JPH11308037A - Base station antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a base station antenna system for simultaneous transmission and reception of plural stations, capable of being applied in high speed transmission as well and of reducing a skip area by applying an adaptive array to plural base station antenna for performing simultaneous transmission and reception of plural stations and forming null in both directions of plural base station antennas respectively. SOLUTION: Since a base station 10a has an antenna provide on a comparatively high building 1a, its skip area is comparatively reduced since beam is irradiated from a high position. Conversely, the skip area exists in the vicinity of the building. Therefore, a base station antenna 10b is installed on a comparatively low building 1b, and the area in the vicinity of the building is irradiated. The skip area is reduced by performing simultaneous transmission and reception of plural stations by two base station antennas 10a, 10b. In reception at the base stations, error rate increases, when received waves from other stations are larger to the received wave from a mobile body. Therefore, interference is reduced by applying an adaptive array to the base station antennas and forming null in the directions of plural stations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-station simultaneous transmission / reception base station antenna apparatus for performing high-speed communication between a base station using a microwave band and a mobile body and reducing an insensitive area.

[0002]

2. Description of the Related Art FIG. 9 shows a general example of mobile communication. In the figure, reference numerals 1a, 1b, 1c denote buildings, 2a, 2
b is a base station antenna using the same frequency in different cells,
3 is a base station antenna having a different frequency, 4 is an antenna beam transmitted and received from a base station antenna 2a using the same frequency, 5 is an antenna beam transmitted and received from a base station antenna 2b using the same frequency, and 6 is a base beam using a different frequency. An antenna beam transmitted and received from the station antenna 3,
7a is an interference area by the antenna beams 5 and 6; 7b is an interference area by the antenna beams 4 and 6; 8a and 8b are moving objects; here, a human is illustrated, and 9a and 9b are moving objects. Here, a car is exemplified.

[0003] Since the base station 2a is an antenna provided in a relatively high building 1a, it can be placed in line of sight by making it higher than the surrounding buildings, and the dead area can be made relatively small.
However, the beam is not irradiated in reverse around the base station, such as directly below the building, so that a dead area is generated near the building.
On the other hand, the base station antenna 2 is positioned lower than the surrounding buildings.
When b is installed, an area relatively near the building is illuminated, but there is an area where communication is not possible because it cannot be illuminated outside the line of sight, which is a shadow area of the building.

As a method of improving propagation characteristics outside the line of sight, for example, as described in Okumura, Shinji, “Basic of Mobile Communication”, Chapter 7 Diversity of IEICE, (1) Route Diversity Or using
(2) There is multi-station simultaneous transmission and reception.

In route diversity, transmission and reception are alternately performed using the same frequency. Therefore, an antenna having the highest reception level is selected, and transmission is performed using the antenna during transmission. Since the assumption is made that the propagation path characteristics of the uplink and downlink are the same, it is limited to the case where the radio access scheme is TDD (time division multiplexing) and the time interval between transmission and reception is small. Therefore, when the propagation path fluctuates greatly,
Diversity gain is reduced.

As another method for reducing the dead area, there is multi-station simultaneous transmission and reception. For route diversity,
Limited to TDD, but FDD for multi-station simultaneous transmission / reception
(Frequency division). Therefore, it is more suitable for high-speed transmission than route diversity. Furthermore, when simultaneous multi-station transmission / reception is used, transmission quality in the vicinity of the boundary of a wireless zone or in an insensitive area due to shielding can be improved, and transmission power can be reduced. Simultaneous transmission methods include a frequency offset transmission method and a modulated waveform offset transmission method.
It is used for kbps FSK transmission.

[0007]

In the prior art, the dead area can be reduced by performing simultaneous transmission and reception of multiple stations in this manner, and this technique is particularly effective for low-speed transmission of voice and the like using a low frequency band. Met. However, in order to perform high-speed transmission using a high frequency band equal to or higher than a microwave band, better transmission quality is required. For reception at the base station,
Signals other than the signal from the mobile unit, which is the desired wave, are interference waves, and radio waves during simultaneous transmission from other base stations are also interference waves. If a received wave from another base station is larger than a received wave from a mobile unit, the error rate is greatly deteriorated, so that there is a problem that the influence of the interference wave must be reduced even a little.

