JP2003008500A - Radio base station apparatus and transmission destination mobile station selection method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To simultaneously form individual beams for a plurality of mobile terminals, reduce the degree of interference between the individual beams, and improve the communication quality with the mobile terminals. To realize a wireless base station apparatus capable of performing the above operations. A radio base station apparatus for forming an individual beam of a carrier transmitting a radio signal toward a mobile terminal to which a radio signal is transmitted, wherein the azimuth angle formed by the azimuths of a plurality of mobile terminals. Is provided with a signal selection unit 2 for selecting a plurality of mobile terminals so that the angle is equal to or larger than a predetermined angle, and an individual beam forming unit 4 for forming an individual beam toward each of the selected mobile terminals. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio base station apparatus for communicating with a mobile terminal by a radio signal such as a spread spectrum signal, and a method of selecting a destination mobile station thereof.

[0002]

2. Description of the Related Art Conventionally, as a digital cellular mobile communication system, when a radio base station apparatus communicates with a mobile terminal, it has a fixed period (slot) on the downlink.
A system is known in which a packet is transmitted by a spread spectrum signal to different mobile terminals.

In this digital cellular mobile communication system, the radio base station apparatus uses an antenna having a sectorized beam or an omnidirectional beam so that only one mobile terminal is provided for each slot in each sector. Packet can be transmitted. Therefore, one radio base station apparatus can simultaneously transmit packets to mobile terminals of the same number of sectors on the same frequency.

Further, if the radio base station apparatus uses an antenna capable of adaptively controlling directivity (adaptive antenna) instead of the sector antenna, the degree of freedom in selecting a mobile terminal as a transmission destination of a radio signal. Can be expanded. The wireless base station device forms an antenna beam (individual beam) having directivity toward each destination mobile terminal by using an adaptive antenna, and each destination mobile terminal is formed by these individual beams. It is possible to send a radio signal to. Thus, it is possible to simultaneously form individual beams for a plurality of mobile terminals and transmit packets to each mobile terminal.

[0005]

However, when the above-mentioned radio base station apparatus increases the number of individual beams formed by the adaptive antenna, the degree of interference between the individual beams also increases. As a result, there arises a problem of deterioration in communication quality such as a decrease in transmission rate and a reduction in signal-to-interference noise ratio.

The present invention has been made in consideration of such circumstances, and an object thereof is to obtain the degree of interference between individual beams when forming individual beams for a plurality of mobile terminals at the same time. And a wireless base station device capable of improving communication quality with a mobile terminal,
And a method of selecting a destination mobile device thereof.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a mobile terminal which is a destination of a radio signal, and an individual carrier wave for transmitting the radio signal. A radio base station device for forming a beam, wherein the plurality of mobile terminals are selected so that the azimuth formed by the azimuths of the plurality of mobile terminals is a predetermined angle or more, and the selected mobile terminals are selected. The individual beams are respectively formed toward the above.

According to a second aspect of the present invention, the radio base station apparatus according to the first aspect is characterized in that the predetermined angle of the mobile terminal is changed according to the azimuth of the mobile terminal. Is.

According to a third aspect of the present invention, the communication quality when the radio signal transmitted by the individual beam is received by the mobile terminal is acquired and is transmitted to the mobile terminal according to the communication quality. The radio base station apparatus according to claim 1, wherein the transmission rate of the radio signal is determined.

According to a fourth aspect of the present invention, as the antenna used for forming the individual beam, an array antenna having a plurality of array elements and capable of adaptively controlling the directivity of the antenna beam is provided, and the selection is performed. The number of mobile terminals to be equal to or less than the number of the array element, the individual beam for the selected mobile terminal, the gain characteristics in the azimuth of the mobile terminal selected other than the mobile terminal becomes a minimum The radio base station apparatus according to any one of claims 1 to 3, wherein the individual beam is formed so as to have.

According to a fifth aspect of the present invention, the individual beam for the selected mobile terminal is formed so that the individual beam for the selected mobile terminal has a zero point in the azimuth of the selected mobile terminal other than the mobile terminal. The wireless base station device according to claim 4.

