JP2008245186A - Intra-train communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable intra-train communication apparatus in which an existent or newly provided transmission line is adaptable to the division or joining of organized cars and high-quality moving picture information or audio information can be easily transmitted as digital data signals. <P>SOLUTION: The intra-train communication apparatus which is organized of a plurality of cars and comprises: a control data communication device 5 and an image data communication device 3 installed for each car for communicating control data and for communicating data containing image information; transmission lines 4, 15 connecting the control data communication devices 5 with each other and the image data communication devices 3 with each other; and a transmission line 8 for interconnecting each of the control data communication devices 5 and each of the image data communication devices 3, wherein training data are transmitted/received between the control data communication devices 5 and between the image data communication devices 3, thereby estimating communication path characteristics when dividing or joining the cars. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a train communication apparatus suitable for performing information communication in a train.

  In recent years, needs for passenger guidance services using an LCD display or the like in a train are increasing, and a technique for distributing various service contents from an on-board server to the display of each vehicle is required.

  In the conventional technology described in (Patent Document 1), train information such as stop station information and arrival time, train position information indicating the distance from the first station, in-vehicle device information such as a door opening / closing command, etc. A train information device for processing is installed in each vehicle, the train information device of the leading car is connected to various control operation devices such as a master controller, and the train information device mounted in each vehicle is connected via a digital transmission line. They are connected to each other and cooperate with each other to perform input / output processing of the various types of train information.

  The video information distribution device mounted on the leading vehicle is connected to the train information device of the vehicle, inputs train information, and outputs still image information. This still image information is output as a digital data signal through the first transmission path connecting the train information devices, and is transmitted to the reception display device mounted on each vehicle via the train information device mounted on each vehicle. The The video information distribution device is connected to a reception display device mounted on each vehicle via a second transmission path that connects the video information distribution devices, and transmits the moving image information as an analog data signal.

  Still image information, which has a smaller data capacity compared to video information, is digitally transmitted with high resolution still image information using the packet system conventionally used in train information devices, while the data capacity is larger than still image information. Moving image information is transmitted using analog transmission methods such as the NTSC method that has been used in television receivers in the past, enabling a train-mounted video distribution display system that realizes moving images and high-quality still images at low cost. ing. In addition, since the video information and the still picture information are transmitted to the reception display device through different paths, even if any one of the transmission paths is abnormal, The display of video information by still images can be continued and the reliability of the display function is improved.

JP 2002-209193 A

  However, in the conventional technique described in (Patent Document 1), when moving image information is transmitted as an analog data signal, a very wide communication frequency band is required to transmit a high-quality image. In trains, multiple vehicles are connected, so even when analog signals are amplified and relayed using an amplifier, etc., signal degradation occurs, and electromagnetic noise generated from inverter devices installed in the train However, it is difficult to distribute high-quality images to each vehicle.

  Also, when video distribution using analog data signals is performed, multiple video information and multi-channel communication that multiplexes voice lines such as telephones are performed on a single transmission line, so a wider frequency band is necessary and realized. There is a difficult point. In addition, there is a problem that trains cannot transmit moving image information or still image information to a display due to disconnection of a transmission line between vehicles or a failure of a communication device, and display is impossible.

  The object of the present invention is to enable splitting and merging of organized vehicles using existing or new transmission lines, and easily realizing transmission of high-quality moving image information and audio information as digital data signals. It is to provide a highly reliable in-train communication device.

  In order to achieve the above object, the in-train communication device of the present invention is composed of a plurality of vehicles, and image data that communicates data including image information with a control data communication device that communicates control information installed in each vehicle. A communication path, a transmission path that interconnects the control data communication apparatus and the image data communication apparatus, and a transmission path that interconnects the control data communication apparatus and the image data communication apparatus. The communication path characteristics are estimated when the vehicle is divided and merged by transmitting and receiving training data between the image data communication apparatuses.

  According to the present invention, splitting and merging of organized vehicles can be handled, and moving image information and still image information converted into digital data are transmitted using the image data communication device, and the image data communication device and the control data communication device are transmitted. Therefore, even if the image data communication device becomes incapable of communication due to a failure or the like, the control data communication device transmits train control information, so that a plurality of image data stored in advance on the display The display can be changed using.

