KR20090108358A - Apparatus and method for interference cancellation using co-channel interferrence in broadband wireless access system - Google Patents

Abstract

PURPOSE: An efficient interference cancellation apparatus using interference occurring when using the same wireless resource in a broadband wireless access system and a method thereof are provided to obtain a cooperation gain, thereby guaranteeing QoS(Quality of Service) of a user. CONSTITUTION: A signal receiving method of a communication system using the same wireless resource comprises the following steps. The first and second terminals receive an interference signal of an adjacent base station and a signal of a serving base station during time slot 1(810). A relay station receives a signal transmitted during time slot 1(820). The relay station retransmits a signal received during time slot 2(830).

Description

Efficient indirect cancellation apparatus and method using interference generated through the use of the same radio resources in a broadband wireless access system {APPARATUS AND METHOD FOR INTERFERENCE CANCELLATION USING CO-CHANNEL INTERFERRENCE IN BROADBAND WIRELESS ACCESS SYSTEM}

According to the present invention, an extreme inter-cell interference (ICI: Inter-Cell Interference) or a relay using a relay node in an area outside a cell generated in an environment having a frequency reuse factor (FRF) of 1 is disclosed. The present invention relates to an apparatus and a method for cooperating and canceling interference by using co-channel interference generated through the use of the same radio resource generated by a relay station during a cooperation.

In a communication environment with a frequency reuse factor of 1, each cell uses up the entire bandwidth and thus has the highest performance in terms of throughput of the entire cell.

1 is a diagram illustrating a case where interference occurs when a conventional frequency reuse factor is 1;

Referring to FIG. 1, when the frequency reuse factor is 1, the base stations 100 and 110 of each cell use up the entire bandwidth, so that the best performance is achieved in terms of throughput of the entire cell, but the outer user is exposed to severe inter-cell interference. Due to this, the performance of the UE is degraded in each time slot.

In particular, in an environment such as OFDMA, interference at the cell edge becomes a significant performance deterioration factor. However, it is not possible to eliminate without loss of resources the interference caused by the use of the same radio resources that cause performance degradation.

In order to avoid severe inter-cell interference in the outer region of the cell, the frequency reuse coefficient is set to a value of 3 or more, so that the occurrence of severe inter-cell interference in the outer region of the cell can be reduced by not overlapping bandwidths used between adjacent cells.

2 is a diagram illustrating a limit of interference control through a conventional frequency reuse coefficient.

Referring to FIG. 2, each cell is assigned a frequency bandwidth for each cell according to the frequency reuse coefficient. In this case, it can be seen that inter-cell interference occurs according to the allocated resources.

As described above, when the frequency reuse factor is 1, all cells use the entire frequency region together as shown in the drawing, and thus may have a high throughput by being allocated a wide bandwidth.

However, in this case, the degradation of performance occurs at the cell edge due to the influence of intercell interference. If the frequency reuse factor is 3, the total bandwidth is divided into three and allocated to each cell as shown in the figure.

In this case, frequency bands B1, B2, and B3 are allocated around the 0 th cell, and a cell in which inter-cell interference occurs does not exist in the first tier. Therefore, the cell edge may exhibit better performance than the case where the frequency reuse factor is 1, but by dividing the entire frequency band, there is a problem in that the performance is lowered than the case where the frequency reuse factor is 1 in terms of total throughput.

3 is a diagram showing an example of interference occurring when a conventional relay station is used.

Referring to FIG. 3, it illustrates interference generated during operation using the central station 302. A base station (BS) B (where a signal transmitted in a second time slot uses the same radio resource) is used. The mobile station B (306) that is being serviced at 310 may interfere.

From the standpoint of the terminal A 304, interference by the signal of the terminal B 302 using the same radio resource is received.

As described above, in the conventional method of combining the signals received by the terminal through the base station and the relay station to obtain transmission cooperative diversity, there is a limitation due to the use of the same radio resource, thereby improving performance of the entire user. There is a difficult problem.

