KR20150044379A - Method and apparatus for stochastic transmission/reception for MU-MIMO scheme in MIMO radio communication system - Google Patents

Abstract

Signal transmission/reception of mobile communications system terminals according to an embodiment of the present specification is made following the steps of: receiving reference signals from a base station; measuring channel information based on the received reference signal; predicting channel measurement errors based on the measured channel information; and transmitting feedback information created based on the prediction back to the base station. According to an embodiment of the present specification, stochastic channel precoding designing and stochastic user selection may maximize system throughputs by predicting errors caused by changes in channels over time, channel measurement errors, channel information quantization errors, and errors occurred during channel feedback.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for stochastic transmission / reception for a multi-antenna multi-user wireless communication system,

The present invention relates to a multi-antenna multi-user wireless communication method. More particularly, to a method and apparatus for exchanging stochastic channel state information in multi-user wireless communication.

Generally, a mobile communication system is developed for providing communication while securing the mobility of a user. Such a mobile communication system has reached a stage where it can provide high-speed data communication services as well as voice communication owing to the remarkable development of the technology.

Recently, as one of the next generation mobile communication systems, standard works for LTE (Long Term Evolution) are underway in 3GPP. LTE is a technology that realizes high-speed packet-based communication with a transfer rate of up to 100 Mbps, which is higher than the data transmission rate currently provided, with the goal of commercialization in 2010 or so. For example, there are discussions on how to reduce the number of nodes on the communication path by simplifying the structure of the network, and to make the wireless protocols as close as possible to the wireless channel.

Unlike the voice service, the data service determines the amount of data to be transmitted and the resources that can be allocated according to the channel status. Therefore, in a wireless communication system such as a mobile communication system, the scheduler manages allocation of transmission resources in consideration of the amount of resources to be transmitted, the channel status, and the amount of data. This is the same in LTE, one of the next generation mobile communication systems, and the scheduler located in the base station manages and allocates wireless transmission resources.

In the wireless communication system, a user equipment (UE) measures a channel from a base station (BS), exchanges the measured channel information, and performs at least one of scheduling, precoding, and modulation based on the measured channel information Thereby improving communication performance. There is a need for a method and apparatus for exchanging channel information to provide such an effective communication environment.

Accordingly, in embodiments of the present invention, in a multi-antenna multi-user wireless communication system, a user terminal generates feedback information considering stochastic information on a channel measurement error, a base station transmits a transmission method using feedback information, Device.

Other embodiments of the present invention provide a method and apparatus for feedback of channel information based on channel measurement error prediction by a user terminal of a multi-antenna multi-user wireless communication system.

Another embodiment of the present invention is to provide a method and apparatus for a base station of a multi-antenna multi-user wireless communication system to receive feedback channel information from a user and to perform probabilistic precoding design and probabilistic user selection.

According to an aspect of the present invention, there is provided a method of transmitting and receiving signals in a terminal of a mobile communication system, comprising: receiving a reference signal from a base station; Measuring channel information based on the received reference signal; Estimating a channel measurement error based on the measured channel information; And transmitting feedback information generated based on the predicted information to a base station.

According to another aspect of the present invention, there is provided a method of transmitting / receiving a signal in a base station of a mobile communication system, including: transmitting a reference signal to a terminal; And receiving feedback information generated based on the reference signal, wherein the feedback information is generated based on channel measurement error information predicted based on the reference signal by the terminal.

A terminal for transmitting and receiving signals in a mobile communication system according to another embodiment of the present invention includes a transmitting and receiving unit for transmitting and receiving signals to and from a base station; Receiving the reference signal from the base station; measuring channel information based on the received reference signal; estimating a channel measurement error based on the measured channel information; And transmitting the generated feedback information to the base station.

According to another aspect of the present invention, a base station for transmitting and receiving signals in a mobile communication system includes a transmitting and receiving unit for transmitting and receiving signals to and from a terminal; And a controller for controlling the transmitter / receiver, transmitting a reference signal to the terminal, and receiving feedback information generated based on the reference signal, wherein the feedback information includes a channel estimated by the terminal based on the reference signal, And is generated based on measurement error information.

