KR101580539B1 - Two-way communication system and method for multiuser - Google Patents

Abstract

The present invention discloses a base station and a method for supporting bi-directional communication for a plurality of users. A base station supporting bidirectional communication for a plurality of users according to an embodiment of the present invention is connected to a plurality of antennas that respectively transmit downlink signals to a plurality of users and includes a precoding matrix And a receiver connected to a plurality of antennas for receiving uplink signals from a plurality of users, respectively, and applying a beamforming filter to the uplink signals, wherein the precoding matrix comprises a receiver for receiving uplink signals and a downlink A self-interference alignment matrix for aligning a plurality of self-interference signals generated by transmission of a downlink signal upon receipt of an uplink signal as a result of simultaneous transmission of a link signal, to a predetermined specific subspace associated with the receiver, , And the beamforming filter includes a self interference elimination filter made up of the null space of the specific subspace.

Description

TECHNICAL FIELD The present invention relates to a two-way communication system and a two-way communication method for a plurality of users,

The present invention relates to a two-way communication system and a two-way communication method for a plurality of users.

Recently, a system supporting bi-directional communication among a large number of users has emerged as an attractive solution for maximizing the efficiency of radio resources. A plurality of wireless terminals in a bi-directional communication system environment can transmit and receive data in relation to a base station utilizing the same radio resource (e.g., time, frequency, or code), thereby increasing data throughput.

In this system, the two-way communication base station provides a full duplexer for a plurality of users, and the full duplexer supports multiple input and multiple output (MIMO) for a plurality of users. However, since the bidirectional communication base station transmits a signal to a plurality of downlink users through a downlink channel and receives signals from a plurality of uplink users through an uplink channel, self-interference Self-Interference) is generated. Therefore, there is a continuing need for a method for effectively mitigating or eliminating self-interference in a two-way communication system and a method for designing an antenna accordingly.

The following are research papers on various methods to solve self interference problem in bidirectional communication system.

Real-time, Full Duplex Wireless ", MobiCom" Real-time, Full-duplex Wireless ", M. Jain, J. Choi, T. Kim, D. Bharadia, S. Seth, K. Srinivasan, P. Levis, S. Katti, 11, September 1923, 2011, Las Vegas, Nevada, USA.

This paper proposes a prototype of a full - duplex wireless communication system using OFDM link layer such as 802.11 in the design of IBFD, and proposed a system model that reduces its own interference using signal inversion and adaptation cancellation techniques.

A. Sabharwal, P. Schniter, D. Guo, D. Bliss, S. Rangarajan, and R. Wichman, "In-Band Full-Duplex Wireless: Challenges and Opportunities", November 3, 2013, http: // arxiv. org / abs / 1311.0456v3.

 This paper discusses various mitigation techniques for magnetic interference, one of the most substantial problems of the IBFD, and other research topics for the design and analysis of IBFD radio systems.

Some embodiments of the present invention provide a bi-directional communication system for a plurality of users capable of efficiently removing a self interference signal generated by transmission of a downlink signal upon reception of an uplink signal in a two-way communication system for a plurality of users, The present invention provides a two-way communication method.

It is to 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 be present.

According to an aspect of the present invention, there is provided a base station supporting bidirectional communication for a plurality of users, the base station including a plurality of antennas for transmitting downlink signals to the plurality of users, A transmitter for applying a precoding matrix to the downlink signal; And a receiver coupled to the plurality of antennas for receiving uplink signals from the plurality of users, respectively, and applying a beamforming filter to the uplink signals.

In this case, the precoding matrix may include a plurality of self interference signals generated by transmission of the downlink signal upon reception of the uplink signal as the reception of the uplink signal and the transmission of the downlink signal occur simultaneously, Wherein the beamforming filter includes a self interference cancellation filter arranged in a predetermined specific subspace in relation to the specific subspace.

In another aspect of the present invention, there is provided a bi-directional communication method for a plurality of users, comprising the steps of: before transmitting a downlink signal to a plurality of users through a plurality of antennas connected to a transmitter of a base station, Applying a precoding matrix to the matrix; And applying a beamforming filter to the uplink signal after receiving an uplink signal from the plurality of users via a plurality of antennas connected to a receiver of the base station, In response to reception of the uplink signal and transmission of the downlink signal, a plurality of self interference signals generated by transmission of the downlink signal upon reception of the uplink signal, Wherein applying the beamforming filter comprises applying a self interference cancellation filter consisting of a null space of the specific subspace.

