Terminal device and base station device

Abstract

The present invention makes it possible to receive a signal related to data communication even when a signal for starting a receiver cannot be received. The terminal device includes a first reception unit, a second reception unit, and a control unit. The first reception unit receives a first signal including first information. The second reception unit receives a second signal. The control unit starts the first reception unit in response to the second reception unit receiving the second signal. The control unit determines whether to start the first reception unit according to whether or not a first condition represented by the first information is satisfied.

Description

Terminal device and base station device

[0001] The present invention relates to a terminal device and a base station device used in a wireless communication system.

[0002] In today's networks, traffic from mobile devices (smartphones, feature phones, etc.) accounts for the majority of network resources, and the traffic used by mobile devices is expected to continue to expand in the future.

[0003] In addition, Internet of Things (IoT) services (e.g., transportation systems, smart meters, monitoring systems for devices, etc.) are being deployed in various fields. Therefore, networks are required to support services with diverse requirements. To support such diverse services, for example, communication standards for fifth-generation mobile communications (5G or New Radio (NR)) (e.g., Non-Patent Documents 1 to 14) have been formulated to support many use cases classified as Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (MTC), and Ultra-Reliable and Low Latency Communication (URLLC). Furthermore, the fifth-generation mobile communications standards also specify technologies for reducing the power consumption of terminal devices.

[0004] Paging Early Indicator (PEI) has been introduced as one of the technologies for reducing the power consumption of terminal devices (UE power saving). PEI is a technology in which a network device (e.g., a base station) notifies a terminal device of the presence or absence of paging before the terminal device receives a paging signal (Non-Patent Documents 6 and 7).

[0005] Furthermore, the 3GPP (3rd Generation Partnership Project (registered trademark)) is studying low-power wake-up signal and receiver as a new technology for reducing power consumption in terminal devices (Non-Patent Document 15). To implement low-power wake-up signal and receiver, a terminal device includes a receiver with low power consumption (low-power receiver) and a receiver for data communication (main radio unit). Here, when the terminal device is not performing data communication (e.g., when in an idle state), the terminal device operates the low-power receiver and controls the main radio unit not to operate. Then, when the terminal device receives a wake-up signal via the low-power receiver, it starts up the main radio unit.

[0006] 3GPP TS 37.324 V17.0.03GPP TS 37.340 V17.7.03GPP TS 38.201 V17.0.03GPP TS 38.202 V17.5.03GPP TS 38.211 V17.6.03GPP TS 38.212 V17.7.03GPP TS 38.213 V17.8.03GPP TS 38.214 V17.8.03GPP TS 38.215 V17.4.03GPP TS 38.300 V17.7.03GPP TS 38.321 V17.7.03GPP TS 38.322 V17.3.03GPP TS 38.323 V17.5.03GPP TS 38.331 V17.7.03GPP TR 38.869 V18.0.0

[0007] In the above-described terminal device, one receiver may be able to detect or receive a signal, but the other receiver may not be able to detect or receive the signal. For example, if the main radio unit can receive a signal but the low-power receiver cannot detect the signal, the main radio unit is not activated, and the terminal device cannot receive a data signal. Note that in the above-described communication method using the PEI, the PEI and the signal specified by the PEI are received by the same receiver (e.g., the main radio unit), so the above-described situation does not occur.

[0008] Therefore, an object of the disclosed technology is to enable a terminal device to receive signals related to data communication even when the terminal device cannot receive a signal for activating the receiver.

[0009] A terminal device according to one aspect of the present invention includes a first receiving unit that receives a first signal including first information, a second receiving unit that receives a second signal, and a control unit that activates the first receiving unit in response to the second receiving unit receiving the second signal. The control unit determines whether to activate the first receiving unit in response to whether a first condition represented by the first information is satisfied.

[0010] According to the above aspect, even if the terminal device cannot receive a signal for activating the receiver, the terminal device can receive a signal related to data communication.

