User equipment and method

Abstract

To provide user equipment and method for establishing an effective process for distributing, by a base station, system information, as well as, for acquiring, by the user equipment, the system information and defining the established effective process.SOLUTION: A method according to the present disclosure is configured to transport, by user equipment, system information on a first radio cell within a minimum system information message and within one or more additional system information messages. The minimum system information message includes system information for accessing the first radio cell, and includes at least one system information index. The method also determines, on the basis of area identification information and an area type, whether or not the user equipment had already acquired before the additional system information message associated with a same area as that of a value tag that is similar to that indicated by the system information index received in the minimum system information message.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present disclosure is directed to user equipment and methods for use in 3GPP communication systems and the like. [Background technology]

[0002] Currently, the 3rd Generation Partnership Project (3GPP) is working on the next release (Release 15) of technical specifications for the next generation of mobile phone technology, also known as the fifth generation (5G). At the 71st meeting of the 3GPP Technical Specification Group (TSG) Radio Access network (RAN) (Gothenburg, March 2016), the first study item for 5G, "Study on new radio access technologies", including RAN1, RAN2, RAN3, and RAN4, was approved and is expected to become a work item for Release 15 that will define the first 5G standard. The objective of this study item is to develop "New Radio (NR)" access technologies (RATs) that operate within the frequency range up to 100 GHz and support a wide range of use cases defined during the study of RAN requirements (see, for example, Non-Patent Document 1, available at www.3gpp.org and incorporated herein by reference in its entirety).

[0003] One objective is to provide a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios defined in Non-Patent Document 1, including at least enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine type communication (mMTC). The second objective is to achieve forward compatibility. Backward compatibility to Long Term Evolution (LTE, LTE-A) mobile phone systems is not required, which facilitates the introduction of entirely new system designs and / or new features.

[0004] The basic physical layer signal waveform is based on OFDM, which may support non-orthogonal waveforms and multiple access. Additional features on top of OFDM, such as DFT-S-OFDM and / or variants of DFT-S-OFDM and / or filtering / windowing, are being further considered. In LTE, CP-based OFDM and DFT-S-OFDM are used as waveforms for downlink and uplink transmissions, respectively. One of the design goals in NR is to find waveforms that are common to the downlink, uplink, and sidelink as much as possible.

[0005] In addition to waveforms, some basic frame structures and channel coding schemes will be developed to achieve the aforementioned objectives. The study must also seek a common understanding of what is needed in terms of radio protocol structures and architectures to achieve the aforementioned objectives. Furthermore, the technical features required for the new RAT to meet the aforementioned objectives must be considered, including efficient multiplexing of traffic of different services and use cases on the same contiguous block of spectrum. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] 3GPP TR 38.913 "Study on Scenarios and Requirements for Next Generation Access Technologies", current version 14.2.0 [Non-Patent Document 2] Technical Report TR 38.804 v14.0.0 [Non-Patent Document 3] TS 38.300 v.0.4.1, section 4 [Non-Patent Document 4] 3GPP TR 38.801 v14.0.0 [Non-Patent Document 5] TR 38.301 [Non-Patent Document 6] TS 38.300 v0.2.0 [Non-Patent Document 7] 3GPP TS 36.321, section 5.1. v14.1.0 [Non-Patent Document 8] 3GPP TS 36.331 v14.2.2, section 5.4 [Non-Patent Document 9] 3GPP 36.423 v14.2.0 section 8.2 [Non-Patent Document 10] 3GPP TS 36.304 v14.2.0 [Non-Patent Document 11] 3GPP TS 24.301 v14.3.0 [Non-Patent Document 12] 3GPP Technical Specification TS 36.331 v14.1.0, section 5.2 "System information" [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] As 3GPP's NR standardization of the 5G system has just begun, there are several issues that remain unclear. For example, there have been discussions on how to handle the provision of system information by the network and the acquisition of system information by the UE. It is important to establish and define an effective process for distributing system information by the base station and for acquiring system information by the UE. [Means for solving the problem]

[0008] One non-limiting example embodiment facilitates improvements to system information procedures involving various entities (UE, gNB).

[0009] In one general aspect, the technology disclosed herein features a user equipment. The user equipment comprises a receiver that receives a minimum system information message from a first radio base station that controls a first radio cell of a mobile communication system. System information of the first radio cell that can be acquired by the user equipment is carried in the minimum system information message and in one or more additional system information messages. The minimum system information message includes system information for accessing the first radio cell and includes at least one system information index. Each system information index is associated with one of the additional system information messages. The index of the system information message includes a value tag and an area pointer, and the area pointer points to one area that has already been defined. The user equipment comprises a processing circuit that determines whether the user equipment has previously acquired an additional system information message associated with the same value tag and the same area as indicated by the system information index received in the minimum system information message. If the determination is positive, the processing circuit determines that the system information included in the previously acquired additional system information message is applicable to the first radio cell.

[0010] In one general aspect, the technology disclosed herein features a radio base station. The radio base station includes a processing circuit that generates a minimal system information message including system information for accessing a first radio cell controlled by the radio base station and including at least one system information index. The system information of the first radio cell that can be acquired by a user equipment is carried in the minimal system information message and in one or more additional system information messages. Each system information index is associated with one of the additional system information messages. The index of the system information message includes a value tag and an area pointer. The area pointer points to one area that has already been defined. The radio base station includes a transmitter that transmits the minimal system information message to the user equipment.

[0011] It should be noted that the general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any combination thereof.

[0012] Other benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings, which benefits and / or advantages may be obtained individually by the various embodiments and features of the specification and drawings, and it is not necessary for the embodiments and features to all be provided in order to obtain one or more of such benefits and / or advantages.

[0013] In the following, example embodiments are described in more detail with reference to the accompanying figures and drawings. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 illustrates an example architecture of a 3GPP NR system. [Diagram 2] FIG. 1 illustrates an example user plane and control plane architecture for an LTE eNB, gNB, and UE. [Diagram 3] FIG. 1 illustrates a protocol stack for the 5G NR user plane. [Figure 4] FIG. 1 illustrates a protocol stack for the 5G NR control plane. [Diagram 5] A diagram showing messages exchanged between an eNB and a UE when performing a contention-based RACH procedure. [Figure 6] FIG. 2 illustrates messages exchanged between an eNB and a UE when performing a contention-free RACH procedure. [Figure 7] FIG. 1 illustrates an example signaling diagram for an X2 handover procedure in an LTE communication system. [Figure 8] A diagram showing three RAN-based notification areas, each consisting of multiple gNBs and a UE connected to gNB1 in Area 1. [Figure 9] FIG. 1 is a diagram showing message exchange for system information acquisition currently being discussed for 5G NR. [Figure 10] FIG. 2 illustrates an exemplary simplified structure of a UE and an eNB. [Figure 11] A diagram showing an exemplary scenario in which a UE located in a radio cell of gNB1 is moving towards radio cell 2 controlled by gNB2. [Figure 12] FIG. 1 shows a flowchart of operations performed in a UE for an improved system information acquisition procedure. [Figure 13] 11A-11C are diagrams showing system information indexes of corresponding additional SI messages, each of which is composed of an area pointer and a value tag. [Figure 14] FIG. 13 illustrates the association between area pointers and area types. [Figure 15] FIG. 14 illustrates an example implementation of the System Information Index already shown in FIG. [Figure 16] A diagram showing an example definition of effective areas of different area types and different system information for different additional SI messages. [Figure 17] FIG. 13 shows system information indexes of corresponding additional SI messages, one of which includes an area ID and a value tag, and the other of which includes an area pointer and a value text. [Figure 18] FIG. 13 illustrates the association between area pointers and lists of area IDs. [Figure 19] 11A-11C are diagrams showing system information indexes of corresponding additional SI messages, each of which is composed of an area pointer and a value tag. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Basis of this Disclosure> <5G NR system architecture and protocol stack> As indicated in the Background section, 3GPP is working on the next release of the fifth generation of mobile phone technology (abbreviated as 5G), which includes the development of a new radio access technology (NR) that will operate at frequencies up to 100 GHz. 3GPP needs to identify and develop the necessary technical elements to successfully standardize an NR system that meets both immediate market needs and longer-term requirements in a timely manner. To achieve this, the evolution of the air interface and radio network architecture is being considered in the study item "New Radio Access Technologies". The results and agreements are summarized in Non-Patent Document 2, which is incorporated herein in its entirety by reference.

[0016] In particular, a tentative agreement was made on the overall system architecture. The NG-RAN (Next Generation - Radio Access Network) consists of gNBs, providing the NG radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocol terminations towards the UEs. The gNBs are interconnected using the Xn interface. The gNBs are also connected to the NGC (Next Generation Core) using the Next Generation (NG) interface, more specifically to the AMF (Access and Mobility Management Function) using the NG-C interface and to the UPF (User Plane Function) using the NG-U interface. The NG-RAN architecture is shown in Figure 1, which is taken from IEEE 802.11b, which is incorporated herein by reference.

