CN111903065A - Base station and transmission method - Google Patents
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- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/022—Site diversity; Macro-diversity
- H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
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- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
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- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
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- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
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- H04B7/0452—Multi-user MIMO systems
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- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
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Abstract
A base station is provided with: a transmission circuit that transmits a wireless signal; and a control circuit that controls transmission of the radio signal based on channel estimation values selected according to a first selection reference and a second selection reference from among a plurality of channel estimation values obtained for respective channels between a plurality of antenna elements included in a plurality of transmission points and a user terminal.
Description
Technical Field
The present disclosure relates to a base station and a transmission method.
Background
In a UMTS (Universal Mobile telecommunications System) network, Long Term Evolution (LTE) is standardized for the purpose of higher data rate, lower latency, and the like (non-patent document 1). Further, for the purpose of further increasing the bandwidth and speed of LTE, systems following LTE have also been studied. Successor systems to LTE include systems known as LTE-a (LTE-Advanced), FRA (Future Radio access), 5G (fifth generation mobile communication system), 5G + (5G plus), New-RAT (Radio access technology), and so on.
In future wireless communication systems (e.g., 5G), use of large-scale (Massive) MIMO (Multiple Input Multiple Output) using a plurality of antenna elements (e.g., 100 or more elements) in a high frequency band (e.g., 4GHz or more) is being studied for further speeding up of signal transmission and interference reduction. In Massive MIMO, a wireless communication system is being studied which is based on an ultra-high density distributed antenna system including a plurality of Transmission Points (TP) each including one or more antenna elements, and a signal processing device (for example, non-patent document 1).
Documents of the prior art
Non-patent document
Non-patent document 13 GPP TS 36.300 V8.12.0 "Evolved Universal Radio Access (E-UTRA) and Evolved Universal Radio Access Network (E-UTRAN); (ii) an Overall description; stage 2(Release 8) ", 4 months 2010
Disclosure of Invention
Problems to be solved by the invention
However, the following methods have not been sufficiently studied: a method for selecting a channel to be used for signal transmission in an environment where a plurality of transmission points and a plurality of User terminals (UE) exist as in an ultra-high density distributed antenna system.
Accordingly, an object of one aspect of the present disclosure is to provide a base station and a transmission method that can appropriately select a channel used for signal transmission.
Means for solving the problems
A base station according to one aspect of the present disclosure includes: a transmission circuit that transmits a wireless signal; and a control circuit that controls transmission of the radio signal based on channel estimation values selected according to a first selection reference and a second selection reference from among a plurality of channel estimation values obtained for respective channels between a plurality of antenna elements included in a plurality of transmission points and a user terminal.
Effects of the invention
According to the present disclosure, a channel used in signal transmission can be appropriately selected.
Drawings
Fig. 1 is a diagram showing a configuration example of a wireless communication system.
Fig. 2 is a block diagram showing an example of the configuration of a base station.
Fig. 3 is a block diagram showing an example of the configuration of the user terminal.
Fig. 4 is a diagram showing an example of a transmission point and a user terminal in a wireless communication system.
Fig. 5 is a flowchart showing an operation example of the base station.
Fig. 6 is a diagram showing an example of selection processing of an antenna element and a user terminal.
Fig. 7 is a flowchart showing an example of the antenna element selection process.
Fig. 8 is a diagram showing an example of a column vector for each antenna element.
Fig. 9 is a flowchart showing an example of the selection process of the user terminal.
Fig. 10 is a diagram showing an example of selection processing of the user terminal.
Fig. 11 is a diagram showing an example of hardware configurations of a base station and a user terminal.
Detailed Description
Embodiments of the present disclosure are described below with reference to the drawings.
[ Structure of Wireless communication System ]
Fig. 1 shows a configuration example of a radio communication system according to the present embodiment. The wireless 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 a gNB)100 including a plurality of transmission points 10a to 10i and a signal processing device 20; and at least one user terminal (also referred to as a wireless terminal or ue) (user equipment) 200.
In the case of describing the elements of the same type by distinguishing them, reference symbols are used as in the case of "transmission points 10a to 10 i" and "user terminal 200 a" and "user terminal 200 b", and in the case of describing the elements of different types by distinguishing them, the common reference numerals in the reference symbols are used as in the case of "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. As shown in fig. 1, for example, cells formed by the transmission points 10a to 10i overlap each other.
For example, in fig. 1, the base station 100 performs radio communication with user terminals 200a and 200b under the control (for example, in cells) of the transmission points 10a to 10 i. For example, the base station 100 selects at least one transmission point 10 from among the transmission points 10a to 10i according to the movement of the user terminal 200, and the selected transmission point 10 transmits a signal to the user terminal 200.
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 is wirelessly transmitted to the user terminal 200. Further, the signal processing device 20 receives signals from the user terminal 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 apparatus 20 selects a channel used in signal transmission from among a plurality of channels between a plurality of antenna elements and a plurality of user terminals 200.
Here, when a plurality of antenna elements are provided as in Massive MIMO, a huge amount of calculation is expected when the signal processing device 20 selects a channel to be used for signal transmission, and the calculation is performed for all combinations that can be used between the antenna elements and the user terminal 200.
Therefore, a method of reducing the amount of calculation when the base station 100 selects a channel used in signal transmission is described in an aspect of the present disclosure.
In fig. 1, 2 user terminals 200 are shown, but the number of user terminals 200 is not limited to this. For example, 1 user terminal 200 may exist under the transmission points 10a to 10i, or 3 or more user terminals 200 may exist. Alternatively, in some cases, the user terminal 200 does not exist under any of the transmission points 10a to 10 i.
The number of transmission points 10 included in the base station 100 is not limited to 9 of the transmission points 10a to 10i, and may be other numbers. The number of antenna elements included in each transmission point 10 may be the same or different.
In addition, the transmission point is also referred to as "extension office" or "RRH (Remote Radio Head)". Further, the signal processing apparatus is also referred to as a "Baseband processing Unit (BBU)".