According to a sixth aspect of the present invention, the direction of the mobile terminal is specified by continuously or intermittently receiving radio signals from the mobile terminal and estimating the arrival direction of the received signal. Claim 1 thru | or Claim 5 characterized by the above-mentioned.
The radio base station device according to any one of items 1 to 3.

According to a seventh aspect of the present invention,
The radio base station apparatus according to claim 6, wherein the orientation of the mobile terminal is updated by performing the identification.

According to an eighth aspect of the present invention, when the wireless signal is not received from the mobile terminal for a predetermined time, the azimuth of the mobile terminal is not updated. The wireless base station device according to 1.

According to a ninth aspect of the present invention, the position information of the mobile terminal located by the mobile terminal is acquired, and the azimuth of the mobile terminal is specified based on the position information. The wireless base station device according to any one of claims 1 to 5.

According to a tenth aspect of the present invention, a method of selecting a destination mobile station in a radio base station apparatus for forming an individual beam of a carrier wave for transmitting the radio signal toward a mobile terminal which is a destination of the radio signal. In forming the individual beams for the plurality of mobile terminals, the plurality of mobile terminals are arranged such that the azimuth formed by the azimuths of the plurality of mobile terminals is equal to or greater than a predetermined angle. It is characterized by the process of selecting a machine.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be sequentially described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a cellular radio base station apparatus according to the first embodiment of the present invention. The radio base station apparatus shown in FIG. 1 has N (N is an integer of 1 or more) transmission buffers 1-1 to 1-1.
N, a signal selection unit 2, M (M is an integer of 1 or more) signal transmission units 3-1 to M, an individual beam forming unit 4, and L (L
Is an integer of 1 or more) and an L-element array antenna 5 composed of antenna arrays 6-1 to L. Figure 1 above
The wireless base station device can transmit data to up to N mobile terminals (hereinafter simply referred to as mobile terminals).

Next, the basic operation of the radio base station apparatus shown in FIG. 1 will be described. First, the transmission buffers 1-1 to N
Corresponds to each mobile device that performs data communication, and when data to be transmitted to each mobile device is input, the data is accumulated.

Next, the signal selection section 2 includes the transmission buffer 1
Any one of -1 to N in which transmission data is accumulated m
Select transmit buffers. Transmission buffers 1-1 to N
Since there is a one-to-one correspondence with mobile stations, m transmission destination mobile stations are selected by selecting this transmission buffer. The number of mobile units selected by the signal selection unit 2 does not always have to be constant, and may change for each slot as long as it is within the range satisfying the expression (1). 1 ≦ m ≦ n (1) However, m is a positive integer not more than M. n is the number of mobile units that can communicate with the wireless base station device, and is a positive integer equal to or less than N. Further, the number M of signal transmission units is determined as a value equal to or larger than the maximum value of the number m of mobile units simultaneously selected by the signal selection unit 2.

Next, the signal selection unit 2 acquires a certain amount of data from the selected transmission buffer, and the signal transmission unit 3
Any one of -1 to M is selected and the acquired data is output to the selected signal transmission unit. The signal transmission unit selected here has a one-to-one correspondence with the transmission buffer of the data acquisition source. As a result, the selected signal transmission unit and the destination mobile device associated with the transmission buffer of the data acquisition source are associated one-to-one.

Next, the signal transmitters 3-1 to 3-1-M convert the input data into spread spectrum signals for transmission and output them to the individual beam former 4. The individual beam forming unit 4 is
The inputted spread spectrum signal for transmission is weighted to form an individual beam for the destination mobile station, and is output to each antenna array 6-1 to L.

In this way, individual beams (m) for transmitting the transmission data are formed toward the m destination mobile stations selected by the signal selecting section 2. The radio base station apparatus can transmit data to the m destination mobile stations at the same frequency by using the m individual beams.

