KR102261004B1 - Full-duplex decode-and-forward relay to increase energy harvesting - Google Patents

Abstract

The present invention provides a full-duplex decode-and-forward relay in a power division-based wireless information and power simultaneous transmission full-duplex decoding and transmission relay system, wherein an obstacle free area (hereinafter, OFR), in which end-to-end SINR(γ) between the base station and the terminal satisfies a predetermined reference SINR(γ^*) or more, is detected from the relationship, between SINR (γ_1) of a first hop channel and SINR (γ_2) of a second hop channel, expressed as a function of the power division ratio (ρ) representing the ratio between power used for decoding and energy harvested from a signal received by a relay and a self-interference channel (hereinafter referred to as SI) transmission weight (ω) indicating a beamforming weight to an SI channel among the second hop channel and the SI channel during transmission beamforming for transmitting a signal to a terminal, a range of the power division ratio (ρ) corresponding to the OFR is divided into K predetermined sections to obtain K+1 representative power division ratios (ρ_k), an SI channel transmission weight (ω_k, j), which maximizes the energy harvest for each of the K+1 representative power split ratios (ρ_k), is detected, and then the representative power division ratio (ρ_k) and the SI channel transmission weight (ω_k,j), which obtain the maximum energy harvest, are selected among energy according to the detected SI channel transmission weight (ω_k,j), so that the energy harvest is maximized while satisfying the end-to-end SINR above the required level.

Description

{FULL-DUPLEX DECODE-AND-FORWARD RELAY TO INCREASE ENERGY HARVESTING}

The present invention relates to a transmission relay after full-duplex decoding, and to a transmission relay after full-duplex decoding for simultaneous transmission of radio information and power.

In a full-duplex (hereinafter FD) transmission/reception scheme, a self-interference (SI) problem occurs in a node operating as an FD. SI is a phenomenon in which the transmission signal of a specific node acts as interference in the signal reception process of the same node. Since SI is interference occurring within the same node, the distance between the transmitter and receiver is very close. Therefore, the size is large compared to other interferences, and in order for FD to have a performance advantage compared to the existing half-duplex (hereinafter referred to as HD), it is a target that must be controlled and removed.

On the other hand, in a power splitting-based Simultaneous Wireless Information and Power Transfer (SWIPT) FD relay, the receiver utilizes a certain percentage of the power of the received signal for data decoding, and uses the remaining percentage of energy from the signal. to harvest In the FD decode-and-forward (DF) relay for implementing such SWIPT, harvest energy and end-to-end signal-to-interference-plus-noise ratio: SINR) should be considered together. However, in the existing FD DF relay, only SINR was considered, and Energy Harvesting was not considered. In particular, in the case of SI, energy harvesting by SI was not even considered as it was only considered a target for removal.

Korean Patent Publication No. 10-2008-0066503 (published on July 16, 2008)

It is an object of the present invention to provide a power division-based SWIPT FD DF relay capable of maximizing energy yield while satisfying end-to-end SINR above a required level, and a method for improving energy yield thereof.

Another object of the present invention is to provide a power division-based SWIPT FD DF relay to which a beamforming technique is applied so that energy can also be harvested by an SI channel, and a method for improving energy yield thereof.

The FD DF relay according to an embodiment of the present invention for achieving the above object beamforms and receives a signal beamformed from a base station and transmitted through a first hop channel, and decodes the signal by dividing the power of the received signal Simultaneous transmission of power division-based wireless information and power (hereinafter referred to as SWIPT) including a relay that harvests energy at the same time as post-recoding, beamforms the re-encoded signal and transmits it to the terminal through the second hop channel (hereinafter referred to as FD) ) In the relay of the relay system after decoding (hereinafter referred to as DF), a power split ratio (ρ) indicating a ratio of power to be used for decoding and energy to be harvested from the received signal and a transmission beam for transmitting a signal to the terminal _{The SINR(γ 1} ) of the first hop channel expressed as a function of the SI channel transmission weight (ω) indicating the beamforming weight to the SI channel among the second hop channel and the self-interference channel (hereinafter referred to as SI) during forming, and _{From the relationship between the SINR(γ 2} ) of the second hop channel, the end-to-end SINR(γ) between the base station and the terminal ^{satisfies a predetermined reference SINR(γ *} ) or more. , the separation of the range of the power split ratio (ρ) corresponding to the OFR group as designated the K interval K + 1 of the representative power split ratio (ρ _k) obtained, and a K + 1 of the representative power split ratio (ρ _k ) _, after detecting the SI channel transmission weight (ω _k,j ) that maximizes the energy yield for each, representative power division to obtain the maximum energy yield among energy according to the detected SI channel transmission weight (ω k,j ) Select the ratio (ρ _k ) and the SI channel transmission weight (ω _k,j ).

