WO2010055270A2

WO2010055270A2 - Communication method and network implementing said method

Info

Publication number: WO2010055270A2
Application number: PCT/FR2009/052186
Authority: WO
Inventors: Nicolas Verdier; Philippe Joussain; Guillaume Dupety
Original assignee: Centre National D'etudes Spatiales (Cnes)
Priority date: 2008-11-17
Filing date: 2009-11-16
Publication date: 2010-05-20
Also published as: WO2010055270A3; FR2938718A1; FR2938718B1

Abstract

The invention relates to a method for peer-to-peer communication between two nodes of a network, as well as to a network suitable for implementing said method. Said communication method enables nodes to send data messages to at least one node, referred to as the collector node (102, 102'). A routing path between any one of the nodes and each collector node is determined by peer-to-peer broadcasting of a message, referred to as the control message, emitted by the collector node (102, 102'), making it possible to assign a rank to each node on a routing path relative to the collector node (102, 102'), and containing a session identification field.

Description

COMMUNICATION METHOD AND NETWORK IMPLEMENTING THIS

PROCESS

The invention relates to a method of communication between electronic communication devices, called nodes, forming a network, and a network adapted to implement this method.

The invention more particularly relates to a communication method adapted for the propagation of data step by step between nodes of a network.

A network composed of nodes exchanging data is said to be wide, if the dispersion of the nodes largely exceeds the range of communication

(wired or wireless) of each of the nodes. In such a network, it is particularly advantageous that the method of communication between the nodes allows the data to be propagated step by step.

Such a method allows the exchange of data from a source node to a distant destination node and can be unrelated and / or out of range of one another, via a relay node chain , connected and / or in communication range from each other two by two, propagating the data step by step until reaching the destination node.

Such a method of routing (also called routing method) of data relies on a method of locating the nodes to determine the optimal path on which to direct a message; the optimal path being one that allows a message to reach the destination node under optimal conditions.

The document "A Survey on Position-Based Routing in Mobile Ad Hoc Networks" Martin Mauve, et al. , published in November / December 2001 in IEEE Network, Volume 15, discusses step-by-step data routing methods between distributed nodes. These methods are based on using the geographical position of the nodes to direct the routing of data to the desired destination. At first, the nodes acquire their geographical position by using a localization system, such as for example the Global Positioning System (GPS). Then, in a second step, the nodes exchange knowledge of their geographical position, in order to create neighborhood tables between the nodes. Finally, a source node must know the geographical position of the destination node to transmit data to it, so that the data propagation takes place step by step by the best path, thanks to the insertion, in the data to be transmitted. , the geographical position of the destination node. One of the methods is to propagate the data, as much as possible in the direction of the destination. These methods can only work if the nodes are all equipped with a tracking system.

Global Environmental Micro Sensors (GEMS): A Revolutionary Observing System for the 21 ^st Century - Phase II Final Report, released August 31, 2005 by NASA Institute for Advanced Concepts, introduces a micro-sensor system (eg, high-altitude micro-balloons positioned by GPS) used for meteorological measurements, and compares several methods for conveying measurement data, either live (eg to a ground station or a satellite), or step by step (for example using the methods presented in the aforementioned Mauve document). For micro-sensors that have only a small energy autonomy, the best solution is to use a step-by-step routing, because the transmission power needed to reach a neighboring micro-sensor is often much lower than that required. to transmit live data to the final destination. However, each receiving node of a message must perform position comparisons to determine which of its neighbors is the most appropriate node to forward the message. All these operations are repeated at each node and for each message to be propagated and are expensive in computing time and energy.

The document "Beacon Vector Routing: Scalable Point-to-Point Routing in Wireless Sensors" Fonseca et al XP002408361 describes a routing protocol using tags ("beacons") defined randomly i

within the different nodes, and by routing trees defined between each node of the network and the different tags. The algorithm (see in particular section 3 pages 331-332) defines, for each node, a set of coordinates with respect to the set of tags and a distance function. Thus, each node knows its distance, in jumps, with respect to each tag, and the coordinates of a node are concretized by a vector comprising all the different distances. The nodes must know the positions of their neighbors in order to allow optimization of the routing by the root node. To do this, the different nodes must periodically send messages containing their coordinates. It is therefore again a system based on the location of the nodes by virtual coordinates.

The document "TAG: A Tiny Aggregation Service for Adhoc Sensor Networks" Madden et al XP008091295 describes a data aggregation service for a wireless sensor network. The aggregation consists of executing at each node a particular function on the transmitted data (for example chosen from the functions COUNT, MIN, MAX, SUM, AVERAGE). The routing algorithm chosen must allow on the one hand the broadcasting of requests to all the nodes, on the other hand the aggregation of the collected data towards the root of the network (one of the nodes where the recipient user is connected to the network). network) from the different nodes. An example is given of an inverse tree-based routing protocol in which the root sends a message to the different nodes to allow their organization according to a routing tree in which each node is defined by a level (c '). that is, a rank) and a parent node. This protocol is however not compatible with a network comprising a plurality of roots. In addition, it does not deal with the problems that arise in case of loss of the quality of communication between two successive nodes during the transmission of the data.

There is therefore still a need for a step-by-step data routing method that is simple, efficient, economical, robust, generic and can be multipoint. A method of routing in a network of nodes is: simple, if it requires few data processing operations to be performed by nodes; effective, if the data reaches its destination quickly, with a minimum of duplicate transmissions, including local loss of communication between a pair of nodes; economical, if it is suitable for sensor networks with low cost and low energy autonomy; robust, if it can continue to work despite unpredictable changes in network topology, and so few messages never reach their destination; generic, if the routing does not require a geographic location system of each node, nor a complex digital processing at each node; multipoint if the data can be transmitted to a plurality of separate collection nodes.

The invention aims to provide these advantages and to provide a communication method for transmitting data step by step, via at least one continuous and optimized path (including a shorter path), from any source node of the network up to to one or more predetermined destination node (s).

The invention also aims to provide a network of nodes for the implementation of this method.

The invention aims in particular to provide such a method and such a network that can be the subject of many different applications, and more particularly that are compatible with a very low power consumption of each node, for example by allowing a long duration of network life with nodes only powered by accumulator batteries or low capacity batteries.

To do this, the invention relates to a method of communication between a plurality of electronic communication devices, called nodes, of a network, adapted to transmit data messages - in particular measurement data produced by integrated sensors in at least some of the nodes-to at least one node, said collector node, wherein:

each node is adapted to be able to send and receive messages,

each node comprises a processing module adapted to interpret and modify a received message, a routing path between any one of the nodes and each collector node is determined by diffusion, step by step, of a message, called a management message, sent by each collecting node, each management message comprising a digital field, said rank field, - the processing module of a node receiving a management message, being adapted to compare the value of the rank field of the management message with a digital value stored in a digital memory of the node, said rank memory,

if the value contained in the rank memory belongs to the set formed of the undefined values, then the processing module increments the contents of the rank field, updates the contents of the rank memory with the contents of the rank field increments, and retransmits the management message, characterized in that:

the processing module of a node receiving a management message is adapted to, if the value contained in the rank memory belongs to the set formed of values greater than the contents of the rank field, incrementing the contents of the rank field , update the contents of the rank memory with the contents of the rank field increment, and retransmit the management message, - the processing module of each collection node is adapted to incorporate in each management message that it emits, a digital field, said session identifier field, the value of which is modified, for each management message sent by the same collector node, according to a predetermined order relation known to the nodes (that is to say represented by data recorded in each node).

The method of communication step by step according to the invention has the advantage of being composed of simple actions and therefore fast and economical to be executed by each node. In addition, a node does not need to have complete knowledge of the path that connects it to the collector node, but it only needs to be part of a chain of connected nodes and / or within range of each other. two by two to be able to send messages to the collector node. The process according to the invention allows automatic connection without a GPS-type positioning system or virtual coordinate system, neither intermediate tags references for such a system, nor complex digital processing, nodes considered to be closest to each other, via a path optimized considered the shortest way possible. Messages to one (or more) sink node (s) travel from node to node along a routing path and converge to each sink node. In addition, a method according to the invention operates without the nodes needing to receive and take into account the geographical position of each collector node receiving messages.

