WO2020084657A1 - Dispositif de station de base, dispositif terminal et système de communication sans fil - Google Patents

Dispositif de station de base, dispositif terminal et système de communication sans fil Download PDF

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Publication number
WO2020084657A1
WO2020084657A1 PCT/JP2018/039183 JP2018039183W WO2020084657A1 WO 2020084657 A1 WO2020084657 A1 WO 2020084657A1 JP 2018039183 W JP2018039183 W JP 2018039183W WO 2020084657 A1 WO2020084657 A1 WO 2020084657A1
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WIPO (PCT)
Prior art keywords
timer
base station
terminal device
handover
unit
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PCT/JP2018/039183
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English (en)
Japanese (ja)
Inventor
三夫 小林
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富士通株式会社
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Priority to PCT/JP2018/039183 priority Critical patent/WO2020084657A1/fr
Publication of WO2020084657A1 publication Critical patent/WO2020084657A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/08—Reselecting an access point

Definitions

  • the present invention relates to a base station device and a terminal device used in a wireless communication system.
  • handover may be executed. For example, it is assumed that the terminal device located in the cell of the base station S moves toward the cell of the base station T. In this case, when the power of the radio signal received from the base station T in the terminal device becomes higher than the power of the radio signal received from the base station S, the handover from the base station S to the base station T is executed.
  • the 5th generation mobile communication 5th generation mobile communication (NR: New Radio)) communication standard has been adopted in order to support services with various requirements. Is being considered.
  • 5G 5th generation mobile communication
  • URLLC Ultra-Reliable and Low Latency Communications
  • URLLC is expected to be applied to, for example, automatic driving, remote medicine, and industrial equipment IoT.
  • Patent Documents 1 to 3 for example. Further, related technologies are described in Non-Patent Documents 1 to 7.
  • 3GPP TS38.331V15.1.0 (2018-03) 3GPPTS38.321 V15.1.0 (2018-03) 3GPPTS38.423 V1.1.0 (2018-06) 3GPP TS38.213 V15.1.0 (2018-03) 3GPP TS38.133 V15.1.0 (2018-03) 3GPP TS36.331V15.1.0 (2018-03) R1-1807300 RLM for URLLC, Ericsson, 3GPP TSG RAN1WG1 Meeting # 93, Busan, South Korea, 21st-25thmay, 2018
  • the handover is executed when the terminal device approaches the edge of the cell.
  • the quality of communication between the terminal device and the base station to which the terminal device is connected hereinafter, “source base station”
  • the time required for the handover procedure may be long.
  • the quality of communication between the terminal device and the source base station is poor, the communication between the terminal device and the source base station is interrupted during the handover process, and the reconnection process (or cell search) is performed. ) May be required.
  • communication delay may increase during handover.
  • An object of one aspect of the present invention is to reduce communication delay during handover in a wireless communication system.
  • a base station apparatus includes a transmitter that transmits control information related to setting of a first timer to a terminal, and an event that triggers a handover is detected in the terminal based on a wireless quality measurement result.
  • a terminal device receives a control information relating to setting of a first timer from a base station, a measuring unit for measuring radio quality, and a handover based on a measurement result by the measuring unit.
  • the measurement result is displayed according to the state of the first timer controlled based on the control information and the state of a second timer different from the first timer.
  • a transmitter that transmits the measurement information to the base station.
  • the communication delay at the time of handover is reduced in the wireless communication system.
  • FIG. 1 shows an example of a wireless communication system according to an embodiment of the present invention.
  • the wireless communication system 100 includes a plurality of base stations 1 (1a, 1b) and a terminal device (UE: User Equipment) 3.
  • the base station 1 is, for example, a next generation base station device (gNB: Next generation Node B).
  • gNB Next generation Node B
  • the terminal device 3 is connected to the base station 1a. However, the terminal device 3 is located near the edge of the cell of the base station 1a. Specifically, the terminal device 3 is located near the boundary between the cell of the base station 1a and the cell of the base station 1b. Therefore, the terminal device 3 measures the radio quality or radio environment with the base station 1b. Then, when a predetermined trigger event is detected in this measurement, the terminal device 3 generates a measurement report (Measurement Report) and transmits it to the base station 1.
  • a measurement report Measurement Report
  • Event A1 represents a state in which the power of the received wave of the serving cell (that is, the cell provided by the base station 1 to which the terminal device 3 is connected) is higher than the threshold value.