The relay may include: a signal receiving unit configured to receive a signal with power of a ratio corresponding to the power division ratio (ρ) among signals received through a plurality of receiving antennas; a reception beamformer for beamforming a signal received by the signal reception unit using a reception beamforming vector (w _R ); a decoding unit for decoding and re-encoding the signal obtained through the reception beamformer; a transmit beamformer for beamforming the signal re-encoded by the decoder according to a transmit beamforming vector w _T and transmitting it to the terminal through a plurality of transmit antennas; and an energy beamformer configured to perform beamforming using an _{energy beamforming vector (w E} ) on a signal of power remaining except for power transmitted to the signal receiving unit among signals received through a plurality of receiving antennas. and a battery for harvesting and storing power of a signal beamformed and transmitted by the energy beamformer as energy.

_{The transmit beamformer sets the transmit beamforming vector (w T} ) according to the SI channel transmission weight (ω), and performs beamforming according to the set transmit beamforming vector (w _T ) to form the second hop channel and the SI It is possible to transmit the re-encoded signal through the channel.

_{The energy beamformer sets the energy beamforming vector (w E} ) according to a forming weight (ζ) that adjusts a reception ratio of a signal transmitted through the first hop channel and a signal transmitted through the SI channel, The forming weight ζ may be determined by the SI channel transmission weight ω.

The relay decreases the power division ratio (ρ) by a _{predetermined unit from a maximum power division ratio (ρ max} = 1) corresponding to a predetermined maximum value, while the SINR (γ ₁ ) of the first hop channel and the second _{SINR (γ 2} ) of the two-hop channel is calculated, respectively, and the calculated SINR (γ ₁ ) of the first hop channel and the SINR (γ ₂ ) of the second hop channel are calculated as the smaller of the end-to-end SINR (γ 2 ). = min(γ ₁ , γ ₂ )) detects whether an OFR equal to or greater than the reference SINR(γ ^* ) exists, and determines the _{minimum power division ratio (ρ min} ) that is the minimum value among the power division ratios (ρ) in which the OFR exists And, by dividing the range from the determined minimum power split ratio (ρ _min ) to the maximum power split ratio (ρ _max ) into K sections, K+1 representative power split ratios (ρ _k ) can be obtained.

)로 반복 차감하여 획득할 수 있다.The relay K+1 representative power split ratio (ρ _k ) is equal to the size unit ( _{ρ max} ) from the maximum power split ratio (ρ max )

) can be obtained by repeatedly subtracting

The relay determines the lower limit (ω _k,LB ) and the upper limit (ω _k,UB ) of the SI channel transmission weight (ω _k ) corresponding to each section divided by the K+1 representative power split ratio (ρ _{k )} , and while varying the lower limit (ω _{k, LB)} and upper limit (ω _{k, UB)} SI channel transmit weights (ω _{k, j)} within the scope of the determination SI channel transmit weights (ω _k) based on a specified equation By calculating the energy yield accordingly, the maximum value among the calculated energy yields may be obtained as an energy yield corresponding _{to the K+1 representative power split ratio (ρ k ).}

The relay is K + 1 of the representative power split ratio (ρ _k) represents the power split ratio (ρ _k) and SI channel corresponding to the maximum energy yield is determined maximum energy yield of the energy yield obtained in correspondence with, respectively, and determines The transmission weight (ω _k,j ) can be selected as the relay power split ratio (ρ) and the SI channel transmission weight (ω).

Therefore, the FD DF relay according to the embodiment of the present invention can maximize the energy harvest by applying the beamforming technique to harvest the energy through the SI channel while satisfying the end-to-end SINR above the required level.

1 shows a schematic structure of a power division based SWIPT FD relay system according to an embodiment of the present invention.
FIG. 2 is a simplified and reconfigured view of the power division-based SWIPT FD system of FIG. 1 .
3 is a diagram for explaining an SI channel and a second hop channel of a relay.
FIG. 4 shows SINR changes of a reception channel and a transmission channel of a relay according to an SI channel transmission weight and a power split ratio.
5 is a diagram for explaining a change in OFR according to a change in a power split ratio.
6 shows a concept of searching for an SI channel transmission weight capable of maximizing energy for K representative power split ratios.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings. However, the present invention may be embodied in various different forms, and is not limited to the described embodiments. In addition, in order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part "includes" a certain component, it does not exclude other components unless otherwise stated, meaning that other components may be further included. In addition, terms such as "... unit", "... group", "module", and "block" described in the specification mean a unit that processes at least one function or operation, which is hardware, software, or hardware. and a combination of software.

1 shows a schematic structure of a power division based SWIPT FD DF relay according to an embodiment of the present invention, FIG. 2 is a simplified and reconfigured view of the power division based SWIPT FD system of FIG. 1, and FIG. 3 is the SI of the relay. It is a diagram for explaining a channel and a second hop channel.

