KR101386394B1 - Achievable rate optimization method for multiuser multi-input multi-output two-way relaying communication system - Google Patents

Abstract

The present invention relates to a communication method capable of effectively improving a communication capacity of a multiuser multi-input multi-output cellular communication system in which a bidirectional relay is performed. In a cellular communication system composed of one base station having a network and a plurality of communication terminal nodes having one relay node and one transmit / receive antenna, a method of effectively improving a communication capacity has been solved. The present invention provides a method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system configured to increase communication capacity effectively.

Description

Achievable rate optimization method for multiuser multi-input multi-output two-way relaying communication system

The present invention relates to a communication method of a multiuser multi-input multi-output cellular communication system in which a bidirectional relay is performed. More particularly, the present invention relates to a base station and a base station having a plurality of transmit and receive antenna systems. In a multi-user multi-input / output cellular communication system composed of a relay node and a plurality of communication terminal nodes having one transmit / receive antenna, multi-user multi-input I / O bidirectional relay communication that can effectively improve the communication capacity of the system through the achievement rate optimization. A method of optimizing the achievement rate of a system.

Conventionally, a communication technique in which a bidirectional relay is performed starts with a model in which communication between two communication nodes is through a relay node.

In addition, when communication between two communication nodes is performed through the relay node in this way, the maximum communication capacity that can be achieved by using the grid code can be achieved.

That is, for example, if there are one relay node and more than two communication nodes and many communication links are formed, each node has multiple transmit / receive antennas or sensors (hereinafter referred to as antennas) or code division. Enabling multiple access enables efficient communication capacity increase.

However, in the cellular communication system composed of one base station having a plurality of transmitting and receiving antenna systems, and a plurality of communication terminal nodes having one relay node and one transmitting and receiving antenna, it is difficult to apply the methods as described above. However, it is not known how to effectively improve the communication capacity.

In particular, in the case of a communication system where communication speed is limited due to a narrow bandwidth, such as an underwater wireless communication system using sound waves and a ship communication system using VHF, the multi-input / multi-user bidirectional relay technology can be used to extend the communication distance and quality. Improvements are possible.

Therefore, in order to solve the problems of the conventional communication system as described above, even in a cellular communication system composed of a plurality of communication terminal nodes having one relay node and one transmit / receive antenna, communication capacity can be efficiently increased. It is desirable to provide a new communication method that can be used.

However, as described in the following [Previous Technical Documents], various researches on the MIMO system have been conducted in the past, but an apparatus or method that satisfies all such requirements has not been provided until now.

[Prior Art Literature]

Prior Document 1: Patent No. 10-0995031 (2010.11.11.)

Prior Document 2: Patent No. 10-0889302 (2009.03.11.)

Prior Document 3: Korean Patent Publication No. 10-2011-0100604 (2011.09.14.)

The present invention is to solve the problems of the conventional communication system as described above, and therefore the object of the present invention is to include one base station and one relay node having a plurality of transmit and receive antenna systems, and one transmit and receive antenna In a multi-user multi-input / output cellular communication system composed of a plurality of communication terminal nodes, the present invention is to provide a method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system that can effectively improve the communication capacity of the system through the achievement rate optimization. .

In addition, another object of the present invention, through the achievement rate optimization as described above is composed of one base station having a plurality of transmit and receive antenna system, one relay node, and a plurality of communication terminal nodes having one transmit and receive antenna It is configured to effectively increase the overall communication capacity of a multi-user multi-input / output cellular communication system, thereby reducing the capital investment cost by solving the problem of the conventional communication system, which had to continuously increase the communication facilities to increase the communication capacity. The present invention aims to provide a method for optimizing the achievement rate of a multi-user multi-input bi-directional relay communication system.

In order to achieve the above object, according to the present invention, a plurality of base stations having one N _B antenna system, one relay node having an N _V antenna system and one transmitting and receiving antenna A multi-user multi-input / output cellular communication system in which bi-directional relaying is performed through a process of transmitting a signal to a base station and a user terminal, each of which transmits signals to a base station and a user terminal. In the multi-user multi-input I / O bidirectional relay communication method using a grid code to increase the communication capacity of the multi-user multi-input and output cellular communication system using a grid code, N N corresponding to the smaller number of N _B and N _V Selecting a user terminal node; Generating a channel matrix from the base station node to the relay node and a channel matrix from the user terminal node to the relay node; A grid encoding step of generating a codeword vector to be transmitted from the user terminal node and the base station through grid coding; Generating a codeword vector indicating a codeword vector to be transmitted from the base station node to a k-th user terminal node and a codeword vector to be transmitted from the k-th user terminal node to the base station node through horizontal encoding of the user terminal nodes, respectively. Generating a coding matrix; A base station transmission signal generation step of generating a transmission signal of the base station node through linear precoding; A user terminal transmission signal generation step of generating a transmission signal of the user terminal node; A reception signal generation step of generating a reception signal received at the relay node based on each of the transmission signals obtained in the base station transmission signal generation step and the user terminal transmission signal generation step; A decoding step of decoding each codeword from the received signal obtained in the received signal generating step by using a horizontal sequential interference cancellation method; A trellis encoding transmission step of encoding the signal obtained in the decoding step through a trellis code at the repeater node and transmitting it to each of the base station node and the user terminal node; And a grid encoding receiving step of decoding a signal of each of the base station node and the user terminal node using a grid code. The multi-user multiple input / output bidirectional relay communication method using a grid code is provided. do.

In the channel matrix generation step, the channel matrix from the base station node to the relay node is defined as a matrix H _BV having a size of N _V × N _B , and N _v × 1 from the selected k th terminal node to the relay node. When the channel vector of size h _{MV, k} , the channel matrix H _MV from the terminal node to the relay node is configured to be defined by the following equation.

