KR100968775B1 - Method for Transmitting and Receiving a Signal in Multiple Antenna system - Google Patents

Method for Transmitting and Receiving a Signal in Multiple Antenna system Download PDF

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KR100968775B1
KR100968775B1 KR20080062865A KR20080062865A KR100968775B1 KR 100968775 B1 KR100968775 B1 KR 100968775B1 KR 20080062865 A KR20080062865 A KR 20080062865A KR 20080062865 A KR20080062865 A KR 20080062865A KR 100968775 B1 KR100968775 B1 KR 100968775B1
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transmitter
receiver
sector
antenna
signal
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KR20080062865A
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Korean (ko)
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KR20100002827A (en
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고영채
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고려대학교 산학협력단
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Abstract

The present invention selects a path of a transmission sector or a transmission antenna in a multi-antenna system having a plurality of transmission antennas per one sector of a transmitter having a plurality of sectors having different directivities, and applies an adaptive modulation scheme accordingly. The present invention relates to a method for transmitting and receiving a signal, the method of transmitting and receiving a signal in a multiple antenna system, using all antennas in a certain transmission sector in a transmitter having a plurality of sectors having different directivity. Transmitting a signal to a receiver by beamforming; Measuring, by the receiver, the SNR of the received signal and comparing it with a reference value; Transmitting a sector switching indicator to the transmitter instructing to switch the transmission sector if the measured SNR is less than the reference value; And transmitting, by the transmitter, the signal to the receiver by beamforming using all antennas of the switched sector after switching the transmission sector by the received sector switching indicator.
Sector Switching, Antenna Switching, Adaptive Modulation, Diversity, Modulation Mode

Description

Method for Transmitting and Receiving a Signal in Multiple Antenna System

The present invention relates to a method for transmitting and receiving signals in a multi-antenna system, and more particularly, to a transmitting sector or a transmission in a multi-antenna system having a plurality of transmit antennas per one sector of a transmitter having a plurality of sectors having different directivities. The present invention relates to a method for transmitting and receiving signals by selecting an antenna path and applying an adaptive modulation scheme accordingly.

The next generation mobile communication system is developing in the form of a mobile communication system for providing services capable of high-speed, high-capacity data transmission and reception to mobile terminals. However, unlike the wired channel environment, the wireless channel environment of the mobile communication system is inevitable due to various factors such as multipath interference, shadowing, propagation attenuation, time-varying noise, interference, and fading. Occurs and loss of information occurs. In addition, the available frequency band of a wireless channel is very limited.

Therefore, next-generation mobile communication systems must utilize limited bandwidth and power resources for reliable transmission at high data rates in a channel with varying wireless environments. Adaptive modulation and antenna diversity are the most important factors that enable this technology in next generation communication systems.

Adaptive Modulation can increase frequency efficiency in a wireless channel environment. Adaptive modulation is a method of adaptively applying a modulation scheme by adjusting modulation parameters such as constellation size and coding rate to overcome a changing channel while maintaining an instantaneous error rate below a target value. The modulation mode is mainly selected based on a comparison result of several predetermined reference values and the received signal strength. That is, the transmitter receives the feedback of the transmission and reception channel state from the receiver and transmits a signal by applying a modulation method having a high transmission rate when the channel state is good, and applies a modulation method having a low transmission rate when the channel state is poor. Can be reduced.

On the other hand, the diversity scheme is used to remove the instability of communication from fading phenomenon, and one of the diversity schemes includes antenna diversity in which a transceiver has a plurality of antennas and transmits and receives using an antenna having a good channel or transmits and receives through multiple paths. There is a way. In case of a large number of receive antennas, an optimal antenna synthesis method using antenna diversity is well known maximum ratio combining (MRC).

Typically the receiver will be user terminals and it will not be easy to have multiple antennas at the receiver. In addition, such diversity combining techniques have been studied in the past independently of the adaptive modulation technique and have not been considered together. Therefore, as a way to improve the reliability while efficiently utilizing the limited resources of the radio channel, the necessity of combining diversity techniques with multiple antennas and adaptive modulation schemes at the transmitting end.

On the other hand, in a communication system using a frequency band above the millimeter band including the tera band, the radio waves have a characteristic of going straight. In order to apply the radio waves having the characteristic of going straight to a wireless personal area network, low power is required. For example, directional antennas are commonly used in wireless personal short-range communications.

However, when a low power directional antenna is used, omnidirectional communication is not possible. In order to overcome this problem, a method for enabling an optimal communication connection through a switching action between a plurality of different directivity antennas has been proposed.

The beam sector selection method, which always selects the optimal directivity among these methods, is inconvenient to monitor all sectors at all times, whereas the beam sector switching method requires a specific required signal-to-noise ratio. (Signal to Noise Ratio, hereinafter referred to as "SNR") If the reference value is exceeded, it is possible to communicate in the connected sector, switch to another sector only when it is lower than the reference value, and then compare the SNR to select the corresponding sector. The complexity of the beam sector selection can be reduced while maintaining the required communication performance. Furthermore, by using multiple antennas per arbitrary sector, the SNR of the received signal of each sector can be improved.

An object of the present invention is to achieve efficient sector selection through switching between sectors having different directivity using multiple antennas, and to use sector switching in a multi-antenna system that can improve the signal-to-noise ratio of a received signal. It is to provide a method for transmitting and receiving signals.

Another object of the present invention is to provide a signal transmission / reception method using sector switching in a multi-antenna system capable of efficiently transmitting data while ensuring reliability by combining an adaptive modulation scheme and a multi-antenna diversity technique of a transmitter.

In the signal transmission / reception method according to the present invention, in a signal transmission / reception method in a multi-antenna system, in a transmitter having a plurality of sectors having different directivities, a receiver may be formed by beamforming using all antennas in an arbitrary transmission sector. Transmitting a signal to the network; Measuring, by the receiver, the SNR of the received signal and comparing it with a reference value; Transmitting a sector switching indicator to the transmitter instructing to switch the transmission sector if the measured SNR is less than the reference value; And transmitting, by the transmitter, the signal to the receiver by beamforming using all antennas of the switched sector after switching the transmission sector by the received sector switching indicator.

