Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0802—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection
  • H04B7/0805—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with single receiver and antenna switching
  • H04B7/0814—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with single receiver and antenna switching based on current reception conditions, e.g. switching to different antenna when signal level is below threshold
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B61—RAILWAYS
  • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
  • B61L15/00—Indicators provided on the vehicle or train for signalling purposes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B61—RAILWAYS
  • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
  • B61L15/00—Indicators provided on the vehicle or train for signalling purposes
  • B61L15/0018—Communication with or on the vehicle or train
  • B61L15/0027—Radio-based, e.g. using GSM-R
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
  • H04B7/0602—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using antenna switching
  • H04B7/0604—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using antenna switching with predefined switching scheme
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0802—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection
  • H04B7/0817—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with multiple receivers and antenna path selection
  • H04B7/082—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with multiple receivers and antenna path selection selecting best antenna path
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0882—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using post-detection diversity
  • H04B7/0885—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using post-detection diversity with combination

Definitions

• Distributed power railroad train operation supplies motive power and braking action from a lead locomotive (or lead unit) and one or more remote locomotives (or remote units) spaced apart from the lead unit in a train.
• a distributed power train comprises a lead locomotive at a head end of the train, a remote locomotive at an end of train (EOT) position and one or more mid-train locomotives disposed between the head end and the end of train.
• EOT end of train
• Distributed train operation may be preferable for long train consists to improve train handling and performance, and especially for trains operating over mountainous terrain.
• each lead and remote locomotive supplies motive power and braking action for the train.
• Motive and braking command messages are issued by an operator in the lead locomotive and supplied to the remote locomotives over a radio frequency communications system, (such as the prior art LOCOTROL® distributed power communications system, available from the General Electric Company of Schenectady, New York) comprising a radio frequency link (channel) and receiving and transmitting equipment at the lead and the remote units.
• the receiving remote locomotives respond to these commands to apply tractive effort or braking effort to the train, and advise the lead unit of the receipt and execution of the command.
• the lead unit also sends other messages to the remote units, including status request messages.
• the remote units respond by sending a status reply message back to the lead unit.
• the coupled locomotives function in unison via control signals transmitted over their connected MU (multiple unit) lines.
• One of the locomotives is designated as a controlling remote unit with respect to the distributed power communications system. Only the controlling remote unit is configured to receive commands transmitted by the lead unit and respond to the lead unit with appropriate reply messages.
• the air brake system comprises locomotive brakes in each locomotive (including the lead locomotive and all the remote locomotives) and car brakes at each railcar.
• the lead unit locomotive brakes are controlled by the locomotive operator in response to a position of a locomotive brake handle, and the rail car brakes are controlled in response to a position of an automatic brake handle.
• the locomotive brakes can also be controlled by the automatic brake handle.
• the automatic brake handle or controller controls a pressure in a fluid carrying brake pipe that extends the length of the train and is in fluid communication with a car brake system for applying or releasing car brakes at each railcar in response to a pressure change in the brake pipe.
• a control valve typically comprising a plurality of valves and interconnecting piping
• the fluid within the brake pipe conventionally comprises pressurized air.
• the control valve at each railcar senses the pressure drop and in response thereto supplies pressurized air from a local railcar reservoir to wheel brake cylinders that in turn draw brake shoes against railcar wheels.
• the railcar reservoir is recharged by air withdrawn from the brake pipe during non-braking operational intervals.
• a brake release is also commanded by the lead operator by controlling the automatic brake handle to effect a pressure increase in the brake pipe.
• the pressure increase is sensed at the railcars and in response the brake shoes are released from the railcar wheels.
• the lead unit commands remote unit brake applications and releases by sending an appropriate signal to the remote units via the communications channel.
• brake applications and releases are thus more rapidly affected along the length of the train due to the participation of both the lead unit and the remote units.
• a brake command or brake release can also be commanded by the lead or the remote locomotives.
• the railcar brakes can be applied in two modes, i.e., a service brake application or an emergency brake application.
• a service brake application braking forces are applied to the railcar to slow or bring the train to a stop at a forward location along the track.
• the brake pipe pressure is slowly reduced and the brakes are applied gradually in response thereto.
• the operator controls the rate at which the pressure is reduced by operation of the automatic brake control handle.
• a penalty brake application is one form of a service brake application in which the brake pipe is reduced to zero pressure, but the evacuation occurs at a predetermined rate, unlike an emergency brake application as described below, and the railcars do not vent the brake pipe during the penalty brake application.
• An emergency brake application commands an immediate application of the railcar brakes through an immediate evacuation or venting of the brake pipe at the lead unit (and the remote units of a distributed power train).
