JP2000332675A - Mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication system for stably operating hand- over in a radio dead zone such as a tunnel even when a mobile station is in transit at a high speed. SOLUTION: The radio waves of a base station A are received by a master station 11, and the radio waves of a base station B are received by a master station 21, and guided to a radio dead zone such as a tunnel, and first area radio waves and second are a radio waves are emitted with a level difference necessary for hand-over from antennas AT1 and AT2 set adjacently to the dead zone. Therefore, a block having an electric field strength difference necessary for the hand-over in which a moving mobile station 3 can continuously receive the radio waves for a period necessary for hand-over can be formed in the dead zone. Thus, the stable hand-over can be executed by the mobile station 3 moving at a high speed. Also, a block having the opposite level difference is formed so that stable hand-over can be executed even when the mobile station 3 is in transit in any direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system for mobile communication such as a mobile phone or a mobile phone, and more particularly to a mobile communication system capable of performing a stable handover in a long blind zone such as a tunnel. The present invention relates to a communication system.

[0002]

2. Description of the Related Art In a mobile communication system such as a cellular phone, external radio waves are collected by an antenna, and respective frequencies are synthesized by a master station to a slave station in order to prevent radio wave insensitive areas such as tunnels, underground malls, and underground parking lots. It transmits and radiates to the radio wave insensitive zone via the antenna of the slave station. Further, in the mobile communication system, base stations are switched according to a change in a radio wave state (hereinafter, referred to as a handover) in order to continue communication without interruption (hereinafter, this is referred to as a handover). The above-mentioned handover is necessary in the zone where radio waves are insensitive because the base station is different at each entrance.

For example, when the entrance side of the tunnel T is the area of the base station A and the exit side is the area of the base station B,
The handover is performed as shown in FIG. As shown in the figure, for example, a master station 1 for transmitting and receiving to and from a base station A is provided, a radio wave A received by the master station 1 is transmitted to a slave station 2 in the tunnel T, and emitted from the slave station 2 into the tunnel T. .
The mobile station 3 such as a mobile phone receives the radio wave A and the radio wave B radiated by the base station B, and the radio wave of the base station A currently used is changed to the radio wave of the next base station B as shown in FIG. In comparison, when the level is lower by a predetermined amount Ld (for example, 5 dB) (point C in the figure) and continues for a predetermined time tm (for example, 5 seconds), the condition for handover switching is satisfied. That process is performed.

[0004]

In the above-mentioned prior art, when a vehicle moving at a high speed, such as a train, enters a tunnel and communicates, a level difference required for handover occurs. Before continuing for a predetermined time from, the radio wave currently in use is weakened, the communication is disconnected, and in some cases, the communication becomes impossible rather than the handover. That is, when the speed of the mobile station 3 moving in the direction of the arrow in FIG. 11 is high, the electric field strength of the radio wave of the base station A is lower by a predetermined amount Ld than the radio wave of the base station B as shown in FIG. (Point C in the figure) before the predetermined time tm elapses, the electric field strength of the radio wave A of the base station A becomes weaker than the reception limit level Lm of the mobile station 3, and communication is disconnected. The problem that communication became impossible occurred.

On the other hand, as shown in FIG. 13, a slave station 2 'is provided, and a blowing antenna for radiating the radio wave of the base station A is mounted near or outside the entrance of the tunnel T, and the radio wave of the base station A is transmitted in the tunnel T. A method of securing the reception level and duration required for handover by radiating the light may be considered. In the above method, it is necessary to radiate a strong radio wave to the outside, and the surroundings are affected. Also, when the mobile station 3 is moving in the direction A in the figure, handover is possible even while the mobile station is moving at high speed, but when the mobile station 3 is moving in the direction B in the figure, As described above, a problem occurs that communication is disconnected. That is, the radio wave of the base station B rapidly attenuates in the tunnel T as shown in FIG. Therefore, as described above, after the difference between the electric field strengths of the radio waves B and A becomes the level difference Ld, the time t
Before the elapse of m, the electric field strength of the radio wave B becomes weaker than the reception limit level Lm of the mobile station 3, which causes a problem that communication is disconnected and communication becomes impossible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a level required for handover in a radio wave insensitive zone even when a mobile station is moving at high speed. It is an object of the present invention to provide a mobile communication system capable of securing a difference and a duration, performing a handover stably, and reducing a total cost.

