JP2011061364A - Transmission device and transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To normally transmit user data by correctly identifying PDCP (Packet Data Convergence Protocol) SDU (Service Data Unit) to be re-transmitted and PCDP SDU to be abandoned by using PDCP status report transmitted after handover. <P>SOLUTION: A determination part 108 receives control information indicating a sequence number of head data among data that are not received by a receiver when performing handover, determines data corresponding to the sequence number shown in control information from the head data among data whose transmission confirmation is not finished to tail end data among data which are transmitted before handover when the control information is received. A transmission instruction part 107 instructs transmission from the head data among data whose transmission confirmation is not completed to data equivalent to one cycle of sequence number, and does not instruct data transmission after the data equivalent to one cycle of the sequence number from the head data among data whose transmission confirmation is not finished. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmission apparatus and a transmission method.

  Currently, Long Term Evolution (hereinafter referred to as LTE), which is a next generation mobile communication system, is being studied in the Technical Specification Group Radio Access Network (TSG RAN) of the 3rd Generation Partnership Project (hereinafter referred to as 3GPP). In 3GPP LTE, a mobile terminal device (hereinafter referred to as UE: User Equipment) is connected to an E-UTRAN (Enhanced Universal Terrestrial Radio Access Network) composed of multiple base station devices (hereinafter referred to as eNB: Evolved Node B). Then, user data is transmitted and received. Here, user data between the UE and the eNB is controlled by layer 1 (physical layer) and layer 2 (data link layer) of a communication protocol used in 3GPP LTE. Layer 2 includes a MAC (Medium Access Control) layer that performs radio resource allocation control, an RLC (Radio Link Control) layer that controls radio links, data encryption / decryption, and packets during handover It is divided into a PDCP (Packet Data Convergence Protocol) layer that performs order control and the like.

  In addition, a communication path (hereinafter referred to as a radio bearer) is set in each PDCP layer of the UE and eNB at the start of communication. A plurality of radio bearers can be set, and a PDCP entity corresponding to each UE and eNB is generated for each radio bearer. Each PDCP entity holds control information for user data transmitted and received using a radio bearer.

  Radio bearers are classified into three. Specifically, the radio bearer transmits the user data in the RLC layer until a signaling radio bearer (SRB (Signaling Radio Bearer)) that transmits and receives layer 3 (RRC / NAS) communication control messages and user data delivery confirmation is obtained. Data radio bearer (DRB: Data Radio Bearer) in retransmission mode (RLC-AM (RLC-Acknowledge Mode)) and mode in which user data delivery is not confirmed in the RLC layer (RLC-UM (RLC-Unacknowledge Mode)) Data radio bearer (DRB).

  Moreover, UE performs the hand-over which switches a connection destination eNB according to a movement of an own apparatus. In the RLC-AM described above, the UE and eNB need to perform control so that user data is not lost before and after handover. However, in the RLC layer that performs retransmission control of user data, the communication state is reset before and after handover. Therefore, state holding before and after handover and data retransmission after handover are performed in the PDCP layer, which is an upper layer of the RLC layer (see, for example, Non-Patent Document 1).

  Specifically, the PDCP entity performs retransmission of user data (hereinafter referred to as PDCP SDU (Service Data Unit)) that has not been acknowledged at the RLC layer before handover (delivery confirmation has not been completed) after handover. . Further, after the handover, a control PDU (Protocol Data Unit) (hereinafter referred to as a PDCP status report) is transmitted between PDCP entities arranged in each of the UE and the eNB. As a result, it is possible to notify the opposite PDCP entity of the PDCP SDU whose delivery has been confirmed before the handover. Then, the PDCP entity that has received the PDCP status report discards the PDCP SDU for which delivery has been confirmed indicated in the PDCP status report, and does not transmit the PDCP SDU. That is, according to the PDCP status report notification, PDCP SDUs that have been received by the PDCP entity on the receiving side before handover but have not yet been acknowledged by the PDCP entity on the transmitting side, that is, data that does not need to be retransmitted. It is possible to reduce unnecessary retransmission.

  Fig. 1 shows the format of PDCP status report. As shown in FIG. 1, the PDCP status report includes FMS (First Missing PDCP SN, FMS) indicating the sequence number (SN: Sequence Number) of the first PDCP SDU among the PDCP SDUs not received by the PDCP entity on the receiving side. 12 bits) and a Bitmap (variable length in multiples of 8 bits (1 octet)) indicating whether or not PDCP SDUs after FMS have been received in the PDCP entity on the receiving side. For example, the bitmap when the PDCP SDU has been received by the PDCP entity on the receiving side is set to ‘1’, and the bitmap when the PDCP SDU is not received is set to ‘0’.

  FIG. 2 shows the format of COUNT. As shown in FIG. 2, COUNT is a value composed of a PDCP SN indicating a sequence number assigned to each PDCP SDU and an HFN (Hyper Frame Number) indicating the number of rounds of the PDCP SN. . When the PDCP entity transmits one SDU, it increments the PDCP SN. The PDCP SN is a finite value (for example, 4096 PDCP SN = 0 to 4095), and when it reaches the maximum value, it becomes 0 next. At this time, HFN is incremented. COUNT is used as an input parameter for encryption processing and decryption processing in the PDCP entity on the transmission / reception side.

