KR102049085B1 - Method of controlling interference in a multi-hop network based on mimo system and a relay node and node pair enabling the method - Google Patents

Method of controlling interference in a multi-hop network based on mimo system and a relay node and node pair enabling the method Download PDF

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KR102049085B1
KR102049085B1 KR1020130125410A KR20130125410A KR102049085B1 KR 102049085 B1 KR102049085 B1 KR 102049085B1 KR 1020130125410 A KR1020130125410 A KR 1020130125410A KR 20130125410 A KR20130125410 A KR 20130125410A KR 102049085 B1 KR102049085 B1 KR 102049085B1
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interference
node
signal
nodes
destination
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KR20140142643A (en
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신원재
노원종
임종부
장경훈
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삼성전자주식회사
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Priority to JP2014114019A priority Critical patent/JP6506919B2/en
Priority to US14/293,348 priority patent/US9531449B2/en
Priority to EP14170907.1A priority patent/EP2819315B1/en
Priority to CN201410245145.8A priority patent/CN104218980B/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/15592—Adapting at the relay station communication parameters for supporting cooperative relaying, i.e. transmission of the same data via direct - and relayed path
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/026—Co-operative diversity, e.g. using fixed or mobile stations as relays
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/04—Arrangements for maintaining operational condition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

Disclosed are a relay node and a node pair using an interference control method and an interference control method in a multi-hop network based on a MIMO system. In an interference control method in a multi-hop network according to an embodiment, relay signals received from source nodes among pairs of nodes are relayed to destination nodes paired with the source nodes, and channel coefficients of the relay nodes. The control unit may remove the interference signal of at least some of the interference signals between two or more node pairs. In addition, in node pairs, a signal received at destination nodes may be used to remove a residual interference signal among interference signals between two or more node pairs.

Description

FIELD OF CONTROLLING INTERFERENCE IN A MULTI-HOP NETWORK BASED ON MIMO SYSTEM AND A RELAY NODE AND NODE PAIR ENABLING THE METHOD}

The following embodiments are related to a relay node and a node pair using an interference control method and an interference control method in a multi-hop network based on a MIMO system.

Until now, communication systems have been used mainly as a means of connecting people. As a result, only about 1% of the devices on the planet are currently connected and used in networks. However, with the development of communication technology and the unification trend of device integration, various devices with smart phones, sensor devices, and other communication functions form a huge network. In addition, users of many communication terminals utilize various applications such as content sharing, synchronization, output, and games through direct connection between devices. In order to respond to the changing demands of the market, there are wireless access technologies capable of supporting device-to-device (D2D communication) beyond cellular communication using an existing infrastructure.

In the early days, D2D communication was a transmission scheme assuming a single hop, but future D2D communication will use multi-hop. In addition, the relay technology up to now has used a plurality of relay nodes to obtain diversity gain or multiplexing gain assuming that there is only one source node and one destination node. In the future, it is expected that a plurality of node pairs transmit signals at once, such as a MULTIPLE UNICAST MULTI-HOP network. Accordingly, research for controlling interference between multiple node pairs and multiple relay nodes continues.

In one embodiment, an interference control method in a multi-hop network includes an interference control method of two or more relay nodes and node pairs in a multi-hop network, wherein the relay nodes include a source of the node pairs. ) A signal received from nodes is relayed to destination nodes paired with the source nodes, but the interference signal between the two or more node pairs is adjusted by adjusting a channel coefficient of the relay nodes. Removing at least some of the interfering signals; And removing, at the node pairs, residual interference signals among the interference signals between the two or more node pairs by using the signals received at the destination nodes.

The steps may be performed in the signal transmission process between the relay nodes and the node pairs.

The step of removing the at least some interference signal comprises: generating an effective interference channel matrix corresponding to the at least some interference signal based on the interference channel matrices between the source nodes and the destination nodes; Generating a reference matrix representing a null space of the effective interference channel matrix by adjusting the channel coefficients; And removing the at least some interference signals using the effective interference channel matrix and the reference matrix.

Generating the effective interference channel matrix comprises: a first channel matrix corresponding to an interference signal of at least some of the first interference signals between the source nodes and the relay nodes and a first channel matrix between the relay nodes and the destination nodes; Obtaining a second channel matrix corresponding to the interference signal of at least some of the two interference signals; And generating the effective interference channel matrix based on the first channel matrix and the second channel matrix.

Generating the effective interference channel matrix may include transposing the first channel matrix; And calculating a Kronecker product of the second channel matrix and the transposed first channel matrix.

The reference matrix may be included in the null space of the effective interference channel matrix and may include a plurality of null space vectors except for a zero vector.

The number of relay nodes may be less than the number of relay nodes designed to eliminate the entirety of the interference signal between the node pairs.

The signal transmission process may be performed using either a time division scheme or a frequency division scheme.

The source node or the destination node is a multiple input multiple output (MIMO) scheme, and may further include removing internal interference signals between two or more antennas included in each of the node pairs. .

The removing of the internal interference signal may include zero-forcing beamforming when there is full-channel state information at transmitter (Full-CSIT) between the source nodes and the destination nodes. It may be a step of removing internal interference signals of the node pairs using a Forcing BeamForming (ZFBF) technique.

The removing of the internal interference signal may include: when there is no transmission channel information between the source nodes and the destination nodes (No-Channel State Information at transmitter: No-CSIT), the destination in another signal transmission process. Based on a signal of some of the signals received by the nodes, it may be a step of removing the internal interference signal using a successive interference cancellation (SIC) technique.

The removing of the residual interference signal may include removing the residual interference signal based on a signal of some of the signals received by the destination nodes in another signal transmission process.

The number of signal transmission processes may be greater than or equal to the number of signals.

When there are two relay nodes, the steps may be performed in a first signal transmission process or a third signal transmission process.

The removing of the at least some of the interference signals may include any of the antennas included in the second destination node in any one antenna included in the first source node among the interference signals between the node pairs. Removing the remaining interference signals except for the interference signal transmitted to one antenna; In the second signal transmission process, interference other than interference signals transmitted from any one antenna included in the second source node among the interference signals between the node pairs to any one antenna included in the first destination node. Removing the signal; And an interference signal transmitted from any one antenna included in the first source node among the interference signals between the node pairs to any one antenna included in the second destination node in the third signal transmission process. The method may include removing any interference signal except for an interference signal transmitted from any one antenna included in the second source node to any one antenna included in the first destination node.

In the third signal transmission process, the relay node is the same as the interference signal transmitted from any one antenna included in the first source node to any one antenna included in the second destination node in the first signal transmission process. The same signal as the interference signal received from the first source node, and transmitted from any one antenna included in the second source node to any one antenna included in the first destination node in the second signal transmission process. Can be received from the second source node.

In the third transmission process, the removing of the residual interference signal may include removing the residual interference signal based on a signal of some of the signals received by the destination nodes in the first transmission process and the second transmission process. Can be.

In another embodiment, a method of controlling interference in a multi-hop network may include: controlling an interference of two or more relay nodes and node pairs in a multi-hop network, in the relay nodes, a source of the node pairs; source relays the real component signal and the imaginary component signal received from the nodes to destination nodes paired with the source nodes, and adjusts the channel coefficients of the relay nodes. Removing at least some of the interference signals among the interference signals between the node pairs; And removing, at the node pairs, residual interference signals of the interference signals between the two or more node pairs using at least one of a real component signal and an imaginary component signal received at the destination nodes. Can be.

The steps may be performed in the signal transmission process between the relay nodes and the node pairs.