[0017] For example, as reflected in 3GPP IEEE 802.11b, which is incorporated herein by reference in its entirety, various different deployment scenarios that are to be supported are currently being discussed. For example, a decentralized deployment scenario (section 5.2 of 3GPP IEEE 802.11b) is presented in which base stations supporting 5G NR can be deployed (section 5.4 of 3GPP IEEE 802.11b shows a centralized deployment). Figure 2 illustrates an exemplary decentralized deployment scenario based on Figure 5.2.-1 of 3GPP IEEE 802.11b, and further illustrates a LTE eNB and a user equipment (UE) connected to both a gNB and an LTE eNB (LTE eNB should be understood as an eNB following previous 3GPP standard releases for LTE and LTE-A, etc.). As mentioned above, the new eNB for NR 5G may be exemplarily referred to as a gNB.

[0018] The eLTE eNB, which is exemplarily defined in Non-Patent Document 4, is an evolved version of the eNB that supports connections to the EPC (Evolved Packet Core) and NGC (Next Generation Core).

[0019] The protocol stack of the user plane for NR, currently defined in Section 4.4.1 of Non-Patent Document 6, is shown in Figure 3. The PDCP sublayer, RLC sublayer, and MAC sublayer are terminated at the gNB on the network side. Furthermore, as described in Section 6.5 of Non-Patent Document 6, a new access stratum (AS) sublayer (SDAP (Service Data Adaptation Protocol)) is introduced above the PDCP. The protocol stack of the control plane for NR, defined in Section 4.4.2 of Non-Patent Document 6, is shown in Figure 4. An overview of the Layer 2 functions is described in Section 6 of Non-Patent Document 6. The functions of the PDCP sublayer, RLC sublayer, and MAC sublayer are shown in Sections 6.4, 6.3, and 6.2 of Non-Patent Document 6, respectively. The function of the RRC layer is shown in Section 7 of Non-Patent Document 6. Each of the above-mentioned sections of Non-Patent Document 6 is incorporated herein by reference.

[0020] The new NR layers currently exemplarily assumed for the 5G system may be based on the user plane layer structure currently used in the LTE(-A) communication system. However, it should be noted that no final agreement has been reached yet regarding all the details of the NR layers.

[0021] <RRC state> In LTE, the RRC state machine consists of only two states: the RRC idle state, which is mainly characterized by significant power savings, UE autonomous mobility, and the failure to establish a connection between the UE and the core network, and the RRC connected state, where mobility is network-controlled to support lossless service continuity while the UE can transmit user plane data.

[0022] The RRC of NR 5G currently defined in Section 5.5.2 of Non-Patent Document 2 incorporated herein by reference supports three states: RRC idle, RRC inactive, and RRC connected, and permits the following state transitions defined in Non-Patent Document 2.

[0023] As is clear, the new RRC state of inactive has been defined for the new radio technology of 5G 3GPP to bring benefits when supporting a wider range of services such as eMBB (enhanced mobile broadband), mMTC (massive machine type communication), and URLLC (ultra-reliable and low-latency communication), which have very different requirements regarding signaling, power savings, latency, etc.

[0024] <RACH procedure> Regarding the RACH (Random Access Channel) procedure of 5G NR, no final agreement has been reached. As described in Section 9.2 of Non-Patent Document 2 incorporated herein by reference, the NR RACH procedure may support both contention-based random access and contention-free random access in the same or a similar manner as defined for LTE. Also, similar to LTE, the design of the NR RACH procedure must support a flexible size for Message 3.

[0025] In the following, the LTE RACH procedure is described in more detail with reference to Figures 5 and 6. In LTE, a mobile terminal can be scheduled for uplink transmission only if its uplink transmission is time synchronized. Therefore, the Random Access Channel (RACH) procedure plays an important role as an interface between asynchronous mobile terminals (UEs) and orthogonal transmission of uplink radio access. Basically, random access in LTE is used to achieve uplink time synchronization for user equipment that has not yet acquired or lost uplink synchronization. After the user equipment achieves uplink synchronization, the eNodeB can schedule the uplink transmission resources of the user equipment. One scenario related to random access is when a user equipment in RRC_CONNECTED state that is handing over from a current serving cell to a new target cell performs a random access procedure to achieve uplink time synchronization in the target cell.

[0026] LTE offers two types of random access procedures, allowing either contention-based (i.e., implying an inherent risk of collision) or contention-free (non-contention-based) access. A detailed description of the random access procedure is also given in IEEE 802.11b, which is incorporated herein by reference.

[0027] In the following, the LTE contention-based random access procedure is explained in more detail with respect to Fig. 5. The procedure consists of four "steps". First, the user equipment transmits a random access preamble to the eNodeB on the Physical Random Access Channel (PRACH) (i.e. message 1 of the RACH procedure). After detecting the RACH preamble, the eNodeB transmits a Random Access Response (RAR) message (message 2 of the RACH procedure) on the PDSCH (Physical Downlink Shared Channel) addressed on the PDCCH, including the (random access) RA-RNTI identifying the time-frequency slot in which the preamble was detected. If multiple user equipments transmit the same RACH preamble in the same PRACH resource (also called collision), they will receive the same random access response message. The RAR message may convey the detected RACH preamble, a timing alignment command (TA) for synchronization of subsequent uplink transmissions, an initial uplink resource allocation (grant) for the first scheduled transmission, and the allocation of a Temporary Cell Radio Network Temporary Identifier (T-CRNTI), which is used by the eNodeB to address the mobile terminal whose RACH preamble was detected until the RACH procedure is finished, since at this point the "real" identifier of the mobile terminal is not yet known to the eNodeB.

[0028] The user equipment monitors the PDCCH for the reception of a random access response message within a specific time window configured by the eNodeB. In response to the RAR message received from the eNodeB, the user equipment transmits a first scheduled uplink transmission on the radio resources allocated by the grant in the random access response. This scheduled uplink transmission carries the message of the actual random access procedure, such as an RRC connection request or a buffer status report.

[0029] In case of a preamble collision occurring at the beginning of the RACH procedure (i.e. when multiple user equipments transmit the same preamble on the same PRACH resource), the colliding user equipments receive the same T-CRNTI in the random access response and also collide in the same uplink resource when transmitting scheduled transmissions in the third step of the RACH procedure. If a scheduled transmission from one user equipment is successfully decoded by the eNodeB, the contention for the other user equipment remains unresolved. For the resolution of this type of contention, the eNodeB transmits a contention resolution message (fourth message) addressed to the C-RNTI or temporary C-RNTI.

[0030] Figure 6 shows a simplified 3GPP LTE contention-free random access procedure compared to the contention-based random access procedure. In a first step, the eNodeB provides the user equipment with a preamble to use for random access, so that there is no risk of collision (i.e. multiple user equipments transmitting the same RACH preamble). The user equipment accordingly transmits the preamble signaled by the eNodeB in the uplink on the PRACH resource from then on. In the case of contention-free random access, the case of multiple UEs transmitting the same preamble is avoided, so that the contention-free random access procedure is essentially terminated after successful reception of the random access response by the UE.

[0031] In this way, the RACH procedure similar to or the same as that described in relation to FIGS. 5 and 6 can be adopted in the future in the new radio technology of 5G. However, 3GPP is also considering a two-step RACH procedure for 5G NR, in which Message 1 corresponding to Message 4 in the four-step RACH procedure is sent first. Next, the gNB responds with Message 2 corresponding to Messages 2 and 4 of the LTE RACH procedure. Since the message exchange is reduced, the latency of the two-step procedure can be reduced compared to the four-step procedure. The radio resources for the messages are optionally configured by the network.

[0032] <LTE Handover Procedure> Mobility is an important procedure in the LTE communication system. For UEs in the active mode in LTE, there are two types of handover procedures: the S1 handover procedure and the X2 handover procedure. In the case of intra-LTE mobility, usually, handover via the X2 interface is used for mobility between eNodeBs. Therefore, by default, the X2 handover is triggered unless the X2 interface is not established or the source eNodeB is not configured to use another handover (e.g., S1 handover) instead.

[0033] FIG. 7 shows an exemplary simplified overview of an X2 intra-LTE handover.

[0034] The X2 handover includes a preparation phase (Steps 4 to 6), an execution phase (Steps 7 to 9), and a completion phase (after Step 9). The X2 in-LTE handover is directly executed between two eNodeBs. In order to trigger the switching of the path to the new eNB, other entities of the core network (e.g., MME (Mobility Management Entity)) are notified only at the end of the handover procedure after the handover procedure has been successful.

[0035] Detailed information on mobility procedures in LTE can be obtained, for example, from Non-Patent Document 8 incorporated herein by reference and from Non-Patent Document 9 incorporated herein by reference.

