JP4258359B2 - In-train data communication system and in-train data communication method - Google Patents

Description

  The present invention relates to a data communication system and a data communication method in a train.

  In recent years, there has been a demand for Mbps-class data communication between vehicles such as image distribution in trains, and as a means to realize this, the installation of LAN cables, coaxial cables, and optical fiber cables has been considered. However, when installing a LAN cable for performing such Mbps-class data communication with an existing train, there is a problem that the cost increases. In particular, in order to lay a LAN cable at a connecting portion between vehicles, the cost has become very high.

  As a method for solving such a cost problem, a method of using an empty cable already laid in a train as disclosed in Japanese Patent Laid-Open No. 7-135477 is disclosed. In this publication, a cable compensator suitable for the characteristics of the cable is provided to compensate for the loss and the video signal is FM modulated and demodulated, thereby enabling image transmission without newly installing a LAN cable. Things are listed.

JP-A-7-135477

  However, in the conventional data communication system in a train, in order to transmit an image to each vehicle, it is necessary to install a pair of cameras and monitors connected by a pair cable. Nothing is disclosed about the influence of interference between the pair cable when using a cable, and there is a problem that a sufficient communication speed cannot be secured due to the influence of the interference. Moreover, when there are many vehicles and there are few empty cables, there existed a subject that it could not respond.

  The present invention has been made to solve the above-described problems, and provides an in-train data communication system and an in-train data communication method capable of ensuring a sufficient communication speed by data communication between a plurality of vehicles. With the goal.

Four or more communication devices having a modem, and four or more communication devices having a modem, for connecting said plurality of communication devices, in-train communication system comprising a cable which is laid in the train, the The communication apparatus has a separate modem for each communication apparatus connected to the communication apparatus, and the modem connected to a different communication apparatus in the communication apparatus transmits two different frequency bands between adjacent communication apparatuses. The two different frequency bands are divided into an upstream communication band and a downstream communication band, respectively, and the upstream communication band and the communication apparatus using the same frequency band of the two different frequency bands are used. Data communication is performed using alternating downlink communication bands .

Four or more communication devices having a modem, and four or more communication devices having a modem, for connecting said plurality of communication devices, in-train communication system comprising a cable which is laid in the train, the The communication apparatus has a separate modem for each communication apparatus connected to the communication apparatus, and the modem connected to a different communication apparatus in the communication apparatus transmits two different frequency bands between adjacent communication apparatuses. The two different frequency bands are divided into an upstream communication band and a downstream communication band, respectively, and the upstream communication band and the communication apparatus using the same frequency band of the two different frequency bands are used. By performing data communication using alternating downlink communication bands, there is an effect that a sufficient communication speed can be ensured by data communication between multiple vehicles. The

Embodiment 1 FIG.
FIG. 1 is an explanatory diagram showing the configuration of the present invention. In FIG. 1, empty cables 101, 102, 103,... Are laid between each vehicle 1, 2, 3, 4,. Each vehicle is provided with a communication device 10, 20, 30, 40,. The communication device 10 includes modems 11 and 12. The communication devices 20, 30, 40,... Are also composed of modems 21 and 22, 31 and 32, 41 and 42. Each of these modems has a repeater function that retransmits data. The communication devices of each vehicle are connected with two laid free cables via a modem. At this time, the cable is disconnected between the two modems in the communication apparatus.
In FIG. 1, the server 14 is connected to the communication device 10, the indicators 13, 23, 33, 43,... Are connected to the communication devices 10, 20, 30, 40,. The case where information is displayed on each display 13, 23, 33, 43,... Is shown.

  Next, the operation of data communication will be described. In the first embodiment, a multicarrier communication system is used as a data communication system. Generally, the frequency band that can be used for communication is determined. The frequency band used for the communication is divided into two. As shown in FIG. 2, for example, the usable frequency bands are a communication band A and a communication band B, respectively. Each communication band A and communication band B includes an upstream signal and a downstream signal.

  First, in the vehicle 1, the modem 11 of the communication device 10 is not used in the communication device 10 of FIG. 1, and the modem 12 of the communication device 10 is provided in the communication device 20 of the vehicle 2 via the empty cables 101 (two) in the section 1. Data communication is performed with the received modem 21. In communication in this section 1, the frequency band A is assigned as the frequency band to be used.

  Next, in the vehicle 2, the display device 23 displays data received by the modem 21 of the communication device 20. Further, the modem 22 having the repeater function retransmits the data received by the modem 21. Based on the retransmitted data, the modem 21 performs data communication with the modem 31 provided in the communication device 30 of the vehicle 3 via the empty cables 102 (two) in the section 2. In communication in this section 2, the frequency band B is assigned as the frequency band to be used.

In the vehicle 3, the display device 33 displays data received by the modem 31 of the communication device 30. Further, the modem 32 having the repeater function retransmits the data received by the modem 31. Based on the retransmitted data, the modem 31 performs data communication with the modem 41 provided in the communication device 40 of the vehicle 4 via the empty cables 103 (two) in the section 3. In communication in this section 3, the frequency band A is assigned as the frequency band to be used.
The same applies to vehicles 4 and thereafter.

As described above, in the intra-train data communication system according to the first embodiment, the communication band to be used is set to the communication band A, the communication band B, and the communication corresponding to the section 1, section 2, section 3,. The band A,... Are alternately changed.
For example, the communication band to be used is made the same communication band as the communication band A, the communication band A, the communication band A,... Corresponding to the section 1, section 2, section 3,. If a configuration for alternately changing the communication band is not employed, the communication signals interfere with each other in adjacent sections. As a result, signals that interfere with each other become noise, and this interference noise causes a reduction in communication speed.
In the first embodiment, a configuration is used in which the communication band to be used is alternately changed to communication band A, communication band B, communication band A,... Corresponding to section 1, section 2, section 3,. Therefore, a decrease in communication speed due to interference noise can be prevented, and a sufficient communication speed can be ensured.

Furthermore, in the in-train data communication system according to the first embodiment, the cable is disconnected at a position where the section changes.
Even if the communication band used corresponding to the section to be communicated is changed alternately, if the cable is not disconnected at the position where the section changes, the signal of the communication band A in section 1 passes through section 2 to section 3 There is a possibility of delivery. Although the signal that reaches this section 3 is attenuated by the cable of section 2, it appears to be interference noise for section 3 that uses a signal in the same communication band A. This interference noise also causes a decrease in communication speed.
In the first embodiment, since the cable is disconnected at the position where the section changes, it is possible to prevent a decrease in communication speed due to interference noise, and to ensure a sufficient communication speed.

  In the first embodiment, the case where the communication bands A and B are alternately allocated from the section 1 has been described. However, even if the communication bands B and A are alternately allocated from the section 1, the same effect can be obtained. it can.

  Moreover, in this Embodiment 1, it is set as a communication area between the adjacent communication apparatuses (between a modem and a modem) connected with the empty cable, and about the case where this communication apparatus and the indicator are installed one each in each vehicle. As described above, it is not limited to this as long as different communication bands are allocated alternately between adjacent communication devices as one communication section, and a plurality of communication devices and indicators may be installed in one vehicle. One communication device and a display may be installed in the vehicle. Also, the number of servers installed is not limited to one per system, and a plurality of servers may be installed.

  In the first embodiment, the case where two empty cables are used has been described. However, the number is not limited to this as long as it is two or more.

  In the first embodiment, the case where two frequency bands are used has been described. However, it is only necessary to reduce interference with an adjacent section using two or more frequency bands, and the present invention is not limited to this. For example, four separate frequency bands may be used so that the uplink communication band in section 1, the downlink communication band, the uplink communication band in section 2, and the downlink communication band do not interfere with each other.

  In the first embodiment, the case where the multicarrier communication method is used as the communication method has been described. However, the same effect can be obtained by using other communication methods such as a single carrier communication method and a spread spectrum communication method. Obtainable.

Embodiment 2. FIG.
In the first embodiment, the case where the communication band A and the communication band B are used has been described. However, in the second embodiment, the uplink signal and the downlink signal in each of the communication bands A and B are selectively used, and more. A train communication system that is resistant to interference noise will be described.

  The basic configuration is the same as in FIG. 1 of the first embodiment, and the basic operation is also the same as in the first embodiment. The differences from the first embodiment will be described below.

  3 and 4 are examples of frequency bands used in the second embodiment. In FIG. 3, the communication band A and the communication band B, which are the same frequency bands as in FIG. 1, are divided into an upstream communication band and a downstream communication band, respectively. 4 uses the same frequency band as that in FIG. 3, but the communication band A ′ is obtained by replacing the uplink communication band and the downlink communication band of the communication band A in FIG. 3, and the communication band B in FIG. A communication band B ′ is obtained by switching the upstream communication band and the downstream communication band.

FIG. 5 is an explanatory diagram showing a configuration according to the second embodiment. The following points differ from FIG. 1 in the first embodiment.
In the first embodiment, the communication band A, the communication band B, the communication band A, the communication band B,... Are used as the communication band A, the communication band B, the communication band A, the communication band A,. And B are alternately changed. In FIG. 2, the uplink signal band and the downlink signal band are not clearly shown, but the uplink signal band and the downlink signal band are divided as shown in FIG. Are alternately changed, the signal in the communication band A in the section 1 is connected to the same communication band A from a completely different route by, for example, coupling between cables other than the cables used for the main communication (two empty cables). There is a possibility of leaking to the section 3 using Also in this case, the leaked signal in section 1 becomes noise in section 3 and causes a decrease in communication speed.

  On the other hand, in the in-train communication system according to the second embodiment, as shown in FIG. 5, the communication band used in section 1, section 2, section 3, section 4, section 5, section 6,. A, communication band B, communication band A ′, communication band B ′, communication band A, communication band B,... Are configured to change the communication bands A, B, A ′, B ′ in order.

  In general, the downlink communication signal is used to transmit a large amount of data such as image transmission, so that the transmission amount is larger than that of the uplink communication signal and the influence of interference on other communication sections is large. On the other hand, since the uplink communication signal is used for a control signal or the like, the transmission amount is small, and even if the communication speed decreases due to the influence of interference from other communication sections, it does not cause a big problem. In the case of the configuration shown in FIG. 5, the downlink communication signal in communication band A in section 1 leaking into section 3 interferes with the upstream communication signal in communication band A ′ used in section 3, and in section 3 leaking into section 1. The downlink communication signal in the communication band A ′ interferes with the uplink communication signal in the communication band A used in the section 1. That is, in the sections 1 and 3, since the downlink communication signal and the uplink communication signal interfere with each other, the downlink communication signal is less affected by the interference from the other sections, and the other sections of the downlink communication signal The effect of interference on the system is not a big problem. Thereby, the fall of the communication speed of a downstream communication signal can be prevented more.

  In the second embodiment, the case where the communication bands A, B, A ′, and B ′ are assigned in order from the section 1 has been described, but the communication bands A, B ′, A ′, and B from the section 1 Communication bands A ′, B ′, A, B, Communication bands B, A, B ′, A ′, Communication bands B, A ′, B ′, A, Communication bands A ′, B ′, B, A Even if they are assigned in this order, the same effect can be obtained.

Embodiment 3 FIG.
FIG. 6 is an explanatory diagram showing a configuration according to the third embodiment. In the first embodiment, the cable is disconnected between the two modems in the communication apparatus for each communication section. However, in the third embodiment, the cables 201, 202, and 203 are not disconnected. ,... Are used to insert a filter for electrically cutting communication signals. Also in this case, the same effect as the above embodiment can be obtained.

Explanatory drawing which shows the structure in Embodiment 1. FIG. Explanatory drawing showing an example of a frequency band used in the first embodiment Explanatory drawing showing an example of a frequency band used in the second embodiment Explanatory drawing showing an example of a frequency band used in the second embodiment Explanatory drawing which shows the structure in Embodiment 2. Explanatory drawing which shows the structure in Embodiment 3.

Explanation of symbols

1, 2, 3, 4, 5, 6 Vehicle 10, 20, 30, 40, 50, 60 Communication device 11, 12, 21, 22, 31, 32, 41, 42 Modem 13, 23, 33, 43, 53 , 63 Display 14 Server 101, 102, 103 Empty cable 201, 202, 203 Filter

Claims (4)

Four or more communication devices having a modem;
Connecting said plurality of communication devices, in-train communication system comprising a cable which is laid in the train,
The communication device has a separate modem for each communication device connected to the communication device,
The modem connected to a different communication device in the communication device uses two different frequency bands alternately between adjacent communication devices, and uses the two different frequency bands as an upstream communication band and a downstream communication band, respectively. And performing data communication between the communication devices using the same frequency band of the two different frequency bands by using the uplink communication band and the downlink communication band alternately. Intra-train data communication system. Wherein between the modem in a communication device, train data communication system of claim 1, wherein the separating the front listen Buru physically. The prior Listen Buru between modems in a communication device, train data communication system of claim 1, wherein inserting a filter for cutting the electrical communication signals. Four or more communication devices having a modem;
Connecting said plurality of communication devices, in-train communication method in train data communication system and a cable laying has been cable to a train,
The communication device has a separate modem for each communication device connected to the communication device,
The modem connected to a different communication device in the communication device uses two different frequency bands alternately between adjacent communication devices, and uses the two different frequency bands as an upstream communication band and a downstream communication band, respectively. And performing data communication between the communication devices using the same frequency band of the two different frequency bands by using the uplink communication band and the downlink communication band alternately. Intra-train data communication method.

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