  • Event A2 represents a state in which the power of the received wave of the serving cell is lower than the threshold value.
  • Event A3 represents a state in which the power of the reception wave of the adjacent cell is higher than the value obtained by adding a predetermined offset to the power of the reception wave of the P cell (Primary Cell).
  • Event A4 represents a state in which the power of the received wave of the adjacent cell is higher than the threshold value.
  • Event A5 represents a state in which the power of the reception wave of the P cell is lower than the threshold value 1 and the power of the reception wave of the adjacent cell is higher than the threshold value 2.
  • Event A6 represents a state in which the power of the reception wave of the adjacent cell is higher than the value obtained by adding a predetermined offset to the power of the reception wave of the S cell (Secondary Cell).
  • the PS cell may be used instead of the P cell.
  • the terminal device 3 stops measuring the peripheral cells.
  • the terminal device 3 starts measuring the neighboring cells.
  • the base station 1 starts the handover procedure.
  • the trigger event A6 is detected, the base station 1 starts the S cell switching procedure.
  • FIG. 3 shows an example of a handover procedure.
  • the terminal device 3 is assumed to be connected to the base station 1a before the start of handover. Then, the handover from the base station 1a to the base station 1b is executed.
  • the base station 1a and the base station 1b may be called a "source base station” and a “target base station”, respectively.
  • the terminal device 3 When the terminal device 3 detects the trigger event A2 shown in FIG. 2, the terminal device 3 starts measuring the peripheral cells. Then, when one or more of the trigger events A3, A4, and A5 are detected in the measurement of the peripheral cells, the terminal device 3 generates a measurement report indicating the detected event. This measurement report is transmitted from the terminal device 3 to the base station 1a.
  • the base station 1a starts the handover procedure when receiving the measurement report indicating the detected event (A3, A4, A5). That is, the base station 1a transmits a handover request to the base station 1b. When permitting handover, the base station 1b transmits a handover request ACK to the base station 1a.
  • the base station 1a Upon receiving the handover request ACK, the base station 1a sends a handover command to the terminal device 3.
  • the handover command is transmitted using the RRC reconfiguration message.
  • the terminal device 3 Upon receiving the handover command, the terminal device 3 starts the random access sequence. As a result, if the connection between the terminal device 3 and the base station 1b is successful, the data communication is started. Also, the base station 1b transmits a UE context release to the base station 1a. As a result, the base station 1a ends the communication with the terminal device 3.
  • Non-Patent Documents 1 and 2 The message procedure between base stations is described in Non-Patent Document 3 described above.
  • FIG. 4 shows an example of timers and counters for controlling handover. These timers and counters are installed in the terminal device 3.
  • the counter N310 counts the number of times out of synchronization detected in the terminal device 3. Out-of-sync is detected in this example when the block error rate of the signal received from the source base station exceeds a threshold. In this case, the threshold is, for example, 10%.
  • the terminal device 3 periodically calculates the block error rate of the received signal in the peripheral cell measurement. Then, when the synchronization loss is continuously detected and the counter N310 reaches “N310”, it is determined that a radio link failure (RLF) has occurred, and the RLF timer T310 is activated. “N310” is, for example, 1, 2, 3, 4, 6, 8, 10, or 20.
  • the counter N310 is reset when the terminal device 3 detects synchronization.
  • the radio link failure RLF is an example of a link failure between the base station and the terminal device.
  • the counter N311 counts the number of synchronizations detected by the terminal device 3. Synchronization is detected in this example when the block error rate of the signal received from the source base station is below a threshold. In this case, the threshold is, for example, 2%. Then, when synchronization is continuously detected and the counter N311 reaches "N311", it is determined that the radio link failure RLF has ended, and the RLF timer T310 is stopped. “N311” is, for example, 1, 2, 3, 4, 5, 6, 8, or 10. The counter N311 is reset when the terminal device 3 detects out of synchronization.
  • the RLF timer T310 is activated when “N310” consecutive times out of synchronization is detected. That is, when the radio link failure RLF occurs, the RLF timer T310 is started. Then, the RLF timer T310 measures the waiting time from when the radio link failure RLF is detected until the terminal device 3 executes the reconnection process.
  • the length of the RLF timer T310 is, for example, 0, 50, 100, 200, 500, 1000, 2000, 4000, or 6000 ms. Then, the RLF timer T310 stops when any of the following events occurs. (1) Synchronization is continuously detected “N311” times (2) Handover command is received from the source base station (3) Reconnection process is started. When the RLF timer T310 expires, the terminal device 3 restarts. The connection process is started (or the operation state of the terminal device 3 transits to the idle state of RRC).
