KR101208543B1 - Method for transmitting signals in multi-antenna system performing cyclic delays based on a plurality of cyclic delay value - Google Patents

Abstract

The present invention relates to a data transmission / reception method in a mobile communication system, and more particularly, to a transmission method in a multi-antenna system performing a cyclic delay according to a plurality of cyclic delay values.

The transmission method according to the present invention is a transmission method in a multi-antenna system for performing a cyclic delay according to a plurality of cyclic delay values in order to achieve the above object, which is to be transmitted through different transmission antennas. Performing a cyclic delay for a plurality of symbols according to the cyclic delay value; Performing data processing such that at least one bit of the plurality of bits corresponding to a first symbol of the plurality of symbols is mapped to a second symbol of the plurality of symbols; And transmitting the plurality of symbols on which the data processing has been performed using a plurality of subcarriers.

Spatial Multiplexing, Time Multiplexing, Bit Level, CDD, Cyclic Delay Diversity

Description

Method for transmitting signals in multi-antenna system performing cyclic delays based on a plurality of cyclic delay value}

1 is a block diagram illustrating a structure of an orthogonal frequency division multiplexing system having one transmit / receive antenna.

2 is a block diagram illustrating a structure of an orthogonal frequency division multiplexing system having a plurality of transmit and receive antennas.

 3 is a block diagram illustrating the basic concept of an adaptive mapper-based retransmission scheme used in the present invention and the prior art.

4A and 4B are diagrams for describing an error rate of bits according to constellation mapping.

FIG. 5 illustrates an example of obtaining a transmission diversity through mapping and time delay while satisfying the maximum spatial multiplexing index 2 when two transmission antennas are used and the constellation mapping method is 16 QAM modulation.

6 shows another example of a spatial and / or temporal multiplexing method at the bit level proposed in this embodiment.

7 is a block diagram showing an example of applying the adaptive mapping proposed by the present invention to a conventional STBC code for obtaining transmit diversity.

FIG. 8A is a diagram illustrating an example of a transmission apparatus using a cyclic delay diversity (CDD) previously proposed.

8B is a cyclic delay diversity apparatus including an adaptive mapper according to the present embodiment.

8C is a cyclic delay diversity apparatus including an adaptive mapper according to the present embodiment.

9 shows an example of applying this embodiment to a cyclic delay diversity method.

10 is an example of performing bit substitution at the bit level according to the present embodiment.

11 is a transmission structure for a cyclic delay diversity scheme that provides multiple rates.

FIG. 12 illustrates a cyclic delay diversity structure using preprocessing as a method for improving link performance of a multi-rate.

13 and 14 illustrate a result of applying the bit-level spatial multiplexing method according to the present embodiment in the system of FIG. 11 or 12.

The present invention relates to a data transmission / reception method in a mobile communication system, and more particularly, to a transmission method in a multi-antenna system performing a cyclic delay according to a plurality of cyclic delay values.

1 is a block diagram illustrating a structure of an orthogonal frequency division multiplexing system having one transmit / receive antenna. 2 is a block diagram illustrating a structure of an orthogonal frequency division multiplexing system having a plurality of transmit and receive antennas.

Data bits corresponding to user data or control data to be transmitted to the receiving end are input to the channel encoder 101. The channel encoder 101 adds redundant bits to data bits to reduce effects on the channel and effects on noise. The output of the channel encoder 101 is input to the mapper 102 and converted into symbols. The symbol is input to the serial / parallel converter 103. The serial / parallel converter 103 converts serial data into parallel data. The serial / parallel converter 103 may transmit data to a receiving end using a plurality of orthogonal subcarriers. When transmitting through a plurality of antennas as shown in FIG. 2, the output of the serial / parallel converter 103 is input to the multi-antenna encoder 104. The multi-antenna encoder 104 converts a data symbol into a space-time signal. In the case of multiple antennas, a transmitting antenna transmits such a space-time signal through a channel, and a receiving antenna plays a role of receiving a space-time signal from a channel. The multiple antenna decoder 105 reconverts the received space-time signals into respective data symbols.

