TERMINAL AND WIRELESS COMMUNICATION METHOD

A terminal includes: a receiving unit which receives a discontinuous reception parameter for a radio resource control (RRC) idle state and a discontinuous reception parameter for an RRC inactive state; and a control unit which controls a discontinuous reception operation in the RRC inactive state in accordance with the discontinuous reception parameter for the RRC idle state instead of the discontinuous reception parameter for the RRC inactive state.

TECHNICAL FIELD

This disclosure relates to a terminal and a wireless communication method.

BACKGROUND ART

In the 3rd Generation Partnership Project (3GPP) as an international standards organization, New Radio (NR) Release 15 as the 5th generation (5G) RAT (Radio Access Technology) is specified as a successor to Long Term Evolution (LTE) as the 3.9th generation RAT and LTE-Advanced as the 4th generation RAT, for example, Non-Patent Document 1: 3GPP TS 38.300 V15.11.0 (2020-09).

Further, considering such a terminal that power consumption is further limited in LTE (Long Term Evolution) like IoT (Internet of Things) equipment, technology called eDRX (extended Discontinuous Reception) to reduce power consumption by limiting a period capable of receiving a radio signal is introduced, for example, Non-Patent Document 2: 3GPP TS 36.300 V15.12.0 (2020-12).

SUMMARY

In the 3GPP, the consideration of functions on the assumption of a new terminal for IoT performing radio access using NR is started so far. Further, eDRX described above is included in the functions being considered. Further, in NR, it is considered that an RRC (Radio Resource Control) idle state and an RRC inactive state may have different configurations for eDRX.

Here, there is such a case that, for some reason, an RRC state recognized by a terminal is different from an RRC state recognized by a network (a base station and/or a core network). In order that the terminal can receive radio signals even in such a case, it is conceivable that the terminal operates in accordance with both an eDRX configuration for the RRC idle state and an eDRX configuration for the RRC inactive state. However, the terminal should receive radio signals in accordance with both of the configurations, and this might increase electric power to be consumed by the terminal.

One object of this disclosure is to provide a terminal and a wireless communication method each of which is able to reduce an increase in electric power to be consumed by a terminal.

A terminal according to one aspect of this disclosure includes: a receiving unit which receives a discontinuous reception parameter for an RRC idle state and a discontinuous reception parameter for an RRC inactive state; and a control unit which controls a discontinuous reception operation in the RRC inactive state in accordance with the discontinuous reception parameter for the RRC idle state instead of the discontinuous reception parameter for the RRC inactive state.

With this disclosure, it is possible to provide a terminal and a wireless communication method each of which is able to reduce an increase in electric power to be consumed by a terminal.

DETAILED DESCRIPTION

With reference to the attached drawings, the following describes the present embodiment. In order to facilitate understanding of the description, identical constituents in the drawings have the same reference sign as far as possible, and redundant descriptions are omitted.

FIG.1is a diagram illustrating an example of the overview of a wireless communication system according to the present embodiment. As illustrated inFIG.1, a wireless communication system1may include a terminal10, a base station20, and a core network30. Note that the number of terminals10and base stations20illustrated inFIG.1is just an illustrative example, and the number is not limited to that illustrated.

As Radio Access Technology (RAT) of the wireless communication system1, for example, NR is assumed, but it is not limited to NR, and various RATs can be utilized, such as LTE, LTE-Advanced, the 6th generation (6G) RAT or later.

The terminal10is a given terminal or equipment such as a smartphone, a personal computer, an in-vehicle terminal, an in-vehicle device, a stationary device, or a telematics control unit (TCU), for example. The terminal10may also be called User Equipment (UE), a Mobile Station (MS), a terminal (User Terminal), a radio apparatus, a subscriber terminal, an access terminal, or the like. The terminal10may be of a mobile type or a fixed type. The terminal10is configured communicably using NR as RAT, for example.

Here, in NR Release 17, support for functions for a terminal on the assumption of lower performance and price range than a terminal for enhanced Mobile Broadband (eMBB) or Ultra-reliable and Low Latency Communications (URLLC) introduced in Release 15 or 16 is being considered. Such a terminal is also called a reduced capability (RedCap) terminal or device, which is assumed to be utilized, for example, in an industrial wireless sensor, a surveillance camera (video surveillance), or a wearable device.

The RedCap terminal is assumed to have higher performance than a terminal for Low Power Wide Area (LPWA), and a carrier used by the RedCap terminal may have a bandwidth of 20 MHz, 50 MHz, 100 MHz, or the like, for example. Further, the maximum terminal bandwidth (the maximum UE bandwidth) supported by a RedCap terminal may be, for example, 20 MHz for Frequency Range 1 (for example, frequency bandwidths of 6 GHz or less), and 100 MHz for Frequency Range 2 (for example, frequency bandwidths higher than 6 GHz). Note that, for example, there are Long Term Evolution for Machine-type-communication (LTE-M) working with LTE-type RAT in Category 1, Narrow Band IoT (NB-IoT) as LPWAs, and so on. The maximum bandwidth for Category 1 is 20 MHz, the maximum bandwidth for LTE-M is 1.4 MHz (6 RB), and the maximum bandwidth for NB-IoT is 180 kHz (1 RB). Thus, the RedCap terminal is expected to be used as a middle-range terminal between use for eMBB or URLLC and use for LPWA. The RedCap terminal and a terminal for LPWA are included as the terminal10according to the present embodiment.