  • the grace timer T312 is activated when the terminal device 3 transmits a measurement report to the base station 1 while the RLF timer T310 is operating.
  • the length of the grace timer T312 is, for example, 0, 50, 100, 200, 300, 400, 500, or 1000 milliseconds. Then, the grace timer T312 stops when any of the following events occurs. (1) Synchronization is continuously detected “N311” times. (2) Handover command is received from the source base station. (3) Reconnection process is started. (4) RLF timer T310 expires. The grace timer T312 expires. Then, the terminal device 3 starts the reconnection process (or the operation state of the terminal device 3 transits to the idle state of RRC).
  • the TTT timer is started when trigger events A1 to A6 are detected in the peripheral cell measurement. Specifically, the TTT timer measures the waiting time from when the trigger events A1 to A6 are detected until the terminal device 3 transmits the measurement report to the base station 1.
  • the length of the TTT timer is, for example, 0, 40, 64, 80, 100, 128, 160, 256, 320, 480, 512, 640, 1024, 1280, 2560, or 5120 ms. Then, when the TTT timer expires, the terminal device 3 transmits a measurement report to the base station.
  • FIG. 5 shows an example of processing after a handover event is detected.
  • the terminal device 3 has started measuring neighboring cells. Then, the terminal device 3 detects a handover event in the neighboring cell measurement.
  • the handover event corresponds to one of the trigger events A3, A4, A5 shown in FIG.
  • the terminal device 3 When the terminal device 3 detects the handover event, it activates the TTT timer as shown in FIG. 5 (a). Then, when this TTT timer expires, the terminal device 3 generates a measurement report indicating that a handover event has occurred and transmits it to the source base station. When the source base station receives the measurement report, the handover procedure is executed as shown in FIG. As a result, the terminal device 3 is connected to the target base station.
  • the RLF timer T310 is activated as shown in FIG. 5 (b).
  • the terminal device 3 determines that the RLF has occurred and executes the reconnection process. That is, the terminal device 3 searches for a new base station. In this case, the handover procedure is not executed.
  • the terminal device 3 can connect to any base station even when the handover procedure is not executed.
  • the time required for the reconnection process is longer than that in the handover procedure. Therefore, a method of suppressing the reconnection process is required.
  • FIG. 6 shows another example of processing after a handover event is detected.
  • the terminal device 3 controls the handover using the grace timer T312 in addition to the TTT timer.
  • the terminal device 3 When the terminal device 3 detects the handover event, it activates the TTT timer as shown in FIG. 6 (a). When this TTT timer expires, the terminal device 3 generates a measurement report indicating that a handover event has occurred and transmits it to the source base station. The terminal device 3 also activates the grace timer T312 due to the transmission of the measurement report. Then, when the source base station receives the measurement report, the handover procedure is executed as shown in FIG. As a result, the terminal device 3 is connected to the target base station. That is, the handover from the source base station to the target base station is completed. When the terminal device 3 receives the handover command in the handover procedure, the grace timer T312 is stopped.
  • the quality of communication between the base station 3 and the source base station is poor, and the RLF timer T310 is activated due to loss of synchronization. Further, it is assumed that the terminal device 3 cannot receive the handover command from the source base station. In this case, the grace timer T312 expires before the terminal device 3 receives the handover command. Then, the handover procedure is interrupted and the terminal device 3 starts the reconnection process. As described above, when the terminal device 3 cannot receive the handover command, the reconnection process is executed with the expiration of the grace timer T312 as a trigger even before the RLF timer T310 expires. That is, when the terminal device 3 cannot receive the handover command, the reconnection process starts earlier, and thus the communication delay is reduced. When the reconnection process is started, the grace timer T312 is stopped.
  • the RLF timer T310 is activated due to the loss of synchronization, as in the example shown in FIG. 6 (b). However, the RLF timer T310 expires before the terminal device 3 receives the handover command. In this case, the terminal device 3 starts the reconnection process when the RLF timer T310 expires.
  • FIG. 7 shows an example of the base station 1.
  • the base station 1 includes a radio reception unit 11, a demodulation unit 12, a decoding unit 13, a measurement report reception unit 14, a handover control unit 15, a base station communication unit 16, a timer cancellation control unit 17, and a cancellation.
  • the information transmission unit 18, the encoding unit 19, the modulation unit 20, the wireless transmission unit 21, and the antenna unit 22 are provided.