Embodiments of the present invention allow a user terminal of a wireless communication system to measure a channel from a base station and to feed back to the base station by estimating a channel measurement error of the measured channel, (Eg, channel precoding design and probabilistic user selection), errors due to channel changes over time, errors coming from channel measurements, errors coming from channel information quantization, and errors coming from channel feedback processes By predicting, system throughputs can be maximized.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the foregoing and further embodiments of the invention, reference should now be made to the following description, taken in conjunction with the accompanying drawings, wherein like reference numerals designate corresponding parts throughout the figures.
1 is a diagram illustrating a system model of a wireless communication system to which an embodiment of the present invention can be applied.
2 is a diagram schematically illustrating the flow of a user terminal channel bi-directional operation in accordance with embodiments of the present invention.
3 is a schematic diagram illustrating a flow of a base station channel demodulator operation in accordance with embodiments of the present invention.
FIG. 4 is a flowchart illustrating a flow of an operation in which a user terminal feedback channel information based on channel measurement error prediction according to embodiments of the present invention. Referring to FIG.
5 is a diagram illustrating a flow of an operation of a probabilistic precoding design and a probabilistic user selection based on feedback channel information from a user station according to embodiments of the present invention.
FIG. 6 is a diagram illustrating an example of performance between a probabilistic transmission and reception scheme to which embodiments of the present invention are applied and a conventional deterministic transmission and reception scheme in a channel change environment over time.
FIG. 7 is a graph illustrating an example of performance between a probabilistic transmission and reception technique and an existing deterministic transmission and reception technique to which the embodiments of the present invention are applied, in a channel-changing environment correlated over time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the embodiments of the present invention, descriptions of techniques which are well known in the technical field of the present invention and are not directly related to the present invention will be omitted. This is for the sake of clarity of the present invention without omitting the unnecessary explanation.

For the same reason, some of the components in the drawings are exaggerated, omitted, or schematically illustrated. Also, the size of each component does not entirely reflect the actual size. In the drawings, the same or corresponding components are denoted by the same reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

At this point, it will be appreciated that the combinations of blocks and flowchart illustrations in the process flow diagrams may be performed by computer program instructions. These computer program instructions may be loaded into a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, so that those instructions, which are executed through a processor of a computer or other programmable data processing apparatus, Thereby creating means for performing functions. These computer program instructions may also be stored in a computer usable or computer readable memory capable of directing a computer or other programmable data processing apparatus to implement the functionality in a particular manner so that the computer usable or computer readable memory The instructions stored in the block diagram (s) are also capable of producing manufacturing items containing instruction means for performing the functions described in the flowchart block (s). Computer program instructions may also be stored on a computer or other programmable data processing equipment so that a series of operating steps may be performed on a computer or other programmable data processing equipment to create a computer- It is also possible for the instructions to perform the processing equipment to provide steps for executing the functions described in the flowchart block (s).

In addition, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative implementations, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may actually be executed substantially concurrently, or the blocks may sometimes be performed in reverse order according to the corresponding function.

Herein, the term " part " used in the present embodiment means a hardware component such as software or an FPGA or an ASIC, and 'part' performs certain roles. However, 'part' is not meant to be limited to software or hardware. &Quot; to " may be configured to reside on an addressable storage medium and may be configured to play one or more processors. Thus, by way of example, 'parts' may refer to components such as software components, object-oriented software components, class components and task components, and processes, functions, , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and components may be further combined with a smaller number of components and components or further components and components. In addition, the components and components may be implemented to play back one or more CPUs in a device or a secure multimedia card.

A user equipment (UE) of a wireless communication system according to an embodiment of the present invention measures a channel from a base station (BS) and measures the measured channel information (e.g., Channel Quality Information The CQI and the channel direction information to the base station 100. The base station then performs channel precoding design and modulation order using the feedback channel information, The user terminal can generate feedback information in consideration of the value of the channel itself, and the base station can receive feedback of the generated channel self information Based on this, at least one of channel precoding, modulation order determination, and user selection can be performed.

The embodiments described to illustrate the principles of the present invention in this patent document are for illustrative purposes only and are not to be construed as limiting the scope of the invention. Those skilled in the art will appreciate that the principles of the present invention may equally well be implemented in any wireless communication system in which it is properly arranged.

Multiple-input multiple-output (MIMO) techniques have been used in many wireless communication systems to increase system capacity and improve link reliability. Recently, a wireless communication system such as a Long Term Evolution (LTE) system supports multi-user communication using multiple antennas at a base station and a user terminal. Thus, information can be transmitted to a plurality of user terminals in the same frequency-time domain. There is a need to effectively control the inter-user interference of the multi-user support. At this time, the BS or the UE controls the interference using the channel information, and the communication performance can be determined according to the accuracy of the channel information.

For example, inaccurate channel information causes inter-user interference, which can not maximize the spatial multiplexing gain provided by multiple antennas.

In the time-division duplex (TDD) system, the uplink and downlink channels of the channel have the same property, so that the channel information can be effectively obtained at the base station. However, in a frequency-division duplex (FDD) system, a user terminal does not have such a channel characteristic, measures a channel for a downlink transmitted from the base station, and feeds back the measured channel information to the base station.