In addition, in the lattice coding step, when the code rates of x _{B, k} and x _{M, k} are R _{B, k} and R _{M, k ,} respectively _, the lattice Λ _{B, k} , Λ _{M, k} , Λ _{C, k} and generate the lattice codes π _{B, k} and π _{M, k} by the following equation.

Where Λ _{B, k} , Λ _{M, k} are all good for mean-square-error quantization or Poltyrev-good, good for covering or Rogers-good, and Λ _{C, k} is a lattice with good mean squared quantization, v _{B, k} and v _{M, k} are transition vectors, Ξ (Λ) represents the fundamental Voronoi region of lattice Λ)

In addition, the grid coding step, the v _{B, k} , v _{M, k} and Λ _{C, k} is selected to satisfy the following equation,

The signal to be sent by the base station node and the signal to be sent by the user terminal node are x _{B, k} ∈ Π _{B, k} and x _{M, k} ∈ Π by the grid codes π _{B, k} and Π _{M, k} , respectively. _It is characterized in that it is configured to be encoded by _{M, k} .

Further, in the encoding matrix generating step, when a code length or a block length is D, a codeword vector having a size of 1 × D to be transmitted from the base station node to a k-th user terminal node is referred to as x _{B, k} , when the k-th user terminal node to be referred to 1 × d size codeword vector of the transfer to the base station node x _{M, k,} the matrix according to the following equation stacked horizontally to the x _{B, k} and the x _{M, k} And to define X _B and X _M.

In addition, the base station transmission signal generating step, the pseudo inverse matrix operation

In this case, the transmission signal matrix S _B to be transmitted by the base station node is

It is characterized in that it is configured to generate the transmission signal matrix S _B by the following equation.

In addition, the user terminal transmission signal generation step, characterized in that configured to generate a transmission signal at each user terminal node based on the following equation.

Further, the transmitting signal generating step is characterized in that the average power γ _{B, k} and γ _{M, k} of the x _{B, k} and x _{M, k} is selected to satisfy the condition shown in the following equation.

(Where P _B and P _{M, k} are the maximum transmit powers of the base station and k-th user, and w _{ZF, k} is the k-th column of W _ZF .)

The receiving signal generating step may include the transmitting signal matrix S _B generated in the base station transmitting signal generating step and the transmitting signal matrix S _M generated in the user terminal transmitting signal generating step based on the following equation. And generate the signal Y _V received by the relay node.

Where Z _V is additive noise

In addition, the decoding step, QR decomposition of the channel matrix H _MV of the received signal generated in the received signal generating step into an orthogonal matrix Q and an upper-triangular matrix U by the following equation,

The received signal Y _V obtained in the received signal generating step is multiplied by Q ^T by the following equation.

/ RTI >

(here,

to be)

When x _{B, k} + x _{M, k} is decoded with respect to n + 1 ≦ _k ≦ N, the following equation is used as an input to the decoder _, so that it is configured to decode x _{B, n} + x _{M, n} . .

(Where u _{i, j} is the (i, j) th element of U)

Further, the lattice coding transmission step generates a D-dimensional lattice Λ _{V, k} , Λ _{C ', k in} which Λ _{V, k} ⊆ Λ _{C', k} , and uses lattice code Π _V using the following equation: generates _{, k} ,

Where Λ _{V, k} is good for mean-square-error quantization or Poltyrev-good and good for covering or Rogers-good, and Λ _{C ', k} is mean square error Is a good quantization grid)

_{V V, k} is a transition vector satisfying the following equation,

(Where Ξ (Λ) is the fundamental Voronoi region of lattice Λ and vol (·) means volume)

It is characterized in that the signal to be sent in the relay node by the grid code π _{V, k} is coded as x _{V, k} ∈ Π _{V, k} .

In addition, in the trellis coding transmission step, when a channel vector having a size of 1 × N _v from the relay node to the selected k th terminal node is h _{VM, k} , a channel matrix H _VM is generated by the following equation. ,

QR decomposition of the H _VM by the following equation,

(Where L is the lower triangular matrix, and if l (n, m) of L is l _{n, m} , if n <m then l _{n, m} = 0 and Ω is an orthogonal matrix)

It is characterized in that it is configured to generate a _precoded codeword x _{PV, k} from the lattice coded x _{V, k} by the following equation.

(Where α _k is a constant, β _{V, k} is a random dither with a uniform distribution in the region Ξ (Λ _{V, k} ), [·] _Λ is a modulo operation on the lattice Λ )

In addition, the trellis coding transmission step is characterized in that the α _k is configured to be defined by the following equation when the channel is modeled as an additive white Gaussian noise channel having a mean of 0 and a variance of N ₀ .

Where γ _{V, k} is the average power of x _{V, k}

Further, in the trellis coding transmission step, using the _precoded codeword x _{PV, k} to generate a matrix X _PV by the following equation,

It is characterized in that it is configured to generate the transmission signal matrix of the relay node by the following equation.

In addition, in the lattice encoding receiving step, in the case of an additive noise channel model, a signal y _{M, k} received by a k-th user terminal node is generated with respect to a signal transmitted by the relay node according to the following equation,

(Where z _{M, k} is additive noise)

It is configured to generate an input signal of a decoder for the k-th user terminal node by the following equation.

In addition, the grid coding receiving step, in the case of an additive noise channel model, generates a signal Y _B received at the base station node by the following equation,

Where z _B is additive noise

QL-decomposes H _VB Ω ^T in Y _B by the following equation,

(here,

Is a matrix of N orthogonal column vectors,

Is the lower triangular matrix)

The (n, m) th element of

In this case, the received signal y ' _{B, k} corresponding to the k-th user terminal node in the base station node is generated by the following equation,

(Where z ' _{B, k} is additive noise)

The base station node generates a decoder input signal for decoding the signal of the k-th user terminal node by the following equation,

(here,

Is a constant representing the minimum mean square error coefficient at the base station node)

The decoding order of x _{PV, k} is characterized in that it is configured to proceed in order from k = 1 to N.