The updating (notably periodic) of the routing paths made possible by the use of the session identifiers is particularly advantageous in the case of networks with variable topology over time to ensure that the paths are still valid and in a simple way, without risk of error, ambiguity or inconsistency. The optimal frequency of updating the routing paths is chosen according to the mobility dynamics of the nodes in order to avoid initiating management messages more often than necessary. In addition, the use of a session identifier field makes it possible to make the invention compatible with the simultaneous use of a plurality of collector nodes, and also allows the dynamic propagation of the indication of a disability. a portion of the routing path when transmitting data from each source node to each sink node. The value of this session identifier field is modified for each management message sent by the collecting nodes, and is the same for all the collecting nodes issuing a management message corresponding to the same session.

Advantageously and according to the invention, the processing module of a node is adapted to record an undefined value in its rank memory when it receives a management message whose session identifier field contains a subsequent numerical value (higher order) than the previous management message received. Thus, an initiating collector node of a management message can, by modifying the value of the field of session identifier contained in the message, to impose on the receiving nodes an update of the message ranks and thus of the routing paths which lead to this collecting node. Such an undefined value can be stored in a permanent memory of the node at its manufacture (eg maximum value of the rank memory of the node).

Advantageously and according to the invention, each collector node is adapted to include an identifier of this collector node in each new management message that it initiates. Advantageously and according to the invention, the network comprises a plurality of collector nodes, each comprising a digital identification code, said collector node identifier, which is specific to it, stored in a permanent memory of this collector node, this collecting node being adapted to include this collector node identifier in each management message it initiates. Deploying multiple collector nodes increases the number of message collection points from other nodes, and therefore extends the network area. The different collecting nodes can be connected by a specific link (wired or not) in permanent communication with each other and / or with a central station and / or regularly visited for the collection of the data they receive.

Advantageously and according to the invention, the processing module of a node stores in a digital memory of the node, said collector node identifier memory, the node identifier of a collector node including a management message that it received resulted in the update of his rank memory with the smallest rank value. In the interval between the receipt of two management messages, each node sends messages to a single collector node. So there are as many subnets as there are collecting nodes.

Advantageously and according to the invention, each node comprises a digital identification code, said node identifier, which is specific to it, stored in a permanent memory of this node, and each management message includes a digital field, called a field of reference. transmitter node identifier, wherein the node identifier of the node that issued this message is last recorded.

Advantageously and according to the invention, the processing module of a node, said receiving node, having received a management message having caused the updating of its rank memory, is adapted to memorize the value of the identifier field of transmitting node of this management message in a digital memory of the receiving node, said closest node identifier memory, and replacing the contents of this field in this management message by the node identifier of the receiving node, and retransmitting the management message. Storing the node ID of the immediately preceding node in the transmission chain allows, if necessary, to avoid sending a message directly to the previous node (which may be the nearest neighbor on the shortest path to a collector node), thus reducing duplication of messages.

Advantageously and according to the invention, each node comprises a device for measuring and recording the signal level of reception of the message, and when a node receives a management message whose rank field value is equal to that of the rank memory, the processing module is adapted to compare the level of the reception signal with that of the previous received message, and then store, in the transmitting node identifier field, the identifier of the node providing the highest signal level . This criterion allows a more efficient management of the placement of the nodes on the path of the management messages. Thus, when two paths of the same length, in number of nodes, are possible for a node, the processing module stores the path by which the node receives a management message with the strongest signal level, which corresponds to the highest number of nodes. short way to the collector node. In addition, combined with the use of the assignment identifier field, this criterion makes it possible to uniquely determine the routing between the different nodes of the network.

Advantageously and according to the invention, each management message contains a digital field, called recipient identifier field (s), containing at least one node identifier of a destination node of the management message. Advantageously and according to the invention, the processing module of a receiving node of a management message compares each value of the recipient identifier field (s) with its node identifier, and the processing module is adapted to access reserved content of the management message if and only if the node identifier corresponds to the value of the recipient identifier field (s). The communication method according to the invention is adapted to include in a content management message reserved for a particular node or a group of nodes (all identified individually or collectively in the recipient identifier field (s)). Thus, all the receiving nodes of the message but not recipients of the message, ignore its reserved content. Such reserved content may for example consist of preventing the retransmission of the management message or forcing its retransmission.

Advantageously and according to the invention, each management message is adapted to be able to convey additional data to be read by at least one node.

Advantageously and according to the invention, each management message is adapted to be able to convey at least one command to be executed by at least one node. This includes, for example, a command for reconfiguring the parameters of a node (for example the frequency of the measurements to be performed by the node, the maximum number of retransmission of a data packet before abandoning, etc.) or a command of restitution of information concerning parameters of the node (for example the maximum waiting time for transmission of a management packet, the maximum waiting times for transmission and retransmission of a data packet, etc. ). Advantageously and according to the invention, the processing module of at least one node, said source node, is adapted to develop messages, called data messages, and transmit them to at least one collecting node. For example, at least some of the nodes perform measurements of their environment, and then include those measurements in data messages. These data messages therefore convey data to be routed to the node (s) collector (s) adapted (s) to process these data. Advantageously and according to a first preferred embodiment of the invention, the processing module of each source node is adapted to incorporate in the data messages a collector node identifier stored in a memory of the source node. In this way, each source node transmits data messages to a collector node whose storage node identifier has been stored.

Advantageously and according to the invention, each transmitting node (source or not) having to transmit a data message transmits it to the node whose node identifier is stored in the node identifier memory closest to the transmitting node. . Each data message is sent for each node to a single destination node, thereby allowing the uniqueness of the path taken by each message and leading to a collector node. This preferred embodiment of the data message routing method allows each collecting node to receive a single copy of each data message sent and does not overload the network.

Advantageously and according to a second embodiment of the invention, each data message is transmitted step by step using a digital field that it contains, said rank field, such as the processing module of any node receiving a data message, compares the value contained in the rank field with that contained in its rank memory, updates the rank field with the contents of its rank memory and retransmits the message if the value contained in the Rank memory is less than that contained in the rank field. This second mode of implementation of the routing method of the data messages, based on the rank values of the nodes, makes reliable the reception of data to the collecting nodes, even in the case where paths are no longer valid. Indeed, the same data message can be forwarded by several receiving nodes, all possessing a field of lower rank to the sending node of the message.

Advantageously and for all modes of implementation of the invention, the data messages are generated asynchronously by the source nodes and then transmitted asynchronously. Each node applies a rule for determining the instant of measurement and the instant of transmission of an associated data message. Several rules can be envisaged, such as: according to a fixed frequency, or as soon as a threshold of variation is exceeded, or as soon as a measurement command is received, ... Thus, the method according to the invention makes it possible to vary the volume of data exchanged by varying the rules to be applied by the nodes dispersed in several points of the network. The messages containing these measurements are transmitted at times to overcome the collisions between messages.

Advantageously and according to the invention, the reception by a node of a data message triggers the sending by this node of a message, called service message, which constitutes an acknowledgment message if it accepts the data message. , and a non-acknowledgment message if it refuses the data message. This mechanism for acknowledging or not acknowledging the data messages makes it possible to indicate to the sender node whether a data message has been received by a node, and whether the reception is accepted or refused by this node. Its purpose is to inform a transmitting node about the status of the reception. Moreover, it can be used indifferently in one or the other of the two modes of implementation of the routing method of the data messages presented above.

Advantageously and according to the invention, a transmitting node retransmits its message only if, after a predetermined time, no service message is received. Retransmission provides another opportunity for the receiving node to be able to receive the data message in the event of a previous bad reception.

Advantageously and according to the invention, a receiving node of an acknowledgment message does not re-transmit this service message. Indeed, an acknowledgment message is used to acknowledge an identified message exchanged between two nodes, it is not intended to be broadcast to other nodes of the network.

