KR101647373B1 - Method of retransmitting Data using Random Linear Coding in a Wireless Access System - Google Patents

Abstract

The present invention relates to a wireless access system, and more particularly, to a data retransmission method using random linear coding. According to an aspect of the present invention, there is provided a method of retransmitting data to a receiving end of a transmitting end, comprising: transmitting a plurality of original data packets corresponding to a single encoding end to at least one receiving end; And transmitting the determined number of encoded data packets to the one or more receiving ends according to the received feedback. At this time, the encoded data packet may be generated by performing Random Linear Coding (RLC) on the plurality of original data packets in the single encoding unit.

Random linear coding, MBS, feedback

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a data retransmission method using random linear coding in a wireless access system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless access system, and more particularly, to a method of retransmitting data using random linear encoding.

Hereinafter, a multicast broadcast service (MBS) will be described.

A terminal receiving a broadcast or MBS service in a wireless communication network obtains information on a service through higher-level procedures with a server providing the service to start the service. When the terminal decides to receive the service, the server transmits the data to the area to which the terminal belongs. The terminal can receive the service from the base station through the connection procedure with the base station located in the area.

More specifically, data transmission between a base station (BS) and a mobile station (MS) in a broadband wireless access system is performed through a "service flow ". The service flow includes an SF ID (Service Flow Identifier) for identifying a corresponding service flow between a base station and an MS, a CID (Connection IDentifier) for identifying a connection for delivering service flow traffic, ) And quality of service (QoS) parameters related to the quality of service.

Generally, the service flow forms a one-to-one connection between the base station and the MS. However, the MBS used for transmitting MBS data in an IEEE 802.16 system features a point-to-multipoint service that transfers data from one source to multiple recipients. Therefore, the base station delivers the same data to multiple MSs through one service flow.

That is, when generating the MBS service flow of the base station and the MS, the base station grants the same CID to the MSs requesting MBS data reception so that the same MBS data can be simultaneously received by several MSs. The coverage that can provide service by giving one CID to several MSs is called MBS zone.

The MBS zone can be composed of several base stations. In a MBS zone, several base stations can provide the same service in a plurality of cells through one service CID. Because of this nature, the MBS typically delivers data common to multiple recipients across multiple base stations from one source.

In order to start the MBS service, the UE establishes a connection with the BS through a dynamic service addition (DSA) process. Through the connection setup, the user receives the connection identifier and QoS information.

Among the information used for the MBS, the configuration of the MBS_MAP message is shown in Table 1 below.

The MBS_MAP message is information that is sent from the base station to the terminal to receive the service and transmits information for reading the service. The MS receiving the MBS_MAP message can confirm the service reception point of the MBS through the additional information such as MBS_DATA_IE or Extended_MBS_DATA_IE.

The MBS_DIUC_Change_Count field may be used to indicate a change in the burst profile used for multi-base station MBS data. If MBS_DIUC_Change_Count is changed, the terminal shall wait until the DCB message is received unless the DL burst profile TLV is included in the MBS_MAP.

The MBS_DATA_IE designates an area to which the current MBS data is allocated and an area to which the MBS data is to be allocated next. This allows the user to receive data at the present time and to know the allocation area to be read next time.

An entity for distributing MBS data to a serving base station in charge of the corresponding terminal is referred to as "MBS " in this specification, so that it can be transmitted to a terminal receiving data from an MBS content provider, Quot; network ". Typically, an MBS server, an MBS gateway, or an MBS controller may be used.

In general, there is no proper data retransmission method for data broadcasted or multicasted from a transmitting end (i.e., base station) to a receiving end (i.e., mobile node) as in the MBS described above. Also, the MBS network transmits MBS data at the lowest data rate that all terminals can receive. Therefore, efficient use of radio resources becomes difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method of efficiently transmitting and receiving data through retransmission.

It is another object of the present invention to provide a data retransmission method in which a transmitting end acquires information of a receiving end through feedback of a receiving end and transmits an efficiently encoded data block so that the receiving end can recover the error.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

According to an aspect of the present invention, there is provided a method of transmitting and receiving data through retransmission by a transmitting end and a receiving end.

According to an aspect of the present invention, there is provided a method of retransmitting data to a receiving end of a transmitting end, the method comprising: transmitting a plurality of original data packets corresponding to one coding unit to one or more receiving ends; Receiving feedback on a reception error and transmitting the determined number of encoded data packets according to the received feedback to the one or more receiving ends. At this time, the encoded data packet may be generated by performing Random Linear Coding (RLC) on the plurality of original data packets in the single encoding unit.

The at least one encoded data packet may be randomly linearly encoded using a first coefficient matrix, and the first coefficient matrix may include at least one of a coding unit and an encoded data packet, which are determined in consideration of a predetermined number of the generated encoded data packets. 2 coefficient matrix and a unit matrix having a size corresponding to the one encoding unit.

Also, the second coefficient matrix may be one in which a matrix formed by arbitrarily selecting a number of columns corresponding to the one coding unit in the first coefficient matrix satisfies a condition independent of a predetermined Galois field .

Transmitting the retransmission parameter information including at least one of the maximum number of times of transmitting the encoded data packet, the transmission condition of the feedback, and the code information according to the error rate of the plurality of original data packets to the one or more receiving terminals, .

The retransmission parameter information is transmitted to the one or more receiving end via at least one of an uplink channel descriptor (UCD), a downlink channel descriptor (DCD), a dynamic service modification (DSC) message, and an MBS-MAP .

In addition, the number of the encoded data packets to be transmitted may be determined by feedback indicating the largest error rate among the feedbacks received from the one or more receiving ends.