[0036] <LTE-Closed Subscriber Group (CSG)> The closed subscriber group identifies a group of subscribers who are permitted to access one or more CSG cells of a PLMN. A cell with a CSG indication set to "TRUE" is called a "CSG cell". A non-CSG cell (i.e., a normal cell) permits a UE to camp on it as long as the UE has the appropriate PLMN information and the cell is not prohibited, while a CSG cell permits only UEs belonging to a specific CSG to camp on it. The closed subscriber group identifies the operator's subscribers who are permitted to access one or more cells (CSG cells) of a PLMN where access is restricted.

[0037] To make a CSG call, the UE must send the CSG ID and access type it belongs to in the Attach Request. Then, the MME performs UE authentication with the HSS before exchanging a Location Update Request and a Location Update Response. In the Location Update Response, the HSS sends the CSG information (CSG ID, Join Timer) in the subscription data. Then, the MME verifies the CSG ID against the CSG received in the Attach Request. If the CSG IDs match, the UE initiates a CSG call and sends a Create Session Request to the SGW with the CSG information. On receipt of a successful response from the SGW, the MME sends an Attach Accept message with the member status as "member". After the expiration of the Join Timer period during which the UE has subscribed and attached to the CSG cell, the MME initiates the PDN connection removal.

[0038] Further information regarding closed subscriber groups is provided throughout the non-patent document 10, which is incorporated herein by reference.

[0039] <Tracking area> To reduce the overhead in E-UTRAN and UE processing, all UE related information in the access network can be released during long periods of data inactivity. The UE then goes into ECM-idle state (EPS Connection Management-Idle). The MME keeps the UE context and information regarding established bearers during those idle periods. To allow the network to contact the UE in ECM-idle state, the UE updates the network about its new location whenever it moves out of its current Tracking Area (TA). This procedure is called "Tracking Area Update". More specifically, LTE introduced a mechanism to provide the size of the UE's individual Tracking Area by allowing the core network to provide a list of Tracking Area Identities (TAIs) that are considered as the UE's actual Tracking Area. When the UE moves away from the combined area of ​​the list of TAs (e.g. the UE may receive a Tracking Area ID from the base station that is not included in the list of TAs), the UE triggers a NAS Tracking Area Update (TAU) procedure. The same or similar approach to support mobility of UEs in RRC idle state in 5G NR may be envisaged: the core network area may be defined to be distinct from the RAN-based notification area, which may possibly be of the same order of magnitude as the core network area or smaller.

[0040] The MME is responsible for tracking the user's location while the UE is in ECM idle state. When downlink data needs to be delivered to a UE in ECM idle state, the MME sends a paging message (core network initiated paging) to all eNodeBs in the UE's current TA, which then send the paging message over the radio interface to reach the UE.

[0041] Further detailed information regarding the tracking area is described in Sections 5.5.3, 8.2.26 to 8.2.29, 9.9.32, and 9.9.33 of Non-Patent Document 11, which is incorporated herein by reference.

[0042] <RRC State and RAN-Based Notification Area> In LTE, the RRC state machine consists of only two states: the RRC idle state, which is mainly characterized by significant power savings, UE autonomous mobility, and the lack of establishment of a connection between the UE and the core network; and the RRC connected state, in which mobility is network-controlled while supporting lossless service continuity so that the UE can transmit user plane data.

[0043] The RRC of NR 5G currently defined in Section 5.5.2 of Non-Patent Document 2, which is incorporated herein by reference, supports three states: RRC idle, RRC inactive, and RRC connected. As is clear, the new RRC state, inactive, is defined for the new radio technology of 5G 3GPP in order to bring benefits when supporting a wider range of services such as eMBB (enhanced mobile broadband), mMTC (massive machine type communication), and URLLC (ultra-reliable and low-latency communication), which have very different requirements regarding signaling, power savings, latency, etc. Therefore, the new RRC inactive state must be designed to minimize signaling, power consumption, and resource costs in the radio access network and the core network while allowing data transfer to be initiated with low latency. The various states are characterized by Section 5.5.2 of Non-Patent Document 2, which is incorporated herein by reference.

[0044] According to one feature of the new RRC inactive state, for a UE in RRC inactive state, the connection (both user plane and control plane) with the RAN and the core network is maintained. In addition, the paging mechanism (sometimes called notification mechanism) of the user equipment in that cell is based on so-called Radio Access Network (RAN)-based notification areas (RNA for short). The radio access network must know the current RAN in which the user equipment is located, and the user equipment may help the gNB to track the UE moving between different RNAs.

[0045] An RNA can cover one or multiple cells. An RNA may be smaller than a core network area used to track UEs in RRC idle state. While a UE in RRC inactive state remains within the boundaries of the current RNA, this UE may not need to update its location with the RAN (e.g., gNB). However, the UE may update its location with the RAN accordingly when it leaves the current RNA (e.g., moves to another RNA). There is no final agreement yet on how the RNA is configured and defined. Section 5.5.2.1 of 3GPP TS 2013-01-13344, incorporated herein by reference, mentions several possible options currently being discussed.

[0046] FIG. 8 shows an exemplary scenario where there are multiple RNAs each constituted by a plurality of gNBs. It is assumed that the UE is connected to gNB1 belonging to RNA1 and moves to gNB2 of RNA2. According to one option, a list of cells constituting the RNA-based notification area is defined. An explicit list of cells is provided to the UE (e.g., via dedicated signaling (i.e., signaling addressed directly to the UE, e.g., RRC connection reconfiguration message)) so that the UE can determine in which current RNA the UE is based on the current cell. According to another option, the RAN area is identified by RNA IDs respectively. Each cell (specifically, gNB) broadcasts (at least one) RNA ID (e.g., in the system information) so that the UE knows to which RAN area the cell belongs (alternatively or additionally, this information can be sent to the UE using dedicated signaling). So far, no decision has been made on whether to support one or both options, and different solutions may be agreed upon in the future. Details regarding the RNA ID, such as the bit size, are not provided either.

[0047] <Obtaining LTE System Information> In LTE, the system information is structured using system information blocks (SIBs), and each of the system information blocks contains a set of functionally related parameters. The MIB (master information block) contains a limited number of the most frequently transmitted parameters that are essential for the UE's initial access to the network. In LTE, various types of system information blocks, namely SIB1 to SIB18, are currently defined to further transmit parameters. For example, SIB1 contains parameters necessary to determine whether the cell is suitable for cell selection and information regarding the time-domain scheduling of other SIBs, and SIB2 contains common shared channel information.

[0048] Three types of RRC (Radio Resource Control) messages can be used to transfer system information, MIB, SIB1 message, and SI message. SIBs other than SIB1 are transmitted within system information messages (SI messages), which are multiple and contain one or more SIBs with the same scheduling requirements (e.g., the same transmission periodicity). Depending on the content of the SI message, the UE needs to acquire different SI messages in idle or connected state (e.g., the third SI message containing SIB5 (inter-frequency cell reselection information) that needs to be acquired only in idle state).

[0049] The time domain scheduling of MIB and SIB1 messages is fixed with periodicities of 40 ms and 80 ms, respectively. The time domain scheduling of SI messages is dynamically flexible, with each SI message being transmitted within a defined, periodically occurring time domain window, during which physical layer control signaling indicates in which subframe within this window the SI is actually scheduled. The scheduling windows of different SI messages (within a short SI window) are contiguous and have a configurable common length. The SI messages may have different periodicities, such that within some clusters of the SI window (many or) all SI messages are scheduled, and within other clusters only SI messages with a shorter repetition period are transmitted.

[0050] System information usually changes in certain radio frames and at certain modification periods. LTE provides two mechanisms to indicate that system information has changed: 1. A paging message that contains a flag indicating whether system information has changed, and 2. A value tag in SIB1 that is incremented every time one or more of the SI messages change.

[0051] When the UE receives a notification of a change in SI, the UE starts acquiring system information from the start of the next change cycle. Until the UE successfully acquires the updated system information, the UE continues to use the existing parameters. Although communication may be significantly affected if important parameters change, the possible service interruptions are considered acceptable because they are short and rare.

[0052] Details regarding system information are described in Non-Patent Document 12, which is hereby incorporated by reference in its entirety.

[0053] <Obtaining NR System Information> In 5G NR, it is currently assumed (although not finally agreed) that system information is generally divided into minimum system information and other system information. The minimum system information is broadcast periodically and includes basic information necessary for initial access to the cell (such as system frame number (SFN), list of PLMNs, cell ID, cell camping parameters, RACH parameters, etc.). The minimum system information may further include information for obtaining any other SI that is broadcast periodically or provided on a per-request basis (e.g., appropriate scheduling information regarding this). The scheduling information may include, for example, SIB type, validity information, SI period, and SI window information as required. Accordingly, the other system information must include all information that is not broadcast within the minimum system information (e.g., cell reselection neighbor cell information).