  When the PDCP entity on the transmitting side receives the PDCP status report from the PDCP entity on the receiving side, the PDCP SDU having a smaller COUNT value than the FMS included in the PDCP status report and the bitmap included in the PDCP status report are '1. PDCP SDUs that are ', that is, PDCP SDUs that have been received by the PDCP entity on the receiving side are discarded and not transmitted.

After the handover, the PDCP entity on the transmission side does not wait for the notification of the PDCP status report, and the first PDCP SDU (hereinafter referred to as this PDCP SDU) of the PDCP SDUs whose delivery confirmation has not been completed in the RLC layer before the handover. PDCP SNs are referred to as “First No Ack SN” in order. On the other hand, after the handover, the PDCP entity on the receiving side receives 2048 SDUs of PDCP SDUs from the FMS.
Can be received as a retransmission waiting reception window (Reordering window).

3GPP TS 36.323 V8.5.0, “Packet Data Convergence Protocol (PDCP) specification (Release 8),” March 2009

  However, although the PDCP status report (FIG. 1) described above includes an FMS indicating the first PDCP SN of PDCP SDUs not received by the PDCP entity on the receiving side, the HFN corresponding to that FMS is included. No information is included. Therefore, the HFN corresponding to FMS needs to be determined by the PDCP entity on the transmitting side that has received the PDCP status report.

  Hereinafter, this will be specifically described with reference to FIG. In the following description, as shown in FIG. 3, the PDCP SDU sequence number (PDCP SN) is 0 to 4095 (that is, 4096 SDUs). Also, the reordering window is half of 4096 SDUs corresponding to one sequence number (that is, all possible sequence numbers), that is, 2048 SDUs. Further, in FIG. 3, the first No Ack SN in the PDCP entity on the transmission side is set to HFN = 1 and SN = 4092, and the sequence number of the last PDCP among the PDCP SDUs that have been transmitted before the handover (hereinafter referred to as the sequence number) , Last Send SN) is set to HFN = 2 and SN = 4094. Further, the FMS included in the PDCP status report from the PDCP entity on the receiving side is assumed to be 4093.

  Therefore, the PDCP entity on the transmitting side is the FMS (in FIG. 3, in FIG. 3) between First No Ack SN (HFN = 1, SN = 4092 in FIG. 3) and Last Send SN (HFN = 2, SN = 4094 in FIG. 3). 4093) is present, and the HFN corresponding to the FMS is determined.

  However, before the handover, the interval between First No Ack SN and Last Send SN is a value corresponding to one PDCP SN round, that is, one round of the value that PDCP SN can take (0 to 4095 in FIG. 3). In the case above (for 4096 SDUs in FIG. 3), there is a possibility that a plurality of SNs matching the FMS exist. For example, in FIG. 3, the interval between First No Ack SN and Last Send SN is 4099 SDU apart (> 4096 SDU), and SN corresponding to FMS (4093) is SN = 4093 with HFN = 1, and There are two FMS candidates with SN = 4093 with HFN = 2. As a result, the PDCP entity on the transmission side cannot uniquely determine the HFN corresponding to the FMS.

  For example, in FIG. 3, a case will be described in which the first PDCP SDU among PDCP SDUs not received by the PDCP entity on the receiving side is HFN = 1 and SN = 4093. In this case, if the PDCP entity on the transmitting side erroneously determines that the HFN corresponding to FMS (4093) is 2, the PDCP entity on the transmitting side will receive a PDCP before the PDCP SDU with HFN = 2 and SN = 4093. It is determined that retransmission of SDU (PDCP SDU before HFN = 2, SN = 4092) is unnecessary. Therefore, the PDCP entity on the transmitting side has 4096 PDCP SDUs (PDCP SDUs that need to be retransmitted) from the PDCP SDU with HFN = 1 and SN = 4093 to the PDCP SDU with HFN = 2 and SN = 4092 shown in FIG. , It will be discarded after receiving PDCP status report.

  Also, the PDCP entity on the transmitting side retransmits in order from the PDCP SDU with HFN = 2 and SN = 4093 shown in FIG. 3, whereas the PDCP entity on the receiving side has the PDCP with HFN = 1 and SN = 4093 shown in FIG. It is possible to receive 2048 SDUs beginning with SDU as a Reordering window. Therefore, the PDCP SDU after HFN = 2 and SN = 4093 is erroneously received as the PDCP SDU after HFN = 1 and SN = 4093 in the PDCP entity on the receiving side. In this case, an HFN mismatch occurs between the PDCP entities on the transmission and reception sides, and the HFN mismatch continues thereafter. Therefore, even if COUNT including HFN is used as parameters for encryption processing and decryption processing, PDCP SDU cannot be normally transmitted due to HFN mismatch between transmission and reception.

  Next, for example, in FIG. 3, a case will be described in which the first PDCP SDU among the PDCP SDUs not received by the PDCP entity on the receiving side is HFN = 2 and SN = 4093. In this case, if the PDCP entity on the transmission side erroneously determines that the HFN corresponding to FMS (4093) is 1, the PDCP entity on the transmission side will have PDCP SDUs after the PDCP SDU with HFN = 1 and SN = 4093. Judge that resending is necessary. Therefore, the PDCP entity on the transmission side includes 4096 PDCP SDUs (PDCP SDUs that do not require retransmission) from PDCP SDUs with HFN = 1 and SN = 4093 to PDCP SDUs with HFN = 2 and SN = 4092 shown in FIG. It resends after receiving PDCP status report. That is, the PDCP entity on the transmission side transmits a PDCP SDU that does not require retransmission in vain.