According to any one of the above-described methods of the present invention, a precoding matrix including a self-interference alignment matrix is applied to a downlink signal before transmitting a downlink signal, and after a uplink signal is received, By applying a beam-forming filter including a self-interference elimination filter to the link signal, it is possible to remove the self-interference signal due to simultaneous transmission and reception of signals, and efficiently detect the uplink and downlink signals required for bidirectional communication And the overall performance of the MIMO system for a large number of users can be improved.

In addition, by applying the user interference alignment matrix to the precoding matrix additionally, an inter-user interference signal that can occur when the first channel corresponding to the first user and the second channel corresponding to the second user are adjacent to each other in the downlink channel, Can be removed. By applying an optimization matrix to the precoding matrix, it is also possible to set the data rate of a plurality of users in the downlink channel to be the maximum.

FIG. 1 is a general view of a two-way communication system for a plurality of users according to an embodiment of the present invention.
2 is a block diagram of a base station supporting two-way communication for a plurality of users according to an embodiment of the present invention.
3 is a diagram illustrating an example of a process of obtaining a self-interference alignment matrix.
4 is a flowchart illustrating a two-way communication method for a plurality of users according to an exemplary 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 "including" an element, it is to be understood that the element may include other elements as well as other elements, And does not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

In this specification, some of the operations or functions described as being performed by the terminal or the device may be performed in the server connected to the terminal or the device instead. Similarly, some of the operations or functions described as being performed by the server may also be performed on a terminal or device connected to the server.

The following examples are intended to further illustrate the present invention and are not intended to limit the scope of the present invention. Accordingly, the same scope of the invention performing the same function as the present invention will also fall within the scope of the present invention.

FIG. 1 is a general view of a two-way communication system for a plurality of users according to an embodiment of the present invention.

The bidirectional communication system 10 of the present invention includes a base station 100 and a plurality of user terminals 100 that support multiple input and multiple output (MIMO) for a plurality of users, 106).

The base station 100 provides a bidirectional communication service through a plurality of channels 108 and 109 to a plurality of user terminals 104 and 105 using a plurality of antennas 102 and 103. [

The Nt transmission multiple antennas 102 transmit data signals to the plurality of downlink user terminals 104 through the downlink channel 108. The Nr receive multiple antennas 103 receive data signals from a plurality of uplink user terminals 105 through an uplink channel 109. [

In this case, the number of transmission multiple antennas 102 and the number of reception multiple antennas 103 may be different from each other, and the number of transmission antennas 102 and 103 and the number of channels 108 and 109 may be the same Or may be configured to be less.

A plurality of downlink user terminals 104 and a plurality of uplink user terminals 105 may be geographically separated so as not to affect each other in performing bidirectional communication. However, the mutual interference generated between the plurality of downlink user terminals 104 or the mutual interference generated between the plurality of uplink user terminals 105 is considered.

The plurality of channels 108 and 109 may be configured to correspond to a plurality of user terminals 104 and 105, respectively. In addition, transmission of the downlink signal and reception of the uplink signal are simultaneously performed through the plurality of channels 108 and 109.

The self interference (SI) is transmitted from the transmission multiple antenna 102 to the reception multiple antenna 103 through the HSI 107, which is a separate channel matrix. In the present invention, a plurality of self interference signals refer to an interference signal generated by interference between reception of an uplink signal and transmission of a downlink signal and reception of an uplink signal due to transmission of a downlink signal. This is one of the problems that arise in systems that support two-way communication.

In a two-way communication system 10 for a plurality of users according to an exemplary embodiment of the present invention, a plurality of antennas 102 and 103 capable of removing a self-interference signal through a software approach can be designed. In particular, the base station 100 in the two-way communication system 100 can align a plurality of self-interference signals in a predetermined specific subspace with respect to a receiver by applying a precoding matrix when transmitting a downlink signal, It is possible to apply a self-interference elimination filter composed of a null space of a specific subspace at the time of reception.

A plurality of user terminals 106 are provided with bidirectional communication service from the base station 100 supporting bidirectional communication. At this time, the plurality of terminals 104 and 105 may be a device having a single antenna or a plurality of antennas, or may be implemented as a computer or a portable terminal capable of accessing a network network such as a radio access network. Such a computer includes, for example, a notebook computer, a desktop computer, a laptop computer, etc. equipped with a web browser (WEB Browser), and the portable terminal may be, for example, a personal computer Communication System, GSM (Global System for Mobile communications), PDC (Personal Digital Cellular), PHS (Personal Handyphone System), PDA (Personal Digital Assistant), IMT (International Mobile Telecommunication) -2000, CDMA (Code Division Multiple Access) -2000, W-Code Division Multiple Access (W-CDMA), Wibro (Wireless Broadband Internet) terminals, and the like. In addition, the plurality of terminals 104 and 105 are intelligent terminals, such as a smart phone, to which a computer-assisted function such as internet communication and information search is added to a mobile phone, and are smart devices capable of installing a desired application .

