JPH1022912A - Interruption relieving system for cellular vehicle telephone system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue a call for a prescribed period by switching to a private antenna even if an idle channel does not exist in a moving adjacent base station and the switching of the channel is impossible in a cellular moving communication system. SOLUTION: If a conversion station MSC recognizes possibility that the received field level of the station M becomes less than a minimum received field level which the station A can service when the moving station M moves to the service area of the adjacent station B while it makes a call from the service area of the station A, a control part CONT switches the channel to the idle channel of the station B in accordance with the moving speed of the moving station M and continues the call. When idle channel does not exists in the station B, the station A adjusts the directivity of the main beam in a direction where the moving station M can obtain a maximum electric field and switches a call interruption relief-only antenna from the fixed one to the private one. Even if the moving station moves to the service area without the idle channel, the received electric field is secured, the call interruption is relieved for the prescribed period and the call can be continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna control system and a call rescue system for a cellular telephone system.

[0002]

2. Description of the Related Art As a conventional technique of this kind, for example, Japanese Patent Laid-Open No. 4-47722 discloses a technique in which first and second antennas are provided, and the reception level of a radio wave from a mobile station at both antennas is determined. There has been proposed a radio channel allocation method in mobile communication in which an antenna used for communication with the mobile device is selected in accordance therewith to improve the frequency utilization rate. That is, in the radio channel assignment method described in the above publication, as shown in FIG.
Mobile antenna having a vertical antenna directivity lower than the vertical antenna directivity of the first antenna, and a second antenna for the second narrow radio zone 24. In this method, an antenna to be used for communication with the mobile device is selected in accordance with the level of reception of the radio wave from the mobile station at both antennas. In FIG. 7, reference numeral 20 denotes a directivity pattern of the first antenna, 21 denotes a directivity pattern of the second antenna, and 2 denotes a base station.

[0003] For example, in Japanese Patent Application Laid-Open No. 6-140985, when a base station is added or added, the device parameters of the base station and the adjacent station are changed without rearranging the frequency for communication. There has been proposed a frequency allocation control method capable of coping only with the above. That is, as shown in FIG. 8, when the traffic in the service area of the base station 35 increases, the service area of the base station 35 is reduced and the service area of the adjacent base stations 33 and 34 is expanded, as shown in FIG. Thus, the traffic of the base station 35 is transferred to the base stations 33 and 34. Then, the antenna tilt angle is adjusted by a parameter to enlarge or reduce the service area.

[0004]

SUMMARY OF THE INVENTION The above-mentioned JP-A-4-477
In the wireless channel assignment method described in No. 22, when the mobile station exits from the second narrow wireless zone (service area) and enters the first wide wireless zone, it is considered that the call can be continued. When the user goes out of the wide wireless zone and enters the adjacent zone, and there is no vacant channel in the adjacent zone, the channel cannot be switched and the call is disconnected.

[0005] The reason is that the beam angle of the antenna is fixed, and there is no means to temporarily widen the second wireless zone to continue the call. Depending on

[0006] Further, Japanese Patent Application Laid-Open No. Hei 6-140 shown in FIG.
The frequency allocation system described in Japanese Patent No. 985 has the following problems.

(1) Even if there is an increase in traffic in the service area adjacent to the base stations 33 and 34 in the service area of the base station 35, the service area of the base station 35 is uniformly reduced. In the opposite direction to 33, 34,
Irrelevant service areas are also reduced.

The reason is that the antenna does not have directivity in a horizontal plane, and only the necessary service area is not reduced.

(2) A desired effect cannot be obtained unless the traffic of the base stations 33 and 34 is low.

[0010] That is, when the base stations 33 and 34 have high traffic, the base stations 33 and 34 have no capacity to capture the traffic of the base station 35, so that the service area cannot be expanded.

(3) Since the direction of travel of the mobile station is not taken into consideration, for example, when the base stations 34 and 35 have high traffic and the mobile station attempts to move from the base station 34 to the service area of the base station 35, If there is no vacant channel in 35, the service area of the base station 34 is not expanded and the call is disconnected.

The reason is that, as described in the above (2), the service area can be expanded only when the traffic is low.

Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cellular mobile communication system in which a mobile station moves from a first base station to a second base station whose service area is adjacent to the first base station. It is an object of the present invention to provide a call rescue method and an antenna control method that allow a call to be continued for a certain period even when there is no free channel in the second base station and channel switching is not possible.