An object of the present invention is to provide an efficient indirect cancellation apparatus and method using the effect of interference generated through the use of the same radio resources in a broadband wireless access system.

It is another object of the present invention to provide an apparatus and method for eliminating interference by using the influence of interference generated through the use of the same radio resources in a broadband wireless access system and improving overall throughput by cooperation.

According to a first aspect of the present invention for achieving the object of the present invention, in the signal receiving method of a communication system using the same radio resources, the first terminal and the second terminal is a signal of each serving base station during time slot 1 and Receiving an interference signal of a neighboring base station; receiving a signal transmitted by the relay station during the time slot 1; and transmitting a signal received by the relay station in the time slot 2;

According to a second aspect of the present invention for achieving the object of the present invention, in a method of receiving a communication system using hierarchical modulation, the first terminal and the second terminal is the signal and neighboring of each serving base station during time slot 1 Receiving an interference signal of a base station; receiving a signal transmitted by the relay station during the time slot 1; and retransmitting the relay station by applying hierarchical modulation to the signal received in the time slot 2. do.

The present invention allows two users using the same channel in neighboring cells to collaborate with a relay station so that one user can achieve transmit cooperative diversity, and the other user can successfully remove interference without any loss of bandwidth. Successive Interference Cancelation (SIC) provides the same performance gains as using one or more frequency reuse coefficients.

In addition, by adopting a hierarchical modulation scheme to maximize the benefits through the frequency usage coefficients (the point of stable reception of signals from both base stations), the benefits of co-operation and successful interference cancellation in good relay-to-terminal channels are good. Get them all.

This effectively utilizes the interference that causes the performance in the outer area of the cell to achieve the benefit of successful interference cancellation, and at the same time, the cooperation gain can also be ensured to ensure the user's quality of service (QoS). There is an advantage.

That is, the technique of the present invention improves performance through successful interference cancellation for users who have been previously interfered in interference environments, and transmits cooperative diversity to users who have caused interference. diversity to achieve better performance.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, 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.

Hereinafter, the present invention will be described an efficient indirect cancellation apparatus and method using the effect of interference generated through the use of the same radio resources in a broadband wireless access system.

According to the present invention, one of the signals received by the relay station using an antenna in order to efficiently receive one of the signals of both base stations coming in through a line of sight (LOS) channel in an area outside the cell By decoding the data or by decoded and forwarding both data using hierarchical modulation (DF), users using the same channel enable transmit cooperative diversity and successful interference cancellation.

First, a case of not using hierarchical modulation is described as follows.

4 is a diagram illustrating a network structure and an operation process thereof according to an embodiment of the present invention.

Referring to FIG. 4, first, in a first step, MS (Mobile Station) A 404 and UE B 406 receive signals from their serving base stations (400, 410, respectively) within a time slot 1 period. Receive. At the same time, interference signals from neighboring base stations (410 and 400, respectively) are received.

Subsequently, in step 2, when the RS 402 receives the signal transmitted in the time slot 1, the RS 402 receives the signal of the base station A 400 using receive beamforming.

Thereafter, in step 3, the RS 402 retransmits its received signal in time slot 2.

Finally, in step 4, the terminal A 404 performs a cooperative operation on its own signal, and the terminal B 406 detects an interference signal from the relay station 402 and receives the signal received in time slot 1. Successful interference cancellation is then performed on the detector to detect its signal and gain.

In the present invention, the relay station 402 performs only modulation and demodulation. In other words, if channel coding is considered, RS 402 receives the coded bits and then modulates them again. When the channel between the base stations 400 and 410 and the relay station 402 is stable, the channel coding itself may be applied to the channel situation between the base stations 400 and 410 and the terminals (404 and 406, respectively).

