阅读说明：本技术 终端设备在待机状态下进行通信的无线通信系统中的终端设备、基站设备、通信方法和程序 (Terminal device, base station device, communication method, and program in wireless communication system in which terminal device communicates in standby state ) 是由 大关武雄 梅原雅人 菅野一生 末柄恭宏 于 2019-08-01 设计创作，主要内容包括：一种终端设备,其能够在多个状态下动作,所述多个状态包括建立与基站设备之间的连接的第一状态以及不建立与基站设备的连接、但该基站设备保持有终端设备的信息的第二状态,该终端设备执行：从该基站设备接收与当在第二状态下向基站设备发送信号时是否应建立时间同步有关的信息；基于该信息确定当在第二状态下向基站设备发送信号时是否将要建立时间同步；以及在确定了将要建立时间同步的情况下执行与基站设备建立时间同步的处理,在确定了不要建立时间同步的情况下不执行该处理,而是在第二状态下对基站设备发送信号。(A terminal device operable in a plurality of states including a first state in which a connection with a base station device is established and a second state in which the connection with the base station device is not established but the base station device holds information of the terminal device, the terminal device performing: receiving information from the base station apparatus as to whether time synchronization should be established when transmitting a signal to the base station apparatus in the second state; determining whether time synchronization is to be established when a signal is transmitted to the base station apparatus in the second state based on the information; and performing a process of establishing time synchronization with the base station apparatus if it is determined that time synchronization is to be established, the process not being performed if it is determined that time synchronization is not to be established, but transmitting a signal to the base station apparatus in the second state.)

1. A terminal device operable in a plurality of states including a first state in which a connection with a base station device is established and a second state in which the connection with the base station device is not established but the base station device holds information of the terminal device, the terminal device performing:

receiving, from the base station apparatus, information on whether time synchronization should be established when transmitting a signal to the base station apparatus in the second state;

determining whether time synchronization is to be established when transmitting a signal to the base station apparatus in the second state based on the information; and

the processing of establishing time synchronization with the base station apparatus is executed in a case where it is determined that time synchronization is to be established, and the processing is not executed in a case where it is determined that time synchronization is not to be established, but a signal is transmitted to the base station apparatus in the second state.

2. The terminal device of claim 1,

the information is indication information indicating whether or not time synchronization is established when a signal is transmitted to the base station apparatus in the second state.

3. The terminal device of claim 1,

the information is condition information representing a condition used by the terminal device in determining whether to establish time synchronization when transmitting a signal to the base station device in the second state.

4. The terminal device of claim 3,

the conditions include at least one of: a condition relating to an amount of change in received power of a prescribed signal from the base station apparatus; and a condition related to a time since the time synchronization with the base station apparatus is established and the signal is transmitted to the base station apparatus.

5. The terminal device according to any of claims 1 to 4,

the information is notified when the terminal device holds predetermined information that enables communication with the base station device in the second state.

6. The terminal device of claim 5,

the information is included in a message for setting the prescribed information transmitted from the base station apparatus.

7. The terminal device according to any of claims 1 to 6,

the information is included in a message transmitted by the base station apparatus for causing the terminal apparatus to transition to the second state.

8. A base station apparatus that transmits, to a terminal apparatus capable of operating in a plurality of states including a first state in which a connection with the base station apparatus is established and a second state in which the connection with the base station apparatus is not established but the base station apparatus holds information of the terminal apparatus, information on whether or not time synchronization should be established when a signal is transmitted to the base station apparatus in the second state.

9. The base station apparatus according to claim 8,

the information is indication information indicating whether or not time synchronization is established when a signal is transmitted to the base station apparatus in the second state.

10. The base station apparatus according to claim 8,

the information is condition information representing a condition used by the terminal device in determining whether to establish time synchronization when transmitting a signal to the base station device in the second state.

11. The base station apparatus according to any one of claims 8 to 10,

the base station apparatus transmits the information when the terminal apparatus holds predetermined information that enables communication with the base station apparatus in the second state.

12. A communication method executed by a terminal device operable in a plurality of states including a first state in which a connection with a base station device is established and a second state in which the connection with the base station device is not established but the base station device holds information of the terminal device, the communication method comprising:

receiving, from the base station apparatus, information on whether time synchronization should be established when transmitting a signal to the base station apparatus in the second state;

determining whether time synchronization is to be established when transmitting a signal to the base station apparatus in the second state based on the information; and

the processing of establishing time synchronization with the base station apparatus is executed in a case where it is determined that time synchronization is to be established, and the processing is not executed in a case where it is determined that time synchronization is not to be established, but a signal is transmitted to the base station apparatus in the second state.

