Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L12/407—Bus networks with decentralised control
  • H04L12/417—Bus networks with decentralised control with deterministic access, e.g. token passing
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks

Definitions

• the invention relates to the transmission system of an on-board computer system, which was designed to make a local network on board railway vehicles.
• the objective of the local network was to substitute a single transmission line for the innumerable wired links which used to be the control and command organs at the driving position.
• this transmission line is shared by equipment close to the control and command members and makes it possible to route the information to be exchanged by this equipment.
• TORNAD A transmission system used within a local network on board rail vehicles is known by the registered name TORNAD, and described in an article by D. DUHOT entitled “TORNAD” High Availability Computer Network, published in the journal Alsthom, number 8, 1987.
• the railway environment imposes a certain number of constraints, taken into account when designing a local network.
• the presence of strong electromagnetic disturbances motivated the choice of a transmission line formed of shielded twisted pair. Immunity to noise is ensured to a certain extent by the choice of a coda ⁇ ge without a continuous component.
• the need for high galvanic isolation (1500 V) between the electronics and the wiring system is satisfied by the use of isolation transformers.
• the large distances (up to 500 meters) between the end fittings of certain rail vehicles require that the signals be reshaped.
• the prior art system also took into account the constraints of the railway environment, but had a certain number of drawbacks, linked to the ring topology and to the joint use of a protocol of token ring.
• the information received had to be interpreted before being re-issued, which significantly affected performance (crossing of equipment in 25 microseconds).
• a break in the transmission line also led to a change in the protocol governing exchanges between the equipment and the passage of the token.
• the transmission system adopts a bus topology, in which the information sent on the initiative of one piece of equipment is received by all of the other pieces of equipment.
• This transmission system is composed of a transmission line and subsystems, housed within each piece of equipment, which connect the equipment to this transmission line.
• the transmission line consists of an open chain of two-way point-to-point links. These subsystems are designated in the following by the term "head of line”.
• the signals are reshaped by repeaters integrated within the head end of each device.
• the concern not to propagate noise along the transmission line has led to associating the repeater function with the function of recognizing preamble signals.
• the availability of the transmission system is increased by the redundancy of the transmission line.
• Access to the transmission line in a limited time is guaranteed for each piece of equipment by using the token bus protocol defined by ISO 8802.4.
• a head end When a head end transmits signals on the initiative of the equipment within which it is housed, the signals are transmitted simultaneously on each of the segments of the transmission line to which the head end is connected.
• Each line head propagates the signals along the transmission line, so that the signals can be received by all of the equipment.
• Each head of line also ensures the reshaping of the signals, by amplifying them and by resynchronizing them.
• a head end listens for signals on each of the segments of the transmission line to which it is connected. As soon as a signal is received from one of the segments, the head end prohibits receiving the opposite segment, and propagates the received signal over this segment. If signals are received simultaneously from each of the segments of the transmission line, the head end arbitrarily chooses the signal received from one of the segments and ignores the signal received from the opposite segment.
• the transmission system according to the invention therefore combines aspects of a bus topology (bidirectional transmission line, reception of identi ⁇ cal information by all the equipment) with aspects of a ring topology (point links point-in-time, reshaping of signals by each device).
• the optional redundancy of the transmission line increases the availability of the transmission system.
• the subject of the invention is therefore a system for transmitting a signal between equipment of an on-board computer system, the equipment being connected to a transmission line, the transmission line being composed of point-to-point links, characterized in that the point-to-point links are bidirectional and form an open chain.
• FIG. 1 represents an overall view of the transmission system according to the invention
• FIGS. 2 and 3 represent a transmission line formed from point-to-point connections, with or without redundancy of the transmission line,
• FIGS. 4 and 5 illustrate the transmission of a signal by equipment with or without redundancy of the transmission line
• FIG. 6 - Figures 6, 7 and 8 illustrate the selective reception of a signal by equipment, with or without redundancy of the transmission line.
• - Figure 9 shows the signal switching mechanism within the head end.
• FIG. 1 In FIG. 1 are shown devices 2 connected by the transmission line 3, to which each of the devices is connected via a line head 4 ensuring the transmission, reception and propagation of the signals.
