KR100834655B1 - Apparatus and method for data signal and receiving make use of reliability between bits and symbols in cdma mobile communication system - Google Patents

Abstract

The present invention relates to a data transmission / reception apparatus and method using bit / symbol reliability in a code division multiple access (CDMA) mobile communication system, and to mapping and retransmitting coded bits classified according to importance using reliability differences between bits. In order to achieve reliability averaging using inter-symbol reliability, the two techniques are optimally integrated.

High speed packet communication system, mobile communication system, interleaver, HARQ, modulation and demodulation, reliability

Description

Apparatus and method for data transmission / reception using reliability between bits / symbols in code division multiple access mobile communication system             

1 is a diagram illustrating symbol mapping coordinates according to a conventional 16 QAM modulation scheme.

2 is a diagram illustrating a transmitter configuration of a typical asynchronous high speed packet transmission system.

3 is a diagram illustrating a configuration of a transmitter to which a symbol mapping technique (SMP) and a retransmission technique (RA) are applied according to an exemplary embodiment of the present invention.

4 is a diagram illustrating a configuration of a receiver to which a symbol mapping technique (SMP) and a retransmission technique (RA) are applied according to an exemplary embodiment of the present invention.

5 is a diagram illustrating a control flow in a transmitter according to an embodiment of the present invention.

6 is a view showing a performance comparison through the experiment of the transmitter and the receiver according to an embodiment of the present invention.

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The present invention relates to an apparatus and method for transmitting and receiving data in a code division multiple access mobile communication system, and more particularly, to an apparatus and method for transmitting and receiving data for improving the reliability of data bits transmitted.

In general, it is practically impossible to receive a signal without any distortion or noise when receiving the transmitted signal in a communication system. In particular, when transmitting and receiving signals through a wireless network, the effects of distortion or noise are more severe than those through a wired network.

Therefore, many efforts have been made to minimize the effects of distortion and noise. As one of the representative examples, an error control coding scheme has been proposed. Codes used in the error control coding scheme are largely classified into memory class codes and memory codes. The memory class code may include a linear block code, and the memory code may include a convolutional code and a turbo code. Such a device for generating a code is called a channel encoder, and its output may be divided into a systematic bit and a parity bit according to an error control coding scheme used. A turbo code is a typical code used for an error control coding scheme that distinguishes and outputs the informational bits and the parity bits. Of course, in addition to the turbo code, the systematic convolutional code among the convolutional codes directly distinguishes the output into the systematic bits and the parity bits.

Herein, the systematic bit means a signal to be transmitted, and the parity bit is a signal added to correct an error occurring during transmission during decoding. However, even in this error control coded signal, if a cluster error occurs in a systematic bit or a parity bit, it is not easy to overcome it. This phenomenon often occurs while passing through a fading channel, and one of the techniques for preventing this phenomenon is a technique called "interleaving". The interleaving technique is used to overcome with error control coding by distributing the damaged part to several places instead of being concentrated in one place.

The encoded bits interleaved as described above are mapped to symbols in a digital modulator. The mapping is determined by the modulation scheme used in the digital modulator. As the modulation scheme, there are QPSK, 8PS, 16QAM, 64QAM, and the like. The mapping means that the position of the symbol is specified in coordinates (hereinafter, referred to as "symbol mapping coordinates") where the value of the I-channel is the x-axis and the value of the Q-channel is the y-axis. On the other hand, the mapping is made by the number of bits and the value of the bits constituting the symbol. The number of bits constituting the symbol is defined corresponding to the respective modulation schemes. The number of bits constituting the one symbol increases as the order of the modulation scheme increases. That is, in the QPSK modulation scheme, two bits represent one symbol (one symbol consists of two bits), and in the 8PSK modulation scheme, three bits represent one symbol (one symbol consists of three bits). In the modulation scheme, four bits represent one symbol (one symbol consists of four bits), and in the 64QAM modulation scheme, five bits represent one symbol (one symbol consists of five bits). In this case, the bits constituting the one symbol are used as information for mapping the symbol to the symbol mapping coordinates and may be classified according to reliability between bits constituting the symbol. In addition, each of the symbols also shows relatively different reliability (reliability between symbols) depending on where in the symbol mapping coordinates (constellation).

Hereinafter, a detailed description of the reliability and an example in which symbols are mapped to the symbol mapping coordinates corresponding to each modulation scheme will be described with reference to FIG. 1 and Table 1 below. Groups A, B, and C of FIG. 1 and Table 1 are groups classified according to relative reliability between symbols, hereinafter referred to as "reliability between symbols". Meanwhile, the reliability between four encoded bits i ₁ , q ₁ , i ₂ , and q ₂ representing the symbol is referred to as “reliability between bits”. The inter-symbol reliability is based on a reliability averaging technique (hereinafter referred to as RA), and the inter-bit reliability is the basis of symbol mapping based on priority (hereinafter, referred to as "SMP") technique. .

In general, a 1X EV / DV system defined by an asynchronous high speed packet transmission system (HSDPA, High Speed Downlink Packet Access) or a synchronous mobile communication standard uses 16QAM as a higher-order modulation method, so that the description below will describe the 16QAM as a higher-order modulation method. An example will be described. However, it should be noted that even if the higher-order modulation scheme other than the 16QAM is used, only the difference in the number of bits mapped to one symbol may be applied.