Advantageously and according to the invention, a receiving node of a non-acknowledgment message sends a message of non-acknowledgment to the sending nodes of the data messages it receives (that is to say to the destination of the message). collector node), until a management message is received containing a subsequent session identifier field value. The indication of invalidity of the path passing through this node is thus propagated each time it is used, until the path is updated. The invention also relates to a network of electronic communication devices, called nodes, adapted to transmit data messages to at least one node, said collector node, in which:

each node comprises a transmitter and a receiver,

each node comprises a processing module adapted to interpret and modify a received message,

each collection node is adapted to transmit a message, said management message, broadcast from one to another by the nodes, each management message comprising a digital field, called a rank field,

the processing module of a node receiving a management message, being adapted to compare the rank field with a digital value stored in a digital memory, called rank memory,

if the value of the rank memory belongs to the set formed by the undefined values, then the processing module is adapted to increment the value of the rank field, update the contents of the rank memory with the content of the field of incremented rank, and retransmit the management message, characterized in that:

the processing module of a node receiving a management message is adapted to, if the value contained in the rank memory belongs to the set formed of values greater than the contents of the rank field, incrementing the contents of the rank field , update the contents of the rank memory with the contents of the incremented rank field, and retransmit the management message,

the processing module of each collection node is adapted to incorporate in each management message that it transmits, a digital field, called session identifier field, the value of which is modified, for each management message sent by the same collector node, according to a predetermined order relationship known to the nodes.

The network according to the invention is suitable for implementing the method according to the invention. In other words, the method according to the invention is implemented in a network according to the invention.

Advantageously, a network according to the invention comprises a plurality of nodes, called source nodes, adapted to generate useful data to be transmitted (for example data representative of measurements), and the processing module of each source node is adapted to include these data useful in data messages sent to at least one collector node. A plurality of nodes serve as a relay to allow the data messages of the source nodes to be able to reach the collector nodes. This mechanism of data transmission step by step makes it possible, on the one hand, to extend the size of the network without having to increase the range of communication of the nodes for example by adding nodes, and on the other hand to increase the energy autonomy of the nodes which are thus more economical to produce. In a network according to the invention, in addition to the node (s) collector (s), all other nodes can be simultaneously sources or relays. In addition, a network according to the invention may comprise several collector nodes distributed over a zone, thus advantageously making it possible to increase the number of collection points of the data messages originating from a plurality of source nodes.

The invention extends to a network characterized by all or part of the above-mentioned characteristics in relation to a method according to the invention.

The invention can be subject to many different applications.

Advantageously and according to the invention, the nodes are at least partly associated with mobile structures, and the nodes are connected to each other by wireless links.

In particular, advantageously and according to the invention, said structures are freely movable with a fluid in which they are placed, so as to follow the currents. Their movements are therefore uncontrolled and in general indeterminate. For example, advantageously and according to the invention said mobile structures are aerostats placed in the Earth's atmosphere, and equipped with Earth observation means generating observation data (for example meteorological) as useful data. According to another application, mobile structures can be satellites of a constellation of satellites in space.

Thus, the nodes are associated with space systems (satellites) or aircraft, more particularly aerostats such as balloons, in particular with a node carried on board each space system or aircraft, and at least one collecting node is adapted to transmitting messages to a central station, in particular a ground station (this collecting node being itself fixed with respect to the central station or with respect to the ground, or carried by a space system or an aircraft and in permanent communication link with such a central station or with such a ground station). Advantageously, especially when the nodes are associated with aircraft, at least one source node is provided with means for observing the Earth, for example means for observing meteorological phenomena, such as cyclones. According to an advantageous application of the invention, each source node, and in particular each transmitter node, is carried on board an aerostat. Advantageously and according to the invention, the nodes are at least partly associated with mobile structures, such as capsules, immersed in a liquid medium (such as the water of a basin, a marine environment, a river, a river , a physiological medium of a living being (for example the blood or the digestive tract ...) At least one collecting node is then adapted to transmit messages to a fixed station immersed or not (this collector node being either itself even fixed, is carried by a capsule and in permanent communication connection with such a fixed station) and at least one source node is provided with means for observing said liquid medium, in particular means for observing currents of the liquid medium. the case of mobile capsules of small dimensions in a physiological medium, the invention makes it possible, for example, to appreciate the characteristics (speed, diffusion ...) of the circulation of said physiological medium in the body.

In another conceivable application of the invention, the nodes are associated with terminals capable of being worn by persons (for example mobile phones, personal assistants (PDAs), etc.), and the transmitted data can be messages in the form of messages. from each person carrying a terminal and / or to each person carrying a collecting node.

Advantageously and according to other applications of the invention, the nodes are at least partly associated with fixed structures relative to the terrestrial ground. Advantageously, for example at least one source node is then equipped with fire monitoring means.

A method and a network according to the invention can be of the monodirectional type, as is the case for the transmission of observation data between source nodes and at least one collecting node. However, nothing prevents us from providing a method and a network according to the invention which are bidirectional in nature, that is to say, allow data exchanges in one direction and in the other, a collector node in a sense of transmission that can act as a source node in the other direction of transmission.

The invention also relates to a method and a network characterized in combination by all or some of the characteristics mentioned above or below.

Other objects, features and advantages of the invention will appear on reading the following description of some of its embodiments given solely by way of nonlimiting examples, and which refers to the appended figures in which:

FIG. 1 is a schematic view of a network of nodes according to the invention,

FIG. 2 is a schematic view of the internal structure of a node of a network according to the invention; FIGS. 3a, 3b and 3c are illustrative schematic views of the digital fields contained in messages exchanged between nodes of a network according to the invention, respectively applying to a management message, a data message and a service message,

FIG. 4 represents a logic diagram of the steps performed by a node of a network according to the invention during the reception of a management message in a method according to the invention,

FIGS. 5a and 5b each represent a logic diagram of the steps performed by a node of a network according to the invention when receiving a data message in a method according to the invention, respectively according to the first (preferential) and the second mode of implementation of the routing of data frames,

FIG. 6 shows an embodiment of a network according to the invention, comprising aerostats balloons and stations, and intended to be used for meteorological measurements,

FIG. 7 presents a second embodiment of a network according to the invention intended to be used for studies of aquatic currents,

- Figure 8 shows a third embodiment of a network according to the invention for use in fire monitoring.

Figures, scales and proportions are not strictly adhered to for the sake of clarity of the illustration. In FIGS. 3a, 3b and 3c, the arrangement of the digital fields inside the messages is only an example given for purposes of illustration.

In Figure 1, solid lines or dotted lines represent links between nodes. In addition, the thick lines (solid or dashed) represent the shortest routing path between the nodes resulting from the application of the method according to the invention.

In a communication network 100 according to the invention, represented in FIG. 1, the communication is carried out step by step between electronic devices, called nodes, geographically dispersed in an environment according to a topology that may be undetermined and / or uncontrolled. . Communication-capable nodes communicate with each other via wired or wireless links. In the case of wired links, the nodes are interconnected by physical links (cables, optical fibers ...), the network thus forming a mesh connecting each node to a plurality of other nodes.

The links described in the following description are preferably wireless links, the invention being particularly advantageous in the case of nodes interconnected by wireless links. As a non-restrictive example, these wireless links use the propagation of electromagnetic (including radio frequency) or acoustic waves to make possible remote communication.

The network 100 according to the invention comprises different types of nodes which are differentiated by their function (s), it being understood that nothing prevents at least one node from accumulating several functions, from one transmission to another. Thus, at least one node, said collector node 102, is a data destination node from at least one other node, said source node, and propagated step by step to this collector node 102. More particularly, a network according to the invention may comprise a plurality of nodes 102, 102 'collectors. It should be noted that, when a plurality of nodes 102, 102 'collectors is deployed in a network according to the invention, the nodes 102, 102' collectors are preferably interconnected by specific links, not shown in the figures (wired or wireless), adapted for the exclusive communication between the collecting nodes and / or between them and a central station. These specific links are intended to essentially allow the retrieval and concatenation of data in a centralized database located in a central information storage station.

