KR101287272B1

KR101287272B1 - data transmission method and hybrid automatic repeat request method using adaptive mapper

Info

Publication number: KR101287272B1
Application number: KR1020060106557A
Authority: KR
Inventors: 박형호; 임빈철; 오민석; 최진수; 정재훈; 조기형; 강승현
Original assignee: 엘지전자 주식회사
Priority date: 2006-08-07
Filing date: 2006-10-31
Publication date: 2013-07-17
Also published as: KR101253175B1; KR20080013682A; EP2057772A1; KR20080013661A; KR20080013662A; EP2057772A4; KR101299911B1; WO2008018742A1

Abstract

The data transmission method performs bit-by-bit remapping on the signal constellation to form a plurality of data symbols. The plurality of data symbols are modulated and transmitted. Remapping of signal constellations allows for additional diversity gain while gaining spatio-temporal diversity gain on the channel without additional complexity. This is easy to apply without changing the receiver structure according to the prior art.

Mapper, diversity, MIMO, HARQ, composite automatic retransmission,

Description

Data transmission method and hybrid automatic repeat request method using adaptive mapper}

1 is a block diagram illustrating a communication system according to an embodiment of the present invention.

2 is an exemplary diagram illustrating an example of adaptive mapping.

3 is an exemplary diagram illustrating another example of adaptive mapping.

4 is a gray mapped signal constellation in 16-QAM modulation.

5 is an exemplary diagram illustrating a distance between symbols in the signal constellation of FIG. 4.

6 is an exemplary diagram illustrating an example of adaptive mapping for STBC.

7 is an exemplary diagram illustrating another example of adaptive mapping for STBC.

8 is a block diagram illustrating a transmitter according to another embodiment of the present invention.

9 is a block diagram illustrating a transmitter according to another embodiment of the present invention.

10 is a block diagram showing a transmitter according to another embodiment of the present invention.

11 is a block diagram illustrating a communication system according to another embodiment of the present invention.

12 is a flowchart illustrating a composite automatic retransmission method using the communication system of FIG. 11.

FIG. 13 is an exemplary diagram illustrating an arrangement of retransmission symbols according to an embodiment of the present invention. FIG.

14 is an exemplary diagram illustrating an arrangement of retransmission symbols according to another embodiment of the present invention.

15 is an exemplary diagram illustrating an arrangement of retransmission symbols according to another embodiment of the present invention.

16 is a diagram illustrating the arrangement of retransmission symbols according to another embodiment of the present invention.

17 is an exemplary diagram illustrating an arrangement of retransmission symbols according to another embodiment of the present invention.

18 is an exemplary view showing a composite automatic retransmission method according to another embodiment of the present invention.

19 is a graph showing SNR versus BER of simulation results of the conventional method and the hybrid automatic retransmission method according to the present invention.

20 is a graph showing SNR vs. FER of simulation results of the conventional method and the hybrid automatic retransmission method according to the present invention.

21 is a graph showing SNR versus BER of the simulation result of the conventional method and the hybrid automatic retransmission method according to the present invention.

22 is a graph showing SNR versus FER of simulation results of the conventional hybrid retransmission method according to the related art.

23 is a block diagram showing a transmitter according to another embodiment of the present invention.

24 is an exemplary diagram illustrating a retransmission symbol using the transmitter of FIG. 23.

25 is a block diagram showing a transmitter according to another embodiment of the present invention.

26 is an exemplary view showing a transmitter and a retransmission symbol according to another embodiment of the present invention.

DESCRIPTION OF REFERENCE NUMERALS OF THE MAIN PARTS OF THE DRAWINGS

100: transmitter

200: receiver

120: adaptive mapper

130: spatial encoder

The present invention relates to wireless communication, and more particularly, to a data transmission method using an adaptive mapper and a complex automatic retransmission method.

The demand for communication services such as the universalization of information communication services, the appearance of various multimedia services, and the emergence of high quality services are rapidly increasing. Various wireless communication technologies are being investigated in various fields to satisfy this demand.

Diversity techniques for transmitting the same data repeatedly have been developed to secure communication reliability. If multiple signals are transmitted independently of each other via diversity, even if signals of some paths are received low, signals of the other paths may have large values. Therefore, the diversity technique is to achieve stable transmission and reception by combining a plurality of signals. Types of diversity include frequency diversity for transmitting signals at different frequencies, time diversity for transmitting signals at different points of time, and spatial diversity using a plurality of transmission antennas. diversity).

Since the spatial diversity scheme using multiple antennas is designed under the assumption that the channel does not change during transmission, inter-symbol interference may occur due to a channel change in fast fading in which the channel changes rapidly. In addition, various space-time codes are being designed to obtain spatial diversity gain, but a maximum likelihood (ML) receiver based on maximum likelihood is required to obtain optimal performance. The ML receiver is not easy to implement in a real communication system because the complexity increases exponentially as the number of transmit antennas and modulation index increases. In addition, since a typical MMSE receiver of space-time codes is decoded through a cumulative combining technique, channel information between time slots must be stored in a buffer. In a multi-carrier system such as an Orthogonal Frequency Division Multiplexing (OFDM) system, it is difficult to store channel response values in a frequency domain in a buffer of a receiver for a predetermined time slot or more. In addition, in space-time coding in symbol units, optimal performance is required when channel decoupling is performed, and performance may be degraded in time varying channels due to the influence of Doppler frequency.

There is a need for a way to increase the additional diversity gain.

An object of the present invention is to provide a data transmission method for remapping between symbols.

Another object of the present invention is to provide a hybrid automatic retransmission method for remapping a symbol to be retransmitted.

A data transmission method according to an aspect of the present invention forms a plurality of data symbols by performing bit-by-bit remapping on a signal constellation. The plurality of data symbols are modulated and transmitted.

A composite automatic retransmission method according to another aspect of the present invention transmits a transmission symbol and receives a retransmission request signal for the transmission symbol. The retransmission symbol obtained by remapping the transmission symbol is transmitted according to the retransmission request signal.

According to another aspect of the invention there is provided a transmitter. The transmitter includes an antenna, an adaptive mapper for performing bit-by-bit rearrangement of signal constellations among a plurality of data symbols, and a modulator for modulating the rearranged data symbols to form transmission symbols for transmission through the antenna.

According to another aspect of the present invention, a transmitter includes an antenna, a controller that receives a retransmission request signal through the antenna, and maps input data into a data symbol indicating a position on a signal constellation, wherein the retransmission is performed according to the retransmission request signal. An adaptive mapper for remapping data symbols and a modulator for modulating the remapped data symbols to form transmission symbols for transmission over the antenna.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals designate like elements throughout the specification.