The terminal B 406 stores the complex value of the signal received in the time slot 1, demodulates the signal received in the time slot 2, and modulates the base station A 400 and the terminal B 406 again. The interference cancellation is performed by multiplying the estimated channel value between < RTI ID = 0.0 >

In addition, the signal of the relay station 402 received in the time slot 2 does not cause interference when using the same radio channel under any circumstances. This is because the time slots to be transmitted are different, and the use of the terminal B 406 may determine whether to use the terminal if necessary.

The present invention can be efficiently used when a terminal using the same radio resource is connected to a relay station in the same region. This can be a limitation, but can be sufficiently solved through resource allocation according to a region.

As in the above process, the transmitting end is a signal transmission without any channel information. This is similar to the traditional process of cooperation. Further, FIG. 4 determines a terminal to perform cooperative and successful interference cancellation based on one base station. When the base station is changed, a terminal to perform cooperative and successful interference cancellation may also be changed.

FIG. 5 is a diagram illustrating channel gains according to an angle α of physically twisting an antenna, assuming that antennas of a relay station according to an embodiment of the present invention are in a line.

Referring to FIG. 5, when the angle is 40 degrees, it can be confirmed that the channel gain is maximized. After such installation, both signals can be stably received even outside the cell through null steering or ZF-receive beamforming.

Formulating the above process is as follows.

Here, Y _A1 represents a signal received by terminal A in timeslot 1, d _A represents a path loss between base station A and terminal A, and h _A represents a Rayleigh channel between base station A and terminal A ( Rayleigh channel), x _A represents the signal transmitted by the base station A, d _B ^I represents the path loss between the base station B and the terminal A, h _B ^I represents the Rayleigh channel between the base station B and the terminal A , x _B represents a signal transmitted from the base station B, n represents the Additive White Gaussian Noise (AWGN), the additional white Gaussian noise.

And, Y _B1 represents the signal received by the terminal B in timeslot 1, d _B represents the path loss between the base station B and the terminal B, h _B is a Rayleigh channel between the base station B and the terminal B represents a (Rayleigh channel), d _a ^I is out Recanati the path loss between base station a and the terminal B, h ^I _a represents the Rayleigh channel between the base station a and the terminal B.

And, Y _R denotes a signal received by the relay station from both base stations, d _R denotes a path loss between the base station and the relay station, and H (θ _D ) denotes an LOS channel according to an input angle of a desired signal. , H (θ _I ) represents the LOS channel according to the input angle of the interference signal.

The above equation represents a signal received by each terminal and relay station in time slot 1. The signal is transmitted by the base station.

,

,

는 널 스티어링 가중치(Null Steering Weight)를 나타내고,

는 널 스티어링을 통해 검출한 신호(심볼)를 나타낸다. here,

Denotes a null steering weight,

Denotes a signal (symbol) detected through null steering.

The above equation assumes that a signal for cooperation among signals transmitted from both base stations in time slot 1 is a desired signal, assumes the signal from the remaining base stations as an interference signal, and null steering or ZF reception weight. Represents the expression for obtaining a vector (ZF receive weight vector).

는 중계국과 각각의 단말 사이의 경로 손실 및 레일리 채널을 나타낸다.그리고, x_A ^C 는 검출한 신호를 복조하고, 변조 후 다시 재구축한 신호(심볼)을 나타낸다. x_A ^C 위에 ~가 붙은 것은 이에 대한 추정치를 나타낸다.here,

Denotes a path loss and a Rayleigh channel between the relay station and each terminal. In addition, x _A ^C demodulates the detected signal and represents a signal (symbol) reconstructed after modulation. x _A ^C The symbol above is about Indicates an estimate.

The above equation represents a signal that each terminal receives from the relay station in time slot 2.

는 MRC(Maximum Ration Combing)등을 이용하여 검출한 신호, 수신 단에서 추정한 채널을 나타낸다. 그리고 *는 켤레 복소수를 나타낸다.here,

Denotes a signal detected by MRC (Maximum Ration Combing) or the like and a channel estimated by the receiver. And * represents a complex conjugate.