Another aspect of the signal transmission and reception method according to the present invention is a signal transmission / reception method in a multi-antenna system, in which a transmitter having a plurality of sectors having different directivity signals to a receiver sequentially from the first antenna of an arbitrary transmission sector. Transmitting; Selecting, by the receiver, an antenna having the largest SNR by comparing the SNRs of signals received for each antenna of the transmission sector; Comparing the SNR of the selected antenna with a reference value; Feeding back a sector switching indicator to the transmitter instructing to switch the transmission sector if the SNR of the selected antenna is less than the reference value as a result of the comparison; And transmitting the signal to the receiver sequentially from the first antenna of the switched sector after the transmitter switches the transmitted sector by the received sector switching indicator.

Another aspect of the method for transmitting and receiving a signal according to the present invention is a method for transmitting and receiving a signal in a multi-antenna system, wherein a transmitter having a plurality of sectors having different directivities transmits a signal to a receiver through an arbitrary antenna of a transmitting sector. Making; Measuring, by the receiver, the SNR of the received signal and comparing it with a reference value; Feeding back an antenna switching indicator indicating to switch the transmitting antenna of the transmitting sector to the transmitter when the measured SNR is less than the reference value; And after the transmitter switches the transmitting antenna by the received antenna switching indicator, transmitting a signal to the receiver through the switched antenna.

According to the present invention, a sector having an optimal directivity can be selected by sector switching without the inconvenience of having to monitor all sectors, and an optimal communication connection is possible by selecting an antenna that can obtain an optimum antenna gain in the sector. Therefore, the present invention can be optimally used for the upcoming millimeter (wave) -based wireless personal area network (WPAN) system.

In addition, according to the present invention, by combining an adaptive modulation scheme and multiple transmit antenna diversity techniques, data can be efficiently transmitted while ensuring reliability.

The present invention provides a method for enabling optimal communication connection through intersector switching when a signal transmitted using a plurality of antennas in any transmission sector of a transmitter having a plurality of sectors having different directivities is lower than a reference signal. Suggest. That is, the present invention relates to a method for transmitting and receiving a signal using a plurality of antennas in any sector of the transmitter, a method for transmitting a signal using beamforming in a plurality of antennas in any sector of the transmitter, any of the transmitter We propose an antenna selection method for optimal communication connection in multiple antennas in one sector and a switching method of multiple antennas in any one sector of a transmitter.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is an exemplary diagram of a transmitter composed of a plurality of antennas each sector has a 90 degree directivity according to a preferred embodiment of the present invention, Figure 2 is a schematic configuration diagram of a signal transmitting and receiving device according to a preferred embodiment of the present invention 3 and 4 are schematic configuration diagrams of a transmitter and a receiver according to a preferred embodiment of the present invention.

1 to 4, a signal transceiving device according to an exemplary embodiment of the present invention includes a transmitter 100 including a plurality of antennas 110-1, 110-2,. And a receiver 200 comprising an antenna 210.

Although FIG. 1 shows that each sector of the transmitter has a directivity of 90 degrees, this may be changed as necessary, and each sector includes a plurality of antennas.

As shown in FIG. 3, the transmitter 100 includes a modulator 120, a switching controller 130, and a transceiver 140. In addition, the receiver 200 includes a transceiver 220, an SNR measurement unit 230, a switching determination unit 240, and a modulation mode determination unit 250 as shown in FIG. 4.

The signal to be transmitted from the transmitter 100 to the receiver 200 is modulated by the modulator 120 and among the plurality of antennas 110-1, 110-2,..., 110 -L in an arbitrary sector. It may be transmitted through either one or through all antennas in any sector by codebook based beamforming.

The transmission signal passing through the wireless channel is input to the receiver 200 through the reception antenna 210. Here, the plurality of antennas 110-1, 110-2,..., 110 -L of the transmitter 100 preferably have directivity. When there are L antennas 110 of the transmitter 100, each antenna has a directivity of 2π / L. When the transmission antennas 110-1, 110-2,..., 110 -L have a specific directivity, power gain can be obtained by the degree of directivity as compared to an omnidirectional antenna of a full orientation. That is, the power gain of the transmitter 101 may be as large as L.

The transmitter 100 has one RF (Radio Frequency) chain to transmit any one of a plurality of antennas (110-1, 110-2, ..., 110-L) in transmitting a transmission signal to the receiver 200 By using one or by codebook based beamforming, all antennas in any sector are used.

That is, when the transmitter 100 transmits a signal to the receiver 200 for the first time, the transmitter 100 selects any one sector and then selects all sectors in the sector selected by codebook-based beamforming. A signal may be transmitted to the receiver 200 through an antenna, a random sector may be selected, and then a signal may be sequentially transmitted to the receiver 200 from the first antenna of the selected sector. Any antenna may be selected in the selected sector, and a signal may be transmitted to the receiver 200 through the selected antenna. Meanwhile, when the transmitter 100 receives a switching indicator indicating switching of a sector or an antenna from the receiver 200, the transmitter 100 switches the current transmission sector to another sector or the current transmission antenna to another antenna.

As the modulation scheme performed by the modulator 120, an adaptive modulation scheme is applied according to the wireless channel environment. In this case, M-ary quadrature amplitude modulation (M-QAM) is applied according to the radio channel environment. In the adaptive modulation scheme according to the present invention, the modulation mode determined by the modulation mode determiner 250 of the receiver 200 may be fed back to perform adaptive modulation accordingly.

The SNR measuring unit 230 of the receiver 200 measures the SNR of the signal received through the receiving antenna 210. Thereafter, the switching determination unit 240 compares the measured SNR with a specific reference value and determines to switch the transmission sector or the transmission antenna of the transmitter 100 when the SNR is smaller than the reference value. When it is determined that the transmitter sector or the transmit antenna of the transmitter 100 is to be switched, the receiver 200 feeds back a switching indicator to the transmitter 100, and thus the transmitter 100 returns the switching controller 130. Switch the current transmission sector or antenna 103 via.

In this case, the switching indicator may be fed back when the switching determination unit 240 determines to switch the transmission sector or the transmission antenna, and may also change the switching indicator value even when it is determined that the switching sector or the transmission antenna is not to be switched. It may be fed back to the transmitter 100. The switching indicator may be represented by 1 bit. For example, '1' may indicate switching and '0' may not switch. Meanwhile, the switching indicator may be fed back from the receiver 200 to the transmitter 100 together with or separately from a modulation mode index to be described later.

