Terminal device, base station device, and control method
Patent Information
- Application Number
- PCT/JP2025/012595
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-27
- Publication Date
- 2026-10-01
Smart Images
Figure JP2025012595_01102026_PF_FP_ABST
Abstract
Description
Terminal device, base station device, and control method
[0001] The present invention relates to a terminal device, a base station device, and a control method.
[0002] In current networks, traffic from mobile terminals (such as smartphones and feature phones) occupies most of the network resources. Furthermore, the traffic used by mobile terminals is expected to continue to expand in the future.
[0003] In addition to traffic used by mobile terminals, IoT (Internet of Things) services (for example, transportation systems, smart meters, and monitoring systems for devices, etc.) are also being developed. For this reason, networks are required to support services with various requirements. To accommodate such diverse services, for example, the communication standard for fifth-generation mobile communication (5G or NR (New Radio)) defines specifications with the assumption of supporting many use cases categorized into eMBB (Enhanced Mobile BroadBand), Massive MTC (Machine Type Communications), and URLLC (Ultra-Reliable and Low Latency Communications).
[0004] In the 3rd Generation Partnership Project (3GPP (registered trademark)), which is an international standardization project, extension technologies for the aforementioned communication standard are continuously being studied and standardized even at present.
[0005] In 3GPP, to reduce power consumption on the network side (i.e., base station devices and core network devices), NES (Network Energy Savings) technology is being studied (Non-Patent Document 1). Hereinafter, a cell (base station device) compatible with the NES function, that is, a cell that supports the NES function, is also referred to as a NES cell.
[0006] 3GPP TR 38.864 V18.0.0 (2022-12) R2-2500257
[0007] Base station equipment broadcasts system information (system information) within the cell as information commonly used by terminal devices within the cell. System information is also called broadcast information. In 3GPP, as one of the network power reduction technologies, a method is being considered to reduce the power consumption of base station equipment by introducing On-demand SIB1 (System Information Block Type 1), which is transmitted as needed (on-demand transmission) from the NES cell in response to requests from terminal devices, in addition to SIB1, which is one of the broadcast information that is transmitted periodically. For example, Non-Patent Document 2 discloses an example of a procedure for a terminal device to request On-demand SIB1.
[0008] Non-Patent Document 2 discloses an RRC Restabilization procedure after detecting a wireless link failure, which involves performing an RRC restabilization procedure using SIB1 request setting information on an NES cell, and reusing the cell selection criteria to evaluate whether the NES cell is a suitable cell for camping. However, there is a problem in that, for example, when On-demand SIB1 (or SIB1) has not been obtained, the cell selection criteria are unknown, and it is not possible to evaluate whether the NES cell is a suitable cell. Non-Patent Document 2 does not mention any solution to this problem.
[0009] One aspect of the present invention is to improve the efficiency of power saving related to wireless communication between terminal equipment and base station equipment when applying network power reduction technology that appropriately transmits system information (SIB1).
[0010] A terminal device according to one aspect of the present invention is a terminal device capable of communicating with a first base station device and a second base station device, comprising: a receiving unit that receives from the first base station device information regarding a request signal setting that requests the second base station device to transmit first system information on demand; a processing unit that, when holding a valid request signal setting and when a timer for the RRC reconnection procedure is being timed, evaluates whether the second base station device satisfies the cell selection criteria by applying first cell selection criterion parameters if first system information has been acquired, and applying second cell selection criterion parameters if first system information has not been acquired, and performs the first cell selection criterion evaluation based on the applied cell selection criterion parameters; and a transmitting unit that transmits a request signal based on the request signal setting to the second base station device that satisfies the cell selection criteria.
[0011] A base station device according to one aspect of the present invention is a base station device in a communication system including a second cell that transmits first system information on demand in response to a request from a terminal device, and a first cell that transmits first system information periodically, comprising: a transmitting unit that transmits to a terminal device via the first cell information relating to a request signal setting that requests on-demand transmission of first system information corresponding to the second cell; a processing unit that, when the terminal device is holding the request signal setting and a timer for the RRC reconnection procedure is being timed, sets information that causes the terminal device to decide whether to apply either a first cell selection criterion parameter or a second cell selection criterion parameter as a first cell selection criterion evaluation that evaluates whether the second cell satisfies the cell selection criteria; and a receiving unit that receives a physical random access channel based on the request signal setting transmitted from the terminal device depending on whether the second cell satisfies the cell selection criteria.
[0012] According to the above-described embodiment, when applying network power reduction technology, the efficiency of power saving related to wireless communication between terminal equipment and base station equipment can be improved.
[0013] This figure shows an example of the configuration of a wireless communication system related to the embodiment. This figure shows an example of the functional configuration of a terminal device related to the embodiment. This figure shows an example of the functional configuration of a base station device related to the embodiment. This figure shows an example of the On-demand SIB1 acquisition procedure. This figure shows an example of the RRC reconnection procedure for an On-demand SIB1 transmission cell. This figure shows another example of the RRC reconnection procedure for an On-demand SIB1 transmission cell. This figure shows an example of the hardware configuration of a terminal device. This figure shows an example of the hardware configuration of a base station device.
[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. The problems and embodiments described herein are examples and do not limit the scope of the rights of this application. In particular, even if the wording of the description differs, the technology of this application is applicable as long as it is technically equivalent and does not limit the scope of the rights. Furthermore, each embodiment can be combined as appropriate, as long as there is no inconsistency in the processing content.
[0015] The wireless communication system according to embodiments of the present invention may utilize known technologies as appropriate. Applicable known technologies may include, for example, 5G (NR), Beyond 5G, 5G-Advanced, or other wireless communication methods, or future wireless communication methods such as 6G. The wireless communication system according to embodiments of the present invention targets NR, but is not limited thereto. For example, embodiments of the present invention are also applicable to LTE (Long Term Evolution) and LTE-Advanced. Furthermore, it is also applicable to wireless communication systems that use NR as part of the wireless communication system.
[0016] Furthermore, embodiments of the present invention are applicable to any wireless communication system comprising at least terminal equipment and base station equipment, and are also applicable to future wireless communication systems. In the following description, LTE and LTE-Advanced will also be referred to as E-UTRA (Evolved Universal Terrestrial Radio Access), but they have the same meaning.
[0017] Hereinafter, embodiments of the base station equipment, terminal equipment, and wireless communication system disclosed in this application will be described with reference to the drawings. Note that the following embodiments are not intended to limit the disclosed technology.
[0018] <Wireless Communication System> Figure 1 is a diagram showing an example of the configuration of a wireless communication system 1 according to an embodiment of the present invention. The wireless communication system 1 according to the embodiment consists of, for example, a terminal device 10, base station devices 20A and 20B, and a core network 30. The wireless communication system 1 is, for example, a wireless communication system that corresponds to NES, in other words, a wireless communication system that supports the functions of NES. Base station device 20A is a base station device 20 (first base station device) that notifies information for accessing base station device 20B which supports NES functions. On the other hand, base station device 20B is a base station device 20 (second base station device) which supports NES functions, and access is attempted based on information from base station device 20A. When base station devices 20A and 20B are not distinguished, they are simply referred to as base station device 20. In addition, there may be multiple terminal devices 10.