[0008] Further, in a mobile body, interference is caused by a plurality of antenna beams from a base station due to simultaneous transmission and reception of multiple stations. When this interference occurs, even within the line of sight, the level fluctuation becomes large, and characteristics similar to fading are obtained. 2
If the irradiation doses from the two beams are equal and they are combined in opposite phases, it becomes a complete null and cannot be received. In order to reduce this effect, it is necessary to provide a diversity function or an adaptive equalizer in the antenna of the moving object, and there is a problem that the antenna cannot be mounted on a moving object that requires low cost and low power consumption. Further, there are a frequency offset transmission method and a modulated waveform offset transmission method for simultaneous transmission and reception at multiple stations. However, in digital communication, PSK (Digital Phase Modulation) is the mainstream, so that if the frequency is offset, synchronous detection cannot be performed. Problem.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a multi-station simultaneous transmission / reception base station antenna apparatus capable of reducing a dead area applicable to high-speed transmission.

[0010]

An antenna apparatus according to a first aspect of the present invention forms a null in the direction of each of a plurality of base station antennas by applying an adaptive array to a plurality of base station antennas performing simultaneous multi-station transmission and reception. It is like that.

An antenna device according to a second aspect of the present invention includes:
The adaptive array is applied to a plurality of base station antennas performing simultaneous multi-station transmission and reception, thereby forming nulls in the directions of the plurality of base station antennas, thereby reducing interference, and nullifying only one of the plurality of radio base stations. Is provided.

An antenna device according to a third aspect of the present invention includes:
At least one of the plurality of radio base station antennas performing simultaneous multi-station transmission / reception is provided with a direction finding function for estimating the arrival direction of the moving body as a desired wave, and the position information of the moving body is transmitted to another plurality of radio base station antennas. Inform the base station that the other base stations have nulls in the direction of the mobile.

The antenna device according to a fourth aspect of the present invention includes:
As a plurality of radio base station antennas for simultaneous transmission and reception of multiple stations, an adaptive array antenna for performing adaptive processing by beam space, a maximum likelihood sequence estimator for simultaneously detecting a desired wave and a part of a delayed wave, A replica reproduction unit that reproduces a combined waveform of the wave and the part of the delayed wave, and a base station antenna that includes a parametric signal estimator that includes the maximum likelihood sequence estimator and the replica reproduction unit. A path diversity effect is obtained by using a waveform as a reference signal for an adaptive array.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows a first embodiment of the present invention, in which 1a, 1b,
1c is a building, 8a and 8b are mobiles (people), 9a and 9b are mobiles (vehicles), 10a is a base station antenna having an adaptive array provided in building 1a, and 10b is an adaptive array provided in building 1b. Base station antennas 10a and 10b perform multi-station simultaneous transmission and reception. 11a is an antenna beam transmitted and received from the base station antenna 10a, 11b is an antenna beam transmitted and received from the base station antenna 2b, 12 is a base station antenna using the same frequency in different cells, and 13 is a base station antenna using the same frequency 12 is an antenna beam transmitted and received from the antenna 12.

Next, the operation will be described. Base station 10a
Is an antenna provided in a relatively high building 1a, and emits a beam from a high position, so that the dead area can be relatively small. However, on the contrary, since the beam is not irradiated directly below the building, a dead area is generated near the building. Therefore, a base station antenna 1
0b is installed to irradiate an area relatively near the building. By performing multi-station simultaneous transmission and reception with these two base station antennas 10a and 10b, the dead area can be reduced. In the related art, in reception at a base station, a signal other than a desired signal from a mobile unit is an interference wave, and a simultaneous transmission wave from another base station is also an interference wave. When the received wave from another base station is larger than the received wave from the mobile unit, there is a problem that the error rate is greatly deteriorated. Therefore, the interference is reduced by applying an adaptive array and forming nulls in the directions of multiple stations.

