Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L45/00—Routing or path finding of packets in data switching networks
  • H04L45/02—Topology update or discovery
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
  • H04W12/12—Detection or prevention of fraud
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W40/00—Communication routing or communication path finding
  • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W40/00—Communication routing or communication path finding
  • H04W40/24—Connectivity information management, e.g. connectivity discovery or connectivity update
  • H04W40/246—Connectivity information discovery
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
  • H04W12/60—Context-dependent security
  • H04W12/63—Location-dependent; Proximity-dependent

Definitions

• the invention relates to the field of communication networks without infrastructure and more particularly to the routing protocols with multiple jumps used in these networks.
• a network without infrastructure also called ad hoc network
• a network without infrastructure is a network comprising nodes, for example sensors, connected step by step, without central control.
• a source node that can not directly reach a destination node, for example due to distance or resource constraints, uses intermediate nodes to relay the message.
• the source node sends the message to one of its neighbors, which in turn relay the message to one of its neighbors, and so on until the final destination is reached.
• Nodes only interact with their direct neighbors and make localized routing decisions. They do not know the overall topology of the network.
• This protocol works in two steps. In a first step, the routes are calculated. Then, in a second step, the data packets are routed by the calculated routes. The routes are periodically recalculated to take into account any changes in network topology.
• the Greedy Forwarding routing protocol described for example in a document by Stojmenovic, Ivan, entitled “Position based routing in ad hoc networks” published in “IEEE Consications magazine", is an example of a multi-hop routing protocol.
• the routes are computed by incremental construction.
• HELLO packets are signaling messages.
• DATA packets are used to transmit data.
• Each node of the network knows its own geographical location and that of the final destination.
• Each node exchanges its location information with its immediate neighbors by periodically sending HELLO packets.
• HELLO packets Thus, each node knows the location of its neighbors.
• a node, having data to be transmitted uses the location information received from its neighbors to select the nearest neighbor node of the final destination and transmits to the selected node the data in one or more DATA packets.
• This protocol is very efficient especially in terms of time, delivery rate and consumption. - -
• HELLO packets transmitted by a malicious node contain erroneous location information, for example close to the final destination.
• this malicious node is therefore systematically chosen from neighboring nodes of a node seeking to determine a next node. Said node then systematically transmits to that malicious node, the DATA packets that it has to transmit but the malicious node does not retransmit the DATA packets to the next node.
• it only takes one malicious neighbor that attracts all the traffic of a node to obtain a total disconnection between a source node and the destination node.
• the invention improves the situation.
• the invention relates to a method of calculating a route for a data transfer between a source node and a destination node in a network comprising a plurality of nodes, the method comprising, for a current node of said route, a step of determining among the plurality of nodes of a set of neighboring nodes of said current node,
• a current node of the route selects the next node from neighboring nodes. This next selected node is either the destination node if it is accessible directly by the current node, or an intermediate node selected from the set of neighboring nodes of the current node.
• This next node is selected by applying a selection law chosen among several laws.
• the choice of the next node varies depending on the selected law.
• the behavior of the routing system is not predictable.
• the routing protocol is robust to hacking.
• the selection law is selected randomly.
• the set of laws comprises at least one random selection law and at least one deterministic selection law.
• a random selection law makes it possible to obtain a different result for each selection of a following node and thus to vary the routes on which the messages transit. Thus with the use of a random selection law, it is not possible to determine in advance the route taken by a data message.
• a deterministic selection law is a law making it possible to select a node from among a set of nodes according to a predetermined criterion.
• Such a selection law is, for example, a law choosing from the neighborhood of a node, the node closest geographically to the destination. With such a law, the nodes progress towards the destination always in the same way.
• the selection law is selected according to at least one value representative of the probability of presence of a malicious node in said set.
• a value representative of the probability of presence of a malicious node in the set of neighbors of a current node, computed by a node according to its neighbors, makes it possible to prejudge the potential presence of malicious nodes among the neighbors.
• the calculated value is then compared to a threshold and the choice of the selection law is made according to the result of this comparison. For example, if this value is greater than a predetermined threshold, the selection law selected is for example a random selection law, for example a uniform selection law. On the other hand, if this value is lower than said threshold, a deterministic selection law can be chosen, for example a selection law choosing the nearest neighbor node of the destination, thus allowing a maximum progression of the messages towards their destination.