The above equation represents a process in which each terminal performs cooperative or successful interference cancellation based on the signals received in time slot 1 and time slot 2.

Considering the case where hierarchical modulation is now applied, it is as follows.

6 illustrates an example of 4/16 QAM hierarchical modulation according to an embodiment of the present invention.

Referring to FIG. 6, in the constellation of 4/16 QAM, the first two bits (in the case of hard decision) are modulated based on the axes of x and y, and the second two bits are constellations of the 16QAM symbol. Demodulated based on the axis value between.

As a result, the error probability of the first two bits is lower than that of the latter two bits, thus enabling stable transmission.

Here too, the power on the beat can be adjusted by adjusting the distance between constellations.

In the present invention, in the case where hierarchical modulation is not used, one user may gain the benefit of cooperation, and one user may obtain the benefit of successful interference cancellation.

However, the data between the base stations and the relay station can be reliably restored from the two base stations through the antenna installation and the receiving beamforming of the relay station, so that the layer can be maximized to allow the cooperative and successful interference cancellation at the same time. Uses an adaptive modulation scheme.

In general, since the channel between the relay station and the terminal is more stable than the channel between the base station and the terminal, assuming that data from both base stations is 2 bits, the relay station transmits a total of 4 bits using hierarchical modulation so that both users When the channel between the relay station and the terminal is stable, the gain through cooperative gain and successful interference cancellation can be simultaneously obtained.

In all situations where the hierarchical modulation is not used, the RS can maximize its gain by DF both bits instead of only one user's bits among the received bits. Where DF means only demodulation and modulation.

If channel coding is renewed at the relay station, the data of the terminal A in the relay station should be encoded in the same manner as in the channel coding between the base station A and the terminal A (the same applies to the base station B and the terminal B). However, when the channel is stable by the LOS between the base station and the terminal as described above, the gain itself through the channel coding will not be very large, and the modulation and demodulation functions without the channel coding in the relay station to reduce the complexity of the relay station It can have a sufficient performance improvement.

 The present invention can be applied in a situation where the base station and the relay station, i.e., the transmitting end do not know any information of the receiving end. Hierarchical modulation can be applied more stably than when receiving channel information.

If the present invention is broken down according to the feedback between the relay station and the terminal as follows.

First, considering the case of no feedback is as follows.

First, when hierarchical modulation is not applied, as shown in FIG. 4, UE A gains through cooperation, and UE B gains through successful interference cancellation.

Second, if error prediction is possible through the CRC or channel estimation information at the receiving end, transmission using hierarchical modulation is possible even when there is no feedback. In this case, since there is no feedback information, power control in the hierarchical modulation scheme is impossible at the transmitting end, and therefore, power should be adjusted within a range in which a bit error rate (BER) performance degradation of high priority bits does not appear. do.

As shown in FIG. 12, when λ is 1/7, it can be seen that the BER performance of 4-QAM is almost similar to the first two bits of 4/16 QAM hierarchical modulation.

Is the ratio of d2 / d1, which is the distance between each symbol, in the hierarchical modulation in FIG. If d2 / d1 = 0.5, the 4/16 QAM hierarchical modulation is uniform 16 QAM, and if d2 / d1 = 0, it is QPSK or 4 QAM.

Therefore, even when information on the channel between the relay station and the terminal is not present in the relay station, data to cooperate and data for successful interference cancellation may be simultaneously transmitted through hierarchical modulation. In addition, this means that the existing terminal A only cooperates, and the terminal B has no performance deterioration compared to the system in which only successful interference cancellation is performed, and at the same time, the terminal A can give the opportunity of successful interference cancellation to the terminal B. . Therefore, both terminals can provide an opportunity for performance improvement.

Now, considering the case of partial feedback as follows.

The partial feedback indicates that the relay station knows only the size or gain of the channel. Therefore, power control in hierarchical modulation was not possible in case of no feedback, but when the signal to noise ratio (SNR) value of the channel is known through partial feedback, it is possible to adjust the power between bits in hierarchical modulation in the relay station. This is possible. Therefore, performance improvement through hierarchical modulation can be expected. However, since the relay station broadcasts data to the terminal A and the terminal B, if the cooperative bit is included in the high priority bit, the other user includes the bit for successful interference cancellation, and the main gain is the cooperative or successful interference. It may be constrained to fit on one side of the removal.

Now consider the case where there is complete feedback as follows.

The complete feedback indicates a case where the relay station knows the channel value of the terminal A and the terminal B accurately.

The RS can provide independent data services to both terminals based on a transmit weight vector and a transmit beam-forming. That is, the service may be provided by selecting the cooperative or successful interference cancellation according to the channel situation of each terminal.

In the above two cases, if UE A only gains through cooperation or obtains major performance improvement through cooperation, UE B obtains only gain through successful interference cancellation or major performance improvement through successful interference cancellation. do.

However, since the data of each user can be distinguished through the configuration of the transmission weight vector, the relay station can transmit the data independently by selecting a technology suitable for the channel situation of each user, that is, cooperation and successful interference cancellation.

In other words, in an environment where the influence of interference is large (in an environment where the cooperative gain may be smaller than the gain by successful interference cancellation if the power of the relay station is limited, etc.), it is possible to actively apply the cooperative gain.

In case there is no feedback or partial feedback, the signal transmitted to each terminal is the same, but if there is complete feedback, it is possible to transmit a different signal to each terminal. Can be sent independently.

This means that when transmitting using hierarchical modulation to perform both coordination and successful interference cancellation, whether to include bits for cooperation in the high priority bits or bits for successful interference cancellation in the channel situation and communication environment. Indicates that you can choose to fit.

Power control in hierarchical modulation can be independently applied to each terminal according to the channel situation between each relay station and the terminal, thereby obtaining optimized performance.

FIG. 7 is a diagram illustrating a network structure and a block structure for entities in the network structure according to an embodiment of the present invention. FIG.

Referring to FIG. 7, the network of the present invention includes a base station 700, a relay station 710, and a terminal 720. The base station 700 of the present invention is composed of a modulator 702, an RF unit 704, and a controller 706. The relay station 710 of the present invention is composed of a receiving unit 712, a DF unit 714, and a transmitting unit 716. The terminal includes an RF unit 722, a demodulator 724, and a controller 725.

The modulator 702 and the demodulator 724 respectively modulate and demodulate the received signal according to a predetermined level (MCS level).

The RF units 704 and 724 convert the modulated signals into RF signals for transmission through the antenna, and provide the demodulation unit 724 with the RF signal received through the antenna. The controller 706, 726 controls the other nodes 702, 704, 722, 724.

The receiving unit 712 receives the signal transmitted from the base station 700 in a determined time slot, and the DF unit 714 demodulates and modulates the signal received by the receiving unit 712. The transmitter 716 transmits the signal modulated by the DF unit 714 in a predetermined time slot.

When hierarchical modulation is not used, the demodulator 724 of the terminal 720 performs the aforementioned cooperative and successful interference cancellation under the control of the controller 726. The cooperative and successful interference cancellation is described in the above formula.

When hierarchical modulation is used, although not shown in FIG. 7, the DF unit 714 of the relay station receives feedback information from the terminal and makes the following decision.

If there is no feedback, it is determined whether a high priority bit is allocated to a terminal performing cooperation or a terminal assigned to successful interference cancellation.

If there is partial feedback, it is determined whether to allocate a high priority bit to a terminal performing cooperation or to a terminal performing successful interference cancellation based on the partial feedback information. do. For example, it is possible to allocate a terminal with a high SNR value to a low priority bit. And the opposite is also possible. Decisions on this may change depending on the implementation environment and deployment policies.

If there is complete feedback, it is independently determined whether to perform cooperation or successful interference cancellation based on the complete feedback information. Then, it is determined whether to assign a high priority bit to a terminal performing cooperation or to a terminal performing successful interference cancellation.