• a railcar senses a predetermined pressure reduction rate indicative of an emergency brake application, the railcar also vents the brake pipe to accelerate propagation of brake pipe evacuation along the train.
• the emergency brake application does not occur instantaneously along the entire length of the brake pipe. Thus the braking forces are not uniformly applied at each railcar to stop the train.
• braking is accomplished by venting the brake pipe at both the lead and remote locomotives, thus accelerating the brake pipe venting and application of the brakes at each railcar, especially for those railcars near the end of the train.
• brake pipe venting at only the lead unit in a conventional train requires propagation of the brake pipe pressure reduction along the length of the train, thus slowing brake applications at railcars distant from the lead unit.
• a brake application e.g., a service or an emergency brake application
• each remote unit also vents the brake pipe.
• braking action at the remote locomotives follows the braking action of the lead unit in response to signals transmitted by the communications system.
• a brake release initiated at the lead unit is also communicated over the radio frequency link to the remote units so that the brake pipe is recharged to a nominal pressure from all locomotives, reducing the brake pipe recharge time.
• the radio frequency communication system sends an emergency brake signal to each of the remote locomotives over the radio frequency link. In response, the remote locomotives evacuate the brake pipe.
• This technique permits faster execution of the emergency brake application since the brake pipe is evacuated from all of the locomotives, rather than from only the lead locomotive as in a conventional train.
• FIGS 1 and 2 schematically illustrate an exemplary distributed power train
• Figures 1 and 2 is that the issuance of commands and messages from the lead unit 14 of Figure 1 is replaced by the control tower 16 of Figure 2 and certain interlocks of the system of Figure 1 are eliminated.
• the control tower 16 communicates with the lead unit 14, which in turn is linked to the remote units 12A-12C.
• a communications channel of the communications system comprises a single half-duplex communications channel having a three kHz bandwidth, where the messages and commands comprise a serial binary data stream encoded using frequency shift keying modulation on one of four available carrier frequencies.
• the various bit positions convey information regarding the type of transmission (e.g., message, command, alarm), the substantive message, command or alarm, the address of the receiving unit, the address of the sending unit, conventional start and stop bits and error detection/correction bits.
• the details of the messages and commands provided by the system and the transmission format of individual messages and commands are discussed in detail in commonly owned US patent number 4,582,280, which is hereby incorporated by reference.
• the distributed power train 10 of Figures 1 and 2 further comprises a plurality of railcars 20 interposed between the remote units 12A/12B and between the remote unit 12C (of Figure 1).
• the arrangement of the locomotives 14 and 12A-12C and railcars 20 illustrated in Figures 1 and 2 is merely exemplary, as the present invention can be applied to other locomotive/railcar arrangements.
• the railcars 20 are provided with an air brake system (not shown in Figures 1 and 2) that applies the railcar air brakes in response to a pressure drop in a brake pipe 22, and releases the air brakes upon a pressure rise in the brake pipe 22.
• the brake pipe 22 runs the length of the train for conveying the air pressure changes specified by the individual air brake controls 24 in the lead unit 14 and the remote units 12 A, 12B and 12C.
• an off board repeater 26 is disposed within radio communication distance of the train 10 for relaying communications signals between the lead unit 14 and the remote units 12A, 12B and 12C.
• the lead unit 14 and the remote units 12A, 12B and 12C are provided with independent transceivers 28A and 28B operative with respective antennas 29A and 29B for receiving and transmitting communications signals over the communications channel.
• the off board repeater 26 and the control tower 16 are each provided with the transceiver 28 operative with the antenna 29 for receiving and transmitting communications signals over the communications channel.
• the lead unit transceiver 28 is associated with a lead station 30 for generating and issuing commands and messages from the lead unit 14 to the remote units 12A-12C, and receiving reply messages therefrom.
• Commands are generated in the lead station 30 in response to operator control of the motive power and braking controls within the lead unit 14, as described elsewhere herein or automatically as required.
• Each remote unit 12A-12C and the off board repeater 26 comprises a remote station 32 for processing, repeating and/or responding to transmissions from the lead unit 14 and for issuing reply messages and commands.
• the lead station 30 and the remote stations 32 are responsive to independent signals from both the transceivers 28A and 28B.
• the four primary types of radio transmissions carried by the communications system include: (1) link messages from the lead unit 14 to each of the remote units 12A-12C that "link" the lead unit 14 and the remote units 12A-12C, i.e., configure or set-up the communications system for use by the lead unit 14 and the remote units 12A-12C, (2) link reply messages that indicate reception and execution of the link message, (3) commands from the lead unit 14 that control one or more functions (e.g., application of motive power or braking) of one or more remote units 12A-12C and (4) status and alarm messages transmitted by the one or more remote units 12A-12C that update or provide the lead unit 14 with necessary operating information concerning the one or more remote units 12A-12C.
