JP2012191326A - Communication apparatus and data retransmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform data transmission with low delay even when a memory size is suppressed, and also to prevent the repetition of retransmission.SOLUTION: A MAC processing part 101 receives reception data constituted of multiple data units. A loss detection part 111 detects loss data which is lost among the reception data input from the MAC processing part 101. When the loss detection part 111 detects multiple pieces of loss data, a timer control part 113 sets a predetermined monitor time whenever the loss data are detected. When the loss data are not received within each monitor time which is set by the timer control part 113, a STATUS PDU generation part 114 generates STATUS PDUs including the sequence numbers (SN) of the loss data in order to request the retransmission of the loss data.

Description

  The present invention relates to a communication apparatus and a data retransmission method, and more particularly to a communication apparatus that performs processing in layer 2 of a communication system such as LTE (Long Term Evolution) and a data retransmission method thereof.

  The LTE system has been standardized as an access method for mobile communication systems. In this system, in order to reduce the memory size, the MAC sublayer function and the RLC sublayer function in layer 2 processing are partially integrated. That is, in the LTE system, data rearrangement processing (Reordering processing) in the MAC layer data retransmission function (HARQ: Hybrid ARQ) and data rearrangement processing in the RLC layer data retransmission function are integrated (for example, Non-Patent Document 1). Thereby, in the LTE system, the data rearrangement process is not performed in the MAC layer but in the RLC layer.

  Specifically, in the MAC layer, after the received data is HARQ combined, the data that is OK in CRC (Cyclic Redundancy Check) is passed to the RLC layer. In the RLC layer, the reception window is controlled according to SN (Sequence Number) added to the header. At this time, if data loss is found in the RLC layer, a retransmission request is made to the RLC layer of the communication partner.

  However, since the RLC layer has a function equivalent to the rearrangement processing of the MAC layer, the retransmission request is made after waiting for completion of the retransmission in the MAC layer without immediately making a retransmission request. That is, in the RLC layer, after a predetermined time measured by a timer (t-Reordering timer) has elapsed, the missing SN is notified to the communication partner RLC layer.

  Retransmission control based on the 3GPP specifications when data loss is detected in the conventional RLC layer will be described in detail with reference to FIG. FIG. 1 is a diagram illustrating a data retransmission method when data loss is detected in a conventional RLC layer.

  As shown in FIG. 1, in the conventional retransmission control, when SN = 1 data is received in the RLC layer, it is detected that SN = 0 data is lost, and a timer (t-Reordering timer) is started. If the data of SN = 0 is not received before the monitoring time T1 measured by this timer expires, information “NACK SN = 0” is put in the STATUS PDU and transmitted to the opposite RLC. Here, since the monitoring time T1 is set to wait for the completion of retransmission in the MAC layer, the monitoring time T1 is set to be equal to or greater than a value obtained by multiplying the HARQ RTT and the maximum number of retransmissions.

  Conventionally, when a plurality of data is missing while the timer is running (SN = 0 and SN = 2 in FIG. 1), measurement is started when the first missing data (SN = 0) is detected. After the monitoring time # 10 expired, measurement for the second missing data (SN = 2) is started. Therefore, conventionally, when a plurality of data whose reception timings are close to each other is lost, the monitoring time # 10 at which the measurement is started when the first missing data is detected expires, and the monitoring time # 11 at which the measurement is started thereafter is Do not request retransmission of second and subsequent missing data until it expires.

3GPP TS36.322 V8.8.0 (2010-08)

  However, in the conventional retransmission control, there is a problem that the amount of delay of received data increases because retransmission is delayed when a plurality of pieces of data with similar reception timing are lost. In addition, when adopting a method of discarding when the amount of data in the buffer exceeds a predetermined value, the amount of data discarded increases as the delay amount increases. As a result, since the discarded data is retransmitted, there is a problem that the delay amount of the received data further increases. In addition, when adopting a method of discarding when the amount of data in the buffer exceeds a predetermined value, the retransmitted data is also discarded, so that the data order is not arranged at the time of data rearrangement. As a result, there is a problem that retransmission is repeated and the number of retransmissions reaches the upper limit at the communication partner, so that the RRC connection is reconnected and it takes time to recover.

  An object of the present invention is to provide a communication apparatus and a data retransmission method capable of performing low-delay data transmission even when the memory size is suppressed and preventing repetition of retransmission.