One symbol used for the 16QAM consists of four coded bits as shown in FIG. 1 and Table 1 below. Table 1 below shows the relative reliability of each symbol in 16QAM.

group Symbol (i ₁ , q ₁ , i ₂ , q ₂ ) Relative reliability A (0000) (1000) (1100) (0100) Low B (0010) (0001) (1001) (1010) (1110) (1101) (0101) (0110) Medium C (0011) (1011) (1111) (0111) High

In FIG. 1, the four encoded bits are represented by i ₁ , q ₁ , i ₂ , and q ₂ , respectively. Meanwhile, the four encoded bits determine a specific coordinate in a symbol mapping coordinate of a corresponding symbol. The symbol mapping coordinates are divided into four macro regions (hereinafter referred to as "quadrants"), such as left / right or up / down depending on positions on the X-axis (I-channel value) and Y-axis (Q-channel value). Each of the quadrants is divided into micro areas of up, down, left, and right areas. The receiver determines a received symbol (or received bit) according to the I-channel value and the Q-channel value of the received signal during demodulation. Accordingly, two encoding bits i ₁ and q ₁ of the four encoding bits designate one quadrant of the large quadrants of the symbol mapping coordinates. The other two coding bits i ₂ and q ₂ designate a small region (demodulation decision region) or a specific coordinate within the quadrant. Hereinafter, coding bits for dividing the large quadrant are referred to as "quadrant determination bits", and coding bits for dividing the demodulation determination region or specific coordinates are referred to as "demodulation determination bits". The quadrants are divided from the first quadrant to the fourth quadrant. The first quadrant is an area in which the values of the I-channel and the Q-channel have both positive values. The second quadrant is an area in which the value of the I-channel has a negative value and the value of the Q-channel has a positive value. The third quadrant is an area in which the values of both the I-channel and the Q-channel have negative values. Finally, the fourth quadrant is an area in which the value of the I-channel has a positive value and the value of the Q-channel has a negative value. The demodulation decision region may be subdivided by the modulation scheme used.

On the other hand, in case of transmission by symbol unit through a wireless channel, most error occurs between demodulation decision regions within the same quadrant, so that the demodulation determination bit has an error rather than a probability that an error occurs in the quadrant determination bits. Are more likely to occur. In other words, the quadrant determination bits may have a high reliability, and the demodulation determination bits may have a lower reliability than the quadrant determination bits. 16QAM is divided into two levels of reliability, but higher order modulation schemes may have two or more levels of reliability. That is, the bits for distinguishing the largest decision region (quadrant) are called high reliability bits, and the bits for distinguishing the smallest region are called low reliability bits, and the other bits are intermediate reliability. It can have This is called inter-bit reliability in each symbol.

A symbol mapping coordinate according to symbol mapping, which may be represented by reliability of bits constituting a symbol corresponding to the 16QAM modulation scheme, is shown in FIG. 1.

In case of using the 16QAM, one symbol is composed of 4 bits of encoded bits. This is a position where the symbol is mapped in the symbol mapping coordinates shown in FIG. 1 by the 4 bits of encoded bits. In other words, two bits of quadrant determination bits ahead of the four bits of encoding bits designate one quadrant of four quadrants. The remaining two bits of demodulation decision bits designate a particular demodulation decision region within the quadrant. In FIG. 1, the first to fourth quadrants each have four demodulation decision regions (first to fourth demodulation determination regions). For example, when a symbol is composed of coding bits of "1011", a second quadrant is designated by quadrant determination bits "10", and the first to fourth demodulation determining regions are defined by "11" which is a demodulation determination bit. The symbol "1011" is mapped to a second demodulation decision region. An important technique for applying the discriminated reliability between bits is a symbol mapping (SMP) method according to importance, which leads to mapping to bits having high reliability. This is described later in detail below.

The reliability of the inter-bit has been described above. The reliability of the inter-symbol is as follows. It has been described that the quadrant decision bits i ₁ and q ₁ have relatively higher reliability than the demodulation decision bits i ₂ and q ₂ in the above-described bit reliability. However, as shown in FIG. 1 and Table 1, the reliability of the quadrant determination bits (i ₁ and q ₁ ) also differs between the symbols. The reason for this is that the probability that a symbol crosses a quadrant for the quadrant decision bit of group A to make an error is relatively greater than that of groups B and C. For example, the second quadrant symbol of the group A is composed of the bit "1000", and the quadrant decision bit is "10". When this symbol is received in the first or fourth quadrant, the first bit "1" indicates an error, and when received in the third or fourth quadrant, the second bit "0" will indicate an error. As can be seen from the position of the symbol of FIG. 1, the probability (error probability) of receiving the symbol in the first, third, or fourth quadrants is relatively higher than the symbols of groups B and C. Accordingly, intersymbol reliability is increased in order of group A, group B, and group C. According to this result, a technique of averaging the reliability between symbols by allowing the same bits to be mapped to symbols at positions different from the initial transmission upon retransmission is called a reliability average (RA).

A schematic structure of a transmitter constituting a conventional High Speed Downlink Packet Access (HSDPA) wireless communication system is shown in FIG. 2 as shown in FIG. 2. The channel encoder 230 and the HARQ operation unit 240 are shown in FIG. It consists largely of an interleaver 250 and a modulator 260.

Referring to FIG. 2, N transport blocks from the data source 210 are provided to the CRC unit 220 to add CRC bits corresponding to each of the N transport blocks. The N transport blocks to which the CRC bits are added are input to a channel encoder 230, and the bits constituting the N transport blocks by the channel encoder 230 are output as encoded bits through a predetermined encoding. do. In addition, the channel encoder 230 supports a plurality of coding rates through encoding bit puncturing or repetition with 1/3 or 1/5 mother codes. Accordingly, an operation of determining a coding rate to be used among a plurality of coding rates supported by the channel encoder 230 may be needed. Referring to the role of the HARQ operation unit 240 in FIG. 2, the coding bits are input to the HARQ operation unit 240, and the coding bits are matched with rate matching by the HARQ operation unit 240. Selection of coding bits for HARQ is made. The rate matching typically performs repetition and puncturing on the coded bits when the number of coded bits from the channel encoder 230 and the number of bits transmitted through the wireless channel do not match. Match this through Another role is to select a redundancy version to retransmit different coded bits than before in each retransmission.