• the method of calculating a road further comprises:
• the first confidence criterion determines whether a malicious node is potentially present among a first subset of neighboring nodes. If the probability of presence of a malicious node among the nodes of the first subset is greater than a predetermined threshold, the selected law is applied to the nodes of the first subset, otherwise, it is applied to the nodes of the second subset.
• the first subset contains the second subset. If the probability of having a malicious node among the nodes of the first subset is greater than a predetermined threshold, the selected law is applied to a larger number of nodes. Thus, the probability of choosing a malicious node is lower.
• the application of the selected law to the second subassembly makes it possible to increase the message transfer speed.
• the determination of the first and / or second subassembly comprises a step of selecting at least one node as a function of a distance criterion between the node and the destination node.
• the distance between two nodes is a simple metric to calculate. Using distance determines nodes closer to the destination.
• the first subset of nodes is for example made up of neighboring nodes closer to the destination than the current node.
• the second subassembly is for example made up of half of the nodes closest to the destination.
• a node following a current node is selected from the nodes of the second subassembly, that is to say among the nodes closest to the destination node.
• the first confidence criterion is checked if the absolute value of the difference between firstly a median distance between the nodes of said first subset and the destination node and secondly a mean distance between said nodes of said first subset and the destination node; first subset and the destination node is less than a predetermined threshold value.
• a malicious node will indicate an erroneous geographical position, for example a position closer to the destination node so as to be selected by the current node.
• the comparison of the median distance and the average distance makes it possible to determine whether a set of nodes may or may not be considered reliable.
• the first subset of nodes is considered reliable and the next intermediate node is selected from the second subset of nodes.
• a suspicion of fraud weighs on the nodes of the first neighboring subset and the next node is selected from the first subset. Selecting one of the first subassembly larger than the second subassembly increases the unpredictability of the choice.
• the method of calculating a road further comprises:
• a second confidence criterion is used to determine whether a malicious node is present among a subset of nodes.
• the applied law applied is different, for example a selection law allowing a faster message progression or on the contrary a more random selection law.
• the second criterion of confidence makes it possible to determine if the set of nodes considered must be considered as resilient or non-resilient. If the probability that a malicious node is below a predetermined threshold, a selection law for advancing the messages faster to the destination can be applied. On the contrary, if the probability that a malicious node is greater than this threshold, a random law is applied. When applying a random law, the malicious node has a reduced chance of being chosen.
• the selected law is weighted by at least one weighting coefficient if the second confidence criterion is verified and the selected law is equiprobable if said second criterion is not verified.
• the selected law is a law equiprobable or not
• the application of weighting coefficients makes it possible to increase the probability of certain nodes and / or to decrease the probability of other nodes, and thus to favor the selection of certain nodes, for example the nodes closest to the destination node.
• the second criterion is checked if the absolute value of the difference between on the one hand a median distance between the nodes of said first subset and the destination node and on the other hand a mean distance between said nodes of said first subset set and the destination node is less than a predetermined threshold value.
• Calculating the difference between a median distance between the nodes of said first subset and the destination node and a mean distance between said nodes of said first subset and the destination node is a simple criterion for determining a probability of presence of a malicious node among the nodes of the first subset .
• the invention also relates to a device forming a node of a network comprising a plurality of nodes, said node comprising means for determining a set of neighboring nodes of said node among the plurality of nodes.
• the device comprises:
• the invention also relates to a sensor capable of collecting data and retransmitting them towards a collection device characterized in that it comprises a device forming a node as described previously.
• the invention further relates to a system comprising a plurality of node devices, comprising at least one node device as previously described.
• the invention finally relates to a computer program product comprising instructions for implementing the steps of a method for calculating a route as described above, when it is loaded and executed by a processor.
• FIG. 1 is a general diagram illustrating the general context of the invention
• FIG. 2 is a block diagram showing a sensor adapted to perform the steps of a route calculation method according to one embodiment of the invention.
• FIG. 3 is a flowchart illustrating the various steps of a route calculation method according to a first embodiment
• FIG. 4 is a flowchart illustrating the various steps of a route calculation method according to a second embodiment
• FIG. 5 is a diagram illustrating subsets of sensors determined according to one embodiment.