  The communication apparatus according to the present invention includes a receiving unit that sequentially receives a plurality of data units, a detecting unit that detects missing data among the data units received by the receiving unit, and a plurality of units by the detecting unit. When the missing data is detected, a setting means for setting a predetermined monitoring time each time the detection is performed, and when the missing data is not received within each of the monitoring times set by the setting means, the missing data A retransmission request means for sequentially requesting retransmission after the monitoring time has elapsed.

  A data retransmission method according to the present invention is a data retransmission method in a communication apparatus, wherein a reception step of sequentially receiving a plurality of data units, and missing data missing from the data units received by the reception step are detected. A detection step, a setting step for setting a predetermined monitoring time each time the detection is performed when a plurality of the missing data is detected by the detection step, and the loss within each of the monitoring times set by the setting step A retransmission requesting step for sequentially requesting retransmission of the missing data after the elapse of each monitoring time when data is not received.

  According to the present invention, it is possible to perform low-delay data transmission even when the memory size is suppressed, and to prevent repetition of retransmission.

The figure which shows the data resending method when the loss of data is detected in the conventional RLC layer The block diagram which shows the structure of the communication apparatus which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the timer control part in Embodiment 1 of this invention. The figure which shows the data resending method in the communication apparatus which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the communication apparatus which concerns on Embodiment 2 of this invention. The block diagram which shows the structure of the defect | deletion detection part in Embodiment 2 of this invention. The figure which shows the data resending method in the communication apparatus which concerns on Embodiment 2 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 2 is a block diagram showing a configuration of communication apparatus 100 according to Embodiment 1 of the present invention.

  The communication apparatus 100 includes a MAC processing unit 101, an RLC processing unit 102, and a PDCP processing unit 103. Further, the communication device 100 can be applied to a wireless terminal device or a wireless base station device.

  The MAC processing unit 101 as a receiving unit performs MAC layer processing on received data received from a communication partner (not shown) and outputs the data to the RLC processing unit 102. Further, the MAC processing unit 101 performs MAC layer processing on the transmission data input from the RLC processing unit 102 and transmits the data to the communication partner. Received data is composed of a plurality of data units. Therefore, the MAC processing unit 101 receives data units.

  RLC processing section 102 performs RLC layer processing on the received data input from MAC processing section 101 and outputs the result to PDCP processing section 103. In addition, when the reception data input from the MAC processing unit 101 is missing, the RLC processing unit 102 performs retransmission control of the missing reception data. At this time, since the RLC processing unit 102 can identify each data unit by SN, retransmission control is performed in units of data units. Further, the RLC processing unit 102 performs RLC processing on the transmission data input from the PDCP processing unit 103 and outputs the transmission data to the MAC processing unit 101.

  The PDCP processing unit 103 performs PDCP layer processing on the reception data input from the RLC processing unit 102 and outputs the result as reception data. The PDCP processing unit 103 performs PDCP layer processing on the input transmission data and outputs the result to the RLC processing unit 102.

  Next, details of the configuration of the RLC processing unit 102 will be described with reference to FIG.

  In FIG. 2, the defect detection unit 111 constitutes detection means. The timer control unit 113 constitutes setting means. The STATUS PDU creation unit 114 and the data creation unit 115 constitute a retransmission request unit.

  The defect detection unit 111 stores the reception data input from the MAC processing unit 101 in the reception buffer. Further, the missing detection unit 111 performs a rearrangement process on the received data stored in the reception buffer, and detects missing data that is missing from the received data. In addition, when the missing data is not detected, the missing data detector 111 outputs the rearranged received data to the SDU generator 112. In addition, when detecting missing data, the missing detection unit 111 notifies the timer control unit 113 of a missing state of received data each time detection is performed. In addition, when detecting missing data, the missing detection unit 111 notifies the STATUS PDU creation unit 114 of the SN of the missing data every time it is detected.

  The SDU generation unit 112 generates an SDU (service data unit) from the rearranged received data input from the loss detection unit 111 and outputs the SDU (service data unit) to the PDCP processing unit 103.

  The timer control unit 113 manages the timer and sets a monitoring time for monitoring the reception of the missing data every time a missing situation is input from the missing detection unit 111. In addition, when the monitoring time measured by the timer expires, the timer control unit 113 outputs a STATUS PDU creation trigger to the STATUS PDU creation unit 114. Details of the configuration of the timer control unit 113 will be described later.

  The STATUS PDU creation unit 114 creates a STATUS PDU including a single SN input from the defect detection unit 111 when a trigger is input from the timer control unit 113. Further, the STATUS PDU creation unit 114 outputs the created STATUS PDU to the data creation unit 115.

  The data creation unit 115 uses the transmission data input from the PDCP processing unit 103 or the STATUS PDU input from the STATUS PDU creation unit 114 to generate transmission data. Further, the data creation unit 115 outputs the created transmission data to the MAC processing unit 101.

