JP4717270B2 - Wireless base station - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio base station used for cellular mobile communication and the like.
[0002]
[Prior art]
In a radio base station for cellular mobile communication, a method of individually controlling beam directivity with respect to one or more mobile stations in a radio zone is considered. There is also null steering control that directs a directional null point in the direction in which the interference wave / jamming wave exists. An antenna having these control functions is called an adaptive antenna, an adaptive antenna, or a smart antenna. For example, a technique for realizing the method is disclosed in 1998 by "Serial Signal Processing with Array Antenna" published by Science and Technology Publishers, Nobuyoshi Kikuma. Yes.
[0003]
Beam directivity control includes a null steering system in a broad sense of controlling a beam. FIG. 5 shows a developed view of the beam when beam directivity control including null steering control is performed.
In FIG. 5, the radio base station 501 performs null steering in which a beam is directed toward the mobile station 51 and a null (gain 0) with zero electric field strength is directed in the direction in which the interference wave exists.
[0004]
Also, as shown in FIG. 6A, the radio base station 601 directs a null toward the mobile station 62 when the beam is directed to the mobile station 61, while as shown in FIG. 6B. When the beam is directed to the mobile station 62, a null is directed to the mobile station 61.
[0005]
[Problems to be solved by the invention]
However, conventionally, the above-described beam directivity control in cellular mobile communication is performed independently for each radio base station. Therefore, when adjacent radio base stations simultaneously direct beams to mobile stations existing in the same area, radio interference (inter-cell interference) occurs due to these beams, and thereby mobile stations existing in the same area. There was a problem that the communication state of the suddenly deteriorated.
For example, as shown in FIG. 7, when radio base stations 701 and 702 are installed adjacent to each other and mobile stations 71 and 72 exist in the same direction as viewed from each radio base station, the radio base station 701 is a mobile station. When the timing at which the downlink signal is transmitted to 71 and the timing at which the radio base station 702 transmits the downlink signal to the mobile station 72 coincide with each other, radio wave interference occurs due to the beam emitted from each radio base station, and There was a problem that the communication quality of the stations 71 and 72 deteriorated.
[0006]
In addition, as shown in FIG. 8, when the radio base station 801 and the radio base station 802 are installed adjacent to each other and the mobile station 81 is located at the zone boundary between them, the radio base station 801 moves. If the radio base station 802 directs the beam toward the mobile station 82 located in the zone of the local station while directing the beam toward the station 81, the radio base station 802 emits the mobile station 82. There is a problem that the mobile station 81 is affected by the leaked radio waves of the beam. Specifically, radio wave interference occurs between the leaked radio wave of the beam emitted from the base station 802 to the mobile station 82 and the radio wave emitted from the radio base station 801 to the mobile station 81, thereby improving the communication quality of the mobile station 81. There was a problem of getting worse.
[0007]
The present invention has been made in view of such circumstances. A radio base station that suppresses the occurrence of radio wave interference between cells and improves the communication state of a mobile station by performing beam directivity control between radio base stations. The purpose is to provide.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a radio base station capable of controlling the beam directing direction, and information on handoff candidate radio base stations that may establish communication with the radio base station that is currently communicating. If the local station is registered as a handoff candidate radio base station in the handoff candidate base station information registered for each mobile station, the mobile station including the local station in the handoff candidate radio base station is not the own station. Provided is a radio base station characterized in that a beam pattern is formed so that the directional beam of the mobile station is not directed to the azimuth or position of the mobile station during a period in which a downlink signal is received from the radio base station.
[0012]
According to such a configuration, when a mobile station including its own station as a handoff candidate radio base station receives a downlink signal from another station, it is ensured by not directing a directional beam toward the mobile station. It is possible to prevent the mobile station from being affected by the radio wave of the directional beam emitted by the own station. The directional beam is a beam directed to a mobile station that transmits downlink data.
[0013]
Further, the present invention provides a wireless base station in the vicinity of the location of the mobile station within a period in which a mobile station including the mobile station as a handoff candidate radio base station receives a downlink signal from a wireless base station other than the mobile station. Also, a beam pattern is formed so that the directional beam is not directed.
