JP2009164842A - Method for establishing synchronization, wireless base station and mobile station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the retransmission of downlink information through DL-SCH by reducing a probability that a mobile station UE may be transited to an "out-of-synchronization state" on contrary to the intention of a wireless base station eNB, and to prevent wireless resources in the downlink from being wasted. <P>SOLUTION: A method for establishing synchronization comprises a step where a wireless base station eNB transmits the TA to a mobile station UE, a step where the wireless base station eNB retransmits the TA to a mobile station UE when the wireless base station eNB cannot receive first delivery confirmation information (ACK) indicating an affirmative reception result within a first predetermined period of time, and a step where the wireless base station eNB retransmits the TA to a mobile station UE when the wireless base station eNB cannot receive second delivery confirmation information (TA-ACK) indicating an affirmative reception result within a second predetermined period of time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a synchronization establishment method, a radio base station, and a mobile station, in which a mobile station establishes uplink synchronization with the radio base station based on a timing adjustment command transmitted from the radio base station.

  In the “LTE (Long Term Evolution) system defined by 3GPP, the mobile station UE is connected to the radio base station eNB based on“ TA (Timing Advance: timing adjustment command) ”transmitted from the radio base station eNB. Are configured to establish synchronization in the uplink.

  Here, the TA is transmitted by “MAC-Control-Element” which is control information in a MAC (Media Access Control) layer.

  Hereinafter, with reference to FIG. 5, an operation in which the mobile station UE establishes uplink synchronization with the radio base station eNB in the conventional LTE scheme will be described.

  As illustrated in FIG. 5, when the mobile station UE is in the “synchronization established state” in which synchronization in the uplink is established (step S51), the radio base station eNB transmits to the mobile station UE in step S52. Whether the received TA has been received or not is monitored.

  Here, the radio base station eNB transmits TA to the mobile station UE via DL-SCH (Downlink-Shared Channel: downlink shared channel).

  HARQ retransmission control is applied to the DL-SCH, and when the mobile station UE receives information via the DL-SCH addressed to the mobile station UE, the PDSCH (Physical) to which the DL-SCH is mapped. HARQ delivery confirmation information (Ack / Nack) for Downlink Shared Channel) is transmitted to the radio base station eNB.

  Here, if the mobile station UE has successfully received / decoded the specific information transmitted via the PDSCH / DL-SCH, the mobile station UE transmits Ack as the HARQ delivery confirmation information, and the PDSCH / DL-SCH is transmitted. If the reception / decoding of the specific information transmitted in this manner has failed, Nack is transmitted as HARQ delivery confirmation information.

  When the radio base station eNB detects Nack as HARQ delivery confirmation information from the mobile station UE for the PDSCH that has transmitted the specific information, the radio base station eNB directs the specific information transmitted through the PDSCH to the mobile station. However, when Nack is detected as the HARQ delivery confirmation information from the mobile station UE, the specific information transmitted via the PDSCH is not retransmitted toward the mobile station.

  In this way, since the HARQ retransmission control is applied to the TA transmission via the DL-SCH, the TA can be transmitted with high reliability.

  However, due to the nature of the encoding of the HARQ delivery confirmation information, even if the mobile station UE transmits Nack (or Ack), the radio base station eNB erroneously detects Ack (or Nack). There is.

  Therefore, even if the mobile station UE has not succeeded in receiving / decoding the TA, the radio base station eNB erroneously detects Ack and erroneously determines that the mobile station UE has successfully received / decoded TA. Due to the determination, there is a case where the radio base station eNB does not retransmit the TA to the mobile station UE via the PDSCH / DL-SCH to which the TA is mapped.

  When the mobile station UE receives the TA transmitted by the radio base station eNB, in step S53, the mobile station UE adjusts the transmission timing in the uplink, thereby synchronizing the uplink established with the radio base station eNB. And the uplink synchronization timer is restarted.

  On the other hand, when the mobile station UE has not received the TA transmitted by the radio base station eNB, the mobile station UE determines whether or not the uplink synchronization timer has expired in step S54.

  If it is determined that the uplink synchronization timer has not expired, the operation returns to step S52. If it is determined that the uplink synchronization timer has expired, the operation proceeds to step S55. The mobile station UE transits to an “uplink synchronization loss state” in which synchronization in the uplink is not established.

  Here, when the radio base station eNB erroneously detects Ack as HARQ delivery confirmation information for the PDSCH / DL-SCH to which the TA is mapped, the radio base station eNB is contrary to the intention of the radio base station eNB. It should be noted that the mobile station UE may transition to an uplink out-of-synchronization state.