In addition, the feedback may be divided into different codes according to the error rate of the plurality of original data packets.

The step of transmitting the encoded data packet may include a step of, when reaching a predetermined maximum number of transmissions, if all the feedbacks received from the one or more receiving ends indicate a certain error rate or less, May be repeated until either one of the cases where it is not transmitted is satisfied.

In addition, the feedback may be received from the one or more receiving ends via any feedback channel and a ranging message for position update.

According to another aspect of the present invention, there is provided a method of retransmitting data by a receiving end, comprising the steps of: receiving a plurality of original data packets corresponding to one coding unit from a transmitting end; Sending feedback on the error to the transmitting end, receiving one or more encoded data packets from the transmitting end, and receiving the received plurality of original data packets, the received one or more encoded data packets and the first And recovering the erroneous packet using the coefficient matrix. The first coefficient matrix may be a coefficient matrix used by the transmitter to generate the at least one encoded data packet through the random linear encoding of the plurality of original data packets in the single encoding unit.

The first coefficient matrix is generated using a second coefficient matrix determined considering the predetermined number of the one encoding unit and the generated encoded data packet and a unit matrix having a size corresponding to the one encoding unit, Lt; / RTI >

Also, the second coefficient matrix may be one in which a matrix formed by arbitrarily selecting a number of columns corresponding to the one coding unit in the first coefficient matrix satisfies a condition independent of a predetermined Galois field .

Also, the feedback may be transmitted to the transmitting end through any one of a feedback channel and a ranging message for position update.

In addition, the step of transmitting the feedback may be performed by a method of transmitting different predetermined codes according to an error rate of the received plurality of original data packets.

In addition, the step of transmitting the feedback may randomly randomly code one of codes corresponding to the error rate in a predetermined plurality of code sets according to an error rate of the received plurality of original data packets. And then transmitting the selected data.

The present invention has the following effects.

First, it is possible to transmit and receive data efficiently through retransmission.

Second, the transmitting end obtains the information of the receiving end through the feedback of the receiving end and transmits the efficiently encoded data block, so that the receiving end can recover the error.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

The present invention relates to a radio access system, and a communication method using random linear coding is disclosed.

The following embodiments are a combination of elements and features of the present invention in a predetermined form. Each component or characteristic may be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, some of the elements and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

Herein, the embodiments of the present invention have been described with reference to the data transmission / reception relationship between the base station and the terminal. Here, the BS has a meaning as a terminal node of a network that directly communicates with the MS. The specific operation described herein as performed by the base station may be performed by an upper node of the base station, as the case may be.

That is, it is apparent that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. The term 'terminal' may be replaced with terms such as User Equipment (UE), Mobile Station (MS), and Mobile Subscriber Station (MSS).

Embodiments of the present invention may be implemented by various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

For a hardware implementation, the method according to embodiments of the present invention may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs) , Field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to embodiments of the present invention may be implemented in the form of a module, a procedure or a function for performing the functions or operations described above. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

The specific terminology used in the following description is provided to aid understanding of the present invention, and the use of such specific terminology may be changed into other forms without departing from the technical idea of the present invention.

1 is a diagram illustrating the operation of each layer for commonly used data transmission.

Referring to FIG. 1, in a transmission layer of a transmitter, header information is added to a message payload received from an application layer, which is an upper layer, to generate a new data unit. The transport layer then forwards it to the lower layer, the network layer. In the network layer, header information used in the network layer is added to the data received from the transport layer to generate a new data unit, and the new data unit is transmitted to the link layer, which is a lower layer. In the link layer, header information used in the link layer is added to the data received from the upper layer to generate a new data unit, and the new data unit is transmitted to the lower layer physical layer. The physical layer transmits the data unit received from the link layer to the receiving end.

The physical layer of the receiving end receives the data unit from the transmitting end and transmits the data unit to the link layer which is its upper layer. The receiver processes the added header for each layer and transmits the message payload with the header removed to the upper layer. Through this process, data transmission / reception between the transmission side and the reception side is performed.

As shown in FIG. 1, a protocol header is added to each layer for data transmission / reception between a transmitter and a receiver to perform control functions such as data addressing, routing, forwarding, and data retransmission.

2 shows a protocol layer model defined in a commonly used IEEE 802.16 system based wireless mobile communication system.

Referring to FIG. 2, the MAC layer belonging to the link layer may be composed of three sublayers. The Service-Specific Convergence Sublayer (Service-Specific CS) transmits data of the external network received through the CS SAP (Service Access Point) to the MAC SDU (Service) of the MAC sub-layer (CPS) Data Units). In this layer, a function of associating the corresponding SDUs of the external network with a corresponding MAC Flow Identifier (SFID) and a CID (Connection IDentifier) may be included.

Next, the MAC CPS is a layer that provides the core functions of the MAC such as system access, bandwidth allocation, connection establishment and management, and receives data classified by a specific MAC connection from various CSs through the MAC SAP . At this time, QoS (Quality of Service) can be applied to data transmission and scheduling through the physical layer.

In addition, the security sublayer may provide authentication, security key exchange, and encryption functions.

In the hierarchical structure described above, various methods can be used to more reliably transmit data to the receiving end of the transmitting end.

As an example of such a method, when a MAC SDU is delivered to the MAC CPS, the delivered MAC SDU can be divided into MAC PDUs within a range not exceeding the maximum transmission size supported by the MAC layer. These MAC PDUs may be encoded using a random linear code. This method is called Random Linear Coding (RLC).

Hereinafter, a Random Linear Coding (RLC) process, which can be performed in order to process data at a transmitter and transmit to a receiver, will be described.