• module may correspond in this document to both a software component, a hardware component or a set of hardware and / or software components, capable of implementing a function or a set of functions, as described below for the module concerned.
• a software component corresponds to one or more computer programs, one or more subroutines of a program, or more generally to any element of a program or software.
• Such software component is stored in memory then loaded and executed by a data processor of a physical entity (terminal, server, gateway, set-topbox, router, etc.) and is likely to access the hardware resources of this physical entity (memories, recording media, communication buses, electronic input / output boards, user interfaces, etc.).
• a material component corresponds to any element of a material set (or hardware). It may be a programmable hardware component or with an integrated processor for running software, for example an integrated circuit, a smart card, an electronic card for executing a firmware, etc.
• FIG. 1 represents a SYS system comprising a plurality of sensors C1, C2, etc. Placed randomly in a uniform distribution in a geographical zone.
• Each sensor Ci is for example a measurement sensor able to periodically perform a set of measurements and to transmit a data message containing the measurements made to a collection device D.
• Each sensor Ci is also able to receive a data message from another sensor of the SYS system and to retransmit it to the collection device D.
• Each sensor Ci as well as the collection device D respectively represents a node.
• the plurality of nodes is organized in a so-called network without infrastructure or Adhoc network.
• the collection device D is also called destination node D and a sensor is also called node.
• a sensor represents a device forming a node.
• Each node is able to communicate with the neighboring nodes of this node via a wireless link, for example a Zigbee link, wifi or another radio type link.
• a wireless link for example a Zigbee link, wifi or another radio type link.
• a neighbor node of a current node is a communication range node of this current node. More precisely, the Euclidean distance between a current node and a neighboring node of this current node is less than the communication range. It is specified that the range of communication may vary according to the propagation conditions.
• the link between two nodes is a bidirectional link. - -
• the limitation of the transmission power for the wireless links does not allow a current node to interact in direct relation with all the nodes of the SYS system.
• the transmission of a data message from a current node to a node out of range of this current node is performed via one or more intermediate nodes. More generally, the transmission of a data message from a source node to the collection device D is performed according to a multi-hop routing protocol.
• a sensor of the set SYS for example a sensor ZI
• the transfer of the data message between the sensor ZI and the collection device D requires the calculation of a route R between the sensor ZI and the collection device D via at least one sensor or intermediate node.
• the data message MD is transmitted step by step via sensors of the SYS system until reaching the collection device D.
• the sensor ZI selects, from among its neighbors, a sensor, here called the first intermediate sensor, to which it sends the data message MD.
• the first intermediate sensor selects, then from among its neighbors, a second intermediate sensor and so on until an intermediate sensor, within range of the collection device D, is selected.
• each intermediate node is performed according to a route calculation method comprising steps E0 to E4, described with reference to FIG. 3.
• the route calculation method is implemented respectively by the source node ZI and the (k-1) first selected intermediate sensors Z2, Z3 ... Zk.
• the last intermediate sensor Zk of the route R directly transmits the data message MD to the destination node D.
• steps E0 to E4 are implemented for only some of the nodes of a group comprising the source node and the (k-1) first intermediate nodes.
• the selection of the other intermediate nodes is then carried out according to a method known from the state of the art.
• the plurality of nodes includes multiple source nodes and / or multiple destination nodes. - -
• a source node when transmitting a message may be considered a destination node when transmitting another message.
• FIG. 2 represents an example of a sensor Ci of the SYS system.
• the sensor Ci comprises, in a known way, in particular a processing unit UT equipped with a microprocessor, a read-only memory of the ROM or EEPROM type 103, a random access memory of the RAM type 104, a communication interface COM with neighboring nodes and / or the destination node D by a wireless link.
• ROM 103 includes registers storing a PG computer program
• the processing unit UT is driven by the computer program PG in order to implement in particular the route calculation method according to an embodiment of the invention described later with reference to FIG.
• the sensor Ci also comprises a neighbor determination module VOI, a selection module SEL, a choice module of an intermediate node CHO as well as a temporary memory MT, for example a memory of the type RAM, able to record a message of data, for example a measurement report, received from a neighboring node.
• a neighbor determination module VOI a neighbor determination module
• SEL selection module
• a choice module of an intermediate node CHO as well as a temporary memory MT, for example a memory of the type RAM, able to record a message of data, for example a measurement report, received from a neighboring node.