Further, in the lattice coding receiving step, in the case of white Gaussian noise in which the additive noise has an average of 0 and the variance of N ₀ ,

Is characterized by the following equation.

In addition, in the achievement rate optimization step, when the additive noise is all white Gaussian noise having an average of 0 and variance of N ₀ , the achievement rate R _Σ of the entire system that can be obtained through bidirectional relaying is represented by the following equation.

In order to maximize the above-described achievement rate R _Σ , gamma _{B, k} , gamma _{M, k} , gamma _{V, k} are respectively determined from an optimization problem expressed by the following equation.

(here,

to be)

In addition, the achievement rate optimization step, converting the optimization problem into a concave problem by the following equation,

(here,

Is an auxiliary variable)

The cost function μ is generated by the following equation,

(here,

Is the Lagrangian constant)

It is characterized by the following equation that the optimal gamma _{B, k} , gamma _{M, k} , gamma _{V, k} are uniquely determined from Karush-Kuhn-Tucker conditions.

Furthermore, according to the present invention, it is composed of one base station node having N _B antenna systems, one relay node having N _V antenna systems, and a plurality of user terminal nodes having one transmit / receive antenna, In order to increase the communication capacity of a multi-user multi-input / output cellular communication system in which a base station and a user terminal each transmit a signal to a repeater, and in the repeater, a signal is simultaneously transmitted to the base station and the user terminal. A communication system is provided which is configured to communicate using the method for optimizing the achievement rate of the multi-user multiple input-output bidirectional relay communication system described above.

As described above, according to the present invention, a multi-user multi-input / output cellular communication system composed of one base station having a plurality of transmit / receive antenna systems, one relay node, and a plurality of communication terminal nodes having one transmit / receive antenna In the present invention, a method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system capable of effectively improving a communication capacity of a multi-user multi-input / output cellular communication system can be provided.

In addition, according to the present invention, by effectively increasing the overall communication capacity of the multi-user multi-input / output cellular communication system by optimizing the achievement rate as described above, the conventional communication system that had to continue to expand the communication facilities to increase the communication capacity In order to solve the problem, it is possible to provide a method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system which can reduce the cost of equipment investment.

1 is a diagram schematically showing the overall configuration of a bidirectional relay communication system model in a multi-user multi-input / output cellular communication environment for applying a communication method according to the present invention.
2 is a flowchart schematically showing the overall configuration of the method for optimizing the achievement rate of the multi-user multi-input bi-directional relay communication system according to the present invention.

Hereinafter, with reference to the accompanying drawings, a specific embodiment of the method for optimizing the achievement rate of the multi-user multi-input I / O bidirectional relay communication system according to the present invention will be described.

Hereinafter, it is to be noted that the following description is only an embodiment for carrying out the present invention, and the present invention is not limited to the contents of the embodiments described below.

In the following description of the embodiments of the present invention, parts that are the same as or similar to those of the prior art, or which can be easily understood and practiced by a person skilled in the art, It is important to bear in mind that we omit.

That is, the present invention, as will be described later, multi-user multi-input / output cellular communication consisting of one base station having a plurality of transmit and receive antenna systems, one relay node, and a plurality of communication terminal nodes having one transmit and receive antenna In the system, in order to solve the problems of the prior art, in which a method of effectively improving the communication capacity of the system has not been proposed, a multi-user multi-input / output cellular communication system configured to increase the communication capacity of the multi-user multi-input / output cellular communication system by optimizing the achievement rate The present invention relates to a method for optimizing the achievement rate of a user input / output bidirectional relay communication system.

In addition, the present invention, as will be described later, multi-user multi-input / output cellular communication consisting of one base station having a plurality of transmit and receive antenna systems, one relay node, and a plurality of communication terminal nodes having one transmit and receive antenna It is configured to effectively increase the overall communication capacity of the system through the achievement rate optimization, thereby solving the problem of the conventional communication system, which had to continuously expand the communication facilities to increase the communication capacity, and reduce the capital investment cost. The present invention relates to a method for optimizing the achievement rate of a user input / output bidirectional relay communication system.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the method for optimizing the achievement rate of the multi-user multi-input I / O bidirectional relay communication system according to the present invention as described above.

First, referring to FIG. 1, FIG. 1 schematically illustrates the overall configuration of a bi-directional relay communication system model in a multi-user multi-input / output cellular communication environment for applying a method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system according to the present invention. It is a figure shown by.

That is, in the following description, as shown in FIG. 1, a plurality of base stations having one N _B antenna system, one relay node having N _V antenna systems, and one transmitting and receiving antenna are provided. A total of two steps, consisting of a communication terminal node, a terminal transmission step (step 1) of transmitting a signal from each terminal to a repeater and a transmitter transmission step (step 2) of transmitting a signal from the repeater to each terminal at a time The present invention will be described by taking a multi-user multi-input / output cellular communication system in which a bi-directional relaying is performed as an example.

More specifically, in the system shown in Fig. 1, when the number of selected terminals is N, N is the smaller number among N _B and N _V.

Complex vector

, Complex matrix

about,

By converting as follows, since complex vectors and matrices can be treated as if they were real numbers, in the present invention, all signals are assumed to be real numbers.

Here, Re (·) and Im (·) denote real and imaginary parts of complex numbers, respectively, and (·) ^T means transpose matrix.

In addition, a channel matrix indicating multiple inputs and outputs is represented by subscripts indicating transmission and reception. That is, the channel matrix from the base station to the relay node is a matrix H _{BV having a} size of N _V × N _B , and the channel from the relay node to the base station. The matrix is a matrix H _{VB having a} size of N _B × N _V , and the channel vector from the selected k th terminal node to the relay node is a vector h _{MV , k having a} size of N _v × 1 _, and from the relay node to the selected k th terminal node. The channel vector is a vector h _{VM , k} of size 1 × N _v .

