JP2009239540A - Mobile terminal and data processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile terminal and a data processing method for reducing unnecessary data discard and unnecessary waiting time upon handover. <P>SOLUTION: In a mobile terminal 100, a PDU sorting unit 130 sends a forwarding PDU after a missing PDU to an upper layer through a sending unit 140 without waiting for the reception of the missing PDU. A data reading unit 160, when a sequence number immediately before the lowest sequence number of the PDUs held by a buffer 150 matches a sequence number informed from the sending unit 140, reads the PDUs in the order of the sequence number from the buffer 150 and sends them through the sending unit 140 to the upper layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mobile terminal and a data processing method.

  Currently, Long Term Evolution (LTE), 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 (3GPP). In LTE, hard handover is adopted as a handover method instead of soft handover.

  Therefore, in LTE, a handover source base station forwards a PDU already held at the time of handover execution among a plurality of protocol data units (PDUs) constituting a series of data strings to a handover destination base station. Then, the handover destination base station transmits the forwarding PDU and a non-forwarding PDU after the forwarding PDU to the mobile terminal. In this way, the mobile station can receive a series of data strings. However, since the forwarding PDU and the non-forwarding PDUs after the forwarding PDU do not necessarily reach the mobile station in this order, the PDCP (Packet Data Convergence of the mobile station). Protocol) is rearranged in order (see Non-Patent Document 1).

Conventionally, a technique has been proposed in which a packet order is maintained by discarding a packet received later than a subsequent packet even though the sequence number is in front (see Patent Document 1).
JP-A-1-27342 3GPP TS36.300 V8.1.0

  However, in the above-described technique, for example, when a PDU is discarded by an RLC (Radio Link Control) discard function of the handover destination base station, there is a problem that a wasteful waiting time occurs in the mobile station. That is, in the above-described reordering process of the mobile station, although it is a discarded PDU, it waits to receive it until a predetermined time elapses, and only after the predetermined time elapses is the sequence number later than the discarded PDU. This is to pass the PDU to the upper layer.

  In addition, the technique disclosed in Patent Document 1 has a problem in that data is discarded wastefully.

  The present invention has been made in view of this point, and an object of the present invention is to provide a mobile terminal and a data processing method that reduce wasteful data discard and wasteful waiting time during handover.

  In the mobile terminal of the present invention, a handover source base station forwards a PDU already held at the time of handover execution among a plurality of protocol data units (PDUs) constituting a series of data strings to the handover destination base station. A mobile terminal in a wireless communication system in which a base station transmits the forwarding PDU and a non-forwarding PDU after the forwarding PDU to the mobile terminal, a data transmission means for transmitting an input PDU to an upper layer, and a missing PDU in a received data sequence A missing PDU detecting means for detecting the received PDU, a judging means for judging whether the received PDU is a forwarding PDU or a non-forwarding PDU, a buffer for temporarily holding a non-forwarding PDU whose sequence number is later than the missing PDU, and the data transmission And the input stage of the buffer, the PDU before the detection of the missing PDU and the forwarding PDU after the detection of the missing PDU are input to the data sending means, while the non-forwarding PDU after the detection of the missing PDU is When a PDU sorting unit that inputs to the buffer and a forwarding PDU immediately before the PDU held in the buffer are sent from the data sending unit, the PDU held in the buffer is read out and sent to the data sending unit And a data reading means for inputting.

  According to the data processing method of the present invention, a handover source base station forwards a PDU already held at the time of handover execution among a plurality of protocol data units (PDUs) constituting a series of data strings to a handover destination base station. A data processing method of a mobile terminal in a wireless communication system in which a base station transmits the forwarding PDU and a non-forwarding PDU after the forwarding PDU to the mobile terminal, the step of detecting a missing PDU in a received data sequence, A step of determining whether the PDU is a forwarding PDU or a non-forwarding PDU, and a PDU before the detection of the missing PDU and a forwarding PDU after the detection of the missing PDU are sent to an upper layer, while the detection of the missing PDU Buffering a downstream non-forwarding PDU, and when the forwarding PDU immediately before the buffered PDU is sent to the upper layer, the buffered PDU is read and sent to the upper layer And the step of performing.

