KR20090101780A - Apparutus and method for controlling status report in mobile communication system - Google Patents

Abstract

PURPOSE: An apparatus and a method for controlling the transmission of a status report in a mobile communication system are provided to prevent the unnecessary status report from being transmitted. CONSTITUTION: A method for controlling the transmission of a status report in a mobile communication system is composed of the steps of driving a re-ordering timer according to the receiving of a packet data unit and triggering the status report(505), generating the status report about the received data(515) or renewing the already generated status report to be proper to the present status(525) after the status prohibit timer is finished if the status prohibit timer is operated, judging the receiving of the loss packet data unit causing the driving of the re-ordering timer(530), and canceling the transmission of the status report if the loss packet data unit was already received(535).

Description

APPARATUS AND METHOD FOR CONTROLLING STATUS REPORT IN MOBILE COMMUNICATION SYSTEM}

The present invention relates to a mobile communication system, and more particularly, to an apparatus and method for controlling generation and transmission of a status report message by a layer device in charge of ARQ.

UMTS (Universal Mobile Telecommunication Service) system is based on the European system of Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), and is a wideband code division multiple access CDMA) is a third generation asynchronous mobile communication system.

The 3rd Generation Partnership Project (3GPP), which is in charge of UMTS standardization, is discussing Long Term Evolution (LTE) as the next generation mobile communication system of the UMTS system. LTE is a technology that implements high-speed packet-based communication having a transmission rate of up to about 100 Mbps, and aims to commercialize it in 2010. To this end, various schemes are discussed. For example, a scheme of reducing the number of nodes located on a communication path by simplifying a network structure, or approaching wireless protocols as close as possible to a wireless channel are under discussion.

1 illustrates an example of a next generation mobile communication system structure. Here, the system structure based on the UMTS system is shown.

Referring to FIG. 1, as illustrated, next-generation radio access networks (hereinafter referred to as E-RANs) 110 and 112 may be referred to as next-generation base stations (Evolved Node B, ENB or Node B) 120 , 122, 124, 126, and 128, and the upper node (referred to as Access Gateway) 130 and 132 are simplified. The user equipment (hereinafter referred to as UE) 101 is connected to the Internet Protocol (hereinafter referred to as IP) network by the E-RANs 110 and 112.

The ENBs 120 to 128 correspond to existing Node Bs of the UMTS system and are connected to the UE 101 by a radio channel. Unlike the existing Node B, the ENBs 120 to 128 play a more complex role. In LTE, all user traffic, including real-time services such as Voice over IP (VoIP) over the Internet protocol, is serviced through a shared channel, which requires a device that collects and schedules UE information. 120 to 128 are in charge. In order to realize a transmission rate of up to 100 Mbps, LTE uses Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology in a bandwidth of up to 20 MHz. In addition, an adaptive modulation & coding (AMC) scheme that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied.

As shown in FIG. 2, the wireless protocol of the LTE system includes packet data convergence protocols (PDCPs) 205 and 240, radio link control (RLC) 210 and 235, and medium access control (MAC) 215 and 230. Packet Data Convergence Protocol (PDCP) 205 and 240 are in charge of operations such as IP header compression / restoration, deactivation / deactivation. The radio link control (hereinafter referred to as RLC) 210 and 235 reconstructs an ARQ by reconfiguring a PDCP PDU (Packet Data Unit, hereinafter referred to as a PDU of the protocol) to an appropriate size. The operation is performed and the order of the RLC PDUs whose order is reversed in the HARQ process is rearranged. The MACs 215 and 230 are connected to several RLC devices configured in one terminal, and multiplex RLC PDUs to MAC PDUs and demultiplex RLC PDUs from MAC PDUs. The physical layers 220 and 225 channel-code and modulate upper layer data, make an OFDM symbol, and transmit it to a wireless channel, or demodulate, channel decode, and transmit an OFDM symbol received through a wireless channel to a higher layer.

However, in the above-described technique, when the RLC layer device performs ARQ, an order reordering operation, a STATUS REPORT prohibit timer, and an RLC STATUS REPORT triggering when a lost PDU is found, There is a problem that RLC STATUS REPORT occurs unnecessarily due to the interaction.

Accordingly, an object of the present invention for solving the above problems is to provide a method and apparatus for discarding a STATUS REPORT without transmitting a STATUS REPORT if a lost RLC PDU has already been received.