The above-mentioned individual beam refers to an antenna beam formed so as to have directivity with respect to a mobile device to which a radio signal is transmitted.

The radio base station apparatus shown in FIG. 1 is provided with an L element array antenna 5 as an adaptive antenna, and the L element array antenna 5 is used to control the directivity of individual beams. Any type of antenna may be provided as long as the antenna can adaptively control the characteristics (adaptive antenna).

Next, the radio base station apparatus shown in FIG.
The operation of selecting a destination mobile station will be described. First, a case will be described in which, when the destination mobile station is selected, two mobile stations are selected from the mobile stations that can communicate with the base station and data is transmitted simultaneously. Here, when an individual beam is simultaneously formed from the base station to two mobile units and data is transmitted, the angle difference (hereinafter, referred to as “angle difference” formed by the azimuths of the two mobile units from the viewpoint of the base station) If the angle difference is referred to as an azimuth angle), interference between individual beams formed for each mobile device is likely to occur. In order to reduce the degree of this interference, in the present embodiment, when selecting two mobile devices that simultaneously transmit data, the signal selection unit 2
Selects the destination mobile station so that the azimuth angle between the two mobile stations becomes a certain angle or more.

Next, with reference to FIGS. 2 to 4, a case will be described in which three or more mobile units are selected from the mobile units capable of communicating with the base station and data is transmitted simultaneously. 2 to 4
3A to 3C are first to third diagrams for explaining an operation in which the signal selection unit 2 shown in FIG. 1 selects a destination mobile device.
First, as shown in FIG. 2, the base station 200 according to the present embodiment of FIG. 1 and ten mobile units 210 to 219 capable of communicating with the base station 200 are located. Here, the signal selection unit 2 selects a transmission destination mobile device that simultaneously transmits data, and an azimuth angle between two mobile devices that are adjacent to each other as a transmission destination mobile device is a constant angle (for example, Select the destination mobile device so that it is 50 ° or more. This fixed angle is preset in the signal selection unit 2 as a threshold value for determining the azimuth angle.

For example, in a time slot,
As shown in FIG. 3, the signal selection unit 2 includes mobile units 210, 2
12, 214, 216, 218 are selected as destination mobile stations. These mobile units 210, 212, 214, 21
The azimuth angles θ1, θ2, θ3, θ4, and θ5 between two mobile units adjacent to each other among the six and 218 are all above a predetermined angle (50 °). This reduces the degree of interference between the individual beams 220-224 formed for each mobile unit 210, 212, 214, 216, 218. As a result, these individual beams 220-22
4 from the base station 200 to the mobile units 210, 212,
The transmission data transmitted to 214, 216, and 218 are received by the mobile devices without any problem.

Further, in another time slot, the signal selection unit 2 is, as shown in FIG.
3, 215, 217 and 219 are selected as destination mobile stations. Also in this case, the mobile unit 21
Among 1, 1, 213, 215, 217, and 219, the azimuth angles θ6, θ7, θ8, θ9 between two adjacent mobile units,
Each of θ10 is equal to or more than a predetermined angle (50 °). As a result, the respective mobile units 211, 213, 215, 2
Individual beams 230-2 formed for 17, 219
Since the degree of interference between 34 is reduced, the mobile device 21
1, 213, 215, 217, and 219 can receive the transmission data transmitted from the base station 200 by these individual beams 230 to 234 without any problem.

The radio base station apparatus shown in FIG. 1 uses, for example, the antenna arrays 6-1 to L for both transmission and reception in order to specify the direction of a mobile station with which communication is possible. A signal is received continuously or intermittently, and the arrival direction of the received signal is estimated. As one method of estimating the direction of arrival, first, for each mobile device, each antenna array 6-1 is arranged so that a radio signal can be optimally received.
Adjust the weighting of ~ L. For example, the reception strength is adjusted to be maximum, or the signal-to-interference noise ratio is adjusted to be maximum. Next, the azimuth of the mobile device is determined based on the direction of the main beam of the antenna reception pattern formed by this weighting. For example, the azimuth of the main beam is the azimuth of the mobile device. In addition, various known methods may be used as other arrival direction estimation methods depending on the signal receiving method and the like. For example, the linear prediction method,
The minimum norm method, MUSIC, ESPRIT, etc. can be used.