In embodiments of the present invention, data can be encoded using a random linear coding technique. The random linear coding method is one of the block coding methods.

A feature of the random linear coding method is that each coded block can include information on all blocks included in an original block set. Therefore, even if some coded blocks are lost during transmission / reception, it is possible to quickly recover data by receiving another coded block without having to receive the coded blocks again. The random linear encoding method is merely a definition of a data processing method exemplified in the present invention, and the term of the method may be variously modified.

3 is a diagram illustrating a process of encoding data block sets using a random linear encoding method applicable to an embodiment of the present invention.

Referring to FIG. 3, original data represents data (SDU: Service Data Unit) transmitted from an upper layer of a transmitter. The transmitting end can divide the original data (SDU) into PDUs within a range not exceeding the maximum transmission size supported by the MAC layer. Hereinafter, such a PDU is referred to as an original data packet or an original block in this specification. The transmitting end can form a block set (or a segment) by grouping the original blocks divided into an arbitrary number (n). Hereinafter, in this specification, a block set generated by grouping original blocks in such a number is called an " original block set ".

At this time, the number (n) of block sets can be determined by the channel environment of the communication network, the performance information of the transmitting and receiving end, and the requirements of the application program. Also, the transmitting end can constitute a total of k original block sets.

The transmitting end generates a random coefficient matrix or a random coefficient matrix (c _ji ) for coding the divided data blocks. The transmitting end can encode the divided data blocks using the random coefficient matrix (c _ji ) generated according to a certain rule.

The transmitting end may perform encoding using a random linear encoding method in units of block aggregates (e.g., every n selected blocks). At this time, the set of n encoded blocks may be referred to as an " encoded block set ". The receiving end can perform decoding if it receives as many encoded blocks as the selected number (n). Hereinafter, the "encoded block" may be referred to as an "encoded data packet ".

Each encoded block generated by applying the random linear encoding method may include information on all the blocks included in the original block set. Therefore, in order to recover a series of original blocks from the encoded blocks received from the receiving end, n coded blocks and random coefficients used in coding each original block are required.

The transmitting end generates new random coefficients until the receiving end completely decodes the data, and transmits the generated random blocks to the receiving end. At this time, the n coded blocks need not be transmitted in the coded order, and each coded block is independent.

)을 부호화하여 생성되는 부호화된 블록집합(

)을 생성하는 방법의 일례를 나타낸다.The following equation (1)

) And the encoded block set (

) Is generated.

를 계수행렬이라 하고, 이는 원본 블록집합(

)을 조합하는 방법을 나타낸다. 계수행렬(

)을 생성하는 방법은 다음과 같다.In Equation (1)

Is called a coefficient matrix,

). ≪ / RTI > Coefficient matrix

) Is generated as follows.

)은 송신단 또는 송신단과 수신단이 일정 범위에서 결정한 난수(random number)를 이용하여 생성될 수 있다. 난수란, 송신단이 또는 송신단과 수신단이 협의를 통해 일정 범위(예를 들어, 0~255)의 수를 정하고, 상기 일정 범위의 수에서 무작위로 추출한 수를 말한다. 또한, 송신단 및 수신단은 랜덤계수를 생성하는데 필요한 시드(seed) 값을 공유하여 계수행렬(

)을 생성할 수도 있다. 이때, 계수행렬의 사이즈는 n×n으로 정의될 수 있다. A coefficient matrix used in the random linear coding method (

May be generated using a random number determined in a certain range by the transmitting end or the transmitting end and the receiving end. The random number refers to the number of random numbers extracted from a certain range of numbers (for example, 0 to 255) through the negotiation between the transmitting end or the transmitting end and the receiving end. In addition, the transmitting end and the receiving end share a seed value necessary for generating a random coefficient,

). ≪ / RTI > At this time, the size of the coefficient matrix may be defined as n x n.

The following Equation (2) represents Equation (1) by another expression method.

The block coded in Equation (2) can be represented by coded-blk _j , and the coefficient matrix can be represented by c _ji . Also, the original block can be represented by blk _i .

It is possible to transmit all the n encoded blocks of the first encoded block set at the transmitting end and restore the original block set when the receiving end receives all the n encoded blocks. Thereafter, the transmitting end performs data communication by transmitting the code blocks included in the next second block set.

In order to use a communication method using random linear coding (RLC), a Galois field (GF) of a size of an original block set, a size of a coded block and a random coefficient : Galois Field). The Galois field (GF) can be determined as follows. If GF (2 ^ 2), 2-bit symbols can be calculated to form 2-bit symbols. If GF (2 ^ 8) is used, 8-bit symbols are calculated to form 8-bit symbols You can give.

When the size of the original block set and the size of the encoded block are determined, the number of encoded blocks necessary for decoding can be determined. The transmitter may perform coding using random coefficients necessary for coding according to predetermined Galois fields. The random coefficients may be transmitted together when transmitting the encoded blocks. Also, if the transmitting and receiving end generates the random coefficients in advance and has information on the same random coefficients at the transmitting and receiving end, the transmitting end may transmit only the index of the random coefficient used for coding each block to the receiving end . In the case of sequential data transmission in which no signal is transmitted during communication, the transmitting and receiving end can sequentially code and decode predetermined random coefficients.

)을 부호화하는데 사용한 계수행렬(

)의 역행렬(

)을 생성한 다음, 생성된 역행렬 및 수신된 부호화된 블록집합(

)을 이용한 연산을 통하여 원본 블록집합(

)을 복원할 수 있는 것이다. 이를 식으로 나타내면 아래 수학식 3과 같다.In other words, the receiving end transmits the original block set (

) ≪ / RTI >

) Inverse matrix (

), And then generates the generated inverse matrix and the received coded block set (

), The original block set (

) Can be restored. This can be expressed by the following equation (3).

According to an embodiment of the present invention, original data packets are transmitted to the receiving end first, and if an error occurs in the receiving end of the transmitted original data packets, the receiving end can receive the encoded data packet for recovering the error from the transmitting end A method of transmitting feedback is provided. Before explaining this, a method of recovering an error by receiving a coded data packet from a transmitting end in a receiving end will be described first.

FIG. 4 illustrates a process of transmitting and receiving data between a transmitting end and a receiving end according to an embodiment of the present invention.

Referring to FIG. 4, the transmitting end first transmits a plurality of original data packets constituting a set of original blocks corresponding to one encoding unit to the receiving end (S411).

In this case, the original data packet may be a PDU generated by dividing original data (e.g., SDU) transmitted from an upper layer by a receiving end into a predetermined size.

The transmitting end transmits the encoded data packet to the receiving end through a random linear encoding process using a predetermined coefficient matrix so that the receiving end can recover the error occurring in the original data packet (S412).

Meanwhile, the receiving end receives the original data packet transmitted from the transmitting end in step S411 (S431).

At this time, depending on the channel environment, the receiving end may not receive all original data packets transmitted from the transmitting end. Accordingly, the receiving end can check whether or not each of the received original data is erroneous by using a method such as CRC check.

If there is an original data packet in which an error occurs, the receiving end receives the encoded data packet from the transmitting end to recover the original data packet in which the error occurred (S432).

At this time, the number of encoded data packets received by the receiving end from the transmitting end can be determined according to the channel environment, and it is preferable that the number of the encoded data packets is not less than the number of original data packets in which errors occur.

The receiver receiving the encoded data packet can recover the original data packet in which the error has occurred by using the coefficient matrix, the received encoded data packet, and the original data packet received without error (S433).

In this case, the coefficient matrix is preferably the same coefficient matrix as the coefficient matrix used when generating the encoded data packet at the transmitting end. For this purpose, it is preferable that the transmitting end and the receiving end share the coefficient matrix before starting data transmission / reception. The coefficient matrix can be shared between the transmitting end and the receiving end through various methods. For example, if a coefficient matrix can be generated according to a certain rule, only a predetermined seed value may be shared, or a plurality of coefficient matrices may be generated and shared in advance and then one of a plurality of coefficient matrixes It may share only the index value to indicate.

Through the above-described data transmission / reception method, the receiving end can preferentially use the received data even if an error occurs in some of the plurality of original data packets. Also, the receiving end can adaptively recover the error using the coded data packet transmitted from the transmitting end.

Further, it may be more effective if the above-described method is used for transmission of data that is broadcast or multicast, such as MBS data. This is because, if the transmitting end transmits only a certain number of encoded data packets to the receiving end irrespective of which data packet has an error in the receiving end, the receiving end can recover the error.

Hereinafter, the data transmission / reception method will be described in more detail by dividing the structure into three sections, 1) structure of original data packet, 2) structure of a coefficient matrix for coding original data packet, and 3) recovery of original data packet at the receiving end .

However, in this embodiment, it is assumed that the size of the Galois field is GF (2 ⁸ ). In addition, it is assumed that random linear encoding is performed in units of 100 original data packets, and that the transmitter generates five encoded data packets through random linear encoding.

1) Structure of original data packet

5 shows an example of a source data packet associated with an embodiment of the present invention.

The transmitting end can divide the upper layer data (e.g., MAC SDU: Medium Access Control Service Data Unit) within a range not exceeding the maximum transmission size supported by the lower layer. The data packet thus generated is referred to as "original data packet" in the embodiments of the present invention. At this time, as shown in FIG. 5, 100 original data packets (X1 to X100) are prepared for transmission from the transmitting end to the receiving end. Each original data packet may include original data (D1 to D100) and a CRC (Cyclic Redundancy Check) for determining whether or not an error has occurred on a packet-by-packet basis at the receiving end.

6 shows a data structure of an original data packet according to an embodiment of the present invention.

Referring to FIG. 6, the original data D _j (j = 1 to 100) of each original data packet includes ten constituent elements B _i (i = 1 to 1000). Here, the number of elements B _i of the original data included in each original data packet is an example, and a different number of elements Bi may constitute each original data as necessary.

At this time, the size of each B _i is determined according to the definition of Galois field or finite field used for random linear coding. That is, assuming that a Galois field of GF (2 ⁿ ), n is an integer, is used for random linear coding, B _i has a size of n bits.

For example, when GF (2 ⁴ ) is used, B _i is 4 bits, and GF (2 ⁸ ) uses 8 bits and GF (2 ¹⁶ ) uses 16 bits. In the embodiments of the present invention, GF (2 ⁸ ) is used as an example, but finite field sizes of different sizes can be expanded in the same manner.

Thus, each original data packet can be composed of several bytes, and in the case of FIG. 7, one original data packet includes 10 bytes of original data.

2) Structure of the coefficient matrix for encoding the original data packet

Next, a structure of a coefficient matrix that can be used to generate data packets encoded through random linear encoding of original data packets configured as described above will be described.

Equation (4) shows an example of a coefficient matrix that can be used for random linear encoding according to an embodiment of the present invention.

라 하면, 계수행렬

는

및

를 나열한 형태로 표시될 수 있다. Referring to Equation (4), a coefficient matrix that can be used for random linear coding related to an embodiment of the present invention

, The coefficient matrix

The

And

As shown in FIG.