In such a process, there is a problem that perfect channel information can not be obtained at the base station due to at least one of measurement of an incomplete channel of the UE, change of the channel status in time, and restriction of the feedback channel. Due to these problems, performance degradation of multi-user communication may occur. In other words, if precoding and user selection are derived based on the damaged channel information, interference can not be appropriately controlled in a multi-user supporting communication system, and a performance degradation problem may occur.

In the present invention, a user terminal of a wireless communication system can measure a channel from a base station, predict a channel measurement error of the measured channel, and feed back to the base station. The channel measurement errors of an embodiment may include a probabilistic distribution. Then, the base station executes at least one of a probabilistic channel precoding design and a probabilistic user selection based on the feedback channel measurement error, thereby detecting an error due to a channel change over time, , Errors from channel information quantization, and channel feedback errors, thereby maximizing system throughputs. Also, the user selection performed by the base station may be determined based on the channel measurement error information.

1. Multi-user channel precoding scheme using channel measurement error information

This section describes the system model under consideration and describes a multi-user channel precoding scheme based on channel measurement errors.

1.1 System model

1 is a diagram illustrating a system model of a wireless communication system to which an embodiment of the present invention can be applied.

Referring to FIG. 1, the base station 100 and the user terminals 110 and 120 can transmit and receive signals.

The base station 100 may include a control unit 102 that controls operations of the base transceiver station 104 and the base station 100 including M transmit antennas and may perform precoding and user selection .

In an embodiment, the first user terminal 110 may include a transceiver 112 including N ₁ antennas, and may include a controller for controlling the operation of the first user terminal 110. The Kth user terminal 120 may include a transceiver 122 including N _K antennas and may include a controller for controlling the operation of the Kth user terminal 120.

In an embodiment, the base station 100 may process the information to be transmitted 106 and transmit it to the user terminals 110 and 112 via the transceiver 104 (108).

시스템으로 구성된 도 1의 실시 예에서,

이며

는 k-번째 사용자 단말을 나타내다. 또한 실시 예에서 각 단말은 L_k-의 데이터 스트림을 수신할 수 있다.( L_k 은 N_k보다 작거나 같음) K-번째 단말에서 수신 신호 벡터를 y_k라고 하면 전체 사용자들의 수신 신호 벡터

는 다음과 같이 나타낼 수 있다. Also, a multi-user multi-antenna downlink

In the embodiment of FIG. 1 configured as a system,

And

Represents the k-th user terminal. Also, in the embodiment, each terminal can receive the data stream of L _k- (L _k is less than or equal to N _k ). Letting the received signal vector be y _k at the K-th UE,

Can be expressed as follows.

이고 P_k는 k-번재 단말의 채널프리코딩이고, 전체 송신 파워 P_tx에 대해

을 만족하고, k-번째 단말의 송신 정보벡터 단위파워(unit-power) s_k에 대해 전체 사용자 송신정보 벡터는

를 의미하며, k-번째 단말의 잡음벡터 w_k에 대해 전체 사용자 잡음벡터는

로 주어질 수 있다. 각 수신안테나에서 잡음은 제로(zero) 평균에 분산(variance)

를 가지는 가우시안(Gaussian) 분포를 가진다고 가정할 수 있다. 또한 K-번째 사용자 단말의 채널행렬

에 대해 전체 사용자 채널 행렬은

로 나타낼 수 있다.In equations (1) and (2)

And P _k is the channel precoding of the k-th UE, and for the total transmission power P _tx

, And the total user transmission information vector for unit-power s _k of transmission information vector units of the k-th UE satisfies

, And the total user noise vector for the noise vector w _k of the _k -th terminal is

Lt; / RTI > The noise at each receive antenna is variance to zero mean,

(Gaussian distribution). The channel matrix of the K-th user terminal

The overall user channel matrix < RTI ID = 0.0 >

.

1.2 Probabilistic channel precoding

 H. Sung, S. Lee, and I. Lee, "Generalized channel inversion methods for multiuser mimo systems," IEEE Trans. Commun., Vol. 57, pp. 3489 3499, November 2009 introduces deterministic channel precoding. In the present invention, the following probabilistic channel precoding technique can be proposed using probabilistic techniques in the same situation. In the embodiment, the probabilistic precoding of the k-th user can be obtained as follows.

,

,

, 그리고

는 기지국에서 바라보는 채널상태 정보(channel status information, CSI)를 의미한다.

