Abstract:
A railway communication system ( 10 ) includes a transmitter ( 12 ) receiving an input and producing a communication signal ( 18 ). The communication signal ( 18 ) includes at least two different portions ( 20,22 ) for separately encoding respective indications ( 38,40 ) of the input. The system also includes a receiver ( 14 ) coupled to a controlled device, the receiver ( 14 ) extracting at least one of the respective indications ( 38,40 ) from the communication signal ( 18 ). The receiver controls the device responsive to the at least one extracted indications ( 38,40 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of U.S. application Ser. No. 12/848,513 filed 2 Aug. 2010, now U.S. Pat. No. 8,112,189 which is a Divisional of U.S. application Ser. No. 10/914,886 filed 10 Aug. 2004, now U.S. Pat. No. 7,783,397 which application claims benefit of the 22 Dec. 2003 filing date of U.S. Provisional Application No. 60/531,796, and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of locomotives, and more particularly to a system for providing redundant communication paths in railroad communication equipment. 
     Electronic communication equipment is widely used in railroad environments for controlling railway assets, such as locomotives operating in a railroad system. For example, it is known to remotely control locomotives in a switchyard using remote radio transmitting devices controlled by rail yard personnel. Such systems may include an operator control unit (OCU) or control tower unit in remote communication with a locomotive control unit (LCU) on board a controlled locomotive. The LCU may direct the locomotive to move and stop according to transmitted commands. Integrity of the communication path between a remotely controlled locomotive and a remote controller is critical to safe remote control operations. A margin of safety may be provided by incorporating redundancy in a remote control system, such as by using redundant hardware, software, and radio messaging. However, a federally allocated radio spectrum bandwidth for locomotive remote control communications may not have sufficient bandwidth to support additional content for providing radio messaging redundancy. Furthermore, portability issues and relatively low power operating requirements may limit incorporating additional hardware and software to provide redundancy. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, a communication system of the present invention comprises a transmitter comprising a first and a second transmitter processor, each transmitter processor separately receiving independent inputs responsive to operator control of an actuator, the transmitter processors operating together producing a communication signal comprising first and second different data areas, each data area separately encoding indications of the independent inputs, wherein each processor operates independently to encode the respective first and second data areas of the communication signal responsive to the independent inputs; the communications signal transmitted from the at least two different transmitters over a free-space communications link; a receiver for receiving the communications signal and comprising at least two receiver processors, each receiver processor coupled to a respective and independently controlled device, a first one of the receiver processors extracting one of the respective indications from the first data area and controlling a first device responsive thereto and a second one of the receiver processors separately extracting one of the respective indications from the second data area and controlling a second device responsive thereto; and the first and the second data areas, the first and the second transmitter processors and the first and the second devices comprising independent parallel data paths from the communications link. 
     In another embodiment, a communication system utilizing multiple processors for encoding both media access information and application information into a single message data stream, embodies a method of the present invention that provides redundancy for a safety-critical function. The method comprises: using a first of the multiple processors but not a second of the processors to encode first safety critical data into the message wherein the first safety critical data is encoded within the media access information, the first safety critical information generated by a first switch controlled by an operator control unit; using the second of the multiple processors but not the first of the processors to encode second safety critical data redundant with the first safety critical data into the message, wherein the second safety critical data is encoded within the application information, the second safety critical information generated by a second switch controlled by the operator control unit, the first switch parallel with the second switch, the first and the second switches simultaneously operable responsive to operation of the operator control unit; transmitting the message over an over-the-air communications link; receiving the first safety critical information at a first receiver; receiving the second safety critical information at a second receiver; a first device responsive to the first receiver responding to the first safety critical information; a second device responsive to the second receiver responding to the second safety critical information; and the first and the second receivers and the first and the second devices comprising two independent parallel data paths from the communications link. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more apparent from the following description in view of the sole FIGURE that shows: 