는 100×100 크기의 단위(Identity)행렬이고,

는 100×5의 크기를 갖는 랜덤계수행렬로서 기 설정된 갈루아 필드(e.g. GF(2⁸))의 원소들 중 랜덤으로 선택된 원소들로 구성될 수 있다. 이때, 랜덤계수행렬

는 수학식 4와 같이 생성된

행렬에서 임의로 100개의 열을 선택하여 100×100 크기의 행렬을 구성하였을 때, 구성된 행렬이 가역(invertible)행렬인 조건을 만족하는 것이 바람직하다. 상기와 같이 구성되는 계수행렬

를 이용하여 랜덤선형부호화를 수행하면, 100개의 원본 데이터 패킷을 입력하면 105개의 부호화된 데이터 패킷이 획득될 수 있다.here

Is a 100 × 100 identity matrix,

Is a random coefficient matrix having a size of 100 × 5 and may be composed of randomly selected elements among elements of a predetermined Galois field (eg, GF (2 ⁸ )). At this time, the random coefficient matrix

Lt; RTI ID = 0.0 > (4)

It is preferable that when a matrix of 100 × 100 is constructed by arbitrarily selecting 100 columns in the matrix, the matrix formed is an invertible matrix. The coefficient matrix

, 105 encoded data packets can be obtained by inputting 100 original data packets.

를 결정하는 방법을 보다 자세히 설명한다.Hereinafter,

Will be described in more detail.

는 한 번에 랜덤선형부호화에 참여하는 원본 데이터 패킷의 갯수에 해당하는 크기를 갖는 것이 바람직하다. 예를 들면, 본 실시예에서와 같이 100개의 원본 데이터 패킷이 하나의 인코딩 단위로 랜덤선형부호화에 참여하는 경우라면

는 수학식 4와 같이 100×100의 크기를 갖게 된다. First,

Preferably has a size corresponding to the number of original data packets participating in the random linear encoding at one time. For example, as in this embodiment, if 100 original data packets participate in the random linear encoding in one encoding unit

Has a size of 100 x 100 as shown in Equation (4).

는 하나의 인코딩 단위에 해당하는 원본 데이터 패킷의 수와 랜덤선형부호화를 통하여 생성하고자 하는 부호화된 패킷의 수에 비례하여 생성된다. 예를 들어, 위에서 가정된 바와 같이 100개의 원본 데이터 패킷이 하나의 인코딩 단위로 랜덤선형부호화에 참여하고, 랜덤선형부호화를 통하여 5개의 부호화된 데이터 패킷을 생성하는 경우라면 100×5의 행렬로 생성된다. Also,

Is generated in proportion to the number of original data packets corresponding to one encoding unit and the number of encoded packets to be generated through random linear encoding. For example, assuming that 100 original data packets are involved in random linear coding in one encoding unit and five encoded data packets are generated through random linear coding as in the above supposition, a 100 × 5 matrix is generated do.

를 이용하여 송신단은 원본 데이터 패킷들에 대하여 랜덤선형부호화를 수행할 수 있으며, 랜덤선형부호화의 수행 결과, 하기 수학식 5와 같은 부호화된 데이터 패킷을 획득할 수 있다.The coefficient matrix generated as described above

The transmitting end can perform random linear encoding on the original data packets, and as a result of the random linear encoding, the encoded data packet as shown in Equation (5) can be obtained.

의 랜덤선형부호화 연산을 통하여 생성될 수 있다. 이때 랜덤선형부호화 연산은 갈루아 필드(Galois Field) 내에서의 연산이다. 즉, 본 실시예에서는 GF(2⁸)인 경우를 가정하였으므로, 각 바이트 내에서 수행되는 연산은 GF(2⁸)인 갈루아 필드 내에서 수행된다.The encoded data packet Pi (i = 1 to 5 under the assumption of this embodiment) is obtained by dividing the original data D _j (j = 1 to 100) of each original data packet (X1 to X100)

Lt; RTI ID = 0.0 > R, < / RTI > In this case, the random linear coding operation is an operation in the Galois field. That is, in the present embodiment, since GF (2 ⁸ ) is assumed, the operation performed in each byte is performed in the Galois field GF (2 ⁸ ).

The code rate is determined by the number of encoded data packets generated through the random linear encoding process performed through the above-described operation. The coding rate can be calculated by the following equation (6).

Therefore, if the encoding rate by the assumption of the present embodiment (generating five encoded data packets with 100 original data packets) is calculated according to Equation (6), it becomes 20/21 since it becomes 100 / (100 + 5).

Next, a method of recovering the original data packet at the receiving end using the encoded data packet generated by the above-described method will be described.

3) Recovery of original data packet at receiving end

The receiving end first receives 100 original data packets (X1 to X100) from the transmitting end as in the assumption. Depending on the channel environment, the receiving end may not receive all 100 original data packets from the transmitting end. Accordingly, the receiving end receives the encoded data packet from the transmitting end to recover the original data packet in which the error occurred.

For example, it is assumed that an error occurs in X2 among original data packets of X1 to X100 received by the receiving end from the transmitting end. At this time, the process of recovering X2 using the encoded data packet P ₁ by the receiving end is as follows.

,

, ...

까지의 10개의 원소를 이용할 수 있다. Referring to FIG. 6, ₂₀ original data elements B ₁₁ to B ₂₀ corresponding to D ₂ can not be recognized as an error occurs in the original data packet X ₂ . Next, referring to Equation (5), the receiving end _extracts , from among the elements constituting U _1,1 to U _1,10 in the encoded data packet P ₁ to recover B ₁₁ to B ₂₀

,

, ...

Can be used.