Systems using multiple or singular antennas input signals received on multiple subcarriers to parallel / serial converter 106. The parallel / serial converter 106 converts a parallel signal into a serial signal. The output of the parallel serial converter is input to a demapper 107. The demapper 107 converts a data symbol into a bit string. The bit string causes the channel decoder 108 to decode the channel code and estimate the data.

In the communication system as shown in FIG. 1 or FIG. 2, existing repetitive transmission schemes are classified as follows. First, a method of using multiple transmit / receive antennas in an orthogonal division multiplexing system can be roughly divided into two methods.

First, there is a multiple transmit / receive antenna system for spatial multiplexing gain. Examples thereof include a V-BLAST system and a D-BLAST system. That is, to obtain a spatial multiplexing gain, there are a V-BLAST method in which each symbol is mapped in an orthogonal form for each antenna and transmitted, and a D-BLAST method in which a symbol is periodically purified and transmitted in a symmetrical form.

Secondly, there is a multiple transmit / receive antenna system for spatial diversity gain. These systems use space-time code to transmit the same signal through different antennas in the next timeslot.

Hereinafter, the space-time code described above will be described.

Spatio-temporal code is a method of obtaining spatial diversity gain by transmitting the same signal continuously in a multi-antenna environment and transmitting it through spatial processing during repeated transmission. The following equation is the most basic space-time code and is usually used in systems with two transmit antennas.

In the above formula, the rows of the matrix represent antennas and the columns represent time. As shown in the above equation, S ₁ data is transmitted through the first antenna and then in complex conjugate form through the second antenna, and S ₂ data is transmitted through the second antenna and then conjugated in complex form with the opposite sign. As is transmitted through the first antenna again. The construction of the corresponding space-time block codes according to the number of transmit antennas is actively studied in the prior arts.

Third, there is a system for selecting a transmit antenna used for transmission by using an adaptive mapper. 3 is a block diagram illustrating the basic concept of an adaptive mapper-based retransmission scheme used in the present invention and the prior art. As shown in FIG. 3, in the application of a hybrid retransmission scheme in a single antenna system and a multi-antenna system, bit- or symbol-wise remapping on a signal constellation is performed for each transmission in consideration of space-time multiplexing so that a mapping gain most suitable for a corresponding channel is obtained. Is a way to secure

As illustrated in the above-described adaptive mapper-based complex retransmission method, symbols mapped to one symbol on the signal constellation through the mapper are allocated to N _T transmit antennas. Transmission symbols sent in timeslots are corrupted by the channel and require retransmission. In this case, every retransmission up to the maximum number of retransmissions, m, transmits symbols mapped appropriately for the channel.

The adaptive mapper can be applied not only to the system considering the single antenna, but also to the system considering the multiple antennas, and the mapping method applied in the retransmission is not only the repositioning and substitution of the signal constellation per bit and symbol, but also the symbol transmitted from each antenna. A mapping scheme considering spatial multiplexing may be applied to a corresponding channel in units of bits and symbols.

This adaptive mapper-based retransmission scheme can be incorporated into all retransmission schemes of the prior art and is a method without additional complexity. In addition, the proposed method can secure additional retransmission gain through mapping diversity.

The demand for communication services is rapidly increasing, including the generalization of information and communication services, the emergence of various multimedia services, and the emergence of high quality services. Various wireless communication technologies are actively researched in various fields to satisfy these demands. Among them, the spatial multiplexing gain and the spatial diversity gain using the above-mentioned multiple transmit / receive antenna have a trade-off relationship. Of course, designs of space-time codes that can obtain the maximum spatial multiplexing gain and the maximum spatial diversity gain are currently in progress, but to obtain optimal performance, an ML receiver based on the maximum likelihood (ML) is required. This ML receiver is not easy to implement in an actual communication system because the computational complexity increases exponentially as the number of transmit antennas and modulation index increase. In addition, since a generalized MMSE 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 system, this involves the complexity of storing channel response values in a frequency domain in a buffer of a receiver for a predetermined slot or more. In addition, symbol-space time-space coding is performed by decoupling of channels by the orthogonal principle of equivalent channels in a block flat fading environment and a rich scattering environment. In the time varying channel due to the effect, the performance is deteriorated.

