KR101066038B1 - Method for packet retransmission of mimo system - Google Patents

Abstract

The present invention can reduce the error occurring during the transmission of the NACK signal when the NACK signal contains information on the retransmission option in the information element, if the NACK signal contains information of which of several sub-packets, and the NACK signal is such a If it does not contain information, it provides a packet retransmission method of a multi-antenna system that allows one of several sub-packets to be selected.

In the packet retransmission method according to the present invention, in performing uplink transmission,

The base station instructing the terminal to transmit data through an information element (IE); Transmitting the corresponding data to the base station according to the instructions of the base station; When an error is detected in the transmission data, transmitting, by the base station, an IE including a NACK signal and specific option information to the terminal; According to the option information, the terminal performs a retransmission process.

MIMO, HARQ

Description

Packet retransmission method in multi-antenna system {METHOD FOR PACKET RETRANSMISSION OF MIMO SYSTEM}

1 shows an ARQ scheme.

2 illustrates a Type I HARQ scheme.

3 shows a Type II HARQ (IR) scheme.

4 illustrates a Type III HARQ scheme.

5 illustrates a Type I with soft combining (Chase Combining) scheme.

6 is a diagram showing a data retransmission procedure according to the first embodiment of the present invention.

7 is a diagram illustrating a data retransmission procedure according to the second embodiment of the present invention.

8 is a diagram showing a data retransmission procedure according to the third embodiment of the present invention.

The present invention relates to a packet retransmission method of a multiple antenna system (MIMO), and more particularly, to a packet retransmission method using antenna shuffling.

In data transmission, an ARQ (Automatic Repeat Request) method is used as a retransmission method of error data that is generally used.

The ARQ is a response message indicating whether the receiver has properly received the data after transmission. There are three ARQ response methods: Stop-and-wait ARQ, Go-back-N ARQ, and Selective-repeat ARQ.

1 illustrates an ARQ scheme.

As shown in FIG. 1, Stop-and-wait ARQ is a method of waiting for an ACK or NACK message after receiving a data and transmitting or retransmitting new data. Go-back-N ARQ continuously transmits data regardless of the response, and when the NACK signal is received, the Go-back-N ARQ retransmits it sequentially from the point indicated by the NACK signal, and Selective-repeat ARQ continues to transmit the data and transmits the NACK signal. Retransmit only received data.

In the packet method, a higher data rate (2 Mbps, 10 Mbps or more) is required, and in order to prevent errors occurring in a high-speed transmission environment, a coding rate or a modulation method is also appropriate (Rc = 5). / 6, 3/4; Mod = 16-QAM, 64QAM) have been applied to communication systems. In addition, an ARQ scheme suitable for a high-speed transmission environment, that is, a hybrid ARQ scheme (hereinafter, referred to as HARQ) has been proposed.

In ARQ, when an error occurs, the corresponding information is discarded, but in HARQ, FEC (Forward Error Correction) is applied by storing the error information in a buffer and combining it with retransmitted information. That is, it can be seen that HARQ = FEC + ARQ.

In addition, HARQ can be divided into four types as follows.

2 illustrates a Type I HARQ scheme.

As shown in FIG. 2, the Type I HARQ scheme always detects FEC by adding an error detection code to data. If an error still exists in the packet, the sender requests retransmission. Error packets are discarded and retransmitted packets use the same FEC code as discarded packets.

3 shows a Type II HARQ scheme.

Type II HARQ is also referred to as incremental redundancy (IR) ARQ.

As shown in FIG. 3, the Type II HARQ scheme combines redundancy bits stored in a buffer without discarding the first transmitted packet. When retransmitting, retransmit only parity bits excluding data bits. The parity bits for retransmission use a different one for each retransmission.

4 shows a Type III HARQ scheme.

Type III HARQ is a special case of Type II HARQ. Each packet is self-decodable. Retransmission consists of a packet containing both an error part and data and is retransmitted. This type of decoding is more accurate than type II HARQ, but has less gain in terms of coding gain.