[0007]

According to the present invention, the above-mentioned problems are solved as follows. (1) The received radio wave in the first area at the mobile station is
In a mobile communication system that performs a handover from the first area to the second area when the received radio wave is lower than the received radio wave of the area by a predetermined level and the state continues for a predetermined time, the radio wave of the first area and the second radio wave are transmitted. The radio wave in the area is received, the radio wave is drawn into the dead zone, the radio wave in the first area and the radio wave in the second area are radiated from the antenna installed in the dead zone, and the hand is moved into the dead zone. The mobile station has a difference in electric field strength necessary for over-travel and forms a section in which radio waves in the first and second areas can be continuously received for a handover time in a moving mobile station. (2) In the above (1), the radio wave of the first area and the second
When the radio waves in the area are radiated from the antenna, the radiation levels of the radio waves in the first and second areas are defined as a level difference required for handover. (3) In the above (1) and (2), the antenna that radiates radio waves in the first area and the antenna that radiates radio waves in the second area are the same or close to each other. (4) In the above (1) to (3), in at least the first section, a radio wave of the second area is radiated more strongly than a radio wave of the first area with a level difference required for handover, and In the second section, a mobile station that is moving is provided with a level difference required for handover, and emits radio waves in the first area more strongly than radio waves in the second area, and has a field strength difference required for handover, and is moving. , A first section in which radio waves of the first and second areas can be continuously received and a second section in which handover is possible. (5) In the above (1), the first antenna and the second antenna having directivities having different gains on the left side and the right side are arranged adjacent to each other along the moving direction of the mobile station, and The antenna is arranged such that the side having a large gain of the antenna faces one side of the moving direction, and the second antenna is arranged such that the side having a large gain of the antenna faces the other side of the moving direction. The first antenna radiates radio waves in the first area from the first antenna, and the second antenna radiates radio waves in the second area to provide a difference in electric field strength required for handover. A first section and a second section in which radio waves in the first and second areas can be continuously received for a period in which the mobile station can perform handover are formed. (6) In the above (1) to (4), a first master station that receives a radio wave of the first area and converts it into a signal of the first area;
A second master station is provided for receiving the radio wave of the second area and converting it into a signal of the second area. The signal of the first area received by the first master station is received by the second master station. The signals in the second area are combined with a level difference required for handover, and the combined signals are radiated from an antenna installed in a radio wave insensitive zone. (7) In the above (6), the second master station receives the second
Is transmitted to the first master station, and the first master station compares the signal transmitted from the second master station with the signal of the first area received by the first master station. Combine with a level difference. (8) In the above (1) to (7), a means for adjusting a level is provided to receive a radio wave of the first area and a radio wave of the second area, and to receive a signal of the first area and a signal of the second area. When the signal of the first area and the signal of the second area are adjusted by the means for adjusting the level when the signal is drawn into the dead zone of the radio wave as the signal of the second area. Claim 1 of the present invention
Since the inventions of (1) to (3) are configured as described in (1) to (3) above, even if the mobile station moves at high speed in the radio wave insensitive zone,
The level difference of the electric field strength required for the handover can be stably maintained, and the handover can be reliably performed. In addition, since the handover section is closed in the radio wave insensitive area, various system configurations can be used without being affected by the external radio wave condition, and adjustments can be made without being affected by the external radio wave condition. And the construction and adjustment costs can be reduced. Since the invention of claim 4 of the present invention is configured as in the above (4), the handover can be stably performed even if the mobile station is moving in any direction. The invention of claim 5 of the present invention provides:
With the configuration as described in (5) above, the handover can be stably performed by the pair of antennas even if the mobile station is moving in any direction. According to the sixth and seventh aspects of the present invention, since the configuration is made as in the above (6) and (7), the first antenna having a level difference from one antenna is provided.
Since the radio wave of the area and the radio wave of the second area can be radiated, the configuration can be simplified and the number of devices can be reduced, so that the total cost can be reduced. In the invention of claim 8 of the present invention, since the configuration is made as in the above (8), the level difference between the radio waves in the first area and the radio waves in the second area can be set to an appropriate value.

[0008]

FIG. 1 is a diagram showing a first embodiment of the present invention. In the figure, T is a tunnel, 11, 21
Is the master station, and the master station 11 is the base station A by the antenna AT.
Of the mobile station 12a,
In addition to transmitting the signal to the base station A via the antenna AT, the signal transmitted from the mobile station 3 is received by the slave stations 12a and 12b. Further, the master station 21 receives the radio wave of the base station B (referred to as the radio wave of the area B) by the antenna AT, transmits the radio wave to the slave stations 22a and 22b, and also receives the slave stations 22a and 22b.
The signal from the mobile station 3 received at 2b is transmitted to the base station B.