• link messages from the lead unit 14 to each of the remote units 12A-12C that "link" the lead unit 14 and the remote units 12A-12C i.e., configure or set-up the communications system for use by the lead unit 14 and the remote units 12A-12C
• link reply messages that indicate reception and execution of the link message
• Each message and command sent from the lead unit 14 is broadcast to all of the remote units 12A-12C and includes a lead unit identifier for use by the remote units 12A- 12C for determining that the sending lead unit is the lead unit of the same train. An affirmative determination causes the remote unit 12A-12C to execute the received command.
• Messages and alarms sent from one of the remote units 12A-12C also include the sending unit's address.
• the receiving unit i.e., the lead or another remote locomotive, can determine whether it was an intended recipient of the received transmission by checking the sending unit's identification in the message, and can respond accordingly.
• RF link and "RF communications” and similar terms describe a method of communicating between two links in a network.
• the communications link between nodes (locomotives) in the system in accordance with the present invention is not limited to radio or RF systems or the like and is meant to cover all techniques by which messages may be delivered from one node to another or to plural others, including without limitation, magnetic systems, acoustic systems, and optical systems.
• the system of the present invention is described in connection with an embodiment in which radio (RF) links are used between nodes and in which the various components are compatible with such links; however, this description is not intended to limit the invention to that particular embodiment.
• the communications system at the lead unit transmits to each remote unit a radio frequency (RF) message representing the command.
• RF radio frequency
• Such commands can include locomotive throttle or traction commands and air brake, dynamic brake and electric brake commands.
• the brake command is executed at each remote unit to accelerate command response at the railcars, since the remote units receive the radio frequency message before they sense the brake pipe pressure change. For example, if the operator commands a brake application, the brake pipe is vented at the lead unit and the pressure reduction propagates along the length of the train until reaching the end-of-train car. Depending on train length, several seconds may elapse before the pressure reduction reaches the last railcar.
• Venting the brake pipe at the lead and remote locomotives the latter in response to the RF message, accelerates the brake pipe venting and application of the brakes at each railcar, especially for the railcars near the end of the train.
• braking actions at the remote locomotives follow the braking actions of the lead unit in response to the RF signals transmitted by the communications system.
• a brake release initiated at the lead unit is also communicated over the radio frequency link to the remote units so that the brake pipe is recharged to its nominal pressure from all locomotives, reducing brake pipe recharge time.
• the communication system sends an emergency brake signal to each of the remote locomotives over the radio frequency link.
• the remote locomotives evacuate the brake pipe to provide faster execution of the emergency brake application since the brake pipe is evacuated from all of the locomotives, rather than from only the lead locomotive as in a conventional train.
• messages sent over the communications system permit the application of more even tractive forces to the railcars and improve braking performance as each locomotive can effect a brake application at the speed of the RF signal, rather than the slower speed at which the pneumatic brake pipe braking signal propagates along the train.
• each remote unit When the distributed power train is operating in an environment where each remote unit is expected to receive command messages sent by the lead unit, for example when the train is traveling along a relatively straight length of track with no proximate obstructions to a radio frequency signal, the communications system is operative in a normal mode. In this mode, no communications losses, interruptions or repeated messages (because the message did not reach its intended destination when first transmitted) are anticipated. Most messages issued in the normal mode are controlled according to a fixed priority message protocol, according to which each remote unit transmits a status message responsive to a lead-issued command message after a predetermined interval from transmission of the command. Thus each remote unit is assigned a time slot, measured from transmission of the lead unit command message, during which each remote unit transmits its message.
• FIG. 3 A timing diagram of Figure 3, where the system is described for a railroad train comprising a lead unit and four remote units, illustrates the concepts associated with the fixed priority message protocol for normal communications.
• the concepts described in conjunction with Figure 3 can be applied to a train comprising more or fewer than four remote locomotives.
• the lead unit transmits a command message (for example, a brake command, a traction command, a dynamic brake command, etc.) that is expected to be received by all remote locomotives in the distributed power train.
• a command message for example, a brake command, a traction command, a dynamic brake command, etc.
• each transceiver also referred to as a radio
• an exemplary command message length is 193 msec.
• the status message is intended for the lead locomotive so that the train operator is advised of the first remote unit's response to the command. Also note that each remote unit retransmits the command message with its status message to maximize the likelihood that the command is received by all remote locomotives.
