terminal simultaneously uses a plurality of cells of different radio access technologies (RATs) operated by different wireless stations. Background Art

[0003] The 3rd Generation Partnership Project (3GPP) has started standardization of the fifth generation mobile communication system (5G) in 2016 (i.e., 3GPP Release 14) to make 5G a commercial reality in or after 2020 (see Non-Patent Literature 1). 5G is expected to be achieved through the continued enhancement / evolution of LTE and Advanced LTE and through the introduction of innovative enhancement / evolution of new 5G air interfaces (i.e., new radio access technologies (RATs)). The new RAT supports, for example, higher frequency bands than those supported by LTE / Advanced LTE and its continued evolution (e.g., below 6 GHz). For example, the new RAT supports centimeter wave bands (above 10 GHz) and millimeter wave bands (above 30 GHz).

[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 radio (NR), a 5G RAT or a NG RAT. The new radio access network (RAN) of the 5G system is referred to as a 5G-RAN or a NextGen RAN (NG RAN). The new base station within the NG-RAN is referred to as a NRNodeB (NR NB) or a gNodeB (gNB). The new core network of the 5G system is referred to as a 5G core network (5G-CN) or a NextGen core (NG core). A wireless terminal (ie, user equipment (UE)) that can be connected to the 5G system is referred to as a 5G UE or a NextGen UE (NG UE), or simply referred to as a UE. As standardization progresses, the official names of the RAT, UE, radio access network, core network, network entity (node) and protocol layer of the NG system will be determined in the future.

[0005] 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 enhancements / evolutions of LTE and advanced LTE used for intercommunication with 5G systems are referred to as advanced LTE Pro, LTE+, or enhanced LTE (eLTE). 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)", "service 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 for 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 QoS for each bearer) 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 via one EPS bearer that meets the QoS. SDF is one or more packet flows that match SDF templates (i.e., packet filters) based on policy and charging control (PCC) rules. In order to achieve packet routing, each packet to be transmitted via the EPS bearer contains information for identifying which bearer (i.e., General Packet Radio Service (GPRS) Tunneling Protocol (GTP) tunnel) the packet is associated with.

[0007] In contrast, with respect to the 5G system, it is discussed that although a radio bearer can be used in 5G-RAN, the bearer is not used in 5G-CN or in the interface between 5G-CN and NG-RAN (see non-patent document 1). Specifically, a PDU flow is defined instead of an EPS bearer, and one or more SDFs are mapped to one or more PDU flows. The PDU 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 PDU flow corresponds to the finest granularity of packet forwarding and processing within the 5G system. That is, instead of the bearer-based QoS concept, the 5G system adopts a flow-based QoS (or QoS for each flow) concept. In the flow-based QoS concept, QoS is processed for each PDU flow. In the QoS framework of the 5G system, the PDU flow is identified by the PDU flow ID contained in the header of the service data unit of the tunnel encapsulating the NG3 interface. The NG3 interface is the user plane interface between the 5G-CN and the gNB (i.e., 5G-RAN). The association between a 5G UE and a data network is called a "PDU session". The term "PDU session" corresponds to the term "PDN connection" in LTE and Advanced LTE. Multiple PDU flows can be configured in one PDU session.

[0008] A PDU flow is also referred to as a "QoS flow". A QoS flow is the finest granularity of QoS processing within a 5G system. User plane traffic within a PDU session with the same NG3 tag value corresponds to a QoS flow. The NG3 tag corresponds to the PDU flow ID mentioned above, and the NG3 tag is also referred to as a QoS flow ID or a flow identification indication (FII).

[0009] Figure 1 The basic architecture of the 5G system is shown. The UE establishes one or more signaling radio bearers (SRBs) and one or more data radio bearers (DRBs) with the gNB. The 5G-CN and the gNB establish a control plane interface and a user plane interface used by the UE. The control plane interface between the 5G-CN and the gNB (i.e., RAN) is called the NG2 interface or NG-c interface, and is used for the transmission of non-access stratum (NAS) information and for the transmission of control information (e.g., NG2 AP information elements) between the 5G-CN and the gNB. The user plane interface between the 5G-CN and the gNB (i.e., RAN) is called the NG3 interface or NG-u interface, and is used for the transmission of packets of one or more PDU flows within a PDU session of the UE.

[0010] Notice, Figure 1 The architecture shown is just one of the 5G architecture options or deployment scenarios (see Appendix J of Non-Patent Document 1 and see Non-Patent Document 2). Figure 1The architecture shown is referred to as "Standalone NR (in NextGen systems)" or "Option 2". In contrast, Figure 2 and Figure 3 Architecture options 3 and 3A referred to as "Non-Standalone NR in EPS" are shown. Figure 2 and Figure 3 In the diagram, the control plane interface is shown as a dashed line, while the user plane interface is shown as a solid line. Architecture options 3 and 3A are dual connectivity (DC) deployments that include E-UTRA as the anchor RAT (or primary RAT or primary RAT) and NR as the secondary RAT. In options 3 and 3A, E-UTRA (LTE eNB) and NR (gNB) are connected to the EPC. In option 3, the NR user plane connection to the EPC goes through the LTE eNB, while in option 3A, the connection goes directly through the user plane interface between the gNB and the EPC.

[0011] Non-patent document 3 proposes that in architecture options 3 and 3A, which are DC architectures where E-UTRA and NR are connected to EPC, NR gNB supports LTE DC functions and procedures. Non-patent document 3 also proposes that in the DC architecture where E-UTRA and NR are connected to EPC, NR gNB applies the LTE QoS framework (i.e., bearer-based QoS) to EPC, LTE eNB, and UE. In addition, non-patent document 3 proposes the following suggestions:

[0012] - In case of adding NR gNB as a secondary node, applying LTEDC procedures (e.g. SeNB addition) to configure the required QoS services (i.e. bearers);

[0013] - Establishment of an E-UTRAN Radio Access Bearer (E-RAB) between the EPC and the NR gNB for the Secondary Cell Group (SCG) bearer option according to LTE;

[0014] - Establishing X2-U between the LTE eNB and the NR gNB for the split bearer option according to LTE; and

[0015] - Establish DRBs between the NR gNB and the UE for use with the SCG bearer option or split bearer option according to LTE.

[0016] Non-patent document 4 proposes that there is a one-to-one mapping (1:1 mapping) between S1-U and the DRB of SCG (i.e., SCG bearer). Non-patent document 4 also proposes to use the QoS attributes of EPC for EPS bearers, so it is necessary to map the QoS parameters used in EPC to the radio bearer parameters used in NR.

[0017] In addition, in the 5G system, system information includes system information that is always broadcast and system information that is not always broadcast. The system information that is always broadcast is called "minimum SI" or "basic SI". On the other hand, the system information that is not always broadcast is called "other SI" or "on-demand SI". The minimum SI needs to be broadcast periodically in the cell. It is assumed that the minimum SI includes at least information for assisting cell selection, information for obtaining on-demand SI, and information for accessing the cell. The term "other SI" indicates various system information that is not broadcast in the minimum SI. Part or all of other SI corresponds to on-demand SI. On-demand SI is sent by the gNB after it is triggered by the UE or the network. In other words, in response to the SI request from the UE, the gNB sends an SI response containing the requested system information to the UE.

[0018] There are several proposals regarding the allocation mechanism of other SI (or SI on demand) (e.g., see non-patent documents 5 to 8). The SI request from the UE can be sent via the first message (Msg1) of the random access procedure (i.e., random access preamble), via the third message (Msg3) of the random access procedure, or via dedicated radio resource control (RRC) signaling after the RRC connection is established. The transmission of the SI response using the gNB can be unicast to the UE that made the request, multicast to a group of UEs including the UE that made the request, or aperiodic broadcast. In the case where the SI response is unicast, the SI response containing other SI (or SI on demand) can be sent via the second message (Msg2) of the random access procedure (i.e., random access response (RAR)), via the fourth message (Msg3) of the random access procedure, or via dedicated radio resource control (RRC) signaling after the RRC connection is established. In the case of groupcast or non-periodic broadcast of SI responses, a paging mechanism may be used and the SI responses containing other SI (or SI on demand) may be broadcast in a paging occasion determined based on an identifier of the UE or UE group (e.g., a paging radio network temporary identifier (P-RNTI)).

