KR101514069B1 - Method of performing arq - Google Patents

Abstract

A method for performing ARQ (Automatic Repeat reQuest) in a wireless communication system is provided. The method includes receiving a data block including a sequence number indicating a transmission sequence, generating a plurality of Negative Acknowledgment (NACK) sequences, which are sequence numbers for data blocks that failed to be received in an ARQ window corresponding to a plurality of consecutive sequence numbers Dividing the plurality of NACK sequence numbers into a plurality of control blocks, and transmitting each of the plurality of control blocks. It is possible to quickly transmit all the NACK sequence numbers in the ARQ window, thereby preventing the transmission delay of the control block. Therefore, the performance of the entire system can be improved.

ARQ, RLC, MAC, PDU, AM

Description

[0001] METHOD OF PERFORMING ARQ [

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to a method for performing ARQ.

The next generation multimedia wireless communication system, which has been actively researched recently, is required to have a high-speed large-capacity system capable of processing and transmitting various information such as image and wireless data beyond the initial voice-oriented service. The purpose of a wireless communication system is to allow multiple users to make reliable communications regardless of location and mobility. However, a wireless channel is a wireless channel that is subject to path loss, noise, fading due to multipath, intersymbol interference (ISI) There is a non-ideal characteristic such as a Doppler effect. Accordingly, various technologies have been developed to overcome the non-ideal characteristics of the wireless channel and to increase the reliability of the wireless communication.

ARQ (Automatic Repeat Request) is one of techniques for increasing the reliability of wireless communication. The ARQ is to retransmit the data at the transmitter if the receiver fails to receive the data. There is also a Hybrid Automatic Repeat reQuest (HARQ) scheme combining FEC (Forward Error Correction) and ARQ.

Generally, layers of a radio interface protocol between a terminal and a base station are divided into a first layer (L1) based on the lower three layers of an open system interconnection (OSI) model widely known in a communication system, , A second layer (L2), and a third layer (L3).

A protocol data unit (PDU) is a data block to which a corresponding layer sends / receives data to and from a peer layer through a lower layer. That is, the layer transfers the protocol data unit to the lower layer or receives the protocol data unit from the lower layer. A service data unit (SDU) is a data block that the layer receives from an upper layer or transmits to an upper layer.

The Radio Link Control (RLC) layer of the second layer includes three operations: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode Mode exists.

The RLC in the acknowledged mode provides a bi-directional data transmission service and supports retransmission (ARQ) in case of transmission failure of an RLC data PDU. The RLC layer transmits the RLC data PDU to the peer RLC layer. The RLC layer may receive an RLC control PDU from the peer RLC layer. The RLC control PDU is used to report the reception state of the RLC data PDU in the peer RLC layer to the RLC layer. The reception state means reception success or reception failure. The RLC layer can retransmit the RLC data PDU that failed to be received in the peer RLC layer using the RLC control PDU.

When the RLC control PDU is frequently transmitted, transmission of the RLC data PDU is limited due to limited radio resources. However, if the transmission of the RLC control PDU is delayed, the recovery of the RLC data PDU using the ARQ is delayed. This causes unnecessary power consumption and lowers the reliability of communication.

Therefore, there is a need for an efficient ARQ performance method capable of quickly recovering data.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an efficient ARQ performance method capable of quickly recovering data.

In one aspect, a method for performing an ARQ in a wireless communication system is provided. The method includes receiving a data block including a sequence number indicating a transmission sequence, obtaining a plurality of NACK sequence numbers that are sequence numbers for data blocks that failed to be received in an ARQ window corresponding to a continuous plurality of sequence numbers Dividing the plurality of NACK sequence numbers into a plurality of control blocks, and transmitting each of the plurality of control blocks.

In another aspect, a method for performing an ARQ in a wireless communication system is provided. The method includes receiving a data block including a sequence number indicating a transmission sequence, obtaining a plurality of NACK sequence numbers that are sequence numbers for data blocks that failed to be received in an ARQ window corresponding to a continuous plurality of sequence numbers Transmitting a first control block including information on some NACK sequence numbers among the plurality of NACK sequence numbers and a second control block including information on remaining NACK sequence numbers of the plurality of NACK sequence numbers, .