  ADVANTAGE OF THE INVENTION According to this invention, the mobile terminal and data processing method which reduce useless data discard and useless waiting time at the time of a handover can be provided.

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

  As shown in FIG. 1, mobile terminal (UE) 100 according to the present embodiment includes reception processing section 110 and PDU order control section 120.

  The mobile terminal (UE) 100 performs handover from a handover source base station (not shown) to a handover destination base station. At the time of this handover, the handover source base station forwards the PDU already held at the time of handover execution among the plurality of protocol data units (PDUs) constituting a series of data strings to the handover destination base station. Then, the handover destination base station transmits the forwarding PDU and a non-forwarding PDU after the forwarding PDU to the mobile terminal 100.

  Here, the PDU includes a sequence number given when a series of data strings is divided into PDUs. The PDU includes identification information for identifying whether it is a forwarding PDU or a non-forwarding PDU. Based on these pieces of information, the mobile terminal 100 can perform an order control process to be described later.

  The reception processing unit 110 receives a data sequence including a plurality of PDUs transmitted from the base station via an antenna, and performs reception processing on the received data sequence. The processing performed in the reception processing unit 110 includes processing in a physical layer, a data link layer, and a layer corresponding to RLC. Specifically, processing such as down-conversion, A / D conversion, demodulation, and decoding is included.

  The PDU order control unit 120 controls the order when the received PDU group after the reception processing of the reception processing unit 110 is transferred to the upper layer in the subsequent stage. The PDU order control unit 120 controls the transmission order of received PDUs based on the detection result of missing PDUs in the received data string and the determination result regarding the type of received PDU to be processed (forwarding PDU or non-forwarding PDU). To do. The PDU order control unit 120 performs a layer process corresponding to the PDPC.

  As shown in FIG. 2, the PDU order control unit 120 includes a PDU sorting unit 130, a sending unit 140, a buffer 150, and a data reading unit 160.

  The PDU sorting unit 130 controls the output destination of the received PDU based on the detection result of the missing PDU in the received data string and the determination result regarding the type of the received PDU to be processed (forwarding PDU or non-forwarding PDU). . This output destination is the sending unit 140 or the buffer 150.

  Here, the PDU distribution unit 130 includes a data loss determination unit 131, a distribution unit 132, a forward determination unit 133, and a distribution unit 134.

  The data missing determination unit 131 detects a missing PDU in the received data string. That is, the data loss determination unit 131 holds the sequence number of the previous input PDU, and determines whether or not the sequence number of the current input PDU is a number subsequent to the held sequence number. That is, the number next to the stored sequence number is the “expected sequence number”, and the data loss determination unit 131 determines whether or not the sequence number of the current input PDU is the expected sequence number.

  The sorting unit 132 outputs the PDU to the sending unit 140 until the missing data PDU is detected by the data missing unit 131, and outputs the PDU to the forward determining unit 133 after the missing PDU is detected.

  The forward determination unit 133 determines whether the input PDU is a forwarding PDU or a non-forwarding PDU. This determination is made based on PDU type information.

  The distribution unit 134 outputs the PDUs determined by the forward determination unit 133 to be forwarding PDUs to the transmission unit 140, while outputting the PDUs determined to be non-forwarding PDUs to the buffer 150.

  The sending unit 140 sends the input PDU to the upper layer. The sending unit 140 outputs the sequence number corresponding to the sending PDU to the data reading unit 160 every time it is sent.

  The buffer 150 temporarily holds a non-forwarding PDU whose sequence number is behind the missing PDU.

  When the “reading condition” is satisfied, the data reading unit 160 reads the PDUs from the buffer 150 in the order of the sequence numbers and outputs them to the sending unit 140 as they are.

  Here, the reading condition is (1) that the sequence number immediately before the youngest sequence number of the PDU held in the buffer 150 matches the sequence number reported from the sending unit 140.

  Further, (2) that the predetermined time elapses from the timing when the PDU with the smallest sequence number is held in the buffer 150 may be further included in the read condition. In this case, the forward determination unit 133 outputs a control signal for starting a timer provided in the data reading unit 160 at a timing when it is determined as a non-forwarding PDU. The counter value of the timer is returned to the initial value every time the data reading unit 160 receives the sequence number from the sending unit 140 (that is, the timer is restarted), and the reading condition is set when the counter value reaches a predetermined value. It is filled.

