KR20180029624A - Apparatus and method for random unitary beamforming in multei-user mimo - Google Patents

Abstract

The present invention relates to a method for random unitary beamforming based on a multi-user multiple input multiple output (MIMO) type, which comprises: a step of transmitting a pilot signal to a plurality of candidate user terminals that require data transmission within coverage; a step of receiving feedback on partial channel information corresponding to the pilot signal by candidate user terminal; a step of selecting at least one user terminal based on the partial channel information by candidate user terminal; a step of calculating an optimal solution of an energy efficiency function that optimizes the number of streams and the value of transmission power respectively based on the partial channel information of the selected user terminals; and a step of transmitting streams to the selected user terminals by applying the number of streams and the value of transmission power according to the calculated optimal solution. In addition, the partial channel information includes the index of beamforming, the size of the received signal, and the size of interference selected based on the pilot signal while the size of the received signal and the size of interference by user terminal are calculated based on a signal-to-interference-plus-noise ratio (SINR) by using the pilot signal. Therefore, a device and the method for random unitary beamforming can optimize energy efficiency when performing random unitary beamforming based on a multi-user MIMO type.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a random unit beamforming apparatus and method in a multi-user multi-

The present invention relates to a random unitary beamforming apparatus and method for transmitting signals to multiple users through MIMO Broadcast Channels in a wireless communication system.

Multi-user MIMO (Multi-User MIMO) is a type of multi-input multiple output (MIMO) technology that allows multiple users to share desired data in the same resource This is a communication technique that enables high data rate to be achieved by making it possible to transmit and receive data.

In a multi-user multi-input / multi-output wireless communication system, when there is no cooperation among users in a cell, inter-user interference greatly increases, resulting in a problem that the quality of a received signal of each user is greatly reduced. To solve this problem, the base station (or access point, etc.) multiplies the downlink signal by the beamforming vector in the direction of minimizing interference between users in the baseband and maximizing the received signal-to-noise ratio (SNR) A digital beamforming technique for transmitting a signal is applied.

Most conventional beamforming techniques (e.g., zeroforcing beamforming and DPC-BF (Dirty-Paper Coding-Beamforming), etc.) receive channel information from each user at the base station, Channel State Information, full CSI).

However, these conventional beamforming schemes are not suitable for massive MIMO systems using a large number of antennas or in a situation where a large number of users exist in a cell (i.e., coverage) a problem such as delay has occurred.

As a solution to this problem, a random unitary beamforming technique has been developed. Random unitary beamforming technique can feed back partial channel information (partial CSI) not only to all channel information but partial CSI for each user differently from other beamforming techniques, thereby reducing feedback amount and achieving high data transmission rate at the same time.

In this regard, Korean Unexamined Patent Publication No. 10-2011-0077157 (entitled " unit precoding apparatus and method in a multi-user multi-antenna system ") is used in a multi-user multi- A technique for generating a unitary matrix for improving transmission capacity while eliminating interference signals and using the generated unitary matrix for precoding is disclosed.

Meanwhile, in a wireless communication system using a multi-input / output antenna technology, energy efficiency is an important performance evaluation index in addition to spectral efficiency. Random unitary beamforming systems also require scheduling and power allocation techniques that can significantly increase this energy efficiency.

An embodiment of the present invention provides a random unitary beamforming apparatus and method that can optimize energy efficiency in a random unitary beamforming based on multi-user multi-input / output.

It should be understood, however, that the technical scope of the present invention is not limited to the above-described technical problems, and other technical problems may exist.