[0014]
According to such a configuration, when the own station is set as a handoff candidate radio base station and there is a mobile station receiving a downlink signal from another station, the beam is not directed to the mobile station. At the same time, the beam is not directed to other mobile stations existing in the vicinity of the mobile station. Since the directional beam is emitted with a certain width, even if it avoids directing the directional beam toward the mobile station receiving the downlink signal from another station, the directional beam is transmitted to the mobile station that is in the immediate vicinity of the mobile station. On the other hand, if the own station emits a beam, both mobile stations are affected by the directional beams emitted from the respective radio base stations, and the communication quality deteriorates. Therefore, if there is a mobile station that is receiving a downlink signal from another station, the directional beam is not directed toward a mobile station that exists in the vicinity of the mobile station. It can be avoided that the beam becomes a jamming wave of the mobile station.
[0015]
In addition, the present invention provides a radio base station in which a mobile station that includes the mobile station as a handoff candidate radio base station receives a downlink signal from a radio base station other than the mobile station. A beam pattern for directing null is formed.
[0016]
According to such a configuration, the mobile station that is communicating with another station directs the null without directing the beam. As a result, it is possible to avoid the generation of an interfering wave that interferes with communication with a mobile station that is communicating with another station, so that the communication quality of the mobile station can be improved.
[0017]
Further, the present invention is characterized in that, in a radio base station, the mobile station that receives a downlink signal from a radio base station other than the own station is determined based on information of a handoff candidate radio base station.
[0018]
The information of the handoff candidate radio base station is information in which information of radio base stations with which the mobile station may receive a downlink signal is registered for each mobile station.
More preferably, it is information in which information of radio base stations of several stations that are more likely to receive a downlink signal among radio base stations that are likely to receive a downlink signal is registered.
This information is like a table in which information of radio base stations that may receive the next downlink signal is registered so that handoff can be performed smoothly. As an example, an active set disclosed in the “CDMA mobile phone system standard ARIB STD-53 version 1.1”.
[0019]
Further, the present invention is characterized in that a radio base station detects the position or orientation of the mobile station based on an uplink signal received from each mobile station.
[0020]
The present invention also provides a radio base station that detects the position or orientation of a mobile station from which the mobile station is receiving an uplink signal by acquiring location information received by each mobile station from the global positioning system. It is characterized by.
[0021]
Further, the present invention provides a radio base station that has a higher reception capability than a mobile station having a higher downlink signal reception capability when the number of mobile station candidates to which the null is directed exceeds the null formation limit number of the local station. It is characterized in that a mobile station with a low priority is given priority and null is directed.
[0022]
Also, the present invention provides a radio base station with an adaptive antenna rather than a mobile station with an adaptive antenna when the number of mobile station candidates to which the null is directed exceeds the null forming limit number of the local station. It is characterized in that nulls are directed by giving priority to mobile stations that are not.
[0023]
There is a limit to the number of nulls that a radio base station can form. Therefore, when there are more mobile station candidates to which nulls are directed than the null forming limit number of the own station, priority is determined according to a predetermined condition, and nulls are formed in descending order of priority.
In the present invention, a mobile station that is easily affected by surrounding interference waves, that is, a mobile station having a low reception capability is set as a mobile station that does not include an adaptive antenna, and a null is formed by giving priority to the antenna that does not include the adaptive antenna In this way, the influence of the interference of the radio waves emitted by the own station is avoided. This makes it possible to stabilize the communication quality of the mobile station.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a radio base station according to an embodiment of the present invention. In the figure, reference numerals 901 to 903 are antenna elements. The arrangement of the antenna elements 901 to 903 can be arbitrarily set.
Reference numeral 904 denotes a steering vector calculation unit, which calculates a steering vector based on an uplink signal from a mobile station received via the antenna elements 901, 902, and 903. This steering vector is a vector indicating the direction of the mobile station.
[0025]
Reference numeral 905 denotes a transmission weight coefficient calculation unit, which includes the steering vector calculated by the steering vector calculation unit 904 and handoff candidate base station information acquired from another cellular radio base station or a higher-level station that manages the radio base station. The mobile station that directs the beam is determined, and the transmission weight coefficient is determined based on the mobile station.
[0026]
Here, the handoff candidate base station information is information on radio base stations that may establish communication for each mobile station (information on radio base stations that may receive downlink signals) and current communication. This is a table in which information of radio base stations performing the registration is registered. The station that manages the handoff candidate base station information may be set to be managed by any radio base station included in the handoff candidate base station information, or all radio base stations, in addition to the above-described upper station. Is possible.
In the present invention, a station that manages handoff candidate base station information may be any station and is not particularly limited. Further, this handoff candidate base station information is registered based on the uplink signal received from the mobile station, and when the information is updated, between the radio base stations or between the radio base station and the upper station. It is assumed that update information is notified between the wireless base stations and the latest information is always held in each radio base station.