The modulation mode determiner 250 of the receiver 200 determines a modulation mode by using the measured SNR. In particular, when the SNR is divided into N regions, the SNR measured by the SNR measuring unit 230 belongs to any one of the N regions. That is, the measured SNR is the nth region of the N regions.

Figure 112008047234709-pat00001
In case of, the receiver 200 feeds back a modulation mode index of n to the transmitter 100, and the transmitter 101 modulates 2 n -QAM. That is, the SNR is
Figure 112008047234709-pat00002
Less than
Figure 112008047234709-pat00003
If greater, the receiver determines the modulation mode scheme as 2 n -QAM. N has a value from 2 to N, and 2 n = M is called a constellation size.

Each boundary point of the N regions

Figure 112008047234709-pat00004
Depends on the target Bit Error Rate (BER). When the target BER is 1%, 0.1%, and 0.01%, the boundary values of the SNR that distinguish each modulation level are shown in Table 1 below.

Figure 112008047234709-pat00005

The receiver 200 feeds back an index indicating the determined modulation mode to the transmitter 100. In this case, it is preferable that a short guard period is periodically inserted into the signal in consideration of a time for determining whether to switch or a modulation mode by measuring SNR of the signal received by the receiver 200.

Meanwhile, the specific reference value may be determined as the minimum modulation size to satisfy the required minimum transmission speed and to limit the number of sector or antenna switching to a minimum, and may also be determined as the maximum modulation size in order to maximize frequency efficiency. The size of the reference value may be determined by the transmitter 100 and transmitted to the receiver 200, or may be determined by the receiver 200.

5 to 7, the signal transmission and reception method according to the first embodiment of the present invention will be described in detail.

5 is a signal flow diagram between a transmitter and a receiver according to the first preferred embodiment of the present invention.

Referring to FIG. 5, first, the transmitter modulates a signal to be transmitted and then transmits the modulated signal to the receiver (S501). In this case, the transmitter selects one of a plurality of sectors and then transmits the signal through all antennas of the selected sector by codebook-based beamforming. When the transmitter and the receiver perform the first communication, the transmitter transmits a signal using all antennas of a specific sector by beamforming, that is, information indicating a beamforming transmission mode. May be transmitted to the receiver. In this case, the beamforming transmission mode indication information may include reference value information for determining whether to switch the transmission sector in the receiver and information on the number of sectors of the transmitter.

Thereafter, the receiver measures the SNR of the received signal and determines whether to switch the transmission sector by comparing the SNR with the reference value (S503). That is, the receiver determines not to switch the transmission sector when the measured SNR is greater than or equal to the reference value, and determines to switch the transmission sector when the measured SNR is less than the reference value. As described above, the reference value may be determined at the transmitter and transmitted to the receiver, and may be a predetermined value or adaptively changed at the receiver.

The receiver transmits a sector switching indicator to the transmitter according to the sector switching determined in step S503 (S505). The sector switching indicator may be sent only when the transmission sector is determined to be switched. Upon receiving the sector switching indicator, the transmitter switches the current transmission sector to another sector when the sector switching indicator indicates to switch the transmission sector (S507). Thereafter, the transmitter transmits a signal to the receiver through all antennas of the transmission sector switched by codebook-based beamforming (S509).

Meanwhile, the receiver may transmit a modulation mode index corresponding to the SNR measured in step S503 to the transmitter. In this case, the receiver transmits the modulation mode index by using the same channel as the switching indicator or by using another channel. Thereafter, in step S509, the transmitter transmits a signal to a receiver according to a modulation scheme according to the modulation mode index.

The receiver determined to switch continuously by the number of transmission sectors, and the SNRs of all paths of the transmission sectors

Figure 112008047234709-pat00006
In the lower case, the receiver may operate with the following two options in the process of transmitting the modulation mode index. Although the receiver does not satisfy the target BER, the receiver may request the transmitter to transmit a signal in a lowest modulation mode, that is, a quadrature phase shift keying (QPSK) modulation method (option 1). Alternatively, the receiver may request the transmitter to store the data in a buffer and wait until the next guard period for a better channel environment (option 2).

Depending on which value the reference value is operated in, it may be operated in Minimum Estimation Schemes and Bandwidth Efficient Schemes.

First, the Minimum Estimation Schemes are explained as follows.

The purpose of the Minimum Estimation Schemes is to minimize the number of sector switching at the transmitter. At this time, the reference value for sector switching in the receiver is the lowest reference value, that is,

Figure 112008047234709-pat00007
Set to. The SNR in the current transmitting sector at the receiver is equal to the reference value.
Figure 112008047234709-pat00008
If greater than the SNR value of the current sector path to the thresholds for modulation mode determination (
Figure 112008047234709-pat00009
). The SNR is
Figure 112008047234709-pat00010
Less than
Figure 112008047234709-pat00011
If greater, the receiver determines the modulation mode to n. At this time, the modulation scheme is 2 n -QAM. The receiver feeds back the determined modulation mode to the transmitter, and the transmitter modulates a subsequent burst of data in the feedback modulation scheme.

Meanwhile, the SNR of the current sector

Figure 112008047234709-pat00012
Is smaller than indicative of sector switching to the transmitter and sector switching for all transmission sectors, i.e., SNR for all transmission sectors
Figure 112008047234709-pat00013
If smaller, the receiver can operate with two options: The receiver may request the transmitter to transmit the signal in the lowest modulation mode, that is, QPSK modulation, even if the target BER is not satisfied (option 1). Alternatively, the receiver may request the transmitter to store the data in a buffer and wait until the next guard period for a better channel environment (option 2). In option 1, the receiver may receive the signal using the most recent sector path or feed back the best sector path to the transmitter to receive the signal over the best transmission sector.

Next, Bandwidth Efficient Schemes will be described.