• the turn- on time, message duration, etc. illustrated in Figure 3 are merely exemplary and can vary depending on the application and specifications of the components that comprise the communications system.
• the second remote locomotive repeats the command message and transmits its status message after a predetermined delay, for example 50 msec, from the end of the first remote's transmission.
• the command repeating and status transmitting process continues until all remote locomotives have repeated the command message and transmitted their respective status message.
• the lead unit When the lead unit transmits a command message, the lead unit will not know whether the message was received by all the remote units in the train until a remote status message is received from each remote unit (wherein the status messages indicates receipt and execution of the command message) or a status message is not received from one or more of the remote units (lack of a status message indicates the command message was not received).
• a remote status message indicates receipt and execution of the command message
• a status message indicates the command message was not received.
• the communications system to ensure that each remote unit receives the command messages, it is repeated by each remote unit.
• the lead unit retransmits the command message and awaits a reply status message from each remote unit in the train.
• One feature of the present invention increases the likelihood that all status messages are received at the lead unit, thus reducing the retransmit probability, without significantly impacting the overall transmission timing for the command and status messages.
• commands e.g., an emergency brake application
• certain commands are classified as high priority command messages and are transmitted according to a different priority protocol than the fixed priority protocol.
• Still other command messages e.g., a communications system check, operate according to other priority protocols that control transmission of these commands and the reply by the remote units.
• a line-of-sight communications link between the sending and the receiving units may be interrupted.
• commands and status messages may not be reliably received by the receiving unit, i.e., the lead locomotive for messages sent from a remote unit, and a remote locomotive for messages sent from the lead unit.
• the receiving unit i.e., the lead locomotive for messages sent from a remote unit
• a remote locomotive for messages sent from the lead unit.
• high-power, robust transceivers may be capable of successfully transmitting the signal to the receiving unit under certain operating conditions, such equipment can be relatively expensive.
• a high-power transceiver cannot successfully effect communications, such as when a long train travels a curved track segment adjacent a natural obstruction such as a mountain, where the communications path between the lead unit and one or more remote units is obstructed by the mountain. Also, as the train passes through a tunnel certain transceivers may be unable to communicate with other transceivers aboard the locomotives.
• one embodiment of the distributed power train communications system comprises the off-board repeater 26 (see Figure 1) for receiving messages sent from the lead unit 14 and repeating (retransmitting) the message for receiving by the remote units 12A-12C.
• This embodiment may be practiced along a length of track that passes through a tunnel, for example.
• the off-board repeater 26 comprises an antenna 29 (e.g., leaky coaxial cable mounted along the tunnel length) and the remote station 32 for receiving and retransmitting lead messages that are received by all the remote units 12A-12C within RF communications range of the repeater antenna 29.
• the present invention comprises a communications method for a vehicle consist comprising a lead powered vehicle and a remote powered vehicle, wherein the lead powered vehicle comprises first and second spaced apart antennas, each antenna associated with a radio, and the remote powered vehicle comprises third and fourth spaced-apart antennas, each antenna associated with a radio, the method comprising.
• the method further comprises transmitting an outbound message from the lead powered vehicle, at the remote powered vehicle, receiving the outbound message at the third antenna and supplying a signal representative thereof to the associated radio for producing a first received signal, and receiving the outbound message at the fourth antenna and supplying a signal representative thereof to the associated radio for producing a second received signal, determining a first signal quality metric of the first received signal, determining a second signal quality metric of the second received signal, selecting the first or the second received signal for processing by the remote powered vehicle in response to the first and the second signal quality metrics, transmitting an inbound message from the remote powered vehicle, at the lead powered vehicle, receiving the inbound message at the first antenna and supplying a signal representative thereof to the associated radio for producing a third received signal, and receiving the outbound message at the second antenna and supplying a signal representative thereof to the associated radio for producing a fourth received signal, determining a third signal quality metric of the third received signal, determining a fourth signal quality metric of the fourth received signal, and selecting the third or the fourth received signal
• the present invention comprises a communications system for a vehicle consist having a lead powered vehicle and a remote powered vehicle, the lead and remote powered vehicles each comprising a forward antenna and a rearward antenna.
• the system further comprises a communications channel, the lead powered vehicle for transmitting an outbound message over the communications channel for receiving by the remote powered vehicle, a first radio associated with the forward antenna in the remote powered vehicle for receiving a first received signal responsive to the outbound message and a second radio associated with the rearward antenna in the remote powered vehicle for receiving a second received signal responsive to the outbound message, wherein the first radio determines a first signal quality metric of the first received signal and the second radio determines a second signal quality metric of the second received signal, a comparator for comparing the first and the second signal quality metrics, a processor for processing one of the first or the second received signals having a better signal quality metric, the remote powered vehicle for transmitting an inbound message over the communications channel for receiving by the lead powered vehicle, a third radio associated with the forward antenna in the
• the present invention comprises a communications method for a vehicle consist comprising a lead powered vehicle having a first antenna associated with a first transceiver and a second antenna associated with a second transceiver and a remote powered vehicle having a third antenna associated with a third transceiver and a fourth antenna associated with a fourth transceiver.