  • the base station 1 may include other circuits or functions not shown in FIG. 7.
  • the wireless reception unit 11 receives the uplink wireless signal transmitted from the terminal device 3 via the antenna unit 22.
  • the demodulation unit 12 demodulates the output signal of the wireless reception unit 11.
  • the decoding unit 13 decodes the output signal of the demodulation unit 12.
  • the output signal of the decoding unit 13 includes data and control information.
  • the control information includes a measurement report.
  • the measurement report includes information indicating the trigger event (A1 to A6) detected in the terminal device 3. Then, the measurement report is received by the measurement report receiving unit 14.
  • the data and other control information are processed by a data processing circuit and a control information processing circuit (not shown), respectively.
  • the handover control unit 15 executes a handover procedure when the measurement report includes a handover event.
  • the handover event corresponds to the trigger events A3 to S5 shown in FIG.
  • the handover control unit 15 transmits a handover request to the target base station via the inter-base station communication unit 16. Further, when the handover control unit 15 receives the handover request ACK from the target base station, it generates a handover command.
  • the handover controller 15 sends a handover request ACK and a UE context release to the source base station.
  • the timer cancellation control unit 17 generates cancellation information indicating whether or not to permit cancellation of the TTT timer based on the communication service used by the terminal device 3. For example, when the terminal device 3 uses the URLLC service, the timer cancellation control unit 17 generates cancellation information that permits cancellation of the TTT timer. Information indicating the communication service used by the terminal device 3 is notified from the terminal device 3 to the base station 1 when the terminal device 3 connects to the base station 1, for example. Further, the cancellation information is an example of control information related to the setting of the TTT timer.
  • the cancellation information transmission unit 18 transmits the cancellation information generated by the timer cancellation control unit 17 to the terminal device 3.
  • the cancellation information is transmitted from the base station 1 to the terminal device 3 by RRC signaling, for example.
  • the cancellation information may be inserted in the information (ReportConfigNR) for setting the trigger event.
  • the cancellation information may be inserted into EventTriggerConfig shown in FIG. 8A.
  • FIG. 8B shows an example of EventTriggerConfig.
  • EventTriggerConfig represents a parameter related to each trigger event A1 to A6 shown in FIG.
  • the cancel information is set as TimeToTriggerCancel in the embodiment shown in FIG.
  • TimeToTriggerCancel is 1-bit information, although not particularly limited thereto. In this case, "1" is set when the cancellation of the TTT timer is permitted, and "0" is set when the cancellation of the TTT timer is not permitted.
  • the cancellation information is a parameter related to the handover procedure, it is set only for the trigger events A3 to A5. Therefore, in FIG. 8B, the description regarding the trigger events A1, A2, and A6 is omitted.
  • the encoding unit 19 encodes data and control information.
  • the control information includes a handover command generated by the handover control unit 15 and cancellation information generated by the timer cancellation control unit 17.
  • the modulator 20 modulates the output signal of the encoder 19. Then, the wireless transmission unit 21 transmits the output signal of the modulation unit 20 to the terminal device 3 via the antenna unit 22.
  • the handover control unit 15 and the timer cancellation control unit 17 are realized by, for example, a processor system.
  • the processor system includes a processor and memory.
  • the processor can provide the functions of the handover control unit 15 and the timer cancellation control unit 17 by executing the software program stored in the memory.
  • the processor system may also provide the functions of the measurement report receiving unit 14, the inter-base station communication unit 16, and the cancellation information transmitting unit 18.
  • FIG. 9 shows an example of the terminal device 3.
  • the terminal device 3 includes a radio reception unit 31, a demodulation unit 32, a decoding unit 33, a cancellation information reception unit 34, a radio link monitoring unit 35, a measurement unit 36, a control unit 37, a measurement report transmission unit 40, an encoding unit 41, and a modulation.
  • the unit 42, the wireless transmission unit 43, and the antenna unit 44 are provided.
  • the terminal device 3 may have other circuits or functions not shown in FIG. 9.
  • the radio receiving unit 31 receives the downlink radio signal transmitted from the base station 1 via the antenna unit 44.
  • the demodulation unit 32 demodulates the output signal of the wireless reception unit 31.
  • the decoding unit 33 decodes the output signal of the demodulation unit 32.
  • the output signal of the decoding unit 33 includes data and control information.
  • the control information includes cancellation information.
