WO2019182134A1

WO2019182134A1 - Base station and transmission method

Info

Publication number: WO2019182134A1
Application number: PCT/JP2019/012178
Authority: WO
Inventors: 達樹奥山; 聡須山; 奥村　幸彦
Original assignee: 株式会社Ｎｔｔドコモ
Priority date: 2018-03-23
Filing date: 2019-03-22
Publication date: 2019-09-26
Also published as: JPWO2019182134A1; CN111903065B; CN111903065A; JP7261223B2

Abstract

A base station comprising: a transmission circuit that sends wireless signals; and a control circuit that controls the transmission of the wireless signals on the basis of a channel estimation value selected in accordance with first and second selection criteria, from among a plurality of channel estimation values obtained for each channel between a user terminal and a plurality of antenna elements included in a plurality of transmission points.

Description

Base station and transmission method

This disclosure relates to a base station and a transmission method.

In the UMTS (Universal Mobile Telecommunication System) network, Long Term Evolution (LTE: Long Term Evolution) has been specified for the purpose of further high data rate and low delay (Non-patent Document 1). In addition, a successor system of LTE is also being studied for the purpose of further widening the bandwidth and speeding up from LTE. LTE successors include LTE-A (LTE-Advanced), FRA (Future Radio Access), 5G (5th generation mobile mobile communication system), 5G + (5G plus), New-RAT (Radio Access Technology), etc. There is a system called.

In future wireless communication systems (for example, 5G), a large number of antenna elements (for example, 100 elements or more) are used in a high frequency band (for example, 4 GHz or more) in order to further increase the speed of signal transmission and reduce interference. The use of massive MIMO (Multiple Input Multiple Output) is being studied. In Massive MIMO, a wireless communication system using an ultra-high-density distributed antenna system including a plurality of transmission points (TP) each having one or more antenna elements and a signal processing device is being studied. (For example, Non-Patent Document 1).

However, in an environment where there are a plurality of transmission points and a plurality of user terminals (UE: UsermentEquipment) as in an ultra-high density distributed antenna system, a method for selecting a channel to be used for signal transmission has been sufficiently studied. Not.

Therefore, an object of one embodiment of the present disclosure is to provide a base station and a transmission method that can appropriately select a channel used for signal transmission.

A base station according to an aspect of the present disclosure includes a plurality of channel estimations obtained for each channel between a transmission circuit that transmits a radio signal, a plurality of antenna elements included in a plurality of transmission points, and a user terminal A control circuit that controls transmission of the radio signal based on a channel estimation value selected according to a first selection criterion and a second selection criterion from among the values.

According to the present disclosure, a channel used for signal transmission can be appropriately selected.

It is a figure which shows the structural example of a radio | wireless communications system. It is a block diagram which shows the structural example of a base station. It is a block diagram which shows the structural example of a user terminal. It is a figure which shows an example of the transmission point in a radio | wireless communications system, and a user terminal. It is a flowchart which shows the operation example of a base station. It is a figure which shows an example of the selection process of an antenna element and a user terminal. It is a flowchart which shows an example of the selection process of an antenna element. It is a figure which shows an example of the column vector for every antenna element. It is a flowchart which shows an example of the selection process of a user terminal. It is a figure which shows an example of the selection process of a user terminal. It is a figure which shows an example of the hardware constitutions of a base station and a user terminal.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[Configuration of wireless communication system]
FIG. 1 shows a configuration example of a radio communication system according to the present embodiment. A radio communication system 1 shown in FIG. 1 is, for example, an ultra-high density distributed antenna system, and includes a base station (also referred to as a radio base station or gNB) 100 including a plurality of transmission points 10a to 10i and a signal processing device 20. And at least one user terminal (sometimes referred to as a radio terminal or UE (User Equipment)) 200.

When the same type of elements are described separately, reference numerals are used such as “transmission points 10a to 10i”, “user terminal 200a”, and “user terminal 200b”, and the same types of elements are not distinguished. In this case, a common number among the reference symbols may be used such as “transmission point 10” and “user terminal 200”.

Each of the transmission points 10a to 10i has one or more antenna elements. Each of the transmission points 10a to 10i is connected to the signal processing device 20. Further, as shown in FIG. 1, the cells formed by the transmission points 10a to 10i, for example, overlap each other.

For example, in FIG. 1, the base station 100 performs wireless communication with the

user terminals

200a and 200b under the transmission points 10a to 10i (for example, in a cell). For example, the base station 100 selects at least one transmission point 10 from the transmission points 10 a to 10 i according to the movement of the user terminal 200, and the selected transmission point 10 transmits a signal to the user terminal 200. To do.

The signal processing device 20 performs signal processing of a signal transmitted to the user terminal 200. The signal processed signal is output to at least one of the transmission points 10a to 10i and wirelessly transmitted to the user terminal 200. Further, the signal processing device 20 receives the signals from the user terminals 200 received by the transmission points 10a to 10i from the transmission points 10a to 10i, respectively.

As described above, in the wireless communication system 1 shown in FIG. 1, there are a plurality of transmission points 10 (a plurality of antenna elements) and a plurality of user terminals 200. The signal processing device 20 selects a channel to be used for signal transmission from a plurality of channels between the plurality of antenna elements and the plurality of user terminals 200.

Here, when a large number of antenna elements are provided, such as Massive MIMO, when selecting a channel to be used for signal transmission in the signal processing device 20, calculation is performed for all possible combinations of the antenna elements and the user terminal 200. Then, enormous amount of calculation is expected.

Therefore, in one aspect of the present disclosure, a method for reducing the amount of calculation when the base station 100 selects a channel to be used for signal transmission will be described.

In FIG. 1, two user terminals 200 are shown, but the number of user terminals 200 is not limited to this. For example, one user terminal 200 may exist under the transmission points 10a to 10i, and three or more user terminals 200 may exist. Alternatively, the user terminal 200 may not exist under any of the transmission points 10a to 10i.

Further, the number of transmission points 10 included in the base station 100 is not limited to nine transmission points 10a to 10i, but may be other numbers. Further, the number of antenna elements included in each transmission point 10 may be the same or different.

Also, the transmission point may be referred to as “overhanging station” or “RRH (Remote Radio Radio Head)”. In addition, the signal processing apparatus may be called “BBU (Baseband processing Unit)”.

[Base station configuration]
FIG. 2 is a block diagram illustrating a configuration example of the base station 100. FIG. 2 shows a configuration related to downlink data transmission, and a configuration related to uplink data reception is omitted.

The base station 100 shown in FIG. 2 includes n (an integer greater than or equal to 1) transmission points 10 and a signal processing device 20. For example, the transmission points 10a to 10i shown in FIG. 1 correspond to the transmission points 10-1 to 10-9 of n = 9 in FIG.