[0054] Other SI may be broadcast or provided in a dedicated manner triggered by the network or upon request from the UE, as shown in Figure 9. Other SI may be broadcast for a specific period with a configurable periodicity. It is determined by the network whether other SI is broadcast or delivered via dedicated UE-specific RRC signaling.

[0055] For other SI that is actually required by the UE, before the UE sends an other SI request, the UE needs to indicate whether the SI is available in the cell and whether the SI is broadcast. For UEs in RRC_CONNECTED state, dedicated RRC signaling may be used, for example, for requesting and delivering other SI.

[0056] In legacy LTE, briefly described above, the UE always needs to (re)acquire system information when a cell change occurs, and the UE also needs to reacquire all system information when the system information changes (e.g., indicated by paging or by an incremented (i.e., changed) value tag). For the new system in 5G NR, it is usually desirable to reduce the need to reacquire system information by identifying the stored system information using a specific index / identifier that is broadcast together with the minimum system information. It is assumed that system information valid in one cell may also be valid in other cells. For example, common radio resource configurations, access class exclusion information, UL carrier frequencies and bandwidths, and MBSFN (Multimedia Broadcast Single-Frequency Network) subframe configurations may be valid between multiple adjacent cells.

[0057] More specifically, a particular index / identifier (which may be illustratively referred to as a system information index) may be used to indicate the validity of related system information in other cells, which may be applicable in more than one cell.

[0058] As a result, if the UE already stores valid system information, it does not need to reacquire the already acquired valid system information, which can reduce the power consumption of the UE and reduce the signaling overhead on the air interface.

[0059] The system information index can be a single index or can be split into two or more items, such as an area identifier (same as or similar to LTE) and a value tag. The value tag can be valid, for example, in one cell, while the complete system information index can be considered valid in two or more cells, as described above, so that reacquisition of the system information can be avoided.

[0060] There is no final agreement on what the system information index is or how it should be signaled. Any signaling procedure defined for 5G NR must provide at least some configuration flexibility regarding the definition of the system information, while at the same time keeping the overhead of transmitting the system information to a minimum.

[0061] Another issue that may arise in the new 5G NR system is that in case of handover, it may take a longer time for the UE to obtain all necessary SI messages from the target eNB (e.g. compared to LTE) since some system information is not automatically broadcast by the gNB but is only available when the UE requests it after sending other corresponding SI requests (see above).

[0062] Therefore, the present disclosure must provide a solution that overcomes one or more of the disadvantages and / or facilitates meeting one or more of the aforementioned requirements.

[0063] Detailed Description of the Disclosure In the following, UEs, base stations, and procedures are described with respect to new radio access technologies assumed in 5G mobile communication systems. Different implementations and variations are also described. The following detailed disclosure is facilitated by and may be based at least in part on the considerations and discoveries described in the previous "Basis of the Disclosure" section.

[0064] However, it should be noted that, since in general, little is actually agreed upon regarding 5G mobile phone communication systems, in the following a number of assumptions must be made in order to be able to explain the principles underlying this disclosure in a clear and understandable manner. However, these assumptions should be understood as merely examples that do not limit the scope of this disclosure. Those skilled in the art will recognize that the principles of the following disclosure and those presented in the claims can be applied to various scenarios in ways not explicitly described herein.

[0065] Furthermore, the terms such as procedures, entities, layers, etc. used below are closely related to the LTE / LTE-A system, or are closely related to the terms used in the current discussion of 3GPP 5G, although the specific terms used in the context of the new radio access technology of the upcoming 3GPP 5G communication system have not yet been fully determined. Therefore, these terms may be changed in the standardization stage without affecting the functionality of the embodiments of the present invention. Therefore, those skilled in the art will recognize that the scope of the present invention and its protection should not be limited to the specific terms used illustratively in this specification, even in the absence of newer or finally agreed terms, but should be more broadly understood in terms of the functions and concepts underlying the functions and principles of the present disclosure.

[0066] For example, a mobile station or mobile node or user terminal or user equipment (UE) is a physical entity in a communication network. A node may include multiple functional entities. A functional entity refers to a software or hardware module that implements a predefined set of functions and / or provides a predefined set of functions to other functional entities of the nodes of the network. A node may include one or more interfaces that attach the node to communication facilities or media via which the node can communicate. Similarly, a network entity may include logical interfaces that attach the functional entity to communication facilities or media via which the network entity can communicate with other functional entities or corresponding nodes.

[0067] The term "base station" or "radio base station" as used herein refers to a physical entity in a communication network. The physical entity performs some control tasks for communication devices, including one or more of scheduling and configuration. It is noted that the functions of a base station and communication devices may be integrated in a single device. For example, a mobile terminal may implement the functions of a base station for other terminals. The term used in LTE is eNB (or eNodeB), while the term currently used in 5G NR is gNB.

[0068] The term "minimal system information message" refers to a specific type of message carrying minimal system information broadcast in a radio cell for UEs accessing the radio cell. The "minimal system information message" is transmitted periodically in the radio cell and its content may change. Therefore, another term used is "minimal SI". The "minimal system information" is functionally similar to the MIB and / or SIB1 used in legacy LTE systems.

[0069] Furthermore, system information of the radio cell can be transmitted using "additional system information messages", which is a term referring to a specific type of message carrying system information about the radio cell that is not broadcast in the minimal system information message. Therefore, another term used is "other SI". The "additional system information messages" are functionally similar to the SIBs used in legacy LTE systems.

[0070] The term "system information index" refers to an information element associated with an "additional system information message" such that there is a one-to-one relationship between the system information index and the associated "additional system information message". However, it should be noted that not all "additional system information messages" need to be associated with a "system information index". The system information index should be used in conjunction with the system information acquisition procedure to determine the validity of the associated "additional system information message" as described in this application, and should allow the UE to avoid re-acquiring system information in certain situations.

[0071] The term "area pointer" refers to an information element that is part of a minimal system information message (specifically, the system information index). The area pointer should not be understood as providing any information about the area alone, but as a pointer to additional information in order to be able to determine the area (e.g., its type and / or ID) in combination. In a particular embodiment, the "area pointer" is functionally used to encode the spatial validity of the additional system information message with which the system information index in which the area pointer is included is associated. In other words, it is assumed that the system information in the additional SI message (additional system information message) is equally applicable (i.e., valid) in multiple radio cells, and that the validity in those multiple cells can be encoded in the "area pointer" to enable the UE to determine the spatial validity of the additional SI message based on the area pointer. The validity in time of the additional SI message is exemplarily encoded using a "value tag".

[0072] The term "value tag" refers to an information element that is part of a minimal system information message (specifically, a system information index). The value tag may be functionally used to encode the temporal validity of an additional system information message with which the system information index in which it is contained is associated. In other words, it is assumed that the value tag is changed (e.g., incremented) each time the content of the additional SI message is changed, in order to enable the UE to determine the temporal validity of the additional SI message.

[0073] FIG. 10 shows a general simplified exemplary block diagram of a user equipment (also called a communication device) and a scheduling device (here assumed to be in a base station (e.g., an LTE eNB or a gNB in ​​5G NR). The UE and the eNB / gNB communicate with each other via a (wireless) physical channel, each using a transceiver.

[0074] A communication device may comprise a transceiver and a processing circuit. The transceiver in turn may comprise a receiver and a transmitter. The processing circuit may be one or more hardware, such as one or more processors or any LSI. Between the transceiver and the processing circuit, there is an input / output point (or node) through which the processing circuit can control the transceiver in operation, i.e., control the receiver and / or the transmitter to exchange receive / transmit data. The transceiver may include an RF (radio frequency) front, including one or more antennas, amplifiers, RF modulators / demodulators, etc. The processing circuit may implement control tasks, such as controlling the transceiver to transmit user data and control data provided by the processing circuit and / or to receive user data and control data that are further processed by the processing circuit. The processing circuit may be responsible for executing processes such as decisions, judgments, calculations, measurements, etc. The transmitter may be responsible for executing the process of transmission. The receiver may be responsible for executing the process of reception.

[0075] In the following, a simple exemplary scenario is assumed. It is assumed that the UE is located within the coverage area of ​​radio cell 1 controlled by gNB1, as shown in Figure 11. One important procedure that is continuously performed by the UE is the system information acquisition procedure. The system information acquisition procedure is used to acquire the necessary system information, for example, when powering up in a radio cell, when moving in a radio cell, and / or when moving to a new radio cell.

[0076] Based on the preliminary agreements and understandings reached currently being discussed in 3GPP regarding the system information acquisition procedures for 5G NR, the provision of the entire system information is divided into a minimum SI message and one or more additional SI messages that are made available to the UE in each radio cell. Although no agreement has yet been reached, it is exemplarily assumed that there are a total of five additional SI messages (e.g., referred to as SI1 to SI5). Any other suitable number of additional SI messages is possible as well.