The present invention has been proposed to improve the above-described prior art, and an object of the present invention is to propose a transmission technique capable of obtaining additional diversity gain at maximum spatial multiplexing index with low complexity.

Summary of the Invention

The transmission method according to the present invention is a transmission method in a multi-antenna system for performing a cyclic delay according to a plurality of cyclic delay values in order to achieve the above object, which is to be transmitted through different transmission antennas. Performing a cyclic delay for a plurality of symbols according to the cyclic delay value; Performing data processing such that at least one bit of the plurality of bits corresponding to a first symbol of the plurality of symbols is mapped to a second symbol of the plurality of symbols; And transmitting the plurality of symbols on which the data processing has been performed using a plurality of subcarriers.

One embodiment of the invention

Specific features and effects of the invention will be further embodied by one embodiment of the invention described below.

The adaptive mapper in the open loop multiple transmit / receive antenna system proposed in this embodiment may follow the example of FIG. 3. That is, as shown in FIG. 3, a diversity gain can be obtained by improving an average channel reliability of bits constituting transmission symbols for a channel in a single antenna system and a multiple antenna system.

In the example of FIG. 3, re-mapping of bits of a signal property for each transmission may be performed in consideration of space-time multiplexing to ensure mapping diversity according to channel changes. Symbols mapped to one symbol on the signal constellation by the mapper of FIG. 3 are allocated to N _T transmit antennas. T _i represents a transmission timeslot, and bits constituting symbols during the mth transmission time slot are remapped and transmitted through exchange and substitution for each transmission timeslot and antenna.

4A and 4B are diagrams for describing an error rate of bits according to constellation mapping. 4A and 4B are diagrams for describing mapping diversity obtained through remapping considering spatial multiplexing in an open loop multiple transmit / receive antenna system. 4A and 4B are based on the Gray mapped signal constellation for 16 QAM modulation.

As shown in FIG. 4A, a certain number of bits are mapped to one symbol. A method of mapping the specific number of bits to one symbol is called constellation mapping. There are various types of constellation mapping (for example, BPSK, QPSK, 8PSK, 16QAM, etc.), and the number of bits mapped to one symbol varies according to the type. The symbol is data corresponding to at least one bit, and is transmitted to the receiver through an in-phase channel and a quadrature channel.

As shown in Fig. 4B, each signal constellation is divided into two partition sets. 4B shows that only the first bit (bit 1) is different from the first constellation (for example, 1011 and 0011), and the remaining bits represent the same symbols. Referring to the first constellation of FIG. 4B, it can be seen that Euclidean distance varies depending on the first bit of four bits constituting one symbol. As such, the partition set is different according to each bit position, which has a different distance as shown in FIG. 4B.

In the case of FIG. 4B, as the first bit position and the second bit position differ, distances between the symbols differ from each other. However, it can be seen that the distance of each symbol at the third bit (bit 3) position and the fourth bit (bit 4) position is constant to the minimum distance. Referring to the four constellations of FIG. 4B, as one bit is changed, the distances between the corresponding symbols are different. Thus, the probability that a bit fails at each bit position depends on the bit position.

In other words, in bits forming one symbol, a difference in error rate occurs depending on the position of each bit. This feature can be utilized in a multiple transmit antenna system. That is, when the symbol is transmitted in consideration of the spatial multiplexing gain of the multiplexing antenna and time diversity according to time delay, additional diversity gain may be obtained by remapping the configuration bits and transmitting them by a method of swapping or replacing. This means that the result is that the channel reliability of each bit is improved overall.

This embodiment transmits data using a method of improving the channel reliability by exchanging or replacing bits. If there are symbols corresponding to the data to be transmitted to the receiving end, the symbols correspond to at least one bit. In this case, the performance of the whole system can be improved when the bits are spatially or temporally multiplexed at the transmitting end.

In other words, this embodiment may be spatially multiplexed or temporally multiplexed so that a plurality of bits corresponding to one symbol are transmitted through a path different from the original transmission path. The multiplexing method may be performed by the adaptive mapper of FIG. 3.