Lastly, the Type I with soft combining method is a type I function that adds a function of storing data initially transmitted from a receiving end and combining the retransmitted data, also called metric combining or chase combining. This method is advantageous in terms of SINR, and the parity bits of retransmitted data are always used as the same. 5 illustrates a Type I with soft combining method.

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과

를 전송하기 위해 아래 [수식1]과 같은 MIMO 매트릭스 A를 사용할 수 있다. 아래 [수식1]은 2-안테나 송신의 경우, STTD 방식의 MIMO매트릭스를 나타낸 것이다.
[수식 1]

[수식1]에서, 매트릭스의 행은 순차적으로 제1안테나와 제2안테나에 실리는 신호를 뜻하고, 매트릭스의 열은 시간 순이다. 즉, 첫번째 채널의 제1안테나에서는

을 제2안테나에서는

를 전송하고 두번째 채널의 제1안테나에서는

을 제2안테나에서는

을 전송한다. 그리고 수신 단에서의 시간에 따른 수신값을

,

라고 했을 때,

과

를 아래 [수식2]와 같이 계산할 수 있으며, [수식2]은 [수식1]의 2-안테나 송신의 경우, 수신신호를 나타낸 것이다.
[수식 2]

[수식2]에서,

과

는 각각 제1안테나와 제2안테나가 겪는 채널 상태를 의미한다. 또한, 기지국이 두개의 안테나를 가지고 있을 때, Collaborative SM 방식으로 신호

과

를 전송하기 위해서는 아래 [수식3]과 같은 MIMO 매트릭스 B를 사용할 수 있다. [수식3]은 2-안테나 송신의 경우 Collaborative SM 방식의 MIMO 매트릭스를 나타낸 것이다.
[수식 3]

재전송이 요구되는 3개 또는 4개의 전송 안테나를 사용하는 시스템에서 첫번째 spatial multiplexing전송 시에는 하기 [표1]과 [표2]에 나타난 벡터와 같이 전송하며, 각 벡터의 각 엘리먼트(element)는 각 안테나로 전송된다. 하기 [표1]은 3-안테나의 경우 HARQ 재전송 벡터의 예를 나타낸 것이고, [표2]는 4-안테나의 경우 HARQ 재전송 벡터의 예를 나타낸 것이다.
*실시예에서, 재전송이 요구될 때는 홀수번째 재전송과 짝수번째 재전송을 구분하여 재전송이 이루어지는데, 홀수번째 재전송 시에는 Option을 선택하여 여러 가지 재전송 벡터들 중의 하나를 선택하여 재전송할 수 있다.
하향링크의 경우, Option을 선택하는 정보는 수신되는 NACK신호의 코드워드를 달리함으로써 나타낼 수 있다. 예를 들어, ACK일 때는 코드워드 0,0,0을 보내고, NACK일 때는 Option1은 4, 7, 2를, Option2는 1, 2, 3를 그리고 Option3은 3, 6, 5를 보내어 ACK/NACK 여부와 NACK일 경우 몇번 째 옵션인지를 구별할 수 있다.
그러나, 상향링크의 경우, ACK/NACK신호는 한 비트로 표현되기 때문에 ACK/NACK 신호만으로는 Option을 선택할 수 없다.
초기 전송 홀수번째 재전송 짝수번째 재전송 Space time code incremental redundancy for matrix C

(Option 1)

(Option 2)

(Option 3)

초기 전송 홀수번째 재전송 짝수번째 재전송 Space time code incremental redundancy for matrix C

(Option 1)

(Option 2)

(Option 3)