The following techniques can be used in various communication systems. Communication systems are widely deployed to provide various communication services such as voice, packet data, and the like. This technique can be used for a downlink or an uplink. The downlink means communication from a base station (BS) to a user equipment (UE), and the uplink means communication from a terminal to a base station. A base station generally refers to a fixed station that communicates with a terminal and may be referred to by other terms such as a node-B, a base transceiver system (BTS), an access point, and the like. A terminal may be fixed or mobile and may be referred to by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device,

Referring to FIG. 1, a communication system includes a transmitter 10 and a receiver 20. In downlink, the transmitter 10 may be part of a base station, and the receiver 20 may be part of a terminal. In uplink, the transmitter 10 may be part of a terminal, and the receiver 20 may be part of a base station. The base station may include a plurality of receivers and a plurality of transmitters. A terminal may include multiple receivers and multiple transmitters.

The transmitter 10 includes a channel encoder 11, an adaptive mapper 12, and a spatial encoder 15. In addition, the transmitter 10 includes Nt (Nt ≧ 1) transmit antennas 19-1,..., 19-Nt.

The channel encoder 11 receives a series of streams of information bits and encodes the encoded data according to a predetermined coding scheme to form coded data. The information bits may include text, audio, video or other data. Symbols composed of encoded data are referred to as encoded symbols hereinafter.

Adaptive mapper 12 maps the coded symbols to data symbols representing locations on the signal constellation. The data symbol refers to the output of the adaptive mapper 12 and may be represented by a set of bit sequences representing a complex value on a signal constellation according to a modulation scheme. If there is no restriction on the modulation scheme performed in the adaptive mapper 12, it may be m-Phase Shift Keying (m-PSK) or m-Quadrature Amplitude Modulation (m-QAM). For example, m-PSK may be BPSK, QPSK, or 8-PSK. The m-QAM may be 16-QAM, 64-QAM, or 256-QAM. The operation of the adaptive mapper 12 will be described later with regard to a data transmission method.

The spatial encoder 15 allocates data symbols output through the adaptive mapper 12 for each transmit antenna 19-1,..., 19 -Nt. Spatial encoder 15 may convert serial data symbols into parallel data according to transmit antennas 19-1,..., 19-Nt. The spatial encoder 15 may process data symbols according to the space-time code scheme and allocate the data symbols to transmit antennas 19-1, ..., 19-Nt.

The modulators 16-1, ..., 16-Nt modulate parallel data according to a multiple access modulation scheme to form transmission symbols. One packet may include one or multiple transmission symbols. The transmit symbol is transmitted through each transmit antenna 19-1, ..., 190-Nt. There is no restriction on the multiple access modulation scheme, and a single-carrier modulation scheme such as Code Division Multiple Access (CDMA) or a multi-carrier modulation scheme such as Orthogonal Frequency Division Multiplexing (OFDM) may be adopted.

In the OFDM scheme, the modulators 16-1,..., 16-Nt may perform an inverse fast fourier transform (IFFT). In this case, one data symbol may be loaded on one subcarrier, and a transmission symbol transmitted through a plurality of carriers may be composed of a plurality of data symbols. In the OFDM scheme, a transmission symbol may be referred to as an OFDM symbol.

Meanwhile, the receiver 20 includes a spatial decoder 22, a demapper 23, and a channel decoder 24. The receiver 20 also includes Nr (Nr ≧ 1) receive antennas 29-1, ..., 29-Nr.

The signals received from the receiving antennas 29-1, ..., 29-Nr are demodulated by the demodulators 21-1, ..., 21-Nr and input to the spatial decoder 22. The data symbols output from the spatial decoder 22 are input to the demapper 23 and demapped into encoded data. The channel decoder 24 decodes the coded data according to a predetermined decoding scheme to restore the original data.

A data transmission method according to an embodiment of the present invention will now be described using the communication system of FIG.

Hereinafter, s _m ⁿ denotes a data symbol transmitted through an n th timeslot of an m th transmit antenna. {Bi b _{i + 1} b _{i + 2} b _{i + 3} } represents a bit sequence of i to i + 3 constituting a corresponding data symbol. However, this is only an example, and the data symbol may include a bit sequence representing a complex value on the signal constellation, and the number of bits representing the data symbol may be 4 bits or more or 4 bits or less.

2 is an exemplary diagram illustrating an example of adaptive mapping. The number of transmit antennas is 2 (Nt = 2), which is represented for two timeslots.

2, the right part represents a mapping according to the prior art, and the left part represents a mapping according to an embodiment of the present invention. s ₁ ¹ is the data symbol transmitted through the first timeslot of the first transmit antenna, s ₁ ² is the data symbol transmitted through the second timeslot of the first transmit antenna, and s ₂ ¹ is the second transmit antenna. S ₂ ² is the data symbol transmitted through the second timeslot of the second transmit antenna. s ₁ ¹ is configured to exchange the bit b ₁₄ to the bit b ₂ s ₂ ^2, and the bit b ₄ to the bit b ₈ s ₂ and the exchange of ^FIG. s ₁ ² is configured by exchanging bit b ₁₀ with bit b ₆ of s ₂ ¹ and bit b ₁₂ with bit b ₁₆ of s ₂ ² . s ₂ ¹ is configured by exchanging bit b ₆ with bit b ₁₀ of s ₁ ² and bit b ₈ with bit b ₄ of s ₁ ¹ . ₂ s ² is configured by replacing the bit b ₁₄ to the bit b ₂ a ₁ s ^1, and the bit b ₁₂ and the replacement of the bit b ₁₆ s ₁ ^2. That is, the adaptive mapper 12 remaps the bits representing the signal constellation between different data symbols. Here, remapping means that exchange and / or substitution between bits is performed between data symbols, and does not necessarily mean that data symbols are mapped and newly mapped between them. The exchange and replacement of bits constituting a symbol through signal property rearrangement methods can design an optimal mapping method according to the number of antennas, modulation index, timeslot, and channel conditions.

Although the number of bits exchanged in space and time is illustrated as two per data symbol, this is not a limitation and the number of bits exchanged is not limited. One bit can be exchanged with each other, and three or more bits can be exchanged with each other. The exchange method is not limited to the illustrated example and may vary depending on the signal constellation.

The number of data symbols sent during two timeslots through two transmit antennas is four, and adaptive mapper 12 rearranges the bits constituting these data symbols temporally and / or spatially. Rearrangement refers to the exchange and / or substitution of bits or bits, and may include omission and / or addition of bits or bits. Spatially rearranging refers to rearranging data symbols for each transmit antenna and may be, for example, rearrangement between s ₁ ¹ and s ₂ ¹ . Rearranging in time refers to rearranging data symbols for each timeslot, and may be, for example, rearrangement between s ₁ ¹ and s ₁ ² .