  In addition, high-speed communication is possible by communication that improves S / N, and even if various inverters attached to the vehicle operate for train operation and electromagnetic noise is generated, it is greatly affected by this. In addition, it is possible to stably communicate information provided to the vehicle, monitoring images from the vehicle, and maintenance data using the communication line. Furthermore, monitoring images and maintenance data can be used to remotely monitor operations such as security and listening status in the train.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an in-train communication system according to the present embodiment.

  The first car 1 which is the driver's cab or the crew room is provided with a server 2, and each of the first car 1, the second car 9 and the Nth car 10 has control data communication devices 5a, 5b, 5c, image data communication. Devices 3a, 3b, 3c, display devices 6a, 6b, 6c, and devices 7a, 7b, 7c are installed.

  The control data communication device 5 is used to transmit control information such as train operation information indicating a stop station, train position information indicating a travel distance from the starting point, control commands for in-vehicle devices such as door opening and closing, and the image data communication device. 3 is a display 6 for displaying image data installed in each vehicle and a device 7 such as a telephone or an air conditioner, which displays image information such as moving images and still images as contents, audio information such as in-car broadcasts, and telop display. Is used to transmit character information and device operation log information.

The control data communication devices 5a, 5b, 5c are connected in series by the transmission line 4, and the image data communication devices 3a, 3b, 3c are connected in series by the transmission line 5. The control data communication devices 5a, 5b, 5c and the image data communication devices 3a, 3b, 3c are respectively connected to the transmission lines 8a,
8b and 8c are connected to each other to perform communication between the first car 1 and the vehicles 9 and 10. Here, two electric wires are used for the transmission lines 4 and 5. This electric wire may be an existing one or a new one.

  The image data communication apparatus 3 includes a modulation unit 9, a control unit 10 connected to the modulation unit 9, and a hub unit 11 connected to the control unit 10. The modulation unit 9 is connected to the transmission path 5, and the control unit 10 is connected to the control unit 10. The hub 11 is connected to the server 2, the display 6 and the device 7 in the control data communication device 5.

Since the hub unit 11 is provided, communication using the Ethernet (registered trademark) protocol is possible between the display unit 6 and a plurality of devices 7, and since the control unit 10 is provided, packet transfer processing in the hub unit 11 is performed. It is possible to control. In addition, since the transmission path 5 is branched inside the image data communication apparatus and connected to the modulation unit 9, the image data communication apparatus 3 performs communication by a multi-drop method sharing one transmission path. As an access method for performing the multi-drop method, a polling method or CSMA / CA (Carrier Sense Multiple Access / Collision)
Avoidance) method may be used.

  The display 6 includes a controller 12, a memory 13, and a screen 14. The controller 12 controls input / output signals to the display 6, and the memory 13 is installed to record the input / output signals of the controller 12. The screen 14 displays image data of moving images or still images stored in the memory 13 and character information for displaying a telop in accordance with instructions from the controller 12. The display 6 is connected to the image data communication device 3 and communicates in accordance with, for example, an Ethernet protocol. The image data communication device 3 is used to transmit and store a plurality of image data from the server 2 to the memory 13 of the display device 6. The display device 6 stores the memory 13 in accordance with the control data transmitted from the control data communication device 5. One of a plurality of image data and text information for displaying a telop is stored on the screen 14.

  Since the image data transmitted to the display 6 of each vehicle may be the same information or different information, the control unit 10 and the hub unit 1 provided in the image data communication device 3 include image data. Check the packet address and determine the direction of transmission.

  In addition, image display timing information is passed from the control data communication device 5 to the display 6 via the image data communication device 3. The timing information is a kilometer indicating the travel distance from the starting point, a passing station name, or time information.

  If the image data communication device 3b breaks down, communication between the image data communication device 3a and the image data communication device 3c cannot be performed, so that new image data can be transmitted from the server 2 to the display 6c. Disappear. However, since a plurality of image data is already stored in the memory 13 of the display device 6c, the screen 14c of the display device 6c can be switched by obtaining timing information from the control data communication device 5c.