[0019] Prior art literature

[0020] Non-patent literature

[0021] [Non-Patent Document 1] 3GPP TR 23.799 V14.0.0 (2016-12) "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on Architecture for Next Generation System (Release 14)", December 2016

[0022] [Non-Patent Document 2] 3GPP TR 38.801 V1.0.0 (2016-12) "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Study on New Radio Access Technology; Radio Access Architecture and Interfaces (Release 14)", December 2016

[0023] [Non-Patent Document 3] 3GPP R2-168400, NTT DOCOMO, INC., "QoS and bearer for DC between LTE and NR", 3GPP TSG-RAN WG2 Meeting#96, Reno, USA, 14-18 November 2016

[0024] [Non-Patent Document 4] 3GPP R2-168686, Nokia, Alcatel-Lucent Shanghai Bell, "EPC-NR PDCP interaction for tight interworking: User Plane aspects", 3GPP TSG-RAN WG2 Meeting#96, Reno, USA, 14-18 November 2016

[0025] [Non-patent document 5] 3GPP R2-166120, China Academy of Telecommunications Technology (CATT), “On-demand system information delivery mechanism”, 3GPP TSG-RAN WG2 Meeting #95bis, Kaohsiung, 10-14 October 2016

[0026] [Non-Patent Document 6] 3GPP R2-166203, Huawei, HiSilicon, “Delivery of “Other SI” in NR”, 3GPP TSG-RAN WG2 Meeting #95bis, Kaohsiung, 10-14 October 2016

[0027] [Non-Patent Document 7] 3GPP R2-166342, ZTE, ZTE Microelectronics, “Consideration on the Other SI delivery in NR”, 3GPP TSG-RAN WG2 Meeting #95bis, Kaohsiung, 10-14 October 2016

[0028] [Non-Patent Document 8] 3GPP R2-166343, ZTE, ZTE Microelectronics, “Consideration on the Other SI delivery in NR”, 3GPP TSG-RAN WG2 Meeting #95bis, Kaohsiung, 10-14 October 2016 Summary of the invention

[0029] Problem that the invention aims to solve

[0030] The inventors have studied the interworking between E-UTRA and NR and found several problems. In the E-UTRA-NR dual connectivity (DC) architecture (i.e., architecture options 3 and 3A) where E-UTRA and NR are connected to EPC, the secondary gNB (SgNB) used as a secondary node supports the above-mentioned additional SI (or SI on demand) allocation. However, it is unclear how the UE knows which additional SI (or SI on demand) is available in the SgNB in ​​E-UTRA-NR DC.

[0031] This issue regarding other SI (or SI on demand) may also occur in other E-UTRA-NR DC architecture options (e.g., architecture options 7 and 7A). Architecture options 7 and 7A are dual connectivity (DC) deployments that include E-UTRA used as the anchor RAT (or primary RAT or main RAT) and NR used as the secondary RAT. In options 7 and 7A, E-UTRA (LTE eNB) and NR (gNB) are connected to 5G-CN. In option 7, the NR user plane connection to 5G-CN passes through the LTE eNB, while in option 7A, the connection passes directly through the user plane interface between the gNB and 5G-CN. Also in options 7 and 7A, in the case where the SgNB supports allocation of other SI (or SI on demand), it is unclear how the UE knows which other SI (or SI on demand) is available in the SgNB.

[0032] In addition, similar problems to those mentioned above regarding other SI (or SI on demand) may also occur in inter-RAT handover from E-UTRA to NR. Specifically, in the case where the UE switches from a source LTE eNB to a target gNB that supports allocation of other SI (or SI on demand), it is unclear how the UE knows which other SI (or SI on demand) is available in the target NR cell.

[0033] Therefore, one of the purposes to be achieved by the embodiments disclosed herein is to provide the following apparatus, method and program, wherein the apparatus, method and program enable notification to a UE of an indication related to on-demand system information, which is on-demand system information available in a cell served by an auxiliary gNB in ​​an inter-RAT dual connection between E-UTRA and NR, or on-demand system information available in a cell served by a target gNB in ​​an inter-RAT handover from E-UTRA to NR. It should be noted that this 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 second radio access network node, i.e., a second RAN node, is used in a wireless communication system. The second RAN node comprises a memory and at least one processor connected to the memory. The at least one processor is configured to send an indication of available on-demand system information available in a cell of the second RAN node to a wireless terminal via a first RAN node. In response to a request from the wireless terminal, the available on-demand system information is sent in the cell of the second RAN node or via the first RAN node.

[0036] In a second aspect, a first radio access network node, i.e., a first RAN node, is used in a wireless communication system. The first RAN node comprises a memory and at least one processor connected to the memory. The at least one processor is configured to: receive an indication of available on-demand system information available in a cell of the second RAN node from a second RAN node; and send the indication to a wireless terminal in the cell of the first RAN node. In response to a request from the wireless terminal, the available on-demand system information is sent in the cell of the second RAN node or via the first RAN node.

[0037] In a third aspect, a wireless terminal is used in a wireless communication system. The wireless terminal comprises at least one wireless transceiver and at least one processor. The at least one wireless transceiver is configured to communicate with a first radio access network node, namely a first RAN node and a second RAN node. The at least one processor is configured to receive an indication of available on-demand system information available in a cell of the second RAN node from the second RAN node via the first RAN node. In response to a request from the wireless terminal, the available on-demand system information is sent in the cell of the second RAN node or via the first RAN node.

[0038] In a fourth aspect, a method for use by a second radio access network node, i.e., a second RAN node, comprises: sending an indication of available on-demand system information available in a cell of the second RAN node to a wireless terminal via a first RAN node. In response to a request from the wireless terminal, the available on-demand system information is sent in the cell of the second RAN node or via the first RAN node.

[0039] In a fifth aspect, a method for use by a first radio access network node, i.e., a first RAN node, comprises: receiving from a second RAN node an indication of available on-demand system information available in a cell of the second RAN node; and sending the indication to a wireless terminal in the cell of the first RAN node. In response to a request from the wireless terminal, the available on-demand system information is sent in the cell of the second RAN node or via the first RAN node.

[0040] In a sixth aspect, a method for a wireless terminal comprises receiving, from a second RAN node via a first radio access network node, i.e., a first RAN node, an indication of available on-demand system information available in a cell of the second RAN node. In response to a request from the wireless terminal, the available on-demand system information is to be sent in the cell of the second RAN node or via the first RAN node.

[0041] In a seventh aspect, a program includes instructions (software codes), wherein when the instructions (software codes) are loaded into a computer, the computer is caused to perform the method according to the fourth aspect, the fifth aspect or the sixth aspect described above.

[0042] Advantageous Effects of the Invention

[0043] According to the above aspects, the following apparatus, method and program can be provided, wherein the apparatus, method and program enable notification of indications related to on-demand system information to the UE, wherein the on-demand system information is on-demand system information available in a cell served by a secondary gNB of inter-RAT dual connectivity between E-UTRA and NR, or on-demand system information available in a cell served by a target gNB of an inter-RAT switching from E-UTRA to NR. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a diagram showing a basic architecture of a 5G system according to the background art;

[0045] Figure 2 is a diagram showing architecture option 3 for dual connectivity of E-UTRA (LTE eNB) and NR (gNB) connected to EPC according to background art;

[0046] Figure 3 is a diagram showing architecture option 3A for dual connectivity of E-UTRA (LTE eNB) and NR (gNB) connected to EPC according to background art;

[0047] Figure 4 is a diagram showing a structural example of a wireless communication network according to various embodiments;

[0048] Figure 5 is a diagram showing another structural example of a wireless communication network according to various embodiments;

[0049] Figure 6 is a diagram showing an example of a process for sending an indication related to available on-demand system information to a UE according to a first embodiment;

[0050] Figure 7 is a diagram showing an example of a process for sending an indication related to available on-demand system information to a UE according to a first embodiment;

[0051] Figure 8 is a diagram showing an example of a process for sending an indication related to available on-demand system information to a UE according to a first embodiment;

[0052] Fig. 9is a sequence diagram showing an example of an SCG establishment procedure according to the second embodiment;

[0053] Fig.10 is a sequence diagram showing an example of an inter-RAT handover procedure according to the third embodiment;

[0054] Fig.11 is a block diagram showing a structural example of an NR gNB according to multiple embodiments; and

[0055] Fig.12 is a block diagram showing a structural example of a UE according to various embodiments. DETAILED DESCRIPTION

[0056] The specific embodiments are described in detail below with reference to the accompanying drawings. In the entire drawings, the same reference numerals are used to represent the same or corresponding elements, and for the sake of clarity, repeated descriptions will be omitted as needed.