Data symbols can be rearranged in time and space in every time slot. Or rearrangement may be made only once.

There is no restriction on the criteria for determining the rearrangement scheme, and may be different for each transmission. The rearrangement of bits constituting the data symbol may vary depending on the number of antennas, modulation index, timeslot, and channel conditions. Or, it can be rearranged in a fixed manner irrespective of the channel situation.

The criterion for remapping can be set in the open-loop manner and sent to the receiver. Alternatively, the reference may be set at the receiver side in a closed loop manner and returned to the transmitter side.

When the data symbols are rearranged in time and space, the signal constellation positions of the data symbols are changed, and thus, the mapping of the signal constellations may be different. That is, in the present invention, diversity is implemented by differently mapping data symbols in time and space for each transmission. This is called mapping diversity.

In the present invention, the diversity gain is obtained by improving the channel reliability of the bits constituting the data symbols for the channel on average. That is, mapping diversity according to channel change can be secured by performing bit-by-bit mapping on a signal property in consideration of space-time multiplexing for each transmission.

3 is an exemplary diagram illustrating another example of adaptive mapping.

Referring to FIG. 3, the right part represents a mapping according to the prior art, and the left part represents a mapping according to another embodiment of the present invention.

Represents a substitute by complement. s _1, ¹ is substituted into the bit b ₂ s ₂ ² of the bit b ₁₄ and the replacement and the maintenance, and the bit b ₄ to the bit b ₈ s ₂ and the exchange and configured by replacing the ^first. s ₁ ² consists of exchanging and replacing bit b ₁₀ with bit b ₆ of s ₂ ¹ , and replacing and replacing bit b ₁₂ with bit b ₁₆ of s ₂ ² . s ₂ ¹ is configured by exchanging and replacing bit b ₆ with bit b ₁₀ of s ₁ ² , and replacing and replacing bit b ₈ with bit b ₄ of s ₁ ¹ . s ₂ ² consists of exchanging and replacing bit b ₁₄ with bit b ₂ of s ₁ ¹ , and replacing and replacing bit b ₁₆ with bit b ₁₂ of s ₁ ² . Here, a substitution is performed for bits exchanged with each other in space and time. However, this is not a limitation and may be substituted for other bits that are not exchanged.

4 is a gray mapped signal constellation in 16-QAM modulation.

Referring to FIG. 4, the signal constellation is composed of two partition sets. That is, the bit values in one position are the same, and the bit values in the remaining positions can be divided into two different partitions. In order from the left, the first partition is divided into two partitions having only the first bit, two partitions having only the second bit, two partitions having only the third bit, and two partitions having only the fourth bit. The set of partitions is different for each bit position because they have different distances between symbols.

Referring to FIG. 5, the distance between each symbol is different according to the difference between the first bit and the second bit, and the interval between symbols is constant when the third bit and the fourth bit are different. The difference between the symbols means that the probability of a bit error at each bit position is different. An additional diversity gain can be obtained by rearranging and transmitting symbols in consideration of the spatial diversity gain caused by multiple transmit antennas and the time diversity gain caused by time delay. That is, the channel reliability of each bit of the data symbol is improved overall.

Hereinafter, a data transmission method using a space-time code method will be described.

Orthogonal Space-Time Block Code (STBC) may be used as the space-time code method. As is well known, Alamouti's STBC in a communication system with two transmit antennas is shown in Table 1 below.

First antenna Second antenna First transfer s ₁ s ₂ Second transmission -s ₂ ^* s ₁ ^*

Here, s ₁ ^* and s ₂ ^* are complex conjugates of s ₁ and s ₂ , respectively. Using Alamouti code can greatly reduce the complexity of the receiver.

6 is an exemplary diagram illustrating an example of adaptive mapping for STBC.

Referring to FIG. 6, the right part represents a mapping according to the prior art, and the left part represents a mapping according to an embodiment of the present invention. s ₁ is the bit b ₂ to the exchange and s ₂ for bit b _5, the bit b ₃ to the bit b ₆ to the exchange of the s _2, is configured to change the position of each of four bits. s ₂ is configured by swapping positions of four bits after exchanging with bits of s ₁ . That is, even in STBC, diversity gain can be given by varying the mapping of signal constellations to data symbols to be transmitted.

Referring to FIG. 7, the right part represents a mapping according to the prior art, and the left part represents a mapping according to an embodiment of the present invention. s is _1, and the bit b ₂ s ₂ bits b ₅ and the exchange and the substitution of, the bit b ₃ s and the _second bit b ₆ to the exchange and the substitution of, consists of replacing one another the positions of the four bits. s ₂ is configured by swapping positions of four bits after swapping and replacing with bits of s ₁ .

Although the STBC system having two antennas has been described herein, the technical idea of the present invention can be applied to a system having three or more antennas as it is. In addition, not only STBC but also the space-time trellis code may be applied without departing from the spirit of the present invention.

In the above description, a case in which one data symbol is transmitted through one time slot is described. However, a plurality of data symbols may be transmitted in one time slot. When one data symbol is transmitted through one timeslot, one data symbol is modulated into one transmission symbol. In a system using multiple subcarriers, since one data symbol is carried on one subcarrier, a plurality of data symbols may be modulated into one transmission symbol and thus, the transmission symbol may be composed of a plurality of data symbols. In this case, the data symbols may not only be rearranged in time and space, but may also be rearranged among a plurality of data symbols transmitted through one time slot. In addition, the data may be rearranged among a plurality of data symbols forming one packet. Accordingly, the present invention includes a case of remapping between at least two different data symbols by subcarriers, by time, and by space.

Hereinafter, a data transmission method using a cyclic delay diversity scheme will be described.

Referring to FIG. 8, the transmitter 50 selects the channel encoder 51, the adaptive mapper 52, the spatial encoder 55, and the delays 57-1, ..., 57- (Nt-1). Include. The transmitter 50 uses IFFT units 56-1, ..., 56-Nt as modulators in the OFDM scheme. Transmitter 50 using cyclic delay diversity repeatedly transmits a symbol through a plurality of transmit antennas 59-1, ..., 59-Nt, but repeats repeated symbols with the same or different power, but with different cyclic delays. Send in the form of. In this cyclic delay diversity, a signal from a plurality of transmit antennas is the same as a case of entering a receiver through multiple paths, so that the complexity of detecting a signal at the receiver can be considerably reduced.

The information bits pass through channel encoder 51 and adaptive mapper 52 to become data symbols. The data symbols are converted into transmission symbols by performing IFFT by the IFFT units 56-1, ..., 56-Nt via the spatial encoder 55. CP is inserted into the transmission symbol by the cyclic prefix insertion unit 58-1, ..., 58-Nt and transmitted by the transmission antenna 59-1, ..., 59-Nt. Delays 57-1, ..., 57- (Nt-) between the IFFT sections 56-1, ..., 56-Nt and the CP insertion sections 58-1, ..., 58-Nt. 1)) is arranged to cyclically delay the symbol.