  Next, the configuration of the timer control unit 113 will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the timer control unit 113.

  A plurality of timer units 201 are provided, measure the time according to the measurement start instruction from the timer management unit 202, and notify the timer management unit 202 when the measurement is completed.

  The timer management unit 202 selects one or a plurality of timer units 201 in accordance with the defect status input from the defect detection unit 111, and instructs the selected timer unit 201 to start measurement. When the timer management unit 202 receives a notification from the timer unit 201 that the measurement time has expired, the timer management unit 202 instructs the trigger generation unit 203 to generate a trigger.

  When receiving a trigger generation instruction from the timer management unit 202, the trigger generation unit 203 generates a STATUS PDU creation trigger and outputs the generated trigger to the STATUS PDU creation unit 114.

  Next, a data retransmission method in communication apparatus 100 will be described using FIG. FIG. 4 is a diagram illustrating a data retransmission method in the communication apparatus 100.

  The loss detection unit 111 of the communication device 100 acquires data of SN = 1 and detects that the data of SN = 0 is lost. Accordingly, the timer control unit 113 selects and starts timer # 1 of the timer unit 201. Thereafter, the loss detection unit 111 of the communication apparatus 100 acquires data of SN = 3 and detects that the data of SN = 2 is lost. Thereby, the timer control unit 113 selects the timer # 2 different from the timer # 1 of the timer unit 201, and starts the timer # 2 without waiting for the measurement of the timer # 1 to expire. That is, the timer control unit 113 starts a plurality of timers simultaneously. When the monitoring time # 401 measured by the timer # 1 expires, the STATUS PDU creation unit 114 creates a STATUS PDU including SN = 0 in order to notify the communication partner of the loss of SN = 0. Then, the communication device 100 transmits the created STATUS PDU to the communication partner. Thereafter, when the monitoring time # 402 measured by the timer # 2 expires, the STATUS PDU creation unit 114 creates a STATUS PDU including SN = 2 in order to notify the communication partner of the loss of SN = 2. Then, the communication device 100 transmits the created STATUS PDU to the communication partner. The monitoring time # 401 and the monitoring time # 402 are each set to wait for the completion of retransmission in the MAC layer, and are set to a value obtained by multiplying the HARQ RTT and the maximum number of retransmissions, for example.

  As described above, in the present embodiment, it is possible to immediately request the communication partner to retransmit data lost in the RLC layer. Thus, according to the present embodiment, low-delay data transmission can be performed even when the memory size is suppressed, and repetition of retransmission can be prevented, and throughput can be improved.

  Further, according to the present embodiment, the data rearrangement waiting time can be shortened, so that the amount of data to be stored on the receiving side can be reduced, and the capacity of the RLC layer buffer can be reduced. be able to.

  In the present embodiment, low-delay data transmission is realized only in the communication device 100. However, the present invention is not limited to this, and the present invention is also applicable to low-delay data transmission in the communication partner in addition to the communication device 100. be able to. As a result, the time until the STATUS Report is returned is shortened, so that the capacity of the buffer on the opposite side can also be reduced.

(Embodiment 2)
FIG. 5 is a block diagram showing a configuration of communication apparatus 500 according to Embodiment 2 of the present invention.

  A communication device 500 shown in FIG. 5 has a defect detection unit 511 instead of the defect detection unit 111 and timer control instead of the timer control unit 113, compared to the communication device 100 according to the first embodiment shown in FIG. Part 512. In FIG. 5, parts having the same configuration as in FIG.

  The communication apparatus 500 includes a MAC processing unit 101, a PDCP processing unit 103, and an RLC processing unit 501. Further, the communication device 500 can be applied to a wireless terminal device or a wireless base station device.

  The MAC processing unit 101 performs MAC layer processing on received data received from a communication partner (not shown) and outputs the data to the RLC processing unit 501. Further, the MAC processing unit 101 performs MAC layer processing on the transmission data input from the RLC processing unit 501, and transmits the data to the communication partner. Received data is composed of a plurality of data units. Therefore, the MAC processing unit 101 receives data units.

  The RLC processing unit 501 performs RLC layer processing on the received data input from the MAC processing unit 101 and outputs the result to the PDCP processing unit 103. In addition, when the reception data input from the MAC processing unit 101 is missing, the RLC processing unit 501 performs retransmission control of the missing reception data. At this time, since the RLC processing unit 501 can identify each data unit by SN, it performs retransmission control in units of data units. Also, the RLC processing unit 501 performs RLC processing on the transmission data input from the PDCP processing unit 103 and outputs the transmission data to the MAC processing unit 101.