[0057] Each embodiment described below can be used alone, or two or more of 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.

[0058] The following description of the embodiments mainly focuses on the DC architecture of E-UTRA and NR connected to EPC. However, these embodiments can be applied to other wireless communication systems that support the DC architecture of different RATs using different QoS frameworks connected to a common core network.

[0059] First embodiment

[0060] Figure 4 An example of a structure of a wireless communication network according to a plurality of embodiments including this embodiment is shown. Figure 4 In the example shown, the wireless communication network includes LTE eNB 1, NR gNB 2, UE 3 and EPC 4. Figure 4The wireless communication network shown supports dual connectivity (DC) and also supports one or both of the above-mentioned options 3 and 3A. Options 3 and 3A support dual connectivity involving E-UTRA and NR as anchor RAT (or primary RAT) and secondary RAT, respectively. In options 3 and 3A, both E-UTRA (i.e., LTE eNB1) and NR (i.e., gNB 2) are connected to EPC 4. In option 3, the NR user plane connection to EPC 4 passes through LTE eNB 1, so the user packets of UE3 are transmitted via the inter-base station interface 403 and via the interface 401 between eNB 1 and EPC. In contrast, in option 3A, the NR user plane connection to EPC 4 passes directly through the user plane interface 404 between gNB 2 and EPC 4.

[0061] UE 3 has the ability to communicate simultaneously with eNB 1 associated with the primary RAT (E-UTRA) and gNB 2 associated with the secondary RAT (NR). In other words, UE 3 has the ability to aggregate the cell of eNB 1 associated with the primary RAT (E-UTRA) with the cell of gNB 2 associated with the secondary RAT (NR). In addition, in other words, UE 3 has the ability to be configured with the cell of eNB 1 associated with the primary RAT (E-UTRA) and the cell of gNB 2 associated with the secondary RAT (NR). In architecture options 3 and 3A, the air interface 402 between eNB 1 and UE 3 provides a control plane connection and a user plane connection. At the same time, the air interface 405 between gNB 2 and UE 3 includes at least a user plane connection, but does not need to include a control plane connection. In the DC architecture where E-UTRA and NR are connected to EPC 4, the master eNB (MeNB) 1 provides one or more E-UTRA MCG cells to UE 3, while the secondary gNB (SgNB) 2 provides one or more NR SCG cells to UE 3.

[0062] The EPC 4 includes a plurality of core network nodes including an MME 5 and an S-GW 6. The MME 5 is a control plane node, and the S-GW 6 is a user plane node. The MME 5 performs mobility management and bearer management of UEs attached to the core network (i.e., UEs in the EMM-REGISTERED state). Mobility management is used to track the current location of each UE, and includes maintaining a mobility management context (MM context) related to each UE. Bearer management includes controlling the establishment of an EPS bearer, and maintaining an EPS bearer context related to each UE, wherein the EPS bearer is used to enable each UE to communicate with an external network (packet data network (PDN)) via the E-UTRAN including the eNB 1 and via the EPC 4. The S-GW 6 is a gateway to the E-UTRAN and is connected to one or both of the eNB 1 and the gNB 2 via an S1-U interface.

[0063] A wireless communication network according to multiple embodiments including the present embodiment may not support architecture options 3 and 3A. Instead, the wireless communication network may support other E-UTRA-NR DC architecture options (e.g., architecture options 7 and 7A). Additionally or alternatively, the wireless communication network may support inter-RAT switching from E-UTRA to NR.

[0064] Figure 5 Another structural example of a wireless communication network according to multiple embodiments including the present embodiment is shown. In one example, the wireless communication network may provide E-UTRA-NR DC architecture option 7 or 7A. In options 7 and 7A, E-UTRA (LTE eNB 1) and NR (gNB 2) are connected to 5G-CN 7. In option 7, the NR user plane connection to 5G-CN 7 is through LTE eNB 1, and therefore the user packets of UE 3 are transmitted via the inter-base station interface 403 and via the interface 501 between eNB 1 and 5G-CN 7. In contrast, in option 7A, the NR user plane connection to 5G-CN 7 is directly through the user plane interface 502 between gNB 2 and 5G-CN 7.

[0065] Additionally or alternatively, Figure 5 The wireless communication network shown can support inter-RAT switching from the E-UTRA cell 11 of LTE eNB 1 to the NR cell 21 of NR gNB 2.

[0066] The following describes a procedure for notifying UE 3 of an indication related to on-demand system information, which is on-demand system information available in the cell 21 served by gNB 2 related to inter-RAT dual connectivity between E-UTRA and NR and inter-RAT handover from E-UTRA to NR. As already explained above, on-demand system information (on-demand SI) corresponds to part or all of other SI.

[0067] Figure 6 6 is a diagram illustrating a process 600, which is an example of a process for sending an indication of on-demand system information available in a cell of SgNB 2 to a UE. gNB 2 operates to send an indication of on-demand system information available in cell 21 of gNB 2 to UE 3 via eNB 1. The indication may be an indication list or indication bitmap indicating a number (e.g., SIB number), an identifier (e.g., SI group identifier), a type (e.g., SIB type), or a category (e.g., SI category) of available on-demand system information. Additionally or alternatively, the indication may be scheduling information related to the available on-demand system information, or information related to radio resources to be used to request each on-demand system information item. Furthermore, the indication may be a combination of such information. For example, the indication may include both scheduling information for on-demand system information that is already being sent (or is to be sent) as system information, and an indication list (or indication bitmap) for on-demand system information that is not being sent as system information. In response to a request from the UE or in response to being triggered by the network (e.g., gNB), the on-demand system information will be sent in the cell 21 of gNB 2. UE 3 can use this indication to determine whether the on-demand system information (i.e., at least a portion of other SI) desired (or wanted) by UE 3 is available in the cell 21 of gNB 2.

[0068] Specifically, in step 601, gNB 2 sends an indication of on-demand system information available in cell 21 of gNB 2 to eNB 1. For example, gNB 2 may send a control message including an indication of available on-demand system information to eNB 1 via an inter-base station interface (e.g., an Xn interface) between eNB 1 and gNB2.

[0069] In step 602, eNB 1 receives an indication of available on-demand system information from gNB 2, and sends the received indication to UE 3 in cell 11 of eNB 1. For example, eNB 1 may send an RRC message including the received indication to UE 3 via an RRC connection between eNB 1 and UE 3 in cell 11 of eNB 1 (i.e., a primary cell (PCell) or a source cell).

[0070] Figure 6The procedure shown enables a UE 3 to receive an indication of on-demand system information available in a cell 21 of a gNB 2 of a second RAT (i.e. NR) from an eNB 1 of a first RAT (i.e. E-UTRA).

[0071] replace Figure 6 The process shown, through Figure 7 or Figure 8 As shown in the process, eNB 1 can receive an indication of on-demand system information available in cell 21 of gNB 2, and then eNB 1 can send the indication to UE 3.

[0072] Figure 7 An example is shown in which eNB 1 receives an indication of on-demand system information available in cell 21 of gNB 2 during a procedure for establishing a direct interface (e.g., Xn) with gNB 2. In step 701, eNB 1 sends a request for establishment of the Xn interface (e.g., an Xn Setup Request message) to gNB 2. In step 702, gNB 2 sends a response to the request for establishment of the Xn interface (e.g., an Xn Setup Request Response message) to eNB 1. At this point, gNB 2 sends an indication of on-demand system information available in cell 21 to eNB 1. In addition, in step 703, in the event that gNB 2 changes its configuration (e.g., the availability of on-demand system information), gNB 2 may send an updated indication to eNB 1 via a message for notifying eNB 1 of the change (e.g., a gNB Configuration Update message).