Although FIG. 1 shows a case where antennas AT are provided in master stations 11 and 21 and transmission and reception are performed with base stations A and B via antennas AT, as shown in FIG. The small base station 30 may be connected by a cable to transmit and receive an RF signal (radio frequency signal). 12a and 12b are slave stations connected to the master station 11, 22
Reference numerals a and 22b denote slave stations connected to the master station 21;
2a, 12b, 22a, and 22b are antenna A
T1 and AT2, RF signals transmitted from the master stations 11 and 21 are radiated from the antennas AT1 and AT2, and a radio wave from the mobile station 3 is received.
1 and 21.

FIG. 2 is a diagram showing a configuration example of the above-mentioned master station and slave stations. FIG. 2A shows a configuration example in the case of transmitting by an RF signal. An RF signal of the base station A (or base station B) received by the antenna AT of the master station 11 is transmitted to the amplifier 14a via the duplexer 13a. To be amplified. Amplifier 14a
Is sent to the combiner / distributor 17 via the duplexer 13b. The combiner / distributor 17 distributes the RF signal to each transmission line L, and distributes the distributed RF signal to each slave station 12 via the transmission line L.
(Hereinafter, this signal is referred to as a downlink signal). The RF signal transmitted to the slave station 12 is amplified by the amplifier 14c via the duplexer 13c, sent to the antenna AT1 via the duplexer 13d, and radiated from the antenna AT1. On the other hand, an RF signal transmitted by a mobile station (not shown) is received by the antenna AT1, and is transmitted through the duplexer 13d to the amplifier 14d.
To be amplified. The output of the amplifier 14d is
3c, transmitted to the master station 11 via the transmission path L (hereinafter, referred to as
This signal is called an up signal). The RF signal transmitted from each slave station 12 is synthesized by the synthesizing distributor 17 of the master station 11,
The signal is sent to the amplifier 14b via the duplexer 13b, amplified, sent to the antenna AT via the duplexer 13a, and radiated from the antenna AT.

FIG. 2B shows an example of a configuration in the case of transmitting an optical signal. An RF signal of the base station A (or base station B) received by the antenna AT of the master station 11 is transmitted via the duplexer 13a. The signal is sent to an amplifier 14a, amplified, and converted into an optical signal by an electric / optical converter 16a. The output of the electrical / optical converter 16a is distributed to each downstream line L1 by an optical distributor 18 and transmitted to each slave station 12 via the downstream line L1 composed of an optical fiber.
Is transmitted to The optical signal transmitted to the slave station 12 is converted into an RF signal by the optical / electrical converter 15b and amplified by the amplifier 14c. The output of the amplifier 14c is sent to the antenna AT1 via the duplexer 13d, and is radiated from the antenna AT1.

On the other hand, an RF signal transmitted from a mobile station (not shown)
The signal is received by the antenna AT1, sent to the amplifier 14d via the duplexer 13d and amplified, and
The signal is converted into an optical signal at 6b, and transmitted to the master station 11 via the uplink L2 constituted by an optical fiber. The optical signal transmitted to the master station 11 is converted into an RF signal by the optical / electrical converter 15a, and is combined by the combining / distributing unit 17. Synthetic distributor 1
The output of 7 is amplified by the amplifier 14a, sent to the antenna AT via the duplexer 13a, and radiated from the antenna AT. Since the handover is performed based on the level difference of the received radio wave at the mobile station as described above, the following description will mainly be directed to the downlink signal in FIG. The electric field strength of the radio waves in the areas A and B in the following description is the electric field strength due to the down signal in FIG.

Returning to FIG. 1, the antennas AT1 and AT2 of the slave stations 12a and 22a and the slave stations 12b and 22b are provided close to each other as shown in FIG. Also, the electric field strengths of radio waves radiated from the slave stations 12a and 22a and the slave stations 12b and 22b (the antennas AT1 and A
The electric field strength of the radio wave emitted from T2)
The level difference is set so that the electric field strength of the radio wave in the area B is larger than the radio wave in the area A within a range not lower than the reception limit level of the mobile station 3. A method of giving a level difference to the radio wave intensity can be realized by, for example, changing the gains of the slave stations 12a and 22a and the slave stations 12b and 22b, changing the capacity, and giving a difference in the output power.