The purpose of the Bandwidth Efficient Schemes is to maximize frequency efficiency. In this case, the highest modulation mode is needed to increase frequency efficiency. That is, the receiver sets the reference value as the highest value,

Figure 112008047234709-pat00014
Set to. The receiver determines that the SNR of the current sector path is the reference value.
Figure 112008047234709-pat00015
If larger, stop sector switching and request that the burst of data leading to the transmitter be modulated and transmitted with 2N- QAM. If the SNR of the current sector path is the reference value
Figure 112008047234709-pat00016
If smaller, the SNR is the reference value
Figure 112008047234709-pat00017
It always feeds back to the transmitter to find and switch to a larger sector path. SNRs for all sectors are above the reference value
Figure 112008047234709-pat00018
If smaller, the receiver determines the modulation mode according to the SNR for the last sector path and feeds back to the transmitter, or compares the SNRs of all sector paths to determine the SNR with the largest value, and transmits corresponding to the determined SNR. Sector information and its modulation mode may be determined and fed back to the transmitter.

In the worst case, the SNR of all antenna paths

Figure 112008047234709-pat00019
If it is smaller, it can be operated with two options as with the Minimum Estimation Schemes. The receiver may request the transmitter to transmit the signal in the lowest modulation mode, that is, QPSK modulation, even if the target BER is not satisfied (option 1). Alternatively, the receiver may request the transmitter to store data in a buffer and wait until the next guard period for a better channel environment (option 2).

6 is a flowchart illustrating a signal transmission and reception procedure in a transmitter according to a first embodiment of the present invention.

Referring to FIG. 6, first, a transmitter modulates a signal to be transmitted to a receiver and transmits it to the receiver (S601). In this case, the transmitter selects one of a plurality of sectors and then transmits the signal through all antennas of the selected sector by codebook-based beamforming. When the transmitter and the receiver perform the first communication, the transmitter transmits a signal using all antennas of a specific sector by beamforming, that is, information indicating a beamforming transmission mode. May be transmitted to the receiver. In this case, the beamforming transmission mode indication information may include reference value information and information on the number of transmission sectors for determining whether to switch the transmission sector in the receiver. Then, the transmitter receives the sector switching indicator and the modulation mode index from the receiver (S603). In this case, the sector switching indicator and the modulation mode index may be received through the same channel or different channels.

In step S605, the transmitter determines whether the sector switching indicator indicates switching of a transmission sector. If the determination indicates that sector switching is instructed, the receiver moves to step S607 to switch the current transmission sector to another sector. If the determination result does not indicate sector switching, the transmitter proceeds to step S609. In step S609, the transmitter modulates the signal according to the modulation mode corresponding to the received modulation mode index and transmits the signal to the receiver.

7 is a flowchart illustrating a signal transmission and reception procedure in a receiver according to a first embodiment of the present invention.

Referring to FIG. 7, the receiver receives a signal transmitted from a transmitter (S701). The receiver measures the SNR of the received signal (S703).

Thereafter, the receiver compares the measured SNR with a specific reference value (S705). At this time, the reference value may be adaptively changed according to the type of communication with the transmitter or a value determined by itself or transmitted through the transmitter as described above.

As a result of the comparison in step S705, the receiver performs step S707 when the SNR is greater than or equal to the reference value, and performs step S709 when the SNR is less than the reference value.

In step S707, the receiver determines thresholds for determining the SNR and modulation mode.

Figure 112008047234709-pat00020
), The SNR is
Figure 112008047234709-pat00021
Less than
Figure 112008047234709-pat00022
If greater, the receiver determines the modulation mode as n and feeds it back to the transmitter.

In step S709, the receiver feeds back a sector switching indicator and a modulation mode index indicating the sector switching to the transmitter. At this time, the method of determining the modulation mode index is the same as in step S707.

Hereinafter, a method of transmitting and receiving a signal according to a second preferred embodiment of the present invention will be described in detail with reference to FIGS. 8 to 10.

8 is a signal flow diagram between a transmitter and a receiver according to a second preferred embodiment of the present invention.

Referring to FIG. 8, the transmitter first modulates a signal to be transmitted and then transmits the modulated signal to the receiver (S801). At this time, the transmitter selects one sector from a plurality of sectors and sequentially transmits the signal to the receiver starting from the first antenna of the sector. The signal is preferably a signal that can measure the state of the channel at the receiving side like the pilot signal. When the transmitter and the receiver perform the first communication, the transmitter may transmit information indicating that a signal is transmitted using multiple antennas of an arbitrary sector, that is, information indicating a multiple transmit antenna mode, to the receiver. In this case, the multi-transmit antenna mode indication information may include reference value information for determining whether a receiver selects a transmit antenna, information on the number of transmit sectors and the number of transmit antennas, and the like.

Then, when the receiver receives signals from all antennas of a certain sector, compares the SNR of the received signal for each antenna, selects the antenna having the largest SNR, and then selects the corresponding transmit antenna by comparing the value with a reference value. Or, it is determined whether to perform sector switching (S803). That is, the receiver determines to select the antenna with the largest SNR when the largest value of the SNRs of signals sequentially received from all antennas of any sector is greater than or equal to the reference value, and from all transmitting antennas of any sector If the largest value of the SNRs of the sequentially received signals is smaller than the reference value, it is determined to switch the sector. As described above, the reference value may be determined at the transmitter and transmitted to the receiver, and may be a predetermined value or adaptively changed at the receiver.

The receiver transmits an antenna selection indicator or a sector switching indicator to the transmitter according to whether antenna selection or sector switching is determined in step S803 (S805). The antenna selection indicator may be transmitted only when it is determined that the transmit antenna having the largest SNR is selected. Receiving the antenna selection indicator or sector switching indicator, the transmitter selects the antenna as the transmitting antenna when the antenna selection indicator indicates to select the antenna having the largest SNR, and when the switching indicator indicates switching the transmission sector, The transmission sector of S is switched to another sector (S807). Thereafter, the transmitter transmits a signal to the receiver through the selected transmission antenna or the switched transmission sector (S809).

Meanwhile, the receiver may transmit a modulation mode index corresponding to the SNR of the signal received in step S803 to the transmitter. In this case, the receiver transmits the modulation mode index by using the same channel as the antenna selector indicator and the sector switching indicator or by using another channel. Thereafter, in step S809, the transmitter transmits a signal to a receiver according to a modulation scheme according to the modulation mode index.

