Method and apparatus for transmitting and receiving status report in a mobile communication system

[0001] The present invention relates generally to a mobile communication system, and in particular to a method and apparatus for transmitting and receiving an Automatic Repeat reQuest (ARQ) status report in the ARQ layer.

[0002] The Universal Mobile Telecommunication Service (UMTS), which is an asynchronous third generation (3G) mobile communication system, uses Broadband

Wideband Code Division Multiple Access

- WCDMA). UMTS is based on the Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), which are part of European mobile communication systems.

[0003] As part of a third generation partner project (3^rd Generation Partnership Project - 3GPP) responsible for UMTS standardization, as the next generation UMTS mobile communication system, the so-called "Long Term Evolution" (LTE). LTE, which is expected to enter into force around 2010, is a technology for implementing high speed packet communication about 100 Mb / s. Accordingly, several projects are under consideration, including a project to reduce the number of nodes in the transmission path by simplifying network configuration, and another project to maximize the implementation of wireless protocols to wireless communication channels.

[0004] Fig. 1 illustrates the configuration of the advanced UMTS mobile communication system (Evolved UMTS - E-UMTS).

[0005] In Fig. 1, the radio access network configuration for the expanded UMTS 135 and 140 (E-UTRAN or E-RAN type) has been simplified to the two-node configuration of the expanded B nodes (ENB or B nodes) 110 to 130 and the base nodes 145 and 150. User Equipment (UE) 105 connects to the Internet Protocol (IP) using E-RAN 135 and 140.

EP 1 845 649 [0006] ENB 110 to 130, corresponding to existing B nodes, are connected to the UE via a wireless communication channel. Compared to existing B nodes, ENB 110 to 130 perform more complex functions.

[0007] In LTE, all user communication, including real-time services, such as voice over IP (VoIP), is supported over a shared channel. This means that there is a need for a device to collect information about the state of UE devices and to plan access granting according to these statuses, and access planning is managed by ENB 110 to 130. The terms "ENB" and "node B" are used interchangeably herein.

[0008] In LTE, as in High Speed ​​Downlink Packet Access (HSDPA) or in the Enhanced Uplink Dedicated Channel (EDCH), between ENB 110 to 130 and UE 105 implemented is Hybrid Automatic Repeat reQuest (HARQ). However, LTE cannot meet different requirements for Quality of Service (QoS) using only HARQ. Therefore, separate ARQs (or external ARQs) between ENB 110 to 130 and UE 105 may be implemented in the upper layer. [0009] LTE is expected to use Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology in the 20 MHz band for data transmission at a maximum speed of 100 Mb / s. In addition, LTE will use Adaptive Modulation & Coding AMC, which determines the modulation system and channel coding speed, depending on the UE channel status. Many mobile communication systems are currently considering, including LTE, using both HARQ and ARQ techniques for error correction.

[0010] HARQ is a technique for combining previously received data programmatically with retransmitted data without discarding previously received data, which increases the rate of reception of valid data. More specifically, the recipient in HARQ (Rx) mode determines the presence / absence of error in the received packet and sends an Acknowledged signal (ACK) or NonAcknowledged signal (NACK) to the sender sending in HARQ (Tx) mode depending on the presence / no error. HARQ Tx retransmits the HARQ packet or

EP 1 845 649 transmission of a new HARQ packet depending on the ACK / NACK signal. HARQ is characterized in that it programmatically combines a retransmitted packet with a previously received packet, thereby reducing the error rate.

[0011] In contrast, ARQ, as a technique for checking the sequence number of a received packet and sending a request to retransmit the missing packet by means of a status report, does not programmatically link the previously received packet with the retransmitted packet.

[0012] Since both ARQ and HARQ have the function of recovering erroneous packets, it is considered that there is no need to simultaneously use ARQ and HARQ. However, since you cannot obtain a sufficiently low error rate when only HARQ is used, most packet data services should use ARQ and HARQ together.

[0013] Since the HARQ ACK / NACK signal is a 1-bit response signal, it is difficult in HARQ to reduce the error rate by channel coding. Therefore, it is difficult to obtain a sufficiently low packet error rate using only HARQ. That is, if the HARQ NACK signal is not recognized as a HARQ signal, the corresponding packet is completely lost at the HARQ layer. Therefore, signal reliability at HARQ ACK / NACK is an important factor in determining the packet error rate at the HARQ layer.