• the method further comprises transmitting an outbound message from the first transceiver via the first antenna or from the second transceiver via the second antenna, the outbound message comprising a plurality of message bytes, receiving the outbound message at the third and the fourth antennas and the associated third and fourth transceivers, determining correct bytes and error bytes in the outbound message as received at the third transceiver, determining correct bytes and error bytes in the outbound message as received at the fourth transceiver, and assembling a reconstructed message using correct bytes from one of the message received at the third transceiver and the message received at the fourth transceiver.
• the present invention comprises a communications method for a vehicle consist comprising a lead powered vehicle and a plurality of remote powered vehicles.
• the method further comprises transmitting an outbound message from the lead powered vehicle, the outbound message comprising a plurality of message bytes, one or more of the plurality of remote powered vehicles receiving and retransmitting the outbound message, receiving a first occurrence of the outbound message at a one of the plurality of remote powered vehicles, receiving a second occurrence of the outbound message at the one of the plurality of remote powered vehicles, determining correct bytes and error bytes in the first occurrence of the outbound message, determining correct bytes and error bytes in the second occurrence of the outbound message, and assembling a reconstructed outbound message at the one of the plurality of remote powered vehicles using correct bytes from the first or the second occurrence of the outbound message.
• Figures 1 and 2 are schematic illustrations of a distributed power train to which the teachings of the present invention can be applied.
• Figure 3 is a timing diagram of a prior art normal message priority protocol for a communications system.
• Figure 4 is a timing diagram of an onboard message priority protocol, according to the teachings of the present invention, for use with a train comprising four remote units.
• Figure 5 is a table illustrating timing parameters for the onboard message priority protocol according to the teachings of the present invention.
• Figure 6 is a timing diagram of another embodiment of an onboard message priority protocol, according to the teachings of the invention, for use with a train comprising four remote units.
• Figure 7 is a timing diagram of an onboard message priority protocol, according to the teachings of the present invention, for use with a train comprising three remote units.
• Figure 8 is a timing diagram for an off-board message repeater system according to the teachings of the present invention.
• Figure 9 is a table illustrating timing parameter comparisons for the normal priority message protocol, the onboard repeater message priority protocol and the off-board repeater message priority protocol.
• Figure 10 is a schematic illustration of a distributed power train according to another embodiment of the present invention.
• Figures 1 1 and 12 are flowcharts depicting processing steps according to two embodiments of the present invention.
• the communications system may automatically switch to the priority protocol for on-board message repeating (OBMR) according to the teachings of the present invention.
• OBMR on-board message repeating
• Such a switch occurs, for example, when the communications system experiences an interrupt of more than a predetermined fixed duration, one minute for example.
• the OBMR protocol is active for fifteen minutes, after which the communications system returns to normal priority message protocol operation, i.e., as described in conjunction with Figure 3.
• the communications system can be configured for continual OBMR operation or OBMR operation can be manually activated by the lead locomotive operator.
• Figure 4 illustrates an exemplary OBMR protocol for a train comprising a lead unit and four remote units.
• the lead unit transmits a command message (i.e., a message that commands a new function at the remote units or a status update message that requests remote unit status information and also includes the most recent previously- transmitted command).
• the first remote unit receives the outbound command message and repeats the message for receiving by other remote units in the train.
• This interval is merely exemplary and represents a predetermined minimum interval between receipt of a message at the lead unit and a transmission of a later command from the lead unit.
• the command messages sent by the lead unit, the messages sent by the remote units and the interval between message transmissions are fixed in length. However, these lengths may vary as needed for a particular application of the present invention and may differ among different railroad operators.
• the first remote does not transmit a return status message upon receipt of the outbound message that was sent from then lead locomotive. Instead, the first remote unit (and each subsequent remote unit) repeats the outbound message, thereby permitting the outbound message to propagate along the length of the train, without incurring the time penalty of the inbound (i.e., in a direction toward the lead locomotive) status messages transmissions from each remote unit.
• each remote unit retransmits the outbound message within its respective predefined time slot, a predetermined time interval after receiving the outbound message, after another remote unit has transmitted the transmitted the outbound message, or after another remote unit has transmitted a response.
• the message leapfrogs down the train for receiving by each remote unit.