[0019] The terminal device 10 may be a wireless terminal such as a mobile phone, smartphone, PDA (Personal Digital Assistant), tablet, wearable device, personal computer, vehicle, or any other device or equipment with wireless communication capabilities (such as a sensor device). Alternatively, the terminal device 10 may be referred to as a wireless communication device, communication device, receiving device, mobile station, UE (User Equipment), user device, etc.
[0020] In the wireless communication system 1, the base station equipment 20 and the core network 30 provide wireless communication services to the terminal device 10. The core network 30 has functions such as managing service subscriber information, managing sessions for voice calls, and managing the location registration of the terminal device 10. The core network 30 also transmits control data and / or user data to the terminal device 10 via the base station equipment 20.
[0021] The core network 30 may be 5G Core (5GC) in 5G (NR) or Evolved Packet Core (EPC) in 4G (E-UTRA). Furthermore, the connection method between the core network 30 and the base station equipment 20 may be NSA (Non-Stand Alone) or SA (Stand Alone).
[0022] The 5G base station equipment 20 connected to the 5GC is a gNB, and the 4G base station equipment 20 connected to the EPC is an eNB. Furthermore, the 5G base station equipment is physically or logically connected to each other via an Xn interface. Similarly, the 4G base station equipment is physically or logically connected to each other via an X2 interface.
[0023] The area (coverage area) formed by the base station device 20 is sometimes called a "cell." E-UTRA and 5G are cellular communication systems constructed from multiple cells. In the wireless communication system according to the embodiment of the present invention, either TDD (Time Division Duplex) or FDD (Frequency Division Duplex) may be applied, and different methods may be applied to each cell.
[0024] Hereinafter, a cell configured by the base station device 20A will also be referred to as a normal cell 20A-1 (first cell). A normal cell 20A-1 is, for example, a cell that does not support NES, or an NES cell (described later) to which power-saving technology has not been applied. A cell configured by the base station device 20B that can transition to a state (sleep state) in which power consumption can be reduced by applying predetermined power-saving technology will also be referred to as an NES cell 20B-1 (second cell). In the sleep state, for example, the NES cell 20B-1 achieves power saving by stopping the transmission and reception of physical signals and physical channels other than predetermined ones, thereby cutting off or reducing the standby power of the wireless equipment inside the base station device 20B. The predetermined physical signals and physical channels are, for example, PDCCH and PDSCH related to On-demand SIB1.
[0025] The normal cell 20A-1 is an anchor cell that provides (transfers, notifies) the terminal device 10 with the information necessary for the terminal device 10 to access the NES cell 20B-1. The NES cell 20B-1 also provides the normal cell 20A-1 with at least control information used by the terminal device 10 to determine whether it can access the NES cell 20B-1, control information for receiving the On-demand SIB1 transmitted by the NES cell 20B-1, and uplink wake-up signal (UL-WUS (UL-Wake Up Signal)) setting information (described later) for requesting the On-demand SIB1 from the NES cell 20B-1. In the following description, unless otherwise specified, the above-mentioned SIB1 request setting information and UL-WUS setting information shall be treated as synonymous setting information that can be used interchangeably.
[0026] In the example shown in Figure 1, a normal cell 20A-1 is illustrated as containing an NES cell 20B-1. However, the size and positional relationship of these two cells are merely illustrative, and other correspondences are possible. For example, the size of the normal cell 20A-1 and the NES cell 20B-1 may be the same, or the NES cell 20B-1 may be larger. A normal cell 20A-1 may contain multiple NES cells 20B-1.
[0027] The sleep state is a state in which, for example, some of the functions related to transmission and reception of the base station device 20B (NES cell 20B-1) are stopped, and at the same time, power supply to internal equipment related to transmission and reception is suppressed, and the base station device 20B does not transmit some messages, and at least one of the transmission and reception of corresponding physical signals and physical channels. Furthermore, when the sleep state of the NES cell 20B-1 is released (the application of a predetermined power saving technology is stopped), or when the sleep state is temporarily released, it enters a non-sleep state and transitions to a cell capable of normal wireless communication (for example, a normal cell 20A-1).
[0028] Terminal device 10 is a communication device that wirelessly connects to base station device 20A or base station device 20B and transmits and receives data. Furthermore, terminal device 10 is a communication device that corresponds to the functions of NES, that is, a communication device that supports the functions of NES.
[0029] Furthermore, the NES cell may include, for example, a base station device 20B that is in a sleep state, and a base station device 20B that may be in a sleep state. Also, the normal cell 20A-1 and the NES cell 20B-1 may each be, for example, cells under the same base station device 20, or cells under different base station devices 20.
[0030] The base station device 20 may be configured as, for example, a CU (Centralized Unit), a DU (Distributed Unit), and a RU (Radio Unit). The CU is connected to the core network. The DU is connected to the terminal device 10 via the RU, for example. The communication path between the CU and the DU is implemented, for example, by a front-haul interface (F1 interface). Multiple DUs may be connected to a single CU.
[0031] In the example shown in Figure 1, the data (DL data, downlink data) transmitted from the core network 30 to the terminal device 10 is transmitted from the core network 30 to the base station device 20, and then transmitted (transferred) from the base station device 20 to the terminal device 10.
[0032] The data (UL data, uplink data) transmitted from the terminal device 10 to the core network 30 is transmitted from the terminal device 10 to the base station device 20, and then transmitted (transferred) from the base station device 20 to the core network 30.
[0033] The terminal device 10 and the base station device 20 transmit and receive RRC messages (also called RRC signaling) at the Radio Resource Control (RRC) layer. Furthermore, the terminal device 10 and the base station device 20 transmit and receive MAC control elements (MAC CE) at the Medium Access Control (MAC) layer.
[0034] RRC messages are transmitted as RRC PDUs (Protocol Data Units) and mapped to logical channels (LCHs) such as the Common Control Channel (CCCH), Dedicated Control Channel (DCCH), Paging Control Channel (PCCH), Broadcast Control Channel (BCCH), or Multicast Control Channel (MCCH).
[0035] A MAC CE is transmitted as a MAC PDU (or MAC subPDU). A MAC subPDU is equivalent to a Service Data Unit (SDU) in the MAC layer with, for example, 8 bits of header information added, and a MAC PDU contains one or more MAC subPDUs.
[0036] Next, as physical channels and physical signals related to the embodiment, there are at least the following: synchronization signals (Primary Synchronization Signal, Secondary Synchronization Signal), Physical Broadcast Channel (PBCH), Physical Random Access Channel (PRACH), Physical Downlink Control Channel (PDCCH), Channel State Information-Reference Signal (CSI-RS), Physical Uplink Control Channel (PUCCH), Physical Downlink Shared Channel (PDSCH), Physical Uplink Shared Channel (PUSCH), Scheduling Reference Signal (SRS), and Demodulation Reference Signal (DMRS), but a detailed explanation is omitted.
[0037] <Terminal Device> Figure 2 is a diagram showing an example of the functional configuration of a terminal device 10 related to the embodiment. As shown in Figure 2, the terminal device 10 includes, for example, a processing unit 11, a control unit 13, a receiving unit 15, a transmitting unit 17, and a transmitting / receiving antenna unit 19. The processing unit 11 is configured to include, for example, a wireless resource processing unit 111 and a control processing unit 113. Note that the functional configuration of the terminal device 10 shown in Figure 2 is merely an example, and the functional classifications and names of each functional block may differ as long as they can perform the operations related to the embodiment. In addition, there may be one or more blocks that realize other functions.