13. A communication method which is a communication method performed by a base station apparatus, characterized by comprising:

transmitting information on whether or not time synchronization should be established when a signal is transmitted to the base station apparatus in a second state to a terminal apparatus capable of operating in a plurality of states including a first state in which a connection with the base station apparatus is established and the second state in which a connection with the base station apparatus is not established but the base station apparatus holds information of the terminal apparatus.

14. A program for causing a computer provided in a terminal device capable of operating in a plurality of states including a first state in which a connection with a base station device is established and a second state in which the connection with the base station device is not established but the base station device holds information of the terminal device to execute a step, the program comprising:

receiving, from the base station apparatus, information on whether time synchronization should be established when transmitting a signal to the base station apparatus in the second state;

determining whether time synchronization is to be established when transmitting a signal to the base station apparatus in the second state based on the information; and

the processing of establishing time synchronization with the base station apparatus is executed in a case where it is determined that time synchronization is to be established, and the processing is not executed in a case where it is determined that time synchronization is not to be established, but a signal is transmitted to the base station apparatus in the second state.

15. A program for causing a computer provided in a base station device to execute a step including transmitting information on whether or not time synchronization should be established when a signal is transmitted to the base station device in a second state to a terminal device operable in a plurality of states including a first state in which a connection with the base station device is established and the second state in which the connection with the base station device is not established but the base station device holds information of the terminal device.

Technical Field

The present invention relates to a terminal device, a base station device, a communication method, and a program, and particularly to a control technique for a terminal device transmitting a signal when in a standby state.

Background

In 3GPP, New Radio (NR) has been standardized as a fifth generation wireless communication scheme (see non-patent document 1). The NR terminal device can migrate not only to two states (i.e., RRC _ CONNECTED and RRC _ IDLE) that a terminal device of Long Term Evolution (LTE) can enter, but also to an RRC _ INACTIVE state. Here, RRC _ CONNECTED refers to a state in which the base station apparatus is CONNECTED to and communicates with, and RRC _ INACTIVE and RRC _ IDLE refer to standby states. Note that the RRC _ INACTIVE state is a state in which context information about a terminal device with which the terminal device communicates with the core network is held by a base station device to which the terminal device has been connected until the terminal device transitions to the RRC _ INACTIVE state (the base station device to which the terminal device was last connected), and the RRC _ IDLE state is a state in which the information is not held by the base station device.

Non-patent document 2 describes that data is transmitted in consideration of a terminal device in an RRC _ INACTIVE state, and describes that a Multiple Access (MA) signature is assigned to the terminal device for such data transmission. The MA signature may be information for specifying a data transmission mode inherent to the terminal device, such as a time/frequency radio resource block, a Modulation and Coding Scheme (MCS), a demodulation Reference Signal (DMRS) for specifying the terminal device, and an interleaving mode. The terminal device transmits data using the MA signature, which the base station device can use to separate and identify the data transmitted from the terminal device.

Documents of the prior art

Non-patent document

Non-patent document 1: 3GPP TS 38.300, V15.2.0, 6 months 2018

Non-patent document 2: 3GPP paper manuscript, RP-171043

Disclosure of Invention

Problems to be solved by the invention

As described above, the terminal device in the RRC _ INACTIVE state can transmit data without transitioning to the RRC _ CONNECTED state by using the MA signature. At this time, the terminal device may establish time synchronization with the base station device to which data is to be transmitted and then transmit the data, but the terminal device may also transmit the data without establishing time synchronization.

Means for solving the problems

The present invention provides a technique that enables flexible control of whether time synchronization is established or not when a data signal is transmitted by a terminal device in a standby state.

A terminal device according to an aspect of the present invention is a terminal device operable in a plurality of states including a first state in which a connection with a base station device is established and a second state in which the connection with the base station device is not established but the base station device holds information of the terminal device, the terminal device executing: receiving, from the base station apparatus, information on whether time synchronization should be established when transmitting a signal to the base station apparatus in the second state; determining whether time synchronization is to be established when transmitting a signal to the base station apparatus in the second state based on the information; and performing a process of establishing time synchronization with the base station apparatus if it is determined that time synchronization is to be established, the process not being performed if it is determined that time synchronization is not to be established, but transmitting a signal to the base station apparatus in the second state.

According to a base station apparatus according to an aspect of the present invention, information on whether or not time synchronization should be established when a signal is transmitted to the base station apparatus in a second state is transmitted to a terminal apparatus operable in a plurality of states including a first state in which a connection with the base station apparatus is established and the second state in which the connection with the base station apparatus is not established but the base station apparatus holds information of the terminal apparatus.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to flexibly control whether time synchronization is established when a data signal is transmitted by a terminal device in a standby state.

Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. Note that the same reference numerals denote the same or similar components throughout the drawings.

Drawings

The accompanying drawings are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

Fig. 1 is a diagram showing a configuration example of a wireless communication system.

Fig. 2 is a diagram representing an exemplary hardware configuration of a device.

Fig. 3 is a diagram showing an exemplary functional configuration of a terminal device.

Fig. 4 is a diagram showing an exemplary functional configuration of a base station apparatus.

Fig. 5 is a diagram showing an example of the flow of processing executed in the wireless communication system.

Fig. 6 is a diagram showing an example of a flow of processing performed by the terminal device.

Detailed Description

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the claimed invention, and all combinations of features described in the embodiments are not essential to the present invention. Two or more features of the plurality of features described in the embodiments may be combined as appropriate. Further, the same or similar configurations are denoted by the same reference numerals, and a repetitive description thereof is omitted.

(configuration of Wireless communication System)

Fig. 1 shows a configuration example of a wireless communication system according to an embodiment of the present invention. The wireless communication system is configured to include, for example, a base station apparatus 101 and a terminal apparatus 102. Note that fig. 1 shows one base station apparatus and one terminal apparatus for simplifying the explanation, but there may be a large number of base station apparatuses and a large number of terminal apparatuses as in a general cellular communication system. Note that in an example to be described below, NR conforming to the fifth generation wireless communication manner is used, but is not limited thereto. The following discussion is applicable to, for example, a fifth generation or higher cellular communication system and any other system including a terminal device (communication device) that can transmit/receive certain data in a standby state, such as the RRC _ INACTIVE state specified for NR. Accordingly, the base station apparatus 101 may be a terminal apparatus capable of communicating not only with a terminal apparatus with which a connection is established but also with a terminal apparatus with which a connection has not been established but with which some data communication is possible. Furthermore, the terminal device 102 is configured to be operable in a first state in which a connection is established with the base station device and a second state; in the second state, a connection is not established with the base station apparatus, but a certain amount of data communication can be performed with the base station apparatus.

The base station apparatus 101 is, for example, a base station apparatus (gNB) operable in accordance with NR. Base station apparatus 101 forms one or more cells/beams and provides communication services to terminal apparatus 102 within the range of the cells/beams. The terminal apparatus 102 is a terminal apparatus operable according to NR, and can communicate with an NR base station apparatus.

The terminal apparatus 102 can acquire, for example, a MA signature from the base station apparatus 101 and perform communication with the base station apparatus 101 using the MA signature. Note that the MA signature is prescribed information that enables data communication at least in the RRC _ INACTIVE state, and other information may be used instead of or in addition to the MA signature. Note that the MA signature may also be used in, for example, RRC _ CONNECTED state. Upon receiving the MA signature, the terminal apparatus 102 may transition to the RRC _ INACTIVE state according to, for example, a rrcreelease message received along with the suspendConfig received from the base station apparatus 101.

The terminal apparatus 102 may transmit a data signal to the base station apparatus 101 while maintaining the RRC _ INACTIVE state. At this time, for example, the terminal apparatus 102 may transmit a Physical Random Access Channel (PRACH) to the base station apparatus 101 and receive a Timing Advance (TA) command from the base station apparatus 101 in order to establish time synchronization with the base station apparatus 101, and then transmit an uplink signal. Specifically, terminal apparatus 102 calculates a relative time difference between the preamble time of the downlink radio frame and the preamble time of the uplink radio frame using the TA command received from base station apparatus 101, and determines the timing for transmitting the uplink data signal based on the calculation result. Since terminal apparatus 102 establishes time synchronization with base station apparatus 101 and transmits a data signal in this manner, base station apparatus 101 can extract a data signal with a relatively low processing load. In this case, it should be noted that the terminal device 102 may transmit a data signal while maintaining the RRC _ INACTIVE state without transitioning to the RRC _ CONNECTED state. In addition, terminal apparatus 102 can transmit a data signal to base station apparatus 101 without establishing time synchronization with base station apparatus 101. Therefore, the above-described processing relating to the TA command for establishing time synchronization between the terminal apparatus 102 and the base station apparatus 101 is not essential, and thus although the processing load of the base station apparatus 101 is relatively large, the transmission delay of the data signal can be suppressed. Therefore, for example, the terminal device 102, which is required to have a low delay, transmits a data signal without establishing time synchronization (asynchronously) to suppress the amount of delay, and it is conceivable, for example, that another terminal device 102 performs an action of establishing time synchronization and transmits a data signal to suppress the processing load.