  In addition, the display 6 informs passengers and crew members of each vehicle of necessary information by voice, for example, notification of the next stop station, calling, etc. A monitoring image of passenger status and maintenance data are displayed.

  The devices 7a, 7b, and 7c include other information providing devices and monitoring devices. The monitoring devices are used for maintenance of image information monitored by a camera, temperature, vibration, voltage, current, etc. of devices such as motors and inverters. Necessary maintenance data is fetched from the image data communication devices 3 a, 3 b, 3 c and output to the server 2.

  The information providing apparatus is for providing various information to passengers of each vehicle. For example, real-time information such as news and baseball received by the wireless receiver is taken from the wireless receiver and stored in the server 2. Thus, the data is periodically output to the image data communication device 3a. In addition, information from a recording medium such as a VTR, CDROM, hard disk, or memory in which various data such as advertisement information, event information, movies, and recording information are recorded is read out and output to the image data communication device 3a. Image data communication device such as train operation information such as information and arrival time information, train position information indicating the current train position and distance from the first station, train information such as door opening / closing information and air conditioning operation status at the stop station Output to 3a. On the other hand, the monitoring device receives image information from the cameras attached to each vehicle by the image data communication devices 3a, 3b, 3c, displays the received image information, and records it in the server 2. The server 2 records image information and provides it outside the train as necessary.

  The image data communication devices 3b and 3c receive the information transmitted from the image data communication device 3a, and output the information to the display devices 6a, 6b, and 6c via the hub unit 11, and display the above-described various types of information on the display devices 6a, 6c. 6b and 6c, and provide common information to passengers. You may make it branch from the image data communication apparatus 3 for every vehicle, and display provision information on a some indicator.

  Also, maintenance data, which is the output of various sensors such as an acceleration vibrometer, a temperature sensor, a voltage sensor, and a current sensor, is taken into the image data communication devices 3a, 3b, and 3c as maintenance data via the hub unit 11. Monitoring image information monitored by the camera is also taken into the image data communication devices 3a, 3b, 3c via the hub unit 11. The maintenance data and monitoring image information are output to the server 2 via the transmission path 5 or the transmission path 4.

  The camera and the image data communication devices 3a, 3b, 3c are connected by a dedicated cable, for example, an Ethernet (registered trademark) (R) cable or a coaxial cable. The monitoring image is transmitted from the image data communication devices 3a, 3b, 3c as a moving image or a dropped image. When the camera is a web camera, for example, a drop image is output from the camera, and thus the drop image is transmitted from the image data communication devices 3a, 3b, and 3c. In the case of a web camera, the camera and the image data communication devices 3a, 3b, and 3c are connected by an Ethernet (R) cable.

As described above, the information communicated between the image data communication device 3a and the image data communication devices 3b and 3c is various information including video information, monitoring images, and maintenance data.
Mbps or higher is required. For this reason, the image data communication device 3a and the image data communication devices 3b and 3c perform high-capacity communication using the MHz band.

  The transmission lines 4 and 5 are laid under the floor of each vehicle, and the respective vehicles are connected to each other by the respective electrical connectors of the vehicle connecting portion. Under the vehicle floor, inverters with various capacities for driving the motor and various controls are mounted for improving driving performance and comfortable driving, and switching elements (eg, IGBTs, bipolar transistors, FETs, thyristors) constituting the inverters are installed. Electromagnetic noise is generated by the on / off operation of the semiconductor switching element. This electromagnetic noise is high-frequency noise that is determined by the inductance or stray capacitance due to the wiring in the circuit and the switching speed of the switching element when the switching element is turned on or off.

  As a result of evaluating this frequency by experiment, the frequency of the motor voltage is variable for speed control ranging from several hundred kHz to several tens of MHz, and in some cases, several hundred MHz. When the wave is generated, electromagnetic noise of several tens of kHz or less is generated. Noise has a higher power as a low frequency component, and electromagnetic noise during train traveling is mainly several MHz or less.

  An example is shown in FIG. FIG. 2 also shows the noise superimposed on the transmission lines 4 and 5, the transmission signal and the reception signal of communication. It can be seen that the noise has a high power of about 1 MHz or less and is not so high at about 5 MHz or more. The communication band is preferably 1 MHz or more and 30 MHz or less, but more preferably 5 MHz or more and 30 MHz or less. However, noise is superimposed in both bands, which becomes an obstacle to communication using this band.