[0038] The processing unit 11 generates control information for controlling the receiving unit 15 and the transmitting unit 17, for example, and outputs it to the control unit 13. The processing unit 11 executes processing related to the wireless resource control layer, the Service Data Adaptation Protocol (SDAP) layer, the Packet Data Convergence Protocol (PDCP) layer, the Radio Link Control (RLC) layer, and the media access control layer, for example.
[0039] The wireless resource processing unit 111 manages various setting information (RRC parameters, information elements (IE)) of the terminal device 10. For example, the wireless resource processing unit 111 generates information to be placed on each channel of the physical uplink and outputs this information to the transmission unit 17. In addition, based on instructions from the base station device 20, the wireless resource processing unit 111 performs the following: measurement of in-service cells and surrounding cells, start and stop of transmission and reception processing, DL synchronization procedures (cell search, cell selection / cell reselection), UL synchronization procedures (random access procedures), UL-WUS transmission procedures, acquisition and reacquisition of system information, event evaluation related to handover, a series of processes related to handover, a series of processes related to On-demand SIB1 acquisition, and a series of processes related to RRC reconnection. Note that RRC reconnection may also be called RRC re-establishment.
[0040] The control processing unit 113 executes a control process to determine whether the cell is an NES cell based on the UL-WUS settings. The control processing unit 113 also executes a control process to determine how to receive the On-demand SIB1 based on the UL-WUS settings and the information in the NES cell's Master Information Block (MIB). Furthermore, the control processing unit 113 executes a control process to determine whether UL-WUS transmission is necessary based on instructions from the radio resource processing unit 111 or from the base station device 20.
[0041] The control unit 13 performs various types of control in the terminal device 10. For example, the control unit 13 generates control signals or control data for controlling the receiving unit 15 and the transmitting unit 17 based on control information from the processing unit 11. The control unit 13 also respectively controls uplink transmission to the base station device 20, scheduling request transmission, UL-WUS transmission, physical random access channel transmission, and downlink reception from the base station device 20 based on determination information related to transmission control from the control processing unit 113.
[0042] The receiving unit 15 separates, demodulates, and decodes various signals received from the base station device 20 via the transmission / reception antenna unit 19 based on a control signal provided from the control unit 13. The receiving unit 15 outputs the decoded information to the processing unit 11.
[0043] The transmitting unit 17 generates, for example, a physical uplink signal based on a control signal provided from the control unit 13, and performs encoding, modulation, and the like on the physical uplink signal or physical uplink channel provided from the processing unit 11. The transmitting unit 17 multiplexes various signals and transmits the multiplexed signals to the base station device 20 via the transmission / reception antenna unit 19.
[0044] Note that the processing unit 11 and the control unit 13 are implemented by, for example, a processor system including a processor and a memory. In this case, the processor provides the functions of the processing unit 11 and the control unit 13 by executing a program describing the operation of the terminal device 10 described later. Furthermore, the processing unit 11 and the control unit 13 may be implemented by a single processor system, or may be implemented by a plurality of processor systems. Alternatively, the processing unit 11 and the control unit 13 may be implemented by a DSP (Digital Signal Processor), a hardware circuit, or the like.
[0045] <Base Station Apparatus> Fig. 3 is a diagram illustrating an example of a functional configuration of a base station apparatus 20 according to the embodiment. As illustrated in Fig. 3, the base station apparatus 20 includes, for example, a processing unit 21, a control unit 23, a receiving unit 25, a transmitting unit 27, and a transmission / reception antenna unit 29. The processing unit 21 is illustratively configured to include a radio resource processing unit 211 and a SIB1 control processing unit 213. Note that the functional configuration of the base station apparatus 20 illustrated in Fig. 3 is merely an example, and the functional divisions and names of functional blocks may be different as long as operations according to the embodiment can be performed. In addition, one or more blocks that implement other functions may be provided.
[0046] The processing unit 21 generates, for example, control information for controlling the receiving unit 25 and the transmitting unit 27, and outputs the control information to the control unit 23. The processing unit 21 executes, for example, processing related to a radio resource control layer, a service data application protocol layer, a packet data convergence protocol layer, a radio link control layer, and a medium access control layer.
[0047] The radio resource processing unit 211 generates, for example, downlink data arranged in a physical downlink shared channel PDSCH, RRC messages, and MAC control elements, and outputs them to the transmitting unit 27. The radio resource processing unit 211 also generates a control signal or control data arranged in a physical downlink control channel PDCCH, and outputs the control signal or control data to the transmitting unit 27. Further, the radio resource processing unit 211 manages various types of setting information of the terminal apparatus 10. Based on notifications from a signal from the terminal apparatus 10 or RRC messages, the radio resource processing unit 211 executes: start and stop of transmission / reception processing, start of UL synchronization procedure (random access procedure), update of system information, start and stop of On-demand SIB1 transmission, adjustment of beam transmission angle, generation of parameters related to UL-WUS transmission procedure, and the like.
[0048] The SIB1 control processing unit 213 performs a series of control processing related to On-demand SIB1 transmission. For example, the SIB1 control processing unit 213 executes control processing for determining whether On-demand SIB1 transmission is necessary based on an instruction from an upper layer or reception of a UL-WUS transmitted from the terminal apparatus 10.
[0049] The control unit 23 performs various controls on the base station device 20. For example, the control unit 23 generates control signals or control data to control the receiving unit 25 and the transmitting unit 27 based on control information from the processing unit 21. The control unit 23 also controls downlink transmission to the terminal device 10 corresponding to On-demand SIB1 based on decision information regarding On-demand SIB1 transmission from the SIB1 control processing unit 213.
[0050] The receiving unit 25 separates, demodulates, and decodes various signals received from the terminal device 10 or core network 30 via the transmitting / receiving antenna unit 29, based on control signals provided by the control unit 23. The receiving unit 25 outputs the decoded information to the processing unit 21.
[0051] The transmitting unit 27 generates, for example, a downlink reference signal based on a control signal provided by the control unit 23. The transmitting unit 27 transmits a signal to the terminal device 10 via the transmitting / receiving antenna unit 29 by encoding, modulating, and multiplexing various information provided by the processing unit 21.
[0052] Furthermore, the transmitting unit 27 transmits data to the terminal device 10, another base station device 20, or the core network 30. The receiving unit 25 receives data from the terminal device 10, another base station device 20, or the core network 30.
[0053] The processing unit 21 and the control unit 23 are implemented, for example, by a processor system including a processor and memory. In this case, the processor provides the functions of the processing unit 21 and the control unit 23 by executing a program that describes the operation of the base station device 20, which will be described later. The processing unit 21 and the control unit 23 may be implemented by a single processor system or by multiple processor systems. Alternatively, the processing unit 21 and the control unit 23 may be implemented by a DSP or hardware circuit, etc.
[0054] <On-demand SIB1> On-demand SIB1 is one of the power saving technologies applied to the base station equipment 20, and is a method of appropriately transmitting SIB1, which is one of the periodically transmitted notification information, based on a request from the terminal equipment 10. The contents of On-demand SIB1 include at least the setting information notified by conventional SIB1 (wireless connection information (cell common resource information, cell selection criterion information, access restriction information, etc.)), and may also include UL-WUS setting information indicating the transmission setting of UL-WUS, which is a signal for requesting On-demand SIB1.
