KR101006766B1 - Signal transferring controller in base station - Google Patents

Abstract

The present invention relates to a transmission control apparatus of a base station.

To this end, the present invention selects at least one terminal capable of obtaining a maximum system capacity based on channel information and interference signal information of each of a plurality of terminals, and a scheduler and a feedback channel for extracting feedback channel information corresponding to the selected terminal. A correlation calculator that calculates a correlation value between the plurality of channels based on the information, and a transmission method of transmitting a signal to the selected mobile terminal based on the correlation value and the feedback channel information between the plurality of channels, and the determined transmission scheme In accordance with the present invention, there is provided a transmission control apparatus of a base station including a transmission control unit generating a control signal for driving a plurality of antennas.

According to the present invention, it is possible to implement a transmission control apparatus of a base station having excellent signal transmission efficiency.

Multiple antenna, base station, channel-to-channel correlation

Description

Transmission control device of base station {SIGNAL TRANSFERRING CONTROLLER IN BASE STATION}

The present invention relates to a transmission control apparatus of a base station.

In general, various multi-antenna transmission techniques proposed for increasing channel capacity of wireless communication are designed based on point-to-point communications between a terminal and a base station antenna.

Recently, an advanced one-to-many communication scheme has been proposed rather than a one-to-one communication scheme. One-to-many communication is a communication method for each individual base station antenna to provide a service to one terminal. If there is a service request from a larger number of terminals than the number of base station antennas, priority is given to a terminal having excellent channel gain. Provide service.

Recently, a multiple antenna transmission / reception scheme (hereinafter, referred to as “MIMO”) that provides a service using two or more base station antennas for a single UE has been proposed. An adaptive MIMO scheme is also proposed to change the MIMO scheme.

The adaptive MIMO scheme provides a service based on a wide range of information such as interference signal, quality of service (hereinafter referred to as "QoS") and feedback information. Better QoS to the terminal than Can provide.

However, the adaptive MIMO scheme does not consider the correlation between the multi-user environment or the antenna channel.

In the one-to-one communication scheme, the spatial diversity obtained by the MIMO system using the MIMO scheme is in conflict with the multi-user diversity obtained in the one-to-many communication scheme. In one-to-one communication, a transmit diversity scheme combines the diversity of independent channel changes to obtain diversity gains that reduce the impact of ultimate channel changes. On the other hand, in the one-to-many communication scheme, spatial diversity attenuates the channel variation of each terminal receiving a service, thereby reducing the multi-user diversity gain depending on the gain through user scheduling due to a large channel variation. .

In a multi-user communication system, the correlation between the antenna and the channel is clearly shown. If the characteristics of the correlation between the antenna and the channel are clearly shown, performance degradation occurs in which the spatial diversity gain and the spatial multiplexing gain obtained through the multi-antenna system are greatly reduced. In particular, the spatial multiplexing method becomes a problem because performance deterioration due to channel correlation is more serious than the spatial diversity method.

The present invention has been made in an effort to provide a transmission control apparatus of a base station having excellent signal transmission efficiency.

A transmission control apparatus of a base station according to an aspect of the present invention is a transmission control apparatus of a base station including a plurality of antennas, and at least one capable of obtaining a maximum system capacity based on channel information and interference signal information of each of the plurality of terminals. A scheduler for selecting a terminal and extracting feedback channel information corresponding to the selected terminal, a correlation calculator for calculating a correlation value between the plurality of channels based on the feedback channel information, and a correlation value between the plurality of channels. And a transmission controller configured to determine a transmission scheme for transmitting a signal to the selected mobile terminal based on the feedback channel information, and to generate a control signal for driving the plurality of antennas corresponding to the determined transmission scheme.

According to an aspect of the present invention, the transmission control apparatus of the base station that greatly improves the signal transmission efficiency by performing the maximum capacity prediction in consideration of the inter-channel correlation and the influence of multi-user diversity, and determining the signal transmission method based on this Can be implemented.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. 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 the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. Also, the term "part" or the like, as described in the specification, means a unit for processing at least one function or operation, and may be implemented by hardware, software, or a combination of hardware and software.

In the present specification, a base station (BS) is an access point (AP), a radio access station (Radio Access Station, RAS), a Node B (Node B), a base transceiver station (Base Transceiver Station, BTS), MMR ( Mobile Multihop Relay) -BS and the like, and may include all or part of functions such as an access point, a radio access station, a Node B, a base transceiver station, and an MMR-BS.