In another aspect, a method for performing an ARQ in a wireless communication system is provided. The method includes a step of transmitting a data block including a sequence number indicating a transmission sequence, a payload including a plurality of NACK sequence numbers that are sequence numbers of data blocks failed to be received, and the header includes a plurality of NACK sequence numbers Receiving a control block including the header and the payload, the NACK sequence number including a control block type field indicating that the data block is for a data block of some of the data blocks that failed to be received; And processing the reception state of the corresponding data block for each sequence number belonging to the largest N NACK sequence number (N? 2, N is a natural number) from the 1 NACK sequence number.

It is possible to quickly transmit all the NACK sequence numbers in the ARQ window, thereby preventing the transmission delay of the control block. By transmitting a number of control blocks consecutively, the probability of the control block being lost can be reduced. This makes it possible to quickly recover the data block using ARQ. In addition, unnecessary power consumption can be reduced and the reliability of communication can be increased. Therefore, the performance of the entire system can be improved.

1 is a block diagram illustrating a wireless communication system. This may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may be referred to as an LTE (Long Term Evolution) system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) includes a base station (BS) 20 that provides a control plane and a user plane.

A user equipment (UE) 10 may be fixed or mobile and may be referred to as another term such as a mobile station (MS), a user terminal (UT), a subscriber station (SS) The base station 20 generally refers to a fixed station that communicates with the terminal 10 and may be referred to as another term such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point have. One base station 20 can provide service for at least one cell. A cell is an area where the base station 20 provides communication services. An interface for transmitting user traffic or control traffic may be used between the base stations 20. Hereinafter, downlink refers to communication from the base station 20 to the terminal 10, and uplink refers to communication from the terminal 10 to the base station 20.

The base stations 20 may be interconnected via an X2 interface. The base station 20 is connected to an EPC (Evolved Packet Core), more specifically, an MME (Mobility Management Entity) / S-GW (Serving Gateway) 30 via an S1 interface. S1 interface supports many-to-many-relations between the base station 20 and the MME / S-GW 30.

2 is a block diagram illustrating a functional split between the E-UTRAN and the EPC. The hatched box represents the radio protocol layer and the white box represents the functional entity of the control plane.

Referring to FIG. 2, the base station performs the following functions. (1) Radio resource management such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, and Dynamic Resource Allocation to the UE (RRM) function, (2) Internet Protocol (IP) header compression and encryption of user data streams, (3) routing of user plane data to the S-GW, (4) Scheduling and transmission, (5) scheduling and transmission of broadcast information, and (6) measurement and measurement reporting setup for mobility and scheduling.

The MME performs the following functions. (1) NAS (Non-Access Stratum) signaling, (2) NAS signaling security, (3) Idle mode UE reachability, (4) Tracking Area list management, , (5) Roaming, and (6) Authentication.

The S-GW performs the following functions. (1) mobiltiy anchoring, (2) lawful interception. The P-GW (PDN-Gateway) performs the following functions. (1) terminal IP (internet protocol) allocation, and (2) packet filtering.

3 is a block diagram showing elements of a terminal; The terminal 50 includes a processor 51, a memory 52, an RF unit 53, a display unit 54, and a user interface unit 55 . The processor 51 implements layers of the air interface protocol to provide a control plane and a user plane. The functions of the respective layers can be implemented through the processor 51. [ The memory 52 is connected to the processor 51 to store the terminal drive system, applications and general files. The display unit 54 displays various information of the terminal and can use well known elements such as a liquid crystal display (LCD) and an organic light emitting diode (OLED). The user interface unit 55 may be a combination of a well-known user interface such as a keypad or a touch screen. The RF unit 53 is connected to the processor to transmit and / or receive a radio signal.

The layers of the radio interface protocol between the terminal and the network are classified into L1 (first layer), L2 (first layer), and L2 (third layer) based on the lower three layers of the Open System Interconnection (Second layer), and L3 (third layer). The physical layer belonging to the first layer provides an information transfer service using a physical channel, and a radio resource control (RRC) layer located at the third layer Controls the radio resources between the UE and the network. To this end, the RRC layer exchanges RRC messages between the UE and the network.

4 is a block diagram illustrating a radio protocol architecture for a user plane. 5 is a block diagram illustrating a wireless protocol structure for a control plane. This represents the structure of the radio interface protocol between the UE and the E-UTRAN. The user plane is a protocol stack for transmitting user data, and the control plane is a protocol stack for transmitting control signals.