Further, the level difference may be provided by changing the gain of the antenna as shown in FIG. That is, as shown in FIG. 3, the gain of the antenna AT2 is made larger than the gain of the antenna AT1, so that the radio waves in the area B are stronger than the radio waves in the area A. As a result, the electric field strengths of the radio waves in the area A and the radio waves in the area B radiated from the antennas AT1 and AT2 are as shown by the dotted line and the solid line in FIG. With the configuration as shown in FIG. 3, the slave stations 11a and 12a
The same apparatus can be used, and the cost can be reduced. Further, as will be described later, the slave stations 12a and 22
a. By adjusting the level of the RF signal or the optical signal input to the slave stations 12b and 22b to change the level, the level difference can be given to the electric field strength as described above.

As described above, the radio waves (radio waves in area A) radiated from the slave stations 12a and 12b and the slave stations 22a and 22b
When the traveling direction of the mobile station 3 is in the direction of the arrow in FIG. 1 (moving from the area A to the area B), the level is shown in FIG. In this way, the radio waves in the area B are transmitted to the
It radiates stronger than radio waves. In addition, the installation positions of the slave stations 12a and 22a and the slave stations 12b and 22b and the power of the radiated radio wave are selected so that the level difference is maintained for the time (distance) required for handover. Thus, the electric field strength of the radio wave in the area A and the electric field strength of the radio wave in the area B are as shown by the solid line and the dotted line in FIG. Area B as above
By providing a level difference between the radio wave of the area A and the radio wave of the area A, a state in which the level of the radio wave of the area A is lower than the level of the radio wave of the area B by a predetermined amount can be stably maintained. For this reason, the mobile station 3 traveling from the left side of the figure can reliably perform the handover.

If the traveling direction is reversed, the area A
Is radiated more strongly than the radio wave in the area B so that the level difference lasts for the time required for handover with a level difference required for setting handover or more. As a result, handover can be reliably performed as described above. By providing at least one slave station for radiating radio waves in the areas A and B as shown in FIG. 1, a handover section having a level difference in electric field strength can be secured for a sufficient distance, and high-speed movement can be achieved. The handover can be reliably performed even in the middle.
As described above, according to the present embodiment, the level difference required for the handover can be stably maintained, so that the handover can be reliably performed. In addition, since the handover section is closed in the tunnel, various system configurations can be adopted without being affected by the outside radio wave condition, and adjustment can be performed without being affected by the outside radio wave condition. As a result, construction and adjustment costs can be reduced.

FIG. 4 is a view showing a second embodiment of the present invention. This embodiment shows an embodiment in which a handover section can be set regardless of the traveling direction. FIG.
In the figure, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the master station 11 receives the radio waves in the area A by the antenna AT and transmits the radio waves to the slave stations 12a and 12b. , 12b from the mobile station 3 to the base station A via the antenna AT. The master station 21 receives the radio wave of the area B by the antenna AT and transmits the radio wave to the slave stations 22a and 22b.
The signal from the mobile station 3 received at 2a, 22b is transmitted to the base station B.

12a and 12b are slave stations connected to the master station 11, 22a and 22b are slave stations connected to the master station 21, and the slave stations 12a, 12b, 22a and 22b are connected to the antennas AT1 and AT2, respectively. Provision, master stations 11 and 21
From the antennas AT1 and AT
2 and receives radio waves from the mobile station 3 and sends them to the master stations 11 and 12. As in the first embodiment, the base stations 11 and 21 and the small base station 30 may be connected by a cable to transmit and receive RF signals.

In this embodiment, as shown in FIG.
Reverse the level difference of the radio wave in two places. That is, in the slave stations 12a and 22a, the radio waves in the area A are radiated more strongly than the radio waves in the area B so that the level difference required for the handover setting is equal to or greater than the level difference.
b, the slave station 22b transmits the radio wave of the area B to the area A.
It radiates stronger than radio waves. Similarly to the first embodiment, the slave stations 12a and 22a and the slave stations 1 and 2 are arranged such that the level difference is maintained for a time (distance) required for handover.
The installation positions of 2b and 22b and the power of the radiated radio wave are selected. Thus, the electric field strength of the radio wave in the area A and the electric field strength of the radio wave in the area B are as shown by the solid line and the dotted line in FIG.

By providing a level difference as described above, a handover section S1 for the traveling direction A and a handover section S2 for the traveling direction B can be secured as shown in FIG. Even if the mobile station 3 comes from any direction, the handover can be stably performed. As described above, in the present embodiment, the handover section can be set regardless of the traveling direction. In addition, as in the first embodiment, since the handover section is closed in the tunnel, various system configurations can be adopted without being affected by the external radio wave condition, and construction and adjustment costs can be reduced. can do.