In one embodiment, a method for controlling interference of a relay node in a multi-hop network includes: receiving a signal from source nodes among node pairs; And relaying the received signal to destination nodes paired with the source nodes, wherein at least some of the interference signals between the two or more node pairs are adjusted by adjusting a channel coefficient of the relay node. It may include removing the interference signal of the.

The steps may be performed in the signal transmission process between the relay nodes and the node pairs.

In one embodiment, a method of controlling interference of two or more node pairs in a multi-hop network includes: transmitting a signal from source nodes of the source node pairs to the destination nodes through relay nodes; And removing residual interference signals among the interference signals between the two or more node pairs by using the signals received at the destination nodes.

The steps may be performed in the signal transmission process between the relay nodes and the node pairs.

1 is a diagram illustrating a multi-hop network and an alternating topology according to an embodiment.
2 is a diagram for describing a multi-hop network based on a MIMO system, according to an exemplary embodiment.
FIG. 3 is a diagram illustrating removal of at least some of interference signals among interference signals between node pairs, according to an exemplary embodiment.
4A and 4B are diagrams illustrating removal of a residual interference signal among interference signals between node pairs when there is no transmission channel information according to an embodiment.
FIG. 5 is a diagram illustrating removal of a residual interference signal among interference signals between node pairs when total transmission channel information exists according to an embodiment.
6 is a diagram for describing an interference control method in a multi-hop network in an SISO system, according to an exemplary embodiment.
7 is a flowchart illustrating an interference control method in a multi-hop network according to an exemplary embodiment.
8 is a flowchart illustrating an interference control method in a multi-hop network in an SISO system according to an exemplary embodiment.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. However, the present invention is not limited or limited by the embodiments. Also, like reference numerals in the drawings denote like elements.

Multi-hop network and Alternate Topology >

1 is a diagram illustrating a multi-hop network and an alternating topology according to an embodiment.

Referring to FIG. 1, multi-hop network 110 includes two or more source nodes, two or more relay nodes, and two or more destination nodes. For example, a multi-hop network may include K source nodes, K relay nodes, and K destination nodes. In multi-hop network 110, source nodes may send signals to destination nodes via relay nodes. An example of the multi-hop network 110 may be a case in which multiple users belonging to a cellular system transmit data to a plurality of base stations through a plurality of relays. When multiple node pairs transmit signals at the same time, inter-stream interference may occur as signals (or streams) between different node pairs are mixed in a multi-hop process. Therefore, the following provides a scheme for controlling interference in a multi-hop network using cooperation between relay nodes and node pairs.

Specifically, in the multi hop network 110,

Figure 112013094941487-pat00001
And
Figure 112013094941487-pat00002
Can represent each source node,
Figure 112013094941487-pat00003
And
Figure 112013094941487-pat00004
Can represent a relay node,
Figure 112013094941487-pat00005
And
Figure 112013094941487-pat00006
May represent the destination node. At this point, the source node
Figure 112013094941487-pat00007
This destination node
Figure 112013094941487-pat00008
The source node if you want to send signals
Figure 112013094941487-pat00009
And destination nodes
Figure 112013094941487-pat00010
May form a fair. Each source node
Figure 112013094941487-pat00011
Is the destination node of each pair
Figure 112013094941487-pat00012
Figure 112013094941487-pat00013
It may include each signal to transmit to. The channel matrix between the source nodes and the relay nodes can be called H 1 ,
Figure 112013094941487-pat00014
The channel between the relay nodes and the destination nodes may be referred to as H 2 ,
Figure 112013094941487-pat00015
It can be represented as. Also, in one embodiment. Channel gains may be real and may be derived by continuous distribution. The channel matrices can be fixed while the node pairs and relay nodes are communicating, and the channel matrices can be known to all nodes.

Source node in time slot k

Figure 112013094941487-pat00016
The transmission signal of the
Figure 112013094941487-pat00017
And the transmission signal at the relay node r is
Figure 112013094941487-pat00018
It can be defined as. Received signal at relay node r in time slot k
Figure 112013094941487-pat00019
Can be expressed as Equation 1 below, and the destination node in time slot k
Figure 112013094941487-pat00020
Received signal from
Figure 112013094941487-pat00021
May be expressed as Equation 2 below.

[Equation 1]

Figure 112013094941487-pat00022

[Equation 2]

Figure 112013094941487-pat00023

here,

Figure 112013094941487-pat00024
And
Figure 112013094941487-pat00025
Respectively may represent iid (independently and identically distributed) noise at the relay node and iid noise at the destination node,
Figure 112013094941487-pat00026
Can be followed.
Figure 112013094941487-pat00027
Random column vector
Figure 112013094941487-pat00028
To define the
Figure 112013094941487-pat00029
when,
Figure 112013094941487-pat00030
Is
Figure 112013094941487-pat00031
It can be defined as.

An interference control scheme in a multi-hop network according to an embodiment may control interference in a multi-hop network by using cooperation between relay nodes and node pairs. Relay nodes may generate alternating topologies, such as topologies 120 to 150 by adjusting the channel coefficients to remove the interfering links. Here, the alternating topology may refer to a network between source nodes and destination nodes that can be equivalently represented as the connectivity of the interference link changes with time or frequency. Node pairs can transmit and receive signals using an alternating topology. For example, when K node pairs transmit N signals at the same time, K source nodes may transmit N signals to the relay node through M (≧ N) transmission steps. In this case, since the channel coefficients of the relay nodes are adjusted differently in each transmission step, the degree of the interference signal that K destination nodes receive from source nodes that are not pairs in each transmission step may vary. This may mean that the interference link from the plurality of source nodes to the plurality of destination nodes varies in each transmission step.

For example, in topology 120, source node

Figure 112013094941487-pat00032
Destination node in
Figure 112013094941487-pat00033
Link and source nodes to the target
Figure 112013094941487-pat00034
Destination node in
Figure 112013094941487-pat00035
All interfering links may exist. In topology 130, source node
Figure 112013094941487-pat00036
Destination node in
Figure 112013094941487-pat00037
Interference link to the node exists but source node
Figure 112013094941487-pat00038
Destination node in
Figure 112013094941487-pat00039
May not exist, and in topology 140, the source node
Figure 112013094941487-pat00040
Destination node in
Figure 112013094941487-pat00041
Source link exists but source node
Figure 112013094941487-pat00042
Destination node in
Figure 112013094941487-pat00043
There may be no interfering link to. In topology 150, source node
Figure 112013094941487-pat00044
Destination node in
Figure 112013094941487-pat00045
Link and source nodes to the target
Figure 112013094941487-pat00046
Destination node in
Figure 112013094941487-pat00047
There may not be any interfering links to.

< MIMO  System-Based Multi-hop Networks>

2 is a diagram for describing a multi-hop network based on a MIMO system, according to an exemplary embodiment.

Referring to FIG. 2, a multi-hop network based on a MIMO system according to an embodiment includes two or more source nodes, two or more relay nodes, and two or more destination nodes. For example, the network may include K source nodes, L relay nodes, and K destination nodes.

Hereinafter, it is assumed that K is 2 and L is 2 for convenience of description. Here, the source nodes may include simultaneous transmission nodes using the same frequency, and the relay nodes may include cooperative relay nodes operating in half-duplex.

The source node and the destination node each include at least two antennas, and the relay node may each include at least one antenna. For example, both the source terminal and the destination terminal may include M antennas, and the i th relay terminal may include N i antennas.

The source node may form a node pair with the destination node. Hereinafter, assume that a first source node S 1 intends to transmit data to a first destination node D 1 , and a second source node S 2 wants to transmit data to a second destination node D 2 . In this case, the first source node S 1 and the first destination node D 1 form a pair, and the second source node S 2 and the second destination node D 2 form a pair.