[0011] 1 is a diagram illustrating an example of a wireless communication system according to an embodiment; FIG. 2 is a diagram illustrating an example of a method by which a terminal device detects paging from a base station; FIG. 3 is a diagram illustrating an example of the configuration of a terminal device; FIG. 4 is a diagram illustrating an example of a wake-up receiver; FIG. 5 is a diagram illustrating an example of a case in which a paging signal cannot be received; FIG. 6 is a diagram illustrating an example of a sequence for realizing a fallback operation; FIG. 7 is a flowchart illustrating an example of a fallback initiation procedure; FIG. 8 is a flowchart illustrating another example of a fallback initiation procedure; FIG. 9 is a flowchart illustrating an example of a fallback termination procedure;

[0012] The embodiments will be described in detail below with reference to the drawings. The problems and examples in this specification are merely examples and do not limit the scope of the rights of this application. In particular, even if the expressions used are different, as long as they are technically equivalent, the technology of this application can be applied even if the expressions are different, and do not limit the scope of the rights. Furthermore, each embodiment can be combined as appropriate within the scope of not causing contradictions in the processing content.

[0013] Furthermore, the terms used and technical contents described in this specification may be those described in specifications and contributions as standards related to communications such as 3GPP, as appropriate. Such specifications are, for example, Non-Patent Documents 1 to 15.

[0014] Hereinafter, embodiments of a base station device, a terminal device, a wireless communication system, and a communication method disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the disclosed technology is not limited to the following embodiments.

[0015] 1 shows an example of a wireless communication system according to an embodiment. The wireless communication system according to the embodiment includes a base station 1 and terminal devices 2 (2a to 2d). The base station 1 is not particularly limited, but in this example, is a gNB (next generation Node B) or NR (New Radio) base station. The terminal device 2 is, for example, a UE (User Equipment).

[0016] A base station 1 forms a cell. The base station 1 accommodates terminal devices 2 located within the cell. That is, the base station 1 transmits radio signals to each terminal device 2 and receives radio signals from each terminal device 2. Each terminal device 2 transmits radio signals to the base station 1 and receives radio signals from the base station 1.

[0017] 2 shows an example of a method for a terminal device 2 to detect a paging from the base station 1. In this embodiment, a terminal device 2a detects a paging from the base station 1.

[0018] Paging is transmitted at a timing designated by the base station 1. In the case shown in FIG. 2A, paging occasions (PO) P1 to P5 are set. The timing of each paging occasion is represented by an SSB (Synchronization Signal Block). The base station 1 then notifies each terminal device 2 of the paging occasion. Each terminal device 2 also acquires the SSB in the SS burst to recognize the paging occasion. Therefore, the terminal device 2a can acquire the paging addressed to itself by detecting the received signal at each paging occasion.

[0019] 2A, however, it takes a long time to establish synchronization with the base station 1. Furthermore, the terminal device 2a needs to monitor all paging occasions. For example, even in a case where a paging signal is transmitted to the terminal device 2a using paging occasion P5, the terminal device 2a needs to monitor not only paging occasion P5 but also paging occasions P1 to P4. This shortens the sleep time, resulting in insufficient reduction in power consumption.

[0020] To address this issue, 3GPP Release 17 proposes a PEI (Paging Early Indicator) as one of the power-saving methods shown in FIG. 2B . The PEI notifies the destination terminal of the transmission of a paging signal in advance. For example, when a paging signal to be received by the terminal device 2a is set, the base station 1 uses the PEI to notify the terminal device 2a of a message indicating the paging occasion at which the terminal device 2a should receive the paging signal. In this case, the terminal device 2a monitors the PEI. The terminal device 2a then receives the paging signal at the paging occasion (P5 in FIG. 2B ) specified by the PEI. This method does not require monitoring all paging occasions, so the sleep time is longer than that of the method shown in FIG. 2A , and power consumption of the terminal device 2 is reduced. However, in use cases where paging is received infrequently, power consumption for monitoring the PEI becomes dominant.

[0021] 3 shows an example of the configuration of a terminal device 2. The terminal device 2 includes a main radio unit 21, a wake-up receiver 22, and a control unit 23. Note that the terminal device 2 may further include other circuits, devices, or functions not shown in FIG.

[0022] The main radio (MR) unit 21 receives radio signals from the base station 1 and transmits radio signals to the base station 1. However, the main radio unit 21 is controlled to be in a sleep mode when the terminal device 2 is not performing data communication. Note that "data communication" is not limited to communication of user data, but also includes communication of control signals related to data communication. The main radio unit 21 may be a functional block for receiving data signals. Furthermore, the main radio unit 21 may include a digital signal processor for processing received signals.