Hereinafter, a method of spatially multiplexing a plurality of bits corresponding to one symbol and a method of temporally multiplexing a plurality of bits corresponding to different symbols will be described. In this embodiment, in order to perform such multiplexing, data processing is performed such that any one of a plurality of bits corresponding to a specific first symbol is included in the specific second symbol and transmitted. Through this data processing, specific bits are transmitted through a path different from the path originally transmitted.

FIG. 5 is an example of obtaining a method of obtaining transmit diversity through mapping and time delay while satisfying the maximum spatial multiplexing index 2 when there are two transmit antennas and the constellation mapping method is 16 QAM modulation.

은 M번째 안테나의 n번째 타임 슬롯을 통해 전송되는 심볼을 나타낸다. 또한,

은 해당 심볼을 구성하는 i~i+3까지의 비트들을 의미한다. 5 consists of two parts. The aspect before the multiplexing on the left is according to the conventional method, and the result after the multiplexing on the right shows the mapping through the exchange proposed in the present invention. here

Denotes a symbol transmitted on an nth time slot of an Mth antenna. Also,

Means bits i to i + 3 constituting the symbol.

As shown in FIGS. 4A and 4B, error rates of bits constituting each symbol vary depending on a signal constellation mapping method and a channel condition. In this case, the total number of symbols transmitted during two timeslots through two transmission antennas is four, and the error rates of bits constituting these symbols are exchanged with each other to obtain spatial diversity over time. In the exchange method, the optimal performance mapping method differs according to the corresponding signal constellation, and the present invention includes all the methods of mapping differently according to the above-described design criteria.

More specifically, it is as follows.

은 {b₁, b₂, b₃, b₄}(501)에 상응한다. 하나의 심볼

(501)에 상응하는 비트들을 공간적으로 다중화시키고, 시간적으로 다중화시킨다. 예를 들 어, b₁(511) 비트와 b₃(512)는 원래 전송되는 안테나를 통해 전송되고, 원래 전송되는 타임 슬롯에 전송된다. 한편, b₄(521) 비트의 경우, 원래 전송되는 안테나와 상이한 안테나를 통해 전송된다. 즉, 공간적으로 다른 경로로 구분하여 전송된다. 한편, b₂(531) 비트의 경우, 원래 전송되는 안테나와 상이한 공간적 경로를 통해 전송될 뿐만 아니라, 원래 전송되는 타임 슬롯과 상이한 타임 슬롯을 통해 전송된다. 즉, 하나의 심볼

(501)에 상응하는 4개의 비트{b₁, b₂, b₃, b₄}는 본래 하나의 송신 안테나 및 하나의 타임 슬롯을 통해 전송되나, 본 실시예에 따라, 서로 다른 송신 안테나 및 서로 다른 타임 슬롯을 통해 전송된다. 5 shows the configuration of conventional symbols before multiplexing. For example, conventional symbols

Corresponds to {b ₁ , b ₂ , b ₃ , b ₄ } (501). One symbol

The bits corresponding to 501 are spatially multiplexed and temporally multiplexed. For example, bits b ₁ 511 and b ₃ 512 are transmitted through the originally transmitted antenna and are transmitted in the time slot originally transmitted. On the other hand, in the case of b ₄ (521) bits, it is transmitted through an antenna different from the antenna originally transmitted. In other words, they are transmitted by being divided into different paths spatially. On the other hand, in the case of the b ₂ (531) bit, not only is transmitted through a spatial path different from the originally transmitted antenna, but also is transmitted through a time slot different from the originally transmitted time slot. That is, one symbol

Four bits {b ₁ , b ₂ , b ₃ , b ₄ } corresponding to 501 are originally transmitted through one transmit antenna and one time slot, but according to this embodiment, different transmit antennas and each other It is sent through another time slot.

By the multiplexing method at the bit level proposed in this embodiment, a signal is transmitted through a path different from the conventional one spatially and / or temporally.