• the sensor Ci may also comprise a measurement module MES adapted to periodically perform a set of measurements and to record the result of these measurements in the temporary memory MT.
• a measurement module MES adapted to periodically perform a set of measurements and to record the result of these measurements in the temporary memory MT.
• the communication module COM is able to receive a data message and to store the received data in the temporary memory MT.
• the sensor Zj is either the source node ZI or an intermediate sensor Z2, Z3 ... or Zk-1.
• the sensor Zj here represents a current node.
• the sensor Zj implements the steps E0 to E4 as described with reference to FIG.
• a data message received by the sensor Zj comprises, in this embodiment, in particular a DATA type identifier, an identifier of the destination node D, the geographical coordinates of the destination node D, an identifier of the source node ZI and the coordinates of the source node ZI.
• a set Ll of selection laws comprises for example 4 selection laws S 1, S 2, S 3 and S 4. - -
• the first selection law SI is for example a uniform probability law.
• a uniform law is a random law according to which the probability p (s) in a set S of nodes is identical for all the nodes s of the set S ..
• the second selection law S2 is for example a maximum entropy law based on the average distance between the nodes of a set of nodes and the destination node.
• the third selection law S3 is for example a maximum entropy law based on the median distance between the nodes of a set of nodes and the destination node.
• the fourth selection law S4 is for example a maximum entropy law based on the distance between the current node considered and the destination node.
• a maximum entropy law is a discrete law of probability which makes it possible to select an element x from the elements x1, x2, ... xn of a set X and is described for example in the document "Random Walks on sensors networks, In Proceedings of the 5th International Symposium On Modeling and Optimization in Mobile, Ad hoc and Wireless Networks- April 2007 "by L. Lima and J. Barros.
• a maximum entropy law based on a value a, denoted P (a), is such that:
• the maximization of the sum (p (x) * ln (l / p (x)) is for example carried out by a known method of Lagrange multipliers .
• the resolution of the linear equations are for example solved using calculation methods For example, simple numerical methods such as the Newton method or the gradient descent method and the arithmetic calculations are performed by executing a CORDIC algorithm (for "COordinate Rotation Digital Computer").
• the median distance between a set of nodes and the destination node is here the distance between the barycentre of the position of the nodes of the set and the destination node.
• the average distance between a set of nodes and the destination node is the average distance calculated over the set of distances from each node of the set to the destination node.
• the number of laws of the set L1 is different from 4 and / or the set of laws L1 comprises one or more laws different from the laws S1, S2, S3 and S4. - -
• the selection module VOI of the current sensor Zj determines, among the plurality of nodes of the system SYS, a set V of nodes Vj neighboring the current node Zj.
• each node of the SYS system broadcasts periodically, for example every 3 seconds, in broadcast mode, a HELLO message.
• a HELLO message transmitted by a node comprises, in this embodiment, in particular a HELLO type identifier, an identifier of this node and the geographical coordinates of this node.
• the current node Zj thus receives HELLO messages from its neighbors.
• the current node Zj maintains a TV neighborhood table (FIG. 2) in which it stores the information relating to each neighbor.
• the TV neighborhood table is for example an area of the RAM 103.
• the stored information expires after 2.5 seconds. Thus a node which no longer communicates, no longer appears in the neighborhood table of its neighbors.
• the step E0 is followed by a step E2, during which the selection module SEL of the sensor Zj selects a selection law S in the set of laws L1.
• the selection law S is selected randomly.
• the laws are selected according to a predefined sequence.
• the choice module of an intermediate node CHO of the sensor Zj chooses an intermediate node Z j + 1 according to the current node Zj by applying the selected law S to the set V of the neighbors Vj .
• the method of calculating a route implemented by the sensor Zj comprises a step E3 of determining a subset of nodes among the neighboring nodes, for example the subset of the neighboring nodes closer to the D collector device that the current node Zj and in step E4, the selection law S selected in step E2 is applied to the determined subassembly.
• the route calculation method here comprises steps E10 to E1 implemented by at least one sensor of a group comprising the source sensor ZI and at least one intermediate sensor or node.
• a set of laws L2 comprises for example 2 selection laws S5 and S6. - -
• the first law S5 is for example an equiprobable law.
