KR20070113679A - Device for transmitting and receiving data in communication system - Google Patents

Abstract

According to the present invention, a transmitter acquires channel information of each receiver existing in a cell for data transmission and reception in a communication system, divides the receivers into at least two groups using the channel information, and then receives a receiver corresponding to the determined group. Data is encoded, the transmission frame is generated using the encoded data, and the generated frame is transmitted. After receiving the data, the receiver checks whether the data includes data position information for restoring the data of the receiver. If the data position information exists, the receiver decodes the data using the position information of the data.

Description

APPARATUS AND METHOD FOR TRANSMITTING / RECEIVING DATA IN A COMMUNICATION SYSTEM}

1 is a view schematically showing the structure of a transmitter in a general communication system,

2 is a view schematically showing the structure of a transmitter in a communication system according to an embodiment of the present invention;

3 is a diagram schematically showing the structure of a non-uniform error protection encoder according to an embodiment of the present invention;

4 is a view schematically showing a structure of a receiver in a communication system according to an embodiment of the present invention;

5 is a view schematically showing the structure of a non-uniform error protection decoder according to an embodiment of the present invention;

6 is a constellation diagram for performing multiple single decoding in a decoder according to an embodiment of the present invention;

7 is a flowchart schematically showing a data transmission operation according to an embodiment of the present invention;

8 is a flowchart schematically illustrating a data receiving operation according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data transmission and reception in a communication system, and more particularly, to an apparatus and method for transmitting and receiving data in a non-uniform error protection (UEP) scheme considering a channel state of a receiver in a wireless communication system. It is about.

Channel coding, which can be said to be the core of the information transmission process in a communication system, is classified into two types: an equal error protection (EEP) method and a UEP method. The EEP method is a channel encoding method for encoding all information bits with the same code, and the UEP method is a channel encoding method for protecting important data by encoding with different codes according to the importance of the information bits.

Next, a structure of a base station using the EEP scheme in a communication system will be described with reference to FIG. 1.

1 is a diagram schematically illustrating a structure of a base station in a general communication system.

Referring to FIG. 1, the base station includes coders 111, 113, and 115, a transmission frame generator 117, and a transmitter 119.

The encoders 111, 113, and 115 are encoders to which the above-described EEP scheme is applied, and data of each receiver, that is, users, is encoded using a constant encoding scheme.

Next, the transmission frame generation unit 117 receives the encoded data and generates a transmission frame for transmission of the data.

The transmitter 119 transmits the generated transmission frame.

Among the communication systems, the wireless channel environment of the wireless communication system is different from the wired channel environment in that multipath interference, shadowing, propagation attenuation, time varying noise, interference, and fading are different. Many factors, such as inevitable errors, cause information loss. Accordingly, in order to transmit and receive data between a transmitter and a receiver, for example, a base station and a terminal, the communication system needs to transmit and receive data in consideration of channel characteristics.

Meanwhile, the UEP method divides input information bits into a predetermined number of streams according to importance. Subsequently, according to the importance of the separated streams, the data stream having low importance is encoded by a code having a low code correcting capability, and the data stream having a high importance is encoded by a code having a high code correcting capability. As described above, the UEP scheme for dividing information bits according to importance has an advantage in use because it adaptively considers characteristics of the information bits as compared to the EEP scheme which does not consider importance.

Accordingly, the UEP method is used to transmit streams of different importance according to a compression method of information bits output from a compressor of an audio or video signal. Therefore, studies are being actively conducted to efficiently transmit data in a communication system using a UEP method having an advantage in use over the EEP method.

As a result, there is a need for a system for performing data transmission / reception in consideration of channel characteristics between a base station and a terminal and performing data transmission and reception by applying the UEP scheme between the base station and the terminal.

Accordingly, an object of the present invention is to provide an apparatus and method for transmitting and receiving data in consideration of channel characteristics in a communication system.

Another object of the present invention is to provide an apparatus and method for transmitting and receiving data using a UEP scheme in a communication system.

In accordance with an aspect of the present invention, a method for transmitting data in a communication system includes: obtaining, by a transmitter, channel information of each receiver present in a cell; and using the channel information, at least two groups of receivers. And a process of encoding data of receivers corresponding to the determined group, and generating a transmission frame using the encoded data and transmitting the generated frame.

According to another aspect of the present invention, there is provided a method of receiving data in a communication system, the receiver receiving data and checking whether the data includes data location information for data restoration of the receiver; Decoding the data using the position information of the data if the data position information exists.

An apparatus of the present invention for achieving the above objects is a data transmission apparatus in a communication system, wherein a transmitter obtains channel information of respective receivers existing in a cell, and uses the channel information to assign receivers to at least two groups. A scheduler for discriminating, at least two encoders for encoding data of receivers corresponding to the determined group, a transmission frame generator for generating a transmission frame using the encoded data, and a transmitter for transmitting the generated frame It is characterized by.

Another apparatus of the present invention for achieving the above object is a data receiving apparatus in a communication system, the receiver for receiving data, and whether the data has data position information for data recovery of the receiver, and the data position If the information is present, characterized in that it includes a decoder for decoding the data by using the position information of the data.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The present invention proposes a system for transmitting and receiving data using different encoders according to channel characteristics between a transmitter and a receiver in a communication system. In particular, the encoder uses an Unequal Error Protection (UEP) encoder and encodes data to be transmitted using different UEP encoders according to channel characteristics. Thus, a component code having a small error correction capability is assigned to a receiver having a good channel state, and a component code having a strong error correction capability is assigned to a terminal having a poor channel state.

Thus, when the transmitter and the receiver of the communication system, for example, the base station (BS) and the mobile station (MS) communicate with each other, a channel between the service area of the base station, that is, the terminals existing in the cell Information is obtained and the terminals are classified into at least two groups using the channel information. Each group is encoded using a different encoder, that is, a UEP encoder, and then data is transmitted to each terminal.

Next, a structure of a transmitter, that is, a base station, according to the present invention will be described with reference to FIG. 2.

2 is a diagram schematically showing the structure of a base station in a communication system according to an embodiment of the present invention.

Referring to FIG. 2, the base station includes a scheduler 211, encoders 213 and 215, a transmission frame generator 217, and a transmitter 219.

The transmission data of the base station transmitting the data may be data of respective terminals, and the data of each terminal is input to the scheduler 211. In addition, the scheduler 211 is input channel information with the receiver obtained by the terminal.

The scheduler 211 may divide each terminal into two or more groups using the channel information. Here, what may be considered using the channel information may be, for example, the location of the terminal existing in the cell of the base station. The terminals may be divided into a group of terminals located at a cell center of the base station and a group of terminals located at a cell boundary. In this case, the channel information used may include, for example, a signal to noise ratio (SNR), a carrier to interference and noise ratio (CINR). The terminal group may be distinguished using a coefficient such as "." By using a predetermined threshold value, for example, the channel information, for example, SNR, CINR, and the like, a group of terminals may be divided into two or more groups based on the threshold value. In this case, the cell may be divided into two or more regions. The number of terminal groups is determined according to the number of regions in which the cells are divided.

Therefore, the closer the terminal is to the center of the cell, the smaller the path loss and the smaller the influence from the neighboring base stations. Therefore, the farther the terminal, the greater the path loss and the greater the influence from the neighboring base stations. It will have channel characteristics. In other words, since a terminal located at the center of a cell has better channel characteristics, the terminal can decode even a channel code having a small error correction capability.

Accordingly, the scheduler 211 classifies terminals into two or more terminal groups by using channel information with the terminals, and receives data of the divided terminals by placing a predetermined buffer in the scheduler 211. In addition, the information bits inputted to the scheduler 211 are classified and received for each terminal group. In this case, the terminal group is a terminal group determined according to the channel state after checking the channel state of the base station and each terminal using the channel information. Data of each terminal group is encoded using a different encoder for each terminal group.

Thus, the data of the groups determined by the scheduler 211 are input to the encoders 213 and 215. Thus, the encoders 213 and 215 may use an encoder that uses the UEP scheme. When the terminal group determined by the scheduler 211 is a terminal group having a good channel environment, the data of the terminal group encodes data using a component code having a relatively small error correction capability, and when the terminal group has a poor channel environment. The data of the terminal group encodes the data using component codes having a relatively large error correction capability.

Thus, the encoders 213 and 215 may use M encoders 213 and 215 when the terminal group is M. And the structure of the encoder will be described in detail with reference to FIG.

 Thus, the data encoded by the encoders 213 and 215 are input to the transmission frame generator 217.

The transmission frame generator 217 configures a transmission frame for data transmission using the input data and outputs the transmission frame to the transmitter 219.

The transmitting unit 219 receiving the transmission frame transmits data by performing a series of radio processing for data transmission on a wireless channel.

3 is a diagram schematically illustrating a structure of a non-uniform error protection encoder according to an embodiment of the present invention.