Hereinafter, a multi-antenna transmission apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically showing a MIMO system according to an embodiment of the present invention, Figure 2 is a schematic block diagram of a transmission control apparatus shown in FIG.

As shown in FIG. 1, the base station 100 and the plurality of terminals 200 perform signal transmission and reception through channels h _{k , 1} to h _{k, M.} The base station 100 includes a plurality of terminals 200 and a plurality of antennas 120 for transmitting and receiving signals and a transmission control apparatus 110 for controlling the plurality of antennas 120.

As shown in FIG. 1, the base station 100 according to the embodiment of the present invention includes a transmission control apparatus 110 and a multiple antenna unit 120.

The multiple antenna unit 120 includes a plurality of antennas 120. For reference, FIG. 1 illustrates each of the first to Mth antennas 120-1 to 120 -M and the first to kth terminals 200-1 to 200 of the base station 100 of the MIMO system according to an embodiment of the present invention. -k) shows an example of signal transmission and reception between. Here, h _{k , 1} to h _{k , M} are channels formed between the first to k th terminals 200-1 to 200-k and the first to M th antennas 120-1 to 120 -M. In FIG. 1, signals transmitted to each of the first to kth terminals 200-1 to 200-k by the first to Mth antennas 120-1 to 120 -M are represented by solid lines. Feedback information transmitted from each of the kth terminals 200-1 to 200-k to the first to Mth antennas 120-1 to 120 -M is indicated by a dotted line.

The transmission control apparatus 110 improves transmission efficiency by controlling the plurality of antennas 120 in consideration of the influence of channel correlation and multi-user diversity.

Referring to FIG. 2, the transmission control apparatus 110 receives feedback information from a plurality of terminals 200 and selects a transmission scheme corresponding to the received feedback information. In this case, each terminal 200 may determine the feedback information using Channel Quality Indicator (CQI), codebook, or the like.

The transmission control apparatus 110 includes a correlation calculator 111, a scheduler 112, a precoder 113, a transmission controller 114, and a switching unit 115.

The switching unit 115 operates under the control of the transmission control unit 114 and selectively transmits input data to the precoder 113 or the plurality of transmitting antennas 120.

The precoder 113 precodes data input through the switching unit 115, and transmits the precoded data to the plurality of transmit antennas 120.

The scheduler 112 selects at least one terminal capable of acquiring a maximum system capacity based on channel information and interference signal information of each of the plurality of terminals 200, and feedback channel information and feedback channel information corresponding to the selected terminal. The number of the terminal for transmitting the information is transmitted to the transmission control unit 114.

The correlation calculator 111 calculates a correlation value between channels h _{k , 1} to h _{k , M} based on the feedback channel information and the interval information between the transmitting antennas, and transmits the correlation value to the transmission control unit 114. . In addition, the correlation calculator 111 selectively performs either a maximum capacity calculation or a sequential statistical calculation to predict the maximum capacity of the MIMO system according to an embodiment of the present invention, and transfers the calculation result to the transmission control unit 114. do.

The transmission control unit 114 based on the calculation result input from the correlation calculator 111, the number of terminals performing signal transmission and reception with the base station, the amount of interference signal, QoS and feedback information, as well as the correlation between the channel (Correlation) and multiplexing The effects of user diversity are combined to determine transmit diversity, spatial multiplexing, and precoding.

In particular, the transmission control unit 114 determines whether or not to precode data by controlling the switching unit 115 according to the amount of feedback information. That is, when the amount of feedback information exceeds the set value, the transmission control unit 114 transfers the data input to the switching unit 115 to the precoder 113 and precodes the plurality of transmission antennas 120-1 to 120 -M. To be delivered). On the other hand, if the amount of feedback information is less than or equal to the set value, the transmission control unit 114 transmits the data input to the switching unit 115 directly to the plurality of transmission antennas 120 without passing through the precoder 113.

The transmission control unit 114 determines a channel capacity allocated to each of the plurality of transmission antennas 120 and a signal transmission method to the terminal 200 based on the determined transmission diversity, spatial multiplexing technique, and precoding technique, and correspondingly. A control signal for controlling the plurality of transmission antennas 120 is generated.

