JP4777394B2 - Radio base station and radio communication method - Google Patents

Description

  The present invention relates to a radio base station provided with an adaptive array antenna, and a radio communication method for the radio base station.

In a radio base station that performs communication using an adaptive array antenna, the effect of the adaptive array antenna differs depending on the arrangement of antenna elements. First, when the interval at which the antenna elements are arranged is small, the antenna correlation is high and can cope with fading fluctuation. On the other hand, when the spacing between the antenna elements is large, the antenna correlation is low and a high diversity effect can be obtained.
Therefore, when it is desired to increase the diversity effect in the radio base station, the antenna elements are arranged (group A) separated by several wavelength intervals in consideration of the antenna correlation described above. However, since the antenna elements are separated from each other, directivity control for separating the transmission wave (desired wave) transmitted from terminal A and the transmission wave (interference wave) transmitted from other terminal B is performed. There is a problem that it is difficult to do. Therefore, when the antenna elements are arranged at different wavelength intervals (group B) and the desired directivity control cannot be performed, any of the antennas of group A used is any of group B. There has been proposed a radio base station antenna device that changes directivity characteristics by switching to an antenna element and separates a desired wave and an interference wave (see Patent Document 1).
JP 2000-252734 A

  The radio base station antenna device described in Patent Document 1 described above separates a desired wave and an interference wave and ensures a diversity effect by simply switching one of the antenna elements used to change the directivity characteristics. Is. Therefore, it is possible to cope with high-speed fading fluctuation that occurs when the above-described terminal A is moving at high speed (for example, 80 km / h or more) by simply switching one of the antenna elements. Therefore, appropriate directivity control could not be performed.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a radio base station capable of performing stable communication by selecting an antenna according to a changing propagation environment, and To provide a wireless communication method.

In order to achieve the above object, a radio base station according to the present invention has a plurality of antennas, and performs radio communication using at least two or more antennas. An acquisition unit that acquires reception quality information, a grasping unit that grasps a variation tendency of a value related to reception quality of each antenna acquired by the acquisition unit, and a value related to reception quality at each antenna that is grasped by the grasping unit A determination unit that determines a correlation degree between the antennas based on a fluctuation tendency of the antenna, and wireless communication from among the plurality of antennas according to the correlation degree of the antennas determined by the determination unit. And a selection unit that selects at least two or more antennas to be used.

  In the variation tendency of the value related to the reception quality at each of the antennas grasped by the grasping unit, the determination unit is equal to or more than a first predetermined value compared to the value related to the reception quality acquired immediately before the value related to the reception quality. It is preferable to detect the time point when the correlation is lowered and to determine the degree of correlation according to the time difference between the detected time points between the antennas.

  The radio base station of the present invention further includes a calculation unit that calculates a weight of each antenna in the plurality of antennas, and the selection unit includes a time interval for calculating a weight in the calculation unit, and the determination unit It is preferable to select at least two or more antennas to be used for the wireless communication based on the cycle in which the time point determined in step 1 occurs.

In addition, the wireless communication method of the present invention is a wireless base station wireless communication method that includes a plurality of antennas and performs wireless communication using at least two or more antennas. An acquisition step for acquiring quality information, a grasping step for grasping a fluctuation tendency of a value related to the reception quality of each antenna obtained in the obtaining step, and a tendency of fluctuation of a value relating to the reception quality in each antenna grasped in the grasping step. A determination step of determining a correlation degree between the antennas based on the at least two antennas used for radio communication from the plurality of antennas according to the correlation degree of the antennas determined in the determination step And a selection step of selecting the antenna described above.