[ Structure of base station ]
Fig. 2 is a block diagram showing a configuration example of the base station 100. Fig. 2 shows a configuration related to downlink data transmission, and omits a configuration related to uplink data reception.
The base station 100 shown in fig. 2 includes n (one or more integers) transmission points 10 and a signal processing device 20. For example, transmission points 10a to 10i shown in fig. 1 correspond to transmission points 10-1 to 10-9 in fig. 2, where n is 9.
The signal processing device 20 includes an encoding section 101, a modulation section 102, a channel estimation section 103, a selection section 104, and a transmission control section 105, and each of the transmission points 10-1 to 10-n includes a radio transmission section 106, an antenna 107, and a radio reception section 108.
In fig. 2, for example, when OFDM (Orthogonal Frequency division multiplexing) transmission is performed, descriptions of a configuration (for example, IFFT (Inverse Fast Fourier Transform) processing section, CP (cyclic prefix) adding section) and the like for causing the base station 100 to generate an OFDM signal are omitted.
The channel estimation section 103 receives a reference signal (reference signal for channel estimation) transmitted from each user terminal 200 and received by an antenna 107 (antenna element) of a transmission point 10 included in the base station 100, as input.
Selection section 104 (e.g., a scheduler) selects a channel to be used for signal transmission based on a channel estimation result between user terminal 200 and transmission point 10 (antenna element) input from channel estimation section 103. For example, the selection unit 104 selects the user terminal 200 of the signal transmission object. Furthermore, selection section 104 selects an antenna element to be used for signal transmission. The selection unit 104 outputs selection information indicating the selected channel to the transmission control unit 105. The details of the channel selection method used for signal transmission in selection section 104 will be described later.
For example, transmission control section 105 may perform beamforming or precoding on transmission data using a plurality of antenna elements. In this case, transmission control section 105 may generate beamforming weights or precoding matrices using the channel estimation results input from channel estimation section 103. Alternatively, transmission control section 105 may perform transmission power control on transmission data of user terminal 200 using the channel estimation result.
In each of the transmission points 10-1 to 10-n, the antenna 107 has one or more antenna elements.
The radio transmission section 106 of each transmission point 10 performs radio transmission processing such as D/a conversion, frequency conversion, and amplification on transmission data (baseband signal) input from the transmission control section 105, thereby generating a radio signal. Radio transmission section 106 transmits the generated radio signal via the antenna element (antenna 107) indicated by the transmission control information input from transmission control section 105.
[ Structure of user terminal ]
Fig. 3 is a block diagram showing an example of the configuration of the user terminal 200. Fig. 3 shows a configuration related to downlink data reception, and omits a configuration related to uplink data transmission.
Note that, in fig. 3, description of a configuration (for example, CP removing section, FFT processing section) for receiving the OFDM signal in the user terminal 200 and the like is omitted.
The antenna 202 has more than one antenna element.
Decoding section 205 decodes the signal input from demodulation section 204 and outputs received data.
[ operation of base station ]
Next, an operation example of the base station 100 is specifically described.
In the following description, as shown in fig. 4, the radio 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, and UE # 4).
Each of the transmission points 10 shown in fig. 4 has four antenna elements. That is, in fig. 4, sixteen antenna elements are included in the wireless communication system 1. In the following, TP # 1 has antenna elements # 1 to #4, TP # 2 has antenna elements #5 to #8, TP # 3 has antenna elements #9 to #12, and TP # 4 has antenna elements #13 to #16, as an example.
The base station 100 selects a channel used in signal transmission from among channel estimation values obtained for a plurality of channels between sixteen antenna elements # 1 to #16 and four user terminals 200(UE # 1 to UE # 4). Hereinafter, for example, the base station 100 selects an antenna element used for signal transmission and the user terminal 200 to which the signal is transmitted.
Fig. 5 is a flowchart showing an example of signal (e.g., data) transmission processing in the base station 100. Fig. 6 shows an example of selection processing of an antenna element and user terminal 200 in base station 100 (e.g., selection section 104).
As shown 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 generates a channel matrix representing the estimated channel (ST 12). For example, as shown in fig. 6, the base station 100 generates a 4-row × 16-column channel matrix having, as elements, channel estimation values h (x, y) (where x is 1, 2, 3, or 4, and y is any one of 1 to 16) between the UE # x and the antenna element # y.
As shown in fig. 5, the base station 100 selects an antenna element to be used in signal transmission using the channel matrix generated in ST12 (ST 13). For example, in fig. 6, the base station 100 selects antenna elements # 1, #4, #12, # 16. Further, the 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 ST 12. For example, as shown in fig. 6, the base station 100 generates a 4-row by 4-column channel matrix having, as elements, channel estimation values h (x, y ') (where x is 1, 2, 3 or 4, and y is 1, 4, 12 or 16) between the UE # x and the antenna element # y' selected in ST 13. The details of the method for selecting an antenna element in ST13 will be described later.
As shown in fig. 5, the base station 100 selects the user terminal 200 to which the signal is transmitted, using the channel matrix generated in ST13 (ST 14). For example, in fig. 6, base station 100 selects UE # 3 and UE # 4. Further, the base station 100 generates a channel matrix including an element related to the selected user terminal 200 among elements included in the channel matrix generated in ST 12. For example, as shown in fig. 6, the base station 100 generates a 2-row × 4-column channel matrix having, as elements, channel estimation values h (x ', y') (where x 'is 3 or 4, y' is 1, 4, 12, or 16) between the UE # x 'selected in ST14 and the antenna element # y' selected in ST 13. The details of the method for selecting an antenna element in ST14 will be described later.
As shown in fig. 5, the base station 100 performs transmission control for the antenna element selected in ST13 and the user terminal 200 selected in ST14 (ST 15). For example, base station 100 may generate a precoding matrix using antenna elements # 1, #4, #12, and #16 for transmission data addressed to UE # 3 and UE # 4, using a channel matrix of 2 rows × 4 columns shown in fig. 6.