1 and 2, the power division-based SWIPT system includes a base station (AP), at least one relay (RS), and at least one terminal (UT). The base station AP transmits a signal and power to the relay RS, and the relay RS transmits the signal and power applied from the base station AP back to the terminal UT. That is, FIG. 1 can be viewed as a multi-hop relay communication system in which a relay (RS) is added between a base station (AP), which is a transmitting node, and a terminal (UT), which is a destination node to transmit signals. Here, a first hop between the base station AP and the relay RS is _{referred to as a first hop (1 st-} hop), and a second hop between the relay RS and the terminal UT is referred to _{as a second hop (2 nd-hop).}

_{The base station beamformer 110 of the base station AP beamforms the signal (x s} ) into (wx _s ) based on the base station beamforming vector w of M × 1 size corresponding to the number (M) of the base station antennas. to the relay (RS), and the relay (RS) converts _{the signal (y R} ) transmitted from the base station (AP) to (w _R ^H ) using the reception beamforming vector (w _{R ) corresponding to the M R reception antennas.} y _R ) (where w _R ^H is the _{Hermitian matrix of w R} ) is beamformed and received. Accordingly, the first hop channel between the base station (AP) and the relay (RS) may be expressed as a first hop matrix (H) having a size of _{(M R × M).}

On the other hand, the DF relay (RS) decodes and re-encodes the received signal transmitted from the base station (AP) to the terminal (UT) using the transmit beamforming vector (w _{T ) corresponding to the M T transmit antennas.} The signal (x _R ) is _{transmitted by beamforming (w T} x _R ), and the terminal (UT) receives the _{signal (y D ) transmitted from the relay (RS).} Here, it is assumed that the terminal (UT) includes a single antenna. Therefore, the second hop channel between the relay (RS) and the terminal (UT) may be expressed as a second hop vector g with a size of _{(M T × 1).}

_{However, the re-encoded signal w T} x _R transmitted by beamforming from the relay (RS) is not only transmitted to the terminal UT through the second hop channel g, but also expressed as an _{SI matrix (H RR ).} It may be transmitted back to the receiving antenna of the relay (RS) along the available SI channel. At this time, the signal (w _T x _{R ) recoded by the SI channel (H RR} ) and the second hop channel (g) by the path loss (α _R ² , α _D ² ) of each relay (RS) and the terminal (UT).

_{Accordingly, the reception signal (y R} ) at the n-th time of the relay (RS) in consideration of both signals transmitted through the first hop channel (H) and the SI channel (H _{RR ) and the reception signal (y D} ) of the terminal (UT) ) may be represented by Equations 1 and 2, respectively.

Here, n _ant and n _D represent noise flowing into the receiving antenna of the relay RS and the terminal UT, respectively, and g ^T represents the transposition of the second hop vector g.

However, in the SWIPT system, the DF relay (RS) is a ratio (ρ, 0 ≤ ρ ≤ 1) according to a predetermined power splitting ratio (ρ, 0 ≤ ρ ≤ 1) in the power (or energy) of the received signal transmitted from the base station (AP). ) is used for data decoding, and the energy of the remaining ratio (1-ρ) is harvested for its own operation.

Accordingly, the relay RS performs beamforming using a _{reception beamforming vector w R} for a signal received by the signal processing unit 210 and the signal processing unit 210 for receiving a signal through the _{M R reception antennas.} The decoder 230 that decodes and re-encodes the signal obtained through the former 220 and the receive beamformer 220 and the signal re-encoded by the decoder 230 according to the transmit beamforming vector w _T It may include a transmit beamformer 240 for beamforming and _{transmitting to the terminal UT through M T} transmit antennas, and a battery 250 for storing harvested energy.

)만큼의 에너지를 이용하여 데이터 복호하고 재부호화하여 단말(UT)로 전달하는 경우, 릴레이(RS)의 수신 처리부(210)와 수신 빔포머(220)를 통해 복호부(230)에 인가되는 수신 신호(y'_R)는 수학식 1의 수신 신호(y_R)로부터 수학식 3과 같이 획득될 수 있다.In this way, the ratio (RS) according to the power division ratio (ρ)

), when the data is decoded and re-encoded and transmitted to the terminal UT, the reception applied to the decoder 230 through the reception processing unit 210 and the reception beamformer 220 of the relay RS. The signal y' _R may be obtained as in Equation 3 from the received signal y _{R of Equation 1}

Where α _'R represents a loss in reflected SI suppression (suppression) effects has been added in the analog configuration of the reception processing unit 210, the path loss (α _R) channel of the SI (H _RR).