[0014]

In order to achieve the above object, a call rescue system according to the present invention detects a moving speed of a mobile station in a cellular car telephone system, and the mobile station transmits the first base station. Second out of the service area
When entering the service area of the base station, the second base station has no vacant channel, and when the electric field below the minimum electric field capable of communication is established, the first base station performs a call rescue operation. By switching to the dedicated antenna and controlling the horizontal and vertical main beams of the dedicated antenna to point in the direction of the mobile station, the service area of the second base station allows the It is characterized in that the reception electric field of the channel is increased so as to prevent a call disconnection.

In the present invention, the mobile station travels from the first base station to the second base station while talking on the communication channel of the first base station, exits the service area of the first base station, and receives the first base station. When entering the service area of the second base station adjacent to the service area of the base station,
If there is no free channel in the base station and the received electric field of the communication channel of the mobile station is lower than the minimum electric field at which communication is possible, the first base station switches from a fixed antenna to a dedicated directional antenna, For the directivity antenna, while directing the main beam directivity in the horizontal plane toward the mobile station, controlling the tilt angle so that the main beam direction in the vertical plane directivity is the moving direction of the mobile station,
The communication may be continued by increasing the reception electric field of the communication channel in the mobile station to be equal to or higher than the minimum electric field at which communication is possible.

Further, the antenna control system according to the present invention comprises:
The speed of the mobile station is recognized by the fading pitch, and the position of the mobile station in the antenna direction is obtained for the mobile station moving at a low speed by using the fact that the electric field having the maximum main beam direction in the vertical plane and the horizontal plane of the antenna is obtained. The main beam in the horizontal plane of the directional antenna is changed by a mechanical mechanism, the tilt angle of the main beam in the vertical plane is changed in real time by electrical phase control, and the directivity is changed in the direction of the mobile station. And controlling both main beams of the directional antenna.

[0017]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining a basic configuration of an embodiment of the present invention.

Referring to FIG. 1, in an embodiment of the present invention, a mobile telephone system includes a controller (CONT) for detecting a speed of a mobile station, confirming a position of the mobile station, and controlling an antenna direction / tilt angle. An exchange (MSC) accommodating an exchange that performs exchange connection processing and call processing, and an exchange (MS)
The mobile station (M) includes a base station (BS) having a control channel and a communication channel based on a command from C) and performing communication connection.

In the embodiment of the present invention, a mobile station (mobile station) is used in contrast to the conventional antenna fixed type system in which the service area of the base station is fixed or the system in which the service area is enlarged or reduced by traffic. And a tilt angle controller for the horizontal and vertical directions of the antenna to change the tilt angle and the direction in the horizontal plane of the dedicated directional antenna having a sharp beam. Referring to FIG. 1, when mobile station M approaches the boundary of a predetermined service area of base station A and there is no available channel in the service area of adjacent base station B, a normal fixed antenna
The antenna is switched to a dedicated antenna for call rescue, the position of the mobile device is recognized by the dedicated antenna for call rescue, and control is performed such that the mobile station can always be maintained at the center of the main beam of the antenna.

Further, in the embodiment of the present invention, the antenna for exclusive use of call disconnection and rescue is changed in its antenna direction and tilt angle by following the position of the mobile station.
The communication channel (F1) of the base station A is configured so that the communication can be continued within the limited service area of the base station B.

In the embodiment of the present invention, by targeting a low-speed moving object having a low moving speed, it is relatively easy to realize that the main beam of the antenna is directed toward the moving object. It is possible to reliably control the operation of the antenna for exclusive use for rescue and relief.

In the embodiment of the present invention,
Using the fact that the gain is lower at the periphery of the directional antenna than at the center of the main beam, the antenna is controlled so that the mobile station is positioned at the center of the main beam in the horizontal and vertical planes of the antenna for call rescue. Thus, when the mobile station enters the predetermined service area of the base station B from the predetermined service area of the base station A using the fixed antenna, even if the base station B does not have an empty channel (F2), the base station B In the limited service area, the reception electric field of the channel (F1) of the base station A can be kept higher than that of the fixed antenna, so that the call can be continued for a certain period of time.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to explain the above-mentioned embodiment of the present invention in more detail, an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining an embodiment of the present invention, and shows a relationship between a system configuration and a service area.