은 {b₉, b₆, b₁₁, b₁₆}(551)에 상응한다. 이 경우, 551 심볼을 이루는 4개의 비트는 본래 서로 다른 심볼에 상응하는 비트들이다. 예를 들어, b₉ 비트와 b₁₁ 비트는 종래의 심볼

(581, 582)에 상응하고, b₁₆ 비트는 종래의 심볼

(571)에 상응하고, b6 비트는 종래의 심볼

(561) 에 상응한다. 즉, 종래의 서로 다른 3개의 심볼(

,

,

)에 상응하는 비트들(b₉, b₆, b₁₁, b₁₆)이 공간적으로 및/또는 시간적으로 다중화되어 본 실시예에 따른 심볼

(551)에 매핑된다.According to the present embodiment, a symbol multiplexed at the bit level will be described below. Embodiment symbol seen in FIG.

Corresponds to {b ₉ , b ₆ , b ₁₁ , b ₁₆ } (551). In this case, the four bits constituting the 551 symbol are bits corresponding to different symbols. For example, bits b ₉ and b ₁₁ are conventional symbols

Corresponds to (581, 582), b ₁₆ bits is a conventional symbol

Corresponds to 571, and the b6 bit is a conventional symbol

Corresponds to 561. That is, three conventional symbols (

,

,

Bits (b ₉ , b ₆ , b ₁₁ , b ₁₆ ) corresponding to

Mapped to 551.

6 shows another example of a spatial and / or temporal multiplexing method at the bit level proposed in this embodiment. FIG. 6 performs a spatial and / or temporal multiplexing method like the method of FIG. 5 and additionally performs substitution for specific bits. That is, when a specific bit is 0, it is converted to 1, and when a specific bit is 1, it is converted to 0. In FIG. 6, a substitution may be performed for a specific bit, for example, b ₂ , b ₄ , b ₆ , b ₈ , b ₁₀ , b ₁₂ , b ₁₄ , b _16, and the like.

The exchange and replacement of bits constituting the symbol may be changed according to the number of antennas, modulation index, timeslot, and channel condition. By such a change, an optimal mapping method can be designed, and the present invention covers all of them.

The multiplexing method applied to FIGS. 5 and 6 may be performed by the adaptive mapper of FIG. 3. The mapper may perform temporal multiplexing, spatial multiplexing, bit substitution, etc. introduced in FIGS. 5 and 6 by performing operations such as adaptive mapping and time delay.

7 is a block diagram showing an example in which the adaptive mapping proposed by the present invention is applied to a conventional STBC code for obtaining transmission diversity. In the case of FIG. 7, through the adaptive mapping of the present embodiment, the configuration bits of S ₁ and S ₂ constituting a transmission symbol are remapped in consideration of spatial multiplexing, and STBC proposed by Alamouti for this result A method of performing encoding. Through this, additional diversity can be obtained through remapping considering spatial multiplexing in a channel having high time selectivity.

Method A-1 of FIG. 7 is an example of temporal and spatial multiplexing, and method A-2 is an example of additional bit substitution.

Hereinafter, an example in which the multiplexing and data processing method at the bit level according to the present embodiment is applied to the cyclic delay diversity scheme will be described.

FIG. 8A is a diagram illustrating an example of a transmission apparatus using a cyclic delay diversity (CDD) previously proposed. When transmitting a repetitive transmission signal in time as shown in Figure 8a, each repeated signal is transmitted in the form of having a different cyclic delay with the same or different power.

8A illustrates a cyclic delay diversity method when the antenna transmission rate is 1. d _i represents the delay value of the i th repeated transmission signal, and g j represents the power of the j th repeated transmission signal. Also, the symbols transmitted for each antenna branch have different cyclic delays, but are symbols corresponding to one data.

The cyclic delay value d _i or the power control value g _j may have a different value depending on an arbitrary time and a user, or may be used by receiving corresponding information from a receiver.

The method using the cyclic delay diversity is the same as the case where the signal from the multiplexed antenna enters the receiver through the multipath, so the complexity required by the detector of the receiver is very low.

심볼을 구성하는 비트들을 공간다중화를 고려하여 교환 또는 치환시켜 전송함으로써 추가적인 다이버시티를 얻을 수 있다.Through the design criteria proposed in this embodiment

Additional diversity can be obtained by transmitting or replacing bits constituting the symbol in consideration of spatial multiplexing.