Accordingly _, by stacking these h _{MV , k} , h _{VM , k} horizontally, the channel matrices H _MV and H _VM are defined as in Equation 1 below.

[Equation 1]

Further, in the present invention, it is assumed that all channel matrix values do not change for the time of one frame.

Subsequently, when the code length or block length is D, the transmission signal matrix of size N _B × D at the base station is referred to as S _B , and the transmission signal vector of size 1 × D of the k-th user is referred to as s _{M , k} . Then, s _{M , k} are stacked horizontally to define the N × D dimensional signal matrix S _M of the terminals as shown in Equation 2 below.

&Quot; (2) &quot;

In addition, in the case of the additive noise channel model, the signal Y _V received at the relay node in step 1 may be expressed as Equation 3 below.

&Quot; (3) &quot;

In Equation 3, Z _V is additive noise of the relay node.

In addition, if the transmission signal of the relay node of size N × D generated from the reception signal Y _V in step 2 is represented by S _V , in the case of the additive noise channel model, the signal Y _B and the terminal node received at the base station in step 2 are represented. The received signal Y _M can be expressed as Equation 4 below.

&Quot; (4) &quot;

Here, in Equation 4, y _{M , k} having a magnitude of 1 × D is a received signal of the k-th user, and Z _B and Z _M are additive noises at base stations and terminal nodes, respectively.

In addition, according to the present invention, in step 1, a channel encoding and zero-forcing linear precoding method for maximizing performance while minimizing computational complexity of user terminals is proposed.

More specifically, since the terminal nodes cannot cooperatively communicate with each other, horizontal encoding is performed, that is, a Bx size codeword vector to be transmitted from the base station to the k-th user terminal node is x _{B. If k} is the 1 × D codeword vector to be transmitted from the k-th user terminal node to the base station, x _{M and k} , the matrixes X _B and X _M horizontally stacked with x _{B , k} and x _{M , k} It can be defined as [Equation 5] below.

&Quot; (5) &quot;

Subsequently, in the communication method according to the present invention, the linear pre-coding method of the base station can be expressed as in Equation 6 below.

&Quot; (6) &quot;

Here, in [Equation 6],

Denotes a pseudo inverse operation.

Therefore, Equation 6 may be rewritten as follows.

In addition, the user terminal node generates a transmission signal as shown in Equation 7 below without performing precoding.

&Quot; (7) &quot;

In addition, the average powers γ _{B, k} and γ _{M, k} of x _{B , k} and x _{M , k} are selected to satisfy the conditions as shown in Equation 8 below.

&Quot; (8) &quot;

Here, in Equation 8, P _B , P _{M , k} are the maximum transmit powers of the base station and the k-th user, and w _{ZF , k} is the k-th column of W _ZF .

Therefore, in step 1, the signal received by the relay node may be represented by Equation 9 below.

&Quot; (9) &quot;

That is, as shown in Equation 9 above, in the embodiment according to the present invention, step 1 described above has H _MV as an equivalent channel matrix.

Also, since each codeword is horizontally encoded, the codewords are horizontally decoded in a sequential interference cancellation method.

More specifically, for horizontal sequential interference cancellation, the matrix H _MV is QR decomposed, as shown in Equation 10 below.

&Quot; (10) &quot;

Here, in [Equation 10], Q is an orthogonal matrix and U is an upper-triangular matrix.

Further, it is to be decoded in the step 1, the symbol X _B + X _M added as well to each of the code words in X _B and X _M, X _B and X _M.

Therefore, multiplying the received signal Y _V by Q ^T can be expressed as Equation 11 below.

&Quot; (11) &quot;

Here, in Equation 11, Z _V represents additive noise of the relay node.

From Equation 11, the equivalent channel matrix is U, and in Equation 11,

to be.

In addition, when x _{B , k} + x _{M , k} is decoded for n + 1 ≦ _k ≦ N, the nth decoding is made of a signal from which interference is removed as shown in Equation 12 below.

&Quot; (12) &quot;

Here, in [Equation 12], u _{i , j} are the (i, j) th elements of U.

Next, will be described with respect to the coding method, code words x _{B, k} and the codeword x _M, in order _k has become a x _{B, k} + x _{M, k} decoding plus x _{B, k} + x _{M, k} is also a code word Should be

In this case, when x _{B , k} , x _{M , and k} are all binary codes, an exclusive OR of x _{B , k} , x _{M , and k} may be decoded.

However, in the case of higher-order codes exceeding binary codes, exclusive OR decoding is impossible, like binary codes.

To this end, the present invention proposes a method for decoding x _{B , k} + x _{M , k} using a lattice code.

That is, the grid code π _{B, k} of the D-dimensional base station and the grid code π _{M, k} of the D-dimensional user terminal node are generated as follows.

More specifically _{, when} the code rates of x _{B , k} and x _{M , k} are R _{B , k} and R _{M , k} , first, the D-dimensional lattice Λ _{B, k} , Λ _{M, k} , Λ Create _{C, k}

Here, Λ _{B, k} , Λ _{M, k} are all good for mean-square-error quantization or Poltyrev-good, good for covering or Rogers-good, and Λ _{C, k} is a lattice with good mean square quantization.

Further, the lattice codes π _{B, k} and π _{M, k} are defined as in the following [Equation 13].

&Quot; (13) &quot;

Here, in Equation 13, v _{B , k} and v _{M , k} are transition vectors, and Λ (Λ) denotes a fundamental Voronoi region of the lattice Λ.

In addition, since Λ _{B, k} , Λ _{M, k} are good covering, Ξ (Λ _{B, k} ) and Ξ (Λ _{M, k} ) have a radius of

and

Is a D-dimensional sphere.

