Train radio communication system

Abstract

To provide a train radio communication system capable of shortening gain adjustment and achieving stable communication over a wide signal level range.SOLUTION: A train radio communication system performs communication between ground radio machines TR11, TR12. TR13, TR 14, ..., TR21, TR22, ... installed along a track and onboard radio machines 16a, 16b mounted on a train 11 traveling on the track. The system preliminarily acquires environment information corresponding to a train position on the track, specifies the current position of a self train on the track, and predicts the level of a target signal and the level of an inference signal on the basis of environment information corresponding a distance between an onboard radio machine and a ground radio machine performing communication and the train position, and sets a parameter of an automatic gain control circuit on the basis of a prediction result.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a train wireless communication system for communication between ground wireless devices installed along a railway line and on-board wireless devices mounted on trains traveling on the railway line. [Background technology]

[0002] In order to receive a wide range of signals, from large to small, radio receiver circuits use an AGC circuit (automatic gain control circuit) that adjusts the gain so that the received signal is at a level suitable for demodulation. The AGC circuit operates automatically according to a specified setting value. Since the received signal contains not only the desired signal but also unwanted signals such as noise, the gain must be adjusted so that the desired signal is at a level suitable for demodulation while avoiding circuit saturation with the unwanted signals. In addition, since there is a high possibility of demodulation errors during level adjustment, this adjustment must be completed quickly.

[0003] Therefore, for example, Patent Document 1 describes a method of adjusting the gain using a prediction pattern. In Patent Document 1, a change in the received power caused by a deviation in the estimation of the own position of the device is corrected by comparing it with the prediction pattern, thereby realizing a gain control with high adjustment speed and high accuracy.

[0004] Furthermore, Patent Document 2 describes a wireless train control system that communicates between wayside radios (ground radios) placed along the line and on-board radios installed on traveling trains. In Patent Document 2, communication is carried out by changing the wayside radios with which the train is communicating while traveling. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-252646 A [Patent Document 2] JP 2008-162548 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the communication conditions of the on-board radios installed on trains are constantly changing as they move. For example, in a radio-based train control (CBTC) system that communicates with multiple communication partners in a time-division manner, the communication partners change from moment to moment, and the distance to the communication partners also varies widely, from a few meters to just under 1 km, making adjustments using AGC necessary.

[0007] In addition, the surrounding environment changes greatly, with a large difference in interference levels between the crowded environment around a station and the quiet environment inside a tunnel (for example, systems using the 2.4 GHz band are affected by wireless LANs, etc.), and the level of the target signal changes greatly depending on the terrain, such as in urban areas, suburban areas, forests, on bridges, and in tunnels.

[0008] This makes prediction difficult, and if the gain is large, it will saturate, and if it is small, demodulation will not be possible. Furthermore, if the AGC circuit is set to be adjustable regardless of the input signal level, it will take a long time to adjust the gain, and depending on the combination of the levels of the received radio wave and the interference radio wave, the gain adjustment may not be completed in time or may be set to an inappropriate adjustment value. Delays in gain adjustment or inappropriate settings may cause frame synchronization to be misrecognized / missed or data to be lost. Even if logarithmic amplifiers are used, it is difficult to accommodate a wide signal level range like that of a CBTC system.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a train wireless communication system that can shorten the time required for gain adjustment and achieve stable communication over a wide range of signal levels. [Means for solving the problem]

[0010] The train radio communication system of the present invention is a system for communication between ground radios installed along the line and on-board radios mounted on trains traveling on the line, and is characterized in that it acquires environmental information corresponding to the train's position on the line in advance, identifies the current position of the train on the line by radio ranging, predicts the level of a target signal and the level of an interference signal based on the distance between the communicating on-board radio and the ground radio and the environmental information corresponding to the train's position, and sets parameters of an automatic gain control circuit based on the prediction result. Effect of the Invention

[0011] In train radio communication systems, the time schedule is fixed, and trains have the function of acquiring position information, so they can recognize the ground radio with which they are communicating, the distance between the radios, the position of the train, etc. In addition, they can acquire environmental information (level of interference signals) in advance and store past data in a database.