는

의 SVD(singular-value decomposition)을 통해 얻어진다. 실시 예에서는 I는 채널의 차원에 대응하는 단위행렬일 수 있다. In Equation (3)

,

,

, And

Quot; refers to channel status information (CSI) as viewed from a base station.

The

Lt; / RTI > SVD (singular-value decomposition). In an embodiment, I may be a unitary matrix corresponding to the dimension of the channel.

의 열(column)들을 쌓아 만든 벡터를

라고 하면, 즉

와 같이 표현될 수 있다. k-번째 단말의 채널측정오류행렬

은 다음과 같이 나타내면

전체 사용자에 대한 채널측정오류행렬

는

관계를 갖는다. 채널행렬

와 채널 측정오류행렬

은 서로 독립적이며, 각각 다음과 같은 가우시안 분포

와

를 가진다. 상기 정의들에 따라서 수학식 (3)의

와

는 아래 관계식으로부터 유도 될 수 있다. 실시 예에서 단말은 채널 측정 오류 행렬의 분산 정보를 기지국으로 피드백 할 수 있다. Channel splitting

A vector created by stacking columns of

That is,

Can be expressed as The channel measurement error matrix of the k-th UE

Is expressed as

Channel measurement error matrix for all users

The

Relationship. Channel matrix

And channel measurement error matrix

Are independent of each other, and each has the following Gaussian distribution

Wow

. According to the above definitions,

Wow

Can be derived from the following relationship. In an embodiment, the UE may feed back the dispersion information of the channel measurement error matrix to the base station.

와

를 의미한다.In equations (4) and (5)

Wow

.

In the embodiment, if the transmission layer of each user is different from the number of the channel rank, there is a need to adaptively select precoding metrics. Therefore, SVD operations can be considered in this specification.

와

는 각 분포의 분산 값을 나타내며, 기지국은 상기 값을 사용자 단말로부터 피드백 받은 채널측정오류정보를 기반으로 구할 수 있다.In the present invention,

Wow

Represents a variance value of each distribution, and the base station can obtain the value based on the channel measurement error information fed back from the user terminal.

는 수신 안테나 개수

보다 작거나 같아야 함으로 수신기에서 랭크최적화를 실시하게 된다.

를 정의하고 높은 신호대잡음비(Singnal-to-noise ratio:SNR) 영역에서 가능한 최대 성능은

로 구할 수 있다. 이를 최대화 하는

는 다음 수학식으로 주어진다.The transmission rank of the k-th terminal

The number of receiving antennas

To be less than or equal to each other.

And the maximum possible performance in a high signal-to-noise ratio (SNR)

. Maximize

Is given by the following equation.

는 다음과 같은 SVD,

, 로 얻어지며, 다음과 같이 정의되는 함수를 사용한다.In Equation (6)

The following SVD,

, And a function defined as follows is used.

를 만족한다. In the embodiment, a ₁ represents the 1 st column vector of A, f (1) represents the column vector arrangement, and in equation (7)

.

2. Channel measurement error feedback method

This section proposes a process in which the user terminal feeds back the information necessary for the design of the base station's coding in the previous section.

의 방향 정도를 반영할 수 있다. 보다 구체적으로 CDI는 채널의 방향(orientation of the channel)을 나타내는 단위 표준 벡터 또는 행렬(unit-norm vector/matrix)일 수 있다. In general, channel state information (CSI) may include at least one of a CQI and a CDI. The CQI reflects the signal-to-interference-plus-noise ratio (SINR) experienced by an actual UE,

As shown in FIG. More specifically, the CDI may be a unit standard vector or a matrix (unit-norm vector / matrix) representing the orientation of the channel.

The present invention may consider quantization prediction and partial CDI feedback to minimize the amount of quantization error and feedback. For example, the distributed information of the quantization error is fed back to the base station so that the base station can perform the probabilistic transmission method according to the method described in the previous section. In the embodiment, the variance information of the quantization error may include variance information of the channel matrix and the quantization error of the measurement error matrix.

이 시간에 따른 변화, 안테나 사이간 차이가 상관관계를 가지면 최적의 채널 코딩 행렬 집(Codebook)은 상관관계함수에 따라 바뀌게 되는 문제가 있다. 하지만, 본 발명에서 고려하는 예측오류정보

는 비상관(uncorrelated)되어서, 상관 함수에 따른 채널 코딩 행렬집을 변경할 필요가 없다. In particular,

If there is a correlation between the change over time and the difference between antennas, there is a problem that the optimal channel coding matrix codebook is changed according to the correlation function. However, the prediction error information considered in the present invention

Is uncorrelated so that there is no need to change the channel coding matrix matrix according to the correlation function.