The information for individual beam forming such as the direction of the main beam extracted from the information on the antenna reception pattern is updated every time a radio signal transmitted from each mobile device is received for a certain period of time. You may do it. However, when the signal transmitted from a certain mobile device cannot be received for a certain period of time, the information for individual beam forming for the mobile device may be unupdated.

As another method for specifying the direction of the mobile device, the mobile device is provided with a direction measuring means such as GPS,
The wireless base station device may acquire the position information of the mobile device that has been positioned using this, and specify the azimuth of the mobile device based on this position information.

In the above-mentioned embodiment, the radio base station apparatus has a value indicating the communication quality when the radio signal transmitted to the mobile station by the individual beam is received by the mobile station,
For example, the signal-to-interference-noise ratio (reception C / I) may be measured or predicted, and the transmission rate of the radio signal transmitted to the mobile device may be determined according to the reception C / I. . For example, if the received C / I is in the range of 0 to 3 dB, the transmission rate is 300 kbps, and if it is in the range of 3 to 6 dB, the transmission rate is 600 kbps, and 6 to 9 dB.
If it is within the range, the transmission rate is 1200kbps.
In this way, if the higher the reception C / I is, the higher the transmission rate is made to correspond to, the data can be transmitted at a higher rate according to the reception C / I, and the transmission efficiency is improved. Is obtained.

As described above, according to the first embodiment of the present invention, the number of individual beams formed at the same time can be reduced as compared with the case of simultaneously transmitting data to all the mobile stations to which data is transmitted. . When the wireless base station device simultaneously forms individual beams for a plurality of mobile devices and transmits data, two mobile devices that are adjacent to each other as transmission destination mobile devices when viewed from the wireless base station device. The radio base station apparatus selects a destination mobile station so that the azimuth angle between them becomes a certain angle or more.

As a result, the degree of interference between the individual beams formed for each mobile unit is reduced, so that it is possible to secure a stable transmission rate and increase the signal-to-interference-noise ratio, etc. The effect that the communication quality between the terminal and the terminal is improved is obtained.

Further, if the radio base station device determines the transmission rate of the radio signal according to the reception C / I for each individual beam, the data is transmitted at a higher rate according to the reception C / I. Therefore, it is possible to obtain the effect that the transmission efficiency with the mobile device is improved.

In the above-described first embodiment, the azimuth angle determination threshold value used for selecting the destination mobile device is constant regardless of the azimuth direction of the mobile device (for example, 5).
Although it is set to 0 °), the angle difference between the two mobile units serving as the determination threshold may be changed at any time. For example, when a linear array antenna is used as the L-element array antenna 5, the minimum beam width that can be formed may differ depending on the azimuth in which the mobile device is located. In such a case, if the angle difference serving as the determination threshold can be changed at any time, the determination threshold can be changed according to the azimuth of the mobile device, and an optimum individual beam can be formed. .

A cellular radio base station apparatus according to the second embodiment of the present invention will be described next. The configuration of the wireless base station device according to the second embodiment is similar to that shown in FIG. The characteristic operation of the wireless base station device according to the second embodiment will be described below. Further, regarding the portions corresponding to the respective blocks shown in FIG.
The same code is added.

As in the first embodiment described above, the radio base station apparatus is such that the azimuth angle between two mobile stations adjacent to each other as destination mobile stations is Select the destination mobile device so that it is at a certain angle or more. However, in the second embodiment, the number of destination mobile stations selected by the signal selection unit 2 with respect to the number L of antenna array elements is set to be equal to or less than the value of L. In addition, the individual beam forming unit 4
Forms an individual beam for each mobile station such that the individual beam for one destination mobile station has nulls (zero points) in the azimuths of all other destination mobile stations. Generally, if the azimuth angle is 50 ° or more, the array antenna
It is possible to form individual beams with nulls in the azimuths of all other destination mobiles.