According to an aspect of the present invention, there is provided a random unitary beamforming apparatus based on a multi-user multi-input / output (I / O) A communication module for transmitting and receiving signals to and from at least one of the plurality of user terminals via the antenna; An energy efficiency optimization program for downlink data transmission; And

And a processor for executing a program stored in the memory, wherein the processor transmits a pilot signal to a plurality of candidate user terminals requesting reception of a signal in response to execution of the program and includes partial channel information as a response thereto To select at least one user terminal based on the feedback partial channel information, and to optimize energy efficiency < RTI ID = 0.0 > And transmits the stream to the selected user terminals by applying the stream number and transmission power according to the calculated optimal solution. Herein, the partial channel information includes an index of a beamforming vector selected based on the pilot signal, a received signal magnitude, and an interference signal magnitude, and the received signal magnitude and the interference signal magnitude for each user terminal are determined using the pilot signal And is calculated based on the signal-to-interference and noise ratio (SINR).

According to another aspect of the present invention, there is provided a random unitary beamforming method based on multiuser multi input / output, comprising: transmitting a pilot signal to a plurality of candidate user terminals requesting data transmission within a coverage; Receiving partial channel information corresponding to the pilot signal for each candidate user terminal; Selecting at least one user terminal based on the partial channel information for each of the candidate user terminals and calculating an optimal solution of an energy efficiency function for optimizing values of the number of streams and transmission power based on the partial channel information of the selected user terminals ; And transmitting a stream to the selected user terminals by applying a stream number and a transmission power according to the calculated optimal solution. In this case, the partial channel information includes a beamforming index selected based on the pilot signal, a received signal magnitude, and a magnitude of interference, and the magnitude and interference magnitude of the received signal for each user terminal are determined using the pilot signal Signal-to-interference and noise ratio (SINR).

According to any one of the above-described objects of the present invention, an optimal number of streams and a transmission power can be set based on partial CSI fed back to multiple users in a MIMO broadcast channel situation, Can be adaptively determined according to the change of the number of users and the number of users capable of receiving signals, thereby improving energy efficiency.

According to any one of the tasks of the present invention, it is possible to adaptively change the number of streams, the number of antennas, and the amount of transmission power having the optimum energy efficiency in an environment where the number of users in a cell is flexible, It is possible to design the number of antennas and transmission power with optimal energy efficiency.

FIG. 1 is a configuration diagram of a random unitary beam forming system to which an embodiment of the present invention is applied.
2 is a configuration diagram of a random unitary beam forming apparatus according to an embodiment of the present invention.
3 is a flowchart illustrating a random unitary beam forming method according to an embodiment of the present invention.
FIG. 4 is a graph illustrating an effect of random unitary beamforming in which energy efficiency is optimized according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . Also, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

Herein, the term " part " or " module " means a unit realized by hardware or software, a unit realized by using both, and a unit realized by using two or more hardware Or two or more units may be realized by one hardware.

FIG. 1 is a configuration diagram of a wireless communication system to which an embodiment of the present invention is applied, and FIG. 2 is a configuration diagram of a random unitary beam forming apparatus according to an embodiment of the present invention.

A random unitary beamforming apparatus 100 according to an embodiment of the present invention shown in FIG. 1 provides a multiple input / output broadcast channel to a plurality of user terminals 200 on a wireless communication system 10. That is, the random unit beamforming apparatus 100 is a device for wirelessly communicating with a plurality of user terminals 200 in a wireless communication system 10, and transmitting a downlink signal by applying a multi-user MIMO scheme. The random unitary beamforming apparatus 100 may be a communication equipment such as a base station or an access point.

Hereinafter, for the sake of convenience, the random unit beamforming apparatus 100 is referred to as a 'base station', and each user terminal 200 is referred to as a 'user'.

The base station 100 transmits a stream through M antennas and transmits a downlink signal to a plurality of users 200 requesting transmission of a signal in a MIMO broadcast channel condition.

At this time, the base station 100 receives channel state information for each of a plurality of users 200, and optimizes the number of streams to be transmitted and the total transmission power based on the feedback result. Then, the base station 100 processes the downlink scheduling for the selected users 200 based on the optimized conditions, precodes the selected beamforming vector for each user 200, and transmits the signal.