The signal processing device 20 includes an encoding unit 101, a modulation unit 102, a channel estimation unit 103, a selection unit 104, and a transmission control unit 105. The transmission points 10-1 to 10-n are A wireless transmission unit 106, an antenna 107, and a wireless reception unit 108 are included.

In FIG. 2, for example, when performing OFDM (Orthogonal Frequency Division Multiplexing) transmission, the base station 100 generates an OFDM signal (for example, IFFT (Inverse Fast Fourier Transform) processing unit, CP (Cyclic Prefix)). (Additional part) etc. are omitted.

The encoding unit 101 encodes input transmission data, and outputs the encoded transmission data to the modulation unit 102.

Modulation section 102 modulates the transmission data input from encoding section 101 and outputs the modulated transmission data to transmission control section 105.

The channel estimation unit 103 receives a reference signal (channel estimation reference signal) transmitted from each user terminal 200 and received by the antenna 107 (antenna element) of the transmission point 10 of the base station 100.

The channel estimation unit 103 estimates a channel between each user terminal 200 and the antenna element of each transmission point 10 using the reference signal, and outputs a channel estimation result to the selection unit 104 and the transmission control unit 105. In the present embodiment, the wireless communication system 1 uses a TDD (Time Division Division Duplex) transmission method. For this reason, the channel estimation unit 103 can estimate the downlink channel between the transmission point 10 and the user terminal 200 using the reference signal (that is, the uplink signal) transmitted from the user terminal 200.

The selection unit 104 (for example, a scheduler) selects a channel to be used for signal transmission based on a channel estimation result input from the channel estimation unit 103 between the user terminal 200 and the transmission point 10 (antenna element). . For example, the selection unit 104 selects the user terminal 200 that is a signal transmission target. The selection unit 104 selects an antenna element used for signal transmission. The selection unit 104 outputs selection information indicating the selected channel to the transmission control unit 105. Details of a method for selecting a channel used for signal transmission in the selection unit 104 will be described later.

Based on the selection information input from the selection unit 104, the transmission control unit 105 indicates the transmission data input from the modulation unit 102 (for example, transmission data addressed to the selected user terminal 200) in the selection information. Transmission control for transmitting using the antenna element. The transmission control unit 105 outputs transmission data and transmission control information (for example, including selection information) to the transmission point 10 including the selected antenna element.

For example, the transmission control unit 105 may perform beam forming or precoding on transmission data using a plurality of antenna elements. In this case, the transmission control unit 105 may generate a beamforming weight or a precoding matrix using the channel estimation result input from the channel estimation unit 103. Or the transmission control part 105 may perform transmission power control with respect to the transmission data of the user terminal 200 using a channel estimation result.

At each of the transmission points 10-1 to 10-n, the antenna 107 has one or more antenna elements.

The radio transmission unit 106 at each transmission point 10 performs radio transmission processing such as D / A conversion, frequency conversion, amplification, etc. on the transmission data (baseband signal) input from the transmission control unit 105 and transmits the radio signal. Generate. The wireless transmission unit 106 transmits the generated wireless signal via the antenna element (antenna 107) indicated by the transmission control information input from the transmission control unit 105.

The radio reception unit 108 at each transmission point 10 performs radio reception processing such as A / D conversion and frequency conversion on the radio signal received from the user terminal 200 via the antenna 107 (antenna element). Radio reception section 108 outputs a reference signal included in the reception signal after the radio reception processing to channel estimation section 103.

[User terminal configuration]
FIG. 3 is a block diagram illustrating a configuration example of the user terminal 200. FIG. 3 shows a configuration related to downlink data reception, and a configuration related to uplink data transmission is omitted.

The user terminal 200 illustrated in FIG. 3 includes a wireless transmission unit 201, an antenna 202, a wireless reception unit 203, a demodulation unit 204, and a decoding unit 205.

In FIG. 3, description of a configuration for receiving an OFDM signal in the user terminal 200 (for example, a CP removal unit, an FFT processing unit) is omitted.

The wireless transmission unit 201 performs wireless transmission processing such as D / A conversion, frequency conversion, and amplification on the input reference signal, generates a wireless signal, and transmits the generated wireless signal via the antenna 202. .

The antenna 202 has one or more antenna elements.

The radio reception unit 203 performs radio reception processing such as A / D conversion and frequency conversion on the radio signal received from the base station 100 via the antenna 202, and demodulates the received signal after the radio reception processing. Output to.

The demodulation unit 204 demodulates the reception signal input from the wireless reception unit 203 and outputs the demodulated signal to the decoding unit 205.

The decoding unit 205 decodes the signal input from the demodulation unit 204 and outputs received data.

[Base station operation]
Next, an operation example of the base station 100 described above will be specifically described.

In the following description, as illustrated in FIG. 4, the wireless communication system 1 includes four transmission points 10 (TP # 1, TP # 2, TP # 3, and TP # 4) and four user terminals 200. (UE # 1, UE # 2, UE # 3, UE # 4).

Each transmission point 10 shown in FIG. 4 has four antenna elements. That is, in FIG. 4, the radio communication system 1 includes 16 antenna elements. In the following, as an example, TP # 1 has antenna elements # 1 to # 4, TP # 2 has antenna elements # 5 to # 8, and TP # 3 has antenna elements # 9 to # 12. , TP # 4 includes antenna elements # 13 to # 16.

The base station 100 transmits a signal from channel estimation values obtained for a plurality of channels between the 16 antenna elements # 1 to # 16 and the four user terminals 200 (UE # 1 to UE # 4). Select the channel used for transmission. In the following, for example, the base station 100 selects the antenna element used for signal transmission and the user terminal 200 for signal transmission.

FIG. 5 is a flowchart showing an example of signal (for example, data) transmission processing in the base station 100. FIG. 6 illustrates an example of the selection process of the antenna element and the user terminal 200 in the base station 100 (for example, the selection unit 104).

The base station 100 receives the reference signal transmitted from each user terminal 200 at the antenna elements of the plurality of transmission points 10 (ST11). For example, in FIG. 4, reference signals transmitted from UE # 1 to UE # 4 are received by antenna elements # 1 to # 16, respectively.

As illustrated in FIG. 5, the base station 100 estimates a downlink channel between each user terminal 200 and each antenna element using the reference signal received in ST11, and obtains a channel matrix representing the estimated channel. Generate (ST12). For example, as illustrated in FIG. 6, the base station 100 determines a channel estimation value h (x, y) between the UE #x and the antenna element #y (where x = 1, 2, 3, or 4, y = Any one of 1 to 16), a 4 × 16 channel matrix is generated.