In FIG. 1, the control unit CONT has a speed detecting unit (not shown), and confirms the position of the mobile station and controls the antenna direction / tilt angle. Further, the mobile telephone exchange MSC performs exchange connection processing and call processing.

The base station BS has a control channel and a communication channel based on a command from the exchange MSC, and establishes a communication connection.

The antenna has a normal antenna for making a call in the service area of its own station, and a directional antenna dedicated to call rescue. In FIG. 1, M is a mobile station, A station is a base station currently in communication with the mobile station M, B station is an adjacent base station, C station is a base station using the same frequency as A station, and F1 is The frequencies of the stations A and C, and F2 indicates the frequency of the station B.

FIG. 2 shows the directivity in the horizontal plane of the directional antenna dedicated to call disconnection and relief.

FIG. 3 shows the relationship between the directivity in the vertical plane of a directional antenna (also referred to as a "dedicated antenna") dedicated to call rescue and tilt angle up-tilt control. As shown in FIG. 3, the service area of the station A exceeds the service area of the station A when the fixed antenna is used, and the service of the station B when the fixed antenna is used, due to the call rescue at the base station A when the dedicated antenna is used. It can be seen that it extends in the area.

FIG. 4 shows the relationship between the received electric field and the up-tilt control.

FIG. 5 is a flowchart showing a process flow of antenna uptilt and channel switching in the embodiment of the present invention.

Next, referring to the flowcharts of FIGS. 1 and 5,
The operation of the embodiment of the present invention will be described.

As shown in FIG. 1, a mobile station M receives a channel (CH) (F
While talking in 1), it is assumed that the service area is moving toward station B adjacent to station A (step S10 in FIG. 5). In this case, a fixed antenna that does not change the directivity is used as the antenna of the base station A.

When the mobile station M leaves the service area of the station A,
When trying to enter the service area of station B, first, when the switching center MSC recognizes that there is a possibility that the reception electric field level below the serviceable minimum level of station A may be lower (YES in step S11), the control unit CONT performs fading. From the pitch, the moving speed of the mobile station M is detected, and it is confirmed that the mobile station is a low-speed mobile body. If the station B has an empty channel (F2) (YES in step S12), the empty channel (F
The communication is continued by switching the channel to 2) (step S13).

When there is no free channel (F2) in station B (NO in step S12), when the channel (F1) in station A is lower than the lowest electric field that can be serviced (step S1).
4), the call was cut off in the conventional method (see step S30), whereas in the embodiment of the present invention, the station A mechanically rotates the call-cutting relief antenna in the horizontal direction. After adjusting the direction to obtain the maximum electric field in the horizontal direction using the directivity shown in FIG.
Switch from the station's normal fixed antenna to an antenna dedicated to call disconnection and relief.

In the case of a low-speed moving object, the horizontal control of the antenna is relatively easy. The tilt angle for determining the directivity in the horizontal plane of the call disconnection antenna is adjusted in advance so that the main beam is directed to the boundary of the service area of the station A.

When the mobile station M further moves in the direction of the station B and the received electric field is about to fall below the minimum electric field that can be serviced by the station A, the phase of the electric tilt is controlled to perform the control shown in FIG.
As shown in FIG. 4, the received electric field is up-tilted,
As shown by the dashed line, control is performed so as to exceed the lowest electric field that can be serviced, thereby relieving the call interruption (step S16).

In the embodiment of the present invention, since the directional antenna having a sharp main beam is used exclusively for relieving call disconnection, only the mobile station to be rescued is controlled.
As shown in (1), the area that can be used for the channel (F1) of the station A within the service area of the fixed antenna of the station B is limited, so that the influence on other mobile stations can be minimized.

[0038] Furthermore, normal calls are economical because they are performed using inexpensive fixed antennas.

Since the station C shown in FIG. 1 repeatedly uses the same frequency as the station A, the control as shown in FIG. 5, for example, is performed in order to minimize the influence of the station A. Referring to FIG. 5, when the channel (F1) of station A is equal to or lower than the lowest electric field that can be serviced (YES in step S14), when the channel (F1) is used in station C, an empty channel is assigned to station C. If there is (X) (YE in step S17)
S), the channel (F1) of the station A is switched to the vacant channel (X) (step S18), the fixed antenna of the station A is switched to the antenna dedicated to call disconnection and rescue, and the up-tilt is performed on the channel (X) to continue the call. (Step S19).
When there is no empty channel (X) in the station C (step S17)
NO), when there is an empty channel (X) in the station A,
The station A is switched to the vacant channel (X), and the call is continued (step S21).