The adaptive array is a technique for adaptively suppressing interference by directing a beam in a desired direction and forming a null in the direction of an interference wave. In general, when the delay time difference between the multipaths increases, the configuration of the equalizer becomes complicated, and the equalizer characteristics deteriorate. For this reason, the adaptive array can be applied to suppression of a multipath having a longer delay time difference or suppression of interference of the same frequency. In FIG. 1, the base station antenna 10a that performs simultaneous multi-station transmission and reception can reduce unnecessary waves between base stations by forming a null in the direction of the other multi-station base station antenna 10b. Since nulls can be formed in the direction of the base station antenna 12 having the same frequency in the cell, interference at the same frequency can also be reduced.

Here, the operation of the adaptive array antenna of the present invention will be described. FIG. 2 shows an example of the configuration of the adaptive array antenna. In the figure, 14 is an element antenna or an array antenna in which a plurality of element antennas are arranged, 15 is a variable complex weight,
Reference numeral 16 denotes a mixer, 17 denotes an error detection circuit, and 18 denotes a complex weight control circuit. The signal Xn (t) received by the n-th element antenna is multiplied by a complex weight in a variable complex weight 15 in order to control its amplitude and phase. The signal whose amplitude and phase have been controlled is mixed in mixer 16 with the signal received by another element antenna 14, and the output y (t) of the adaptive array antenna is output.
Becomes The error signal circuit 17 detects an error from the reference signal calculated using the output signal y (t). The detected error information is sent to the complex weight control circuit 18 and controls the complex weight Wn given to the variable complex weight 15 so as to reduce the error. Representative algorithms for optimization include an LMS algorithm and a CMA algorithm. With such a feedback loop,
The adaptive array antenna operates to output a desired signal. By this adaptive processing, a null can be formed in the direction of the base station antenna for simultaneous transmission and reception of multiple stations, which is an interference wave, and the interference wave can be reduced.

As a specific hardware configuration of the adaptive array antenna, a DBF (Digital B
3 is shown in FIG. In the figure, 19 is an LNA (low noise amplifier), 20 is a down converter, 21 is an A / D converter, and 22 is a signal processing unit. In the drawing, the case of reception is shown. In the DBF antenna, the signal of each element antenna 14 is first amplified by the LNA 19, and the frequency is reduced to the IF band or the base band by the down converter 20. A / D
Convert to digital signal with converter and take in, signal processing unit 2
In step 2, calculation and control of the complex weight are performed. Because it is processed digitally, multi-beams can be easily created,
Large degree of freedom.

Although the case of reception at the base station has been described here, the effect of transmission is not as great as that of reception, but a similar effect can be expected. A complex weight is obtained at the time of reception and a beam is formed. However, if the weight is used as it is for transmission, a slight error occurs. However, when a beam is formed by the transmitting antenna, a null is formed in the direction of the base station that causes interference in the same way as the reception, so that the radio wave is not radiated in an unnecessary direction. This operation is performed by each base station, and as a result, a path diversity effect such as that at the time of reception cannot be obtained. However, since the SIR of each mobile unit is improved, a similar effect can be expected.

Although the embodiment has shown the case where there are two base station antennas for simultaneous transmission and reception of multiple stations, the present invention is effective even with three or more stations. Further, the type of element antenna such as a dipole antenna and a patch antenna is not limited to the base station antenna. By using a planar antenna as a specific configuration of the antenna, manufacture becomes easy, and mass production and weight reduction become possible. Also, here, an example is shown in which the heights of the base station antennas for simultaneous transmission / reception of multiple stations are different, but it goes without saying that the heights may be the same.

Embodiment 2 FIG. FIG. 4 is a schematic diagram showing Embodiment 2 of the present invention. It is the top view which looked at the base station antenna from the upper part, and has shown the figure which cut | disconnected the base station antenna and the antenna beam. In the figure, 23, 24,
25 is a base station antenna for simultaneous transmission and reception of multiple stations;
Reference numerals 7 and 28 denote antenna beams radiated from the base station antennas 23, 24 and 25, respectively.