The first source node S 1 may transmit data to the first destination node D 1 through two relay nodes. The second source node S 2 may send data to the second destination node D 2 through two relay nodes.

The channel between the plurality of antennas included in each of the source nodes and at least one antenna included in each of the relay nodes may be represented by a first channel matrix H as a first hop channel. For example, referring to Equation 3, the first channel matrix H is

Figure 112013094941487-pat00048
It can be a matrix of magnitudes.

[Equation 3]

Figure 112013094941487-pat00049

The received signal vector received by the i-th relay node through the first hop channel is represented by Equation 4.

[Equation 4]

Figure 112013094941487-pat00050

here,

Figure 112013094941487-pat00051
Is a Nl x 1 channel output vector and H l , i is an Nl x M channel matrix from the i th source node to the first relay node. z l is a noise vector received at the first relay node.

The i relay node receives the received

Figure 112013094941487-pat00052
New transmission signal based on
Figure 112013094941487-pat00053
Can be generated. New transmission signal generated by relay node i
Figure 112013094941487-pat00054
Is the same as Equation 5.

[Equation 5]

Figure 112013094941487-pat00055

here,

Figure 112013094941487-pat00056
For the first relay node
Figure 112013094941487-pat00057
Relay beamforming matrix of magnitude.

Meanwhile, a channel between at least one antenna included in each of the relay nodes and a plurality of antennas included in each of the destination nodes may be represented by a second channel matrix G as a second hop channel. have. For example, referring to equation (6), the second channel matrix G is

Figure 112013094941487-pat00058
It can be a matrix of magnitudes.

[Equation 6]

Figure 112013094941487-pat00059

The received signal vector received by the jth destination node through the second hop channel is represented by Equation 7.

[Equation 7]

Figure 112013094941487-pat00060

here,

Figure 112013094941487-pat00061
Is a channel matrix of M × Nl size from the first relay node to the jth destination node,
Figure 112013094941487-pat00062
Is a noise vector received at the jth destination node.

Hereinafter, inter-user interference and intra-user interference between node pairs in a MIMO-based multi-hop network according to an embodiment will be described in detail.

< MIMO  Nodes in a System-Based Multi-hop Network Pairs  Interference Cancellation Techniques

FIG. 3 is a diagram illustrating removal of at least some of interference signals among interference signals between node pairs, according to an exemplary embodiment.

Referring to FIG. 3, a relay node may relay a signal received from a source node among node pairs to destination nodes paired with source nodes. In this case, the relay node may remove interference of at least some of the interference signals between two or more node pairs through an interference neutralization technique by adjusting a channel coefficient.

In one embodiment, the relay node uses a relay beamforming matrix in which the first hop channel and the second hop channel are considered simultaneously, such that a signal transmitted from other source nodes other than the source node in which the destination node is paired with the corresponding destination node. You can prevent it from interfering. In this case, the relay node may perform linear beamforming.

Depending on the number of relay nodes, the interference signal between the node pairs may be eliminated entirely, or at least partly. The number of relay nodes may be less than the number of relay nodes designed to eliminate the entirety of the interfering signal between the node pairs. In the interference neutralization scheme, the number of relay nodes that can eliminate the entirety of the interfering signal between the node pairs is

Figure 112013094941487-pat00063
The number of relay nodes that can remove at least a portion of the interference signal between the node pairs is
Figure 112013094941487-pat00064
It can be represented as. Here, L represents the number of relay nodes and K represents the number of source nodes or destination nodes. In one embodiment, the relay node may determine whether to remove all of the interference signals between the node pairs or at least some of the interference signals between the node pairs in consideration of the number of node pairs and the number of relay nodes.

(1) When the number of relay nodes is L≥K (K-1) +1

The number of relay nodes

Figure 112013094941487-pat00065
If, the relay node can eliminate the entirety of the interference signal between the node pairs. In this case, the received signal received by the destination nodes can be represented by Equation (8).

[Equation 8]

Figure 112013094941487-pat00066

Here, x i is a symbol transmitted by the i th source node. Also, h ij is a MIMO channel from the j th source node to the i th relay node, and g ij is a MIMO channel from the j th relay terminal to the i th destination terminal. w i is a beamforming matrix of the i-th relay terminal, and can be generated by adjusting channel coefficients.

In equation (8)

Figure 112013094941487-pat00067
The zero elements of the off-diagonal block matrix of means that interference by other source nodes that are not paired with a specific destination node is removed.

In this case, all but w i may be a given environmental value. For example, a relay node may know in advance values other than wi by receiving feedback from a base station or the like. The relay node may use w i to make the entire effective channel a block diagonal matrix.

The condition for removing the interference between node pairs may be expressed as in Equation (9).

[Equation 9]

g 11 w 1 h 12 + g 12 w 2 h 21 + g 13 w 3 h 32 = 0 MxM

g 21 w 1 h 11 + g 22 w 2 h 21 + g 23 w 3 h 31 = 0 MxM

Equation 10 is a Kronecker product

Figure 112013094941487-pat00068
Relation due to property of column vector stacking operation.

[Equation 10]

Figure 112013094941487-pat00069

Here, vec (X) is an operation to vectorize the matrix X. For example, if the size of the matrix X is mxn, the size of the vector vec (X) is mn x 1. Equation 9 may be modified as in Equation 11 according to Equation 10.

[Equation 11]

Figure 112013094941487-pat00070

here,

Figure 112013094941487-pat00071
Relay beamforming matrix
Figure 112013094941487-pat00072
Is a vector representation generated by column vector stacking operation.

The plurality of linear equations included in Equation 11 may be expressed in a matrix form of Equation 12.

[Equation 12]

Figure 112013094941487-pat00073

In this case, a solution that satisfies Equation 12 may be represented by Equation 13. Since matrix T is not a square matrix, the reference channel matrix

Figure 112013094941487-pat00074
Can always be present. The relay method according to an embodiment may generate a matrix T, that is, an effective interference channel matrix, using Equation 12.

[Equation 13]

Figure 112013094941487-pat00075

Here, null (A) is a null space of the matrix A. The null space of matrix A may be the set of all vectors y that satisfy Ay = 0. Therefore, the relay node is calculated through Equation 12

Figure 112013094941487-pat00076
The beamforming matrices for the plurality of relay terminals can be obtained by matrixing the vec (w i ) vectors included in the.

(2) When the number of relay nodes is L <K (K-1) +1

The number of relay nodes

Figure 112013094941487-pat00077
If, relay nodes can remove at least some of the interference signals between the pair of nodes. For example, if the number of node pairs is two, the number of relay nodes may be two. In this case, the received signals received by the destination nodes may be represented by Equation 14.

[Equation 14]

Figure 112013094941487-pat00078

Here, x i is a symbol transmitted by the i th source node. In addition, h ij is a MIMO channel from the j-th source node to the i-th relay node, g ij is a MIMO channel from the j-th relay terminal to the i-th destination terminal. w i is a beamforming matrix of the i-th relay terminal, and can be generated by adjusting channel coefficients.

The condition for removing the interference between the node pairs may be expressed as in Equation 15, and Equation 15 may be modified as in Equation 16 according to the Kronecker product operation.

[Equation 15]

g 11 w 1 h 12 + g 12 w 2 h 21 = 0 MxM

g 21 w 1 h 11 + g 22 w 2 h 21 = 0 MxM

[Equation 16]

Figure 112013094941487-pat00079

here,

Figure 112013094941487-pat00080
Relay beamforming matrix
Figure 112013094941487-pat00081
Is a vector representation generated by column vector stacking operation.

The plurality of linear equations included in Equation 16 may be expressed in a matrix form of Equation 17.