According to the present embodiment, in order to perform such a flexible action, base station apparatus 101 can notify terminal apparatus 102 of information about whether terminal apparatus 102 is to establish time synchronization and then transmit a data signal or asynchronously transmit a data signal.

The notified information may be, for example, indication information indicating that time synchronization should be established or not established. In this case, according to the indication information, if it is indicated that time synchronization should be established, the terminal apparatus 102 establishes time synchronization and then transmits a data signal; if instructed not to establish time synchronization, the terminal device 102 transmits the data signal asynchronously. For example, the base station apparatus 101 can instruct the terminal apparatus 102 or others performing service communication requiring low delay to asynchronously transmit a data signal, and instruct another terminal apparatus 102 to establish time synchronization and then transmit a data signal. Therefore, the base station apparatus 101 can flexibly perform setting of whether or not time synchronization should be established for each terminal apparatus 102. Note that the indication information may be notified only when an indication that time synchronization is not established is issued, for example. Specifically, the following configuration is adopted: if the indication information is not notified, the terminal apparatus 102 establishes time synchronization and then transmits the data signal, and only when the indication information is notified, the terminal apparatus 102 asynchronously transmits the data signal. In this manner, the notification that time synchronization should be established is implicitly performed by not transmitting the indication information. In this way, the amount of indication information transmitted is reduced, and thus signaling overhead can be reduced.

Note that terminal apparatus 102 in the RRC _ CONNECTED state is in a state of receiving a TA command from base station apparatus 101, and therefore does not asynchronously transmit a signal. In addition, the terminal apparatus 102 in the RRC _ IDLE state transitions to the RRC _ CONNECTED state when transmitting a data signal, and therefore does not transmit a signal asynchronously. Therefore, both synchronous communication and asynchronous communication here are related to communication performed by the terminal apparatus 102 in the RRC _ INACTIVE state (standby state).

Note that the information notified to the terminal apparatus 102 by the base station apparatus 101 may be condition information indicating a condition under which the terminal apparatus 102 should establish time synchronization, and in this case, the following configuration may be employed: when a condition that time synchronization should be established is satisfied, the terminal apparatus 102 establishes time synchronization and then transmits a data signal, and when the condition is not satisfied, the terminal apparatus 102 asynchronously transmits a data signal. As such, the condition information in this case is information indicating a condition for determining whether the terminal apparatus 102 establishes time synchronization and then transmits the data signal. The condition may be, for example, that data to be transmitted is generated in a communication requiring low delay such as real-time communication.

Note that even when asynchronous communication is performed, the change in the timing at which the terminal apparatus 102 transmits a data signal is required to converge within a certain time range with reference to the state in which time synchronization is established. This is because, if the variation is large, it is difficult for the base station apparatus 101 to detect a signal. Therefore, an event in which the timing at which the terminal device 102 is supposed to transmit the data signal exceeds a certain time range may be set as the above-described condition.

For example, as the condition information, it is indicated that time Synchronization should be established when the variation amount of the reception power of a prescribed Signal such as a Synchronization Signal (SS) or a notification Signal (PBCH) from the base station apparatus 101 exceeds a prescribed value. Note that the amount of change may be an amount of change in the average power value per unit time, or may be an amount of change in the instantaneous power value. When the reception power value of the signal from base station apparatus 101 significantly changes, it can be assumed that the distance between base station apparatus 101 and terminal apparatus 102 (for example, the distance of the transmission path) has significantly changed, and therefore this condition can be provided. When the amount of change in the reception power of the prescribed signal has changed significantly, it is conceivable that the time until the signal transmitted from the terminal apparatus 102 reaches the base station apparatus 101 will change significantly, and therefore, when this condition is satisfied, the terminal apparatus 102 can establish time synchronization and then resume communication asynchronously.

Further, for example, as the condition information, it may be indicated that time synchronization should be established when the length of time elapsed since the terminal apparatus 102 established time synchronization and transmitted the data signal exceeds a prescribed length. This is because, when the terminal apparatus 102 establishes time synchronization, the time synchronization is accurately established at this time, but it is conceivable that the synchronization gradually loses as time passes. Note that when data to be transmitted is generated and data is transmitted, it is sufficient to reestablish time synchronization based on determining whether synchronization is lost, and it is not necessary to reestablish time synchronization when the length of time since time synchronization was established and data transmission was performed reaches a prescribed length.