FIG. 2 is a schematic diagram illustrating a flow of a user terminal channel bi-directional operation in accordance with embodiments of the present invention, and FIG. 3 is a schematic diagram illustrating a flow of a base station channel demodulator operation according to embodiments of the present invention. More specifically, FIGS. 2 and 3 schematically illustrate that the k-th user-related predictive quantization process is performed in the user terminal and the base station in the embodiment.

자체 정보는 기지국(300)에 피드백하지 않는다. 대신 사용자 단말(200)은 채널예측오류 정보인

에 대한 양자화오류 정보를 기지국(300)에 피드백할 수 있다. 또한 기지국(300)은 이를 이용하여 채널정보

를 예측할 수 있다. 실시 예에서 채널 예측 오류의 크기와 방향 정보를 피드백 할 수 있다. 보다 구체적으로 상기 크기와 방향 정보는 양자화 되어 피드백 될 수 있으며, 양자화 방법은 실시 예에 따라 다르게 결정될 수 있다. Referring to FIGS. 2 and 3, the user terminal 200 of FIG.

The self information does not feed back to the base station 300. Instead, the user terminal 200 transmits channel estimation error information

Can be fed back to the base station 300. The base station 300 may also use the channel information

Can be predicted. The size and direction information of the channel prediction error can be fed back in the embodiment. More specifically, the size and direction information can be quantized and fed back, and the quantization method can be determined differently according to the embodiment.

를 기반으로 CQI를 재생성할 수 있다. 다시 말하면 CQI는

와

를 통해 묵시적(implicity)으로 피드백 될 수 있다. 실시 예에서

이며,

는 양자화 함수이다. In the embodiment, the terminal 200 does not transmit the explicit CQI information to the base station 300. The base station 300 transmits the channel information

It is possible to regenerate the CQI based on the CQI. In other words, CQI

Wow

Can be implicitly fed back via. In the example

Lt;

Is a quantization function.

와

를 피드백 할 수 있다. More specifically, the user terminal 200 of the embodiment may include at least one of a predictor 210 and a magnet 220. The magnetometer 220 of the embodiment can quantize information associated with the channel. The predictor 210 may also predict errors in channel measurements. This allows the quantization value of the channel measurement error to be obtained. Also, the user terminal 200 of the embodiment may be connected to the base station 300

Wow

Can be fed back.

The base station 300 of the embodiment may also include a predictor 310 and may optionally include a filter 320 for signal reception. The predictor 310 of the base station 300 may operate in correspondence with the predictor 210 of the user terminal 200. The base station may further include a first extractor for deriving a channel measurement error based on channel information fed back by the UE, and a second extractor for deriving a probabilistic precoding based on the channel measurement error, A selector for performing a probabilistic user selection, a controller for adjusting a transmission rank for each user during the probabilistic user selection process, and a transmitter for transmitting according to the probabilistic pricing method.

는 CDI 피드백을 위해 할당된 비트양이며 관계식

을 만족한다. 또한 실시 예에서

는 짝수의 정수일 수 있으며, h_k는는 길이 n의 벡터일 수 있다. 또한 T_CDI는 정수일 수 있으며, e_k는 e의 k번째 원소일 수 있다. 또한 Δ 값은 실시 예에 따라 다양하게 선택될 수 있으나 0보다 크고 1보다 작은 값을 가질 수 있다. 즉 시스템 Subframe 마다 보내는 피드백 양을 변수

를 통해 조절하여 CDI 관련 정보 피드백양을 효과적으로 조절할 수 있으며 다양한 추가효과를 얻을 수 있다. 예를 들어 이를 통해 기지국에서 CSI-RS 전송 주기를 조절하여 하향링크 Resource를 절약할 수 있다. 보다 구체적으로 부분 CDI 업데이트는 각 서브프레임에서 기준 신호의 수를 줄일 수 있다. 이는 기지국이 부분 CDI를 업데이트 하지 않는 서브프레임의 안테나 포트에는 CSI-RS를 전송할 필요가 없기 때문에 가능하다. 더욱이, 표 1에서 보여진 실시의 예를 통해 제안하는 기술은 기존 양자화 방법과 달리 복소수 곱셈 연산을 필요로 하지 않는다. 이와 같이 실시 예의 피드백 방법은 연산의 복잡도를 줄일 수 있다. 실시 예에서 표1의 연산은 사용자 단말의 도출기에서 수행될 수 있다. The feedback amount can be drastically reduced using the partial CDI information. An example of the proposed CDI information formation method is given in Table 1 as a brief pseudo-code. In Table 1,