In addition, the base station 100 and the plurality of user terminals 106 are generally connected through the following networks. Examples of the network include a 3rd Generation Partnership Project (3GPP) network, a Long Term Evolution (LTE) network, a World Interoperability for Microwave Access (WIMAX) network, the Internet, a LAN (Local Area Network) Network, a Wide Area Network (WAN), a Personal Area Network (PAN), a Bluetooth network, a satellite broadcast network, an analog broadcast network, a DMB (Digital Multimedia Broadcasting) network, and the like.

2 is a block diagram of a base station supporting two-way communication for a plurality of users according to an embodiment of the present invention.

2, a base station 200 supporting bi-directional communication for a plurality of users includes a transmit multiple antenna 201, a transmitter 201, a receive multiple antenna 203, and a receiver 204 .

Since the base station supporting two-way communication for a plurality of users shown in FIG. 2 is only one embodiment of the present invention, the present invention is not limited to FIG. 2, and various applications are possible from FIG.

The base station 200 provides a bidirectional communication service for simultaneously transmitting and receiving a downlink signal and an uplink signal through a channel allocated to each of a plurality of users.

The transmission multiple antenna 201 transmits downlink signals to the downlink users.

The receiving multiple antenna 203 receives the downlink signals from the uplink user.

That is, a plurality of transmission multiple antennas 201 and a plurality of reception multiple antennas 203 are connected to the base station 200 to transmit downlink signals to a plurality of uplink user terminals, respectively, Respectively.

In this case, a plurality of antennas generally refers to a MIMO (Multiple Input Multiple Output) antenna, and two or more antennas may be arranged at both ends of the transmission multiple antenna 201 and the reception multiple antenna 203, Depending on the system design, the arrangement and number of antennas can be changed.

In addition, multiple antennas may be generated by transmission of a downlink signal upon receipt of an uplink signal as the uplink signal is received and the downlink signal is simultaneously transmitted through a separate device connected thereto or its own optimization design scheme A plurality of self interference signals can be removed.

The transmitter 202 is connected to the transmission multiple antenna 201 and applies a precoding matrix to the downlink signals.

In this case, the precoding matrix may include a plurality of self interference signals generated by transmission of a downlink signal upon receipt of an uplink signal as a result of reception of an uplink signal and transmission of a downlink signal at the same time, Lt; RTI ID = 0.0 > a < / RTI > specific subspace.

Also, the precoding matrix may further include a user interference alignment matrix set based on a block diagonalization technique to remove a plurality of inter-user interference signals generated by transmission of a downlink signal. At this time, the user interference sorting matrix may be applied to the downlink signal before the self interference sorting matrix.

Further, the precoding matrix further includes an optimization matrix based on a user interference sorting matrix and a singular value decomposition process for a self-interference sorting matrix so as to maximize a data rate of a plurality of users when transmitting a downlink signal . At this time, the optimization matrix may be applied to the downlink signal later than the user interference alignment matrix and the self interference interference sorting matrix.

In other words, the precoding matrix applied to the multiple transmit multiple antennas 201 or the transmitters 202 can be designed to remove not only the self-interference occurring at the receiving end due to the transmitting end of the base station but also the inter-user interference of the downlink users have. In addition, the precoding matrix can optimize the transmission rate of downlink users.

[Equation 1] is a formula for obtaining a precoding matrix, and a specific process will be described.

는 블록 대각화(Block Diagonalization) 기법을 기반으로 설정된 사용자 간섭정렬 행렬로, 하향링크 신호의 송신에 의해 발생된 다수의 사용자 간 간섭 신호를 제거한다.In Equation (1)

Is a user interference alignment matrix set on the basis of a block diagonalization technique and removes a plurality of inter-user interference signals generated by transmission of a downlink signal.

의 영공간에 각각의 하향링크 사용자의 신호가 머물도록 해야한다.In order to obtain the user interference sorting matrix, first, a block diagonalization technique is applied

So that the signals of the respective downlink users remain in the null space of the downlink user.