In addition, as the condition information, it may be indicated that time synchronization should be established according to that the terminal apparatus 102 has moved across cells. Also in this case, there are the following cases: since the terminal apparatus 102 has moved across the cell, the propagation distance of the signal transmitted from the terminal apparatus 102 and reaching the base station apparatus 101 changes by an amount larger than assumed, and therefore, if this condition is satisfied, the terminal apparatus 102 can establish time synchronization and then resume asynchronous communication.

Note that a plurality of conditions may be set, or only one condition may be set. For example, the terminal apparatus 102 may be notified of at least one of the above conditions as condition information, the conditions being: a condition relating to the amount of change in the received power of a predetermined signal from the base station apparatus 101, a condition relating to the time elapsed since the time synchronization was established and the data signal was transmitted; and conditions relating to whether the terminal device 102 has moved across cells. Note that at least some of these condition information may be set for the terminal apparatus 102 in advance, and in this case, the terminal apparatus 102 may independently determine whether to establish time synchronization regardless of the notification from the base station apparatus 101.

Note that the base station apparatus 101 can separate/extract a signal component from a reception signal that includes the signal component and is asynchronously transmitted from the terminal apparatus 102, using the MA signature set for the terminal apparatus 102. The following configuration can therefore also be adopted: the above-described information is not notified to the terminal apparatus 102 to which the MA signature is not set based on the assumption that the terminal apparatus 102 is to establish time synchronization, but is notified to the terminal apparatus 102 to which the MA signature has been set. In this way, it is not necessary to notify the terminal apparatus 102 to which the MA signature is not set that time synchronization should be established at the time of signal transmission, and thus unnecessary signaling can be prevented from being performed. In addition, this information may also be included in a message for setting the MA signature and transmitted to the terminal device 102. In this manner, it is possible to effectively notify the terminal apparatus 102 to which the MA signature is set whether to establish time synchronization. The base station apparatus 101 may notify the terminal apparatus 102 of the information using, for example, a message (RRCRelease message including suspendConfig) for transitioning the state of the terminal apparatus 102 to the RRC _ INACTIVE state. In this way, unnecessary notification of the information is not performed to the terminal apparatus 102 that has not transitioned to the RRC _ INACTIVE state, and it is possible to individually set whether or not time synchronization should be established for each terminal apparatus 102 that has transitioned to the RRC _ INACTIVE state. Note that the base station apparatus 101 may notify the information using any message that can transmit information to the terminal apparatus 102 in the RRC _ INACTIVE state or any message that is transmitted to the terminal apparatus 102 when the state is the RRC _ CONNECTED state, for example. Accordingly, the notification of the above information may also be performed using a message for performing notification of an MA signature or a message for transitioning a state to an RRC _ INACTIVE state, or using any other message (signal).

(Equipment configuration)

Next, an exemplary hardware configuration of the base station apparatus 101 or the terminal apparatus 102 that performs the above-described processing will be described with reference to fig. 2. Each of these devices is constituted by, for example, a processor 201, a ROM 202, a RAM 203, a storage device 204, and a communication circuit 205. The processor 201 is a computer configured to include one or more processing circuits such as a general-purpose central computing device (CPU) and an Application-Specific Integrated Circuit (ASIC), and the processor 201 executes the entire processing of each device or the processing described above by reading out a program stored in the ROM 202 or the storage device 204 and executing the program. The ROM 202 is a read-only memory that stores information such as programs related to processes performed by the apparatus and various parameters. The RAM 203 is a random access memory that is used as a work space when the processor 201 executes a program, and stores temporary information. The storage device 204 is constituted by, for example, a removable external storage device. The communication circuit 205 is configured by a circuit for wired communication or wireless communication, for example. The base station apparatus 101 is configured to include an antenna and a baseband circuit for NR, an RF circuit, and the like as a communication circuit 205 for communicating with the terminal apparatus 102. In addition, the communication circuit 205 of the base station apparatus 101 may also include, for example, a circuit for (wired or wireless) communication with another base station apparatus or a network node. Further, the communication circuit 205 of the terminal apparatus 102 is configured to include an antenna and a baseband circuit for NR, an RF circuit, and the like. In addition, the terminal apparatus 102 may include a communication circuit 205 for performing wireless LAN communication or communication conforming to another communication standard. Note that fig. 2 shows one communication circuit 205, but each device may include a plurality of communication circuits.