The receiver determined to switch continuously by the number of transmit sectors, and the SNRs of all paths of the transmit antenna

Figure 112008047234709-pat00023
In the lower case, the receiver may operate with the following two options in the process of transmitting the modulation mode index. The receiver may request the transmitter to transmit the signal in the lowest modulation mode, that is, QPSK modulation, even if the target BER is not satisfied (option 1). Alternatively, the receiver may request the transmitter to store the data in a buffer and wait until the next guard period for a better channel environment (option 2).

Depending on which value the reference value is operated in, it may be operated in Minimum Estimation Schemes and Bandwidth Efficient Schemes.

First, the Minimum Estimation Schemes are explained as follows.

The purpose of the Minimum Estimation Schemes is to minimize the number of sector switching at the transmitter. At this time, the reference value for sector switching in the receiver is the lowest reference value, that is,

Figure 112008047234709-pat00024
Set to. The largest value of the SNRs of the signals received from all antennas of any one sector is the reference value.
Figure 112008047234709-pat00025
If it is greater than the SNR value of the antenna path having the largest SNR of the sector, the threshold values for determining the modulation mode (
Figure 112008047234709-pat00026
). The SNR is
Figure 112008047234709-pat00027
Less than
Figure 112008047234709-pat00028
If greater, the receiver determines the modulation mode to n. At this time, the modulation scheme is 2 n -QAM. The receiver feeds back the determined modulation mode to the transmitter, and the transmitter modulates a subsequent burst of data in the feedback modulation scheme.

Meanwhile, the largest value of the SNRs of the signals received from all antennas of the current transmission sector is

Figure 112008047234709-pat00029
Is smaller than indicative of sector switching to the transmitter and sector transmission for all transmission sectors, i.e., the largest value of the SNRs of signals received from the antennas of all transmission sectors
Figure 112008047234709-pat00030
If smaller, the receiver can operate with two options: The receiver may request the transmitter to transmit the signal in the lowest modulation mode, that is, QPSK modulation, even if the target BER is not satisfied (option 1). Alternatively, the receiver may request the transmitter to store the data in a buffer and wait until the next guard period for a better channel environment (option 2). In option 1, the receiver may receive the signal using the most recent antenna path or feed back the best antenna path to the transmitter to receive the signal through the best transmitting antenna.

Next, Bandwidth Efficient Schemes will be described.

The purpose of the Bandwidth Efficient Schemes is to maximize frequency efficiency. In this case, the highest modulation mode is needed to increase frequency efficiency. That is, the receiver sets the reference value as the highest value,

Figure 112008047234709-pat00031
Set to. The receiver determines that the largest value of the SNRs of the signals received from all antennas of the current transmission sector is the reference value.
Figure 112008047234709-pat00032
If larger, do not perform sector switching and transmit the SNR of the sector in the largest antenna, while the data burst leading to the transmitter requests transmission by modulating 2 N -QAM. If the SNR of the current antenna path is the reference value
Figure 112008047234709-pat00033
If smaller, the SNR is the reference value
Figure 112008047234709-pat00034
Feed back to the transmitter to find a larger antenna path and sector switch. The SNR for the antennas of all sectors is equal to the reference value
Figure 112008047234709-pat00035
If smaller, the receiver determines the modulation mode according to the SNR for the last antenna path and feeds it back to the transmitter, or compares the SNRs of the antenna paths of all sectors to determine the SNR with the largest value and corresponds to the determined SNR. Antenna information of a transmission sector and a modulation mode thereof may be determined and fed back to the transmitter.

In the worst case, the SNR of all antenna paths

Figure 112008047234709-pat00036
If it is smaller, it can be operated with two options as with the Minimum Estimation Schemes. The receiver may request the transmitter to transmit the signal in the lowest modulation mode, that is, QPSK modulation, even if the target BER is not satisfied (option 1). Alternatively, the receiver may request the transmitter to store the data in a buffer and wait until the next guard period for a better channel environment (option 2).

9 is a flowchart illustrating a signal transmission and reception procedure in a transmitter according to a second embodiment of the present invention.

Referring to FIG. 9, first, the transmitter modulates a signal to be transmitted to the receiver and transmits the signal to the receiver (S901). At this time, the transmitter selects one sector from a plurality of sectors and sequentially transmits the signal to the receiver starting from the first antenna of the sector. In this case, the transmitter may transmit multi-transmit antenna mode information indicating that the multi-transmit antenna is used to the receiver, and the multi-transmit antenna mode information may include the number of transmit antennas and reference value information for determining sector switching. . Thereafter, the transmitter receives the modulation mode index together with the antenna selection indicator and / or the sector switching indicator from the receiver (S903). In this case, the antenna selection indicator, sector switching indicator, and modulation mode index may be received through the same channel or different channels.

The transmitter determines whether the antenna selection indicator indicates the selection of a transmitting antenna (S905). If the determination indicates that the antenna is selected, the transmitter moves to step S907 to select the antenna selected by the antenna selection indicator in the current transmission sector. The transmitter proceeds to step S909 when sector determination is instructed without indicating antenna selection. In step S909, the transmitter switches the current transmission sector to another sector and proceeds to step S901. In step S911, the transmitter modulates a signal according to the modulation mode corresponding to the received modulation mode index and transmits the signal to the receiver through the selected antenna.

10 is a flowchart illustrating a signal transmission and reception procedure in a receiver according to a second embodiment of the present invention.

Referring to FIG. 10, the receiver receives signals sequentially transmitted from all antennas in any one sector of the transmitter (S1001). The receiver measures the SNR of the signal received for each antenna and receives the signal from all antennas of one sector, and selects the antenna having the largest SNR value (S1003).

Thereafter, the receiver compares the SNR of the selected antenna with a specific reference value (S1005). At this time, the reference value may be adaptively changed according to the type of communication with the transmitter or a value determined by itself or transmitted through the transmitter as described above.

As a result of the comparison in step S1005, when the SNR value of the selected antenna is greater than or equal to the reference value, the receiver performs step S1007, and performs the step S1009 when the SNR value of the selected antenna is smaller than the reference value.

In step S1007, the receiver feeds back to the transmitter a sector switching indicator indicating no sector switching, an antenna selection indicator indicating a signal transmission on an antenna having the largest SNR value, and a modulation mode index. In this case, the switching indicator may be represented by 1 bit. For example, '1' may indicate switching and '0' may not switch. In addition, as the information for the antenna selection indicator, the number of bits of the minimum integer value larger than Log 2 X is required (where 'X' is the number of antennas in the corresponding sector).