[0040]

As described above, according to the present invention,
Even if a mobile station moves to a service area where there is no available communication channel, the effect on other mobile stations can be minimized, and the effect of being able to rescue a call disconnection for a certain period is exhibited.

The reason is that, by using the directivity of the horizontal and vertical planes of the antenna for exclusive use of call disconnection and rescue, by directing the main beam to the mobile station, it is possible to control the received electric field so as to exceed the minimum electric field for communication. It depends.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining one embodiment of the present invention;
FIG. 1 is a diagram schematically illustrating a relationship between a system configuration and a service area.

FIG. 2 is a diagram illustrating an example of directivity in a horizontal plane of a dedicated antenna for call rescue according to an embodiment of the present invention.

FIG. 3 is a diagram schematically illustrating the relationship between the directivity in a vertical plane and the tilt angle control of a dedicated antenna for call rescue according to an embodiment of the present invention.

FIG. 4 is a diagram for explaining one embodiment of the present invention;
FIG. 4 is a diagram illustrating a relationship between a reception electric field and up-tilt control.

FIG. 5 is a flowchart illustrating a process flow of antenna uptilt and channel switching according to an embodiment of the present invention.

FIG. 6 is a diagram for explaining a method described in a conventional technique (Japanese Patent Laid-Open No. 4-47722).

FIG. 7 is a diagram for explaining a method described in the related art (Japanese Patent Laid-Open No. 6-140985).

[Explanation of symbols]

 A Base station that is currently talking B Base station (adjacent station) C Base station having the same frequency as station A BS base station CONT control unit F1 Frequency of stations A and C F2 Frequency of station B M Mobile station MSC Mobile phone switching center 20, 21 Directivity pattern 22 Base station 23 First wireless zone 24 Second wireless zone 31, 32, 33, 34, 35 Base station 41, 42, 43, 44, 45 Service area

Claims (4)

[Claims] In a cellular mobile telephone system, when a moving speed of a mobile station is detected, the mobile station exits a service area of a first base station and enters a service area of an adjacent second base station. If the second base station has no vacant channel and falls below the minimum electric field capable of communication, the first base station switches to a dedicated antenna for call rescue, By controlling the horizontal and vertical main beams to point in the direction of the mobile station, in the service area of the second base station,
A communication disconnection remedy method comprising: increasing the reception electric field of the channel of the first base station so as to prevent the communication interruption. 2. In a cellular mobile phone system, a mobile station communicates with a first base station while talking on a communication channel of a first base station.
Proceeding from the base station to the second base station, exiting the service area of the first base station and entering the service area of the second base station adjacent to the service area of the first base station, If there is no free channel in the second base station, and the received electric field of the communication channel of the mobile station decreases and falls below the minimum electric field at which communication is possible, the first base station switches from a fixed antenna to a dedicated directional antenna, For the dedicated directivity antenna, while directing the main beam of the directivity in the horizontal plane toward the mobile station, the tilt angle is controlled such that the main beam direction of the directivity in the vertical plane is the moving direction of the mobile station. A call disconnection and rescue method, wherein a call is continued by raising a reception electric field of a communication channel in the mobile station to a minimum electric field at which communication is possible. 3. The method according to claim 1, wherein the speed of the mobile station is recognized based on the fading pitch, and the maximum electric field is obtained for the mobile station moving at a low speed in the vertical and horizontal planes of the directional antenna. The position of the mobile station is confirmed in the antenna direction, and the main beam having the directivity in the horizontal plane is directed toward the mobile station, and the main beam having the directivity in the vertical plane is tilted such that the main beam direction is the moving direction of the mobile station. 3. The method according to claim 2, wherein the corner is controlled. 4. A mobile station moving at a low speed by recognizing the speed of the mobile station based on the fading pitch and utilizing the fact that an electric field having the maximum main beam direction in the vertical plane and the horizontal plane of the directional antenna is obtained for the mobile station moving at a low speed. Confirm the position of the mobile station in the antenna direction, change the main beam in the horizontal plane of the directional antenna by a mechanical mechanism, and change the tilt angle in real time by controlling the electrical phase of the main beam in the vertical plane. An antenna control method for controlling both main beams of the directional antenna to be directed to the direction of the mobile station.