       The FIGURE is a block diagram of a system for providing redundant communication paths in locomotive remote control transceivers. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In many railway communication systems, an ability to provide redundant information is desired and may, in some cases, be required by regulating agencies to ensure reliable and safe operation of the railway assets served by the communication system. While information redundancy may be provided for all information that may be transmitted among transceivers in a railway communication system, it is particularly desired to provide redundancy for certain safety-critical functions in a locomotive remote control system to prevent accidents that might occur should a certain safety critical piece of information fail to be transmitted and/or received. Such functions may include: ensuring that an operator initiated emergency command is delivered to a locomotive; ensuring that control messages are received at a desired periodic rate; ensuring that a locomotive being remotely controlled only responds to a single designated remote controller; and ensuring that data errors cannot cause erroneous operation. Such functions may need more than a single communication path through the remote control system. The inventors have innovatively realized that command redundancy may be incorporated into a railway communication system, such as a locomotive remote control system, with minimal modification by sending a command in two different locations of a radio message packet, such as by embedding the redundant messages in two different layers of the radio packet. To add further redundant capability, the two different locations may be processed in two different processors of each transceiver. These two different processors may include existing processors used to process communications or application information, and/or they may include a processor dedicated to the safety-critical function. Accordingly, separate, redundant communication paths may be established between transceivers in a locomotive remote control system to provide continuous communication capability should one communication path fail. Advantageously, such redundant communication paths may insure that information, such as safety-critical commands, are transmitted without requiring redundant transmission of an entire message packet, which may be difficult to achieve in narrow bandwidth applications. In addition, redundant communication paths within each of the transceivers provides a margin of safety for ensuring that message packets are transmitted and received to prevent, for example, inadvertent stopping of a locomotive expecting to receive radio packets at a desired repetition rate. In another aspect, redundant confirmation of received control commands are provided to ensure the locomotive only responds to an authorized remote controller. Furthermore, received commands may be redundantly checked to ensure that data errors do not cause incorrect operation. 
     The sole FIGURE shows a block diagram of a railroad communication system  10  for providing redundant communication paths in locomotive remote control transceivers. In an embodiment of the invention, the system  10  may include a portable OCU  12  transceiver in communication with an LCU  14  transceiver located onboard a locomotive. Two-way communication between the OCU  12  and LCU  14  may be provided over communication link  16 . The OCU  12  and LCU  14  may communicate using packetized radio messages. For example, a radio message packet  18  transmitted between the OCU  12  and LCU  14  may include an application layer  20  encapsulated within a media access layer  22 . The application layer may include control information responsive to switch settings on the OCU  12 , and the media access layer  22  may include transmission information, such as transceiver identification data. In an aspect of the invention, each transceiver  12 ,  14  may include two processors for encoding transmitted message packets  18  and for decoding received radio message packets  18 . One of the two processors may be configured to process application layer information, and the other processor may be configured to process media access layer information. For example, the OCU  12  may include an application processor  26  for encoding OCU actuator conditions indicative of desired remote control commands, and a media access processor  24  for generating the media access layer information. The LCU  14  may include a media access processor  28  for stripping the media access layer information from a received message packet  18  and a LCU processor  30  for decoding received OCU actuator conditions in the application layer information. 
     In an embodiment of the invention, two different processors may be used to independently detect condition of an actuator, such as an emergency actuator  32 . The emergency actuator  32  may be coupled to include two redundant switches  34 ,  36 , each switch coupled to a respective processor. For example, application processor  26  may be coupled to switch  36 , and media access processor  24  may be coupled to switch  34 . In an aspect of the invention, the media access processor  24  may include an input line  35  responsive to the position of the switch  34 . Each processor  26 ,  24  may encode a detected switch position  38  in a different portion, or different layer, of the transmitted packet  18  without impacting or depending upon the operation of the other processor  24 ,  26 . For example, application processor  26  may encode the detected switch position  38  for switch  34  as a single bit in the application layer  20  of a transmitted packet  18 , while media access processor  24  may encode the detected switch position  40  for switch  36  as a single bit in the media access layer  22  of a transmitted packet  18 . A physical layer microprocessor  42  may assemble the application layer  20  and the media access layer  22  into the packet  18  for transmission to the LCU  14 . Accordingly, the packet  18  may be encoded with redundant control information for an actuator condition, such as the emergency switch  32  setting, for incorporation in the packet  18 . Advantageously, actuator condition information, such as a single bit set responsive to a two-position switch, may be provided for incorporation in the packet  18  along redundant paths. If one of the switches  34 ,  36  or one of the processors  24 ,  26  should fail, the other switch  36 ,  34  or other processor  26 ,  24  in the redundant path may still provide the appropriate information for incorporation into at least one layer of the packet  18  for transmission to the LCU  14 . 