  • the cancellation information is generated by the base station 1 as described above and represents whether or not the cancellation of the TTT timer is permitted. Then, the cancellation information is received by the cancellation information receiving unit 34.
  • the data and other control information are processed by a data processing circuit and a control information processing circuit (not shown), respectively.
  • the wireless link monitoring unit 35 monitors the uplink state based on the signal received from the terminal device 3. As an example, the wireless link monitoring unit 35 regularly monitors the uplink block error rate. The monitoring result is notified to the control unit 37.
  • the measuring unit 36 measures the radio quality of the serving cell and the peripheral cells based on the signal received from the terminal device 3. As an example, the measurement unit 36 measures the reception strength of the reference signal transmitted from the base station for each of the serving cell and the peripheral cells. In this case, the measuring unit 36 may determine whether or not the trigger events A1 to A6 shown in FIG. 2 have been detected. Then, the measurement result (or the determination result) by the measurement unit 36 is notified to the control unit 37.
  • the control unit 37 includes a timer control unit 38 and a measurement report generation unit 39.
  • the control unit 37 also includes a TTT timer, an RLF timer T310, a grace timer T312, a counter N310, and a counter N311.
  • the control unit 37 may have other functions not shown in FIG.
  • the timer control unit 38 controls the TTT timer, the RLF timer T310, the grace timer T312, the counter N310, and the counter N311 based on the cancellation information, the monitoring result by the wireless link monitoring unit 35, and the measurement result by the measuring unit 36. Specifically, when the uplink block error rate exceeds the out-of-synchronization threshold value, the timer control unit 38 increments the counter N310 and resets the counter N311. Further, when the uplink block error rate is lower than the synchronization threshold, the timer control unit 38 increments the counter N311 and resets the counter N310.
  • the timer control unit 38 activates the RLF timer T310.
  • the timer control unit 38 activates the grace timer T312.
  • the measuring unit 36 detects one of the trigger events A1 to A6
  • the timer control unit 38 activates the TTT timer.
  • the “stop condition” described with reference to FIG. 4 is satisfied, the timer control unit 38 stops the corresponding timer.
  • the timer control unit 38 may cancel the TTT timer based on the cancellation information. For example, when the cancellation information permits cancellation of the TTT timer and the RLF timer T310 is operating, the timer control unit 38 may cancel the TTT timer.
  • the measurement report generation unit 39 generates a measurement report when the TTT timer expires. Further, when the TTT timer is canceled according to the cancellation information, the measurement report generating unit 39 generates the measurement report even if the TTT timer has not expired.
  • the measurement report includes information for identifying the detected trigger event (any one of A1 to A6).
  • the measurement report transmitting unit 40 transmits the measurement report generated by the measurement report generating unit 39 to the base station 1.
  • the encoding unit 41 encodes data and control information.
  • the control information includes the measurement report generated by the measurement report generation unit 39.
  • the modulator 42 modulates the output signal of the encoder 41.
  • the wireless transmission unit 43 transmits the output signal of the modulation unit 42 to the base station 1 via the antenna unit 44.
  • the control unit 37, the timer control unit 38, and the measurement report generation unit 39 are realized by, for example, a processor system.
  • the processor system includes a processor and memory.
  • the processor can provide the functions of the control unit 37, the timer control unit 38, and the measurement report generation unit 39 by executing the software program stored in the memory. Further, this processor system may provide the functions of the cancellation information receiving unit 34, the wireless link monitoring unit 35, the measuring unit 36, and the measurement report transmitting unit 40.
  • FIG. 10 shows an example of a handover procedure according to the embodiment of the present invention.
  • the trigger event A2 shown in FIG. 2 has been detected, and the terminal device 3 has started measuring neighboring cells. Then, the terminal device 3 detects a handover event in the neighboring cell measurement.
  • the handover event corresponds to one of the trigger events A3, A4, or A5 shown in FIG.
  • the quality of the wireless link between the source base station and the terminal device 3 is poor, and the terminal device 3 has detected out-of-sync. That is, the counter N310 that counts the number of times of synchronization is performing the counting operation.
  • the terminal device 3 is assumed to have received the cancellation information permitting cancellation of the TTT timer from the source base station.
  • This cancellation information is stored in, for example, a memory area accessible by the timer control unit 38.
  • the terminal device 3 when the terminal device 3 detects a handover event, it activates the TTT timer as shown in FIG.
  • the TTT timer measures the waiting time from when the handover event is detected until the terminal device 3 transmits the measurement report to the base station 1. That is, the terminal device 3 transmits the measurement report to the base station 1 when the TTT timer expires.