  PDCP processing section 103 performs PDCP layer processing on the reception data input from RLC processing section 501 and outputs the result as reception data. Further, PDCP processing section 103 performs PDCP layer processing on the input transmission data and outputs the result to RLC processing section 501.

  Next, details of the configuration of the RLC processing unit 501 will be described with reference to FIG.

  The defect detection unit 511 stores the reception data input from the MAC processing unit 101 in the reception buffer. The missing detection unit 511 performs a rearrangement process on the received data stored in the reception buffer, and detects missing data that is missing from the received data. In addition, when missing data is not detected, the missing detection unit 511 outputs the rearranged received data to the SDU generation unit 112. In addition, the loss detection unit 511 instructs the timer control unit 512 to measure time when the loss data is detected. Further, when the missing data is detected, the missing detector 511 notifies the STATUS PDU creator 114 of the SN of the missing data according to the empty area of the reception buffer, or the reception received from the MAC processor 101. Discard data and perform flow control. Details of the configuration of the defect detection unit 511 will be described later.

  The SDU generation unit 112 generates an SDU (service data unit) from the rearranged received data input from the loss detection unit 511 and outputs the SDU (service data unit) to the PDCP processing unit 103.

  The timer control unit 512 measures time according to the time measurement instruction from the defect detection unit 511. In addition, the timer control unit 512 outputs a STATUS PDU creation trigger to the STATUS PDU creation unit 114 when the time measurement by the timer has expired.

  When a trigger is input from the timer control unit 512, the STATUS PDU creation unit 114 creates a STATUS PDU including the SN input from the loss detection unit 511. Further, the STATUS PDU creation unit 114 outputs the created STATUS PDU to the data creation unit 115.

  Next, the structure of the defect | deletion detection part 511 is demonstrated using FIG. FIG. 6 is a block diagram illustrating a configuration of the defect detection unit 511.

  When the reception control unit 601 does not receive the reception control notification from the flow control unit 605, the reception control unit 601 stores the reception data input from the MAC processing unit 101 in the reception buffer 602. In addition, when receiving a reception control notification from the flow control unit 605, the reception control unit 601 determines whether or not the RLC processing unit 501 processes the reception data input from the MAC processing unit 101. In addition, when it is determined that the RLC processing unit 501 performs processing, the reception control unit 601 outputs the SN of the reception data input from the MAC processing unit 101 to the STATUS PDU creation unit 114. In addition, when it is determined that the RLC processing unit 501 does not process the reception control unit 601, the reception data input from the MAC processing unit 101 is discarded. Note that a method for determining whether or not to perform processing in the RLC processing unit 501 will be described later.

  The reception buffer 602 stores the reception data input from the reception control unit 601 for rearrangement processing.

  The rearrangement unit 603 extracts the received data stored in the reception buffer 602 from the reception buffer 602 and performs a rearrangement process. Further, rearrangement section 603 detects the presence or absence of missing data in the rearranged received data. Further, the rearrangement unit 603 outputs the rearranged reception data to the SDU generation unit 112 when it detects that there is no loss of reception data. In addition, when the rearrangement unit 603 detects that the received data is missing, the rearrangement unit 603 notifies the STATUS PDU creation unit 114 of the missing single SN and instructs the timer control unit 512 to start measuring time. .

  The depletion detection unit 604 notifies the flow control unit 605 of a flow control notification when detecting that the free area of the reception buffer 602 has become equal to or less than the threshold value.

  When the flow control unit 605 receives a flow control notification from the depletion detection unit 604, the flow control unit 605 notifies the reception control unit 601 of an acceptance control notification.

  Next, a data retransmission method in communication apparatus 500 will be described using FIG. FIG. 7 is a diagram illustrating a data retransmission method in the communication apparatus 500.

  The loss detection unit 511 of the communication device 500 acquires data of SN = 1 and detects that the data of SN = 0 is lost. Thereby, the timer control part 512 starts a timer. Thereafter, the loss detection unit 511 of the communication device 500 acquires data of SN = 3 and detects that the data of SN = 2 is lost. Also, the timer control unit 512 outputs a trigger to the STATUS PDU creation unit 114 when the monitoring time # 701 measured by the timer expires. Thereby, the STATUS PDU creation unit 114 creates a STATUS PDU including SN = 0 in order to notify the communication partner of the data loss of SN = 0. In addition, the communication device 500 transmits the created STATUS PDU to the communication partner. Thereafter, the timer control unit 512 starts the timer again because the data of SN = 2 is missing. Further, the timer control unit 512 outputs a trigger to the STATUS PDU creation unit 114 when the monitoring time # 702 measured by the timer expires. As a result, the STATUS PDU creation unit 114 creates a STATUS PDU including SN = 2 in order to notify the communication partner of the data loss of SN = 2. In addition, the communication device 500 transmits the created STATUS PDU to the communication partner. Thereafter, new data is received until data with SN = 2 is retransmitted.