However, since the purpose of the existing FD DF relay was to maximize the end-to-end SINR, only a method of suppressing the SI removal was considered. _{That is, the SI power is induced to 0 (H RR} w _T = 0) according to a null-space projection (NSP) technique using the null-space of the SI channel, and the SNR of the second hop channel is It was induced to be maximized (max |g ^T w _T | ^{2 ).}

_{Therefore, in the FD DF relay, the receive beamformer 220 configures the receive beamforming vector w R} to direct the direction of the base station AP in order to increase the SINR for the signal transmitted from the base station AP, and the transmit beamformer _{(240) configures the transmission beamforming vector (w T} ) to direct the direction of the terminal (UT) in order to increase the SINR for the signal transmitted to the terminal (UT) _{(H RR} w _T = 0).

However, in the SWIPT system according to the present embodiment, the FD DF relay (RF) must not only transmit a signal transmitted from the base station (AP) to the terminal (UT) but also receive energy from the base station (AP). And when the FD DF relay RS harvests only energy by the power of the signal transmitted from the base station AP, both the target for transmitting the signal and the target for transmitting the energy are the same as the base station AP. _{Therefore, in the FD DF relay, the receive beamformer 220 may configure the receive beamforming vector w R} to direct the direction of the base station AP in order to increase the SINR and energy harvest for a signal transmitted from the base station AP. have. _{In addition, the transmit beamformer 240 may configure the transmit beamforming vector w T} to direct the direction of the terminal UT in order to increase the SINR and energy harvest for a signal transmitted to the terminal UT.

However, in actual operation, the terminal (UT) only needs to be able to receive a signal greater than or equal to the required SINR. Accordingly, in this embodiment, the FD DF relay RS can additionally harvest energy not only through the base station AP but also through the SI channel, thereby improving the energy harvest of the FD DF relay RS.

To this end, in the present embodiment, the FD DF relay RS further includes an energy beamformer 260, and the energy beamformer 260 uses an energy beamforming vector w _E to SI through M _{R reception antennas.} Improves the yield of energy delivered to the channel. _{However, when the transmit beamformer 240 configures the transmit beamforming vector w T} to suppress the signal to the SI channel as much as possible in order to increase the SINR for the signal transmitted to the terminal UT, the energy beamformer 260 . It is difficult to expect an increase in the energy yield even if the energy beamforming vector (w _{E ) is used to improve the energy yield.}

Therefore, in the present embodiment, the transmit beamformer 240, as shown in FIG. 3, allows the SINR of the signal transmitted to the terminal (UT) to satisfy a predetermined required SINR, and the remaining M _R numbers are received through the SI channel. It is transmitted to the antenna to increase the energy harvest. In Figure 3 u _R and v _R are SI matrix (H _RR) from the M _R receive antennas and M corresponds to the _T transmit antennas M _R × 1 size and M _T × 1 size units him to expressing SI channels each It is a unit-norm vector.

Referring to FIG. 3 , the transmit beamformer 240 must configure _{the transmit beamforming vector w T in} consideration of the SINR of the signal transmitted to the terminal UT and the energy harvest fed back to the SI channel.

Accordingly, the channel corresponding to the transmit beamforming vector (w _T ) is the component (v _R ^H _{) from the SI channel (H RR} ) to the M _T transmit antennas and the second hop channel (g ^T ) as shown in Equation 4 It can be expressed in the form of QR decomposition. In FIG. 3 , it is expressed as a modified second hop channel (g ^T ) as the components (v _R ^H ) of the SI channel (H _RR ) to the M _{T transmit antennas must be considered together.}

는 단위 놈 벡터(v_R)에 대한 직교 칼럼 벡터로서 단위 놈 벡터(v_R)에 대한 널 스페이스를 나타낸다. 그리고 R_1,1, R_1,2, R_2,2 는 QR 분해로 획득되는 상삼각 행렬(R)의 원소들로서 복소수이다.where g ^* is the conjugate transpose matrix of the second hop channel (g),

denotes the null space for the unit norm vector (v _R ) as an orthogonal column vector for the unit norm vector (v _{R ).} And R _1,1 , R _1,2 , R _2,2 are complex numbers as elements of an upper triangular matrix R obtained by QR decomposition.

From Equation (4), the directional component (w _T /|| _{w T} ||) of the transmit beamforming vector (w _T ) can be derived by Equation (5).