[0027]
Reference numeral 906 denotes a transmission unit that notifies the transmission weight coefficient calculation unit 905 of a mobile station in a transmission waiting state in which transmission data is generated, and outputs transmission data.
Reference numeral 907 denotes a transmission beam pattern forming circuit, which branches transmission data output from the transmission unit 906 for each antenna element based on the transmission weight coefficient acquired from the transmission weight coefficient calculation unit 905, and determines the amplitude and Manipulate the phase.
Then, transmission data is transmitted to the mobile station via the circulators 111 to 113 and the antenna elements 901 to 903 by the beam pattern formed by the transmission beam pattern forming circuit 907.
Here, the weighting factor is information containing the amount of change in amplitude and phase operated for each of the antenna elements 901 to 903, and is represented by a complex vector having N elements as the number of antenna elements.
[0028]
Next, the operation of the radio base station having the above configuration will be described.
<< First Embodiment >>
[0029]
First, the radio base station receives an uplink signal from a mobile station existing near the own station (in the own station zone and near the own station zone). These uplink signals are output to the steering vector calculation unit 904 via the antenna elements 901 to 903 of the radio base station. The uplink signal includes various information such as identification information of the mobile station and radio wave information.
Note that a zone is a range where radio waves emitted from a radio base station reach.
[0030]
The steering vector calculation unit 904 obtains the direction of the mobile station by performing a predetermined calculation process based on the uplink signal of the mobile station received via the antenna elements 901 to 903. Then, the obtained azimuth information is output to transmission weight coefficient calculation section 905 together with various information of the mobile station.
[0031]
The transmission weight coefficient calculation unit 905 holds the latest azimuth information of the mobile station obtained by the steering vector calculation unit 904 and the latest handoff candidate base station information transmitted from the upper station. On the other hand, when the transmission unit 906 receives the transmission data, the mobile station information is notified as transmission-waiting radio base station information.
[0032]
Upon receiving the notification, the transmission weight coefficient calculation unit 905 first refers to the above-described handoff candidate base station information, and the own station is registered as a handoff candidate radio base station, and a radio other than the current own station A mobile station that receives a downlink signal from the base station (hereinafter, this mobile station is referred to as a mobile station X) is extracted.
Then, mobile stations located around the mobile station X are extracted from the mobile stations in the transmission standby state notified earlier, and beam weighting processing is performed so that the directional beam is not directed to the extracted mobile stations. That is, the extraction of the mobile station existing around the mobile station X is performed by comparing the azimuth information of the mobile station X with the azimuth information of the mobile station in the transmission standby state obtained by the steering vector calculation unit 904. This is performed by extracting a mobile station in a transmission standby state that exists within a predetermined angle range set in advance from the azimuth.
[0033]
By performing the above-described processing, the transmission weight coefficient calculation unit 905 performs the beam pattern weighting process so that the beam is not directed to the mobile stations located around the mobile station X among the mobile stations in the transmission standby state. The weighted result is output to the transmission beam pattern forming circuit 907.
The transmission beam pattern forming circuit 907 forms a transmission beam pattern by assigning transmission data to each antenna 901 to 903 based on the transmission weight coefficient acquired from the transmission weight coefficient calculation unit 905, and outputs the transmission beam pattern. Thereby, transmission data is transmitted to the mobile station via the circulators 111 to 113 and the antenna elements 901 to 903 by the beam pattern formed by the transmission beam pattern forming circuit 907.
[0034]
Next, the operation of the radio base station in the first embodiment described above will be described with a specific example.
Now, as shown in FIG. 2, radio base stations 301 and 302 are installed, and mobile stations 31 and 32 exist in the same region near the boundary between the zone of the radio base station 301 and the zone of the radio base station 302. ing. The mobile station 31 is currently establishing communication with the radio base station 301.
A process performed by the radio base station 302 when the radio base station 302 receives a plurality of transmission data including transmission data addressed to the mobile station 32 in the state as described above will be described.
[0035]
In addition, the handoff candidate base station information in the above-described state has registration contents as shown in FIG. That is, in the mobile station 31, a radio base station 301 is registered as a radio base station with which communication is established, and a radio base station 302 is registered as a handoff candidate radio base station. In the mobile station 32, 301 and 302 are registered as handoff candidate radio base stations.