In this case, the modulation mode index is the SNR of the receiver having the largest value and thresholds for determining a modulation mode (

Figure 112008047234709-pat00037
), The SNR is
Figure 112008047234709-pat00038
Less than
Figure 112008047234709-pat00039
If larger, the modulation mode is determined as n and fed back to the transmitter.

In step S1009, the receiver feeds back a sector switching indicator indicating the sector switching to the transmitter.

Hereinafter, a signal transmission and reception method according to a third embodiment of the present invention will be described in detail with reference to FIGS. 11 to 13.

11 is a signal flow diagram between a transmitter and a receiver according to a third preferred embodiment of the present invention.

Referring to FIG. 11, first, a transmitter modulates a signal to be transmitted and then transmits a modulated signal to a receiver (S1101). At this time, the transmitter transmits the signal through an arbitrarily selected antenna in any sector. When the transmitter and the receiver perform the first communication, the transmitter may transmit information indicating that a signal is transmitted using multiple antennas, that is, information indicating a multiple transmit antenna mode, to the receiver. In this case, the multi-transmit antenna mode indication information may include reference value information for determining whether to switch the transmit antenna in the receiver, information on the number of transmit sectors and transmit antennas.

Thereafter, the receiver measures the SNR of the received signal and determines whether to switch the transmission antenna by comparing the SNR with the reference value (S1103). That is, the receiver determines not to switch the transmitting antenna when the measured SNR is greater than or equal to the reference value, and determines to switch the transmitting antenna when the measured SNR is smaller than the reference value. As described above, the reference value may be determined at the transmitter and transmitted to the receiver, and may be a predetermined value or adaptively changed at the receiver.

The receiver transmits an antenna switching indicator to the transmitter according to whether the antenna is switched in step S1103 (S1105). The antenna switching indicator may be transmitted only when the transmitting antenna is determined to be switched. The transmitter receiving the antenna switching indicator switches the current transmission antenna to another antenna when the antenna switching indicator indicates to switch the transmission antenna (S1107). Thereafter, the transmitter transmits a signal to the receiver through the switched transmission antenna (S1109).

Meanwhile, the receiver may transmit a modulation mode index corresponding to the SNR measured in step S1103 to the transmitter. In this case, the receiver transmits the modulation mode index by using the same channel as the switching indicator or by using another channel. Thereafter, in step S1109, the transmitter transmits a signal to a receiver according to a modulation scheme according to the modulation mode index.

Although the receiver determines to switch continuously by the number of transmit antennas in any sector, sector switching is performed when the SNR values of all paths of the transmit antennas are lower than the reference value.

The receiver determined to switch continuously by the number of transmission sectors, and the SNRs of all antennas of the transmission sector

Figure 112008047234709-pat00040
In the lower case, the receiver may operate with the following two options in the process of transmitting the modulation mode index. The receiver may request the transmitter to transmit the signal in the lowest modulation mode, that is, QPSK modulation, even if the target BER is not satisfied (option 1). Alternatively, the receiver may request the transmitter to store the data in a buffer and wait until the next guard period for a better channel environment (option 2).

Depending on which value the reference value is operated in, it may be operated in Minimum Estimation Schemes and Bandwidth Efficient Schemes.

First, the Minimum Estimation Schemes are explained as follows.

The purpose of the Minimum Estimation Schemes is to minimize the number of antenna switching at the transmitter. At this time, the reference value for the antenna switching in the receiver is the lowest reference value, that is,

Figure 112008047234709-pat00041
Set to. The SNR at the current transmitting antenna at the receiver is equal to the reference value.
Figure 112008047234709-pat00042
If greater than the SNR value of the current antenna path to the thresholds for modulation mode determination (
Figure 112008047234709-pat00043
). The SNR is
Figure 112008047234709-pat00044
Less than
Figure 112008047234709-pat00045
If greater, the receiver determines the modulation mode to n. At this time, the modulation scheme is 2 n -QAM. The receiver feeds back the determined modulation mode to the transmitter, and the transmitter modulates a subsequent burst of data in the feedback modulation scheme.

Meanwhile, the SNR of the current antenna

Figure 112008047234709-pat00046
Is smaller than instructing the transmitter to switch the antenna and instructing the antenna switching for the antennas of all transmission sectors, i.
Figure 112008047234709-pat00047
If smaller, the receiver can operate with two options: The receiver may request the transmitter to transmit the signal in the lowest modulation mode, that is, QPSK modulation, even if the target BER is not satisfied (option 1). Alternatively, the receiver may request the transmitter to store the data in a buffer and wait until the next guard period for a better channel environment (option 2). In option 1, the receiver may receive the signal using the most recent antenna path or feed back the best antenna path to the transmitter to receive the signal through the best transmitting antenna.

Next, Bandwidth Efficient Schemes will be described.

The purpose of the Bandwidth Efficient Schemes is to maximize frequency efficiency. In this case, the highest modulation mode is needed to increase frequency efficiency. That is, the receiver sets the reference value as the highest value,

Figure 112008047234709-pat00048
Set to. The receiver indicates that the SNR of the current antenna path is the reference value.
Figure 112008047234709-pat00049
If larger, switch off the antenna and request that the data burst leading to the transmitter be modulated and transmitted with 2N- QAM. If the SNR of the current antenna path is the reference value
Figure 112008047234709-pat00050
If smaller, the SNR is the reference value
Figure 112008047234709-pat00051
It always feeds back to the transmitter to find and switch to the larger antenna path. The SNRs for the antennas of all transmit sectors are above the reference value
Figure 112008047234709-pat00052
If smaller, the receiver determines the modulation mode according to the SNR for the last antenna path and feeds it back to the transmitter, or compares the SNRs of all antenna paths to determine the SNR with the largest value, and transmits corresponding to the determined SNR. Antenna information and a modulation mode thereof may be determined and fed back to the transmitter.

In the worst case, the SNR of all antenna paths

Figure 112008047234709-pat00053
If it is smaller, it can be operated with two options as with the Minimum Estimation Schemes. The receiver may request the transmitter to transmit the signal in the lowest modulation mode, that is, QPSK modulation, even if the target BER is not satisfied (option 1). Alternatively, the receiver may request the transmitter to store data in a buffer and wait until the next guard period for a better channel environment (option 2).