[0073] Figure 8The following example is shown: in response to a request from UE 3, eNB 1 requests gNB 2 to send an indication of on-demand system information available in cell 21. In step 801, UE 3 sends a message (e.g., an on-demand SI information request message) to eNB 1 for requesting gNB 2 to send an indication of on-demand system information available in cell 21. The message may be an explicit message or may be an implicit message (e.g., a measurement report of cell 21). In step 802, eNB 1 sends a UE association message (e.g., an on-demand SI status request message) for requesting the indication from gNB 2. In step 803, gNB 2 sends a message (e.g., an on-demand SI status response message) including the indication to eNB 1 in response to the UE association message of step 802. In step 804, eNB 1 sends the indication to UE 3 via dedicated signaling (e.g., an RRC connection reconfiguration message including an indication of available on-demand SI). The eNB 1 may send the indication as system information (e.g., a class X system information block including an indication of available on-demand SI in a neighboring NR cell) in cell 11 (step 805). These procedures enable the eNB 1 and the UE 3 to receive an indication of the on-demand system information available in the cell 21 of the gNB 2. The indication of the on-demand system information available in the cell 21 may be sent from the gNB 2 to the eNB 1 as an information element of the RRC layer (e.g., an RRC container), or may be sent as an information element of the Xn protocol layer (e.g., an Xn information element).

[0074] Second embodiment

[0075] The configuration example of the wireless communication network according to the present embodiment is Figure 4 or Figure 5 The structural examples shown are the same. This embodiment provides a specific example of a process for sending an indication of on-demand system information available in a cell 21 of a secondary gNB (SgNB) 2 from the SgNB 2 to a UE 3 via a master eNB (MeNB) 1 in an inter-RAT dual connection using E-UTRA as the primary RAT and NR as the secondary RAT.

[0076] In this embodiment, MeNB 1 and SgNB 2 may support E-UTRA-NR DC architecture option 3 or 3A. That is, MeNB 1 and SgNB 2 may be connected to EPC 4. Optionally, MeNB 1 and SgNB 2 may support E-UTRA-NR DC architecture option 7 or 7A. That is, MeNB 1 and SgNB 2 may be connected to 5G-CN 7.

[0077] According to this embodiment, SgNB 2 is configured to send a first radio resource control (RRC) message including the configuration of NR DRB to UE 3 via MeNB 1 during the process for configuring NR DRB used for E-UTRA-NR DC. The first RRC message also includes an indication of the on-demand system information available in the cell of SgNB 2. The indication at least indicates the on-demand system information available in the cell of SgNB 2 for configuring the NR DRB of UE 3. MeNB 1 is configured to forward the first RRC message received from SgNB 2 to UE 3 in the cell (e.g., PCell) of MeNB 1. This enables UE 3 to know which on-demand system information (i.e., at least a portion of other SI) is available in the cell of SgNB 2 during the process for configuring NR DRB used for E-UTRA-NR DC.

[0078] Fig. 9 Processing 900 is shown, which is an example of an SCG establishment procedure for configuring UE 3 using the NR data radio bearer (NRDRB) of the cell of SgNB 2. Fig. 9 The process shown basically follows the SeNB addition process in LTE DC. Fig. 9 In the process shown, UE 3 receives an indication of on-demand system information available in the cell of SgNB 2 when performing the SCG establishment process (i.e., the process for configuring NR DRB).

[0079] In step 901, MeNB 1 sends an SgNB add request message to SgNB 2. The SgNB add request message requests SgNB 2 to configure the radio bearers (i.e., SCG DRBs or separated DRBs) used for DC using E-UTRA and NR as the primary RAT and secondary RAT, respectively. Specifically, the SgNB add request message includes the "SgNB security key (used for SCG bearer)" information element (IE), the "List of E-RABs to be added" IE, and the "MeNB to SgNB container" IE. The "List of E-RABs to be added" IE includes the E-RAB ID and E-RAB-level QoS parameters of each E-RAB required by MeNB 1 to be established. The "MeNB to SgNB container" IE includes the RRC: SCG-ConfigInfo message. The RRC: SCG-ConfigInfo message is used by MeNB to request SgNB to establish, modify or release SCG. The SCG-ConfigInfo message includes, for example, EPS bearer identifier, DRB identifier, and DRB type. The security policy (e.g., security algorithm) used in the cell (e.g., radio link, AS layer) of the secondary RAT (NR) may be different from the security policy used in the cell (e.g., radio link, AS layer) of the primary RAT (E-UTRA). In this case, the SgNB security key IE may include information about the security policy used in the cell of the secondary RAT (NR). In addition, the SgNB 2 may include the security policy related information in the RRC: SCG-Config message to be sent to the UE 3.

[0080] In step 902, SgNB 2 sends an SgNB add request confirmation message to MeNB 1. The SgNB add request confirmation message is a response message to the SgNB add request message. Specifically, the SgNB add request confirmation message includes the "List of E-RABs accepted for addition" IE and the "SgNB to MeNB container" IE. The "SgNB to MeNB container" IE includes an RRC: SCG-Config message. The RRC: SCG-Config message corresponds to the "first RRC message" mentioned above. The RRC: SCG-Config message is used to transmit the radio resource configuration of the SCG DRB (or separated DRB) created by SgNB2. The RRC: SCG-Config message also includes an indication of the on-demand system information available in the cell of gNB 2 where the NR DRB of UE3 is to be configured. The RRC: SCG-Config message also includes the minimum SI of the cell of SgNB2.

[0081] In step 903, MeNB 1 sends an RRC connection reconfiguration message to UE 3 in response to receiving an SgNB add request confirmation message from SgNB 2. The RRC connection reconfiguration message includes an RRC:SCG-Config message sent from SgNB 2 to MeNB 1 via the SgNB add request confirmation message. The AS layer of the primary RAT (i.e., E-UTRA (LTE)) in UE 3 receives the RRC connection reconfiguration message in the E-UTRA cell (i.e., primary cell (PCell)) of MeNB 1. The AS layer of the secondary RAT (i.e., NR) in UE 3 configures the SCG DRB or separated DRB in the NR cell of SgNB 2 according to the RRC:SCG-Config message.

[0082] UE 3 (ie, NR AS layer) further checks the "indication of available on-demand SI" taken from the RRC:SCG-Config message, and determines whether other SI desired (or wanted) by UE 3 is available in the cell of SgNB 2. Fig. 9 In the example shown, UE 3 (i.e., E-UTRA AS layer) sends an RRC connection reconfiguration complete message including an SI request in the E-UTRA cell (i.e., primary cell (PCell)) of MeNB 1 (step 904). The SI request is a request for sending on-demand system information from SgNB 2. MeNB 1 forwards the SI request received from UE 3 to SgNB 2. MeNB 1 may send an SgNB reconfiguration complete message including the SI request to SgNB 2 (step 905).

[0083] Fig. 9 The sending of the SI request in steps 904 and 905 is an example. After receiving the RRC connection reconfiguration message (step 903), UE 3 (i.e., the NR AS layer) starts a random access procedure in the cell of SgNB 2 (e.g., the primary secondary cell (PSCell)) to synchronize with the cell of SgNB 2. In some implementations, UE 3 (i.e., the NR AS layer) may send an SI request during the random access procedure. For example, UE 3 may send an SI request via the first message (Msg1) (i.e., the random access preamble) of the random access procedure. In this case, UE 3 may select a random access preamble associated with the number or identifier of the on-demand SI (other SI) desired by UE 3 from the preamble pool, and then send the selected preamble. Optionally, UE 3 may send an SI request via the third message (Msg3) of the random access procedure.

[0084] Optionally, in some implementations, after completing the configuration of the SCG DRB (or separate DRB), UE 3 (i.e., NR AS layer) may send an SI request in the cell (e.g., PSCell) of SgNB 2 via RRC signaling or via a media access control (MAC) control element (CE).

[0085] Optionally, in some implementations, after completing the configuration of the SCG DRB (or separate DRB), UE 3 (i.e., E-UTRAAS layer) can send an SI request to MeNB 1 via RRC signaling in the cell (e.g., PCell) of MeNB 1, and MeNB1 can forward the received SI request to SgNB 2.