을 신호 처리와 통계학 등의 분야에서 자주 사용되는 특정한 구조로 분해하는 방식으로 특이치 분해 (SVD: Singular Value Decomposition)를 고려하여

과 같이 구할 수 있다.Next,

(SVD) in a way that decomposes a signal into a specific structure frequently used in fields such as signal processing and statistics

Can be obtained as follows.

을 구할 수 있다.Next, a user interference sorting matrix satisfying the condition of the foaming forcing

Can be obtained.

는 자체 간섭 정렬 행렬로, 상향링크 신호의 수신과 하향신호의 송신이 동시에 이루어짐에 따라 상향링크 신호의 수신시 하향링크 신호의 송신에 의해 발생된 다수의 자체 간섭 신호를 수신기와 관련하여 기정의된 특정 서브공간에 정렬시킨다.In Equation (1)

A plurality of self interference signals generated by transmission of a downlink signal upon reception of an uplink signal as a result of reception of an uplink signal and transmission of a downlink signal at the same time, Align to a specific subspace.

(301)(span)되도록 해야한다.In order to obtain the self-interference alignment matrix, first,

(301) (span).

3 is a diagram illustrating an example of a process of obtaining a self-interference alignment matrix.

(301) 의 공간으로

와 같이 스팬(span) 되는 조건을 충족하기 위해서

(304) 의우측 영공간 (Right Null Space)을 구함으로써 자체 간섭정렬 행렬

을 구할 수 있다.Referring to FIG. 3, first, K _d1 self-interference signals

(301)

In order to satisfy the condition of span as shown in Fig.

(Right Null Space) of the self interference sorting matrix 304,

Can be obtained.

는 하향링크 사용자들의 데이터 속도를 최적화 시키는행렬로, 하향링크 신호의 송신시 다수의 사용자의 데이터 비율을 최대화하도록 사용자 간섭정렬 행렬 및 자체 간섭정렬 행렬에 대한 특이치 분해 과정을 기반으로 설정될 수 있으며,

와 같이 표현할 수 있고, 데이터 속도를 최대화시키기 위한

을 선택하여 구할 수 있다.In Equation (1)

Is a matrix that optimizes the data rate of the downlink users and can be set based on the disassociation disassembly process for the user interference sort matrix and the self interference sort matrix so as to maximize the data ratio of a plurality of users when transmitting the downlink signal ,

And to maximize the data rate.

Can be obtained.

Referring again to FIG. 2, the receiver 204 is connected to the receive multi-antenna 203 to apply a beam-forming filter for removing an interference signal from the uplink signal and performing an additional function.

At this time, the beamforming filter includes a self interference cancellation filter consisting of the null space of the specific subspace referred to in the self interference interference matrix in the precoding matrix.

Further, the beamforming filter may further include a zero-forcing filter for decoding the uplink signal, and the zero-forcing filter may be applied to the uplink signal later than the self interference elimination filter.

Equation (2) is a formula for applying a beam-forming filter, and a concrete procedure will be described.

는 상향링크 수신시 하향 링크로 인해 발생하는 자체 간섭을 제거하기 위한 간섭 제거 필터로, 다수의 사용자로부터 수신단이 받은 상향링크 신호는

의 조건을 만족하는

(301)의 영공간으로 이루어진 필터

를 통과함으로써 자체간섭을 제거할 수 있다.In Equation (2)

Is an interference cancellation filter for eliminating self-interference caused by a downlink in uplink reception, and the uplink signal received from a plurality of users

Satisfy the condition of

Lt; RTI ID = 0.0 > 301 < / RTI &

It is possible to eliminate the self interference.

는 상향링크 사용자들의 신호를 복호하기 위한 제로 포싱 필터로

이와 같이 나타낼 수 있다.In Equation (2)

Is a zero forcing filter for decoding signals of uplink users

This can be expressed as follows.

4 is a flowchart illustrating a two-way communication method for a plurality of users according to an exemplary embodiment of the present invention.

In step S410, the base station applies a precoding matrix to the downlink signals before transmitting the downlink signals to the plurality of users through a plurality of antennas connected to the transmitter of the base station, respectively.

In applying the precoding matrix, as the reception of the uplink signal and the transmission of the downlink signal are simultaneously performed in the base station, a plurality of self interference signals generated by the transmission of the downlink signal upon reception of the uplink signal, And applies a self-interference sorting matrix that aligns to a predetermined specific subspace in relation to the received signal.

In this case, a user interference alignment matrix set based on a block diagonalization scheme is additionally applied to remove a plurality of inter-user interference signals generated by transmission of a downlink signal, and a user interference alignment matrix is defined as a self- It can be applied to the downlink signal before.