Fig. 3 shows a schematic example of the functional configuration of the terminal apparatus 102. The terminal apparatus 102 includes, for example, a communication unit 301, a control unit 302, and an information holding unit 303. The communication unit 301 performs communication with the base station apparatus. Note that the communication unit 301 is operable in one of three states, RRC _ CONNECTED, RRC _ INACTIVE, and RRC _ IDLE, under the control of the base station device, and the communication unit 301 is configured to be capable of transmitting/receiving data to/from the base station device CONNECTED thereto in the RRC _ CONNECTED state. In addition, also in the RRC _ INACTIVE state, the communication unit 301 may transmit a small amount of data to the base station apparatus using the MA signature held in the information holding unit 303 described below. The control unit 302 may control the communication unit 301 to execute various types of processing such as described above of the terminal apparatus 102. Specifically, the control unit 302 controls the communication unit 301, for example, in accordance with the instruction information received from the base station apparatus 101, so as to establish time synchronization with the base station apparatus 101 and transmit a data signal to the base station apparatus 101 in the case where an instruction to establish time synchronization is received, and asynchronously transmit a data signal to the base station apparatus 101 while maintaining the RRC _ INACTIVE state in the case where an instruction to not establish time synchronization is received. The control unit 302 may also determine whether to establish time synchronization and then transmit a signal, for example, based on the information on the condition notified from the base station apparatus 101 and held in the information holding unit 303, and control the communication unit 301 to establish time synchronization and then transmit a data signal to the base station apparatus 101, or asynchronously transmit a data signal while maintaining the RRC _ INACTIVE state, according to the determination. The information holding unit 303 holds the MA signature set by the base station device in, for example, the RRC _ CONNECTED state. In addition, the information holding unit 303 may hold information on a condition for determining whether to establish time synchronization, that is, information that has been notified from the base station apparatus 101.

Fig. 4 shows a schematic example of the functional configuration of the base station apparatus 101. The base station apparatus 101 includes, for example, a communication unit 401, a control unit 402, and an information management unit 403. The communication unit 401 communicates with the terminal apparatus 102 and another base station apparatus. Note that a communication unit for performing wireless communication with the terminal apparatus 102 and a communication unit for performing communication with another base station apparatus may be prepared separately, but only one communication unit 401 is prepared in the case where communication with another base station apparatus is performed according to the NR standard, for example.

The control unit 402 can control the communication unit 401 to execute various processes of the base station apparatus such as described above. For example, the control unit 402 controls the information management unit 403 to set the MA signature for the terminal apparatus 102 and hold the MA signature. In addition, the following configuration may also be adopted: the control unit 402 determines whether time synchronization should be established for each terminal apparatus 102, for example, based on a condition for determining whether time synchronization should be established for information indicating a service for which the terminal apparatus 102 managed by the information management unit 403 is performing communication, or the like, and controls the communication unit 401 to transmit an instruction based on the determination. In addition, the control unit 402 may control the communication unit 401, for example, to notify the terminal apparatus 102 of the above-described condition relating to the amount of change in radio quality (such as the reception power of a prescribed signal received from the base station apparatus 101) or the condition relating to the time elapsed since the time synchronization was established and the data was transmitted. Note that when the notification of the condition is performed, for example, a common condition may be notified to a plurality of terminal apparatuses 102 based on a classification such as a category of the terminal apparatus 102 (e.g., specified by 3 GPP), or a different condition may be notified to each terminal apparatus 102. The information management unit 403 can manage conditions under which time synchronization should be established, such as an MA signature set for each terminal apparatus 102 and information for determining whether or not to be a service indicating that the terminal apparatus 102 is performing communication. The information management unit 403 may also hold information such as a measurement value for the determination.

(treatment procedure)

Fig. 5 shows an example of the flow of processing performed by the wireless communication system according to the present embodiment. Fig. 5 shows an example in which the base station apparatus 101 transmits an indication that time synchronization should be established and then signals should be transmitted and an indication that signals should be transmitted asynchronously to the two terminal apparatuses 102, respectively. Note that two terminal apparatuses 102 (terminal apparatus a and terminal apparatus B) are in a state of establishing connection with base station apparatus 101 (RRC _ CONNECTED state) (step S501). At this time, for example, MA signatures (not shown) are set for these terminal apparatuses 102 in the RRC _ CONNECTED state, respectively. The base station apparatus 101 transmits a RRCRelease message including suspendConfig, which is used to cause the terminal apparatus a and the terminal apparatus B to transition from the state to the RRC _ INACTIVE state. At this time, the base station apparatus 101 transmits to the terminal apparatus a RRCRelease message including indication information indicating that time synchronization should be established and then uplink data is to be transmitted (step S502). Accordingly, the terminal device a performs setting for establishing time synchronization when transmitting uplink data, and then transitions to the RRC _ INACTIVE state (step S503). On the other hand, the base station apparatus 101 transmits to the terminal apparatus B a RRCRelease message including indication information indicating that the uplink data is asynchronously transmitted without establishing time synchronization (step S504). Accordingly, the terminal device B performs setting for the uplink data to be asynchronously transmitted, and then transitions to the RRC _ INACTIVE state (step S505). Note that, in the example of fig. 5, indication information indicating whether or not time synchronization should be established is notified in the rrcreelease message, but the base station apparatus 101 may also perform the notification of the indication information in a message (not shown) for setting an MA signature, for example.