[0086] Third embodiment

[0087] The configuration example of the wireless communication network according to the present embodiment is Figure 5 The structural example shown is the same. This embodiment provides a specific example of the following process, which is used to send an indication of on-demand system information available in the cell of the target gNB 2 from the target gNB 2 to the UE 3 via the source eNB 1 in an inter-RAT handover from E-UTRA to NR.

[0088] According to this embodiment, the target gNB 2 is configured to send an RRC message including NR radio resource configuration to UE 3 via the source eNB 1 during the inter-RAT handover process from E-UTRA to NR. The RRC message also includes an indication of the on-demand system information available in the cell of the target gNB 2. The indication at least indicates the on-demand system information available in the cell of the target gNB 2. The source eNB 1 is configured to forward the RRC message received from the target gNB 2 to the UE 3 in the cell of the source eNB1. This enables UE 3 to know which on-demand system information (i.e., at least part of other SI) is available in the cell of the target gNB 2 during the handover process to the target gNB 2.

[0089] Fig.10 1 is a sequence diagram showing a process 1000 as an example of an inter-RAT handover procedure according to the present embodiment. In step 1001, the source LTE eNB 1 sends an NR handover request message to the target gNB 2 on the direct inter-base station interface 403 (e.g., Xn interface or X3 interface). The NR handover request message in step 1001 may include a handover type information element (IE) indicating a handover from LTE to NR. For example, the handover type IE is set to "LTE to NR".

[0090] In step 1002, the target gNB 2 creates a UE context and allocates resources based on the NR handover request message. Then, the target gNB 2 sends an NR handover request confirmation message to the source eNB 1. The NR handover request confirmation message is a response message to the NR handover request message. The NR handover request confirmation message includes the radio resource configuration of the target NR cell 21 created by the target gNB 2. The radio resource configuration is sent to the UE 3 via the source eNB 1. The NR handover request confirmation message in step 1002 also includes an indication of the on-demand system information available in the cell of the target gNB 2.

[0091] In step 1003, the source eNB 1 sends an RRC message to the UE 3, wherein the RRC message includes a handover command message including the radio resource configuration information created by the target gNB 2. The RRC message may be, for example, a mobility command message from the Evolved Universal Terrestrial Radio Access (EUTRA), or may be an RRC connection reconfiguration message. The source eNB 1 may include the radio resource configuration information created by the target gNB 2 in the "MobilityControlInfoNR" IE within the RRC connection reconfiguration message. In addition, the source eNB 1 includes the "Indication of Available On-Demand SI" received from the target gNB 2 in the RRC message to be sent to the UE 3. The "Indication of Available On-Demand SI" may be included in the "MobilityControlInfoNR" IE within the RRC connection reconfiguration message.

[0092] In step 1004, UE 3 moves to the target RAN (i.e., NR) in response to receiving the RRC message containing the handover command message, and performs handover according to the radio resource configuration information provided by the handover command message. Thus, UE 3 establishes a radio connection with the target gNB 2.

[0093] In step 1005, UE 3 sends a handover confirmation for NR message to the target gNB 2 after it successfully synchronizes with the target NR cell 21. The message in step 1005 can be a (NR)RRC connection reconfiguration complete message.

[0094] UE 3 (i.e., NR AS layer) checks the "indication of available on-demand SI" and determines whether other SI expected (or desired) by UE 3 is available in the cell of target gNB 2. UE 3 may include the SI request in the RRC message (e.g., (NR)RRC connection reconfiguration complete message) of step 1005. The SI request is a request for sending on-demand system information from target gNB 2.

[0095] Fig.10The sending of the SI request in step 1005 is an example. UE 3 (i.e., the NR AS layer) may send the SI request in the random access procedure of step 1004. UE 3 may, for example, send the SI request via the first message (Msg1) (i.e., the random access preamble) in the random access procedure. In this case, UE 3 may select a random access preamble associated with the number or identifier of the on-demand SI (other SI) desired by UE 3 from the preamble pool, and then send the selected preamble. Optionally, UE 3 may send the SI request in the third message (Msg3) of the random access procedure.

[0096] The following provides a structural example of LTE eNB 1, NR gNB 2 and UE 3 according to the above embodiment. Fig.11 1 is a block diagram showing a structural example of NR gNB 2 according to the above embodiment. The structure of LTE eNB 1 can be similar to Fig.11 The structure shown is the same. Fig.11 , NR gNB 2 includes a radio frequency transceiver 1101, a network interface 1103, a processor 1104, and a memory 1105. The RF transceiver 1101 performs analog RF signal processing to communicate with NG UEs including UE 3. The RF transceiver 1101 may include multiple transceivers. The RF transceiver 1101 is connected to an antenna array 1102 and a processor 1104. The RF transceiver 1101 receives modulation symbol data from the processor 1104, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 1102. In addition, the RF transceiver 1101 generates a baseband receive signal based on the receive RF signal received by the antenna array 1102, and supplies the baseband receive signal to the processor 1104. The RF transceiver 1101 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, multiple phase shifters and multiple power amplifiers.

[0097] The network interface 1103 is used to communicate with network nodes, such as the LTE eNB 1, the MME 5, and the S-GW 6. The network interface 1103 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0098] The processor 1104 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for wireless communication. The processor 1104 may include multiple processors. The processor 1104 may include, for example, a modem processor (e.g., a digital signal processor (DSP)) for performing digital baseband signal processing and a protocol stack processor (e.g., a central processing unit (CPU) or a microprocessing unit (MPU)) for performing control plane processing. The processor 1104 may include a digital beamformer module for beamforming. The digital beamformer module may include a multiple-input multiple-output (MIMO) encoder and a precoder.

[0099] The memory 1105 is composed of a combination of volatile memory and non-volatile memory. 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 1105 may include a memory configured separately from the processor 1104. In this case, the processor 1104 may access the memory 1105 via the network interface 1103 or an I / O interface (not shown).

[0100] The memory 1105 may store one or more software modules (computer programs) 1106 including instructions and data for performing the processing using the gNB 2 described in the above embodiments. In some implementations, the processor 1104 may be configured to load the software module 1106 from the memory 1105 and execute the loaded software module, thereby performing the processing of the gNB 2 described in the above embodiments.

[0101] Fig.12 1 is a block diagram showing a structural example of UE 3. A radio frequency (RF) transceiver 1201 performs analog RF signal processing to communicate with eNB 1 and gNB 2. The RF transceiver 1201 may include a plurality of transceivers. The analog RF signal processing performed by the RF transceiver 1201 includes up-conversion, down-conversion, and amplification. The RF transceiver 1201 is connected to an antenna array 1202 and a baseband processor 1203. The RF transceiver 1201 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1203, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 1202. In addition, the RF transceiver 1201 generates a baseband receive signal based on the receive RF signal received by the antenna array 1202, and supplies the baseband receive signal to the baseband processor 1203. The RF transceiver 1201 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.

[0102] The baseband processor 1203 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) generation / decomposition of transmission format (i.e., transmission frame), (d) channel coding / decoding, (e) modulation (i.e., symbol mapping) / demodulation, and (f) generation of OFDM symbol data (i.e., baseband OFDM signal) using inverse fast Fourier transform (IFFT). Meanwhile, control plane processing includes layer 1 communication management (e.g., transmission power control), layer 2 communication management (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and layer 3 communication management (e.g., signaling related to attachment, mobility, and call management).

[0103] The digital baseband signal processing performed by the baseband processor 1203 may include, for example, signal processing of a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a MAC layer, and a PHY layer. In addition, the control plane processing performed by the baseband processor 1203 may include processing of a non-access stratum (NAS) protocol, an RRC protocol, and a MAC CE.

[0104] The baseband processor 1203 may perform MIMO encoding and precoding for beamforming.

[0105] The baseband processor 1203 may include a modem processor (e.g., DSP) for performing digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) for performing control plane processing. In this case, the protocol stack processor for performing control plane processing may be integrated with the application processor 1204 described below.

[0106] The application processor 1204 is also referred to as a CPU, an MPU, a microprocessor, or a processor core. The application processor 1204 may include a plurality of processors (processor cores). The application processor 1204 loads a system software program (operating system (OS)) and various application programs (e.g., a call application, a WEB browser, a mail program, a camera operation application, and a music player application) from the memory 1206 or from other memories (not shown), and executes these programs, thereby providing various functions of the UE 3.

