KR100556908B1 - Harq in multi-level trellis encoded modulation system - Google Patents

Abstract

The multilevel trellis coding method can be configured in various forms, shows excellent performance in fading channels, can be applied to commercially available block codes and convolutional codes, and iterative decoding through soft-decoding. decoding is possible. According to the present invention, the HARQ technique can be implemented in the form of type II by proposing a HARQ technique to a multilevel trellis coding scheme having various advantages. The reliability of the communication system can be improved by increasing the flexibility of the error control system design. I was able to step up. HARQ method according to the invention is a process for decoding the data transmitted to the receiving side; Detecting an error in the decoded signal; If there is an error detected, setting an encoding scheme and a modulation scheme to be applied to data retransmission, and transmitting the setting information and the retransmission request signal to a transmitting side; By referring to the information, it is a process of retransmission after processing the data to be resent.

Multilevel trellis coding, HARQ

Description

HARQ method of multilevel trellis coded modulation system {HARQ IN MULTI-LEVEL TRELLIS ENCODED MODULATION SYSTEM}

1 is a flowchart illustrating a HARQ scheme according to an embodiment of the present invention.

2 is a block diagram of a multilevel trellis coded modulation system, in accordance with an embodiment of the present invention.

3 is a diagram illustrating a decoding method of a multilevel trellis coded modulation system according to an embodiment of the present invention.

The present invention relates to an error control method for wired and wireless communication, and more particularly, to an error control method according to a hybrid automatic repeat request (HARQ) technique.

The HARQ method is an error control method that combines the Forward Repeat Correction (FEC) method with an Automatic Repeat Request (ARQ) method that transmits information on a packet basis and requests retransmission of an error packet.

The FEC adds a separate code to the data block to be transmitted in order to give error correction capability to the receiver.

When an error is detected in the transmitted data block, the ARQ continuously requests the transmitting side to retransmit the corresponding data until no error detection occurs. There are three types of HARQ, and the description thereof is as follows.

type I: An error received packet is discarded and a new copy of the same packet is retransmitted and decoded separately. There is no combination of versions received before and after the packet.

type II: The error received packet is not discarded, but combined with some incremental redundancy bits provided by the transmitter for subsequent decoding. Retransmitted packets are sometimes combined at the receiver with stored values with higher coding rates. This means that only small redundancy is added for each retransmission.

type III: Same as type II except that each retransmitted packet has its own decoding capability. This implies that the transmitted packet is decodable without combining with the previous packet. This is useful when some packets are corrupted in such a way that almost all of the information is not available again.

The HARQ scheme can be combined with the trellis coding scheme, which is a band efficient coding scheme, and the basic transmission unit when the two schemes are combined is a symbol.

When the two schemes are combined, the data block to be retransmitted is generally completely identical to the originally transmitted data block, but a more efficient system configuration is possible through a design considering the combing of metrics. Even in this case, a data block of the same size as that of the originally transmitted data block may be retransmitted. That is, the HARQ scheme combined with the trellis coding scheme exists only in the form of type I or type III.

Therefore, the HARQ scheme combined with the trellis coding scheme has a design limitation and a disadvantage that the applicable system is limited.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a "HARQ scheme of a multilevel trellis coded modulation system" for performing error data retransmission of a Type II HARQ scheme.

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

Decoding the data transmitted to the receiving side; Detecting an error in the decoded signal; If there is an error detected, setting an encoding scheme and a modulation scheme to be applied to data retransmission, and transmitting the setting information and the retransmission request signal to a transmitting side; By referring to the information, it is a process of retransmission after processing the data to be resent.

Preferably, the information includes a modulation scheme setting value; A position value of the error data; An encoding scheme setting value; And a retransmission method setting value.

Preferably, the retransmission method setting value is a value that determines whether to retransmit only a channel of the lowest level among the channels in which an error is detected or to combine and retransmit all the error detected channel blocks.

The present invention focuses on the fact that combining the multilevel trellis coding scheme with the HARQ scheme enables the implementation of an improved error data retransmission scheme. A mapping scheme, an error detection scheme, and the like are proposed.

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

1 is a flowchart illustrating a HARQ processing procedure according to an embodiment of the present invention, and illustrates data transmission between a transmission and reception system employing a multilevel trellis coding scheme.