Furthermore, v _{B , k} , v _{M , k} , Λ _{C, k} are selected to satisfy the following equation (14).

&Quot; (14) &quot;

Therefore, the message that the base station wants to send

Messages to be sent by the user and node

Is encoded by x _{B , k} ∈ Π _{B, k} and x _{M , k} ∈ Π _{M, k ,} respectively, by the lattice codes π _{B, k} and π _{M, k} generated as described above.

Here, without loss of generality γ _{M, k} ≤ γ _B, assuming that _k, Λ _{B, k} ⊆ Λ _{M, k} ⊆ Λ _C, Λ satisfying the _{k B, k,} Λ _{M, k,} Λ _{C, k} Since x _{B , k} + x _{M , k} ∈ Λ _{C, k} from the algebraic group nature of the gratings, x _{B , k} + x _{M , k} can be decoded by the lattice decoding process. have.

In addition, the pre-coding performed by the above Equation 6 should be N _B ≥ N _V , in this case, in order to enable the pre-coding according to the present invention even when N _B <N _V , W _ZF in 6] may be expressed as in Equation 15 below.

&Quot; (15) &quot;

Thus, in the case of white Gaussian noise where the mean of additive noise is zero and the variance is N ₀ , the maximum capacity of step 1 that can be achieved in accordance with the present invention using a lattice code as described above is given by Equation 16 below. ]

&Quot; (16) &quot;

Subsequently, in step 2, the symbols of x _{B , k} + x _{M , k} obtained in step 1 are transmitted to the base station and the user terminal node, respectively, where the base station transmits the signals x _{B , k} sent by the base station itself in step 1. Since the k-th user terminal node knows the signal x _{M , k} sent by the k-th terminal node itself in step 1, when it receives x _{B , k} + x _{M , k} from the relay node, the signal sent by it in step 1 You can get the symbol you want by removing.

Subsequently, the processing in step 2 will be described.

If the number of all cases where x _{B , k} + x _{M , k} can take is 2 ^{DRadd , k} , that is, R _{add , k} is the transmission rate of x _{B , k} + x _{M , k} , the step according to the invention For coding of the relay node at 2, the D-dimensional lattice code π _{V, k} is generated as follows.

First, we create a D-dimensional lattice Λ _{V, k} , Λ _{C ' , k} where Λ _{V, k} ⊆ Λ _{C' , k} , where Λ _{V, k} is good for mean-square quantization. error quantization or Poltyrev-good and good for covering or Rogers-good, and Λ _{C ' , k} are lattice with good mean square error quantization.

Further, the volume of Λ _{V, k} is infinitely close to γ _{V, k} , and γ _{V, k} is the average power of the relay node assigned to the k-th user.

In addition, when the average power of the relay node is P _V , and the lattice code π _{V, k} is defined as in Equation 17 below.

&Quot; (17) &quot;

Here, in [Equation 17], v _{V , k} is a transition vector satisfying the following Equation 18, and Ξ (Λ) is a fundamental Voronoi region of the lattice Λ.

&Quot; (18) &quot;

Here, in [Equation 18], vol (·) means a volume.

Therefore, the message that the relay node wants to send

Is encoded as x _{V , k} ∈ Π _{V, k} by the lattice codes π _{V, k} generated as described above.

Subsequently, in the present invention, x _{V, k} encoded by the lattice code as described above is precoded as follows.

First, the translocation QR-decomposes the H _VM as shown in Equation 19 below.

&Quot; (19) &quot;

In Equation 19, L is a lower triangular matrix, and Ω is an orthogonal matrix.

In addition, when n (m) m elements of L are _{n n and m} , if n <m, then l _{n , m} = 0. In the present invention, x _{V , k} is expressed by Equation 20 below. Generate the _precoded codeword x _{PV , k} .

&Quot; (20) &quot;

Here, in [Equation 20], when modeled as an additive white Gaussian noise channel having a mean of 0 and a variance of N ₀ , the constant α _k is given by Equation 21 below.

&Quot; (21) &quot;

Further, β _{V, k} is a random dither having a uniform distribution in the Ξ (Λ _{V, k} ) region, [·] _Λ is a modulo operation on the lattice Λ, and γ _{V, k} Is the average power of the codeword vectors x _{V , k} .

Therefore, x _{PV , k} is uniformly distributed in Ξ (Λ _{V, k} ) due to random dither β _{V, k} , and the matrix X _PV is defined using Equation 22 below using a precoded codeword. .

&Quot; (22) &quot;

Therefore, the transmission signal matrix of the relay node according to the present invention is expressed by Equation 23 below.

&Quot; (23) &quot;

In addition, in the case of the additive noise channel model, the signal y _{M , k} received by the k-th user terminal node in step 2 according to the present invention is expressed by Equation 24 below.

&Quot; (24) &quot;

Here, in Equation 24, z _{M and k} are additive noises.

The input signal of the decoder for the k-th user terminal node from Equation 24 is obtained as shown in Equation 25 below.

&Quot; (25) &quot;

In addition, the following [Equation 26] can be obtained by substituting [Equation 20] and [Equation 24] described above in [Equation 25].

&Quot; (26) &quot;

Here, in [Equation 26], e _k is equal to the following [Equation 27].

&Quot; (27) &quot;

Since the signal x _{M , k} sent by the k-th user in step 1 is known, the k-th user terminal node eventually receives the base station's signals x _{B , k} from the decoder input signals given by Equations 25 and 26. The total number of cases of codebook that must be found to decode

.

Therefore, in the case where the additive noise is a white Gaussian noise having an average of 0 and a variance of N ₀ , the achievement rate is expressed by the following Equation 28 when the minimum mean square error method is decoded.

&Quot; (28) &quot;

In addition, in the case of the additive noise channel model, the signal Y _B received at the base station in step 2 according to the present invention is represented by Equation 29 below.