User terminals 200 are devices that are in wireless communication with base station 100, respectively, and include one or more antennas and communication modules. In an embodiment of the present invention, it is assumed that one user terminal 200 has one antenna (that is, one stream is received one by one). However, in the wireless communication system 10 to which the embodiment of the present invention is applied, there may be a plurality of antennas provided for each user terminal 200, and accordingly, two or more downlink streams are allocated to one user terminal 200 . At this time, in solving the energy efficiency optimization problem of the base station 100, which will be described below, it is also possible to recognize and process the plurality of antennas of one user terminal 200 as user terminals 200 one by one.

2, the base station 100 includes a multi-input / output antenna 110, a communication module 120, a memory 130, and a processor 140. The multi-

The base station 100 has M antennas 110, and in FIG. 2, four or less streams can be transmitted through four antennas 110 as an example.

The communication module 120 transmits and receives data signals to and from a plurality of users 200 in a set communication format. At this time, the communication module 120 transmits a downlink signal through at least one of the M antennas 110 under the control of the processor 140.

The memory 130 stores an energy efficiency optimization program for downlink data transmission. At this time, the energy efficiency optimization program stored in the memory 130 includes a program for adaptively changing and setting the number of streams and the total transmission power that are optimized at the time of transmission of the downlink signal, and a program for optimizing the downlink signal And programs for scheduling and sending are stored in a single or a plurality of programs operating in conjunction with each other.

For reference, the memory 130 is collectively referred to as a non-volatile storage device that keeps stored information even when no power is supplied, and a volatile storage device that requires power to maintain stored information.

The processor 140 executes a program stored in the memory 130 and performs processes according to the program.

Hereinafter, with reference to FIG. 3, a process of a processor 140 of a random unitary beamforming apparatus 100 according to an exemplary embodiment of the present invention will be described in detail with respect to a process of processing energy-efficient downlink signal transmission.

3 is a flowchart illustrating a random unitary beam forming method according to an embodiment of the present invention.

First, a plurality of users (hereinafter referred to as "candidate users") 200 requesting signal transmission within the coverage (that is, the cell or wireless communication coverage) of the base station (or access point) 100 are detected (S301 ).

Next, based on the detected number of candidate users (hereinafter referred to as "K"), the number of streams (hereinafter referred to as " N ") and the amount of transmitted power Is calculated (S302).

Then, a random unitary matrix of N * N is generated based on the calculated number of streams (S303).

The N * N random unitary matrix is transmitted for each user and is shared with each user in advance.

Next, pilot signals are transmitted to the candidate users 200 (S304), and partial channel state information (hereinafter referred to as "partial channel state information") is fed back from each of the candidate users 200 (S305).

For reference, the partial channel status information refers to a predetermined type of channel status information among all kinds of channel status information set in advance for measuring the downlink channel status. In one embodiment of the present invention, as partial channel state information, a beamforming index, which is information of any one of the column vectors of a unitary matrix to be used by a user (i.e., a beamforming vector), and a signal to interference and noise ratio interference and noise ratio (SINR), and the magnitude of the interference according to another user's received signal.

The partial channel status information will be described in more detail.

First, it is assumed that each of the K users has a single antenna, and one stream is allocated to one user. The base station 100 includes M antennas 110 and a transmission signal of the base station 100 in a random unitary beamforming system in which a total of N streams are transmitted can be defined as Equation (1). At this time, the number N of streams is equal to or less than the number M of antennas.

&Quot; (1) "

의 전력 제한을 갖는다.At this time, s _j And f _j are data symbols and beamforming vectors assigned to the jth selected user (i.e., stream), respectively. This transmission signal

Lt; / RTI >

The signal received by the i-th user (i.e., the received signal y _i ) is expressed by the following equation (2).

&Quot; (2) "

는 i번째 사용자가 받아야 할 신호이며,

는 다른 사용자에게 보낸 신호가 i번째 사용자에게 미치는 간섭이다.At this time, a Rayleigh fading channel vector with h _i = [h _i1 , h _i2 , ..., h _iN ] is modeled, and n _i is a white color having N ₀ as a spectral density Gaussian noise. And

Is the signal to be received by the i-th user,

Is the interference of the signal sent to the other user to the i-th user.