[0107] In some implementations, such as Fig.12 As shown by the dashed line (1205) in FIG. 1 , the baseband processor 1203 and the application processor 1204 may be integrated on a single chip. In other words, the baseband processor 1203 and the application processor 1204 may be implemented on a single system on chip (SoC) device 1205. The SoC device may be referred to as a system large scale integration (LSI) or a chipset.

[0108] The memory 1206 is a volatile memory, a non-volatile memory, or a combination thereof. The memory 1206 may include a plurality of memory devices that are physically independent of each other. The volatile memory is, for example, an SRAM, a DRAM, or any 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 1206 may include, for example, an external memory device accessible from the baseband processor 1203, the application processor 1204, and the SoC 1205. The memory 1206 may include an internal memory device integrated in the baseband processor 1203, the application processor 1204, or the SoC 1205. In addition, the memory 1206 may include a memory in a universal integrated circuit card (UICC).

[0109] The memory 1206 may store one or more software modules (computer programs) 1207 including instructions and data for performing the processing using the UE 3 described in the above embodiments. In some implementations, the baseband processor 1203 or the application processor 1204 may load these software modules 1207 from the memory 1206 and execute the loaded software modules, thereby performing the processing of the UE 3 described in the above embodiments with reference to the drawings.

[0110] As mentioned above Fig.11 and Fig.12 As described, the processors included in the eNB 1, gNB 2 and UE 3 according to the above-mentioned embodiment execute one or more programs including instructions for causing the computer to perform the algorithm described with reference to the accompanying drawings. Any type of non-transitory computer-readable medium can be used to store these programs and provide these programs to the computer. Non-transitory computer-readable media include any type of tangible storage media. Examples of non-transitory computer-readable media include: magnetic storage media (such as floppy disks, tapes, hard disk drives, etc.), optical magnetic storage media (for example, 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), etc.). Any type of temporary computer-readable medium can be used to provide these programs to the computer. Examples of temporary computer-readable media include electrical signals, optical signals, and electromagnetic waves. Temporary computer-readable media can provide programs to the computer via wired communication lines (for example, wires and optical fibers) or wireless communication lines.

[0111] Other examples

[0112] The above embodiment describes an example of using an SgNB addition procedure that follows the SeNB addition procedure. In the above embodiment, instead of the SgNB addition procedure, an SgNB modification procedure that follows the SeNB modification procedure may be used. For example, instead of the SgNB addition request message (e.g., Figure 6 As shown in step 601), MeNB1 can send an SgNB modification request message to SgNB 2.

[0113] MeNB 1 may perform UE capability coordination between MeNB 1 and SgNB 2 before sending a radio bearer setup request (e.g., an SgNB add request message or an SgNB modify request message) to SgNB 2. For example, MeNB 1 may send a UE capability coordination request message to SgNB 2 and receive a UE capability coordination response message from SgNB 2. In this coordination, MeNB 1 and SgNB 2 may share (or negotiate) only fixed UE capabilities (e.g., capabilities that do not substantially change when data is being sent or received in DC, or hard separation capabilities), such as RF capabilities (e.g., band combining, measurement capabilities), etc. MeNB 1 and SgNB 2 may also negotiate static UE capabilities (e.g., capabilities that do not dynamically change during DC, or capabilities that are dynamically shared), such as capabilities related to UE category specifications (e.g., soft buffer / soft channel bits). Optionally, MeNB 1 and SgNB 2 may share static UE capabilities in the step of exchanging SeNB add request / confirmation messages (or SeNB modify request / confirmation messages).

[0114] The information elements included in the messages described in the above embodiments (e.g., SgNB add request message, SgNB add request confirmation message, RRC connection reconfiguration message, RRC connection reconfiguration complete message, SgNB reconfiguration complete message, NR handover request message, NR handover request confirmation message) are not limited to the above information elements. For example, for the purpose of DC between LTE eNB 1 and NRgNB 2, or for the purpose of switching from E-UTRA to NR, the information elements contained in the above messages may be communicated and negotiated in a direction different from the direction described in the above embodiments or between nodes different from the nodes described in the above embodiments. As a more specific example, at least some of the information elements included in the SgNB add request message may be included in the SgNB add request confirmation message. Additionally or optionally, at least a portion of the information elements included in the SgNB add request message may be included in an S1AP message (e.g., S1AP: E-RAB setup request message) sent from EPC 4 (i.e., MME 5) to LTE eNB 1. Nodes related to DC between LTE eNB 1 and NR gNB 2 may be allowed to share information required for DC.

[0115] The operations and processing of UE 3, base stations (LTE eNB 1 and NR gNB 2) and core network (EPC4 and 5G-CN7) described in the above embodiments can also be applied to intra-NR dual connectivity (DC) and inter-gNB switching. For example, it is possible that the availability of on-demand system information may be different even between adjacent cells of one NR system. Therefore, the secondary gNB or target gNB can send an indication of the on-demand system information available in one or more of its NR cells to UE3 via the primary gNB or source gNB. This enables UE 3 to know in advance which on-demand system information is available (or which on-demand system information is supported) in the secondary cell or target cell when initiating DC or switching. Thus, UE 3 can obtain the required information immediately after completing the configuration of the SCG used for DC or immediately after completing the switching.

[0116] The LTE eNB 1 and NR gNB 2 described in the above embodiments can be implemented based on the concept of cloud radio access network (C-RAN). C-RAN is also called centralized RAN. In this case, the processing and operations performed by the LTE eNB 1 and gNB 2 described in the above embodiments can be provided by a digital unit (DU) included in the C-RAN architecture, or by a combination of a DU and a radio unit (RU). DU is also called a baseband unit (BBU) or a central unit (CU). RU is also called a remote radio head (RRH), a remote radio equipment (RRE), a distributed unit (DU) or a transmit receive point (TRP). That is, the processing and operations performed by the LTE eNB 2 and gNB 3 described in the above embodiments can be provided by one or more wireless stations (or RAN nodes).

[0117] In addition, the above-described embodiments are merely examples of application of the technical ideas obtained by the present inventors. These technical ideas are not limited to the above-described embodiments, and various modifications can be made.

[0118] For example, all or part of the above-described embodiments may be described as, but not limited to, the following supplementary descriptions.

[0119] (Supplementary Note 1)

[0120] A second radio access network node, i.e., a second RAN node, is used in a wireless communication system, wherein the second RAN node includes:

[0121] Memory; and

[0122] at least one processor connected to the memory and configured to send an indication of available on-demand system information that can be utilized in the cell of the second RAN node to the wireless terminal via the first RAN node,

[0123] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0124] (Supplementary Note 2)

[0125] The second RAN node according to Supplementary Note 1, wherein:

[0126] The second RAN node is associated with a second radio access technology, i.e. a second RAT,

[0127] The at least one processor is configured to send a first radio resource control message, i.e., a first RRC message, to the wireless terminal via the first RAN node associated with a first RAT, the first RRC message including a configuration of a radio bearer of the second RAT for dual connectivity using the first RAT as a primary RAT and the second RAT as a secondary RAT, and

[0128] The indication is included in the first RRC message.

[0129] (Supplementary Note 3)

[0130] The second RAN node according to Supplementary Note 1, wherein:

[0131] The second RAN node is associated with a second radio access technology, i.e. a second RAT,

[0132] The at least one processor is configured to send a second RRC message to the wireless terminal via the first RAN node associated with a first RAT, the second RRC message including a radio resource configuration of the second RAT for inter-RAT handover of the wireless terminal from the first RAT to the second RAT, and

[0133] The indication is included in the second RRC message.

[0134] (Supplementary Note 4)

[0135] The second RAN node according to any one of Supplementary Notes 1 to 3, wherein the indication comprises an indication list or an indication bitmap indicating numbers or identifiers of the available on-demand system information.