An embodiment of the present invention for achieving the above object is a method of controlling a status report message transmission in a mobile communication system, a process of driving an order reordering timer according to whether the packet data unit is received, and triggering a status report message Generating a status report message for data received after the status report prohibit timer expires, or updating a status report message already generated according to a current reception condition; Determining whether to receive the lost packet data unit that caused the sequence reordering timer to be driven, and canceling transmission of a STATUS REPORT if it is determined that the lost packet data unit has already been received. do.

The present invention examines whether a lost RLC PDU that has triggered the operation of the T_reordering timer has been received prior to generating and sending a STATUS REPORT that occurred as the T_reordering timer expires, and then the lost RLC. If a PDU has already been received, the PDU may be discarded without transmitting a STATUS REPORT, thus preventing unnecessary transmission of a STATUS REPORT.

1 is a diagram illustrating a structure of an LTE mobile communication system;

2 is a diagram illustrating a radio protocol structure of an LTE mobile communication system;

3 is a view for explaining the problems of the prior art,

4 is a view illustrating a situation where a problem of the prior art occurs;

5 is a diagram illustrating an operation of a terminal;

6 is a diagram illustrating another operation of a terminal;

7 shows a device of the invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

According to the RLC protocol of the current LTE mobile communication system, if the unreceived RLC PDU is not received until a certain time elapses after the unreceived RLC PDU is found, the RLC receiving apparatus considers that the RLC PDU is lost and RLC STATUS REPORT ( Triggers a status report message). This is called a missing PDU detection trigger. For reference, a trigger means a condition for generating an RLC STATUS REPORT. When an RLC STATUS REPORT is triggered, the RLC device generates and sends an RLC STATUS REPORT on the next transmission opportunity, unless transmission of the RLC STATUS REPORT is prohibited for any reason. do.

In the current LTE mobile communication system, when a lost RLC PDU is found, a lost PDU discovery trigger that triggers an RLC STATUS REPORT and an RLC PDU containing information requesting the transmission of a STATUS REPORT are received. A polling PDU Receive Trigger is defined that triggers an RLC STATUS REPORT upon receipt of an incoming RLC PDU. This is so as not to mistake the RLC PDU in the HARQ reception process as a lost RLC PDU.

Hereinafter, the operation of the lost PDU discovery trigger and the problem to be solved in the present invention will be described in more detail with reference to FIG. 3.

Referring to FIG. 3, an RLC PDU [2] 310 is received in a state in which no RLC PDU [1] is received by the RLC receiving apparatus at any T1. The receiving device drives a T_reordering timer to determine whether the RLC PDU [1] is a lost PDU. Thereafter, the RLC PDU [3] 320 and the RLC PDU [4] 315 were received by the RLC receiving apparatus, but the RLC PDU [1] was not received. After T_reordering expires at any point in time T2, i.e., when T_reordering has elapsed while the unreceived RLC PDU has not been received, the receiving device receives a RLC STATUS REPORT ( Generate a status report message, and store a reception status of RLC PDUs in which HARQ order rearrangement is completed in the RLC STATUS REPORT. For reference, HARQ order rearrangement of any RLC PDU [x] satisfying the following conditions is completed.

[HARQ Order Reorder Condition]

If there is no unreceived RLC PDU with a serial number lower than x or the unreceived RLC PDU is already an unreceived RLC PDU whose HARQ sequence reordering has been completed, the HARQ sequence reordering is considered to be completed until the serial number x.

The completion of HARQ order reordering of any unreceived RLC PDU means that the T_reordering timer for the unreceived RLC PDU has expired. The highest serial number RLC PDUs among the RLC PDUs that have completed HARQ sequence reordering at T2 are RLC PDUs [4] (unreceived RLC PDUs of RLC PDUs with serial numbers lower than 4 are already RLC PDUs having HARQ sequence reordering [1]). ], The receiver generates and transmits an RLC STATUS REPORT (status report message) containing the reception status to RLC PDUs having a serial number lower than the RLC PDU [4], including the RLC PDU [4]. The highest serial number of the RLC PDUs of which the HARQ sequence rearrangement is completed at any point plus 1 is stored in a variable called VR (MS), and the receiving device has a lower serial number of RLC PDUs than VR (MS). Receive the reception status information for the RLC STATUS REPORT (status report message).

In order to prevent the RLC STATUS REPORT from occurring too frequently, the receiving device drives the STATUS_PROHIBIT tier after completing the transmission of the RLC STATUS REPORT. While the timer is running, the generation and transmission of the RLC STATUS REPORT is prohibited even if the RLC STATUS REPORT trigger is satisfied, and the RLC STATUS REPORT, which has been forbidden to transmit, is the STATUS_PROHIBIT timer. It can be sent after the driving of is completed. The size of the STATUS_PROHIBIT timer is normally set to a value larger than Round Trip Time (RTT).