  The mobile station UE that is out of uplink synchronization cannot perform uplink transmission other than RACH (Random Access Channel). Uplink transmission other than RACH includes UL-SCH (Uplink-Shared Channel: uplink shared channel) and PUCCH (Physical Uplink Control Channel).

  Here, HARQ delivery confirmation information (Ack / Nack) for DL-SCH (Downlink-Shared Channel: downlink shared channel) is transmitted on PUCCH.

  In step S56, the mobile station UE that is out of uplink synchronization transmits whether or not uplink user data to be transmitted to the radio base station eNB has occurred, and is transmitted to the mobile station UE by the radio base station eNB. It is determined whether or not the received “RACH transmission request” has been received.

  When it is determined that uplink user data to be transmitted to the radio base station eNB is not generated, and when it is determined that the RACH transmission request transmitted by the radio base station eNB is not received, The operation repeats step S56, and when it is determined that uplink user data to be transmitted to the radio base station eNB has occurred, or it is determined that the RACH transmission request transmitted by the radio base station eNB has been received. In this case, the operation proceeds to step S57.

  In step S57, the mobile station UE transmits predetermined information to the radio base station eNB via the RACH.

When receiving the TA transmitted by the radio base station eNB in step S58, the mobile station UE adjusts the transmission timing in the uplink and restarts the uplink synchronization timer in step S59. Transition to "state". Here, the radio base station eNB is configured to generate and transmit TA based on the measurement result for the predetermined information transmitted via the RACH by the mobile station UE in step S57.
3GPP TS 36.300 V8.2.0 (2007-09) 3GPP TS 36.321 V8.0.0 (2007-12)

  However, in the conventional LTE scheme, when the mobile station UE is out of uplink synchronization, the mobile station UE is transmitted until uplink user data to be transmitted to the radio base station eNB is generated or transmitted by the radio base station eNB. It is not possible to transition to the “synchronization established state” until a received RACH transmission request is received.

  Therefore, when the mobile station UE is out of uplink synchronization, the mobile station UE receives downlink information (for example, downlink user data) addressed to the mobile station UE via the DL-SCH ( Step S107 in FIG. 6), the acknowledgment information (ACK / NACK) for the PDSCH (Physical Downlink Shared Channel) to which the DL-SCH is mapped cannot be transmitted (step S108 in FIG. 6).

  As a result, the downlink information is retransmitted via the DL-SCH, and there is a problem in that downlink radio resources are wasted.

  Here, if the radio base station eNB does not receive an ACK for the PDSCH (a signal notifying that the mobile station UE has succeeded in decoding), the downlink information addressed to the mobile station UE is retransmitted via the DL-SCH. Is configured to do.

  Therefore, the present invention has been made in view of the above-described problem, and by reducing the probability that the mobile station UE transitions to the “out of synchronization state” against the intention of the radio base station eNB, DL-SCH An object of the present invention is to provide a synchronization establishment method, a radio base station, and a mobile station that can reduce the retransmission of downlink information through the network and prevent a situation where radio resources in the downlink are wasted.

  A first feature of the present invention is a synchronization establishment method in which a mobile station establishes uplink synchronization with a radio base station based on a timing adjustment command transmitted from the radio base station, A step in which the radio base station transmits the timing adjustment command to the mobile station; and a reception result of a physical channel from which the mobile station has transmitted the timing adjustment command to the radio base station. Transmitting the first delivery confirmation information indicating the second delivery confirmation information indicating the reception result of the timing adjustment command, and the wireless base station sends a positive reception result within the first predetermined period. If the first delivery confirmation information is not received, a step of retransmitting a previous timing adjustment command to the mobile station; and In the case which could not receive the second acknowledgment information indicating positive reception result, to the mobile station, and summarized in that a step of retransmitting the timing adjustment command.

  In the first aspect of the present invention, when the mobile station does not receive the timing adjustment command within a third predetermined period in the first state in which synchronization in the uplink is established, the uplink The mobile station establishes synchronization in the uplink based on the timing adjustment command transmitted by the radio base station in the second state. By doing so, you may have the process of changing to the said 1st state.

  In the first aspect of the present invention, each time the mobile station receives the timing adjustment command, the mobile station restarts an uplink synchronization timer for measuring the predetermined period, and the mobile station When it expires, it may transit to the second state.