An example in which the method proposed in this embodiment is applied to the conventional cyclic delay diversity method will be described.

8B is a cyclic delay diversity apparatus including an adaptive mapper according to the present embodiment. 8B includes an adaptive mapper that performs temporal and spatial multiplexing at the bit level or performs substitution, as described above. The adaptive mapper performs temporal and spatial multiplexing or substitution at the bit level according to various control information generated in the cyclic delay diversity apparatus or fed back from the outside.

는 k번째 안테나에서 전송되는 심볼의 i번째 비트들을 나타낸다. In the transmitting method of FIG. 8, the transmitting apparatus transmits a symbol S ₁ to be transmitted through a spatial optimal mapping of corresponding bits with respect to a symbol cyclically delayed for each transmission antenna. here

Denotes i th bits of a symbol transmitted by the k th antenna.

In the embodiment, it is assumed that four S ₁ , S ₁ (d ₁ ), S ₁ (d ₂ ), and S ₁ (d ₃ ) symbols are transmitted. In addition, the four symbols S ₁ , S ₁ (d ₁ ), S ₁ (d ₂ ), and S ₁ (d ₃ ) are transmitted through different transmit antennas. In addition, different cyclic delays may be applied to the four symbols S ₁ , S ₁ (d ₁ ), S ₁ (d ₂ ), and S ₁ (d ₃ ). For example, no cyclic delay is performed on symbol S ₁ , a cyclic delay is performed on cyclic delay value d ₁ for symbol S (d1), and a sequential or delay value d on symbol S ₁ (d ₃ ). Cyclic delay can be performed by ₃ .

Meanwhile, the four symbols S ₁ , S ₁ (d ₁ ), S ₁ (d ₂ ), and S ₁ (d ₃ ) all correspond to the same data. In other words, different cyclic delays are applied to one data.

As shown in FIG. 8B, different symbols S ₁ , S ₁ (d ₁ ),..., S ₁ (d _N ) correspond to one OFDM symbol. That is, this embodiment applies different cyclic delays to the same one data as described above. An OFDM symbol represents data processed through an IFFT operation during the same time unit, and includes at least one symbol (a symbol generated by constellation mapping of at least one bit).

The adaptive mapper proposed in this embodiment may operate at all stages of a module that performs a cyclic delay. One such example may be as shown in FIG. 8C.

As shown in FIG. 8C, the adaptive mapper proposed in this embodiment performs temporal or spatial multiplexing. That is, data processing may be performed to map the bits originally included in the specific symbol S ₁ to another symbol S ₁ (d ₁ ).

The result of applying the multiplexing method of this embodiment to four symbols S ₁ , S ₁ (d ₁ ), S ₁ (d ₂ ), and S ₁ (d ₃ ) is shown in FIG. 9. That is, FIG. 9 shows an example in which the present embodiment is applied to the cyclic delay diversity method.

(901)로 이루어진다. 상기 심볼 S₁에 상응하는 4개의 비트는 본 실시예에 따라 공간적으로 다중화된다. 도 9에 도시된 바와 같이,

(911) 비트와

(913) 비트는 첫 번째 안테나를 통해 전송되는 본 실시예의 S₁ 심볼에 매핑된다. 또한,

(912) 비트는 네 번째 안테나를 통해 전송되는 본 실시예의 S₁(d₃) 심볼에 매핑된다. 또한,

(914) 비트는 세 번째 안테나를 통해 전송되는 본 실시예의 S₁(d2) 심볼에 매핑된다.As shown in FIG. 9, the conventional symbol S ₁ is

901. Four bits corresponding to the symbol S ₁ are spatially multiplexed according to this embodiment. As shown in FIG. 9,

With 911 beats

Bit 913 is mapped to the S ₁ symbol of this embodiment transmitted via the first antenna. Also,

Bit 912 is mapped to the S ₁ (d ₃ ) symbol of the present embodiment transmitted through the fourth antenna. Also,

Bit 914 is mapped to the S ₁ (d2) symbol of the present embodiment transmitted through the third antenna.