The base station20forms one or more cells C to communicate with the terminal10using each of the cells C. The cell C may also be mutually rephrased as a serving cell, a carrier, a component carrier (CC), and the like. The base station20may also be called a gNodeB (gNB), an en-gNB, a Next Generation-Radio Access Network (NG-RAN) node, an eNB, a low-power node, a Central Unit (CU), a Distributed Unit (DU), a gNB-DU, a Remote Radio Head (RRH), an Integrated Access and Backhaul/Backhauling (IAB) node, or the like. The base station20is not limited to one node and may be constituted by a plurality of nodes (for example, a combination of a lower node such as a DU and an upper node such as a CU).

The core network30is, for example, an NR-compatible core network (5G Core Network: 5GC), but the core network30is not limited thereto. A device on the core network30(hereinafter, which may also be called a “core network device”) performs mobility management such as paging and location registration of the terminal10. The core network device may be connected to the base station20through a given interface (for example, S1 or NG interface).

The core network device includes, for example, at least one of multiple functions such as AMF (Access and Mobility Management Function) for managing information related to access and mobility management, SMF (Session Management Function) for session management, User Plane Function (UPF) for U plane transmission control, and NSSF (Network Slice Selection Function) for network slice management. Each of these functions is implemented in one or more physical or logical devices.

In the wireless communication system1, the terminal10receives a downlink (DL) signal from the base station20and/or transmits an uplink signal (UL). In the terminal10, one or more carriers may be configured. The bandwidth of each carrier is, for example, in a range of 5 MHz to 400 MHz. One or more bandwidth parts (BWPs) may be configured on one carrier. One BWP has at least part of the bandwidth of the carrier.

UE State

Next will be described an RRC state of the terminal10, defined in NR. The RRC state of the terminal10includes an RRC idle state (hereinafter referred to as an “idle state”), an RRC inactive state (hereinafter referred to as an “inactive state”), and an RRC connected state (hereinafter referred to as a “connected state”).

FIG.2is a diagram illustrating an example of transition of the state of the terminal10. InFIG.2, the idle state is a state where an RRC connection between the terminal10and the base station20is not established and is also called RRC_IDLE, an idle mode, an RRC idle mode, or the like.

The terminal10in the idle state camps on a cell C selected by cell selection and/or cell reselection (hereinafter referred to as “cell selection/reselection”) and receives system information broadcast in the cell C. When the RRC connection is established, the terminal10in the idle state transitions to the connected state.

The inactive state is a state where an RRC connection is established but is suspended and is also called RRC_INACTIVE, an inactive mode, an RRC inactive mode, or the like. The inactive state does not exist in LTE and is a RRC state newly defined in NR. The terminal10in the inactive state camps on a cell C selected by cell selection/reselection and receives system information broadcast in the cell C. Like the idle state, the inactive state can save power of the terminal10, but unlike the idle state, an RRC context and a NAS context are held among the terminal10, the base station20, and the core network30.

The core network30manages the position of the terminal10by a unit called TA (Tracking Area), and the core network30instructs a plurality of base stations20to transmit a paging signal, the plurality of base stations20constituting TA in which the terminal10to be called is present. Further, one or more base stations20that has received the instruction transmit paging signals all at once.

Further, in NR, a RAN notification area (RNA) as an area obtained by subdividing a TA (Tracking Area) is newly defined, and the base station20manages the RAN notification area in which the terminals10in the connected state and the inactive state are present. Further, in NR, technology called “RAN paging” for performing paging in units of RAN notification areas used to call the terminal10in the inactive state is introduced. In RAN paging, all paging signals are transmitted at once from two or more base stations20constituting each RAN notification area in which the terminal10in the inactive state is present. The terminal10in the inactive state that has received a paging signal resumes the RRC connection and transitions to the connected state. In the following description, a process of transmitting paging signals in units of TAs in response to the instruction from the core network30is referred to as “CN paging,” distinguished from “RAN paging.” Further, in a case where CN paging is not distinguished from RAN paging, CN paging is referred to as “paging.”

The connected state is a state where the RRC connection is established and is also called RRC CONNECTED, a connected mode, an RRC connected mode, and the like. The terminal10in the connected state monitors PDCCH (Physical Downlink Control Channel) and controls reception of PDSCH (Physical Downlink Shared Channel) based on detected DCI (Downlink Control Information). When the RRC connection is released, the terminal10in the connected state transitions to the idle state, and when the RRC connection is suspended, the terminal10transitions to the inactive state.

Next will be described eDRX (extended DRX) technology according to the present embodiment. In NR, a slot with a variable length of time, a subframe with a length of time of 1 ms, a radio frame with a length of time of 10 ms, and a hyperframe with a length of time of 10.24 seconds are defined. The position of each radio frame is represented by a number in SFNs (System Frame Numbers) of 0 to 1023. Further, in order to manage a length of time longer than that of the 1024 radio frames, a hyperframe with a length of time of the SFN (that is, 10.24 seconds) of the 0 to 1023 radio frames is defined. The hyperframe is represented by a number in H-SFNs (Hyper-SFN (System Frame Numbers)) of 0 to 1023.

FIG.3is a diagram to describe the operation of DRX (Discontinuous Reception). As illustrated inFIG.3, the terminal10in the idle state or the inactive state monitors downlink control channel candidates (PDCCH candidates) during periods called POs (Paging Occasions) to receive paging signals. While the terminal10is working according to the DRX configuration, the base station20transmits paging signals during the PO periods and does not transmit paging signals during the other periods. The terminal10that has received a paging signal in each PO period establishes communication with the base station20and transitions to the connected state. The DRX cycle is a maximum of 2.56 seconds.