Referring to FIG. 3, a UEP encoder of the UEP scheme is illustrated, and is divided into component encoders 311 and 313 and a mapper 315 that generate a plurality of component codes. The mapper 315 refers to a baseband mapper that generates a baseband channel symbol. In general, several bits are combined to form a channel symbol. Thus, the mapper 315 has the same meaning as a modulator.

In addition, the UEP encoder will be described as an example of an encoder of a multilevel code, and the multilevel code is one of the UEP schemes. Accordingly, the multilevel encoder is composed of a modulator, that is, a mapper 315 and a combination of component encoders 311 and 313 generating several component codes. The component code refers to a code connected for individual input bits or a plurality of input bits. The component codes may be applied to all codes generally applied regardless of the type of codes. For example, a block code such as a hamming code, a convolution code, and a recursive decoding turbo may be applied. It is possible to apply a turbo code and a low density parity check (LDPC).

Thus, the component encoders 311 and 313 encode the input data using the codes described above, and the coded codes, that is, code 0 to code N-1, are input to the mapper.

의 형태를 가진다. 그리하여 상기한 다중레벨 부호를 사용하여 UEP를 구현할 수 있으며, 성분부호의 부호강도(coding strength)와 기저대역 사상기의 사상법(mapping rule)을 변화시킨다. 따라서 오류정정능력을 크게 하기 위해서는 낮은 부호율의 성분부호와 사상기에서 상대적으로 오류특성에 강한 사상비트에 할당하며, 오류정정능력을 작게 해도 되는 경우에는 높은 부호율의 성분부호와 사상기에서 상대적으로 오류특성이 약한 사상비트를 할당한다. If N is assumed to be the number of input bits of the mapper 315, then the channel symbol is

Has the form Thus, the UEP can be implemented using the multilevel code described above, and the coding strength of the component code and the mapping rule of the baseband mapper are changed. Therefore, in order to increase the error correcting capability, it is allocated to the low bit rate component code and the mapping bit that is relatively strong in the error characteristics in the mapper. As a result, map bits having weak error characteristics are allocated.

Thus, the mapped bits and component codes assigned with low error correction capability are referred to as 'low level', and the mapped bits and component codes assigned with high error correction capability are defined as 'high level'. do.

In addition, the base station determines terminal information for identifying each terminal, that is, group information to which the terminal belongs, level information assigned to the terminal, and an identifier for identifying the terminal to receive data corresponding to the terminal. Send the information. In this case, the group information and the level information may be transmitted to the terminal in the form of a kind of control information, and the identifier information may be transmitted in a frame. Thus, when the base station does not transmit the control information, the base station includes the identifier information in a frame so that the base station can receive data from the terminal. The base station transmits the control information to the corresponding terminals at regular intervals when the group of the terminals is changed.

In order to obtain terminal information for distinguishing the terminals, the base station may acquire channel information during a setup process of initially establishing a call with the terminals. Terminals are divided into groups using the determined threshold value. The channel information is updated at regular intervals, and the terminals are divided into groups according to the update of the channel information. As described above, the channel information may be, for example, uplink or downlink SNR or CINR information.

Next, a structure of a receiver, that is, a terminal, receiving data transmitted from the base station will be described with reference to FIG. 4 below.

4 is a diagram schematically illustrating a structure of a receiver in a communication system according to an embodiment of the present invention.

Referring to FIG. 4, the terminal includes a receiver 411 and a decoder 413. The receiver 411 receives the data transmitted from the base station and outputs the data to the decoder 413. When the decoder 413 receives control information from the base station, the decoder 413 may acquire location information of data corresponding to the terminal using the group information and the level information. Thus, the decoder 413 can decode the data corresponding to the terminal from the data when the position information of the data exists in the terminal.

However, if the control information does not exist, the decoder 413 needs to receive data using the identifier information, so that multi-stage decoding is performed to obtain identifier information and to decode the data. The decoder 413 performs the lowest level decoding and extracts identifier information from the decoded information. Then, it is checked whether the extracted identifier information is identifier information corresponding to the terminal itself. When the extracted identifier information is identifier information assigned to the terminal, it is possible to obtain data position information of the terminal and to decode data by acquiring data position information of the terminal. Next, the structure of the decoder will be described below with reference to FIG. 5. The decoder may be referred to as a UEP decoder since it is a decoder of a terminal that receives data of a base station using an encoder using the UEP scheme.

5 is a diagram schematically illustrating a structure of a non-uniform error protection decoder according to an embodiment of the present invention.

Referring to FIG. 5, the decoder includes a plurality of decoders 511, 515, and 519 and re-encoders 513 and 517. Here, the decoder decodes the multilevel code described in the UEP encoder, and the decoding of the multilevel code is performed through multi-stage decoding. Performing the multi-stage decoding is because it has an optimized performance in terms of code complexity and performance. It is also possible to perform Maximum Likelihood (ML) decoding on the multilevel code.

In the case of the multi-stage decoding, the low level decoding is performed in advance. Accordingly, the first decoder 511 decodes the lowest level component code, and the first decoder 511 receives a value obtained by calculating a constant matrix from the received channel symbols. Perform

Decoding is performed by the second decoder 515 having a lower level after the lowest level. In this case, the second decoder 515 uses the code bits re-coded by the first re-encoder 513 to the bits decoded in the first decoder 515 of the previous level. This is to select candidate groups capable of matrix calculation among the received channel symbols, and to improve the performance and reduce the computation amount when performing a high level decoding.

The first re-encoder 515 has a structure similar to that of the encoder used in the transmitter, and the components inside the re-encoder to prevent errors of data of the current level due to errors of re-encoded data of previous levels. It is possible to have a structure of a re-encoder further comprising an interleaver between the encoder and the mapper.

6 is a constellation diagram for performing multiple single decoding in a decoder according to an embodiment of the present invention.

Referring to FIG. 6, quadrature phase shift keying (QPSK) will be described as an example. The natural mapping is a method of mapping from 0 to 1 (0, 1, 2, 3, 4, ...) on the basis of an arbitrary constellation point.

In the case of the QPSK, the bit is expressed in the form of 'ab', where b represents '0 level' and a represents '1 level'. In addition, it is assumed that codes having the same performance are applied to the level 0 and the level 1 having the same complexity and the same complexity.

In the case of performing the multi-stage decoding, the decoding is performed on the 0 level, and the information decoded at the 0 level is recoded to be used for the 1 level decoding, which is shown in the constellation located on the right. The free Euclidean distance with respect to level 0 has a value of 2, and after the value of b is determined, the minimum free Euclidean distance at level 1 is improved. As described above, when b is found to be 0, the minimum free Euclidean distance becomes 4 according to the value of a.

For example, the map information transmitted from the base station to the user in the cell will be described. A convolutional turbo code (CTC) having a code rate of 1/2 will be referred to as 'CTC'. 6 times is transmitted according to the QPSK modulation scheme. In this case, the QPSK modulation scheme has a mapping rule according to the gray mapping method, and the component code for each level is 1/2 of the code rate as described in the original form and repeats 6 times to perform a 1/12 code. It is possible to construct a CTC code having a rate.

At this time, the minimum Euclidean distance between modulated signals corresponding to zero level mapping bits becomes two, and the minimum Euclidean distance between modulated signals corresponding to one level mapping bits becomes four. Therefore, it has the same complexity as the code rate as the component code, and map information for the terminal located in the cell center is transmitted to the zero level component stream, and the terminal for the terminal located in the cell boundary region is transmitted to the one level component stream. Allocate map information. Therefore, it is possible to improve the reception performance of the terminal in the cell boundary area, depending on the actual performance and the position of the terminal. Then, the operation of the transmitter and the receiver, that is, the base station and the terminal will be described below, and the operation of the base station will be described in FIG. 7.

7 is a flowchart schematically illustrating a data transmission operation according to an embodiment of the present invention.

In step 701, the base station acquires channel information of each terminal and proceeds to step 713. As described above, the channel information may use, for example, SNR or CINR. In this case, the terminal may check the distance from the center of the cell through the channel information, and for each terminal using the channel information. It is possible to perform encoding corresponding to the channel state.

In step 703, the base station determines the group of each terminal using the channel information, and proceeds to step 715. The base station may divide the terminal group into two or more, and may distinguish the terminal group and perform different encoding for each terminal group. In the case of determining the terminal group, the terminal group is determined by comparing channel information for each terminal with a threshold value, which is set in advance.

In step 715, the base station encodes data of terminals of each group and proceeds to step 717. When the base station encodes the data of the terminals, the base station performs encoding of the UEP method using component codes using different component codes according to the importance of the data.

In step 717, the base station generates a transmission frame using data of the terminals of each group in which encoding is performed, and proceeds to step 719. FIG.

In step 719, the base station transmits the generated frame.

In FIG. 7, the operation of the base station has been described, and an operation of the terminal for receiving data of the base station will be described with reference to FIG.

8 is a flowchart schematically illustrating a data receiving operation according to an embodiment of the present invention.

In step 801, the terminal receives the frame transmitted from the base station and proceeds to step 803. As described with reference to FIG. 7, the terminal receives data encoded according to a group preset in the base station.

In step 803, the terminal checks whether there is data location information for data restoration in the base station. If there is the data position information, for example, the group information and the level information received from the base station in the terminal, the process proceeds to step 813 to decode the data. However, if there is no location information of the data as a result of the check, step 805 is performed.

In step 805, the terminal sets the K value to 0 and proceeds to step 807. The K value is information indicating a level, and is set to 0 in order to decode from the lowest level.

In step 807, the terminal decodes the lowest zero level information and proceeds to step 709. In this case, it is determined whether the identifier information corresponding to the terminal is included when the zero-level information, that is, the data is decoded. If it is determined that the identifier information corresponding to the terminal is not included, the process proceeds to step 815 to increase the K value by 1 and proceeds to step 807 to decode the information on the next level. However, in the case where the identifier information corresponding to the terminal is included in the determination result, the process proceeds to step 811.

In step 811, the terminal acquires data location information using the identifier information, and then proceeds to step 813.

In step 813, the terminal can restore the data using the location information of the data.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention has the advantage that it is possible to adaptively transmit and receive data in response to a channel change between the transmitter and the receiver by transmitting and receiving data in consideration of channel characteristics between the transmitter and the receiver in a communication system. In addition, since the transmitter and the receiver use a non-uniform error protection scheme between the transmitter and the receiver, an efficient encoding technique may be applied to transmit and receive data.

Claims (22)

A data transmission method in a communication system, The transmitter acquires channel information of each receiver existing in the cell; Classifying receivers into at least two groups using the channel information; Encoding data of receivers corresponding to the determined group; And generating a transmission frame by using the encoded data and transmitting the generated frame. The method of claim 1, Wherein the channel information is one of a signal to noise ratio and a carrier to interference noise ratio. The method of claim 2, The group is determined using the receiver position information according to the channel information. The method of claim 1, The encoding is a data transmission method, characterized in that for performing the non-uniform error protection scheme encoding. The method of claim 4, wherein And encoding by setting different code strengths and mapping methods of component codes for each group. The method of claim 1, And transmitting the group information of the terminal for data reception and the level information allocated to the terminal at intervals of a predetermined period. The method of claim 6, And the level is set based on mapped bits and component codes allocated according to the error correction capability. The method of claim 1, The transmitter is a data transmission method, characterized in that for transmitting the identifier information of the terminal for data reception. In the communication system receiving data, Receiving the data and checking whether the data has data position information for restoring data of the receiver; And decoding the data using the location information of the data if the data location information exists. The method of claim 9, Extracting identifier information corresponding to the receiver by decoding from a low level through the decoder if the data position information does not exist; And acquiring data position information using the identifier information to decode the data. The method of claim 9, The location information of the data is determined using the group information and the level information to which the terminal belongs. A data transmission apparatus in a communication system, The transmitter obtains channel information of each receiver existing in the cell and uses the channel information to divide the receiver into at least two groups; At least two encoders for encoding data of receivers corresponding to the determined group; A transmission frame generator for generating a transmission frame using the encoded data; And a transmitter for transmitting the generated frame. The method of claim 12, And the channel information is one of a signal-to-noise ratio and a carrier-to-interference noise ratio. The method of claim 13, And the scheduler establishes a group using receiver position information according to the channel information. The method of claim 12, And the encoder is a coder of a non-uniform error protection method. The method of claim 15, The encoder is a component encoder using a plurality of component codes, And a mapper for generating baseband channel symbols from the codes coded using the component codes. The method of claim 12, And the transmitter transmits group information of the terminal for data reception and level information allocated to the terminal at intervals of a predetermined period. The method of claim 17, And the level is set based on mapped bits and component codes allocated according to the error correction capability. The method of claim 12, And the transmitter transmits identifier information of a terminal for data reception. A data receiving apparatus in a communication system, A receiver receiving the data, And a decoder for checking whether the data includes data position information for data restoration of the receiver, and if the data position information exists, decoding the data using the position information of the data. The method of claim 20, If the data position information does not exist, the decoder performs decoding from a low level through the decoder to extract identifier information corresponding to the receiver, and acquires data position information using the identifier information to decode the data. Characterized in that the data receiving device. The method of claim 20, And the decoder determines location information of data using group information and level information to which the terminal belongs.

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