  An operation of the mobile terminal 100 having the above configuration will be described.

  FIG. 3 is a diagram for explaining the determination in the PDU distribution unit 130 and the PDU distribution processing based on the determination result.

  In the PDU sorting unit 130, the data missing determination unit 131 detects whether or not there is a missing PDU in the received data string (step S201).

  The forward determination unit 133 determines whether the PDU is a forwarding PDU or a non-forwarding PDU (step S202).

  The PDU before the missing PDU (step S201: NO) and the forwarding PDU after the missing PDU (step S202: NO) are output to the sending unit 140 (step S203), while the non-forwarding PDU after the missing PDU (step S203). (S202: YES) is output to the buffer 150 (step S204).

  As described above, the PDU sorting unit 130 sends out the forwarding PDU after the missing PDU and sends it to the upper layer via the sending unit 140 without waiting for the reception of the PDU. In addition, when the data reading unit 160 matches the sequence number immediately before the smallest sequence number of the PDU held in the buffer 150 with the sequence number reported from the transmission unit 140, the PDUs from the buffer 150 are ordered in the sequence number order. Is sent to the upper layer via the sending unit 140.

  By doing so, it is possible to reduce wasteful data discard and wasteful waiting time during handover.

  Here, when forwarding at the time of handover, it is most likely that the order of reception is reversed and PDUs are discarded at the handover destination base station. Therefore, there is a high possibility that the missing PDU is a forwarding PDU.

  Therefore, a wasteful waiting time can be reduced by sending the forwarding PDUs after the missing PDU to the higher layer via the sending unit 140 without waiting for the missing PDU to be received.

  Next, the operation of the mobile terminal 100 will be described for each specific case.

  (Case 1) When the non-forwarding PDU after the missing PDU is received by the mobile terminal 100 before the forwarding PDU

  In FIG. 4, the handover source base station receives PDU1 to PDU4, and PDU1 is transmitted to the UE100 (step S301). This PDU1 is transferred from the RLC layer to the PDCP layer in step S302, and is sent to the upper layer via PDCP in step S303.

  In step S304, handover is executed. At this time, since the PDUs 2 to 4 are not transmitted from the handover source base station to the mobile terminal 100, they are forwarded from the handover source base station to the handover destination base station. At the time of this forwarding, PDU2 is discarded at the handover destination base station.

  Since the handover destination base station receives the non-forwarding PDU from the upper station before the forwarding PDU, the handover destination base station transmits PDU5 which is a non-forwarding PDU in step 305 before the forwarding PDU is transmitted.

  The PDU 5 is transferred from the RLC to the PDU order control unit 120 (PDCP) in step S306. Here, the PDU 5 does not have an expected sequence number (the expected sequence number here is 2 which is the next number after the sequence number 1 of the previous PDU 1) and is a non-forwarding PDU. Temporarily retained. At this timing, the timer is started.

  The PDU 3 transmitted from the handover destination base station in step S307 is input to the PDU order control unit 120 in step S308.

  Here, since a missing PDU has already been detected and PDU3 is a forwarding PDU, PDU3 is not held in the buffer 150 but is passed to the upper layer via the sending unit 140 in step S309. At this time, the timer is restarted.

  The PDU4 transmitted in step S310 and further input from the RLC to the PDU order control unit 120 in step S311 is an expected sequence number (the expected sequence number here is the next of the sequence number 3 of PDU3 transmitted to the previous upper layer). 4), which is passed to the upper layer via the sending unit 140 in step S312.

  At this time, the sequence number 4 of the PDU transmitted from the transmission unit 140 is a number immediately before the sequence number 5 of the PDU held in the buffer 150. Accordingly, since the read condition is satisfied, the PDU 5 is read from the buffer 150 and passed to the upper layer via the sending unit 140 in step S313.

  Thus, since it is possible to pass PDU3 to PDU5 to the upper layer without waiting for reception of PDU2 that is not received by mobile terminal 100, it is possible to reduce useless waiting time.