FIG.4is a diagram to describe the operation of eDRX. As illustrated inFIG.4, the terminal10in the idle state or the inactive state monitors downlink control channel candidates in PO periods within each period called a PTW (Paging Time Window) to receive paging signals. One PTW is configured in each hyperframe called a PH (Paging Hyperframe). One PH may be present in each eDRX cycle.

While the terminal10is working according to the eDRX configuration, the base station20transmits a paging signal during each PTW period and each PO period and does not transmit any paging signal during the other periods. The terminal10that has received a paging signal establishes communication with the base station20and transitions to the connected state.

Here, the PH may be an H-SFN that satisfies Formula 1 below.

“TeDRX,H” indicates the eDRX cycle, which is configured with a length of an integral multiple of the Hyperframe. The UE_ID_H is 10 or 12 most significant bits of a hashed ID defined based on 5G-S-TMIS (5G S-Temporary Mobile Subscriber Identity).

An SFN as the starting position of the PTW (PTW start) (start timing) may be expressed by Formula 2 and Formula 3 below.

An SFN as the ending position of the PTW (PTW end) (end timing) may be expressed by Formula 4 below.

L is a time length of the PTW (Paging Time Window length). A parameter (hereinafter referred to as “eDRX parameter”) to determine the eDRX operation, e.g., the eDRX cycle, the time length of the PTW, and the like, is configured in the terminal10by use of a higher layer (NAS (Non Access Stratum)) message, an RRC message, broadcast information, or the like.

In the following description, the “eDRX parameter” may indicate only the parameter to determine the eDRX operation, e.g., the eDRX cycle, the time length of the PTW, or the like, or may indicate that a parameter to determine the DRX operation, e.g., the DRX cycle, the configuration of a PO position, or the like, is also included in addition to the parameter to determine the eDRX operation.

Further, in the present embodiment, an “eDRX parameter for the inactive state” indicates an eDRX parameter applied to the terminal10in the inactive state. Further, an “eDRX parameter for the idle state” indicates an eDRX parameter applied to the terminal10in the idle state.

Further, in the present embodiment, the eDRX parameter for the idle state and the eDRX parameter for the inactive state may be different from each other.

Problem to achieve eDRX both in Idle State and Inactive State

The RRC state of the terminal10is managed both by the terminal10and by the network (the base station20and/or the core network30). Generally, the RRC state managed by the terminal10is the same as the RRC state managed by the network. However, in a case where the context (context of RRC) of a UE is lost due to software abnormality in the base station20or the like, for example, the terminal10and the network may be inconsistent in terms of the RRC state of the terminal10for some reason.

Accordingly, in a case where the occurrence of such an inconsistent state is taken into account, in order to receive paging signals without exception, it is desired that the terminal10performs the eDRX operation according to both the eDRX parameter for the idle state and the eDRX parameter for the inactive state, regardless of whether the terminal10recognizes that it is in the idle state or the terminal10recognizes that it is in the inactive state.

FIG.5is a diagram illustrating a pattern where a PTW in the inactive state and a PTW in the idle state overlap with each other. The upper side ofFIG.5illustrates the eDRX operation in the inactive state, and the lower side ofFIG.5illustrates the eDRX operation in the idle state. In the example ofFIG.5, a PH in the inactive state and a PH in the idle state overlap with each other at the fifth H-SFN. Further, part of the PTW in the idle state overlaps with the PTW in the inactive state. In this case, the terminal10starts a receiving circuit in accordance with the eDRX parameter for the idle state in the fifth H-SFN and monitors downlink control channel candidates, and when the PTW in the idle state is ended, the terminal10stops the receiver circuit.

FIG.6is a diagram illustrating a pattern where the PTW in the inactive state and the PTW in the idle state do not overlap with each other. The upper side ofFIG.6illustrates the eDRX operation in the inactive state, and the lower side ofFIG.6illustrates the eDRX operation in the idle state. In the example ofFIG.6, the PH in the inactive state overlaps with the PH in the idle state at the fifth H-SFN In the meantime, unlikeFIG.5, the PTW in the idle state and the PTW in the inactive state do not overlap with each other. In this case, in the fifth H-SFN, the terminal10performs such an operation that the terminal10starts the receiving circuit in accordance with the PTW in the idle state to monitor downlink control channel candidates, stops the receiver circuit when the TW is ended, and then, the terminal10starts the receiving circuit in accordance with the PTW in the inactive state to monitor downlink control channel candidates and stops the receiver circuit when the PTW is ended. That is, in the same H-SFN, the terminal10performs a process of starting the receiving circuit twice.

Thus, in a case where the PH in the inactive state and the PH in the idle state overlap with each other, and the PTW in the inactive state and the PTW in the idle state do not overlap with each other in the PHs, it is necessary for the terminal10to start its receiving circuit twice in the PH thus overlapping, so that electric power to be consumed by the terminal10may increase.

In view of this, in the present embodiment, in a case where the terminal10transitions to the inactive state, the starting position of the PTW in the idle state or the starting position of the PTW in the inactive state are made the same as (aligned with) the starting position of the PTW in the other state. Hereby, the process of starting the receiving circuit in the same H-SFN is performed once, thereby making it possible to reduce an increase in electric power to be consumed by the terminal10.

Configuration of eDRX parameters for Idle State and Inactive State

FIG.7is a diagram illustrating an example of a routine in a case where the eDRX parameter for the idle state is configured by the core network30for the terminal10. Note that it is assumed that the core network30is AMF, for example, but the core network30is not limited to this.

