JPH09154168A - Service area variable system for radio base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain an optimum communication service environment by allowing a center to calculate an optimum tilt angle in response to a traffic of each base station, commanding it to each base station and allowing each station to set a tilt angle of the antenna according to the command so as to keep each service area to have an optimum width at all times. SOLUTION: A signal received by an antenna 12 is given to a BPF 10-6, an amplifier 10-5 and a BPF 10-4, in which a prescribed frequency signal is selected and amplified via a tilt angle control phase shifter 5 and a changeover switch 4. On the other hand, the signal is modulated by a modulator 10-9 of a radio circuit section 10, converted into a transmission frequency by a mixer 10-10 and amplified via a BPF 10-11, an amplifier 10-12 and an LPF 10-13. Each base station always measures the traffic and sends data to a center 7, the center 7 calctulates an optimum tilt angle in response to the traffic of each base station and commands it to each base station and the base station uses the tilt angle control phase shifter 5 according to the command to set the tilt angle of the antenna. Thus, each service area keeps a communication service environment with an optimum area at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention In mobile communication, the present invention adjusts the service area by controlling the tilt angle of the antenna of the radio base station according to the traffic amount (communication amount) of the radio base station, and always optimizes the service area. The present invention relates to a variable service area system of a wireless base station that provides a call service environment.

[0002]

2. Description of the Related Art In mobile communication, when the traffic amount (communication amount) of a wireless base station is small, it is necessary to secure a large-zone service area by producing a large output so that the number of base stations is smaller. It is economical, and since the mobile terminal can move without frequent handoffs, good call quality can be provided. However, in a high output and a small number of wireless base stations, as the traffic amount increases, the line busy and the like often cause a call from the terminal to become busy. Therefore, it is necessary to increase the number of radio base stations, but the output is large as it is, and it interferes with other radio base stations and mobile terminals. As a countermeasure, reduce the output of the wireless base station
I made the screw area smaller. As the number of base stations increases in the above process, the service area is changing from a large zone to a small zone.

As described above, a radio base station in mobile communication is a type that secures a high output and a wide service area, which is called a large zone, and a small output and a narrow service area, which is called a small zone. Is secured, and is divided into types that do not interfere with other areas, and it is decided which type to install depending on the regional characteristics of each area (large or small traffic volume, etc.).

As a method of adjusting the range of the service area of the wireless base station, there is a method of controlling the tilt angle of the antenna in addition to the method of controlling the output. FIG. 3 is a diagram showing the relationship between the tilt angle of the antenna and the radio wave reaching distance in the maximum radiation direction. FIGS. 3A to 3D show the radio wave reaching distance when the tilt angle is changed using the antenna AT having a height of 20 m. Indicates.

FIG. 3A shows the case where the tilt angle is 0 degree,
In this case, the maximum radiation direction of the radio wave is horizontal and the electric field strength is attenuated by the propagation loss due to the free space, so that the service area becomes wider. FIG. 11B shows the case where the tilt angle is 5 degrees, and in this case, the distance that the radio wave in the maximum radiation direction reaches the ground surface is 220 m. FIG. 6C shows the case where the tilt angle is 10 degrees, and in this case, the distance that the radio waves in the maximum radiation direction reach the ground surface is 113 m. FIG. 6D shows the case where the tilt angle is 15 degrees, and in this case, the distance at which the radio wave in the maximum radiation direction reaches the ground surface is 75 m. In this way, the radio wave arrival distance becomes shorter as the tilt angle increases. The tilt angle physically changes the length of each element of the antenna, or
It can be controlled by adjusting the phase angle of the carrier wave supplied to each element of the antenna.

FIGS. 4A and 4B are views showing changes in the service area depending on the tilt angle of the antenna. FIG. 4A shows a case where the tilt angle is small, and FIG. 4B shows a case where the tilt angle is large. As shown in the figure, (a) when the tilt angle of the antenna is small, the service areas of the base stations A, B, and C are expanded to cause an interference area. Further, (b) when the tilt angle of the antenna is large, an area which does not belong to any service area occurs. Each base station adjusts the length of each element in the vertical direction of the antenna or adjusts the phase angle of the carrier wave supplied to each element to control the tilt angle by using a tilting control phaser. The size of each service area is appropriately determined and operated by setting the tilt angle.

[0007]

However, the traffic volume between the mobile terminal and the base station varies depending on time, season, or
Since it changes due to the renovation or movement of buildings such as stations, at some point the output can be adjusted according to the traffic volume, or by setting an appropriate tilt angle, a large zone type or
Even if a small zone type service area is selected, it is difficult to always maintain an optimum communication service environment. Further, in the method of adjusting the output, there is a problem in that, in a base station such as a rooftop of a building, if the output is lowered to narrow the service area, the radio wave may be weakened immediately below the building and the telephone call may not be possible.

