JP4070311B2 - Wireless communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless communication system for performing wireless communication between a mobile station and a ground station, and relates to a wireless zone switching method in a wireless communication system including a plurality of base stations and mobile stations.
[0002]
[Prior art]
Conventionally, in this type of wireless communication system, when a mobile station communicates across a plurality of base station zones, a different base station identification signal is transmitted from each base station, and the received base station identification signal is transmitted from the mobile station. A method of connecting a mobile station and a base station by using a series of sequences such as returning as a base station designation signal has been common. According to this method, when the next zone is vacant, the connection can be continued, and only the zone in which the required mobile station exists is occupied.
[0003]
FIG. 2 shows an example of a conventional wireless communication system. In FIG. 2, reference numerals 1 and 2 denote leaky coaxial cables (hereinafter referred to as LCX cables) that radiate and receive radio waves, and configure different radio zones for each cable.
Reference numeral 3 denotes an LCX1 zone base station A connected to the LCX1, and the duplexer 5, the receiver 6, the transmitter 10, and the base station identification signal generator 11 constitute a radio base station. Similarly, reference numeral 4 denotes an LCX2 zone base station B connected to LCX2, which comprises a duplexer 5 ', a receiver 6', a transmitter 10 ', and a base station identification signal generator 11' to constitute a radio base station. .
Each base station transmits a different base station identification signal, and the mobile station returns the received base station identification signal as a base station designation signal. Each base station is connected to the control device 30 and supplies a base station designation signal returned from the mobile station to the control device 30.
Based on the base station designation signals detected by the base station designation signal detectors 7 and 7 ', the control device 30 selects the base station system to be received by switching the switch 8, and similarly transmits by the switch 12 The base station system is selected. The line connection device 9 is connected to the control device 30 and a terminal such as a telephone.
On the other hand, 13 is an antenna 13 connected to the mobile station 40, and radio waves received by this antenna 13 are demodulated by the receiver 14 via a duplexer and supplied to the line connection device 19. The other output from the receiver 14 is supplied to the base station identification signal detector 16, and the result is output to the line connection device 19. The transmission output from the line connection device 19 is combined with the base station designation signal in accordance with the base station identification signal and transmitted by the antenna 13 via the transmitter 20 and the duplexer.
[0004]
Next, the operation of the conventional example shown in FIG. 2 will be described. In the figure, a signal generated from the base station identification signal generator 11 in the base station A 3 is transmitted from the transmitter 10 and is always transmitted from the LCX 1 via the duplexer 5. Similarly, a signal generated from the base station identification signal generator 11 ′ in the base station B4 is transmitted from the transmitter 10 ′ and is always transmitted from the LCX 2 via the duplexer 5 ′. However, this identification signal is different between the LCX1 zone and the LCX2 zone.
When the mobile station 40 passes through the LCX1 zone, the radio wave from the LCX1 is received by the antenna 13 of the mobile station 40, and the base station identification signal detector 16 receives the base station identification signal via the duplexer and the receiver 14. Is detected. At this time, when the mobile station 40 transmits, the communication line is connected to the base station A3 in the LCX1 zone by adding a signal designating the LCX1 zone as a base station designating signal and transmitting it.
When the mobile station 40 leaves the LCX1 zone and enters the adjacent LCX2 zone, the antenna 13 of the mobile station 40 receives the radio wave from the LCX2 zone, and the base station identification signal detector detects the base station of the LCX2 zone. The identification signal of B4 is detected. The base station designation signal for transmission connects the communication line with the base station B4 in the LCX2 zone by designating the LCX2 zone.
[0005]
On the other hand, when the mobile station 40 is in the middle of different zones, the signal cannot be received during a period in which radio waves from the LCX1 zone and radio waves from the LCX2 zone are mixed, and the connection is broken. Further, the period until the next LCX2 zone identification signal is detected is also disconnected. This is due to the nature of radio waves that can be received at close distances even if they are off the LCX cable. If the distance between multiple LCXs is short, this crosstalk section will be longer, but longer. In this case, the time until entering the next zone becomes long, so the time for interference is small, but the state of extremely weak radio waves continues for a long time, and as a result, the radio waves cannot be received sufficiently.
As described above, in the conventional technique, in a place where radio waves are mixed, such as at the boundary of the zone, an instantaneous interruption between the time of interference and the time required for redetection occurs reliably. This problem is not different from the case where the basic sequence is received by a single antenna because the operation of the receiving system is single even if the conventional spatial diversity technique is used.
For example, when antennas are arranged on the left and right, the reception state of radio waves is exactly the same as in the case of a single antenna, and a similar momentary interruption occurs because a time during which reception of radio waves is difficult occurs. In addition, when antennas are arranged at the front and rear, the received radio waves are different for each zone, and as a result, there is a state where sufficient radio waves cannot be received.
[0006]
[Problems to be solved by the invention]
As described above, in the zone switching method according to the conventional technique, after the previous base station designation signal is received and the next base station designation signal is received, the zone has been moved in a difficult reception area due to radio wave interference. It takes time to detect the base station designation signal. For this reason, if the call is in progress, the call cannot be heard temporarily, and if the data is being transmitted, the data is interrupted.
[0007]
[Means for Solving the Problems]
In order to solve the above problem, the present invention demodulates a mobile station with a front antenna, a rear antenna disposed at a predetermined distance d behind the front antenna, and a signal received by the front antenna. 1 receiver, a second receiver that demodulates a signal received by the rear antenna, and a switching control unit that controls switching between the output of the first receiver and the output of the second receiver, By this switching control unit, when the same base station identification signal is received by the first and second receivers, control is performed so that diversity reception is performed, and when reception is disabled by the first receiver, the second is received. Only the first receiver output is selectively controlled when different base station identification signals are received by the first and second receivers.
[0008]
In addition, the distance d between the front antenna and the rear antenna of the mobile station is detected after the base station identification signal is received by the mobile station after the interval length L of the mobile station in the wireless communication system that cannot be received by the mobile station. Is set longer than the distance L + x, which is the sum of the distance converted distance x.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is LCX1 constituting the LCX1 zone, 1 is LCX2 constituting the LCX2 zone, 3 is a base station A in the LCX1 zone connected to the LCX1, and 4 is a base station B in the LCX2 zone connected to the LCX2. is there.
In the figure, the radio waves received by the base stations in each zone are demodulated by receivers 6 and 6 'via duplexers 5 and 5'. When transmitting from each base station, the base station identification signal and the transmission signal from the base station identification signal generators 11 and 11 'are combined and modulated by the transmitters 10 and 10'. It transmits from each LCX cable via '.
[0010]
The control device 30 is given a signal demodulated by the base station in each zone, and the designation signal is detected by the base station designation signal detectors 7 and 7 '. The base station side designated by the designation signal is selected by the switch 8 and output to the line connection device 9 to configure a communication line. On the other hand, the base station side designated by the identification signal is selected by the switch 12 based on the signal output from the line connection device 9 and connected to the transmission line of the designated base station.
[0011]
On the other hand, in the mobile station 50, 13 is a front antenna installed in front of the mobile station, and 13 'is behind the front antenna 13 at least a section length L that is difficult to receive and a time t for detecting a base station identification signal. (For example, the maximum speed or the average speed of the mobile station) is a rear antenna that is installed at a distance d longer than a distance L + x that is a sum of the distance converted distance x. The radio waves received by the antennas 13 and 13 'are demodulated by the receivers 14 and 14' via a duplexer. This demodulated output is input to the diversity receiver 15, and one of the receiver outputs having a good reception state (for example, the output having the stronger received electric field strength) is selected. After this diversity selection is performed, one demodulated output is output to the switch 18 as a diversity output.
Further, the other output of the receivers 14 and 14 'is divided into two, one of which is input to the switch 18, and the other is supplied to the base station identification signal detectors 16 and 16'. A base station identification signal is detected by the detectors 16 and 16 ′ and input to the switching controller 17. The switching controller 17 controls the switches 18 and 21 according to the flowchart shown in FIG. 3, and the switched reception signal is input to the line connection device 19.
The line connection device 19 synthesizes the base station designation signal, modulates it with the transmitter 20, and outputs it to the antenna 13 or 13 ′ via the switch 21.
The identification signals generated from the base station identification signal generators 11 and 11 'in each base station are transmitted from the transmitters 10 and 10', and are always transmitted from the LCX cable via the duplexer. However, this identification signal is different between the LCX1 zone and the LCX2 zone. The identification signal is a tone signal if it is an analog signal, a unique keyword code signal if it is a digital signal, etc., and a signal that does not significantly affect the original transmission / reception is used.
[0012]
In the present embodiment, it is possible to realize a wireless communication system in which instantaneous interruption is significantly reduced at the time of zone switching by using the switching controller that performs the control operation shown in FIG. Next, the operation will be described.
When the mobile station 50 passes through the LCX1 zone, the base station identification signal from the LCX1 is received by both antennas 13 and 13 'of the mobile station 50, and the detection result is given to the switching controller 17. Since the switching controller 17 detects the identification signal of the LCX1 zone from both reception procedures, the switching controller 17 controls the switching unit 18 to pass the diversity result of the receiver to the control device. In addition, the transmitting antenna is a rear antenna, and the base station designation signal selects the base station of the base station identification signal received by the rear antenna.
[0013]
Next, when the mobile station 50 moves to the boundary between the LCX1 zone and the LCX2 zone, the antenna 13 in front of the mobile station is in a state where reception is difficult. At this time, since the switching controller 17 cannot receive by the front antenna 13, the switching controller 17 controls the switch 18 so that only the rear antenna 13 'is effective. The transmitting antenna is the rear antenna, and the base station designation signal selects the base station of the base station identification signal received by the rear antenna.
As the mobile station 50 travels, the forward antenna 13 enters the LCX2 zone and receives the base station identification signal of the LCX2 zone. At this time, since the rear antenna 13 'is installed with a sufficient distance l from the front antenna 13, the base station identification signal of the LCX1 zone is still received.
Since the base station identification signal received by the front antenna 13 is different from the base station identification signal received by the rear antenna 13 ′, the switching controller 17 recognizes that it is a zone boundary and receives the front antenna 13. Control the output to pass to the controller. Further, the transmitting antenna is also a front antenna, and the base station designation signal is a base station designation signal received by the front antenna. At this stage, the base station performs zone switching.
[0014]
Further, when the mobile station advances, the rear antenna 13 'becomes difficult to receive. In this case, the upper state is maintained, and transmission / reception is performed only by the front antenna 13.
At the stage where the mobile station 50 moves completely through the zone boundary and moves within the LCX2 zone, the same base station designation signal is received by both the front antenna and the rear antenna. In the same manner as above, control is performed by switching control so that diversity reception and rear antenna transmission are performed.
As described above, even if the front antenna can no longer be received, it can be received by the rear antenna, and when the front antenna is ready to receive radio waves in the next zone, only the front antenna can be transmitted and received. By switching and establishing transmission / reception with the next base station, the instantaneous interruption time can be made substantially only the switching time. After that, when reception from the rear antenna is established, it is possible to return to the normal mode by performing diversity reception.
[0015]
【The invention's effect】
According to the present invention, it is possible to perform switching with almost no interruption even at the boundary between base station zones, and it is possible to realize a wireless communication system in which the risk of communication failure is significantly reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram showing a conventional technique.
FIG. 3 is a flowchart showing an example of a wireless zone switching method according to the present invention.
[Explanation of symbols]
1, 2: LCX cable, 3: LCX1 zone base station,
4: LCX2 zone base station, 5, 5 ′: duplexer,
6, 6 ': Base station receiver, 7, 7': Base station designation signal detector,
8: Receiving system switching unit, 9: Line connection device,
10, 10 ': base station transmitter, 11, 11': base station identification signal transmitter,
13, 13 ': Mobile station antenna, 14, 14': Mobile station receiver,
15: Diversity receiver 16, 16 ': Base station identification signal detector,
17: Switching controller, 18: Mobile station reception system switching unit,
19: Line connection device, 20: Mobile station transmitter,
21: Mobile station transmission system switch, 30: Control device,
40, 50: Mobile station.

Claims (4)

A plurality of base stations each transmitting a different base station identification signal;
In a wireless communication system including a mobile station connected to the base station via a wireless line,
The mobile station has a front antenna,
A rear antenna disposed rearward from the front antenna;
A first receiver for demodulating a signal received by the front antenna;
A second receiver for demodulating the signal received by the rear antenna;
A switching control unit that controls switching between the output of the first receiver and the output of the second receiver;
The switching control unit controls to perform selective diversity reception when the same base station identification signal is received by the first and second receivers,
If one receiver fails to receive, select the other receiver output,
A radio communication system characterized in that when the first and second receivers receive different base station identification signals, one of the predetermined receiver outputs is selected. The wireless communication system according to claim 1, wherein
The distance between the front antenna and the rear antenna of the mobile station
Section length of the mobile station incapable of receiving in the wireless communication system,
A radio communication system, characterized in that a time for detecting the base station identification signal at a mobile station is set longer than a distance obtained by combining a distance converted to a distance. The wireless communication system according to claim 1, wherein
The plurality of base stations are connected to different LCX cables,
A wireless communication system configured to communicate with the mobile station via the LCX cable. A plurality of base stations each transmitting a different base station identification signal;
A method of selecting an output of a radio communication system including a mobile station connected to the base station via a radio line and having at least two antennas, a first antenna at the front and a second antenna at the rear. ,
The output selection method includes a first demodulation step for demodulating a signal received by the front antenna;
A second demodulation step for demodulating a signal received by the rear antenna;
A detection step of detecting a base station identification signal of the signal demodulated by the first and second demodulation steps;
As a result of the detection step , when the base station identification signals received by the first and second antennas are different , one predetermined reception signal of each antenna is output , and the first and second antennas are output . An output selection method for a radio communication system, comprising a switching step of switching to a selection diversity output when the base station identification signals received by two antennas are the same .

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