  Also, the PDCP entity on the transmitting side retransmits in order from the PDCP SDU with HFN = 1 and SN = 4093 shown in FIG. 3, whereas the PDCP entity on the receiving side has the PDCP with HFN = 2 and SN = 4093 shown in FIG. It is possible to receive 2048 SDUs (not shown) starting from the SDU as a reordering window. Therefore, in the PDCP entity on the receiving side, PDCP SDUs after HFN = 1 and SN = 4093 are erroneously received as PDCP SDUs after HFN = 2 and SN = 4093. Also in this case, as described above, an HFN mismatch occurs between the PDCP entities on the transmitting and receiving sides, and the HFN mismatch continues thereafter. Therefore, even if COUNT including HFN is used as parameters for encryption processing and decryption processing, PDCP SDU cannot be normally transmitted due to HFN mismatch between transmission and reception.

  As described above, the PDCP entity may not be able to accurately identify the PDCP SDU to be retransmitted and the PDCP SDU to be discarded when receiving the PDCP status report after the handover. It may not be possible.

  An object of the present invention is to accurately identify a PDCP SDU to be retransmitted and a PDCP SDU to be discarded using a PDCP status report transmitted after a handover, and always transmit user data normally. It is to provide a transmission device and a transmission method.

  The transmission device of the present invention cyclically assigns a finite sequence number to data, transmits the data to which the sequence number and a number indicating the number of the sequence number are respectively assigned, and A transmission apparatus that retransmits data for which delivery confirmation has not been completed in a first layer before a handover in a second layer, which is a higher layer than the first layer, after the handover, Instructing the transmission of data at the same time, and instructing the retransmission of data in the second layer after the handover, and the sequence number of the head data of the data not received by the receiving device at the time of the handover Receiving means for receiving the control information indicating the first data of the data for which the delivery confirmation is not completed when the control information is received And specifying means for specifying data corresponding to the sequence number indicated in the control information until the tail data of the data that has been transmitted before the handover, the transmission instruction means, Instructs transmission from the top data of the data for which delivery confirmation has not been completed to data corresponding to one cycle of the sequence number, and the sequence number of one cycle from the top data of data for which the delivery confirmation has not been completed. A configuration is adopted in which transmission of data after data corresponding to minutes is not instructed.

  The transmission method of the present invention cyclically assigns a finite sequence number to data, transmits the data to which the sequence number and a number indicating the sequence number are respectively assigned, and A transmission method in a transmission apparatus for retransmitting data for which delivery confirmation has not been completed in a first layer before a handover in a second layer, which is a higher layer than the first layer, after the handover, A transmission instruction step for instructing the transmission of data in the first layer and instructing the retransmission of the data in the second layer after the handover, and the first data of the data not received by the receiving apparatus at the time of the handover A receiving step for receiving control information indicating the sequence number; and if the control information is received, the delivery confirmation is incomplete A specifying step of specifying data corresponding to the sequence number indicated in the control information from the first data of the data to the tail data of the data that has been transmitted before the handover. The transmission instruction step instructs transmission from the top data of the data for which delivery confirmation has not been completed to the data corresponding to one sequence number, and the top of the data for which delivery confirmation has not been completed. The data is not instructed to be transmitted after the data corresponding to one cycle of the sequence number.

  According to the present invention, it is possible to accurately identify the PDCP SDU to be retransmitted and the PDCP SDU to be discarded using the PDCP status report transmitted after the handover, and always transmit user data normally. .

Figure showing the format of PDCP status report Diagram showing the format of COUNT The figure which shows the subject of this invention The block diagram which shows the structure of the transmitter which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the receiver which concerns on Embodiment 1 of this invention. The figure which shows the transmission control process which concerns on Embodiment 1 of this invention. The figure which shows the subject which concerns on Embodiment 2 of this invention The figure which shows the transmission control process which concerns on Embodiment 2 of this invention.

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

(Embodiment 1)
The configuration of the transmission apparatus according to this embodiment is shown in FIG. 4 shows a configuration of a PDCP entity (that is, a PDCP entity on the transmission side) arranged in the PDCP layer. The transmission device 100 illustrated in FIG. 4 is, for example, a UE (mobile terminal device).

  In the following description, a finite sequence number (PDCP SN) is cyclically assigned to data. Further, the data transmitted by the transmitting apparatus 100 is assigned a COUNT composed of a sequence number (PDCP SN) and an HFN indicating how many times the sequence number is. Further, the transmission apparatus 100 retransmits data for which delivery confirmation has not been completed in the RLC layer before the handover, in the PDCP layer, which is a higher layer than the RLC layer, after the handover.

  In the transmission apparatus 100 illustrated in FIG. 4, the delivery confirmation management unit 101 performs delivery in the RLC layer before handover based on information indicating a delivery confirmed PDCP PDU input from a lower layer (for example, RLC layer) after handover. The first PDCP PDU among the PDCP PDUs corresponding to data that has not been confirmed is identified. And the delivery confirmation management part 101 manages First No Ack SN which is the sequence number of identified PDCP PDU. Then, delivery confirmation management section 101 outputs First No Ack SN to retransmission management section 102, transmission instruction section 107, and determination section 108.