&Quot; (29) &quot;

Since Z _B in Equation 29 is additive noise, H _VB Ω ^T in Equation 29 is QL-decomposed as shown in Equation 30 below.

&Quot; (30) &quot;

Where [Equation 30]

Is a matrix of N orthogonal column vectors,

Is the lower triangular matrix.

The (n, m) th element of

In terms of Equation 29,

When multiplying by, the received signal y ' _{B , k} at the base station corresponding to the k-th user is expressed by Equation 31 below.

&Quot; (31) &quot;

Here, in Equation 31, z ' _{B and k} are additive noises.

Therefore, in step 2 according to the present invention, the decoder input signal for the base station to decode the signal of the k-th user terminal node is represented by Equation 32 below.

(32)

Here, in [Equation 32],

Is the minimum mean square error coefficient at the base station, and is expressed formally in the case of white Gaussian noise with an average of 0 and a variance of N ₀ , to be.

Therefore, when Equation 32 is arranged using Equation 20 and Equation 31, Equation 33 is as follows.

&Quot; (33) &quot;

Where [Equation 33]

Has the meaning of intersymbol interference.

In addition, in the process of decoding using Equation 32 according to the present invention, it should be noted that the decoding order of x _{PV and k} must be sequentially performed while keeping the order from k = 1 to N.

Because in Equation 32

This is because x _{PV , 1} , ...., x _{PV , k-1} is necessary for the first decoding process.

That is, in the case where the additive noises are all white Gaussian noises having an average of 0 and a variance of N ₀ , the achievement rate for the k-th user of the base station in step 2 according to the present invention is expressed by Equation 34 below.

&Quot; (34) &quot;

Next, the process of optimizing the achievement rate obtained as mentioned above is demonstrated.

In the case where the additive noises are all white Gaussian noises with an average of 0 and a variance of N ₀ , from the above-described equations (16), (28), and (34), multiple users as shown in FIG. The overall achievement rate R _Σ obtained through bidirectional relaying of a multiple input / output cellular communication system is expressed by Equation 35 below.

&Quot; (35) &quot;

Therefore, in the present invention, γ _{B, k} , γ _{M, k} , γ _{V, k} are determined by solving the optimization problem expressed by Equation 36 below to maximize the achievement rate R _Σ .

&Quot; (36) &quot;

here,

to be.

Also, since the problem given in [Equation 36] is not a convex or concave problem, an auxiliary variable

By using Equation 3, it converts into a concave problem as shown in Equation 37 below.

&Quot; (37) &quot;

Subsequently, for Equation 37, the Lagrangian constant defined as follows to use the Lagrangian method.

And

Using the equation, the cost function μ is defined as in Equation 38 below.

&Quot; (38) &quot;

Therefore, from Equation 38, the optimal γ _{B, k} , γ _{M, k} , γ _{V, k} according to the present invention is uniquely determined by the Karush-Kuhn-Tucker condition given in Equation 39 below. .

[Equation 39]

Therefore, as described above, it is possible to implement a method for optimizing the achievement rate of the multi-user multiple input-output bidirectional relay communication system according to the present invention.

That is, referring to FIG. 2, FIG. 2 is a flowchart schematically showing the overall configuration of the method for optimizing the achievement rate of the multi-user multi-input / output bidirectional relay communication system according to the present invention.

More specifically, the method for optimizing the achievement rate of the multi-user multi-input / output bidirectional relay communication system according to the present invention includes one base station node having N _B antenna systems and N _V antenna systems, as shown in FIG. Comprised of a plurality of user terminal nodes having one relay node and one transmitting and receiving antenna, each of the base station and the user terminal transmits a signal to the repeater, the repeater transmits the signal to the base station and the user terminal at once In a multi-user multi-input / output cellular communication system in which a bi-directional relay is performed through a process, first, N user terminal nodes corresponding to a small number of N _B and N _V are selected, and with reference to [Equation 1] As described, the channel matrix from the base station node to the relay node and the user terminal node Each generate a channel matrix of a relay node from (step S21).

Next, as described above with reference to [Equations 2] to [Equation 16], a codeword vector to be transmitted by the user terminal node and the base station is generated through lattice coding (step S22), and the user Generating a codeword vector to be transmitted from the base station node to the k-th user terminal node and a coding matrix representing a codeword vector to be transmitted from the k-th user terminal node to the base station through horizontal encoding of the terminal nodes (step H). S23), generating a transmission signal of the base station node through linear precoding (step S24), generating a transmission signal of the user terminal node (step S25) and a reception signal received at the relay node (step S26), respectively. Decode each codeword from the received signal obtained in step by using horizontal sequential interference cancellation (step S27), and repeat the decoded signal. By encoding via the grid marks from DE transmits to each base station node and a user equipment node (step S28).

Further, each base station node and user terminal node selects and receives only its own signal from the signal encoded by the lattice code as described with reference to Equations 17 to 33 above. Step S29).

In this case, as described with reference to Equations 34 to 38, the base station, the repeater, and the user terminal are optimized by optimizing the achievement rate of the entire communication system so that the achievement rate in the bidirectional transmission process is maximized. Bi-directional relay communication between them is made more efficient.

Therefore, as described above, it is possible to implement a method for optimizing the achievement rate of the multi-user multiple input-output bidirectional relay communication system according to the present invention.

In addition, according to the present invention, by implementing a method for optimizing the achievement rate of the multi-user multi-input I / O bidirectional relay communication system according to the present invention, one base station and one relay node having a plurality of transmit and receive antenna systems, and The communication capacity of a multi-user multi-input / output cellular communication system composed of a plurality of communication terminal nodes having one transmit / receive antenna can be effectively improved.