[0036]
First, when the transmission weight coefficient calculation unit 905 of the radio base station 302 receives a notification from the transmission unit 906 that a plurality of transmission data including transmission data addressed to the mobile station 32 has been received, the handoff candidate base shown in FIG. From the station information, the mobile station 31 is extracted as a mobile station in which the own station is registered as a handoff candidate radio base station and communication is currently established with another station.
Subsequently, a mobile station located around the mobile station 31 is extracted from a plurality of mobile stations including the mobile station 32 in a transmission standby state. This process is performed based on the mobile station 31 obtained by the steering vector calculation unit 904 and the direction information of the mobile station in the transmission standby state.
[0037]
As a result, when the mobile station 32 is extracted as a mobile station in the transmission standby state existing around the mobile station 31, the transmission weight coefficient calculation unit 905 directs the directional beam toward the mobile station that is not the mobile station 32. Determine the transmission weighting factor. Thus, a mobile station in a transmission standby state to which a directional beam is directed is a mobile station in which no mobile station communicating with a base station other than its own station exists around the mobile station. Then, when the transmission weight coefficient calculation unit 905 determines the transmission weight coefficient, it outputs the result to the transmission beam pattern forming circuit 907.
[0038]
In the above-described embodiment, the mobile station is registered in the handoff candidate radio base station and is located in the vicinity of the mobile station (mobile station X) that has established communication with the radio base station other than the mobile station. However, instead of the method of determining based on such azimuth information, a method of determining based on the amount of radio wave interference may be used.
Hereinafter, this method will be briefly described.
[0039]
First, the transmission weight coefficient calculation unit 905 obtains a transmission weight coefficient for each mobile station from which the own station receives an uplink signal in addition to the mobile station X, and calculates the transmission beam pattern of each mobile station. Then, a mobile station that provides radio wave interference that is equal to or greater than a predetermined numerical value preset in the direction of the mobile station X is extracted.
Then, the weighting coefficient of the transmission beam pattern is determined so that the directed beam is not directed to the extracted mobile station, and the weighting coefficient is output to the transmission beam pattern forming circuit.
[0040]
As described above, according to the present embodiment, even when a mobile station is in a transmission standby state, there is a mobile station in communication with a radio base station other than its own station around the mobile station. Does not direct a directional beam toward the mobile station. That is, transmission data is not transmitted to such a mobile station. Then, when a mobile station existing near the mobile station cuts off communication with another radio base station, and there is no mobile station communicating near the mobile station, the mobile station The transmission data is transmitted by directing a directional beam toward it.
Thereby, it is possible to avoid the influence of radio wave interference due to interference waves or the like on other mobile stations, and to improve the call quality of the mobile station.
[0041]
<< Second Embodiment >>
In this embodiment, in order to further reduce the influence of radio wave interference due to interference waves or the like given to the mobile station, a null is formed for the mobile station determined not to direct the beam in the first embodiment.
A specific operation will be described below.
[0042]
For example, as shown in FIG. 4, wireless base stations 401 and 402 are now installed, and the mobile station 41 is located near the boundary of each zone. In such a situation, when the mobile station 41 and the radio base station 401 establish communication, the radio base station 402 directs null to the mobile station 41. The determination of the mobile station 41 is the same as in the first embodiment described above.
Normally, when the beam is directed, leakage occurs in directions other than the direction in which the beam is directed. That is, there is a possibility that the influence of the leaked radio wave may occur in the direction in which the beam is not directed.
In the present embodiment, the mobile station that is registered in the handoff candidate radio base station and that has established communication with another radio base station does not direct the beam and directs the null. As a result, the radio wave interference of the mobile station can be remarkably reduced by not emitting leaked radio waves to the mobile station.
[0043]
By controlling the directivity of the beam and null in this way, it is possible to prevent emission of jamming radio waves to mobile stations communicating with radio base stations other than its own station, and the communication quality of the mobile station Can be further increased.
[0044]
There is a limit to the number of wireless base stations that can form a null (hereinafter, this limit number is referred to as a null formation limit number). Therefore, when the number of mobile stations determined to form nulls exceeds the null formation limit number, nulls are formed in preference to those meeting a predetermined condition. Hereinafter, the priority order for forming the null will be described.
[0045]
For example, when there are a plurality of mobile stations that are currently transmitting downlink signals (hereinafter referred to as transmitting mobile stations) in the zone of the local station, first, the mobile station that is in communication is given priority first. Form a null. That is, when the beam is directed to one mobile station, a null is formed for other mobile stations that are transmitting.