That is, four bits corresponding to the conventional S ₁ symbol are spatially multiplexed through a plurality of antennas by the multiplexing method according to the present embodiment.

In addition, four bits corresponding to the conventional S ₁ symbols are temporally multiplexed through a plurality of antennas by the multiplexing method according to the present embodiment. As shown in FIG. 8B, s to s (d _N ) symbols are transmitted through a plurality of antennas, and in this case, any one of s to s (d _N ) symbols may be transmitted during one time slot. . That is, the symbol may be transmitted through any one of a plurality of antennas.

가 서로 다른 타임슬롯 동안 송신된다. In the case of FIG. 9, for example, s ₁ symbols to s ₁ (d ₃ ) symbols may be transmitted during different time slots. In this case, four bits conventionally transmitted during one timeslot

Are transmitted during different timeslots.

That is, four bits corresponding to one conventional symbol are transmitted during different time slots by the multiplexing method according to the present embodiment.

In the case of spatial multiplexing, configuration bits are spatially multiplexed for each antenna and transmitted as shown in FIG. 9. 9 and 10 are only examples for describing the present embodiment, and bit-level multiplexing may be performed according to various rules. That is, a method of providing near optimal is not limited to FIGS. 9 and 10. In addition, this embodiment is based on the case through four antennas, but this is only for convenience of description. Modification of this embodiment may suggest a multiplexing method that supports various antenna numbers.

10 is an example of performing bit substitution at the bit level according to the present embodiment. As shown in FIG. 10, spatial and temporal multiplexing can be performed at the bit level, and additionally, a bit substitution is also possible.

One example above relates to a method of transmitting a plurality of symbols corresponding to one data through a plurality of transmit antennas. In other words, it relates to a transmission method having a transmission rate of 1.

Hereinafter, a method of transmitting a plurality of symbols corresponding to each of a plurality of data through a plurality of transmit antennas. In other words, a transmission method in which a transmission rate corresponds to the number of transmission antennas will be described.

11 is a transmission structure for a cyclic delay diversity scheme that provides multiple rates. As illustrated in FIG. 11, the transmitting apparatus of FIG. 11 may also perform different power control on each data stream, and may perform a cyclic delay by applying different cyclic delay values. However, the difference between FIG. 8B and FIG. 11 is that different symbols are transmitted by cyclic delay for each antenna. That is, the first antenna transmits symbol 1, the second antenna transmits symbol 2, and the M-th antenna transmits symbol M.

Of course, the above-described temporal and spatial multiplexing method can also be applied to a transmission apparatus such as the structure of FIG. Specific examples will be described below.

12 is a cyclic delay diversity method using precoder as a method for improving link performance of a multi-rate. As illustrated in FIG. 12, a precoder controlled by an internally generated control signal or a control signal generated by external feedback is additionally included. The precoder may improve the performance of the system by adjusting components of each symbol by using a numerical value such as a precoding vector.

The transmitting apparatus of FIGS. 11 and 12 may include a separate adaptive mapper (not shown), and the adaptive mapper may change the mapping method according to an external control signal or an internally generated control signal. Can produce

13 and 14 illustrate a result of applying the bit-level spatial multiplexing method according to the present embodiment in the system of FIG. 11 or 12. That is, in the cyclic delay diversity transmission system that provides multiple data rates, it is a diagram showing the symbols transmitted through the mapper considering the various multiplexing described above and the bits of the corresponding symbols. 9 and 10 show a case in which the transmission rate is 1, and FIGS. 13 and 14 provide multiple transmission rates and thus may provide a transmission rate corresponding to the number of transmitting antennas. Since the example of FIG. 13 is only an example for describing the present embodiment, the present invention is not limited to the example of FIG. 13. In other words, the mapping method exhibiting optimal performance includes all mappings considering spatial multiplexing and time transition in addition to the mapping method below. In addition, the design criteria proposed in the present invention can be designed for all the number of antennas.