The image data communication apparatuses 3a, 3b, and 3c have the same configuration and enable communication with the above-described noise greatly reduced. The modulation unit 9 and the control unit 10 are as shown in FIG. Band-pass filters (BP filters) 50 and 60, reception amplifier 51, transmission amplifier 59, analog / digital converter (A / D) 52, digital / analog converter (D / A) 58, equalizer 53, It comprises a demodulator 54, a modulator 57, an access controller 55, and a protocol converter 56. The control data communication devices 5a, 5b, and 5c may be configured in the same manner as the image data communication devices 3a, 3b, and 3c, or may be configured more simply.

  The image data communication device 5 is provided with a protocol converter 56 for interfacing with an information providing device and a monitoring device. When the information providing device and the monitoring device are constituted by a personal computer based device, various general-purpose software can be used, and information management, data processing, and the like are facilitated. For this reason, the protocol converter 56 is used as an interface such as Ethernet or USB. Yes. When the protocol converter 56 receives data to be provided to the passengers of the vehicle from the information providing device, the protocol converter 56 converts the data into a communication packet in a format handled by the image data communication device 3.

  When receiving the communication packet from the protocol converter 56, the access controller 55 outputs this data to the modulator 57. The modulator 57 assigns data to each carrier (also referred to as bit assignment) based on the input data allocation amount information 55b for each carrier. The signal in which data is assigned to the carrier wave is converted into an analog signal by the D / A 58, amplified by the transmission amplifier 59, output to the transmission line 5 via the BP filter 60, and communicated.

On the other hand, the signal transmitted from the other image data communication device 3 is suppressed by the BP filter 50 except for the communication band, and the signal in the communication band is output to the reception amplifier 51. The reception amplifier 51 amplifies the reception signal and outputs the amplified signal to the A / D 52, and the signal converted into a digital signal by the A / D 52 is output to the equalizer 53. The equalizer 53 is for correcting channel distortion (also referred to as transmission channel distortion) of the transmission path 5, and a signal subjected to the processing for correcting the channel distortion is output to the demodulator 54. The demodulator 54 extracts the data allocated to each carrier based on the input data allocation amount information 55 a for each carrier and outputs the data to the access controller 55. The access controller 55 converts the extracted data into a communication packet of a predetermined format and outputs it to the protocol converter 56. The protocol converter 56 converts the protocol of the communication packet so that an interface (for example, Ethernet or USB) with the information providing device or the monitoring device can be obtained, and outputs the information to the information providing device or the monitoring device.

  The access controller 55 outputs data allocation amount information 55a and 55b to the demodulator 54 and the modulator 57, but the data allocation amount indicated by this information is not constant, and the image data communication device 3 is set at every set time. The S / N is estimated (also referred to as measurement or determination) for each carrier by performing training (also referred to as learning) on the communication characteristics, or the transmission error rate at the time of communication is evaluated. The data allocation amount is changed for each or all carriers. In addition, the data allocation amount may be changed by using both S / N estimation and transmission error rate evaluation.

  As described above, the communication characteristics (transmission error and S / N) of the transmission path 5 are dynamically evaluated between the image data communication apparatuses 3, and the modulation / demodulation processing (change of the data allocation amount) is changed based on the result. Thus, communication can be performed without causing a transmission error.

  As shown in FIG. 2, the noise superimposed on the transmission line 5 is higher as the frequency is lower, particularly 1 MHz or less, and not so high at 5 MHz or more. Even if the intensity of the signal transmitted between the image data communication apparatuses 3 is constant as shown in FIG. 2, the characteristics of the transmission path 5 have frequency dependence, so that the image data communication apparatus 3 on the receiving side receives the signal. The strength of the received signal decreases and fluctuates as the frequency increases. This is due to attenuation of the communication signal, reflection at the end point of the transmission path 5, and the like due to the inductance of the communication line and the capacitance between the forward path and the return path of the communication line.

