JP2009164832A - Method for establishing synchronization and mobile station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To transit an out-of-synchronization mobile station to a synchronization establishment state even if the mobile station does not generate uplink user data which should be transmitted to a wireless base station eNB, and does not receive an RACH transmission request transmitted by the wireless base station eNB. <P>SOLUTION: A method for establishing synchronization comprises a step where a mobile station UE is transited to an out-of-synchronization state if it does not receive a TA within a predetermined period of time in a synchronization establishment state, a step where the mobile station UE transmits predetermined information through an RACH for a wireless base station eNB if the mobile station UE receives downlink information addressed thereto through DL-SCH in the out-of-synchronization state, a step where the wireless base station eNB transmits the TA for the mobile station UE according to the predetermined information received through the RACH, and a step where the mobile station UE is transited to a first state by establishing synchronization in an uplink based on the received TA. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  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.

  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 the mobile station UE in an out-of-synchronization state is a case where uplink user data to be transmitted to the radio base station eNB is not generated, and An object of the present invention is to provide a synchronization establishment method and a mobile station that enable a transition to a synchronization establishment state even when a RACH transmission request transmitted by a radio base station eNB is not received.

  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, If the mobile station does not receive the timing adjustment command within a predetermined period in the first state in which synchronization in the uplink is established, the mobile station enters a second state in which synchronization in the uplink is not established. When the mobile station receives the downlink information addressed to the mobile station via the downlink shared channel in the second state, the process A transits and the random access channel is transmitted to the radio base station. And transmitting the predetermined information via the random access channel to the mobile station according to the predetermined information received via the random access channel. Then, the step C of transmitting a timing adjustment command, and the mobile station establishes synchronization in the uplink based on the timing adjustment command transmitted by the radio base station in the step C, The gist of the present invention is to include the step D of transition to the first 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 mobile station configured to establish uplink synchronization with the radio base station based on a timing adjustment command transmitted from the radio base station. The synchronization is configured to manage whether the state of the mobile station is a first state in which synchronization in the uplink is established or a second state in which synchronization in the uplink is not established When the state management unit and the state of the mobile station are the second state, and when downlink information addressed to the mobile station is received via a downlink shared channel, the wireless base station A random access channel transmission unit configured to transmit predetermined information via a random access channel, and the synchronization state management unit includes the mobile station When the state is the first state and the timing adjustment command is not received within a predetermined period, the mobile station is configured to transition to the second state, The synchronization state management unit detects the timing when the state of the mobile station is the second state and when the timing adjustment command transmitted according to the predetermined information is received by the radio base station. The gist of the invention is that the state of the mobile station is shifted to the first state by establishing synchronization in the uplink based on an adjustment command.

  In the second aspect of the present invention, comprising the uplink synchronization timer management unit configured to restart the uplink synchronization timer for measuring the predetermined period each time the timing adjustment command is received, The synchronization state management unit may be configured to transition the state of the mobile station to the second state when the uplink synchronization timer expires.

  As described above, according to the present invention, when the mobile station UE that is out of synchronization has not generated uplink user data to be transmitted to the radio base station eNB, and the radio base station eNB Even when a transmitted RACH transmission request is not received, a synchronization establishment method and a mobile station that can make a transition to a synchronization establishment state can be provided.

(Configuration of mobile communication system according to the first embodiment of the present invention)
With reference to FIG.1 and FIG.2, the structure of the mobile communication system which concerns on the 1st Embodiment of this invention is demonstrated.

  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 receiver 11, a synchronization state manager 12, an uplink synchronization timer manager 13, a DL-SCH receiver 14, a RACH transmitter 15, and a PUCCH transmitter. 16.

The TA reception 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 a 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 sets the state of the mobile station UE to “synchronization” when the state of the mobile station UE is “synchronization established state” and TA is not received within a predetermined period. It is configured to make a transition to the “out of 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 DL-SCH receiving unit 14 is configured to receive downlink information (for example, downlink user data) via the DL-SCH.

  The PUCCH transmission unit 16 transmits the acknowledgment information (ACK / NACK) for the PDSCH to which the DL-SCH received by the DL-SCH reception unit 14 is mapped to the radio base station eNB via the PUCCH. It is configured.

  The RACH transmission unit 15 is configured to transmit predetermined information to the radio base station eNB via the RACH.

  Specifically, the RACH transmission unit 15 is configured to provide downlink information (for example, downlink user data or the like) addressed to the mobile station UE via the DL-SCH when the state of the mobile station UE is “out of synchronization”. ) Is received, the predetermined information is transmitted to the radio base station eNB via the RACH.

(Operation of the mobile communication system according to the first embodiment of the present invention)
With reference to FIG.3 and FIG.4, operation | movement of the mobile communication system which concerns on the 1st Embodiment of this invention is demonstrated.

  First, with reference to FIG. 3, an operation in which the mobile station UE establishes uplink synchronization with the radio base station eNB in the mobile communication system according to the present embodiment will be described.

  As illustrated in FIG. 3, when the mobile station UE is in the “synchronization established state” in which synchronization in the uplink is established (step S151), the radio base station eNB transmits to the mobile station UE in step S152. Whether the received TA has been received or not is monitored.

  When the mobile station UE receives the TA transmitted by the radio base station eNB, in step S153, the mobile station UE adjusts the transmission timing in the uplink to thereby synchronize in 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 S154.

  If it is determined that the uplink synchronization timer has not expired, the operation returns to step S152. If it is determined that the uplink synchronization timer has expired, the operation proceeds to step S155. The mobile station UE transits to an “out of synchronization state” where uplink synchronization is not established.

  In step S156, the mobile station UE that has transitioned to the “out of synchronization state” determines whether or not uplink user data to be transmitted to the radio base station eNB has occurred, and is addressed to the mobile station UE by the radio base station eNB. Whether or not downlink information (eg, downlink user data) addressed to the mobile station UE is received via the DL-SCH. To do.

  When it is determined that uplink user data to be transmitted to the radio base station eNB is not generated, and when a RACH transmission request transmitted by the radio base station eNB is not received, and DL− When it is determined that the downlink information addressed to the mobile station UE is not received via the SCH, this operation repeats step S156.

  On the other hand, when it is determined that uplink user data to be transmitted to the radio base station eNB has occurred, or when it is determined that a RACH transmission request transmitted by the radio base station eNB has been received, or DL- When it is determined that downlink information addressed to the mobile station UE is received via the SCH, the operation proceeds to step S157.

  In step S157, the mobile station UE transmits predetermined information to the radio base station eNB via the RACH.

  Upon receiving the TA transmitted by the radio base station eNB in step S158, the mobile station UE adjusts the uplink transmission timing and restarts the uplink synchronization timer in step S159. Transition to "state". Here, the radio base station eNB is configured to generate and transmit TA based on the measurement result for the predetermined signal transmitted via the uplink by the mobile station UE in step S157.

  2ndly, with reference to FIG. 4, the whole operation | movement of the mobile communication system which concerns on this embodiment is demonstrated.

  As illustrated in FIG. 4, when the radio base station eNB transmits TA to the mobile station UE in step S201, the mobile station UE transmits transmission timing in the uplink based on the received TA in step S202. Is maintained in the uplink synchronization established with the radio base station eNB, and the uplink synchronization timer is restarted.

  Similarly, when the radio base station eNB transmits a TA to the mobile station UE in step S203, the mobile station UE adjusts the transmission timing in the uplink based on the received TA in step S204. Thus, the uplink synchronization established with the radio base station eNB is maintained and the uplink synchronization timer is restarted.

  However, although the radio base station eNB transmits TA to the mobile station UE in step S205, the mobile station UE fails to receive the TA, and in step S206, the uplink synchronization timer is set. When it expires, the mobile station UE transits to the “out of synchronization state”.

  Thereafter, when the mobile station UE receives the downlink information transmitted via the DL-SCH by the radio base station eNB when the mobile station UE transitions to the “out of synchronization state” in step S207, Even when the uplink user data to be transmitted has not occurred and the RACH transmission request transmitted by the radio base station eNB has not been received, in step S208, for the radio base station eNB, Predetermined information is transmitted via the RACH.

  In step S209, the radio base station eNB generates and transmits a TA based on the measurement result for the predetermined information transmitted via the RACH by the mobile station UE in step S208.

  Here, the mobile station UE establishes uplink synchronization with the radio base station eNB based on the received TA, and transitions to the “synchronization established state”.

  After that, the radio base station eNB receives delivery confirmation information for the above-described downlink information (specifically, delivery confirmation information for the PDSCH to which the above-described DL-SCH is mapped) even after a predetermined period has elapsed. In step S210, the downlink information is retransmitted via the DL-SCH.

  In step S211, since the mobile station UE is in the “synchronization established state”, the mobile station UE may transmit a delivery confirmation response (ACK / NACK) for the PDSCH to which the DL-SCH is mapped to the radio base station eNB. it can.

(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 in the “out of synchronization state” has no uplink user data to be transmitted to the radio base station eNB, and the radio base station Even when the RACH transmission request transmitted by the eNB is not received, when downlink information addressed to the mobile station UE is received via the DL-SCH, the transition to the “synchronization establishment state” may occur. Therefore, retransmission of redundant downlink information can be prevented, 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. 3 is a flowchart showing an operation of the mobile station according to the first embodiment of the present invention. It is a figure for demonstrating operation | movement of the mobile communication system which concerns on the 1st Embodiment of this 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 UE ... mobile station 11 ... TA receiver 12 ... synchronization state manager 13 ... uplink synchronization timer manager 14 ... DL-SCH receiver 15 ... RACH transmitter 16 ... PUCCH transmitter

Claims (4)

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,
If the mobile station does not receive the timing adjustment command within a predetermined period in the first state in which synchronization in the uplink is established, the mobile station enters a second state in which synchronization in the uplink is not established. A transition process A;
When the mobile station receives downlink information addressed to the mobile station via a downlink shared channel in the second state, the mobile station transmits predetermined information to the radio base station via a random access channel. Transmitting process B;
A step C in which the radio base station transmits a timing adjustment command to the mobile station according to the predetermined information received via the random access channel;
The mobile station comprises a step D of transitioning to the first state by establishing synchronization in the uplink based on the timing adjustment command transmitted by the radio base station in the step C; A characteristic synchronization establishment method. 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 mobile station configured to establish uplink synchronization with the radio base station based on a timing adjustment command transmitted from the radio base station,
Synchronization state configured to manage whether the state of the mobile station is a first state in which synchronization in the uplink is established or a second state in which synchronization in the uplink is not established The management department,
When the mobile station is in the second state, and when downlink information addressed to the mobile station is received via a downlink shared channel, a random access channel is transmitted to the radio base station. A random access channel transmitter configured to transmit predetermined information via
The synchronization state management unit sets the state of the mobile station to the second state when the state of the mobile station is the first state and when the timing adjustment command is not received within a predetermined period. Configured to transition to a state,
The synchronization state management unit detects the timing when the state of the mobile station is the second state and when the timing adjustment command transmitted according to the predetermined information is received by the radio base station. A mobile station configured to shift the state of the mobile station to the first state by establishing synchronization in the uplink based on an adjustment command. An uplink synchronization timer manager configured to restart an uplink synchronization timer for measuring the predetermined period each time the timing adjustment command is received;
The mobile station according to claim 3, wherein the synchronization state management unit is configured to transition the state of the mobile station to the second state when the uplink synchronization timer expires.

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