The present invention has been made in view of the above points, and in order to eliminate the above problems, there is provided a service area variable system for optimally adjusting a service area by monitoring traffic and controlling a tilt angle. The purpose is to provide.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 is a base station connected to a center through a line, and a tilt angle control means for controlling a tilt angle of an antenna. In a service area variable system of a base station for mobile communication, which has a service area of the wireless base station adjusted and operated by controlling the tilt angle by the tilt angle control means, A means for determining an optimum antenna tilt angle for each base station based on the traffic of the station and instructing to the base station, and the base station is provided with means for setting the tilt angle of the antenna by the tilt angle control means in accordance with the instruction. Is characterized by.

The invention according to claim 2 is a radio base station center-connected via a line, comprising tilt angle control means for controlling a tilt angle of an antenna, wherein the tilt angle control means In the service area variable system of the wireless base station for mobile communication, which adjusts and operates the service area of the wireless base station by controlling the tilt angle,
The center measures the traffic data of each wireless base station,
An optimum antenna tilt angle is obtained for each radio base station based on the data and is instructed to the radio base station, and the tilt angle control means of the radio base station sets the tilt angle of the antenna according to the instruction. To do.

By configuring the service area variable system of the radio base station as described above, the center calculates the optimum tilt angle according to the traffic of each base station and gives an instruction to the base station. Since the tilt angle of the antenna is set according to the instruction, each service area is always kept in the optimum area, and the optimum communication service environment can be maintained.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing the configuration of a service area variable system for a wireless base station according to the present invention. As shown in the figure, the base station has a line interface 1 and a frame interface.
It includes a processor 2, a diversity circuit 3, a changeover switch 4, a tilt angle control phaser 5, a control unit 6, and a plurality (two sets in the figure) of wireless circuit units 10 and 20.

The base station has a plurality of (two in the figure) radio circuit sections 10 and antennas 12 and 22 in a diversity communication system, and signals are optimally selected by the diversity circuit 3 and the changeover switch 4. To the ISDN line via the line interface 1 to a wire terminal (not shown in the figure) and to the center 7 that monitors the call status of each base station for billing etc. Connected. The frame processor 2 encodes the call signal,
The tilt angle controlling phase shifter 5 controls the tilt angles of the antenna 12 and the antenna 22 (details will be described later). The control unit 6 controls the line interface 1, the frame processor 2, the diversity circuit 3, the changeover switch 4, and the tilt angle control phase shifter 5 to control the entire base station.

The radio circuit section 10 includes an intermediate frequency circuit 10-1,
Bandpass filter 10-2, mixer 10-3, bandpass filter 10-4, amplifier 10-5, bandpass filter 10-6, bandpass filter 10-7, synthesizer 10-8, modulator 10-9, mixer. 10-10,
It is composed of a bandpass filter 10-11, an amplifier 10-12, and a lowpass filter 10-13, and is connected to the diversity circuit 3 via the modem 11. Radio circuit unit 2
0 is similarly configured.

The signal received by the antenna 12 passes through the changeover switch 4 via the tilt angle controlling phase shifter 5, and a predetermined frequency signal is generated by the bandpass filter 10-6, the amplifier 10-5 and the bandpass filter 10-4. It is selectively amplified. Further, it is converted into an intermediate frequency signal by the mixer 10-3, amplified by the band pass filter 10-2 and the intermediate frequency circuit 10-1, and output to the diversity circuit 3 via the modem 11. The diversity circuit 3 compares the signal of the other system and sends an appropriate signal to the frame processor 2, where the signal is decoded and sent to the ISDN line via the line interface 1 and sent to the partner terminal. To be done.

The signal from the ISDN line is sent to the frame processor 2 via the line interface 1 and encoded, and the diversity circuit 3 selects an appropriate system. For example, the radio circuit section 10 is used. When the communication system is selected, the data is input to the wireless circuit unit 10 via the modem 11. In the radio circuit unit 10, the signal is modulated by the modulator 10-9 and the mixer 10-
Converted to the transmission frequency at 10 and the bandpass filter 10
-11, amplifier 10-12, low-pass filter 10-1
Amplified through 3. Further, it is transmitted to the mobile terminal via the changeover switch 4, the tilt angle control phase shifter 5, and the antenna 22. The synthesizer 10-8 and the bandpass filter 10-7 are local oscillating devices that perform frequency conversion of a received signal into an intermediate frequency, or perform modulation and frequency conversion into a transmission frequency.

In this embodiment, the control unit 6 measures the traffic volume (call volume) with which the mobile terminal communicates via the base station through the line interface 1 and notifies the center 7 of the data. . In the center 7, the traffic amount of each base station is totaled and statistically processed to calculate the tilt angle of the antenna for maintaining the optimum communication service environment, and the tilt angle is transmitted to each base station to instruct the tilt angle. .