In the first embodiment, nulls are formed in all directions of the base station serving as interference waves. By forming this null, it was possible to reduce interference with the antennas of the multi-station simultaneous transmission / reception base station and the base station using the same frequency. However, if nulls are formed with each other, there is a possibility that a dead area where a call cannot be made can be formed in a strip shape because the nulls are formed in that direction. Therefore, if no null is formed in only one base station antenna in that direction, the dead area can be eliminated. In FIG. 4, the base station antennas 24 and 25 are indicated by arrows 29a to 29.
By forming a null in the direction of d, interference with each of the other two base stations is reduced. On the other hand, the base station antenna 23 does not form a null in the direction of the base station antennas 24 and 25, so that there is no dead area in all desired areas.

Embodiment 3 FIG. FIG. 5 is a schematic diagram showing Embodiment 3 of the present invention. In the figure, 8 is movement, 30
a and 30b denote base station antennas for simultaneous transmission and reception of multiple stations, 3
1a and 31b are direction detectors and controllers, and 32 is a cable connecting between the two direction detectors and controllers 31a and 31b.

In the first and second embodiments, the interference wave is reduced by forming a null in the direction of the base station antenna causing interference. On the other hand, also on the mobile body side, interference of a plurality of antenna beams also occurs due to simultaneous transmission and reception at multiple stations. In this interference area, even within the line of sight, the level fluctuation in the area is large due to the interference, and the fading has the same characteristics. If the irradiation amounts from the two beams are equal and the two beams are combined in the opposite phases, a complete null will be generated and reception will not be possible. Especially in high-speed communication, the error rate is degraded. It is necessary to provide a diversity function or an adaptive equalizer in the antenna on the moving body side, and it cannot be mounted on a moving body that requires low cost and low power consumption. Therefore, if transmission is performed from only one base station at the position of the moving object, interference can be reduced. First, the base station determines the direction of arrival of a desired radio wave from a mobile object by a direction finder 31.
a, 31b. This detection may be performed by a plurality of base stations performing multi-station simultaneous transmission and reception, but may be performed by at least one base station and the information may be transmitted to another base station. Next, the reception level from the mobile unit is compared between a plurality of base stations performing simultaneous multi-station transmission and reception, and the base station 10a having the highest reception level is compared.
Communicates with the mobile unit 8a. The communicating base station transmits, from the controllers 31a and 31b, a control signal indicating that communication is being performed to another base station that performs multi-station simultaneous transmission. The second or lower base station 1 whose level is lower than that of the base station 1
0b forms a null in the direction of the moving body. The direction has already been detected by the direction finder. As a result, since the radio wave arrives at the mobile only from the base station in one direction,
Fading can be reduced.

FIG. 6 shows the structure of this direction finder. The configuration up to the A / D converter is the same as the configuration of the DBF. For detecting the direction, an interferometer that detects a phase difference between the element antennas is generally used. Here, the MUSIC algorithm is applied to improve the accuracy. The MUSIC processor 33 incorporates the MUSIC algorithm in the signal processing unit.

FIG. 7 shows an example of the angle measurement data processed using the MUSIC processing. The horizontal axis indicates the azimuth, and the vertical axis indicates the detected angle component. Now, a case is shown in which the directions of the moving body are θ1 and θ2, and light enters from both directions. The feature of MUSIC is that a sharp component in the incident direction can be detected as shown in FIG. By detecting the direction of the mobile unit, a beam is formed in the directions of θ1 and θ2 between a plurality of base stations or a null is formed, thereby reducing a fluctuation level due to interference on the mobile unit side. Can be.