[0012] By taking advantage of these unique system circumstances, the automatic gain control circuit used in the radios of the train radio communication system can predict the power level from the ground radio and the type and level of interference waves due to the surrounding environment, set parameters, and perform gain control appropriate to the situation in a short period of time.

[0013] Therefore, according to the present invention, it is possible to provide a train wireless communication system that can shorten the time required for gain adjustment and achieve stable communication over a wide range of signal levels. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram illustrating a schematic configuration of a CBTC system for explaining a train wireless communication system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a general operation flow of the CBTC system shown in FIG. 1. [Diagram 3]FIG. 2 is a block diagram of a superheterodyne radio, showing an example of the configuration of an on-board radio used in the CBTC system shown in FIG. 1. [Figure 4] FIG. 2 is a block diagram showing another example of the configuration of an on-board radio used in the CBTC system shown in FIG. 1, which is a block diagram of a direct conversion radio. [Diagram 5] FIG. 5 is a diagram showing an example of the operation of the AGC circuit in the on-board radio shown in FIG. 3 and FIG. 4, and is a waveform diagram of an actual radio wave acquired by the on-board radio. [Figure 6] 5 is a flowchart showing a procedure for creating control data for an AGC circuit in the on-board wireless device shown in FIGS. 3 and 4. [Figure 7] 1 is a flowchart showing the procedure of AGC during communication between a ground radio and an on-board radio. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a diagram illustrating a schematic configuration of a CBTC system for explaining a train radio communication system according to an embodiment of the present invention. In the ground facility 100, ground devices SC1, SC2, ..., SCn for controlling a train 11 are arranged in each zone of the line, and a plurality of ground radios (radio devices) TR11, TR12, TR13, TR14, ..., TR21, TR22, ... are arranged along the line in correspondence with the ground devices SC1, SC2, ..., SCn, respectively.

[0016] The ground devices SC1, SC2, ..., SCn are connected to a network NW, and each of the ground devices SC1, SC2, ..., SCn is managed by a traffic management device 110. Track location information AS is transmitted from the ground device SC1 in the zone where the train 11 is located to the traffic management device 110 via the network NW. Meanwhile, track information BS is transmitted from the traffic management device 110 via the network NW to the ground device SC1 in the zone where the train 11 is located.

[0017] The on-board equipment 10 includes a vehicle cab 14a, an on-board device 15a, and an on-board radio (radio) 16a provided at the front (leading car 11a) of the train 11 in the direction of travel indicated by the arrow, and a vehicle cab 14b, an on-board device 15b, and an on-board radio (radio) 16b provided at the rear (last car 11b) of the train 11. The on-board radio 16a or the on-board radio 16b transmits and receives radio waves to and from the radio of the ground equipment 100 via the antenna ATa or ATb. The on-board radio 16a and the on-board radio 16b are commonly connected, and communication is performed by one of the on-board radios selected by the on-board device.

[0018] Train control information TCS output from the ground device SC1 in the zone where the train 11 is located is sent to a ground radio TR1m (m=1, 2, 3, 4, ...) and then transmitted from an antenna AR1m (m=1, 2, 3, 4, ...) to the train 11. FIG. 1 shows an example in which the train control information TCS is sent by wire or wireless to a ground radio TR13 adjacent to the train 11 via the ground radios TR11 and TR12, and then transmitted from the antenna AR13 to the train 11 on the track 12. On the on-board equipment 10 side, the train control information TCS is received by an antenna ATb of the on-board radio 16b and transferred to the on-board device 15b (or the on-board device 15a via the on-board radio 16a) for controlling the train 11.