FIG. 2 is a diagram showing a flow for controlling the tilt angle of the antenna according to the traffic volume. A program for executing this flowchart is stored in the control unit 6 of each base station and executed by the CPU (not shown). Hereinafter, description will be given with reference to FIG. The control unit 6 measures the traffic volume per hour through the line interface 1 and measures
(ST step 11). In the center 7, the traffic amount sent from each base station is totaled (ST step 21), the mutual influence of a plurality of adjacent base stations is statistically calculated, and the optimum tilt angle for the traffic amount of each base station is obtained. Calculate (0, 5, 15 degrees) and give an instruction to the base station (S
T step 22).

In the base station, the control unit 6 controls the ISD from the center.
An instruction value of the tilt angle of the antenna is received via the N line and the line interface 1 (ST step 12), and it is determined what the instruction value of the tilt angle is. When the tilt angle is 0 degree (ST step 13), the control unit 6 controls the tilt angle control phase shifter 5 to control the antenna 12 (or the antenna 2).
The tilt angle of 2) is set to 0 degree (ST step 1
4). Similarly, when the tilt angle is 5 degrees (ST step 15), the tilt angle is set to 5 degrees (ST step 1).
6). In the case of an instruction of a tilt angle of 10 degrees (ST step 1
7), set the tilt angle to 10 degrees (ST step 1
8). In the case of an instruction of a tilt angle of 15 degrees (ST step 1
9), set the tilt angle to 15 degrees (ST step 2
0). If no instruction is given, step 11 is left as it is.
Repeat from

As described above, according to the present embodiment, each base station constantly measures the traffic amount and transmits the data to the center 7. The center 7 selects the optimum tilt angle according to the traffic amount of each base station. Is calculated and instructed to each base station, and the base station sets the tilt angle of the antenna by using the tilt angle control phase shifter 5 according to the instruction, so that each service area is always kept in an optimum area, The communication service environment can be maintained. In the above-mentioned embodiment, each base station measures its own traffic volume, but the present invention determines the traffic volume of each base station at the center that monitors the entire system such as the communication status of each base station. You may make it measure.
Further, although the above-described embodiment is based on the actual traffic amount in order to calculate the tilt angle, the present invention is not limited to the actual traffic amount, and the busy occurrence status of each base station and the service area of each base station In consideration of the number of existing mobile stations (the number of location registrations) and the like, individual data or total data of these may be measured as traffic data at each base station or center.

[0021]

As described above, according to the present invention, the following excellent effects are expected. The center calculates the optimum tilt angle according to the traffic of each base station and gives an instruction to the base station. The base station sets the tilt angle of the antenna according to the instruction, so that each service area is always kept to the optimum size. Therefore, the optimum communication service environment can be maintained. In particular, in the base station on the rooftop of a building, if the output is reduced as in the past to narrow the service area, the radio wave may be weakened directly below the building, and it may not be possible to talk, but if the tilt angle is increased, the base station will be adversely affected. In a place near to, the radio wave becomes stronger and the interference becomes stronger.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of a service area variable system for a wireless base station according to the present invention.

FIG. 2 is a flowchart for controlling a tilt angle of an antenna according to a traffic amount.

FIG. 3 is a diagram showing a relationship between a tilt angle of an antenna and a radio wave reaching distance in a maximum radiation direction.

FIG. 4 is a diagram showing a change in a service area depending on a tilt angle of an antenna. FIG. 4A shows a case where the tilt angle is small, and FIG. 4B shows a case where the tilt angle is large.

[Explanation of symbols]

 1 Line Interface 2 Frame Processor 3 Diversity Circuit 4 Changeover Switch 5 Tilt Angle Control Phaser 6 Control Section 10 Radio Circuit Section 10-1 Intermediate Frequency Circuit 10-2 Bandpass Filter 10-3 Mixer 10- 4 band pass filter 10-5 amplifier 10-6 band pass filter 10-7 band pass filter 10-8 synthesizer 10-9 modulator 10-10 mixer 10-11 band pass filter 10-12 amplifier 10-13 low pass filter 11 modem 12 antenna 20 wireless circuit section 21 modem 22 antenna

Claims (2)

[Claims] 1. A wireless base station center-connected via a line, comprising tilt angle control means for controlling a tilt angle of an antenna, wherein the tilt angle control means controls the tilt angle to provide the wireless communication. In a service area variable system of a mobile communication wireless base station that adjusts and operates a service area of a base station, the wireless base station measures traffic data, transmits the data to the center, and the center Then, the optimum tilt angle of the antenna is calculated for each radio base station based on the data from each radio base station and instructed to the radio base station. In the radio base station, the tilt angle of the antenna is controlled by the tilt angle control means. Is set according to the above instruction, and the service area variable system of the radio base station is characterized. 2. A wireless base station center-connected via a line, comprising tilt angle control means for controlling a tilt angle of an antenna, wherein the tilt angle control means controls the tilt angle to thereby provide the wireless communication. In a service area variable system of a mobile communication wireless base station that adjusts and operates a service area of a base station, the center measures traffic data of each wireless base station, and based on the data, each wireless base station The optimum tilt angle of the antenna is calculated and instructed to the wireless base station, and the tilt angle control means of the wireless base station sets the tilt angle of the antenna according to the instruction. Visarea variable system.