As shown in FIG. 5, the base station 100 selects an antenna element used for signal transmission using the channel matrix generated in ST12 (ST13). For example, in FIG. 6, the base station 100 selects antenna elements # 1, # 4, # 12, and # 16. Also, base station 100 generates a channel matrix including elements related to the selected antenna element among the elements included in the channel matrix generated in ST12. For example, as illustrated in FIG. 6, the base station 100 determines the channel estimation value h (x, y ′) between the UE #x and the antenna element #y ′ selected in ST13 (where x = 1, 2). 3 or 4, y ′ = 1, 4, 12 or 16), and a 4 × 4 channel matrix is generated. Details of the antenna element selection method in ST13 will be described later.

As shown in FIG. 5, the base station 100 uses the channel matrix generated in ST12 to select a user terminal 200 that is a signal transmission target (ST14). For example, in FIG. 6, the base station 100 selects UE # 3 and UE # 4. Moreover, the base station 100 generates a channel matrix including elements related to the selected user terminal 200 among elements included in the channel matrix generated in ST12. For example, as illustrated in FIG. 6, the base station 100 determines a channel estimation value h (x ′, y ′) between the UE #x ′ selected in ST14 and the antenna element #y ′ selected in ST13 (however, , X ′ = 3 or 4, y ′ = 1, 4, 12 or 16), a 2 × 4 channel matrix is generated. Details of the antenna element selection method in ST14 will be described later.

As shown in FIG. 5, the base station 100 performs transmission control on the antenna element selected in ST13 and the user terminal 200 selected in ST14 (ST15). For example, the base station 100 uses antenna elements # 1, # 4, # 12, and # 16 for transmission data addressed to UE # 3 and UE # 4 using the channel matrix of 2 rows × 4 columns shown in FIG. The used precoding matrix may be generated.

Then, base station 100 performs signal transmission to UE # 3 and UE # 4 selected in ST14 using antenna elements # 1, # 4, # 12, and # 16 selected in ST13 according to the transmission control in ST15. (ST16).

As shown in FIG. 6, base station 100 obtains channel estimation values (for example, a channel matrix of 4 rows × 16 columns in FIG. 6) between antenna elements # 1 to # 16 and UEs # 1 to # 4. The antenna elements (antenna elements # 1, # 4, # 12, and # 16 in FIG. 6) used for transmitting the radio signal are determined from among the plurality of antenna elements # 1 to # 6. In addition, as shown in FIG. 6, the base station 100 selects one of the channel estimation values included in the 4 × 16 channel matrix corresponding to the determined antenna elements # 1, # 4, # 12, and # 16. Select the channel estimate for the part. Then, base station 100 uses the selected partial channel estimation values (channel matrix of 4 rows × 4 columns in FIG. 6) to transmit radio signals from UE # 1 to UE # 4. User terminal 200 (UE # 3 and # 4 in FIG. 6) is determined.

For example, in FIG. 6, the base station 100 extracts a column vector corresponding to the selected antenna element from the channel matrix of 4 rows × 16 columns used for selection of the antenna element, and uses it for selection of the user terminal 200. A 4 × 4 channel matrix is generated. In other words, the base station 100 performs the selection process of the user terminal 200 by degenerating the channel matrix of 4 rows × 16 columns used for selecting the antenna elements into a channel matrix of 4 rows × 4 columns.

By this process, the base station 100 can execute the selection process of the user terminal 200 without using the channel estimation value regarding the antenna element that has not been selected, so that the calculation amount of the selection process of the user terminal 200 can be reduced. In other words, the base station 100 can reduce the amount of calculation for selecting a channel used for transmitting a radio signal.

[Selection method of antenna element]
Next, details of the antenna element selection method in ST13 shown in FIG. 5 will be described.

FIG. 7 is a flowchart showing an example of antenna element selection processing (processing of ST13 in FIG. 5) in the base station 100.

When the base station 100 performs the process shown in FIG. 7, as shown in FIG. 8, the channel direction channel estimated value [h (1, y), column vectors h ₁ to h ₁₆ including h (2, y), h (3, y), h (4, y)] (where y = 1 to 16) are calculated. Column vectors h ₁ to h ₁₆ correspond to the channels of antenna elements # 1 to # 16, respectively.

In FIG. 7, the base station 100 initializes a variable k (k = 1) (ST131).

Base station 100 selects antenna element #y (1) (column vector h _{y (1)} ) (that is, k = 1) from the plurality of antenna elements (ST132). For example, the base station 100 may select an antenna element with the best propagation environment. Specifically, the base station 100 may calculate the received power or eigenvalue using the column vector h corresponding to the antenna element, and may select the antenna element (column vector h) having the largest calculated value. Alternatively, for example, the base station 100 may select an antenna element (column vector h) having an eigenvalue equal to or higher than a predetermined threshold that satisfies a predetermined reception quality from among column vectors h corresponding to a plurality of antenna elements. Good. Note that parameters used in selection criteria for selecting an antenna element used for transmitting a radio signal are not limited to received power and eigenvalues. The parameter used in the selection criterion for selecting the antenna element used for transmitting the radio signal may be a parameter related to the communication quality between the antenna element and the UE, for example.

The base station 100, except for the antenna element #y (i) (column vector h _{y (i)} ) (where i = 1 to k) selected in the processing of ST132 or the past ST133 among a plurality of antenna elements Antenna element #y (k + 1) (column vector h _{y (k + 1)} ) is selected (ST133). The antenna element #y (k + 1) is a candidate antenna element to be added to the already selected antenna element #y (k).

Specifically, in ST133, base station 100 selects column vector h _{y (k + 1)} that provides the maximum gain when added to a combination of column vectors h _{y (i)} (where i = 1 to k). To do. For example, the base station 100 may determine the magnitude of the gain by comparing eigenvalues, correlation values, chordal distances, or the like calculated using the combination of the column vectors h. Note that the gain-related parameters are not limited to eigenvalues, correlation values, and chordal distances.

Base station 100 combines antenna element #y (k + 1) (column vector h _y ) selected in ST133 with a combination of antenna element #y (i) (column vector h _{y (i)} ) (where i = 1 to k). By adding _{(k + 1)} ), it is determined whether or not a further gain can be obtained than the combination of antenna elements #y (i) (where i = 1 to k) (ST134).

When determining that further gain can be obtained by adding antenna element #y (k + 1) in ST134 (ST134: YES), base station 100 increments variable k (ST135). By incrementing variable k, base station 100 adds antenna element #y (k + 1) to the combination of antenna elements used for signal transmission.

If all antenna elements have been selected after the process of ST135, base station 100 may end the antenna element selection process (not shown). Alternatively, if a predetermined number of antenna elements are selected after ST135, base station 100 may end the antenna element selection process (not shown).

Further, after the process of ST135, the base station 100 returns to the process of ST133, and antenna element #y (i) (column vector h _{y (i)} ) selected in ST132 and the previous process of ST133 (where i = 1) (K + 1) -th antenna element is newly selected from the antenna elements other than .about.k).

On the other hand, if it is determined in ST134 that further gain cannot be obtained by adding the antenna element #y (k + 1) (ST134: NO), the base station 100 ends the antenna element selection process.