Then, the base station 100 performs signal transmission to the UE # 3 and the UE # 4 selected in ST14 by using the antenna elements # 1, #4, #12, and #16 selected in ST13 in accordance with transmission control in ST15 (ST 16).
As shown in fig. 6, the base station 100 determines antenna elements (antenna elements # 1, #4, #12, and #16 in fig. 6) to be used for transmission of radio signals from among the plurality of antenna elements # 1 to #6, using channel estimation values (for example, a 4-row × 16-column channel matrix in fig. 6) between the antenna elements # 1 to #16 and the UEs # 1 to # 4. As shown in fig. 6, base station 100 selects a part of the channel estimation values corresponding to determined antenna elements # 1, #4, #12, and #16 from among the channel estimation values included in the channel matrix of 4 rows × 16 columns. Then, the base station 100 determines the user terminal 200(UE # 3 and #4 in fig. 6) to be transmitted with the radio signal from among the UE # 1 to UE # 4, by using the selected partial channel estimation values (the channel matrix of 4 rows × 4 columns in fig. 6).
For example, in fig. 6, base station 100 extracts a column vector corresponding to a selected antenna element from a 4-row × 16-column channel matrix used for selecting the antenna element, and generates a 4-row × 4-column channel matrix used for selecting user terminal 200. In other words, the base station 100 reduces the 4-row × 16-column channel matrix used for selecting the antenna elements to the 4-row × 4-column channel matrix, and performs the selection process of the user terminal 200.
By this processing, base station 100 can execute the selection processing of user terminal 200 without using the channel estimation values for unselected antenna elements, and therefore, the amount of calculation for the selection processing of user terminal 200 can be reduced. In other words, the base station 100 can reduce the amount of calculation of the channel selection process used for transmission of the radio signal.
[ method for selecting antenna element ]
Next, details of the method for selecting an antenna element in ST13 shown in fig. 5 will be described.
Fig. 7 is a flowchart showing an example of the antenna element selection process (process ST13 in fig. 5) in base station 100.
When the processing shown in fig. 7 is performed, base station 100 calculates channel estimation values [ h (1, y), h (2, y), h (3, y), h (4, y) in the column direction of the channel matrix obtained in the processing including ST12 in fig. 5 as shown in fig. 8](wherein y is any one of 1 to 16) column vector h1～h16. Column vector h1～h16Corresponding to the channels of antenna elements # 1 to #16, respectively.
In fig. 7, the base station 100 initializes (k equals 1) a variable k (ST 131).
Specifically, in ST133, the base station 100 selects a nematic vector hy(i)(where i is 1 to k) and a column vector h that obtains the highest gain when addedy(k+1). For example, the base station 100 may determine the magnitude of the gain by comparing a feature value, a correlation value, or a chord distance (chord distance) calculated using a combination of the column vectors h. In addition, the parameters related to the gain are not limited to the characteristic value, the correlation value, and the chord distance.
The base station 100 transmits the signal at the antenna element # y (i) (column vector h)y(i)) (where i is 1 to k) the antenna element # y (k +1) (column vector h) selected in ST133 is added to the combinationy(k+1) It is determined whether or not a larger gain is obtained than the combination of the antenna elements # y (i) (where i ═ 1 to k) (ST 134).
If it is determined in ST134 that a larger gain is obtained by adding antenna element # y (k +1) (ST 134: yes), base station 100 increments variable k (ST 135). By incrementing the variable k, the base station 100 adds the antenna element # y (k +1) to the combination of antenna elements used in signal transmission.
Further, when all antenna elements are selected after the process of ST135, base station 100 may end the antenna element selection process (not shown). Alternatively, base station 100 may end the antenna element selection process (not shown) when a predetermined number of antenna elements are selected after the process of ST 135.
Further, after the process of ST135, base station 100 returns to the process of ST133, selected from the processes except for the process of ST132 and past ST133Selected antenna element # y (i) (column vector h)y(i)) (where i is 1 to k), the (k +1) th antenna element is newly selected.
On the other hand, if it is determined in ST134 that a larger gain cannot be obtained by adding antenna element # y (k +1) (ST 134: no), base station 100 ends the antenna element selection process.
In this manner, by the antenna element selection processing shown in fig. 7, the base station 100 determines a combination of k antenna elements as an antenna element to be used for signal transmission.
Here, a specific example of the antenna element selection process shown in fig. 7 will be described. Hereinafter, a procedure in which the antenna elements # 1, #4, #12, and #16 are selected as antenna elements to be used for signal transmission will be described as an example, as shown in fig. 6.
When k is 1 in fig. 7, base station 100 selects column vector h corresponding to antenna elements # 1 to #16 in ST1321～h16Among them, the antenna element #4 (column vector h4) having the largest eigenvalue is selected (i.e., y (1) ═ 4).
In ST133, base station 100 excludes antenna element #4 (column vector h)4) Among the other antenna elements # 1 to #3 and #5 to #16, antenna element #4 (column vector h) is selected4) Additional antenna element # y (2) (column vector h)y(2)) Is used as a candidate of (1). For example, the base station 100 calculates a column vector h4And antenna element # y (2) (column vector h) having the largest eigenvalue, which is the eigenvalue between column vectors h of antenna elements # 1 to #3 and #5 to #16y(2)) Antenna element #1 (column vector h) is selected1)。
At this time, in ST134, it is determined that column vector h is added to column vector h41And the obtained eigenvalues are larger than the column vector h4The characteristic value of (2). By this processing, the antenna element # 1 is newly added as an antenna element used in signal transmission (i.e., y (2) ═ 1).