The coding bits selected by the HARQ operation unit 240 are input to an interleaver 250, and the selected bits are interleaved and output by the interleaver 250. The interleaving operation is to increase the decoding probability by spreading the error distribution even when a cluster error occurs during transmission. The interleaved coded bits are input to a M_ary modulator 260, and the interleaved coded bits are pre-determined among modulation schemes such as QPSK, 8PSK, 16QAM, and 64QAM. According to the symbol may be transmitted. However, in the following description, only 16QAM determined to be used in an asynchronous high speed packet transmission system (HSDPA) or 1X EV / DV system will be discussed. Meanwhile, although the controller is omitted in FIGS. 2 and 3, the controller controls the operation of the HARQ operation unit 240 and the encoder 230 and the modulation scheme of the modulation unit 260 according to the current wireless channel state. do. The HSDPA wireless communication system uses an adaptive modulation and coding scheme (AMCS) scheme that selectively uses QPSK and 16QAM as a modulation scheme according to a wireless environment, and a modulation scheme is determined by the controller. In addition, although not shown in the above-described drawings, a mobile communication system using a code division multiple access method spreads data using an orthogonal code, that is, a Walsh code, an orthogonal variable spreading factor (OVSF) code, or the like for transmission. The mobile terminal can distinguish a channel transmitting the data and use a PN code or a scrambling code to distinguish a base station transmitting the data.

On the other hand, in the structure of the transmitter described above, the systematic bits and the parity bits are not distinguished and are expressed by being integrated into encoded bits. However, the coding bits output from the channel encoder 230 and the HARQ operation unit 240 constituting the transmitter may be divided into informational bits and parity bits. Meanwhile, the priority of the systematic bits and the parity bits output from the channel encoder 230 are different. In other words, if the data to be transmitted has an error at a certain rate, the error in the parity bits can be decoded more accurately at the receiver rather than the error in the systematic bits. will be. The reason for this is that the actual data bits are systematic bits, and the parity bits are bits of data added to correct the error occurring during transmission as demodulated.

Accordingly, there is a need for a method of differentiating information bits having a high importance from redundant bits having a less importance than the information bits in performing symbol mapping on encoded bits by a predetermined modulation scheme. The SMP technique combines the importance of coded bits with inter-bit reliability in symbols of the higher-order modulator. The purpose of the SMP technique is to map encoded bits of high importance to bits of high reliability, and map bits of relatively low importance to bits of low reliability. This is to improve the reception performance by reducing the probability that an error occurs with relatively important bits.

Hereinafter, examples of applying SMP technology to the 16QAM will be described.

First, when 16QAM is applied and information bits and redundant bits are the same amount, each symbol of the modulator 390 has a structure of (i ₁ , q ₁ , i ₂ , q ₂ ). Thus, two bits of information bits are mapped to high reliability i ₁ or q ₁ , and two bits of surplus bits are mapped to low reliability i ₂ or q ₂ .

Second, if 16QAM is not the same amount of information bits and surplus bits, as many information bits as possible map to high reliability and the remaining information bits that do not map to high reliability map to low reliability, such as redundant bits. Therefore, since each symbol of the modulator 390 has a structure of (i ₁ , q ₁ , i ₂ , q ₂ ) similarly to the first example, the reliability of the information bit is low (i ₂ or q ₂ ) in some cases. Can be mapped to.

The commonality between the above-described two techniques, namely, SMP-Symbol Mapping based on Priority technique and Reliability Average (RA), which is one of advanced retransmission techniques, utilizes a difference in reliability. On the other hand, the difference is that the first technique attempts to match the importance with the inter-bit reliability, while the second technique attempts to average the reliability between symbols regardless of the importance.

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Accordingly, an object of the present invention to solve the above problems is to provide a method that can show the optimal performance for the integration of SMP and RA technology.

Accordingly, an object of the present invention is to provide a data transmission / reception apparatus and method for improving the performance of a wireless communication system.

Another object of the present invention is to provide an apparatus and method for more reliable data transmission / reception in a wireless communication system.

It is still another object of the present invention to provide a data transmission / reception apparatus and method capable of receiving bits of high importance with a relatively high reception probability in initial transmission and retransmission in a receiver of a wireless communication system.

It is still another object of the present invention to provide a data transmission / reception apparatus and method for combining a symbol mapping technique (SMP) and an inter-symbol reliability averaging technique (RA) according to importance to have a synergistic effect in a wireless communication system. .

It is still another object of the present invention to provide a data transmission / reception apparatus and method for always mapping information bits to high reliability when initial transmission and retransmissions occur several times.

It is still another object of the present invention to provide an apparatus and method for transmitting / receiving data that averages reliability between information bits when initial transmission and retransmissions occur several times.

It is another object of the present invention to provide differential averaging by making the average reliability of information bits superior to the average reliability of redundant bits.

The present invention according to the first aspect for achieving the above object is divided into two coded bit groups for encoding bits to be transmitted in symbol units during initial transmission and retransmission in a mobile communication system, and the two coded bit groups In the method of symbol mapping corresponding to the number of times of the initial transmission and the retransmission, the step of mapping the coded bits constituting one coded bit group of the two coded bit groups to a location having a high reliability of the symbol, and Inverting the coded bits constituting the other coded bit group among the two coded bit groups under different conditions corresponding to the number of retransmissions, and inverting the inverted coded bits to the high reliability of the symbol. Maps to locations with relatively lower confidence A it characterized in that it comprises.

According to a second aspect of the present invention for achieving the above object, the present invention divides encoded bits to be transmitted in symbol units during first transmission and retransmission into first and second encoding bit groups in a mobile communication system. In the method of symbol mapping the second coded bit groups corresponding to the number of times of initial transmission and retransmission, the first coded bits constituting the first coded bit group and the second coded bits constituting the second coded bit group Inverting each of the nodes according to a different condition corresponding to the number of retransmissions, mapping the inverted first encoding bits to a location having a high reliability of the symbol, and inverting the second Mapping encoded bits to positions having a relatively low reliability compared to the high reliability of the symbol. The.