  • the count value of the counter N310 reaches “N310” and the RLF timer T310 is activated before the TTT timer expires.
  • the terminal device 3 has received the cancellation information that permits cancellation of the TTT timer.
  • the timer control unit 38 cancels the TTT timer when the RLF timer T310 is activated.
  • the TTT timer cancel processing corresponds to processing for forcibly expiring the TTT timer.
  • the measurement report generation unit 39 executes the same process as when the TTT timer expires. That is, when the TTT timer is canceled, the measurement report generation unit 39 generates a measurement report. This measurement report includes information indicating that a handover event has occurred. The measurement report transmitting unit 40 also transmits this measurement report to the source base station. Then, when the measurement report is transmitted, the timer control unit 38 activates the grace timer T312.
  • handover preparation is started, as shown in FIG.
  • the source base station transmits a handover command to the terminal device 3.
  • the timer control unit 38 stops the RLF timer T310 and the grace timer T312. Then, the terminal device 3 executes the handover according to the handover command.
  • the TTT timer when the RLF timer T310 is activated during the operation of the TTT timer, the TTT timer is canceled and the terminal device 3 transmits the measurement report to the source base station. That is, when the RLF timer T310 is activated during the operation of the TTT timer, the terminal device 3 immediately transmits the measurement report to the source base station without waiting for the expiration of the TTT timer. Therefore, as compared with the procedure shown in FIG. 6, the handover procedure is started earlier, so that the communication delay at the time of handover is reduced. Further, if the handover procedure is started early, there is a high possibility that the terminal device 3 receives the handover command before the RLF timer T310 expires. That is, there is a high possibility that handover will be completed without reconnection.
  • the RLF timer T310 is activated before the terminal device 3 detects the handover event. That is, when the terminal device 3 detects the handover event, the RLF timer T310 is operating.
  • the timer control unit 38 activates the TTT timer due to the detection of the handover event, and then immediately cancels the TTT timer.
  • the timer control unit 38 may give information indicating that the TTT timer has been canceled to the measurement report generation unit 39 without activating the TTT timer.
  • the measurement report generation unit 39 generates a measurement report
  • the measurement report transmission unit 40 transmits the measurement report to the source base station.
  • the timer control unit 38 activates the grace timer T312. Subsequent procedures are substantially the same in FIGS. 10 (a) and 10 (b), so description thereof will be omitted.
  • FIG. 11 is a flowchart showing an example of processing of the base station 1. It should be noted that this flowchart shows the processing related to the handover.
  • the base station 1 receives a connection request from the terminal device 3.
  • the connection request is transmitted from the terminal device 3 to the base station 1.
  • the target base station receives the connection request from the terminal device 3.
  • the timer cancellation control unit 17 In S2 to S4, the timer cancellation control unit 17 generates cancellation information based on the type of service requested by the terminal device 3. Specifically, the timer cancellation control unit 17 determines in S2 whether or not the terminal device 3 uses the designated service. For example, when the terminal device 3 uses the URLLC service, the timer cancellation control unit 17 generates cancellation information that permits cancellation of the TTT timer in S3. Further, when the terminal device 3 uses another service, the timer cancellation control unit 17 generates cancellation information not permitting cancellation of the TTT timer in S4. After that, data communication is performed between the base station 1 and the terminal device 3.
  • the measurement report receiving unit 14 waits for the measurement report transmitted from the terminal device 3. Then, when the measurement report receiving unit 14 receives the measurement report indicating the handover event (A3, A4, or A5), the handover control unit 15 executes the handover procedure.
  • the handover control unit 15 transmits a handover request to the target base station.
  • the handover control unit 15 waits for a handover request ACK corresponding to the handover request.
  • the handover control unit 15 transmits a handover command to the terminal device 3 in S8.
  • the base station 1 receives the UE context release from the target base station, the base station 1 ends the connection with the terminal device 3.
  • FIG. 12 is a flowchart showing an example of processing of the terminal device 3. It should be noted that this flowchart shows the processing related to the handover.
  • the control unit 37 determines whether or not the terminal device 3 can execute the handover based on the measurement result of the measurement unit 36. In this embodiment, when any one of the trigger events A3 to A5 shown in FIG. 2 is detected, the control unit 37 determines that the terminal device 3 can execute the handover. That is, it is determined whether or not an event that triggers handover is detected based on the measurement result of the wireless quality.