  At this time, the flow control unit 605 of the loss detection unit 511 sends a flow control notification for flow control to the reception control unit 601 of the loss detection unit 511 when the amount of data stored in the reception buffer 602 exceeds a threshold value. Notify Thereby, the acceptance control unit 601 determines whether or not the received new data is processed in the RLC processing unit 501. In other words, the reception control unit 601 determines that the RLC processing unit 501 does not process received data other than SN = 2 waiting for retransmission. As a result, the acceptance control unit 601 stops accepting received data other than SN = 2 and starts discarding the acquired received data. On the other hand, the reception control unit 601 determines that the RLC processing unit 501 processes received data of SN = 2 waiting for retransmission. As a result, the reception control unit 601 outputs the reception data of SN = 2 to the reception buffer 602 when acquiring the reception data of SN = 2. Accordingly, the loss of received data with SN = 2 is eliminated, and the received data can be transferred to the upper layer by arranging the order. Accordingly, the loss detection unit 511 can release the reception buffer 602 and acquire the next new reception data. The monitoring time # 701 and the monitoring time # 702 are each set to wait for the completion of retransmission in the MAC layer, and are set to a value obtained by multiplying the HARQ RTT and the maximum number of retransmissions, for example.

  Here, when receiving the flow control notification, the reception control unit 601 may determine that all the reception data waiting for retransmission is processed in the RLC processing unit 501, or only the oldest reception data waiting for retransmission is RLC processed. It may be determined that processing is performed in the unit 501. In addition, when receiving the flow control notification, the reception control unit 601 may determine that only the received control data (STATUS PDU) is processed in the RLC processing unit 501. At this time, the communication apparatus 500 may retransmit data to the communication partner.

  Thus, in this embodiment, when the reception buffer is exhausted, only reception data waiting for retransmission is accepted. Thus, according to the present embodiment, low-delay data transmission can be performed even when the memory size is suppressed, and repetition of retransmission can be prevented, and throughput can be improved.

  Also, in this embodiment, when the reception buffer is exhausted, only control data is accepted, and even if one of the uplink and the downlink is in the flow control state, the other line that is not in the flow control state Receive control information. Thereby, according to this Embodiment, the communication of the line | wire which is not in a flow control state can be continued.

  In the present embodiment, the low-delay data transmission function is installed only in the communication device 500. However, the present invention is not limited to this, and the low-latency data transmission function is installed in the communication partner in addition to the communication device 500. can do. As a result, the time until the STATUS Report is returned can be shortened, and the buffer capacity of the communication partner can also be reduced.

  In this embodiment, the RLC processing unit detects the reception buffer exhaustion and performs flow control. However, the present invention is not limited to this, and flow control notification may be received from an upper layer. .

  The communication apparatus and the data retransmission method according to the present invention are suitable for performing processing in layer 2 of a communication system such as LTE (Long Term Evolution).

DESCRIPTION OF SYMBOLS 100 Communication apparatus 101 MAC process part 102 RLC process part 103 PDCP process part 111 Missing detection part 112 SDU production | generation part 113 Timer control part 114 STATUS PDU creation part 115 Data creation part

Claims (4)

Receiving means for sequentially receiving a plurality of data units;
Detecting means for detecting missing data among the data units received by the receiving means;
A setting means for setting a predetermined monitoring time each time the detection is performed when a plurality of the missing data is detected by the detection means;
Retransmission request means for sequentially requesting retransmission of the missing data after each of the monitoring times when the missing data is not received within each of the monitoring times set by the setting means;
A communication apparatus comprising:   A wireless terminal device comprising the communication device according to claim 1.   A radio base station apparatus comprising the communication apparatus according to claim 1. A data retransmission method in a communication device,
A receiving step for sequentially receiving a plurality of data units;
A detecting step for detecting missing data among the data units received by the receiving step;
A setting step of setting a predetermined monitoring time for each detection when a plurality of the missing data is detected by the detection step;
When not receiving the missing data within each monitoring time set by the setting step, a retransmission request step for sequentially requesting retransmission of the missing data after each monitoring time has elapsed,
A data retransmission method comprising:

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