And, as a result of directing null to the above-described transmitting mobile station, if the null formation limit number has not yet been reached, it has received handoff transmission from a radio base station other than its own station, and A null is formed in preference to a mobile station with low reception capability.
This is because a mobile station with a low reception capability is affected by the communication quality even if the radio interference is such that it does not affect the communication quality if it is a high mobile station.
[0046]
In this way, by giving priority to mobile stations that are easily affected by radio waves emitted from the own station and directing nulls, it is possible to improve the communication quality of the mobile stations and provide a stable communication environment.
In addition, as a mobile station with the above low reception capability, the mobile station which does not have an adaptive antenna is mentioned, for example.
[0047]
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within a scope not departing from the gist of the present invention.
In the above-described embodiment, for example, a case where a mobile station exists near the zone boundary between two radio base stations is described, but instead, a mobile station near the boundary between cells obtained by further dividing the zone. Even in the case where there is, a similar effect can be obtained by performing similar beam directing control.
[0048]
【The invention's effect】
As described above, according to the radio base station of the present invention, using mobile handoff candidate base station information, the mobile radio base station cooperates between cellular radio base stations and the mobile station directs the beam for each transmission beam and the mobile that directs null. By selecting a station, it becomes difficult to simultaneously direct the beam to the mobile station to which the adjacent cellular radio base station is approaching, and the adjacent cellular radio base station directs a null in the direction in which the cellular radio base station directs the beam. Interference between downlink cells is reduced. Thereby, the effect that the communication quality of the mobile station located in the cell boundary area which performs handoff is improved is acquired.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an internal configuration of a radio base station according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining beam directivity control according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a data configuration of handoff candidate base station information;
FIG. 4 is a diagram for explaining beam directivity control according to a second embodiment of the present invention.
FIG. 5 is a diagram for explaining conventional beam directivity control;
FIG. 6 is a diagram for explaining conventional beam directivity control.
FIG. 7 is a diagram for explaining conventional beam directivity control;
FIG. 8 is a diagram for explaining conventional beam directing control.
[Explanation of symbols]
31, 32, 41, 42, 51, 61, 62, 71, 72, 81, 82 ... mobile stations 301, 302, 401, 402, 501, 601, 701, 702, 801, 802 ... radio base station 100 ... higher rank Stations 111 to 113 circulators 901 to 903 antenna elements 904 steering vector calculation unit 905 transmission weight coefficient calculation unit 906 transmission unit 907 transmission beam pattern forming circuit

Claims (8)

In a radio base station that can control the beam direction,
As handoff candidate radio base stations, information on handoff candidate radio base stations that may establish communication and information on radio base stations that are currently communicating are registered in the handoff candidate base station information registered for each mobile station. When the own station is registered, the mobile station including the own station in the handoff candidate radio base station automatically follows the direction or position of the mobile station during the period in which the mobile station receives a downlink signal from a radio base station other than the own station. A radio base station characterized in that a beam pattern is formed so as not to direct a directional beam of a station. Do not direct the directional beam around the location of the mobile station during the period in which the mobile station including the local station as a handoff candidate radio base station receives a downlink signal from a radio base station other than the local station. The radio base station according to claim 1 , wherein a beam pattern is formed. Forms a beam pattern that directs null with respect to the direction or position of the mobile station during a period in which the mobile station including the local station as a handoff candidate base station receives a downlink signal from a base station other than the base station the radio base station according to claim 1 or claim 2, characterized in that. Based on the handoff candidate information of the wireless base station, to any one of claims 1 to claim 3, characterized in that to determine the mobile station receives downlink signals from a base station other than own station The radio base station described. Based on the uplink signal received from each mobile station, a radio base station according to any of claims 1 to claim 4, characterized in that to detect the position or orientation of the mobile station. By each mobile station acquires position information received from the global positioning system, claims 1 to 5 by the own station, and detects the position or orientation of the mobile station receiving the uplink signal The radio base station according to any one of the above. When the number of mobile station candidates to which the null is directed exceeds the null forming limit number of the own station, the mobile station having the lower reception capability is prioritized and the null is directed to the mobile station having a higher downlink signal reception capability. the radio base station according to any one of claims 1 to claim 6, characterized in that to. When the number of mobile station candidates to which the null is directed exceeds the null forming limit number of the own station, the mobile station without the adaptive antenna is prioritized over the mobile station with the adaptive antenna and the null is directed. the radio base station according to any one of claims 1 to claim 7, characterized in that to.

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