[0077] The minimum SI message is broadcast periodically by the gNB1 and is initially acquired by the UE. The five additional SI messages are broadcast periodically or are available to the UE in the radio cell upon request (i.e., when requesting additional SI messages from the gNB1). In either case, the UE can acquire the additional SI messages and the embodiments can be applied in the same way. The minimum SI message includes minimum system information broadcast in the radio cell for the UE to access the radio cell, and further includes necessary scheduling information to enable the UE to further acquire the system information by acquiring some or all of the additional SI messages.

[0078] Different additional SI messages include different types of system information, some or all of which may not be strictly necessary for the operation of the UE. Thus, for each additional SI message, the UE may determine whether the system information is necessary for the operation of the UE in the radio cell. For example, an additional SI message for Earthquake and Tsunami Warning Serving (ETWS) notification may not be considered necessary for the UE. According to an example embodiment, the UE may exemplarily first determine which of the additional SI messages signaled in the minimum SI message are necessary for the operation of the UE, before continuing to determine whether the acquisition of the required additional SI message can be avoided, as will be described in detail below. To simplify the description of the various embodiments and their variants, it is exemplarily assumed that the UE considers all additional SI messages (here, SI1 to SI5) to be important for its operation and in principle determines to acquire all corresponding system information contained in those messages. Whether the system information is really acquired by the UE depends on the specific case for avoiding the acquisition of the same system information in a specific situation, as will be described below.

[0079] As previously explained, it has been agreed in 3GG that the system information acquisition procedure should be improved to avoid reacquiring system information in certain situations. Accordingly, the following embodiments described herein use a system information index in association with an additional SI message to encode the validity of the associated additional SI message over time and space (i.e., area), thus enabling the UE to first determine the validity of the signaled additional SI message relative to a previously acquired additional SI message, and then determine whether acquisition of that additional SI message is actually required.

[0080] At least one of the additional SI messages may be associated with a system information index, in which case the minimum SI message includes, at least for one of the five additional SI messages (e.g., SI1), the system information index associated with that additional SI message (i.e., SI1). In the following description, in one example embodiment, to provide the most benefits, the concept of encoding the validity of the system information using a system information index is applied to all five additional SI messages. Thus, the minimum SI message includes a system information index for each of the five existing additional SI messages that can be acquired by a UE in radio cell 1.

[0081] The embodiments described herein relate to a system information acquisition procedure performed between a UE and a gNB. They focus on improving the way in which the validity of system information can be encoded and decoded (by the gNB and the UE, respectively) in order to be able to avoid (re)acquisition of system information (in additional SI messages) and to reduce the overhead of transmission of the system information and to maintain flexibility in defining the validity of the system information across space (different areas / cells).

[0082] According to some example embodiments, each of the system information indexes is assumed to be composed of a value tag and an area pointer, and both the value tag and the area pointer can be distinguished by the UE so that they are processed separately from each other. Instead of directly containing information about a particular area, the area pointer in the system information index "points" to an area that has already been defined (the area may be network specific, but the user equipment must be aware of this area). The UE must be able to interpret the area pointer, i.e., correctly determine which area the area pointer in the system information index actually points to. In this regard, the UE and the gNB must have a common understanding on how to decode or encode the area into the area pointer, respectively. For example, the UE and the gNB1 can store a list that associates possible values ​​of the area pointer with corresponding areas that have already been defined.

[0083] Based on the area pointer and the list of stored areas, the UE can determine for which area the signaled additional SI message is considered valid when receiving a system information index including the area pointer.

[0084] As will be explained later in a more detailed embodiment, the value tag can be used to determine the time validity of the announced additional SI message.

[0085] The UE then needs to determine whether it needs to acquire any of the signaled additional SI messages from gNB1. In order to be able to avoid acquiring any of the previously acquired additional SI messages, the UE must have already previously received the same additional SI message containing the same value tag and associated to the same area. In that case, the system information contained in this already acquired additional SI message can be considered as still applicable to the current radio cell (within the same area) and the UE does not need to acquire again the corresponding additional SI message containing the same system information.

[0086] On the other hand, if the value tag and / or area (indicated by the area pointer) of the additional SI message signaled in the system information index of the minimum SI message is different from the corresponding value tag and / or corresponding area associated with the corresponding already acquired additional SI message, the UE determines that the system information contained in that already acquired additional SI message is not applicable in the radio cell. In this way, the UE determines that the UE needs to acquire the signaled additional SI message from the gNB in ​​order to obtain valid system information applicable to the current radio cell.

[0087] Therefore, since the area pointer simply points to the area instead of directly providing the identification information of the area, the size of the area pointer can be smaller than the system information index that directly identifies the area, thus generating less overhead compared to the system information index that directly includes the identification information of the area.

[0088] Since within the minimum SI message, separate area pointers (which can be set differently from each other) can be used for each additional SI message, the aforementioned improved SI acquisition procedure also enables the gNB1 to flexibly determine the valid area of ​​the system information separately for each additional SI message.

[0089] FIG. 12 shows an exemplary flow diagram of UE operation, particularly with respect to the basic system acquisition procedure described above.

[0090] The functionality of the aforementioned improved SI acquisition procedure will now be described in detail based on the following two exemplary scenarios described in relation to Figs. 11-13. In the first scenario, it is exemplarily assumed that a UE is powered up in a radio cell 1 of gNB1 and is attempting to access the radio cell 1 of gNB1 (which then becomes the serving gNB of this UE). The gNB1 is periodically broadcasting a minimum SI message, and the UE acquires the same minimum SI message. The minimum SI message contains system information required for the UE for initial access to the radio cell 1, including additional SI messages SI1-SI5 and information on how to acquire their contents. Thus, in particular, the minimum SI message contains, for each additional SI message, a corresponding system information index, and further includes a specific value tag and an area pointer. This is exemplarily illustrated in Fig. 13, which shows five system information indexes (SI_index_1-5) for five available additional SI messages SI1-SI5. For example, SI_index_1 associated with additional SI message SI1 includes area_pointer_1 and value_tag1, SI_index_2 associated with additional SI message SI2 includes area_pointer_2 and value_tag2, and so on.

[0091] Considering that the UE is powered on for the first time, no additional SI messages have been acquired before and therefore no system information is available for the signaled additional SI messages. The UE therefore determines that for each additional SI message it needs to acquire the same additional SI message in order to acquire the corresponding system information contained therein. The UE can therefore start acquiring the additional SI messages SI1 to SI5 indicated in the minimal SI message, for example, by receiving the additional SI messages broadcast by gNB1 on a specific radio resource that occurs periodically and / or by first requesting and then receiving the additional SI messages that are available in the radio cell 1 only upon request. Upon reception of the additional SI messages, the UE may store, for each additional SI message, the area and value tag obtained from the system information index associated with the additional SI message. For example, for the additional SI message SI1, the UE stores information about the area indicated by the value_tag_1 and the area pointer area_pointer_1 (e.g., the area ID and / or type of the identified area). For the other additional SI messages SI2 to SI5, the same or similar information can be stored by the UE. In this way, the UE stores the validity information for each additional SI message and can use this validity information in subsequent system information acquisition procedures.

[0092] It is now assumed that the UE continues to move within radio cell 1 and eventually moves to another radio cell 2 controlled by gNB2 (see FIG. 11). The UE further receives a minimum SI message within radio cell 1 and also when entering the coverage area of ​​radio cell 2. For example, the above-mentioned SI acquisition procedure may be repeatedly performed by the UE each time a minimum SI message is received.

[0093] For example, gNB2 broadcasts a minimal SI message that includes the system information necessary for the UE to perform an initial access to the radio cell 2 and further includes a system information index for each additional SI message SI1 to SI5. The structure of the system information index must be the same as that described above for the minimal SI message broadcast by gNB1 and therefore consists of a value tag and an area pointer. The UE then determines whether it needs to obtain any of the announced additional SI messages from gNB2. As previously described, the UE has already obtained all the additional SI messages from gNB1, but it needs to determine whether those additional SI messages are also applicable to the new radio cell 2. This determination is performed by the UE based on the system information index and the contents of the stored value tags and area information. For each additional SI message (e.g., SI1), the UE checks the validity of the already acquired additional SI message (e.g., SI1) in the radio cell 2 by comparing the stored value tag (e.g., value_tag_1) of the already acquired additional SI message (e.g., SI1) with the value tag (value_tag_1) included in the system information index (SI_index_1) of the announced additional SI message (SI1) in the newly received minimal SI message. Furthermore, the UE checks the validity of the already acquired additional SI message (e.g., SI1) in the radio cell 2 by comparing the stored area of ​​the already acquired additional SI message (e.g., SI1) with the area indicated by the area pointer (area_pointer_1) included in the system information index (SI_index_1) of the announced additional SI message (SI1) in the newly received minimal SI message.If both the value tag and area signaled in the new minimal SI message are the same as the stored value tag and area of ​​an already acquired additional SI message (e.g., SI1), the corresponding system information contained in that already acquired additional SI message (SI1) can also be applied in the radio cell 2, and the UE does not need to acquire the additional SI message via the radio cell 2. This determination can be performed for each additional SI message. The order of checking the validity of the value tag and the validity of the area information is not limited, i.e., the spatial validity can be checked before the temporal validity, or in the reverse order, or they can be checked simultaneously.