For example, when data is transmitted to the four mobile units A to D in a certain slot, the individual beam forming unit 4 has the gain characteristic of the waveform W1 shown in FIG. 5, that is, the mobile unit B. ~ To have a null in the azimuth,
An individual beam for mobile unit A is formed. However, when a complete null cannot be formed, the individual beam forming unit 4
The individual beams for the mobile device A are formed so that the gains in the directions of the mobile devices B to D are minimized. For example, in the waveform W1 shown in FIG. 5, the gain in the azimuth of the mobile device D is set to be minimum as compared with the adjacent azimuth. Thus, the gain in the direction in which the waveform of the gain characteristic forms a valley is referred to as the minimum gain. Similarly, the individual beam forming unit 4 forms the individual beams for the mobile units B to D, respectively.

As in the first embodiment, the signal-to-interference-plus-noise ratio (reception) is used as a value indicating the communication quality when the radio signal transmitted to the mobile station by the individual beam is received by the mobile station.
C / I) may be measured or predicted, and the transmission rate of the transmission signal may be determined according to the received C / I.

Further, a method for specifying the azimuth of each mobile unit can be realized by the same method as in the first embodiment.

As described above, according to the second embodiment, an array antenna capable of adaptively controlling the directivity of an antenna beam is used as an antenna for forming an individual beam, and a destination mobile station for transmitting data at the same time. When the number of array elements is equal to or less than L and each individual beam for the mobile station selected as the transmission destination is formed, a null is formed in the azimuth of another mobile station simultaneously selected as the transmission destination. Alternatively, the individual beam for the selected mobile unit is made to have a gain characteristic in which the gain in the azimuth of the mobile unit other than the mobile unit is minimized. This allows
It is possible to further reduce the degree of interference between individual beams formed for each mobile device. As a result, the excellent effect that the communication quality with the mobile terminal is further improved is obtained.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention. included.

[0044]

As described above, according to the present invention,
Since the azimuth angle formed by the azimuths of the plurality of mobile terminals is equal to or larger than a predetermined angle, the plurality of mobile terminals are selected, and individual beams are formed toward the selected mobile terminals. , When forming individual beams for a plurality of mobile terminals at the same time, it is possible to reduce the degree of interference between the individual beams and improve the communication quality with the mobile terminals. To be

Further, if the predetermined angle (threshold for judgment) about the mobile terminal is changed according to the azimuth of the mobile terminal, the judgment threshold is changed according to the azimuth of the mobile terminal. , It becomes possible to form an optimum individual beam.

Further, the communication quality when the radio signal transmitted by the individual beam is received by the mobile terminal is acquired,
If the transmission speed of the radio signal transmitted to the mobile terminal is determined according to the communication quality, data can be transmitted at a higher speed according to the communication quality related to the reception of the mobile terminal. Therefore, the effect of improving the transmission efficiency with the mobile terminal can be obtained. A signal to interference plus noise ratio can be used as an indicator of this communication quality.

As an antenna used for forming an individual beam, an array antenna having a plurality of array elements and capable of adaptively controlling the directivity of the antenna beam is provided, and the number of mobile terminals to be selected is determined by the array antenna. The number of elements is equal to or less than the number of elements, and each selected movement is performed so that the individual beam for the selected mobile terminal has a gain characteristic in which the gain in the azimuth of the selected mobile terminal other than the mobile terminal is minimized. If the individual beams for the terminal are formed, it is possible to further reduce the degree of interference between the individual beams. Accordingly, it is possible to further improve the communication quality with the mobile terminal.

Further, if the individual beams for the selected mobile terminals are formed so that the individual beams for the selected mobile terminals other than the mobile terminal have a zero point in the azimuth of the selected mobile terminals, the individual beams are separated. It is possible to further reduce the degree of interference.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a wireless base station device according to a first embodiment of the present invention.

