Method for constructing flattened subnet of ad hoc network

Abstract

A construction method of a flattened subnet of an ad hoc network comprises the following steps: step 1, in a plurality of nodes which are not networked, setting the nodes to be in a maintenance state and a search state respectively; forming an initial subnet; 2, if the node of the initial subnet continuously senses time slot information different from the time sequence of the subnet where the node is located, the node of the initial subnet is combined with the subnet where the node sending the asynchronous time slot information is located according to a combination principle; and step 3, establishing or updating a gateway node between any two combined subnetworks. According to the method, the multi-subnet flattening architecture is realized only by configuring node numbers, the construction method is still effective even if the network topology is dynamically changed in a subnet limit split scene, namely, under the condition that one subnet is formed by one node, the method is simple in configuration and high in network robustness, and the construction efficiency is greatly improved especially in a subnet node moving and split scene. The integrity of the network can be effectively maintained, and the survivability and robustness of the network are further enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communication, relates to wireless ad hoc network communication, and specifically to a method for constructing a flattened subnet of an ad hoc network. Background Art

[0002] Ad hoc network is a type of wireless network that does not require fixed access points or routers. A single device can be used as a router or a terminal device. It does not rely on a central node and automatically forms a network topology. Through routing between nodes, nodes can communicate with any node in the network. Therefore, ad hoc networks include the following characteristics: no central control, dynamic topology structure, and multi-hop routing.

[0003] Self-organizing networks are limited by the requirements of wireless bandwidth and service latency. The maximum number of nodes in a subnet is generally around 10-30. In some application scenarios, the number of nodes that need to communicate in the entire network may reach hundreds. In this scenario, it is necessary to build multiple subnets to form a self-organizing network that can accommodate hundreds of nodes.

[0004] At present, most ad hoc networks only support a small network structure of a single flat subnet due to their limited capacity, or adopt a hierarchical network architecture to expand the capacity of network nodes. A flat small network can meet the needs of a small-capacity network when the network node capacity is small, but it is not applicable to a large-capacity node network.

[0005] The hierarchical networking architecture divides different nodes into different types of subnets, and at the same time divides subnets into different types. The typical hierarchical networking architecture divides subnets into central subnets and ordinary subnets. The ordinary subnet is connected to the central subnet through a gateway. Nodes in the ordinary subnet can directly communicate with the central subnet nodes through the gateway. Communication between ordinary subnets must pass through the central subnet and be forwarded through the central subnet. This hierarchical architecture has the following defects: 1. If a common subnet cannot connect to the central subnet, the subnet cannot communicate with other subnets and becomes an isolated subnet.

[0006] 2. A common subnet node roams to another common subnet and cannot directly communicate with the nodes in that subnet, so the node becomes an isolated node.

[0007] 3. The gateway node between the central subnet and the ordinary subnet needs to deploy two radios, which increases the cost and power consumption, and has duplicate functions; the two radios of the gateway node cannot conduct messages to each other, and additional switching equipment needs to be deployed, which increases the cost and power consumption; 4. The gateway node is statically planned. The entire network is highly dependent on the gateway node. Once the gateway node is destroyed, the internal nodes of the subnet will not be able to communicate with other external nodes. Summary of the invention

[0008] In view of the defects of the above-mentioned prior art, the present invention discloses a method for constructing a flat subnet of an ad hoc network.

[0009] The present invention.

[0010] The present invention realizes the multi-subnet flat architecture only by configuring the node number. Even if the network topology changes dynamically, in the scenario of extreme splitting of the subnet, that is, one node forms a subnet, the construction method is still effective. The present invention has simple configuration and strong network robustness, especially in the scenario of subnet node movement and splitting, it can effectively maintain the network integrity and further enhance the network's anti-destruction robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 FIG. 1 is a schematic diagram showing a specific implementation of step 1 of the method for constructing a flat subnet of an ad hoc network according to the present invention; Figure 2 FIG. 1 is a schematic diagram of a specific implementation of the method for constructing a flat subnet of a self-organizing network according to the present invention; Figure 3 FIG. 3 is a schematic diagram of a specific implementation of step 3 of the method for constructing a flat subnet of an ad hoc network according to the present invention; Figure 4 FIG. 2 is another specific implementation diagram of step 3 of the method for constructing a flat subnet of an ad hoc network according to the present invention; Figure 5 Shown is a schematic diagram of a specific application mode of the present invention; Figure 6 Shown is a schematic diagram of another specific embodiment of the present invention; Figure 7 Shown is a schematic diagram of another specific embodiment of the present invention. DETAILED DESCRIPTION

[0012] In order to more intuitively and clearly describe the specific details of the technical solution of the present invention, a detailed description will be given below in conjunction with specific embodiments and example drawings.