  A second feature of the present invention is a radio base station configured to establish uplink synchronization with a mobile station by transmitting a timing adjustment command to the mobile station. The timing adjustment command is generated based on a measurement result for a predetermined signal transmitted by the mobile station via an uplink, and the timing adjustment command is transmitted to the mobile station via a physical channel. A timing adjustment command transmitter configured as described above, wherein the timing adjustment command transmitter is configured to provide a first delivery indicating a positive reception result for the physical channel from the mobile station within a first predetermined period. When the confirmation information is not received, the timing adjustment command is retransmitted to the mobile station. When the second delivery confirmation information indicating a positive reception result for the timing adjustment command is not received within the second predetermined period, the timing adjustment command transmission unit transmits the timing to the mobile station. The gist is that the adjustment command is retransmitted.

  A third feature of the present invention is a mobile station that establishes uplink synchronization with the radio base station based on a timing adjustment command transmitted from the radio base station. A timing adjustment command receiving unit that receives the timing adjustment command, and a first delivery that transmits, to the radio base station, first delivery confirmation information indicating a reception result for a physical channel to which the timing adjustment command is transmitted. A confirmation information transmission unit and a second delivery confirmation information transmission unit that transmits second delivery confirmation information indicating a reception result of the timing adjustment command, and the timing adjustment command is received from the radio base station Further, it is configured to transmit the first delivery confirmation information and the second delivery confirmation information to the radio base station. To.

  As described above, according to the present invention, by reducing the probability that the mobile station UE transitions to the “out of synchronization state” against the intention of the radio base station eNB, the downlink information via the DL-SCH is reduced. It is possible to provide a synchronization establishment method, a radio base station, and a mobile station that can reduce retransmission and prevent a situation where radio resources in the downlink are wasted.

(Configuration of mobile communication system according to the first embodiment of the present invention)
The configuration of the mobile communication system according to the first embodiment of the present invention will be described with reference to FIGS.

  In the mobile communication system according to the present embodiment, as shown in FIG. 1, the radio base station eNB makes a PDCCH (Physical Downlink Control Channel), PDSCH, P-HICH (Physical HARQ Indicator Channel) to the mobile station UE. ) And the like.

  Further, in the mobile communication system according to the present embodiment, as illustrated in FIG. 1, the mobile station UE performs a PUSCH (Physical Uplink Shared Channel), a PUCCH (Physical Uplink Control Channel), It is comprised so that PRACH (Physical Random Access Channel) may be transmitted.

  Here, the radio base station eNB transmits downlink information (for example, downlink user data, etc.) to the mobile station UE via the DL-SCH mapped to the PDSCH, and the mobile station UE It is comprised so that uplink information (for example, uplink user data etc.) may be transmitted with respect to the base station eNB via UL-SCH mapped by PUSCH.

  Also, the radio base station eNB transmits ACK / NACK, which is HARQ delivery confirmation information for the above-described PUSCH, to the mobile station UE via P-HICH, and the mobile station UE transmits to the radio base station eNB. On the other hand, it is configured to transmit ACK / NACK, which is HARQ delivery confirmation information for the above-described PDSCH, via the PUCCH.

  Furthermore, the mobile station UE is configured to transmit predetermined information to the radio base station eNB via the RACH mapped to the PRACH.

  Further, the mobile station UE is configured to transmit “CQI (Channel Quality Indicator)” defined in 3GPP to the radio base station eNB via PUCCH.

  Furthermore, the mobile station UE is configured to transmit control information such as “Scheduling Request” and “UL Sounding Reference Signal” defined in 3GPP to the radio base station eNB.

  As shown in FIG. 2, the mobile station UE includes a TA receiving unit 11, a synchronization state management unit 12, an uplink synchronization timer management unit 13, a PUCCH transmission unit 14, a TA-ACK transmission unit 15, and an RLC-ACK. The transmitter 16, the DL-SCH receiver 17, and the RACH transmitter 18 are provided.

  The TA receiving unit 11 is configured to receive a TA included in the MAC-Control-Element transmitted via the DL-SCH by the radio base station eNB.

  The uplink synchronization timer management unit 13 is configured to manage an uplink synchronization timer for measuring the third predetermined period. Specifically, the uplink synchronization timer management unit 13 is configured to restart the uplink synchronization timer every time a TA is received by the TA reception unit 11.

  The synchronization state management unit 12 is configured to manage whether the state UE of the mobile station is “synchronization established state (first state)” or “out of synchronization state (second state)”.