The difference between the transmitter 50 and the transmitter 10 of FIG. 1 is that the delay units 57-1, ..., 57- (Nt-1) which cyclically delay the time domain samples included in the transmission symbol are provided. It is added. The delay times Δ ₁ ,..., Δ _Nt-1 , which are delayed by the delays 57-1, ..., 57- (Nt-1), may have a constant value, or depending on the user. It can have a different value. The delay time Δ ₁ ,..., Δ _Nt-1 may be adjusted by receiving feedback from the receiver.

A plurality of data symbols may be modulated in the transmission symbol. The adaptive mapper 42 rearranges the data symbols by temporal, spatial and subcarriers to obtain diversity gain. The rearranged data symbols are modulated into transmission symbols, which in turn are cyclically delayed to obtain multiple diversity gains.

9 is a block diagram illustrating a transmitter according to another embodiment of the present invention. The transmitter 60 moves the retarder to the frequency domain in the transmitter 50 of FIG.

9, phase delays 67-1, ..., 67- (Nt-1) are provided between the spatial encoder 65 and the IFFT units 68-1, ..., 68-Nt. Arranged to cyclically delay the phase of the symbols. In the frequency domain, the phase retarders 67-1, ..., 67- (Nt-1) are delayers 57-1, ..., 57 in the time domain included in the transmitter 50 of FIG. Equivalent to-(Nt-1)). The time delay in the time domain and the phase delay in the frequency domain are due to the duality.

The communication system according to the technical idea of the present invention can be applied to a system having one transmission antenna as well as a plurality of transmission antennas. That is, the communication system according to the present invention is not only a multiple-input multiple-output (MIMO) system or a multiple-input single-output (MISO) system, but also a single-input single-input. It may be a single-output (SISO) system or a single-input multiple-output (SIMO) system. A MIMO system uses multiple transmit antennas and multiple receive antennas. The MISO system uses multiple transmit antennas and one receive antenna. The SISO system uses one transmit antenna and one receive antenna. The SIMO system uses one transmit antenna and multiple receive antennas.

Referring to FIG. 10, the transmitter 70 includes a channel encoder 71, an adaptive mapper 72, and a modulator 73. In addition, the transmitter 70 includes one antenna 79.

The adaptive mapper 72 may increase the diversity gain by remapping data symbols s ₁ transmitted in the first timeslot T1 and data symbols s ₂ transmitted in the second timeslot T2. That is, data symbols can be remapped in time.

In another embodiment, one timeslot may include a plurality of data symbols. For example, in the case of a packet transmission scheme, one packet may include a plurality of data symbols. In this case, data symbols included in one timeslot may be remapped.

The adaptive mapper considering space-time multiplexing remaps the bits constituting the data symbols output from the mapper stage through exchange and / or substitution according to a mapping method, channel environment, number of transmit antennas, and timeslots. By transmitting the remapped data symbols, an additional diversity gain can be obtained in addition to the time and spatial diversity gain for the existing channel. The receiver may perform final decoding by exchanging only positions of soft decision bits coming from the demapper stage by using a mapping method in transmission.

The adaptive mapper can obtain the additional diversity gain while gaining the space-time diversity gain on the channel without any additional complexity. In addition, it is easy to apply without changing the receiver structure according to the prior art, such as a linear receiver (MMSE or zero-forcing (ZF)). In addition, an additional diversity gain may be obtained even in a channel environment in which space-time code technology and cyclic delay diversity technology may show performance degradation.

Hereinafter, a hybrid automatic retransmission method according to an embodiment of the present invention will be described.

A system employing spatial diversity is generally referred to as a MIMO system because it includes a plurality of transmit and receive antennas. Types of space diversity include space-time transmit diversity (STTD) and vertical-bell laboratories layered space-time (V-BLAST). The STTD scheme transmits the same data through respective transmit antennas. The V-BLAST scheme transmits different data through respective transmit antennas. Examples of spatial diversity include S. M. Alamouti, A Simple Transmit Diversity Technique for Wireless Communications, IEEE J. Selec. Areas Commun., Vol. 16, pp. 1451-1458, Oct. See 1998.

Meanwhile, another repetitive transmission scheme is an automatic repeat request (ARQ) scheme. The ARQ method retransmits data when an error occurs in the transmitted data. ARQ methods include stop and wait (SAW), go-back-N (GBN), and selective repeat (SR). The ARQ method has a time delay and a poor system efficiency in a poor channel environment. To solve these shortcomings, a hybrid automatic repeat request (HARQ) method combining forward error correction (FEC) and ARQ is proposed. HARQ improves performance by requiring retransmission when the received data contains errors that cannot be decoded.

In general, HARQ can be classified into Type I, Type II, and Type III. Type I discards the data from which an error was detected and requires retransmission of new data. Type II combines retransmitted data with previous data without discarding the data from which an error was detected. The retransmitted data and the previous data may have different code rates or modulation schemes. Type III differs from Type II in that the retransmitted data is a self-decodable code. That is, the retransmitted data can be decoded without combining with previous data.

Alternatively, HARQ may be classified into chase combining and incremental redundancy (IR). Chase combining is a modified method of Type I, which combines the retransmitted data without discarding the data where the error is detected. IR refers to the Type II or Type III scheme. The difference between chase combining and IR is that chase combining retransmits the same data, whereas IR incrementally transmits additional redundant information. Distinguishing between Type II and Type III, Type II is also known as full IR and Type III is partial IR.

For examples of HARQ, see S. Lin, D.J. Costello, M.J. Miller, Automatic repeat request error control schemes, IEEE Communications Magazine, Vol. 22, no. 12, pp. 5-17, Dec. 1984 and D. Chase, Code Combining: A maximum-likelihood decoding approach for combining an arbitrary number of noisy packets, IEEE Trans. on Commun., Vol. 33, pp. 593-607, May 1985.

Referring to FIG. 11, a communication system includes a transmitter 100 and a receiver 200. The communication system implements HARQ. Here, the transmitter 100 and the receiver 200 may be referred to as a transceiver that performs both a transmission function and a reception function. However, in order to clarify the description of data retransmission, hereinafter, one in charge of data transmission and retransmission is referred to as a transmitter, and the other in receiving data and requesting retransmission is referred to as a receiver.

The transmitter 100 includes a channel encoder 110, an adaptive mapper 120, a spatial encoder 130, a controller 150, and a receive circuitry 180. In addition, the transmitter 100 includes Nt (Nt ≧ 1) transmit antennas 190-1,..., 190-Nt.