12 is a flowchart illustrating a signal transmission and reception procedure in a transmitter according to a third embodiment of the present invention.

Referring to FIG. 12, first, a transmitter modulates a signal to be transmitted to a receiver and transmits the signal to the receiver (S1201). In this case, the transmitter may transmit multiple transmit antenna mode information indicating that the multiple transmit antenna is used to the receiver. In this case, the multi-transmit antenna mode information may include the number of transmit antennas and reference value information for determining the switching. Then, the transmitter receives the antenna switching indicator and the modulation mode index from the receiver (S1203). In this case, the antenna switching indicator and the modulation mode index may be received through the same channel or different channels.

The transmitter determines whether the antenna switching indicator instructs the switching of the transmitting antenna (S1205). If the determination indicates that the antenna is switched, the receiver moves to step S1207 to determine whether there is an antenna remaining in the current transmission sector, and if there is a remaining antenna, the receiver moves to step S1209 to switch the current transmission antenna to another antenna. . If there is no antenna remaining in the current transmission sector as a result of the determination in step S1207, the process moves to step S1211 to switch the current transmission sector to another sector. If the determination result of step S1205 does not indicate antenna switching, the transmitter proceeds to step S1213. In step S1213, the transmitter modulates the signal according to the modulation mode corresponding to the received modulation mode index and transmits the signal to the receiver.

13 is a flowchart illustrating a signal transmission and reception procedure in a receiver according to a third embodiment of the present invention.

Referring to FIG. 13, a receiver receives a signal transmitted from a transmitter (S1301). The receiver measures the SNR of the received signal (S1303).

Thereafter, the receiver compares the measured SNR with a specific reference value (S1305). At this time, the reference value may be adaptively changed according to the type of communication with the transmitter or a value determined by itself or transmitted through the transmitter as described above.

As a result of the comparison in step S1305, if the SNR is greater than or equal to the reference value, the receiver performs step S1307. If the SNR is less than the reference value, the receiver performs step S1309.

In step S1307, the receiver sets thresholds for determining the SNR and modulation mode.

Figure 112008047234709-pat00054
), The SNR is
Figure 112008047234709-pat00055
Less than
Figure 112008047234709-pat00056
If greater, the receiver determines the modulation mode as n and feeds it back to the transmitter.

In step S1309, the receiver feeds back an antenna switching indicator and a modulation mode index indicating the antenna switching to the transmitter. At this time, the method of determining the modulation mode index is the same as in step S1307.

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

1 exemplarily shows a transmitter according to a preferred embodiment of the present invention.

2 is a view schematically showing a signal transmission and reception apparatus according to a preferred embodiment of the present invention.

3 is a diagram schematically showing a configuration of a transmitter according to a preferred embodiment of the present invention.

4 is a diagram schematically showing a configuration of a receiver according to a preferred embodiment of the present invention.

5 is a signal flow diagram between a transmitter and a receiver according to the first preferred embodiment of the present invention.

6 is a flowchart illustrating a signal transmission and reception procedure in a transmitter according to a first embodiment of the present invention.

7 is a flowchart illustrating a signal transmission and reception procedure in a receiver according to a first embodiment of the present invention.

8 is a signal flow diagram between a transmitter and a receiver according to a second preferred embodiment of the present invention.

9 is a flowchart illustrating a signal transmission and reception procedure in a transmitter according to a second embodiment of the present invention.

10 is a flowchart illustrating a signal transmission and reception procedure in a transmitter according to a second preferred embodiment of the present invention.

11 is a signal flow diagram between a transmitter and a receiver according to the third preferred embodiment of the present invention.

12 is a flowchart illustrating a signal transmission and reception procedure in a transmitter according to a third embodiment of the present invention.

13 is a flowchart illustrating a signal transmission and reception procedure in a transmitter according to a third embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

100 transmitter 120 modulator

130: switching control unit 200: receiver

230: SNR measurement unit 240: switching determination unit

250: modulation mode determination unit

Claims (26)