Is the amount of bits allocated for CDI feedback,

. Also in the examples

May be an even integer and h _k may be a vector of length n. T _CDI may also be an integer, and e _k may be the kth element of e. Also, the value of DELTA may be variously selected according to the embodiment, but may have a value larger than 0 and smaller than 1. In other words, the amount of feedback sent per system subframe

To control the amount of CDI-related information feedback effectively and to obtain various additional effects. For example, the base station can reduce the downlink resources by adjusting the CSI-RS transmission period. More specifically, the partial CDI update can reduce the number of reference signals in each subframe. This is possible because the base station does not need to transmit the CSI-RS to the antenna port of the subframe that does not update the partial CDI. Furthermore, the technique proposed in the embodiment shown in Table 1 does not require a complex multiplication operation unlike the conventional quantization method. Thus, the feedback method of the embodiment can reduce the computational complexity. In an embodiment, the operations of Table 1 may be performed at the derivator of the user terminal.

In this manner, partial channel direction information to be transmitted can be transmitted differently according to the amount of information used for feedback.

FIG. 4 is a flowchart illustrating a flow of an operation in which a user terminal feedback channel information based on channel measurement error prediction according to embodiments of the present invention. Referring to FIG.

Referring to FIG. 4, a terminal of the embodiment can transmit and receive signals to and from a base station.

In step 410, the terminal can measure the channel between the base station and the terminal. More specifically, the channel information can be measured based on the reference signal transmitted from the base station. The reference signal may be variously applied according to a communication system.

In step 420, the terminal can quantize the channel information based on the received channel information. The method of quantizing the channel may be variously applied according to the embodiment. For example, a method of determining a precoding vector most similar to the channel based on predetermined codebook information. In addition to the precoding vector, a channel may be quantized based on a method of determining an index corresponding to channel information in a separate codebook that can represent the base channel information.

In step 430, the UE can estimate a channel measurement error. More specifically, the UE can estimate a channel measurement error based on channel information and channel quantization information, and this can be performed in a predictor of a UE. According to an embodiment, a channel measurement error may include a difference between channel information measured by the terminal and channel information quantized by the terminal.

In step 440, the UE can derive a channel direction based on at least one of the channel information, channel quantization information, and channel measurement error prediction information. More specifically, the channel direction can be performed in the same manner as the code of Table 1, and only a part of the channel direction information can be derived according to the allocated information amount.

In step 450, the UE may feed back at least one of the channel estimation error information and the channel direction information to the base station. More specifically, the channel measurement error prediction information may include a channel measurement error size and direction information, and such information may be quantized and fed back to the base station.

3. User selection technique using channel measurement error information

A user selection scheme for a multi-user wireless communication system based on channel measurement error is described below.

5 is a diagram illustrating a flow of an operation of performing probabilistic precoding design and probabilistic user selection by receiving base station feedback channel information from a user according to embodiments of the present invention. More specifically, FIG. 5 is a diagram illustrating a flow of an operation of performing probabilistic precoding design and probabilistic user selection by receiving base station feedback channel information from a user according to embodiments of the present invention.

Referring to FIG. 5, in step 510, a base station may receive channel information fed back from a user terminal. The channel information may include at least one of channel measurement error prediction information and channel direction information. The channel measurement error prediction information may include a channel measurement error size and direction information. Also, at least one of the information may be quantized and transmitted.

In step 520, the base station may derive a channel measurement error based on the received information. This step may be performed in the derivator of the base station. More specifically, the base station can derive a channel measurement error based on the quantized received information.

In step 530, the base station may derive a probabilistic precoding based on the derived information. The precoding that can maximize the channel transmission amount can be determined based on the channel measurement error derived more specifically.

In step 540, the BS may perform probabilistic user selection based on the derived channel measurement error information and the derived probabilistic precoding. In the embodiment, the sum of the transmission rates is dependent on the selected user terminal, so that the user can select the user to maximize the transmission amount, and the user selection can be performed based on the information fed back by the user terminal.

In step 550, the base station can perform signal transmission to the selected user using the derived probabilistic precoding.

The reception vector at the k-th user terminal can be expressed by the following equation.

을 의미한다.In Equation (8)

.

가 수신기에서 적용된다면 관계식

를 기반으로 출력은

와 같을 수 있으며,

는

으로 나타낼 수 있다. 상기 백색화 필터를 수신 벡터에 적용하면, k번째 사용자에게 기대되는 전송속도(rate)는 다음식으로 주어진다. From equation (8)

Is applied at the receiver,

Based on the output

, ≪ / RTI >

The

. If the whitening filter is applied to the received vector, the rate of transmission expected for the k-th user is given by:

를 나타내며

는 선택된 사용자집합을 의미한다.In Equation (9)

Represents the

Means a selected set of users.