FIGS. 5 and 6 show a third embodiment of the present invention. This embodiment shows an embodiment in which a handover section is secured by giving directivity to an antenna of a slave station. ing. In FIG. 5, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the master station 11 receives the radio wave of the area A by the antenna AT and transmits the radio wave to the slave station 12a. Transmits the signal received from the mobile station 3 to the base station A via the antenna AT. Further, the master station 21 receives the radio wave of the area B by the antenna AT, transmits the radio wave to the slave station 22a, and transmits the signal from the mobile station 3 received by the slave station 22a to the base station B.

Reference numeral 12a denotes a slave station connected to the master station 11, 22
a is a slave station connected to the master station 21;
2a is provided with antennas AT1 and AT2, respectively, radiates the RF signals transmitted from the master stations 11 and 21 from the antennas AT1 and AT2, and transmits the RF signals transmitted from the antennas AT1 and AT2.
And sends them to the master stations 11 and 12. As in the first embodiment, the base stations 11 and 21 and the small base station 30 may be connected by a cable to transmit and receive RF signals.

FIG. 6 shows the antennas AT of the slave stations 12a and 22a.
1 and 2 show characteristics of AT2. As shown in FIG.
In this embodiment, directional antennas having different gains are used as the antennas AT2 and AT2. That is, the antenna AT1 has a larger gain on the left side than the gain on the right side in the figure, and the antenna AT2 has a larger gain on the right side than the gain on the left side. Therefore, the electric field strength of the radio wave in the area A is as shown by the solid line in the figure, and the electric field strength of the radio wave in the area B is as shown by the dotted line in the figure.
In the present embodiment, since the antenna having the above characteristics is used, as shown in FIG. 5, a handover section S1 for the traveling direction A and a handover section S1 for the traveling direction B by a pair of slave stations. The handover section S2 can be secured, and the handover can be stably performed even when the mobile station 3 comes from any direction.

As described above, in this embodiment, a handover section can be set by a pair of slave stations irrespective of the traveling direction, and the cost can be reduced.
In addition, as in the first embodiment, since the handover section is closed in the tunnel, various system forms can be implemented without being affected by the outside radio wave condition.
Adjustment costs can be reduced. In addition, each slave station 12
a, 22a and the antennas AT1 and AT2 have the same configuration, and the directions of the antennas AT1 and AT2 need only be reversed, so that the apparatus cost can be reduced. In the embodiment described above, the antenna AT1 that emits the radio wave of the area A and the antenna AT2 that emits the radio wave of the area B are provided respectively. However, the radio waves of the area A and the area B are combined and radiated from one antenna. You may do so.

FIG. 7 is a view showing a fourth embodiment. In this embodiment, the radio waves of the area A and the area B are synthesized using the synthesizing distributor as described above. In FIG. 7, 12 is a slave station connected to the master station in area A, 22 is a slave station connected to the master station in area B, 17 is a combiner / distributor (for example, a directional coupler, two dividers), AT3 is an antenna. In the present embodiment, as shown in the figure, the combiner / divider 17 combines RF signals from the slave stations 12 and 22 and radiates them from one antenna AT3. The level difference between the radio waves in the area A and the area B is the difference between the slave station 12 and the slave station 22.
This is done by giving a difference to the output of In the present embodiment, the radio waves of the area A and the area B can be radiated from one antenna as described above, so that the cost can be reduced.

FIG. 8 is a diagram showing a fifth embodiment of the present invention. In this embodiment, radio waves in the area B are converted into optical signals and transmitted to the master station in the area A. Are synthesized by the master station and transmitted to the slave station. In the following description, a case will be described in which an RF signal is converted into an optical signal and transmitted via an optical fiber. However, the RF signal may be transmitted using a coaxial cable without converting the optical signal into an optical signal. . In FIG. 8, for the sake of simplicity, only the upper and lower signals are shown for convenience, but the upstream signal is also transmitted in the configuration shown in FIG. In the figure, reference numeral 11 denotes a master station of the area A, reference numeral 21 denotes a master station of the area B, and the master station 21 of the area B receives the duplexer 13f for demultiplexing the uplink signal and the downlink signal of the area B. Electric / optical converter 1 for converting an RF signal in area B into an optical signal
6c is provided. An optical fiber for transmitting a signal received by the master station 21 and converted into an optical signal to the master station 11 in the area A is provided between the master station 11 in the area A and the master station 21 in the area B. Transmission line L3 is provided.