When k is 2 in fig. 7, in ST133, base station 100 excludes antenna elements # 1 and #4 (column vector h)1、h4) Selecting the antenna elements # 2, #3, #5 to #16 from the other antenna elements1h4Additional antenna element # y (3) (column vector h)y(3)) Is used as a candidate of (1). For example, the base station 100 calculates h1h4And antenna element # y (3) (column vector h) having the largest eigenvalue, and the eigenvalues between column vectors h of antenna elements # 2, #3, #5 and #16y(3)) Antenna element #12 (column vector h) is selected12)。
At this time, ST134 judges that the direction is h1h4Additional column vector h12And the obtained eigenvalues are larger than the column vector h1h4The characteristic value of (2). By this processing, the antenna element #12 is newly added as an antenna element used in signal transmission (i.e., y (3) ═ 12).
Similarly, when k is 3 in fig. 7, in ST133, base station 100 selects antenna element # y (4) from among antenna elements # 2, #3, #5 to #11, #13 to #16 other than antenna elements # 1, #4 and # 12. For example, as a direction h1h4h12Antenna element # y (4) having the largest eigenvalue when column vector h is added (column vector h)y(4)) The base station 100 selects the antenna element #16 (column vector h)16)。
At this time, ST134 judges that the direction is h1h4h12Additional column vector h16And the obtained eigenvalues are larger than the column vector h1h4h12The characteristic value of (2). By this processing, the antenna element #16 is newly added as an antenna element used in signal transmission (i.e., y (4) ═ 16).
When k is 4 in fig. 7, it is determined that antenna element # y (5) (column vector h) to be selected in ST133 is to be usedy(5)) Addition to h1h4h12h16Also, no more than h can be obtained1h4h12h16The antenna element combination of the characteristic value (ST 134: NO). In this case, the base station 100 decides the column vector h that has been selected1、h4、h12、h16The corresponding antenna elements # 1, #4, #12, #16 are combinations of antenna elements used for signal transmission.
In the base station 100, selecting a channel estimation value in accordance with a selection reference for selecting an antenna element used in transmission of a radio signal includes the following operations. Specifically, base station 100 calculates a gain by changing a combination of matrix elements (for example, column vectors) corresponding to the antenna elements in a channel matrix having matrix elements as channel estimation values obtained for respective channels between the antenna elements and user terminal 200. Further, 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. The base station 100 determines an antenna element corresponding to the combination of the matrix elements with increased gain as an antenna element to be used for transmission of a radio signal.
For example, by the processing shown in fig. 7, the base station 100 can determine the combination of antenna elements having the highest gain among the combinations of antenna elements # 1 to # 16.
In the antenna element selection process, the base station 100 sequentially selects one antenna element having the largest gain (e.g., eigenvalue) from among the plurality of antenna elements, and determines the combination of antenna elements to be used for signal transmission. In base station 100, it is determined whether or not the number of antenna elements to be newly added (antenna elements to be selected in ST133) is decreasing every time one antenna element to be used for signal transmission is selected (every time the value of k increases in fig. 7).
By this processing, the base station 100 does not need to calculate a gain for all combinations of column vectors, and thus the amount of calculation in the selection processing of antenna elements can be reduced. Further, since the base station 100 does not need to calculate a gain for the combination of all the column vectors, the time for the antenna element selection process can be shortened.
[ method for selecting user terminal ]
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 user terminal 200 in base station 100 (the process of ST14 in fig. 5).
In addition, in the process shown in fig. 9, the base station 100 uses a channel matrix including column vectors corresponding to the antenna elements selected by the antenna element selection process shown in fig. 7 (for example, refer to the intermediate channel matrix shown in fig. 6).
In fig. 9, the base station 100 initializes a variable l (l ═ 1) (ST 141).
The parameters used for selecting the selection criteria for selecting the UE to be transmitted with the radio signal are not limited to the received power, the eigenvalue, and the proportional fairness. The parameter used as the selection criterion for selecting the UE to be transmitted with the radio signal may be, for example, a parameter related to the communication quality between the antenna element and the UE.
For example, the base station 100 may determine the transmission rate based on an eigenvalue calculated using the channel matrix when precoding is applied at the time of signal transmission, and may determine the transmission rate based on a channel estimation value (or other parameter than the eigenvalue) included in the channel matrix when precoding is not applied at the time of signal transmission.
Alternatively, in ST142, base station 100 may select a predetermined user terminal 200 (fixed UE or UE selected separately). Alternatively, the base station 100 may preferentially select the user terminal 200 that has not been selected in the past signal transmission.
Specifically, in ST143, the base station 100 selects UE # x (l +1) that obtains the highest transmission rate when adding to the combination of UE # x (j) (where j is 1 to l). For example, base station 100 may determine the magnitude of the obtained transmission rate by comparing eigenvalues 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.
In ST144, if it is determined that a larger transmission rate is obtained by adding UE # (l +1) (ST 144: yes), base station 100 adds 1 to variable l (ST 145). By adding 1 to the variable l, the base station 100 adds UE # x (l +1) to the combination of the user terminals 200 to which the signal is transmitted.
After the process in ST145, base station 100 returns to the process in ST143, and reselects the (l +1) th UE from among UEs other than UE # x (j) (where j is 1 to l) selected in the processes in ST142 and past ST 143.
On the other hand, in ST144, if it is determined that a larger transmission rate cannot be obtained by adding UE # (l +1) (ST 144: no), base station 100 ends the selection process of user terminal 200.
In this way, by the selection processing of the user terminal 200 shown in fig. 9, the base station 100 determines the combination of l user terminals 200 as the user terminal 200 to which the signal is transmitted.
Here, a specific example of the selection process of the user terminal 200 shown in fig. 9 will be described.
Hereinafter, a procedure of selecting UEs # 3 and #4 by the user terminal 200 to which a signal is transmitted will be described as an example, as shown in fig. 6. In addition, in base station 100, antenna elements # 1, #4, #12, and #16 are selected as shown in fig. 6 before user terminal 200 is selected. For example, the base station 100 uses the channel matrix shown in fig. 10.
In ST142, when l is 1 in fig. 9, for example, base station 100 selects UE # 3 having the largest eigenvalue (i.e., x (1) ═ 3) from among the row vectors (submatrices) corresponding to UE # 1 to UE # 4.