Embodiment 4 FIG. 8 is a schematic diagram showing Embodiment 4 of the present invention. In the figure, 34 is a maximum likelihood sequence estimator, 35 is a replica regenerator, 36 is a parametric signal estimator, 37 is a parameter estimator, and 38 is a multi-beamformer. In high-speed transmission, a transmission signal from a mobile is divided into many paths and received by a base station. Since this propagation difference causes intersymbol interference, it is better to combine these paths in order to obtain high reliability. When a DBF is used, a multi-beam can be easily created. Therefore, adaptive processing can be performed in a beam space to form a null in the direction of an interference wave. Since the beam space has directivity, the reception level of some of the beams is considerably high, and the processing time can be reduced by using only the beam outputs. However, the adaptive array has a limit on the number of interference waves that can be removed in accordance with the number of elements. In particular, when a part of the path of the interference wave has an arrival angle very close to the path of the path of the desired wave, it cannot be spatially separated. Furthermore, it is impossible to separate the interference wave components in the same direction. Therefore, the reference signal itself must be a time-variable variable waveform pattern instead of a fixed waveform pattern. For this purpose, the maximum likelihood sequence estimator 34
A parametric signal estimator 36 composed of a replica regenerator 35 is connected to the latter stage of the adaptive array.
The maximum likelihood sequence estimator 34 simultaneously detects the desired wave and a part of the delayed wave, reproduces the composite waveform of the desired wave and the part of the delayed wave detected by the replica reproducing unit 35, and converts the composite waveform into an adaptive array. By using it as a reference signal, a path diversity effect can be obtained.

[0028]

According to the first aspect of the present invention, an adaptive array is applied to a plurality of base station antennas performing simultaneous multi-station transmission and reception, and nulls are formed in the directions of a plurality of radio base stations to thereby provide interference between the multi-stations. Therefore, there is an effect that high-speed transmission becomes possible. In addition, the dead area can be eliminated by changing the height of the base station that performs simultaneous transmission and reception of multiple stations. Further, the use of the planar antenna has the effect of obtaining a lightweight base station antenna with good mass productivity.

According to the second aspect of the present invention, a null is formed in a direction of a plurality of base station antennas by applying an adaptive array to a plurality of base station antennas which perform simultaneous transmission and reception of a plurality of base stations. By providing only one base station antenna in which no null is formed in the direction, there is an effect that the dead area can be eliminated.

According to the third aspect of the present invention, an adaptive array is applied to a plurality of radio base station antennas performing simultaneous multi-station transmission and reception, and at least one of the plurality of radio base station antennas is used.
One radio base station antenna is provided with a direction finding function for estimating the arrival direction of a mobile unit, which is a desired wave, and the position information of the mobile unit is notified to a plurality of base stations, and one radio base station antenna is used for the mobile unit. By forming a beam in the direction and the other base stations forming nulls in the direction of the mobile, fading at the position of the mobile can be reduced, and the configuration of the wireless communication device of the mobile can be simplified. is there.

According to the fourth aspect of the present invention, as a plurality of radio base station antennas for simultaneous transmission and reception of multiple stations, an adaptive array antenna for performing adaptive processing by a beam space, a maximum likelihood sequence estimator, and a replica reproduction unit are configured. A parametric signal estimator is connected to an adaptive array antenna, and the maximum likelihood sequence estimator simultaneously detects the desired wave and some delayed waves, and combines the desired wave and some delayed waves detected by the replica reproduction unit. Is reproduced, and the synthesized waveform is used as a reference signal of the adaptive array,
There is an effect that path diversity can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of Embodiment 1 of a base station antenna apparatus for performing simultaneous transmission and reception of multiple stations according to the present invention.

FIG. 2 is a diagram illustrating a basic configuration of an adaptive array according to a first embodiment of a base station antenna apparatus for performing simultaneous transmission and reception of multiple stations according to the present invention.

FIG. 3 is a diagram showing a basic configuration of a DBF according to the first embodiment of the base station antenna apparatus for performing simultaneous transmission and reception of multiple stations according to the present invention.

FIG. 4 is a diagram showing a concept of a radiation pattern according to a second embodiment of the base station antenna apparatus for performing simultaneous multi-station transmission and reception according to the present invention.

FIG. 5 is a diagram illustrating a concept of a radiation pattern according to a third embodiment of the base station antenna apparatus for performing simultaneous transmission and reception of multiple stations according to the present invention.