Further, the master station 11 in the area A includes the master station 2
An optical / electrical converter 15d for converting an optical signal sent from the first unit to an RF signal, level setting units 19a and 19b for adjusting the signal strength transmitted to the slave stations 32a and 32b,
Amplifiers 14e and 14f, a combiner / divider 17 for combining the outputs of the amplifiers 14e and 14f, an electric / optical converter 16d for converting the output of the combiner / divider 17 into an optical signal, and an RF signal from the small base station 30 or A duplexer 13e that splits a radio signal from the antenna AT as an uplink signal and a downlink signal.
Is provided. In the following description, it is assumed that the master station 11 transmits the radio wave of the area A received by the antenna AT to the slave station. Although not shown, the slave stations 32a and 32b are provided with an optical / electrical converter, and the slave stations 32a and 32b convert the optical signal sent from the master station 11 by the optical / electrical converter. Convert to RF signal, antenna A
Emit from T3.

In FIG. 8, the master station 21 receives the radio wave in the area B, converts the RF signal into an optical signal by the electric / optical converter 16c, and transmits the optical signal to the master station 11 via the transmission line L3. The optical signal transmitted from the master station 21 to the master station 11 is
The signal is converted into an RF signal by the electric converter 15d, level-adjusted by the level setter 19b, and sent to the amplifier 14f. On the other hand, the RF signal in area A received by master station 11 is level-adjusted by level adjuster 19a and sent to amplifier 14e. The level difference between the electric field strengths of the areas A and B radiated from the slave stations 32a and 32b is set to a desired value by adjusting the level setting units 19a and 19b. Amplifiers 14e and 14f are level adjusters 19a,
The signal sent from 19b is amplified. Amplifier 14
The RF signals of the area A and the area B amplified by e and 14f are combined by the combiner / distributor 17, converted into optical signals by the electric / optical converter 16d, and sent to the slave stations 32a and 32b. In the slave stations 32a and 32b, the optical signal combined with the above-mentioned level difference is converted into an RF signal by the above-mentioned optical / electrical converter and radiated from the antenna AT3.

As described above, in this embodiment, the master station 1
In step 1, the RF signals of the area A and the area B are combined with a level difference and transmitted to the slave station. Therefore, it is necessary to provide the slave stations that emit the radio waves of the area A and the area B as in the above-described embodiment. In addition, the number of slave stations can be reduced and cost can be reduced. Further, since the level difference between the RF signals of the area A and the area B can be adjusted only by the master station 11, the workability of the level adjustment is good. In the above embodiment, the RF signals of the area A and the area B are combined and the combined signal is converted into an optical signal. However, after converting the RF signals of the area A and the area B into optical signals, respectively, the optical combiner is used. May be combined with each other.

FIG. 9 is a diagram showing a sixth embodiment of the present invention. In this embodiment, the RF signals in the areas A and B are converted into optical signals and transmitted, and the optical signals are combined to produce an RF signal. And radiate it from the antenna of the slave station. FIG. 9 shows both the downlink and the uplink. FIG.
, 11 is a master station for transmitting and receiving to and from the base station A, 21 is a master station for transmitting and receiving to and from the base station B, and the master stations 11 and 21 are antennas AT1 and AT2, respectively,
And amplifiers 14a and 14b, amplifiers 14c and 14d,
Combining / distributing devices 17a, 17b, and electric / optical converters 16e,
16f, the photoelectric converters 15e and 15f, and the optical distributor 1
8b and 18c. Reference numeral 42 denotes a slave station. The slave station 42 includes an electrical / optical converter 16g, an optical / electrical converter 15g, a duplexer 13, amplifiers 14e and 14f, and an antenna AT3.

L1 is a downlink for transmitting a downlink signal (optical signal of wavelength λ1) from the master station 11, and L1 'is a master line 2
L2 transmits an uplink signal from the slave station 42 to the master station 11, and L2 'transmits an uplink signal from the slave station 42 to the master station 21. This is the uplink for transmission. Downlink line L1 has master station 1
Level setting device 19 for setting the level of the downstream signal from
a is provided, and the downlink L1 ′ is provided with a level setter 19b for setting the level of the downlink signal from the master station 21, and the downlinks L1 and L1 ′ are connected to the downlink signal from the master station 11 and It is connected to the optical combiner 18a that combines the downlink signal from the master station 21. The uplink lines L2 and L2 'are connected to an optical distributor 18d which distributes an uplink signal from the slave station 42 to the master station 11 and the master station 21.