이상, 기술된 다중 안테나 시스템은 재전송을 수행할 때에 몇 번째 전송인지를 알려주는 field를 IE(Information Element)에 포함하고 있었으나, NACK신호의 여러 Option 중, 하나를 선택하여 재전송 벡터를 보내는 부분에 있어서, 기지국과 단말 중에 누가 재전송 벡터를 선택하여 보내고, 어떻게 선택하는지에 대해서는 정해진 바가 없다는 문제점을 가지고 있다.
본 발명은 전술한 바와 같은 문제점을 해결하기 위한 것으로 그 목적은, The following is a description of a multiple antenna system.
A multi-antenna system, that is, a MIMO system, is a wireless system in which a base station and a terminal have one or more antennas to transmit and receive a signal, and can obtain diversity gains on a time axis or a frequency axis. There are two types of MIMO systems: STTD and Collaborative SM. Space-Time Transmit Diversity (STTD) is a method of obtaining diversity gain by using two or more signals on two or more antennas to transmit diversity gain using information on the antenna and time axis, and collaborative spatial multiplexing (SM) is performed on two radio resources. The above method is for allocating terminals.
For example, when the base station has two antennas, the signal is STTD

and

MIMO matrix A as shown in [Equation 1] can be used to transmit. [Equation 1] below shows the MIMO matrix of the STTD method in the case of two-antenna transmission.
[Equation 1]

In Equation 1, the rows of the matrix sequentially indicate signals carried on the first antenna and the second antenna, and the columns of the matrix are in chronological order. That is, in the first antenna of the first channel

In the second antenna

In the first antenna of the second channel

In the second antenna

Send it. And the receiving value according to the time at the receiving end

,

When I say

and

Equation 2 can be calculated as shown in Equation 2 below, and Equation 2 shows a reception signal in the case of 2-antenna transmission of Equation 1.
[Formula 2]

In [Equation 2],

and

Denotes a channel state experienced by the first antenna and the second antenna, respectively. In addition, when the base station has two antennas, the signal in the Collaborative SM method

and

In order to transmit the MIMO matrix B as shown in Equation 3 below can be used. [Equation 3] shows the MIMO matrix of the Collaborative SM scheme in the case of 2-antenna transmission.
[Equation 3]

In a system using three or four transmit antennas requiring retransmission, the first spatial multiplexing transmission is performed as shown in the following Tables 1 and 2, and each element of each vector Transmitted to the antenna. [Table 1] shows an example of the HARQ retransmission vector in the case of 3-antenna, and [Table 2] shows an example of the HARQ retransmission vector in the case of 4-antenna.
In an embodiment, when retransmission is required, retransmission is performed by dividing odd-numbered and even-numbered retransmissions. In odd-numbered retransmissions, an option may be selected and retransmitted by selecting one of several retransmission vectors.
In the case of downlink, information for selecting an option may be indicated by different codewords of a received NACK signal. For example, for ACK, codewords 0,0,0 are sent. For NACK, Option1 sends 4, 7, 2, Option2 sends 1, 2, 3, and Option3 sends 3, 6, 5. In case of NACK, the number of options can be distinguished.
However, in the uplink, since the ACK / NACK signal is represented by one bit, the ACK / NACK signal alone does not allow the option to be selected.
Initial transfer Odd numbered retransmission Even Retransmission Space time code incremental redundancy for matrix C

(Option 1)

(Option 2)

(Option 3)

Initial transfer Odd numbered retransmission Even Retransmission Space time code incremental redundancy for matrix C

(Option 1)

(Option 2)

(Option 3)

In the above-described multi-antenna system, a field indicating the number of transmissions when performing retransmission is included in an information element (IE), but in the part of transmitting a retransmission vector by selecting one of several options of the NACK signal, In addition, there is a problem in that the base station and the terminal select and send a retransmission vector and how to select it.
The present invention is to solve the problems described above, the object is,

By including information about retransmission options in the Information Element, if the NACK signal contains information of which sub-packets to use, the error that occurs during the transmission of the NACK signal can be reduced, and the NACK signal contains such information. In case of failure, the present invention provides a packet retransmission method of a multi-antenna system that allows one of several sub-packets to be selected.