  Thereafter, PDU 6 and subsequent PDUs received by the mobile terminal 100 are sequentially transmitted to the upper layer.

(Contrast technology of Case 1)
In the case of the conventional LTE mentioned in the background art, in the case 1, since the PDU 2 is continuously received as shown in FIG. 5, the PDUs after the PDU 3 are not passed to the upper layer until the count value of the timer reaches a predetermined value. . Therefore, useless waiting time occurs.

  Further, in the technique disclosed in Patent Document 1 described above, when a missing PDU is detected as shown in FIG. 6, PDU 3 and PDU 4 having a sequence number before PDU 5 are unconditionally received after PDU 5. It will be deleted.

  On the other hand, as described above, the mobile terminal 100 according to the present embodiment can reduce a useless waiting time at the time of handover and can also prevent useless data discard.

  (Case 2) When non-forwarding PDUs behind missing PDUs are received by the mobile terminal 100 before some forwarding PDUs

  In FIG. 7, since the handover destination base station receives the forwarding PDU 3 before receiving the non-forwarding PDU 5 from the upper station, it transmits PDU 3 that is a forwarding PDU in step 401.

  In step S402, the PDU 3 is transferred from the RLC to the PDU order control unit 120 (PDCP). Here, PDU3 does not have an expected sequence number (here, the expected sequence number is 2 which is the next number of sequence number 1 of the previous PDU1), but since it is a forwarding PDU, it is temporarily stored in buffer 150. Without being held, it is passed to the upper layer via the sending unit 140 in step S403.

  Since the handover destination base station receives the non-forwarding PDU from the upper station before receiving the next forwarding PDU4, it transmits PDU5, which is a non-forwarding PDU, in step S404.

  The PDU 5 transmitted from the handover destination base station in step S404 is input to the PDU order control unit 120 in step S405.

  Here, a missing PDU has already been detected, and since PDU 5 is a non-forwarding PDU, PDU 5 is held in the buffer 150. At this timing, the timer is started.

  The PDU4 transmitted in step S406 and further input to the PDU order control unit 120 from the RLC in step S407 is an expected sequence number (the expected sequence number here is the next of the sequence number 3 of PDU3 transmitted to the previous upper layer). 4), which is passed to the upper layer via the sending unit 140 in step S408.

  At this time, the sequence number 4 of the PDU transmitted from the transmission unit 140 is a number immediately before the sequence number 5 of the PDU held in the buffer 150. Therefore, since the read condition is satisfied, the PDU 5 is read from the buffer 150 and passed to the upper layer via the sending unit 140 (step S409).

  Thus, since it is possible to pass PDU3 to PDU5 to the upper layer without waiting for reception of PDU2 that is not received by mobile terminal 100, it is possible to reduce useless waiting time.

(Contrast technology of Case 2)
In the case of the conventional LTE described in the background art, in the case 2, the PDU 2 and subsequent PDUs are not passed to the upper layer until the count value of the timer reaches a predetermined value in order to wait for the reception of the PDU 2 as shown in FIG. . Therefore, useless waiting time occurs.

  Further, in the technique disclosed in Patent Document 1 described above, when a missing PDU is detected as shown in FIG. 9, it is received after PDU 5 and PDU 4 having a sequence number before PDU 5 is unconditionally deleted. End up.

  On the other hand, as described above, the mobile terminal 100 according to the present embodiment can reduce a useless waiting time at the time of handover and can also prevent useless data discard.

  (Case 3) When the forwarding PDU after the missing PDU is received by the mobile terminal 100 before the non-forwarding PDU

  In FIG. 10, PDU3 transmitted from the handover destination base station in step S401 is input to the PDU order control unit 120 in step S402.

  Here, PDU3 does not have an expected sequence number (here, the expected sequence number is 2 which is the next number of sequence number 1 of the previous PDU1), but since it is a forwarding PDU, it is temporarily stored in buffer 150. Without being held, it is passed to the upper layer via the sending unit 140 in step S403.

  The PDU4 transmitted in step S501 and further input from the RLC to the PDU order control unit 120 in step S502 is an expected sequence number (the expected sequence number here is a number next to the sequence number 3 of the previous PDU3 4). ) And passed to the upper layer via the sending unit 140 in step S503.