In FIG. 9, the RF signal in area A received by the master station 11 is sent to an amplifier 14a via a duplexer 13f and amplified, and is converted into an optical signal having a wavelength of λ1 by an electric / optical converter 16e. Is converted. Electric / optical converter 16e
Is output by the optical distributor 18b, is set to a desired level by the level setter 19a, and is transmitted to the optical combiner 18a via the downlink L1. On the other hand, the RF signal in area B received by the master station 21 is sent to the amplifier 14c via the duplexer 13g and amplified, and is converted into an optical signal having a wavelength of λ2 by the electrical / optical converter 16f. The wavelength output from the electrical / optical converter 16f is λ2
Is distributed to each downlink L1 'by the optical distributor 18c, set to a desired level by the level setter 19b, and transmitted to the optical combiner 18a via the downlink L1'.

The optical signals of the wavelengths λ1 and λ2 of the areas A and B transmitted via the downlinks L1 and L1 'are combined in the optical combiner 18a and sent to each slave station 42. Here, the wavelength of the optical signal from the master station 11 input to the optical combiner 18a and the wavelength of the optical signal from the master station 21 are λ1 and λ2, which are sufficiently different wavelengths.
In combining optical signals, the effect of beat noise can be prevented. The slave station 42 converts the optical signal sent from the optical combiner 18a into an RF signal in the optical / electrical converter 15g. The RF signal output from the optical / electrical converter 15g is amplified by the amplifier 14f and passed through the duplexer 13 to the antenna AT3.
And radiated into the tunnel.

On the other hand, the RF signal from the mobile station received by the slave station 42 is sent from the duplexer 13 to the amplifier 14e, amplified, and converted into an optical signal by the electrical / optical converter 16g.
The optical signal output from the electrical / optical converter 16g is transmitted to the optical distributor 1
8d, and distributed to the master station 11,
21. In the master stations 11 and 21, the upstream signals transmitted from the respective slave stations 42 are converted into optical / electrical converters 15e and 15f.
Is converted into an electric signal, and is synthesized by the synthesizing distributors 17a and 17b. The combined RF signal is amplified by the amplifiers 14b and 14d and passed through the duplexers 13f and 13g to the antenna AT.
1, AT2 and transmitted to base stations A and B.

In the configuration of FIG. 9, the level difference between the radio waves in the area A and the radio waves in the area B radiated from the slave station 42 for securing the handover section is adjusted by the level setting units 19a and 19b. It is obtained by doing. Here, when the optical / electrical converter 15g is composed of a pin photodiode, RF
In order to obtain a signal level difference of 1 dB, the level difference of the optical signal may be approximately 0.5 dB.

That is, the optical signal OPTinA [dBm] of the area A received by the optical / electrical converter 15g and the area B
, The level difference of the optical signal OPTin B [dBm], the RF signal RFout A [dBm] of the area A radiated from the slave station 42, and the R of the area B
The following relationship holds for the difference between the F signal RFout B [dBm] (however, the optical / electrical converters 16 of the master station 11 and the master station 21).
e, where the power of the RF signal input to 16f is the same). RFout A-RFout B = 2 x (OPTin A-OPTin
B) Therefore, by adjusting the level of the optical signal by the level setting units 19a and 19b based on the above relation, the level difference between the radio wave of the area A radiated from the slave station 42 and the area B is set to a desired value. can do.

In the above embodiment, the level of the optical signal is adjusted by the level setting units 19a and 19b. However, as shown in FIG. Distribute the signal to each downlink,
After the distributed RF signal is adjusted to a desired level by the level setter 19c, it may be converted to an optical signal by the electric / optical converter 16e. Also, a desired level difference may be obtained by combining this embodiment and the above embodiment. As described above, in the present embodiment, the radio waves of the area A and the area B are transmitted as optical signals, combined by the optical combiner and radiated from the antenna of the slave station, so that the configuration of the slave station is simplified. And cost reduction can be achieved. Furthermore, since the level difference radiated at each slave station can be changed arbitrarily, the handover section can be easily set regardless of the traveling direction as shown in FIG.

[0038]

As described above, in the present invention,
The following effects can be obtained. (1) Even if the mobile station is moving at a high speed in the radio wave insensitive zone, the level difference of the electric field intensity required for the handover can be stably maintained, and the handover can be reliably performed. In addition, since the handover section is closed in the tunnel, various system configurations can be adopted in a state where it is hardly affected by the outside radio wave condition, and adjustment can be performed in a state where the handover section is hardly affected by the outside radio wave condition. Can,
Construction and adjustment costs can be reduced. (2) In the first section, radio waves in the second area are radiated more strongly than radio waves in the first area with a level difference required for handover, and necessary for handover in the second section. By radiating the radio wave of the first area more strongly than the radio wave of the second area with a level difference, it is possible to perform handover stably regardless of which direction the mobile station is moving. (3) The signal of the first area received by the first master station and the signal of the second area received by the second master station are combined with a level difference required for handover, and combined. By radiating the signal from the antenna installed in the radio wave insensitive area, it becomes possible to take measures against handover in the radio wave insensitive area with a relatively simple configuration, thereby reducing the total cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a master station and slave stations.