• no status messages have been returned to the lead locomotive.
• each locomotive of the train receives (e.g., "hears") messages sent from the lead locomotive and from the remote locomotive(s), although this may not always be true due to interference, low signal strength, etc.
• the signal timing parameters and actions at the lead and remote units as described herein are based on this premise. If a remote unit fails to receive a lead message, for example, this situation is discovered when the lead unit fails to receive a response from that remote locomotive. The lead locomotive takes corrective action, including retransmitting the original message.
• each remote locomotive waits a predetermined time from receiving the message (either from receiving the outbound message or from receiving the inbound message) from the lead locomotive or from a prior remote locomotive, where "prior" refers to a locomotive that received the message earlier in time and transmits a response message or retransmits the received message.
• the prior remote locomotive did not receive the message, it obviously cannot transmit a response message or retransmit the original message.
• a remote locomotive expecting a response from the prior locomotive will not receive that response.
• the remote locomotive expecting the response will therefore wait a predetermined time from receipt of the last message until sending its own message or retransmitting the original message.
• each locomotive is configured to reflect its position in the train.
• each message sent by a locomotive includes an identifier of the transmitting locomotive.
• Each locomotive receiving the message can therefore determine the locomotive that transmitted the message and can also determine the position of the transmitting locomotive in the train relative to the position of the receiving locomotive.
• the last remote When the last remote (the nth remote) receives the command message, the last remote sends its status message (i.e., an inbound message) back to the previous (n-l)th remote.
• the remote unit farthest from the lead unit is configured as the last remote, i.e., the last remote "knows" that it is the last remote in the train.
• the last remote unit receives the outbound message it responds with its status message.
• Remote unit three receives the status message from remote unit four and stores the received status message until its designated time slot, at which time remote unit three repeats the remote unit four status message and appends its own status message, transmitting both status messages in a direction of the lead unit, i.e., to the second remote.
• Remote unit two receives the status messages from remote units four and three, and transmits these status messages, plus its own status message, in the direction of the lead unit. The process continues until each remote unit's status message reaches the lead unit as a concatenated message comprising the status message from each remote unit.
• a non-receiving remote unit will not have a status message to report back to the lead unit.
• the lead unit expects a status message from each of the remote units and can determine from the received status messages (each remote unit status message includes a remote unit identifier) which if any of the remote units did not receive the command message.
• each remote unit status message includes a remote unit identifier
• the command is retransmitted by the lead unit.
• the lead operator is informed of this remote unit miss by an appropriate indication on a lead unit display.
• a status message transmitted by a remote unit may be received by remote units in addition to the intended receiving remote unit, i.e., where the intended receiving remote unit is that remote unit adjacent to the transmitting remote unit in a direction toward the lead unit of the train.
• both remote units two and three may receive the status message transmitted by the remote unit four.
• Remote unit two stores the remote four status message until its designated transmitting time slot or until a designated time interval from receipt of the message from the last remote to transmit the message.
• remote unit two may receive the remote four status message twice: (1) when initially transmitted by the remote unit four, and (2) when retransmitted by remote unit three.
• the capability of multiple receptions of a status message improves the probability that the lead unit receives the status message from each remote unit that received the command message.
• a remote unit receiving the message twice, as described immediately above compares the two messages, byte by byte.
• Each byte of the message includes an error detection code (for example, a parity check), thus permitting a determination that each byte is error-free (the parity check indicated that no errors had occurred) or contains errors (the parity check indicated that at least one error occurred). If a byte in a first message failed the parity check and the same byte in a second message passed the parity check, then the failed byte in the first message is replaced by the correct byte from the second message.
• error detection code for example, a parity check
• a message is received at both antennas 29A and 29B and processed through associated transceivers 28A and 28B of any of the remote locomotives
• Both messages are the processed through the lead station 30 or the remote station 32, as appropriate, where the two messages are compared byte by byte.
• Each byte of each message includes an error detection code (for example, a parity check), thus permitting a determination that a byte is error-free
• the parity check indicating that at least one error is present. If a byte in a first message failed the parity check and the same byte in a second message passed the parity check, then the failed byte in the first message is replaced by the correct byte from the second message to assemble a corrected message. The corrected message is then processed through the associated lead station 30 or the remote station 32.
• Figure 5 is a table indicating the relative transmission order, delay time, and message content for the message priority protocol for on-board message repeating for a train comprising one lead locomotive and four remote locomotives as illustrated in Figure 4. However, when a remote unit transmits, the time delay period from the third column of Figure 5 for each later-transmitting remote is decremented as explained below.