  1. In the signal transmission and reception method in a multi-antenna system,
    Transmitting beamforming transmission mode information indicating that signals are transmitted using all antennas of a specific sector by beamforming in a transmitter having a plurality of sectors having different directivities;
    Transmitting a signal from the transmitter to the receiver by beamforming using all antennas in any transmission sector;
    Measuring, by the receiver, the SNR of the received signal and comparing it with a reference value;
    Transmitting a sector switching indicator to the transmitter instructing to switch the transmission sector if the measured SNR is less than the reference value; And
    Transmitting, by the transmitter, a signal to the receiver by beamforming using all antennas of the switched sector after switching the transmission sector by the received sector switching indicator;
    The beamforming transmission mode information includes at least one of the reference value and the information of the number of transmission sectors.
  2. The method according to claim 1,
    Determining, by the receiver, a modulation mode corresponding to the measured SNR; And
    Transmitting a modulation mode index to the transmitter according to the determined modulation mode,
    And the transmitter transmits a signal in a modulation mode corresponding to the received modulation mode index.
  3. The method according to claim 2,
    SNR of the signal received by the receiver is a threshold for determining a modulation mode,
    Figure 112008047234709-pat00057
    (Where n = N, N-1, ..., 2) the SNR is
    Figure 112008047234709-pat00058
    Less than
    Figure 112008047234709-pat00059
    If greater, the modulation mode index is determined as n.
  4. delete
  5. delete
  6. The method according to claim 1,
    When the receiver continuously feeds sector switching indicators to the transmitter by the number of sectors of the transmitter, the receiver feeds back the information of the sector having the highest SNR among the multiple sectors of the transmitter to the transmitter, and the transmitter returns the SNR. A method for transmitting and receiving a signal, characterized in that for transmitting a signal through the highest sector.
  7. The method according to claim 1,
    The receiver continuously feeds sector switching indicators back to the transmitter by the number of sectors of the transmitter, and all SNRs for the plurality of transmission sectors are bounded.
    Figure 112010010267258-pat00060
    If smaller, the receiver transmits and receives a signal to the transmitter to transmit a signal in a QPSK (Quadrature Phase Shift Keying) modulation scheme.
  8. The method according to claim 1,
    The receiver continuously feeds sector switching indicators back to the transmitter by the number of sectors of the transmitter, and all SNRs for the plurality of transmit antennas are bounded.
    Figure 112010010267258-pat00061
    If smaller, the receiver transmits a request to the transmitter to store and wait for data in a buffer during a next guard period.
  9. In the signal transmission and reception method in a multi-antenna system,
    Transmitting multiple transmit antenna mode information indicating that a transmitter having a plurality of sectors having different directivity transmits a signal through multiple transmit antennas in a transmitting sector;
    Transmitting signals to the receiver sequentially from the first antenna of any transmission sector at the transmitter;
    Selecting, by the receiver, an antenna having the largest SNR by comparing the SNRs of signals received for each antenna of the transmission sector;
    Comparing the SNR of the selected antenna with a reference value;
    Feeding back a sector switching indicator to the transmitter instructing to switch the transmission sector if the SNR of the selected antenna is less than the reference value as a result of the comparison; And
    Transmitting, by the transmitter, the signal to the receiver sequentially from the first antenna of the switched sector after switching the transmitting sector by the received sector switching indicator;
    The multi-transmission antenna mode information includes at least one of the information of the transmission sector and the number of transmission antennas or the reference value.
  10. The method according to claim 9,
    If an SNR of the selected antenna is greater than the reference value as a result of the comparison, feeding back an antenna selection indicator indicating to transmit a signal from the selected antenna to the transmitter; And
    And transmitting, by the transmitter, a signal to the receiver through the selected antenna by the received antenna selection indicator.
  11. The method according to claim 9,
    Determining, by the receiver, a modulation mode corresponding to the SNR of the received signal; And
    Transmitting a modulation mode index according to the determined modulation mode to the transmitter,
    And the transmitter transmits a signal in a modulation mode corresponding to the received modulation mode index.
  12. The method of claim 11,
    SNR of the signal received by the receiver is a threshold for determining a modulation mode,
    Figure 112008047234709-pat00062
    (Where n = N, N-1, ..., 2) the SNR is
    Figure 112008047234709-pat00063
    Less than
    Figure 112008047234709-pat00064
    If greater, the modulation mode index is determined as n.
  13. delete
  14. delete
  15. The method according to claim 9,
    When the receiver continuously feeds sector switching indicators to the transmitter by the number of sectors of the transmitter, the receiver feeds back information of the antenna having the highest SNR among the multiple antennas of the transmitter to the transmitter, and the transmitter returns the SNR. Signal transmission and reception method characterized in that for transmitting the signal through the highest antenna.
  16. The method according to claim 9,
    The receiver continuously feeds sector switching indicators back to the transmitter by the number of sectors of the transmitter, and all SNRs for the multiple transmit antennas of the transmitter are bounded.
    Figure 112010010267258-pat00065
    If smaller, the receiver transmits and receives a signal to the transmitter to transmit a signal in a QPSK (Quadrature Phase Shift Keying) modulation scheme.
  17. The method according to claim 9,
    The receiver continuously feeds sector switching indicators back to the transmitter by the number of sectors of the transmitter, and all SNRs for the multiple transmit antennas of the transmitter are bounded.
    Figure 112010010267258-pat00066
    If smaller, the receiver transmits a request to the transmitter to store and wait for data in a buffer during a next guard period.
  18. In the signal transmission and reception method in a multi-antenna system,
    Transmitting multiple transmit antenna mode information indicating that a transmitter having a plurality of sectors having different directivity transmits a signal through multiple transmit antennas in a transmitting sector;
    Transmitting a signal at the transmitter to a receiver via any antenna of a transmitting sector;
    Measuring, by the receiver, the SNR of the received signal and comparing it with a reference value;
    Feeding back an antenna switching indicator indicating to switch the transmitting antenna of the transmitting sector to the transmitter when the measured SNR is less than the reference value; And
    Transmitting, by the transmitter, a signal to the receiver through the switched antenna after switching the transmitting antenna by the received antenna switching indicator;
    The multi-transmission antenna mode information includes at least one of the information of the transmission sector and the number of transmission antennas or the reference value.
  19. 19. The method of claim 18,
    After the transmitter receives the antenna switching indicator, determining whether there is a remaining antenna in the transmission sector; And
    And switching the transmission sector if there is no antenna remaining in the transmission sector as a result of the determination.
  20. 19. The method of claim 18,
    Determining, by the receiver, a modulation mode corresponding to the SNR of the received signal; And
    Transmitting a modulation mode index according to the determined modulation mode to the transmitter,
    And the transmitter transmits a signal in a modulation mode corresponding to the received modulation mode index.
  21. The method of claim 20,
    SNR of the signal received by the receiver is a threshold for determining a modulation mode,
    Figure 112008047234709-pat00067
    (Where n = N, N-1, ..., 2) the SNR is
    Figure 112008047234709-pat00068
    Less than
    Figure 112008047234709-pat00069
    If greater, the modulation mode index is determined as n.
  22. delete
  23. delete
  24. 19. The method of claim 18,
    When the receiver continuously feeds back an antenna switching indicator to the transmitter by the number of antennas of the transmitter, the receiver feeds back information on the antenna having the highest SNR among the multiple antennas of the transmitter to the transmitter, and the transmitter returns the SNR. Signal transmission and reception method characterized in that for transmitting the signal through the highest antenna.
  25. 19. The method of claim 18,
    The receiver continuously feeds back an antenna switching indicator to the transmitter by the number of antennas of the transmitter, and all SNRs for the multiple transmit antennas of the transmitter are bounded.
    Figure 112010010267258-pat00070
    If smaller, the receiver transmits and receives a signal to the transmitter to transmit a signal in a QPSK (Quadrature Phase Shift Keying) modulation scheme.
  26. 19. The method of claim 18,
    The receiver continuously feeds back an antenna switching indicator to the transmitter by the number of antennas of the transmitter, and all SNRs for the multiple transmit antennas of the transmitter are bounded.
    Figure 112010010267258-pat00071
    If smaller, the receiver transmits a request to the transmitter to store and wait for data in a buffer during a next guard period.
KR20080062865A 2008-06-30 2008-06-30 Method for Transmitting and Receiving a Signal in Multiple Antenna system KR100968775B1 (en)

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