  The retransmission management unit 102 manages retransmission of user data (PDCP SDU) after handover. Specifically, when nothing is input from the determination unit 108 (that is, when the device itself has not received the PDPC status report), the retransmission management unit 102 receives the First No Ack SN input from the delivery confirmation management unit 101. The PDCP SDU corresponding to is used as the retransmission start position. On the other hand, when the FMS and the HFN corresponding to the FMS are input from the determination unit 108, the retransmission management unit 102 sets the PDCP SDU corresponding to the FMS and the HFN as a retransmission start position. Then, retransmission management section 102 outputs the set SN (First No Ack SN or FMS) and the HFN corresponding to the SN to SN / HFN management section 103.

  SN / HFN management section 103 manages transmission data (PDCP SDU) input from higher layer to pre-encryption data buffer 104 and SN and HFN corresponding to the transmission data (PDCP SDU). That is, the SN / HFN management unit 103 assigns SN and HFN to the PDCP SDU input from the higher layer, and the SN and HFN corresponding to the PDCP SDU in the pre-encryption data buffer 104 are assigned to the encryption processing unit 105. Instruct to encrypt using COUNT (FIG. 2) generated from HFN. Also, the SN / HFN management unit 103 inputs SN and HFN information for starting retransmission when a handover occurs from the retransmission management unit 102, and instructs the encryption processing unit 105 to perform encryption processing.

  The pre-encryption data buffer 104 stores transmission data (PDCP SDU) input from an upper layer and outputs it to the encryption processing unit 105. The pre-encryption data buffer 104 discards the transmission data indicated in the data discard request input from the data discard processing unit 110.

  The encryption processing unit 105 performs encryption processing on transmission data input from the pre-encryption data buffer 104 using COUNT (SN and HFN) sequentially input from the SN / HFN management unit 103. Then, the encryption processing unit 105 outputs the encrypted transmission data to the encrypted data buffer 106.

  The encrypted data buffer 106 stores the transmission data input from the encryption processing unit 105 and outputs it to the transmission instruction unit 107. Further, the encrypted data buffer 106 discards the transmission data data indicated by the data discard request input from the data discard processing unit 110.

  The transmission instruction unit 107 attaches a PDCP PDU header to the transmission data to instruct the RLC layer to transmit, and manages the last SN / HFN instructed to transmit to the RLC layer. Specifically, the transmission instructing unit 107 instructs transmission of data corresponding to one sequence number from the First No Ack SN input from the delivery confirmation managing unit 101 before the handover. That is, the transmission instruction unit 107 does not instruct the transmission of PDCP SDU after the data corresponding to one sequence number from First No Ack SN. That is, the transmission instruction unit 107 determines the interval between the First No Ack SN and the Last Send SN that is the sequence number corresponding to the last transmission data of the transmission data that has been transmitted, as a sequence number (PDCP SN). The transmission of the PDCP SDU is instructed so as to be within one round of the possible value. For example, when a possible value for the sequence number (PDCP SN) is 0 to 4095, the transmission instruction unit 107 causes the PDCP so that the interval between the First No Ack SN and the Last Send SN is within 4096 SDU. Instructs transmission of SDU. Also, when the device itself receives a PDCP status report after handover, the transmission instruction unit 107 receives the PDCP SDU / PDCP PDU before the sequence number indicated in the FMS, and the PDCP SDU / PDCP for which the delivery confirmation has been obtained by Bitmap. Discard the PDU and do not give any further transmission instructions. On the other hand, after the handover, if the own apparatus has not received the PDCP status report after the handover, the transmission instructing unit 107 transfers the data after the first data (First No Ack SN) of the data for which delivery confirmation has not been completed to the PDCP layer. Control to retransmit with. Then, transmission instruction section 107 outputs transmission data (PDCP PDU) to the RLC layer. Also, the transmission instruction unit 107 manages the transmission data output to the RLC layer, that is, the SN and HFN corresponding to the transmitted transmission data. Also, the transmission instruction unit 107 outputs a sequence number (Last Send SN) corresponding to the last transmission data of the transmission data output to the RLC layer to the determination unit 108. Details of the PDCP SDU transmission control process in the transmission instruction unit 107 will be described later.

  The determination unit 108 receives a PDCP status report including an FMS indicating the sequence number of the first PDCP SDU among PDCP SDUs that have not been received by the receiving apparatus at the time of handover from the receiving apparatus (that is, the PDCP entity on the receiving side). . Then, the determination unit 108 determines the HFN corresponding to the FMS included in the PDCP status report based on the First No Ack SN input from the delivery confirmation management unit 101 and the Last Send SN input from the transmission instruction unit 107. . Specifically, the determination unit 108 specifies data corresponding to the sequence number indicated in the FMS between First No Ack SN and Last Send SN. Then, the determination unit 108 determines the HFN of the specified data as the HFN corresponding to the FMS. Then, determination section 108 sets PDCP SDUs less than the PDCP SDU corresponding to the determined HFN and FMS as PDCP SDUs for which delivery confirmation has been completed. Further, the determination unit 108 outputs the FMS and the HFN corresponding to the FMS to the retransmission management unit 102. On the other hand, when the PDCP status report is not received after the handover, the determination unit 108 sets a PDCP SDU less than the PDCP SDU corresponding to the First No Ack SN as a PDCP SDU for which delivery confirmation has been completed. Then, the determination unit 108 outputs information indicating the PDCP SDU for which delivery confirmation has been completed to the data discard processing unit 110.