값을 알 수 있다. 또한, 수신단은 오류 없이 수신된 원본 데이터 패킷을 이용하여 B₁₁ 내지 B₂₀ 을 제외한 모든 원본 데이터의 원소 값(B)을 알 수 있다. 따라서, 단순한 1차 연립방정식의 풀이 방법으로 수신단은 B₁₁ 내지 B₂₀의 값을 계산할 수 있으며, 그에 따라 오류 있는 원본 데이터 패킷 X2를 복구할 수 있다.In other words, if the process for recovering B ₁₁ to B ₂₀ is a process of solving a linear equation with 10 unknowns, U _1,1 to U _1,10 can be regarded as ten expressions for _obtaining ten unknowns . Therefore, if the receiving end knows the coefficient matrix used when the transmitting end generates the encoded packet as described above in step S433 of FIG. 4,

The value is known. Also, the receiving end can know the element value (B) of all the original data except B ₁₁ to B ₂₀ by using the original data packet received without error. Therefore, the receiving end can calculate the values of B ₁₁ to B ₂₀ by solving the simple first order simultaneous equations, thereby recovering the erroneous original data packet X 2.

As another example, it is assumed that there are errors in two original data packets out of 100 original data packets received from the transmitting end in the receiving end. In other words, a total of 20 original data elements must be recovered, one for every 10 original data packets. In this case, unlike when there is an error in one data packet, at least two encoded data packets are required at the receiving end to recover two original data packets.

When the receiving end receives two encoded data packets P ₁ and P ₂ of the form of Equation (5) from the transmitting end, the receiving end receives the encoded data packets corresponding to U _1,1 to U _1,10 and U _2,1 to U _2,10 It can be seen that it has acquired 20 expressions. That is, when there are errors in two original data blocks in the receiving end and two encoded data blocks are received, the process of recovering the two original data blocks is a process of obtaining 20 unknowns using 20 different equations . Therefore, the receiving end can obtain 20 original data elements constituting the two original data packets by using the coefficient matrix, the original data packet received without streaming, and the encoded data packet as a method of solving the first-order equation. As a result, the receiving end can recover the two original data packets in error.

In the data transmission / reception method using general random linear coding, if the number of received encoded data packets is smaller than the number of original data packets in which errors occur, error recovery can not be performed as a whole. However, with the above-described data transmission / reception method, the receiving end can advantageously use a portion corresponding to the original data packet received without error, without decoding through random linear coding.

Hereinafter, a data retransmission method according to an embodiment of the present invention will be described with reference to the above-described data transmission / reception method.

7 shows an example of a data retransmission process according to an embodiment of the present invention.

Referring to FIG. 7, the transmitting end may transmit the retransmission parameter to the receiving end to share the retransmission condition with the receiving end (S701).

The retransmission parameters may include a maximum number of retransmissions, a feedback transmission condition of a receiving end, a transmission form of feedback, and the like. At this time, the maximum number of retransmissions means the maximum number of times that a transmitting end transmits an encoded packet for error recovery of a receiving end.

In addition, the feedback transmission condition of the receiving end may be set according to the error rate of the original data packet received from the transmitting end of the receiving end, and may be set to two or more steps.

The feedback transmission mode is a parameter for how the receiving end feeds back the original data packet to the transmitting end. For example, the transmission type of the feedback may be a form that notifies the transmitting end of the number of original data packets in which an error occurs, or a type that notifies an error rate. In this case, a method of transmitting a predetermined code set for each error rate section may be used to more efficiently feed back the error rate to the transmitting end. This will be described with reference to Tables 2 and 3.

Table 2 shows an example of a feedback code according to the error rate that can be used in an embodiment of the present invention.

Error Rate Code 10% One 5% 2 3% 3 2% 4 One% 5

Referring to Table 2, the error rate is divided into five levels from 1% to 10%, and different codes are assigned to each step.

In addition to the method of allocating one code according to each error rate as shown in Table 2, a method of allocating a code set according to the error rate may be used.

Table 3 shows an example of a feedback code set according to the error rate that can be used in an embodiment of the present invention.

Error Rate Code Set 10% 1-10 5% 11-20 3% 21-30 2% 31-40 One% 41-50

Referring to Table 3, the error rate is divided into 5 steps from 1% to 10%, and 10 code sets are assigned to each step. The receiving end calculates the error rate of the original data packet received from the transmitting end and selects one code randomly from the code set corresponding to the error rate and transmits the selected code to the transmitting end. Here, Table 2 and Table 3 are illustrative, and the size, number, type of code, and number of allocated codes per section of the code set can be variously changed as needed.

The above-mentioned retransmission parameters include an Uplink Channel Descriptor (UCD) / Downlink Channel Descriptor (DCD), a Dynamic Service Change (DSC) message or an MBS-MAP (MBS-MAP) And the like.

Next, the transmitting end transmits a plurality of original data packets constituting a set of original blocks corresponding to one encoding unit to the receiving end. In this case, the original data packet may be a PDU generated by dividing original data (e.g., SDU) transmitted from an upper layer by a receiving end into a predetermined size. The original data packet may be unicasted to the receiving end, or broadcasted or multicasted to a plurality of receiving ends if MBS data is received (S702).

The transmitting end receives the feedback from the receiving end according to the condition and the type defined in the retransmission parameter in accordance with the reception result of the original data packet of the receiving end. The transmitting end receiving the feedback determines the number of encoded data packets to be transmitted to the receiving end according to the error rate indicated in the feedback. Here, the encoded data packet transmitted to the receiving end may also be referred to as a "retransmission packet ". If feedback is received from a plurality of receivers, it is preferable that the number of encoded data packets to be transmitted is determined according to the feedback indicating the highest error rate (S703).

