JP3290823B2 - Wireless communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system applied to, for example, a C-type train radio system.

[0002]

2. Description of the Related Art Conventionally, various radio communication systems have been developed for making a call with a train (mobile station). One of them is a C-type train radio system.

FIG. 6 is a diagram showing a configuration of a C-type train radio system. The base station 61 shown in the figure is installed at each station. Each base station 61 has a function of performing wireless communication with the train 62. Adjacent base stations 61 are connected by a communication cable 63. The base station 61 closest to the central office 64 is connected to the central office 64 by a communication cable 63. Then, a call is made between the train 62 and the base station 61 or between the train 62 and the central office 64 (in this case , via the base station 61).

[0004] In the C-type train radio system,
Only one of the plurality of base stations 61 is train 6
The following switch switching is performed so as to form a wireless line between the two. FIG. 7 is a diagram illustrating a configuration of a switch unit included in each base station 61. As shown in the figure, the terminal a connected to the communication cable 63 connected to the central office 64 side (upstream side) is connected to the terminal b connected to the communication cable 63 connected to the opposite side (downstream side). Alternatively, it is connected to one of the terminals c connected to the communication unit of the base station 61. Then, when a wireless line is not formed between the base station 61 and the train 62,
Terminal a and terminal b are connected. In this state, when a wireless line is formed between the base station 61 and the train 62, the terminals a and c are connected. Thereby, the base station 61 on the downstream side from the base station 61 is excluded from a target for forming a wireless line with the train 62, and the plurality of base stations 6
Only one of the base stations 61 forms a wireless line with the train 62.

[0005] By the way, the radio wave radiated from the train 62 is received at, for example, each base station with electric field strength as shown in FIG. Here, three base stations A, B, and C are arranged in the order of base station A, base station B, and base station C, and a train 62 exists between base station B and base station C. in this case,
When the train 62 is between the base station B and the point α (the point at which the electric field strength received at the base station B matches the electric field strength received at the base station C), the train 62 and the base station B When a wireless line is formed between the train 62 and the base station C, the wireless line is most preferably formed between the train 62 and the base station C.

[0008] However, in the C-type train radio system, since the switches shown in FIG. 7 are performed, a problem of a far talk connection due to so-called overreach occurs. For example, assume that the squelch of three base stations A, B, and C is set to 0 dBμ in FIG. In this case, the train 62 is the base station B and β point (the electric field strength of the base station A
0 dBμ ), three base stations A,
A wireless line can be connected between B and C, but the base stations B and C downstream from the base station A are disconnected by the switch switching shown in FIG. A wireless line is formed between them. That is, a far talk connection is established.

To prevent this distant talk connection, it is conceivable to increase the set value of the squelch. However, since the variable range of the squelch set value is generally as narrow as -5 dB to +3 dB, the far talk connection is sufficiently prevented. I can't. Therefore, it is conceivable to modify the squelch circuit itself. However, even with this modification, it is difficult to suppress the reception electric field strength so that the incoming signal is received at +10 dB to +25 dB or more.

Further, by also disposed between the just not the station and the station yard of the station base station, by narrowing the interval between the base station and scan with an increased base station obtained a high received field strength <br/> Tem is considered. However, in the train radio system with such an improvement, when simultaneous transmission is performed between the central station and each base station, a call failure (beat failure) occurs due to a short interval between the base stations. The problem is easy.

[0009]

As described above, in the conventional C-type train radio system, the only base station is selected by disconnecting the downstream base station by the switch switching shown in FIG. There was a talk connection problem.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and can be prevented by a simple configuration without deteriorating distant call connection and call quality due to overreach. It is intended to provide a wireless communication system.

[0011]

According to a first aspect of the present invention, there is provided a wireless communication system in which adjacent base stations are connected by a transmission medium, and a single base station is connected to a mobile station by separating a downstream base station. In the wireless communication system configured to form a wireless line, each base station attenuates a first line through which a signal transmitted to and received from the mobile station passes as it is and an electric field strength of the signal by a predetermined amount. A line unit having a second line to be transmitted, a selecting unit for selecting any one of the first line and the second line, and transmission / reception between the mobile station, Controlling the selecting means to select the first line,
And a control unit for controlling the selection unit to select the second line in a standby reception state.

In the wireless communication system according to the second aspect, adjacent base stations are connected by a transmission medium, and a single base station forms a wireless line with a mobile station by separating a downstream base station. In the wireless communication system configured as described above, each of the base stations includes a first line that directly passes a signal transmitted to and received from the mobile station, and a second line that attenuates the electric field strength of the signal by a predetermined amount. A line unit having: a selection unit that selects one of the first line and the second line; a detection unit that detects an incoming call from the mobile station and a transmission to the mobile station;
In a standby reception state, the selection unit controls to select the second line, and when the detection unit detects an incoming call or a transmission, controls the selection unit to select the first line. Control means for performing the operation.

[0013] Incidentally, the electric field strength is attenuated by the second line as described above, if the order 20DBmyu, can be sufficiently prevented far talk connection by overreach.

[0014]

According to the present invention, the second line for attenuating the electric field intensity of the received signal by a predetermined amount in the standby reception state is selected, so that a far-talk connection due to overreach can be prevented. When a call is established with a mobile station,
Since selecting a first line which passes through the signal never call quality is degraded.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a C-type train radio system according to one embodiment of the present invention. In the figure, 1 is a train, 2 is a base station, and 3 is a central office. The base station 2 is provided in the premises of each station, and includes a Yagi antenna 6, an air distributor 7, a coaxial lightning arrester 8, a station device 9, and a trunk wheel 10. The adjacent base stations 2 are connected by a communication cable 4. The base station 2 closest to the central office 3 is connected to the central office 3 by a communication cable 4. An amplifier 5 is inserted at a predetermined position on the communication cable 4. This amplifier 5 includes a communication cable 4
The signal transmitted above is amplified to compensate for transmission loss. In addition, the central station 3 is connected to a central control device 11 that controls each base station 2 using a wired line with each base station 2, an operation panel 12 for operating the central control device 11, and the train 1. And a long-time recording device 13 for recording the contents of the wireless communication as needed. The remote controller 14 connected to the station device 9 of the D station is a device installed on the premises of the station, and for operating the station device 9 when a station staff transmits and receives the train 1. Reference numeral 15 denotes a mobile station that transmits and receives wireless signals to and from each base station 2.

FIG. 2 is a diagram showing the configuration of the station device 9. The station device 9 includes an antenna alarm 21, a dummy switching device 22, an auxiliary receiving unit 23, a radio 24, a radio interface 26, a control unit 25, and a power supply. The unit 27 includes a plurality of units. In this way, the maintenance and inspection are facilitated by configuring each unit as a unit. The wireless device 24 has a transmitting unit and a receiving unit for performing transmission and reception with the train 1. Control unit 2
Reference numeral 5 exchanges communication signals and control signals with the wireless device 24, and exchanges communication signals and control signals with the central office 3 via the trunk wheel 10. And
The control unit 25 controls the antenna alarm 21, the dummy switching device 22, and the auxiliary receiving unit 23 based on the control signal.

FIG. 3 is a diagram showing a configuration of the auxiliary receiving unit 23. In the figure, 31 is a terminal to which an incoming signal is input from the control unit 25, and 32 is a terminal to which a press-talk signal is input from the control unit 25. A relay switch K1 and a resistor R1 connected in series are interposed between the terminal 31 and the voltage terminal Vcc. Similarly, a relay switch K2 and a resistor R2 connected in series are interposed between the terminal 32 and the voltage terminal Vcc. A first circuit group in which a relay switch K3 connected in series and a resistor R3 and a relay switch K4 and a resistor R4 connected in series with each other are connected in parallel between the ground G and the voltage terminal Vcc ; A second circuit group in which the contact k1 and the contact k2 of the relay switch K2 are connected in parallel is interposed in series. Further, between a terminal 33 connected to the antenna side and a terminal 34 connected to the radio device side, a first line connecting the terminals 33 and 34 as they are and a second line connected via the attenuator ATT. Tracks are provided. Then, connect the relay switches K3 and K4 .
Either the first line or the second line is selected by switching between the points k3 and k4 . Note that the attenuator ATT is set to about 20 dBμ.

Next, in such a system, the operation of the station device 9 when receiving the call communication from the train side will be described with reference to FIG.
This will be described based on the flowchart shown in FIG. In the station device 9 in the standby reception state, the control unit 25
, The OFF signal (HIGH) is input to the terminals 31 and 32 of the auxiliary receiving unit 23. In this case, since the contacts k1 and k2 of the relay switches K1 and K2 are open (the state shown in FIG. 3), the contact k3 of the relay switches K3 and K4 .
, K4 are connected to the second line having an attenuator ATT (state of FIG. 3). Therefore, the radio signal input to the terminal 33 has the electric field strength in the auxiliary receiving unit 23.
The signal is attenuated by 20 dBμ and input to the radio 24. Therefore, when the wireless device 24 receives a wireless signal exceeding 20 dBμ ,
(Step 401, Yes) , and transmits the received signal to the control unit 25 via the radio interface 26. When the control unit 25 receives the received signal, the control unit 25 transmits the incoming signal (LOW) to the terminal 31 of the auxiliary receiving unit 23.
(Step 402). Then, the contact k1 of the relay switch K1 is closed, and the relay switches K3, K4
Contact points k3 and k4 are the first without the attenuator ATT.
(Step 403). Therefore, the wireless signal input to the terminal 33 is input to the wireless device 24 without the electric field intensity being attenuated in the auxiliary receiving unit 23. At this time, at the same time, the control unit 25 makes a line connection with the central office 3. Then, the radio line formed between the train 1 and the base station 2 and the base station 2
And a wired line formed between the central office 3 and
A call can be made between the train 1 and the central office 3. After this,
When the transmission from the train 1 is completed (step 404 , Ye
s ), an OFF signal (HIGH) is output from the control unit 25 to the terminal 31 of the auxiliary receiving unit 23 (step 405). Then, the contact k1 of the relay switch K1
Is open, and the contacts k3 and k4 of the relay switches K3 and K4 are
Each is connected to a second line having an attenuator ATT (step 406). At this time, the control unit 25 releases the line (wired) connected to the central office 3 at the same time. Next, the operation of the station device 9 when transmitting from the central station or the base station (including the operation from the remote controller 14 ) to the train will be described based on the flowchart shown in FIG. In the station 9 in waiting accept reception state in the same manner as described above, contact of the relay switch K3, K4
Points k3 and k4 are respectively connected to the second line side having an attenuator ATT. Central station or base station (remote control 1
The operation from step 4 is also included. ) Is input from the control unit 25 to the terminal 32 of the auxiliary receiving unit 23 (step 50).
1) The contact k2 of the relay switch K2 is closed, and the contacts k3 and k4 of the relay switches K3 and K4 are respectively attenuators.
Connected to the first line without ATT (Step 5
02). Therefore, the transmission signal input to the terminal 34 is output from the Yagi antenna 6 without the electric field intensity being attenuated in the auxiliary receiving unit 23. In this state, a voice is transmitted to the train 1 (step 503), and when the transmission is completed (step 504 , Yes ), the input of the press talk signal from the control unit 25 to the terminal 32 of the auxiliary receiving unit 23 is stopped (step 503). 505). Then, the contact k2 of the relay switch K2 is opened, and the contacts k3 and k4 of the relay switches K3 and K4 are respectively connected to the attenuator ATT.
(Step 506).

Therefore, in the present system, distant call connection due to overreach can be prevented, and the communication quality does not deteriorate. Referring to FIG. 8 as an example, the electric field strength of each of the base stations A, B, and C in the standby reception state is attenuated by 20 dBμ, so that the train between the base stations B and C is Are never connected. A train between the base station B and the α point is always connected to the base station B, and a train between the α point and the base station C is always connected to the base station C. That is, the present system eliminates the occurrence of distant talk connection due to overreach. Further, when a call is established with the train, the first line that allows the transmission / reception signal to pass as it is is selected, so that the communication quality is not degraded. Further, in this case, the selection of the first line and the second line is performed using the incoming signal and the press-talk signal, so that it is possible to prevent the far talk connection and the deterioration of the call quality due to overreach with a simple configuration. .

[0020]

As described above, according to the present invention,
This can be prevented with a simple configuration without deteriorating distant call connection and call quality due to overreach.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a C-type train radio system according to one embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a station device shown in FIG.

FIG. 3 is a diagram illustrating a configuration of an auxiliary receiving unit illustrated in FIG. 2;

FIG. 4 is a flowchart illustrating an operation according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating an operation according to an embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a C-type train radio system.

FIG. 7 is a diagram showing the relationship between the station device reception line switch unit and the communication line
Is a diagram showing the engagement.

FIG. 8 is a diagram for explaining a problem of distant talk connection due to overreach.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Train, 2 ... Base station, 3 ... Central station, 4 ... Communication cable, 5 ... Amplifier, 6 ... Yagi antenna, 9 ... Station device, 10
... Relay wire wheel, 11 .. Central control unit. 23: auxiliary receiving unit, 24: radio, 25: control unit,
26 ... Wireless device interface. 31-34 ... Terminal, K1
~ K4 ... Relay switch, ATT ... Attenuator. k1 to k4 ...
Relay switch contacts

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kiyoyuki Hatakeyama 3-1-1 Asahigaoka, Hino-shi, Tokyo Toshiba Communication Systems Engineering Co., Ltd. (56) References JP-A-60-20648 (JP, A) 62-112426 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B ^7/ 24-7/26 113 H04Q ^7/ 00-7/38

Claims (2)

(57) [Claims] 1. A wireless communication system in which adjacent base stations are connected by a transmission medium, and a single base station forms a wireless line with a mobile station by disconnecting a downstream base station. A line unit having a first line through which a signal transmitted to and received from the mobile station passes as it is, and a second line to attenuate the electric field strength of the signal by a predetermined amount; Selecting means for selecting one of the first line and the second line, and performing transmission / reception with the mobile station, so that the selecting means selects the first line. And a control means for controlling the selection means to select the second line in a standby reception state. 2. A wireless communication system in which adjacent base stations are connected by a transmission medium, and a single base station forms a wireless line with a mobile station by disconnecting a downstream base station. A line unit having a first line through which a signal transmitted to and received from the mobile station passes as it is, and a second line to attenuate the electric field strength of the signal by a predetermined amount; Selection means for selecting one of the first line and the second line; detection means for detecting an incoming call from the mobile station and transmission to the mobile station; in a standby reception state, the selection means Control means for controlling the selection of the second line, and controlling the selection means to select the first line when an incoming call or a transmission is detected by the detection means. Wireless communication system, wherein the door.