The channel encoder 110 receives a series of information bits and encodes the encoded data according to a predetermined coding scheme. The adaptive mapper 120 modulates the encoded data according to a predetermined modulation scheme to provide data symbols. The adaptive mapper 120 maps the encoded data into data symbols representing positions on the signal constellation. In addition, the adaptive mapper 120 adaptively remaps the encoded data according to the retransmission request signal of the controller 150. The HARQ method associated with the adaptive mapper 120 will be described later.

The spatial encoder 130 processes data symbols output through the adaptive mapper 120 according to a space-time code coding scheme. The modulators 140-1, ..., 140-Nt modulate the symbols output from the spatial encoder 130 and transmit them through the antennas 190-1, ..., 190-Nt. A set of symbols transmitted in one period (or one time slot) as an output of the modulators 140-1, ..., 140-Nt is called a transmission symbol. The receiving circuit 180 receives the signal transmitted from the receiver 200 through the antennas 190-1,..., 190 -Nt. The receiving circuit 180 digitizes the received signal and sends the received signal to the controller 150.

The controller 150 controls the overall operation of the transmitter 100. The controller 150 extracts information from the signal received from the receiving circuit 180. Extracting information includes general demodulation and decoding. The extracted information may include a retransmission request signal. The controller 150 controls the adaptive mapper 120 according to the retransmission request signal to prepare a retransmission symbol.

Information extracted from the signal received from the receiving circuit 180 may include channel quality information (CQI). The CQI may be information about a channel environment from the receiver 200 to the transmitter 100 or index information on a modulation and coding scheme. Through the CQI, the controller 150 may control the channel encoder 110 or the adaptive mapper 120 to adaptively change the coding scheme of the channel encoder 110 or the mapping scheme of the adaptive mapper 120.

The receiver 200 includes a spatial decoder 220, a demapper 230, a channel decoder 250, an error detector 260, a controller 270, and a transmit circuitry 280. In addition, the receiver 200 includes Nr antennas (Nr≥1) of antennas 290-1, ..., 290-Nr.

The signals received from the antennas 290-1,..., 290 -Nr are demodulated by the demodulators 210-1,..., 210 -Nr and input to the spatial decoder 220. The spatial decoder 220 recovers the symbols according to the decoding control signal provided from the controller 270. The decoding control signal controls decoding based on the space-time coded coding scheme of the receiver 100. The decoding control signal may be preset in a memory (not shown) of the controller 270. Alternatively, the decoding control signal may be received from the transmitter 100.

The demapper 230 demaps the data symbols back from the data symbols into encoded data according to the demapping control signal provided from the controller 270. The demapping control signal controls the demapper 230 based on the mapping scheme in the adaptive mapper 120 of the transmitter 100. The demapping control signal may be preset in the memory of the controller 270. Alternatively, the demapping control signal may be received from the transmitter 100.

The receiver 200 may include a combiner 240 for combining the retransmitted symbol with the previous symbol. That is, in the case of chase combining or IR HARQ, the combiner 240 combines previous symbols with retransmitted symbols. The combining method may use an equal-gain combining method in which weights of the previous data and the retransmitted data are equal to each other and combined through an average value. Alternatively, an MRC (maximum ratio combining) method may be used to weight each data. There is no limit to the coupling method, and various other methods can be used.

However, the present invention is not limited to the chase combining or the IR method, and can be applied to the Type I method which performs channel decoding only through retransmitted symbols without combining with the previous symbol. In this case, the coupling unit 240 may be excluded from the receiver 200.

The channel decoder 250 decodes the encoded data according to a predetermined decoding scheme. The error detector 260 detects whether there is an error in the decoded data bit through a CRC check.

The controller 270 controls the overall operation of the receiver 200 and provides a retransmission request signal or the like to the transmitting circuit 280. To this end, the controller 270 may perform general channel encoding, modulation, and the like. The controller 270 receives an error from the error detector 260 and determines whether to request retransmission. The controller 270 may generate a positive acknowledgment (ACK) signal if no error is detected and a negative acknowledgment (NACK) signal if an error is detected. The NACK signal may be a retransmission request signal.

In addition, the controller 270 may provide a CQI signal by measuring channel quality from the received signal. This becomes a feedback signal to the transmitter 100 regarding channel quality, such as signal-to-noise ratio (SNR) or error rate. In order to measure channel quality, a transmission symbol transmitted by the transmitter 100 may further include a pilot symbol. The transmitting circuit 280 receives a retransmission request signal from the controller 270 and transmits the same through the antennas 290-1,..., 290 -Nr.

Hereinafter, a hybrid automatic retransmission method according to an embodiment of the present invention will be described using the communication system of FIG. 11.

Assume that there are four transmit antennas (Nt = 4), and s _m ⁿ represents the nth retransmitted data symbol through the mth transmit antenna. And {i _i i _{i + 1} q _{i + 2} q _{i + 3} } represents a bit sequence from i to i + 3 constituting a corresponding data symbol. Here, i and q represent bits constituting the data symbol, and the order and contents thereof are not limited. The data symbol is composed of a bit sequence representing a complex value on the signal constellation, and the number of bits representing the data symbol may be 4 bits or more or 4 bits or less. The data symbols are modulated into transmission symbols and transmitted through modulators 140-1, ..., 140-Nt. For clarity, it is assumed that one transmission symbol is modulated from one data symbol, but the transmission symbol may be made in a group unit of data symbols.

Referring to FIG. 12, the transmitter 100 transmits data symbols s ₁ , s ₂ , s ₃ , and s ₄ (S110). Data symbol s ₁ is transmitted through the first antenna 190-1, symbol data s ₂ ¹ is transmitted through the second antenna 190-2, and data symbol s is transmitted through the third antenna 190-3. ₃ is transmitted and the data symbol s ₄ is transmitted through the fourth antenna 190-4.

The receiver 200 performs time-space decoding on the received data symbols s ₁ , s ₂ , s ₃ , and s ₄ , and performs channel decoding to determine whether there is an error (S120). If an error is not detected, an ACK signal is transmitted to the transmitter 100 and the transmission waits for the next symbol. However, it is assumed here that the receiver 200 detects an error and transmits a NACK signal as a retransmission request signal (S130).

When the NACK signal is received, the transmitter 100 transmits retransmission symbols s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , and s ₄ ¹ (S140). The retransmission symbol s ₁ ¹ is transmitted through the first antenna 190-1, the retransmission symbol s ₂ ¹ is transmitted through the second antenna 190-2, and the retransmission symbol s ₃ ¹ is the third antenna 190-. 3) and the retransmission symbol s ₄ ¹ is transmitted through the fourth antenna 190-4. When the NACK signal is received, the controller 150 spatially remaps the data symbols s ₁ , s ₂ , s ₃ , and s ₄ through the adaptive mapper 120, thereby retransmitting symbols s ₁ ¹ , s ₂ ^1. , s ₃ ¹ and s ₄ ¹ . The spatial remapping method used in retransmission may have various methods, which will be described later with reference to FIG. 13 or below.