[0013] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the specific implementation methods of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] like Figure 1 and Figure 2As shown, the method for constructing a flat subnet of a self-organizing network described in the present invention is based on a wireless node set including multiple nodes as a starting node set, and the starting node set includes at least two wireless nodes; in order to save networking time, a master station node can be preset in the starting node set, and the master station node can be in a maintenance state for a long time during networking and send a time slot signal for determining whether the timing is synchronized, thereby saving networking time; compared with the case where there is no master station, each node needs to be in a maintenance state and a search state at intervals, the networking time can be significantly shortened.

[0015] Step 1. Each node in the starting node set has two network states: search and maintenance. In the initial state, the master node is in the maintenance state and continuously sends time slot signals, and other nodes are in the search state.

[0016] Each node in the search state in the starting node set takes turns searching for the time slot signal sent by the main station node. The time slot signal includes a signaling time slot and a cross-network time slot. After receiving the signaling time slot, the node time is adjusted according to the timing information of the signaling time slot to complete the network access. The node that has completed the network access and the main station node form a subnet with a mutual communication connection relationship.

[0017] The master node continuously sends time slot information including networking control messages, wherein the networking control messages include the ID of the master node and the number of nodes in the existing subnet.

[0018] Step 2. If the nodes in the starting node set that have completed the establishment of the initial subnet continue to perceive time slot information that is different from the timing of their own subnet, such as Figure 1 As shown, that is, if the existence of asynchronous signaling time slots is continuously sensed, the merging principle is determined based on the networking control message in the asynchronous time slot information. The so-called merging principle means that after the subnet where the subnet itself is located and the subnet that sends the asynchronous signaling time slot are merged, the time base of the subnet before the merger will be used as the time base of the merged subnet.

[0019] In reality, depending on the signal strength of the main station node, spatial distance or application method, a main station node will usually quickly combine with multiple other nodes to form an initial subnet. The nodes at the edge of the initial subnet will perceive the different time slot information of the adjacent network, and after merging, they can form a larger subnet.

[0020] If the asynchronous signaling time slot is not sensed, then proceed to step 1 to continue expanding the initial subnet.

[0021] The basis for determining the merging principle may be the number of subnet nodes and the ID size of the master node.

[0022] Can be set to: Step 21. First determine whether the number of nodes in the subnets is equal. If not, the time base of the subnet with more nodes is used as the time base of the merged subnet; Step 22. If the number of nodes in two subnets is equal, the time base of the subnet with the smaller master node ID is used as the time base of the merged subnet; For example, there is a subnet 1, which contains 3 nodes and the master node ID is 0; subnet 2, which contains 4 nodes and the master node ID is 1; after subnet 1 and subnet 2 are merged, the time base of subnet 2 is used as the time base of the merged subnet; For example, there is already a subnet 1, which contains 4 nodes and the master node ID is 0; subnet 2, which also contains 4 nodes and the master node ID is 1; after subnet 1 and subnet 2 are merged, since the number of nodes in the two is equal, but the master node ID of subnet 1 is smaller, the time base of subnet 1 is used as the time base of the merged subnet.

[0023] In step 2, after the two subnets are merged, the subnet that needs to change the time base will diffuse the subnet merger message in the network to all nodes in the subnet, and all nodes configure the physical layer to adjust the time base to the new subnet time base.

[0024] The merged subnets use the same time base, but the data communication protocols within the subnets may still be different. The two merged subnets need to elect a pair of gateway nodes through the gateway to achieve communication between the two subnets.

[0025] The two subnets communicate through gateway nodes. Each subnet contributes a node as a gateway node. The two subnets communicate through two gateway nodes. The gateway nodes are generated from the symmetric cross-network neighbor nodes generated during the establishment of cross-network neighbors. That is, only those that become symmetric cross-network neighbor nodes first can become gateway nodes.

[0026] Each gateway node communicates only with one subnet outside of its own subnet.

[0027] Step 3. Conduct gateway election and establish or update gateway nodes.

[0028] Gateway election is divided into two processes. The first process is the cross-network neighbor establishment process, and the second process is the distributed gateway election process.

[0029] The inter-network neighbor establishment process is used to generate a pair of nodes with a symmetric inter-network neighbor relationship. The symmetric inter-network neighbor relationship refers to a symmetric inter-network neighbor relationship established between the node of the local subnet and the node of the opposite subnet through the inter-network neighbor message.

[0030] A symmetric cross-network neighbor relationship includes two neighbor nodes, namely nodes in two adjacent subnets. Once two neighbor nodes form a symmetric cross-network neighbor relationship, the two neighbor nodes can be transformed into gateway nodes and form a gateway from the local subnet to the opposite subnet through gateway notification.

[0031] Each node in the subnet sends an inter-network neighbor message when the inter-network time slot belonging to the node arrives.