)에 대한 가중 합(weighted sum)으로 구성될 수 있음을 알 수 있다. 여기서 ω(0≤ ω ≤1))는 SI 채널(H_RR)의 M_R 개의 수신 안테나로의 성분(v_R ^H)과 제2 홉 채널(g^T) 중 SI 채널 성분(v_R ^H)에 대한 지향 성분의 비율을 나타내는 SI 채널 전송 가중치이고,

로서 두 복소수(R_1,1, R_1,2)의 위상을 매칭하는 위상 매칭 파라미터이다.Oriented component of a transmission beamforming vector (w _T) from equation _{5 (w T / ∥w T ∥} ) is the SI unit of he channel vector matching the M _T transmit antennas in the (H _RR) (v _R) and the unit he null space in vector (v _{R ) (}

It can be seen that it can be composed of a weighted sum of ). where ω(0≤ ω ≤1)) is the component of the SI channel (H _RR ) to the M _R receive antennas (v _R ^H ) and the SI channel component (v _R ^H ) of the second hop channel (g ^{T ).} SI channel transmission weight indicating the ratio of directional components to

It is a phase matching parameter that matches the phases of two complex numbers (R _1,1 , R _{1,2 ).}

이고,

이므로, 수학식 5의 송신 빔포밍 벡터(w_T)를 이용하는 경우, SI 채널(v_R ^H)과 제2 홉 채널(g^T) 각각에 대한 유효 채널(effective channel)은 수학식 6으로 표현될 수 있다.

ego,

Therefore, when using the transmit beamforming vector (w _T ) of Equation 5, the effective channel for each of the SI channel (v _R ^H ) and the second hop channel (g ^{T ) is expressed by Equation 6} can

_{From Equation 6, it can be seen that the transmit beamforming vector w T} expressed by the SI channel transmission weight ω has a form that can comprehensively express the channel environment and energy/data performance measures. This is the maximum ratio transmission to the SI channel to maximize the energy yield of the FD DF relay (RS) from the null space projection (NSP) case (ω = 0) to completely remove the SI according to the SI channel transmission weight (ω). (maximal-ratio transmission: MRT) can be viewed as a generalized beamforming vector expressed to cover all cases (ω = 1). _{Here, it may be expressed as (H RR} w _T = 0) as a case of null space projection (NSP) to completely remove SI, and interpreted as a case of maximum ratio transmission (MRT) to the second hop channel, 3 may be expressed as a case where |g ^T w _{T |}

On the other hand, the reception beamforming vector w _R is basically concerned only with the SINR of the first hop channel (H). Accordingly, the reception beamformer 220 configures the _{reception beamforming vector w R} such that the SINR of a signal transmitted through the first hop channel is maximized. The end-to-end SINR (γ) in a first hop channel (H) SINR (γ ₁₎ and the smaller of the SINR (γ ₂₎ of the second hop channel (g) (γ = min ( γ 1, γ 2)) of Therefore, in order to improve the end-to-end SINR, it is necessary to increase both the SINRs (γ ₁ , γ ₂ ) of the first hop channel (H) and the second hop channel (g).

The effective channel vector (h) of the first hop is a SI channel considering the first hop channel (H) and can be represented by h = Hw from the base station beamforming vector (w), transmission beamforming vector (w _T) ( The effective channel vector (h _RR ) _{for H RR} ) may be expressed as _{h RR} = H _RR w _{T .} Accordingly, the SINR(γ ₁ ) of the first hop may be expressed by Equation (7).

Here, P _s and P _R are the strengths of _{a signal (x s} ) transmitted from the base station (AP _{) and a signal (x R} ) transmitted from the relay (RS), respectively.

이고,

라 할 때,

를 최대화하는 문제이며, 이는 일반화된 고유값 문제(generalized eigenvalue problem)로 해석될 수 있다.The problem of obtaining a reception beamforming vector (w _{R ) for maximizing the SINR (γ 1} ) of the first hop channel (H) according to Equation 7 is

ego,

When you say

is a problem of maximizing , which can be interpreted as a generalized eigenvalue problem.

And the solution of this maximization problem is the eigenvector corresponding to the largest eigenvalue of the ^{matrix A -1} B (where A ^{-1 is the inverse of A).} Therefore, for eigen analysis of the matrix A ^-1 B, eigen decomposition may be first performed on ^{the inverse matrix A -1} of A as shown in Equation (7).

Based on the eigen decomposition of Equation 8, the channel vector (h) constituting B of the ^{matrix A −1} B may be expressed again by Equation 9, which is a basis vector constituting ^{A −1 .}

where δ=h ^H h _RR and δ _i =h ^H u _i .

And from Equation (9), the matrix A ^-1 B may be expressed as a rank-one matrix as in Equation (10).

Using that the eigenvector of the rank one matrix (xy ^H ) defined as the product of two vectors x and y is x, the final reception beamforming vector (w _R ) for maximizing the SINR (γ _{1 ) of the first hop} The solution may be calculated by Equation (11).

이고, 이는

로 표현될 수 있으며, 임의의 송신 빔포밍 벡터(w_T)로 획득할 수 있는 최대 SINR을 나타낸다. _{And the maximum SINR (max γ 1} ) of the first hop channel (H) that can be obtained according to Equation 11 is

and this is

It can be expressed as , and represents the maximum SINR obtainable with an _{arbitrary transmit beamforming vector (w T ).}

_{When a generalized transmit beamforming vector (w T} ) is applied in the form of a function for the SI channel transmission weight (ω) of Equation (6) together with Equation (11), the first hop channel (H) and the second hop channel (g) SINR(γ ₁ , γ ₂ ) of is expressed by Equations 12 and 13, respectively.