Thus, the base station 100 determines a combination of k antenna elements as antenna elements used for signal transmission by the antenna element selection processing shown in FIG.

Here, a specific example of the antenna element selection process shown in FIG. 7 will be described. Hereinafter, as an example, a process of selecting antenna elements # 1, # 4, # 12, and # 16 as antenna elements used for signal transmission will be described as shown in FIG.

When k = 1 in FIG. 7, in ST132, base station 100 determines antenna element # 4 (column vector having the largest eigenvalue from column vectors h ₁ to h ₁₆ corresponding to antenna elements # 1 to # 16. h ₄ ) is selected (ie, y (1) = 4).

In ST133, base station 100 adds antenna element # 4 (column vector h ₄ ) out of antenna elements # 1 to # 3 and # 5 to # 16 other than antenna element # 4 (column vector h ₄ ). A candidate for the antenna element #y (2) (column vector h _{y (2)} ) is selected. For example, the base station 100 calculates eigenvalues between the column vector h ₄ and the column vectors h of the antenna elements # 1 to # 3 and # 5 to # 16, and the antenna element #y () having the maximum eigenvalue. 2) Select antenna element # 1 (column vector h ₁ ) as (column vector h _{y (2)} ).

In this case, in ST134, the eigenvalues obtained by adding a column vector _{h 1} column vector _{h 4} is determined to be larger than the eigenvalue of column vector _{h 4.} Through this process, antenna element # 1 is newly added as an antenna element used for signal transmission (that is, y (2) = 1).

When k = 2 in FIG. 7, in ST133, base station 100 determines that antenna elements # 2, # 3, # 5 to # 16 other than antenna elements # 1 and # 4 (column vectors h ₁ and h ₄ ) are included. Then, a candidate for antenna element #y (3) (column vector h _{y (3)} ) to be added to h ₁ h ₄ is selected. For example, the base station 100 calculates an eigenvalue between h ₁ h ₄ and each column vector h of the antenna elements # 2, # 3, # 5 to # 16, and the antenna element #y () having the largest eigenvalue. 3) Select antenna element # 12 (column vector h ₁₂ ) as (column vector h _{y (3)} ).

In this case, in _ST134, the eigenvalues obtained by adding a column vector _{h 12} to h 1 _{h 4} is determined to be larger than the eigenvalue of the column vectors _h 1 _{h 4.} By this processing, antenna element # 12 is newly added as an antenna element used for signal transmission (that is, y (3) = 12).

Similarly, when k = 3 in FIG. 7, in ST133, base station 100 determines antenna elements # 2, # 3, # 5 to # 11, # 13 to # 13 other than antenna elements # 1, # 4, and # 12. Antenna element #y (4) is selected from # 16. For example, the base station 100 uses the antenna element # 16 (column vector h _{y (4)} ) as the antenna element #y (4) (column vector h _{y (4)} ) having the largest eigenvalue when the column vector h is added to h ₁ h ₄ h _12. Select the column vector h ₁₆ ).

In this case, in _ST134, the eigenvalues obtained by adding a column vector _{h 16} to _h ₁ h ₄ h ₁₂ is determined to be larger than the eigenvalue of the column vectors _{_{_h}} 1 _h 4 _h _12. By this processing, antenna element # 16 is newly added as an antenna element used for signal transmission (that is, y (4) = 16).

Then, when k = 4 in FIG. 7, the antenna element #y selected in ST133 (5) (column vector _{h y _(5)),} be added to _{_{_{h 1 h 4 h 12 h 16}}} h 1 h It is determined that a combination of antenna elements that is larger than the eigenvalue of ₄ h ₁₂ h ₁₆ cannot be obtained (ST134: NO). In this case, the base station 100 uses the already selected antenna elements # 1, # 4, # 12, and # 16 corresponding to the column vectors h ₁ , h ₄ , h ₁₂ , and h ₁₆ for signal transmission. It is determined as a combination of antenna elements.

In the base station 100, selecting a channel estimation value according to a selection criterion for selecting an antenna element used for radio signal transmission includes the following. Specifically, base station 100 has a matrix element (for example, a column vector) corresponding to an antenna element in a channel matrix having a channel estimation value obtained for each channel between the antenna element and user terminal 200 as a matrix element. ) To calculate the gain. In addition, the base station 100 determines whether or not the gain calculated by changing the combination of matrix elements (for example, column vectors) corresponding to the antenna elements increases. Then, base station 100 determines an antenna element corresponding to a combination of matrix elements that increase the gain as an antenna element used for transmitting a radio signal.

For example, the base station 100 can determine the combination of antenna elements having the maximum gain among the combinations of antenna elements # 1 to # 16 by the process shown in FIG.

Further, as described above, in the antenna element selection process, the base station 100 sequentially selects antenna elements having a maximum gain (for example, eigenvalue) from a plurality of antenna elements one by one, and performs signal processing. Determine the combination of antenna elements used for transmission. In the base station 100, each time an antenna element used for signal transmission is selected one by one (every time the value of k in FIG. 7 increases), an antenna element to be determined whether or not it should be newly added The number of (antenna elements to be selected in ST133) decreases.

By this process, the base station 100 does not have to calculate gains for all combinations of column vectors, so the amount of calculation in the antenna element selection process can be reduced. Further, since base station 100 does not have to calculate gains for all combinations of column vectors, it is possible to shorten the time for antenna element selection processing.

[User terminal selection method]
Next, details of the selection method of user terminal 200 in ST14 shown in FIG. 5 will be described.

FIG. 9 is a flowchart showing an example of the selection process of the user terminal 200 in the base station 100 (the process of ST14 in FIG. 5).

In the process shown in FIG. 9, the base station 100 uses the channel matrix (for example, the middle stage channel matrix shown in FIG. 6) including the column vector corresponding to the antenna element selected by the antenna element selection process shown in FIG. Reference) is used.

In FIG. 9, base station 100 initializes variable l (l = 1) (ST141).

The base station 100 selects UE # x (1) (that is, l = 1) from the plurality of user terminals 200 (UE # 1 to UE # 4 in FIG. 4) (ST142). For example, the base station 100 calculates the received power, eigenvalue, or proportional fairness (Proportional Fairness) using a row vector (also referred to as a sub-matrix) corresponding to each UE in the channel matrix. The UE with the largest value may be selected. Or base station 100 may select user terminal 200 which has the above-mentioned value more than a predetermined threshold which satisfies predetermined reception quality from a row vector corresponding to each of a plurality of user terminals 200, for example.

Note that the parameters used in the selection criteria for selecting a target UE to transmit a radio signal are not limited to received power, eigenvalues, and proportional fairness. The parameter used in the selection criteria for selecting the target UE for transmitting the radio signal may be a parameter related to the communication quality between the antenna element and the UE, for example.