[0136] (Supplementary Note 5)

[0137] A first radio access network node, namely a first RAN node, is used in a wireless communication system, wherein the first RAN node includes:

[0138] Memory; and

[0139] at least one processor connected to the memory and configured to:

[0140] receiving, from a second RAN node, an indication of available on-demand system information that can be utilized in a cell of the second RAN node; and

[0141] sending the indication to a wireless terminal in a cell of the first RAN node,

[0142] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0143] (Supplementary Note 6)

[0144] The first RAN node according to Supplementary Note 5, wherein:

[0145] The first RAN node is associated with a first radio access technology, i.e., a first RAT,

[0146] The at least one processor is configured to: receive a first radio resource control message (i.e., a first RRC message) from the second RAN node associated with a second RAT, the first RRC message including a configuration of a radio bearer of the second RAT for dual connectivity using the first RAT as a primary RAT and the second RAT as a secondary RAT; and forward the first RRC message to the wireless terminal in a cell of the first RAN node, and

[0147] The indication is included in the first RRC message.

[0148] (Supplementary Note 7)

[0149] The first RAN node according to Supplementary Note 6, wherein the at least one processor is configured to:

[0150] During a process for configuring the radio bearer used for the dual connectivity, receiving a second RRC message sent by the wireless terminal in response to the first RRC message; and

[0151] A request for sending the on-demand system information is retrieved from the second RRC message and the request is forwarded to the second RAN node.

[0152] (Supplementary Note 8)

[0153] The first RAN node according to Supplementary Note 5, wherein:

[0154] The first RAN node is associated with a first radio access technology, i.e., a first RAT,

[0155] The at least one processor is configured to: receive a third RRC message from the second RAN node associated with a second RAT, the third RRC message including a radio resource configuration of the second RAT for inter-RAT handover of the wireless terminal from the first RAT to the second RAT; and forward the third RRC message to the wireless terminal in a cell of the first RAN node, and

[0156] The indication is included in the third RRC message.

[0157] (Supplementary Note 9)

[0158] The first RAN node according to any one of Supplementary Notes 5 to 8, wherein the indication comprises an indication list or an indication bitmap indicating numbers or identifiers of the available on-demand system information.

[0159] (Supplementary Note 10)

[0160] A wireless terminal, used in a wireless communication system, comprising:

[0161] at least one wireless transceiver configured to communicate with a first radio access network node, namely a first RAN node and a second RAN node; and

[0162] at least one processor configured to receive, from the second RAN node via the first RAN node, an indication of available on-demand system information that can be utilized in a cell of the second RAN node,

[0163] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0164] (Supplementary Note 11)

[0165] The wireless terminal according to Supplementary Note 10, wherein:

[0166] The at least one processor is configured to receive, via the first RAN node associated with a first radio access technology (first RAT), from the second RAN node associated with a second RAT, the first RRC message including configuration of radio bearers of the second RAT for dual connectivity using the first RAT as a primary RAT and the second RAT as a secondary RAT, and

[0167] The indication is included in the first RRC message.

[0168] (Supplementary Note 12)

[0169] The wireless terminal according to Supplementary Note 11, wherein the at least one processor is configured to send a second RRC message in response to the first RRC message during a process for configuring the radio bearer used for the dual connectivity,

[0170] The second RRC message includes a request for sending the available on-demand system information using the second RAN node.

[0171] (Supplementary Note 13)

[0172] The wireless terminal according to Supplementary Note 11 or 12, wherein the at least one processor is configured to, after receiving the first RRC message, send a request for sending the available on-demand system information during a random access procedure for synchronization with a cell of the second RAN node.

[0173] (Supplementary Note 14)

[0174] A wireless terminal according to Supplementary Note 11 or 12, wherein the at least one processor is configured to, after configuring the radio bearer of the second RAT used for the dual connection, send a request for sending the available on-demand system information in the cell of the second RAN node via RRC signaling or via a media access control control element, i.e., MAC CE.

[0175] (Supplementary Note 15)

[0176] The wireless terminal according to Supplementary Note 10, wherein:

[0177] The at least one processor is configured to receive, via the first RAN node associated with a first radio access technology (i.e., a first RAT), a third radio resource control message (i.e., a third RRC message) from the second RAN node associated with a second RAT, the third RRC message including a radio resource configuration of the second RAT for inter-RAT handover of the wireless terminal from the first RAT to the second RAT, and

[0178] The indication is included in the third RRC message.

[0179] (Supplementary Note 16)

[0180] The wireless terminal according to any one of Supplementary Notes 10 to 15, wherein the indication comprises an indication list or an indication bitmap indicating numbers or identifiers of the available on-demand system information.

[0181] (Supplementary Note 17)

[0182] A method used by a second radio access network node, i.e., a second RAN node, the second RAN node being used in a wireless communication system, the method comprising:

[0183] sending an indication of available on-demand system information that can be utilized in the cell of the second RAN node to the wireless terminal via the first RAN node,

[0184] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0185] (Supplementary Note 18)

[0186] A method used by a first radio access network node, i.e., a first RAN node, the first RAN node being used in a wireless communication system, the method comprising:

[0187] receiving, from a second RAN node, an indication of available on-demand system information that can be utilized in a cell of the second RAN node; and

[0188] sending the indication to a wireless terminal in a cell of the first RAN node,

[0189] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0190] (Supplementary Note 19)

[0191] A method used by a wireless terminal, wherein the wireless terminal is used in a wireless communication system, the method comprising:

[0192] receiving, via a first radio access network node, i.e. a first RAN node, from a second RAN node an indication of available on-demand system information that can be utilized in a cell of the second RAN node,

[0193] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0194] (Supplementary Note 20)

[0195] A non-transitory computer-readable medium storing a program for causing a computer to perform a method used by a second radio access network node, i.e., a second RAN node, the second RAN node being used in a wireless communication system, wherein the method comprises:

[0196] sending an indication of available on-demand system information that can be utilized in the cell of the second RAN node to the wireless terminal via the first RAN node,

[0197] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0198] (Supplementary Note 21)

[0199] A non-transitory computer-readable medium storing a program for causing a computer to perform a method used by a first radio access network node, i.e., a first RAN node, the first RAN node being used in a wireless communication system, wherein the method comprises:

[0200] receiving, from a second RAN node, an indication of available on-demand system information that can be utilized in a cell of the second RAN node; and

[0201] sending the indication to a wireless terminal in a cell of the first RAN node,

[0202] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0203] (Supplementary Note 22)

[0204] A non-transitory computer-readable medium storing a program for causing a computer to perform a method used by a wireless terminal, the wireless terminal being used in a wireless communication system, wherein the method comprises:

[0205] receiving, via a first radio access network node, i.e. a first RAN node, from a second RAN node an indication of available on-demand system information that can be utilized in a cell of the second RAN node,

[0206] In response to a request from the wireless terminal, the available on-demand system information is sent in a cell of the second RAN node or via the first RAN node.

[0207] This application is based upon and claims the benefit of priority from Japanese patent application No. 2017-000799, filed on January 5, 2017, the entire contents of which are incorporated herein by reference.

[0208] Description of Reference Numerals

[0209] 1 eNodeB (eNB)

[0210] 2 gNodeB (gNB)

[0211] 3 User Equipment (UE)

[0212] 4 Evolved Packet Core (EPC)

[0213] 5 Mobility Management Entity (MME)

[0214] 1101 RF Transceiver

[0215] 1104 Processor

[0216] 1105 Memory

[0217] 1201 RF Transceiver

[0218] 1203 Baseband Processor

[0219] 1204 Application Processor

[0220] 1206 Memory

Claims

1. A method used by a source radio access network node, i.e., a source RAN node, the method comprising: During an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., a 5G-CN, a handover request message is sent to a target RAN node; receiving a handover request confirmation message from the target RAN node during the inter-RAT handover procedure, wherein the handover request confirmation message comprises a radio resource control message (RRC message), wherein the RRC message comprises first information indicating a radio resource to be used by the wireless terminal to request on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; and The RRC message is sent to the wireless terminal.

2. The method according to claim 1, wherein: The RRC message is related to the reconfiguration of RRC.

3. The method according to claim 1 or 2, wherein: The RRC message further includes information indicating a system information block type, ie, a SIB type, of the on-demand system information.

4. The method according to claim 1 or 2, wherein: The RRC message also includes scheduling information of at least one system information being broadcast by the target RAN node.