In Equations 12 and 13, the SINR(γ ₁ (ω, ρ)) of the first hop channel H is a monotonic decreasing function for the SI channel transmission weight ω, and a monotonic increasing function for the power division ratio ρ to be. _{Also, the SINR (γ 2} (ω)) of the second hop channel g is a concave function with respect to the SI channel transmission weight ω. _{Accordingly, the SINRs (γ 1} (ω, ρ), γ ₂ (ω)) of the first and second hop channels (H, g) are shown as a graph as shown in FIG. 4 .

4 shows the SINR change of each of a reception channel and a transmission channel of the relay according to the SI channel transmission weight and the power split ratio.

_{As described above, the SINR (γ 1} (ω, ρ)) of the first hop channel (H), which is the reception channel of the relay (RS), is a monotonic decreasing function for the SI channel transmission weight (ω), and the power split ratio ( _{ρ), and the SINR(γ 2} (ω)) of the second hop channel g, which is the transmission channel, is a concave function with respect to the SI channel transmission weight ω, so the x-axis in FIG. 4 is the SI channel transmission weight (ω), and the y-axis represents the SINR (γ ₁ ) of the first hop channel (H).

_{And the change in the SINR (γ 1} (ω, ρ)) of the first hop channel (H) according to the change in the SI channel transmission weight (ω) at different power division ratios (ρ = 0.3, 0.4, 0.6, 1), respectively _{is represented by a number of different curves, and in order to contrast with the SINR (γ 1} ) of the plurality of first hop channels (H), the SINR of the second hop channel (g) according to the change of the SI channel transmission weight (ω) (γ ₂ (ω)) is plotted together.

To a value of the end-to-end SINR (γ) is SINR (γ ₂₎ of the first hop channel (H) SINR (γ ₁₎ and the second hop channel (g) of as described above is determined according to the equation (14).

And the energy yield (E) of the relay (RS) is _{a signal received through the first hop channel (H) and the SI channel (H RR} ), the energy beamformer 260 is a beam using the _{energy beamforming vector (w E )} Since it can be defined as a result of forming, it can be defined by Equation (15).

Where λ _max is the first represents the square of the maximum singular value (largest singular value) of the hop channel (H), u is the first hop channel (H) units of M _R × 1 size corresponding to M _R receive antennas in bastard vector and with it the first hop the receiving unit he vector, u _R is, SI channel (H _RR) from the received SI as the unit he vector of M _R × 1 size corresponding to M _R receive antennas as described above, It can be called a unit norm vector.

From Equation 15, the energy beamforming vector (w _E ) can be designed as Equation 16 as a weighted sum of the first hop reception unit norm vector (u) and the SI reception unit norm vector (u _{R )} can be known

Here, ζ is a forming weight for the first hop channel (H) among the first hop channel (H) and the SI channel (H _{RR ).}

로 설정될 수 있다. 그리고 수학식 16의 에너지 빔포밍 벡터(w_E)를 적용하게 되면, 수학식 15의 릴레이(RS)의 에너지 수확량은 수학식 17과 같이, SI 채널 전송 가중치(ω)에 대한 유리 함수(rational function)(f(ω))의 형태로 표현될 수 있다.If the first hop reception unit norm vector (u) and the SI reception unit norm vector (u _R ) are interpreted as branches having powers of α _R ² P _R ω ² and λ _max P _{S , respectively, the forming weight (ζ} ) is

can be set to And when the energy beamforming vector w _E of Equation 16 is applied, the energy yield of the relay RS of Equation 15 is a rational function for the SI channel transmission weight ω as shown in Equation 17 )(f(ω)).

And the final expression for the energy yield (E) considering the power split ratio (ρ) for energy harvesting is simplified as in Equation 18 from the rational function (f(ω)) for the SI channel transmission weight (ω) of Equation 17 can be

The relay RS according to this embodiment considers the end-to-end SINR (γ) of Equation 14 and the energy yield (E) of Equation 18 at the same time, and the reference SINR (γ ^* ) for which the end-to-end SINR (γ) is required The energy yield (E) should be maximized while satisfying the ideal.

In this embodiment, the _{SINR (γ 1 (ω, ρ} )) and second ₍₂ γ (ω)) SINR of the second hop channel (g), the power split ratio (ρ) of the above-described first hop channel (H) and Considering the relationship between the SI channel transmission weights (ω), the SI channel transmission weights (ω) where the end-to-end SINR (γ = min(γ ₁ , γ ₂ )) in FIG. 4 satisfies the reference SINR(γ ^* ) or more The region is important, and this region is defined herein as an outage-free region (hereinafter, OFR).