[0014] A system in which ARQ and HARQ operate together can increase the efficiency of ARQ using information from the HARQ layer. For example, the HARQ Tx unit sends the ARQ packet end time information to the ARQ transmitting unit (Tx), and the ARQ Tx unit compares the status report arrival time with the ARQ packet end time, thereby preventing unnecessary retransmission.

[0015] If the appearance and transmission of a status report occur at the same time, then the time at which the HARQ packet containing this status report was originally received is substantially equal to the time at which the status report appeared. However, if the time the status report appears differs from the time the status report was transmitted, the ARQ Tx unit cannot evaluate the time the status report appeared and recognizes as the time the status report appears only the time at which the HARQ packet containing this status report was originally received. .

[0016] For example, the receipt of success / failure information for a specific ARQ packet (s) received delayed relative to the time the status report appears in the ARQ Rx receiving unit cannot be included in the previously generated status report. Because the status report does not include the receipt of success / failure information for a specific ARQ packet, the ARQ Tx unit retransmits the specified ARQ packet to the ARQ Rx unit, considering that it failed to transmit that ARQ packet. Thus, unnecessary retransmissions may occur in a conventional mobile communication system.

[0017] EP 1286491 A1 describes a method and apparatus for multi-channel ARQ. An ARQ string is provided in which data packets are transmitted from the transmitter to the receiver at the first specified time intervals, and the positive, ACK, and negative, NACK, acceptance signals are transmitted from the transmitter to the receiver at the second specified time intervals. For each data packet that has been transmitted from transmitter to receiver, at least two second intervals can be used to transmit acknowledgment signals, thereby improving synchronous reverse transmission without including feedback asynchronous transmission systems known to have a large signal layer.

[0018] EP 1263159 A1 relates to a method and a receiver for improved packet data transfer in a transmission request requesting a repetition. In the case of transmission of data packets from the transmitter to the receiver, damaged data packets are detected and the first status message is sent from the receiver to the transmitter, which includes an indication of the damaged data packets. According to this first status message, retransmission of damaged data packets is carried out. The receiver initializes the timing unit according to the sending of the first status message and then determines that another status message is needed indicating the damaged data packets. Then, corrupted data packets for this next status message are selected. A damaged data packet is selected if it was not indicated in the first status message or if the timing unit reached the threshold. Only indications of selected data packets are included in the next status message and the receiver sends this next status message.

[0019] An aspect of the present invention is to address at least the above-mentioned problems and / or disadvantages, and to provide at least the advantages indicated below.

[0020] Accordingly, it is an object of the present invention to provide a method and apparatus in which an ARQ Rx receiving unit generates and sends a status report at a time when it can substantially send this status report in a mobile communication system.

[0021] This object is achieved by the essence of the independent claims.

[0022] Preferred embodiments are defined in the dependent claims.

[0023] Another aspect of the present invention is to provide a method and apparatus in which the ARQ (Tx) transmitting entity estimates the time of arrival of a status report after receiving this status report in a mobile communication system.

[0024] Still another aspect of the present invention is to provide a method and apparatus in which the ARQ Tx entity estimates the time of appearance of a status report in the HARQ layer in a mobile communication system in which ARQ and HARQ operate simultaneously.

[0025] Still another aspect of the present invention is to provide a method and apparatus in which an ARQ Tx unit removes the time error associated with a scheduled HARQ packet transmission delay when it estimates the time the status report appeared during the initial receipt of the HARQ packet containing the status report in the mobile communication system in which ARQ and HARQ operate simultaneously.

[0026] In accordance with one aspect of the present invention, there is provided a method of transmitting a status report in an Automatic Repetition Request (ARQ) layer in a mobile communication system comprising an ARQ layer and a Hybrid Automatic Replay Request (HARQ) layer. The method of transmission includes recording by determining by the receiving unit ARQ Tx whether transmission of the status report is allowed when the predetermined condition for generating the status report is met; if transmission of the status report is allowed, generating a status report, depending on the receiving state of the ARQ packets, until consent to the transmission of the status report and transmitting the generated status report to the ARQ transmitting unit (Tx) via the allocated means of transmission.