FIG. 2 is a first diagram for explaining an operation in which the signal selection unit 2 shown in FIG. 1 selects a destination mobile device.

FIG. 3 is a second diagram for explaining an operation in which the signal selection unit 2 shown in FIG. 1 selects a destination mobile device.

FIG. 4 is a third diagram for explaining the operation of the signal selection unit 2 shown in FIG. 1 selecting a destination mobile device.

FIG. 5 is a waveform diagram for explaining an operation of the wireless base station device according to the second embodiment of the present invention.

[Explanation of symbols]

1-1 to N transmission buffer 2 Signal selection section 3-1 to M signal transmitter 4 Individual beam forming unit 5 L element array antenna 6-1 to L antenna array 200 Wireless base station device (base station) 210-219 Mobile Terminals (Mobile) 220-224, 230-234 individual beams θ1 to θ10 Azimuth

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04B 7/26 D (72) Inventor Akira Yamaguchi 2-1-115 Ohara, Kamifukuoka-shi, Saitama KDD Corporation In-house (72) Inventor Yoshiaki Amano 2-15-1, Ohara, Kamifukuoka-shi, Saitama F-term in CDI Co., Ltd. (reference) 5J062 AA08 BB05 CC07 5K059 CC02 CC04 DD10 5K067 AA03 AA23 BB03 CC10 CC24 DD20 EE02 EE10 EE22 FF03 GG01 KK02 KK03

Claims (10)

[Claims] 1. A radio base station apparatus for forming an individual beam of a carrier wave for transmitting the radio signal to a mobile terminal which is a destination of the radio signal, wherein a plurality of directions of the mobile terminals are formed. A radio base station apparatus, wherein the plurality of mobile terminals are selected so that the azimuth is equal to or larger than a predetermined angle, and the individual beams are respectively formed toward the selected mobile terminals. 2. The radio base station apparatus according to claim 1, wherein the predetermined angle of the mobile terminal is changed according to the azimuth of the mobile terminal. 3. Obtaining communication quality when the radio signal transmitted by the individual beam is received by the mobile terminal,
The radio base station apparatus according to claim 1, wherein a transmission rate of a radio signal transmitted to the mobile terminal is determined according to the communication quality. 4. An array antenna having a plurality of array elements and capable of adaptively controlling the directivity of the antenna beam is provided as an antenna used for forming the individual beam, and the number of mobile terminals to be selected is set. The number of the array elements is equal to or less than, and the individual beam for the selected mobile terminal has a gain characteristic in which the gain in the azimuth of the mobile terminal selected other than the mobile terminal has a minimum,
The radio base station apparatus according to claim 1, wherein the individual beam is formed. 5. The individual beam is formed so that the individual beam for the selected mobile terminal has a zero point in the azimuth direction of the selected mobile terminal other than the mobile terminal. The radio base station device according to. 6. The azimuth of the mobile terminal is specified by continuously or intermittently receiving radio signals from the mobile terminal and estimating the arrival direction of the received signal. The radio base station apparatus according to any one of claims 1 to 5. 7. The radio base station apparatus according to claim 6, wherein the orientation of the mobile terminal is updated by performing the identification at predetermined time intervals. 8. The radio base station apparatus according to claim 7, wherein when the wireless signal is not received from the mobile terminal for a predetermined time, the direction of the mobile terminal is not updated. . 9. The method according to claim 1, wherein position information of the mobile terminal located by the mobile terminal is acquired, and the azimuth of the mobile terminal is specified based on the position information. 5. The wireless base station device according to item 5. 10. A method of selecting a destination mobile station in a radio base station apparatus for forming an individual beam of a carrier wave for transmitting the radio signal, to a mobile terminal as a destination of a radio signal, comprising: A step of selecting the plurality of mobile terminals so that the azimuth formed by the azimuths of the plurality of mobile terminals is equal to or greater than a predetermined angle when forming the individual beams for the mobile terminals. A method of selecting a destination mobile device, comprising: