Information transmission system and information transmission method for rail transport

Abstract

An economical information transmission system for rail transport includes a transmitter having a known transmission power for communication between a track section and a rail vehicle. A receiver has at least one first adjustable receive level threshold, with which a maximum distance between the transmitter and the receiver can be defined in a particular application, within which the receiver is able to receive with respect to the transmitter. An information transmission method is also provided.

Claims

1. An information transmission system for rail transport using communication between a track and a rail vehicle, the system comprising: a transmitter having a known transmit power; and a receiver having at least one first adjustable receive level threshold defining a maximum distance between said transmitter and said receiver within which said receiver can receive with respect to said transmitter in a respective application; a second receive level threshold being higher than said at least one first adjustable receive level threshold; said receiver producing a warning signal if said at least one first adjustable receive level threshold is exceeded and generating a train approaching signal if said second receive level threshold is exceeded.

2. The information transmission system according to claim 1, wherein a minimum distance between said transmitter and said receiver ensuring reliable reception is predefined by determining the maximum distance using a relation:
dmax=dmin*2{circumflex over ()}(A/6 dB), where A denotes a maximum likely receive level attenuation in dB in addition to free space loss over the minimum distance.

3. The information transmission system according to claim 1, wherein said transmitter is positioned on the track and said receiver is mounted on the rail vehicle.

4. The information transmission system according to claim 3, which further comprises at least one of a route or destination indicating device disposed on the rail vehicle and connected to said receiver.

5. The information transmission system according to claim 1, wherein said receiver is disposed on the track and said transmitter is disposed on the rail vehicle.

6. The information transmission system according to claim 5, which further comprises a control device for at least one fixed rail transport installation, said receiver being disposed adjacent said control device.

7. The information transmission system according to claim 6, wherein the rail transport installation is a signaling installation, a switch or a grade crossing.

8. The information transmission system according to claim 1, wherein at least one of said transmitter or said receiver has an antenna with a directional characteristic dependent on a direction of travel of the rail vehicle.

9. The information transmission system according to claim 1, wherein said receiver produces a train receding signal if a receive level threshold midway between said at least one first adjustable receive level threshold and said second receive level threshold is undershot for a longer period of time than a predefined train receding detection period.

10. The information transmission system according to claim 9, wherein said receiver ignores receive signals from said transmitter during a train receding period beginning with a start of the train receding detection period and lasting longer than the train receding detection period.

11. The information transmission system according to claim 9, which further comprises: a transmit device associated with said receiver, said transmit device receiving the train receding signal of said receiver and transmitting an identifier signal being characteristic of the rail transport installation just left; and a receive device associated with said transmitter, said receive device using the received identifier signal to cause said transmitter to produce signals having a marking being interpreted by said receiver as an ignore command.

12. An information transmission method for rail transport using communication between a track and a rail vehicle, the method comprising the following steps: providing a transmitter having a known transmit power and a receiver having at least one first adjustable receive level threshold; and adjusting the at least one first adjustable receive level threshold in a particular application to define a maximum distance between the transmitter and the receiver within which the receiver is able to receive with respect to the transmitter; and generating a warning signal if the at least one first adjustable receive level threshold is exceeded, and generating a train approaching signal if a second receive level threshold being higher than the at least one first adjustable receive level threshold is exceeded.

13. The information transmission method according to claim 12, which further comprises: predefining a minimum distance between the transmitter and the receiver ensuring reliable reception; and calculating the maximum distance using a relation:
dmax=dmin*2{circumflex over ()}(As/6 dB), where As is a maximum likely receive level attenuation in dB in addition to free space loss over the minimum distance.

14. The information transmission method according to claim 12, wherein the transmitter is on the track and the receiver is on the rail vehicle.

15. The information transmission method according to claim 14, which further comprises using the receiver to transmit information to at least one of a route or destination indicating device on the rail vehicle.

16. The information transmission method according to claim 12, wherein the receiver is on the track and the transmitter is on the rail vehicle.

17. The information transmission method according to claim 16, which further comprises using the receiver to transmit information to an adjacent control device for at least one adjacent rail transport installation.

18. The information transmission method according to claim 17, which further comprises providing a signaling installation, a switch or a grade crossing as the rail transport installation.

19. The information transmission method according to claim 12, which further comprises providing at least one of the transmitter or the receiver with an antenna having a directional characteristic dependent on a direction of travel of the rail vehicle.

20. The information transmission method according to claim 12, which further comprises generating a train receding signal if a receive level threshold midway between the at least one first adjustable receive level threshold and the second receive level threshold is undershot for a longer period of time than a predefined train receding detection period.

21. The information transmission method according to claim 20, which further comprises disregarding signals from the transmitter during a train receding period beginning when the train receding detection period has elapsed and lasting longer than the train receding detection period.

22. The information transmission method according to claim 20, which further comprises: using a transmit device associated with the receiver, in response to the train receding signal of the receiver, to transmit an identifier signal being characteristic of a rail transport installation just being left; and using a receive device associated with the transmitter to cause the transmitter, in response to the received identifier signal, to emit signals having a marking being interpreted by the receiver as ignore commands.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows a graph illustrating the basic mode of operation of the information transmission system/method according to the invention,

(2) FIG. 2 shows an exemplary embodiment of the information transmission system/method according to the invention in the case of an automatic light signal system at a grade crossing, and

(3) FIG. 3 shows another graph illustrating the mode of operation of the exemplary embodiment.