Referring to FIGS. 4 and 5, a physical layer (PHY) layer of the first layer provides an information transfer service to an upper layer using a physical channel. The physical layer is connected to a medium access control (MAC) layer at an upper layer through a transport channel, and data is transferred between the MAC layer and the physical layer through the transport channel. Data moves between physical layers between different physical layers, that is, between a transmitting side and a receiving physical layer.

The MAC layer of the second layer provides a service to a radio link control (RLC) layer, which is an upper layer, through a logical channel. The RLC layer of the second layer supports transmission of reliable data. There are three operation modes of the RLC layer according to the data transmission method, namely, a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (AM). The AM RLC provides a bi-directional data transmission service and supports retransmission when a RLC PDU (Protocol Data Unit) transmission fails.

The Packet Data Convergence Protocol (PDCP) layer of the second layer performs a header compression function to reduce the IP packet header size.

The third layer of Radio Resource Control (RRC) layer is defined only in the control plane. The RRC layer is responsible for the control of logical channels, transport channels and physical channels in connection with the configuration, re-configuration and release of radio bearers (RBs). RB denotes a service provided by the second layer for data transmission between the UE and the E-UTRAN. If there is an RRC connection between the RRC of the UE and the RRC of the network, the UE is in the RRC Connected Mode, and if not, the UE is in the RRC Idle Mode.

The non-access stratum (NAS) layer located at the top of the RRC layer performs functions such as session management and mobility management.

6 is a block diagram illustrating a data transmission and reception method of an RLC entity. The RLC entity may be an RLC entity of the base station or an RLC entity of the terminal.

Referring to FIG. 6, the RLC entity transmits or receives an RLC PDU. The RLC PDU is divided into an RLC data PDU or an RLC control PDU. The RLC entity transmits the RLC control PDU prior to the RLC data PDU.

First, a method of transmitting and receiving an RLC data PDU will be described.

The RLC entity receives an RLC SDU (Service Data Unit) from an upper layer. For example, the upper layer is an RRC layer or a PDCP layer. The RLC entity can receive an RLC SDU from an upper layer through an SAP (Service Access Point).

The RLC entity stores the received RLC SDU in a transmission buffer. The RLC entity forms an RLC data PDU from the RLC SDU. The RLC entity segments and concatenates the RLC SDUs according to the total size of the RLC PDUs. In addition, the RLC entity 100 forms a RLC data PDU by adding a header to the RLC SDU. An RLC entity delivers an RLC data PDU to a lower layer at a particular transmission opportunity. In addition, the RLC entity stores an RLC data PDU transmitted to a lower layer in a retransmission buffer.

The total size of the RLC PDU and the specific transmission time are indicated by the lower layer. For example, the lower layer is the MAC layer or the physical layer. The RLC entity may forward the RLC data PDU to the MAC layer over the logical channel. For example, the logical channels include DCCH (Dedicated Control Channel), DTCH (Dedicated Traffic Channel), and the like.

The RLC entity supports retransmission of RLC data PDUs. The RLC can retransmit the RLC data PDU stored in the retransmission buffer. If the RLC data PDU to be retransmitted does not match the overall size of the RLC PDU, the RLC entity may re-partition and concatenate the RLC data PDU into RLC data PDU segments.

The RLC entity receives an RLC PDU from a lower layer. An RLC entity may receive an RLC PDU over a logical channel. The RLC entity processes and processes the received RLC PDUs as RLC data PDUs or RLC control PDUs. If the RLC PDU is an RLC data PDU, the RLC entity stores the received RLC data PDU in a reception buffer. The RLC entity performs HARQ reordering of the RLC data PDUs in the transmission order. The RLC entity removes the header from the RLC data PDU. The RLC entity reassembles the RLC SDUs from the rearranged RLC PDUs. The RLC entity transmits the RLC SDU to the upper layer. If the RLC entity detects loss of the RLC data PDU, it requests retransmission to the peer RLC entity.

Hereinafter, a method of performing ARQ through transmission and reception of an RLC control PDU will be described. The RLC entity transmits the RLC control PDU to the peer RLC entity that transmitted the RLC data PDU. The RLC control PDU is used to report the reception status of the RLC data PDU. The reception state means reception success or reception failure. The RLC control PDU has a STATUS PDU.