  The timer control unit 109 measures the elapsed time after each PDCP SDU is input to the PDCP layer. That is, in the timer control unit 109, the PDCP SDU discard timer operates for each PDCP SDU. Then, the timer control unit 109 controls to discard the PDCP SDU and remove it from the transmission target when the elapsed time being measured has elapsed for a preset time. That is, PDCP SDUs that have expired in advance after being input to the PDCP layer are not retransmitted. Then, the timer control unit 109 outputs information indicating the PDCP SDU whose elapsed time has expired to the data discard processing unit 110.

  The data discard processing unit 110, based on the PDCP SDU managed by the SN / HFN management unit 103 and the SN and HFN information corresponding to the PDCP SDU, the PDCP SDU (that is, the delivery) indicated in the information input from the determination unit 108 (PDCP SDU that has been confirmed) and a PDCP SDU (that is, a PDCP SDU whose elapsed time has expired) indicated in the information input from the timer control unit 109, a data discard request that requests the discard of the data buffer 104 before encryption It outputs to the data buffer 106 after encryption.

  Next, FIG. 5 shows the configuration of the receiving apparatus according to the present embodiment. Note that the receiving apparatus 200 shown in FIG. 5 shows a configuration of a PDCP entity (that is, a PDCP entity on the receiving side) arranged in the PDCP layer. The receiving device 200 illustrated in FIG. 5 is, for example, an eNB (base station device).

  In the receiving apparatus 200 illustrated in FIG. 5, the determination unit 201 determines whether the PDU received from the RLC layer is a data PDU or a control PDU. Specifically, when the received PDU is a control PDU, the determination unit 201 determines that the PDCP status report transmitted from the PDCP entity of the opposite transmission apparatus 100 has been received, and the PDCP status report is transmitted to the transmission apparatus 100. Send to PDCP entity. Then, after the handover, the determination unit 201 outputs information indicating a delivery-confirmed PDCP PDU to the transmission apparatus 100 (that is, the transmission-side PDCP entity).

  The pre-decoding data buffer 202 stores the reception data (PDCP PDU) input from the determination unit 201 and outputs the PDU header portion of the reception data to the SN / HFN management unit 203, and the payload portion (PDCP SDU) Is output to the decryption processing unit 204. For example, the PDU header portion includes information indicating the PDCP SN of the received data.

  The SN / HFN management unit 203 manages SNs and HFNs corresponding to PDCP PDUs received so far. Specifically, the SN / HFN management unit 203 manages SN and HFN information corresponding to PDCP PDUs received so far, and based on the information, SN / HFN information expected to be received next And the SN included in the PDU header input from the pre-decoding data buffer 202, the HFN is specified. The SN / HFN management unit 203 generates a COUNT value from the SN / HFN, passes the COUNT value to the decoding processing unit 204, and requests decoding of the corresponding PDCP PDU in the pre-decoding data buffer 202. Then, the SN / HFN management unit 203 manages COUNT composed of SN and HFN. Then, the SN / HFN management unit 203 sequentially outputs the managed COUNT to the decryption processing unit 204.

  The decoding processing unit 204 uses the COUNT input from the SN / HFN management unit 203 to perform decoding processing on the received data (PDCP SDU) input from the pre-decoding data buffer 202. Then, the decoding processing unit 204 outputs the received data after decoding to the decoded data buffer 205.

  The decoded data buffer 205 stores the reception data input from the decoding processing unit 204 and outputs SN / HFN information to the Reordering window management unit 206.

  The reordering window management unit 206 waits for retransmission of the SDU set in advance from the top data (that is, PDCP SDU corresponding to FMS) among the received data (PDCP SDU) that has not been received when receiving the received data up to the previous time. It is managed as a Reordering window that is a receiving window. Then, the reordering window management unit 206 outputs the reception data input from the decoded data buffer 205 to the upper layer as reception data in the reordering window. At this time, if the received data is out of the range of the reordering window, the reordering window management unit 206 discards the out-of-range data. In addition, when a handover occurs and the sequence number of received data is discontinuous, the Reordering window management unit 206 stores the received data in the decoded data buffer 205 without outputting the received data to an upper layer. In addition, the reordering window management unit 206 sets the sequence number of the top data of the received data that has not yet been received as a new FMS after receiving the received data. Then, the reordering window management unit 206 outputs the sequence number of the PDCP SDU that has been received among the FMS and PDCP SDUs after the FMS to the generation unit 207. In addition, when a handover occurs, the Reordering window management unit 206 sets the FMS and the sequence number based on the received data stored in the post-decoding data buffer 205 when all the data before the handover is received, The data is output to the generation unit 207.

  The generation unit 207 generates a PDCP status report based on the FMS input from the Reordering window management unit 206 and the sequence number of the PDCP SDU that has been received after the FMS. Specifically, as illustrated in FIG. 1, the generation unit 207 generates a bitmap based on the sequence number of the PDCP SDU that has been received after the FMS. Then, the generation unit 207 generates a PDCP status report including FMS and Bitmap, and outputs the generated PDCP status report to the transmission device 100 (FIG. 4).

  Next, details of PDCP SDU transmission control processing in transmission instruction section 107 of transmitting apparatus 100 according to the present embodiment will be described.

  In the following description, as shown in FIG. 6, the sequence number (PDCP SN) of the PDCP SDU is set to 0 to 4095 (that is, 4096 SDUs) as in FIG. Also, the reordering window is set to 2048 SDU (half of 4096 SDU). In FIG. 6, First No Ack SN is assumed to be HFN = 1 and SN = 4092 in the transmission apparatus 100 (PDCP entity on the transmission side). Further, the first PDCP SDU among the PDCP SDUs not received by the receiving apparatus 200 (PDCP entity on the receiving side) is set to HFN = 1 and SN = 4093. Therefore, the FMS included in the PDCP status report from the receiving apparatus 200 indicates 4093.