The receiver 200 performs time-space decoding on the received retransmission symbols s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , and s ₄ ¹ , and performs channel decoding to determine whether there is an error (S150). In this case, the combiner 240 may combine the previous symbols s ₁ , s ₂ , s ₃ , and s ₄ with the retransmission symbols s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , and s ₄ ¹ . In general chase combining, the log-likelihood ratio (hereinafter referred to as LLR) values of retransmission symbols are combined with the LLR values of previous symbols.

If no error is detected, the receiver 200 transmits an ACK signal to the transmitter 100 and waits for transmission of the next symbol. However, it is assumed here that the receiver 200 detects an error and transmits a NACK signal as a retransmission request signal (S160).

When the NACK signal is received, the transmitter 100 transmits the remapped retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , and s ₄ ² again (S170). The retransmission symbol s ₁ ² is transmitted through the first antenna 190-1, the retransmission symbol s ₂ ² is transmitted through the second antenna 190-2, and the retransmission symbol s ₃ ² is the third antenna 190-. 3) and the retransmission symbol s ₄ ² is transmitted through the fourth antenna 190-4. Adaptive mapper 120 spatially remaps data symbols s ₁ , s ₂ , s ₃ , and s ₄ to construct retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , s ₄ ² .

The receiver 200 performs time-space decoding on the received retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , and s ₄ ² , and performs channel decoding to determine whether there is an error (S180). At this time, the coupling unit 240 is the previous symbols s ₁ , s ₂ , s ₃ , s ₄ , s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , s ₄ ¹ and retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , s ₄ ² can be combined.

The receiver 200 transmits an ACK signal or a NACK signal to the transmitter 100 according to whether an error is detected (S190). When the ACK signal is transmitted, retransmission for the corresponding symbols ends. The retransmission request by the NACK signal may be made up to the n th repetition number (n ≧ 1). If the error is still detected by the nth retransmission, the retransmission process can be reset and transmission for the next symbols can be started. Or transmission may be done again from the beginning for the current symbols.

The retransmission symbols are formed by remapping data symbols s ₁ , s ₂ , s ₃ , and s ₄ from each other. Remapping of data symbols may be referred to as remapping on signal constellations. Remapping of data symbols refers to rearrangement of the bits representing the data symbols from one another, and rearrangement includes replacement and / or exchange of bits.

13 is an exemplary diagram illustrating an arrangement of retransmission symbols according to an embodiment of the present invention.

Referring to FIG. 13, a retransmission symbol is formed by performing bit-by-bit remapping on a signal constellation for data symbols. At the first retransmission (T2), the retransmission symbols s ₁ ¹ and s ₄ ¹ are re-bits in the bits (i _1, i ₂₎ and s bits of ₄ (i _7, i ₈₎ for the exchange of symbols s ₁ Arrange and form. Retransmitting symbols s ₂ and s ₃ ¹ ¹ is formed by replacing the bit (q _3, q ₄₎ and bits (q _5, q ₆₎ of s ₃ s ₂ of each other, and rearranges the bits within a symbol. That is, the retransmission symbols s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , and s ₄ ¹ spatially exchange bits of the data symbols s ₁ , s ₂ , s ₃ , and s ₄ , and rearrange the bit data within the symbol. Form.

In the second retransmission (T3), the retransmission symbols s ₁ and s ₃ ² ² is formed by a bit (q _1, q ₂₎ and bits (q _7, q ₈₎ of s ₃ s ₁ of the exchange. Retransmitting symbols s ₂ and s ₄ ² ² is formed by a bit (q _3, q ₄₎ and bits (q _7, q ₈₎ of the s ₄ s ₂ interchangeably. That is, the retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , and s ₄ ² are formed by spatially exchanging bits of the data symbols s ₁ , s ₂ , s ₃ , and s ₄ .

Although the number of bits exchanged with each other is illustrated as two above, this is not a limitation and the number of bits exchanged is not limited. One bit can be exchanged with each other, and three or more bits can be exchanged with each other.

In the first retransmission T2, the bits of the data symbols are spatially exchanged and retransmitted, and in the second retransmission T3, the bits of the data symbol are newly exchanged spatially and retransmitted. An additional diversity gain can be obtained by the exchange of bit data of data symbols.

Here, only up to the second retransmission is described, but the third retransmission and subsequent retransmissions may also retransmit the retransmission symbol in which the data symbols are spatially remapped.

Referring to FIG. 14, in the first retransmission T2, retransmission symbols s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , and s ₄ ¹ spatially exchange bits of data symbols s ₁ , s ₂ , s ₃ , and s ₄ . And rearranging the bits in the symbol.

Data symbols s ₁ , s ₂ , s ₃ , s ₄ at the second retransmission (T3) The bits of the liver can be replaced with each other. That is, retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , s ₄ ² are data symbols s ₁ , s ₂ , s ₃ , s ₄ In this case, the least significant bit (LSB) and the most significant bit (MSB) are replaced with their complements. Substitution is not limited to LSB and MSB, and can be substituted independently by complement with respect to LSB and MSB. Alternatively, the bit in the middle portion can be replaced by its complement.

In the first retransmission T2, data symbols are spatially exchanged with each other for retransmission. In the second retransmission T3, data symbols are spatially replaced with each other and retransmitted. Additional diversity gain can be obtained by remapping data symbols.

Referring to FIG. 15, in the first retransmission T2, retransmission symbols s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , and s ₄ ¹ are formed by remapping data symbols s ₁ , s ₂ , s ₃ , and s ₄ . That is, the bits of the data symbols are spatially exchanged with each other, rearranged, and then the LSBs and the MSBs are replaced by their complements.

In the second retransmission (T3), the retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , and s ₄ ² spatially exchange bits of the transmission symbols s ₁ , s ₂ , s ₃ , and s ₄ , rearrange them, and then intermediate them. It forms by replacing the bit data of the part by its complement. That is, the new retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , and s ₄ ² are formed by substituting different bits from the replaced bits of the first retransmission symbols s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , s ₄ ¹ . do. In the first retransmission T2, the data symbols are spatially replaced with each other and retransmitted. In the second retransmission T3, the data symbols are spatially newly replaced and retransmitted.

Referring to FIG. 16, in a first retransmission T2, retransmission symbols s ₁ ¹ , s ₂ ¹ , s ₃ ¹ , s ₄ ¹ spatially exchange data symbols s ₁ , s ₂ , s ₃ , s ₄ , After rearrangement, LSB and MSB are formed by substituting their complement.