The processor 140 of the base station 100 uses a user-specific signal-to-interference-and-noise ratio (SINR) for user selection and scheduling.

)은 다음의 수학식 3과 같이 표현된다.The SINR of the i-th user (i.e.,

) Is expressed by the following equation (3).

&Quot; (3) "

는 신호대잡음비(SNR)로서

로 정의되고,

는 i번째 사용자가 수신할 신호의 크기로서

로 정의되고,

는 i번째 사용자에게 미치는 간섭신호의 크기로서

로 정의된다. 그리고, W는 시스템의 대역폭이다.At this time,

(SNR) as a signal-to-noise ratio

Lt; / RTI >

Is the size of the signal to be received by the i-th user

Lt; / RTI >

Is the magnitude of the interference signal to the i-th user

. And W is the bandwidth of the system.

및

가 위와 같이 계산될 수 있다.That is, among the information that the user 200 feeds back to the base station 100

And

Can be calculated as above.

의 컬럼 벡터 중 하나를 선택한다. 이때, 유니터리 행렬에서 컬럼 벡터를 선택하는 기준은 다음의 수학식 4와 같이 나타낼 수 있다.Next, the user 200 selects, as a beam forming vector f _i to be used for receiving a downlink signal, a randomly generated unitary matrix

One of the column vectors of FIG. In this case, the criterion for selecting the column vector in the unitary matrix can be expressed by Equation (4).

&Quot; (4) "

및

값을 기지국(100)에 피드백한다.The i-th user 200 receives the pilot symbol from the base station 100 and then transmits the index of the beamforming vector having the highest SINR to the i-

And

Value to the base station 100.

및

)에 기초하여, 총 N개의 사용자(즉, 전송할 스트림의 개수)를 선택한다(S306).3, the information fed back from all user candidates (i.e., the index of the beamforming vector,

And

), A total of N users (i.e., the number of streams to be transmitted) is selected (S306).

At this time, the processor 140 of the base station 100 allocates a beamforming vector corresponding to each user based on the beamforming index included in the fed back partial channel information.

Next, in step S307, a transmission condition for maximizing energy efficiency is determined based on the feedback partial channel information of each of the N users 200 selected in step S306.

The process of calculating and determining the transmission conditions that maximize the energy efficiency (i.e., the optimal number of streams and the transmission power) is as follows.

The target performance in the random unitary beamforming system, that is, the achievable data rate is expressed by Equation (5).

Equation (5)

Based on the statistical characteristics, the ergodic sum capacity, which means the average data rate of the random unitary beam forming system, is calculated by Equation (6).

&Quot; (6) "

의 확률밀도함수(probability density function, pdf)인

는 다음의 수학식 7과 같이 유도될 수 있다.In Equation (6)

Of the probability density function (pdf)

Can be derived as shown in Equation (7) below.

&Quot; (7) "

은 "에르고딕 합 커패시티/전력 소모량"으로 정의되며, 다음의 수학식 8과 같이 스트림 개수인 N, 전송 전력량인 P, 사용자의 수인 K의 함수로 표현될 수 있다.This means that the energy efficiency of the random unitary beam forming system

Is defined as "Ergothic sum capacity / power consumption ", and can be expressed as a function of N as a stream number, P as a transmission power amount, and K as a number of users as shown in Equation (8).