Transmission control apparatus 110 according to an embodiment of the present invention, when transmitting a signal to a plurality of terminals 200, based on the correlation (Correlation) between the channels (h _{k , 1} ~ h _{k , M} ) Spacial Diversity In consideration of the mutual organic relationship between the gain and the diversity (hereinafter, referred to as "multi-user diversity") gain corresponding to the number of terminals, the second gain is combined to maximize the final gain.

If the correlation between channels becomes large, spatial diversity decreases, but multi-user diversity increases, so that both spatial diversity and multi-user diversity cannot be increased. For this reason, the correlation calculator 111 selectively performs either a maximum capacity calculation or a sequential statistical calculation, and based on this, the switching controller 114 determines a signal transmission scheme for the terminal, thereby allowing spatial diversity. And multi-user diversity gain, thereby maximizing the final gain.

Hereinafter, the maximum capacity calculation among the maximum capacity calculation and the sequential statistical calculation, which are the maximum capacity prediction techniques performed by the correlation calculator 111, will be described first.

In the MIMO system according to the embodiment of the present invention of FIG. The allocated channel h _k is a matrix of channels allocated to each of the first to k th terminals 200-1 to 200-k, which is represented by Equation 1 below.

과 같으면, 상관 행렬 R_T는 수학식 2와 같다. Assuming that there is no correlation between the first to Mth antennas 120-1 to 120 -M, a correlation matrix indicating a correlation between the first to Mth antennas 120-1 to 120 -M ( R _T )

And equal, the correlation matrix R _T is equal to the equation (2).

는제1 내지 제M 안테나(120-1 ~ 120-M)들 상호간의 상관계수(correlation))(From here,

Is a correlation coefficient between the first to Mth antennas 120-1 to 120-M)

Assuming that a signal transmission scheme that maximizes multi-user diversity gain is applied, the maximum capacity C obtained through the transmit diversity scheme (TD) based on the correlation matrix R _T shown in Equation 2 _TD is represented by Equation 3 below.

는 평균 신호 대 잡음비(Average Signal-to-Noise Ratio; ASNR))(From here,

Is the Average Signal-to-Noise Ratio (ASNR)

The transmit diversity scheme in a multi-user environment is as follows.

The base station 100 selects one terminal having the best channel state among the terminals 200-1 to 200 -K, and connects antennas of the first to Mth antennas 120-1 to 120 -M to the selected terminal. All of them are allocated and a signal is transmitted to the selected terminal through a space-time code (STC). This allows for both spatial diversity gain and multi-user diversity gain.

In contrast, in the antenna selection (AS) scheme, each of the first to K-th terminals 200-1 to 200 -K is a channel for each of the first to Mth transmit antennas 120-1 to 120 -M. The transmit antenna having the largest gain is selected and fed back. In this case, each of the first to Mth transmission antennas 120-1 to 120 -M may have K terminals 200-1 to 200 -K based on feedback information of each of the K terminals 200-1 to 200 -K. Select one terminal having the maximum channel gain and transmit a signal to the selected terminal. By doing so, a spatial diversity gain and a multi-user diversity gain can be obtained. The maximum capacity C _AS obtained through the antenna selection (AS) method can be expressed by Equation 4 below.

Meanwhile, a spatial multiplexing (SM) technique is used to obtain a multiplexing gain in a multi-user environment. In the multi-user environment, each of the first to Mth antennas 120-1 to 120 -M is the first to kth. A terminal having a maximum signal-to-interference and noise ratio (hereinafter referred to as " SINR ") among the terminals 200-1 to 200-k is selected and transmitted. Such a signal transmission using a spatial multiplexing technique can simultaneously obtain a multiplexing gain and a multi-user gain, but has a disadvantage in that a spatial diversity gain cannot be obtained.

The maximum capacity C _SM in the signal transmission using the spatial multiplexing technique is expressed as follows.

In this case, SINR is represented by Equation 6 below.

의 역수)Where σ ² is the average signal-to-noise ratio

Reciprocal of)

는 다음과 같다.In addition, the transmit antenna index having the maximum SINR among the first to k-th terminal

Is as follows.

In addition, TD-Maximum Ratio at Transmitter (TD) and TD (Maximum Ratio Combining; hereinafter referred to as "MRC") techniques are simultaneously applied in a multi-user environment. . -MRT technique referred to as ") when on, if the user have selected the optimum maximum capacity C _TD can be obtained _- indicates the _MRT by the following equation as the equation 8 below.