[0055] The base station device 20B may also be configured to transmit system information other than On-demand SIB1 (SIB2, SIB3, ...) on demand. Access restriction information may also be referred to by similar terms such as access restriction information, access control information, or access prohibition information. Similarly, On-demand SIB1 may be referred to by similar terms such as OD-SIB1, Non-periodic SIB1, or it may continue to be referred to as SIB1, but the description may indicate that it is transmitted on demand from the surrounding text.
[0056] The terminal device 10 receives the On-demand SIB1 from the base station device 20B (NES cell 20B-1), detects and acquires the synchronization signal / physical broadcast channel block (SSB) from the base station device 20B, and uses the SSB to adjust the synchronization of the downlink. The SSB includes a synchronization signal and a physical broadcast channel (PBCH). The synchronization signal is composed of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS).
[0057] Next, the terminal device 10 obtains the transmission resource information of the PDCCH and the SSB subcarrier offset information (ssb-SubcarrierOffset) from the MIB (Master Information Block) transmitted in SSB (PBCH). The transmission resource information of the PDCCH (pdcch-ConfigSIB) is information that specifies the area in which the PDCCH that instructs the scheduling information of On-demand SIB1 (or SIB1) may be transmitted (also called the common search area or common search space).
[0058] The common search space may also be referred to as the Type Zero Search Space / Control Resource Set Zero (Type0 SS / CORESET0). SSB subcarrier offset information is a parameter that indicates the frequency offset of the SSB transmission position in subcarrier units. The base station device 20B may be configured to indicate that the cell is an NES cell 20B-1 (i.e., an SIB1 non-transmitting cell) by setting a predetermined value for the SSB subcarrier offset information. Furthermore, the base station device 20B does not need to include the PDCCH transmission resource information in the MIB.
[0059] Terminal device 10 monitors the PDCCH that schedules SIB1 based on the acquired transmission resource information, and acquires the PDSCH (On-demand SIB1) indicated by the Downlink Control Information (DCI) contained in the detected PDCCH. Base station device 20 scrambles the CRC with System Information-Radio Network Temporary Identifier (SI-RNTI), which is composed of a known bit sequence, and transmits it to the PDCCH that schedules SIB1. In the area where terminal device 10 monitors the PDCCH, it may attempt to reverse scramble the CRC of the PDCCH using SI-RNTI, and if the PDCCH is decoded correctly, it may then acquire the On-demand SIB1 based on the DCI. Here, MIB and SIB1 (On-demand SIB1) are both Essential System Information.
[0060] Furthermore, the terminal device 10 calculates the cell quality (reception quality) for each cell by measuring SSB or the channel status information reference signal (CSI-RS). Cell quality can be expressed using one of the following: RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), SINR (Signal to Interference plus Noise Ratio), or path loss.
[0061] <UL-WUS Configuration Information> The UL-WUS configuration information may include some or all of the following information: cell information that identifies the cell transmitting UL-WUS (physical cell identifier (PCI), downlink frequency information, etc.), information related to UL-WUS transmission (PRACH resource information, SSB receive power threshold, TDD UL / DL slot settings, uplink frequency, etc.), information related to SIB1 reception (SSB subcarrier offset information, PDCCH transmission resource information, etc.), and information related to PRACH response reception (reception window length, reception start offset information, etc.).
[0062] The terminal device 10 may determine, based on cell information, whether the cell belonging to the base station device 20 is a normal cell 20A-1 or an NES cell 20B-1. The base station device 20B may also include SSB subcarrier offset information and PDCCH transmission resource information (PDCCH transmission resource information) used for SIB1 reception within the NES cell 20B-1 in the corresponding UL-WUS configuration information.
[0063] <Cell Selection Criteria> The cell selection criterion, also called cell selection criterion S, is a criterion used by the terminal device 10 to evaluate whether a cell detected by cell search is a cell that can be camped. In other words, the cell selection criterion is a threshold that indicates whether a detected cell can be considered a candidate cell for cell selection. Specifically, the terminal device 10 evaluates cells using Srxlev and Squal. Srxlev represents the cell selection reception level value (RSRP) calculated by (Equation 1) below. Squal represents the cell selection quality value (RSRQ) calculated by (Equation 2) below.
[0064] Srxlev=Qrxlevmeas-(Qrxlevmin+Qrxlevminoffset)-Pcompensation-Qoffsettemp...(Formula 1)
[0065] Squal=Qqualmeas-(Qqualmin+Qqualminoffset)-Qoffsettemp...(Formula 2)
[0066] Here, Qrxlevmin, Qrxlevminoffset, Qqualmin, and Qqualminoffset are cell selection parameters transmitted in the system information. Qrxlevmeas indicates the cell reception level value (RSRP) measured by the terminal device 10. Qrxlevmin indicates the minimum requested reception level in the cell, in dBm. Qrxlevminoffset indicates the offset value applied to Qrxlevmin, which is considered when evaluating Srxlev. Pcompensation indicates the offset value corresponding to the maximum uplink transmission power of the terminal device 10.
[0067] Qoffsettemp is an offset value that is temporarily applied when cell selection fails a predetermined number of times consecutively. Qqualmeas indicates the cell quality value (RSRQ) measured by the terminal device 10. Qqualmin indicates the minimum required quality level in the cell, and its unit is dB. Qqualminoffset indicates the offset value applied to Qqualmin, which is considered when evaluating Squal. Qoffsettemp is an offset value that is temporarily applied when cell selection fails a predetermined number of times consecutively.
[0068] The terminal device 10 determines that a cell satisfies the cell selection criteria and is a target cell for cell selection when both cell selection criteria S are greater than zero (i.e., when the following equation (3) is satisfied).
[0069] Srxlev>0 AND Squal>0…(Formula 3)
[0070] If Qqualmin is not notified by the base station device 20, the terminal device 10 may assume that a value of negative infinity has been set as the default value. If Qrxlevminoffset is not notified, the terminal device 10 may assume that a value of zero has been set as the default value. Similarly, if Qqualminoffset is not notified, the terminal device 10 may assume that a value of zero has been set as the default value. The base station device 20 may set all or some of the parameters for calculating Pcompensation in the UL-WUS configuration information.
[0071] Taking the above points into consideration, embodiments of the present invention will be described with reference to the drawings. In the description of embodiments of the present invention, if a specific explanation of known functions or configurations related to embodiments of the present invention would obscure the gist of the embodiments of the present invention, such detailed explanation will be omitted.
[0072] <First Embodiment> Figure 4 is an example of a sequence diagram showing the On-demand SIB1 acquisition procedure (On-demand SIB1 control procedure) of the terminal device 10 and base station device 20 related to the first embodiment. Here, On-demand SIB1 (or simply SIB1) is the first system information. Also, base station device 20A is the first base station device (first cell), and base station device 20B is the second base station device (second cell).
[0073] The terminal device 10 in Figure 4 is a terminal device 10 that supports NES functionality, and the base station device 20A (normal cell 20A-1) provides (notifies, sets, and transmits) the information necessary for the terminal device 10 to request On-demand SIB1 from the NES cell, and the setting information (UL-WUS setting information) necessary for receiving On-demand SIB1. The information necessary for requesting On-demand SIB1 and the setting information necessary for receiving On-demand SIB1 are examples of information related to request signal settings that request the on-demand transmission of the first system information to the second cell (NES cell). The method by which the base station device 20A provides setting information to the terminal device 10 may be to periodically or on-demand within the cell using existing system information or dedicated system information, or to transmit using individual RRC messages. Individual RRC messages include, for example, RRCReconfiguration messages and RRCRelease messages.