For example, when applying precoding at the time of signal transmission, the base station 100 determines a transmission rate based on an eigenvalue calculated using a channel matrix, and does not apply precoding at the time of signal transmission. The transmission rate may be determined based on the channel estimation value (or other parameter other than the eigenvalue) included in the channel matrix.

Alternatively, in ST142, base station 100 may select a preset user terminal 200 (a fixed UE or a separately selected UE). Alternatively, the base station 100 may preferentially select the user terminal 200 that has not been selected in the past signal transmission.

Base station 100 selects UE #x (l + 1) other than UE #x (j) (j = 1 to l) selected in ST142 or the process of previous ST143 from among a plurality of user terminals 200. (ST143). UE # x (l + 1) is a candidate for the user terminal 200 to be added to the already selected UE # x (l).

Specifically, in ST143, base station 100 selects UE # x (l + 1) that provides the highest transmission rate when added to the combination of UE # x (j) (where j = 1 to 1). To do. For example, the base station 100 compares eigenvalues and the like calculated using a combination of a row vector corresponding to UE # x (j) and a row vector corresponding to UE # x (l + 1) in the channel matrix. The magnitude of the obtained transmission rate may be determined.

The base station 100 adds UE # x (l + 1) selected in ST143 to the combination of UE # x (j) (where j = 1 to 1), thereby adding UE # x (j) (where j = 1 to l), it is determined whether or not a further transmission rate can be obtained (ST144).

When determining that a further transmission rate can be obtained by adding UE # (l + 1) in ST144 (ST144: YES), base station 100 increments variable l (ST145). By incrementing the variable l, the base station 100 adds UE # x (l + 1) to the combination of user terminals 200 that are signal transmission targets.

In addition, after the processing of ST145, the base station 100 returns to the processing of ST143, and from among UEs other than UE # x (j) (where j = 1 to 1) selected in ST142 and the past processing of ST143 ( l + 1) A new UE is selected.

On the other hand, when it is determined in ST144 that a further transmission rate cannot be obtained due to the addition of UE # (l + 1) (ST144: NO), base station 100 ends the selection process of user terminal 200.

As described above, the base station 100 determines a combination of l user terminals 200 as the user terminals 200 to be signal-transmitted by the selection process of the user terminals 200 shown in FIG.

Here, a specific example of the selection process of the user terminal 200 shown in FIG. 9 will be described.

Hereinafter, as an example, a process in which UEs # 3 and # 4 are selected as user terminals 200 to be signal-transmitted as illustrated in FIG. 6 will be described. Further, in the base station 100, it is assumed that the antenna elements # 1, # 4, # 12, and # 16 are selected before the user terminal 200 is selected, as shown in FIG. For example, the base station 100 uses the channel matrix shown in FIG.

When 1 = 1 in FIG. 9, in ST142, base station 100 selects UE # 3 having the largest eigenvalue from row vectors (sub-matrices) corresponding to UE # 1 to UE # 4, for example. (That is, x (1) = 3).

In ST143, the base station 100 selects a candidate for the user terminal 200 to be added to the UE # 3 from the UEs # 1, # 2, and # 4 other than the UE # 3. For example, the base station 100 calculates eigenvalues of the submatrix including the row vector of UE # 3 and the row vectors of UE # 1, # 2, and # 4, and sets UE # x (2) having the largest eigenvalue as , UE # 4 is selected.

At this time, in ST144, it is determined that the eigenvalue of the sub-matrix obtained by adding UE # 4 to UE # 3 is larger than the eigenvalue of the row vector of UE # 3. Through this process, UE # 4 is newly added as a user terminal 200 that is a signal transmission target (ie, x (2) = 4).

Then, when l = 2 in FIG. 9, even if the UE # (3) selected in ST143 is added to UE # 3 and # 4, the user becomes larger than the eigenvalues of the submatrices of UE # 3 and # 4 It is determined that a combination of terminals 200 cannot be obtained (ST144: NO). In this case, base station 100 determines UE # 3 and # 4 that have already been selected as a combination of user terminals 200 that are signal transmission targets.

In the base station 100, selecting a channel estimation value according to a selection criterion for selecting a user terminal to which a radio signal is to be transmitted includes the following. Specifically, base station 100 corresponds to user terminal 200 in a channel matrix (in other words, a degenerated channel matrix) having a part of channel estimation values selected according to a selection criterion related to antenna elements as matrix elements. A transmission rate is calculated by changing a combination of matrix elements (for example, row vectors). In addition, the base station 100 determines whether or not the transmission rate calculated by changing the combination of matrix elements (for example, row vectors) corresponding to the user terminal 200 increases. Then, the base station 100 determines the user terminal 200 corresponding to the combination of matrix elements whose transmission rate increases as a target for transmitting a radio signal.

For example, the base station 100 can determine the combination of the user terminals 200 having the maximum transmission rate among the combinations of the UEs # 1 to # 4 by the process shown in FIG.

Further, as described above, in the selection process of the user terminal 200, the base station 100 sequentially selects the user terminals 200 having the maximum transmission rate (for example, eigenvalue) from the plurality of user terminals 200 one by one. Thus, the combination of the user terminals 200 that are signal transmission targets is determined. In the base station 100, each time one user terminal 200 to be signal-transmitted is selected (each time the value of l increases in FIG. 9), the user terminal 200 (target to determine whether or not to add a new one) ( The number of user terminals 200) to be selected in ST143 decreases.

By this process, the base station 100 does not have to calculate the transmission rate for all combinations of the user terminals 200 (row vectors), so that the calculation amount in the selection process of the user terminals 200 can be reduced. Moreover, since the base station 100 does not have to calculate the transmission rate for all combinations of user terminals 200 (row vectors), it is possible to shorten the time for selection processing of the user terminals 200.

The operation example of the base station 100 has been specifically described above.

As described above, the base station 100 obtains a plurality of channel estimation values for each channel between the plurality of antenna elements included in the plurality of transmission points 10 and the user terminal 200. Then, base station 100 selects some channel estimation values according to a selection criterion for selecting a channel estimation value corresponding to an antenna element used for transmitting a radio signal from among a plurality of channel estimation values. Further, the base station 100 selects a part of the channel estimation values from the selected part of the channel estimation values according to a selection criterion for selecting the user terminal 200 to which the radio signal is to be transmitted. Then, base station 100 controls transmission of a radio signal based on a channel estimation value selected according to a selection criterion for selecting a user terminal.

This process allows the base station 100 to select the user terminal 200 using a part of channel estimation values corresponding to the already selected antenna elements when selecting the user terminal 200 to which the radio signal is to be transmitted. In other words, the base station 100 can select a user terminal to which a radio signal is to be transmitted using a channel matrix obtained by degenerating a channel matrix having a plurality of channel estimation values as matrix elements. Therefore, the base station 100 can reduce the amount of calculation in the selection process of the user terminal 200 that is the signal transmission target.