In ST143, base station 100 selects a candidate for user terminal 200 to be added to UE # 3 from among UEs # 1, #2, and #4 other than UE # 3. For example, the base station 100 calculates an eigenvalue of a submatrix including a row vector of the UE # 3 and each row vector of the UEs # 1, #2, and #4, as the UE # x (2) having the largest eigenvalue, and selects the UE # 4.
In this case, in ST144, the eigenvalue of the submatrix obtained by adding UE # 4 to UE # 3 is determined to be larger than the eigenvalue of the row vector of UE # 3. By this processing, the user terminal 200 to which the signal is transmitted newly adds UE #4 (that is, x (2) ═ 4).
When l is 2 in fig. 9, it is determined that a combination of user terminals 200 larger than the eigenvalues of the sub-matrices of UE # 3 and #4 cannot be obtained even if UE # 3 selected in ST143 is added to UE # 3 and #4 (ST 144: no). In this case, the base station 100 determines a combination of the user terminals 200 to which the selected UEs # 3 and #4 are to be transmitted.
The base station 100 selects a channel estimation value according to a selection criterion for selecting a user terminal to transmit a radio signal, and includes the following items. Specifically, base station 100 changes a combination of matrix elements (for example, row vectors) corresponding to user terminal 200 in a channel matrix (in other words, a degraded channel matrix) having matrix elements of some channel estimation values selected according to a selection criterion for an antenna element, and calculates a transmission rate. Further, 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 the matrix elements in which the transmission rate is increased as the target of transmitting the radio signal.
For example, the base station 100 can determine, through the processing shown in fig. 9, the combination of the user terminals 200 whose transmission rates are the largest among the combinations of UEs # 1 to # 4.
In the selection process of the user terminal 200, the base station 100 selects, from among the plurality of user terminals 200, the user terminal 200 having the highest transmission rate (for example, a characteristic value) in order, and determines the combination of the user terminals 200 to be signal-transmitted. In the base station 100, each time one signal transmission destination user terminal 200 is selected (each time the value of l increases in fig. 9), it is determined whether or not the number of destination user terminals 200 to be newly added (ST143 destination user terminals 200 to be selected) is decreasing.
By this processing, the base station 100 does not need to calculate the transmission rate for all combinations of the user terminals 200 (row vectors), and therefore the amount of calculation in the selection processing of the user terminals 200 can be reduced. Further, the base station 100 does not need to calculate the transmission rate for all combinations of the user terminals 200 (row vectors), and therefore the time for the selection process of the user terminals 200 can be shortened.
The operation example of the base station 100 is specifically explained above.
As explained above, the base station 100 obtains a plurality of channel estimation values for respective channels between the plurality of antenna elements included in the plurality of transmission points 10 and the user terminal 200. Then, the base station 100 selects a part of the channel estimation values from among the plurality of channel estimation values, according to a selection reference for selecting a channel estimation value corresponding to an antenna element used for transmission of a radio signal. Further, the base station 100 selects a part of the channel estimation values further in accordance with a selection criterion for selecting the user terminal 200 to transmit the radio signal from among the selected part of the channel estimation values. The base station 100 controls transmission of radio signals based on the channel estimation value selected according to the selection reference for selecting the user terminal.
Through this process, when selecting the user terminal 200 to be transmitted with a radio signal, the base station 100 can select the user terminal 200 using the channel estimation values of a part corresponding to the antenna element that has been selected. In other words, the base station 100 can select a user terminal to which a radio signal is transmitted, using a channel matrix that degrades a channel matrix having a plurality of channel estimation values as matrix elements. Therefore, in the base station 100, the amount of calculation in the selection process of the user terminal 200 to be signal-transmitted can be reduced.
Further, the base station 100 sequentially selects one antenna element having the largest gain. Similarly, the base station 100 sequentially selects a user terminal 200 whose transmission rate becomes the maximum. By these processes, base station 100 can reduce the amount of calculation in each of antenna element selection and user terminal 200 selection, and can appropriately select an antenna element and user terminal 200.
(other embodiments)
(1) In the above-described embodiment, as shown in fig. 5 or 6, the case where the selection of user terminal 200 is performed after the selection of the antenna element is described. However, base station 100 may select the antenna element after selection of user terminal 200. For example, base station 100 selects user terminal 200 to be transmitted with a radio signal, using the channel estimation values obtained for a plurality of channels between all antenna elements and all user terminals 200 shown in fig. 6 (for example, the processing of fig. 9). Further, base station 100 may select an antenna element to be used for transmission of a radio signal, using a part of the channel estimation values corresponding to the selected user terminal 200 (for example, the processing in fig. 7).
In this case, the base station 100 can select an antenna element using a channel matrix including channel estimation values related to the user terminal 200 that has been selected (in other words, a degraded channel matrix) when selecting an antenna element. Therefore, in the base station 100, the amount of calculation in the selection process of the antenna element used for signal transmission can be reduced.
The base station 100 may select a channel (for example, an antenna element or the user terminal 200) to be used for signal transmission, using a part of channel estimation values selected from among a plurality of channel estimation values between the antenna element and the user terminal 200.
When selecting an antenna element prior to user terminal 200, base station 100 can preferentially select an antenna element having a high power value, for example. Furthermore, in the case where the user terminal 200 is selected earlier than the antenna elements, the base station 100 can preferentially select the user terminal 200 to which data transmission is to be allocated, for example.
(2) In the above-described embodiment, the selection of the antenna element unit (column vector unit of the channel matrix) is described. However, the selection processing of the antenna element is not limited thereto. 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 an antenna element for each group unit. For example, each packet may be a unit of the transmission point 10. This process can further reduce the amount of computation in the selection process of the antenna element in the base station 100.
Similarly, base station 100 may group a plurality of user terminals 200 into a plurality of groups, and select user terminal 200 for each group. This process can further reduce the amount of calculation for the selection process of user terminal 200 in base station 100.
(3) In the above-described embodiment, in the selection processing of the user terminal 200, as shown in fig. 9, the case where the base station 100 selects one user terminal 200(UE # x (1) in fig. 9) has been described. However, the selection process of the user terminal 200 is not limited thereto. 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 transmits a signal among a plurality of user terminals 200, the base station 100 may include the user terminal 200 that has a priority as a signal transmission target and select the user terminal 200 based on the transmission rate obtained in the same manner as in the above-described embodiment. By this processing, when there is a user terminal 200 that needs to perform priority signal transmission, the user terminal 200 can be added to the signal transmission target regardless of the transmission rate.
(4) In the above-described embodiment, a case has been described in which, when the base station 100 determines the combination of antenna elements, one antenna element that obtains a larger gain is sequentially added to the already selected antenna elements. However, the selection method of the antenna element is not limited to this process. For example, the base station 100 may sequentially add two or more antenna elements of a predetermined number to obtain a larger gain.
Similarly, when determining the combination of the user terminals 200, the base station 100 may sequentially add two or more predetermined number of user terminals 200 that have been selected and that have higher transmission rates to the already selected user terminals 200.
This process can reduce the amount of calculation for the selection process of the antenna element or the user terminal 200.
(5) In the above-described embodiment, a case has been described in which a channel matrix indicating a channel between a plurality of antenna elements included in a plurality of transmission points 10 and at least one user terminal 200 included in the wireless communication system 1 is used. 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 the plurality of antenna elements included in the plurality of transmission points 10 and the plurality of antenna elements included in each of the at least one user terminal 200.
(hardware construction)
The block diagrams used in the description of the above embodiments represent blocks in functional units. These functional blocks (structural units) are implemented by any combination of hardware and/or software. The method of implementing each functional block is not particularly limited. That is, each functional block may be implemented by 1 apparatus which is physically and/or logically combined, or may be implemented by a plurality of apparatuses which are directly and/or indirectly (for example, wired and/or wireless) connected with two or more apparatuses which are physically and/or logically separated.
For example, a base station, a user terminal, or the like in one 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 hardware configurations of the base station 100 and the user terminal 200 according to the embodiment of the present disclosure. The base station 100 and the user terminal 200 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 "device" may be replaced with a circuit, an apparatus, a unit, or the like. The hardware configuration of base station 100 and user terminal 200 may include one or more of each illustrated device, or may be configured without including some devices.
For example, only 1 processor 1001 is shown, but there may be multiple processors. The processing may be executed by 1 processor, or the processing may be executed by 1 or more processors simultaneously, sequentially, or by using another method. The processor 1001 may be implemented by 1 or more chips.
Each function of the base station 100 and the user terminal 200 is realized by reading specific software (program) into hardware such as the processor 1001 and the memory 1002, performing an operation by the processor 1001, and controlling communication via the communication device 1004 or 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 constituted 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, encoding section 101, modulating section 102, channel estimating section 103, selecting section 104, transmission control section 105, demodulating section 204, decoding section 205, and the like described above can be implemented by processor 1001. In addition, the above table may be stored in the memory 1002.
Further, the processor 1001 reads a program (program code), a software module, data, or the like from the storage 1003 and/or the communication device 1004 to the memory 1002, and executes various processes based on them. 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, the functional blocks constituting at least a part of base station 100 and user terminal 200 may be realized by a control program stored in memory 1002 and operated by processor 1001, and the other functional blocks may be similarly realized. Although the various processes described above are described as being executed by one processor 1001, the processes may be executed sequentially by two or more processors 1001 at the same time. The processor 1001 may be implemented by 1 or more chips. In addition, the program may be transmitted from a network via an electric communication line.
The memory 1002 is a computer-readable recording medium, and may be configured by at least 1 of ROM (Read only memory), EPROM (erasable Programmable ROM), EEPROM (erasable Programmable ROM, electrically erasable Programmable ROM), RAM (Random access memory), and the like. The memory 1002 may also be referred to as a register, cache, main memory (primary storage), or the like. The memory 1002 can store executable programs (program codes), software modules, and the like for implementing the wireless communication method of an embodiment of the present disclosure.
The storage 1003 is a computer-readable recording medium, and may be configured of at least 1 of an optical disk such as a CD-rom (compact Disc rom), a hard disk drive, a flexible disk, an optical disk (e.g., an optical disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory device (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic stripe, or the like. The storage 1003 may also be referred to as a secondary storage device. The storage medium may be, for example, a database including the memory 1002 and/or the memory 1003, a server, or other suitable medium.
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. For example, the above-described radio transmission units 106 and 201, antennas 107 and 202, and radio reception units 108 and 203 may be implemented by the communication device 1004.
The input device 1005 is an input device (for example, a keyboard, a mouse, a microphone, a switch, a key, a sensor, and the like) that receives an input from the outside. The output device 1006 is an output device (for example, a display, a speaker, an LED (light emitting diode) lamp, or the like) that performs output to the outside. The input device 1005 and the output device 1006 may be integrated (for example, a touch panel).
The processor 1001 and the memory 1002 are connected to each other via a bus 1007 for information communication. The bus 1007 may be constituted by 1 bus or by buses different among devices.
The base station 100 and the user terminal 200 may be configured to include hardware such as a microprocessor, a Digital Signal Processor (DSP), an ASIC (Application Specific integrated circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array), and some or all of the functional blocks may be implemented by the hardware. For example, the processor 1001 may be implemented with at least 1 of these hardware.
(information Notification, Signaling)
Note that the information notification is not limited to the embodiment and embodiment described in the present specification, and may be performed by other methods. For example, the notification of the Information may be implemented by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling), broadcast Information (master Information Block (MIB), System Information Block (SIB), etc.), 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 (rrcconnectionsetup) message, an RRC Connection Reconfiguration (RRC Connection Reconfiguration) message, or the like.