At any time point T3 after T2, an RLC PDU [5] 325 was received. When a non-received RLC PDU is present and a new RLC PDU is received instead of the unreceived RLC PDU, the UE drives a T_reordering timer. Thereafter, the T_reordering timer expires at any point in time T4, but the STATUS_PROHIBIT timer is still running. In general, the above situation may occur because the size of the STATUS_PROHIBIT timer is larger than that of the T_reordering timer. The RLC STATUS REPORT is triggered due to the expiration of the T_reordering timer, but the RLC receiving device does not send the STATUS REPORT because the STATUS_PROHIBIT timer is running. Thereafter, at any point in time, an RLC PDU [1] that is an unreceived RLC PDU is received, and the STATUS_PROHIBIT timer expires at T5. The receiving device updates and transmits the STATUS REPORT (status report message) triggered at T4 according to the current situation.

As mentioned above, as the T_reordering timer expires, i.e., as the lost PDU discovery trigger is met, the generated RLC STATUS REPORT is delayed by the STATUS_PROHIBIT timer and during the delayed transmission period. There may be a case where a lost RLC PDU is received that triggered the running of the T_reordering timer. This may occur when the STATUS REPORT on the receiving side and the transmission of a new RLC PDU on the transmitting side are simultaneously performed.

This will be described by way of example with reference to FIG. 4.

Referring to FIG. 4, the RLC transmitting device transmits an RLC PDU [5] at any time before the RLC STATUS REPORT 425 transmitted by the RLC receiving device arrives at T2 415, and the RLC PDU [5] is transmitted. When the receiving device receives 420, the RLC receiving device drives a T_reordering timer. The RLC transmitting device receiving the RLC STATUS REPORT retransmits an RLC PDU [1] (430), which is randomly expired before the T_reordering timer expires but before the STATUS_PROHIBIT timer expires. It may arrive at the receiving device at that time. According to the current standard, after the STATUS_PROHIBIT timer expires, the receiving device generates / transmits an RLC STATUS REPORT triggered by the expiration of the T_reordering timer. The RLC STATUS REPORT was triggered because PDU [1] was a lost PDU, but PDU [1] is no longer a lost PDU when the RLC STATUS REPORT is sent. In other words, it does not satisfy the condition to send RLC STATUS REPORT.

In order to solve the problem, the present invention relates to whether a lost RLC PDU that caused the T_reordering timer to be driven prior to generating / transmitting a STATUS REPORT generated as a T_reordering timer expires has been received. And a method and apparatus for not sending a STATUS REPORT if the lost RLC PDU has already been received.

5 is a signal flowchart illustrating an operation of an RLC receiving apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 5, when T_reordering expires in step 505, the receiving device triggers an RLC STATUS REPORT (status report message). In step 510, the receiving device checks whether the STATUS_PROHIBIT timer is running. If the STATUS_PROHIBIT timer is not running as a result of the check in step 510, in step 515, the receiving device generates and transmits a STATUS REPORT (status report message) containing the reception states of the RLC PDUs whose HARQ order rearrangement is completed until the corresponding time.

However, if the check result of step 510 indicates that the STATUS_PROHIBIT timer is driven, the receiving device waits until the STATUS_PROHIBIT timer expires in step 520.

When the STATUS_PROHIBIT timer expires, the terminal proceeds to step 525 to generate a STATUS REPORT triggered in step 505 or, if a STATUS REPORT has already been generated, the STATUS REPORT of the STATUS REPORT. Update the contents to the current reception status. Since the RLC STATUS REPORT generated or updated in step 525 is triggered according to the expiration of the T_reordering timer, the transmission is delayed by the STATUS_PROHIBIT timer, so that the receiving device transmits the STATUS REPORT transmission. The process proceeds to step 530 to see if there is still meaning, that is, whether a lost PDU that caused the T_reordering timer to run has not been received.

In step 530, the receiving device determines whether a lost PDU that has caused the driving of the T_reordering timer has been received. The determination process may be embodied as a process of checking whether information on a lost RLC PDU is stored in a STATUS REPORT to be transmitted or whether the VR (R) at that time is the same as the VR (MS). .

Here, the fact that the information on the lost RLC PDU is not stored in the STATUS REPORT (ie, that the retransmission request information or the NACK information is not stored) means that the lost RLC PDU does not exist and T_reordering ( Reordering) means that a lost PDU has been received that caused the timer to run. VR (R) equals VR (MS) means that no lost PDU is present among the RLC PDUs that have completed HARQ order reordering, and that a lost PDU that triggered the T_reordering timer has been received. do.