The multilevel trellis coding method is a band-efficient modulation method that configures a level for input bits of a signal mapper and transmits information through different encoding processes for each level. The multilevel trellis coding scheme can be configured in various forms, shows excellent performance in fading channels, can be configured by applying commercially available block codes and convolutional codes, and iterative decoding through soft-decoding. decoding is possible.

As shown in Figure 1, according to an embodiment of the present invention, HARQ scheme is

Decoding the data transmitted to the receiving side (S20); Detecting an error in the decoded signal (S30); If there is an error detected, setting a coding scheme and a modulation scheme to be applied to data retransmission (S40), and transmitting the setting information and the retransmission request signal to a transmitting side (S50); Referring to the above information, after processing the data to be retransmitted, it is configured to re-send (S60).

When the data of the transmitting side is received, the receiving side checks the Cyclic Redundancy Check (CRC) code included in each level of the received data to check whether there is a block in which an error has occurred.

When an error is detected in the received data block, the receiver generates information about where the error occurred, what modulation scheme and encoding scheme to use for retransmission, and how to retransmit. The information is transmitted to the transmitting side using a response signal such as an "acknowledgement signal (ACK)" or a retransmission request signal.

When the retransmission request signal of the receiving side is received, the transmitting side reprocesses the retransmission target data in accordance with the request of the receiving side indicated in the information. The retransmission target data is transmitted to the receiving side.

Among the above information, the information on the retransmission method is a determination value for determining whether to retransmit only the lowest level channel data or retransmit all channel levels in which an error occurs among the channels in which an error occurs. The reason for specifying the modulation method and the encoding method separately for the data retransmission is that the retransmission targets only the error data unlike in the case of the previous transmission. Therefore, a modulation method and an encoding method suitable for a small amount of data transmission are designated. This is to obtain transmission efficiency.

2 is a block diagram of a multilevel trellis coded modulation system according to an embodiment of the present invention, and FIG. 3 is a decoding scheme of a multilevel trellis coded modulation system according to an embodiment of the present invention. The figure shows. The decoding method of the multilevel trellis coded modulation system is a multi-stage decoding method.

Referring to Figure 2, the operation and features of a multilevel trellis coded modulation system (hereinafter referred to as "modulation system") according to an embodiment of the present invention will be described.

When a signal of M bits (M = m_0 + m_1 + ... + m_i-1) is input to the modulation system, the encoders C_0, C_1, ..., C_i-1 of the modulation system receive the input signal m_0, m_1, ..., m_i-1) are encoded and code bits of n_0, n_1, ..., n_i-1 are output. The N-bit mapper of the modulation system receives the code bits n_0, n_1, ..., n_i-1 and outputs a corresponding modulation signal (symbol) (n_0 + n_1 + ... + n_i-1 = N). If n_0 = n_1 = ... = n_i-1 = 1, i = N, and the input for each input bit of the mapper has a serial form.

The multilevel trellis coded modulation system using the HARQ scheme can be modeled to have i independent channels, and has the following characteristics and characteristics for data retransmission.

one. The error checking method is applied to each channel independently. That is, attach independent CRC to transmission data of each channel)

second. HARQ is applied to each channel independently.

Three. HARQ decoding for high level channel data is performed after HARQ decoding for low level channel data is completed. This is based on the fact that the multi-stage decoding method takes the form of a high level decoding after a low level decoding.

four. HARQ decoding is not performed if no error occurs in the high level channel as well as the low level.

five. The data block of the lowest level among the channels in which an error is detected is selected as the data block to be retransmitted so that only these are retransmitted. As a modulation method applied to retransmission, various modulation methods may be applied. For example, binary phase shift keying (BPSK) or gray-coded quadrature phase shift keying (QPSK), 8 phase shift keying (8PSK), orthogonal Quadrature Amplitude Modulation (QAM) may be applied.

Although the modulation scheme at the time of initial transmission was 8PSK or QAM, since the amount of retransmission data is not large, the modulation scheme at the time of retransmission can use the BPSK scheme with good characteristics.

six. Unlike the fifth item, a multilevel trellis coding scheme for combining data blocks of an error detected channel and retransmitting them can be configured. At this time, various multilevel trellis coding schemes may exist, and error information according to error detection is transmitted to the transmitting side in reverse of the transmission path of the received data block. For example, the error information may be transmitted in a "response signal (eg, a Nack packet)" or a "retransmission request signal".