The transmitting end transmits the encoded data packet to the receiving end by a predetermined number in consideration of the feedback received from the receiving end so that the receiving end can recover the error of the original data packet. At this time, it is preferable that the encoded data packet is generated by applying random linear encoding to a plurality of original data packets transmitted to the receiver in step S702 in one encoding unit. Also, a coefficient matrix as in Equation (4) can be used for random linear encoding. The coded data packet may be unicasted to the receiving end, or broadcasted or multicasted to a plurality of receiving ends in case of MBS data. However, it is preferable that the coded data packet conforms to the type of transmission used in step S702 (S704).

After receiving the above-described retransmission parameter in step S701, the receiving terminal can receive the original data packet transmitted from the transmitting terminal (steps S721 and S722).

At this time, the receiver can determine whether the original data packet is erroneous or not. As a method of determining whether or not an error exists, a CRC check method using a CRC (Cyclic Redundancy Check) included in the original data packet can be used.

The receiving end which has confirmed the error of the original data packet can calculate the error rate. For example, if the receiving end receives 100 original data packets from the transmitting end and it is determined that five original data packets have failed, the error rate is 5%.

The receiving end can transmit the feedback according to the error rate to the transmitting end using the retransmission parameter (S723).

For example, it is assumed that the condition for transmitting the feedback from the receiving end to the transmitting end in the retransmission parameter is at least 5% of the error rate, and the form of feedback transmission is set according to Table 2. If the error rate is 5% in step S722, the receiving terminal satisfies the condition for transmitting the feedback, and the receiving terminal transmits the code '2' corresponding to 5% to the transmitting terminal according to Table 2. The transmission of such feedback may be performed through a predetermined feedback channel or a ranging message for location update.

The receiving end receives the coded data packet according to the feedback from the transmitting end (S724).

If the coded data packet received from the transmitting end is equal to or larger than the number of original data packets in which the error has occurred, the receiving end can recover the original data packet in which the error has occurred through the data recovery method described above (S725).

The transmission and reception of the feedback and the transmission and reception of the encoded data packet may be repeatedly performed in the transmitter and receiver until a predetermined condition is satisfied (S730).

That is, even if the transmitting terminal transmits the number of encoded data packets corresponding to the error rate indicated in the feedback to the receiving end, errors may occur in the encoded data packets according to the channel state. In this case, the receiving end can not acquire a coded data packet sufficient to recover the error, and the receiving end can request the retransmission of the coded data packet by transmitting the feedback to the transmitting end again.

For example, if the receiving end receives all the original data packets transmitted by the transmitting end or if the error rate is lower than the feedback transmission condition defined in the retransmission parameter, the receiving end receives no feedback from the receiving end Is not transmitted. In another example, even if the feedback transmitted from the receiving end indicates a certain reference error rate or less, the transmitting end may not transmit the encoded data packet any more. As another example, even when the maximum number of retransmission times defined in the retransmission parameter is exceeded, the transmitting end can stop the retransmission of the encoded data packet.

When the transmitting end ends the retransmission of the encoded data packet, it can transmit the next original data packet to the receiving end.

8 shows an example of a data retransmission process for a plurality of receiving terminals according to an embodiment of the present invention.

In FIG. 8, it is assumed that a transmitting terminal transmits data packets to a plurality of receiving terminals in a broadcast or multicast manner. It is also assumed that the transmitting end is a base station (BS) and the receiving end is a plurality of terminals MS1 to MS4. It is assumed that a set of original blocks corresponding to one random linear encoding encoding unit is composed of N original data packets.

First, the base station shares retransmission parameters with the terminals (S801).

Then, the base station transmits N original data packets to each of the terminals in a multicast or broadcast manner (S802).

Each terminal that has received the N original data packets calculates an error rate for the received packet and selects a feedback code corresponding to the transmission rate and error rate of the feedback according to the retransmission parameter (S803).

The terminal 3 (MS3) and the terminal 4 (MS4) do not transmit all the original data packets without error or do not transmit the feedback to the base station when the feedback transmission condition defined in the retransmission parameter is not satisfied.

When the error rate satisfies the feedback transmission condition, the terminal 1 (MS1) and the terminal 2 (MS2) transmit a feedback (NACK) code corresponding to the error rate of the original data packet received by itself to the base station (S804, S805) .

The base station that has received the feedback from the terminal 1 and the terminal 2 determines the number (P) of encoded data packets (retransmission packets) according to the error rate indicated by the feedback (S806).

At this time, the number of retransmission packets can be determined in consideration of the highest error rate among received feedbacks. For example, assume that N is 100, the feedback received from terminal 1 represents an error rate of 5%, and the feedback received from terminal 2 represents an error rate of 10%. In this case, the base station can determine 10, which is 10% of N, as the number P of retransmission packets, considering the feedback error rate received from the terminal 2. [

If the base station determines the number P of retransmission packets, it can transmit P coded data packets to each terminal (S807).

Each terminal can receive the retransmission packet and recover the error. A terminal having a small number of received retransmission packets to recover an error may send a feedback to a base station within a range not exceeding the maximum number of retransmissions, and may additionally request and receive a retransmission packet.

As another embodiment of the present invention, a terminal and a base station will be described as a transmitter or receiver capable of performing the above-described embodiments of the present invention.

The terminal may operate as a transmitter in an uplink and as a receiver in a downlink. In addition, the base station can operate as a receiver in an uplink and operate as a transmitter in a downlink. That is, the terminal and the base station may include a transmitter and a receiver for transmission of information or data.

The transmitter and receiver may comprise a processor, module, part and / or means, etc., for performing embodiments of the present invention. In particular, the transmitter and receiver may include a module (means) for encrypting the message, a module for interpreting the encrypted message, an antenna for transmitting and receiving the message, and the like.