[0023] The wake-up receiver (WUR) 22 receives a wake-up signal (LP-WUS: Low Power Wake-Up Signal) transmitted from the base station 1. Here, when the base station 1 communicates with the terminal device 2, it transmits a wake-up signal to the terminal device 2. Then, when the wake-up receiver 22 detects the wake-up signal, the main radio unit 21 is activated. Thereafter, the terminal device 2 receives a radio signal transmitted from the base station 1 using the main radio unit 21. As an example, the terminal device 2 receives a paging signal transmitted from the base station 1 using the main radio unit 21. In this case, the main radio unit 21 receives the paging signal using the method shown in FIG. 2A or 2B .

[0024] The wake-up receiver 22 receives a synchronization signal (LP-SS: Low Power Synchronization Signal) to establish synchronization of the wake-up signal with the base station 1. The synchronization signal LP-SS is a broadcast signal transmitted from the base station 1 at a predetermined period, and is also used to measure the RRM (Radio Resource Management) of the serving cell.

[0025] The wake-up signal (and the synchronization signal LP-SS) is transmitted, for example, by OOK (On-Off Keying), although this is not a particular limitation. In this case, the wake-up receiver 22 can detect the wake-up signal by time-domain detection. Therefore, the configuration of the wake-up receiver 22 is simple, and power consumption is much lower than that of the main radio unit 21. The main radio unit 21 and the wake-up receiver 22 may share an antenna.

[0026] 4 shows an example of the wake-up receiver 22. In this embodiment, the wake-up receiver 22 receives an OOK signal. The wake-up receiver 22 includes a matching circuit 31, a band-pass filter (BPF) 32, an amplifier 33, a detector 34, an amplifier 35, a low-pass filter (LPF) 36, an analog-to-digital converter (ADC) 37, and a signal processing unit 38.

[0027] The matching circuit 31 adjusts the impedance between the antenna and the receiving circuit. The bandpass filter 32 extracts frequency components in the RF (Radio Frequency) region where signals (such as a wake-up signal and a synchronization signal LP-SS) are located. The amplifier 33 is an RF low-noise amplifier that amplifies the output signal of the bandpass filter 32. The detector 34 is, for example, an envelope detector that detects the envelope (i.e., the amplitude-modulated signal) from the received signal.

[0028] The amplifier 35 is a baseband amplifier and amplifies the output signal of the detector 34. The low-pass filter 36 removes high-frequency components. The analog-to-digital converter 37 converts the output signal of the low-pass filter 36 into digital data. That is, digital data representing the received signal is generated. The signal processing unit 38 then processes the digital data representing the received signal. That is, the signal processing unit 38 processes the received signal.

[0029] The control unit 23 controls the main radio unit 21 and the wake-up receiver 22. That is, the control unit 23 can activate the main radio unit 21 in response to the wake-up receiver 22 receiving a wake-up signal. "Activating the main radio unit 21" includes enabling the main radio unit 21 to receive a signal transmitted from the base station 1. The control unit 23 can also control the operation or function of the wake-up receiver 22 based on information notified from the base station 1. The control unit 23 is configured to include, for example, a processor and a memory. In this case, the processor executes a program stored in the memory to provide the functions of the terminal device 2.

[0030] The base station 1 includes a transmission unit 11 and a control unit 12. The transmission unit 11 can transmit a control signal, a wake-up signal, a paging signal, and the like, which will be described later, to the terminal device 2 in accordance with instructions from the control unit 12. The control unit 12 controls the transmission unit 11.

[0031] In this way, the terminal device 2 activates the main radio unit 21 in response to the wake-up signal being received by the wake-up receiver 22. That is, the main radio unit 21 is activated (triggered) in response to the reception of the wake-up signal. The activated main radio unit 21 can then receive a paging signal transmitted from the base station 1.

[0032] However, the paging signal is received by the main radio unit 21, and the wake-up signal is received by the wake-up receiver 22. Therefore, a case may occur in which the wake-up signal cannot be received even though the paging signal can be received. For example, in the case shown in FIG. 5, the wake-up signal coverage is narrower than the paging coverage. In this case, the terminal device 2a can receive both the wake-up signal and the paging signal. That is, after receiving the wake-up signal, the terminal device 2a can then receive the paging signal. On the other hand, the terminal device 2b can receive the paging signal but cannot receive the wake-up signal. That is, even though the terminal device 2b can receive the paging signal, the main radio unit 21 is not activated, and therefore the terminal device 2b loses the opportunity to receive the paging signal.