[0074] Furthermore, the base station device 20B (NES cell 20B-1) in Figure 4 transmits On-demand SIB1 when it receives UL-WUS from the terminal device 10, or when the base station device 20B determines that it is necessary (for example, to update the contents of SIB1). Similarly, when the base station device 20B determines that it is not necessary (for example, when a predetermined time has elapsed since the start time of SIB1 transmission), it stops transmitting On-demand SIB1.
[0075] Base station device 20B provides UL-WUS configuration information to base station device 20A via the transmission path between base station devices 20 (step S100). The UL-WUS configuration information includes at least NES cell information that uniquely identifies the NES cell (e.g., a combination of physical cell identifier (PID) and downlink frequency information), information regarding SIB1 reception, information regarding UL-WUS transmission, and information regarding PRACH response reception.
[0076] The base station device 20A transmits (forwards, notifies, broadcasts) the received UL-WUS configuration information within the cell, including at least one piece of UL-WUS configuration information (step S101). It is preferable for the base station device 20A to transmit the received UL-WUS configuration information as a System Information message. The base station device 20B also periodically transmits MIBs corresponding to the On-demand SIB1 cell to the NES cell 20B-1 (step S102). The terminal device 10 receives the MIBs transmitted by the base station device 20B and retains the information. Then, the terminal device 10 performs a UL-WUS transmission decision, determining whether to transmit UL-WUS to the base station device 20B (NES cell 20B-1) using the system information received from the base station device 20A, the UL-WUS configuration information, and the MIB information received from the base station device 20B (step S103).
[0077] In step S103, the terminal device 10 compares the reception quality of the base station device 20A (normal cell 20A-1), which is the cell currently in service, with the reception quality of one or more base station devices 20B (NES cell 20B-1), which are candidates for cell reselection. The terminal device then decides whether to transmit UL-WUS to the cell with the best reception quality among those cells that meet the cell selection criteria and have better reception quality than the cell currently in service. If the NES cell information corresponding to the cell detected by the cell search (i.e., the cell from which the MIB was received in step S102) is not included in the UL-WUS configuration information (or does not possess valid UL-WUS configuration information itself), the detected cell does not need to be considered as a cell for which UL-WUS transmission is to be determined.
[0078] The terminal device 10 may decide to transmit UL-WUS to an NES cell 20B-1 that satisfies all of the following conditions: (1) The detected base station device 20B (NES cell 20B-1) is a cell corresponding to the UL-WUS setting information. (2) The measured cell's reception quality satisfies the cell selection criteria and is of better reception quality than the cell currently in service. (3) When cells that satisfy (1) and (2) are ranked considering the offset for each cell, it is the cell with the best reception quality. The terminal device 10 may decide not to transmit UL-WUS to an NES cell 20B-1 that does not satisfy one or more of the following conditions: (1) satisfies one or more of the following conditions: (1) The detected base station device 20B (NES cell 20B-1) is a cell corresponding to the UL-WUS setting information. (2) The measured cell's reception quality satisfies the cell selection criteria and is of better reception quality than the cell currently in service. (3) When cells that satisfy (1) and (2) are ranked, it is the cell with the best reception quality.
[0079] If the terminal device 10 determines in step S103 to transmit UL-WUS, it also performs the processes in the following steps S104 to S106. On the other hand, if it determines not to transmit UL-WUS, the terminal device 10 does not need to perform the following steps S104 to S106.
[0080] When terminal device 10 determines that it should transmit UL-WUS, it transmits UL-WUS to base station device 20B (NES cell 20B-1) based on the corresponding UL-WUS configuration information (step S104). UL-WUS is transmitted by applying individual transmission resources in the physical random access channel. Individual transmission resources are, for example, random access preambles reserved for UL-WUS. Terminal device 10 determines the target transmission power for UL-WUS, the random access sequence to be used, the transmission time position, etc., using the same procedure as in conventional random access procedures. UL-WUS is an example of a request signal that requests on-demand transmission of first system information, and is also an example of a request signal based on request signal settings.
[0081] The terminal device 10 that sent the UL-WUS expects a UL-WUS response (UL-WUS response, Random Access Response (RAR)) to be transmitted from the base station device 20B, and attempts to receive (monitor) the UL-WUS response (RAR) for a predetermined window length (Random Access window) (step S105). Information for receiving the UL-WUS response (RA-RNTI (Random Access-Radio Network Temporary Identifier), window length, etc.) is determined using the same procedure as for the random access procedure. The base station device 20B may include the setting information necessary for receiving the UL-WUS response in the UL-WUS setting information and transmit it. If the UL-WUS response cannot be detected, the terminal device 10 may retransmit the UL-WUS. The terminal device 10 may use the same procedure as the conventional random access procedure (setting the maximum number of retransmissions, power ramping, etc.) as the method for retransmitting UL-WUS. The base station device 20B may include the setting information necessary for UL-WUS retransmission in the UL-WUS setting information and transmit it.
[0082] The base station device 20B indicates the transmission resource location of the UL-WUS response (RAR) using a PDCCH whose CRC is scrambled with RA-RNTI calculated in accordance with the transmission resources used by the terminal device 10. In other words, the base station device 20B transmits the UL-WUS response (RAR) to the terminal device 10 using the PDSCH indicated by the DCI of the PDCCH. The base station device 20B also transmits the received random access preamble information included in the UL-WUS response (RAR). The UL-WUS response may be transmitted in a format that consists only of header information including at least random access preamble information, and does not include scheduling information for user data.
[0083] If the terminal device 10 determines that it has successfully received the corresponding UL-WUS response (RAR) in step S105 and that the (On-demand) SIB1 will be transmitted, or if it determines that the UL-WUS transmission procedure has been completed, it attempts to receive the (On-demand) SIB1 (step S106).
[0084] From a power saving perspective, it is desirable that On-demand SIB1 be transmitted only temporarily within a predetermined time window (SIB1 Time Window), rather than periodically as in the conventional method. The base station device 20B may specify the predetermined time window on a per-NES cell 20B-1 basis using UL-WUS configuration information or system information, or on a per-terminal device 10 basis using UL-WUS response (RAR). Alternatively, the base station device 20B may specify information indicating the interval (time offset) from the receipt of the UL-WUS response (RAR) to the predetermined time window on a per-terminal device 10 basis using UL-WUS response (RAR). The terminal device 10 attempts to acquire On-demand SIB1 within the predetermined time window determined using one of the methods described above. If the terminal device 10 obtains an On-demand SIB1, it retains the information of the obtained (On-demand) SIB1, applies the necessary settings, and continues the cell reselection procedure.
[0085] Figure 5 shows an example of a sequence diagram when a Radio Link Failure (RLF) is detected in terminal device 10 in connected mode, and an RRC Restabilization procedure (RRC restabilization control procedure) is performed, and a cell of base station device 20B (NES cell 20B-1) is selected as a candidate cell for RRC restabilization. It is assumed that terminal device 10 has received the necessary UL-WUS configuration information from base station device 20A (or base station device 20B).
[0086] In step S200, the terminal device 10 detects that the wireless quality between it and the base station device 20 has deteriorated and that a radio link failure (RLF) has occurred. Here, the method for detecting the RLF is not specifically defined, but the terminal device 10 can detect the radio link failure (RLF) using, for example, any of the conventional methods (detection of deterioration in wireless quality exceeding a timer time, failure of a random access procedure, or occurrence of RLC retransmission errors exceeding a predetermined number of times).