_{Considering the SINRs (γ 1} , γ ₂ ) of the first hop channel (H) and the second hop channel (g) expressed in Equations 12 and 13, when the power division ratio ρ increases, that is, the SINR is If you want to improve, there are two trade-offs.

First, a trade-off occurs in that the energy harvest ratio (1-ρ) decreases in the relay RS, and thus the energy harvest decreases. And secondly, the SINR(γ ₁ ) of the first hop channel H decreases, resulting in a trade-off in which the OFR decreases. If this is expressed as a graph, it is shown in FIG. 5 .

5 is a diagram for explaining a change in OFR according to a change in a power split ratio.

Referring to FIG. 5 , the SINR(γ ₁ ) of the first hop channel H is maximum at the maximum power division ratio (ρ _max = 1). If the OFR is not formed even at the maximum power split ratio (ρ _max ), it may be regarded as an outage occurrence. However, if OFR is formed, the power division ratio ρ is gradually decreased from the _{maximum power division ratio ρ max = 1 .} As the power split ratio ρ decreases, the OFR gradually decreases, reducing the number of poles that are likely to maximize energy yield. _{Accordingly, the minimum power division ratio (ρ = ρ min} ) at which the OFR can be formed by the reduced power division ratio ρ is searched for. When the power division ratio (ρ) is _{less than the minimum power division ratio (ρ min} ), an OFR is not formed and the reference SINR(γ ^* ) cannot be satisfied, so a failure occurs, so the power less than the _{minimum power division ratio (ρ min )} The split ratio ρ does not need to be considered.

However, if the two parameters of the power division ratio ρ and the SI channel transmission weight ω can be selected with a high degree of freedom even in the OFR region in which the power division ratio ρ is equal to or greater than the minimum power division ratio ρ _{min , the optimal power} A very complex operation is required to calculate the split ratio (ρ) and the SI channel transmission weight (ω).

Accordingly, in the present invention, the power division ratio (ρ) is _{divided into a predetermined range of the minimum power division ratio (ρ min} ) and the maximum power division ratio (ρ _max = 1) by K, and K+1 representative power division ratios (ρ _k , where k = 0 ~ K) is set first. Then, an SI channel transmission weight (ω) capable of maximizing energy for each of the K+1 representative power split ratios (ρ _{k ) is searched.}

6 shows a concept of searching for an SI channel transmission weight capable of maximizing energy by setting K representative power split ratios.

) 단위로 차감하여, 나머지 K개의 대표 전력 분할비(ρ_k)를 설정한다.Referring to FIG. 6 , first, the ranges of the minimum power split ratio (ρ _min ) and the maximum power split ratio (ρ _max = 1) found in FIG. 5 are divided into K predetermined, and K+1 representative power split ratios (ρ) _k ) is set. Here, the K+1 representative power split ratio (ρ _{k ) is an equal size ( ρ 0} = ρ _max = 1) from the maximum power split ratio (ρ 0 = ρ max = 1).

) to set the remaining K representative power division ratios (ρ _k ).

And determine the lower limit (ω _k,LB ) and upper limit (ω _k,UB ) of the SI channel transmission weight (ω _k ) corresponding to each section divided by the set K+1 representative power split ratio (ρ _{k ),} , it is determined SI channel transmit weights lower limit of the _{(ω k) (ω k,} LB) and the variable upper limit (ω _{k, UB)} SI channel transmit weights (ω _{k, j)} in the range, energy according to the equation (18) _{The SI channel transmission weight max ω k,j} corresponding to the extreme value of the rational function f(ω) capable of maximizing the yield E is detected.

In this case, an SI channel transmission weight (ω) for detecting an energy harvest (E _k ) corresponding to a plurality of representative power split ratios (ρ _k ) may be detected, and in this case, a search _{is performed at each representative power split ratio (ρ k )} The power split ratio (ρ _k ) and the SI channel transmission weight (ω _k,j ) representing the maximum energy yield (E _max = max (E _k | _k=0,…,K )) among the energy harvests (E _{k ).} ) may be determined as the power division ratio ρ and the SI channel transmission weight ω for the FD DF relay RS according to the present embodiment.

Although the present invention has been described with reference to the embodiment shown in the drawings, which is only exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

Accordingly, the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims.