In addition, according to the present invention, by providing a method for optimizing the achievement rate of the multi-user multi-input I / O bidirectional relay communication system as described above, to solve the problem of the conventional communication system that had to continue to expand the communication facilities to increase the communication capacity Therefore, the cost of equipment investment can be reduced.

As described above, the details of the method for optimizing the achievement rate of the multi-user multi-input / output bidirectional relay communication system according to the present invention have been described through the embodiments of the present invention as described above, but the present invention is limited only to the contents described in the above embodiments. Therefore, it is a matter of course that the present invention can be variously modified, changed, combined and replaced by those skilled in the art according to the design needs and various other factors. would.

Claims (20)

It consists of one base station node having N _B antenna systems, one relay node having N _V antenna systems, and a plurality of user terminal nodes having one transmit / receive antenna. A communication capacity of a multi-user multi-input / output cellular communication system by optimizing the achievement rate in a multi-user multi-input / output cellular communication system in which a bidirectional relay is performed by transmitting a signal and transmitting the signals to the base station and the user terminal at the repeater. In the achievement rate optimization method of a multi-user multi-input bi-directional relay communication system to increase the
Selecting N user terminal nodes corresponding to a smaller number of N _B and N _V ;
Generating a channel matrix from the base station node to the relay node and a channel matrix from the user terminal node to the relay node;
A grid encoding step of generating a codeword vector to be transmitted from the user terminal node and the base station through grid coding;
An encoding matrix indicating a codeword vector to be transmitted from the base station node to a k-th user terminal node and a codeword vector to be transmitted from the k-th user terminal node to the base station node through horizontal encoding of the user terminal nodes. A coding matrix generating step of generating each;
A base station transmission signal generation step of generating a transmission signal of the base station node through linear precoding;
A user terminal transmission signal generation step of generating a transmission signal of the user terminal node;
A reception signal generation step of generating a reception signal received at the relay node based on each of the transmission signals obtained in the base station transmission signal generation step and the user terminal transmission signal generation step;
A decoding step of decoding each codeword from the received signal obtained in the received signal generating step by using a horizontal sequential interference cancellation method;
A trellis encoding transmission step of encoding the signal obtained in the decoding step through a trellis code at the repeater node and transmitting it to each of the base station node and the user terminal node;
A grid encoding reception step of decoding a signal of the base station node and the user terminal node using a grid code; And
A method for optimizing the achievement rate of a multi-user multi-input I / O bidirectional relay communication system, comprising: an achievement rate optimization step of optimizing the achievement rate of the entire communication system so that the achievement rate obtained through the two-way relay is maximized.
The method of claim 1,
The channel matrix generation step,
A channel matrix from the base station node to the relay node is defined as a matrix H _BV having a size of N _V × N _B ,
When the channel vector of size N _v × 1 from the selected kth terminal node to the relay node is h _{MV , k} , the channel matrix H _MV from the terminal node to the relay node is defined by the following equation. Achievement optimization method of a multi-user multi-input bi-directional relay communication system characterized in that the.

3. The method of claim 2,
The grid coding step,
When the code rates of x _{B, k} and x _{M, k} are R _{B, k} and R _{M, k ,} respectively, a D-dimensional lattice Λ _{B, k} , Λ _{M, k} , Λ _{C, k} is generated. A method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system, characterized by generating lattice codes π _{B, k} and π _{M, k} by the following equation.

Where Λ _{B, k} , Λ _{M, k} are all good for mean-square-error quantization or Poltyrev-good, good for covering or Rogers-good, and Λ _{C, k} is a lattice with good mean squared quantization, v _{B, k} and v _{M , k} are transition vectors, Ξ (Λ) represents the fundamental Voronoi region of lattice Λ)
The method of claim 3,
The grid coding step,
Wherein v _{B, k} , v _{M, k} and Λ _{C, k} are selected to satisfy the following equation,

The signal to be sent by the base station node and the signal to be sent by the user terminal node are x _{B, k} ∈ Π _{B, k} and x _{M, k} ∈ Π by the grid codes π _{B, k} and Π _{M, k} , respectively. _A method for optimizing the achievement rate of a multi-user multi-input bi-directional relay communication system, characterized in that is encoded to _{M, k} .
5. The method of claim 4,
The coding matrix generation step,
When the code length or block length is D, a 1 × D codeword vector to be transmitted from the base station node to a k-th user terminal node is referred to as x _{B , k} , and the base station node at a k-th user terminal node. When a codeword vector of size 1 × D to be transmitted as x _{M , k} is configured to define matrices X _B and X _M horizontally stacking the x _{B , k} and x _{M , k} by the following equation: Achievement optimization method of a multi-user multi-input bi-directional relay communication system characterized in that the.

6. The method of claim 5,
The base station transmission signal generation step,
Pseudo inverse operations

In this case, the transmission signal matrix S _B to be transmitted by the base station node is

Respectively,
A method for optimizing the achievement rate of a multi-user multi-input bi-directional relay communication system, characterized in that for generating the transmission signal matrix S _B by the following equation.

The method according to claim 6,
The user terminal transmission signal generation step,
A method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system, characterized in that it is configured to generate a transmission signal at each user terminal node based on the following equation.

8. The method of claim 7,
The transmitting signal generating step,
Achievement rate of the multi-user multi-input / output bidirectional relay communication system _, wherein the average powers γ _{B, k} and γ _{M, k} of the x _{B , k} and x _{M , k} are selected to satisfy the following conditions. Optimization method.

(Where P _B and P _{M , k} are the maximum transmit powers of the base station and k-th user, and w _{ZF , k} is the k-th column of W _ZF .)
The method of claim 8,
The receiving signal generating step,
Based on the following equation, the signal Y _V received by the relay node with respect to the transmission signal matrix S _B generated in the base station transmission signal generation step and the transmission signal matrix S _M generated in the user terminal transmission signal generation step is determined. A method for optimizing achievement of multi-user multi-input bi-directional relay communication system, characterized in that it is configured to generate.