In order to achieve the above object, the packet retransmission method according to the present invention

In performing uplink transmission, the base station instructs the terminal to transmit data through an information element (IE), and transmits the corresponding data to the base station according to the instructions of the base station, and an error occurs in the transmission data. When detected, the base station transmits an IE including information for selecting a specific option from a NACK signal and a sub-packet to the terminal, and the terminal performs retransmission according to the option information.

Preferably, the option information is information for selecting a specific option of a plurality of sub-packet during retransmission.

In order to achieve the above object, the packet retransmission method according to the present invention

In performing the downlink transmission, the base station transmits the data and the first IE for the data, and if an error is detected in the transmission data, the terminal determines the option of the sub-packet to be retransmitted. Transmitting the NACK signal according to the option to the base station, and when the NACK signal is received, the base station transmits the sub-packet signal of the option selected for the second retransmission according to the retransmission option, and the option information of the received NACK signal. Is included in the second IE and transmitted to the terminal.

Preferably, the option information included in the second IE is for reconfirming the NACK signal sent by the terminal to the terminal.

Preferably, the first IE is characterized in that the retransmission option field is not used for this purpose. (00: use default)

Preferably, the second IE uses a retransmission option field.

In order to achieve the above object, the packet retransmission method according to the present invention

In performing the downlink transmission, the base station transmits a predetermined IE and data to the terminal, and if an error is detected in the transmission data, the terminal determines the retransmission option with reference to the IE, The NACK signal is transmitted to the base station, and when the NACK signal is received, the base station transmits a second retransmission signal according to a predetermined IE and the retransmission option to the terminal.

Preferably, the base station determines in advance the option of the NACK signal to be determined by the terminal when an error occurs in the data, characterized in that included in the IE.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

The present invention relates to Information Element (IE) information for selecting a retransmission vector. That is, the multiple antenna system employing the HARQ scheme is intended to include information on which of the retransmission vectors is used in the information element. In addition, a case of transmitting IE information in uplink and a case of transmitting IE information in downlink will be described with reference to FIGS. 6, 7, and 8, respectively. 6, 7, and 8, the portions indicated by dotted lines are contents proposed by the present invention.

6 is a diagram illustrating a data retransmission procedure according to the first embodiment of the present invention, and shows a case of uplink HARQ data transmission.

As shown in Fig. 6, the base station first informs the terminal of data to be transmitted through the IE in order to receive a signal of the terminal (S10). Then, the terminal transmits the corresponding data to the base station (S20), and the base station transmits the data. Received to determine whether the ACK or NACK. If the result of determining the received signal is NACK, that is, if an error is detected in the received data, the base station transmits the NACK signal and the IE to the terminal (S30). At this time, as in the conventional method, the NACK signal is converted into one bit. Inform and tell the IE how to use the retransmission vector, the terminal retransmits accordingly (S40).

The second and third embodiments of the present invention to be described below show a case of downlink HARQ data transmission.

7 is a diagram illustrating a data retransmission procedure according to the second embodiment of the present invention.

As shown in FIG. 7, the base station first transmits the first data and the IE to the terminal (S110). At this time, the IE leaves the retransmission option as a default.

When the first data arrives at the terminal and an error is detected in the received data, the terminal selects one of retransmission options and transmits a NACK signal according to the option to the base station (S120).

The base station receiving the NACK signal from the terminal transmits the second retransmission data, and checks the received NACK option information to confirm to the terminal which number of options the received NACK signal belongs to. Include in IE and send. In this case, the NACK option information of the IE is for reconfirming the signal sent by the terminal to the terminal.

8 is a diagram illustrating a data retransmission procedure according to a third embodiment of the present invention.

As shown in FIG. 8, the base station selects a NACK option number to be transmitted by the terminal and sends it to the terminal (S210). That is, while transmitting data, the base station selects a number of options (Option) when an error occurs in the data. It also decides in advance to select and transmit NACK. The determined option information is included in the IE and transmitted to the terminal.