8 is a flowchart illustrating an operation process when there is no hierarchical modulation according to an embodiment of the present invention.

Referring to FIG. 8, terminal A and terminal B receive signals of each serving base station and interference signals of neighboring base stations during timeslot 1 (step 810).

Thereafter, the RS receives the signal transmitted during the time slot 1 and receives the signal of the base station A using the reception beamforming (step 820). The relay station retransmits the signal received in time slot 2 (step 830).

Thereafter, the terminal A cooperates with its own signal, and the terminal B detects a signal from the relay station and detects its own signal after removing interference with respect to the signal received in time slot 1 (step 840). That is, successful interference cancellation is performed.

The above process assumes that any terminal A performs cooperation and any terminal B performs successful interference cancellation.

9 illustrates an operation process when there is a hierarchical modulation and when there is no feedback according to an embodiment of the present invention.

Referring to FIG. 9, the RS selects a terminal to use successful interference cancellation or cooperation (step 910). Thereafter, the method is applied to the terminal according to the selected result (step 920).

10 illustrates an operation process when there is a hierarchical modulation and when there is partial feedback information according to an embodiment of the present invention.

Referring to FIG. 10, the RS selects a terminal to perform successful interference cancellation based on the partial feedback information (step 1010). The other terminal selects cooperation (step 1020). Thereafter, each predetermined method is applied (step 1030).

In the above process, it may be determined to which UE to allocate the bits of the high priority and the bits of the low priority.

11 illustrates an operation process when there is hierarchical modulation and complete feedback information according to an embodiment of the present invention.

Referring to FIG. 11, the RS independently selects a terminal for successful interference cancellation and a terminal for cooperation based on the complete feedback information (step 1110). That is, the processing method for each terminal is determined.

Subsequently, the corresponding method determined for each terminal is applied (step 1120).

In the above process, it may be determined to which UE to allocate the bits of the high priority and the bits of the low priority.

13 is a diagram showing the performance of the technology according to an embodiment of the present invention.

FIG. 13 is a BER performance for a technique proposed in the present invention, an inter-cell interference proposed in FIG. 1, and a frequency reuse coefficient of 3 in FIG. 2, that is, no inter-cell interference at 1 tier. This is a graph comparing.

In the case of the terminal receiving its own data from the relay station, it can be seen that the performance is improved by cooperative diversity. In addition, the terminal receiving the interference signal from the relay station, it can be seen that the same performance as the case of the frequency reuse coefficient of 3 can be obtained by the effect of successful interference cancellation.

In case of the UE which has improved performance through successful interference cancellation, the BER performance of the frequency reuse factor of 3 is the same, but the gain of bandwidth is 3 times in terms of bandwidth utilization, so it is 3 times in throughput. You can expect a degree of benefit.

It can be confirmed through FIG. 12 that at least the performance when hierarchical modulation is applied as shown in FIG. 13 can be obtained at least as shown in FIG. 13. Further, if a hierarchical modulated signal is successfully received, It can expect big performance improvement and can be applied flexibly to communication environment.

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

1 is a diagram illustrating a case where interference occurs in a situation where a conventional frequency reuse factor is 1;

2 is a diagram illustrating a limit of interference control through a conventional frequency reuse coefficient;

3 is a diagram showing an example of interference occurring when a conventional relay station is used;

4 is a diagram illustrating a network structure and an operation process thereof according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating channel gain according to an angle α of physically twisting an antenna, assuming that antennas of a relay station are in a line according to an embodiment of the present invention; FIG.