[0032] The cross-network neighbor establishment process is a process for a node to find a node with which it is expected to establish a symmetric neighbor relationship when its current subnet has no gateway node and no node with which it has established a symmetric neighbor relationship. The specific steps are as follows: Step 31. If the node in the current subnet does not receive the inter-network neighbor message from the neighboring subnet, it continues to send inter-network neighbor messages, and the sent inter-network neighbor messages carry the information of the online nodes of the subnet to which the node belongs; The online node information refers to all online nodes currently included in the current subnet; Step 32. When the initial state node receives the inter-network neighbor message from other subnet nodes, it adds the node information of the node as a candidate inter-network neighbor to the inter-network neighbor message sent by itself and sends it, indicating that it expects to establish a symmetric neighbor relationship with the node; If cross-network neighbor messages are received from multiple nodes in the same subnet, one of the nodes is selected as a candidate cross-network neighbor. The screening method can be to select the node with the best link quality as the cross-network neighbor. If the link qualities are the same, select the node with the smallest node ID as the desired cross-network neighbor.

[0033] The inter-network neighbor message in step 31 carries the online node information of the subnet to which the node belongs. Through the online node information, it can be determined whether the sending nodes of each inter-network neighbor message belong to the same subnet.

[0034] Step 33. When the nodes of two different subnets list each other as their own cross-network neighbor, the two nodes successfully establish a cross-network neighbor relationship. The two nodes of different subnets that establish a cross-network neighbor relationship are called symmetric cross-network neighbor nodes.

[0035] When there is no gateway node, the first pair of symmetric cross-network neighbor nodes formed becomes the gateway node; If there is a gateway node in the current subnet, a link quality judgment is performed. When the node that receives the cross-network message finds that the link quality of the link receiving the cross-network message is better than the link quality of the existing gateway node, it is assumed here that the reverse link quality is the same as the forward link quality; the sending node of the cross-network message is regarded as the node with which the node that receives the cross-network message hopes to establish a cross-network neighbor relationship, and a distributed gateway election is performed to determine whether the gateway node needs to be updated.

[0036] For example, if a symmetric neighbor relationship is established between node A1 in subnet N1 and node A2 in other subnet N2, nodes A1 and A2 become symmetric cross-network neighbor nodes of subnets N1 and N2.

[0037] If neither subnet N1 nor N2 has a gateway, the symmetric cross-network neighbor node automatically becomes the gateway node.

[0038] If at least one of the starting network and the above subnet has a gateway node, whether the cross-network neighbor node becomes a gateway node is determined according to the gateway election principle.

[0039] After the gateway node is generated or updated, the gateway information is notified to the subnet connected to the gateway node through the gateway notification message. The subnet node receives the gateway notification message and updates the gateway node information. Since the same gateway election principle is implemented in the entire subnet, the nodes in the subnet eventually select the same node as the gateway node.

[0040] A specific distributed gateway election method is as follows: Step 41: Compare the connection costs between the existing gateway node pair and the symmetric inter-network neighbor node pair. If the connection cost between the symmetric inter-network neighbor node pair is lower, the symmetric inter-network neighbor node pair is updated to become a new gateway node, otherwise it is not updated. Step 42. If the connection costs are the same, compare the sum of the IDs of the gateway node pair and the symmetric cross-network neighbor node pair, and update the pair with the smaller node ID to become the new gateway node, otherwise do not update; Step 43. If the node IDs and are also the same, the node pair containing the node with the smallest ID becomes the gateway node, that is, the symmetric cross-network neighbor node pair containing the node with the smallest ID is updated to become the new gateway node, otherwise it is not updated; The update of the gateway node pair ensures that only one gateway node is reachable in the adjacent subnet; after the previous gateway node pair fails, it will be automatically marked from a symmetric cross-network neighbor node to a non-cross-network neighbor node, and no cross-network messages will be sent subsequently.

[0041] The present invention only needs to add three new messages based on the OLSR routing protocol (optimized link state routing protocol), namely, the online node notification message of each subnet, the cross-network neighbor message and the gateway notification message.

[0042] The online node notification message is generated by the local gateway to inform the online nodes of the peer subnet. This message needs to be propagated not only within the subnet but also between subnets. Therefore, the multipoint relay (MPR) nodes in the subnet need to forward the message, and the gateway nodes also need to forward it.

[0043] The inter-network neighbor message is generated by the local gateway to the nodes on the peer subnet. This message needs to be propagated not only within the subnet but also between subnets. Both the nodes within the subnet and the gateway nodes need to forward the inter-network neighbor message.

[0044] All nodes in the entire network, including gateway nodes, will send cross-network messages in their own cross-network signaling time slots, and decide whether to process the information of cross-network neighbor nodes based on whether there is a gateway and whether it is a gateway.