In addition, the base station 100 sequentially selects antenna elements having the maximum gain one antenna element at a time. Similarly, the base station 100 sequentially selects the user terminals 200 having the maximum transmission rate one by one. Through these processes, the base station 100 can reduce the amount of calculation in each of the antenna element selection and the user terminal 200 selection, and can appropriately select the antenna element and the user terminal 200.

(Other embodiments)
(1) In the above embodiment, as shown in FIG. 5 or FIG. 6, the case where the user terminal 200 is selected after the antenna element is selected has been described. However, the base station 100 may select an antenna element after selecting the user terminal 200. For example, the base station 100 uses the channel estimation values obtained for a plurality of channels between all antenna elements and all user terminals 200 as shown in FIG. Is selected (for example, the process of FIG. 9). And the base station 100 may select the antenna element used for transmission of a radio signal using the partial channel estimation value corresponding to the selected user terminal 200 (for example, the process of FIG. 7).

In this case, when selecting an antenna element, the base station 100 can select an antenna element by using a channel matrix (in other words, a degenerated channel matrix) including a channel estimation value related to the user terminal 200 that has already been selected. Therefore, the base station 100 can reduce the amount of calculation in the selection process of the antenna element used for signal transmission.

The base station 100 uses a part of channel estimation values selected from a plurality of channel estimation values between the antenna element and the user terminal 200 to use a channel (for example, an antenna element or a user) for signal transmission. The terminal 200) may be selected.

When selecting an antenna element prior to the user terminal 200, the base station 100 can preferentially select an antenna element having a high power value, for example. Further, when the user terminal 200 is selected before the antenna element, the base station 100 can preferentially select the user terminal 200 to which data transmission is to be assigned, for example.

(2) In the above embodiment, selection of antenna element units (channel vector column vector units) has been described. However, the antenna element selection process is not limited to this. For example, the base station 100 may group a plurality of antenna elements included in the plurality of transmission points 10 into a plurality of groups, and select the antenna elements for each group. For example, each group may be a unit of the transmission point 10. This processing can further reduce the amount of calculation of the antenna element selection processing in the base station 100.

Similarly, the base station 100 may group a plurality of user terminals 200 into a plurality of groups and select the user terminal 200 for each group unit. By this process, the calculation amount of the selection process of the user terminal 200 in the base station 100 can be further reduced.

(3) In the above embodiment, in the selection process of the user terminal 200, as shown in FIG. 9, the base station 100 selects one user terminal 200 (UE #x (1) in FIG. 9). explained. However, the selection process of the user terminal 200 is not limited to this. For example, the base station 100 may select a plurality of user terminals 200. For example, when there is a user terminal 200 that preferentially performs signal transmission among a plurality of user terminals 200, the base station 100 includes the user terminal 200 to be prioritized as a signal transmission target, and the above-described embodiment. The user terminal 200 may be selected based on the transmission rate obtained in the same manner. With this process, when there is a user terminal 200 that needs to perform signal transmission with priority, the user terminal 200 can be added to a signal transmission target regardless of the transmission rate.

(4) Further, in the above embodiment, when base station 100 determines a combination of antenna elements, antenna elements that can obtain further gain with respect to already selected antenna elements are sequentially added one antenna element at a time. explained. However, the antenna element selection method is not limited to this processing. For example, the base station 100 may sequentially add two or more predetermined number of antenna elements in order to obtain further gain.

Similarly, when the base station 100 determines a combination of the user terminals 200, the user terminals 200 that can obtain a higher transmission rate with respect to the user terminals 200 that have already been selected are sequentially ordered by two or more predetermined numbers of user terminals 200. May be added.

This process can further reduce the calculation amount of the selection process of the antenna element or the user terminal 200.

(5) In the above embodiment, a channel matrix indicating a channel between a plurality of antenna elements included in the plurality of transmission points 10 and at least one user terminal 200 included in the wireless communication system 1 is used. Explained. However, in the present disclosure, each user terminal 200 may include at least one antenna element. In this case, the base station 100 may use a channel matrix between a plurality of antenna elements included in the plurality of transmission points 10 and a plurality of antenna elements included in each of at least one user terminal 200.

(Hardware configuration)
In addition, the block diagram used for description of the said embodiment has shown the block of the functional unit. These functional blocks (components) are realized by any combination of hardware and / or software. Further, the means for realizing each functional block is not particularly limited. That is, each functional block may be realized by one device physically and / or logically coupled, and two or more devices physically and / or logically separated may be directly and / or indirectly. (For example, wired and / or wireless) and may be realized by these plural devices.

For example, a base station, a user terminal, and the like according to an embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. FIG. 11 is a diagram illustrating an example of a hardware configuration of the base station 100 and the user terminal 200 according to an embodiment of the present disclosure. The base station 100 and the user terminal 200 described above may be physically configured as a computer device including a processor 1001, a memory 1002, a storage 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, and the like. .

In the following description, the term “apparatus” can be read as a circuit, a device, a unit, or the like. The hardware configuration of the base station 100 and the user terminal 200 may be configured to include one or a plurality of each device illustrated in the figure, or may be configured not to include some devices.

For example, although only one processor 1001 is shown, there may be a plurality of processors. Further, the processing may be executed by one processor, or the processing may be executed by one or more processors simultaneously, sequentially, or in another manner. Note that the processor 1001 may be implemented by one or more chips.

Each function in the base station 100 and the user terminal 200 is obtained by reading predetermined software (program) on hardware such as the processor 1001 and the memory 1002, so that the processor 1001 performs computation and communication by the communication device 1004, or This is realized by controlling reading and / or writing of data in the memory 1002 and the storage 1003.

The processor 1001 controls the entire computer by operating an operating system, for example. The processor 1001 may be configured by a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic device, a register, and the like. For example, the above-described encoding unit 101, modulation unit 102, channel estimation unit 103, selection unit 104, transmission control unit 105, demodulation unit 204, decoding unit 205, and the like may be realized by the processor 1001. In addition, the above table may be stored in the memory 1002.

Further, the processor 1001 reads a program (program code), software module, or data from the storage 1003 and / or the communication device 1004 to the memory 1002, and executes various processes according to these. As the program, a program that causes a computer to execute at least a part of the operations described in the above embodiments is used. For example, at least a part of the functional blocks constituting the base station 100 and the user terminal 200 may be realized by a control program stored in the memory 1002 and operated by the processor 1001, and other functional blocks are similarly realized. May be. Although the above-described various processes have been described as being executed by one processor 1001, they may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. Note that the program may be transmitted from a network via a telecommunication line.

The memory 1002 is a computer-readable recording medium, and includes, for example, at least one of ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), RAM (Random Access Memory), and the like. May be. The memory 1002 may be called a register, a cache, a main memory (main storage device), or the like. The memory 1002 can store a program (program code), a software module, and the like that can be executed to implement the wireless communication method according to an embodiment of the present disclosure.