[0033] Therefore, even if the terminal device 2 according to the embodiment does not detect a wake-up signal, when a predetermined condition is satisfied (or when the predetermined condition is not satisfied), the terminal device 2 activates the main radio unit 21. As a result, when the base station 1 transmits a paging signal, the terminal device 2 can receive the paging signal via the main radio unit 21.

[0034] 6 shows an example of a sequence for realizing the fallback operation of the terminal device 2. As shown in FIG. 3 , the terminal device 2 includes a main radio unit 21, a wake-up receiver 22, and a control unit 23. When no data communication is being performed between the base station 1 and the terminal device 2, the main radio unit 21 is controlled to be in sleep mode. When the wake-up receiver 22 receives a wake-up signal from the base station 1, the control unit 23 activates the main radio unit 21.

[0035] The base station 1 notifies the terminal device 2 of conditions C1 and C2 related to the fallback operation of the terminal device 2. Condition C1 is used to determine whether the terminal device 2 starts the fallback operation. Condition C2 is used to determine whether the terminal device 2 ends the fallback operation. In this embodiment, conditions C1 and C2 are notified from the base station 1 to the terminal device 2 using, for example, an SIB (System Information Block).

[0036] When the main radio unit 21 of the terminal device 2 is controlled to be in the sleep mode, the wake-up receiver 22 monitors the wake-up signal transmitted from the base station 1. At this time, the wake-up receiver 22 monitors the wake-up signal based on the synchronization signal LP-SS transmitted from the base station 1.

[0037] The terminal device 2 monitors whether or not condition C1 is satisfied. If condition C1 is satisfied, the terminal device 2 starts a fallback operation. That is, if condition C1 is satisfied, the control unit 23 activates the main radio unit 21 even if the wake-up receiver 22 has not received a wake-up signal from the base station 1. Then, the main radio unit 21 monitors paging from the base station 1. Note that an example of condition C1 will be described later.

[0038] After the main wireless unit 21 is started, the terminal device 2 monitors whether or not condition C2 is satisfied. If condition C2 is satisfied, the terminal device 2 terminates the fallback operation. Specifically, the state of the main wireless unit 21 returns to sleep mode. An example of condition C2 will be described later.

[0039] As described above, according to the sequence of the embodiment, if the condition C1 is satisfied while the main radio unit 21 is controlled to be in the sleep mode, the main radio unit 21 is activated even if the wake-up receiver 22 has not received a wake-up signal from the base station 1. Therefore, if the condition C1 is set appropriately, the terminal device 2 can monitor paging even when it cannot receive a wake-up signal. This avoids or suppresses a situation in which "the terminal device 2 cannot receive a paging signal because the wake-up receiver 22 cannot detect a signal even though the main radio unit 21 can receive a signal."

[0040] 7 is a flowchart showing an example of a fallback initiation procedure. It is assumed that the terminal device 2 receives a control signal representing conditions C1 and C2 from the base station 1. In this embodiment, the control signal is transmitted from the base station 1 to the terminal device 2 using an SIB. Therefore, the terminal device 2 receives the control signal using the main radio unit 21.

[0041] In the case shown in FIG. 7 , condition C1 is expressed using a threshold value related to the signal reception level. Specifically, condition C1 is "the reception power of the synchronization signal LP-SS is lower than a predetermined threshold level." This threshold level is not particularly limited, but may be the same as the threshold value used to determine whether the terminal device 2 has received the wake-up signal, for example, when the transmission power of the synchronization signal LP-SS and the transmission power of the wake-up signal are the same or nearly the same. The synchronization signal LP-SS is a synchronization signal used by the wake-up receiver 22 of each terminal device 2 to receive the signal, and is broadcast by the base station 1 at predetermined time intervals.

[0042] 7, after the terminal device 2 receives the above-mentioned control signal, the main radio unit 21 is controlled to be in sleep mode. Then, the terminal device 2 waits for signals (synchronization signal LP-SS and wake-up signal) transmitted from the base station 1 using the wake-up receiver 22.