When data of the base station arrives and an error is detected in the received data, the terminal transmits an NACK signal of an option designated by the base station to the base station.

Subsequently, even when transmitting other data, the base station includes predetermined option information in the IE and transmits it to the terminal. (S230)

The following table shows the format of an information element (IE) for application to each of the above embodiments, and each information element (IE) newly includes a re-transmission option field.

[Table 3] below shows the format of MIMO DL STC H-ARQ Sub-burst IE.

MIMO_DL_STC_H-ARQ_Sub-Burst_IE { For (j = 0; j <N sub-burst; j ++) { Tx count 00: first transmission
01: second transmission
10: third transmission
11: fourth transmission Retransmission Option 00: option 1 / default
01: option 2
10: option 3
11: reserved Length If (Tx count == 0) { MU Indicator } } }

[Table 4] below shows the format of the MIMO UL STC H-ARQ Sub-burst IE.

MIMO_UL_STC_H-ARQ_Sub-Burst_IE { Tx count 00: first transmission
01: second transmission
10: third transmission
11: fourth transmission Retransmission Option 00: option 1 / default
01: option 2
10: option 3
11: reserved Duration If (Tx count == 0) { } }

The method proposed by the present invention has an effect that is distinguished from the prior art in both uplink and downlink as follows.

In case of uplink (first embodiment of the present invention), when an error is detected in the transmission data of the terminal, the base station informs the terminal of the NACK bit and the retransmission vector through the IE, so that the terminal selects one of several retransmission vectors. To allow retransmission.

In case of the first method of the downlink (second embodiment of the present invention), when the base station receives a NACK according to a specific option from the terminal, the NACK signal is transmitted by confirming the fact to the terminal once again through the IE. There is an effect that can reduce the possibility of errors that can occur.

In addition, in the second method of the downlink (third embodiment of the present invention), the terminal selects an option from the base station without selecting the option of the NACK, so that the terminal selects an option. In other words, the base station performs a complicated operation such as the calculation of the channel state, thereby reducing the power consumption of the terminal.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (8)

In uplink transmission of a multi-antenna system, The base station instructing the terminal to transmit data through an information element (IE); Transmitting the corresponding data to the base station according to the instructions of the base station; When an error is detected in the transmission data, transmitting, by the base station, an IE including a NACK signal and specific option information to the terminal; According to the option information, the packet retransmission method comprising the step of performing a retransmission by the terminal. The method of claim 1, wherein the option information is Packet retransmission method characterized in that the retransmission option information. In a multi-antenna system for retransmitting packet data between a base station having three antennas and a terminal, a method of retransmitting packet data, The process of receiving the packet data transmitted from the three antennas of the base station by the terminal, wherein the space time code (STC) matrix of the packet data received by the terminal

ego,; When an error occurs in the received packet data, the terminal receives the retransmitted packet data from the three antennas of the base station, wherein the space time code (STC) matrix of the retransmitted packet data received by the terminal

Packet data retransmission method in a multi-antenna system, characterized in that. The method of claim 3, further comprising: when an error is detected in the received packet data, determining, by the terminal, a retransmission option to the base station, and transmitting a NACK signal according to the option to the base station. And the retransmission option is associated with an antenna assignment of the packet data retransmission. delete delete In a multi-antenna system for retransmitting packet data between a base station having three antennas and a terminal, a method of retransmitting packet data, The terminal transmits each packet data to the base station through the three antennas, wherein the space time code (STC) matrix of the packet data transmitted by the terminal

ego,; When an error occurs in the transmitted packet data, the terminal retransmits the packet data to the base station, wherein the space time code (STC) matrix of the retransmission packet data received by the terminal is

Packet data retransmission method in a multi-antenna system, characterized in that. The method of claim 7, further comprising: when an error is detected in the transmitted packet data, the base station determines a retransmission option to the terminal, and the terminal receives a NACK signal according to the option from the base station; , And the retransmission option is associated with an antenna assignment of the packet data retransmission.

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