&Quot; (8) "

이며

는 기지국(100)의 송신기(미도시)의 전력 증폭 효율(power amplifier efficiency)이다. 그리고 회로 사용 전력은 기지국(100)의 신호 전송 시 각 회로에서 소모되는 전력이며, 고정 전력은 기지국(100)의 시스템 쿨링 및 제어 신호 전송 등에 사용되는 고정된 전력을 의미한다. 즉, 상기 수학식 8의 상수값인 C₁, C₂, C₃는 기지국(100)(즉, 랜덤 유니터리 빔포밍 장치)의 성능에 따라 변경되는 값들이다. 또한, 수학식 8에서 분자에 포함된 K 값은 셀 크기 또는 장치의 송신 반경 등에 의해 결정되며, 별도로 제어할 수 없다. 따라서, 랜덤 유니터리 빔포밍 시스템의 에너지 효율성은 N과 P의 함수에 의해 정해지게 되며, 이 두 변수에 의한 최적화 문제(two-variable optimization problem)를 해결함으로써 에너지 효율성을 최대화할 수 있다.The power consumption model of the denominator in Equation (8) is expressed as a linear combination of P, which is the transmission power, N, the number of streams, and a constant (i.e., C) . For reference, the power consumption model may be composed of a sum of data transmission power, circuit use power, and static power. At this time, the data transmission power is

And

Is the power amplifier efficiency of the transmitter (not shown) of the base station 100. The circuit power is power consumed in each circuit at the time of signal transmission of the base station 100, and the fixed power is a fixed power used for system cooling and control signal transmission of the base station 100. That is, the constants C ₁ , C ₂ , and C ₃ in Equation (8) are values that change according to the performance of the base station 100 (i.e., a random unit beamforming apparatus). In Equation (8), the K value included in the numerator is determined by the cell size or the transmission radius of the apparatus, and can not be separately controlled. Therefore, the energy efficiency of the random unit beamforming system is determined by the function of N and P, and energy efficiency can be maximized by solving the two-variable optimization problem.

는 다음의 수학식 9과 같이 정의될 수 있다다.By statistical characteristics of the random unitary beam forming system, the average energy efficiency

Can be defined as the following equation (9).

를 나타냈다.The following equation (9) is used to calculate the optimized N and P

Respectively.

&Quot; (9) "

In order to optimize both variables N and P in Equation (9), a process of fixing one variable and solving the optimization problem for the other is performed for each of the two variables.

First, if the transmission power P is fixed and an optimization problem is set for the number of streams N, this problem becomes a quasi-concave problem, so that it is possible to calculate the following equation (10) simply.

&Quot; (10) "

Similarly, if the number of streams N is fixed and an optimization problem with respect to the electric power P is set, this is also a quasi-convex problem, so that it can be calculated as shown in the following expression (11).

Equation (11)

As described above, since the solutions of the respective optimization problems affect each other, the joint optimization problem for the two variables is solved by repeating the equations (10) and (11).

을 구하고, 구한

값을 수학식 10에 대입하여

을 구한다. 이에 따라 업데이트된

값을 다시 수학식 11에 대입하여

을 구하는 방식으로 계산을 반복한다. 이러한 반복 계산을 통해 정수인

값에 대해 수렴의 특성을 적용하여,

값 이 변화없이 고정될 때 수렴이 선언되어 그 값이 확정된다.That is, when an appropriate initial value N = 1, using Equation 11

, And

The value is substituted into Equation 10

. As a result,

The value is substituted into the equation 11 again

The calculation is repeated. These iterations are

By applying the property of convergence to the value,

When the value is fixed without change, convergence is declared and its value is fixed.

In order to solve the joint optimization problem as described above, the processor 140 may perform the processing shown in Table 1 below.

개의 선택된 사용자(200)들(즉, 최적화된 스트림 개수)에 기설정된 빔포밍 벡터를 곱한 신호(즉, 다운링크 신호)를 전송 전력

로 전송한다(S308).Then, by applying the stream number and transmission power according to the optimal solution,

(I.e., the downlink signal) obtained by multiplying the selected users 200 (i.e., the number of optimized streams) by a predetermined beamforming vector is multiplied by the transmit power

(S308).

That is, the processor 140 processes the scheduling for the set N streams, applies a beamforming vector allocated to each user to each stream, and transmits the beamforming vector with the set transmission power.