Thereafter, if data to be transmitted is generated (step S506), the terminal apparatus a transmits PRACH to the base station apparatus 101 (step S507), receives a TA command (step S508), and establishes time synchronization with the base station apparatus 101. Then, the terminal device a transmits a data signal at a timing determined by the time synchronization established in steps S507 and S508 (step S509). On the other hand, when data to be transmitted is generated (step S510), the terminal apparatus B asynchronously transmits a data signal without transmitting the PRACH and without receiving the TA command (step S511). Note that "asynchronous" here means that accurate time synchronization has not been established yet, and the terminal apparatus B can transmit a data signal to the base station apparatus 101 within a prescribed time range based on a radio resource specified from the MA signature, for example. Accordingly, the base station apparatus 101 does not need to perform processing for detecting a signal outside a prescribed time range determined based on the MA signature, for example.

In this way, the base station apparatus 101 can flexibly perform setting on synchronization/asynchronization for each terminal apparatus 102 by, for example, performing an instruction to asynchronously transmit a signal when a delay time allowed by a service performed by the terminal apparatus 102 is shorter than or equal to a prescribed value, and performing an instruction to establish time synchronization and then transmit a signal when the delay time exceeds the prescribed value.

Note that the base station apparatus 101 may also notify condition information such as described above instead of the indication signal. In this case, the terminal device 102 may determine whether to establish time synchronization at the time of signal transmission based on whether the condition of the terminal device 102 satisfies the notified condition. As described above, the condition may be, for example, a condition relating to a change amount of radio quality of reception power of a predetermined signal transmitted from the base station apparatus 101 or a condition relating to an elapsed time since the time synchronization was established and the signal was transmitted. Fig. 6 shows an example of the flow of processing when these conditions are used. Note that only one of these conditions, for example, a condition relating to elapsed time, may also be used, or another condition may alternatively or additionally be used. For example, the following configuration may also be employed: the terminal device 102 extracts an identifier of a cell (e.g., physical cell ID or PCI) from the received synchronization signal or notification signal, and when the identifier changes, the terminal device 102 establishes time synchronization and transmits a signal.

Note that fig. 6 shows an example in which the terminal apparatus 102 determines to establish time synchronization when the elapsed time has reached the prescribed time and the amount of change in the reception power of the prescribed signal exceeds the prescribed value, but these may also be processed in parallel. Specifically, when the elapsed time reaches the prescribed time, the terminal apparatus 102 may determine that time synchronization is established even if the amount of change in the reception power of the prescribed signal does not exceed the prescribed value, and when the amount of change in the reception power of the prescribed signal exceeds the prescribed value, the terminal apparatus 102 may determine that time synchronization is established even if the elapsed time has not reached the prescribed time. Thus, when a plurality of conditions are used, it is also possible to determine to transmit a signal asynchronously unless two or more conditions are not satisfied simultaneously, or to determine to establish time synchronization and then transmit a signal when only one of the conditions is satisfied.

In fig. 6, the terminal apparatus 102 acquires information on an expiration value of a timer and a predetermined value of a change amount of reception power of a predetermined signal (e.g., a synchronization signal/notification signal) as condition information from the base station apparatus 101, and stores the information in advance. Then, the terminal apparatus 102 measures and holds the value of the reception power of the prescribed signal from the base station apparatus 101, for example, at the time point when the terminal apparatus 102 transitions to the RRC _ INACTIVE state (or within a prescribed time period before and after the time point) (step S601). The terminal apparatus 102 starts a timer in this state (step S602). Thereafter, when the terminal apparatus 102 detects that data to be transmitted has been generated (step S603), the terminal apparatus 102 determines whether the data should be transmitted in the RRC _ INACTIVE state (step S604). If it is determined that data should not be transmitted in the RRC _ INACTIVE state (in other words, data should be transmitted after the state has transitioned to the RRC _ CONNECTED state) (no at step S604), the terminal device 102 transitions to the RRC _ CONNECTED state, transmits a data signal including the data (step S605), and ends the processing in fig. 6. In the RRC _ CONNECTED state, the terminal apparatus 102 establishes time synchronization and then transmits data. Note that if the terminal device 102 becomes the RRC _ INACTIVE state again after transmitting the data signal in step S605, the terminal device 102 may resume the process in fig. 6.

On the other hand, if it is determined that data should be transmitted in the RRC _ INACTIVE state (yes at step S604), the terminal apparatus 102 determines whether the timer started at step S602 reaches the expiration value notified from the base station apparatus 101 (step S606). If the timer has not expired (no in step S606), the terminal apparatus 102 still in the RRC _ INACTIVE state transmits a data signal including the data generated in step S603 without establishing time synchronization (step S607). On the other hand, if the timer has expired (yes at step S606), the terminal apparatus 102 measures the reception power of the prescribed signal from the base station apparatus 101 (step S608). Then, the terminal apparatus 102 specifies the value of the difference between the measured value and the value held in step S601 as the amount of change, and determines whether the specified amount of change exceeds a prescribed value of the amount of change notified from the base station apparatus 101 (step S609). If the amount of change in the received power does not exceed the prescribed value (no in step S609), the terminal device 102 transmits a data signal including the data generated in step S603 while maintaining the RRC _ INACTIVE state (step S607). Note that, thereafter, the timer is in an expired state, and therefore, the terminal apparatus 102 can determine whether the amount of change in the reception power exceeds a prescribed value every time data to be transmitted is generated. Note that there is no limitation to this, and if it is determined in step S609 that the amount of change in the received power does not exceed the prescribed value, the terminal apparatus 102 may reset the timer. If the amount of change in the received power exceeds the prescribed value (yes at step S609), the terminal apparatus 102 establishes time synchronization with the base station apparatus 101, and then transmits a data signal while maintaining the RRC _ INACTIVE state (step S610). Note that the terminal apparatus 102 may establish time synchronization and then transmit the data signal only in accordance with the timer having expired or only in accordance with the amount of change in the reception power exceeding a prescribed value. The terminal apparatus 102 updates the value of the reception power of the prescribed signal obtained in step S601 (or updated in the previous step S611) to the value measured in step S608, according to the time synchronization that has been established (step S611), and resets the timer (step S612). Then, the process returns to step S603.

Note that, in the above-described illustrated example, the determination as to whether or not the amount of change in the received power of the prescribed signal exceeds the prescribed value is performed after it is detected that the timer has expired, but the order of determination may be reversed. Therefore, the following configuration may also be adopted: after determining that the amount of change in the received power of the prescribed signal has exceeded the prescribed value, the timer value is referenced. As such, the processing in fig. 6 is merely exemplary, and the processing order may be changed, or the processing may be partially omitted or processing (not shown) may be added.

Further, as described above, the terminal apparatus 102 may determine to establish time synchronization based on only the value of the timer regardless of the amount of change in the reception power, but even if such a determination is made, the terminal apparatus 102 may update the held measurement value of the reception power to the measurement value of the reception power at the time point at which the time synchronization is established and the data signal is transmitted. Similarly, if it is determined that time synchronization is to be established based only on the amount of change in the reception power, the terminal apparatus 102 may reset the timer at the point of time when time synchronization is established and the data signal is transmitted, when the timer value is conditioned. In addition, for example, when the terminal device 102 establishes time synchronization and transmits a data signal according to being moved to a cell different from the cell that has changed to the RRC _ INACTIVE state, the terminal device 102 may reset the timer and update the held measurement value of the reception power. Note that when determining whether or not time synchronization can be established based on movement on a cell, the terminal apparatus 102 may update information on the PCI so as to maintain the PCI at a time point when time synchronization is established and data is transmitted. Further, even when the terminal apparatus 102 establishes time synchronization for a reason other than a change in the PCI and transmits a data signal, the terminal apparatus 102 may update the value of the PCI to the value of the PCI of the serving cell when transmitting the data signal.

As described above, since the condition that time synchronization should be established and a data signal transmitted is set to the terminal apparatus 102, the base station apparatus 101 can flexibly perform the setting as to whether or not time synchronization is established according to the situation of the terminal apparatus 102. In addition, for example, the base station apparatus 101 may notify only the terminal apparatus 102 whose allowable delay amount is small of the condition, and for the terminal apparatus 102 to which the condition is not notified, the base station apparatus 101 may make a setting to establish time synchronization and transmit the data signal regardless of the condition. Therefore, for at least some terminal apparatuses 102, for example, for terminal apparatuses 102 or the like that do not strictly require delay, the processing load of the base station apparatus 101 can be reduced because time synchronization is established without considering the conditions.

The present invention is not limited to the above embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.

This application claims priority from japanese patent application No. 2018-175781, filed on 20/9/2018, which is incorporated herein by reference.