[0087] If a wireless link failure (RLF) is detected, the terminal device 10 starts timing an RRC timer (reconnection timer (also referred to as Timer T311)) that indicates the maximum time to attempt the RRC reconnection procedure, and also autonomously releases RRC settings that are not necessary for the RRC reconnection procedure and starts the cell selection procedure (not shown). The terminal device 10 may determine whether or not the RRC reconnection procedure is being performed based on whether or not the reconnection timer (Timer T311) is timing.
[0088] Figure 5 shows an example in which the terminal device 10 evaluates the base station device 20B (NES cell 20B-1) as a candidate cell during cell selection associated with the RRC reconnection procedure. In other words, the base station device 20B periodically transmits MIBs corresponding to the On-demand SIB1 cell to the NES cell 20B-1 (step S201). The terminal device 10 receives the MIBs transmitted by the base station device 20B and stores that information.
[0089] The base station device 20 may implicitly or explicitly instruct the terminal device 10 which of the cell selection parameter or the cell re-selection parameter to apply as the cell selection criterion and perform the evaluation by setting a predetermined value (a value indicating that it is an untransmitted SIB1 cell) in the MIB's SSB subcarrier offset information (ssb-SubcarrierOffset).
[0090] Then, the terminal device 10 uses the system information, UL-WUS setting information received from the base station device 20A, and MIB information received from the base station device 20B, which it had held before detecting the radio link fault (RLF), to perform a cell selection criterion evaluation (referred to as the first cell selection criterion evaluation) on the base station device 20B (NES cell 20B-1) (step S202).
[0091] In step S202, the terminal device 10 may decide to transmit UL-WUS to an NES cell 20B-1 that satisfies all of the following conditions: (a) The detected base station device 20B (NES cell 20B-1) is a cell corresponding to the UL-WUS setting information. (b) The measured cell reception quality meets the cell selection criteria. (c) The reconnection timer (timer T311) is still ticking (not expired). In the cell selection criterion evaluation, the terminal device 10 may decide not to consider an NES cell 20B-1 that does not satisfy one or more of the above conditions (a) to (c) as a candidate cell for attempting the RRC reconnection procedure, or to decide not to transmit UL-WUS.
[0092] Regarding condition (a), if the NES cell information corresponding to the cell detected by the terminal device 10 through cell search (i.e., the cell from which the MIB was received in step S201) is not included in the UL-WUS configuration information (or does not possess valid UL-WUS configuration information itself), the terminal device 10 does not need to consider the detected cell as a target cell (candidate cell) for the RRC reconnection procedure.
[0093] Regarding condition (b), the terminal device 10 evaluates (determines) whether the cell selection criteria are met based on the cell selection parameters (referred to as the first cell selection criterion parameters) of SIB1 obtained from the base station device 20B (NES cell 20B-1). However, since NES cell 20B-1 does not transmit SIB1 periodically but transmits it on demand, the conventional method cannot be applied. Therefore, the terminal device 10 uses the cell re-selection parameters (referred to as the second cell selection criterion parameters) notified by SIB2 to SIB4 of the base station device 20A (normal cell 20A-1) instead to evaluate (determine) condition (b). Here, some or all of SIB2 to SIB4 are second system information. The base station device 20 may set information that causes the terminal device 10 to decide whether to apply either the first cell selection criterion parameters or the second cell selection criterion parameters. The information that causes the terminal device 10 to decide whether to apply the first cell selection criterion parameter or the second cell selection criterion parameter is, for example, that at least one of SIB2 to SIB4 contains a cell re-selection parameter, or information that indicates which cell selection parameter to use as the cell selection criterion. Alternatively, the specification may define that the terminal device 10 should set a preferred cell selection parameter.
[0094] Specifically, if base station device 20B (NES cell 20B-1) is a cell of the same frequency (intra-frequency), terminal device 10 applies the cell reselection parameters notified in SIB2 and SIB3 of the system information of base station device 20A (normal cell 20A-1) to the cell selection criteria. Specifically, if Qrxlevmin and Qqualmin are notified (set, instructed) in SIB2 (intraFreqCellReselectionInfo), terminal device 10 applies the notified values, and if not notified, it applies the default values. Also, if Qrxlevminoffset and Qqualminoffset corresponding to base station device 20B (NES cell 20B-1) are notified (set, instructed) in SIB3 (IntraFreqNeighCellInfo), terminal device 10 applies the notified values for each base station device 20B, and if not notified, it applies the default values.
[0095] In this case, if the Qrxlevmin parameter for SIB2 is defined as "Parameter "Qrxlevmin" applicable for intra-frequency neighbor cells," the definition may be changed to "Parameter "Qrxlevmin" applicable for intra-frequency neighbor cells, and if timer T311 is running, applicable for intra-frequency on-demand SIB1 cells for cell selection."
[0096] Alternatively, if base station device 20B (NES cell 20B-1) is an inter-frequency cell, terminal device 10 applies the cell reselection parameters notified by SIB4 (interFreqCellReselectionInfo) from the system information of base station device 20A (normal cell 20A-1) to the cell selection criteria. Specifically, if Qrxlevmin and Qqualmin are notified (set, instructed) by SIB4, terminal device 10 applies the notified values; otherwise, it applies the default values. Furthermore, if Qrxlevminoffset and Qqualminoffset corresponding to base station device 20B (NES cell 20B-1) are notified (set, instructed) by SIB4 (InterFreqNeighCellInfo), terminal device 10 applies the notified values for each base station device 20B; otherwise, it applies the default values.
[0097] In this case, the definition of Qrxlevmin for SIB4 may be changed to "Parameter "Qrxlevmin" applicable for inter-frequency neighbor cells, and if timer T311 is running, applicable for inter-frequency on-demand SIB1 cells for cell selection."
[0098] Alternatively, the base station device 20A (normal cell 20A-1) may notify the terminal device 10 of an offset value to be applied to the cell reselection parameter notified in SIB2 to SIB4. The terminal device 10 may apply the notified offset value to the cell reselection parameter and evaluate the cell selection criteria by considering the applied value as the cell selection parameter of the base station device 20B (NES cell 20B-1).
[0099] Alternatively, the terminal device 10 may always apply a predetermined default value as a cell selection parameter of the base station device 20B (NES cell 20B-1) to evaluate the cell selection criteria. The default value may be zero or a fixed value. For example, the default value of Qrxlevmin may be considered to be a fixed value of 23 dBm, or the transmission power value corresponding to the maximum transmission power class of the terminal device 10 may be considered as the default value. For example, if the maximum transmission power class of the terminal device 10 is class 3 (corresponding to a handheld terminal device), the default value may be considered to be 23 dBm, and if the maximum transmission power class is class 2 (corresponding to a high-power terminal device), the default value may be considered to be 26 dBm.
[0100] Alternatively, the base station device 20A (normal cell 20A-1) may include cell selection parameters in the UL-WUS configuration information corresponding to the cell and notify the terminal device 10 of this. The base station device 20A sets at least the minimum requested reception level Qrxlevmin in the UL-WUS configuration information. If the UL-WUS configuration information includes cell selection parameters, the terminal device 10 may evaluate the cell selection criteria by applying the cell selection parameters corresponding to the base station device 20B (NES cell 20B-1). If the UL-WUS configuration information does not include cell selection parameters, the terminal device 10 may evaluate the cell selection criteria of the base station device 20B (NES cell 20B-1) by applying the cell re-selection parameters notified in SIB2 to SIB4 of the base station device 20A (normal cell 20A-1).