     The LCU  14  may include at least two processors for separately extracting the redundant control information from a received packet  18  and at least two separate control paths for providing control commands to a locomotive responsive to the redundant control information encoded in the packet  18 . For example, in one control path, the media access processor  28  of the LCU  14  may be configured to extract the redundant control information from the media access  22  layer of the packet  18  and to provide an output  44  to control an actuator responsive to the extracted control information for controlling the locomotive, such as by opening an emergency control valve  46 ,  50  in response to receiving an emergency switch  32  activation indication in the control information. In an aspect of the invention, a dedicated or special check processor  48  may be provided and coupled to the media access processor  28  to extract the redundant control information from the media access  22  layer or to forward a control signal generated by the media access processor  28  to an appropriate actuator. 
     In a parallel control path, the LCU processor  30  may be configured to extract the redundant control information from the application layer  20  of the packet  18  and control the locomotive in response to the extracted control information. In an aspect of the invention, redundant actuators, such as redundant emergency control valves  46 ,  50  may be provided in the respective control paths to achieve redundant, independent control responsive to separate control signals provided via separate control paths. Advantageously, the control information extracted from a received packet may be provided along redundant, independent paths to provide a safety margin should a component fail in any one of the control paths. If one of the actuators, such as one of the emergency control valves  46 ,  50 , or one of the processors  28 ,  30  should fail, the other valve  50 ,  46 , or other processor  30 ,  28 , in the redundant path may still provide the received control information for controlling the locomotive. 
     In yet another embodiment, redundant control paths as described above may be used to detect and respond to a loss of communication between the OCU  12  and LCU  14 . Typically, the LCU  14  expects to receive a packet  18  from a controlling OCU  12  at a predetermined repetitive rate. For example, the LCU  14  may be configured to expect a subsequent packet  18  within five seconds of receiving a previous packet  18 . If the LCU  14  does not detect a packet  18  within a predetermined period of time after a prior received packet  18 , the LCU may determine that a loss of communication has occurred and may, as a safety measure, place the locomotive in an emergency stop condition. To avoid an unintentional loss of communication, independent redundant paths to two independent processors, such as the LCU processor  30  and check control processor  48 , may be provided to ensure that communications have indeed been lost and that a detected loss of communication is not the result of a failure within the LCU  14  or missing data in the packet  18 , potentially rendering the packet  18  unidentifiable. 
     A typical packet  18  includes radio identification information, such as radio source identifiers  52 ,  54  and radio destination identifiers  56 ,  58 , encoded, for example, in the header of both the media access layer  22  and the application layer  20 . Radio identification information from the media access layer  22  may be passed through the media access processor  28  to the check processor  48  to verify presence of expected header information, such as a radio source identifier  52  in the media access layer  22 . In an aspect of the invention, the verification process performed in the check processor  48  may be performed in the media access processor  28 . To provide redundancy, the media access processor  28  may also forward the radio identification information from the application layer  22  along an independent path to the LCU processor  30 . Accordingly, presence of expected header information, such as a radio source identifier  54  in the media access layer  20  may be independently verified in each processor  48 ,  28 . By innovatively providing redundant processors and redundant pathways in the LCU  30 , loss of one set of header information, for example, one of the radio source identifiers  52 ,  54 , or one of the processors  30 ,  48  (which might otherwise result in a failure of the LCU to identify a valid packet  18 ) may be verified to prevent the LCU from inadvertently ignoring an otherwise valid packet  18 . The other processor  48 ,  30  in the redundant path may still be able to identify a received packet as a valid packet and response to encoded command appropriately instead of indicating a lost communication condition. 
     In a further aspect, the media access processor  28  and LCU  14  processor  30  may act independently to verify that a received packet is intended for the receiving LCU  14 . For example, the media access processor  28  may be configured to check the radio source identifier  52  and the radio destination identifier  56  in the media access layer  22  to verify that the packet  18  is intended for the receiving LCU  14  and that a radio source, or OCU  12 , generating the packet  18  is recognized as a controller for the LCU  14 . In addition, independent LCU processor  30  may be configured to check the radio source identifier  54  and the radio destination identifier  58  in the application layer  20  to verify that the packet  18  is intended for the receiving LCU  14  and that the radio source that generated the packet  18  is recognized as a controller for the LCU  14 . Accordingly, redundant checking of a received packet  18  may be provided to determine if the received packet is valid for controlling the receiving LCU  14 . For example, if the results of checking the radio source identifiers  52 ,  54  and radio destination identifiers  56 , 58  in the respective processors  30 ,  48  don&#39;t match, the received packet may be ignored by the LCU  14 . 
     While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein.