KR101754990B1 - Method and apparatus for cooperation transition in communication system - Google Patents

Abstract

Embodiments of the present invention relate to a cooperative communication method and apparatus using relays moving in a communication system. In particular, the transmitting end can perform cooperative communication with the target receiving end by selectively using the relay in a high-speed mobile environment. Also, the relay can adaptively perform cooperative communication with a receiving terminal capable of current cooperative communication while moving at high speed. Also, the receiving end can receive cooperative communication having a higher transmission success rate than the previous one through the relay capable of cooperative communication in the present position and situation among the plurality of relays moving at high speed.

Description

[0001] METHOD AND APPARATUS FOR COOPERATION TRANSITION IN COMMUNICATION SYSTEM [0002]

The following embodiments relate to a cooperative communication method and apparatus using relays moving in a communication system.

If the coherence time of the channel in the communication system is shorter than the time for feedback and processing the channel information at the receiving end, the transmitting end may not have sufficient channel information for the receiving end.

Particularly, when the moving speed of the terminal is fast, the fading coefficient of the channel changes rapidly. Accordingly, since the coherence time of the channel is shortened, it is difficult for the transmitter to secure channel information for the receiver.

If the terminal moves at a high speed, it may be difficult for the transmitting end to know the number of available relays. In addition, in this case, it may be difficult for the transmitting end to select an optimal relay.

According to the embodiment of the present invention, a relay capable of knowing whether cooperative communication is possible based on the channel quality information with the transmitting end and the channel quality information with the receiving end, and a relay capable of cooperative communication among one or more candidate relays moving at high speed The present invention provides a cooperative communication method and apparatus in a communication system that provides a transmitting terminal capable of selecting a cooperative communication method.

A cooperative communication method of a relay according to an embodiment of the present invention is a cooperative communication method of a target relay which is any one of at least one candidate relay that moves, comprising: information about a first channel quality between the target relay and a transmitting end; Obtaining information on a second channel quality between the target relay and the receiving end and determining whether the target relay is capable of cooperative communication with the receiving end using at least one of the first channel quality and the second channel quality And transmitting an indicator indicating the determination result to the transmitting terminal.

The cooperative communication method of the relay may further include a step of comparing a channel having a low quality among the first channel quality and the second channel quality with a preset threshold value and determining whether cooperative communication with the receiving end is possible May determine a cooperative communication possibility for the receiving end based on the comparison result.

The step of acquiring the information on the first channel quality and the information on the second channel quality may include the steps of receiving a reference signal from the transmitting end and receiving an uplink reference signal from the receiving end, Calculating information on a first channel quality between the target relay and the transmitting terminal on the basis of a reference signal of the transmitting terminal, calculating a second channel quality between the target relay and the receiving terminal based on the uplink reference signal of the receiving terminal, And a step of calculating the information on the information.

The cooperative communication method of the relay may further include initiating cooperative communication with the receiving end according to whether information for instructing cooperating communication with the receiving end is received from the transmitting end.

In addition, when the current network environment is an LOS interference cooperative channel network, initiating cooperative communication with the receiving end may include receiving a data signal from the transmitting end to the at least one receiving end in a first time slot, And in a time slot thereafter, sequentially transmit the data signals received respectively to the one or more receiving ends to respective corresponding receiving ends.

In addition, when the current network environment is the LOS broadcast network, the step of initiating the cooperative communication with the receiving end receives the data signals for one target receiving end from at least one transmitting end in at least one time slot, In a slot, the received data signal may be transmitted to the destination receiver.

A cooperative communication method of a transmitting end according to another embodiment of the present invention is a cooperative communication method of a transmitting end linked with at least one candidate relay that moves, comprising: determining whether a cooperative transmission is necessary for a receiving end; Transmitting a reference signal to the one or more candidate relays when it is determined that a candidate relay is needed, and transmitting a reference signal to the destination relay of the cooperative transmission, .

At this time, the cooperating communication method of the transmitting end includes: determining a threshold for limiting the number of relays to be used for the cooperative transmission among the one or more candidate relays; and notifying the determined threshold to the one or more candidate relays .

The cooperative communication method of the transmitting end may further include transmitting information for instructing the target relay to the cooperative communication with the receiving end.

A relay according to another embodiment of the present invention is characterized in that, in a target relay which is one of at least one candidate relay moving, information on a first channel quality between the target relay and a transmitting end, Determining whether the target relay is capable of cooperative communication with the receiving end using at least one of the first channel quality and the second channel quality, And a possibility determination unit for transmitting an indicator indicating a result to the transmitting terminal.

At this time, the possibility judging unit may compare the channel having the low quality among the first channel quality and the second channel quality with a predetermined threshold, and determine the cooperative communication possibility for the receiving end according to the comparison result.

The acquiring unit may calculate information on a first channel quality between the target relay and the transmitting terminal using the reference signal received from the transmitting terminal, and transmit the information on the target relay and the target relay using the uplink reference signal received from the receiving terminal. Information about the second channel quality between the receiving ends can be calculated.

The relay may further include a cooperative communication unit for initiating cooperative communication with the receiving end according to whether information for instructing cooperative communication with the receiving end is received from the transmitting end.

A transmitting terminal according to another embodiment of the present invention is a transmitting terminal that performs cooperative communication with a receiving terminal in cooperation with at least one of moving one or more candidate relays. The transmitting terminal determines whether cooperative transmission is required to the receiving terminal, A cooperative judgment unit for transmitting a reference signal to the one or more candidate relays when it is determined that the cooperative communication with the receiving terminal is required; And a relay determination unit for determining the transmitted candidate relay as a target relay of cooperative communication with the receiving end.

At this time, the cooperation determination unit may determine a threshold for limiting the number of relays to be used for the cooperative transmission among the one or more candidate relays, and notify the determined threshold to the one or more candidate relays.

The transmitting end may further include a data transmitting unit for transmitting information for instructing a cooperative communication to the receiving end to the determined target relay and for transmitting the data signal of the cooperative communication to the receiving end to the receiving end and the target relay have.

Embodiments of the present invention can achieve multi-path and improve data transmission performance by selectively using relays moving in a high-speed mobile environment and performing cooperative communication.