In a second retransmission T3, the bits of the data symbol are exchanged with each other. That is, the retransmission symbols s ₁ ² , s ₂ ² , s ₃ ² , and s ₄ ² are formed by spatially exchanging bits of the data symbols s ₁ , s ₂ , s ₃ , and s ₄ , and rearranging the positions of the bits. do.

In the first retransmission T2, the data symbols are spatially replaced and retransmitted, and in the second retransmission T3, the data symbols are spatially exchanged with each other for retransmission. Additional diversity gain can be obtained through remapping by exchange and substitution between data symbols.

Referring to FIG. 17, a retransmission symbol is formed by exchanging data symbols with each other. Retransmitting symbols s ₁ and s ₂ ¹ ¹ is formed by the bits (i _3, i ₄₎ of the bits (i _1, i ₂₎ and s ₂ s ₁ of the exchange. Bits (q ₁ , q ₂ ) and (i ₃ , i ₄ ) of retransmission symbol s ₁ ¹ intersect each other. Bits (q ₃ , q ₄ ) and (i ₁ , i ₂ ) of retransmission symbol s ₂ ¹ intersect each other. Retransmission symbols s ₃ ¹ and s ₄ ¹ are formed by exchanging bits s ₃ (i ₅ , i ₆ ) and bits s ₄ (i ₇ , i ₈ ). Bits (q ₅ , q ₆ ) and (i ₇ , i ₈ ) of retransmission symbol s ₃ ¹ intersect each other. Bit data q ₇ and q ₈ of retransmission symbol s ₄ ¹ and (i ₅ , i ₆ ) intersect each other.

The rearrangement of bits between data symbols can be done in a variety of other ways. The retransmission symbols may be configured by remapping data symbols on a temporal, spatial and subcarrier basis. The retransmission symbols can be remapped at every retransmission. Alternatively, remapping may be performed for only one retransmission. Each remapping can have a different remapping scheme, or the same remapping scheme can be used.

There is no limit to the criteria for determining the remapping method. In one embodiment, the controller 150 may determine the remapping method appropriately according to the situation in an open loop manner. As a parameter for determining the remapping scheme, the maximum Doppler frequency and the delay spread may be referred to. In another embodiment, the controller 150 may receive the CQI signal and determine the remapping scheme according to the channel quality returned to the closed loop scheme.

Since the retransmission symbol is formed by remapping the data symbols, it can be referred to as a composite automatic retransmission of the Type I or chase combining method in which the entire symbol is retransmitted again. However, the technical idea of the present invention can be applied to the complex automatic retransmission of the IR method. That is, in the IR method, only the redundant symbol is retransmitted, not the entire symbol. In this case, additional retransmission gain can be secured by spatially remapping and transmitting the extra symbols.

Hereinafter, a hybrid automatic retransmission method using the space-time code method will be described.

18 is an exemplary view showing a composite automatic retransmission method according to another embodiment of the present invention. Hereinafter, it is assumed that two transmit antennas (Nt = 2), and data symbols are s ₁ and s ₂ for each transmit antenna. The space time coding method may use STBC. Alamuti's STBC in a communication system with two transmit antennas is shown in Table 1 above.

Referring to FIG. 18, first, data symbols s ₁ are transmitted through the first antenna 190-1, and data symbols s ₂ are transmitted through the second antenna 190-2.

When an error is detected in the transmitted symbols and a NACK signal is transmitted, at the first retransmission (T2), the retransmission symbol -s ₂ ^* is transmitted through the first antenna 190-1, and the second antenna 190-2 Transmit retransmission symbol s ₁ ^*

In the case where an error is also detected by the retransmission symbol and the NACK signal is transmitted, the data symbols s ₁ and s ₂ are remapped at the second retransmission (T3) to form retransmission symbols s ₁ ′ and s ₂ ′. When a second retransmission (T3) is to transmit a first retransmission symbols through an antenna (190-1) s ₁ 'transmission, the second antenna ₂ through the retransmitted symbol s (190-2) to ".

If an error is detected and a NACK signal is transmitted again, the third retransmission (T4) remaps the retransmission symbols s ₁ ^* and -s ₂ ^* to form new retransmission symbols s ₁ ' ^* and -s ₂ ' ^* . do. In the third retransmission T3, the retransmission symbol-s ₂ ' ^* is transmitted through the first antenna 190-1 and the retransmission symbol s ₁ ' ^* is transmitted through the second antenna 190-2.

Although a system having two antennas has been described above, the technical idea of the present invention may be applied to a system having three or more antennas as it is. In addition, not only STBC but also the time-space trellis code may be applied to the technical idea of the present invention.

19 is a graph showing SNR versus BER (bit error rate) of a simulation result of a conventional hybrid retransmission method according to the prior art and the present invention, and FIG. 20 is a SNR of a simulation result of the conventional hybrid retransmission method according to the prior art and the present invention. This is a graph of FER (frame error rate).

19 and 20, it can be seen that the effect of the present invention in the channel environment with high mobility is superior to the prior art. For reference, chase combining is used as a retransmission scheme in the 3GPP downlink for simulation, and a 16-QAM modulation scheme and a 1/2 turbo code are used. The number of antennas was two, and the user's speed was set at 100 km / h.

21 is a graph showing SNR versus BER of the simulation result of the conventional method and the hybrid automatic retransmission method according to the present invention, and FIG. 22 is a graph showing SNR versus FER of the simulation result of the conventional method and the hybrid automatic retransmission method according to the present invention. to be. 21 and 22 are simulation results of the user's speed of 30km / h and 150km / h, unlike Figures 19 and 20.

21 and 22, it can be seen that the effect of the present invention is superior to the prior art, in particular, the greater the moving speed, the better the performance. According to the present invention, data degradation can be prevented by compensating for diversity gain even in an environment having high mobility, that is, a channel having high time selectivity.

Hereinafter, a hybrid automatic retransmission method using a cyclic delay diversity scheme will be described.

Referring to FIG. 23, the transmitter 500 includes a channel encoder 510, an adaptive mapper 520, a spatial encoder 530, a controller 550, and a receiving circuit 580. The transmitter 500 uses IFF units 540-1,..., 540-Nt as modulators in the OFDM scheme.

The information bits are data symbols past channel encoder 510 and adaptive mapper 520. The data symbols are converted into transmission symbols by performing IFFT by the IFFT units 540-1,..., 540-Nt via the spatial encoder 530. A CP is inserted into a transmission symbol by a cyclic prefix insertion unit 545-1,..., 545 -Nt and transmitted through a transmission antenna 590-1,..., 590 -Nt. Delays 570-1, ..., 570- (Nt-) between the IFFT sections 540-1, ..., 540-Nt and the CP insertion sections 545-1, ..., 545-Nt. 1)) is arranged to cyclically delay the symbol.