In addition, an optimization matrix is additionally applied based on a user interference sorting matrix and a self-interference sorting matrix based on a singular value decomposition process to maximize a data ratio of a plurality of users when a downlink signal is transmitted, May be applied to the downlink signal later than the user interference alignment matrix and the self interference sorting matrix

After receiving an uplink signal from a plurality of users through a plurality of antennas connected to a receiver of the base station, the base station applies a beamforming filter to the uplink signals at step S420.

In applying the beamforming filter, the base station applies its own interference elimination filter consisting of null space of a specific subspace.

At this time, a zero-forcing filter for decoding the uplink signal is additionally applied, and the zero-forcing filter can be applied to the uplink signal later than the self interference elimination filter.

In the above description, steps S410 to S420 may be further divided into additional steps, or combined in fewer steps, according to an embodiment of the present invention. Also, some of the steps may be omitted as necessary, and the order between the steps may be changed.

Through these steps S410 to S420, it is possible to remove the self-interference signal due to simultaneous signal transmission and reception, efficiently detect the uplink and downlink signals required for bidirectional communication, Can be improved.

The two-way communication method for multiple users described with reference to FIG. 4 may also be implemented in the form of a recording medium including instructions executable by a computer, such as program modules, being executed by a computer. 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.

It is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. .

10: Two-way communication system for multiple users
100: base station 102: transmission multiple antennas
103: receive multiple antenna 104: downlink user terminal
105: Uplink user terminal 107: Self-interference channel
108: downlink channel 109: uplink channel

Claims (7)

A base station supporting bi-directional communication for a plurality of users,
A transmitter connected to a plurality of antennas that respectively transmit downlink signals to the plurality of users, and applying a precoding matrix to the downlink signals; And
And a receiver coupled to the plurality of antennas for receiving the uplink signals from the plurality of users and applying a beamforming filter to the uplink signals,
Wherein the precoding matrix includes a plurality of self interference signals generated by transmission of the downlink signal upon receipt of the uplink signal as the reception of the uplink signal and the transmission of the downlink signal are simultaneously performed, A user interference sorting matrix based on a block diagonalization scheme for eliminating a plurality of inter-user interference signals generated by transmission of the downlink signal, / RTI >
Wherein the beamforming filter supports bidirectional communication including a self interference cancellation filter of zero space of the specific subspace,
Wherein the user interference ordering matrix is applied to the downlink signal prior to the self-interference sorting matrix.
delete The method according to claim 1,
Wherein the precoding matrix is configured to maximize a data rate of the plurality of users at the time of transmission of the downlink signal by using an optimization matrix based on a singular value decomposition process for the user interference order matrix and the self- Further comprising:
Wherein the optimization matrix is applied to the downlink signal after the user interference ordering matrix and the self interference allocation matrix. The method according to claim 1,
Wherein the beamforming filter further comprises a zero-forcing filter for decoding the uplink signal,
Wherein the zero-forcing filter is applied to the uplink signal later than the self-interference cancellation filter. A two-way communication method for a plurality of users,
Applying a precoding matrix to the downlink signal before transmitting a downlink signal to a plurality of users through a plurality of antennas connected to a transmitter of the base station; And
Applying a beamforming filter to the uplink signal after receiving an uplink signal from the plurality of users through a plurality of antennas connected to a receiver of the base station,
The step of applying the precoding matrix
A plurality of self interference signals generated by transmission of the downlink signal upon reception of the uplink signal as the reception of the uplink signal and the transmission of the downlink signal are concurrently performed, Applying a self interference sorting matrix to the subspace; And
The method of claim 1, further comprising: applying a user interference alignment matrix based on a block diagonalization scheme to remove a plurality of inter-user interference signals generated by transmission of the downlink signal, The method comprising the steps of:
The step of applying the beam-forming filter
And applying a self interference cancellation filter consisting of null space of the specific subspace. 6. The method of claim 5,
The step of applying the precoding matrix
Applying an optimization matrix based on a singular value decomposition process for the user interference alignment matrix and the self interference interference sorting matrix to maximize a data rate of the plurality of users when transmitting the downlink signal, Further comprising applying an optimization matrix for the downlink signal later than the user interference alignment matrix and the self interference sorting matrix. 6. The method of claim 5,
The step of applying the beam-forming filter
Applying a zero-forcing filter to decode the uplink signal, and applying the zero-forcing filter to the uplink signal later than the self-interference cancellation filter.

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