[0101] Alternatively, the terminal device 10 may perform evaluation by changing the formula for the cell selection criteria of the base station device 20B (NES cell 20B-1). For example, instead of (Formula 1) and (Formula 2), the following (Formula 4) and (Formula 5) may be used, respectively. Qrxlevmin_odsib1 and Qqualmin_od-sib1 are cell selection parameters corresponding to the base station device 20B (NES cell 20B-1), and may be notified in UL-WUS configuration information or new system information. Qrxlevmin_odsib1 is the minimum requested reception level RSRP of the base station device 20B (NES cell 20B-1), and Qqualmin_od-sib1 is the minimum requested quality level of the base station device 20B (NES cell 20B-1).
[0102] Srxlev=Qrxlevmeas−Qrxlevmin_odsib1−Pcompensation…(Formula 4)
[0103] Squal=Qqualmeas−Qqualmin_od-sib1…(Equation 5)
[0104] Regarding condition (c), the terminal device 10 may determine that condition (c) is no longer met if the reconnection timer (timer T311) expires or stops.
[0105] If the terminal device 10 determines in step S202 that the base station device 20B (NES cell 20B-1) satisfies the cell selection criteria and therefore transmits UL-WUS, it also performs the processing in the following steps S203 to S206. On the other hand, if it determines that it will not transmit UL-WUS, the terminal device 10 does not need to perform the following steps S203 to S206.
[0106] Furthermore, if the terminal device 10 is timing the reconnection timer and holds UL-WUS setting information corresponding to the detected base station device 20B (NES cell 20B-1), but does not hold cell reselection parameters notified by base station device 20A (normal cell 20A-1), it does not need to consider base station device 20B as a target cell (candidate cell) for the RRC reconnection procedure.
[0107] Specifically, if the terminal device 10 does not hold the entire SIB2 or the cell reselection parameters for the same frequency, it does not need to consider the base station device 20B operating at the same frequency as the base station device 20A as a target cell (candidate cell) for the RRC reconnection procedure. Alternatively, if the terminal device 10 does not hold the entire SIB4 or the cell reselection parameters for different frequencies, it does not need to consider the detected base station device 20B operating at a different frequency as a target cell (candidate cell) for the RRC reconnection procedure.
[0108] The operation of the terminal device 10 and the base station device 20B (NES cell 20B-1) in steps S203 to S205 is the same as in steps S104 to S106 in Figure 4, so the explanation is omitted.
[0109] If the terminal device 10 has obtained the (On-demand) SIB1 of the base station device 20B (NES cell 20B-1) in step S205, it may retain the information of the obtained SIB1, apply the necessary settings, and continue the RRC reconnection procedure for the cell. At this time, if the setting information (information elements) included in the UL-WUS setting information is also set in the obtained (On-demand) SIB1, the terminal device 10 may overwrite the setting information of the UL-WUS setting information with the information of the obtained (On-demand) SIB1.
[0110] On the other hand, if the (On-demand) SIB1 of the base station device 20B (NES cell 20B-1) could not be obtained in step S205, the terminal device 10 may consider the NES cell 20B-1 from which the SIB1 could not be obtained to be a barred cell. The terminal device 10 may decide not to consider the cell as a target cell (candidate cell) for the RRC reconnection procedure and not to continue the RRC reconnection procedure on the cell. The terminal device 10 may release the UL-WUS configuration information corresponding to the cell, or it may decide that it is invalid.
[0111] If the RRC reconnection procedure for the cell in question is to be continued, the terminal device 10 can reuse the conventional RRC reconnection procedure (step S206). In summary, the terminal device 10 transmits a physical random access channel based on the (on-demand) SIB1 information received from the candidate cell.
[0112] Upon receiving a physical random access channel, the base station device 20B adjusts its transmission timing to receive a random access response (RAR) within a pre-set window length (Random access window) and transmits it to the terminal device 10. The random access response may be transmitted in a format that includes header information containing at least random access preamble information, an uplink grant (uplink resource allocation information) to be assigned to the terminal device 10, and uplink timing adjustment information (Timing Advance Command). The terminal device 10 monitors the physical downlink control channel PDCCH within the window length (Random access window) and attempts to receive the random access response (RAR).
[0113] Upon successfully receiving a Random Access Response (RAR), terminal device 10 generates an RRC Restabilization Request message and sends it to base station device 20B using the uplink resource specified in the uplink grant. Base station device 20B monitors the specified uplink resource and detects that terminal device 10 has sent the RRC Restabilization Request message.
[0114] Thus, according to the first embodiment, the base station device 20 can efficiently notify the terminal device 10 of the parameters necessary for the RRC reconnection procedure in cells that appropriately transmit system information (SIB1) for power saving. The terminal device 10 can appropriately determine whether or not to designate a cell as a candidate cell for the RRC reconnection procedure without acquiring the system information (SIB1) of that cell. As a result, the power saving efficiency of the base station device 20 can be improved.
[0115] <Second Embodiment> The second embodiment is described below. Note that the configurations, functions, or procedures common to both the first and second embodiments will not be explained. In other words, the following will mainly describe the differences from the first embodiment.
[0116] Figure 6 is a sequence diagram showing another example of the RRC reconnection procedure for an On-demand SIB1 transmission cell in the second embodiment. The operation of the terminal device 10 and the base station device 20 is the same as in Figure 5 up to a certain point (up to step S204), so the details are omitted. That is, Figure 6 starts from the point when step S204 in Figure 5 is completed.
[0117] In step S300, the base station device 20B (NES cell 20B-1) transmits an On-demand SIB1 (and a PDCCH indicating the downlink transmission resources) to the terminal device 10. The On-demand SIB1 includes at least cell selection parameters that apply to the base station device 20B (NES cell 20B-1) itself.
[0118] If the terminal device 10 can acquire the (On-demand) SIB1 of the base station device 20B (NES cell 20B-1) in step S300, it stores the acquired SIB1 information and applies the necessary settings. It also performs a second cell selection criterion evaluation (step S301).
[0119] In the second cell selection criterion evaluation, the terminal device 10 performs another cell selection criterion evaluation of the base station device 20B (NES cell 20B-1) based on the cell selection parameters (i.e., the first cell selection criterion parameters) obtained from the information of (On-demand) SIB1, similar to the conventional cell selection criterion evaluation. If the base station device 20B (NES cell 20B-1) satisfies the second cell selection criterion evaluation, the terminal device 10 decides that it may continue the RRC reconnection procedure for the candidate cell.
[0120] On the other hand, if the base station device 20B (NES cell 20B-1) does not meet the cell selection criteria in step S301, the candidate may be considered a barred cell. The terminal device 10 may decide not to consider the cell as a target cell (candidate cell) for the RRC reconnection procedure and not to continue the RRC reconnection procedure on the cell. The terminal device 10 may release the UL-WUS configuration information corresponding to the cell, or it may decide that it is invalid.
[0121] If it is determined in step S301 that the RRC reconnection procedure may be continued, the terminal device 10 can reuse the conventional RRC reconnection procedure (step S302).