In step S100, the terminal10desiring to validate eDRX transmits, to the core network30, a Registration Request message including an “eDRX parameter” indicative of an eDRX operation desired to be configured. In step S101, the core network30determines an eDRX parameter for the idle state based on the registration request received from the terminal10. In step S102, in order to configure the determined eDRX parameter in the terminal10, the core network30transmits, to the terminal10, an NAS message (in particular, a Registration Accept message) including the determined eDRX parameter for the idle state. In step S103, the terminal10configures the eDRX parameter for the idle state, included in the NAS message (that is, the terminal10stores the eDRX parameter for the idle state in a storage device).

FIG.8is a diagram illustrating an example of a routine in a case where the eDRX parameter for the inactive state is configured by the base station20for the terminal10.

In step S200, the core network30transmits, to the base station20, an N2 message including information indicating that the terminal10desires to validate eDRX, for example. The N2 message includes core network assistance information related to RRC inactive (Core Network Assistance Information for RRC INACTIVE), and the core network assistance information may include information indicating that the terminal10desires to validate eDRX.

In step S201, the base station20determines an eDRX parameter for the inactive state to be configured in the terminal10. In step S202, at the time when the base station20instructs the terminal10to transition to the inactive state, the base station20transmits, to the terminal10, an RRC Release message in which the eDRX parameter for the inactive state, determined in step S201, is included in a suspend configuration (SuspendConfig). In step S203, the terminal10configures the eDRX parameter for the inactive state, included in the RRC Release message (the terminal10stores the eDRX parameter in the storage device).

Note that the eDRX parameter in the inactive state may be configured in the terminal10by use of the NAS message from the core network30, using the routine illustrated inFIG.7. In this case, the routine illustrated inFIG.8is omitted.

eDRX Operation in Inactive State

FIG.9is a flowchart to describe the eDRX operation in the inactive state. In the routine ofFIG.9, the eDRX parameter for the idle state is configured in the terminal10.

In step S300, when the terminal10receives, from the base station20, an RRC Release message including a suspend configuration (SuspendConfig) to instruct the terminal10to transition from the active state to the inactive state, the terminal10transitions to the inactive state. Here, the suspend configuration includes the eDRX parameter for the inactive state, and the terminal10configures the received eDRX parameter for the inactive state.

In step S301, the terminal10determines whether or not a “specific flag” is configured in the RRC Release message received in the routine of step S300. More specifically, the terminal10may determine whether or not the “specific flag” is present in the eDRX parameter for the inactive state, included in the RRC Release message received in the routine of step S300.

Here, the “specific flag” may be defined as an information element to, in a case where the PTW in the idle state and the PTW in the inactive state overlap with each other, instruct the terminal10to configure the starting position of either of the PTWs (or the PTW in the inactive state) to be the same as (aligned with) the starting position of the other one of the PTWs (or the PTW in the idle state). In a case where the specific flag is configured in the terminal10, the routine advances to step S302, and in a case where the specific flag is not configured in the terminal10, the routine advances to the routine of step S304.

In step S302, the terminal10configures the starting position of the PTW in the inactive state to be the same as the starting position of the PTW in the idle state, for the PH where the PTW in the idle state and the PTW in the inactive state overlap with each other. A concrete example of the specific flag and the routine in a case where the specific flag is present will be described later. Here, the PH where the PTW in the idle state and the PTW in the inactive state overlap with each other indicates, more specifically, any of the following cases: a case where the PH is an H-SFN corresponding to both the PH in the idle state and the PH in the inactive state (that is, an H-SFN where the eDRX cycle for the idle state is the same as the eDRX cycle for the inactive state), and in the H-SFN, the PTW in the inactive state is included in part of the PTW in the idle state (for example, the case corresponds to the example ofFIG.5); a case where part of the PTW in the idle state overlaps with part of the PTW in the inactive state; and a case where the PTW in the idle state is included in part of the PTW in the inactive state.

In step S303, the terminal10performs eDRX control in accordance with the eDRX parameter for the idle state and the eDRX parameter for the inactive state with the starting position of the PTW being configured to be the same as that of the idle state. That is, the terminal10monitors downlink control channel candidates in SFNs included in either one of “the starting position of the PTW in the idle state and the ending position of the PTW” and “the starting position of the PTW in the inactive state and the ending position of the PTW, the PTW being configured such that the starting position is made the same as that in the idle state.”

In step S304, the terminal10does not configure the starting position of the PTW in the inactive state to be the same as the starting position of the PTW in the idle state, and the terminal10performs eDRX control in accordance with both the eDRX parameter for the idle state and the eDRX parameter for the inactive state. That is, in an H-SFN corresponding to the PH in the idle state, the terminal10monitors downlink control channel candidates in accordance with the starting position of the PTW in the idle state and the ending position of the PTW. Further, in an H-SFN corresponding to the PH in the inactive state, the terminal10monitors downlink control channel candidates in accordance with the starting position of the PTW in the inactive state and the ending position of the PTW. Further, in an H-SFN that does not correspond to either of the PH in the idle state and the PH in the inactive state, the terminal10does not monitor downlink control channel candidates.

Process in Case where Specific Flag is Configured

In a pattern 1, it is premised that the PTW in the idle state and the PTW in the inactive state are calculated by use of Formula 1 to Formula 4.

In a case where a “specific flag” for the pattern 1 is configured in an RRC Release message, the terminal10calculates the starting position of the PTW in the inactive state by substituting the eDRX cycle included in the eDRX parameter for the idle state into “TeDRX,H” in Formula 3, instead of the eDRX cycle included in the eDRX parameter for the inactive state. Further, in accordance with Formula 4, the ending position of the PTW in the inactive state is calculated by adding the time length of the PTW, included in the eDRX parameter for the inactive state, to the calculated starting position of the PTW.

The terminal10monitors downlink control channel candidates in an SFN where at least either of the PTW in the idle state and the PTW in the inactive state is configured, in accordance with the PTWs. For example, it is assumed that the starting position of the PTW in the idle state is SFN=0 and the ending position of the PTW is SFN=299 (that is, the time length of the PTW is three seconds). Further, it is assumed that the starting position of the PTW in the inactive state is SFN=0 and the ending position of the PTW is SFN=99 (that is, the time length of the PTW is one second). In this case, the terminal10monitors downlink control channel candidates in POs present from SFN=0 to SFN=299.

In the pattern 1, the “specific flag” may be expressed as “information indicating that the starting position of the PTW in the inactive state is the same as the starting position of the PTW in the idle state.” The information may be an information element in an RRC message.

Hereby, the starting position of the PTW in the inactive state becomes the same as the starting position of the PTW in the idle state. Accordingly, in a case where the PH in the inactive state and the PH in the idle state overlap with each other, the terminal10can receive paging signals by starting the receiver circuit included in the terminal10just once.

FIG.10illustrates a specification change example of TS38.304 in the pattern 1.FIGS.11and12illustrate specification change examples of TS38.331 in the pattern 1. Here, “pagingTimeWindowStart-r17” illustrated inFIG.11may be expressed as “information indicating whether or not the starting position of the PTW in the inactive state is made the same as the starting position of the PTW in the idle state.” Further, inFIG.11, the “specific flag” may indicate that a parameter value corresponds to the information element “pagingTimeWindowStart-r17” configured in “sameAsIdle.” Note that, in a case where the value of “pagingTimeWindowStart-r17” is configured to “differentFrom Idle,” the terminal10does not perform a process of changing the starting position of the PTW in the inactive state.

In a pattern 2, it is premised that the PTW in the idle state is calculated by use of Formula 1 to Formula 4. Meanwhile, the PTW in the inactive state is calculated by use of Formula 5 described below, instead of Formula 2. That is, the PTW in the inactive state is calculated by use of Formula 1 and Formula 3 to Formula 5.

Here, ieDRX for RRC_IDLE is a value to be provided by substituting the eDRX cycle in the idle state into Formula 3. Further, offset is a value specified with the specific flag and may be any of 0 to 3, for example. Note that ieDRX in the idle state, calculated by Formula 3, may be any of values of 0 to 3. Note that, in a case where the SFN calculated by Formula 5 exceeds 1023, the terminal10may consider a value obtained by subtracting 1024 from the calculated value to be the SFN. For example, in a case where the calculation result of Formula 5 is 1536 (256×6), the terminal10may consider the SFN to be 512 (1536-1024).

In the pattern 2, the case where the specific flag is configured may be a “case where information indicating that a starting position shifted by an offset value from the starting position of the PTW in the idle state is taken as the starting position of the PTW in the inactive state is configured in the terminal10and the offset value is configured to 0.” The information may be an information element in an RRC message. For example, the information element may be called PagingTimeWindowOffset.

In a case where a “specific flag” for the pattern 2 is configured in an RRC Release message, the terminal10configures zero in offset of Formula 5. That is, the starting position of the PTW in the inactive state becomes the same as the starting position of the PTW in the idle state.

Like the pattern 1, the terminal10monitors downlink control channel candidates in an SFN where at least either of the PTW in the idle state and the PTW in the inactive state is configured, in accordance with the PTWs.

Hereby, the starting position of the PTW in the inactive state becomes the same as the starting position of the PTW in the idle state. Accordingly, in a case where the PH in the inactive state and the PH in the idle state overlap with each other, the terminal10can receive paging signals by starting the receiver circuit included in the terminal10just once.

FIG.13illustrates a specification change example of TS38.304 in the pattern 2.FIGS.14and15illustrate specification change examples of TS38.331 in the pattern 2. Here, “pagingTimeWindowOffset-r17” illustrated inFIG.14is information indicating that a starting position shifted by an offset value from the starting position of the PTW in the idle state is taken as the starting position of the PTW in the inactive state. InFIG.14, the “specific flag” may correspond to an information element “pagingTimeWindowOffset-r17” with a parameter value configured to be “0.”

Modifications

The eDRX parameter for the inactive state is not limited to the RRC Release message and may be configured in the terminal10by use of other messages. The other messages may be, for example, an RRCReconfiguration message, an RRCReestablishment message, an RRCResumeRequest/RRCResumeRequest1 message, an RRCResume message, an RRCSetup message, or broadcast information (system information, SIB1, SIB2, or the like).

The specific flag may be part of the eDRX parameter in the inactive state or may be defined as information separate from the eDRX parameter in the inactive state.

In a case where the specific flag is defined as information separate from the eDRX parameter for the inactive state, the eDRX parameter for the inactive state and the specific flag may be configured in the terminal10by use of different messages. For example, the eDRX parameter for the inactive state may be configured in the terminal10by use of an RRC Release message, and the specific flag may be configured in the terminal10by use of an RRCReconfiguration message, an RRCReestablishment message, an RRCResumeRequest message, an RRCResume message, an RRCSetup message, broadcast information (system information, SIB1, SIB2, or the like), or the like.