5. The method according to claim 1 or 2, wherein: The inter-RAT handover process is to switch the wireless terminal from Evolved Universal Terrestrial Radio Access (E-UTRA) to New Radio (NR).

6. A method used by a wireless terminal, the method comprising: receiving, during an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., 5G-CN, for handover from a source radio access network node, i.e., a source RAN node, to a target RAN node, a radio resource control message, i.e., an RRC message, from the source RAN node, wherein the RRC message is included in a handover request confirmation message received by the source RAN node from the target RAN node, wherein the RRC message includes first information indicating a radio resource to be used by the wireless terminal for requesting on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; and A request message is sent to the target RAN node based on the first information.

7. The method according to claim 6, wherein: The RRC message is related to reconfiguration of the RRC, and the request message is related to completion of the reconfiguration of the RRC.

8. The method according to claim 6 or 7, wherein: The RRC message further includes information indicating a system information block type, ie, a SIB type, of the on-demand system information.

9. The method according to claim 6 or 7, wherein: The RRC message also includes scheduling information of at least one system information being broadcast by the target RAN node.

10. The method according to claim 6 or 7, wherein: The request message is a message to be sent during the random access process.

11. The method according to claim 6 or 7, wherein: The inter-RAT handover process is to switch the wireless terminal from Evolved Universal Terrestrial Radio Access (E-UTRA) to New Radio (NR).

12. A method used by a target radio access network node, i.e., a target RAN node, the method comprising: During an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., a 5G-CN, receiving a handover request message from a source RAN node; sending a handover request confirmation message to the source RAN node during the inter-RAT handover procedure, wherein the handover request confirmation message comprises a radio resource control message (RRC message), wherein the RRC message comprises first information indicating a radio resource to be used by the wireless terminal to request on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; receiving a request message from the wireless terminal in a case where the RRC message is received by the wireless terminal; as well as An acknowledgement including the on-demand system information is sent to the wireless terminal based on receipt of the request message.

13. The method according to claim 12, wherein: The RRC message is related to reconfiguration of the RRC, and the request message is related to completion of the reconfiguration of the RRC.

14. The method according to claim 12 or 13, wherein: The RRC message further includes information indicating a system information block type, ie, a SIB type, of the on-demand system information.

15. The method according to claim 12 or 13, wherein: The RRC message also includes scheduling information of at least one system information being broadcast by the target RAN node.

16. The method according to claim 12 or 13, wherein: The request message is a message to be sent during the random access process.

17. The method according to claim 12 or 13, wherein: The inter-RAT handover process is to switch the wireless terminal from Evolved Universal Terrestrial Radio Access (E-UTRA) to New Radio (NR).

18. A source radio access network node, namely a source RAN node, comprising: Means for sending a handover request message to a target RAN node during an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., 5G-CN; means for receiving a handover request confirmation message from the target RAN node during the inter-RAT handover procedure, wherein the handover request confirmation message comprises a radio resource control message (RRC message), wherein the RRC message comprises first information indicating a radio resource to be used by the wireless terminal to request on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; and Means for sending the RRC message to the wireless terminal.

19. The source RAN node according to claim 18, wherein: The RRC message is related to the reconfiguration of RRC.

20. The source RAN node according to claim 18 or 19, wherein: The RRC message further includes information indicating a system information block type, ie, a SIB type, of the on-demand system information.

21. The source RAN node according to claim 18 or 19, wherein: The RRC message also includes scheduling information of at least one system information being broadcast by the target RAN node.

22. The source RAN node according to claim 18 or 19, wherein: The inter-RAT handover process is to switch the wireless terminal from Evolved Universal Terrestrial Radio Access (E-UTRA) to New Radio (NR).

23. A wireless terminal, comprising: means for receiving a radio resource control message, i.e., an RRC message, from a source radio access network node, i.e., a source RAN node, during an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., a 5G-CN, for handover from the source RAN node to a target RAN node, wherein the RRC message is included in a handover request confirmation message received by the source RAN node from the target RAN node, wherein the RRC message includes first information indicating a radio resource to be used by the wireless terminal to request on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; as well as means for sending a request message to the target RAN node based on the first information.

24. The wireless terminal according to claim 23, wherein: The RRC message is related to reconfiguration of the RRC, and the request message is related to completion of the reconfiguration of the RRC.

25. The wireless terminal according to claim 23 or 24, wherein: The RRC message further includes information indicating a system information block type, ie, a SIB type, of the on-demand system information.

26. The wireless terminal according to claim 23 or 24, wherein: The RRC message also includes scheduling information of at least one system information being broadcast by the target RAN node.

27. The wireless terminal according to claim 23 or 24, wherein: The request message is a message to be sent during the random access process.

28. The wireless terminal according to claim 23 or 24, wherein: The inter-RAT handover process is to switch the wireless terminal from Evolved Universal Terrestrial Radio Access (E-UTRA) to New Radio (NR).

29. A target radio access network node, namely a target RAN node, comprising: Means for receiving a handover request message from a source RAN node during an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., 5G-CN; means for sending a handover request confirm message to the source RAN node during the inter-RAT handover procedure, wherein the handover request confirm message comprises a radio resource control message (RRC message), wherein the RRC message comprises first information indicating a radio resource to be used by the wireless terminal to request on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; means for receiving a request message from the wireless terminal if the RRC message is received by the wireless terminal; as well as means for sending an acknowledgement including the on-demand system information to the wireless terminal based on receipt of the request message.

30. The target RAN node according to claim 29, wherein: The RRC message is related to reconfiguration of the RRC, and the request message is related to completion of the reconfiguration of the RRC.

31. The target RAN node according to claim 29 or 30, wherein: The RRC message further includes information indicating a system information block type, ie, a SIB type, of the on-demand system information.

32. The target RAN node according to claim 29 or 30, wherein: The RRC message also includes scheduling information of at least one system information being broadcast by the target RAN node.

33. The target RAN node according to claim 29 or 30, wherein: The request message is a message to be sent during the random access process.

34. The target RAN node according to claim 29 or 30, wherein: The inter-RAT handover process is to switch the wireless terminal from Evolved Universal Terrestrial Radio Access (E-UTRA) to New Radio (NR).

35. A non-transitory computer readable medium storing one or more programs, the one or more programs comprising computer readable instructions, which when loaded into one or more computers, cause the one or more computers to perform a method used by a source radio access network node, i.e., a source RAN node, comprising: During an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., a 5G-CN, a handover request message is sent to a target RAN node; receiving a handover request confirmation message from the target RAN node during the inter-RAT handover procedure, wherein the handover request confirmation message comprises a radio resource control message (RRC message), wherein the RRC message comprises first information indicating a radio resource to be used by the wireless terminal to request on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; and The RRC message is sent to the wireless terminal.

36. A non-transitory computer readable medium storing one or more programs, the one or more programs comprising computer readable instructions which, when loaded into one or more computers, cause the one or more computers to perform a method for a wireless terminal, the method comprising: receiving, during an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., 5G-CN, for handover from a source radio access network node, i.e., a source RAN node, to a target RAN node, a radio resource control message, i.e., an RRC message, from the source RAN node, wherein the RRC message is included in a handover request confirmation message received by the source RAN node from the target RAN node, wherein the RRC message includes first information indicating a radio resource to be used by the wireless terminal for requesting on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; and A request message is sent to the target RAN node based on the first information.

37. A non-transitory computer readable medium storing one or more programs, the one or more programs comprising computer readable instructions, which when loaded into one or more computers, cause the one or more computers to perform a method used by a target radio access network node, i.e., a target RAN node, the method comprising: During an inter-radio access technology handover procedure, i.e., an inter-RAT handover procedure, via a 5G core network, i.e., a 5G-CN, receiving a handover request message from a source RAN node; sending a handover request confirmation message to the source RAN node during the inter-RAT handover procedure, wherein the handover request confirmation message comprises a radio resource control message (RRC message), wherein the RRC message comprises first information indicating a radio resource to be used by the wireless terminal to request on-demand system information from the target RAN node, and wherein the on-demand system information is not being broadcast by the target RAN node; receiving a request message from the wireless terminal in a case where the RRC message is received by the wireless terminal; as well as An acknowledgement including the on-demand system information is sent to the wireless terminal based on receipt of the request message.

Images