At this time, the processor 140 may randomly select N antennas and perform beamforming when the number of selected N streams is smaller than the number M of antennas 110. [

For reference, when the number of candidate users (i.e., K) is not changed after the initial downlink transmission, the processor 140 omits the above-described steps S301 to S303, ) To (S308) can be repeatedly performed.

In addition, when the number of candidate users K is greatly changed (for example, when at least one of the change time range and the change amount exceeds the respective threshold values), the processor 140 determines whether or not the process from the step S301 Can be reprocessed.

은 채널의 변화에 따라 큰 변화가 없으나 실수인

는 채널의 통계적 특징에서 약간의 오차를 가질 수 있다. 따라서, 프로세서(140)는 즉각적인 (instantaneous) 피드백 정보인

와

에 기반하여 적응적인 전력 제어(adaptive power control)를 처리한다.Meanwhile,

There is no big change according to the channel change,

May have some errors in the statistical characteristics of the channel. Thus, the processor 140 may generate instantaneous feedback information < RTI ID = 0.0 >

Wow

To handle adaptive power control.

를 아래의 수학식 12와 같이 정의할 수 있다.Specifically, based on the feedback information,

Can be defined as Equation (12) below.

&Quot; (12) "

라 하며, 이는 수학식 12를 이용한 언덕오르기(hill-climbing) 알고리즘을 적용하여 구할 수 있다. 이때, 초기값은 채널의 통계적 특징을 이용해 계산한 수학식 11의 값을 사용한다.Instantaneous channel information provides more finely controlled power

, Which can be obtained by applying a hill-climbing algorithm using Equation (12). At this time, the initial value uses the value of Equation 11 calculated using the statistical characteristic of the channel.

For the adaptive power control as described above, the processor 140 can perform the processing shown in Table 2 below.

에 대해 새롭게 피드백된 부분 채널 정보를 적용하여

를 산출하고, 선택된 사용자(200)들에 산출된

를 적용하여 스트림을 송출할 수 있다.That is, the transmission power of the calculated optimal solution

The newly fed-back partial channel information is applied

Calculated for the selected users 200,

To transmit the stream.

FIG. 4 is a graph illustrating an effect of random unitary beamforming in which energy efficiency is optimized according to an embodiment of the present invention.

Referring to FIG. 4, as compared with the case of scheduling the maximum power amount and the maximum number of streams in the conventional random unit beamforming, the optimized stream number and transmission power amount according to the embodiment of the present invention are adaptively applied, Energy efficiency is greatly increased.

The energy efficiency-enhanced random unit beamforming apparatus and its energy efficiency method according to an embodiment of the present invention may be implemented in the form of a recording medium including instructions executable by a computer such as a program module executed by a computer Can be implemented. Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, the computer-readable medium may include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Communication media typically includes any information delivery media, including computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, or other transport mechanism.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

10: Random Unitary Beam Forming System
100: Random unitary beam forming apparatus
200: user terminal
110: antenna
120: Communication module
130: memory
140: Processor

Claims (10)