• the second law S6 is a probability law in which the probabilities are weighted according to weighting coefficients.
• a weighting factor P applied for a node is a function of the distance between this node and the destination node D. This weighting allows messages to reach the destination node more quickly D.
• the selection law S6 is for example the law S5 in which the probabilities are weighted according to the weighting value P.
• the selection probabilities of the selection law S6 are determined by applying, for example, the principle of maximum entropy in order to obtain, with the weighting, a mean distance equal to the median distance without weighting.
• the determination module VOI of the sensor Zj determines, among the plurality of sensor nodes of the SYS system, a set V of neighboring nodes Vj of current node Zj.
• the determination module VOI determines a set W of nodes on which will be applied a selection law of the set of laws L2.
• step El 2 here comprises sub-steps El 20, El 22 and El 24.
• the determination module VOI of the sensor Zj determines a first subset VP1 and a second subset VP2 of nodes.
• the first subset VP1 is a subset of the set V of neighboring nodes of the current node Zj.
• the first subset VP1 is for example the set of neighboring nodes of the sensor Zj closer to the collection device D than the current node Zj.
• a node of the first subset VP1 is a node such that the distance between this node and the destination node D is less than the distance between the current node Zj and the destination node D.
• the first subset VP1 is the set V of neighboring nodes.
• the second subset VP2 is a subset of the first subset VPl.
• the second subset VP2 is, for example, consisting of half of the nodes of the first subset VP1, the closest to the destination node D.
• FIG. 5 illustrates an example of a first subset VP1 and a second subset VP2 determined by a current node Zj.
• the first and second subassemblies are determined according to a metric.
• the metric used here is the distance between a node and the destination node D.
• the distance between a neighboring node and the destination node D is calculated by the sensor Zj by using on the one hand the geographical position of the destination node D contained in the received data message and on the other hand the geographical position of this node neighbor contained in the TV neighborhood table.
• the metric used is a number of jumps connecting a node to the destination node D.
• a number of hops is obtained by broadcasting a message sent by the destination node D containing a number of hops equal to zero. and propagated step by step by the nodes after incrementing the number of jumps.
• the determination module VOI of the sensor Zj verifies a first confidence criterion CRI.
• the verification of the first confidence criterion CRI comprises calculating a first M1 and a second metric M2 representative of the first subset VP1 and then comparing the calculated metrics.
• the first metric Ml is for example the median distance between the nodes of the first subset VP1 and the destination node D, that is to say the distance between the barycentre of the nodes of the first subset VP1 and the destination node D.
• the second calculated metric M2 is the average distance between the nodes of the first subset VP1 and the destination node D.
• the comparison of the median distance and the average distance is a criterion for detecting potential fraud.
• a fraudulent node wishing to attract traffic transmits in the HELLO packets to its neighbors, a false geographical position. For example, it indicates a geographical position closer to the destination node D than its actual position. This erroneous geographic position influences differently the average distance more than the median distance, calculated on the nodes.
• a difference between the median distance and the average distance greater than a first predetermined threshold Sel indicates a possibility of presence of a fraudulent node
• the sub-step El 22 is followed by a sub-step 124 in which the determination module VOI of the sensor Zj chooses a set W of nodes on which will be applied a selection law S of the set L2.
• the set W chosen is the second subset VP2.
• the set W chosen is the first subset VP1.
• Step E12 is followed by a step E14 of checking a second confidence criterion
• the verification of the second confidence criterion CR2 comprises the computation of a third M3 and a fourth metric representative of the set of nodes W chosen during the step E12 and the comparison of the computed metrics. - -
• the third metric M3 is for example the median distance, that is to say the distance between the barycentre of the nodes of the set W and the destination node D.
• the fourth metric M4 calculated is the average distance between the nodes of the set W and the destination node D.
• the selection module SEL of the sensor Zj selects in the set of laws L2 a selection law S according to the verification of the second confidence criterion CR2.
• the selection law S6 is selected if the absolute value of the difference between the median distance M3 and the average distance M4 is less than a second predetermined threshold Se2 (
• the current node Ci selects the next intermediate node Z j + ipar application of the law S selected during step El 6 to the set of nodes W determined during step El 2 .
• the method does not include step E12, and in step El 8, the law S selected in step E16 is applied to the set V of the neighbors.

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