The storage 1003 is a computer-readable recording medium such as an optical disc such as a CD-ROM (Compact Disc ROM), a hard disc drive, a flexible disc, a magneto-optical disc (eg, a compact disc, a digital versatile disc, a Blu-ray). (Registered trademark) disk, smart card, flash memory (for example, card, stick, key drive), floppy (registered trademark) disk, magnetic strip, and the like. The storage 1003 may be referred to as an auxiliary storage device. The storage medium described above may be, for example, a database, server, or other suitable medium including the memory 1002 and / or the storage 1003.

The communication device 1004 is hardware (transmission / reception device) for performing communication between computers via a wired and / or wireless network, and is also referred to as a network device, a network controller, a network card, a communication module, or the like. For example, the above-described

wireless transmission units

106 and 201,

antennas

107 and 202,

wireless reception units

108 and 203, and the like may be realized by the communication device 1004.

The input device 1005 is an input device (for example, a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that accepts an input from the outside. The output device 1006 is an output device (for example, a display, a speaker, an LED lamp, etc.) that performs output to the outside. The input device 1005 and the output device 1006 may have an integrated configuration (for example, a touch panel).

Also, each device such as the processor 1001 and the memory 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured with a single bus or may be configured with different buses between apparatuses.

The base station 100 and the user terminal 200 include a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), and a field programmable gate array (FPGA). Hardware may be configured, and a part or all of each functional block may be realized by the hardware. For example, the processor 1001 may be implemented by at least one of these hardware.

(Information notification, signaling)
The notification of information is not limited to the aspect / embodiment described in the present specification, and may be performed by other methods. For example, information notification includes physical layer signaling (for example, DCI (Downlink Control Information), UCI (Uplink Control Information)), upper layer signaling (for example, RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling), It may be implemented by broadcast information (MIB (Master Information Block), SIB (System Information Block))), other signals, or a combination thereof. The RRC signaling may be referred to as an RRC message, and may be, for example, an RRC connection setup message, an RRC connection reconfiguration message, or the like.

(Adaptive system)
Each aspect / embodiment described herein includes LTE (Long Term Evolution), LTE-A (LTE-Advanced), SUPER 3G, IMT-Advanced, 4G, 5G, FRA (Future Radio Access), W-CDMA. (Registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, UWB (Ultra-WideBand), Bluetooth (Registered trademark), a system using another appropriate system, and / or a next generation system extended based on the system may be applied.

(Processing procedure etc.)
As long as there is no contradiction, the order of the processing procedures, sequences, flowcharts, and the like of each aspect / embodiment described in this specification may be changed. For example, the methods described herein present the elements of the various steps in an exemplary order and are not limited to the specific order presented.

(Operation of base station)
The specific operation assumed to be performed by the base station (radio base station) in this specification may be performed by the upper node in some cases. In a network composed of one or more network nodes having a base station, various operations performed for communication with a terminal may be performed by the base station and / or other network nodes other than the base station (e.g., It is obvious that this can be performed by MME (Mobility Management Entity) or S-GW (Serving Gateway). In the above, the case where there is one network node other than the base station is illustrated, but a combination of a plurality of other network nodes (for example, MME and S-GW) may be used.

(I / O direction)
Information, signals, and the like can be output from the upper layer (or lower layer) to the lower layer (or upper layer). Input / output may be performed via a plurality of network nodes.

(Handling of input / output information, etc.)
Input / output information and the like may be stored in a specific location (for example, a memory) or may be managed by a management table. Input / output information and the like can be overwritten, updated, or additionally written. The output information or the like may be deleted. The input information or the like may be transmitted to another device.

(Judgment method)
The determination may be performed by a value represented by 1 bit (0 or 1), may be performed by a true / false value (Boolean: true or false), or may be performed by comparing numerical values (for example, a predetermined value) Comparison with the value).

(software)
Software, whether it is called software, firmware, middleware, microcode, hardware description language, or other names, instructions, instruction sets, codes, code segments, program codes, programs, subprograms, software modules , Applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc. should be interpreted broadly.

Further, software, instructions, etc. may be transmitted / received via a transmission medium. For example, software may use websites, servers, or other devices using wired technology such as coaxial cable, fiber optic cable, twisted pair and digital subscriber line (DSL) and / or wireless technology such as infrared, wireless and microwave. When transmitted from a remote source, these wired and / or wireless technologies are included within the definition of transmission media.

(Information, signal)
Information, signals, etc. described herein may be represented using any of a variety of different technologies. For example, data, commands, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description are voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, light fields or photons, or any of these May be represented by a combination of

Note that the terms described in this specification and / or terms necessary for understanding this specification may be replaced with terms having the same or similar meaning. For example, the channel and / or symbol may be a signal. The signal may be a message. Further, the component carrier (CC) may be called a carrier frequency, a cell, or the like.

("System", "Network")
As used herein, the terms “system” and “network” are used interchangeably.

(Parameter, channel name)
In addition, information, parameters, and the like described in this specification may be represented by absolute values, may be represented by relative values from a predetermined value, or may be represented by other corresponding information. . For example, the radio resource may be indicated by an index.

The names used for the above parameters are not limited in any way. Further, mathematical formulas and the like that use these parameters may differ from those explicitly disclosed herein. Since various channels (eg, PUCCH (Physical Uplink Control Channel), PDCCH (Physical Downlink Control Channel), etc.) and information elements (eg, TPC, etc.) can be identified by any suitable name, these various channels and information The various names assigned to the elements are not limiting in any way.

(base station)
A base station (radio base station) can accommodate one or more (eg, three) cells (also referred to as sectors). When the base station accommodates multiple cells, the entire coverage area of the base station can be partitioned into multiple smaller areas, each smaller area being a base station subsystem (eg, indoor small base station RRH: Remote Radio Head) can also provide communication services. The term “cell” or “sector” refers to part or all of the coverage area of a base station and / or base station subsystem that provides communication services in this coverage. Further, the terms “base station”, “eNB”, “cell”, and “sector” may be used interchangeably herein. A base station may also be referred to in terms such as a fixed station, NodeB, eNodeB (eNB), access point, femtocell, small cell, and the like.

(Terminal)
A user terminal is a mobile station, subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile by a person skilled in the art It may also be referred to as a terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, UE (User Equipment), or some other appropriate terminology.

(Meaning and interpretation of terms)
As used herein, the terms “determining” and “determining” may encompass a wide variety of actions. “Judgment” and “determination” are, for example, judgment, calculation, calculation, processing, derivation, investigating, looking up (eg, table , Searching in a database or another data structure), considering ascertaining as “determining”, “deciding”, and the like. In addition, “determination” and “determination” include receiving (for example, receiving information), transmitting (for example, transmitting information), input (input), output (output), and access. (accessing) (e.g., accessing data in a memory) may be considered as "determined" or "determined". In addition, “determination” and “decision” means that “resolving”, “selecting”, “choosing”, “establishing”, and “comparing” are regarded as “determining” and “deciding”. May be included. In other words, “determination” and “determination” may include considering some operation as “determination” and “determination”.