• the time delay between the end of a transmission from one unit and the beginning of a transmission from another unit is 50 msec in the illustrated embodiment. As each remote unit transmits, the time delay for each subsequent remote to transmit is reduced by 50 msec thus allowing each remote unit to transmit in order while maintaining 50 msec between each unit's transmission. If a remote unit does not transmit after its defined time delay then each subsequent remote recognizes this and adjusts its own time delay accordingly when a subsequent unit's transmission is received.
• remote unit two waits 100 msec from the end of the lead unit transmission before it transmits. If remote unit two transmits, then each subsequently transmitting remote unit recognizes that two remotes should have transmitted in this time frame and subtracts 100 msec from its time delay; remote unit three transmits 50 msec (150 - 100 msec) after the end of the remote unit two transmission, with remote four transmit delay adjusted to 100 msec (200 - 100 msec) after the end of the remote unit two transmission, etc.
• remote unit three is set to transmit 150 msec after the end of the lead unit transmission and when remote unit three transmits each subsequently transmitting remote unit recognizes that three remote units should have transmitted in this time frame and each subtracts 150 msec from its time delay.
• remote unit four waits 200 msec from the end of the lead unit transmission to transmit and when remote four transmits each subsequently transmitting remote unit will recognize that four remote units should have transmitted in this time frame and each therefore subtracts 200 msec from its time delay.
• the third and fourth remote units also subtract 50 msec from their delay period and they are set to transmit at 100 msec and 150 msec, respectively, from the end of the first remote transmission if remote unit two does not transmit.
• each remote unit transmits and the message is received by all other remote units, then each remote unit that has not yet transmitted the message subtracts 50 msec from its assigned time delay period. This shortening of the time delay period reduces the time required for the message to leap frog up and down the train.
• Remote unit three therefor transmits at 150 msec from the end of the lead unit transmission.
• Remote unit four will transmit 50 msec after the end of the remote unit three transmission.
• the 50 msec interval is a sliding interval, such that whenever a remote unit transmits a signal, the next remote waits 50 msec from the end of the transmission before initiating its transmission. If a remote unit does not transmit a signal then the subsequent remote units wait their assigned time delay period less 50 msec for each remote unit that transmitted or should have transmitted the signal.
• Figure 7 is a timing diagram for the message priority protocol for on-board message repeater for a train comprising a lead locomotive and three remote locomotives.
• the implementation principles for a distributed power train comprising three remote units are identical to the implementation for a four remote unit distributed power train as described above in conjunction with Figure 4.
• the embodiment illustrated in Figure 6 wherein the remote units retransmit the command message can also be applied to a train comprising a lead unit and three remote locomotives (or a train comprising any number of remote units).
• Figure 8 is a timing diagram for the normal communications timing protocol when operative with the off-board message repeater 26 described above in conjunction with Figure 1.
• the lead unit transmits a command message during time interval 200 that is received and retransmitted by the message repeater 26 during time interval 202.
• Each of four remote units receives the repeated command message and responds with its status message during its allotted time slot.
• the repeater 26 receives all the remote unit status messages and retransmits them for receiving by the lead unit 14 during time interval 206, after which the message interval ends.
• a utility message 210 referenced in Figure 8 is a message sent by the repeater
• the utility message prevents a lead unit that is outside of a tunnel from transmitting simultaneously with a remote unit that is inside the tunnel.
• Figure 9 compares message delay times of the prior art normal message protocol, the OBMR protocol of the present invention, and the normal message timing protocol when operative with the off-board message repeater.
• the communications system of the present invention further comprises an antenna/radio diversity feature and/or a signal selection feature that are advantageous to overcome signal transmission path impairments such as caused by multi- path signal propagation, signal reflections and signal obstructions (such as due to a locomotive-mounted pantograph for supplying electrical power to the locomotive from overhead power cables).
• Each consist of two locomotives comprises a forward locomotive
• each locomotive further comprising a forward radio 260A/260B/260C and a rearward radio 262A/262B/262C, each forward radio operative in conjunction with an antenna 266A/266B/266C and each rearward radio operative in conjunction with an antenna 268A/268B/268C, respectively for receiving messages sent from other locomotives of a train 270.
• the consist locomotives are coupled by an MU (multiple unit) cable 253A/253B/253C.
• the forward locomotive 250A/250B/250C is designated the "A” unit controlling the locomotive 252A/252B/252C or "B” unit by control signals initiated by the train operator in the "A” unit and supplied to the "B” unit over the MU cable 253A/253B/253C.
• both radios in each consist receive messages transmitted by other units in the train 270.
• Both the forward radios 260A/260B/260C and the rearward radios 262A/262B/262C determine a signal quality metric (such as the signal strength, bit error rate, or the reception of valid data) for each received message.