• FIG. 2 In Figure 2 are shown three equipment S 1, S2, S3, connected to the transmission line according to the invention.
• a signal sent by the head of the equipment S2 is routed along the transmission line.
• the head ends of the equipment S 1 and S 3 receive the signal from one of the segments of the transmission line and propagate it after reshaping on the opposite segment.
• FIG 3 is shown the redundancy of the transmission line.
• the two segments 11 and 12 connect the head of line of equipment S2 to the head of line of equipment S 1
• the two segments 21 and 22 connect the head of line of equipment S2 to the head of equipment S3. Reception and transmission on each of the four segments 11, 12, 21, 22 can be inhibited or activated under the control of the equipment S2.
• the head end of a device transmits its signals on each of the segments of the transmission line to which it is connected. This is shown, for an equipment S 1, in FIG. 4 in the case of a transmission line without redundancy, and in FIG. 5 in the case of a transmission line with redundancy. For the duration of the transmission of the signals, the head of line is prohibited from receiving signals from each of the segments of the transmission line to which it is connected.
• Equipment is ready to receive signals on each of the segments of the transmission line to which it is connected. This is shown, for equipment S 1, in FIG. 6 in the case of a transmission line without redundancy, and in FIGS. 7 and 8 in the case of a transmission line with redundancy.
• the head of line of the equipment SI selects the first signal received from one of the two segments of the transmission line (segment 31 of FIG. 6) and transmits the signal to the equipment.
• the head of line is prohibited from receiving from the opposite segment 32 and propagates on this segment the signal received after having reshaped it. This polarization in the direction defined by the first received signal lasts as long as this signal is present.
• the line head of the equipment S 1 selects the first signal received from one of the four segments of the transmission line (segment 41 of FIG. 7), and transmits the signal to the equipment.
• the head of line is prohibited from receiving from the opposite segment 42 and propagates on this segment the signal received after having reshaped it.
• This polarization in the direction defined by the first received signal lasts as long as this signal is present.
• a signal can be received from one of segments 43 or 44, for example segment 44.
• This second signal is not transmitted to the equipment.
• the headend is therefore prohibited from receiving from the opposite segment 43 and propagates on this segment the signal received from segment 44 after getting it back in shape. This polarization in the direction defined by the second received signal lasts as long as this signal is present
• Another policy can be implemented by the head end after it has selected the first signal received from one of the four segments of the transmission line (segment 41 of FIG. 8).
• the head of line transmits the signal received to the equipment is prohibited from receiving other segments 42, 43 and 44, and propagates the signal received on segments 42 and 44 after having reshaped it.
• This polarization in the direction defined by the first received signal lasts as long as this signal is present
• FIG. 9 illustrates the signal switching mechanisms within the head end of the transmission system according to the invention, provided with redundancy of the transmission line.
• the transmission line is represented by two twisted pairs (A and B).
• the KA and KB relays ensure electrical continuity of the transmission line when the equipment is de-energized or wishes to isolate in the event of a malfunction
• the equipment is not isolated from the line transmission, it is connected to the four segments A1, A2, B 1 and B2.
• the signals are received via the differential receivers RAI, RA2, RB 1 and RB2.
• the signals are transmitted by means of the differential transmitters EA1, EA2, EB 1 and EB2, which are activated by the control lines ACTA1, ACTA2, ACTB1 and ACTB2 respectively.
• the block CHOLX_Al / A2 controls the switch SWA (respectively SWB) according to the origin (Al or A2, respectively B 1 or B2) of the received signal.
• the CHOLX_A / B block controls the SWAB switch according to the origin (A or B) of the received signal.
• the TRANSMISSION block controls the switches SWA1, SWA2, SWB1 and SWB2 so as to emit the signal from the equipment or to propagate the signal received from one of the segments A1, A2, Bl or B2.
• the equipment presents the signal to be emitted on its output OUT, and validates it by means of the control line ACT.
• the ACT information acts on the CHOLX_A / B block, which controls the SWAB handler so that no signal is transmitted to the equipment on its IN input (SWAB is in ZERO position).
• the ACT information also acts on the TRANSMISSION block, which controls the switches S WA1, SWA2, SWB 1 and S WB2 so as to present the output signal OUT at the input of the transmitters EA1, EA2, EB 1 and EB2.
• These transmitters are activated by the control lines ACTA1, ACTA2, ACTB1 and ACTB2 according to the control information INHOA1, INHOA2, LNHOB1 and INHOB2 which the equipment can validate to selectively inhibit the emission on the segments A1, A2, B 1 and B2.
• the ACT control line is not validated.