[Equation 17]

Figure 112013094941487-pat00082

In this case, since the effective interference channel matrix T is a square matrix, the reference matrix

Figure 112013094941487-pat00083
Cannot exist. Accordingly, the relay nodes may remove only some of the interference signals among the interference signals between the pair of nodes by adjusting the channel coefficients to generate the beamforming matrix of the relay terminal. Here, the reference matrix is included in the null space of the effective interference channel matrix and may include a plurality of null space vectors except for a zero vector.

In one embodiment, the node pair and the relay node may remove the internal interference signal and the interference signal between the node pairs by transmitting signals over the first to third transmission steps. (a), (b) and (c) illustrate an example of an interference cancellation technique for removing interference signals of at least some of interference signals between node pairs. The number of source antennas included in the source node and the destination antennas included in the destination node may be M. Antennas included in the first node pair may be represented by 1 to M, and antennas included in the second node pair may be represented by M + 1 to 2M.

(a) indicates the step of allowing only the interference signal from antenna 1 included in the first source node to antenna M + 1 included in the second destination node and removing the remaining interference signal (first transmission step), and (b ) Denotes a step of allowing only the interference signal from antenna M + 1 included in the second source node to antenna 1 included in the first destination node and removing the remaining interference signal (second transmission step), and (c) Only the interference signal from antenna 1 included in the first source node to antenna M + 1 included in the second destination node and the interference signal from antenna M + 1 included in the second source node to antenna 1 included in the first destination node Allowing and removing the remaining interference signal (third transmission step).

The first to third transmission steps may be performed using either a time division method or a frequency division method. When the first to third transmission steps are performed using a time division scheme, each transmission step may correspond to a respective time slot. When the first to third transmission steps are performed using a frequency division scheme, each transmission step may correspond to each frequency band. In one embodiment, the number of transmitting steps may be equal to or greater than the number of signals that the source node transmits to the destination node paired with the source node.

(a) shows the first transmission step. Each antenna of the first source node may transmit signals a 1 to a M , and each antenna of the second source node may transmit signals b 1 to b M. In order to remove the interference signal of at least some of the interference signals between the node pairs, the relay node only permits the interference signal from antenna 1 included in the first source node to antenna M + 1 included in the second destination node, and remaining interference The signal can be removed. In this case, the condition for removing the remaining interference signal except for the interference signal from the antenna 1 included in the first source node to the antenna M + 1 included in the second destination node may be represented by Equation 18.

 Equation 18

Figure 112013094941487-pat00084

Here, h ij is a MIMO channel from the j-th antenna included in the source node to the i-th relay node, and represents a first channel matrix corresponding to at least some of the interference signals between the source nodes and the relay nodes. Expressed in Equation 18

Figure 112013094941487-pat00085
Means that the first channel matrix is transposed. g ij is a MIMO channel from the j-th relay terminal to the i-th antenna included in the destination node, and means a second channel matrix corresponding to at least some of the interference signals between the relay nodes and the destination nodes. W i is a beamforming matrix of the i-th relay terminal, and may be generated by adjusting channel coefficients. In (a), since only the interference signal from antenna 1 included in the first source node to antenna M + 1 included in the second destination node is allowed, the antenna 1 from the first source node passes through the first relay node to the second. A component representing an interference signal transmitted to antenna M + 1 of a destination node.
Figure 112013094941487-pat00086
And a component representing an interference signal transmitted from antenna 1 of the first source node to antenna M + 1 of the second destination node via the second relay node.
Figure 112013094941487-pat00087
May be excluded from the effective channel matrix of Equation 18. Therefore, the number of linear equations in the effective channel matrix
Figure 112013094941487-pat00088
And the size of the effective channel matrix is
Figure 112013094941487-pat00089
Can be. Reference matrix
Figure 112013094941487-pat00090
The size of
Figure 112013094941487-pat00091
Can be. The relay node may remove the remaining interference signal except for the interference signal from the antenna 1 included in the first source node to the antenna M + 1 included in the second destination node by adjusting the channel coefficient to satisfy Equation 18.

(b) shows a second transmission step. Each antenna of the first source node may transmit signals a M + 1 to a 2M , and each antenna of the second source node may transmit signals b M +1 to b 2M . In order to remove the interference signal of at least some of the interference signals between the node pairs, the relay node allows only the interference signal from antenna M + 1 included in the second source node to antenna 1 included in the first destination node, and the remaining interference The signal can be removed. In this case, the condition for removing the remaining interference signal except for the interference signal from antenna M + 1 included in the second source node to antenna 1 included in the first destination node may be represented by Equation 19.

 [Equation 19]

Figure 112013094941487-pat00092

In (b), since only the interference signal from antenna M + 1 included in the second source node to antenna 1 included in the first destination node is allowed, the antenna M + 1 of the second source node passes through the first relay node. A component representing an interference signal transmitted to antenna 1 of the first destination node

Figure 112013094941487-pat00093
And a component representing an interference signal transmitted from antenna M + 1 of the second source node to antenna 1 of the first destination node through the second relay node.
Figure 112013094941487-pat00094
May be excluded from the effective channel matrix of Equation 19. Therefore, the number of linear equations in the effective channel matrix
Figure 112013094941487-pat00095
And the size of the effective channel matrix is
Figure 112013094941487-pat00096
Can be. Reference matrix
Figure 112013094941487-pat00097
The size of
Figure 112013094941487-pat00098
Can be. The relay node may remove the remaining interference signal except for the interference signal from the antenna M + 1 included in the second source node to the antenna 1 included in the first destination node by adjusting the channel coefficient to satisfy Equation 19.

(c) shows the third transmission step. Each antenna of the first source node transmits signals a 1 , a2 M +1 to a 3M -1 , and each antenna of the second source node transmits signals b M +1, b2 M + 1 to b 3M -1 Can be transmitted. In order to remove the interference signal of at least some of the interference signals between the node pairs, the relay node may transmit the interference signal from the antenna 1 included in the first source node to the antenna M + 1 included in the second destination node and the second source node. Only the interference signal from the included antenna M + 1 to the antenna 1 included in the first destination node may be allowed, and the remaining interference signal may be removed. In this case, the interference signal from antenna 1 included in the first source node to antenna M + 1 included in the second destination node and from antenna M + 1 included in the second source node to antenna 1 included in the first destination node The condition for removing other interference signals except for the interference signal may be represented by Equation 20.

[Equation 20]

Figure 112013094941487-pat00099

In the third transmission step of (c), the relay node transmits an interference signal (for example, transmitted from one antenna included in the first source node to one antenna included in the second destination node in the first transmission step (eg, , an interference signal transmitted from any one antenna included in the second source node to any one antenna included in the first destination node in the second transmission step, and receiving the same signal from the first source node (a 1 ). For example, the same signal as b M +1 ) may be received from the second source node.

Only the interference signal from antenna 1 included in the first source node to antenna M + 1 included in the second destination node and the interference signal from antenna M + 1 included in the second source node to antenna 1 included in the first destination node Is allowed, which is a component representing an interference signal transmitted from antenna 1 of the first source node to antenna M + 1 of the second destination node via the first relay node.

Figure 112013094941487-pat00100
A component representing an interference signal transmitted from antenna 1 of the first source node to antenna M + 1 of the second destination node via the second relay node;
Figure 112013094941487-pat00101
Component representing an interference signal transmitted from antenna M + 1 of the second source node to antenna 1 of the first destination node via the first relay node;
Figure 112013094941487-pat00102
A component representing an interference signal transmitted from antenna M + 1 of the second source node to antenna 1 of the first destination node via the second relay node;
Figure 112013094941487-pat00103
May be excluded from the effective channel matrix of Equation 20. Therefore, the number of linear equations in the effective channel matrix
Figure 112013094941487-pat00104
And the size of the effective channel matrix is
Figure 112013094941487-pat00105
Can be. Reference matrix
Figure 112013094941487-pat00106
The size of
Figure 112013094941487-pat00107
Can be. The relay node adjusts the channel coefficient so as to satisfy Equation 20, thereby interfering with the interference signal from antenna 1 included in the first source node to antenna M + 1 included in the second destination node and antenna M + included in the second source node. The remaining interference signals except for the interference signal from antenna 1 included in the first destination node to 1 may be removed.