The terms “connected”, “coupled”, or any variation thereof, means any direct or indirect connection or coupling between two or more elements and It can include the presence of one or more intermediate elements between two “connected” or “coupled” elements. The coupling or connection between the elements may be physical, logical, or a combination thereof. As used herein, the two elements are radio frequency by using one or more wires, cables and / or printed electrical connections, and as some non-limiting and non-inclusive examples By using electromagnetic energy, such as electromagnetic energy having a wavelength in the region, microwave region, and light (both visible and invisible) region, it can be considered to be “connected” or “coupled” to each other.

The reference signal may be abbreviated as RS (Reference Signal), and may be referred to as a pilot depending on an applied standard. Further, the correction RS may be referred to as TRS (Tracking 、 RS), PC-RS (Phase Compensation RS), PTRS (Phase Tracking RS), or Additional RS. Further, the demodulation RS and the correction RS may be called differently corresponding to each. Further, the demodulation RS and the correction RS may be defined by the same name (for example, the demodulation RS).

As used herein, the phrase “based on” does not mean “based only on”, unless expressly specified otherwise. In other words, the phrase “based on” means both “based only on” and “based at least on.”

The “unit” in the configuration of each device described above may be replaced with “means”, “circuit”, “device”, and the like.

As long as “including”, “comprising” and variations thereof are used in the specification or claims, these terms are inclusive, as are the terms “comprising”. Is intended. Furthermore, the term “or” as used herein or in the claims is not intended to be an exclusive OR.

The radio frame may be composed of one or a plurality of frames in the time domain. One or more frames in the time domain may be referred to as subframes, time units, etc. A subframe may further be composed of one or more slots in the time domain. The slot may be further configured with one or a plurality of symbols (OFDM (Orthogonal-Frequency-Division-Multiplexing) symbol, SC-FDMA (Single-Carrier-Frequency-Division-Multiple-Access) symbol, etc.) in the time domain.

The radio frame, subframe, slot, and symbol all represent a time unit when transmitting a signal. Radio frames, subframes, slots, and symbols may be called differently corresponding to each.

For example, in the LTE system, the base station performs scheduling to allocate radio resources (frequency bandwidth, transmission power, etc. that can be used in each mobile station) to each mobile station. The minimum time unit of scheduling may be called TTI (Transmission Time Interval).

For example, one subframe may be called a TTI, a plurality of consecutive subframes may be called a TTI, and one slot may be called a TTI.

The resource unit is a resource allocation unit in the time domain and the frequency domain, and may include one or a plurality of continuous subcarriers in the frequency domain. In the time domain of the resource unit, one or a plurality of symbols may be included, and one slot, one subframe, or a length of 1 TTI may be included. One TTI and one subframe may each be composed of one or a plurality of resource units. The resource unit may also be called a resource block (RB: Resource Block), a physical resource block (PRB: Physical RB), a PRB pair, an RB pair, a scheduling unit, a frequency unit, or a subband. Further, the resource unit may be composed of one or a plurality of REs. For example, 1 RE may be any resource (for example, the smallest resource unit) smaller than a resource unit serving as a resource allocation unit, and is not limited to the name RE.

The structure of the radio frame described above is merely an example, and the number of subframes included in the radio frame, the number of slots included in the subframe, the number of symbols and resource blocks included in the slots, and the subframes included in the resource block The number of carriers can be variously changed.

Throughout this disclosure, if articles are added by translation, for example, a, an, and the in English, these articles must be clearly not otherwise indicated by context, Including multiple things.

(Aspect variations, etc.)
Each aspect / embodiment described in this specification may be used independently, may be used in combination, or may be switched according to execution. In addition, notification of predetermined information (for example, notification of being “X”) is not limited to explicitly performed, but is performed implicitly (for example, notification of the predetermined information is not performed). Also good.

Although the present disclosure has been described in detail above, it is obvious for those skilled in the art that the present disclosure is not limited to the embodiments described in the present specification. The present disclosure can be implemented as modifications and changes without departing from the spirit and scope of the present disclosure determined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present disclosure.

This patent application incorporates the entire contents of Japanese Patent Application No. 2018-056839 filed on Mar. 23, 2018.

One embodiment of the present disclosure is useful for a mobile communication system.

DESCRIPTION OF SYMBOLS 1 Radio | wireless communications system 10a-10i, 10-1-10-n Transmission point 20 Signal processing apparatus 100 Base station 101 Encoding part 102 Modulation part 103 Channel estimation part 104 Selection part 105 Transmission control part 106,201

Wireless transmission part

107, 202

Antennas

108 and 203 Wireless receiver 200 User terminal 204 Demodulator 205 Decoder

Claims

A transmission circuit for transmitting a radio signal;
A plurality of channel estimation values obtained for each channel between a plurality of antenna elements included in a plurality of transmission points and a user terminal are selected according to a first selection criterion and a second selection criterion. A control circuit for controlling transmission of the radio signal based on the estimated channel value;
With a base station.
The first selection criterion is a criterion for selecting a channel estimation value corresponding to an antenna element used for transmission of the radio signal,
The second selection criterion is a criterion for selecting a channel estimation value corresponding to a user terminal to which the radio signal is transmitted.
The base station according to claim 1.
The first selection criterion is a criterion for selecting a channel estimation value corresponding to a user terminal to which the radio signal is transmitted,
The second selection criterion is a criterion for selecting a channel estimation value corresponding to an antenna element used for transmission of the radio signal.
The base station according to claim 1.
Selecting a channel estimate according to the second selection criterion comprises:
Calculated by changing a combination of matrix elements corresponding to the user terminal in a channel matrix having matrix estimation elements selected from the plurality of channel estimation values according to the first selection criterion. To determine whether the transmission rate increases,
Determining a user terminal corresponding to a combination of the matrix elements for increasing the transmission rate as a target for transmitting the radio signal,
The base station according to claim 2.
Selecting a channel estimate according to the second selection criterion comprises:
Calculated by changing a combination of matrix elements corresponding to the antenna elements in a channel matrix having matrix estimation elements selected from the plurality of channel estimation values according to the first selection criterion. Determine whether the gain will increase,
Determining an antenna element corresponding to the combination of the matrix elements that increase the gain to be an antenna element used for transmitting the radio signal,
The base station according to claim 3.
A method of transmitting a radio signal by a base station,
A plurality of channel estimation values obtained for each channel between a plurality of antenna elements included in a plurality of transmission points and a user terminal are selected according to a first selection criterion and a second selection criterion. Controlling transmission of the radio signal based on the estimated channel value;
Transmission method.