  Therefore, before the handover, the transmission instruction unit 107 of the transmission apparatus 100 performs PDCP after First No Ack SN (HFN = 1, SN = 4092) to 4096 SDUs (that is, SDUs corresponding to one sequence number). Control not to send SDU. That is, as shown in FIG. 6, when First No Ack SN is HFN = 1 and SN = 4092, the transmission instruction unit 107 is separated from the First No Ack SN (HFN = 1, SN = 4092) by 4096 SDU. PDCP SDU up to HFN = 2 and SN = 4091 can be transmitted. In other words, the transmission instructing unit 107 does not transmit PDCP SDUs after HFN = 2 and SN = 4092 that are more than 4096 SDUs away from First No Ack SN (HFN = 1, SN = 4092). The effect of the above processing can also be achieved by the SN / HFN management unit 103 not instructing the encryption processing unit 105 to perform encryption processing.

  As a result, as shown in FIG. 6, the maximum interval between First No Ack SN and Last Send SN is 4096 SDU (≦ 4096 SDU). In this case, there is no PDCP SDU having the same sequence number (PDCP SN) between First No Ack SN and Last Send SN.

Therefore, a sequence number (PDCP SN) that matches the FMS included in the PDCP status report transmitted from the receiving apparatus 200 after the handover between the First No Ack SN and the Last Send SN.
There will be only one. For example, in FIG. 6, the determination unit 108 of the transmission device 100 is between the First No Ack SN (HFN = 1, SN = 4092) and the maximum possible Last Send SN (HFN = 2, SN = 4091). SN = 4093 with HFN = 1 is determined as the sequence number (PDCP SN) that matches FMS (4093). That is, the determination unit 108 can uniquely determine the HFN corresponding to the sequence number (PDCP SN) that matches the FMS.

  Then, the data discard processing unit 110 of the transmission device 100 receives the PDCP SDU before the PDCP SDU that has not been received by the reception device 200 (in FIG. 6, PDCP SDU less than HFN = 1 and SN = 4093 (FMS)). Target for destruction. The data discard processing unit 110 further includes a PDCP SDU corresponding to “1 (received)” in the PDCP status report from the receiving apparatus 200 and a PDCP SDU ( PDCP SDUs whose elapsed time has expired are also subject to destruction.

  Thereby, after the handover, the transmission apparatus 100 retransmits the PDCP SDUs in order from the PDCP SDU that is not received by the reception apparatus 200 (that is, PDCP SDU corresponding to HFN = 1, SN (FMS) = 4093).

  As described above, in the present embodiment, before the handover, the transmitting apparatus starts from the first PDCP SDU among the PDCP SDUs for which delivery confirmation has not been completed, and after the PDCP SDU corresponding to one round of the sequence number. Control transmission of PDCP SDU so as not to transmit PDCP SDU. Thereby, the transmission apparatus can reliably determine the HFN corresponding to the FMS included in the PDCP status report transmitted from the reception apparatus after the handover. That is, the transmission apparatus can reliably identify the PDCP SDU that should be retransmitted after handover and the PDCP SDU that should be discarded because retransmission is unnecessary. Further, since the transmission device can reliably determine the HFN corresponding to the FMS, the HFN used between transmission and reception matches. Therefore, according to the present embodiment, PDCP SDU encryption and decryption are performed using the same HFN between transmission and reception, so that PDCP SDU can be transmitted normally. Therefore, according to the present embodiment, the PDCP status report transmitted after the handover is used to accurately identify the PDCP SDU to be retransmitted and the PDCP SDU to be discarded and always transmit user data normally. can do.

(Embodiment 2)
As described above, after the handover, the PDCP entity on the transmission side starts retransmission in order from the PDCP SDU of the First No Ack SN without waiting for the notification of the PDCP status report. At this time, the PDCP entity on the receiving side may erroneously recognize the HFN corresponding to the PDCP SDU retransmitted from the PDCP entity on the transmitting side.

  Hereinafter, this will be specifically described with reference to FIG. In the following description, the sequence number (PDCP SN) of the PDCP SDU is assumed to be 0 to 4095 (that is, 4096 SDU) as in FIG. Further, the reordering window is set to 2048 SDU (half of 4096 SDU corresponding to one sequence number). In FIG. 7, First No Ack SN is set to HFN = 1 and SN = 10 in the PDCP entity on the transmission side. Also, the first PDCP SDU among the PDCP SDUs not received by the PDCP entity on the receiving side is set to HFN = 1 and SN = 2059. Therefore, FMS included in the PDCP status report indicates 2059.

  In FIG. 7, the difference between First No Ack SN (the beginning of the PDCP SDU at which the PDCP entity on the transmission side starts retransmission) and FMS (the beginning of the PDCP SDU that can be received by the PDCP entity on the receiving side) is 2049 SDU.