[0019] On the other hand, the train position information TPS output from the on-board equipment 15b (or the on-board equipment 15a) is transmitted by the on-board radio 16b (or the on-board radio 16a) via the antenna ATb, received by the antenna AR13, and then received by the ground equipment SC1 via the ground radios TR12 and TR11 from the ground radio TR13 via wired or wireless connection. All adjacent terrestrial radio devices, for example, radio devices TR11 and AR12, radio devices TR12 and AR13, and radio devices TR13 and AR14, communicate with each other via wires or wirelessly.

[0020] Next, the general operation of the CBTC system configured as above will be described with reference to Fig. 2. To simplify the description, an example will be taken in which communication is performed between four ground radios 1-4 and one on-board radio. The ground radios 1-4 emit radio waves (data frames for synchronization) according to a time schedule, and the on-board radio can know the location of the ground radio with which it will communicate next by combining the time schedule with the location data of the ground radios 1-4. In addition, a distance measuring device mounted on the train 11 acquires distance information from the ground radios 1-4, so it can know where on the route the train is traveling.

[0021] That is, each of the ground radios 1 to 4 always transmits a data frame for synchronization even if the train 11 is not present. As indicated by the arrows, each of the ground radios 1 to 4 transmits in sequence so as not to overlap in timing. At this stage, the on-board radio sets the AGC circuit based on the information acquired in the previous zone, and the ground radio sets the AGC to prepare for communication from outside the zone (operation A1).

[0022] Next, when the on-board radio confirms communication from the wayside radio in the new zone, it responds in synchronization with this by sending the ID of its own train, etc. (Action A2). The wayside side can use any wayside radio to receive this response.

[0023] Next, when the ground equipment recognizes the presence of a train, it assigns the train and requests train information (operation A3). In response to this, the on-board equipment creates a report on the position, speed, etc. of the train itself, and sends it back. Then, distance measurement communication is performed between the radio sets, and accurate position information of the train is obtained (operation A4).

[0024] The ground equipment creates and sends out train control commands based on the acquired information on the train's position, speed, etc. Thereafter, the ground radio sets the AGC circuit so that it tracks the train's position. The on-board radio also sets the AGC based on the information from the ground equipment and the distance measurement information (operation A5). Next, the above-mentioned "Action A4" and "Action A5" are repeatedly performed until the zone is passed.

[0025] Then, when the zone boundary is reached, the process returns to "action A1" for sending a data frame for synchronization. By repeating such an operation, the ground devices SC1, SC2, ..., SCn are switched in sequence.

[0026] Fig. 3 shows an example of the configuration of the on-board radios 16a and 16b used in the CBTC system shown in Fig. 1, and is a block diagram of a superheterodyne radio. A signal radio wave is input from an antenna to the LNA / BPF 21. The input weak signal radio wave is amplified by an LNA (low noise amplifier), and a signal in a specific frequency range is passed by a BPF (band pass filter), and the signal is output to a variable gain circuit 22. The gain of this variable gain circuit 22 is set by the output of an automatic gain control circuit (AGC circuit) 23.

[0027] The variable gain circuit 22 has the functions of an amplifier (AMP) that amplifies an input signal or an attenuator (ATT) that attenuates an input signal, and a detector (Power Det) that detects the received power. In addition, the automatic gain control circuit 23 is set with parameters according to the level of the target signal and the level of the interference wave predicted based on the distance to the radio device performing communication and the environmental information of the current location. The environmental information includes, for example, information identifying whether the location is inside a station, in an urban area, in the suburbs, in a forest, on a bridge, or in a tunnel, and the level of the interference signal corresponding to each environment is stored in a database in the on-board devices 15a and 15b mounted on the train 11.

[0028] The output signal of the variable gain circuit 22 is input to a mixer 24. A pulse signal of a predetermined frequency is input to the mixer 24 from a PLL circuit 25, and the mixer 24 multiplies the two signals and outputs signal voltages of the frequency components of their sum and difference to a filter 26. The filter 26 removes interference waves from these signal voltages and outputs them to a variable gain circuit 27. The gain of the variable gain circuit 27 is set by the output of an automatic gain control circuit (AGC circuit) 28.