Transmitter 500 The difference from the transmitter 100 of FIG. 11 is that the retarder between the modulators 540-1, ..., 540-Nt and the transmit antennas 590-1, ..., 590-Nt. (570-1, ..., 570- (Nt-1)) is added. Other operations are the same as in the embodiment of FIG. Delays 470-1, ..., 470- (Nt-1) cyclically delay transmission symbols transmitted through each transmit antenna 590-1, ..., 590-Nt. You can. The delay time Δ ₁ , ..., Δ _Nt-1 delayed by the delays 570-1, 570- (Nt-1) may have different values depending on the user, and the receiver The information can be retrieved from and adjusted.

Referring to FIG. 24, the data symbol s ₁ is initially modulated into a transmission symbol at the initial T1, and is repeatedly transmitted by cyclically delaying through all transmission antennas 590-1,..., 590 -Nt. When an error is detected in the transmitted symbol and a NACK signal is transmitted, the retransmission symbol s ₁ ¹ is formed by remapping the data symbol s ₁ through the adaptive mapper 420 in the first retransmission T2. The retransmission symbol s ₁ ¹ is modulated into a transmission symbol and cyclically delayed through the transmission antennas 590-1,..., 590-Nt.

If an error is also detected by the retransmission symbols s ₁ ¹ and the NACK signal is transmitted, the retransmission symbols s ₁ ² remapped by the adaptive mapper 520 also in the second retransmission T3. .., 590-Nt) transmits with a cyclic delay.

In another embodiment, the arrangement of the retarders 570-1,..., 570-(Nt-1) and the CP inserters 545-1,. That is, the CP may insert the symbol after delaying the symbol, but may also delay the symbols after inserting the CP.

25 is a block diagram showing a transmitter according to another embodiment of the present invention. The transmitter 600 moves the delay unit to the frequency domain in the transmitter 500 of FIG.

Referring to FIG. 25, phase delays 670-1,..., 670-(Nt-1) are provided between the spatial encoder 630 and the IFFT units 640-1,..., 640 -Nt. Arranged to cyclically delay the phase of the symbol. In the frequency domain, the phase delays 670-1, ..., 670- (Nt-1) are delayers 570-1, ..., 570- in the time domain included in the transmitter 500 of FIG. Equivalent to Nt). The time delay in the time domain and the phase delay in the frequency domain are due to the duality.

Hereinafter, a SISO system having one transmit antenna will be described.

Referring to FIG. 26, the transmitter 800 includes a channel encoder 810, an adaptive mapper 820, a modulator 830, a controller 850, and a receiving circuit 860. The transmitter 800 includes one antenna 890.

The data symbols output from the adaptive mapper 820 are modulated into transmit symbols by the modulator 830. Therefore, the transmission symbol may include a plurality of data symbols. In this case, one transmission symbol may be one packet. Here, it is assumed that one transmission symbol includes three data symbols s ₁ , s ₂ , and s ₃ . However, this is only an example, and a plurality of data symbols may be included in a transmission symbol according to the number of subcarriers.

The operation of the transmitter 800 is as follows. First, three data symbols s ₁ , s ₂ , and s ₃ are transmitted in the initial T1. When an error is detected in the transmitted symbol and a NACK signal is transmitted, the retransmitted symbols s ₁ ¹ , s ₂ ¹ , and s ₃ ¹ remapped through the adaptive mapper 820 are transmitted in the first retransmission T2. The retransmission symbols may be formed by remapping each other between three previous data symbols. When an NACK signal is also transmitted by an error detected by the retransmission symbol, the retransmission symbols s ₁ ² , s ₂ ² , and s ₃ ² remapped through the adaptive mapper 820 are also transmitted to the second retransmission T3. New retransmission symbols may be formed by remapping each other between the previous three data symbols.

The present invention implements diversity through remapping between data symbols. Remapping involves rearranging the bits that make up two or more different data symbols. This includes not only temporal and spatial but also rearrangements between data symbols transmitted within one time slot.

The present invention may be implemented in hardware, software, or a combination thereof. (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microprocessor, and the like, which are designed to perform the above- , Other electronic units, or a combination thereof. In the software implementation, the module may be implemented as a module that performs the above-described function. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

As described above, according to the present invention, it is possible to obtain an additional diversity gain while obtaining a space-time diversity gain in a corresponding channel without additional complexity through the adaptive mapper. This is easy to apply without changing the receiver structure according to the prior art.

In addition, according to the present invention, a diversity gain can be additionally secured by transmitting temporally remapped symbols during retransmission, thereby minimizing retransmission requests and improving communication quality.

Claims

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In a wireless communication system using a plurality of orthogonal subcarriers, a hybrid automatic repeat request (HARQ) is performed according to an incremental redundancy (IR) technique through a plurality of antennas including a first antenna and a second antenna. In the method,

Transmitting an initial 16 Quadrature Amplitude Modulation (QAM) symbol through the plurality of antennas using an orthogonal frequency division multiplexing (OFDM) symbol;

Receiving a retransmission request signal for the first 16 QAM symbols;

Constructing a retransmission 16 QAM symbol in response to the retransmission request signal; And

Transmitting the retransmitted 16 QAM symbols through the plurality of antennas using an OFDM symbol,

The bit mapping order applied to the first 16 QAM symbols and the bit mapping order applied to the retransmitted 16 QAM symbols are different,

The number of bits spatially exchanged between the first 16 QAM symbols corresponding to the first antenna and the retransmission 16 QAM symbols corresponding to the second antenna is determined to be two,

The number of bits spatially exchanged between the first 16 QAM symbols corresponding to the second antenna and the retransmitted 16 QAM symbols corresponding to the first antenna is determined as two.

Compound automatic retransmission method.

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9. The method of claim 8,

The first 16 QAM symbols and the retransmission 16 QAM symbols are encoded with a space-time block code.

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In a wireless communication system using a plurality of orthogonal subcarriers, a hybrid automatic repeat request (HARQ) is performed according to an incremental redundancy (IR) technique through a plurality of antennas including a first antenna and a second antenna. In the transmitter,

First 16 QAM (Quadrature Amplitude Modulation) symbols are transmitted through the plurality of antennas using orthogonal frequency division multiplexing (OFDM) symbols,

Receive a retransmission request signal for the first 16 QAM symbols;

Configure a retransmission 16 QAM symbol in response to the retransmission request signal,

And a controller configured to transmit the retransmission 16 QAM symbols through the plurality of antennas by using an OFDM symbol.

Transmitter for complex automatic retransmission.

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