  • the timer control unit 38 determines whether or not the cancellation information received from the base station 1 permits cancellation of the TTT timer. When cancellation of the TTT timer is not permitted, the timer control unit 38 activates the TTT timer in S13. Then, when the TTT timer expires in S14, the processing of the control unit 37 proceeds to S21.
  • the timer control unit 38 activates the TTT timer in S15. Subsequently, in S16 to S17, the timer control unit 38 monitors the expiration of the TTT timer and the activation of the RLF timer T310. Then, when the TTT timer expires before the RLF timer T310 is activated (S16: Yes), the process of the control unit 37 proceeds to S21. On the other hand, when the RLF timer T310 is started before the TTT timer expires (S17: Yes), the timer control unit 38 cancels the TTT timer in S19. When the TTT timer is canceled, the process of the control unit 37 proceeds to S21.
  • the measurement report generation unit 39 generates a measurement report, and the measurement report transmission unit 40 transmits the measurement report to the source base station.
  • the timer control unit 38 activates the grace timer T312.
  • the control unit 37 receives a handover command from the source base station. At this time, if the RLF timer T310 is operating, the timer control unit 38 stops the RLF timer T310 in S23. If the grace timer T312 is operating, the timer control unit 38 stops the grace timer T312. In S24, the control unit 37 executes the handover process according to the received handover command.
  • the handover process includes a random access sequence executed with the target base station.
  • the process of the flowchart shown in FIG. 12 will be described with reference to the embodiment shown in FIG.
  • the RLF timer T310 has not been started yet. Therefore, after the TTT timer is started in S15, the timer control unit 38 monitors the expiration of the TTT timer and the start of the RLF timer T310 in S16 to S17. After that, when the RLF timer T310 is activated, the processing of the control unit 37 proceeds from S17 to S18, and the TTT timer is canceled. Then, the processing of S21 to S24 is executed, and the handover is completed.
  • the RLF timer T310 is operating when a handover event is detected.
  • S18 is immediately executed and the TTT timer is canceled.
  • the processing of S21 to S24 is executed, and the handover is completed.
  • the terminal device 3 interrupts the handover procedure and executes the reconnection process. To do.
  • the cancellation information is transmitted from the base station 1 to the terminal device 3, but the present invention is not limited to this procedure.
  • the base station 1 sends the cancellation information to the terminal device 3. No need to send.
  • the terminal device 3 can execute the process of the flowchart shown in FIG. 12 without receiving the cancellation information from the base station 1. In this case, for example, when the terminal device 3 uses the URLLC service, cancellation of the TTT timer is permitted, and when the terminal device 3 uses the eMBB (Enhanced Mobile BroadBand) service, cancellation of the TTT timer is not permitted.
  • eMBB Enhanced Mobile BroadBand
  • FIG. 13 is a flowchart showing a variation of the processing of the terminal device 3.
  • the timer control unit 38 determines in S31 whether the RLF timer T310 is operating. That is, it is determined whether the RLF timer T310 is operating when the handover event is detected. It should be noted that the RLF timer T310 is activated when downlink synchronization is lost, as described above. Then, when the RLF timer T310 is operating when the handover event is detected (S31: Yes), the process of the control unit 37 proceeds to S21. Then, in S21, the measurement report is transmitted to the base station 1.
  • the measurement report transmitting unit 40 transmits the measurement report to the base station 1 regardless of the state of the TTT timer.
  • the timer control unit 38 gives the measurement report generation unit 39 information indicating that the TTT timer has been canceled.
  • the terminal device 3 if the RLF timer T310 is operating when the handover event is detected, the terminal device 3 immediately transmits the measurement report to the base station 1 without activating the TTT timer. For example, as shown in FIG. 14A, when a handover event is detected, the terminal device 3 immediately transmits a measurement report to the base station 1 and activates the grace timer T312. When the terminal device 3 receives the handover command before the grace timer T312 expires, the timer control unit 38 stops the RLF timer T310 and the grace timer T312. In this case, the reconnection process is not executed and the handover is executed.
  • the processing of the terminal device 3 and the base station 1 may be complicated depending on the remaining time of the RLF timer T310 when the handover event is detected.
  • the remaining time of the RLF timer T310 when the handover event is detected is shorter than the timer length of the grace timer T312.
  • the RLF timer T310 may expire before the terminal device 3 receives the handover command.
  • the terminal device 3 starts the reconnection process. That is, in the case shown in FIG. 14B, the reconnection process is executed without completing the handover, although the measurement report is transmitted from the terminal device 3 to the base station 1.