In order to perform stable monitoring image communication at a communication speed of 1 Mbps or higher, it is necessary to set the S / N, which is the ratio of the received signal and noise (difference in dB), to a predetermined value or higher in the high frequency band of the received signal Is evaluated, it is desirable to use a frequency band of 30 MHz or less as a communication band. When the band is narrowed, there is a problem that the communication speed is lowered. Therefore, the communication band is preferably 1 MHz or more and 30 MHz or less. 30 for communication bandwidth of 5MHz or more
When a band of MHz or lower is used, the influence of noise is reduced, and more stable high-speed communication is possible.

  The equalizer 53 is necessary for correcting the channel distortion of the transmission path 5 and correctly restoring the data when demodulating. This is corrected using a preamble signal in communication to evaluate channel distortion and using this evaluation result. In general, when the attenuated received signal is amplified, the noise component is also amplified and the S / N is not improved. Therefore, without the equalizer 53, data cannot be restored due to the influence of channel distortion, resulting in a transmission error. End up.

  A mechanism for evaluating the S / N and changing the data allocation amount will be described below, taking as an example the case where a plurality of carriers (multicarrier) are used in the use band as the carrier. FIG. 4 shows a multicarrier spectrum. A plurality of carriers in the band Δf are allocated to the use band, but it is general to take a predetermined band between the carriers in order to prevent the carriers from overlapping with each other. Each carrier wave is assigned a bit of predetermined transmission data.

  As shown in FIG. 5, OFDM (orthogonal frequency division division), which is a type of multicarrier, is arranged in such a way that the power of other carriers is zero at the peak point of the carrier as shown in FIG. If the band of each carrier is Δf, the orthogonality is maintained by inverse Fourier transform at time 1 / (Δf / 2). For this reason, unlike a general multicarrier, the signal can be restored even if each carrier overlaps, and the use band may be narrower than that of a general multicarrier, and the frequency utilization efficiency is higher than that of a general multicarrier. Have

  There are multi-carrier communication methods and single-carrier communication methods that use a single carrier (also referred to as a single carrier) as communication methods using carrier waves, both of which are data (bits) on the carrier wave. Is assigned and transmitted.

  Although the data allocation amount is limited by the S / N for each carrier to which data is allocated and transmitted, the noise superposed on the transmission line 5 matches a specific frequency with a high noise level and a low S / N. A high data allocation amount can be maintained for all carriers simply by making the data allocation amount of the carrier lower than the data allocation amount of other carriers. As a result, it is possible to ensure a high transmission rate.

  As described above, in the multi-carrier communication system, communication is performed using a plurality of carriers, so only the data allocation amount of a specific carrier wave (carrier) having a low S / N is reduced. In the communication system, even if the noise level at a specific frequency is only high, there is only one carrier, so the amount of data allocated to that carrier is low, and the transmission speed is considerably reduced compared to the multicarrier communication system. In particular, since a transmission speed of 1 Mbps or more is required to transmit a monitoring image with movement in a vehicle, the multicarrier communication method is better than the single carrier communication method.

A plurality of waveforms with different amplitudes and phases are used for each carrier wave, and data (bits) are allocated to this waveform for transmission. Multi-level modulation is used for modulation using a large number of transmission waveforms. be called. The data allocation amount (also referred to as bit allocation amount) is limited by the S / N for each carrier, and the relationship is as shown in FIG. For example, if the transmission error rate is set to 1E-5, in 256 QAM, 64 QAM, 16 QAM, QPSK, and BPSK, the S / N is about 22.5 dB, about 17.7 dB, about 13.5 dB, about 9.5 dB, respectively. About 6.3 dB or more is required. In this case, 8 bits can be allocated in 256QAM, 6 bits in 64QAM, 4 bits in 16QAM, 2 bits in QPSK, 1 bit in BPSK, and S / N is less than about 6.3 dB. If there is, do not assign bits.

QAM is Quadrature Amplitude Modulation, QPSK is Quadrature Phase
Shift Keying, BPSK is called Binary Phase Shift Keying, QAM is amplitude modulation,
QPSK and BPSK are phase modulations. Here, 128 QAM, 32 QAM, etc. are not shown, but there are other QAMs.

  By adding an error correction function, it is possible to reduce the transmission error rate from 1E-5 to 1E-7. Therefore, for example, if the transmission rate is 1 Mbps, an error occurs probabilistically once every 10 seconds, and stable transmission can be performed without any problem by retransmitting the transmission frame in which the error has occurred. .

  The S / N evaluation will be described with reference to FIG. This S / N evaluation, that is, the estimation of the channel characteristics, is effective when the train formation is divided and merged. FIG. 7 shows an example in which S / N is calculated by transmitting training data for evaluating S / N from the image data communication device 3a to the image data communication devices 3b and 3c. In the evaluation of S / N, when the training data is transmitted from the image data communication device 3a to the image data communication devices 3b and 3c, the training data is transmitted from the image data communication devices 3b and 3c to the image data communication device 3a. It is done in the same way.

  When normal data is transmitted from the image data communication device 3a, the procedure from step 1 to step 5 is performed, and the processing for S / N evaluation is performed by interrupt processing. Here, an example of interrupt processing that is activated at regular intervals is shown.

The processing shown in FIG. 7 is performed by the access controller 55. In normal data transmission, in step 1, packet data in the communication apparatus is created based on the data fetched from the protocol converter 56. In step 2, the created packet data is output to the modulator 57. As a result, the data is modulated and output to the image data communication device 3b. For the data transmitted from the image data communication device 3b, the packet data from the demodulator 54 is taken in as shown in step 3. In step 4, CRC (Cycle Redundancy Check) is evaluated to detect transmission errors. If there is a transmission error, a retransmission request is sent to the image data communication device 3b in step 5, and if there is no transmission error, the captured data is output to the protocol converter 56.

  Interrupt processing for S / N evaluation is performed in a state where such normal data communication processing is performed. As shown in step 6, when training data prepared in advance is output to the modulator 57, the training data is modulated and transmitted to the image data communication device 3b.

  The image data communication device 3b receives the training data in step 10, and calculates the S / N for each carrier wave in step 11 as described later. In step 12, the carrier number and the bit allocation amount are converted into packet data as a pair and output to the modulator. As a result, the bit allocation information is transmitted from the image data communication device 3a to the image data communication device 3b. Here, a carrier number and bit allocation amount pair is referred to as bit allocation information.

  The bit allocation information table is rewritten in order to update the bit allocation information of the image data communication device 3b which is the local station. This bit allocation information is used when the data transmitted from the image data communication device 3a is demodulated by the demodulator of the image data communication device 3b.

  In step 7, the image data communication device 3a receives the bit allocation information transmitted from the image data communication device 3b, and in step 8, rewrites the bit allocation information table. When this process ends, in step 9, an ACK indicating completion of rewriting of the bit allocation information table is transmitted.

  In the image data communication device 3b, ACK is received in step 13, and the process is terminated. When this processing ends, the training information is transmitted from the image data communication device 3b to the image data communication device 3a, and the S / N for the transmission from the image data communication device 3b to the image data communication device 3a is evaluated. These steps are not necessary if the S / N of the communication line is symmetric, but are effective when the S / N is not symmetric.

  In the case of a train, an inverter that is a noise source is often on the image data communication device 3b side, and it is conceivable that the noise on the image data communication device 3b side is stronger than the noise of the image data communication device 3a. As a result, since the S / N in the image data communication device 3b is lowered, when data is transmitted from the image data communication device 3a to the image data communication device 3b, the bit assigned to each carrier wave is lowered according to the S / N. Need to do. Thus, when there is a difference in S / N in each communication device, bidirectional S / N evaluation is performed, and bit allocation information obtained as a result is stored in each access controller, and modulation and Used in response to demodulation.

  Although it is necessary to distinguish between transmitting training data and normal data, this can be realized by configuring a transmission format as shown in FIG. This transmission format includes a preamble signal 20, a header 21, data 22, and a CRC 23, and information in the header 21 indicates training information or normal data information. If the header 21 is training information, training data is included in the data, and if the header is data information, normal communication data is included in the data. The preamble signal is used for symbol synchronization.

  This training may be performed when S / N deteriorates, that is, event-driven training), that is, training may be performed at regular intervals, but event-driven training is more efficient in transmission efficiency. Is expensive.