  Here, the “synchronization established state” means that synchronization in the uplink is established between the mobile station UE and the radio base station eNB, and the mobile station UE transmits to the radio base station eNB in uplink other than the RACH. For example, it is a state in which transmission of uplink information via UL-SCH and transmission confirmation information (ACK / NACK) of HARQ for PDSCH via PUCCH can be performed.

  On the other hand, in the “out of synchronization state”, uplink synchronization is not established between the mobile station UE and the radio base station eNB, and the mobile station UE transmits to the radio base station eNB in uplink other than the RACH. For example, it is a state in which transmission of uplink information via UL-SCH and transmission confirmation information (ACK / NACK) of HARQ for PDSCH via PUCCH cannot be performed.

  The synchronization state management unit 12 displays the state of the mobile station UE when the state of the mobile station UE is “synchronization establishment state” and the TA is not received within the third predetermined period. It is configured to shift to the “out of synchronization state”.

  Here, the synchronization state management unit 12 is configured to transition the state of the mobile station UE to the “out of synchronization state” when the uplink synchronization timer managed by the uplink synchronization timer management unit 13 expires. Also good.

  In addition, when the state of the mobile station UE is “out-of-synchronization” and when the TA transmitted from the radio base station eNB is received, the synchronization state management unit 12 determines whether the uplink is based on the TA. By establishing synchronization, the state of the mobile station UE is changed to the “synchronization establishment state”.

  The PUCCH transmission unit 14 sends the first delivery confirmation information (ACK / NACK) indicating the reception result for the PDSCH (physical channel) to which the DL-SCH received by the DL-SCH reception unit 16 is mapped via the PUCCH. To the radio base station eNB.

  For example, the PUCCH transmission unit 14 transmits the first acknowledgment information (ACK / NACK) indicating the reception result of the PDSCH (physical channel) transmitted with the TA to the radio base station eNB via the PUCCH. It is configured.

  Here, the first delivery confirmation information is transmitted without being subjected to the encoding process via the PUCCH, and “ACK” indicating a positive reception result by the reception power in the radio base station eNB. Or “NACK” indicating a negative reception result.

  Therefore, it is generally considered that the reliability of the reception result indicated by the first acknowledgment information (ACK / NACK) is not so high.

  The TA-ACK transmission unit 15 is configured to transmit second delivery confirmation information (TA-ACK) indicating a reception result for each TA to the radio base station eNB via the UL-SCH.

  Here, unlike the first acknowledgment information (ACK / NACK), the second acknowledgment information (TA-ACK) is encoded via the UL-SCH (for example, error correction encoding processing such as CRC). The reliability of the reception result indicated by the second acknowledgment information (TA-ACK) is the reliability of the reception result indicated by the first acknowledgment information (ACK / NACK). taller than.

  Furthermore, since error detection code (CRC) is added to the second acknowledgment information (TA-ACK) transmitted via UL-SCH, the mobile station UE has successfully received / decoded TA. In the case where there is not, the possibility that the radio base station eNB erroneously determines that the mobile station UE has successfully received / decoded the TA is extremely low.

  The second acknowledgment information (TA-ACK) is different from RLC-ACK (described later) indicating reception results for a plurality of RLC-PDUs in that it indicates reception results for each TA.

  Here, when the PUCCH transmission unit 14 and the TA-ACK transmission unit 15 receive TA from the radio base station eNB, the PUCCH transmission unit 14 and the TA-ACK transmission unit 15 send the first acknowledgment information (ACK / NACK) and the first 2 It is configured to transmit delivery confirmation information (TA-ACK).

  The DL-SCH receiving unit 16 is configured to receive downlink information (for example, downlink user data) via the DL-SCH.

  The RLC-ACK transmission unit 17 is configured to transmit an RLC-ACK indicating a reception result for an RLC-PDU including downlink information (for example, downlink user data) transmitted via the DL-SCH. Yes.

  Here, RLC-ACK is delivery confirmation information (STATUS-Report) in an RLC (Radio Link Control) layer, and reception results for a plurality of RLC-PDUs can be reported together.

  The RACH transmission unit 18 is configured to transmit predetermined information to the radio base station eNB via the RACH.

  Specifically, when the state of the mobile station UE is “out of synchronization”, the RACH transmission unit 15 determines whether or not uplink user data to be transmitted to the radio base station eNB occurs or Until the RACH transmission request transmitted by the station eNB is received, predetermined information cannot be transmitted to the radio base station eNB via the RACH.

  However, even if the state of the mobile station UE is “out of synchronization”, the RACH transmission unit 15 transmits downlink information (for example, downlink user data) addressed to the mobile station UE via the DL-SCH. If received, the radio base station eNB may be configured to transmit predetermined information via the RACH.

  As illustrated in FIG. 3, the radio base station eNB includes a RACH receiving unit 21, a timer managing unit 22, a TA transmitting unit 23, a PUCCCH receiving unit 24, a TA-ACK receiving unit 25, and an RLC-ACK receiving unit. 26.

  The RACH receiving unit 21 is configured to receive the transmitted predetermined information transmitted via the RACH by the mobile station UE.

  The timer management unit 22 is configured to manage a timer for measuring the first predetermined period and the second predetermined period.

  Specifically, the timer management unit 22 receives both positive first delivery confirmation information (ACK) and positive second delivery confirmation information (TA-ACK) for the transmitted TA. The timer is configured to stop.

  The PUCCH receiving unit 24 is configured to receive, from the mobile station UE, first delivery confirmation information (ACK / NACK) indicating a reception result for the PDSCH to which the TA has been transmitted, via the PUCCH.

  The TA-ACK receiver 25 is configured to receive second delivery confirmation information (TA-ACK) indicating a reception result for each TA from the mobile station UE via the UL-SCH.

  The RLC-ACK receiving unit 26 is configured to receive RLC-ACK (STATUS-Report) indicating a reception result for one or a plurality of RLC-PDUs from the mobile station UE.

  The TA transmitter 23 measures a predetermined signal in the uplink according to the predetermined information received by the RACH receiver 21 and the PUCCH receiver 24, generates a TA based on the measurement result for the predetermined signal, This TA is configured to be transmitted to the mobile station UE via the PDSCH (physical channel).

  Also, the TA transmission unit 23 transmits the TA to the mobile station UE, and then, within a first predetermined period, from the mobile station UE, first delivery confirmation information (a positive reception result for the PDSCH) ( ACK) is received, the TA is configured to be HARQ retransmitted to the mobile station UE, and after the TA is transmitted to the mobile station UE, a second predetermined period of time is transmitted. If the second delivery confirmation information (TA-ACK) indicating a positive reception result for the TA is not received from the mobile station UE, the TA is sent to the mobile station UE. It is configured to retransmit.

(Operation of the mobile communication system according to the first embodiment of the present invention)
With reference to FIG. 4, the operation of the radio base station eNB in the mobile communication system according to the first embodiment of the present invention will be described.

  As shown in FIG. 4, in step S201, the radio base station eNB transmits TA to the mobile station UE at a predetermined timing.

  In step S202, the radio base station eNB attempts to receive first delivery confirmation information transmitted from the mobile station UE via the PUCCH at a timing determined according to the HARQ scheme.

  Here, when the radio base station eNB receives positive first acknowledgment information (ACK) via the PUCCH in step S202, the radio base station eNB is transmitted from the mobile station UE via the UL-SCH in step S203. Attempts to receive second delivery confirmation information (TA-ACK).

  On the other hand, if the radio base station eNB receives negative first delivery confirmation information (NACK) via the PUCCH in step S202, or has not received the first delivery confirmation information itself at the timing described above. In the case (DTX), in step S204A, this TA is HARQ retransmitted.

  Here, when the radio base station eNB receives the positive second delivery confirmation information (TA-ACK) via the UL-SCH in step S203, this operation ends.

  On the other hand, when the radio base station eNB does not receive the positive second delivery confirmation information (TA-ACK) via the UL-SCH within the second predetermined period in step S203, in step S204B, Retransmit such TA.

(Operations and effects of the mobile communication system according to the first embodiment of the present invention)
According to the mobile communication system according to the present embodiment, the mobile station UE not only transmits the first delivery confirmation information to the radio base station eNB via the PUCCH, but also via the UL-SCH. Since it is configured to transmit the second delivery confirmation information (TA-ACK) with high reliability, the probability that the mobile station UE transitions to the “out of synchronization state” is reduced against the intention of the radio base station eNB. In addition, retransmission of downlink information via the DL-SCH can be reduced, and waste of radio resources in the downlink can be minimized.

  The operations of the mobile station UE and the radio base station eNB described above may be implemented by hardware, may be implemented by a software module executed by a processor, or may be implemented by a combination of both. .

  Here, the software module may be, for example, a protocol stack layered in a layer structure. The processor may be implemented as a hardware as a chip set, for example, and may execute a protocol stack.