The other nodes 103 _b 103 _2, 103 _3, 103 _4, 103 _5, 103 _6, 103 ₇ (denoted hereinafter 10S ₁ when it is any of these nodes) of the network 100, called relay nodes , have a function of relaying (receiving and transmitting) data messages, allowing communication between source (s) and collector (s) nodes, and possibly between relay nodes, out of range of each other. By for example, the node 103 ₃ (Figure 1) is located between the nodes 103 ₄ and 103i and serves as relay node for communication between these nodes.

The source nodes also have a function of generating data messages, for example from a measurement of their environment, and at least transmission of these data messages. A network 100 according to the invention comprises at least one source node, in particular a plurality of source nodes, and a plurality of relay nodes. Some relay nodes can act as source nodes. Some relay nodes can act as collection nodes.

In a network according to the invention, each node 102, 102 'collector must be in connection with at least one other node, and at least one routing path must be established between each source node and each collector node. To do this, particularly when the links 7 are of the wireless type, the density and the number of relay nodes must be sufficiently large, depending on the range of the wireless links 7. Each node, whatever its type, comprises at least one transmitter 75 and at least one receiver 76 (FIG. 2) connected to at least one antenna 74, adapted to establish wireless communication links (radiofrequency) with the other nodes to be connected. scope.

In addition, each node, regardless of its type, comprises digital data storage memories. A digital memory, known as a node identifier memory 11, formed of a node's read-only memory, contains a digital node identifier code, making it possible to uniquely distinguish each node of the network. The contents of this memory are not erased when the node is powered off. The memories described below are memories of the node, and their content can be modified and is quickly accessible read / write. A node comprises: a digital memory, called rank memory 12, for storing a natural integer representing the rank of the node; a digital memory, called reception signal level memory 13, for storing a value representative of the reception signal level of a management message; a digital memory, called memory 14 of identifier of collector node, for storing the identifier of the collector node to which the data messages are sent from this node; a digital memory, called session identifier memory 15, for storing a value (natural integer) representative of the current session; a digital memory, called the closest node identifier memory 16, for storing a node identifier of a node transmitting a received message.

Each node also comprises a processing module 88 adapted for interpreting received data and for extracting the contents of a memory, modifying its value or storing a value therein. A processing module 88 comprises calculation means such as a computer (not shown in the figures) and buffers for temporarily storing data necessary for a calculation or waiting to be transmitted or stored (not shown in the figures). ).

In practice, the digital memories of each node are advantageously organized according to three buffers or groups of memory buffers:

a first buffer or group of service buffers memorizing all the service data of the network: the data identifying the optimal routing path; data identifying other nodes in range; a second buffer or group of data packet buffers storing the data packets of the data messages to the collector node (s);

a third buffer or group of acknowledgment buffers memorizing the acknowledgment or non-acknowledgment signals received by this node for the data of the currently transmitting data messages still present in the second buffer or group of packet buffers; data; and the acknowledgment or non-acknowledgment signals transmitted by this node for the data messages it receives.

Each node also includes a time measurement module 77, such as a clock, at least substantially synchronized with all nodes of the network. This module allows the node to include data representative of a time (dating) in the exchanged messages.

The source nodes most often comprise a payload composed of measuring means 10 comprising a plurality of sensors (for example: temperature sensors, hygrometry, pressure) and a measurement control module 89 adapted to parameterize the measurements to be made, storing the measurements made and sending the processing module 88 of the node the measurements so that they can be stored and sent to the collector node. As a variant, said measurements may consist solely of data stored in the memories of the node because of the operation of the network (rank of the node, etc.).

Each node comprises bidirectional communication buses 78 connecting the processing module 88 with the other modules, as well as with the various memories of the node. A bidirectional communication bus 78 also connects the measurement control module 89 with the measurement means 10 of the node. These two-way communication buses 78 make it possible to pass data from one module to another within a node.

Each node comprises a power supply module 79 connected by power cables (not shown in the figures) to the other modules of the node and allowing their supply of electricity from at least one source of electrical energy (sector, batteries, accumulators, photovoltaic cells, alternators, wind turbines, ...).

Communication links 7 between nodes constitute the medium for exchanging messages of different types. In FIG. 1, the nodes in visibility (within range) of each other are connected by at least one line (solid or dashed) symbolizing a link 7 between these nodes.

Each node is adapted to receive and retransmit management messages (FIG. 3a) making it possible to establish and / or update the topology of the network, and by this means to inform the nodes of the network that a new session begins. The management messages 19 are initiated exclusively by the collector node (s) 102, 102 ', of the network.

Each node is adapted to receive and retransmit data messages (FIG. 3b), initiated exclusively by source node (s) and including measurement data made by source node (s). (s).

Each node is adapted to transmit and receive service messages (FIG. 3c). Such a message may be initiated by any type of node upon receipt by the latter of a data message as confirmation that the data message has been received.

The data contained in the messages exchanged between the nodes are partitioned into several digital fields.

Whatever the type of message considered, it comprises a digital field, called type identification field 24, allowing the processing module 88 of a receiving node to distinguish the type of message received, among the management messages 19, data messages and service messages.

In addition, all types of messages comprise a digital field, said issuer node identifier field 22, making it possible to identify, on reception, which node sent the message last, and a digital field, said field 23 recipient identifier (s), for identifying, on reception, which node (or group of nodes) is intended for the message, thereby forcing the non-destination nodes to ignore the message at least in part. This recipient identifier field 23 may contain one and only node identifier, or a plurality of node identifiers, or an identifier of a list of nodes whose identifiers are stored by a read-only memory of the different nodes. .

However, some digital message fields differ depending on the type of message being considered.

Thus, a management message 19 further comprises at least: a digital field, said collector node identifier field, containing the identifier of the collector node having initiated this management message; a digital field, said session identifier field 26, containing the value (integer natural), the last session in progress for the collector node that initiated this message; a numeric field, said field 27 of rank, containing the value (natural integer) of rank of the management message modified by the last node transmitting the message. A data message 20 further comprises at least for example: a digital field, called a payload field, containing the measurement data made by the source node; and in one embodiment (second embodiment described hereinafter), a digital field, said rank field, and a digital field, said collector node identifier field. A service message furthermore comprises at least one digital field, called service field, containing data representative of a signal to be transmitted, for example a signal for acknowledging the reception of a data message, or a signal of not acknowledging receipt of a data message. The method according to the invention is adapted to be implemented by a network 100 described above, and makes it possible to establish an optimal routing path between any of the nodes 103j and a node 102, 102 'collector. This optimal routing path is determined by the broadcast of a management message 19, issued by the node 102, 102 'collector. In addition, the propagation of a management message 19 from a node 102, 102 'to the other nodes collector determines the topology of the network 100 and order these nodes along a path adapted to allow, in return , the propagation of data messages to this node 102, 102 'collector. A routing path consists of several segments, one segment being the portion of the routing path that separates two nodes located one after the other on the path, without being separated by another node. A vehicle management message 19, via the rank field 27, the number of segments that already counts the path from its initial end (at the node 102, 102 'collector).

In FIG. 1, each value included in a square next to a node (solid line or dotted line) represents the value contained in its rank memory 12, as determined by the method according to the invention. A line square full, respectively dotted line, is used when a node is located on a routing path of a management message from the first node 102 collector, respectively the second node 102 'collector. Thus, the content of the rank memory 12 of the collector node 102 is equal to 0, and that of the first node 103i located on the routing path from the first collector node 102 is 1.

As shown in FIG. 1, the first collector node 102 sends a first management message 19 comprising a rank field 27 containing the value 0. The bold solid lines represent the routing path followed by this first management message 19. The node 103i, within the communication range of the first collector node 102, receives this message 19, increments the content of the message rank field 27 by one (resultant value equal to 1) and assigns it to its rank memory 12. (resultant value equal to 1), then reissues the management message 19. It should be noted that a node 102, 102 'collector ignores all the management messages that it possibly receives from the other nodes of the network 100.