[0029] The variable gain circuit 27 has the functions of an amplifier (AMP) that amplifies the input signal or an attenuator (ATT) that attenuates the input signal, and a detector (Power Det) that detects the received power. In addition, a parameter is set in the automatic gain control circuit 28 to adjust the target signal to a level suitable for demodulation.

[0030] The output of the variable gain circuit 27 is input to a quadrature modulator 29. A pulse signal of a predetermined frequency is input to the quadrature modulator 29 from a PLL circuit 30. The quadrature modulator 29 performs modulation by modulating two carriers (sine wave and cosine wave) that have the same frequency but a phase difference of 90 degrees, and then performing vector synthesis. The modulated signal output from the quadrature modulator 29 is input to a demodulator 31 where it is demodulated, and is also input to a distance measurement circuit 32 where it is used to measure the distance between the ground radio and the on-board radio.

[0031] Fig. 4 is a block diagram of a direct conversion radio, showing another example of the configuration of the on-board radios 16a, 16b used in the CBTC system shown in Fig. 1. A signal radio wave is input from an antenna to an LNA / BPF 41. The input weak signal radio wave is amplified by an LNA (low noise amplifier), and a signal in a specific frequency range is passed by a BPF (band pass filter), and the signal is output to a variable gain circuit 42. The gain of this variable gain circuit 42 is set by the output of an automatic gain control circuit (AGC circuit) 43.

[0032] The variable gain circuit 42 has the functions of an amplifier (AMP) that amplifies an input signal or an attenuator (ATT) that attenuates an input signal, and a detector (Power Det) that detects the received power. In addition, the automatic gain control circuit 43 is set with parameters according to the level of the target signal and the level of the interference wave predicted based on the distance to the radio device performing communication and the environmental information of the current location. The environmental information includes, for example, information identifying whether the location is inside a station, in an urban area, in the suburbs, in a forest, on a bridge, or in a tunnel, and the level of the interference signal corresponding to each environment is stored in a database in the on-board devices 15a and 15b mounted on the train 11.

[0033] The output of the variable gain circuit 42 is input to a quadrature modulator 44. A pulse signal of a predetermined frequency is input to the quadrature modulator 44 from a PLL circuit 45. The quadrature modulator 44 multiplies the two signals and outputs the signal voltage of the frequency components of the sum and difference of the multiplied signals to a filter 46. The filter 46 removes interference waves from the signal voltage and outputs the signal to a variable gain circuit 47. The gain of the variable gain circuit 47 is set by the output of an automatic gain control circuit (AGC circuit) 48. A parameter is set in the automatic gain control circuit 48 to adjust the target signal to a level suitable for demodulation. The output of the variable gain circuit 47 is input to a demodulator 49 for demodulation, and is also input to a distance measurement circuit 50 for use in measuring the distance between the ground radio and the on-board radio.

[0034] Fig. 5 shows an example of the operation of the AGC circuits 23, 43 in the on-board radios shown in Fig. 3 and Fig. 4, and is a waveform diagram of an actual radio wave acquired by the on-board radio 16a or 16b. Fig. 5(a) is a diagram of the entire waveform, and Fig. 5(b) is an enlarged waveform diagram between times T1 and T2 in Fig. 5(a). During period t1 (input signal not yet detected), even a small signal may possibly be the target signal, so the circuit operates to amplify with maximum gain.

[0035] When the target signal is received, the circuit amplifies it at maximum gain during period t1, so that during period t2 the received signal becomes too large, saturating the circuit and making demodulation difficult. In the next period t3, the gain is adjusted so that the target signal is at a level suitable for demodulation. Because the waveform is still saturated, demodulation is difficult, but over time the signal gradually converges to a level that allows demodulation. In period t4 after a predetermined time has elapsed, the gain is lowered to a level suitable for demodulation, the gain adjustment is completed, and demodulation begins.