  As described above, there is a frequency at which sufficient S / N cannot be secured by performing communication using a multi-carrier communication system including OFDM, and as a result, there are other frequencies to which data cannot be allocated. If the S / N ratio is high, a large amount of data can be allocated to the carrier waves of these frequencies, and there is an effect that a sufficient communication speed of 1 Mbps or more can be secured as a whole. Also, since OFDM has high frequency utilization efficiency, it is possible to ensure the same communication speed in a narrower band than a general multicarrier communication system. For this reason, the S / N varies depending on the frequency due to the inverter noise. However, since the S / N variation extends over a certain frequency range, a frequency band having a relatively high S / N is set as a use frequency band in OFDM. Cheap.

A single carrier may be used, and to achieve the same transmission rate as a multicarrier using a single carrier, it is possible to increase the transmission rate by widening the band of the single carrier Become. Since the modulation method is the same as that of multi-carrier, the training shown in FIGS. 7 and 11 can be applied as it is.

  In addition, spread spectrum communication schemes may be applied. In multicarrier schemes including OFDM, bit allocation is changed for each carrier, but spread spectrum communication schemes do not have such processing, and instead baseband In this method, data is restored by spreading the communication bandwidth to a wider bandwidth and compressing the bandwidth to the baseband bandwidth during demodulation. This spread spectrum communication method can increase the S / N with respect to communication under the situation where random noise is superimposed on the communication path, enables stable communication, and allows noise (in a specific frequency band from an inverter device ( This is suitable for communication when the level of frequency selective noise is high.

  By communicating using the spread spectrum communication method, it is not necessary to carry out training to determine the bit allocation amount that was necessary in the multicarrier communication method. Transmission interruption does not occur.

It is a block diagram of the in-train communication system which is one Example of this invention. It is a figure explaining a communication characteristic. It is a block diagram of a communication apparatus. It is a figure explaining the spectrum of a general multicarrier. It is a figure explaining the spectrum of OFDM. It is a figure explaining the communication error characteristic under Gaussian noise. It is a processing flow figure for S / N evaluation for every fixed time. It is a figure explaining a transmission format.

Explanation of symbols

1 Car 1 Server 3a, 3b, 3c Image data communication device 4, 8, 15 Transmission path 5a, 5b, 5c Control data communication device 6 Display device 7 Device 9 Modulation unit 10 Control unit 11 Hub unit

Claims (6)

  A control data communication device that is composed of a plurality of vehicles and communicates control information installed in each vehicle, an image data communication device that communicates data including image information, and the control data communication device and image data communication device are mutually connected. A transmission path for connecting the data communication apparatus and the image data communication apparatus to each other, and dividing the vehicle by transmitting / receiving training data between the control data communication apparatuses and between the image data communication apparatuses An in-train communication device that estimates the channel characteristics when merging and merging.   The control data communication device and the image data communication device communicate with each other by allocating transmission data to each carrier signal using a plurality of carrier signals, and the ratio of signal to noise with respect to each carrier signal. The in-train communication device according to claim 1, wherein communication is performed by estimating or measuring S / N, and changing a transmission data allocation amount to each carrier signal according to the estimated or measured S / N value.   Between the control data communication devices, between the image data communication devices, the transmission data is assigned to each carrier signal using a plurality of carrier signals and communicated, and the transmission error rate is evaluated for each carrier signal, The in-train communication device according to claim 1, wherein communication is performed by changing a transmission data allocation amount to each carrier signal according to the evaluated transmission error rate.   The in-train communication device according to claim 2 or 3, wherein the plurality of carrier signals are communicated by an orthogonal frequency division division communication system.   The control data communication device and the image data communication device use at least one carrier wave signal and allocate transmission data to the carrier wave signal for communication. It is determined whether or not the S / N that is the noise ratio is obtained, and when the determination result is equal to or lower than the predetermined S / N, the frequency of the carrier signal is changed to a predetermined different frequency. The in-train communication device according to claim 1 which performs communication.   The in-train communication device according to claim 1, wherein communication between the control data communication devices and between the image data communication devices is performed by a spread spectrum communication method in which communication signals are spread and communicated in a wider band.

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