Nodes 103 ₂ and 103 _3, within communication range of node 103 _l5 receive the message from node 103i. Each of nodes 103 ₂ and 103 ₃ increments the content of field 27 of rank of the received message by one unit (resulting value equal to 2) and assigns it to its rank memory 12 (resultant value equal to 2) and then re-transmits the management message 19. In addition, the nodes 103 ₂ and 103 ₃ store the node identifier of the node 103i in their closest node identifier memory 16, corresponding to the fact that the node 103i is their nearest neighbor on the routing path starting by the collector node 102.

The node 103 ₂ (respectively 103 ₃ ) ignores the management message 19 from the node 103 ₃ (respectively 103 ₂ ) because it contains a field value 27 of rank equal to that contained in its memory 12 of rank. In addition, the node 103i ignores the management messages 19 from the nodes 103 ₂ and 103 ₃ because they each contain a field value 27 of higher rank than the contents of its rank memory 12. Node 103 ₄ receives management messages 19 from nodes 103 ₂ and 103 ₃ . The message from node ₃ 103 being received with a higher signal level, the node 103 stores the node ₄ of node identifier 103 ₃ in its memory 16 to the nearest node identifier (corresponding to the fact that the node ₃ is 103 its nearest neighbor), and then increments by one unit the value contained in the field 27 of the message rank (resulting value equal to 3) and assigns it to the contents of its rank memory 12 (resultant value equal to 3), then reissues the management message 19. The 103 node ₅ receives management messages from the node ₂ 103 and node ₄ 103. Node 103 ₂ having sent a management message 19 comprising a field value 27 of smaller rank (value equal to 2) than that of the message sent by node 103 ₄ (value equal to 3), then the node

103 ₅ stores the node identifier of the node 103 ₂ in its closest node identifier memory 16 (corresponding to the fact that the node 103 ₂ is its nearest neighbor). ₅ the node 103 increments by one unit the value contained in the field 27 of row (resulting value equal to 3) and assigns it to the memory 12 of row (resulting value equal to 3), and then retransmits the message management 19 . Nodes

103 ₆ and 103 ₇ , in the communication range of the node 103 ₅ , receive the management message 19 from the node 103 ₅ . Each of nodes 103 ₆ and 103 ₇ increments the content of field 27 of received message rank (resulting value equal to 4) and assigns it to its rank memory 12 (resulting value equal to 4), then reissues message 19 of management. In addition, nodes 103 ₆ and 103 ₇ stores the identifier of node ₅ of the node 103 in their memory 16 of the closest node ID, corresponding to the fact that the 103 node ₅ is their nearest neighbor.

In a network 100 having a plurality of nodes 102, 102 'collectors, each collector node sends a management message 19 which differs from other messages by a collector node identifier field it contains. In addition, sending management messages 19 by each node 102, 102 'collector is done asynchronously with respect to other collector nodes.

The network 100 represented in FIG. 1 comprises two nodes 102 and 102 'collectors. Like the first collector node 102, the second collector node 102 sends a second management message 19 comprising a field 27 of rank value 0. The routing path followed by the second management message 19 is represented by dashed lines. fat. Node 103 ₆ , within range of communication of the second node 102 'collector, receives this message. However, as previously described, the value contained in the rank memory 12 of the node 103 ₆ is equal to 4. The node may be positioned on a shorter routing path if it is attached to the second node 102 'collector rather than at the first collector node 102. Therefore, the node ₆ 103 increments by one unit the contents of field 27 of the message rank (resulting value equal to 1) and assigns it to the contents of its memory 12 to row (resulting value equal to 1), then retransmits the management message 19. The nodes 103 ₅ and 103 ₇ , within the communication range of the node 103 ₆ , receive the management message 19 from the node 103 ₆ . For the same reason as the node 103 ₆ , each of the nodes 103 ₅ and 103 ₇ increments the content of the rank field 27 of the received message by a unit (resulting value equal to 2) and assigns it to the contents of its memory 12 of rank (resultant value equal to 2), then reissues the management message 19. In addition, the nodes 103 and ₅ 103 ₇ stores the identifier of node 103 node ₆ in their memory 16 of the closest node ID, corresponding to the fact that the 103 node ₆ is their nearest neighbor. The node 103 ₅ (respectively 103 ₇₎ ignores the message 19 management from 103 ₇ node (respectively 103 ₅₎ because it contains a field value 27 of equal rank (value 2) to that contained in their memory value 12 rank. In addition, nodes 103 and ₆ 103 ₂ within communication range of node 103 _5, receive the message 19 from the management node 103 ₅ because they ignore the 27 largest field contains a value (2) or greater to the value (2 and 1 respectively) contained in their rank memory 12. The node 103 ₄ , in communication range of the node 103 ₅ , does not receive the management message 19 from the second node 102 'collector, because this management message is not re-transmitted by the node 103 ₅ . In the method according to the invention, a session corresponds to the time interval during which the method considers that the topology of the network 100, as determined by the broadcast of a management message by a node 102, 102 'collector , remains valid. After this time interval, the node 102, 102 'collector returns a new management message to update the network topology. Therefore, a session can also be seen as the interval of time separating two transmissions of a management message 19 by the same node 102 collector.

At the instant indicated by its time measurement module 77, a collector node 102 issues a new management message whose session identifier field 26 contains a new value.

Each session corresponds to a session identifier modified with respect to the previous one according to a known order relationship of the nodes. For example, a session identifier may be an incremented value for each new session, the value being reset to 0 after reaching a maximum value. A single management message 19 is initiated by each node 102, 102 'collector for each new session, and has a new value contained in the session identifier field 26.

In a network 100 having a plurality of nodes 102, 102 'collectors, a session is unique for a given collector node. The establishment of a new session is managed asynchronously between the nodes 102, 102 'collectors.

The preparation of the transmission of a management message 19 to be sent by a node 102, 102 'collector follows the following steps. First, the processing module 88 of the collector node 102 includes a predefined initial value in the rank field 27 of the management message.

Then, the collector node 102, 102 'includes its collector node identifier on the one hand in the digital field of the message corresponding to the collector node identifier field, and on the other hand in the node identifier field 22. transmitter. In addition, the collector node 102, 102 'includes a predetermined initial digital value in the session identifier field. For example, it is considered in the remainder of the description that the initial value of the session identifier is 0, and that the evolution order relation of the session identifiers follows an increment of one unit each. new session established. The processing module 88 of the collector node 102 includes the value of the recipient identifier in the recipient identifier field 23, the possible values being able to correspond to a group of nodes, for example the nodes in direct communication range of the node 102, 102 'collector (also called nodes in visibility), or a node in particular.

In the method according to the invention, it should be noted that for all the nodes and for all the types of message, the moment of transmission of a message by a node is determined so as to limit the collisions with other messages transmitted by separate nodes, for example by sending the message at a random time in a predetermined time interval.

Each node performs the steps of the method in the order shown in Figures 4, 5a and 5b. According to the method described in FIG. 4, in step 31, the module

88 treatment of a relay node 10S ₁ interprets a message has been received, extracts the contents of the field 24 of the message type identifier and determines that it is a message 19 Management, which in this case, the processing module 88 then executes step 32. In step 32, the processing module 88 of the node 103j determines whether it is the reception of the first management message 19. If the knot

103 _J receives a management message 19 for the first time, then the processing module 88 executes step 43, otherwise it executes step 33.

In step 33, the processing module 88 of the node 103j extracts the content of the destination node identifier field 23 from the message and then executes the step 34.

In step 34, the processing module 88 of the node 103j determines whether it receives the management message 19 by comparing the content of the recipient identifier field 23 of the message with its node identifier stored in its memory. node identifier memory 11. If the processing module 88 of a node 103j determines that it is one of the recipients of the management message 19, then it executes step 35, otherwise it executes step 47.

In step 35, the processing module 88 of node 103j extracts from the message the contents of the collector node identifier field 25 and executes step 36. In step 36, the processing module 88 of the node 1 (B ₁ compares the content of the collector node identifier field extracted from the message with the value contained in the node collector node memory 14

1 (B _1. If the two values are different then it executes step 39, otherwise it executes step 37.

In step 37, the processing module 88 of the node 1 (B ₁ extracts from the received message the content of the session identifier field 26 and executes the step 38.

In step 38, the processing module 88 of the node 1 (B ₁ compares the value extracted from the session identifier field 26 of the message with the value contained in its session identifier memory. message is prior (according to the order relationship governing the evolution of the session identifiers) to that of the node 1 (B ₁ , then it executes the step 47. If the value from the message is identical to that memorized by the node 1 (B ₁ , then it executes step 39. Finally, if the value from the message is later than that of node 1 (B ₁ , then the processing module 88 of node 1 (B ₁ executes step 43.

In step 39, the processing module 88 of node 1 (B ₁ extracts from the message the contents of the rank field 27, then executes step 40.

In step 40, the processing module 88 of the node 103j compares the value contained in the rank field 27 extracted in step 39 with the value contained in the rank memory 12 of the node. If the value of the message rank field 27 is greater than or equal to the value contained in the rank memory 12, then the processing module 88 of the node 103j executes step 47. Otherwise (i.e. the value contained in the rank memory 12 is greater than the value of the message rank field 27, or is an undefined value (for example the maximum value that can be taken by this memory 12 recorded by default during manufacture in the latter) ), it performs step 41.

In step 41, the processing module 88 of the node 103, tests

The value contained in the rank memory 12 is equal to the value resulting from the incrementation of the message rank field 27 (ie value of the rank field 27). plus one unit if each increment is equal to one). If so, the node 10S ₁ executes step 42. Otherwise, it executes step 43.

In step 42, the processing module 88 of the node 1 (B ₁₎ compares the reception signal level of the message with that of the preceding received message, as stored in the reception signal level memory 13. is less than or equal to the level of the received message, then the node _J 103 executes step 47. Otherwise, it proceeds to step 43.

In step 43, the processing module 88 of the node 103j increments the value contained in the rank field 27 of the received message by one unit, and then executes step 44. It should be noted that nothing precludes the provision of an increment value different from 1 if this is considered useful.

In step 44, the processing module 88 of the node 103j assigns the value thus incremented in step 43 to the contents of its rank memory 12, and then performs step 45. In step 45, the module 88 processing node 103j replaces, in the management message, the content of the issuer node identifier field 22 by the value contained in its node identifier memory 11; stores the receive signal level of the message (accessible value when the node receives the message from step 31) in the reception signal level memory 13; extracted from the management message and stores respectively the content of the collector node identifier field 25 in the collector node identifier memory 14, the content of the session identifier field 26 in the memory

15, the content of the transmitter node identifier field 22 in the identifier memory 16 of the nearest node. Then the processing module 88 of node 103j executes step 46.

In step 46, the processing module 88 of the node 103j retransmits the management message 19, that is to say the transmitter with its transmitter 75

In step 47, the processing module 88 of the node 103j ignores the received management message, and does not retransmit it. Advantageously, a management message can convey either additional data to be read by the nodes (for example the value of the measurement frequency), ie a command to be executed by the nodes (for example the start or the stop of the measurements). Therefore, a node 1 (B ₁ , if included in the recipient (s) of a message (step 34), retrieves and stores said additional data contained in the message, and then, if applicable, executes the command associated with the message As a non-limiting example, for a method according to the invention considered as operating at a low bit rate, the measurement period by the source nodes may be of the order of 30 seconds, and the bit rate transmission of a node can be of the order of 9.5kbps.

At a time determined by the time tracking module 77, the sensors equipping each source node make measurements of their environment. The moment of measurement depends on the considered node and the rule to be applied by the nodes (according to a fixed frequency, or if a parameter exceeds a threshold, ...). The measurement control module 89 sends the measurements to the processing module 88 so that they can be stored and sent to a node 102, 102 'collector. The processing module 88 of the 10S node ₁ inserts the measurement data into the measurement data field 30 of a data message.

The method according to the invention makes it possible to collect data messages sent from source nodes to at least one node 102, 102 'collector, relayed step by step via relay nodes 103,.

The data messages of a source node are sent to the collector node 102, 102 'whose value it has stored in its collector node identifier memory 14, and these data messages take the previously defined routing path by a management message 19 to determine the optimal path to reach the node 102, 102 'collector.

Preferably, the use of service messages 21 makes it possible to trace the reception of an emitted data message. The sending by a node 10S ₁ of a service message 21 is performed before the node 103j reissues the data message 20 (to a next node of the path). However, the use such service messages are optional for the operation of a method according to the invention. Furthermore, a node 1 (B ₁ transmitter transmits a message 20 received data if, after a predetermined time, no message 21 service is received. A receiving node 21 of a message service transmitting a signal This acknowledgment does not reissue this service message 21. Finally, a receiving node of a service message 21 transmitting a non-acknowledgment signal returns a non-acknowledgment message to the sending nodes of the data messages it receives, until upon receipt of a new management message containing a subsequent session identifier, which propagates the invalidity indication of a portion of the path each time a data message is received.

According to a first embodiment of the routing method of the data messages 20, a data message 20 is sent by a node to the last node 103j whose node identifier it has stored in its memory identifier 16. closest node (in the previous step 45 resulting from the receipt of a management message). To do this, the processing module 88 of the node inserts its node identifier, contained in its node identifier memory 11, in the identifier field 22 of the sending node of the data message, and then inserts the contents of the node. its closest node identifier memory 16 in the destination node identifier field 23 of the data message 20, then the node transmits the message.

Taking the example of topology of FIG. 1, considering that all the nodes 10S ₁ are source nodes carrying out measurements to be transmitted but supposing that the second node 102 'collector does not exist, the network comprising only a single collector node 102, the nodes 103 ₆ and 103 ₇ transmit a data message 20 to the node 103 _5; their nearest neighbor. The node 103 ₅ receives these two messages 20 of data and transmits each to the node ₂ 103 neighbor closest in range. ₅ the node 103 also transmits another message data 20 containing measurement data performed by the node 103 to the node ₅ 103 _2. The node 103 ₄ also transmits a data message 20 containing the measurements made by this node 103 _4; to node 103 _3; his nearest neighbor. Node 103 ₂ also emits a data message 20 containing the measurements made by this node 103 _{2, as} well as the three data messages 20 from the node 103 ₅ , to the node 103i its nearest neighbor. Node 103 ₃ receives and retransmits the data message 20 from node 103 ₄ , and also transmits a data message 20 containing its own measurement data, all transmitted to node 103i _; his nearest neighbor. Finally, the node 103i also transmits a data message 20 containing its own measurement data, as well as all the data messages that it has received and originating from the nodes 103 ₇ , 103 ₆ , 103 ₅ , 103 ₂ , 103 ₄ and 103 ₃ , to the collector node 102. The collector node 102 and receives all messages 20 data of all nodes 103 _^

In the case where the network comprises two nodes 102, 102 ', as represented in FIG. 1, the nodes 103 ₂ , 103 ₃ , 103 ₄ and 103i send their data messages 20 to the first collector node 102 as described above. On the other hand, nodes 103 ₇ , 103 ₆ and 103 ₅ send their data messages to the second node 102 'as follows. The nodes 103 ₅ and 103 ₇ each issue a data message 20 to the node 103 ₆ , their nearest neighbor. ₆ the node 103 transmits a message containing data 20 of its own measurement data, and retransmits the 20 data messages from the nodes 103 ₅ and 103 _7, all being transmitted to the second node 102 'collector. Thus, the network collects data messages at two points which are nodes 102 and 102 'collectors.

According to the method described in FIG. 5a, in step 49, the processing module 88 of the node 10S ₁ interprets that a message has been received, extracts from the message the value contained in the type identifier field 24 and determines that it is a data message and, if so, executes step 50.

In step 50, the processing module 88 of the node 103j extracts the contents of the destination identifier memory 22 of the message and executes the step 51. In the step 51, the processing module 88 of the node 103j compares the content of the destination node identifier field 22 extracted from the message with the contents of its node identifier memory 11. If the two values are different, then the node 1 (B ₁ executes the stopping step 58. Otherwise, it executes the step 52.