The present invention according to the third aspect for achieving the above object is divided into first and second coded bit groups for encoding bits to be transmitted in symbol units during initial transmission and retransmission in a mobile communication system. In the apparatus for symbolly mapping each of the second coded bit groups through a different interleaver and corresponding to the initial transmission and the number of retransmissions, the coded bits constituting the second coded bit group correspond to the number of retransmissions. Inverters that are inverted under different conditions and coded bits constituting the first coded bit group are mapped to positions having a high reliability of the symbol, and the inverted coded bits are relatively low compared to the high reliability. And a modulator for mapping to a position having reliability.

According to a fourth aspect of the present invention for achieving the above object, the present invention divides encoded bits to be transmitted in symbol units during first transmission and retransmission into first and second encoding bit groups in a mobile communication system. In the apparatus for symbolly mapping each of the second coded bit groups through a different interleaver and corresponding to the initial transmission and the number of retransmissions, the coded bits constituting the second coded bit group correspond to the number of retransmissions. Inverters that are inverted under different conditions and coded bits constituting the first coded bit group are mapped to positions having a high reliability of the symbol, and the inverted coded bits are relatively low compared to the high reliability. And a modulator for mapping to a position having reliability.

According to a fifth aspect of the present invention, a plurality of encoded bit groups are divided into two encoded bit groups for encoding bits to be transmitted in symbol units during initial transmission and retransmission in a mobile communication system. In a method of receiving data transmitted by mapping each of the encoded bits to locations having different reliability in response to the initial transmission and the retransmission number of times, demodulating the data and mapping to the location having the high reliability Outputting first encoding bits and second encoding bits mapped to a position having a relatively low reliability compared to the high reliability, and corresponding to the number of retransmissions of the first encoding bits and the second encoding bits Inverting under different conditions, the inverted first encoding bits and the Interleaving the second coded bits to the inverting each post is characterized in that it comprises the step of combining the dining coded bits previously received and.

According to a sixth aspect of the present invention, a plurality of encoded bit groups are divided into two encoded bit groups for encoding bits to be transmitted in symbol units during initial transmission and retransmission in a mobile communication system. In the apparatus for receiving the data to be transmitted corresponding to the number of times of the initial transmission and the re-transmission, each of the encoded bits are mapped to a position having a different reliability, the first demodulated data mapped to the position having a high reliability A demodulator for outputting encoded bits and second encoding bits mapped to positions having a relatively lower reliability than the high reliability, and the first encoding bits and the second encoding bits corresponding to the number of retransmissions. The inverter inverting by another condition and the inverted first encoding bits And a combiner for interleaving each of the inverted second encoding bits and combining with the previously received encoding bits.

According to a seventh aspect of the present invention to achieve the above object, a method of transmitting a mobile communication system includes: encoding coded bits to be transmitted and generating coded bits; Dividing into a first group consisting of two bits and a second group consisting of two bits of low importance, and determining a large quadrant with the bits of the first group during initial transmission, and demodulating with the bits of the second group. Determining a symbol mapping process, wirelessly transmitting a symbol determined by the symbol mapping process, inverting the bits of the second group at the time of retransmission, and determining a large quadrant with the bits of the first group. A symbol mapping process for determining a demodulation decision region using bits in which the second group of bits is inverted, and the symbol mapping process And the ball, characterized in that it comprises the step of transmitting a radio.

According to an eighth aspect of the present invention for achieving the above object, a method of transmitting a mobile communication system includes: encoding coded bits to be transmitted and generating coded bits; Dividing into a first group consisting of two bits and a second group consisting of two bits of low importance, and determining a large quadrant with the bits of the first group during initial transmission, and demodulating with the bits of the second group. Outputting a symbol having a first reliability through symbol mapping to determine a symbol, transmitting the symbol wirelessly, inverting bits of the second group when retransmitting, and bits of the first group Second reliability through symbol mapping to determine a large quadrant and determine a demodulation decision region from bits in which the second group of bits is inverted. Having the steps of: outputting the retransmission symbols, the retransmission symbols, characterized in that it comprises the step of transmitting a radio.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. DETAILED DESCRIPTION In the following detailed description, one representative embodiment of the present invention is set forth in order to achieve the above technical problem. And other embodiments that can be presented with the present invention are replaced by the description in the configuration of the present invention.

First, before the present invention will be described in detail, there is a matter to be kept in order to use the RA technique as the SMP technique that performs symbol mapping based on the importance of coded bits. The RA technique is to change the coded bits initially transmitted by a certain rule and to map them to other symbols. Therefore, a change rule for mapping to another symbol should be determined, and a method for this may be proposed in two ways. The first method uses a plurality of modulation constellations without changing the coding bits, and the second method uses a single symbol mapping coordinate and changes the coding bits according to a predetermined rule. In the first method, since both the transmitting and receiving end store a plurality of symbol mapping coordinates and change modulation accordingly, complexity can be increased. The second scheme is more efficient than the first scheme in terms of increased complexity.

On the other hand, there are two main methods for implementing the second method: swapping and inverting. For example, in the case of the position change, when the transmission (1011) belonging to the group C in the initial transmission, the symbols of (1110) belonging to the group B by changing the position of i ₁ , q ₁ and i ₂ , q ₂ during retransmission Inter-symbol averaging can be obtained by mapping to. However, this rule violates the SMP rule. This is because the SMP rule maps bits of high importance to bits of high reliability, so that the position change allows mapping of bits of high importance to bits of low reliability. Accordingly, the rule for changing the reliability group for the RA technology should be used only for the inverting method that continues to maintain the inter-bit reliability of the coded bits of high importance during initial transmission and retransmission. Therefore, an embodiment of the present invention to be described below is implemented by the second rule. That is, the present invention shows that the optimal gain can be obtained by integrating the SMP technology using the RA technology using only the inverting without using the position change method.