  In this case, at the time of retransmission after handover, the PDCP entity on the transmission side starts retransmission in order from the PDCP SDU with HFN = 1 and First No Ack SN = 10 shown in FIG. On the other hand, after handover, the PDCP entity on the receiving side sets 2048 SDUs from the FMS as a retransmission waiting reception window (Reordering window). At this time, information regarding HFN is not added to the retransmitted PDCP SDU. Therefore, the PDCP entity on the receiving side determines the HFN corresponding to the PDCP SDU to be retransmitted based on the HFN in the Reordering window. Therefore, the PDCP entity on the receiving side erroneously receives the PDCP SDU with HFN = 1 and SN = 10 transmitted by the PDCP entity on the transmitting side as the PDCP SDU with HFN = 2 and SN = 10 in the Reordering window. . Therefore, the PDCP entity on the receiving side moves the Reordering window so that the PDCP SDU of HFN = 2 and SN = 10 to 2048 minutes (range of Reordering window) shown in FIG. 7 can be received.

  As described above, after the handover, the PDCP entity on the transmitting side does not wait for the notification of the PDCP status report and retransmits in order from the PDCP SDU of the First No Ack SN, and the PDCP entity on the receiving side retransmits the PDCP entity on the transmitting side. PDCP SDU to be received may be received by mistake. Specifically, the difference between First No Ack SN in the PDCP entity on the transmitting side and the FMS in the PDCP entity on the receiving side (2049 SDU in FIG. 7) is the SDU (4096 SDU) corresponding to one sequence number and the Reordering window. When the difference is larger than the difference (here, 2048 SDU in FIG. 7) (here, 2048 SDU), the PDCP entity on the receiving side may erroneously receive the PDCP SDU retransmitted by the PDCP entity on the transmitting side. . In this case, an HFN mismatch occurs between the PDCP entities on the transmission and reception sides, and the HFN mismatch continues thereafter. Therefore, even if COUNT including HFN is used as parameters for encryption processing and decryption processing, PDCP SDU cannot be normally transmitted due to HFN mismatch between transmission and reception.

  Therefore, the transmitting apparatus according to the present embodiment does not retransmit the PDCP SDU until a PDCP status report is received from the receiving apparatus after the handover. That is, when the transmitter receives a PDCP status report from the receiver after the handover, the transmitter retransmits the PDCP SDU.

  Hereinafter, this embodiment will be specifically described.

  Transmission instructing section 107 (FIG. 4) of transmitting apparatus 100 according to the present embodiment does not retransmit transmission data until the own apparatus receives PDCP status report transmitted from receiving apparatus 200 after handover. Then, when the own apparatus receives the PDCP status report transmitted from the receiving apparatus 200 (FIG. 5) after the handover, the transmission instruction unit 107 transmits transmission data corresponding to the sequence number indicated in the FMS included in the PDCP status report. The transmission data is retransmitted in order.

  Next, details of PDCP SDU transmission control processing in transmission instruction section 107 of transmitting apparatus 100 according to the present embodiment will be described.

  In the following description, as shown in FIG. 8, the sequence number (PDCP SN) of the PDCP SDU is set to 0 to 4059 (that is, 4096 SDUs) as in FIG. Further, the reordering window is set to 2048 SDU (half of 4096 SDU corresponding to one sequence number). In FIG. 8, as in FIG. 7, First No Ack SN is set to HFN = 1 and SN = 10 in the transmission apparatus 100 (PDCP entity on the transmission side). In addition, the first PDCP SDU among the PDCP SDUs not received by the receiving apparatus 200 (the PDCP entity on the receiving side) is set to HFN = 2 and SN = 2059. Therefore, FMS included in the PDCP status report indicates 2059.

  The transmission instruction unit 107 of the transmission apparatus 100 controls to retransmit the PDCP SDU when the own apparatus receives the PDCP status report from the reception apparatus 200 after the handover. That is, the transmission instruction unit 107 does not retransmit the PDCP SDU until the own device receives the PDCP status report from the receiving device 200 after the handover.

  Here, when the PDCP status report is received from the receiving apparatus 200, as shown in FIG. 8, the determination unit 108 of the transmitting apparatus 100 is based on FMS (2059), and HFN = 1 and SN is less than 2059. PDCP SDUs (PDCP SDUs prior to HFN = 2, SN = 2058) are determined to be delivery confirmation completed. Therefore, the data discard processing unit 110 instructs the pre-encryption data buffer 104 and the post-encryption data buffer 106 to discard the PDCP SDU before HFN = 2 and SN = 2958.

  As a result, as shown in FIG. 8, the transmission instruction unit 107 starts retransmission of PDCP SDUs in order from the PDCP SDU with HFN = 2 and SN = 2059 (that is, PDCP SDU indicated by FMS).

  On the other hand, the receiving apparatus 200 has a PDCP SDU of 2048 SDUs (ie, HFN = 1, SN = 2059 to HFN) starting from the PDCP SDU of HFN = 2 and SN = 2059 (that is, PDCP SDU indicated by FMS) shown in FIG. = 2 and SN = 10). Therefore, the receiving apparatus 200 normally receives the PDCP SDU with HFN = 1 and SN = 2059 transmitted from the transmitting apparatus 100 as the PDCP SDU with HFN = 1 and SN = 2059 in the Reordering window.

  As described above, the transmitting apparatus 100 does not retransmit the user data (PDCP SDU) until the PDCP status report is received from the receiving apparatus 200 after the handover. Thereby, after the handover, the transmitting apparatus 100 always discards the PDCP SDUs from the first retransmission target (First No Ack SN) to the PDCP SDU less than FMS. In other words, transmitting apparatus 100 retransmits PDCP SDUs after FMS after handover. Therefore, transmitting apparatus 100 retransmits PDCP SDUs in order from the PDCP SDU that can be received by receiving apparatus 200, that is, PDCP SDUs in the Reordering window. Note that the same effect can also be achieved when the SN / HFN management unit 103 does not instruct the encryption processing unit 105 to perform encryption processing instead of processing for not retransmitting transmission data.