Where Z _V is additive noise
10. The method of claim 9,
The decoding step,
QR decomposition of the channel matrix H _MV of the received signal generated in the received signal generation step into an orthogonal matrix Q and an upper-triangular matrix U by the following equation,

The received signal Y _V obtained in the received signal generating step is multiplied by Q ^T by the following equation.

/ RTI &gt;

(here,

to be)

When x _{B , k} + x _{M , k} is decoded with respect to n + 1 ≦ _k ≦ N, the following equation is used as an input to the decoder _, so that it is configured to decode x _{B , n} + x _{M , n} . Achievement optimization method of multi-user multi-input bi-directional relay communication system.

(Where u _{i , j} are the (i, j) th elements of U)
The method of claim 10,
The grid coding transmission step,
D-dimensional lattice Λ _{V, k} , Λ _{C ' , k} of Λ _{V, k} ⊆ Λ _{C' , k} is generated, and lattice code Π _{V, k} is generated using the following equation,

Where Λ _{V, k} is good for mean-square-error quantization or Poltyrev-good and good for covering or Rogers-good, and Λ _{C ' , k} is mean square error Is a good quantization grid)

Where v _{V , k} is a transition vector satisfying the following equation,

(Where Ξ (Λ) is the fundamental Voronoi region of lattice Λ and vol (·) means volume)

A method for optimizing the achievement rate of the multi-user multi-input / output bidirectional relay communication system _, characterized in that the signal to be sent from the relay node by the grid code π _{V, k} is encoded as x _{V , k} ∈ Π _{V, k} .
12. The method of claim 11,
The grid coding transmission step,
When a channel vector having a size of 1 × N _v from the relay node to the k-th terminal node selected is h _{VM , k} , a channel matrix H _VM is generated by the following equation,

QR decomposition of the H _VM by the following equation,

(Wherein, L is a lower triangular matrix and, wherein the (n, m) th element of L l _n, when referred to as _m, n <m is l _{n, m} = _0, Ω is an orthogonal matrix)

A method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system, characterized by generating the codeword x _{PV , k} pre-coded from the lattice coded x _{V , k} by the following equation.

(Where α _k is a constant, β _{V, k} is a random dither with a uniform distribution in the region Ξ (Λ _{V, k} ), [·] _Λ is a modulo operation on the lattice Λ )
13. The method of claim 12,
The grid coding transmission step,
When the model is modeled as an additive white Gaussian noise channel with an average of 0 and a variance of N ₀ , the α _k is configured to be defined by the following equation. Optimization method.

Where γ _{V, k} is the average power of x _{V , k}
14. The method of claim 13,
The grid coding transmission step,
A matrix X _PV is generated by the following equation using the _precoded codeword x _{PV , k} ,

A method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system, characterized by generating the transmission signal matrix of the relay node according to the following equation.

15. The method of claim 14,
The grid encoding receiving step,
In the case of an additive noise channel model, a signal y _{M , k} received by a k-th user terminal node is generated with respect to a signal transmitted by the relay node by the following equation,

Where z _{M and k} are additive noise

A method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system, characterized by generating the input signal of the decoder for the k-th user terminal node by the following equation.

16. The method of claim 15,
The grid encoding receiving step,
In the case of an additive noise channel model, a signal Y _B received at the base station node is generated by the following equation,

Where z _B is additive noise

QL-decomposes H _VB Ω ^T in Y _B by the following equation,

(here,

Is a matrix of N orthogonal column vectors,

Is the lower triangular matrix)

The (n, m) th element of

In this case, the received signal y ' _{B , k} corresponding to the k th user terminal node in the base station node is generated by the following equation,

(Where z ' _{B , k} is additive noise)

The base station node generates a decoder input signal for decoding the signal of the k-th user terminal node by the following equation,

(here,

Is a constant representing the minimum mean square error coefficient at the base station node)

A decoding rate optimization method of the multi-user multi-input bi-directional relay communication system, characterized in that the decoding order of x _{PV , k} proceeds in order from k = 1 to N.
17. The method of claim 16,
The grid encoding receiving step,
In the case of white Gaussian noise where the additive noise is 0 in average and the variance is N ₀ , the

A method for optimizing the achievement rate of a multi-user multi-input / output bidirectional relay communication system characterized by the following equation.

18. The method of claim 17,
The achievement rate optimization step,
In the case where the additive noises are all white Gaussian noises with an average of 0 and a variance of N ₀ , the system-wide achievement rate R _Σ obtained through bidirectional relaying is represented by the following equation,

In order to maximize the above achievement rate R _Σ , the multi-user multi-input I / O relay is configured to determine γ _{B, k} , γ _{M, k} , γ _{V, k} from the optimization problem represented by the following equation. Method of optimizing achievement rate of communication system.

(here,

to be)
19. The method of claim 18,
The achievement rate optimization step,
Converting the optimization problem into a concave problem by the following equation,

(here,

Is an auxiliary variable)

The cost function μ is generated by the following equation,

(here,

Is the Lagrangian constant)

Achievement rate of multi-user multi-input bi-directional relay communication system characterized in that the optimum γ _{B, k} , γ _{M, k} , γ _{V, k} is uniquely determined from the Karush-Kuhn-Tucker condition by the following equation Optimization method.

It consists of one base station node having N _B antenna systems, one relay node having N _V antenna systems, and a plurality of user terminal nodes having one transmit / receive antenna. In order to increase the communication capacity of a multi-user multi-input / output cellular communication system in which a two-way relay is performed by transmitting a signal and transmitting a signal to the base station and the user terminal at a time in the repeater. A communication system configured to perform communication using the achievement rate optimization method of the multi-user multiple input-output bidirectional relay communication system according to any one of claims.

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