The RA parameters presented in Table 2 below are classified into four types by implementing the RA technology using only the inverting, and can determine the parameter b in a fixed or random order when retransmitting. This results in partial inverting of the interleaver output 4 bits. For example, when parameter b becomes 1, bits of i ₁ q ₁ are passed without inverting, and i ₂ q ₂ is inverted. Alternatively, bits of i ₁ q ₁ may be inverted at the same time, but the same performance may be selected by the designer. In other words, in the case of b + 1 to 3, the inverting of i ₁ q ₁ also does not change the reliability and shows the same performance as the case of no inverting. For example, in the case of (1000) of group A, when the RA parameter is b + 2, inverting only q ₂ becomes (1001) and maps to group B when i ₁ q ₁ is also inverted simultaneously ( 0101) and mapped to group B as described above, and the two symbols show the same performance because they have the same inter-bit reliability.

Hereinafter, described with reference to the accompanying drawings in accordance with an embodiment of the present invention. Specifically, the present invention proposes a result of a transmission scheme of a mobile communication system having improved performance by using the difference between reliability between symbols and the difference between reliability between bits.

First, before considering the present invention in detail, the intersymbol reliability averaging technique RA, which is aimed at the reliability average for each bit as two techniques to be applied in the present invention, may be replaced with the SMP technique. That is, the information bits (high importance bits) are mapped to high reliability (H) at the time of initial transmission by the SMP technique, but when the RA technique applies a swapping method between bits, the information bits (high importance) are retransmitted. Can be mapped to low reliability (L). Therefore, in the present invention, in order to combine the RA technology and the SMP technology, the RA technology performs only the bit-by-bit inverting method without applying the inter-bit position change method so that the information bits are always mapped to high reliability (H). .

Typically, the retransmission scheme is classified into chase combining (CC), full incremental redundancy (FIR), and partial incremental redundancy (PIR) according to the redundant version parameter a used for channel encoding. Meanwhile, some data operations are different according to the retransmission schemes. The reason is that in the case of CC, the same data is transmitted during initial transmission and retransmission, while different data types are transmitted in FIR and PIR. In addition, the FIR transmits only the surplus bits, whereas the PIR is slightly different in operating the SMP technology because the information bits and the surplus bits are retransmitted at the same time. In other words, when there are information bits to be transmitted, the information bits and the redundant bits may be mapped to high reliability and relatively low reliability, respectively. However, if there are no information bits to transmit, the surplus bits should be arbitrarily separated into high reliability and relatively low reliability.

3 is a diagram illustrating a transmitter configuration of a code division multiple access mobile communication system according to an exemplary embodiment of the present invention.

First, referring to FIG. 3, a transmitter configuration according to an exemplary embodiment of the present invention is provided. The data to be transmitted from the data source 310 is provided to the CRC unit 320, and the error correction is performed by the CRC unit 320. CRC bit for is added to the data and output. The data to which the CRC bit is added is provided to the channel encoder 330.

The channel encoder 330 encodes the data provided from the CRC unit 320 using a predetermined code. The predetermined code collectively refers to a code for outputting bits to be transmitted and error control bits of the bits by encoding the input data. As an example, the bits to be transmitted may be information bits S, and the error control bits may be redundant bits P. As described above, the predetermined code includes a turbo code, a systematic convolutional code, and the like. More specifically, the channel encoder 330 includes a plurality of encoders for encoding the provided data by a mother code rate, and performs puncturing by rate matching on the coded bits output from the encoders. HARQ operation unit 340 is required. In this case, the HARQ operation unit 340 changes the initial error parameter e _ini , which is one of the rate matching parameters, when the IR is used as a retransmission method, and performs puncturing by changing the puncturing position each time retransmission is performed. For example, when the PIR is used as the retransmission method, the initial transmitted information bits are retained at every retransmission, and only a plurality of initial error parameters e _ini are output so that the redundant bits are changed and output. On the other hand, when the FIR is used as the retransmission method, a plurality of initial error parameters e _ini outputting information bits only during initial transmission, and during retransmission, all the information bits are punctured and different redundant bits are output for each retransmission. Have them.

Therefore, when PIR is used, information bits and surplus bits are output from the HARQ operation unit 340 during retransmission. However, when FIR is used, only excess bits are transmitted from the HARQ operation unit 340 during retransmission. Is output.

The distributor 350 receives the information bits and the redundant bits from the HARQ operation unit 340 and distributes the information bits and the redundant bits to a plurality of interleavers. For example, when two interleavers 360 and 370 exist in the plurality of interleavers, the distributor 350 divides the two interleavers into two bit groups so that the two interleavers have the same number of bits. For example, when the number of information bits and the number of surplus bits in the HARQ operation unit 340 are symmetric, the divider 350 distributes information bits to the first interleaver 360 and the surplus bits to the second interleaver. Dispense to 370. When the number of information bits and the number of surplus bits in the HARQ operation unit 340 is not symmetric and there are more information bits than the surplus bits, the distributor 350 preferentially assigns the information bits and the surplus bits to the information bits. The first interleaver 840 is provided to the first interleaver 840, and a bit string including the remaining information bits and the redundant bits is distributed to the second interleaver 850. When the number of information bits and the number of surplus bits in the HARQ operation unit 340 is not symmetrical and there are more surplus bits than information bits, the divider 350 divides the information bits and the surplus bits from the information bits. The surplus bits of are provided to the first interleaver 360 and the remaining surplus bits are distributed to the second interleaver 370. On the other hand, when the retransmission is not the initial transmission when using the CC method and the PIR method, the distributor 350 performs the same operation as the case of the initial transmission described above. However, when the FIR scheme is used, the distributor 350 equally distributes the redundant bits provided from the channel encoder 330 into two redundant bit sequences, and one redundant bit sequence is used for the first interleaver 360. The remaining one bit stream is distributed to the second interleaver 370. The criterion of the distribution scheme is that as many information bits as possible can be distributed to the first interleaver 360.

The first interleaver 360 receives the information bit-oriented bits from the distributor 350 or the HARQ operation unit 340 and interleaves the input information-oriented bits. The first interleaver 360 interleaves the redundant bits distributed from the divider 350 upon retransmission by the FIR. The second interleaver 370 receives the excess bit-oriented bits from the distributor 350 or the HARQ operation unit 340 and interleaves the input redundant bit-oriented bits. The second interleaver 370 interleaves the redundant bits distributed from the distributor 350 when retransmitted by the FIR.