In a random unitary beamforming apparatus based on multiuser multi input / output,
A plurality of antennas;
A communication module for transmitting and receiving signals to and from at least one of the plurality of user terminals via the antenna;
An energy efficiency optimization program for downlink data transmission; And
And a processor for executing a program stored in the memory,
Wherein the processor is responsive to execution of the program to transmit a pilot signal to a plurality of candidate user terminals requesting signal reception and receive feedback including partial channel information as a response thereto, Based on partial channel information of the selected user terminals, an optimal solution of an energy efficiency function that optimizes values of stream number and transmission power, respectively, based on the partial channel information of the selected user terminals, Stream number and transmission power to transmit the stream to the selected user terminals,
Wherein the partial channel information includes an index of a beamforming vector selected based on the pilot signal, a received signal magnitude, and an interference signal magnitude,
Wherein the reception signal magnitude and the interference signal magnitude for each user terminal are calculated based on a signal-to-interference and noise ratio (SINR) using the pilot signal.
The method according to claim 1,
The processor comprising:
Calculating an optimum number of streams and a transmission power by obtaining an optimal solution of a function obtained by dividing an average data rate by the total power consumption,
Wherein the average data rate is an ergodic sum capacity with parameters as the number of streams, the transmission power and the number of candidate user terminals,
Wherein the total power consumption is calculated based on a sum of data transmission power, circuit use power, and fixed power.
3. The method of claim 2,
The processor comprising:
Calculating a number of streams and a transmission power such that a value of a function obtained by dividing the average data rate by the total power consumption is maximized as an optimal solution,
In the above function, a solution of the transmission power variable is obtained by assuming an initial value of a stream number variable and a transmission power variable of 1, and then a solution of the stream number variable is obtained by applying the solution of the transmission power variable And repeats the process of obtaining the solution of the transmission power variable by applying a solution of the obtained number of streams to the stream number variable solution until the stream number variable solution converges to a fixed value.
3. The method of claim 2,
The processor comprising:
And performs adaptive power control by applying newly fed-back partial channel information to the transmission power among the calculated optimal solutions.
The method according to claim 1,
The processor comprising:
Detecting the plurality of candidate user terminals requesting data transmission in coverage,
Calculating a number of streams and transmission power based on the number of the candidate user terminals,
Generating a random unitary matrix based on the number of streams and providing the random unitary matrix to the plurality of candidate user terminals,
And receives any one of the column vector vectors of the random unitary matrix from the plurality of candidate user terminals as an index of the beamforming vector.
A method for random unitary beamforming based on multiuser multi input / output through a random unitary beamforming apparatus.
Transmitting a pilot signal to a plurality of candidate user terminals requesting data transmission within a coverage;
Receiving partial channel information corresponding to the pilot signal for each candidate user terminal;
Selecting at least one user terminal based on the partial channel information for each of the candidate user terminals and calculating an optimal solution of an energy efficiency function for optimizing values of the number of streams and transmission power based on the partial channel information of the selected user terminals ; And
And transmitting a stream to the selected user terminals by applying a stream number and a transmission power according to the calculated optimal solution,
Wherein the partial channel information comprises:
A beamforming index selected based on the pilot signal, a received signal magnitude, and a magnitude of interference,
Wherein a magnitude of a received signal and a magnitude of interference of each user terminal are calculated based on a signal-to-interference and noise ratio (SINR) using the pilot signal.
The method according to claim 6,
The energy efficiency function is a function that divides the average data rate by the total power consumption,
Wherein the average data rate is an ergodic sum capacity with parameters as the number of streams, the transmission power and the number of candidate user terminals,
Wherein the total power consumption is calculated based on a sum of data transmission power, circuit use power, and fixed power.
8. The method of claim 7,
Wherein the step of calculating the optimal solution of the energy efficiency function comprises:
Calculating a number of streams and a transmission power such that a value of a function obtained by dividing the average data rate by the total power consumption is maximized as an optimal solution,
(a) obtaining a solution of the transmission power parameter by assuming an initial value of a stream number variable of a stream number variable and a transmission power parameter in the energy efficiency function;
(b) obtaining a solution of the stream number variable by applying a solution of the obtained transmission power variable; And
(c) obtaining a solution of the transmission power variable by applying a solution of the obtained stream number variable,
And repeating steps (b) and (c) until the solution of the stream number variable converges to a fixed value.
8. The method of claim 7,
After calculating the optimal solution of the energy efficiency function,
And applying the newly pitched partial channel information to the transmit power of the calculated optimal solution to change transmit power. ≪ Desc / Clms Page number 19 >
The method according to claim 6,
Prior to transmitting the pilot signal,
Detecting the plurality of candidate user terminals requiring data transmission in coverage;
Calculating a number of streams and a transmission power based on the number of the candidate user terminals; And
Generating a random unitary matrix based on the number of streams and providing the random unitary matrix to the plurality of candidate user terminals,
And receives any one of the column vector vectors of the random unitary matrix from the plurality of candidate user terminals as an index of the beamforming vector.

Images