  Since the present invention can select an antenna according to a changing propagation environment, stable communication can be performed.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of a configuration example of a radio base station according to the present invention. A radio base station 20 shown in FIG. 1 includes a plurality of antenna elements 1, a plurality of radio (RF) units 2 provided for each of a plurality of antennas, and up / down-converting radio signals from a counterpart communication device, and a transmission The control unit 3 and the reception control unit 4 are configured. The transmission control unit 3 includes a transmission processing unit 5. The reception control unit 4 acquires a weight calculation unit (calculation unit) 11 that calculates the weight of each antenna in a plurality of antennas and reception quality information indicating reception quality of each antenna for each of the plurality of antennas at predetermined intervals. A reception quality information acquisition unit (acquisition unit) 12, a reception quality fluctuation trend grasping unit (grasping unit) 13 for grasping a fluctuation tendency of a value related to reception quality of each antenna acquired by the reception quality information acquisition unit 12, and a reception quality A correlation determination unit (determination unit) 14 that determines the degree of correlation between the antennas based on the variation tendency of the value regarding the reception quality at each antenna, which is grasped by the variation tendency grasping unit 13, and the correlation determination unit 14 determine the correlation degree. An antenna selection unit (selection unit) 7 that selects an antenna to be used for wireless communication from a plurality of antennas according to the degree of correlation between the antennas; And a reception processing unit 8 for performing processing for forming a beam emitted from the antennas. In this embodiment, the weight calculation unit 11, the reception quality information acquisition unit 12, the reception quality fluctuation tendency grasping unit 13, and the correlation determination unit 14 are provided in the reception control unit 4. However, the present invention is not limited to this. It may be configured independently.

  The reception quality information acquisition unit 12 acquires reception quality information of a reception radio signal from a communication device that is a communication partner. As a value related to reception quality in the reception quality information, a value indicating reception power measured at each antenna of a plurality of antennas and a value indicating reception quality such as SINR are acquired. The reception quality fluctuation tendency grasping unit 13 grasps the fluctuation tendency of the value related to the reception quality of each acquired antenna.

  The correlation determination unit 14 determines the degree of correlation based on the variation tendency of the value related to reception quality at each antenna, which is grasped by the reception quality variation tendency grasping unit 13.

  The antenna selection unit 7 selects at least two or more antenna elements to be used for wireless communication from a plurality of antennas according to the degree of correlation between the antennas determined by the correlation determination unit 14. The antenna selected by the antenna selector 7 is used for receiving a radio signal from the counterpart communication device and is used for transmitting a radio signal to the counterpart communication device.

  Next, an antenna selection method by the antenna selection unit 7 based on the degree of correlation between the antennas determined by the correlation determination unit 14 will be described with reference to the flowchart of FIG. The plurality of antennas are configured by array antennas, and the weight calculation unit 11 calculates the weight of each antenna in the plurality of array antennas.

  When the reception control unit 4 of the radio base station starts communication with the communication device that is the communication partner (step 101), the reception quality information acquisition unit 12 acquires the reception quality information of the reception radio signal of each antenna, and receives it. The quality fluctuation tendency grasping unit 13 grasps the fluctuation tendency of the value related to the reception quality in the received reception quality information of each antenna (step 102). Correlation determination unit 14 determines the degree of correlation between the antennas according to the variation tendency of each antenna grasped by reception quality variation tendency grasping unit 13 (step 103) (details regarding the determination of the correlation degree will be described later). . Then, the antenna selection unit 7 selects at least two or more antennas to be used for wireless communication using the information regarding the fluctuation tendency of the value related to the reception quality determined by the correlation determination unit 14 (steps 104 to 112). .

  In the flowchart of FIG. 2, as an antenna selection method in the antenna selection unit 7, the antenna selection unit 7 changes the value related to the weight update time interval in which the weight calculation unit 11 calculates the weight and the reception quality determined in the correlation determination unit 14. Using the information regarding the trend, at least two or more antennas used for wireless communication are selected. First, the antenna selection unit 7 compares the weight update time interval with a cycle (falling time interval) in which a time point (timing) at which a value related to reception quality becomes a predetermined value or less in a variation tendency of each antenna (step 104). ). As a result of comparison, when the drop time interval is larger than the weight update time interval (in the case of Yes) (in this case, it is a case where it is not possible to cope with a change in the propagation environment, it is preferable to select an antenna having a correlation as high as possible. ), The degree of correlation of the antennas of the arbitrary antenna group (first antenna group) is investigated (step 105), and it is determined whether the antenna has a high degree of correlation (step 106). If the antenna selection unit 7 determines that the antenna has a high degree of correlation (in the case of Yes), the antenna selection unit 7 selects at least two antennas to be used for wireless communication from the first antenna group (step 107). When the antenna selection unit 7 determines that the antenna has a low degree of correlation (in the case of No), the antenna selection unit 7 investigates the degree of correlation of the antennas of other arbitrary antenna groups, and performs wireless communication from among the antenna groups having the highest degree of correlation. At least two or more antennas to be used are selected (step 108).

  In step 104, when the drop time interval is smaller than the weight update time interval (in the case of No), the antenna selection unit 7 determines the correlation degree of the antennas of another arbitrary antenna group (second antenna group). It investigates (step 109) and it is determined whether it is an antenna with a low correlation degree (step 110). If the antenna selection unit 7 determines that the antenna has a low degree of correlation (in the case of Yes), the antenna selection unit 7 selects at least two or more antennas used for wireless communication from the second antenna group (step 111). When the antenna selection unit 7 determines that the antenna has a high degree of correlation (in the case of No), the antenna selection unit 7 selects at least two or more antennas to be used for wireless communication from the antenna group having the lowest degree of correlation (step 112). .

  Then, the reception processing unit 8 generates a weight, and transmits / receives a radio signal to / from a communication apparatus serving as a communication partner using the generated weight by using the antenna selected by the antenna selection unit 7.

  Next, the correlation determination unit 14 uses the fluctuation tendency of the value related to the reception quality at each antenna grasped by the reception quality fluctuation tendency grasping unit 13 to determine the degree of correlation between the antennas (in FIG. 2). Step 103) in the flowchart will be described.

(Method 1 for determining the degree of correlation between antennas)
Correlation determination unit 14 is a predetermined value compared with a value indicating the reception power obtained immediately before the value indicating the reception quality in the variation tendency of the value related to the reception quality at each antenna, which is grasped by reception quality variation tendency grasping unit 13. A time point at which the value (first predetermined value) is decreased is detected, and the degree of correlation is determined according to the time difference between the detected time points between the antennas. At this time, immediately after the time point detected by a certain antenna, when a time point that is lower than a predetermined value (first predetermined value) is detected in another antenna, the degree of correlation is high if the time difference is small. If the time difference from the time point when the other antennas are lower than the predetermined value is large, the degree of correlation is low.

(Method 2 for determining correlation between antennas)
Correlation determining unit 14 determines a time point when the value indicating the received power is equal to or less than a predetermined value (second predetermined value) in the variation tendency of the value related to reception quality at each antenna, as grasped by reception quality variation tendency grasping unit 13. The degree of correlation is determined according to the frequency at which the detected power is detected between the antennas, that is, the number of times that the value indicating the received power falls below a predetermined value (second predetermined value) per time. May be.

(Method 3 for determining correlation between antennas)
The correlation determination unit 14 may determine the degree of correlation according to a time average obtained by performing complex multiplication (multiplication with a complex conjugate) between the reception signals of the two antennas. If the degree of correlation is high, the time average is high, and if the degree of correlation is low, the time average is a numerical value close to zero.

(Method 4 for determining correlation between antennas)
Correlation determination unit 14 determines a weighting factor to be given to each value related to reception quality of each antenna according to a variation tendency indicating a tendency that the value related to reception quality varies with time in each antenna. The degree of correlation between the antennas may be determined or estimated based on an estimated received power value calculated by assigning a weighting factor to a quality-related value.

Below, the case where the correlation degree between each antenna is determined based on an estimated received power value is demonstrated.
The fluctuation tendency of the value indicating the received power is configured by combining three kinds of trends A, B, and C. The tendencies A, B, and C will be described with reference to FIG. FIG. 3 schematically shows how the reception quality information (value regarding reception quality) X varies from X1 to any one of X2 to X5 as time (one frame period) elapses.
The tendency A indicates that the reception quality information has changed within a predetermined threshold value α as in the case where the reception quality information changes from X1 to X2 and from X1 to X3. Here, the predetermined threshold α is set to a range in which the reception quality can be determined to be stable (about the fluctuation width due to the noise of the reception quality). The tendency B indicates that the reception quality information has changed in a direction in which the reception quality increases by exceeding a predetermined threshold value α, as in the case where the reception quality information changes from X1 to X4. The tendency C indicates that the reception quality information has changed below the predetermined threshold value α, and the reception quality has decreased in a direction that the reception quality decreases, as in the case where the reception quality information changes from X1 to X5.

  The correlation determination unit 14 determines a variation tendency by a combination of the trends A, B, and C. FIG. 4A is an example of a graph showing the variation of the reception quality information X over time. In FIG. 4A, new reception quality information is plotted as time elapses from time t1 to t6. FIG. 4B is a table for explaining a method for determining a weighting factor.

Since the change from X11 to X12 is a change within a predetermined threshold value α, as shown in FIG. Further, since the change from X12 to X13 is a change in the direction in which the reception quality increases exceeding the predetermined threshold value α, it is indicated as a trend B as shown in FIG. Similarly, each of the three variations from X13 to X16 is shown as a trend B of 3 times.
The correlation determination unit 14 determines that the variation tendency is an improved variation tendency based on a combination of one trend A and four trends B (ABBBB), and a weighting coefficient D1 to be assigned to each of X11 to X16. ˜D6 is increased with time to satisfy D1 <D2 <D3 <D4 <D5 <D6.

Further, the correlation determination unit 14 determines that the fluctuation tendency is a decreasing fluctuation tendency when the fluctuation tendency is, for example, a combination of the tendency A twice and the tendency C three times (ACACC). The coefficients D1 to D6 are increased with time to satisfy D1 <D2 <D3 <D4 <D5 <D6.
Further, when the fluctuation tendency is, for example, a combination of five tendency A (AAAAAA), the correlation determination unit 14 determines that the fluctuation tendency is a stable fluctuation tendency, and uniformizes the weighting factors D1 to D6. In other words, D1 = D2 = D3 = D4 = D5 = D6 ≠ 0.

  Correlation determining section 14 multiplies reception quality information X11-X16 and weighting coefficients D1-D6 corresponding to X11-X16, respectively, and calculates an average value of the multiplication values, thereby calculating an estimated reception power value. Then, the correlation determination unit 14 estimates a fluctuation tendency based on the calculated estimated received power value, and determines the degree of correlation between the antennas based on the estimated fluctuation tendency.

  As described above, the present invention enables stable communication by selectively using antennas having different arrangement configurations according to a changing propagation environment and selecting an antenna most suitable for the situation.

It is a block diagram which shows an example of a structure of the wireless base station of this invention. It is a flowchart explaining the antenna selection method by the antenna selection part based on the correlation degree between each antenna determined in the correlation determination part. It is a figure which shows typically a mode that the reception quality information X fluctuates with progress of time. It is a figure explaining the tendency to change the fluctuation | variation of the reception quality information X with progress of time, and the determination method of a weighting coefficient.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna element 2 Radio | wireless (RF) part 3 Transmission control part 4 Reception control part 5 Transmission processing part 7 Antenna selection part 8 Reception processing part 11 Weight calculation part 12 Reception quality information acquisition part 13 Reception quality fluctuation tendency grasp part 14 Correlation determination part 20 radio base stations

Claims (4)

In a radio base station having a plurality of antennas and performing radio communication using at least two or more antennas,
For the plurality of antennas, an acquisition unit that acquires reception quality information of each antenna;
A grasping unit for grasping a variation tendency of a value related to reception quality of each antenna obtained in the obtaining unit;
A determination unit that determines the degree of correlation between the respective antennas based on a tendency of fluctuation of a value related to reception quality at each of the antennas grasped by the grasping unit ;
A selection unit that selects at least two antennas to be used for wireless communication from the plurality of antennas according to the degree of correlation of each of the antennas determined by the determination unit ;
A radio base station comprising: The determination unit
In the fluctuation tendency of the value related to the reception quality at each of the antennas grasped by the grasping unit, the value related to the reception quality is lower than the first predetermined value as compared with the value related to the reception quality acquired immediately before. Detecting a time point, and determining the degree of correlation according to the time difference between the detected time points between the antennas,
The radio base station according to claim 1 . A calculation unit for calculating a weight of each antenna in the plurality of antennas,
The selection unit includes:
Selecting at least two or more antennas to be used for the wireless communication based on a time interval for calculating a weight in the calculation unit and a cycle in which the time point determined in the determination unit occurs;
The radio base station according to claim 2 . In a radio communication method of a radio base station having a plurality of antennas and performing radio communication using at least two antennas,
An obtaining step of obtaining reception quality information of each antenna for the plurality of antennas;
A grasping step for grasping a fluctuation tendency of a value related to reception quality of each antenna obtained in the obtaining step;
A determination step of determining a degree of correlation between the antennas based on a variation tendency of a value related to reception quality at each antenna grasped in the grasping step ;
A selection step of selecting at least two or more antennas to be used for wireless communication from the plurality of antennas according to the degree of correlation of each antenna determined in the determination step ;
A wireless communication method for a wireless base station, comprising:

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