[0094] Although the above scenario exemplarily assumes that the UE moves to a new radio cell 2, the improved system acquisition procedure can also be performed by a UE staying in the cell. For example, it can be exemplarily assumed that the spatial validity of the system information is maintained as long as the UE stays in the same radio cell. Accordingly, the area pointer broadcasted in the system information index of the additional SI message continues to point to the same area as before. However, the gNB1 may decide to modify some system information parameters included in one or more of the additional SI messages (e.g., SI1). Accordingly, the gNB1 also changes the value of the corresponding value tag (e.g., increments value_tag_1, e.g., by 1) and broadcasts the value of the modified value tag in relation to the modified additional SI message in the minimal SI message. The UE, which has determined that the value of the value tag of the additional SI message has changed, derives from this determination that the corresponding system information acquired via the previous additional SI message is no longer valid and decides to reacquire the corresponding additional SI message (e.g., SI1) transmitted by the gNB1 in the radio cell 1.

[0095] In the above, it was assumed that the area pointer points to an area already defined before. In this regard, there may be various areas that can be used. It should be noted that in general, one or more areas are usually already defined for other UE procedures. For example, one or more tracking areas may be defined to control network-based mobility, as explained before. In addition, RAN-based notification areas may be defined to implement a paging mechanism when the UE is in a new RRC inactive state, as explained before. Another example is a closed subscriber group area, consisting of radio cells that only certain UEs can access, as explained in detail before.

[0096] Instead of using another area type to define the valid area of ​​the system information (i.e. an area including multiple gNBs to which part of the system information can be applied in the same way), a new area type can be defined for the aforementioned purpose. Thus, a further area that can be used is the system information area, which should be generally understood as an area of ​​multiple radio cells to which at least part of the system information can be applied in the same way. In other words, within one system information area, the radio cells use the same system information parameters from one or more additional SI messages and thus transmit the same system information within each radio cell. In this regard, there is no agreement in 3GPP as to whether and how the system information area is defined, configured, maintained, etc.

[0097] The above description mainly focuses on the procedures performed on the UE side. However, the gNB also participates in the above-mentioned improved system information acquisition procedure by performing corresponding steps for providing the minimum SI message, additional SI message to the UE. The gNB needs to be able to generate the contents of the minimum SI message, in particular the system information index associated with the additional SI message, as described above and below.

[0098] Furthermore, since certain system information (of one or more additional SI messages) must be equally applicable within multiple radio cells of a certain area (such as a tracking area, or a CSG area, or a RAN-based notification area, or simply a system information area), gNBs in those areas need to coordinate the system information of the additional SI messages and the system information indexes that they broadcast in the minimal SI messages. For example, if the system information of one additional SI message is changed, all gNBs belonging to the validity area of ​​that one additional SI message need to be synchronized so that the same changed additional SI message is sent and the same updated system information index (e.g. updated value tag) is broadcast in the minimal SI message.

[0099] In the following, an example embodiment is described, according to which the area pointer of the system information index encodes an area type, based on which the UE then determines the corresponding area to which the area type points. It is exemplarily assumed that the area pointer has a length of 2 bits and can therefore encode up to four different types of areas. An example association between different values ​​of the area pointer and the corresponding area type is shown in FIG. 14 in the form of an area type list with different items, where 00 encodes the tracking area type, 01 encodes the RAN-based area type, 10 encodes the SI area type, and 11 encodes the cell type. In order to be able to encode and correctly decode the area pointer information, it can be assumed that this association information is stored not only in the gNB, but also by the UE.

[0100] The system information index shown in Figure 13 consists of a value tag, which may have a length of, for example, 8 bits, and an area pointer containing 2 bits. Each system information index is therefore 10 bits, and the additional information carried by the minimum SI message is 50 bits (10 bits for each of the 5 additional SI messages in which the system information index is included).

[0101] In response, the UE determines the area type based on the area pointer and the area type association described above. The UE may then determine the actual area (e.g., the area's identity) based on the identified area type by using the identity already acquired for each type of area. For example, assuming exemplarily that the area pointer points to a tracking area type (i.e., 00 in the example of FIG. 14), the UE may know about one or more IDs of the tracking area and thus make a proper association between the tracking area type and the tracking area identity. Thus, the UE first determines that the signaled additional SI message is associated with a tracking area type, and then determines the current tracking area ID (broadcast by gNB1). Then, according to the improved system information acquisition procedure described above, if that additional SI message has already been acquired before and is valid for the same tracking area as the tracking area signaled in the current minimum SI message, the UE does not need to reacquire that additional SI message.

[0102] In other words, when a UE moves to a target cell that belongs to the same tracking area as the source cell, the additional SI messages that the UE acquired in the source cell can be applied in the same way in the target cell, and reacquisition of the same additional SI messages can be avoided.

[0103] A similar approach is envisaged if the area pointer points to any of the other possible area types (e.g., RAN-based notification area, CSG area, or system information area). In either case, the UE determines the area ID based on the area pointer, the association of said area types, and finally the area ID of said identified area type. The IDs of the RAN-based notification area, CSG area, and system information area are known to the UE beforehand, e.g., broadcasted by the gNB or provided to the UE in dedicated signaling.

[0104] Based on the area ID thus determined, the UE can determine whether the system information already acquired in the additional SI message is also applicable in the current situation (e.g. in the new cell). In short, if the target cell belongs to the same area (RAN-based notification area, CSG area, or system information area) as the source cell, the additional SI message acquired by the UE in the source cell can be applied in the same way in the target cell, and reacquisition of the same additional SI message can be avoided.

[0105] In an exemplary scenario, different types of areas are described in relation to Figures 14, 15, and 16. As is exemplarily assumed, the same additional SI message SI1 (specifically, the system information contained therein) can be applied within one tracking area, the same additional SI message SI2 (specifically, the system information contained therein) can be applied within one RAN-based notification, the same additional SI message SI3 (specifically, the system information contained therein) can be applied within one system information area, and the same additional SI message SI4 / SI5 (specifically, the system information contained therein) can be applied within only one cell. Figure 15 shows the corresponding area pointer values ​​to reflect the described scenario.

[0106] Accordingly, for SI1, if the new cell and the old cell have the same tracking area ID (and the same value_tag_1), the system information contained in the additional SI message SI1 obtained in the old cell can also be used by the UE in the new cell. For SI2, if the new cell and the old cell have the same RAN-based notification area ID (and the same value_tag_2), the system information contained in the additional SI message SI2 obtained in the old cell can also be used by the UE in the new cell. For SI3, if the new cell and the old cell have the same system information area ID (and the same value_tag_3), the system information contained in the additional SI message SI3 obtained in the old cell can also be used by the UE in the new cell. On the other hand, the system information in the additional SI messages SI4 and SI5 is cell-specific (area pointer 11), so the UE has to obtain the additional SI messages SI4 and SI5 in any case when entering the new cell.

[0107] According to yet another example embodiment, flexibility should be further improved regarding how the spatial validity is encoded into the system information index of the additional SI message. In the above embodiment, the valid area of ​​the system information is encoded into the area pointer field of the system information index, allowing the UE to first determine the area type and then the area ID. However, this solution requires that the UE can simply determine the area ID from the area type, which may require, for example, that the area ID is known to the UE in advance (e.g., broadcasted in the radio cell). The next example embodiment facilitates having the advantage that the area ID is directly encoded into the system information index of the additional SI message, and therefore no prior knowledge of the area ID is required.

[0108] Figure 17 shows an example configuration of the system information index of the five additional SI messages. As is clear from this figure, it is assumed that the system information index of the additional SI message SI4 does not contain an area pointer like the system information index of the other additional SI messages, but contains the area ID itself (e.g., a system information area ID containing 8 bits). Accordingly, the UE can determine the area ID from the area pointer as described above, but can also process the system information index containing the area ID directly as shown in Figure 17.