A terminal used in embodiments of the present invention may include a low power RF (Radio Frequency) / IF (Intermediate Frequency) module. In addition, the terminal includes a controller function for performing the above-described embodiments of the present invention, a MAC (Medium Access Control) variable control function according to service characteristics and propagation environment, a handover function, A packet modulating / demodulating function for transmission, a fast packet channel coding function and a real-time modem controlling function, and the like.

The base station can transmit the data received from the upper layer to the terminal wirelessly or by wire. The base station may include a low power RF (Radio Frequency) / IF (Intermediate Frequency) module. In addition, the base station includes a controller function for performing the above-described embodiments of the present invention, orthogonal frequency division multiple access (OFDMA) packet scheduling, time division duplex (TDD) packet scheduling and channel multiplexing , MAC frame variable control function according to service characteristics and propagation environment, high speed traffic real time control function, hand over function, authentication and encryption function, packet modulation / demodulation function for data transmission, high speed packet channel coding function and real time modem control Functions or the like, modules or parts, or the like.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention. In addition, claims that do not have an explicit citation in the claims may be combined to form an embodiment or be included in a new claim by amendment after the filing.

Figure 1 shows the operation of each layer for commonly used data transmission.

2 shows a hierarchical structure of a general IEEE 802.16 system.

FIG. 3 illustrates a process of encoding data block sets using random linear encoding.

FIG. 4 illustrates an example of a data transmission and reception process using random linear coding in a transmitter and a receiver according to an embodiment of the present invention.

Figure 5 shows a source data packet associated with an embodiment of the present invention.

6 shows a data structure of an original data packet according to an embodiment of the present invention.

7 shows an example of a data retransmission process according to an embodiment of the present invention.

8 shows an example of a data retransmission process for a plurality of receiving terminals according to an embodiment of the present invention.

Claims (15)

A method for retransmitting data by a transmitting end in a wireless access system, Transmitting a plurality of original data packets corresponding to one encoding unit to one or more receiving terminals; Receiving feedback on an error rate of the plurality of original data packets from the one or more receiving ends; Determining a size of the first coefficient matrix based on the error rate; And And randomly linearly encoding the plurality of original data packets in the one encoding unit based on a first coefficient matrix of the determined size to generate a coded data packet. The method according to claim 1, And transmitting the retransmission parameter information including at least one of the maximum number of times the encoded data packet is transmitted, the transmission condition of the feedback, and the code information according to the error rate of the plurality of original data packets to the one or more receiving terminals A data retransmission method. 3. The method of claim 2, Wherein the retransmission parameter information includes: Is transmitted to the at least one receiving end through at least one of an uplink channel descriptor (UCD), a downlink channel descriptor (DCD), a dynamic service modification (DSC) message, and an MBS-MAP (MBS-MAP). . The method according to claim 1, The size of the first coefficient matrix used for the random linear encoding may be, Wherein the feedback is determined based on feedback indicating the largest error rate among the feedbacks received from the one or more receiving ends. The method according to claim 1, The feedback, Wherein the plurality of original data packets are divided into different codes according to an error rate of the plurality of original data packets. 6. The method of claim 5, Wherein the step of transmitting the encoded data packet comprises: When a predetermined maximum number of transmissions is reached, when all the feedbacks received from the one or more receivers indicate a certain error rate or less and when the feedback is not transmitted from any one of the one or more receivers, And repeating the data transmission. The method according to claim 1, The second coefficient matrix, A first coefficient matrix and a unit matrix having a size corresponding to the one encoding unit, Wherein the number of encoded data packets is determined based on the second coefficient matrix. 8. The method of claim 7, Wherein the first coefficient matrix comprises: Wherein a matrix constructed by arbitrarily selecting a number of columns corresponding to the one coding unit in the second coefficient matrix satisfies a condition independent of a predetermined Galois field. The method according to claim 1, The feedback, A predetermined feedback channel, and a ranging message for location update. ≪ Desc / Clms Page number 19 > A method for a receiver to retransmit data in a wireless access system, Receiving a plurality of original data packets corresponding to one encoding unit from a transmitting end; Feeding back an error rate of the error to the transmitting end if at least a part of the plurality of original data packets is erroneous; Receiving one or more encoded data packets from the transmitting terminal; And And recovering the erroneous packet based on the received plurality of original data packets, the received one or more encoded data packets and the first coefficient matrix, Wherein the first coefficient matrix comprises: Wherein the first coefficient matrix is a random coefficient matrix used for generating the at least one encoded data packet through the random linear encoding of the plurality of original data packets in the encoding unit, Wherein the error rate is determined based on a reception error rate of the data packet. 11. The method of claim 10, The second coefficient matrix, A first coefficient matrix and a unit matrix having a size corresponding to the one encoding unit, Wherein the number of the encoded data packets is determined based on the second coefficient matrix. 12. The method of claim 11, Wherein the first coefficient matrix comprises: Wherein a matrix constructed by arbitrarily selecting a number of columns corresponding to the one coding unit in the second coefficient matrix satisfies a condition independent of a predetermined Galois field. 11. The method of claim 10, The feedback, A predetermined feedback channel, and a ranging message for location update. 11. The method of claim 10, Wherein the transmitting the feedback comprises: And transmitting a predetermined code according to an error rate of the plurality of original data packets. 11. The method of claim 10, Wherein the transmitting the feedback comprises: And randomly selecting one of codes corresponding to the error rate from a plurality of predetermined code sets according to an error rate of the plurality of original data packets received and transmitting the code Wherein the data reception method comprises:

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