[0122] Thus, according to the second embodiment, the base station device 20 can efficiently notify the terminal device 10 of the parameters necessary for the RRC reconnection procedure in cells that appropriately transmit system information (SIB1) for power saving. The terminal device 10 can prevent attempting RRC reconnection to unnecessary cells by making a decision on whether or not to designate a cell as a candidate cell for the RRC reconnection procedure before and after acquiring the system information (SIB1) of the cell. As a result, the RRC reconnection procedure can be optimized, and the power saving efficiency of the base station device 20 can be improved.
[0123] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its scope. The present invention can be modified or improved without departing from its spirit, and includes equivalents thereof. Furthermore, the embodiments described herein may be used individually, in combination, or switched between as needed during execution.
[0124] <Hardware Configuration of Each Device in Each Embodiment> Based on Figures 7 and 8, the hardware configuration of each device in the wireless communication system of each embodiment will be described.
[0125] Figure 7 shows an example of the hardware configuration of the terminal device 10. As shown in Figure 7, the terminal device 10 has, as hardware components, an RF (Radio Frequency) circuit 32 equipped with an antenna 31, a CPU (Central Processing Unit) 33, and a memory 34. Furthermore, the terminal device 10 may have a display device such as an LCD (Liquid Crystal Display) connected to the CPU 33. The memory 34 includes, for example, at least one of RAM (Random Access Memory) such as SDRAM (Synchronous Dynamic Random Access Memory), ROM (Read Only Memory), and flash memory, and stores programs, control information, and data signals.
[0126] The correspondence between the functional configuration of the terminal device 10 shown in Figure 2 and the hardware configuration of the terminal device 10 shown in Figure 7 will be explained. The transmitting / receiving antenna unit 19, the transmitting unit 17, and the receiving unit 15 are realized by, for example, an RF circuit 32, or an antenna 31 and an RF circuit 32. The control unit 13 and the processing unit 11 are realized by, for example, a CPU 33, memory 34, and a digital electronic circuit (not shown). Examples of digital electronic circuits include ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), and LSI (Large Scale Integration).
[0127] Figure 8 shows an example of the hardware configuration of the base station device 20. As shown in Figure 8, the base station device 20 has, as hardware components, an RF circuit 42 equipped with an antenna 41, a CPU 43, a DSP 44, a memory 45, and a network IF (Interface) 46. The CPU 43 is connected via a bus to enable input and output of various signals and data signals. The memory 45 includes, for example, RAM such as SDRAM, ROM, and flash memory, and stores programs, control information, and data signals.
[0128] The correspondence between the functional configuration of the base station device 20 shown in Figure 3 and the hardware configuration of the base station device 20 shown in Figure 8 will be explained. The transmitting / receiving antenna unit 29, the transmitting unit 27, and the receiving unit 25 are realized by, for example, an RF circuit 42, or an antenna 41 and an RF circuit 42. The control unit 23 and the processing unit 21 are realized by, for example, a CPU 43, a DSP 44, a memory 45, and a digital electronic circuit (not shown). Examples of digital electronic circuits include ASICs, FPGAs, and LSIs.
[0129] 1 Wireless Communication System 10 Terminal Devices 20A, 20B Base Station Device 20A-1 Normal Cell 20B-1 NES Cell 30 Core Network 11, 21 Processing Units 13, 23 Control Units 15, 25 Receiving Units 17, 27 Transmitting Units 19, 29 Transmitting / Receiving Antenna Units 31, 41 Antennas 32, 42 RF Circuits 33, 43 CPU 34, 45 Memory 44 DSP 46 Network IF 111, 211 Wireless Resource Processing Unit 113 Control Processing Unit 213 SIB1 Control Processing Unit
Claims
1. A terminal device capable of communicating with a first base station device and a second base station device, comprising: a receiving unit that receives from the first base station device information regarding a request signal setting that requests the second base station device to transmit first system information on demand; a processing unit that, when holding a valid request signal setting and while a timer for the RRC reconnection procedure is being timed, performs a first cell selection criterion evaluation to evaluate whether the second base station device satisfies the cell selection criteria, applying first cell selection criterion parameters if the first system information has been acquired, and applying second cell selection criterion parameters if the first system information has not been acquired, and performing the first cell selection criterion evaluation based on the applied cell selection criterion parameters; and a transmitting unit that transmits a request signal based on the request signal setting to the second base station device that satisfies the cell selection criteria.
2. The terminal device according to claim 1, wherein the first cell selection criterion parameter is obtained from the first system information of the second base station device, and the second cell selection criterion parameter is obtained from the second system information of the first base station device.
3. The terminal device according to claim 2, wherein when the second base station device obtains the first system information based on the request signal setting, a second cell selection criterion evaluation is performed using the first cell selection criterion parameter.
4. The terminal device according to claim 1, wherein, when the timer for the RRC reconnection procedure is being timed, and the request signal setting is held but the second cell selection criterion parameter is not held, the second base station device is not considered a candidate cell for the RRC reconnection procedure.
5. A base station device in a communication system including a second cell that transmits first system information on demand in response to a request from a terminal device, and a first cell that transmits the first system information periodically, the base station device comprising: a transmitting unit that transmits to the terminal device via the first cell information relating to a request signal setting that requests the on-demand transmission of the first system information corresponding to the second cell; a processing unit that, when the terminal device is holding the request signal setting and a timer for the RRC reconnection procedure is being timed, sets information that causes the terminal device to decide whether to apply either a first cell selection criterion parameter or a second cell selection criterion parameter as a first cell selection criterion evaluation that evaluates whether the second cell satisfies the cell selection criteria; and a receiving unit that receives a physical random access channel based on the request signal setting transmitted from the terminal device depending on whether the second cell satisfies the cell selection criteria.
6. The base station device according to claim 5, wherein the first cell selection criterion parameter is transmitted from the first system information of the second cell, and the second cell selection criterion parameter is transmitted from the second system information of the first cell.
7. The base station device according to claim 6, which transmits first system information, including the first cell selection criterion parameters used in a second cell selection criterion evaluation performed after the first cell selection criterion evaluation, based on the request signal setting.
8. A method for controlling a terminal device that can communicate with a first base station device and a second base station device, comprising: receiving means for receiving from the first base station device information regarding a request signal setting that requests the second base station device to transmit first system information on demand; processing means for performing a first cell selection criterion evaluation that evaluates whether the second base station device satisfies the cell selection criteria when a valid request signal setting is held and a timer for the RRC reconnection procedure is being timed, by applying first cell selection criterion parameters if the first system information has been acquired, and applying second cell selection criterion parameters if the first system information has not been acquired, and performing the first cell selection criterion evaluation based on the applied cell selection criterion parameters; and transmitting means for transmitting a request signal based on the request signal setting to the second base station device that satisfies the cell selection criteria.
9. A method for controlling a base station device in a communication system including a second cell that transmits first system information on demand in response to a request from a terminal device, and a first cell that transmits the first system information periodically, comprising: transmitting means for transmitting to the terminal device, via the first cell, information relating to a request signal setting that requests the on-demand transmission of the first system information corresponding to the second cell; processing means for setting information that causes the terminal device to decide whether to apply either a first cell selection criterion parameter or a second cell selection criterion parameter as a first cell selection criterion evaluation for evaluating whether the second cell satisfies the cell selection criteria, when the terminal device is holding the request signal setting and a timer for the RRC reconnection procedure is being timed; and receiving means for receiving a physical random access channel based on the request signal setting transmitted from the terminal device depending on whether the second cell satisfies the cell selection criteria.