[0109] One exemplary way for a UE to know whether a system information index includes an area pointer field (e.g., 2 bits) or an area ID (e.g., 8 bits) is to use ASN.1 encoding. For the area pointer field of each system information index, a suitable ASN.1 encoding allows for distinguishing and selecting different fields (area pointer field and area ID field). An exemplary ASN.1 encoding may be as follows: Area_Pointer CHOICE { area-pointer INTEGER (0 ..3), -- 0: Refer to the tracking area type -- 1: Refer to the RAN area type -- 2: Refer to SI area type -- 3: Cell type si-area-ID INTEGER (0..255) }

[0110] In the following, an example embodiment is described, according to which the area pointer of the system information index encodes the area list items of the area list using area identification information. An example list of area IDs is shown in FIG. 18, and the system information index corresponding to five additional SI messages is shown in FIG. 19. As is clear from this figure, each system information index includes an area pointer field, whose value points to a list item of the area ID list of FIG. 18. It is exemplarily assumed that 3 bits are used for the area list pointer field in the system information index, thus making it possible to distinguish up to 8 different area IDs (the size of the actual area list can be dynamic, with a maximum number of list items being 8). In order to be able to decode the area pointer of the system information index, it is assumed that the UE has acquired the area ID list. One example option is that the area list is also transmitted in the minimum SI message, in which case the minimum SI message carries not only the area list but also all the system information indexes. Another exemplary option is that the area list has already been obtained from the previous cell, for example during a handover procedure, as will be explained in more detail in a later embodiment.

[0111] To carry the system information index of all additional SI messages, exemplarily assuming 3 bits for the area list pointer and 8 bits for the value tag, 55 bits are needed. Furthermore, the size of the area list depends on its length (i.e., the number of list items), and 8 bits per list item (i.e., 8 bits for ID) can be exemplarily assumed, e.g., an ASN.1 code allowing the UE to distinguish between different list items. Optionally, 3 bits can be assumed for the list item field in the area list.

[0112] This solution is particularly useful when only a small number of different areas are used for spatial validity of system information. If multiple additional SI messages are associated with the same area (e.g., the same SI area), one list item containing the ID of that SI area in the list is sufficient, and the area list carried in the minimal SI message does not become large. Also, when a cell contains multiple area IDs (e.g., tracking area IDs or RAN-based notification area IDs), the described solution allows the gNB to unambiguously identify the area IDs.

[0113] According to yet another embodiment, which may be used independently of the embodiments described above (e.g., may be combined or used standalone), the system information acquisition procedure must be improved in relation to the handover procedure. As previously explained, some additional SI messages are only available on request (i.e., when the UE explicitly requests it at the gNB). In line with the exemplary handover shown in FIG. 7, when performing a handover procedure from a source cell to a target cell, the UE reads the minimum SI messages of the target cell after the handover is completed (e.g., after step 9 of FIG. 7). Only then can the UE determine which additional SI messages it should acquire in the new target cell, for example according to the improved system information acquisition procedure described above with respect to one of the various embodiments. However, this determination is time-consuming and involves many transactions between entities.

[0114] According to these further embodiments, the handover procedure has to be improved in order to allow the UE to obtain the additional SI messages early on request.

[0115] According to one of these embodiments, during the handover preparation phase, the target gNB transmits to the source gNB the system information index broadcast by the target gNB in ​​the minimal SI message, for example in the handover request ACK message (see step 6 in FIG. 7). The source gNB can then provide the UE with the system information index related to the target cell for the additional SI message during the handover procedure, for example as part of the handover command message. The UE can use the system information index related to the target cell to determine which additional SI message available in the target cell to obtain upon request. Thus, the UE already knows which additional SI message to obtain before the handover is completed and can transmit the corresponding additional SI message request at an early point in time. For example, the UE can transmit the additional SI message request during the handover execution phase, for example when performing a random access channel procedure with the target gNB (the RACH procedure between the UE and the target gNB can be performed by the UE after receiving the handover command message from the source gNB). In this regard, one of the messages of the RACH procedure may be used by the UE, for example using the random access preamble transmission of the contention-free RACH procedure (see FIG. 6). A further message of the RACH procedure in a handover scenario (similar to the third message in the contention-based RACH procedure, not shown in FIG. 6) may carry an RRC connection reconfiguration complete message (referred to as the handover complete message in FIG. 7).

[0116] The target cell's additional SI message requested by the UE may be delivered to the UE, for example, within a message of the RACH procedure (e.g., a random access response message of a contention-free RACH procedure after receiving the additional SI request in the first message). Alternatively, the target gNB may provide the requested additional SI message to the UE using a different dedicated message after receiving the additional SI request in the RRC Connection Reconfiguration Complete message.

[0117] In an alternative embodiment, the UE itself does not need to request additional SI messages on request from the target cell, but this request is performed by the source gNB during handover preparation. In particular, the source gNB is informed by the UE, e.g. via a Measurement Report message (see step 2 of FIG. 7), as to which additional SI messages the UE would like to receive. The source gNB then requests these additional SI messages from the target gNB, e.g. during the handover preparation procedure (e.g. in a Handover Request message (see step 4 of FIG. 7)). As with the previous alternative, the target gNB can then deliver the additional SI messages of the target cell requested by the UE to the UE, e.g. in a message of the RACH procedure (e.g. a Random Access Response message of a contention-free RACH procedure). Alternatively, the target gNB may provide the requested additional SI messages to the UE using a different dedicated message.

[0118] <Other aspects> According to a first aspect, a user equipment is provided. The user equipment comprises a receiver for receiving a minimal system information message from a first radio base station controlling a first radio cell of a mobile communication system. System information of the first radio cell that can be acquired by the user equipment is carried in the minimal system information message and in one or more additional system information messages. The minimal system information message includes system information for accessing the first radio cell and includes at least one system information index. Each system information index is associated with one of the additional system information messages. The index of the system information message includes a value tag and an area pointer, and the area pointer points to one area already defined. The user equipment comprises a processing circuit for determining whether the user equipment has previously acquired an additional system information message associated with the same value tag and the same area as indicated by the system information index received in the minimal system information message. If the determination is positive, the processing circuit determines that the system information included in the previously acquired additional system information message is applicable to the first radio cell.

[0119] According to a second response provided in addition to the first aspect, if this determination is negative, the processing circuit determines that the system information comprised in said previously acquired additional system information message is not applicable to the first radio cell and decides to acquire an additional system information message for the first radio cell from the first radio base station.

[0120] According to a third aspect provided in addition to the first or second aspect, an area type list is stored in the user equipment, each item in the area type list is associated with a list number and an area type, and an area pointer indicates the list number of the area type list. The processing circuit, in operation, determines an area type based on the area pointer and the area type list, and determines an area identification based on the determined area type and already obtained area identification information of the determined area type. Optionally, the processing circuit, in operation, determines whether a previously obtained additional system information message can be applied to the same area based on the determined area type and the determined area identification information.

[0121] According to a fourth aspect provided in addition to the third aspect, the area type is one of a tracking area, a radio access network, a RAN-based notification area, a closed subscriber group area, a radio cell, and a system information area.

[0122] According to a fifth aspect provided in addition to the third or fourth aspect, the receiver, in operation, receives a second minimal system information message from a first radio base station of a first radio cell. The second minimal system information message includes system information for accessing the first radio cell and includes one extended system information index. The extended system information index is associated with one of the additional system information messages. The extended system information index includes a value tag and an identification of a system information area. The processing circuit, in operation, determines whether the user equipment has previously acquired an additional system information message associated with the same value tag and the same system information area as included in the extended system information index. If the determination is positive, the processing circuit, in operation, determines that the system information included in the previously acquired additional system information message is applicable to the first radio cell.

[0123] According to a sixth aspect provided in addition to the first or second aspect, a user equipment obtains an area list including a corresponding area identification. Each item in the area list is associated with a list number and an area identification, and an area pointer indicates a list number of the area list. The processing circuit, in operation, determines the area identification based on the area pointer and the area list. Optionally, the user equipment obtains the area list from a received minimal system information message. Optionally, the processing circuit, in operation, determines whether a previously obtained additional system information message can be applied to the same area based on the determined area identification.

[0124] According to a seventh aspect provided in addition to one of the first to sixth aspects, the minimum system information message includes one system information index for each additional system information message that may be obtained by the user equipment in the first radio cell.

[0125] According to an eighth aspect, provided in addition to any of the first to seventh aspects, one or more of the additional system information messages may be broadcast by a first radio base station in the first radio cell or may be obtained by the user equipment when requesting the same additional system information message from the first radio base station.

[0126] According to a ninth aspect provided in addition to one of the first to eighth aspects, the processing circuit, in operation, stores, in association with an associated additional system information message, a received value tag of the system information index and information regarding an area indicated by the system information index. Optionally, the stored information regarding the area includes information regarding a type of the indicated area and information regarding an identification of the indicated area.

[0127] According to a tenth aspect provided in addition to one of the first to ninth aspects, the receiver, in operation, receives a second minimal system information message from a first radio base station of a first radio cell. The second minimal system information message includes system information for accessing the first radio cell and includes a second system information index. The second system information index is associated with an additional system information message already previously acquired by the user equipment. The processing circuit, in operation, determines that content of the already acquired system information message has changed when it determines that a value of a value tag associated with the already acquired additional system information message is different from a value of a value tag included in the second system information index of the minimal system information message. The processing circuit, in operation, determines to reacquire the additional system information message when it determines that content of the already acquired additional system information message has changed.