  The PDU 5 transmitted from the handover destination base station in step S504 is input to the PDU order control unit 120 in step S505.

  The PDU 5 input to the PDU order control unit 120 has an expected sequence number (here, the expected sequence number is 5 which is the number next to the sequence number 4 of the previous PDU 4), and in step S506, the transmission unit It is passed to the upper layer via 140.

  Thus, since it is possible to pass PDU3 to PDU5 to the upper layer without waiting for reception of PDU2 that is not received by mobile terminal 100, it is possible to reduce useless waiting time.

(Contrast technology for Case 3)
In the case of the conventional LTE mentioned in the background art, in the case 3, the PDU 2 and subsequent PDUs are not passed to the upper layer until the count value of the timer reaches a predetermined value because the PDU 2 is kept waiting as shown in FIG. . Therefore, useless waiting time occurs.

  In case 3, the technique disclosed in Patent Document 1 causes no particular problem as shown in FIG. This is because, in case 3, a discard PDU has occurred, but the order in which the PDUs are received has not been reversed.

  The mobile terminal and data processing method of the present invention are useful for reducing wasteful data discard and wasteful waiting time during handover.

The block diagram which shows the structure of the mobile terminal which concerns on one embodiment of this invention The block diagram which shows the structure of the PDU order control part shown by FIG. FIG. 2 is a diagram for explaining the determination in the PDU distribution unit shown in FIG. 2 and the PDU distribution processing based on the determination result. Diagram for explaining operation of mobile terminal (Case 1) Diagram for explaining the contrast technique of Case 1 Diagram for explaining the contrast technique of Case 1 Diagram for explaining the operation of mobile terminals (Case 2) Diagram for explaining the contrast technique of Case 2 Diagram for explaining the contrast technique of Case 2 Diagram for explaining the operation of mobile terminals (Case 3) Diagram for explaining the contrast technology of Case 3 Diagram for explaining the contrast technology of Case 3

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Mobile terminal 110 Reception processing part 120 PDU order control part 130 PDU distribution part 131 Data omission determination part 132,134 Distribution part 133 Forward determination part 140 Sending part 150 Buffer 160 Data reading part

Claims (2)

Of the plurality of protocol data units (PDUs) constituting a series of data strings, the handover source base station forwards PDUs already held at the time of handover execution to the handover destination base station, and the handover destination base station transmits the forwarding PDU and A mobile terminal in a wireless communication system that transmits a non-forwarding PDU after the forwarding PDU to the mobile terminal,
Data sending means for sending an input PDU to an upper layer;
Missing PDU detection means for detecting missing PDUs in the received data sequence;
Determining means for determining whether the received PDU is a forwarding PDU or a non-forwarding PDU;
A buffer that temporarily holds a non-forwarding PDU whose sequence number is behind the missing PDU;
Provided at the input stage of the data sending means and the buffer, the PDU before detection of the missing PDU and the forwarding PDU after detection of the missing PDU are input to the data sending means, while the non-forwarding after detection of the missing PDU PDU distribution means for inputting PDUs to the buffer;
A data reading means for reading out the PDU held in the buffer and inputting it to the data sending means when a forwarding PDU immediately before the PDU held in the buffer is sent from the data sending means;
A mobile terminal comprising: Of the plurality of protocol data units (PDUs) constituting a series of data strings, the handover source base station forwards PDUs already held at the time of handover execution to the handover destination base station, and the handover destination base station transmits the forwarding PDU and the relevant PDU A data processing method for a mobile terminal in a wireless communication system for transmitting a non-forwarding PDU after a forwarding PDU to the mobile terminal,
Detecting missing PDUs in the received data sequence;
Determining whether the received PDU is a forwarding PDU or a non-forwarding PDU;
Sending the PDU before the detection of the missing PDU and the forwarding PDU after the detection of the missing PDU to an upper layer, while buffering the non-forwarding PDU after the detection of the missing PDU;
When the forwarding PDU immediately before the buffered PDU is sent to the upper layer, reading the buffered PDU and sending it to the upper layer;
A data processing method comprising:

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