  • FIG. 15 is a flowchart showing an example of processing of the terminal device 3 in the second embodiment.
  • S31 and S32 are executed in addition to the processes of the flowchart shown in FIG.
  • the timer control unit 38 determines whether or not the RLF timer T310 is operating. That is, it is determined whether the RLF timer T310 is operating when the handover event is detected. Then, if the RLF timer T310 is operating, the process of the control unit 37 proceeds to S32. That is, S32 is executed when cancellation of the TTT timer is permitted (S12: Yes) and when the RLF timer T310 is operating when a handover event is detected (S31: Yes).
  • the timer control unit 38 compares the remaining time of the RLF timer T310 when the handover event is detected with a predetermined threshold value.
  • the threshold is, for example, the timer length of the grace timer T312.
  • the timer length of the delay timer T312 is set to be slightly longer than the time required from when the terminal device 3 sends the measurement report to the base station 1 until the base station 1 sends the handover command to the terminal device 3.
  • the process of the control unit 37 proceeds to S15.
  • the TTT timer is once activated in S15 and then immediately canceled in S18.
  • the terminal device 3 can receive the handover command before the RLF timer T310 expires, as shown in FIG. Probability is high. Therefore, as compared with the case where the TTT timer is not canceled, the communication delay is reduced by the timer length of the TTT timer.
  • the control unit 37 may generate the measurement report without activating the TTT timer.
  • the process of the control unit 37 proceeds to S13. That is, when the remaining time of the RLF timer T310 is shorter than the timer length of the grace timer T312, the timer control unit 38 ignores the cancel information. In this case, the TTT timer is started in S13. Therefore, the terminal device 3 does not transmit the measurement report to the base station 1 before the TTT timer expires. Then, when the RLF timer T310 expires before the TTT timer expires, the terminal device 3 executes the reconnection process without transmitting the measurement report to the base station 1. Therefore, as compared with the case shown in FIG. 14A, the processing related to the transmission of the measurement report (including the processing of transmitting the handover request and the handover request ACK between the base stations) is reduced.
  • Base station 3 Terminal device 14 Measurement report receiving unit 15 Handover control unit 17 Timer cancel control unit 18 Cancel information transmitting unit 34 Cancel information receiving unit 35 Radio link monitoring unit 36 Measuring unit 37 Control unit 38 Timer control unit 39 measurement report generation unit 40 measurement report transmission unit

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

La station de base d'après la présente invention transmet à un dispositif terminal des informations de commande relatives à un réglage d'un premier temporisateur. Le dispositif terminal mesure la qualité sans fil. Lors d'une détection d'un événement déclenchant un transfert intercellulaire, sur la base de résultats de mesure de la qualité sans fil, le dispositif terminal transmet à la station de base des informations de mesure exprimant les résultats de mesure en fonction de l'état du premier temporisateur qui est commandé sur la base d'informations de commande et de l'état d'un second temporisateur différent du premier. La station de base exécute le transfert intercellulaire après réception des informations de mesure.
PCT/JP2018/039183 2018-10-22 2018-10-22 Dispositif de station de base, dispositif terminal et système de communication sans fil WO2020084657A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010521119A (ja) * 2007-03-09 2010-06-17 インターデイジタル テクノロジー コーポレーション 再選択タイマおよびセルランキング基準を調整し、サービングセルの劣化信号測定を報告するための方法および機器
WO2015079729A1 (fr) * 2013-11-26 2015-06-04 日本電気株式会社 Système de communication sans fil, station de base, dispositif de gestion de réseau, procédé de commande de transfert intercellulaire et programme
JP2017514418A (ja) * 2014-04-25 2017-06-01 インテル アイピー コーポレイション ハンドオーバ開始のためのユーザイクイップメント及び方法

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Publication number Priority date Publication date Assignee Title
JP2010521119A (ja) * 2007-03-09 2010-06-17 インターデイジタル テクノロジー コーポレーション 再選択タイマおよびセルランキング基準を調整し、サービングセルの劣化信号測定を報告するための方法および機器
WO2015079729A1 (fr) * 2013-11-26 2015-06-04 日本電気株式会社 Système de communication sans fil, station de base, dispositif de gestion de réseau, procédé de commande de transfert intercellulaire et programme
JP2017514418A (ja) * 2014-04-25 2017-06-01 インテル アイピー コーポレイション ハンドオーバ開始のためのユーザイクイップメント及び方法

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