[0128] According to an eleventh aspect, provided in addition to one of the first to tenth aspects, the previously obtained system information message was received by a receiver of the user equipment when the user equipment was in a different radio cell or in the first radio cell.

[0129] According to a twelfth aspect provided in addition to any of the first to eleventh aspects, a user equipment is moving to a second radio cell under the control of a second radio base station. The receiver, in operation, receives from the first radio base station at least one system information index associated with one additional system information message that can be acquired in the second radio cell when the user equipment requests the additional system information message. The transmitter of the UE, in operation, transmits to the second radio base station a request for acquiring the one additional system information message indicated by the system information index associated with the second radio cell. Optionally, the request is transmitted by the transmitter in a message of a random access channel procedure performed between the user equipment and the second radio base station when moving to the second radio base station. Optionally, the receiver, in operation, receives the requested additional system information message from the second radio base station in a message of the random access channel procedure after the message used to transmit the request.

[0130] According to a thirteenth aspect provided in addition to any of the first to eleventh aspects, a user equipment is moving to a second radio cell under control of a second radio base station. At least one additional system information message that the user equipment can obtain in the second radio cell becomes available upon requesting the same additional system information message. In operation, the receiver receives the additional system information message from the second radio base station in a random access channel procedure message.

[0131] According to a fourteenth aspect, a radio base station is provided. The radio base station comprises a processing circuit that generates a minimal system information message including system information for accessing a first radio cell controlled by the radio base station and including at least one system information index. The system information of the first radio cell that can be acquired by a user equipment is carried in the minimal system information message and in one or more additional system information messages. Each system information index is associated with one of the additional system information messages. The index of the system information message includes a value tag and an area pointer. The area pointer points to one area already defined. The radio base station comprises a transmitter that transmits the minimal system information message to the user equipment.

[0132] According to a fifteenth aspect provided in addition to the fourteenth aspect, the transmitter, in operation, transmits one or more of the additional system information messages to the user equipment. Optionally, the processing circuit, in operation, determines a value of an area pointer of the system information index to indicate an area to which the associated additional system information message is applicable.

[0133] According to a sixteenth aspect provided in addition to the fourteenth or fifteenth aspects, an area pointer indicates a list number of an area type list, and each item in the area type list is associated with a list number and an area type. The processing circuit, in operation, determines a list number associated with an area type to which the additional system information message is applicable, and sets an area pointer in a system information index of the additional system information message to indicate the determined list number. Optionally, the area type is one of a tracking area, a radio access network, a RAN-based notification area, a closed subscriber group area, a radio cell, and a system information area.

[0134] According to a 17th aspect provided in addition to any of the 14th to 16th aspects, the processing circuit, in operation, generates a system information index associated with one additional system information message to include a value tag and identification information of the system information area.

[0135] According to an 18th aspect provided in addition to the 14th or 15th aspects, an area pointer indicates a list number of an area list, and each item in the area list is associated with a list number and an area identification. The processing circuit, in operation, determines a list number associated with the area identification to which the additional system information is applicable, and sets an area pointer in a system information index of the additional system information message to indicate the determined list number. Optionally, the processing circuit, in operation, generates a minimal system information message to include the area list.

[0136] According to a 19th aspect provided in addition to any of the 14th to 18th aspects, a user equipment is moving to a second radio cell under a control of a second radio base station. The radio base station comprises a receiver, which in operation receives from the second radio base station at least one system information index associated with one additional system information message that can be acquired in the second radio cell when the user equipment requests the additional system information message. The transmitter in operation transmits to the user equipment the received at least one system information index related to the second radio cell. The receiver in operation receives from the user equipment a request to acquire one additional system information message indicated by the system information index associated with the second radio cell. Optionally, the request is received by the receiver in a message of a random access channel procedure performed between the user equipment and the second radio base station when moving to the second radio base station.

[0137] Hardware and Software Implementations of the Disclosure The present disclosure may be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of each embodiment above may be partially or entirely realized by an LSI such as an integrated circuit, and each process described in each embodiment may be partially or entirely controlled by the same LSI or a combination of LSIs. The LSI may be formed as multiple chips individually, or one chip may be formed to include some or all of the functional blocks. The LSI may include data inputs and data outputs coupled thereto. The LSI may be referred to herein as an integrated circuit (IC), a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. However, the method of implementing the integrated circuit is not limited to an LSI, and may be realized using a dedicated circuit, a general-purpose processor, or a special-purpose processor. In addition, an FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells arranged in the LSI may be used. The present disclosure may be realized as digital processing or analog processing. If future integrated circuit technologies replace LSI as a result of advances in semiconductor technology or other derived technologies, the functional blocks may be integrated using the future integrated circuit technologies. Biotechnology may also be applied.

[0138] Furthermore, the various embodiments may be implemented by means of software modules executed by a processor or directly in hardware. A combination of software modules and hardware implementations may also be possible. The software modules may be stored on any kind of computer-readable storage medium (e.g. RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc.). It should further be noted that individual features of the different embodiments may be the subject of another embodiment individually or in any combination.

[0139] It will be understood by those skilled in the art that numerous variations and / or modifications may be made to the present disclosure as shown in the specific embodiments, and the present embodiments are therefore to be considered in all respects as illustrative and not restrictive.

Claims

1. a receiver for receiving a minimal system information message including system information for accessing a first radio cell and including at least one system information index, each said system information index being associated with one of the additional system information messages; a receiver, the system information index including information indicating an association with the additional system information, a value tag, and an area pointer, the area pointer being encoded with an area identification and an area type; a processing circuit that determines, based on the area identification and the area type, whether the user equipment has previously acquired the additional system information message associated with the same value tag and the same area as indicated by the system information index received in the minimal system information message; Equipped with If the determination is positive, the processing circuit determines that system information included in the previously obtained additional system information message is applicable to the first radio cell; The area type is at least: One of the area types including a radio cell and a system information area. User equipment.

2. If the determination is negative, the processing circuit determines that system information included in the previously acquired additional system information message is not applicable to the first radio cell, and determines to acquire the additional system information message of the first radio cell from a first radio base station. The user equipment of claim 1 .

3. the receiver receives a second minimal system information message from a first radio base station of the first radio cell, the second minimal system information message including system information for accessing the first radio cell and including one extended system information index, the extended system information index being associated with one of the additional system information messages; the extended system information index includes a value tag and a system information area identification; the processing circuit determines whether the user equipment has previously acquired the additional system information message associated with the same value tag and the same system information area as included in the extended system information index; If the determination is positive, the processing circuit determines that the system information included in the previously acquired additional system information message is applicable to the first radio cell. The user equipment of claim 1 .

4. the minimum system information message includes one system information index for each additional system information message that may be acquired by the user equipment in the first radio cell. The user equipment of claim 1 .

5. one or more of the additional system information messages may be broadcast by a first radio base station in the first radio cell or may be obtained by the user equipment when requesting the same additional system information message from the first radio base station. The user equipment of claim 1 .

6. the receiver receives a second minimal system information message from a first radio base station of the first radio cell, the second minimal system information message including system information for accessing the first radio cell and including a second system information index, the second system information index being associated with an additional system information message previously acquired by the user equipment; determining that content of the previously obtained system information message has changed when the processing circuit determines that a value of the value tag associated with the previously obtained additional system information message is different from a value of the value tag included in the second system information index of the minimal system information message; determining to reacquire the additional system information message when the processing circuit determines that the content of the already acquired additional system information message has changed; The user equipment of claim 1 .

7. the previously obtained system information message was received by the receiver of the user equipment when the user equipment was in a different radio cell or in the first radio cell; The user equipment of claim 1 .

8. the user equipment is moving to a second radio cell under the control of a second radio base station, and the receiver receives from a first radio base station at least one system information index associated with one additional system information message that can be obtained in the second radio cell when the user equipment requests an additional system information message; a transmitter sending a request to the second radio base station to obtain the one additional system information message indicated by the system information index associated with the second radio cell, optionally when moving to the second radio base station, the transmitter sending the request via a message of a random access channel procedure performed between the user equipment and the second radio base station; Optionally, the receiver receives the requested additional system information message from the second radio base station in a message of the Random Access Channel procedure after the message used to transmit the request. The user equipment of claim 1 .

9. 1. A method performed by a user equipment, comprising: receiving a minimal system information message including system information for accessing the first radio cell and including at least one system information index, each said system information index being associated with one of the additional system information messages; a receiving step, the system information index including information indicating an association with the additional system information, a value tag, and an area pointer, the area pointer being encoded with an area identification and an area type; a processing step in which the user equipment determines whether the user equipment has previously acquired the additional system information message associated with the same value tag and the same area as indicated by the system information index received in the minimal system information message; Including, If the determination is positive, the processing step determines that the system information included in the previously acquired additional system information message is applicable to the first radio cell; determining whether the additional system information messages are associated with the same area based on the area identification and the area type; The area type is at least: One of the area types including a radio cell and a system information area. method.

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