If the RLC receiving apparatus determines that a lost PDU that has caused the T_reordering timer has already been received as a result of step 530, that is, if the VR (R) and the VR (MS) are the same, the RLC receiving apparatus proceeds to step 535. If the determination result of step 530 is false, go to step 540.

Proceeding to step 535 means that a lost PDU that has triggered the operation of the T_reordering timer has been received, so that the receiving device discards the generated STATUS REPORT and sends a STATUS REPORT. Cancels the transfer.

Proceeding to step 540 means that a lost PDU that triggered the T_reordering timer has not been received, and thus, the receiving device transmits the generated STATUS REPORT.

For reference, the VR (R) will be described. VR (R) is the lower serial number of the reception buffer at the present time. RLC PDUs with serial numbers lower than VR (R) have already been delivered to a higher layer, and these RLC PDUs are said to be ordered at the ARQ level. The RLC receiving apparatus assembles RLC PDUs arranged in ARQ level into RLC SDUs and delivers them to higher layers. After transmitting the RLC SDU to the upper layer, the RLC receiving apparatus stores a serial number that is one greater than the highest serial number among the serial numbers of the RLC PDUs corresponding to the RLC SDU in the VR (R). Ordering at the ARQ level up to PDU [x] means that all RLC PDUs with serial numbers lower than x have been received, or even unreceived RLC PDUs with RLC PDUs with serial numbers lower than x are received. The RLC PDUs with serial numbers lower than x were all assembled into RLC SDUs and delivered to the upper layer since it was determined that they were no longer likely to be received, and only the RLC PDUs with serial numbers higher than x were stored in the RLC receive buffer. It means.

The RLC STATUS REPORT contains the reception status for RLC PDUs with serial numbers equal to or higher than VR (R), which is typically the serial number of the first lost RLC PDU. Matches As described above, the RLC STATUS REPORT stores a value higher than the highest serial number among the serial numbers of the RLC PDUs whose order reordering is completed in the VR (MS), and in the RLC STATUS REPORT (status report message). Only the reception status report of the realigned RLC PDUs is received. Therefore, the same VR (R) and VR (MS) means that there are no lost PDUs among the RLC PDUs in the reordered order.

6 illustrates the operation of the RLC receiving apparatus processing a STATUS REPORT (status report message) after the STATUS_PROHIBIT timer expires.

If the STATUS_PROHIBIT timer expires in step 605, the RLC receiving apparatus proceeds to step 610 to check whether there is an RLC STATUS REPORT triggered by the STATUS_PROHIBIT timer, but the transmission is delayed. If there is no STATUS REPORT to transmit as a result of the determination of step 610, the RLC receiving apparatus ends the process.

However, as a result of the determination in step 610, if there is a STATUS REPORT to be transmitted, that is, if there is a STATUS REPORT whose status is delayed by the STATUS_PROHIBIT timer, the RLC receiving apparatus is triggered in step 620. Create an RLC STATUS REPORT or update the contents of the STATUS REPORT to reflect the RLC PDU reception status at that time, if already generated.

In step 625, the RLC receiving apparatus checks whether the RLC STATUS REPORT is triggered by a lost PDU discovery trigger, that is, by expiration of a T_reordering timer. If the determination result of step 625 is false, the RLC receiving apparatus proceeds to step 635 and, if true, to step 630.

Proceeding to step 635 indicates that an RLC STATUS REPORT was not triggered by a lost PDU discovery trigger, so that an event that occurred while the creation and transmission was delayed by the STATUS_PROHIBIT timer, for example, an unreceived RLC PDU It means that the utility of RLC STATUS REPORT (status report message) is not destroyed by the receiving event. Therefore, the RLC receiving apparatus starts the transmission procedure of the RLC STATUS REPORT (status report message) in step 635.

If the RLC receiving apparatus is a terminal, the transmission procedure refers to a process of requesting transmission resources from a base station and transmitting an RLC STATUS REPORT using a requested transmission resource. At this time, the terminal may update the contents of the RLC STATUS REPORT once again before transmitting the RLC STATUS REPORT.

Proceeding to step 630, the RLC STATUS REPORT was triggered by a lost PDU discovery trigger, so that an event occurred while the generation and transmission was delayed by the STATUS_PROHIBIT timer, for example, an unreceived RLC PDU. This means that the utility of RLC STATUS REPORT may have expired. Therefore, the RLC receiving apparatus checks whether it is still meaningful to transmit the triggered RLC STATUS REPORT (status report message) in step 630. That is, the RLC receiving apparatus determines whether to receive a lost PDU that caused the T_reordering timer to drive. In other words, it is checked whether information on the lost RLC PDU is stored in the STATUS REPORT to be transmitted or whether the VR (R) at that time is the same as the VR (MS). If the STATUS REPORT to be transmitted does not contain information on the lost RLC PDU, that is, no retransmission request information or NACK information is stored, it means that there is no lost RLC PDU, and T_reordering (Reorder) Indicates that a lost PDU has been received that caused the timer to run. VR (R) equals VR (MS) means that no lost PDU is present among the RLC PDUs that have completed HARQ order reordering, and that a lost PDU that triggered the T_reordering timer has been received. do.

If the determination result of step 630 is true, the RLC receiving apparatus proceeds to step 640 if the VR (R) and VR9MS) are the same, and proceeds to step 635 if the determination result of step 630 is false.

Proceeding to step 640 means that a lost PDU has been received that caused the T_reordering timer to run, so the receiving device cancels the triggered STATUS REPORT and cancels the STATUS REPORT. Do not send.

 7 is a diagram illustrating an internal configuration of an RLC device according to a preferred embodiment of the present invention.

Referring to FIG. 7, the RLC device 740 includes a transmission control unit 705, a transmission buffer 710, a framing device 715, a retransmission buffer 720, a STATUS REPORT processing unit 740, and a reception buffer. 745, a STATUS REPORT control unit 755, and the like. Throughout the present invention, the term RLC receiver is used. The RLC apparatus includes both an RLC receiver and an RLC transmitter, and includes a reception buffer 745 and a status report message processing unit 740 of FIG. 7. , STATUS REPORT control unit 755 corresponds to the RLC receiving apparatus. The RLC device is connected to the multiplexing device 725 and the demultiplexing device 750. The multiplexing device 725 multiplexes RLC PDUs delivered from multiple RLC devices into one HARQ packet. The demultiplexer 750 demultiplexes the HARQ packet transmitted from the HARQ processor and delivers the demultiplexed HARQ packet to the appropriate RLC device.

The HARQ processor 730 is a device that transmits and receives an HARQ packet through a predetermined HARQ operation, and the transceiver 735 is a device that modulates and transmits a HARQ packet into a radio signal and demodulates the radio signal.

Next, an internal configuration operation of the RLC device 740 will be described in detail. The data delivered from the upper layer is stored in the transmission buffer 710, and is then framed and transmitted into an RLC PDU of an appropriate size under the control of the transmission control unit 705. The transmission control unit 705 reports the amount of data to be transmitted to the lower layer, receives notification of the amount of data to be transmitted in the next transmission period from the lower layer, and determines the data to be transmitted in the next transmission period according to the amount of data to be transmitted.

The amount of data to be transmitted includes the amount of data stored in the transmission buffer 710, the amount of data stored in the retransmission buffer, and the size of other control information such as a reception status report.

The framing unit 715 attaches an RLC header to data transmitted from the transmission buffer to create an RLC PDU. The RLC PDU is transmitted to the multiplexer 725 and stored in the retransmission buffer 720. The RLC PDU stored in the retransmission buffer 720 is retransmitted at the request of the other RLC device or removed when it is confirmed to be successfully transmitted. do.

The RLC PDU delivered from the demultiplexer 750 is stored in the reception buffer 745, and the STATUS REPORT control unit 755 considers whether the STATUS REPORT trigger is satisfied and whether the STATUS_PROHIBIT timer is driven. To instruct the STATUS REPORT processing unit 740 to generate a STATUS REPORT. The STATUS REPORT control unit 755 also handles a STATUS REPORT delayed transmission after the STATUS_PROHIBIT timer expires, so that the STATUS REPORT is triggered by a lost PDU discovery trigger. In consideration of whether VR (R) and VR (MS) are the same at this time, it is determined whether to cancel the triggered STATUS REPORT (status report message).

The STATUS REPORT processing unit 740 generates and updates a STATUS REPORT under the control of the STATUS REPORT control unit 755.

Claims (2)

 A method for controlling a status report message transmission by a receiving device in a mobile communication system, Driving an order reordering timer according to whether the packet data unit is received, and triggering a status report message; If the status report prohibit timer is driven, generating a status report message for data received after the status report prohibit timer expires, or updating a status report message already generated according to a current reception condition; Determining whether to receive a lost packet data unit that caused the sequence reordering timer to be driven; If it is determined that the lost packet data unit has already been received, canceling the transmission of a STATUS REPORT. The method of claim 1, And if it is determined that the lost packet data unit has not been received, transmitting the generated status report message.