[0036] The automatic gain control circuit cannot demodulate when reception begins in a saturated state. Also, if gain adjustment takes a long time, demodulated data will be lost. Furthermore, if there is interfering noise (interference wave), saturation due to the noise will occur, and only that part cannot be demodulated. For this reason, it is necessary to consider a margin for noise, but as described above, by predicting the level of the target signal and the level of the interference wave and setting the parameters, the gain in the state of period t1 can be reduced to a gain level close to that of period t4, so that a demodulatable level can be reached in a short time.

[0037] It is advisable to not only store noise (interference signal) data in a database, but also to acquire it while the train 11 is running. By feeding back noise level data from data acquired while the train is running, it becomes possible to perform AGC operation more suited to the situation, improving accuracy. At this time, the noise can be recorded in conjunction with position information, and can be used the next time the train runs or transmitted to subsequent trains, allowing it to be reflected in the CBTC system.

[0038] Fig. 6 is a flow chart showing a procedure for creating control data for the AGC circuits 23, 43 in the on-board radios shown in Fig. 3 and Fig. 4. First, distance measurement is performed by the distance measuring devices mounted on the on-board devices 15a, 15b of the train 11, or location information of the current location is obtained by GPS (step S1).

[0039] Next, the distance between the on-board radio and the ground radio that communicate with each other and the environmental information of the current location are acquired (step S2). Here, the distance between the on-board radio and the ground radio that communicate with each other is information on the distance from the on-board radio to the closest ground radio due to the running of the train.

[0040] Next, the target signal level and the interference wave level are predicted based on the acquired distance and environmental information (step S3). The target signal level is predicted based on the distance from the on-board radio to the ground radio that is closer due to the running train and the train speed. The interference signal level is predicted based on the environmental information.

[0041] Then, based on the prediction result, parameters are set in the automatic gain control circuit 23 (or 43) (step S4). The parameters of the automatic gain control circuit 23 (or 43) are set by acquiring the received power within the bandpass filter band of the LNA / BPF 21 (or 41), acquiring the received power of the frequency band of the target signal, and adjusting the gain of the automatic gain control circuit 23 (or 43) based on the acquired received power value and the control parameter value so that the target signal is at a level suitable for demodulating the target signal.

[0042] Fig. 7 is a flow chart showing the procedure of AGC during communication between a ground radio and an on-board radio. First, the control parameters of AGC are set according to the procedure shown in Fig. 6 (step S11). Next, the received power within the BPF band of the LNA / BPF 21 (or 41) is obtained (step S12). Next, the received power of the frequency band of the target signal is acquired (step S13).

[0043] Next, the gain of the automatic gain control circuit is adjusted based on the received power value acquired in steps S12 and S13 and the control parameters (step S14). Thereafter, it is determined whether or not the reception has ended (step S15), and the operations of steps S12 to S14 are repeated until it is determined that the reception has ended.

[0044] As described above, according to the present invention, by combining distance / direction and topographical information to the ground radio, interference wave level data corresponding to the position of the on-board radio on the route, and environmental information at that location and the traveling speed, it is possible to make highly accurate predictions of the target signal level and the interference signal level, and provide setting values ​​based on this to the AGC circuit.

[0045] In this way, since the level of the target signal and the level characteristics of the interference wave are known in advance, reception can be started from gain conditions close to optimal, and AGC adjustment can be completed in a short time. This reduces false positives / misses in frame synchronization, improving communication stability. Furthermore, in an environment with good conditions, it is also possible to increase the speed and efficiency of communication by shortening the frame length used for synchronization.

[0046] Furthermore, because ground radios transmit radio signals according to a time schedule, the on-board radio can determine the location of the next ground radio with which to communicate by combining the time schedule with the location data of the ground radio. In addition, since the distance to the ground radio is obtained by radio ranging during wireless communication, it is possible to know where on the route the vehicle is traveling.