The output of the first interleaver 360 outputs a bit mapped to the high reliability bit i ₁ q ₁ , and the output of the second interleaver 370 outputs a bit mapped to the low reliability bit i ₂ q ₂ . The inverter 380 receives the encoded bits interleaved from the first interleaver 360 and the encoded bits interleaved from the second interleaver 370 and receives the encoded bits as shown in Table 2 below. Inverting is performed and output according to the reliability averaging parameter of. The reliability averaging parameter of Table 2 is determined as “0” for initial transmission, and any parameter among 0, 1, 2, and 3 is selected during retransmission. In the retransmission, selection of "0" means transmitting the same bit as the initial transmission, selection of "1" means inverting the low reliability bits i ₂ q ₂ , and selection of "2" means low. Means to invert only q ₂ of the reliability bits, and selection of “3” means to invert only i ₂ of the low reliability bits. Inverting the high reliability bits i ₁ q ₁ in the output bit form according to the reliability averaging parameter selection in Table 2 may be selected according to the designer's choice, but there is no difference in performance.

The modulator 390 maps the encoded bits from the inverter 380 to modulation symbols and transmits the encoded bits to the receiver. The modulator 390 uses the symbol mapping coordinates of FIG. 1 in mapping the encoded bits to the modulation symbols. Only one symbol mapping coordinate is used in the modulator 380.

As described above, the transmitter shown in FIG. 3 has a configuration in which information bits of relatively high importance are mapped to bits i ₁ and q ₁ of relatively high reliability. In addition, when a packet is retransmitted due to a failure in initial transmission, a structure for averaging reliability between symbols by changing a parameter for averaging reliability is shown. That is, the coded bits are divided into information bits and redundant bits and output from the bit divider 350 through a series of operations. The information bits are provided to the first interleaver 360 to be interleaved between the information bits, and output. The surplus bits are provided to the second interleaver 370 to be interleaved between the redundant bits. In other words, in order to enable symbol mapping according to importance, encoded bits may be interleaved in the first interleaver 360 and the redundant bits in the second interleaver 370 by using the interleavers. This is to prevent mixing of information bits and redundant bits having different importance levels from each other. The interleaved information bits are output as i ₁ and q ₁ mapped to relatively high reliability positions, and the interleaved surplus bits are output as i ₂ and q ₂ mapped to relatively low reliability positions. In this case, since the amount between the information bits and the redundant bits from the HARQ operation unit 340 is changed according to the code rate and the redundant version selection of the HARQ operation unit 340, the bit divider 350 may use the information bits and the redundant bits. Is divided into equal amounts and input into the interleavers 360 and 370. That is, the divider 350 controls the input of the two interleavers 360 and 370 to divide the output of the HARQ operation unit 340 by the same amount but input as many information bits as possible to the first interleaver. The encoded bits from the two interleavers are provided to the inverter 380 and perform inversion of each bit according to the retransmission parameter b for the reliability average described in Table 2 below. Table 2 below shows parameter b applied to retransmission technique (RA) for reliability average and the output of inverter accordingly.

Reliability averaging parameter, b Output bit sequence of inverter Operation 0 i ₁ , q ₁ , i ₂ , q ₂ None One

or

or

Inverse i ₂ and q ₂ (or inverse all 4 bits) 2

or

Inverse q ₂ (or inverse i ₁ , q ₁ and q ₂ ) 3

or

Inverse i ₂ (or inverse i ₁ , q ₁ and i ₂ )

는 i_k의 역을 의미한다. 즉, 1이면 0으로, 0이면 1로 출력한다.In Table 2 above

Means the inverse of i _k . That is, 1 is outputted as 0 and 0 is outputted as 1.

The output of the inverter is input to the modulator 390, and the encoded bits are mapped to predetermined symbols and transmitted to the receiver. When the modulation scheme of the modulator 390 is 16QAM, the coding bits are mapped to a symbol having a structure of (i ₁ , q ₁ , i ₂ , q ₂ ).

4 is a diagram illustrating a receiver configuration of a code division multiple access mobile communication system according to an embodiment of the present invention.

Referring to FIG. 4, a receiver configuration according to an exemplary embodiment of the present invention is described. The demodulator 410 receives data received from a transmitter, and modulates the input data in the modulator 390 of the transmitter. Demodulation is performed by a demodulation method corresponding to the scheme. Accordingly, the demodulator 410 outputs bit unit information back to the inverter unit 420 through demodulation according to the demodulation scheme. The demodulation constellation used in the demodulator 410 uses the same constellation used in the transmitter. The receiver should restore the inverting made at the transmitter to its original state, and the operation is performed by the inverting unit 420. On the other hand, the inverting unit 420 uses the same value as the reliability averaging parameter used in the transmitter with reference to the <Table 2> for the re-inverting.

The encoded bits output from the inverting unit 420 are provided to the deinterleavers 430 and 440, and the deinterleaved bits are provided to the bit collector 450 corresponding to the performance of the divider 350. If the bits are retransmitted, then the output of the bit collector 450 performs combining with the bits previously transmitted by the HARQ combiner 460. The previously transmitted bits are stored in the HARQ buffer 470, and if the packet transmission is successful, the stored information may be erased.

The combiner 460 combines the bit units with the same coded bits previously received by the combiner 460 and then outputs them to the channel decoder 480. That is, when retransmission using CC is performed, the combiner 460 performs bit-by-bit cambinding whenever coded bits are received. In the case of using the PIR, the information bits are combined at every transmission, and the remaining bits are combined with a predetermined period. On the other hand, in the case of using the FIR, as only transmission bits are transmitted during retransmission, combining is performed for a predetermined period on the received residual bits. The predetermined period is determined as a period in which the redundant version parameter used in the transmitter is repeatedly used. The output from the combiner 460 is input to the channel decoder 480, and decodes the encoded bits by a predetermined decoding method to output desired reception bits. In this case, the predetermined decoding method uses a method of decoding the information bits by inputting the information bits and the redundant bits, and is determined by the coding method of the transmitter.