< No - CSIT  Internal Interference and Nodes in the Environment Pairs  Residual Interference Cancellation Technique

4A and 4B illustrate removal of residual interference signals among interference signals between node pairs when transmission channel information does not exist (No-CSIT (Channel State Information at Transmitter) environment) according to an embodiment. to be.

Referring to FIG. 4A, in the No-CSIT environment, internal interference between node pairs may be removed by applying a serial interference cancellation (SIC) technique to the destination node. Since the number of variables to be applied and the number of equations may be applied to the serial interference cancellation scheme, the serial interference cancellation scheme may be applied in the example of FIGS. 4A and 4B. The number of antennas of the node must be the same to apply the same.

(a) shows the internal interference and residual interference cancellation between node pairs in the first transmission step of FIG. In (a), each of the M antennas of the first destination node receives M signals (eg, signals a 1 to signal a M ) including M-1 interference signals from M antennas of the first source node. can do. A serial interference cancellation technique is applied to the first destination node, so that the first destination node can extract signals a 1 to signal a M. Accordingly, internal interference between node pairs at the first destination node can be eliminated.

Each of the antennas M + 2 to 2M of the second destination node may receive M signals including M-1 interference signals from M antennas of the second source node. Antenna M + 1 of the second destination node receives M signals (eg, signals b 1 to b b) from M antennas of the second source node, and one interference from antenna 1 of the first source node. May receive a signal (eg, signal a 1 ). As the second destination node receives M + 1 signals, the number of signals received at each antenna of the second destination node and the number of antennas of the second destination node may be different. Therefore, the serial interference cancellation technique cannot be applied to the second destination node of (a).

(b) shows the internal interference and residual interference cancellation between node pairs in the second transmission step of FIG. In (b), each of antennas 2 to M of the first destination node may receive M signals including M-1 interference signals from M antennas of the first source node. Antenna 1 of the first destination node receives M signals (e.g., signals a M +1 to signals a 2M ) from M antennas of the first source node and one from antenna M + 1 of the second source node. May receive an interference signal of (eg, signal b M +1 ). As the first destination node receives M + 1 signals, the number of signals received at each antenna of the first destination node and the number of antennas of the first destination node may be different. Therefore, the serial interference cancellation technique cannot be applied to the first destination node of (b).

Each of the M antennas of the second destination node may receive M signals (eg, signals b M +1 to b 2M ) including M−1 interference signals from M antennas of the second source node. . Therefore, a serial interference cancellation technique is applied to the second destination node, so that the second destination node can extract the signals b m +1 to b 2M . Accordingly, internal interference between node pairs at the first destination node can be eliminated.

(c) shows the internal interference and residual interference cancellation between node pairs in the third transmission step of FIG. In (c), the antenna M + 1 of the second destination node receives M signals (eg, signals a 1 , a 2M +1 to signals a 3M −1 ) from M antennas of the second source node and In addition, one interference signal (for example, signal b M + 1 ) may be received from antenna 1 of the first source node. Antenna 1 of the first destination node receives M signals (eg, signals b M +1, b 2M +1 to signals b 3M −1 ) from M antennas of the first source node, and a second source node One interference signal (for example, signal a 1 ) may be received from antenna M + 1. Since the first and second destination nodes receive M + 1 signals, the number of signals received by the antennas of the first and second destination nodes and the antennas of the first and second destination nodes are determined. The number can vary. Accordingly, the serial interference cancellation technique cannot be applied to the first destination node and the second destination node of (c). In order to apply the serial interference cancellation scheme to the first and second destination nodes of (c), the first destination node applies the signal a 1 extracted in the first transmission step of (a) to be subjected to the serial interference cancellation scheme. The second destination node may exclude the signal b M +1 extracted in the second transmission step of (b) from the application of the serial interference cancellation scheme. For example, the first destination node and the second destination node, each signal a and the signal b 1 M hayeoteumeuro advance extract + 1, a signal 1 and the signal b the signal seen M + 1 to the constant a 1 and a signal b + M 1 may be excluded from the serial interference cancellation scheme. Since the signal a 1 and the signal b M +1 are excluded from the application object, the number of variables and the number of equations to which the serial interference cancellation technique is applied are equal. Thus, the interference cancellation techniques on the first destination node and the second destination node is applied, the first destination node signal L 1 (a 1, b M +1), a 2M +1 signal to signal a 3M - 1 a can be extracted, the second destination node signal L 2 (a 1, b M +1), b 2M +1 signal to signal b 3M - it is possible to extract one. Here, the signal L 1 (a 1 , b M +1 ) and the signal L 2 (a 1 , b M +1 ) may refer to an equation in which the signal a 1 and the signal b M +1 are linearly combined. By applying serial interference cancellation techniques to the first and second destination nodes, internal interference between node pairs at the first and second destination nodes can be eliminated. A first destination node by applying a first transmission stage with a signal derived from one of (a) the signal L 1 (a 1, b M +1), it is possible to extract the signal b M +1. The second destination node may extract the signal a 1 by applying b M +1 extracted in the second transmission step of (b) to the signal L 2 (a 1 , b M +1 ). By extracting the interference signal b M +1 received by antenna 1 of the first destination node and the interference signal a1 received by antenna M + 1 of the second destination node, residual interference between node pairs in the third transmission step may be eliminated. Can be.

Referring to FIG. 4B, (d) shows a residual interference cancellation technique of the first node pair in the second transmission step of FIG. 4A. In (d), antenna 1 of the first destination node receives M signals (eg, signals a M +1 to signals a 2M ) from M antennas of the first source node, and antennas of the second source node. One interfering signal (eg, signal b M +1 ) may be received from M + 1. Since the first destination node receives M + 1 signals, the number of signals received at each antenna of the first destination node and the number of antennas of the first destination node may be different from each other, and thus, the first of (d) Serial interference cancellation cannot be applied to the destination node. In order to apply the serial interference cancellation scheme to the first destination node of (d), the first destination node will exclude the signal b M +1 extracted in the third transmission step of (c) from the application of the serial interference cancellation scheme. Can be. Since the signal b M +1 is excluded from the application object, the number of variables and the number of equations to which the serial interference cancellation technique is applied are equal. Accordingly, a serial interference cancellation technique is applied to the first destination node, so that the first destination node can extract signals L 3 (a M +1 , b M +1 ), signals a M +2 to signals a 2M . . Here, the signal L 3 (a M +1 , b M +1 ) may mean an equation in which the signals a M +1 and the signal b M +1 are linearly combined. By applying a serial interference cancellation scheme to the first destination node, internal interference between node pairs of the first destination node can be eliminated. A first destination node (c) of claim 3 by applying the signal L (M +1 a, b M +1) the signal b M +1 extracted from the third transfer stage, it is possible to extract a signal of the M +1 . By extracting the signal a M +1 and the interference signal b M +1 received by antenna 1 of the first destination node, the residual interference between the node pairs in the second transmission step may be eliminated.

(e) shows a residual interference cancellation scheme of the second node pair in the first transmission step of FIG. 4A. In (e), antenna M + 1 of the second destination node receives M signals (eg, signals b 1 to signal b M ) from M antennas of the second source node, and antennas of the first source node One interference signal (eg, signal a 1 ) can be received from one. As the second destination node receives M + 1 signals, the number of signals received at each antenna of the second destination node and the number of antennas of the second destination node may be different from each other. Serial interference cancellation cannot be applied to the destination node. In order to apply the serial interference cancellation scheme to the second destination node of (e), the second destination node may exclude the signal a 1 extracted in the third transmission step of (c) from the application of the serial interference cancellation scheme. . Since the signal a 1 is excluded from the application object, the number of variables and the number of equations to which the serial interference cancellation technique is applied are equal. Accordingly, the serial interference cancellation technique is applied to the second destination node, so that the second destination node can extract the signals L 4 (a 1 , b 1 ), signals b 2 to signal b M. Here, the signal L 4 (a 1 , b 1 ) may mean an equation in which the signal a 1 and the signal b 1 are linearly combined. By applying a serial interference cancellation scheme to the second destination node, internal interference between node pairs of the second destination node can be eliminated. The second destination node may signal a 1 by applying the extract in a third transmission step of (c) to the signal L 4 (a 1, b 1 ), extracts the signal b 1. By extracting the signal b 1 and the interference signal a 1 received by the antenna M + 1 of the second destination node, residual interference between the node pairs in the first transmission step may be eliminated.

In the first transmission step and the second transmission step, each of the first source node and the second source node may transmit M signals that are not interference signals. In the third transmission step, each of the first source node and the second source node may transmit M-1. In the first to third transmission steps, each of the first destination mode and the second destination node may receive 3M signals including one interference signal and extract 3M-1 signals. For each transmission step, each node pair can obtain the degrees of freedom (DoF) of the node pairs,

Figure 112013094941487-pat00108
Sum DoF can be obtained. This may mean that as the number of antennas increases, a maximum of twice DoF can be obtained than a time division multiplexer (TDM).

< Full - CSIT  Internal Interference and Nodes in the Environment Pairs  Residual Interference Cancellation Technique

FIG. 5 is a diagram illustrating removal of residual interference signals among interference signals between node pairs when full transmission channel information is present (full-CSIT environment) according to an embodiment.

Referring to FIG. 5, in a full-CSIT environment, internal interference between node pairs may be removed by applying a zero-forcing beamforming (ZFBF) technique to the source node.

(a) and (b) show the internal interference and residual interference cancellation between node pairs in the first transmission step of FIG. In (a), each of the M antennas of the first source node transmits M signals (eg, signals a 1 to signal a M ) including M-1 interference signals to M antennas of the first destination node. Can be. In this case, antenna 1 of the first source node may transmit one interference signal (for example, signal a 1 ) to antenna M + 1 of the second destination node. Antenna M antennas, each of the second source node may transmit the first M number of signals (e.g., signal b 1 to b M signal) containing the M-1 of the interference signal to the M antennas of the destination node. A zero forcing beamforming technique may be applied to the first source node and the second source node so that internal interference between node pairs at the first and second destination nodes can be eliminated as shown in (b). By node pair internal interference is to be eliminated between the first destination node signals a 1 to signal a it is possible to extract the M, the second destination node L 1 (a 1, b 1), the signal b 2 to the signal b M Can be extracted. Here, L 1 (a 1 , b 1 ) may mean an equation in which the signal a 1 and the signal b 1 are linearly combined.

(c) and (d) show the internal interference and residual interference cancellation between node pairs in the second transmission step of FIG. 3. In (c), each of the M antennas of the first source node is an M signal including M-1 interference signals as M antennas of the first destination node (eg, signals a M +1 to signals a 2M ). Can be transmitted. Each of the M antennas of the second source node may transmit M signals (eg, signals b M +1 to b 2M ) including M-1 interference signals to M antennas of the second destination node. . In this case, the antenna M + 1 of the second source node may transmit one interference signal (for example, the signal b M + 1 ) to antenna 1 of the first destination node. A zero forcing beamforming technique is applied to the first source node and the second source node so that internal interference between the node pairs at the first and second destination nodes can be eliminated as shown in (d). By eliminating internal interference between node pairs, the first destination node can extract signals L 2 (a M +1 , b M +1 ), a M +2 to signals a 2M , and the second destination node can extract signal b M +1 to signal b 2M can be extracted.

(e) and (f) show the internal interference and residual interference cancellation between node pairs in the third transmission step of FIG. In (e), each of the M antennas of the first source node is an M signal including M-1 interference signals as M antennas of the first destination node (eg, signals a 1 , a 2M +1 to a signal). a 3M −1 ), and antenna 1 of the first source node may transmit one interference signal (eg, signal a 1 ) to antenna M + 1 of the second destination node. Each of the antennas M antennas of the second source node is M antennas of the second destination node and includes M signals including M-1 interference signals (for example, signals b M +1, b 2M +1 to signals b 3M). -1 ), and the antenna M + 1 of the second source node may transmit one interference signal (for example, the signal b M +1 ) to antenna 1 of the first destination node. The zero forcing beamforming technique is applied to the first source node and the second source node, so that internal interference between node pairs at the first destination node and the second destination node can be eliminated as shown in (f). By eliminating internal interference between node pairs, the first destination node can extract signals L 3 (a 1 , b M +1 ), a 2M +2 to signals a 3M -1 , and the second destination node can extract signal L 4 (a 1 , b M +1 ), b 2M +1 to signal b 3M −1 can be extracted.

A first destination node can be extracted by applying the first signal a first extraction step in the transmitted signal to L 3 (a 1, b M +1), M +1 signal b. The second destination node may extract the signal a 1 by applying b M +1 extracted in the second transmission step to the signal L 4 (a 1 , b M +1 ). By extracting the interference signal b M +1 received by antenna 1 of the first destination node and the interference signal a1 received by antenna M + 1 of the second destination node, residual interference between node pairs in the third transmission step may be eliminated. Can be.

In the first transfer step, the second destination node may extract the third by applying the interference signals a 1 extracted from the transmission step to the first signal L 1 (a 1, b 1) of the transfer phase, the signal b 1. By extracting the signal b 1 and the interference signal a 1 received by the antenna M + 1 of the second destination node, residual interference between the node pairs in the first transmission step may be eliminated.

In the second transmission step, the first destination node applies the interference signal b M +1 extracted in the third transmission step to the signal L 2 (a M +1 , b M +1 ) of the second transmission step, whereby the signal b M You can extract +1 . By extracting the signal a M +1 and the interference signal b M +1 received by antenna 1 of the first destination node, the residual interference between the node pairs in the second transmission step may be eliminated.

For each transmission phase, each node pair can obtain the degrees of freedom (DoF) of the node pairs,

Figure 112013094941487-pat00109
Sum DoF can be obtained. This may mean that as the number of antennas increases, a maximum of twice DoF can be obtained than a time division multiplexer (TDM).

The above-described interference control scheme in the multi-hop network assumes a case where the number of node pairs is 2 and the number of relay nodes is 2 for convenience of description, but is not limited thereto. For example, when the number of node pairs is three, the number of relay nodes is six, so that the interference control scheme in the multi-hop network can be performed.

< SISO  Interference Control Scheme Using Signal Separation in System-Based Multi-hop Networks>

6 is a diagram for describing an interference control method in a multi-hop network in an SISO system, according to an exemplary embodiment.