[0047] By combining this information with interference wave level data according to the position on the line, environmental information (inside stations, urban areas, suburban areas, forests, on bridges, inside tunnels, etc.) and running speed, it is possible to make highly accurate predictions of the levels of the target signal and the interference signal, and by providing a setting value based on this to the AGC circuit, it is possible to complete the AGC circuit adjustment operation in a short period of time.

[0048] As described above, according to the present invention, it is possible to obtain a train wireless communication system that can reduce the time required for gain adjustment and achieve stable communication over a wide range of signal levels. This allows smooth AGC adjustment, making communication faster, more stable, more efficient, and more optimized. In addition, by optimizing the reception operation of the radio, it is possible to increase the interval between terrestrial radio units, making it possible to reduce the number of terrestrial radio units in suburban areas.

[0049] The circuit configurations, control procedures, etc. described in the above embodiments are merely schematic illustrations to enable the present invention to be understood and implemented. Therefore, the present invention is not limited to the described embodiments, and may be modified in various forms without departing from the scope of the technical ideas set forth in the claims. [Explanation of symbols]

[0050] 10...on-board equipment, 11...train, 11a...leading car, 11b...rearmost car, 12...track, 14a, 14b...vehicle cab, 15a, 15b...on-board equipment, 16a, 16b...radio (on-board radio), 21, 41...LNA / BPF, 22, 42...gain variable circuit, 23, 43...automatic gain control circuit (AGC circuit), 24...mixer, 25, 45...PLL circuit, 26, 46... Filter, 27, 47... variable gain circuit, 28, 48... automatic gain control circuit (AGC circuit), 29, 44... quadrature modulator, 30... PLL circuit, 31, 49... demodulator, 32, 50... ranging circuit, 100... ground equipment, 110... traffic control device, NW... network, SC1 to SCn... ground equipment, TR11, TR12, TR13, TR14, TR21, TR22... ground radio

Claims

1. A system for communication between ground-based radios installed along the line and on-board radios installed on trains running on the line, Obtaining environmental information according to the train's position on the route in advance; Identifying the current position of the train on the route, Based on the distance between the on-board radio and the ground radio that communicate, and on environmental information according to the train's position, the levels of the target signal and the interference signal are predicted. A train radio communication system that sets parameters of an automatic gain control circuit based on the prediction results.

2. 2. The train wireless communication system according to claim 1, wherein the environmental information includes information for identifying whether the environment is inside a station, in an urban area, in a suburban area, in a forest, on a bridge, or inside a tunnel, and an interference signal level corresponding to each environment is stored in a database installed in the train.

3. 2. The train wireless communication system according to claim 1, wherein the current position of the train on the line is identified by performing distance measurement using a distance measuring device mounted on the train, or by acquiring position information using a GPS.

4. 2. The train wireless communication system according to claim 1, wherein the distance between the on-board wireless device and the ground wireless device performing said communication is information on the distance from the on-board wireless device to the ground wireless device that is closest to the on-board wireless device due to the running of the train.

5. The train wireless communication system according to claim 1 , wherein data on the level of the interference signal is fed back from data acquired while the train is running.

6. 2. The train wireless communication system according to claim 1, wherein the prediction of the level of the target signal is performed based on a distance from an on-board wireless device to a ground wireless device that is closer to the on-board wireless device due to the movement of the train and on the speed of the train, and the prediction of the level of the interference signal is performed based on the environmental information.

7. 2. The train wireless communication system according to claim 1, wherein the parameter setting of the automatic gain control circuit involves obtaining a received power in a bandpass filter, obtaining a received power in a frequency band of a target signal, and adjusting a gain of the automatic gain control circuit based on the obtained received power value and a control parameter value so that the target signal is at a level suitable for demodulation.

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