In the case of the 8PSK modulation scheme, the modulation system can be thought of as being mapped to three bits and having three channels. By applying a 2/3 convolution code to each bit, a multilevel coding system having three levels of 0, 1, and 2 can be configured.

The receiving side performs error detection for each level (0, 1, 2 level) on the data blocks transmitted through the 0 and 2 channels, and informs the transmitting side when there is no detected error. The transmitting side then constructs a multilevel trellis coding system with original 0 and 2 blocks.

For each level (0, 1, 2 level), the receiving end checks for the data block sent to the receiving side through 0 and 2 channels, and if the error cannot be detected at the second side, it notifies the transmitting side. It is possible to construct a multilevel trellis coding system with the original zero-level and two-level blocks. For example, the transmitting side may adopt a QPSK modulation scheme in which a 1/3 convolutional code is applied at the 0 level and a 2/3 convolutional code at the 2nd level.

seven. In the sixth item, a coding scheme for retransmission data may employ a coding scheme other than a multilevel system. For example, the trellis coding scheme can be employed.

The multilevel trellis coding scheme can be configured in various forms, shows excellent performance in fading channels, can be applied to commercially available block codes and convolutional codes, and iterative decoding through soft-decoding. decoding is possible.

HARQ method according to the present invention is not limited to the above-described embodiment, it can be carried out in various modifications within the range allowed by the technical idea of the present invention.

 According to the present invention, the HARQ technique can be implemented in the form of type II by proposing a HARQ technique to a multilevel trellis coding scheme having various advantages. The reliability of the communication system can be improved by increasing the flexibility of the error control system design. I was able to step up.

Claims (17)

In a modulation system, Decoding the data transmitted to the receiving side; Detecting an error in the decoded signal; If there is an error detected, setting an encoding scheme and a modulation scheme to be applied to data retransmission, and transmitting the setting information and the retransmission request signal to a transmitting side; And a retransmission process after processing the retransmission target data with reference to the information. The method of claim 1, wherein the information is A modulation method setting value; A position value of the error data; An encoding scheme setting value; Error control method comprising a retransmission method setting value. The method of claim 2, wherein the retransmission method setting value is And determining whether to retransmit only the channel of the lowest level among the channels in which an error is detected or to combine and retransmit all the error-detected channel blocks. The method of claim 1, wherein the decoding process Error control method characterized in that according to the multi-stage decoding method. The method of claim 1, wherein the error detection process is performed. Error control method characterized in that performed using a cyclic redundancy check (Cyclic Redundancy Check). The method of claim 1, wherein the data transmitted to the receiving side is Error control method characterized in that the transmission through a plurality of independent channels. The method of claim 6, wherein the data transmitted through each channel is Error control method, characterized in that each having an independent CRC code. The method of claim 1, wherein the error detection process is performed. Error control method characterized in that performed independently for each channel. The system of claim 1, wherein the modulation system is Error control method, characterized in that the multilevel trellis coded modulation system. The system of claim 1, wherein the modulation system is Error control method characterized in that to perform a hybrid automatic repeat request (HARQ) based error control. In the transmission side apparatus of the modulation system, Receiving a retransmission request signal and predetermined setting information; Determining a modulation scheme and an encoding scheme with reference to the configuration information and processing retransmission data according to the determined scheme; And transmitting the processed retransmission data to a receiving side. The method of claim 11, wherein the predetermined setting information is A modulation method setting value; A position value of the error data; An encoding scheme setting value; Error control method comprising a retransmission method setting value. The method of claim 12, wherein the retransmission method setting value is And determining whether to retransmit only the channel of the lowest level among the channels in which an error is detected or to combine and retransmit all the error-detected channel blocks. The method of claim 11, wherein the data transmitted to the receiving side is Error control method, characterized in that transmitted through a plurality of channels, each independent. 15. The method of claim 14, wherein the data transmitted on each channel is Error control method, characterized in that each having an independent Cyclic Redundancy Check (CRC) code. 12. The system of claim 11, wherein the modulation system is Error control method, characterized in that the multilevel trellis coded modulation system. 12. The system of claim 11, wherein the modulation system is Error control method characterized in that to perform a hybrid automatic repeat request (HARQ) based error control.

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