The transmission of the RLC control PDU may be triggered in the following two cases.

First, when the RLC entity receives the polling information from the peer RLC entity, the RLC control PDU transmission may be triggered. The polling information is to request the RLC entity to receive status reports. The polling information may be included in the RLC data PDU. For example, the RLC entity receives an RLC data PDU with a polling bit field of '1'. Also, when the HARQ (Hybrid Automatic Repeat reQuest) reordering of the RLC data PDU with the polling bit field of '1' is completed, the RLC entity may cause the RLC control PDU transmission.

Secondly, when the RLC entity detects a reception failure of the RLC data PDU, the RLC control PDU transmission may be triggered. For example, the RLC entity starts a reordering timer if an RLC data PDU that failed to be received occurs. If the reordering timer expires, the RLC entity may be caused to transmit an RLC control PDU.

7 shows an example of an RLC control PDU. The RLC control PDU 100 comprises an RLC control PDU header and a status PDU payload. The RLC control PDU may include a padding bit at the end for octet alignment.

Referring to FIG. 7, the RLC control PDU header includes a data / control (D / C) field 110 and a control PDU type (CPT) field 120. The data / control field 110 indicates whether the RLC PDU is an RLC data PDU or an RLC control PDU. The length of the data / control field 110 may be one bit. The control PDU type field 120 indicates the type of the RLC control PDU. The length of the control PDU type field 120 may be three bits.

The following table shows an example of the control PDU type field 120.

Here, the size of the control PDU type field is set to 3 bits. When the value of the control PDU type field is '000', the RLC control PDU is a status PDU. If the value of the control PDU type field is '001' to '111', the RLC discards the RLC control PDU.

The Status PDU payload includes an ACK (ACK_SN) field 130 and a first Extension bit 1 (E1) field 140. The status PDU payload may include a Negative Acknowledgment (NACK) set. The status PDU payload may also include a Segment Offset (SO) set for each NACK set. NACK set includes a NACK sequence number (NACK_SN) field 151, a first extension bit field 152 and a second extension bit (Ext2 bit 2, E2) field 153. The segment offset set is composed of an SO start field 161 and an SO end field 162.

The ACK sequence number field 130 indicates the sequence number of the next RLC data PDU that is not included in the status PDU. Indicates the first sequence number that is larger than the sequence number of the NACK sequence number field 151 among the sequence numbers of RLC data PDUs not completely received. The length of the ACK sequence number field 130 may be 10 bits. The RLC entity that has received the RLC control PDU determines that the peer RLC entity has received all the RLC data PDUs up to 'ACK sequence number-1' except for the NACK sequence number.

The first extended bit field 140, 152 indicates whether a set of NACKs follows. The length of the first extension bit field 140, 152 may be one bit. The first extension bit field 140 may follow the ACK sequence number field 130. Also, the first extension bit field 152 may follow the NACK sequence number field 151.

The NACK sequence number field 151 indicates the sequence number of the RLC data PDU detected as loss in the RLC entity. Also, the NACK sequence number field 151 indicates the sequence number of the RLC data PDU even when a part of the RLC data PDU is lost. The length of the NACK sequence number field 151 may be 10 bits.

The second extension bit field 153 indicates whether or not a set of segment offsets follows. The length of the second extension bit field 153 may be one bit.

The SO start field 161 and the SO end field 162 indicate the lost fragment of the RLC data PDU corresponding to the NACK sequence number. The length of the SO start field 161 or the SO end field 162 may be 15 bits.

The SO initiation field 161 indicates the first position of the RLC data PDU fragment missing in the RLC data PDU. When the RLC data PDU is composed of a header and a data field, the SO start field 161 may indicate the first byte position of the missing RLC data PDU fragment in the data field of the RLC data PDU. The SO termination field 162 indicates the last position of the RLC data PDU fragment missing in the RLC data PDU.

8 is a flowchart illustrating an example of an ARQ method.

Referring to FIG. 8, the RLC of the MS transmits a buffer size to the MAC of the MS (S10). The buffer size identifies the total amount of data available across all logical channels of the logical channel group after the MAC PDU is complete. The amount of data can be indicated by the number of bytes. The buffer size may contain all available data to be transmitted in the RLC and PDCP. When the RLC control PDU transmission is triggered, the UE regards the RLC control PDU as valid data and estimates the size of the RLC control PDU.