(applicable system)
Each of the schemes and embodiments described in this specification can also be applied to LTE (Long term evolution), LTE-a (LTE-Advanced), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), FRA (Future radio access), W-CDMA (registered trademark) (Wideband Code Division multiple access), etc., GSM (registered trademark) (Global System for Mobile communications), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11(Wi-Fi (registered trademark)), IEEE 802.16(WiMAX), IEEE 802.20, UWB (Ultra-wide band), Bluetooth (registered trademark), and systems using other appropriate systems and/or next generation systems expanded based thereon.
(treatment Processes, etc.)
The processing procedures, sequences, flowcharts, and the like of the embodiments and embodiments described in the present specification may be changed in order as long as they are not contradictory. For example, elements of the method described in the present specification are presented in the order of illustration, and are not limited to the specific order presented.
(operation of base station)
In this specification, a specific operation performed by a base station is sometimes performed by an upper node (upper node) of the base station. In a network configured by 1 or more network nodes (network nodes) having a base station, it is obvious that 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 (for example, an MME (Mobility Management Entity), an S-GW (Serving-Gateway), or the like is considered, but not limited thereto). Although the above illustrates the case where a network node other than the base station exists, a combination of a plurality of other network nodes (e.g., MME and S-GW) may be used.
(direction of input/output)
Information, signals, and the like can be output from a higher layer (or lower layer) to a lower layer (or higher layer). Or may be input/output via a plurality of network nodes.
(processing of input/output information and the like)
The information to be input and output may be stored in a specific area (for example, a memory) or may be managed using a management table. Information input/output and the like may also be overwritten, updated or added. The output information and the like may be deleted. The inputted information and the like may be transmitted to other devices.
(determination method)
The decision may be made by a value (0 or 1) represented by 1 bit, by a true or false value (Boolean: true or false), or by a comparison of values (e.g., with a particular value).
(software)
Software, whether referred to as software, firmware, middleware, microcode, hardware description language, or by other names, is intended to be broadly interpreted as representing instructions, instruction sets, code segments, program code, programs, subroutines, software modules, applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, and the like.
Further, software, instructions, etc. may be transmitted or received via a transmission medium. For example, where the software is transmitted from a website, server, or other remote source using a wireline technology such as a coaxial cable, fiber optic cable, twisted pair, or Digital Subscriber Line (DSL), and/or a wireless technology such as infrared, wireless, or microwave, the wireline and/or wireless technology is included in the definition of transmission medium.
(information, Signal)
Information, signals, and the like described in this specification can be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or photons, or any combination thereof.
In addition, terms described in the specification and/or terms necessary for understanding the specification may be replaced with terms having the same or similar meanings. For example, the channels and/or symbols may also be signals (signaling). Further, the signal may also be a message. Further, a Component Carrier (CC) may also be referred to as a Carrier frequency, a cell, etc.
("System", "network")
The terms "system" and "network" used in this specification may be used interchangeably.
(parameter, name of channel)
The information, parameters, and the like described in the present specification may be expressed by absolute values, relative values to specific values, or other corresponding information. For example, the radio resource may also be indicated by a specific index.
The names used for the above parameters and the like are not limitative names in any way. Further, the formula using these parameters may be different from the formula explicitly disclosed in the present specification. Various channels (e.g., PUCCH (Physical Uplink Control Channel), PDCCH (Physical Downlink Control Channel), etc.) and information elements (e.g., TPC, etc.) can be identified by all appropriate names, and thus various names assigned to these various channels and information elements are not limitative names in any point.
(base station)
A base station (radio base station) can accommodate 1 or more (e.g., three) (also referred to as sectors) cells. When a Base Station accommodates a plurality of cells, the entire coverage area of the Base Station can be divided into a plurality of smaller areas, and each smaller area can also provide communication services through a Base Station subsystem (e.g., an indoor small cell RRH (remote radio Head)), which means a part or all of the coverage area of the Base Station and/or the Base Station subsystem performing communication services in the coverage area.
(terminal)
A user terminal is also sometimes referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a UE (user terminal), or some other suitable terminology.
(meaning and interpretation of terms)
The terms "determining" and "determining" used in the present specification may include various operations. For example, "determining" or "determination" may include "determining" or "determining" as to whether to perform determination (rounding), calculation (calculating), processing (processing), derivation (deriving), investigation (investigating), retrieval (retrieving) (e.g., in a table, a database, or other data structure), or confirmation (authenticating), for example. The terms "determining" and "deciding" may include determining and deciding reception (e.g., reception information), transmission (e.g., transmission information), input (input), output (output), access (access) (e.g., access to data in a memory), and the like. The terms "determining" and "decision" can include determining and deciding a solution (resolving), a selection (selecting), a selection (sounding), a building (evaluating), a comparison (comparing), and the like. That is, "determining" and "deciding" can include determining and deciding certain operations.
The terms "connected", "coupled", and the like, or all variations thereof, mean that all connections or couplings, direct or indirect, between two or more elements, and can include the case where 1 or more intermediate elements exist between two elements that are "connected" or "coupled" to each other. The coupling or connection between the elements may be physical, logical, or a combination thereof. As used in this specification, it can be considered that 2 elements are "connected" or "coupled" to each other by using one or more wires, cables, and/or printed electrical connections, and as a few non-limiting and non-exhaustive examples, electromagnetic energy having wavelengths in the wireless frequency domain, the microwave region, and/or the optical (both visible and invisible) region, and the like.
The Reference Signal can also be referred to simply as RS (Reference Signal) and, depending on the standard of application, may also be referred to as Pilot (Pilot) or the like. The RS for correction may be referred to as TRS (Tracking RS), PC-RS (Phase Compensation RS), PTRS (Phase Tracking RS), or additional RS (additional RS). The demodulation RS and the correction RS may be referred to as "other terms". The demodulation RS and the correction RS may be defined by the same name (for example, demodulation RS).
As used in this specification, a statement that "is based on" does not mean "is based only on" unless explicitly stated otherwise. In other words, the expression "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", or the like.