In step 52, the processing module 88 of node 1 (B ₁ determines whether it accepts the data message intended for it, if it accepts it, it executes step 53. If it refuses it, it carries out step 57. This last case can intervene, for example, when the path is broken after the node 1 (B ₁ , or when its outgoing message processing buffer is saturated.

In step 53, the processing module 88 of the node 1 (B ₁ sends a message 21 of the message acknowledgment service to the transmitting node of the data message 20, then it executes the step 54.

In step 54, the processing module 88 of node 1 (B ₁ inserts the identifier of the next node on the path (corresponding to the contents of the closest node identifier memory 16) in the field 23 of FIG. message recipient identifier 20. Next, the processing module 88 of the node 10S ₁ executes step 55.

In step 55, the processing module 88 of node 103, inserts the contents of its node identifier memory 11 into the sending node identifier field 22 of the message, and then executes step 56. step 56, the processing module 88 of the node 103, retransmits the data message via its transmitter 75.

In step 57, the processing module 88 of the node 10S ₁ sends a message 21 of service of non-acknowledgment of the message to the node transmitting the message 20 of data. In the stopping step 58, the processing module 88 of the node 10S ₁ ignores the received data message 20 and does not retransmit it.

According to this first embodiment of the routing of the data messages, each data message follows a single path to the appropriate collector node, and it reaches the collector node in a single copy. In a second embodiment of message routing data 20, 20 message data is transmitted by a 10S node ₁ to the nodes in range with a smaller value of rank. Thus, a data message propagates in the decreasing direction of the rank values contained in the rank memories 12 of the nodes, until reaching a collector node 102 (where appropriate 102 ').

Taking the example of topology of FIG. 1, considering that all the nodes 10S ₁ are source nodes carrying out measurements to be transmitted but supposing that the second node 102 'collector does not exist, the network comprising only only one node 102 collector, the nodes 103 ₆ and 103 ₇ emit a data message 20 containing a field value 27 of rank equal to 4. The node 103 ₅ receives these two messages. Since the content of its rank memory 12 is 3 and is less than the rank field 27 of each of the received messages, it re-transmits these messages by changing their field value 27 of rank to the value 3 (equal value to the contents of his memory 22 of rank). The ₅ 103 node also transmits a data message containing its own measurement data, and a field containing 27 of rank equal to 3. The nodes 103 ₂ and 103 ₄ receive three messages. But only the node 103 ₂ will retransmit them since the value of its rank memory 12 is equal to 2 and therefore less than the values contained in the rank 27 fields of the received messages. Node 103 ₂ also transmits its own data message as well as the other three receipts, all of which now have a field value 27 of rank equal to 2, as a result of assigning the contents of rank memory 12 to messages made by the node 103 ₂ . The node 103 ₄ sends its own data message with a field of 27 content of rank equal to that of his memory 12 of rank, that is to say equal to 3. The nodes 103 and ₃ 103 ₂ receive this message, and both will reissue it since the value contained in their rank memory 12 is less than that contained in the rank field 27 of the message initiated by the node 103 ₄ . The node ₃ 103 also transmits its own data message with a field 27 of rank equal to his rank memory 12, that is to say equal to 2. The 103i node receives all the messages sent by the nodes 103 and ₃ 103 ₂ and retransmits them, along with its own data message, to node 102 manifold. Thus, a data message from the nodes 103 ₇ and 103 ₆ is conveyed by the following path: 103 ₅ then 103 ₂ and 103i, to the node 102 collector. A data message from the node 103 is supplied ₅ by the following path: 103 then ₂ 103i, to the node 102 collector. A data message from the node 103 ₄ is routed through the following paths: 103 ₂ and 103 ₁₅ to the collector node 102, and also by 103 ₃ and then 1 (B ₁ , to the collector node 102. A message of data from the node 103 ₃ or 103 ₂ is routed by the node 103i to the collector node 102. Finally, a data message from the node 103i is transmitted directly to the collector node 102, without passing through an intermediate node.

In the case where the network 100 comprises two nodes 102 and 102 'collectors as shown in Figure 1, the nodes 103 ₄ , 103 ₃ , 103 ₂ and 103i send their data messages to the first node 102 collector as described above. For against, nodes 1 (B _7, 103 ₆ and 103 ₅ send their to data messages from the second node 102 'collector as follows. The 103 node ₅ transmits a data message containing its measurement data, and containing a field The nodes 103 ₆ and 103 ₇ receive this message, but only node 103 ₆ will transmit it, since the value contained in its rank memory 12 is equal to 1, less than that contained in the field. 27 of rank of the message, while the contents of the rank memory 12 of the node 103 ₇ is equal to 2. The node 103 ₇ transmits a data message 20 containing its own measurement data, and containing a field 27 of equal rank at 2. This message is received by the nodes 103 ₆ and 103 _5. But only the node 103 ₆ will retransmit it since the value contained in its memory 12 of rank is equal to 1, and is therefore lower than that of the field 27 of rank of this message Finally, the node 103 ₆ sends a message of data containing its own measurement data, as well as the other two messages received from the nodes 103 ₇ and 1 (B ₅ , all containing a rank field 27 updated by the node 103 ₆ and equal to 1. All these messages data are received by the node 102 'collector. Thus, a data message from the nodes 103 ₇ and 103 ₅ is conveyed by the node 103 ₆ to the node 102 'collector. A data message from node 103 ₆ is transmitted directly to the node 102 'collector, without passing through an intermediate node. Thus, the network collects data messages at two points which are nodes 102 and 102 'collectors.

According to the method described in FIG. 5b, in step 59, the processing module 88 of the node 10S ₁ interprets that a message has been received, extracts the contents of the type identifier field 24 and determines that it This is a data message and, if so, executes step 60.

In step 60, the processing module 88 of the node 103j extracts from the data message 20 the value contained in the collector node identifier field 25 and executes step 61.

In step 61, the processing module 88 of the node 103j extracts from the message the value contained in the collector node identifier field 25 and compares it with that contained in the collector node identifier memory 14 stored in the node . If the two values are different, the processing module 88 of the node 103j executes the stop step 70, this node 103j not being on the routing path for the collector node of this message. If they are identical, it executes step 62.

In step 62, the processing module 88 of the node 103j extracts from the message the contents of the rank field 27, then executes step 63. In step 63, the processing module 88 of the node 103j compares the extracted value of the message that was contained in the rank field 27 with the value contained in its rank memory 12. If the message value is greater than or equal to that of the node, then the node executes stop step 70. Otherwise, it executes step 64. In step 64, the processing module 88 of node 103j determines whether to accept the received data message. If he refuses, then he executes step 66. If he accepts, then he performs step 65.

In step 65, the processing module 88 of node 103j returns a message acknowledging service message 21 to the sending node of the data message, and then executes step 67. In step 66, the processing module 88 of the node 1 (B ₁ returns a service message 21 of non-acknowledgment of the message to the node transmitting the data message.

In step 67, the processing module 88 of the node 1 (B ₁ replaces, in the data message 20, the value of the rank field 27 by that contained in its rank memory 12, then it executes the step 68 .

In step 68, the processing module 88 of the node 1 (B ₁ inserts its node identifier, contained in its node identifier memory 1 1, in the sending node identifier field 22 of the data message 20 , then it performs step 69.

In step 69, the processing module 88 of node 103j re-transmits the data message 20 via its transmitter 75.

In the stopping step 70, the processing module 88 of the node 103 ignores the received data message and does not retransmit it. According to this second embodiment, a data message potentially follows several paths, and arrives in multiple copies at the node 102, 102 'collector. This redundancy of the message at the reception can make it possible to compensate for a damaged path problem.