[0043] In S1, the wake-up receiver 22 receives the synchronization signal LP-SS. Then, the control unit 23 detects the power of the synchronization signal LP-SS received by the wake-up receiver 22. That is, the received power of the synchronization signal LP-SS is detected.

[0044] In S2, the control unit 23 monitors a wake-up signal using the wake-up receiver 22. The timing at which the wake-up signal is transmitted from the base station 1 can be recognized based on the synchronization signal LP-SS. When the wake-up signal is detected, the control unit 23 starts the main radio unit 21 in S4. Thereafter, the main radio unit 21 monitors paging. That is, the terminal device 2 performs the operation shown in FIG. 2A or 2B.

[0045] Here, the reason why the terminal device 2 does not receive the wake-up signal is considered to be either of the following two cases: (1) The base station 1 does not transmit the wake-up signal; or (2) The base station 1 transmits the wake-up signal, but the terminal device 2 cannot receive the wake-up signal.

[0046] When the cause of the terminal device 2 not receiving the wake-up signal is case (2), a situation may occur in which "even though the main radio unit 21 can receive the signal, the wake-up receiver 22 cannot detect the signal, and therefore the terminal device 2 cannot receive the paging signal." Therefore, in order to identify the cause of the not receiving the wake-up signal, the control unit 23 compares the received power of the synchronization signal LP-SS with the threshold level used by condition C1 in S3. As a result, if the received power of the synchronization signal LP-SS is lower than the threshold level, it is estimated that case (2) may have occurred. In this case, the control unit 23 determines that condition C1 is satisfied. Then, in S5, the control unit 23 activates the main radio unit 21. Thereafter, the main radio unit 21 monitors paging. In S5, the control unit 23 activates the main radio unit 21 in fallback mode. When the main radio unit 21 is activated in fallback mode, a fallback termination procedure, which will be described later, is executed.

[0047] The case where the wake-up signal is not detected and the received power of the synchronization signal LP-SS is higher than the threshold level occurs when the terminal device 2 can receive the wake-up signal but the base station 1 has not transmitted the wake-up signal. Therefore, in this case, the processing of the terminal device 2 returns to S1 to continue waiting for the wake-up signal.

[0048] As described above, in the embodiment shown in FIG. 7 , when the received power of the synchronization signal LP-SS is lower than the threshold level, the main radio unit 21 is activated regardless of whether the wake-up receiver 22 receives a wake-up signal. Here, when the received power of the synchronization signal LP-SS is lower than the threshold level, it is considered that the terminal device 2 cannot receive the wake-up signal either. In other words, when the received power of the synchronization signal LP-SS is lower than the threshold level, there is a possibility that the wake-up receiver 22 is unable to receive the wake-up signal even though the wake-up signal is transmitted from the base station 1. Then, when a wake-up signal is transmitted from the base station 1, there is a possibility that a paging signal will be transmitted from the base station 1 thereafter. Therefore, the control unit 23 monitors paging by activating the main radio unit 21. Therefore, when a paging signal is transmitted from the base station 1, the terminal device 2 can receive the paging signal using the main radio unit 21.

[0049] 8 is a flowchart showing another example of a fallback initiation procedure. In the case shown in FIG. 8, condition C1 is expressed using a timer period for waiting for a wake-up signal. Specifically, condition C1 is "not receiving a wake-up signal within a predetermined timer period." This timer period is not particularly limited, but may be, for example, several seconds to several minutes. Furthermore, this timer period is notified from the base station 1 to the terminal device 2 using the SIB.

[0050] When a predetermined time has elapsed after the terminal device 2 receives the SIB, the main radio unit 21 transitions to sleep mode. When the main radio unit 21 transitions to sleep mode, the control unit 23 starts a timer in S11. The timer is implemented, for example, in the control unit 23. Thereafter, the terminal device 2 waits for a synchronization signal LP-SS and a wake-up signal using the wake-up receiver 22.

[0051] In S12, the terminal device 2 receives the synchronization signal LP-SS, and the control unit 23 then sets the reception timing for receiving the wake-up signal.

[0052] In steps S13 and S14, the control unit 23 monitors whether the wake-up receiver 22 receives a wake-up signal. If the wake-up receiver 22 receives a wake-up signal before the timer expires, the control unit 23 starts the main radio unit 21 in step S4. Thereafter, the main radio unit 21 monitors paging.

[0053] On the other hand, if the timer expires without the wake-up receiver 22 transmitting a wake-up signal, the control unit 23 determines that the condition C1 is satisfied. In this case, the control unit 23 starts up the main radio unit 21 in S5. Thereafter, the main radio unit 21 monitors paging. In S5, the control unit 23 starts up the main radio unit 21 in fallback mode.

[0054] As described above, in the embodiment shown in Fig. 8, when the terminal device 2 does not receive a wake-up signal for a predetermined period of time, the main radio unit 21 is activated. Therefore, if the wake-up receiver 22 cannot receive a wake-up signal but the main radio unit 21 can receive a paging signal, the terminal device 2 can receive the paging signal. For example, in the case shown in Fig. 5, the terminal device 2b cannot receive a wake-up signal. In this case, when the main radio unit 21 is activated according to the procedure shown in Fig. 8, the terminal device 2 can receive the paging signal.

[0055] 8, the timer is reset when the wake-up receiver 22 receives a wake-up signal, but the processing of the control unit 23 is not limited to this procedure. That is, the timer does not have to be reset when the wake-up receiver 22 receives a wake-up signal. In this case, the control unit 23 will periodically start up the main radio unit 21 regardless of whether the wake-up receiver 22 receives a wake-up signal.

[0056] In the above-described embodiment, the control unit 23 activates the main radio unit 21 when the condition C1 is satisfied. However, depending on the description of the condition C1, the control unit 23 may activate the main radio unit 21 when the condition C1 is not satisfied. In the example shown in FIG. 7 , if the condition C1 is "the received power of the synchronization signal LP-SS is lower than a predetermined threshold level," the main radio unit 21 is activated when the condition C1 is satisfied. However, if the condition C1 is "the received power of the synchronization signal LP-SS is higher than a predetermined threshold level," the main radio unit 21 is activated when the condition C1 is not satisfied. Also, in the example shown in FIG. 8 , if the condition C1 is "a wake-up signal is not received within a predetermined timer period," the main radio unit 21 is activated when the condition C1 is satisfied. However, if the condition C1 is "a wake-up signal is received within a predetermined timer period," the main radio unit 21 is activated when the condition C1 is not satisfied.

[0057] Fig. 9 is a flowchart showing an example of a fallback termination procedure. The fallback termination procedure is executed, for example, when the main radio unit 21 is started in the fallback mode in S5 shown in Fig. 7 or 8. Furthermore, as described with reference to Fig. 7, the terminal device 2 recognizes condition C2 by receiving the SIB from the base station 1.

[0058] In this embodiment, condition C2 is "not receiving a paging signal for a predetermined period of time." The predetermined period may be "time" measured by a timer or the number of paging opportunities (POs). In the embodiment shown in FIG. 9, the predetermined period is expressed as the number of paging opportunities. In this case, condition C2 is "not receiving a paging signal for a predetermined number of paging opportunities." Note that the paging opportunities are set at predetermined time intervals, for example, based on SSB.

[0059] In S21, the terminal device 2 monitors paging using the main radio unit 21. In S22, when a paging opportunity arrives, the control unit 23 counts the number of paging opportunities. That is, the PO count value indicating the number of paging opportunities is incremented.

[0060] In S23, the control unit 23 determines whether the main radio unit 21 has received a paging signal. When the main radio unit 21 has received a paging signal, the terminal device 2 processes the paging signal. Furthermore, the control unit 23 resets the PO count value in S25. After this, the processing of the terminal device 2 returns to S21. In this way, when the main radio unit 21 has received a paging signal, the terminal device 2 continues to monitor paging.

[0061] If the main radio unit 21 does not receive a paging signal, the control unit 23 determines in S24 whether the PO count value has reached a threshold value. This threshold value is used in condition C2. If the PO count value has not reached the threshold value, the control unit 23 returns to S22. That is, if the main radio unit 21 does not receive a paging signal, the processes of S22 to S24 are repeatedly executed until the PO count value reaches the threshold value. If the PO count value reaches the threshold value, the control unit 23 determines that the predetermined period represented by condition C2 has elapsed. In this case, the control unit 23 transitions the main radio unit 21 to sleep mode in S26.

