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
  • H04L12/413—Bus networks with decentralised control with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• • 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
  • H04L12/4013—Management of data rate on the bus

Definitions

• the present invention relates to logical communication networks formed by transceiver equipment, and more particularly to networks allowing multi-point type communication, ie in which each transceiver can communicate with each of the other transmitters - network receivers.
• networks have been developed which allow multipoint communications, in which direct communication from a sender to a recipient can be carried out.
• these devices use the principle of contention, that is to say that each transceiver connected to the network can transmit if no other transmission is in progress.
• the transmission is of the synchronous type, at high speed, with suppression of the carrier wave when there is no transmission, so that any transceiver s quickly realizes that the network is free or busy
• French patent 2306478 describes such a device: a message transmission begins with a binary synchronization signal, and an interruption at any time is interpreted as an end of message, the network is immediately in the resting state.
• This device can only work with a vehicle code the sender's clock, and the transmission is synchronous.
• the messages contain the addresses of the sender and the recipient.
• the senders stop and resume the transmission after waiting for a random duration, this duration possibly being practically zero. No collision signal is sent over the network.
• European patent application 0023105 also describes such a device using the principle of contention, but in which the message is transmitted in a particular code containing packets of eight binary signals. The transmission is synchronous, the message conveying the clock, but no recipient address is sent, so that all the receivers are recipients of all the messages. The particular code obliges to wait at least the duration of a packet before resuming an interrupted transmission.
• British patent application 2 013 452 describes a device in which the sending equipment designates its successor, the equipment being thus authorized to transmit one after the other in a modifiable order. It is a technique very different from restraint.
• Asynchronous type transmission networks make it possible to produce installations at a lower speed but much less expensive; detecting network availability is more difficult, so that multipoint connections have never been made using the principle of contention.
• the messages are formed of a series of characters separated by intervals during which the carrier wave is suppressed, so that it is insufficient to verify that this carrier wave is absent to know if a message is not being transmitted.
• multipoint links have been produced in which a master device in turn interrogates the secondary equipment to acquire the information that the secondary equipment has to transmit, and directly selects the secondary equipment to which it wants transmit information. This leads to the achievement of relatively complex and rigid hierarchical networks.
• the object of the present invention is in particular to obviate the drawbacks of known networks by proposing a method and a device allowing the transmission of information at medium speed in asynchronous mode between several logical transceivers to produce networks having the following characteristics: low cost compared to synchronous mode transmission networks; multi-point configuration; direct communication from sender to recipient.
• the network is made up of transceivers each composed of a transmitter circuit and a receiver circuit.
• the transceiver wanting to send a message will be called the sender, the transceiver for whom the message is intended will be called the recipient.
• Another object of the present invention is to provide a method and a device for making networks in which one can modify at will the physical position and the number of transceivers connected to the network.
• the device comprises means for carrying out several steps: after reception of a character which is not intended for it, the equipment awaiting transmission remains listening for a duration greater than a predetermined minimum waiting time; if during this waiting period it has not detected a character, it emits a message start signal; it then transmits the characters of the message, at least one of which designates the address of the recipient and the address of the sender; it finally sends an end of message signal; at each character or signal transmission, the sender compares the signals corresponding to the characters transmitted and the signals detected simultaneously while listening; if the signals are identical, it continues the transmission of the message, and if the signals are different, it interrupts the transmission of the message, transmits on the network a character interrupt, stay tuned for a random time greater than the minimum waiting time, and restart the transmission.
• this arrangement allows the use of the contention principle for asynchronous communication of the multipoint type of logical messages, these messages being formed of a series of binary signals grouped in coded characters of the same length separated by interruptions.
• the start of message, end of message and interruption signals are substantially identical.
• the interrupt characters commonly used in the asynchronous communication technique are used, so that their recognition by the receiving circuits can be carried out by the conventional circuits usually used for point-to-point asynchronous transmissions. point.
• interrupt characters comprise a continuous signal of duration greater than the duration of the characters forming the message, so that their form is different from all the codes used in the characters composing the message.
• the network thus produced is independent of the encodings used to encode the characters forming the messages to be transmitted, so that it can support the most diverse applications.
• the predetermined minimum waiting time is at least equal to the transmission time of a character, increased by the maximum internal processing time of a transceiver between the end of transmission of a character and the start of the transmission of the next, and increased the signal propagation time between the extreme points of the network. This ensures that a signal not received during the waiting time means that no message is being transmitted. In addition, if a transmitting circuit breaks down during transmission, the other senders can occupy the network without waiting for an end of message which would only intervene after the repair of the defective transmitting circuit.
• the comparison can be made at the end of the character transmission.
• two senders can start a transmission simultaneously, the error being detected only at the end of the first or second character.
• the risks of such a collision phenomenon can be reduced by carrying out this comparison at the end of transmission of each binary signal contained in the character.
• FIG. 1 schematically shows a network of transceivers according to the present invention
• FIG. 2 shows an example of waveform characterizing a character forming a message transmitted by a network according to the present invention
• FIG. 3 shows a waveform characterizing an interrupt signal
• - Figure 4 shows the waveforms of a message to be transmitted according to the present invention
• - Figure 5 shows the waveforms of another message according to the present invention
• - Figure 6 shows schematically the main functional elements of a transceiver constituting the network according to the present invention
• - Figure 7 shows schematically the main elements of a transceiver according to the present invention.
• the method of the present invention makes it possible to communicate, as shown diagrammatically in FIG. 1, several transceivers on the same network according to an asynchronous mode.
• the transmitters 1 to 4 are connected in parallel to the same line 5o.
• the line and the connections have only one conductor, but it is clear that two conductors are necessary.
• wireless transmission networks can be produced, the transmitters 1 to 4 being connected in parallel via radio waves, or optical links such as infrared, fibers optical.
• the information transmitted does not carry the clock, that is why the characters are surrounded by a binary signal at the start of the character and a binary signal at the end of the character.
• the recipient uses the binary start of character signal to readjust his own clock and his own sampling device on a transition. Sampling is performed at a higher frequency, so that the timing is sufficient for the entire duration of transmission of a character.
• the timing thus achieved is a function essentially different from the synchronization obtained by the binary signals at the start of transmission of the synchronous transmissions.
• FIG. 2 shows a possible form of character, comprising a starting binary signal 6, followed by eight binary signals whose coding makes it possible to designate the character to be transmitted, the last binary signal being followed by an end binary signal of character 7.
• the character 8 thus formed is separated from the following character 9 by an interval 10 of essentially variable length.
• the length of this interval 10 depends on the speed of processing of the transmitter circuits between two consecutive characters.
• the length of the characters 8 or 9 depends on the number of binary signals forming these characters, generally one can use five to eight binary signals, more possibly a parity signal.
• FIG. 3 represents, in relation to FIG. 2, an interrupt character 11 whose characteristic is to be continuous and of a duration greater than that of a character defined in FIG. 2, forming the message.
• FIG. 4 shows the constitution of a complete message according to the method of the present invention: this message comprises a message start signal 12, preferably formed by an interrupt character such as character 11, a second character 13 designating for example the address of the recipient of the message, a third character 14 designating for example the address of the sender, a series of characters 15 to 16 containing the characters of the message itself to be transmitted, and a signal end of message 17, preferably consisting of an interrupt character such as character 11. All these signals and characters forming the mes sage are formed as described in connection with Figure 2, and are separated by intervals such as interval 10 during which no signal is transmitted on the network.
• the sender Before starting the transmission of a message as shown in FIG. 4, the sender must first of all respect a waiting time, represented by the arrow 18, after the last signal 19 detected on the network.
• the waiting time 18 must have a duration greater than a predetermined minimum waiting time. This minimum waiting time is at least equal to the transmission time of a character on the network, increased by the usual internal processing time of a transmitting circuit between the end of transmission of a character and the start of transmission of the following, and increased the propagation time of the signals between the extreme points of the network.
• the sender compares the signals corresponding to the character to be transmitted and the signals detected simultaneously while listening. According to the result of this comparison, if the signals are identical, the sender continues sending the message. On the other hand, if the signals are different, the sender interrupts the transmission of the message, transmits an interrupt character on the network, stays tuned for a waiting period, and starts the transmission again after this listening time.
• the waiting time must be different for each transceiver so that, if several senders are waiting for transmission while a third is in use, there will not be a systematic collision when resuming transmissions.
• this waiting time has a random duration so as not to introduce a hierarchy between the various transceivers.
• This phase of the process makes it possible, on the one hand, to avoid bad transmission of messages, and on the other hand, collisions occurring when several transceivers start a transmission at the same time.
• the first characters of the two messages sent by two collision senders are interrupt characters, so that each of the two senders detects the identity of the characters received on the network and of the characters sent. Each of the two senders therefore continues the transmission by transmitting the characters designating the address of the recipient.
• the signals present on the network are formed by the combination of the two transmitted signals, and several cases are then possible:
• the mixing of the information can give a reading error and / or parity of so that the two senders stop the transmission, transmit an interrupt signal and wait for a random delay before resuming this transmission;
• this sender detects the error and sends an interrupt signal, so that all senders stop sending and wait for a random delay before resuming;
• the senders will transmit their own addresses which are necessarily different. In this case, at least one of the senders will detect a difference and produce the interruption.
• a first way consists in verifying that no complete character was received during this initial listening phase; in this case, the risk of collision is relatively high since it is very likely that two senders can start a transmission during the transmission period of a character.
• a second method which consists in checking on the one hand that no character was received during the initial listening phase and that the network is in the idle state when the sender plans to to start the show. Time during which a collision can occur is thus considerably reduced
• the method of the present invention also provides a phase making it possible to immediately produce an acknowledgment signal sent by the recipient to the sender, so as to occupy the network for a minimum time.
• This acknowledgment message may include a character designating the address of the sender, a character designating the address of the recipient, possibly characters of information, and a final character of interruption.
• the recipient sends the first acknowledgment character before the end of the predetermined minimum waiting time which follows the interrupt character of the sender signifying the end of the message.
• the recipient is the only one able to send a message before the end of this predetermined minimum waiting time, so that it is useless for him to send an interrupt character at the start of the acknowledgment message, the other senders cannot send before the end of this predetermined minimum waiting time.
• FIG. 5 shows the succession of characters appearing on the network during such an acknowledgment message: the last character 20 of the sender's message is followed by the interrupt character 21, which character 21 is followed , during the minimum waiting period represented by arrow 22, by a first character 23 sent by the recipient and designating the address of the sender, a second character 24 designating the address of the recipient and the interrupt character 25 marking the end of the acknowledgment message. All other transmissions can only start after the end of a new waiting period 26.
• the transceiver During an awake state, the transceiver has recognized a message start signal and is waiting to recognize its own address for find out if he is the recipient of the message. This state may only last for the reading time of the message start signal and of the first character containing the address of the recipient. If the transceiver does not recognize its address, it returns to the idle state. - If the transceiver recognizes its address, it enters a listening state in which the processing unit takes into account the message received until receipt of an end of message signal. - There is also a transmission state in which the transceiver transmits messages on the network or an acknowledgment of receipt while remaining attentive to the signals present on this network.
• FIG. 6 represents the main functional elements of a transceiver according to the present invention.
• This transceiver comprises a message generation and processing unit 30 comprising several output lines 31 conveying the character to be transmitted to a serialization circuit 36, an output line 32 controlling the transmission of characters between the communication unit generation 30 and the serialization circuit 36, an output line 33 connected to an input terminal of an AND gate 51 and an AND gate 52 to validate the emission of an interrupt signal 11 in the event of collision detection during the transmission phase, an output line 34 for controlling the transmission of the end of message signal 17, an output line 35 for controlling the transmission of the start of message signal 12 by an AND gate 58.
• a circuit 37 for generating the messages at the start of the message, at the end of the message and in the event of an interruption in the event of a collision is controlled by an OR gate 53 whose input terminals are connected to line 34 and to the output terminals AND gates 51, 52 and 58.
• An OR gate 38 is interposed between the output of the serialization circuit 36, the output of the circuit 37 and the input of a line amplifier 39 whose output is connected to the network 40.
• the message generation and processing unit 30 also includes several input lines 57 conveying the character received, an input line 55 controlling the transmission of characters between a deserialization circuit 44 and the processing unit 30, a input line 56 connected to a circuit 43 for detecting the interrupt signal, an input line 54 connected to the output of a comparator circuit 50 intended to compare the character received on lines 57 at the address of the transceiver equipment defined by a circuit 49.
• the deserializer circuit 44 and the signal detection and interruption circuit 43 are connected to the output of a line adaptation circuit 42 itself directly connected to the network 40.
• the OR gate 46 detects the reception of a character or an interrupt signal and controls a timer circuit 47 responsible for prohibiting the transmission of a new message before a predetermined minimum time.
• the output of this timing circuit 47 controls a random timing generation circuit 48 which will authorize the transmission of the command 35 for transmitting the message start signal to circuit 37 through AND gate 58 and OR gate 53.
• Circuit 41 is used if the comparison between signal transmitted and. signal received takes place after transmission of each binary element composing the characters and during the intervals between each character.
• Circuit 45 is used when the comparison is made after the transmission of each character.
• the AND gates 51 and 52 validated by the output line 33 of the generation unit, allow the transmission of the collision detection signal to the circuit generating the interruption signal 37 through the OR gate 53.
• the circuits constituting the transceiver can be produced by electronic means well known to specialists. For this reason, it is unnecessary to describe in detail the construction of these circuits.
• the realization of these functions can be obtained in a particularly simple way using the microprocessor technique, as described in the following embodiment shown diagrammatically in FIG. 7.
• the logic control unit 70 performs the functions of address recognition, comparison, collision detection, time delay, memorization of information and blocking of transmissions as previously described.
• this logical unit is connected with a part to the line adapter 42 by the line 71, making it possible to detect the absence of emission and possibly the collisions on the network 40, on the other hand to a serialization-deserialization circuit 72 connected itself to the network to through the line amplifier 39 and the line adapter 42, finally to circuit 49 defining the address of the transceiver.
• Serial-parallel interface circuits such as circuit 72 are commonly used in logic communication techniques, and some of these circuits include a special command, not shown in the figure, making it possible to directly generate an interrupt signal 11. In the case where these circuits do not have such a command, it will be possible in a simple way, as shown in FIG.
• the logic control unit, 30 or 70 makes it possible to prevent transmission inhibition in order to send an acknowledgment message without waiting for the minimum waiting time.

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

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ID=9259499

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Cited By (6)

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Citations (3)

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• 1981
  • 1981-06-05 FR FR8111687A patent/FR2507415A1/fr active Granted
• 1982
  • 1982-06-03 US US06/464,499 patent/US4584575A/en not_active Expired - Fee Related
  • 1982-06-03 DE DE8282901720T patent/DE3261051D1/de not_active Expired
  • 1982-06-03 EP EP82901720A patent/EP0080481B1/fr not_active Expired
  • 1982-06-03 WO PCT/FR1982/000092 patent/WO1982004366A1/fr not_active Ceased

Patent Citations (3)

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