  As a result, the PDCP SDU at which the transmission apparatus 100 starts retransmission and the head PDCP SDU at which the reception apparatus 200 waits for retransmission match. That is, the receiving apparatus 200 can normally specify the HFN corresponding to the PDCP SDU retransmitted by the transmitting apparatus 100 as the HFN in the Reordering window set by the own apparatus. Therefore, as shown in FIG. 8, the difference between the First No Ack SN in transmitting apparatus 100 and the FMS in receiving apparatus 200 (2049 SDU in FIG. 8) is the same as FIG. 4096 SDU) and the reordering window (in FIG. 8, 2048 SDU), even when the difference becomes larger (here, 2048 SDU), the receiving apparatus 200 does not receive the PDCP SDU retransmitted by the transmitting apparatus 100 by mistake. . Therefore, since PDCP SDU encryption and decryption are performed using the same HFN between transmission and reception, PDCP SDU can be transmitted normally.

  Thus, according to the present embodiment, the transmission apparatus can accurately grasp the reception status of the PDCP SDU at the reception apparatus by retransmitting the PDCP SDU after receiving the PDCP status report. A PDCP SDU that needs to be retransmitted can be retransmitted accurately. Thereby, the receiving apparatus can receive the PDCP SDU retransmitted from the transmitting apparatus without error within the Reordering window set by the own apparatus. Therefore, according to the present embodiment, as in the first embodiment, the PDCP SDU to be retransmitted and the PDCP SDU to be discarded are accurately identified using the PDCP status report transmitted after the handover. Therefore, user data can always be transmitted normally.

  The embodiments of the present invention have been described above.

  In the present invention, the first embodiment and the second embodiment may be combined. Specifically, the transmitting apparatus 100 (FIG. 4) according to the present invention starts from the first PDCP SDU (First No Ack SN) among the PDCP SDUs for which delivery confirmation has not been completed before the handover. The PDCP SDU after the PDCP SDU corresponding to the minute is not transmitted, and after the handover, the PDCP SDU is not retransmitted until the own device receives the PDCP status report from the receiving device. Thereby, in the transmission apparatus, the HFN corresponding to the FMS included in the received PDCP status report can be reliably determined as in the first embodiment. Further, the receiving apparatus can prevent erroneously specifying the HFN corresponding to the PDCP SDU retransmitted from the transmitting apparatus in the same manner as in the second embodiment.

  The present invention is useful for a packet communication system that communicates packets between a user communication device such as a mobile terminal device and an operator communication device such as a base station device.

DESCRIPTION OF SYMBOLS 100 Transmission apparatus 200 Reception apparatus 101 Delivery confirmation management part 102 Retransmission management part 103,203 SN * HFN management part 104 Pre-encryption data buffer 105 Encryption processing part 106 Encrypted data buffer 107 Transmission instruction part 108,201 Determination part 109 Timer control unit 110 Data discard processing unit 202 Pre-decoding data buffer 204 Decoding processing unit 205 Decoded data buffer 206 Reordering window management unit 207 Generation unit

Claims (3)

A finite sequence number is cyclically assigned to the data, the sequence number and the number indicating the sequence number of the sequence number are respectively transmitted, and the first data before the handover is transmitted. A transmission apparatus that retransmits data for which delivery confirmation has not been completed in a layer in a second layer, which is a higher layer than the first layer, after handover,
A transmission instruction means for instructing data transmission in the first layer and instructing retransmission of data in the second layer after handover;
Receiving means for receiving control information indicating the sequence number of the top data of data not received by the receiving device at the time of handover;
When the control information is received, the sequence number indicated in the control information from the first data in the unacknowledged data to the last data in the data that has been transmitted before handover Specifying means for specifying data corresponding to
The transmission instructing unit instructs transmission from the top data of the data for which the delivery confirmation has not been completed to the data corresponding to one sequence number, and the top data of the data for which the delivery confirmation has not been completed Does not instruct transmission of data after the data corresponding to one sequence number from
A transmission apparatus comprising: The transmission instruction means does not instruct retransmission of data until the control information is received after the handover. When the control information is received after the handover, the data is sequentially transmitted from the data corresponding to the sequence number indicated in the control information. Instruct to resend
The transmission device according to claim 1. A finite sequence number is cyclically assigned to the data, the sequence number and the number indicating the sequence number of the sequence number are respectively transmitted, and the first data before the handover is transmitted. A transmission method in a transmission apparatus for retransmitting data that has not been acknowledged in a layer in a second layer that is a higher layer than the first layer after handover,
A transmission instruction step for instructing transmission of data in the first layer and instructing retransmission of data in the second layer after handover;
A receiving step of receiving control information indicating the sequence number of the head data of data not received by the receiving device at the time of handover;
When the control information is received, the sequence number indicated in the control information from the first data in the unacknowledged data to the last data in the data that has been transmitted before handover And a specific step of specifying data corresponding to
The transmission instruction step instructs transmission from the top data of the data for which the delivery confirmation has not been completed to the data corresponding to one sequence number, and the top data of the data for which the delivery confirmation has not been completed. Does not instruct transmission of data after the data corresponding to one sequence number from
Transmission method.

Images