는 상기 선택된 사용자 집합에 따라 변하게 되고, 수학식 (9)는 상기 선택된 사용자 집합에 따라 전송속도가 다름을 보여준다. 따라서 전송률의 합

는 사용자 선택에 종속적(dependent)이다. The precoding given in equation (3)

Is changed according to the selected set of users, and Equation (9) shows that the transmission rates are different according to the selected set of users. Therefore,

Is dependent on user selection.

을 알 수 없다. 이로 인해, 기존의 결정론적 송수신 방법에서는 하향링크 채널

대신 피드백 채널정보

이용하여 수학식 (9)의

를 구할 수 있다. Table 2 is a brief pseudocode showing the flow of operations to select a user based on Equation (9). Generally, a base station transmits a complete downlink channel

Can not be known. Therefore, in the conventional deterministic transmission / reception method,

Instead,

(9) < RTI ID = 0.0 >

Can be obtained.

와

을 사용하였다. 또한

는

를 기반으로 얻어질 수 있다. In the equation (10)

Wow

Were used. Also

The

. ≪ / RTI >

을 이용하여 수학식 (9)의

를 다음과 같이 구한다. 예를 들어 수학식 (11)과 같이 구할 수 있다. However, in the proposed probabilistic transmission / reception method,

(9) using Equation

Is obtained as follows. For example, it can be obtained by the following equation (11).

와

을 사용하였다. 수학식 (11)에서

값은 채널측정오류 피드백 정보를 이용하게 구할 수 있다.In the equation (10)

Wow

Were used. In Equation (11)

The value can be obtained using channel measurement error feedback information.

The transmission rates that can be obtained through the probabilistic transmission / reception method through Equations (9) and (11) are as follows.

4. Simulation Results In this section, the proposed probabilistic transmission / reception method will be evaluated in comparison with the conventional deterministic transmission / reception method in order to demonstrate the efficiency of the proposed method according to the embodiments of the present invention. Table 3 describes the simulation assumptions used for the simulation.

In particular, in this example simulations, we can compare the performance considering Doppler channel change and channel information error due to quantization.

FIG. 6 is a graph showing an example of performance between a probabilistic transmission and reception technique to which embodiments of the present invention are applied and a conventional deterministic transmission and reception technique in a time-varying channel change environment. FIG. FIG. 2 is a diagram illustrating a performance example between a conventional STN technique and a conventional deterministic STN technique in a channel-changing environment correlated with time. FIG.

Figure 6 compares the performance of the proposed method with that of the existing method. In FIG. 6, it is assumed that there is no correlation between the antennas. The solid line shows the transmission rate obtained by the proposed probabilistic transmission / reception method, and the dotted line shows the transmission rate obtained by the conventional deterministic transmission / reception method. The dotted line at the top shows the ideal transmission rate maximum, assuming perfect channel information without errors in the base station. As can be seen in FIG. 6, as the Doppler effect increases, that is, as the channel information error increases in the base station, the performance difference between the proposed probabilistic method and the existing deterministic method increases. In FIG. 7, it is assumed that there is a correlation between the antennas. It can be seen from the results in FIG. 7 that the proposed method effectively utilizes the correlation and increases the performance improvement compared to the conventional method.

As a result, as can be seen from Figs. 6 and 7, a remarkable improvement can be obtained by using the proposed stochastic transmission / reception method as compared with the existing deterministic method.

5. Conclusion

Embodiments of the present invention are directed to a stochastic transmission and reception method and apparatus in a multi-antenna multi-user wireless communication system. The embodiment may include a process of predicting a channel measurement error, a process of determining a stochastic precoding, and a process of selecting a probabilistic user. It is not necessary to change the codebook according to the channel environment through the CDI feedback based on the quantization prediction and complex complex multiplication operation during the quantization process is not necessary. Simulation results show that using the proposed probabilistic transmission / reception method results in a significant performance improvement compared to the conventional deterministic method.

According to an embodiment of the present invention, a method of operating a measuring device for obtaining link channel information from a base station of a user terminal of a wireless communication system includes the steps of quantizing a channel measured by the terminal, Estimating a measurement error, and deriving channel direction information to feed back the channel measurement error.

According to another embodiment of the present invention, a measuring apparatus for obtaining a link channel from a base station of a user terminal of a wireless communication system includes: a quantizer which quantizes the measured channel; An estimator for deriving channel direction information for feeding back the channel measurement error, and a transmitter for feeding back the channel direction information to the base station. Also, in the first embodiment, the transmitter may be included in the transmission / reception unit.

According to another embodiment of the present invention, a base station of a wireless communication system designs stochastic precoding using feedback channel information from a terminal and performs probabilistic user selection by deriving a channel measurement error using the feedback channel information , Deriving probabilistic precoding using the channel measurement error, selecting a probabilistic user based on the precoding, and adjusting a transmission rank for each user during the probabilistic user selection process And transmitting in accordance with the stochastic transmission method.

According to another embodiment of the present invention, an apparatus for stochastic precoding designing and probabilistic user selection using feedback channel information from a terminal in a wireless communication system derives a channel measurement error using the feedback channel information A second derator for deriving a probabilistic precoding using the channel measurement error, a selector for selecting a probabilistic user based on the precoding, and a transmitter for selecting a transmission rank per user in the probabilistic user selection process Transmit Rank), and a transmitter for transmitting according to the probabilistic method.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Do. The scope of the present invention should, therefore, be determined not only by the details of the embodiments described, but also by the appended claims and their equivalents.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And is not intended to limit the scope of the invention. It is to be understood by those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

100: base station
110, 120: user terminal
210: User terminal predictor
220: User terminal magnetism
310: base station predictor

Claims (20)

A method of transmitting and receiving signals in a terminal of a mobile communication system,
Receiving a reference signal from a base station;
Measuring channel information based on the received reference signal;
Estimating a channel measurement error based on the measured channel information; And
And transmitting feedback information generated based on the predicted information to a base station. The method according to claim 1,
The step of predicting the channel measurement error
Quantizing the measured channel information based on preset information; And
And estimating a channel measurement error based on the quantized channel measurement information and the measured channel information. The method according to claim 1,
The step of transmitting the feedback information to the base station
Quantizing size information and direction information of the channel measurement error; And
And transmitting the quantized size information and direction information to the base station. 2. The method of claim 1, wherein the feedback information includes direction information of the measured channel. The method according to claim 1,
And receiving a signal to which the precoding method determined based on the feedback information is applied from the base station. A method of transmitting and receiving signals in a base station of a mobile communication system,
Transmitting a reference signal to a terminal; And
And receiving feedback information generated based on the reference signal,
Wherein the feedback information is generated based on channel measurement error information predicted by the terminal based on the reference signal. The method according to claim 6,
The predicted channel measurement error
Wherein the channel estimating unit includes quantization of channel information measured based on the reference signal based on predetermined information and information determined based on the quantized channel measurement information and the measured channel information. . The method according to claim 6,
The feedback information
And quantizing the size of the channel measurement error and direction information. The method according to claim 6,
Wherein the feedback information includes direction information of the measured channel. The method according to claim 6,
Selecting a user terminal based on the feedback information;
Determining a precoding method based on the feedback information; And
And transmitting the signal by applying the determined precoding to the selected user terminal. A terminal for transmitting and receiving signals in a mobile communication system,
A transmission / reception unit for transmitting / receiving signals to / from a base station; And
Receiving a reference signal from the base station, measuring channel information based on the received reference signal, estimating a channel measurement error based on the measured channel information, And transmitting the generated feedback information to the base station. 12. The method of claim 11,
The control unit
Quantizes the measured channel information based on preset information, and estimates a channel measurement error based on the quantized channel measurement information and the measured channel information. 12. The method of claim 11,
The control unit
Quantizes size information and direction information of the channel measurement error, and transmits the quantized size information and direction information to the base station. 12. The method of claim 11,
Wherein the feedback information includes direction information of the measured channel. 12. The method of claim 11,
The control unit
And receives a signal to which the precoding method determined based on the feedback information is applied from the base station. A base station for transmitting and receiving signals in a mobile communication system,
A transmitting and receiving unit for transmitting and receiving signals to and from the terminal; And
And a controller for controlling the transceiver, transmitting a reference signal to the terminal, and receiving feedback information generated based on the reference signal,
Wherein the feedback information is generated based on channel measurement error information predicted by the UE based on the reference signal. 17. The method of claim 16,
The predicted channel measurement error
Wherein the terminal comprises channel information measured based on the reference signal on the basis of predetermined information, and information determined based on the quantized channel measurement information and the measured channel information. 17. The method of claim 16,
The feedback information
And quantizing the size of the channel measurement error and direction information. 17. The method of claim 16,
Wherein the feedback information includes direction information of the measured channel. 17. The method of claim 16,
The control unit
Selects a user terminal based on the feedback information, determines a precoding method based on the feedback information, and transmits the signal by applying the determined precoding to the selected user terminal.

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