In the pattern 1, in a case where the specific flag is configured in the terminal10, when the terminal10calculates the ending position of the PTW by Formula 4, the terminal10may calculate the ending position of the PTW in the inactive state by substituting the time length of the PTW in the idle state into Formula 4.

In the routine described in the pattern 1, instead of changing the eDRX parameter for the inactive state to the eDRX parameter for the idle state, the eDRX parameter for the idle state may be changed to the eDRX parameter for the inactive state. For example, in a case where the “specific flag” related to the pattern 1 is configured in an RRC Release message, the terminal10may substitute the eDRX cycle included in the eDRX parameter for the inactive state into “TeDRX,H” in Formula 3, instead of the eDRX cycle included in the eDRX parameter for the idle state, to calculate the starting position of the PTW in the idle state. Further, in accordance with Formula 4, the ending position of the PTW in the idle state may be calculated by adding the time length of the PTW, included in the eDRX parameter for the idle state, to the calculated starting position of the PTW in the idle state. In this case, the “specific flag” may be defined as an information element to, in a case where the PTW in the idle state and the PTW in the inactive state overlap with each other, instruct the terminal10to configure the starting position of the PTW in the idle state to be the same as (aligned with) the starting position of the PTW in the inactive state.

In the routine described in the pattern 2, instead of calculating the eDRX parameter for the inactive state by adding an offset to the eDRX parameter for the idle state, the eDRX parameter for the idle state may be calculated by adding an offset to the eDRX parameter for the inactive state. For example, in a case where the “specific flag” related to the pattern 1 is configured in an RRC Release message, the terminal10may calculate the PTW in the inactive state by use of Formula 1 to Formula 4 and calculate the PTW in the idle state by use of Formula 1 and Formula 3 to Formula 5.

Regardless of whether there is a PH in which the PTW in the idle state and the PTW in the inactive state overlap with each other, the terminal10may configure the starting position of either of the PTWs to be the same as (aligned with) the starting position of the other one of the PTWs in all PHs. For example, the terminal10may configure the starting position of each PTW in the inactive state to be the same as the starting position of the PTW in the idle state. In this case, the terminal10may configure the starting position of the PTW in the inactive state to be the same as the starting position of the PTW in the idle state, for each PH corresponding to the inactive state, in the routine of step S302. In this case, the “specific flag” may indicate an information element to instruct the terminal10to configure the starting position of either of the PTWs to be the same as (aligned with) the starting position of the other one of the PTWs. Further, in a case where the PTW in the idle state and the PTW in the inactive state overlap with each other, the “specific flag” may be defined as an information element to instruct the terminal10to configure the starting position of the PTW in the inactive state (or in the idle state) to be the same as (aligned with) the starting position of the PTW in the idle state (or in the inactive state).

In the routine described in the pattern 1, the terminal10may further calculate the ending position of the PTW in the inactive state by adding the time length of the PTW, included in the eDRX parameter for the idle state, to the calculated starting position of the PTW, in accordance with Formula 4. That is, in addition to the eDRX cycle, the time length of the PTW may be also made the same as the eDRX parameter for the idle state. In other words, the terminal10may configure the starting position and the ending position of the PTW in the inactive state to be the same as the starting position and the ending position of the PTW in the idle state.

Modifications of eDRX Parameter

The terminal10, the base station20, and the core network30according to the present embodiment may flexibly configure the starting position of a PTW by including given information about the configuration of the starting position of the PTW in the eDRX parameter for the idle state and/or the eDRX parameter for the inactive state. For example, the given information about the configuration of the starting position of the PTW may include information indicative of the number of starting positions for the PTW in a PH (the number of SFNs that can be configured as starting SFNs for the PTW). Further, the starting position of a PTW may be determined by inputting the information indicative of the number of starting positions for the PTW in the PH into Formula 6 and Formula 7 instead of Formula 2 and Formula 3. Further, the ending position of the PTW may be determined in accordance with Formula 4.

In Formula 6 and Formula 7, NPTWis information indicative of the number of starting positions for the PTW in the PH. For example, in a case of NPTW=8, since possible values of ieDRX are 0 to 7, the starting position of the PTW is any one of eight values of SFN=0, 128, 256, 384, 512, 640, 768, 896. Note that, in a case of NPTW=4, Formula 6 and Formula 7 are the same as Formula 2 and Formula 3, respectively. In other words, the starting position of the PTW can be configured flexibly by utilizing Formula 6 and Formula 7.

In a case where the starting position of the PTW is determined in accordance with Formula 6 and Formula 7 and the ending position of the PTW is determined by Formula 4, the eDRX parameter includes an eDRX cycle (TeDRX,Hin Formula 7), the time length of the PTW (L in Formula 4), and the number of starting positions for the PTW in the PH (NPTWin Formula 6) are included in the eDRX parameter.

Further, in the wireless communication system1according to the present embodiment, the given information on the configuration of the starting position of the PTW may also include information for specifying a radio frame indicative of the starting position of the PTW. For example, the information for specifying a radio frame indicative of the starting position of the PTW may be information for specifying a specific radio frame number such as SFN=0 or SFN=64. Further, the eDRX parameter may include information for specifying a radio frame indicative of the ending position of the PTW (for example, SFN=64, SFN=128, or the like). Thus, the ending position of the PTW can be configured flexibly. In this case, in the eDRX parameter, information for specifying an eDRX cycle and a radio frame indicative of the starting position of a PTW, and information for specifying a radio frame indicative of the ending position of the PTW are included.