AP: base station RS: relay
UT: terminal 110: base station beamformer
210: signal receiving unit 220: receiving beamformer
230: decoder 240: transmit beamformer
250: battery 260: energy beamformer

Claims (8)

A signal beamformed from the base station and transmitted through the first hop channel is beamformed and received, the power of the received signal is divided to decode and re-encode the signal, and at the same time harvest energy, and beamform the re-encoded signal. In the relay of the relay system, power division-based wireless information and power simultaneous transmission (hereinafter SWIPT), full-duplex (hereinafter FD), and forward (hereinafter DF), including a relay for transmitting to the terminal through the second hop channel,
A power split ratio (ρ) indicating a ratio of power to be used for decoding and energy to be harvested from the received signal, and the second hop channel and the self-interference channel (hereinafter referred to as SI) during transmission beamforming for transmitting a signal to the terminal From the relationship between the _{SINR(γ 1} ) of the first hop channel and the SINR(γ ₂ ) of the second hop channel expressed as a function of the SI channel transmission weight (ω) representing the beamforming weight to the SI channel in The end-to-end SINR (γ) between the base station and the terminal ^{detects a failure free region (hereinafter, OFR) that satisfies a predetermined reference SINR (γ *} ) or more, and the range of the power division ratio (ρ) corresponding to the OFR SI channel transmission weight ( ) that obtains K+1 representative power split ratios (ρ _k ) by dividing into K predetermined sections, and maximizes the energy harvest for each of K+1 representative power split ratios (ρ _{k )} after detecting ω _{k, j),} the detected SI channel transmit weights (representing the power split ratio (ρ _k) and SI channel transmit weights to obtain the maximum energy yield of the energy according to ω _{k, j)} (ω _{k, j} ) relay to select. According to claim 1, wherein the relay
a signal receiving unit for receiving a signal with power of a ratio corresponding to the power division ratio (ρ) among signals received through a plurality of receiving antennas;
a reception beamformer for beamforming a signal received by the signal reception unit using a reception beamforming vector (w _R );
a decoding unit for decoding and re-encoding the signal obtained through the reception beamformer;
a transmit beamformer for beamforming the signal re-encoded by the decoder according to a transmit beamforming vector w _T and transmitting it to the terminal through a plurality of transmit antennas; and
an energy beamformer for beamforming a signal of power remaining except for power transmitted to the signal receiver among signals received through a plurality of reception antennas using an energy beamforming vector (w _E ); and
and a battery for harvesting and storing power of a signal beamformed and transmitted by the energy beamformer as energy. 3. The method of claim 2, wherein the transmit beamformer
_{The transmit beamforming vector w T} is set according to the SI channel transmission weight ω, and the second hop channel and the SI channel are recoded by beamforming according to the set transmit beamforming vector w _{T .} A relay that transmits a signal. 4. The method of claim 3, wherein the energy beamformer is
_{The energy beamforming vector w E} is set according to a forming weight ζ that adjusts a reception ratio of a signal transmitted through the first hop channel and a signal transmitted through the SI channel, and the forming weight ζ ) is the relay determined by the SI channel transmission weight (ω). 5. The method of claim 4, wherein the relay
_{SINR(γ 1} ) of the first hop channel and the second hop channel while decreasing the power division ratio (ρ) by a predetermined unit from a maximum power division ratio (ρ _{max = 1) corresponding to a predetermined maximum value} SINR(γ ₂ ) of each is calculated, and the end-to-end SINR calculated as the smaller of the calculated _{SINR(γ 1} ) of the first hop channel and the SINR(γ _{2 ) of the second hop channel (γ = min(} γ ₁ , γ ₂ )) detects whether an OFR equal to or greater than the reference SINR(γ ^* ) exists, and determines the _{minimum power division ratio (ρ min} ), which is the minimum value among the power division ratios (ρ) in which the OFR exists, and determines A relay for obtaining K+1 representative power split ratios (ρ _k ) by dividing the range from the minimum power split ratio (ρ _min ) to the maximum power split ratio (ρ _{max ) into K sections.} The method of claim 5, wherein the relay
The K+1 representative power split ratio (ρ _k ) is an equal size unit ( _{ρ max} ) from the maximum power split ratio (ρ max )

) by repeatedly subtracting the relay. 7. The method of claim 6, wherein the relay
Determine the lower limit (ω _k,LB ) and the upper limit (ω _k,UB ) of the SI channel transmission weight (ω _k ) corresponding to each section divided by the K+1 representative power split ratio (ρ _{k ), and determine} the SI channel transmit weights (ω _k) of the lower limit (ω _{k, LB)} and upper limit (ω _{k, UB)} while varying a SI channel transmit weights (ω _{k, j)} to the extent, electrical energy yield according to a specified formula A relay for obtaining the maximum value among the calculated energy yields as an energy yield corresponding to the K+1 representative power split ratio (ρ _{k ) by calculating .} The method of claim 7, wherein the relay
K + 1 of the representative power split ratio (ρ _k) represents the power split ratio (ρ _k) and SI channel transmission weight corresponding to the maximum energy yield is determined maximum energy yield of the energy yield obtained in correspondence with, respectively, and determine ( A relay that selects ω _k,j as the relay's power split ratio (ρ) and SI channel transmission weight (ω).

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