Referring to FIG. 6, in a single input single output (SISO) system, a relay node may relay a signal received from a source node among node pairs to destination nodes paired with the source nodes. The source node may separate the signal into a real component signal and an imaginary component signal and transmit the signal to a destination node paired with the source node. The relay node may relay the real component signal and the imaginary component signal to the destination nodes paired with the source nodes. In one embodiment, the channel matrix from the source node to the relay node may appear as, which in the MIMO system may correspond to the channel matrix from the source node with two antennas to the relay node. Therefore, in the SISO system, when a signal is separated into a real component signal and an imaginary component signal and transmitted, the interference cancellation scheme between the node pairs and the residual interference cancellation between the internal interference and the node pairs in the multi-hop network described above are the SISO system. Can be applied to

In one embodiment, when the number of node pairs is two and the number of relay nodes is two, the relay node may remove the interference signal of at least some of the interference signals between the node pairs by adjusting a channel coefficient. The destination node may remove the residual interference signal among the interference signals between two or more node pairs by using at least one of a real component signal and a complex component signal received by the relay node relay. For example, the node pair and the relay node may transmit signals through the first to third transmission steps.

(a) shows the first transmission step. In the first transmission step, the first source node may transmit the real component signal a R1 and the imaginary component signal a I1 , and the second source node may transmit the real component signal b R1 and the imaginary component signal b I1 . In order to eliminate the interference signal of at least some of the interference signals between the node pairs, the relay node adjusts the channel coefficient to allow only the transmission of the real component signal a R1 of the first source node to the second destination node, and the remaining interference signal Can be removed

(b) shows a second transmission step. In a second transmission step, the first source node may transmit a real component signal a R2 and an imaginary component signal a I2 , and the second source node may transmit a real component signal b R2 and an imaginary component signal b I2 . In order to eliminate the interference signal of at least some of the interference signals between the node pairs, the relay node adjusts the channel coefficient to allow only the transmission of the real component signal b R2 of the second source node to the first destination node, and the remaining interference signal Can be removed

(c) shows the third transmission step. In a third transmission step, the first source node may transmit a real component signal a R1 and an imaginary component signal a I3 , and the second source node may transmit a real component signal b R2 and an imaginary component signal b I3 . In order to eliminate the interference signal of at least some of the interference signals between the node pairs, the relay node adjusts the channel coefficient to transmit the real component signal a R1 of the first source node to the second destination node and the real component of the second source node. Only the transmission of the signal b R2 to the first destination node can be allowed, and the remaining interference signal can be eliminated.

In a no-CSIT environment, internal interference between node pairs can be eliminated by applying a serial interference cancellation scheme to the destination node. In the first transmission step, the first destination node may extract the real component signal a R1 and the imaginary component signal a I1 by eliminating internal interference between the first node pairs using a serial interference cancellation technique.

In the second transmission step, the second destination node may extract the real component signal a R2 and the imaginary component signal a I2 by eliminating internal interference between the second node pairs using a serial interference cancellation technique.

In the third transmission step, the first destination node excludes the real component signal a R1 extracted in the first transmission step from the application of the serial interference cancellation technique, thereby removing the signal L 1 (a R1 , b R2 ) and the imaginary component signal a I3 . The second destination node extracts the signal L 2 (a R1 , b R2 ) and the imaginary component signal b I3 by excluding the real component signal b R2 extracted in the second transmission step from the application of the serial interference cancellation technique. can do. By applying a serial interference cancellation technique to the first and second destination nodes, internal interference between node pairs at the first and second destination nodes can be eliminated. A first destination node may extract a real component signal b R2 by applying the real component signal a R1 extracted from the first transfer step to the signal L 1 (a R1, b R2 ). The second destination node may extract a real component signal R1 by applying the real component signal b R2 extracted in the second transmitting step the second signal L (R1 a, R2 b). By extracting the interference signal b R2 received by the first destination node and the interference signal a R1 received by the second destination node, the residual interference signal between the node pairs in the third transmission step may be eliminated.

In the second transmission step, the first destination node excludes the real component signal b R2 extracted in the third transmission step from the application of the serial interference cancellation scheme to remove the internal interference between the first node pairs so that the signal L 3 (a R2 , b R2 ) and the imaginary component signal a I2 can be extracted. The first destination node may extract the signal a R2 by applying the real component signal b R2 extracted in the third transmission step to the signal L 3 (a R2 , b R2 ). Signal a R2 received by first destination node And the interference signal b R2 is extracted, so that residual interference between the node pairs in the second transmission step can be eliminated.

In the first transmission step, the second destination node removes the internal interference between the pair of second nodes by excluding the real component signal a R1 extracted in the third transmission step from the application of the serial interference cancellation technique, thereby eliminating the signal L 4 (a R1 , b R1 ) and the imaginary component signal b I1 can be extracted. The second destination node may extract the signal b R1 by applying the real component signal a R1 extracted in the third transmission step to the signal L 4 (a R1 , b R1 ). Signal b R1 received by second destination node And the interference signal a R1 is extracted, so that residual interference between the node pairs in the first transmission step can be eliminated.

In a full-CSIT environment, internal interference between node pairs can be eliminated using a zero forcing beamforming technique at the source node. In the first transmission step, a zero forcing beamforming technique is applied to the first source node and the second source node so that internal interference between node pairs can be eliminated. By eliminating internal interference between node pairs, the first destination node can extract signals a R1 and signal a I1 , and the second destination node can extract L 1 (a R1 , b R1 ) and signal b I1 . .

In a second transmission step, a zero forcing beamforming technique is applied to the first source node and the second source node to remove internal interference between the pair of nodes, so that the first destination node receives the signal L 2 (a R2 , b R2 ) and the signal. a I2 can be extracted and the second destination node can extract signal b R2 and signal b I2 .

In a third transmission step, a zero forcing beamforming technique is applied to the first source node and the second source node to eliminate internal interference between the pair of nodes, so that the first destination node receives the signal L 3 (a R1 , b R2 ) and the signal. a I3 can be extracted and the second destination node can extract L 4 (a R1 , b R2 ) and the signal b I3 . A first destination node may extract a real component signal b R2 by applying the real component signal a R1 extracted from the first transfer step to the signal L 3 (R1 a, R2 b). The second destination node may extract a real component signal R1 by applying the real component signal b R2 extracted in the second transfer step to a signal L 4 (R1 a, R2 b). By extracting the interference signal b R2 received by the first destination node and the interference signal a R1 received by the second destination node, the residual interference signal between the node pairs in the third transmission step may be eliminated.

In the second transmission step, the first destination node may extract the signal a R2 by applying the real component signal b R2 extracted in the third transmission step to the signal L 2 (a R2 , b R2 ). Signal a R2 received by first destination node And the interference signal b R2 is extracted, so that residual interference between the node pairs in the second transmission step can be eliminated.

In the first transmission step, the second destination node may extract the signal b R1 by applying the real component signal a R1 extracted in the third transmission step to the signal L 1 (a R1 , b R1 ). Signal b R1 received by second destination node And the interference signal a R1 is extracted, so that residual interference between the node pairs in the first transmission step can be eliminated.

In the No-CSIT environment and the Full-CSIT environment, through the first to third transmission steps, the first destination node and the second destination node have 5/3 DoF (

Figure 112013094941487-pat00110
, M = 2) can be obtained.

<Interference Control Method in Multi-hop Network>

7 is a flowchart illustrating an interference control method in a multi-hop network according to an exemplary embodiment.

Referring to FIG. 7, in the interference control method of a multi-hop network according to an embodiment, relay signals received from source nodes among node pairs are relayed to destination nodes paired with source nodes. The channel coefficients of the relay nodes may be adjusted to remove interference signals of at least some of the interference signals between two or more node pairs (710).

In addition, the interference control method in a multi-hop network according to an embodiment may remove residual interference signals among the interference signals between the two or more node pairs by using signals received at destination nodes in node pairs ( 720). Steps 710 to 720 may be performed in a signal transmission process between relay nodes and node pairs.