In particular, if the coherence time of the channel is shorter than the time required to feed back and process the channel information at the receiving end, it may be difficult to obtain the channel information at the transmitting end. However, according to the embodiment of the present invention, since the transmitting terminal transmits a threshold for relay selection to each relay, it is not necessary to receive feedback from the relay, and the embodiments of the present invention are applicable to relays that move at high speed .

In addition, in a situation where a transmitter in the LOS MU-MIMO (multiuser-multiple-input-muti-output) channel environment does not know the channel information, the relay is used as a virtual active scatter for cooperative communication, the multipath can be ensured and the transmission rate of the entire system can be increased by increasing the channel rank.

Since the embodiment of the present invention does not necessarily require all the channel information, the overhead of communication can be reduced. In addition, since the linear beam-forming technique can be applied to the embodiments of the present invention, the present invention can be applied to a low-complexity, high-speed mobile environment.

Furthermore, the embodiments of the present invention may use the relays provided in the moving vehicle, so that the available relay sets may be flexible and may not require the installation of separate relays for each cell.

Brief Description of the Drawings Fig. 1 is a diagram illustrating a communication situation for performing a cooperative communication method according to an embodiment of the present invention. Fig.
2 is an operational flow diagram illustrating a collaborative communication method in accordance with an embodiment of the present invention.
3 is a diagram for explaining a process of performing a symbol extension through a 3-time slot in a cooperative communication method according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating performance of the cooperative communication method according to FIG. 3; FIG.
5 is a diagram illustrating a communication environment in which a relay moving at high speed and a receiver moving at a fixed or low speed are arranged in a LOS interference channel network in order to explain a cooperative communication method according to another embodiment of the present invention.
FIG. 6 is a diagram for explaining a process of performing a symbol extension through a 2-time slot in a cooperative communication method according to another embodiment of the present invention. FIG.
FIG. 7 is a diagram illustrating performance improvement by a cooperative communication method according to another embodiment of the present invention; FIG.
FIG. 8 is a diagram illustrating a communication environment in which a high-speed moving relay and a receiving end are arranged in a LOS broadcast network in order to explain a cooperative communication method according to another embodiment of the present invention; FIG.
FIG. 9 is a diagram for explaining a process of performing symbol extension through a 4-time slot in the cooperation communication method of FIG. 8;
10 illustrates performance of the cooperative communication method of FIG. 8;
11 is a diagram showing an environment in which a relay moves at a high speed and a receiving end moves at a fixed or low speed in a LOS broadcast network in order to explain a cooperative communication according to another embodiment of the present invention.
FIG. 12 is a diagram for explaining a process of performing a symbol extension through a 3-time slot in the cooperation communication method of FIG. 11;
13 is a diagram for illustrating performance of the cooperative communication method of FIG.
FIG. 14 illustrates a configuration of an apparatus for performing a cooperative communication method according to an embodiment of the present invention; FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The terminologies used herein are terms used to properly represent preferred embodiments of the present invention, which may vary depending on the user, the intent of the operator, or the practice of the field to which the present invention belongs. Therefore, the definitions of these terms should be based on the contents throughout this specification. Like reference symbols in the drawings denote like elements.

1 is a diagram illustrating a communication state for performing a cooperative communication method according to an embodiment of the present invention. The above embodiment selectively uses relays capable of high-speed movement in a high-speed mobility environment and performs cooperative communication. In particular, the embodiments described below present a beam design and / or relay selection scheme suitable for various communication environments. In addition, embodiments of the present invention consider broadcast channels and interfering channels in the LOS MIMO noCSIT context.

1, the communication system includes a transmitting terminal 100, a relay 110, and a receiving terminal 120. As shown in FIG. The communication system is modeled considering the mobility of each of the relay 110 and the receiver 120. In particular, the relay 110 is constituted by one or more candidate relays, and can be moved at a high speed as in a case mounted on a vehicle. The receiving end 120 can move at a high speed, move at a low speed, or be fixed.

The transmitting terminal 100 selects a target relay to perform cooperative communication with the receiving terminal 120 among one or more candidate relays moving at high speed and performs cooperative communication with the receiving terminal 120 in conjunction with the selected target relay.

2 is a flowchart illustrating a cooperative communication method according to an embodiment of the present invention.

Referring to FIG. 2, in step 200, the receiving end transmits a Received Signal Strength Indication (RSSI) to the transmitting end.

In step 201, the transmitting terminal determines whether a cooperative communication is necessary for the receiving end based on the RSSI received in step 200. [ In step 201, the transmitter determines whether it is necessary to acquire a diversity gain or a multiplexing gain based on the received RSSI. If it is determined that the diversity gain or the multiplexing gain needs to be acquired, It can be determined that a cooperative communication is necessary.

Further, in step 201, the transmitting terminal may determine a threshold for limiting the number of relays to be used for the cooperative communication, and notify the determined threshold to the one or more candidate relays. At this time, depending on the communication environment, there may be cases in which the transmitting end can acquire information on the positions of the relay and the receiving end, or may not be able to acquire the information.

If the transmitting terminal can acquire information on the positions of the candidate relay and the receiving terminal, in step 201, the transmitting terminal acquires information on the position of the receiving terminal and the relay through scanning. Then, the transmitting end reflects the obtained information on the actual model value of the channel path loss, and predicts the channel gain according to the distance between each of the receiving end and the candidate relay and the transmitting end based on the result. Also, the transmitting terminal may determine a threshold corresponding to the relay limit number to be used for the cooperative transmission based on the predicted channel gain.

For example, when the number of relays searched through the scanning is equal to or greater than a reference value, the transmitting terminal sets a threshold for allowing a predetermined number of relays among the searched relays to be selected. When the number of relays detected is less than a reference value, It is possible to determine an appropriate threshold value for all of the searched relays to be selected.

를 가능한한 크게 설정할 수 있다. 즉, 상기 송신단은 상기 협력 통신에 필요한 릴레이 수를 최대한 충족시키기 위하여 상기 임계치(

를 협력 전송 시 이득이 발생하는 범위에서 가장 크게 설정할 수 있다. Meanwhile, if the transmitting terminal is in a communication environment in which information on the positions of the candidate relay and the receiving terminal can not be obtained, in step 201,

Can be set as large as possible. That is, the transmitting end transmits the number of relays required for the cooperative communication to the maximum value

Can be set to the largest value within a range in which a gain is generated in cooperative transmission.