[0027] According to yet another aspect of the present invention, there is provided a method of receiving a status report in an Automatic Repetition Request (ARQ) layer

EP 1 845 649 in a mobile communication system comprising an ARQ layer and a Hybrid Automatic Repetition Request (HARQ) layer. The receiving method includes recording by the transmitting / receiving unit (Tx / Rx) in the HARQ of the original receipt time of the HARQ packet, when the HARQ packet is originally received from the receiving unit ARQ (Rx); if it is determined that the HARQ packet has been received successfully, detecting the status report contained in the HARQ packet and sending the detected status report to the ARQ transmitting unit (Tx) together with the time of the original receipt of this HARQ packet; and the ARQ Tx entity recognizing the original receipt time as the time of generating this status report, and retransmitting the desired ARQ retransmission packets, according to the status report.

[0028] According to a further aspect of the present invention, there is provided a device for transmitting a status report in an Automatic Repetition Request (ARQ) layer in a mobile communication system comprising an ARQ layer and a Hybrid Automatic Replay Request (HARQ) layer. The transmission device includes a status report generator to determine if a status report transmission is allowed when a predetermined condition report generation condition is met at an ARQ receiving unit (Rx), and if status report transmission is allowed , it generates a status report depending on the packet receipt status ARQ until transmission of the status report is allowed; and a transmitting unit for transmitting the generated status report to the ARQ transmitting unit (Tx) via the allocated means of transmission.

[0029] In accordance with yet another aspect of the present invention, there is provided a device for receiving a status report in an Automatic Repetition Request (ARQ) layer in a mobile communication system comprising an ARQ layer and a Hybrid Automatic Replay Request (HARQ) layer. The receiving apparatus includes a transmitting / receiving unit (Tx / Rx) in HARQ for recording the original receipt time of the HARQ packet when the HARQ packet is originally received from the receiving ARQ unit (Rx), and if it is determined that the HARQ packet has been successfully received , for detecting the status report contained in this HARQ packet and sending the detected status report together with the time of the original receipt of the HARQ packet; and an ARQ transmitting unit (Tx) for detecting the original receipt time as the time of generating this status report, and retransmitting the ARQ packets whose retransmission was requested, according to the status report.

EP 1 845 649 [0030] The above objectives and other aspects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

Fig. 1 illustrates the configuration of the advanced UMTS mobile communication system;

Fig. 2 is a flowchart illustrating a status report transmission procedure in a general mobile communication system;

Fig. 3 is a flow chart illustrating the status report transmission procedure of the present invention;

Fig. 4 is a flowchart illustrating the process of generating and transmitting a status report in an ARQ Rx unit according to the present invention;

Fig. 5 is a flow chart of the HARQ Rx unit of the present invention;

Fig. 6 is a flow diagram of the operation of an ARQ Tx unit according to the present invention; and

Fig. 7 is a block diagram illustrating the structure of an ARQ Tx / Rx unit according to the present invention.

[0031] Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The following description omits the detailed description of known functions and configurations for clarity and brevity.

[0032] The present invention provides a system in which the ARQ sending unit removes the error associated with the delay of scheduled status report transmission when it expects a status report to appear in the HARQ layer in a mobile communication system in which ARQ and HARQ operate simultaneously.

[0033] Referring to Fig. 2, the illustrated status report transmission procedure includes a delayed scheduled transmission. The ARQ transmitting unit (Tx) 205 transmits ARQ packet (s) in operation 225 from the ARQ receiving unit (Rx) 220 via the HARQ transceiver units (Tx / Rx) 210 and 215. In 3GPP, instead of the term "packet," usually the term "Protocol Data Unit" (PDU). Thus, in the present invention, the terms "packet" and "PDU" will be used simultaneously. In operation 230, if

EP 1 845 649 any condition for generating a status report is met, the ARQ Rx 220 unit generates a status report and then sends this status report to the ARQ Tx 205 unit to request retransmission of missing (or unsuccessful reception) ARQ PDU and / or notify successful ARQ PDU receipt.

[0034] The conditions in which the ARQ Rx 220 generates a status report may be defined in the connection configuration process and these conditions may include the following states.

- The ARQ Rx 220 unit generates a status report when it detects a missing ARQ PDU.

- The ARQ Rx 220 unit generates a status report in set cycles.

[0035] If any of the conditions for generating a status report are met, then the ARQ Rx unit 220 generates a status report.

[0036] Preferably, a status report is sent immediately after it is generated. However, in a communication system that uses scheduled ENB transmission, such as LTE, there is a high probability of using a scheduled transmission delay 235. For example, if an ARQ Rx 220 unit containing the UE does not have the allocated transmission medium at the time 230 when the status report is generated, the UEs should first undergo a transmission planning process involving sending a request for the transmission medium and receiving the allocated transmission medium, i.e. in the transmission planning process a 235 scheduled transmission delay of a minimum of several dozen ms may be required.

[0037] After the ARQ Rx unit 220 experiences a scheduled transmission delay 235, the status report is stored in the HARQ packet in operation 240, and then, ultimately sent to the ARQ Tx / Rx 210 unit, i.e. the bottom layer of the ARQ Tx 205 unit, via the HARQ Tx / Rx 215 unit.

[0038] The following description assumes, for example, that the HARQ packet containing the status report successfully reaches the ARQ Tx 205 as a result of three repetitive transmissions.

[0039] This occurs if the ARQ Rx unit 220 sends a status report to the HARQ Tx / Rx 215 unit (i.e. to the HARQ Tx / Rx unit at the receiving unit) in operation 240, the receiving HARQ Tx / Rx 215 unit retains this status report in the HARQ packet and sends this HARQ packet to the transmitting HARQ Tx / Rx 210 unit (i.e.

EP 1 845 649 HARQ Tx / Rx units in the transmitting unit) in operation 245 (first transmission). The transmitting HARQ Tx / Rx unit 210 checks in operation 250 the original receipt time in which it originally received the HARQ packet and determines whether this HARQ packet has been received successfully without errors. If it is determined that the sending HARQ Tx / Rx 210 unit failed to receive the HARQ packet successfully, then in operation 255 the sending HARQ Tx / Rx 210 unit sends a NACK signal to the receiving HARQ Tx / Rx 215 unit, and in response to the receiving NACK signal the HARQ Tx / Rx 215 unit in operation 260 retransmits the HARQ packet to the transmitting HARQ Tx / Rx 210 unit (second transmission). The transmitting HARQ Tx / Rx unit 210 combines the HARQ packet from the second transmission with the HARQ packet from the first transmission and then determines whether this HARQ packet has been received successfully.

[0040] If the sending HARQ Tx / Rx 210 unit failed to receive the HARQ packet again successfully, then in operation 265 the sending HARQ Tx / Rx 210 unit sends the NACK signal again to the receiving HARQ Tx / Rx 215 unit. In response to the NACK signal the receiving HARQ Tx / Rx 215 unit in operation 270 re-transmits the HARQ packet to the transmitting HARQ Tx / Rx 210 unit (third transmission). If the transmitting HARQ Tx / Rx 210 unit has successfully received the HARQ packet now, the transmitting HARQ Tx / Rx 210 unit downloads the status report contained in the HARQ packet and in operation 275 sends the downloaded status report to the ARQ Tx 205 unit, and then sends the ACK signal for that packet HARQ to the receiving HARQ Tx / Rx 215 unit in operation 280.

[0041] The ARQ Tx 205 prevents unnecessary retransmission of the ARQ PDU by recognizing the time 230 to generate the status report in which the time report was generated. Regarding the time 230 to generate the status report, it is directly expressed in the status report or the ARQ Tx 205 unit estimates the time 230 to generate the status report using the original receipt time 250 of the HARQ packet containing this status report. However, the method using the time of the original receipt 250 of the HARQ packet is imprecise because it omits the delay of the scheduled transmission 235 used in the status report transmission.

[0042] In view of the above, the preferred embodiment of the present invention removes the error associated with the use of a scheduled transmission delay state in the transmission report when assessing the time of generating the status report based on the time of the original receipt of the HARQ packet containing this state report. Although condition

When the status report generation is satisfied, the ARQ Rx unit does not immediately generate the status report, but generates this status report after preparing its transmission, such as the allocation of the means of transport. In addition, the ARQ Tx unit recognizes as the time of generating the status report the time of the original receipt of the HARQ packet containing the status report.

[0043] With reference to Fig. 3, a status report is initiated in operation 325 if one of the requirements for generating a status report is met in the ARQ Rx 320 unit. A condition for generating a status report may be periodic generation of a status report or detection of a missing ARQ PDU. Although the status report is initialized, the ARQ Rx 320 performs the next operation without generating the status report immediately.

[0044] This means that the ARQ Rx unit 320 notifies the lower layer (not shown) of data for transmission, and the lower layer allows the ARQ Rx 320 to provide data for transmission if some transmission medium is currently allocated. For example, the bottom layer, i.e. the unit responsible for managing the means of transmission, is the planner in ENB mode and is the administrator of the means of transmission for the UE. If, at the current time, when the ARQ Rx 320 unit notifies about the presence of data for transmission, no transmission medium is allocated, then the lower layer obtains the allocation of the transmission medium by an appropriate process. If the ARQ Rx 320 unit belongs to the UE, the bottom layer sends a demand for the transmission medium to the ENB and waits until the transmission medium is allocated by the ENB. When the transmission medium is allocated, the bottom layer allows the ARQ Rx unit to provide this data for transmission.

[0045] After obtaining consistent transmission from the bottom layer, the ARQ Rx unit 320 generates a status report in operation 330. This status report contains the serial numbers of the missing ARQ PDUs for the retransmission request and the ARQ PDU serial numbers received successfully until the status report was generated. Missing ARQ PDUs apply to those ARQ PDUs that have failed to receive (NACK), where ARQ PDUs whose receipt is not yet known do not match the missing ARQ PDUs.

[0046] The ARQ Rx unit 320 sends a status report to the receiving HARQ Tx / Rx 315 unit in operation 335, and the receiving HARQ Tx / Rx 315 unit generates a packet

EP 1 845 649

The HARQ containing this status report and then in operation 345 transmits this HARQ packet to the transmitting HARQ Tx / Rx 310 unit using the allocated transmission means.

[0047] The transmitting HARQ Tx / Rx unit 310 stores the time 340 of the original receipt of the HARQ packet and determines whether this HARQ packet has been successfully received. If the HARQ packet was received successfully, in operation 350 the sending HARQ Tx / Rx 310 unit sends the time of the original receipt of the HARQ packet to the ARQ Tx 305 unit together with the status report contained in the HARQ packet.

[0048] In operation 355, the ARQ Tx unit 305 recognizes, as the status report generation time, the original receipt time 340 transmitted in operation 350 along with the status report. If there is an ARQ PDU that was transmitted before the time the status report was generated, but the AKC has not yet confirmed the status report, then the ARQ Tx 305 determines that the ARQ PDU requires retransmission.

[0049] With reference to Fig. 4, the condition for generating a status report is met and in operation 405 a status report is initiated, and then the ARQ Rx unit in operation 410 indicates the presence of data for transmission, the lower layer responsible for managing the transmission means. Data for transmission include the status report to be sent. If the lower layer allows data transmission in operation 415 by granting a transmission means to be used for data transmissions containing a status report, then the ARQ Rx unit proceeds to operation 420, and if data transmission is not authorized, the ARQ Rx unit waits for data transmission permission. For example, if the UE containing the ARQ Rx unit is determined in the current transmission time interval, or if the ENB containing the ARQ Rx unit has designated a specific UE for transmission of the status report, the ARQ Rx unit determines that the transmission of data containing the status report is possible.

[0050] In operation 420, the ARQ Rx unit generates a status report depending on the ARQ PDU receipt status up to the present time. The status report contains the ARQ PDU serial numbers received successfully until the present time, i.e. confirmed ACK ARQ PDU, and ARQ PDU serial numbers whose receipt until the present time has failed, i.e. unacknowledged NACK ARQ PDU for which the status report was generated. Because the ARQ Rx unit cannot recognize the existence of an ARQ PDU that is in the HARQ procedure in its lower HARQ Tx / Rx unit or is completely lost in the delivery process, the ARQ Rx unit does not include the number

EP 1 845 649 serial of this ARQ PDU for status report. Then, in operation 425, the ARQ Rx unit forwards the status report to its lower HARQ Tx / Rx unit, and this HARQ Tx / Rx unit contains the status report in the HARQ packet and sends the HARQ packet to the ARQ Rx unit via the equivalent of the HARQ Tx / Rx unit.

[0051] In summary, if the condition for generating a status report is met, the ARQ Rx unit waits until it can actually send this status report and generates this status report at the time when it can send this status report. In this way, the ARQ Rx unit maximally approximates the time of generating the status report to the time of starting the transmission of this status report. Therefore, the ARQ Rx entity may determine that the "status report receipt time" is substantially equal to the "status report generation time". Consideration may be given to the delay resulting from the transmission, i.e. the time between the moment when the HARQ packet containing the status report is sent from the receiving HARQ Tx / Rx unit and the moment when the HARQ packet is received by the sending HARQ Tx / Rx unit. However, this is not related to the present invention, so a detailed description will be omitted.

[0052] Referring to Fig. 5, a new HARQ packet is received in operation 505, i.e. if this HARQ packet was originally received, then the HARQ Tx / Rx unit records the original receipt time of this HARQ packet in operation 510.

[0053] The HARQ Tx / Rx unit recognizes the receipt of a new HARQ packet depending on the decoding of control information in the HARQ packet transmitted on the control channel, such as the Retransmission Sequence Number RSN or New Data Indicator (NDI). For example, if RSN is set to "0" or NDI is set to a value different from the previous value, then the transmission of the new HARQ packet begins.

[0054] In operation 515, the HARQ Tx / Rx unit performs the receiving process in the HARQ mode of the HARQ packet. This means that the HARQ Tx / Rx unit determines the presence / absence of an error in the HARQ packet using the Cyclic Redundancy Checking (CRC) procedure in the HARQ packet. If a CRC error occurs, the HARQ Tx / Rx unit stores the HARQ packet in the software buffer of the appropriate HARQ processor for the software connection. However, if the CRC error does not occur, the HARQ Tx / Rx entity processes and forwards this HARQ packet to its higher layer.

[0055] If the receipt 520 is successful in operation 520, i.e. there are no more errors in the HARQ packet, the HARQ Tx / Rx unit proceeds to operation 525 in which it de-multiplexes the higher layer data contained in the HARQ packet. Then, in operation 530, the HARQ Tx / Rx unit forwards the de-multiplexed higher layer data to the corresponding higher layer. In particular, a status report contained in de-multiplexed upper layer data is sent to the ARQ Rx unit. At this time, the initial receipt time of the HARQ packet saved in operation 510 is sent to the ARQ Rx unit simultaneously. In operation 535, the HARQ Tx / Rx unit removes the initial receipt time of the HARQ packet stored in operation 510, and then proceeds to operation 540, in which it clears HARQ processor buffer.

[0056] If the operation 520 fails to receive the HARQ packet, i.e. if the transmission of the new HARQ packet begins, although there are still errors in the given HARQ packet, the HARQ Tx / Rx unit in the operation 535 removes the original receipt time of the HARQ packet and clears the program HARQ processor buffer in operation

540.

[0057] Referring to Fig. 6, if the ARQ Tx unit receives in operation 605 the status report and the time of the original receipt from the transmitting HARQ Tx / Rx unit, which is its lower layer, the ARQ Tx unit recognizes in the operation 610 the time of the original receipt as the time generate a status report and perform the necessary operations in accordance with the contents of this status report. In other words, the ARQ Tx unit retransmits the missing ARQ PDUs indicated in the status report and the ARQ PDUs that were sent before the time the status report was generated but were not confirmed by the ACK via the status report.

[0058] The term "time" as used throughout the present description will now be discussed in detail.

[0059] The present invention uses a variety of different "time" segments that should be recognized by both the UE and ENB, such as "status report generation time", "original receipt time" and "transmission completion time". To allow the simplest way to recognize the same index indicating a given time by both nodes the same, both UE and ENB contain synchronized clocks. However, in general mobile communication is

EP 1 845 649 more widely accepted that UEs use the time system transmitted by the ENB, rather than individual synchronized clocks.

[0060] In mobile communication, a "frame" is used as the unit of time. "Frame" means the period of time used as the basic unit for sending and receiving. For example, in UMTS, the length of one frame is 10ms.

[0061] In a conventional mobile communication system such as UMTS, the ENB includes a clock (or counter) that increases by 1 at each frame border. The counter value increases by 1 every 10 ms, and the counter starts when the frame is initialized. The counter's output value increases at each frame border and is called the frame number. Because the ENB periodically broadcasts the frame number, both UE and ENB can identify the frame number for the specific frame.

[0062] Accordingly, the frame number broadcast by ENB can be used as the "time" described in the present invention. For example, the status report generation time may be replaced by the frame number for the frame in which the status report was generated, and the transmission end time may be replaced by the number of the frame in which the transmission was completed. In particular, the frame number has a hierarchical structure. For example, in LTE, because the send / receive unit has a short interval, i.e. 0.5 ms, the system uses a period longer than 10 ms as the frame unit instead of using a 0.5 ms frame, and can use 0.5 ms as the sub-frame unit. Thus, in a system in which one 10 ms frame consists of 20 0.5 ms subframes, a combination of frame number and subframe number can be used as the time index. For example, time 2505.11 means sub-frame # 11 in frame # 2505.

[0063] As shown in Fig. 7, the ARQ 700 unit includes a transmit controller 705, send buffer 710, frame assembly 715, retransmission buffer 720, status report generator 740 and receive buffer 745. The ARQ 700 unit is connected to multiplexer 725 and de multiplexer 750. Although only one ARQ 700 unit is shown, multiple ARQ units not shown may be provided. The 725 multiplexer multiplexes ARQ packets (i.e. ARQ PDU packets) supplied from multiple ARQ 700 units into one HARQ packet, and the de-multiplexer 750 de-multiplexes the HARQ packet received from the HARQ 730 processor into multiple ARQ packets (i.e., ARQ PDU packets) and provides ARQ packets to the corresponding ARQ units.

EP 1 845 649 [0064] The HARQ processor 730 is a device for transmitting / receiving a HARQ packet by means of a specific HARQ operation, and the transceiver 735 is a device for modulating the HARQ packet to a radio signal before it is transmitted and demodulating the received radio signal. De-multiplexer 750 stores the received ARQ PDU in the receive buffer 745.

[0065] The status report generator 740, if any of the specified conditions for generating the status report are met, notifies the transmitting controller 705 about the initiation of the status report. Then, if the 705 sending controller allows the status report to be sent, the 740 status report generator checks the ARQ PDU serial numbers stored in the receive buffer 745, recognizes the successfully received ARQ PDU numbers and the successfully received ARQ PDU serial numbers that need to be retransmitted and, accordingly , generates a status report. The status report generator 740 sends the generated status report to the appropriate node via the 725 multiplexer.

[0066] The packet generated in the upper layer is stored in the transmit buffer 710. The packet from the upper layer is formatted to the appropriate size in the frame assembly 715, configured in the ARQ packet having the header with the serial number placed in it, and then delivered to the 725 multiplexer. Copy ARQ packet is stored in the retransmission buffer 720. [0067] Transmission controller 705 analyzes the status report initiation report provided from the status report generator 740 and controls the data transmission from the transmission buffer 710 and the retransmission buffer 720 depending on the result of this analysis. In particular, the transmitting controller 705 notifies the lower layer about the amount of data stored in buffers 710 and 720, and, depending on the amount of data to be transmitted in the next transmission period indicated by the lower layer, the transmitting controller 705 determines the data to be transmitted in the next transmission period and controls the buffers 710 and 720 so that they issue the appropriate data. The amount of data to be transmitted is determined depending on the means of transmission allocated.

[0068] In particular, after receiving the status report initiation report from the status report generator 740, the transmitting controller 705, if it receives permission to transmit data from the lower layer, notifies the status report generator 740 to generate the status report. Accordingly, the status report generator 740 in the ARQ 700 generates a status report at the moment when it is actually

EP 1 845 649 data transmission is allowed and this status report is sent immediately by the allocated means of transmission.

[0069] In a mobile communication system using a transmission planning ENB system, the present invention adapts the time in which a status report is generated in the ARQ Rx unit to the time in which this status report is actually transmitted so that the ARQ Tx unit can read the time the status report was generated from the original receipt time of the HARQ packet containing this status report, and can minimize errors associated with an invalid status report.

[0070] As can be understood from the present description, the ARQ Rx unit generates and sends a status report after a scheduled delay, and the ARQ Tx unit adopts as the status report generation time the original receipt time of the HARQ packet containing this status report, thereby preventing unnecessary retransmission in connection with error of discrepancy between the time the status report was generated and the time of the original receipt.

[0071] Although the present invention has been described and illustrated with reference to some preferred embodiment thereof, those skilled in the art understand that various changes in form and detail can be made therein without departing from the scope of the present invention as defined in the appended claims.

Proxy:

Ewa Grenda, patent attorney

EP 1 845 649