8 is a flowchart illustrating an interference control method in a multi-hop network in an SISO system according to an exemplary embodiment.

Referring to FIG. 8, in the multi-hop network in the SISO system according to an exemplary embodiment, an interference control method may include a real component signal and an imaginary component signal received from source nodes among pairs of nodes at a relay node and a source node. While relaying to destination nodes that are pairs, at least some of interference signals between two or more node pairs may be removed by adjusting channel coefficients of relay nodes (810).

In addition, the interference control method in a multi-hop network in the SISO system according to an embodiment uses the at least one of the real component signal and the imaginary component signal received at the destination nodes in the node pairs, the interference between two or more node pairs The residual interference signal may be removed from the signal (820). Steps 810 to 820 may be performed in a signal transmission process between relay nodes and node pairs.

The interference control method in the multi-hop network according to the embodiment shown in FIG. 7 and the interference control method in the multi-hop network in the SISO system according to the embodiment shown in FIG. 8 are described with reference to FIGS. 1 to 6. Since the content may be applied as it is, a more detailed description will be omitted.

The method according to the embodiment may be embodied in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the media may be those specially designed and constructed for the purposes of the embodiments, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine code, such as produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

Although the embodiments have been described by the limited embodiments and the drawings as described above, various modifications and variations are possible to those skilled in the art from the above description. For example, the described techniques may be performed in a different order than the described method, and / or components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different form than the described method, or other components. Or even if replaced or substituted by equivalents, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are within the scope of the claims that follow.

Claims (20)

In the interference control method of two or more relay nodes and node pairs in a multi-hop network,
In the relay nodes, a signal received from source nodes of the node pairs is relayed to destination nodes that are paired with the source nodes, and the channel coefficients of the relay nodes are relayed. Coefficient) to remove the interference signal of at least some of the interference signal between the two or more node pairs; And
In the node pairs, removing a residual interference signal among the interference signals between the two or more node pairs using a signal received at the destination nodes
Including,
Removing the at least some interfering signal,
Generating an effective interference channel matrix corresponding to the at least some interference signal based on the interference channel matrices between the source nodes and the destination nodes; And
Removing the at least some interference signals using the effective interference channel matrix
Including,
Interference control method in multi-hop network.
The method of claim 1,
Removing the at least some interfering signal,
Generating a reference matrix representing a null space of the effective interference channel matrix by adjusting the channel coefficients
More,
Removing the at least some of the interference signals using the effective interference channel matrix,
Removing the at least some interference signal using the effective interference channel matrix and the reference matrix
Interference control method in a multi-hop network comprising a.
The method of claim 2,
Generating the effective interference channel matrix,
Corresponds to an interference signal of at least some of a first channel matrix corresponding to an interference signal of at least some of the first interference signals between the source nodes and the relay nodes and a second interference signal between the relay nodes and the destination nodes Obtaining a second channel matrix; And
Generating the effective interference channel matrix based on the first channel matrix and the second channel matrix
Interference control method in a multi-hop network comprising a.
The method of claim 3,
Generating the effective interference channel matrix,
Transposing the first channel matrix; And
Computing a Kronecker product of the second channel matrix and the transposed first channel matrix
Interference control method in a multi-hop network comprising a.
The method of claim 2,
The reference matrix,
And a plurality of null space vectors included in the null space of the effective interference channel matrix and excluding a zero vector.
The method of claim 1,
The number of relay nodes is
And an interference control method in a multi-hop network smaller than the number of relay nodes designed to eliminate the entirety of the interference signal between the node pairs.
The method of claim 1,
The signal transmission process,
An interference control method in a multi-hop network performed using either time division or frequency division.
The method of claim 1,
The source node or the destination node is a multiple input multiple output (MIMO) scheme,
Removing an internal interference signal between two or more antennas included in each of the node pairs
Interference control method in a multi-hop network further comprising.
The method of claim 8,
Removing the internal interference signal,
When full-channel state information (FULL-CSIT) exists between the source nodes and the destination nodes, the zero-forcing beamforming (ZFBF) technique is used. Removing the internal interference signal of the node pairs,
Interference control method in multi-hop network.
The method of claim 8,
Removing the internal interference signal,
When there is no transmission channel information between the source nodes and the destination nodes (No-CSIT), some of the signals received by the destination nodes in another signal transmission process are transmitted. On the basis of the step of removing the internal interference signal using a successive interference cancellation (Successive Interference Cancellation (SIC) technique,
Interference control method in multi-hop network.
The method of claim 1,
Removing the residual interference signal,
In another signal transmission process, the step of removing the residual interference signal based on the signal of some of the signals received by the destination node,
Interference control method in multi-hop network.
The method of claim 1,
The number of the signal transmission process,
An interference control method in a multi-hop network that is equal to or greater than the number of signals.
The method of claim 1,
If there are two relay nodes,
The steps are performed in the first signal transmission process, the second signal transmission process and the third signal transmission process,
Removing the at least some interfering signal,
In the first signal transmission process, any one of the interference signals between the node pairs except for the interference signal transmitted from any one antenna included in the first source node to any one antenna included in the second destination node Removing;
In the second signal transmission process, any one of the interference signals between the node pairs except for the interference signal transmitted from any one antenna included in the second source node to any one antenna included in the first destination node Removing; And
In the third signal transmission process, an interference signal and the second signal transmitted from any one antenna included in the first source node among the interference signals between the node pairs to any one antenna included in the second destination node. Removing any interference signal except for an interference signal transmitted from one antenna included in a source node to any one antenna included in the first destination node
Including,
Interference control method in multi-hop network.
The method of claim 13,
In the third signal transmission process, the relay node is
Receiving the same signal from the first source node as the interference signal transmitted from any one antenna included in the first source node to any one antenna included in the second destination node in the first signal transmission process,
Receiving from the second source node the same signal as the interference signal transmitted from any one antenna included in the second source node to any one antenna included in the first destination node in the second signal transmission process,
Interference control method in multi-hop network.
The method of claim 13,
In the third signal transmission process, removing the residual interference signal,
In the first signal transmission process and the second signal transmission process, removing the residual interference signal based on a signal of some of the signals received by the destination nodes,
Interference control method in multi-hop network.
In the interference control method of two or more relay nodes in a multi-hop network,
Relaying signals received from source nodes among node pairs through a plurality of signal transmission processes to destination nodes paired with the source nodes; And
Removing a part of the interference signal between the node pairs using the signals from the source nodes through a plurality of signal transmission processes
Including,
Removing a part of the interference signal between the node pairs,
Generating an effective interference channel matrix corresponding to a portion of the interference signal based on the interference channel matrices between the source nodes and the destination nodes; And
Removing a portion of the interference signal using the effective interference channel matrix
Including,
Wherein channel coefficients of the relay nodes are dependent on the plurality of signal transmission processes,
Interference control method in multi-hop network.
A computer-readable recording medium having recorded thereon a program for performing the method of any one of claims 1 to 16.
Relay nodes in a multi-hop network,
Relaying signals received from a source node of a node pair through a plurality of signal transmission processes to a destination node paired with the source node-the relay node according to the plurality of signal transmission procedures The channel coefficients of the processor are different, the processor removes a part of the interference signal between the node pair and another node pair
Including,
The processor generates an effective interference channel matrix corresponding to the portion of the interference signal based on the interference channel matrices between the source node and the destination node to remove a portion of the interference signal, and generates the effective interference channel matrix. To remove a portion of the interfering signal,
Relay node. delete delete
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EP14170907.1A EP2819315B1 (en) 2013-06-04 2014-06-03 Method of controlling interference in multi-hop network based on mimo system and relay node and node pair using the method
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