6 illustrates an example of 4/16 QAM hierarchical modulation according to an embodiment of the present invention;

7 is a block diagram illustrating a network structure and entities within the network structure according to an embodiment of the present invention;

8 is a flowchart illustrating an operation process when there is no hierarchical modulation according to an embodiment of the present invention;

9 is a flowchart illustrating an operation process when there is no hierarchical modulation and when there is no feedback according to an embodiment of the present invention;

10 is a flowchart illustrating an operation process when there is a hierarchical modulation and when there is partial feedback information according to an embodiment of the present invention;

11 is a flowchart illustrating an operation process when there is a hierarchical modulation and when there is complete feedback information according to an embodiment of the present invention;

12 is a diagram illustrating BER performance of 4-QAM and the first two bits of 4/16 QAM hierarchical modulation according to an embodiment of the present invention, and

Figure 13 illustrates the performance of a technique in accordance with an embodiment of the present invention.

Claims (22)

In the signal receiving method of a communication system using the same radio resources, Receiving, by the first terminal and the second terminal, a signal of each serving base station and an interference signal of an adjacent base station during time slot 1; Receiving a signal transmitted by the relay station during the time slot 1; And retransmitting the signal received by the relay station in time slot 2. The method of claim 1, Receiving, by the first terminal, a signal transmitted from the RS, performing a cooperation on the received signal, and detecting the signal; And receiving, by the second terminal, a signal transmitted by the relay station, performing a successful interference cancellation on the received signal to detect the signal. The method of claim 2, Receiving a signal transmitted by the relay station during the time slot 1, And receiving, by the relay station, a signal of the first base station using receive beamforming in time slot 1. The method of claim 1, Receiving, by the first terminal, a signal transmitted by the relay station, performing a successful interference cancellation on the received signal, and detecting the signal; And receiving, by the second terminal, a signal transmitted by the relay station, performing a cooperative operation on the received signal to detect the signal. The method of claim 4, wherein Receiving a signal transmitted by the relay station during the time slot 1, And receiving, by the relay station, a signal of the second base station using receive beamforming in time slot 1. The method of claim 2, The first terminal receives the signal transmitted by the relay station, and then performs cooperation with the received signal to detect the signal; and the second terminal receives the signal transmitted by the relay station and then receives the received signal. The method of detecting a signal by performing a successful interference cancellation on the signal uses Equation 5 below.

Where Y _A represents a signal received by the first terminal, d _A represents a path loss between the first base station and the first terminal, and h _A represents a Rayleigh channel between the first base station and the first terminal (Rayleigh channel), x _A represents a signal transmitted by the first base station, d _B ^I represents the path loss between the second base station and the first terminal, h _B ^I represents the second base station and the first terminal Represents a Rayleigh channel between, x _B represents a signal transmitted from the second base station, n represents Additive White Gaussian Noise (AWGN), and additional white Gaussian noise. In addition, Y _B represents a signal received by the second terminal, d _B represents a path loss between the second base station and the second, and h _B represents a Rayleigh channel between the second base station and the second terminal ( Rayleigh channel), d _A ^I denotes a path loss between the first base station and the second terminal, and h _A ^I denotes a Rayleigh channel between the first base station and the second terminal. here,

Denotes a signal detected by MRC (Maximum Ration Combing) or the like and a channel estimated by the receiver. And * represents a complex conjugate. In a communication system for receiving a signal using the same radio resources, A first base station transmitting a signal during time slot 1, A second base station transmitting a signal during the time slot 1; Receiving a signal transmitted during the time slot 1 and retransmitting the signal received in the time slot 2. A first terminal receiving a signal of a first base station and an interference signal of the second base station during the time slot 1; And a second terminal receiving a signal of a second base station and an interference signal of the first base station during the time slot 1. The method of claim 7, wherein The first terminal receives the signal transmitted by the relay station, and then cooperates with the received signal to detect the signal, And the second terminal detects the signal by performing a successful interference cancellation on the received signal after receiving the signal transmitted from the relay station. The method of claim 8, The relay station receiving a signal of the first base station using receive beamforming in time slot 1; The method of claim 7, wherein After receiving the signal transmitted by the RS, the first terminal performs a successful interference cancellation on the received signal and detects the signal. And the second terminal detects the signal by cooperating with the received signal after receiving the signal transmitted by the relay station. The method of claim 10, And the RS receives the signal of the second base station using receive beamforming in time slot 1. The method of claim 8, After the first terminal receives the signal transmitted by the relay station, the first terminal detects the signal by cooperating with the received signal, and after the second terminal receives the signal transmitted by the relay station, And detecting the signal by performing a successful interference cancellation with respect to Equation (6).

Where Y _A represents a signal received by the first terminal, d _A represents a path loss between the first base station and the first terminal, and h _A represents a Rayleigh channel between the first base station and the first terminal (Rayleigh channel), x _A represents a signal transmitted by the first base station, d _B ^I represents the path loss between the second base station and the first terminal, h _B ^I represents the second base station and the first terminal Represents a Rayleigh channel between, x _B represents a signal transmitted by a second base station, n represents Additive White Gaussian Noise (AWGN), and additional white Gaussian noise. In addition, Y _B represents a signal received by the second terminal, d _B represents a path loss between the second base station and the second, and h _B represents a Rayleigh channel between the second base station and the second terminal ( Rayleigh channel), d _A ^I denotes a path loss between the first base station and the second terminal, and h _A ^I denotes a Rayleigh channel between the first base station and the second terminal. here,

Denotes a signal detected by MRC (Maximum Ration Combing) or the like and a channel estimated by the receiver. And * represents a complex conjugate. A reception method of a communication system using hierarchical modulation, Receiving, by the first terminal and the second terminal, a signal of each serving base station and an interference signal of an adjacent base station during time slot 1; Receiving a signal transmitted by the relay station during the time slot 1; And retransmitting by applying the hierarchical modulation to the signal received in time slot 2 by the RS. The method of claim 13, To the relay station, And transmitting partial feedback information before the first terminal and the second terminal receive the signal of each serving base station and the interference signal of the neighboring base station during time slot 1. The method of claim 14, Retransmitting the RS by applying hierarchical modulation to the signal received in time slot 2, Determining a terminal to which a bit of high priority is to be allocated in the hierarchical modulation, and a terminal to which a bit of low priority is to be allocated; Determining a terminal to select cooperation and a terminal to select a successful interference cancellation by using the partial feedback information. The method of claim 13, To the relay station, And transmitting complete feedback information before the first terminal and the second terminal receive the signal of each serving base station and the interference signal of the neighboring base station during time slot 1. The method of claim 16, Retransmitting the RS by applying hierarchical modulation to the signal received in time slot 2, Determining a terminal to which a bit of high priority is to be allocated in the hierarchical modulation, and a terminal to which a bit of low priority is to be allocated; And independently determining a terminal to select cooperation and a terminal to select a successful interference cancellation using the complete feedback information. A communication system for receiving using hierarchical modulation, A first base station transmitting a signal during time slot 1, A second base station transmitting a signal during the time slot 1; And a relay station receiving the signal transmitted during the time slot 1 and retransmitting the signal received in the time slot 2 by applying hierarchical modulation. The method of claim 18, And a first terminal and a second terminal for transmitting partial feedback information to the relay station before receiving a signal of each serving base station and an interference signal of a neighboring base station during time slot 1. The method of claim 19, The relay station, In the hierarchical modulation, a terminal to allocate a high priority bit and a terminal to allocate a low priority bit are determined, and a terminal to select cooperation and a terminal to select successful interference cancellation are determined using the partial feedback information. And retransmit by applying hierarchical modulation to the signal received in time slot 2. The method of claim 18, And a third terminal and a fourth terminal for transmitting partial feedback information to the relay station before receiving the signal of each serving base station and the interference signal of the neighboring base station during time slot 1. The method of claim 21, The relay station, In the hierarchical modulation, a terminal to allocate a high priority bit and a terminal to allocate a low priority bit are determined, and a terminal to select cooperation and a terminal to select successful interference cancellation are independently used using the complete feedback information. Determine and retransmit by applying hierarchical modulation to the signal received in time slot 2.

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