The terms "comprising", "including" and variations thereof, as used in the specification or claims, are intended to be inclusive in a manner similar to the term "comprising". Further, the term "or" as used in the present specification or claims means not a logical exclusive or.
The radio frame may be formed of 1 or more periods (frames) in the time domain. One or more individual frames in the time domain may be referred to as a subframe, a time unit, or the like. Further, the subframe may also be composed of 1 or more slots in the time domain. Further, the slot may be formed of 1 or more symbols in the time domain (OFDM (orthogonal frequency Division Multiplexing) symbol, SC-FDMA (Single carrier frequency Division Multiple Access) symbol, or the like).
The time unit when the signal is transmitted is represented by any one of a radio frame, a subframe, a slot, and a symbol. The radio frame, subframe, slot and symbol may also correspond to other terms, respectively.
For example, in the LTE system, the base station performs scheduling of radio resources (frequency bandwidth, transmission power, and the like that can be used by each mobile station) for each mobile station. The minimum time unit of the scheduling may also be referred to as TTI (Transmission time interval).
For example, 1 subframe may also be referred to as a TTI, a plurality of consecutive subframes may also be referred to as a TTI, and 1 slot may also be referred to as a TTI.
The resource element is a resource allocation unit in the time domain and the frequency domain, and may include 1 or more consecutive subcarriers (subcarriers) in the frequency domain. The resource element may include 1 or more symbols in the time domain, and may have a length of 1 slot, 1 mini-slot, or 1 TTI. Each of the 1 TTI and 1 subframe may be formed of 1 or more resource elements. The Resource element may also be referred to as a Resource Block (RB), a Physical Resource Block (PRB), a PRB pair, an RB pair, a scheduling element, a frequency element, or a subband. Further, the resource unit may also be composed of one or more REs. For example, 1 RE is not limited to the term RE or the like, as long as it is a resource of a unit smaller than a resource element that is a resource allocation unit (for example, the smallest resource unit).
The above-described structure of the radio frame 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 slot, and the number of subcarriers included in the resource block can be variously changed.
In the context of the present disclosure, where the article is added by translation, as in, for example, a, an, and the in english, the article includes a plurality in addition to the case where the article is explicitly stated in the context.
(variation of the protocol, etc.)
The embodiments and modes described in the present specification may be used alone, may be used in combination, or may be switched depending on execution. Note that the notification of the specific information (for example, the notification of "X") is not limited to the explicit notification, and may be performed implicitly (for example, by not performing the notification of the specific information).
The present disclosure has been described in detail above, but it is obvious to 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 variations without departing from the spirit and scope of the present disclosure determined based on the description of the claims. Accordingly, the description of the present specification is for the purpose of illustration and is not intended to have any limiting meaning to the present disclosure.
This patent application incorporates the entire contents of japanese patent application No. 2018-056839, filed on 23/3/2018.
Industrial applicability
An aspect of the present disclosure is useful for a mobile communication system.
Description of the symbols
1 radio communication system
10 a-10 i, 10-1-10-n sending points
20 Signal processing device
100 base station
101 coding unit
102 modulation unit
103 channel estimation unit
104 selection unit
105 transmission control unit
106. 201 radio transmitting unit
107. 202 antenna
108. 203 radio receiving unit
200 user terminal
204 demodulation unit
205 decoding unit
Claims (6)
1. A base station is provided with:
a transmission circuit that transmits a wireless signal; and
and a control circuit configured to control 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 a plurality of channel estimation values obtained for respective channels between a plurality of antenna elements included in the plurality of transmission points and the user terminal.
2. The base station of claim 1, wherein,
the first selection reference is a reference for selecting a channel estimation value corresponding to an antenna element used in 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 to be transmitted.
3. The base station of claim 1, wherein,
the first selection criterion is a criterion for selecting a channel estimation value corresponding to a user terminal to which the radio signal is to be transmitted,
the second selection reference is a reference for selecting a channel estimation value corresponding to an antenna element used for transmission of the radio signal.
4. The base station of claim 2, wherein,
selecting the channel estimation value according to the second selection reference comprises:
determining whether or not a transmission rate calculated by changing a combination of matrix elements corresponding to the user terminal increases in a channel matrix having, as matrix elements, a part of channel estimation values selected from among the plurality of channel estimation values according to the first selection criterion; and
and determining a user terminal corresponding to the combination of the matrix elements of which the transmission rate is increased as an object to transmit the radio signal.
5. The base station of claim 3, wherein,
selecting the channel estimation value according to the second selection reference comprises:
determining whether or not a gain calculated by changing a combination of matrix elements corresponding to the antenna elements increases in a channel matrix having, as matrix elements, a part of channel estimation values selected from among the plurality of channel estimation values according to the first selection criterion; and
an antenna element corresponding to the combination of the matrix elements of which the gain is increased is determined as an antenna element used in transmission of the wireless signal.
6. A transmission method for transmitting a radio signal by a base station,
the transmission of the radio signal is controlled based on channel estimation values selected in accordance with a first selection reference and a second selection reference, from among a plurality of channel estimation values obtained for respective channels between a plurality of antenna elements included in a plurality of transmission points and a user terminal.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2018-056839 | 2018-03-23 | ||
| JP2018056839 | 2018-03-23 | ||
| PCT/JP2019/012178 WO2019182134A1 (en) | 2018-03-23 | 2019-03-22 | Base station and transmission method |
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| Publication Number | Publication Date |
|---|---|
| CN111903065A true CN111903065A (en) | 2020-11-06 |
| CN111903065B CN111903065B (en) | 2023-12-05 |
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| CN201980021579.0A Active CN111903065B (en) | 2018-03-23 | 2019-03-22 | Base station and transmission method |
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| Country | Link |
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| JP (1) | JP7261223B2 (en) |
| CN (1) | CN111903065B (en) |
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| WO2019182134A1 (en) | 2019-09-26 |
| CN111903065B (en) | 2023-12-05 |
| JP7261223B2 (en) | 2023-04-19 |
| JPWO2019182134A1 (en) | 2021-04-08 |
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