The CRC checker 490 checks the CRC bits included in the encoded bits decoded and output from the channel decoder 480 to determine whether to retransmit, and transmits a NACK to the transmitter when retransmission is required due to an error. However, if the received bits are normally received without error, the ACK is transmitted to the transmitter as an acknowledgment signal and then the next data is received.

According to the above description, the present invention maps the encoded bits (information bits) of high importance to the highly reliable bit positions during retransmission as well as initial transmission, and transmits the encoded bits (remaining bits) of relatively low importance. Is mapped to a relatively low confidence bit position and transmitted. Therefore, in averaging the reliability between symbols during retransmission through the RA technique, the information bits are averaged only at the high reliability (H) position, and the redundant bits are averaged only at the relatively low reliability (L) position, thereby recalling the average reliability of the information bits. It is superior to the average reliability of surplus bits.

5 is a flowchart illustrating the operation principle of the proposed transmitter. After channel coding including CRC, HARQ parameter a and reliability averaging parameter b are determined according to initial transmission and retransmission.

In the case of initial transmission, a and b are initialized to perform an HARQ operation unit, an interleaving process, and a reliability averaging operation, and are finally modulated and output.

In case of retransmission, the HARQ parameter a is determined by considering the number of retransmissions and the maximum period (RVmax) of the HARQ parameter, and the reliability averaging parameter b is determined by considering the maximum period (RAmax) of the reliability averaging parameter. The subsequent process is the same as the initial transmission.

6 is a graph showing a difference in performance from the prior art when the bar proposed by the present invention is applied.

In FIG. 6, the performance comparison between the existing Chase combining technique, which is a retransmission technique, and the symbol mapping technique (SMP) and the reliability averaging technique (RA) according to the importance of the presently discussed, is compared by throughput. It became. At this time, each of the techniques can be performed in combination with the IR, but the bar shown in Figure 6 is basically a result of combining with the CC. Method 1 uses the SMP technique and the reliability average parameters b = 0 and 2, and method 2 uses the SMP technique and the reliability average parameters b = 0, 1, 2, and 3 sequentially, and Method 3 uses the SMP technique. The reliability average parameters b = 0, 1, 2, and 3 are all used sequentially, and Method 4 is the case in which only the existing CC technology, which neither SMP technology nor RA technology is applied, is applied. When only the RA technology is applied without the SMP technology of the method 3, the performance is superior to the conventional method, but the combination of the two technologies proposed in the present invention shows a large synergistic effect of about 1 dB. However, since the performance of Method 1 and Method 2 is similar or Method 1 is slightly superior, it is best to use only 0 and 2 reliability averaging parameters when SMP and RA technologies are combined. The reason is that the performance is slightly better, but the reliability averaging parameter must be informed to the receiver, the less information the better. In other words, two reliability averaging parameters are represented by two bits, and two types are represented by one bit.

As described above, the present invention provides a symbol mapping SMP technique that can obtain excellent transmission efficiency in the field of error-control-coding, modulation and demodulation, and data transmission by mapping bits of high importance to symbols of high reliability. Reliability averaging, an advanced retransmission technique, can be combined appropriately to produce a significant synergistic effect, where high-priority bits are modulated into high-reliability bits that are relatively less affected by noise or the environment, and larger by means of reliability averages between symbols during retransmission. A performance gain is obtained, which results in an improved overall system performance with lower packet error rate (FER) than conventional systems.                     

In addition, the present invention can be applied to all transmission and reception devices such as wired / wireless communication, and can be used for the current generation 3G wireless communication (IMT-2000) to improve overall system performance.

Claims (26)

In the method for splitting the coded bits to be transmitted in symbol units at the time of initial transmission and retransmission in a mobile communication system into two coded bit groups and symbol mapping the two coded bit groups corresponding to the number of times of the initial transmission and the retransmission, Mapping coded bits constituting one coded bit group among the two coded bit groups to a location having high reliability of the symbol; Inverting the coded bits constituting the other coded bit group among the two coded bit groups under different conditions corresponding to the number of retransmissions; And mapping the inverted coded bits to a location having a relatively low reliability compared to the high reliability of the symbol. The symbol mapping method of claim 1, wherein the coded bits constituting the coded bit group mapped to the position having high reliability are coded bits of relatively high importance. 3. The symbol of claim 2, wherein the coded bits constituting the coded bit group mapped to the location having the relatively low reliability are coded bits having a relatively low importance compared to the coded bits having the high importance. Mapping method. The process of claim 1, wherein the inverting under different conditions comprises: Inverting both encoded bits constituting the other encoded bit group in the first retransmission; Inverting only the second coded bit of the two coded bits constituting the other coded bit group during a second retransmission; And inverting only the first coded bit among two coded bits constituting the other coded bit group during a third retransmission. In the mobile communication system, the coded bits to be transmitted in symbol units during initial transmission and retransmission are divided into first and second coded bit groups, and the first and second coded bit groups are symbols corresponding to the initial transmission and retransmission times. In the mapping method, Inverting each of the first encoding bits constituting the first encoding bit group and the second encoding bits constituting the second encoding bit group under different conditions corresponding to the number of retransmissions; Mapping the inverted first encoding bits to a location having a high reliability of the symbol; And mapping the inverted second encoding bits to a location having a relatively low reliability compared to the high reliability of the symbol. 6. The symbol mapping method of claim 5, wherein the first encoding bits are encoding bits having a relatively high importance. 7. The symbol mapping method of claim 6, wherein the second coded bits are coded bits having a relatively low level of importance compared to the coded bits having a high level of importance. The method of claim 5, wherein the step of inverting under different conditions, Inverting both the first encoding bits and the second encoding bits in a first retransmission; Inverting both of the first coded bits constituting the first coded bit group at the second retransmission, and inverting only the second coded bit of the two second coded bits constituting the second coded bit group Process, Inverting both of the first coded bits constituting the first coded bit group at the third retransmission, and inverting only the first coded bit of the two second coded bits constituting the second coded bit group Symbol mapping method comprising the step of. In the mobile communication system, the encoded bits to be transmitted on a symbol basis in initial transmission and retransmission are divided into first and second encoded bit groups, and each of the first and second encoded bit groups is interleaved through different interleavers. In the apparatus for symbol mapping corresponding to the number of initial transmission and the retransmission, An inverter for inverting the coded bits constituting the second coded bit group under different conditions corresponding to the number of retransmissions; And a modulation unit for mapping the coded bits constituting the first coded bit group to a location having a high reliability of the symbol and mapping the inverted coded bits to a location having a relatively low reliability compared to the high reliability. Symbol mapping device characterized in that. 10. The symbol mapping apparatus of claim 9, wherein the coded bits constituting the first coded bit group mapped to the position having high reliability are coded bits of relatively high importance. 12. The method of claim 10, wherein the encoding bits constituting the second coded bit group mapped to the position having a relatively low reliability are encoded bits having a relatively low importance compared to the encoding bits having a high importance. Symbol mapping device. The method of claim 9, wherein the inverter, Inverting two coded bits constituting the other coded bit group at the first retransmission, and second coded bits of the two coded bits constituting the other coded bit group at the second retransmission. And inverting only and inverting only the first coded bit among two coded bits constituting the other coded bit group during a third retransmission. In the mobile communication system, the encoded bits to be transmitted on a symbol basis in initial transmission and retransmission are divided into first and second encoded bit groups, and each of the first and second encoded bit groups is interleaved through different interleavers. In the apparatus for symbol mapping corresponding to the number of initial transmission and the retransmission, An inverter for inverting each of the first and second coded bits constituting the first and second coded bit groups under different conditions corresponding to the number of retransmissions; And a modulator for mapping the inverted first encoding bits to a position having a high reliability of the symbol, and mapping the inverted second encoding bits to a position having a relatively low reliability compared to the high reliability. Symbol mapping device characterized in that. The symbol mapping apparatus of claim 13, wherein the first encoding bits mapped to the position having the high reliability are encoded bits of relatively high importance. The symbol mapping apparatus of claim 14, wherein the second encoding bits mapped to the relatively low reliability positions are encoding bits having a relatively low importance compared to the encoding bits having a high importance. The method of claim 13, wherein the inverter, Inverting both of the first encoding bits and the second encoding bits in the first retransmission, inverting both of the first encoding bits constituting the first encoding bit group in the second retransmission; Inverting only the second coded bit of the two second coded bits constituting the second coded bit group, and inverting both of the first coded bits constituting the first coded bit group at the third retransmission. And inverting only the first coded bit among two second coded bits constituting the second coded bit group. In the mobile communication system, the encoded bits to be transmitted in symbol units during initial transmission and retransmission are divided into two encoded bit groups, and the encoded bits of each of the two encoded bit groups are mapped and transmitted at positions having different reliability. In the method for receiving data corresponding to the initial transmission and the retransmission number of times, Demodulating the data and outputting first encoding bits mapped to the position having the high reliability and second encoding bits mapped to the position having a relatively low reliability compared to the high reliability; Inverting the first encoding bits and the second encoding bits under different conditions corresponding to the number of retransmissions; And interleaving each of the inverted first encoding bits and the inverted second encoding bits and combining them with previously received encoding bits. 18. The method of claim 17, wherein the first encoding bits are encoding bits of relatively high importance. 19. The method of claim 18, wherein the second encoding bits are encoded bits having a relatively low importance compared to the first encoding bits of high importance. The method of claim 17, wherein the inverting under different conditions comprises: Inverting all of the second encoding bits consisting of two bits during the first retransmission; Inverting only the second encoded bit of the second encoded bits consisting of two bits upon a second retransmission; And inverting only the first coded bit among the second coded bits consisting of two bits upon a third retransmission. The method of claim 17, wherein the inverting under different conditions comprises: Inverting both the first encoding bits and the second encoding bits in a first retransmission; Inverting all of the first encoded bits consisting of two bits and inverting only the second encoded bit of the second encoded bits consisting of two bits during a second retransmission; And inverting all of the first encoded bits consisting of two bits and inverting only the first encoded bit of the second encoded bits consisting of two bits during a third retransmission. In the mobile communication system, the encoded bits to be transmitted in symbol units during initial transmission and retransmission are divided into two encoded bit groups, and the encoded bits of each of the two encoded bit groups are mapped and transmitted at positions having different reliability. An apparatus for receiving data corresponding to the initial transmission and the retransmission number of times, A demodulator for demodulating the data and outputting first encoding bits mapped to the position having the high reliability and second encoding bits mapped to the position having a relatively low reliability compared to the high reliability; An inverter for inverting the first encoding bits and the second encoding bits under different conditions corresponding to the number of retransmissions; And a combiner which interleaves each of the inverted first encoding bits and the inverted second encoding bits and combines the previously received encoding bits. 23. The apparatus of claim 22, wherein the first encoding bits are encoding bits of relatively high importance. 24. The apparatus of claim 23, wherein the second encoding bits are encoding bits having a relatively low importance level compared to the first encoding bits of high importance. The method of claim 22, wherein the inverter, Inverting all of the second encoding bits consisting of two bits in the first retransmission, inverting only the second encoding bit of the second encoding bits consisting of two bits in the second retransmission, and two bits in the third retransmission. And inverting only the first coded bit among the second coded bits. The method of claim 22, wherein the inverter, Inverting both the first encoding bits and the second encoding bits in the first retransmission, inverting all of the first encoding bits consisting of two bits in the second retransmission, and the second encoding bit consisting of two bits. Inverting only the second coded bit among the second coded bits, and inverting all of the first coded bits consisting of two bits in the third retransmission, and inverting only the first coded bit of the second coded bits consisting of two bits. A data receiving device.

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