• the signal quality metrics are compared in a comparator/processor 276A/276B/276C, and the message having the better signal quality metric is selected as the operative message for use by the locomotives consist.
• the signal quality metric is determined for all messages received at the forward radios 260A/260B/260C and the rearward radios 262A/262B/262C to select the operative message for that consist.
• each received radio message can be verified to be correct by subjecting the message to an error detection and correction algorithm, followed by processing according to the present invention to determine the signal quality metric of the signal received at each radio of the consist, from which the operative message for the consist is selected.
• outbound messages are transmitted from the antenna/radio
• one of the antennas 266A/266B/266C (and the corresponding radio 260A/20B/260C) or one of the antenna 268A/268B/268C (and the corresponding radio 262A/262B/262C) is selected as the transmitting antenna in response to a desired direction for the transmitted signal.
• the antennas 266A/266B/266C are disposed proximate a forward end of the associated locomotive consist (assuming a direction of travel indicated by the arrowhead 1 1) and the antennas 268A/268B/268C are disposed at a rearward end of the associated locomotive consist.
• the radio 260A/260B/260C/262A/262B/262C determines an intended direction for the transmitted signal (e.g., inbound or outbound based on the type of signal and/or information contained in the signal) and selects the transmitting antenna/radio that is closest to the intended receiving antenna/radio. For example, if the locomotive consist comprising the locomotives 250A and 252A is the lead consist and it is desired to transmit an outbound message to the locomotive consist comprising the locomotives 250B and 252B, then the antenna/radio 268A/262A is selected as the operative antenna. This feature can be especially beneficial when each locomotive comprises a pantograph 280 for supplying current to the locomotives from an overhead current source (not shown in Figure 10).
• an antenna (and corresponding radio) is selected such that the desired signal direction is away from the pantograph.
• the remote locomotive consist comprising the locomotives 250B and 252B is to send a signal to the locomotive consist comprising the locomotives 250A and 252A, then the antenna/radio 266B/260B is selected as the operative antenna/radio.
• Figure 1 1 is a flow chart illustrating the method for implementing the signal selection function according to one embodiment of the present invention.
• the Figure 1 1 method is implemented in a microprocessor and associated memory elements within the locomotives of the railroad train, for example, within the locomotives 260A/260B/260C/262A/262B/262C.
• the Figure 11 steps represent a program stored in the memory element and operable in the microprocessor.
• program code configures the microprocessor to create logical and arithmetic operations to process the flow chart steps.
• the invention may also be embodied in the form of computer program code written in any of the known computer languages containing instructions embodied in tangible media such as floppy diskettes, CD-ROM's, hard drives, DVD's, removable media or any other computer-readable storage medium.
• program code When the program code is loaded into and executed by a general purpose or a special purpose computer controlled by a microprocessor, the computer becomes an apparatus for practicing the invention.
• the invention can also be embodied in the form of a computer program code, for example, whether stored in a storage medium loaded into and/or executed by a computer or transmitted over a transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electro-magnetic radiation, wherein when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention.
• the Figure 11 flow chart begins at a step 300 where the communications system is activated, thus the forward radios (260A/260B/260C in Figure 10) and the rearward radios (262A/262B/262C in Figure 10) in each locomotive consist are activated.
• both radios in each consist receive messages transmitted by other units in the train 270.
• both the forward radios and the rearward radios determine a signal quality metric (such as the signal strength, bit error rate, or the reception of valid data) for each received message.
• the signal quality metrics are compared at a step 306 and the message having the better signal quality metric is selected (see a step 310) as the operative message for use by the locomotive consist.
• a flowchart of Figure 12 depicts the antenna/radio diversity feature of one embodiment of the present invention.
• a signal is produced for transmitting to another locomotive in the train.
• an intended direction for the transmitted signal is produced for transmitting to another locomotive in the train.
• the transmitting antenna/radio is selected as the antenna/radio that is closest to the intended receiving antenna/radio.
• a “powered vehicle” is a vehicle (marine, on-road, off-road, etc.) capable of self-propulsion.
• a “powered rail vehicle” is a vehicle configured for self-propulsion along a pair of rails or other guideway.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mechanical Engineering (AREA)
• Mobile Radio Communication Systems (AREA)
• Train Traffic Observation, Control, And Security (AREA)
• Electric Propulsion And Braking For Vehicles (AREA)
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• 2011
  • 2011-01-25 EP EP11705066A patent/EP2529493A2/de not_active Ceased
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  • 2011-01-25 CN CN201510509786.4A patent/CN105128889A/zh active Pending
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• 2012
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