Meanwhile, an optimal user may be selected when transmitting a signal using a transmission diversity (TD) technique and a phase adjustment (PS) technique (hereinafter, referred to as a "TD-PS technique"). when _TD maximum capacity C can be obtained _- represents the _PS as shown in equation 9, equation below.

The TD-MRT technique requires all channel information of each of the first to k th terminals, whereas the TD-PS technique requires only channel phase information of each of the first to k th terminals, compared to the TD-MRT technique. The amount of feedback information required when applying the PS technique is relatively small.

On the other hand, the maximum capacity that can be obtained when applying a power loading technique (hereinafter referred to as "SM-PL technique") that allocates power according to a channel to a spatial multiplexing (SM). C _{SM - PL} can be expressed as

In this case, SINR, σ, and β are represented by Equation (11). Here, β is a power loading portion (Portion) that is loaded for each channel of the total power.

The correlation calculator 111 calculates the maximum capacity using the above-described Equations 1 to 11. To this end, the correlation calculator 111 may include a database storing the above-described Equations 1 to 11.

In addition, the switching control unit 114 is a correlation between the channel, the number of terminals performing signal transmission and reception with the base station 100, the interference signal, the amount of QoS and feedback information, the correlation between channels in the calculation result input from the correlation calculator 111 It may include a table that stores values such as (Correlation) and multi-user diversity, and a functional relationship between them, and may generate a selection signal based on this.

The transmission control device 110 may obtain a relatively more accurate calculation value when performing the maximum capacity calculation than when performing the sequential statistical calculation. However, the maximum capacity calculation requires channel information of all terminals performing signal transmission and reception with the base station 100. Thus, if the number of terminals performing signal transmission and reception with the base station 100 increases by more than a predetermined level when the transmission control apparatus 110 performs the maximum capacity calculation, the feedback information required by the transmission control apparatus 110 is required. There is a disadvantage in that the amount of is greatly increased.

On the other hand, the sequential statistical calculation is a reception that each of the base station antennas 120-1 to 120-M receives from the terminals 200-1 to 200-k instead of the channel information of all terminals that transmit and receive signals with the base station 100. The signal-to-noise ratio (hereinafter referred to as "SNR") of the signal is calculated based on statistics. For this reason, the sequential statistical calculation has an advantage in that the amount of feedback information required is significantly smaller than in the case of performing the maximum capacity calculation.

The correlation calculator 111 according to an embodiment of the present invention calculates the amount of feedback information to be predicted, and based on this, selects either a maximum capacity calculation or a sequential statistical calculation to be set to predict the maximum capacity. It may be. That is, the correlation calculator 111 according to an embodiment of the present invention performs a maximum capacity calculation that can extract a more accurate result when the size of the feedback information is small, and the size of the feedback information is larger when performing the maximum capacity calculation. If the cursor load is large, it may be set to perform sequential statistical calculation.

When scheduling is applied in a multi-user environment, the sequential statistical equation performed by the correlation calculator 111 is expressed by Equation 12.

은 랜덤 변수에 대한 기대값(expectation),

은 랜덤 변수에 대한 분산(variation))(From here,

Is the expectation for a random variable,

Is the variance of a random variable)

Referring to the sequential statistical equation of Equation 12, the expected value of the signal-to-noise ratio (SNR) of the received signal after scheduling is distributed and the number of terminals transmitting and receiving signals to and from the base station 100 increases. It can be seen that the larger.

For reference, among the aforementioned multi-antenna transmission schemes, the spatial multiplexing technique has a disadvantage in that the maximum capacity is largely determined by the correlation between channels as in the one-to-one communication scheme. On the other hand, the antenna selection technique exhibits an insensitive effect on the correlation between channels. In addition, unlike the one-to-one communication scheme, the transmission diversity scheme has a characteristic that the maximum capacity increases as the correlation between channels increases. Therefore, by effectively reflecting these characteristics, it is possible to maximize the gain that can be obtained in a given multi-user environment by adaptively selecting the multi-antenna transmission technique.

Hereinafter, the signal transmission scheme selection of the transmission control apparatus 110 according to the embodiment of the present invention illustrated in FIG. 2 will be described with reference to FIGS. 3 and 4.

FIG. 3 exemplarily illustrates a correlation between channel correlation and channel capacity according to a signal transmission method when the number of terminals K is 20 and the average signal-to-noise ratio ASR is 6 dB. Figure is shown. 4 is a diagram illustrating a correspondence relationship between the number of terminals that transmit and receive a signal to and from a base station 100 according to a signal transmission method and a channel capacity when the channel correlation value is 0.1.

Referring to FIG. 3, when the channel correlation value is 0.2 or less, the channel capacity of the SM-PL scheme is the largest, and when 0.2 or more, the channel capacity of the TD-MRT technique is the largest.

4, the channel capacity of the TD-MRT scheme is the largest when the number of terminals that transmit and receive signals with the base station 100 is 20 or less, and when the number of terminals is 20 or greater, the SM-PL scheme or the SM scheme is used. Channel capacity is larger than other techniques.

Transmission control apparatus 110 according to an embodiment of the present invention is a base station 100 according to the correlation between the correlation (Correlation) and channel capacity (Throughput) according to the signal transmission method of Figure 3 and the signal transmission method of Figure 4 ) May be configured to determine a signal transmission scheme in consideration of any one or both of the correspondence between the number of terminals transmitting and receiving a signal and the channel throughput. In addition, the transmission control apparatus 110 according to the embodiment of the present invention transmits signals based on specific variables and thresholds set by a system administrator, that is, interference signals, QoS, and feedback information amounts, which are different from those shown in FIGS. 3 and 4. It may be set to change the manner.

The MIMO system according to the above-described embodiment of the present invention selectively performs two calculation methods of maximum capacity calculation and sequential statistical calculation to perform maximum capacity prediction. Here, whether one of the two calculation methods, the maximum capacity calculation and the sequential statistical calculation, is used for the maximum capacity prediction, the number of terminals performing signal transmission / reception with the base station, the interference signal, the QoS and the amount of feedback information, It is determined considering both the correlation between channels and the effects of multi-user diversity. MIMO system according to an embodiment of the present invention has the advantage that the memory capacity to be provided to implement the optimum transmission efficiency, and to store the amount of feedback information can be greatly reduced.

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a view schematically showing a MIMO system according to an embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating a transmission control unit included in the base station of FIG. 1 to control a plurality of antennas.

FIG. 3 exemplarily illustrates a correlation between channel correlation and channel capacity according to a signal transmission method when the number of UEs is 20 and the average signal-to-noise ratio (ANSR) is 6 dB. Figure is shown.

FIG. 4 is a diagram exemplarily illustrating a correspondence relationship between the number of terminals that transmit and receive a signal to and from a base station according to a signal transmission method and channel capacity when the channel correlation value is 0.1.

Claims (6)

In the transmission control apparatus of a base station including a plurality of antennas, A scheduler for selecting at least one terminal capable of obtaining a maximum system capacity based on the feedback channel information and the interference signal information of each of the plurality of terminals transmitted from the plurality of terminals, and extracting the feedback channel information corresponding to the selected terminal. ; A correlation calculator configured to calculate a correlation value between the plurality of channels based on the feedback channel information; And Based on the correlation value between the plurality of channels, the number of terminals transmitting the feedback channel information, and the feedback channel information, a transmission scheme for transmitting a signal to the selected mobile terminal is determined, and corresponding to the determined transmission scheme Transmission control unit for generating a control signal for driving the plurality of antennas Transmission control apparatus of the base station comprising a. The method of claim 1, A precoder for precoding an input signal and transferring the signal to the plurality of antennas; And And a switching unit which is driven under the control of the transmission control unit and selectively transmits the signal to the precoder or the plurality of antennas. The method of claim 2, The transmission control unit, Transmission control apparatus of the base station for controlling the operation of the switching unit in response to the amount of the feedback channel information. The method of claim 3, The transmission control unit, Transmitting a signal to the precoder when the amount of the feedback channel information exceeds the set value, and transmitting the signal to the plurality of antennas when the amount of the feedback channel information is equal to or less than the set value. controller. The method of claim 1, And the correlation calculator selectively performs either a maximum capacity calculation or a sequential statistical calculation to predict the maximum system capacity. 6. The method according to any one of claims 1 to 5, The determined transmission scheme is And a base station's transmission control apparatus for maximizing a gain obtained by combining a spatial diversity gain corresponding to the correlation between the plurality of channels and a multi-user diversity gain corresponding to the number of terminals.

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