DESCRIPTION OF THE INVENTION

(4) In the graph according to FIG. 1, the measurable power P of a transmitter of an information transmission system is plotted against the distance d from the transmitter. It is assumed that the transmitter is located at d=0. Here the maximum power is measurable which, in the context of the information transmission system, is predefined as known quantity Pb. Also pre-selected is a minimum distance dmin within which information can be transmitted from the transmitter to the receiver taking all likely level attenuations into account. The level attenuations to be taken into account are the free space loss Af over the minimum distance dmin and all the likely maximum receive level attenuations As over the minimum distance, such a weather effects, antenna contamination, aging of the transmission components, etc. This results in a minimum receive level threshold Pm according to the following relation:
Pm=PbAfAs

(5) So long as the receive level at the receiver is not lower than Pm, the receiver will be able to process received information.

(6) From the minimum distance dmin and the maximum likely receive level attenuations As, a maximum distance dmax can be calculated according to the approximation formula
dmax=dmin*2{circumflex over ()}(As/6 dB);

(7) this formula is only valid if it is assumed that, apart from the free space loss Af, no other level attenuations occur up to the maximum effective distance. The maximum distance dmax thus denotes the smallest required distance of the receiver from the transmitter so that information from the transmitter can be acquired by the receiver.

(8) The minimum distance dmin is therefore the distance over which information transmission operates reliably even allowing for all conceivable external influences. The maximum distance dmax is the distance over which receive levels above the receive level threshold Pm are likely.

(9) The above remarks indicate thatif it to be ensured that the receive threshold of the receiver is always exceeded and therefore that data received at a particular location is always processedthe transmitter and receiver at that location need only be spaced the minimum distance apart. If it is to be ensured that the level Pm is always undershot at a particular location, the transmitter and receiver must be spaced at least the maximum distance dmax apart.

(10) In a specific implementation of the information transmission system, a transmitter having a known transmit power Pb of 10 dBm was selected on the basis of the constraints and characteristics according to an IEEE standard and a minimum distance dmin of 2 m was predefined. A free space loss of 46.1 dB and a maximum likely receive level attenuation As produced a receive level threshold Pm of 56.1 dBm, resulting in a maximum distance of 20.2 m between transmitter and nearest receiver. If a transmitter is here used on a moving rail vehicle and the transmitter's antenna has a pronounced directional characteristic in the direction of travel, an upstream receiver can then be disposed relatively close before the distance of 20.2 m from a receiver without simultaneous influencing of both receivers being able to occur.

(11) Therefore, the smaller the maximum distance dmax, the more independently addressable the receivers that can be installed on a section of track. The maximum distance dmax can then be reduced by selecting the minimum distance dmin as small as possible and minimizing the likely receive level attenuations As.

(12) FIG. 2 shows a rail transport installation in the form of a grade crossing 1 having an automatic light signal system comprising two color light signals 2 and 3 between which a line 4 of a section of track (not shown in greater detail) crosses a road 5. The color light signals 2 and 3 are connected to a control device 6 of the automatic light signal system. Also connected to the control device 6 is a receiver 7a which, in the example shown, is part of a transceiver 7.

(13) As FIG. 2 also shows, a rail vehicle 10 equipped with a control unit 11 and moving in the direction the arrow 8 is approaching the light signal system. Connected to the control unit 11 is a transmitter 12a which is implemented by means of a transceiver 12.

(14) Prior to its approach to the light signal system, the rail vehicle 10 or rather its transmitter 12a cyclically transmits a data telegram containing information concerning the rail vehicle's identity. The rail vehicle 10 is not within range, i.e. the maximum distance dmax, of the receiver 7a of the transceiver 7, so that the color light signals 2 and 3 are on green.

(15) If the rail vehicle 10 comes within range of the receiver 7a of the transceiver 7, i.e. the distance of the rail vehicle 10 from the receiver 7a is less than the maximum distance dmax, the (first) receive level threshold Pm (cf. FIG. 1) is exceeded for the first time at time T1 (see FIG. 3); the control device 7 is acted on by the receiver 7a of the transceiver 7 and generates the information train approaching. The color light signals 2 and 3 remain on green.

(16) When the rail vehicle 10 is close enough to the light signal system that a second, higher receive level threshold Panr is exceeded, at this point in time T2 (cf. FIG. 3) a train approaching signal Sanr is generated which causes the control device 6, to switch the color light signals 2 and 3 to red.

(17) If the rail vehicle 10 is in the area of the automatic light signal system, it is continuously checked whether a receive level threshold Pabr midway between the receive level threshold Pm and the second receive level threshold Panr is undershot for a longer period than a predefined train receding detection period tabre. If this is the casein this example at time T3the color light signals 2 and 3 change to green.

(18) With the beginning of the train receding detection period tabre, a train receding period tabr is started and ensures that the receiver 7a of the transceiver 7 ignores the possibly still being received data telegrams of the transmitter 12a on the rail vehicle 10 which contain the rail vehicle's identity, so that the color light signals 2 and 3 remain set to green in the desired manner.

(19) The exemplary embodiment shown, comprising two transceivers 7 and 12, offers the possibility of incorporating the transmit device 7b of the transceiver 7 and the receive device 12b of the transceiver 12 in the transmission system by the transmit device 7b of the transceiver 7 receiving the train receding signal Sabr of the receiver 7a of said transceivers 7 and then generating an identifier signal. This signal is typical of the automatic light signal system just left and is transmitted to the receive device 12b of the transceiver 12. This means that the transmitter 12a of this transceiver is controlled such that it emits signals having a marking which is interpreted by the receiver 7a of the transceiver 7 as ignore commands. The color light signals 2 and 3 then remain on green.