[0062] In this way, when no paging signal is received for a predetermined period of time, the main radio unit 21 goes into sleep mode. After this, the terminal device 2 uses the wake-up receiver 22 to wait for a wake-up signal.

[0063] Condition C2 may be described using other parameters. For example, in the embodiment shown in Fig. 10, condition C2 is expressed using the received power of the main radio unit 21. For example, condition C2 is "the received power of SSB is higher than a predetermined threshold level." Here, SSB is synchronization information used by the main radio unit 21 of each terminal device 2 to receive a signal, and is broadcast at a predetermined transmission power to each terminal device within the cell of the base station 1.

[0064] In S31, the terminal device 2 receives SSB using the main radio unit 21. The control unit 23 then detects the received power of the SSB. In S32, the control unit 23 compares the received power of the SSB with the threshold level used in condition C2. If the received power of the SSB is higher than the threshold level, the control unit 23 determines that the terminal device 2 is in a state where it can receive a signal from the base station 1. In this case, in S26, the control unit 23 transitions the main radio unit 21 to sleep mode.

[0065] In this way, when the radio wave condition of the terminal device 2 is good, the main radio unit 21 transitions to sleep mode. After this, the terminal device 2 uses the wake-up receiver 22 to wait for a wake-up signal.

[0066] REFERENCE SIGNS LIST 1 base station 2 terminal device 21 main radio unit 22 wake-up receiver 23 control unit

Claims

1. A terminal device comprising: a first receiving unit that receives a first signal including first information; a second receiving unit that receives a second signal; and a control unit that activates the first receiving unit in response to the second receiving unit receiving the second signal, wherein the control unit determines whether to activate the first receiving unit in response to whether a first condition represented by the first information is satisfied.

2. The terminal device according to claim 1, characterized in that the control unit activates the first receiving unit when the first condition is satisfied, even if the second receiving unit does not receive the second signal.

3. The terminal device described in claim 1, characterized in that the first information represents a threshold value related to the reception level of a signal, and when the reception level of a synchronization signal for receiving the second signal is lower than the threshold value, the control unit activates the first receiving unit.

4. The terminal device described in claim 1, characterized in that the first information represents a predetermined period of time, and when the second receiving unit does not receive the second signal for the predetermined period of time, the control unit activates the first receiving unit.

5. The terminal device according to claim 1, characterized in that the first information represents a predetermined period of time, and the control unit activates the first receiving unit each time the predetermined period of time elapses.

6. The terminal device described in claim 1, characterized in that the first signal includes second information representing a second condition, and after activating the first receiving unit depending on whether the first condition is satisfied, when the second condition is satisfied, the control unit controls the first receiving unit to a state in which it does not receive signals.

7. The terminal device described in claim 6, characterized in that the second information represents a second predetermined period, and when the second predetermined period has elapsed since the first receiving unit was started, the control unit controls the first receiving unit to a state in which it does not receive signals.

8. The terminal device according to claim 7, wherein the predetermined period is expressed by the number of opportunities for the first receiving unit to receive the third signal.

9. The terminal device described in claim 6, characterized in that the second information represents a second threshold value related to the reception level of a signal, and when the reception level of the synchronization information received by the first receiving unit is higher than the second threshold value, the control unit controls the first receiving unit to a state in which it does not receive a signal.

10. A base station device connected to a terminal device, comprising: a transmitting unit that transmits a first signal and a second signal containing first information to the terminal device; the first signal is received by a first receiving unit in the terminal device; the second signal is received by a second receiving unit in the terminal device; when the second receiving unit in the terminal device receives the second signal, the first receiving unit is activated; and when the second receiving unit in the terminal device does not receive the second signal, whether or not to activate the first receiving unit is determined depending on whether or not a first condition represented by the first information is satisfied.

11. A wireless communication system including a base station device and a terminal device, wherein the terminal device comprises a first receiving unit, a second receiving unit, and a control unit, wherein the base station device transmits a first signal including first information to the terminal device, the first receiving unit receives the first signal, the base station device transmits a second signal to the terminal device, the control unit activates the first receiving unit in response to the second receiving unit receiving the second signal, and when the second receiving unit does not receive the second signal, the control unit determines whether to activate the first receiving unit in response to whether a first condition represented by the first information is satisfied.

Images