  The software modules include RAM (Random Access Memory), flash memory, ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable and Programmable ROM, Hard Disk, ROM, etc.). It may be provided in a storage medium of an arbitrary format such as a removable disk or a CD-ROM.

  Such a storage medium is connected to the processor so that the processor can read and write information from and to the storage medium. Further, such a storage medium may be integrated in the processor. Such a storage medium and processor may be provided in the ASIC. Such an ASIC may be provided in the mobile station UE and the radio base station eNB. Moreover, this storage medium and processor may be provided in the mobile station UE and the radio base station eNB as a discrete component.

  Although the present invention has been described in detail using the above-described embodiments, it is obvious to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as modified and changed modes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

1 is an overall configuration diagram of a mobile communication system according to a first embodiment of the present invention. FIG. 3 is a functional block diagram of a mobile station according to the first embodiment of the present invention. FIG. 3 is a functional block diagram of a radio base station according to the first embodiment of the present invention. 5 is a flowchart showing an operation of the radio base station according to the first embodiment of the present invention. It is a flowchart which shows operation | movement of the conventional mobile station. It is a figure for demonstrating operation | movement of the conventional mobile communication system.

Explanation of symbols

eNB ... radio base station 21 ... RACH receiver 22 ... timer manager 23 ... TA transmitter 24 ... PUCCH receiver 25 ... TA-ACK receiver 26 ... RLC-ACK receiver UE ... mobile station 11 ... TA receiver 12 ... Synchronization state management unit 13 Uplink synchronization timer management unit 14 PUCCH transmission unit 15 TA-ACK transmission unit 16 DL-SCH reception unit 17 RLC-ACK transmission unit 18 RACH transmission unit

Claims (5)

A synchronization establishment method in which a mobile station establishes synchronization in an uplink with a radio base station based on a timing adjustment command transmitted from the radio base station,
The wireless base station transmitting the timing adjustment command to the mobile station;
The mobile station transmits to the radio base station first delivery confirmation information indicating a reception result for the physical channel to which the timing adjustment command is transmitted, and second delivery indicating a reception result for the timing adjustment command. Sending confirmation information;
A step of retransmitting the timing adjustment command to the mobile station when the radio base station fails to receive the first acknowledgment information indicating a positive reception result within a first predetermined period; When,
A step of retransmitting the timing adjustment command to the mobile station when the radio base station fails to receive the second acknowledgment information indicating a positive reception result within a second predetermined period; A method for establishing synchronization. If the mobile station does not receive the timing adjustment command within the third predetermined period in the first state in which the synchronization in the uplink is established, the synchronization in the uplink is not established. A transition to a state;
The mobile station having a transition to the first state by establishing synchronization in the uplink based on the timing adjustment command transmitted by the radio base station in the second state. The synchronization establishment method according to claim 1, wherein: The mobile station restarts an uplink synchronization timer for measuring the predetermined period each time the timing adjustment command is received,
The synchronization establishment method according to claim 1, wherein the mobile station transitions to the second state when the uplink synchronization timer expires. A radio base station configured to establish uplink synchronization with the mobile station by transmitting a timing adjustment command to the mobile station,
The timing adjustment command is generated based on a measurement result for a predetermined signal transmitted by the mobile station via an uplink, and the timing adjustment command is transmitted to the mobile station via a physical channel. Comprising a timing adjustment command transmitter configured in
If the timing adjustment command transmitter does not receive the first acknowledgment information indicating the positive reception result for the physical channel from the mobile station within the first predetermined period, the timing adjustment command transmitter On the other hand, it is configured to retransmit the timing adjustment command,
If the timing adjustment command transmitter cannot receive second delivery confirmation information indicating a positive reception result for the timing adjustment command from the mobile station within a second predetermined period, the mobile station In contrast, a radio base station configured to retransmit the timing adjustment command. Based on a timing adjustment command transmitted from a radio base station, a mobile station that establishes uplink synchronization with the radio base station,
A timing adjustment command receiving unit for receiving the timing adjustment command from the radio base station;
A first delivery confirmation information transmitting unit that transmits first delivery confirmation information indicating a reception result of the physical channel to which the timing adjustment command is transmitted to the radio base station;
A second delivery confirmation information transmitting unit that transmits second delivery confirmation information indicating a reception result of the timing adjustment command;
When receiving the timing adjustment command from the radio base station, the radio base station is configured to transmit the first delivery confirmation information and the second delivery confirmation information to the radio base station. Mobile station.

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