• the SWAB switch remains in the ZERO position, and the equipment receives nothing.
• the control lines ACTA1, ACTA2, ACTB1 and ACTB2 do not activate the transmitters EA1, EA2, EB1 and EB2.
• the position of the switches SWA1, SWA2, SWB1 and SWB2 is indifferent.
• the block CHOLX_Al / A2 receives the signals coming from the transmission line, IN Al and INA2 (respectively INB 1 and INB2) present at the output of the receivers RAI and RA2 (respectively RB1 and RB2) , and reshapes them for transmission to equipment and spread.
• the blocks CHOIX_Al / A2 and CHOLX_Bl / B2 include shift registers making it possible to compare, after sampling, the signals received with predefined patterns (start of frame, end of frame). These blocks also verify that the signals received meet the required amplitude criteria.
• the equipment can validate the control information LNHIA1, LNHIA2, INHIB1 and INHIB2, to selectively inhibit reception on the segments A 1, A2, B 1 and B2.
• the block CHOIX_A 1 / A2 (respectively CHOLX_B 1 / B2) acts as a function of this control information to control the switch SWA (respectively SWB) according to the origin of the first signal received (INA1 or INA2, respectively INB 1 or INB2).
• the first signal received is reshaped and presented at the output of the block on one of the lines INA1R or INA2R (respectively INB 1R or INB2R).
• the block CHOIX_Al / A2 validates the signal selected by means of the control line INAVAL (respectively INB VAL), and indicates its choice by validating one and only one of the control lines INA 1 VAL or INA2VAL (respectively INB 1 VAL or INB2VAL).
• the CHOLX_A / B block controls the SWAB switch according to the INAVAL and INB VAL information, depending on the origin (A or B) of the first signal received. In the event of simultaneous reception of signals on A and B, an arbitrary choice is made.
• the CHOLX_A / B block indicates its choice by means of the A / B control line intended for the TRANSMISSION block.
• the TRANSMISSION block controls the switches SWA1, SWA2, SWB1 and SWB2 so as to propagate the signals received as a function of a part of the policy defined by the equipment using the control information BRA (patching), on the other hand, control information INHOA1, INHOA2, LNHOB1 and INHOB2 that the equipment can validate to selectively inhibit the emission on the segments A1, A2, B1 and B2.
• the inputs INAlVALetINA2VALd'unepart, INBlVALetINB2VALd'autre hand, indicate the presence on the INA and or INB lines of signals to be propagated.
• the propagation of the signals is carried out as follows: a signal received from the segment A 1 (respectively B 1) is propagated on the segment A2 (respectively B 2), and a signal received from segment A2 (respec- tivelyB2) is propagated on the Al segment (respectivelyBl).
• the pairs of switches SWA1 / SWA2 and SWB1 / SWB2 are controlled independently of one another.
• the TRANSMISSION block presents the signal INA (respectively INB) at the input of the transmitters EA1 and EA2 (respectively EB1 and EB2).
• ACTA1 and ACTA2 are activated by the control lines ACTA1 and ACTA2 (respectively ACTB 1 and ACTB2) according to the control information INHOA1 and INHOA2 (respectively INHOB 1 and INHOB2), and the validation inputs 1NA1 VAL and INA2VAL (respectively INB 1 VAL and INB2VAL).
• This signal propagation policy is the one shown in Figure 7.
• the propagation of the signals is carried out in the following manner: a signal received from the segment A1 or dusegmentBl is propagated on the segments A2 and B2, and a signal received from the segment A2 or segment B2 is propagated on the segments Al and B 1.
• the conflict resulting from the simultaneous reception of signals of the segments Al or A2 on the one hand, Bl or B2 on the other hand, is resolved by adopting the choice made by the block CHOD _A / B, as indicated by A / B control information.
• the switches SWA1, S WA2, SWB 1 and SWB2 are then controlled so as to present either the signal INA or the signal INB at the input of the transmitters EA1, EA2, EB1 and EB2.
• These transmitters are activated by the control lines ACTAl, ACTA2, ACTBl and ACTB2 according to the control information INHOA1, INHOA2, INHOB 1 and INHOB2, and validation inputs INA1VAL, INA2VAL, INB 1 VAL, INB2VAL and A B.
• This signal propagation policy is that shown in FIG. 8.
• the implementation of the invention on board rail vehicles has good performance characteristics. and quality.
• the headend propagates a signal from one segment of the transmission line to the opposite segment in approximately 3 microseconds. On a 500 meter segment, the bit error rate is 10 ⁇ 9 for a noise level equal to 200 effective millivolts.
• the system according to the invention tolerates a segment cut without any alteration of the operation of the token bus protocol used.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Small-Scale Networks (AREA)

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Citations (1)

• 1991
  • 1991-06-19 FR FR9107524A patent/FR2678083B1/fr not_active Expired - Lifetime
• 1992
  • 1992-06-19 CA CA002089382A patent/CA2089382A1/fr not_active Abandoned
  • 1992-06-19 KR KR1019930700466A patent/KR930701878A/ko not_active Ceased
  • 1992-06-19 EP EP92401724A patent/EP0519833A1/fr not_active Withdrawn
  • 1992-06-19 WO PCT/FR1992/000565 patent/WO1992022968A1/fr active Application Filing
  • 1992-06-30 TW TW081105177A patent/TW283769B/zh active

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Non-Patent Citations (2)

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