FIG. 6 is a schematic configuration diagram illustrating a configuration of a direction finder according to a third embodiment of the base station antenna device according to the present invention;

FIG. 7 is a diagram illustrating an angle resolution by a direction finder of a base station antenna apparatus according to a third embodiment of the present invention;

FIG. 8 is a schematic configuration diagram showing a configuration of an antenna device according to a fourth embodiment of the base station antenna device according to the present invention.

FIG. 9 is a schematic configuration diagram illustrating an example of a conventional base station antenna device.

[Explanation of symbols]

1 building, 2 base station antennas using the same frequency in different cells, 3 base station antennas using different frequencies,
4 Base station antenna beam using the same frequency, 5 Base station antenna beam using the same frequency, 6 Base station antenna beam using different frequencies, 7 Antenna beam interference area, 8 Moving object (human), 9 Mobile (vehicle), 10 adaptive base station antenna, 11 adaptive base station antenna transmit / receive antenna beam, 12 base station antenna using the same frequency in different cells, 13 base station antenna using the same frequency in different cells 12 Antenna beam, 14 element antenna or array antenna, 15 variable complex weight, 16 mixer, 17 error detection circuit, 18 complex weight control circuit, 19 LNA
(Low noise amplifier), 20 D / C (down converter), 21 A / D (AD converter), 22 signal processing unit, 23 base station antenna for simultaneous multi-station transmission and reception, 24
Base station antenna for simultaneous transmission and reception of multiple stations, 25 Base station antenna for simultaneous transmission and reception of multiple stations, 26 antenna beams, 27 antenna beams, 28 antenna beams, 2
9 Null direction, 30 base station antenna for simultaneous transmission and reception of multiple stations, 31 direction detector and controller, 32 connection cable, 33 MUSIC processor, 34 maximum likelihood sequence estimator, 35 replica regenerator, 36 parametric signal estimator, 37 parameter estimator, 38 multi-beamformer.

 ──────────────────────────────────────────────────の Continued from the front page (72) Inventor Yukihiro Honda 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (7)

[Claims] 1. A radio base station for performing simultaneous multi-station transmission / reception to reduce a dead area, an array antenna having a plurality of element antennas provided in the radio base station, and a signal received by each element antenna. A circuit for arbitrarily controlling both or one of the amplitude and the phase, a signal circuit for synthesizing an output signal of each element antenna from the circuit, and a control amount for the amplitude and / or the phase; And a base station antenna using the adaptive array antenna, wherein a null is formed in the direction of the plurality of radio base stations. 2. The method for controlling the directivity of antennas of a plurality of radio base stations, wherein a radio base station which does not form only one null in the direction of the plurality of radio base stations is provided. 2. The base station antenna device according to 1. 3. The method for controlling the directivity of antennas of a plurality of radio base stations, wherein one radio base station forms a beam in the direction of a mobile object that is a desired wave, and the other plural radio base stations form a beam. 2. The base station antenna device according to claim 1, wherein a null is formed in the direction of the moving body. 4. A method according to claim 1, wherein at least one of said plurality of radio base stations has a direction detecting function for estimating a direction of arrival of a mobile unit as a desired wave, and transmits position information of said mobile unit to another plurality of radio base stations. The other base stations, the other plurality of base stations,
4. The base station antenna device according to claim 3, wherein a null is formed in the direction of the moving body. 5. An adaptive array antenna for performing adaptive processing by a beam space, a maximum likelihood sequence estimator for simultaneously detecting a desired wave and a part of a delayed wave, and a maximum likelihood sequence estimator for detecting the desired wave and the part of the delayed wave. A replica reproduction unit for reproducing a synthesized waveform, and a base station antenna including a parametric signal estimator including the maximum likelihood sequence estimator and the replica reproduction unit, wherein the synthesized waveform is referred to as an adaptive array. The base station antenna device according to any one of claims 1 to 4, wherein a path diversity effect is obtained by using the signal as a signal. 6. The base station antenna device according to claim 1, wherein the heights of the plurality of base stations are changed. 7. The base station antenna device according to claim 1, wherein a planar antenna is used as the base station antenna.