The MAC of the MS transmits a Buffer Status Report (BSR) to the BS (S11). The buffer status report includes the buffer size.

The MAC of the terminal receives an UL grant (UL grant) from the base station (S12). The uplink grant allocates uplink radio resources. The uplink grant may be transmitted through a physical downlink control channel (PDCCH), which is a downlink control channel.

The MAC of the UE transmits the total size of the RLC PDU to the RLC of the UE (S13). The MAC indicates a transmission opportunity to the RLC and the total size of the RLC PDU to be transmitted in the transmission opportunity. The RLC of the UE constructs an RLC PDU according to the total size of the RLC PDU.

The RLC of the MS transmits the RLC control PDU to the MAC of the MS (S14). When the RLC control PDU is transmitted, the RLC of the UE starts a status prohibition timer (T_status_prohibit). The state prohibition timer is to prohibit the transmission of the RLC control PDU during operation. The RLC does not forward the RLC control PDU to the MAC even if the RLC control PDU transmission is caused while the status prohibition timer is operating. When the status quench timer expires, the RLC may forward the RLC control PDU to the MAC. The RLC transmits the RLC control PDU prior to the RLC data PDU. Therefore, the RLC control PDU is frequently transmitted by the RLC to prevent the RLC data PDU from being transmitted.

The RLC configures the RLC control PDU according to the overall size of the RLC PDU. Hereinafter, the range of the sequence number that can be indicated in the NACK sequence number field of the RLC control PDU is called an ARQ window. For example, the ARQ window can be expressed by the following equation.

Here, VR (R) is a Receive State Variable and VR (MS) is a Maximum STATUS Transmit State Variable. The receive state variable has the next value of the sequence number of the completely received RLC data PDU in sequence. The maximum state transmission state variable has the highest sequence number value that can be indicated in the ACK sequence number field when configuring the RLC control PDU.

The RLC obtains the NACK sequence number in the ARQ window. The NACK sequence number is a sequence number for an RLC data PDU that has not yet completely received the RLC data PDU in the ARQ window. The RLC sequentially packs the acquired NACK sequence numbers into a NACK sequence number field to configure an RLC control PDU. At this time, the RLC control PDU must be configured according to the overall size of the RLC PDU. Accordingly, the RLC control PDU may not include all of the plurality of NACK sequence numbers. If a byte segment of the RLC data PDU is not received, the RLC packs the SO start field and the SO end field together with the NACK sequence number field to form an RLC control PDU. In the ACK sequence number field, the RLC sets the sequence number of the RLC data PDU, which is not received in the status PDU but not received next.

9 is a flowchart showing another example of the ARQ performing method. This is a method of performing ARQ in a terminal, but it is also applicable to an ARQ method in a base station. The STATUS information is the reception state of the RLC data PDU in the RLC.

9, the reception state variable VR (R) is 0, and the maximum state transmission state variable VR (MS) is 9. Also, the RLC data PDU with sequence numbers 0. 3, 4, and 7 is not received. That is, the NACK sequence numbers, which are the state information of the RLC, are 0. 3, 4, and 7.

The MAC transmits the total size of the RLC PDU to the RLC (S20). The RLC forms a short status PDU with NACK sequence numbers 0 and 3 and an ACK sequence number 4 according to the total size of the RLC PDU. Hereinafter, the short status PDU means an RLC control PDU that does not include all of a plurality of NACK sequence numbers in the ARQ window but only a part of NACK sequence numbers. An RLC control PDU including all of a plurality of NACK sequence numbers in an ARQ window is called a status PDU by distinguishing it from a short status PDU.

The RLC transmits the short status PDU to the MAC (S21). The first state inhibit timer is started in accordance with the short state PDU transfer. While the first state prohibition timer is operating, the RLC control PDU is not transmitted even if the RLC control PDU transmission is caused. That is, the RLC knows the state information for the NACK sequence numbers 4 and 7, but can not transmit the RLC control PDU until the first state prohibition timer expires.

The RLC receives the RLC data PDU having the sequence number 0 from the peer RLC layer through the MAC (S22). In addition, the RLC receives the RLC data PDU having the sequence number 3 from the peer RLC layer (S23).

The reception state variable VR (R) is updated to 4, and the maximum state transmission state variable VR (MS) is 9. The RLC does not receive RLC data PDUs with sequence numbers 4 and 7.

The MAC transmits the total size of the RLC PDU to the RLC (S24). The RLC configures an RLC control PDU having NACK sequence numbers of 4 and 7 and an ACK sequence number of 9 according to the total size of the RLC PDU. The RLC control PDU is a status PDU since it includes all of a plurality of NACK sequence numbers in the ARQ window.

After the first state prohibition timer expires, the RLC transfers the status PDU to the MAC (S25). The second state inhibit timer is started in accordance with the transfer of the status PDU.

It is assumed that the RLC does not retransmit the RLC data PDUs of sequence numbers 0 and 3 after transmitting the short status PDU to the MAC. In addition, it is assumed that the total size of the RLC PDU received from the MAC is still small. At this time, after the first state prohibition timer expires, the RLC can construct a short state PDU with NACK sequence numbers 0 and 3 and ACK sequence number 4, as before.

The operation period of the state prohibition timer is information set by the RRC for RLC entity formation. This is the 3GPP TS 36.331 V8.2.0 (2008-05) Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) Radio Resource Control (RRC); See Section 6.3.2 of Protocol specification (Release 8). For example, the operation period of the state prohibition timer may be set between 0 ms (milliseconds) and 500 ms. The longer the operation duration of the status quench timer, the more time the RLC has to wait to send another RLC control PDU. Even if transmission of the RLC control PDU is caused, the RLC control PDU can not be transmitted until the state prohibition timer expires while the state prohibition timer is operating. This leads to a delay in data recovery using ARQ. Also, even if the short status PDU is lost during transmission, the short status PDU can not be sent again until the status prohibition timer expires. This also causes a delay in data recovery using ARQ.

Therefore, there is a need for an efficient ARQ performance method to solve such a problem.

10 is a flowchart illustrating an ARQ method according to an embodiment of the present invention. This does not drive the status prohibition timer when transmitting the short status PDU.

10, the reception state variable VR (R) is 0, and the maximum state transmission state variable VR (MS) is 9. In addition, the NACK sequence numbers, which are the RLC state information, are 0. 3, 4, and 7.

The MAC transmits the total size of the RLC PDU to the RLC (SlOO). The RLC configures a first short PDU with a NACK sequence number of 0, 3 and an ACK sequence number of 4 according to the total size of the RLC PDU.

The RLC transmits the first short status PDU to the MAC (S110). Since the short state PDU has been delivered, the RLC does not initiate the state inhibition timer. Therefore, if transmission of the RLC control PDU is triggered immediately after the transmission of the first short status PDU, the RLC uses the remaining status information to generate a second short status PDU having NACK sequence numbers of 4 and 7 and an ACK sequence number of 9 Can be configured. The RLC transmits the second short status PDU to the MAC (S120). Since the short state PDU has been delivered, the RLC does not initiate the state inhibition timer.

10, a first short status PDU is transmitted using some NACK sequence numbers among a plurality of NACK sequence numbers in an ARQ window, and a second short status PDU is transmitted using the remaining NACK sequence numbers of the plurality of NACK sequence numbers . However, this is merely an example, and a plurality of NACK sequence numbers in the ARQ window may be divided into a plurality of short status PDUs of 2 or more according to the total size of the RLC PDU.

In this manner, when the short-state PDU is transmitted, the operation of the state prohibition timer is advantageous in that the operation is simple.

11 is a flowchart illustrating an ARQ method according to another embodiment of the present invention. Unlike FIG. 10, FIG. 11 discloses a status prohibition timer after transmitting all status information in the ARQ window when transmitting a short status PDU.

Referring to FIG. 11, the reception state variable VR (R) is 0 and the maximum state transmission state variable VR (MS) is 9. In addition, the NACK sequence numbers, which are the RLC state information, are 0. 3, 4, and 7.

The MAC transmits the total size of the RLC PDU to the RLC (S200). The RLC configures a first short PDU with a NACK sequence number of 0, 3 and an ACK sequence number of 4 according to the total size of the RLC PDU. The RLC transmits the first short status PDU to the MAC (S210). The RLC transmits a second short state PDU having a NACK sequence number of 4, 7 and an ACK sequence number of 9 to the MAC (S220). Because the RLC has delivered all of the NACK sequence numbers in the ARQ window, the RLC starts the state inhibit timer.

FIG. 11 shows a case in which a plurality of NACK sequence numbers in the ARQ window are divided into two short PDUs and transmitted, but this is merely an example. A plurality of NACK sequence numbers in the ARQ window may be divided into a plurality of short status PDUs of 2 or more according to the total size of the RLC PDUs. In this case, the RLC starts a state inhibition timer after all of a number of short state PDUs have been transmitted.

In this manner, when all status information is transmitted after the short status PDU is transmitted and the status prohibition timer is started, all the NACK sequence numbers in the ARQ window can be transmitted quickly, and the transmission delay of the short status PDU can be prevented have. By transmitting a plurality of short status PDUs consecutively, the probability of the short status PDU being lost can be reduced. This makes it possible to quickly recover the RLC data PDU using the ARQ. In addition, unnecessary power consumption can be reduced and the reliability of communication can be increased. Therefore, the performance of the entire system can be improved.

However, when receiving the short status PDU in the RLC of the receiver, a method of processing the short status PDU of the RLC may be problematic. The receiver may be a base station or a terminal.

First, the RLC must identify whether the received RLC control PDU is a status PDU or a short status PDU. In order to identify whether the PDU is a status PDU or a short PDU, the RLC control PDU may use a control PDU type field indicating the type of the RLC control PDU.

The following table shows an example of a control PDU type field.

Value Description 000 STATUS PDU 001 short STATUS PDU 010-111 Reserved
(PDUs with this coding will be discarded by the receiving entity for this release of the protocol)

Here, the size of the control PDU type field is set to 3 bits. When the value of the control PDU type field is '000', the RLC control PDU is a status PDU. When the value of the control PDU type field is '001', the RLC control PDU is a short status PDU. When the value of the control PDU type field is '010' to '111', the RLC discards the RLC control PDU.

Hereinafter, a method of processing the short status PDU when the RLC control PDU received by the RLC is the RLC short status PDU will be described in detail.

12 shows a method of performing an ARQ when receiving a short status PDU according to another embodiment of the present invention. It is assumed that the RLC transmits RLC data PDUs with sequence numbers 0 to 8. [

Referring to FIG. 12, in step S300, RLC data PDUs of sequence numbers 0 to 8 are stored in the retransmission buffer of the RLC. The acknowledgment state variable VT (A) is 0 and the send state variable VT (S) is 8. The acknowledgment status variable has the next value of the RLC data PDU sequence number that has been acknowledged in order. The acknowledgment status variable is the lower edge of the transmission window. The acknowledged state variable is updated when the RLC receives an acknowledgment for an RLC data PDU of the same sequence number as the acknowledged state variable. The transmission status variable has the sequence number of the next RLC data PDU to be newly generated. The transmission status variable is updated when the RLC delivers an RLC data PDU of the same sequence number as the transmission status variable.

In step S310, the RLC receives a short status PDU with a first NACK sequence number of 4, a second NACK sequence number of 7, and an ACK sequence number of 9. Here, the first NACK sequence number is the lowest NACK sequence number among the values included in the NACK sequence number field of the short state PDU.

If the short status PDU is processed in the same manner as the status PDU, the RLC ACK processes the RLC data PDUs having the sequence numbers 0 to 8 except for the sequence numbers 4 and 7 among the RLC data PDUs. In this case, the acknowledgment state variable VT (A) is updated to 4.

However, in step S310, the peer RLC transmits the first short state PDU and the second short state PDU as in the case of FIG. 10 or 11, but the RLC does not receive the first short state PDU and only the second short state PDU Or the like. Therefore, in the case of a short status PDU, a different processing method than the status PDU is required.

In step S320, the RLC retransmits the RLC data PDU with the sequence number 4 and retransmits the RLC data PDU with the sequence number 7. In addition, the RLC receives an RLC data PDU having sequence numbers 5, 6, and 8, and performs ACK processing. At this time, the RLC does not ACK process the RLC data PDUs from the sequence numbers 0 to 3. That is, the RLC receives all the RLC data PDUs up to the 'ACK sequence number-1' excluding the NACK sequence number included in the short status PDU except for the interval from the acknowledged status variable to the first NACK sequence number, . For example, it is assumed that the short status PDU includes a first NACK sequence number, an n-th NACK sequence number (n is a natural number), and an ACK sequence number. Here, the RLC includes a period from the first NACK sequence number to the second NACK sequence number, a period from the second NACK sequence number to the third NACK sequence number, except for the interval from the acknowledged status variable to the first NACK sequence number. , ACK processing is performed only on the interval from the n-th NACK sequence number to the ACK sequence number.

As another method of processing the short status PDU, in the case of the short status PDU including the NACK sequence number, there is a method of not performing ACK processing. In this case, the RLC can perform the ACK processing upon receiving the status PDU after receiving the short status PDU. Alternatively, the RLC may perform ACK processing upon receiving a short status PDU including only the ACK sequence number after receiving the short status PDU.

In this manner, when the RLC receives the short PDU, it is possible to prevent an ACK processing error in the RLC data PDU by making the processing method different from that when the status PDU is received. Therefore, the reliability of communication can be increased.

All of the functions described above may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), etc. according to software or program code or the like coded to perform the function. The design, development and implementation of the above code will be apparent to those skilled in the art based on the description of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

1 is a block diagram illustrating a wireless communication system.

2 is a block diagram showing functional division between E-UTRAN and EPC.

3 is a block diagram showing elements of a terminal;

4 is a block diagram illustrating a wireless protocol structure for a user plane.

5 is a block diagram illustrating a wireless protocol structure for a control plane.

6 is a block diagram illustrating a data transmission and reception method of an RLC entity.

7 shows an example of an RLC control PDU.

8 is a flowchart illustrating an example of an ARQ method.

9 is a flowchart showing another example of the ARQ performing method.

10 is a flowchart illustrating an ARQ method according to an embodiment of the present invention.

11 is a flowchart illustrating an ARQ method according to another embodiment of the present invention.

12 shows a method of performing an ARQ when receiving a short status PDU according to another embodiment of the present invention.

Claims (15)

A method for performing Automatic Repeat reQuest (ARQ) in a wireless communication system, The method comprising: receiving a data block including a sequence number indicating a transmission order; Obtaining a plurality of Negative Acknowledgment (NACK) sequence numbers that are sequence numbers for data blocks that failed to receive in an ARQ window corresponding to a successive plurality of sequence numbers; Dividing the plurality of NACK sequence numbers into a plurality of control blocks; Transmitting each of the plurality of control blocks; Initiating a prohibition timer for prohibiting transmission of a control block during operation after transmitting all of the plurality of control blocks; And Initiating a reordering timer when a failed data block occurs, And when the reordering timer expires, the plurality of control blocks are transmitted. The method according to claim 1, Wherein the number of the plurality of control blocks is determined according to the amount of radio resources capable of transmitting one control block at a time. The method according to claim 1, Each of the plurality of control blocks including a header and a payload, The header includes a break field indicating that the header is a control block, Wherein the payload comprises at least one of the plurality of NACK sequence numbers. The method according to claim 1, Wherein the plurality of control blocks are transmitted when polling information requesting a reception status report is received. The method of claim 1, wherein each of the plurality of control blocks includes a Radio Link Control (RLC) control PDU (Protocol Data Unit). An apparatus for performing Automatic Repeat reQuest (ARQ) in a wireless communication system, Memory; And And a processor coupled to the memory, wherein the processor Receiving a data block containing a sequence number representing a transmission order; Obtaining a plurality of Negative Acknowledgment (NACK) sequence numbers that are sequence numbers for data blocks that failed to receive in an ARQ window corresponding to a successive plurality of sequence numbers; Classifying the plurality of NACK sequence numbers into a plurality of control blocks; Transmitting each of the plurality of control blocks; After transmitting each of the plurality of control blocks, initiating a prohibition timer for prohibiting transmission of the control block during operation; And If a failed data block occurs, initiates a reordering timer, And the plurality of control blocks are transmitted when the rearrangement timer expires. A method for performing an ARQ in a wireless communication system, The method comprising: receiving a data block including a sequence number indicating a transmission order; Obtaining a plurality of NACK sequence numbers that are sequence numbers for data blocks that failed to receive in an ARQ window corresponding to a successive plurality of sequence numbers; Transmitting a first control block including information on some NACK sequence numbers among the plurality of NACK sequence numbers; And And transmitting a second control block including information on a remaining NACK sequence number among the plurality of NACK sequence numbers. delete delete delete delete delete delete delete delete

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