According to a first application of a network according to the invention shown in FIG. 6, the nodes are associated with aircraft moving in the air, such as probe balloons 71, whereas the nodes 102, 102 'collectors are stationary stations. , for example on the ground. This embodiment allows observation of meteorological phenomena, including monitoring and study of cyclones. The balloons 71 move in the direction 72. According to a second application of a network according to the invention shown in FIG. 7, the network 100 is such that the nodes 102, 102 'are collectors fixed stations, for example at the bottom of the sea, and the nodes 103, are associated with mobile capsules 74 in the water (marine environment) according to the dynamics of the aquatic environment in which they are immersed. The network formed in this form is suitable for being applied for the observation of aquatic currents. According to a third application of a network according to the invention shown in FIG. 8, the network is such that the collecting nodes 102, 102 'are stationary stations on the terrestrial ground and the nodes 103j remain motionless at their drop point in a terrestrial soil environment to watch. The network formed in this form is suitable to be applied for example for monitoring fires, for example in a forest.

The invention can be the subject of many alternative embodiments and applications other than those described above.

In particular, the invention is advantageously applicable to networks in which the nodes (in any case at least part of them) are mobile along indeterminate trajectories (random, ballistic ...), and are connected by links without wire, including radio frequencies, GSM telephone ...

Management messages broadcast step by step from each collection node according to a transmission that can be described as "rising" (as opposed to transmission, which can be described as "downward") of the data messages from the source nodes to at (x) node (s) collector (s)) allow to establish a topology of the network and to optimize the routing paths between the nodes.

Furthermore, a network according to the invention may be provided with additional functionalities improving its operation, such as for example the fact that the processing module 88 of each node is adapted to issue a PING type service message:

- to a predetermined node (closest node most recently identified in its memory 16), so as to verify that this node is still in range, and / or

- all nodes to identify the nodes that are in range. In this case, the processing module of each node is also adapted to respond to such a PING service message that it receives by returning to the sending node a service message of PONG type to validate the good reception of the message of PING service and returning the corresponding identification information and, where appropriate, other information, such as its rank, reception level ... Such a PING / PONG protocol for wireless link validation is well known per se. It can be implemented automatically by each node, for example after a certain predetermined duration has elapsed without receiving a message.

Likewise, preferably, the messages are transmitted in the form of serial frames with header and checksum, but any suitable transmission protocol or coding can be envisaged.

Claims

A method of communication between a plurality of electronic communication devices, called nodes, of a network (1), adapted to transmit messages (20) of data to at least one node, said node (102) collector , in which :

each node is adapted to be able to send and receive messages,

each node comprises a processing module adapted to interpret and modify a received message; a routing path between any one of the nodes and each collection node is determined by diffusion, step by step, of a message, said management message, sent by each node (102) collector, each management message (19) comprising a digital field, said field (27) of rank,

the module (88) for processing a node receiving a management message (19) being adapted to compare the value of the message rank field (27) with a digital value stored in a digital memory of the node, said memory ( 12) of rank,

if the value contained in the rank memory (12) belongs to the set formed of the undefined values, then the processing module (88) increments the content of the rank field (27), updates the contents of the memory (12) of rank with the contents of the rank field (27) increments, and retransmits the management message (19), characterized in that:

the module (88) for processing a node receiving a management message is adapted to, if the value contained in the rank memory (12) belongs to the set formed by values greater than the content of the field (27) of rank, incrementing the contents of the rank field (27), updating the contents of the rank memory (12) with the contents of the rank field (27) incrementing, and retransmitting the management message (19), - the processing module (88) of each collecting node (102) is adapted to incorporate in each management message (19) that it transmits a digital field, said session identifier field (26), the value of which is modified for each management message (19) sent by the same collector node, according to a known order relation of the nodes.

2. Method according to claim 1, characterized in that the value contained in the memory (12) rank of a node is undefined when the processing module of the node receives a management message containing a numerical value whose field (26) session identifier contains a numerical value subsequent to that of the previous received management message (19).

3. Method according to one of claims 1 to 2, characterized in that each collector node is adapted to include a collector node identifier in each new management message (19) that it initiates.

4. Method according to claim 3, characterized in that the module (88) for processing a node stores in a digital memory, said memory (25) collector node identifier, the node identifier of a node. collector whose management message (19) allows updating of its rank memory (12) with the smallest rank value.

5. Method according to one of claims 1 to 4, characterized in that each management message (19) comprises a digital field, said issuer node identifier field (22), in which the node identifier is registered. the node that issued this message last.

6. Method according to claim 5, characterized in that a node said receiving node (1030, having received a management message (19) for updating its memory (12) of rank, stores the value of the field d transmitting node identifier of the message in a digital memory of the receiving node (1030, said closest node identifier memory, and replacing the contents of this field in this management message with the node identifier of the receiving node ( 103j), then retransmits the management message.

7. Method according to one of claims 5 to 6, characterized in that each node comprises a device for measuring the reception signal level of the message, and when a node (103j) receives a management message (19) of which the rank field value is equal to that of the memory (12) of rank, the processing module (88) is adapted to compare the level of the reception signal with that of the preceding received message, and then store, in the transmitting node identifier field, the identifier of the node providing the highest level of reception. signal.

8. Method according to one of claims 1 to 7, characterized in that each management message (19) contains a digital field, said field (23) recipient identifier (s), containing at least one node identifier a destination node of the management message.

9. Method according to claim 6 and one of claims 1 to 8, characterized in that each node (1 (B ₁ ) transmitter having to transmit a message (20) of data transmits it to the node whose identifier node is stored in the node identifier memory closest to the transmitting node.

10. Method according to one of claims 1 to 9, characterized in that the reception by a node of a message (20) data triggers the sending by this node of a message, said message (21) service , which constitutes an acknowledgment message if it accepts the data message, and a non-acknowledgment message if it refuses the data message.

11. The method as claimed in claim 10, characterized in that a receiving node of a service message transmitting a non-acknowledgment signal returns a non-acknowledgment message to the sending nodes of the data messages that it receives, and this until upon receipt of a new management message (19) containing a subsequent session identifier.

12. Network (1) of electronic communication devices, called nodes, adapted to transmit messages (20) of data to at least one node, said node (102, 102 ') collector, wherein:

each node comprises a transmitter (5) and a receiver

(6)

each node comprises a processing module (88) adapted to interpret and modify a received message, each collection node is adapted to transmit a message, said management message, broadcast from one to another by the nodes, each management message comprising a digital field, called a rank field, module (88) for processing a node receiving a management message (19) being adapted to compare the value of the message rank field (27) with a digital value stored in a digital memory of the node, said memory (12) of rank,

if the value contained in the rank memory (12) belongs to the set formed of the undefined values, then the processing module (88) is adapted to increment the value of the rank field (27), update the content of the rank memory (12) with the content of the incremented rank field (27), and retransmitting the management message (19), characterized in that: the module (88) for processing a node receiving a message of management is adapted to, if the value contained in the memory (12) of rank belongs to the set formed of values greater than the contents of the field (27) of rank, incrementing the contents of the field (27) of rank, put in day the contents of the rank memory (12) with the contents of the incremented rank field (27), and retransmit the management message (19),

the processing module (88) of each collection node (102) is adapted to incorporate in each management message (19) that it transmits, a digital field, called a session identifier field (26), whose value is modified for each management message (19) sent by the same collector node, according to a known order relation of the nodes.

13. The network of claim 12, characterized in that it comprises a plurality of nodes, said source nodes, adapted to generate useful data to be transmitted, and a plurality of nodes (102, 102 ') collectors, and in that the processing module (88) of each source node is adapted to include such useful data in the transmitted data messages (20) to each collector node (102, 102 ').

14. Network according to one of claims 12 or 13, characterized in that the nodes (1 (B ₁ ) are, at least partly, associated with structures (71, 74) movable and in that the nodes are connected to each other by wireless links.

15. Network according to claims 13 and 14, characterized in that said mobile structures are aerostats (71) placed in the Earth's atmosphere, and equipped with Earth observation means generating observation data as data. helpful.

16. Network according to claim 14, characterized in that the movable structures are placed in a liquid medium.

17. Network according to one of claims 12 to 14, characterized in that the nodes are associated with terminals capable of being worn by people.

18. Network according to one of claims 12 or 13, characterized in that the nodes are at least partly associated with fixed structures relative to the terrestrial ground.