Hardware Configuration

FIG.16is a diagram illustrating an example of the hardware configuration of each equipment in the wireless communication system. Each equipment in the wireless communication system1(for example, the terminal10, the base station20, or the core network30) includes a processor11, a storage device12, a communication device13for performing wired or wireless communication, and an input/output device14for accepting various input operations and outputting various information.

The processor11is, for example, a CPU (Central Processing Unit) to control each equipment in the wireless communication system1. The processor11may read a program from the storage device12and execute the program to perform various processing to be described in the present embodiment. Each equipment in the wireless communication system1may also be configured to include one or more processors11. Further, each equipment concerned may also be called a computer.

The storage device12is constituted by, for example, storages such as a memory, an HDD (Hard Disk Drive), and/or an SSD (Solid State Drive). The storage device12may also store various information required to perform processing by the processor11(for example, programs and the like executed by the processor11).

The communication device13is a device for performing communication through wired and/or wireless networks and may include a network card, a communication module, a chip, an antenna, and the like, for example. Further, an amplifier, an RF (Radio Frequency) device for performing processing on radio signals, and a BB (Base Band) device for performing processing on baseband signals may be included in the communication device13.

The RF device performs D/A conversion, modulation, frequency conversion, power amplification, and the like on a digital baseband signal, for example, received from the BB device to generate a radio signal to be transmitted from the antenna. Further, the RF device performs frequency conversion, demodulation, ND conversion, and the like on a radio signal received from the antenna to generate and transmit a digital baseband signal to the BB device. The BB device performs processing for converting the digital baseband signal to a packet and processing for converting the packet to a digital baseband signal.

The input/output device14includes input devices such as a keyboard, a touch panel, a mouse, and/or a microphone, and output devices such as a display and/or a speaker, for example.

Note that the hardware configuration described above is just an example. In each equipment inside the wireless communication system1, part of the hardware illustrated inFIG.16may be omitted, or any other hardware unillustrated inFIG.16may be included. Further, the hardware illustrated inFIG.16may be constituted by one or more chips.

Functional Configuration

Terminal

FIG.17is a diagram illustrating an example of the functional configuration of the terminal10. The terminal10includes a receiving unit101, a transmitting unit102, and a control unit103. All or some of the functions implemented by the receiving unit101and the transmitting unit102can be realized by using the communication device13. Further, all or some of the functions implemented by the receiving unit101and the transmitting unit102, and the control unit103can be achieved by the processor11executing a program stored in the storage device12. Further, the program can be stored in a storage medium. The storage medium with the program stored thereon may be a non-transitory computer readable medium. The non-transitory medium is not limited particularly but may be a storage medium such as a USB memory or a CD-ROM, for example.

The eDRX parameters and the specific flag used in the above description are examples of an eDRX configuration and given information in the following description, respectively.

The receiving unit101receives downlink signals. Further, the receiving unit101may also receive information and/or data transmitted through each downlink signal. Here, for example, the verb “receive” may also include the meaning of performing processing related to reception including at least one of the reception, demapping, demodulation, decoding, monitoring, and measurement of a radio signal.

Further, the receiving unit101receives an eDRX configuration (hereinafter referred to as a “first eDRX configuration”) for the idle state and an eDRX configuration (hereinafter referred to as a “second eDRX configuration”) for the inactive state. The receiving unit101may receive an NAS message including the first eDRX configuration from the core network30. Further, the receiving unit101may receive an RRC message or broadcast information including the second eDRX configuration from the base station20. The RRC message may be, for example, an RRC Release message an RRCReconfiguration message, an RRCReestablishment message, an RRCResumeRequest message, an RRCResume message, an RRCSetup message, or the like. Further, the receiving unit101may receive an NAS message including the second eDRX configuration from the core network30.

The transmitting unit102transmits uplink signals. Further, the transmitting unit102may also transmit information and/or data to be transmitted through each uplink signal. Here, for example, the verb “transmit” may also include the meaning of performing processing related to transmission including at least one of encoding, modulation, mapping, and transmission of a radio signal.

The control unit103performs various processing related to eDRX based on the eDRX configuration received at the receiving unit101. Further, in the idle state, the control unit103performs control to monitor control channel candidates (PDCCH Candidates) in a paging search space during a PTW (reception period) in a PH (given H-SFN) indicated by the first eDRX configuration. Further, in the inactive state, the control unit103performs control to monitor control channel candidates (PDCCH Candidates) in a paging search space during a PTW (reception period) in a PH (given H-SFN) indicated by the second eDRX configuration.

Further, the control unit103configures at least part of configuration information of the second eDRX configuration to be the same as configuration information of the first eDRX configuration and performs eDRX control in the inactive state in accordance with the second eDRX configuration with the configuration information at least part of which is configured to be the same as the configuration information of the first eDRX configuration. The at least part of the configuration information of the second eDRX configuration may be the eDRX cycle of the eDRX configuration in the inactive state. The “second eDRX configuration with the configuration information at least part of which is configured to be the same as the configuration information of the first eDRX configuration” may be called a “third eDRX configuration” for convenience to distinguish it from the second eDRX configuration received by the receiving unit101.

Further, the control unit103may configure the configuration information of the second eDRX configuration to be the same as the configuration information of the first eDRX configuration and perform eDRX control in the inactive state in accordance with the second eDRX configuration with the configuration information configured to be the same as the configuration information of the first eDRX configuration. The configuration information of the second eDRX configuration may be the eDRX cycle and the time length of a PTW of the eDRX configuration in the inactive state (corresponding to the modification).

Further, in a case where given information is included in the second eDRX configuration, the control unit103may configure at least part of the configuration information of the second eDRX configuration to be the same as the configuration information of the first eDRX configuration (corresponding to S302-YES, S303inFIG.9). Here, the given information may be the specific flags in the pattern 1 and the pattern 2. For example, in the pattern 1, and the given information may be “pagingTimeWindowStart-r17” with a parameter value configured to be True, or in the pattern 2, and the given information may be “pagingTimeWindowOffset-r17” with a parameter value (offset) configured to be zero.

Further, in a case where the given information is not included in the second eDRX configuration, the control unit103may perform eDRX control in the RRC inactive state in accordance with the second eDRX configuration without configuring at least part of the configuration information of the second eDRX configuration to be the same as the configuration information of the first eDRX configuration (corresponding to S305inFIG.9).

Further, in a case where a PTW (a first reception period) for monitoring control channel candidates, indicated by the first eDRX configuration, and a PTW (a second reception period) for monitoring control channel candidates, indicated by the second eDRX configuration, overlap with each other, the control unit103may perform eDRX control in the RRC inactive state in accordance with the “second eDRX configuration with the configuration information at least part of which is configured to be the same as the configuration information of the first eDRX configuration.”

Further, in a case where the PTW (the first reception period) for monitoring control channel candidates, indicated by the first eDRX configuration, and the PTW (the second reception period) for monitoring control channel candidates, indicated by the second eDRX configuration, do not overlap with each other, the control unit103may perform eDRX control in the RRC inactive state in accordance with the second eDRX configuration configured in the terminal10(that is, without configuring at least part of the configuration information of the second eDRX configuration to be the same as the configuration information of the first eDRX configuration).

Further, the at least part of the configuration information of the second eDRX configuration may be an eDRX cycle (information used to calculate the starting position of the second reception period), and the configuration information of the first eDRX configuration may be an eDRX cycle (information used to calculate the starting position of the first reception period).

Further, the control unit103may change (or replace) the eDRX cycle in the second eDRX configuration to (or with) the eDRX cycle in the first eDRX configuration. Further, the “second eDRX configuration with the configuration information at least part of which is configured to be the same as the configuration information of the first eDRX configuration” may be expressed as a “changed second eDRX configuration” (corresponding to the pattern 1).

Further, the control unit103may determine the eDRX cycle in the second eDRX configuration by adding an offset value included in the second eDRX configuration to the eDRX cycle in the first eDRX configuration. Further, the offset value may be zero (corresponding to the pattern 2).

Supplement

The eDRX may be called discontinuous reception, extended discontinuous reception, reception spacing control, extended reception spacing control, or the like.

The wording “monitor control channel candidates in a paging search space” may also be expressed as the wording “monitor control channel candidates in a search space set configured by paging search space information (pagingSearchSpace).”

In the aforementioned embodiment, an example of a first time unit may be one hyperframe (10.24 sec), an example of a second time unit may be one radio frame (10 ms), and an example of a third time unit may be one subframe (1 ms). Further, it may be defined that the second time unit is shorter in time than the first time unit, and the third time unit is shorter in time than the second time unit. Further, an example of a number indicative of each position of the second time unit cyclically repeated may be an SFN, and an example of a number indicative of each position of the first time unit cyclically repeated may be an H-SFN. For example, the H-SFN may also be expressed as a first time interval of a position indicated by a given number among cyclically repeated first time intervals. Further, the PH may be configured in a plurality of hyperframes among H-SFNs of 0 to 1023.

Various signals, information, and parameters in the aforementioned embodiment may be signaled in any layer. In other words, the various signals, information, and parameters mentioned above may also be replaced with signals, information, and parameters in any layer such as the higher layer (for example, NAS layer, RRC layer, MAC layer, or the like), the lower layer (for example, physical layer), or the like. Further, given information is not limited to be explicitly informed and may also be implicitly informed (for example, by not informing the information or using any other information).

Further, the names of various signals, information, parameters, IE, channels, time units, and frequency units are just illustrative examples in the aforementioned embodiment, and the names may be replaced with other names. For example, each slot may be any other name as long as it is a time unit having a given number of symbols. Further, RB may be any other name as long as it is a frequency unit having a given number of subcarriers.

Further, the applications of the terminal10in the aforementioned embodiment (for example, for RedCap, IoT, and the like) are not limited to those described herein, and the terminal10may also be used for any other purpose (for example, for eMBB, URLLC, Device-to-Device (D2D), Vehicle-to-Everything (V2X), or the like) as long as it has similar functions.

Further, the format of various information is not limited to that in the aforementioned embodiment, and it may be changed accordingly such as to bit representation (0 or 1), Boolean (true or false), integer values, or characters. Further, the singular and the plural in the aforementioned embodiment may be mutually changed.

The above description has dealt with the present embodiment with reference to concrete examples. However, this disclosure is not limited to these concrete examples. Embodiments obtained by adding design changes to the concrete examples by a person skilled in the art appropriately are also included in the scope of this disclosure, as long as the embodiments have the features of this disclosure. Each element provided in each of the concrete examples and its arrangement, condition, shape, and the like are not limited to those described herein and can be changed appropriately. Combinations of the elements included in each of the concrete examples can be changed appropriately, provided that they do not cause any technical inconsistency.