FIG. 3 is a diagram illustrating a method of giving a level difference between radio waves in a first area and radio waves in a second area by changing the gain of an antenna.

FIG. 4 is a diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is a diagram illustrating characteristics of an antenna according to a third embodiment.

FIG. 7 is a diagram showing a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a fifth embodiment of the present invention.

FIG. 9 is a diagram showing a sixth embodiment of the present invention.

FIG. 10 is a diagram showing a modification of the sixth embodiment of the present invention.

FIG. 11 is a diagram illustrating a handover in a radio wave blind spot such as a tunnel.

FIG. 12 is a diagram illustrating a handover condition.

FIG. 13 is a diagram illustrating a case where a blowing antenna is mounted near an entrance of a radio wave blind spot such as a tunnel.

[Explanation of symbols]

 3 mobile station 11 master station 12, 12a, 12b slave station 13, 13a to 13g duplexer 14a to 14f amplifier 15a to 15g optical / electrical converter 16a to 16g electrical / optical converter 17, 17a to 17b combining / distributing 18, Reference Signs List 18a Optical synthesizer 18b-18d Optical distributor 19a-19d Level setting device 21 Master station 22a, 22b Slave station 30 Small base station 32a, 32b Slave station 42 Slave station

Claims (8)

[Claims] 1. A mobile station in which a received radio wave in a first area is lower than a received radio wave in a second area by a predetermined level,
And when the state continues for a predetermined time, in a mobile communication system that performs handover from the first area to the second area, a radio wave of the first area and a radio wave of the second area are received, and the radio wave of the second area is received. The antenna is located in the dead zone, the first area radio wave and the second area radio wave are radiated from the antenna installed in the dead zone, and the electric field strength difference required for handover is obtained in the dead zone. A mobile communication system wherein a section in which radio waves in the first and second areas can be continuously received for a handover time in a middle mobile station is formed. 2. When the radio waves in the first area and the radio waves in the second area are radiated from the antenna, the radiation levels of the radio waves in the first and second areas are set to a level difference required for handover. The mobile communication system according to claim 1, wherein: 3. The antenna for radiating radio waves in the first area and the antenna for radiating radio waves in the second area are the same or close to each other.
3. The mobile communication system according to any one of 2. 4. At least in a first section, a radio wave of a second area is radiated more strongly than a radio wave of a first area with a level difference required for handover, and a handover is performed in a second section. The radio wave of the first area is radiated more strongly than the radio wave of the second area with the required level difference, and the electric field strength required for the handover is maintained. The mobile communication system according to any one of claims 1 to 3, wherein a first section in which radio waves in the first and second areas can be received and a second section are formed. 5. A first antenna and a second antenna having directivities having different gains with respect to a moving direction of a mobile station are arranged adjacent to each other along the moving direction of the mobile station; The antenna is arranged such that the side having a large gain of the antenna faces one side of the moving direction, and the second antenna is arranged such that the side having a large gain of the antenna faces the other side of the moving direction. The first antenna radiates radio waves in the first area from the first antenna, and the second antenna radiates radio waves in the second area to provide a difference in electric field strength required for handover. 2. The mobile communication according to claim 1, wherein a first section and a second section in which the radio waves of the first and second areas can be continuously received for a period in which the mobile station can perform handover are formed. system. 6. A first master station that receives a radio wave in a first area and makes a signal in the first area, and a radio wave in a second area and makes a signal in a second area. Providing a second master station, combining the signal in the first area and the signal in the second area with a level difference required for handover, and combining the combined signal in an antenna installed in a radio wave insensitive zone The mobile communication system according to any one of claims 1 to 4, wherein the mobile communication system radiates from the mobile phone. 7. The signal of the second area received by the second master station is transmitted to the first master station, and the first master station transmits the signal of the second area to the first master station.
7. The mobile communication system according to claim 6, wherein a signal transmitted from the second master station and a signal of the first area received by the first master station are combined with a level difference. 8. A level adjusting means for receiving a radio wave in the first area and a radio wave in the second area, and as a signal in the first area and a signal in the second area, a signal in a dead zone of the radio wave. The mobile communication system according to any one of claims 1 to 7, wherein the level adjusting means adjusts the level of the signal of the first area and the level of the signal of the second area. .