As shown in FIG. 13, the bits b ₁ , b ₂ , b ₃ , and b ₄ 1301 corresponding to the conventional symbol S ₁ are spatially multiplexed according to this embodiment. According to the present embodiment, the b ₁ bit 1311 and the b ₃ bit 1313 are mapped to the s ₁ symbol according to the present embodiment. Also, according to the present embodiment, the b ₂ bit 1312 is mapped to the S ₄ (d ₃ ) symbol according to the present embodiment, and the b ₄ bit 1314 is mapped to the S ₃ (d ₂ ) symbol according to the present embodiment. do. That is, bits corresponding to symbols transmitted through one antenna are conventionally mapped to symbols transmitted through different antennas. In this case, different cyclic delays are applied to each symbol.

Note that the conventional symbol S ₁ S ₄ (d ₃ ) are symbols corresponding to different data, respectively. That is, the symbol S ₁ generated by performing IFFT on different data as shown in FIG. 11 or 12. To S ₄ (d ₃ ).

Figure 14 _{b 5, b 6, b 7} , b 8 -bit 1401 was equivalent to the conventional S2 (d1) symbol, as a further example of this embodiment, illustrated it is, according to this embodiment Spatially multiplexed at the bit level. However, in this case bit substitution is performed on the b ₅ bit 1411 and the b ₇ bit 1413 and the b ₈ bit 1414.

The above-described spatial spatial multiplexing method and bit substitution method of FIGS. 13 and 14 are merely examples for describing the present invention. Therefore, the present invention is not limited to the above specific example.

In the open-loop multiple transmit / receive antenna system proposed in this embodiment, the adaptive mapper considering the spatial multiplexing exchanges and replaces bits composing the symbols output from the mapper stage according to the mapping method, channel environment, transmission antenna number, and timeslot. Remapping it through the method. By transmitting the remapped modulation symbols, it is possible to secure time and spatial diversity of the channel. The receiving side can perform final decoding by exchanging only the positions of the soft decision bits coming from the demapper stage by the alignment scheme at the time of transmission.

Those skilled in the art through the above description can be seen that various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention is not limited to the contents described in the detailed description of the specification but by the claims.

The effects of the present invention are as follows.

The adaptive mapper considering the spatial multiplexing of the multiple transmit / receive antenna system proposed in the present invention is a method of additionally securing space and time diversity while obtaining maximum spatial multiplexing gain in a corresponding channel without additional complexity. In addition, it is easy to apply without changing the conventional receiver structure such as linear receiver (MMSE, ZF), OSIC, ML, Sphere decoder. In addition, the space-time code technology and the cyclic delay diversity technology have an advantage of obtaining additional diversity even in a channel environment in which performance is deteriorated.

Claims (6)

A transmission method in a multi-antenna system for performing a cyclic delay according to a plurality of cyclic delay values, Performing a cyclic delay for a plurality of symbols to be transmitted through different transmit antennas according to the cyclic delay value; Performing data processing such that at least one bit of the plurality of bits corresponding to a first symbol of the plurality of symbols is mapped to a second symbol of the plurality of symbols; And Transmitting a plurality of symbols on which the data processing has been performed using a plurality of subcarriers Containing A transmission method in a multiple antenna system performing a cyclic delay according to a plurality of cyclic delay values. The method of claim 1, The step of performing the data processing, Substituting at least one bit of the plurality of bits corresponding to the first symbol A transmission method in a multi-antenna system for performing a cyclic delay according to a plurality of cyclic delay values characterized in that. The method of claim 1, The plurality of symbols to be transmitted through the different transmission antennas are transmitted through different time slots A transmission method in a multi-antenna system for performing a cyclic delay according to a plurality of cyclic delay values characterized in that. The method of claim 1, A plurality of symbols to be transmitted through different transmit antennas, Corresponding to one first piece of data A transmission method in a multi-antenna system for performing a cyclic delay according to a plurality of cyclic delay values characterized in that. The method of claim 1, A plurality of symbols to be transmitted through different transmit antennas, Corresponding to a plurality of data A transmission method in a multi-antenna system for performing a cyclic delay according to a plurality of cyclic delay values characterized in that. The method of claim 1, Wherein the first symbol and the second symbol that have performed the data processing include the same number of bits A transmission method in a multi-antenna system for performing a cyclic delay according to a plurality of cyclic delay values characterized in that.

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