For example, when a relay is cooperatively transmitted using a virtual active scatter as in an embodiment of the present invention, a higher throughput than a direct transmission based on a received signal strength between the transmitting end and the receiving end throughput can be achieved.

Meanwhile, in step 202, the transmitting terminal transmits a reference signal (RS) to a plurality of candidate relays and a receiving terminal. At this time, the reference signal may include MAP information including the determined threshold value. In step 202, the transmitting terminal may transmit uplink SRS information of a receiving end requiring a cooperative communication (i.e., a receiving end having a small RSSI size) to the candidate relay.

In step 203, the receiving terminal transmits an uplink reference signal to the plurality of candidate relays and the transmitting terminal.

In step 204, one candidate relay calculates information on the first channel quality between the candidate relay and the transmitter using the reference signal received from the transmitter, and uses the received uplink reference signal from the receiver And calculates information on the second channel quality between the candidate relay and the receiving end.

In step 205, the candidate relay determines whether the candidate relay is capable of cooperative communication with the receiving end using at least one of the calculated first channel quality and the second channel quality. Here, the candidate relay may compare at least one of the calculated first channel quality and the second channel quality with a previously received threshold, and determine whether cooperative communication with the receiving end is possible according to the comparison result .

In step 206, the candidate relay transmits an indicator indicating the determination result to the transmitting terminal to notify the cooperative communication possibility determined in step 205. [

Other candidate relays may be performed in steps 207 to 209 in the same manner as 204 to 206 described above.

In step 210, the transmitting terminal determines the relay that transmitted the indicator among the one or more candidate relays to be a target relay of cooperative communication with the receiving terminal.

In step 211, the transmitting end transmits information for instructing the cooperative communication to the target relay in step 211, and performs cooperative communication on the receiving end through interlocking with the target relay in step 212.

The cooperative communication with the receiver can be performed by: 1) a relay moving in a LOS interference channel, and 2) a relay moving at a high speed in an LOS interference channel; (LOS IC networks with fixed Rx & moving relay), and 3) a relay station and a receiving station which are moving at a high speed in a LOS broadcast channel (LOS Broadcast networks with moving Rx & and 4) a relay moving at high speed in a LOS broadcast channel and a receiver moving at a fixed or low speed (LOS BC (Broadcast networks) with fixed Rx & moving relay) .

One) LOS IC networks with moving Rx  & relay

A communication environment in which relays and receivers moving at a high speed in the LOS interference channel are arranged can be described using Fig.

Referring to FIG. 1, a transmitting terminal 100 is fixed, and one or more candidate relays 110 and a receiving terminal 120 are moved at a high speed. Although the number of the transmitting terminal 100, the candidate relay 110 and the receiving terminal 120 is not limited, in the present embodiment, two transmitting terminals 100, a candidate relay 110, 120). It is also assumed that each of the transmitting terminals 100 has four antennas, the candidate relay 110 has two antennas, and the receiving terminal 120 has three antennas. Hereinafter, it is assumed that the transmitting terminal 100 can grasp the positions of the receiving terminal 120 and the candidate relay 110, respectively.

2, the transmitting terminal 100 selects a target relay to be used in the cooperative communication among the candidate relays 110 and can start the cooperative communication through interlocking with the selected target relay have. Likewise, the candidate relay 110 may selectively perform cooperative communication with the receiving end through the operation procedure of FIG. 2 described above.

Below, a beam forming scenario in a communication environment in which relays and receivers moving at a high speed in the LOS interference channel are arranged will be described. Particularly, FIG. 3 shows a cooperative communication situation when a symbol extension is performed through a 3-time slot in the communication environment.

Referring to Fig. 3, in the first time slot, the transmitting terminals A1 and A2 transmit data signals to the target relays B1 and B2 and the receiving terminals C1 and C2. At this time, the receiving terminals C1 and C2 can remove the interference from the data signals received from the transmitting terminals A1 and A2 by using the receiving terminal zero-forcing for interference.

In the second time slot, each of the target relays B1 and B2 transmits a data signal for the first one of the receiving ends C1 and C2 to the first receiving end.

In the third time slot, each of the target relays B1 and B2 transmits a data signal for the second one of the receiving ends C1 and C2 to the second receiving end.

Here, the signals received by the first receiving end and the second receiving end from the transmitting end (A1 and A2) in the first time slot can be expressed by the following equation (1).

[Equation 1]

,

는 송신단(A1 및 A2) 각각에서 송신한 신호이고,

,

는 제1 수신단 및 제2 수신단에서 각각 수신한 신호이다. 그리고,

,

는 제1 수신단 및 제2 수신단의 각각에서의 노이즈(noise)를 나타내고, (.)는 시간 인덱스(index)를 나타낸다. 또한, 는 송신단(A1 및 A2)의 각각과 상기 제1 수신단 간의 채널 이득을 나타내고,

는 송신단(A1 및 A2)의 각각과 상기 제1 수신단 간의 채널 이득을 나타낸다. here

,

Is a signal transmitted from each of the transmitting terminals A1 and A2,

,

Is a signal received by the first receiving end and the second receiving end, respectively. And,

,

Denotes noise in each of the first and second receiving ends, and () denotes a time index. Also, Represents a channel gain between each of the transmitting terminals A1 and A2 and the first receiving terminal,

Represents a channel gain between each of the transmitting terminals A1 and A2 and the first receiving end.

Since the receiving terminals C1 and C2 know channel information from the transmitting terminals A1 and A2 and the target relays B1 and B2, the interference signal can be removed through zero forcing. At this time, in the first receiving end and the second receiving end, the signal from which the interference signal has been removed can be expressed by the following Equation (2).

&Quot; (2) "

,

,

는 제i 수신단에서의 제로포싱을 나타내고,

,

은 상기 제로포밍 이후의 제1 및 제2 수신단에서의 노이즈를 나타낸다.here

Represents the zero forcing at the i < th > receiving end,

,

Represents the noise at the first and second receiving ends after the zero-forming.

In the second timeslot, the target relays B1 and B2 perform receiving stage zero-forcing based on the signals received from each of the transmitting stages A1 and A2, And removes a signal received from a transmitting terminal other than the transmitting terminal. Then, the target relays B1 and B2 transmit the signal from which the signal received from the other transmitting terminal is removed to the first receiving terminal.

Here, the signal received from the transmitting terminals A1 and A2 in the first relay may be expressed by Equation (3) below, and a signal from which the signal received from the other transmitting terminal through the zero forcing is removed may be expressed as Can be expressed by Equation (4).

 &Quot; (3) "

는 제2 타임 슬롯에서, 제1 송신단과 제1 수신단 사이의 채널 이득을 나타낸다. 또한,

는 제1 및 제2 송신단 각각과 제1 릴레이 사이의 채널 이득을 나타내고,

는 제1 및 제2 송신단의 각각과 제2 릴레이 2 사이의 채널이득을 나타내고, (.)는 시간 인덱스를 나타낸다. 또한

는 제1 및 제2 릴레이의 각각과 제1 수신단 사이의 채널이득을 나타내고,

는 제1 및 제2 릴레이의 각각과 제2 수신단 사이의 채널 이득을 나타낸다.

는 제i 릴레이에서 제2 송신단이 송신한 신호를 제거하기 위한 제로포밍을 나타낸다.here,

Represents the channel gain between the first transmitting end and the first receiving end in the second time slot. Also,

Represents a channel gain between each of the first and second transmitting terminals and the first relay,

Represents a channel gain between each of the first and second transmitting terminals and the second relay 2, and (.) Represents a time index. Also

Represents the channel gain between each of the first and second relays and the first receiving end,

Represents the channel gain between each of the first and second relays and the second receiving end.

Represents zero-forming for eliminating the signal transmitted by the second transmitting terminal in the i-th relay.

 &Quot; (4) "

In the third timeslot, the target relays B1 and B2 perform the receiving end zero forging based on the signals received from the transmitting ends A1 and A2, respectively, And removes signals received from other transmitting terminals. Then, the target relays B1 and B2 transmit the removed signal to the second receiving end.

As a result of the transmission, the signal received by the second receiving end can be expressed by the following equation (5).

&Quot; (5) "

As a result, a signal received by the first and second receiving terminals during the three time slots can be expressed by Equation (6) below.

&Quot; (6) "

4 is a view for explaining performance enhancement according to beam forming according to an embodiment of the present invention.

Referring to FIG. 4, in the case of cooperative communication in which general time division multiplexing is applied, the throughput at a slope of 400 is shown at a constant interval (for example, 0 to 20). Assuming that the slope of 400 is 1, the cooperative communication in which the receiving end zero forcing is applied shows the throughput of slope 2 as 410 in the same section.

The cooperative communication according to the embodiment of the present invention shows the throughput of 8/3 of the slope as 420 at the same interval by selectively using the relay in the interference channel environment.

As a result, it can be seen that the cooperative communication according to the embodiment of the present invention has a DoF gain as compared with the cooperative communication using the general time division multiplexing, as well as the cooperative communication using the receiving end zero-pointing.

Further, when the number of antennas of the transmitting terminal is N + 2, the number of receiving antennas is N + 1, the number of relays is N, and each antenna has two antennas, the DoF gain is 2 * (N + 2) / 3 As shown in Fig. Therefore, it can be seen that the DoF gain increases in proportion to N.

Furthermore, a transmission gain can be obtained even at a finite signal-to-noise-ratio (SNR). That is, the higher the transmission speed of the relay and the receiving end, the larger the transmission rate gain for the relay, and the slope of the DoF increases at the lower SNR. In extreme cases, when the relay and the receiver are stopped, there will be no DoF gain and there will be only power gain through the relay.

When the transmitting end or the receiving end are very close to each other, the relay can receive the signal by multiplying it by a random matrix for the multipath effect upon receipt of the signal (corresponding to 430). In this case, it can be seen that the transmission rate gain increases as the number of relays increases. Here, the random matrix scheme is applied when the relays are adjacent to each other, so that the channels are highly correlated with each other. In such a case, there may be a problem that the channel becomes the same in phase and performance degradation occurs at a low SNR. In order to solve this problem, in the present invention, each relay multiplies the received signal random matrix from the transmitting end, and transmits information on the multiplied matrix value to the receiving end.

On the other hand, the transmitting end can determine how much DoF gain and diversity gain can be obtained depending on how the signal transmission is performed. For example, the transmitting end may transmit [aaaa] to obtain maximum diversity gain and [abcd] signal to obtain maximum DoF gain.

2) LOS IC networks with fixed Rx  & moving relay

5 is a diagram showing a communication environment in which a high-speed moving relay and a receiving station moving at fixed or low speed are arranged in the LOS interference channel network. For example, the relay may be mounted on a vehicle and moved at a high speed, and the receiving end may be a case of a user moving on foot. The following description will be made based on an environment in which the transmitting terminal 500 can acquire information on the positions of the receiving terminal 520 and the candidate relays 510. [

In the present embodiment, four candidate relays exist for convenience of explanation, and two transmission terminals 500 and two reception terminals 520 exist in the embodiment, but the present invention is not limited thereto no. It is also assumed that each of the transmitting terminals 500 has four antennas and that the receiving terminal 520 and the candidate relay 510 each have two antennas. It is also assumed that the number of relays to be used in the cooperative communication method among the four candidate relays 510 is two.

The candidate relay 510 can know the channel information between the transmitting end 500 and the receiving end 520 and the channel information between the candidate relay 510 and the receiving end 520 using a pilot signal. Therefore, there is a channel status information at receiver (CSIR) between all nodes.

On the other hand, the transmitting terminal 500 may not know channel information between the relay 510 and the transmitting terminal 500 because the candidate relay 510 moves at a high speed. However, since the receiving end 520 is fixed or moves at a low speed, the transmitting end 500 can know channel information (e.g., angle information) between the receiving end 520 and the transmitting end 500.

The transmitting end 500 locates the receiving end 520 and the candidate relay 510 through scanning and reflects the position to the actual model value for the channel path loss so that the receiving end 120 and the candidate relay 110 according to the distance between the transmitting end 500 and the transmitting end 500. At this time, the transmitting terminal 500 may not know the channel phase.

Based on the predicted channel gain, the transmitting end 500 determines a channel gain threshold for operating as a relay to be used for the cooperative transmission, considering the number of relay limits (i.e., two) to be used for the cooperative transmission . In addition, the transmitting terminal 500 performs symbol extension and linear beamforming suitable for the relay limiting number, and performs cooperative communication with the receiving terminal 520.

In the above-described embodiment, the transmission terminal BS, the Donor Remote Radio head (Donor RRH) or the like transmits a data to a receiving terminal (a user walking on the road) fixed or moving at a low speed by using a vehicle moving at high speed as a relay . In this case, there is a DoF gain compared to normal receiver zero-forcing (ZF), and there may be an advantage in increasing the transmission rate even at the finite SNR.

The concrete beam forming process in the above embodiment is as follows. In particular, FIG. 6 illustrates a cooperative communication situation in which a symbol extension is performed through a 2-time slot in a cooperative communication method according to another embodiment of the present invention.

Referring to FIG. 6, in a first time slot, the transmitting terminals A11 and A12 transmit data signals for the first receiving terminal and the second receiving terminal to the first receiving terminal, the second receiving terminal, and the first To the target relays B11 and B12, and to the second target relays B13 and B14 of the cooperative communication to the second receiving end.

At this time, the receiving terminals C11 and C12 remove interference through receiving terminal zeroing for interference when receiving data from the transmitting terminals A11 and A12. Each of the first target relays B11 and B12 and the second target relays B13 and B14 performs receiving stage zeroing using the CSIR and receives only signals corresponding to the respective receiving stages from the transmitting stages A11 and A12 .

In the second timeslot, the first target relays B11 and B12 and the second target relays B13 and B14 respectively transmit signals corresponding to the corresponding receiving ends to the corresponding receiving ends. That is, the first target relays B11 and B12 transmit signals received in the first timeslot to the first receiving end, and the second target relays B13 and B14 transmit signals received in the first time slot 2 to the receiving end.

At this time, the signals received by the receiving terminals C11 and C12 in the first time slot can be expressed by Equation (7) below.

&Quot; (7) "

,

는 송신단(A11 및 A12) 각각에서 송신한 신호를 나타내고,

,

는 수신단(C11 및 C12) 각각에서 수신된 신호를 나타내고,

,

는 수신단(C11 및 C12) 각각에서의 노이즈를 말한다. 또한, (.)는 시간 인덱스를 말하며,

는 송신단(A11 및 A12)의 각각과 제1 수신단 간의 채널 이득을 나타내고,

는 송신단(A11 및 A12)의 각각과 제2 수신단 사이의 채널 이득을 나타낸다. 수신단(C11 및 C12)의 각각은 송신단(A11 및 A12) 및 대상 릴레이들 각각과, 수신단(C11 및 C12) 사이의 채널 정보를 알기 때문에, 제로 포싱을 통해 간섭 신호를 제거할 수 있다.here

,

Represents signals transmitted from the transmitting terminals A11 and A12, respectively,

,

Represents the signal received at each of the receiving ends C11 and C12,

,

Quot; refers to noise at each of the receiving ends C11 and C12. Also, (.) Denotes a time index,

Represents a channel gain between each of the transmitting ends A11 and A12 and the first receiving end,

Represents a channel gain between each of the transmitting ends A11 and A12 and the second receiving end. Each of the receiving ends C11 and C12 knows the channel information between the transmitting ends A11 and A12 and the target relays and the receiving ends C11 and C12 so that the interference signal can be removed through zero forcing.

At this time, in each of the receiving terminals C11 and C12, the interference canceled signal can be expressed by Equation (8) below.

&Quot; (8) "

,

,

는 제i 수신단에서의 제로포밍을 나타내고,

,

는 각각의 제로 포싱 이후의 제1 및 제2 수신단에서의 노이즈를 나타낸다.here

Represents the zero-forming at the i < th > receiving end,

,

Represents the noise at the first and second receiving ends after each zero-forcing.

Then, in the second timeslot, each of the target relays performs beamforming using the position information of the corresponding receiving end, and transmits the signal to the target receiving end via the performed beamforming.

The zero-forming in the target relays can be expressed as Equation (9) below.

&Quot; (9) "

Through the above-described zero-forming, the signals received by the first and second receiving terminals can be expressed by Equation (10) below.

&Quot; (10) "

FIG. 7 is a diagram for explaining performance enhancement of beam forming according to the cooperative communication method of FIG. 6; FIG.

Referring to FIG. 7, a cooperative communication 720 according to an embodiment of the present invention includes not only cooperative communication 700 with time-division multiplexing, but also cooperative communication with receiving end zero- ), It can be seen that there is a DoF gain.

Generally, when the number of antennas of the transmitting end is N + 1, the number of receiving antennas is N, the number of relays is 2N, and each relay has two antennas, the DoF gain is 2 , But may be 2 * (N + 1) / 2 in the cooperative communication method to which the beamforming scheme of FIG. 6 is applied. Therefore, the DoF gain can be increased in proportion to N. [

Also, it can be confirmed that a transmission rate gain can be obtained even at a finite SNR. Even when the transmitting end and the receiving end are very close to each other, the relay can receive the signal by multiplying it by a random matrix for the multipath effect upon reception of the signal. This case corresponds to 730, and it can be seen that the transmission rate gain increases as the number of relays increases.

3) LOS BC ( Broadcast ) networks with moving Rx  & relay

FIG. 8 is a diagram showing a communication environment in which a relay and a receiving terminal are moved at a high speed in an LOS broadcast network. In this communication environment, two fast moving candidate relays 810 are disposed between the transmitting end 800 and the receiving end 820 for the sake of convenience. In the communication environment, one transmitting end 800 having three antennas, two receiving ends 820 having two antennas, two candidate relays 810 each having one antenna, And the transmitter 800 assumes that the receiver 820 and the candidate relay 820 can be located.

The transmitting terminal 800 does not know the channel information between the candidate relay 810 and the receiving terminal 820 and the candidate relay 810 does not know the channel information between the candidate relay 810 and the receiving terminal 820 because the receiving terminal 820 and the candidate relay 810 are moving at high speed. The receiver 820 does not know the channel information. Therefore, there is no transmission channel information (Channel Status Information at Transmit, CSIT) between all nodes.

By using the pilot signal, the candidate relay 810 can know the channel information between the transmitting terminal 800 and the candidate relay 810, and the receiving terminal 820 can acquire channel information between the transmitting terminal 800 and the receiving terminal 820, , The channel information between the candidate relay 810 and the receiving end 820 can be known. Therefore, there is a channel status information at receiver (CSIR) between all nodes.

2, the transmitting terminal 800 may select a target relay to be used in the cooperative communication among the candidate relays 810, and may start the cooperative communication by interworking with the selected target relay . Likewise, the candidate relay 810 may selectively perform cooperative communication with the receiving end through the operation procedure of FIG. 2 described above.

9 illustrates a cooperative communication situation in which a symbol extension is performed through a 4-timeslot in a cooperative communication method according to another embodiment of the present invention. A detailed beam forming process in the cooperative communication situation is as follows.

Referring to FIG. 9, in a first time slot, the transmitting terminal al transmits a signal for the first receiving terminal c1 to the first receiving terminal c1 and the target relays b1 and b2.

In the second timeslot, the target relays b1 and b2 transmit the received signal in the first timeslot to the first receiving end c1.

In the third time slot, the transmitting terminal a1 transmits the signal for the second receiving terminal c2 to the second receiving terminal c2 and the target relays b1 and b2.

In the fourth timeslot, the target relays b1 and b2 transmit signals received in the third timeslot to the second receiving station c2.

10 is a diagram for explaining performance enhancement of a cooperative communication method according to another embodiment of the present invention.

Referring to FIG. 10, it can be seen that the cooperative communication method (see 1010) according to another embodiment of the present invention has a DoF gain as compared with the general time division multiplex communication method (1000).

If the number of antennas in the transmitting terminal is N + 1, the number of antennas in the receiving terminal is N, the number of relays is N, and each antenna has one antenna, the DoF gain can be expressed as (N + 1) / 2. Therefore, it can be seen that the DoF gain increases in proportion to N. It can be seen that the transmission gain can be obtained even at the finite SNR, and the transmission gain increases as the number of relays increases.

4) LOS BC ( Broadcast ) networks with fixed Rx  & moving relay

11 shows an environment in which a relay moves at a high speed and a receiving end moves at a fixed or a low speed in an LOS broadcast network in which collaborative communication in another embodiment of the present invention is performed.

Referring to FIG. 11, it is assumed that there are two relays between the transmitting end and the receiving end in the above environment for convenience of explanation. Further, it is assumed that the transmitting end can acquire information on the position of the receiving end and the relay. It is assumed that the number of transmitting terminals having four antennas is 1, the number of receiving terminals having three antennas is two, and the number of relays used for cooperative communication is three and each has three antennas.

In this environment, since the relay moves at a high speed, the transmitting end does not know the channel information between the transmitting end and the relay. On the other hand, since the receiving end is fixed or moving at low speed, the transmitting end can know the angle information of the channel between the transmitting end and the receiving end, and the relay can know the angle information of the channel between the relay and the receiving end. Also, according to the pilot signal, the relay can know the channel information between the transmitting end and the relay, the receiving end can know the channel information between the transmitting end and the receiving end, and the relay can know the channel information between the relay and the receiving end. Therefore, there is reception channel information (CSIR) between each node.

The transmitting terminal 1100 can select a target relay to use for the cooperative communication among the candidate relays 1110 through the operation of FIG. 2 described above, and can start the cooperative communication through interworking with the selected target relay. Likewise, the candidate relay 1110 may selectively perform cooperative communication with the receiving end 1120 through the operation procedure of FIG. 2 described above.

FIG. 12 shows a cooperative communication situation when a symbol extension through a 3-time slot is performed in a cooperative communication according to another embodiment of the present invention. The concrete beam forming process in the above embodiment is as follows.

Referring to FIG. 12, in the first time slot, the transmitting terminal a11 transmits a signal for the first receiving terminal among the receiving terminals c11 and c12 to the first receiving terminal and the object relays b11 to b13.

In the second time slot, the transmitting terminal al transmits a signal for the second receiving terminal of the receiving terminals c11 and c12 to the second receiving terminal and the object relays b11 to b13.

In the third time slot, the target relays b11 to b13 carry out zero-forming using the first receiving end and the second receiving end position information on the signals respectively received in the first time slot and the second time slot, And transmits each of the applied signals to the first receiving end and the second receiving end, respectively.

At this time, in the third timeslot, the signals transmitted by the target relays b11 to b13 can be expressed by the following Equation (11), and the zero forcing in each of the target relays b11 to b13 can be expressed by Equation (12) .

&Quot; (11) "

&Quot; (12) "

,

는 제1 송신단에서의 송신 신호 및 제2 송신단에서의 송신 신호를 의미하고,

는 제1 내지 제3 대상 릴레이 각각에서의 송신신호를 의미한다. 또한,

,

,

는 제1 내지 제3 대상 릴레이 각각에서 제로포밍 이후의 노이즈를 의미하고, (.)는 시간 인덱스를 나타낸다. 또한,

는 제1 송신단 및 제2 송신단 각각에서 제1 대상 릴레이로의 채널 이득을 의미한다.

는 제i 대상 릴레이에서 제j 수신단으로의 신호의 간섭신호를 제거하기 위한 제로포밍을 의미한다. here,

,

Denotes a transmission signal at the first transmission terminal and a transmission signal at the second transmission terminal,

Means a transmission signal in each of the first to third target relays. Also,

,

,

Denotes noise after zero-forming in each of the first to third target relays, and () denotes a time index. Also,

Denotes a channel gain from the first transmitting terminal and the second transmitting terminal to the first target relay.

Means zero-forming for eliminating the interference signal of the signal from the i-th relay to the j-th receiver.

At this time, since the receiving terminals c11 and c12 know the channel information between the receiving terminals c11 and c12 and the target relays b11 to b12, the interference signals can be removed through zero forcing. The signal from which the interference signal has been removed can be expressed by Equation (13) below.

&Quot; (13) "

FIG. 13 is a diagram for explaining performance enhancement of a cooperative communication method according to another embodiment of the present invention.

Referring to FIG. 13, it can be seen that the cooperative communication method (see 1320) has a DoF gain as compared with the conventional time division multiplex communication method 1300 as well as the receiving end zero forcing method 1310.

If the number of antennas in the transmitting end is N + 1 and the number of receiving antennas is N and the N relays each have two antennas, the DoF gain is calculated from 2 to 2 * (N + 1) / 3, . Also, it can be seen that the transmission gain can be obtained even at a finite SNR, and the data rate gain increases as the number of relays increases.

14 is a view for explaining an apparatus for performing a cooperative communication method according to an embodiment of the present invention.

Referring to FIG. 14, the cooperative communication method is performed by a transmitting terminal 1400, a relay 1410, and a receiving terminal 1420. The cooperative communication method is modeled considering the mobility of the relay 1410 and the receiver 1420, respectively. In particular, the relay 1410 is composed of one or more candidate relays, and can move at a high speed as in the case of being mounted on a vehicle. The receiving end 1420 may be fast moving, slow moving, or fixed depending on the situation.

The transmitting terminal 1400 selects a target relay to perform cooperative communication with the receiving terminal 1420 among the one or more candidate relays moving at high speed and performs cooperative communication with the receiving terminal 1420 in conjunction with the selected target relay.

The transmission terminal 1400 may include a cooperation determination unit 1401, a relay determination unit 1402, and a data transmission unit 1403.

The cooperation determination unit 1401 determines whether cooperative transmission is required for the receiving terminal 1420 and transmits the reference signal 1402 to the one or more candidate relays when it is determined that the cooperative transmission is necessary. At this time, the cooperation determination unit 1401 receives the RSSI from the receiver 1420 and determines whether it is necessary to acquire a diversity gain or a multiplexing gain based on the received RSSI. If it is determined that the diversity gain or the multiplexing gain needs to be obtained as a result of the determination, the cooperation determination unit 1401 may determine that the cooperative transmission is necessary.

In addition, the cooperative determination unit 1401 may determine a threshold for limiting the number of relays to be used for the cooperative transmission among the one or more candidate relays, and notify the determined threshold to the one or more candidate relays.

At this time, depending on the communication environment, there may be cases where the transmitting terminal 1400 can acquire information about the positions of the relay 1410 and the receiving terminal 1420, or may not acquire the information.

First, if the transmitting terminal 1400 can acquire information on the positions of the relay 1410 and the receiving terminal 1420, the cooperation determining unit 1401 determines whether the receiving terminal 1420 and the relay 1410 Obtain information about the location. The cooperation determination unit 1401 reflects the obtained information on the actual model value of the channel path loss and calculates the distance between each of the receiving end 1420 and the candidate relay 1410 and the transmitting end 1400 It is possible to predict the channel gain according to the channel gain. The cooperation determination unit 1401 may determine a threshold corresponding to the relay limit number to be used for the cooperative transmission based on the predicted channel gain.

The cooperation determination unit 1401 may transmit the determined threshold to the relay that is found through the scanning. That is, the cooperative determination unit 1401 may transmit MAP information including the determined threshold, together with a reference signal (RS), to the searched relay. In addition, the cooperation determination unit 1401 may transmit the uplink SRS information of the receiving end requiring a cooperative communication (i.e., the receiving end having a small RSSI size) to the searched relay.

 On the other hand, in the case of a communication environment in which the transmitter 1400 can not acquire information on the positions of the relays 1410 and 1420, the cooperation determiner 1401 may set the threshold as large as possible

On the other hand, the relay determining unit 1402 receives an indicator from the relay 1410 indicating that cooperative communication is possible with the receiving end 1420. Then, the relay determination unit 1402 determines the relay that transmitted the indicator as the target relay of the cooperative communication with the receiving end 1420.

The data transmission unit 1403 transmits information for instructing the target terminal 1420 to cooperate communication with the determined target relay 1420 and transmits the data signal of the cooperative communication to the receiving terminal 1420 and the target relay.

Meanwhile, the relay 1410 may be one of one or more candidate relays moving at high speed, and may include an acquisition unit 1411, a possibility determination unit 1412, and a cooperation communication unit 1413.

The acquiring unit 1411 acquires information on the first channel quality between the relay 1410 and the transmitting terminal 1400 and information on the second channel quality between the relay 1410 and the receiving terminal 1420. [ That is, the acquiring unit 1411 may receive the reference signal from the transmitting terminal 1400 and calculate the information about the first channel quality between the relay 1410 and the transmitting terminal 1400. The acquiring unit 1411 may receive the uplink reference signal from the receiving end 1420 and calculate information about the second channel quality between the relay 1410 and the receiving end 1420. [

The possibility determining unit 1412 determines whether the relay 1410 can perform cooperative communication with the receiving terminal 1420 using at least one of the first channel quality and the second channel quality and outputs an indicator indicating the determination result To the transmitting terminal 1400.

) 또는 상기 제2 채널 품질(

)를 기초로 릴레이 채널 이득(

)을 추정할 수 있다. Here, the possibility judging unit 1412 judges whether the first channel quality (

) Or the second channel quality (

) On the basis of the relay channel gain (

) Can be estimated.

If the current communication environment is a high-speed movement of the relay and the receiver in the LOS broadcast cooperative channel, only one transmission / reception pair is considered at a time, so that the relay channel gain can be expressed as Equation (14) below.

 &Quot; (14) "

In other cases, if the relay in which the current communication environment moves at a high speed in the LOS broadcast cooperative channel is arranged and a low-speed or fixed reception end is arranged, the relay needs to serve all of the plurality of reception ends. In this case, the relay channel gain can be expressed as Equation (15) below, taking into account the relay channel between all transmission and reception ends.

&Quot; (15) "

In another case, in the LOS interference cooperative channel, if the relay and the receiver are in a high-speed communication environment, the relay has to service a plurality of receivers. Therefore, the relay channel gain can be expressed by the following Equation (16) in consideration of the relay channel between all the transmitting and receiving ends.

&Quot; (16) "

)과 상기 임계치를 비교하고, 상기 비교결과에 따라, 수신단(1400) 각각에 대하여 협력 통신이 가능한 지를 나타내는 지시자를 송신단(1400)로 전송한다.The possibility judging unit 1412 judges whether the relay channel gain (

And transmits the indicator indicating whether cooperative communication is possible to each of the receiving terminals 1400 to the transmitting terminal 1400 according to the comparison result.

The possibility determining unit 1412 compares the first channel quality or the second channel quality calculated by the obtaining unit 1411 with the threshold value and determines that cooperative communication with the receiving terminal 1420 is possible according to the comparison result You can decide.

The cooperation communication unit 1413 receives the information instructing the cooperative communication with the receiving terminal 1420 from the transmitting terminal 1400 after transmitting the indicator indicating the determination result by the possibility judging unit 1412. [ In this case, the cooperative communication unit 1413 performs cooperative communication with the receiving end 1420 through interworking with the transmitting end 1400.

On the other hand, if the current communication environment is a LOS interference cooperative channel, if the relay moves at a high speed and the receiving end is fixed or moves at a low speed, since the transmitting end and the receiving end are fixed, scatter) is determined. In this case, instead of selecting a separate relay, an active area for serving each receiving end may be set in advance, and the relay entering the active area may be controlled to be performed as a target relay of cooperation communication. That is, the possibility determining unit 1412 of the relay 1410 can transmit an indicator to the transmitting terminal 1400 indicating whether cooperative communication is possible according to whether or not the mobile terminal has entered the active area.

The methods according to embodiments of the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and configured for the present invention or may be available to those skilled in the art of computer software.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

Claims (16)

A collaborative communication method of a target relay which is one of at least one candidate relay moving,
Obtaining information on a first channel quality between the target relay and the transmitting end and information on a second channel quality between the target relay and the receiving end;
Determining whether the target relay is capable of cooperative communication with the receiving end using at least one of the first channel quality and the second channel quality; And
Transmitting an indicator indicating the determination result to the transmitting terminal
Lt; / RTI >
Wherein the acquiring comprises:
Receiving a reference signal from the transmitting terminal
Lt; / RTI >
The reference signal of the transmitting terminal,
(MAP) information including a threshold determined by the transmitting terminal to limit the number of relays to be used for the cooperative communication,
Wherein the determining step comprises:
And determining whether the cooperative communication is possible by comparing at least one of the first channel quality and the second channel quality with the threshold. The method according to claim 1,
Comparing the channel having the lower quality of the first channel quality and the second channel quality with a predetermined threshold
Further comprising:
The step of determining whether cooperative communication with the receiving terminal is possible
And determining a cooperative communication possibility for the receiving terminal based on the comparison result
Cooperative communication method of target relay. The method according to claim 1,
Wherein the step of acquiring information on the first channel quality and information on the second channel quality comprises:
Receiving an uplink reference signal from the receiving end;
Calculating information on a first channel quality between the target relay and the transmitter based on the received reference signal of the transmitter; And
Calculating information on a second channel quality between the target relay and the receiving end based on the uplink reference signal of the receiving end
And a destination relay. The method according to claim 1,
Initiating cooperative communication with the receiving end according to whether information for instructing cooperating communication with the receiving end is received from the transmitting end
Further comprising the steps of: 5. The method of claim 4,
If the current network environment is an LOS interference cooperative channel network,
The step of initiating the collaborative communication to the receiving end
Receiving data signals for the one or more receiving ends from the transmitting end in a first time slot and sequentially receiving data signals received for each of the one or more receiving ends in a second time slot and a subsequent time slot, Transmitting
Cooperative communication method of target relay. The method of claim 4, wherein
If the current network environment is an LOS broadcast network,
The step of initiating the collaborative communication to the receiving end
In at least one timeslot, receives a data signal for one destination destination from one or more destinations, respectively, and then forwards the received data signal to the destination destination in a timeslot
Cooperative communication method of target relay. A collaborative communication method of a transmitting end for interworking with at least one moving candidate candidate relay,
Determining whether cooperative transmission is necessary for the receiving end;
Determining a threshold for limiting the number of relays to be used for the cooperative transmission among the one or more candidate relays if the cooperative transmission is determined to be necessary;
Transmitting a reference signal to the one or more candidate relays if the cooperative transmission is determined to be necessary, the reference signal including map information including the determined threshold; And
Determining a candidate relay among the one or more candidate relays as an object relay of the cooperative transmission to transmit an indicator indicating that cooperative communication is possible to the receiving end;
Lt; / RTI >
The candidate relay includes:
And determining whether the cooperative communication is possible using the threshold value. delete 8. The method of claim 7,
Transmitting information for instructing the target relay to the coordinated communication to the receiving end
Further comprising the steps of: A target relay, which is one of at least one candidate relay moving,
An acquiring unit acquiring information on a first channel quality between the target relay and the transmitting end and information on a second channel quality between the target relay and the receiving end; And
A possibility determination unit for determining whether the target relay is capable of cooperative communication with the receiver using at least one of the first channel quality and the second channel quality and transmitting an indicator indicating the determination result to the transmitter;
Lt; / RTI >
Wherein the obtaining unit comprises:
(MAP) information including a threshold determined by the transmitting end to limit the number of relays to be used for the cooperative communication,
The possibility judging unit judges,
And compares at least one of the first channel quality or the second channel quality with the threshold to determine whether the cooperative communication is possible. 11. The method of claim 10,
The possibility judging unit
Compares at least one of the first channel quality or the second channel quality with a predetermined threshold and determines a cooperative communication possibility for the receiving terminal according to the comparison result
Target Relay. 11. The apparatus of claim 10, wherein the obtaining unit
Calculating information on a first channel quality between the target relay and the transmitting terminal using the reference signal received from the transmitting terminal, and calculating information on a first channel quality between the target relay and the receiving terminal using the uplink reference signal received from the receiving terminal, To calculate information about channel quality
Target Relay. 11. The method of claim 10,
A cooperative communication unit for starting cooperative communication with the receiving end according to whether information for instructing cooperative communication with the receiving end is received from the transmitting end;
The target relay further comprising: A transmitting terminal for performing cooperative communication with a receiving end in cooperation with at least one of moving one or more candidate relays,
A cooperative determination unit for determining whether cooperative transmission is required to the receiving end and transmitting a reference signal to the at least one candidate relay when it is determined that the cooperative transmission is necessary; And
A relay determining unit that determines a candidate relay that has transmitted the indicator as a target relay of cooperative communication with the receiving end, when an indicator indicating that cooperative communication with the receiving end is possible is received from at least one of the one or more candidate relays;
Lt; / RTI >
The cooperative determination unit
Determining a threshold for limiting the number of relays to be used for the cooperative transmission among the one or more candidate relays, notifying the determined threshold to the one or more candidate relays,
The candidate relay includes:
And determining whether the cooperative communication is possible using the threshold value. delete 15. The method of claim 14,
A data transmission unit for transmitting information for instructing cooperative communication to the receiving end to the determined target relay and for transmitting a data signal of cooperative communication to the receiving end to the receiving end and the target relay;
Further comprising:

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