[0045] When there is no gateway in this subnet, send cross-network neighbor node information to establish a symmetric cross-network neighbor to form a gateway. After the node becomes a gateway, the opposite gateway is the cross-network neighbor node. The cross-network neighbor node information needs to be carried in the cross-network neighbor message. The cross-network neighbor message does not need to be forwarded and is only sent for one hop.

[0046] When a node becomes a gateway, it sends a gateway announcement to the subnet where the node is located. The node selects the gateway from this subnet to the destination subnet based on the gateway announcement message and the gateway selection principle. The gateway announcement message only needs to be forwarded within the subnet.

[0047] like Figure 3 A specific embodiment of the present invention is shown in FIG. Figure 3 In the scenario shown, each node in subnet 2 selects node 2 in subnet 1 as the cross-network node to reach subnet 1. Node 2 receives cross-network neighbor messages from nodes 17, 18, 19, 20, and 21 in subnet 2. Node 2 selects the node with the best link quality as the cross-network neighbor node. If multiple nodes have the same optimal link quality, the node ID is selected from the optimal link quality node set.

[0048] like Figure 4 Another specific embodiment of the present invention is shown in FIG. Figure 4 In the scenario shown, subnet 1 and subnet 2 have formed a gateway node, including node 2 of subnet 1 and node 18 of subnet 2. Node 1 finds that the link quality of node 17 is better than the existing gateway node 18 based on the reverse link quality, and expects to establish a symmetric connection relationship with node 17. After receiving the information, node 17 compares the forward and reverse link qualities. If it is better than the existing gateway node 2, it agrees to establish a symmetric cross-network neighbor relationship with node 1. After node 1 and node 17 become symmetric cross-network neighbors, according to the gateway recommendation principle, since node 1 and node 17 are better than the existing gateway node pair, namely node 2 and node 18, node 1 and node 17 become new gateway nodes, and through the gateway notification message, all nodes in the subnet complete the final gateway switching through the gateway selection principle.

[0049] Figure 4 In the scenario shown, according to the current cross-network neighbor selection principle, if the link quality of node 1 and node 2 to subnet 2 is the same, the node with a smaller node ID, that is, node 1, is selected as the subnet cross-network neighbor. At this time, all nodes in subnet 2 will select node 1 as the cross-network neighbor, making node 1 the gateway node of subnet 1.

[0050] In a self-organizing network with a large number of nodes, the present invention completes the implementation of a multi-subnet flat architecture only by configuring the node number. Even if the network topology changes dynamically, in the scenario of extreme subnet splitting, that is, one node forms a subnet, the dynamic subnet construction method in the invention is still effective. The configuration of the invention is simple and the network is robust. Especially in the following scenarios, the invention can effectively solve the problems in network construction and further enhance the network's anti-destruction robustness.

[0051] like Figure 5 and Figure 6 Another specific embodiment of the present invention is shown in FIG. Figure 5 In the subnet self-organizing network, communication between subnets 1, 2, and 3 only requires passing through two gateway nodes, and communication between subnets 1, 2 and subnet 4 must first pass through the subnet 3 gateway relay.

[0052] Due to external reasons, Figure 5 Subnet 1 in the example is split into three subnets 11, 12 and 13 that cannot communicate with each other. The split subnets cannot communicate directly with each other, but each split subnet can communicate after being relayed by subnet 2 or subnet 3.

[0053] like Figure 7 Another specific embodiment of the present invention is shown. Figure 7 There is a mobile node M in subnet 1. During the movement, the node first leaves the coverage of subnet 1 and enters the coverage of subnet 2. At this time, the mobile node M becomes an isolated node. After subnet 2 senses the isolated node M, it automatically selects a gateway node to communicate with it. Then, the mobile node M continues to move out of the coverage of subnet 2 and enters the coverage of subnet 3. After subnet 3 senses the isolated node M, it will still select a gateway node to communicate with it, thereby realizing the self-organizing network of a single node with different subnets during the movement. It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0054] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0055] The foregoing describes various preferred embodiments of the present invention. Unless the preferred implementation modes in various preferred embodiments are obviously self-contradictory or based on a certain preferred implementation mode, various preferred implementation modes can be arbitrarily superimposed and used in combination. The embodiments and specific parameters in the embodiments are only for clearly describing the invention verification process of the inventor, and are not used to limit the patent protection scope of the present invention. The patent protection scope of the present invention shall still be based on its claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for constructing a flat subnet of an ad hoc network, characterized in that , including the following steps: Step 1. Among multiple nodes that are not networked, set at least one node to be in a maintenance state and at least one node to be in a search state; The maintenance state node continuously sends out time slot signals, which include signaling time slots and cross-network time slots. When the search state node receives the signaling time slot, it adjusts the node time according to the timing information of the signaling time slot to complete the network access. The signaling time slot also includes a networking control message, which includes the ID of the maintenance state node and the number of nodes in the existing subnet; In step 1, the nodes in the maintenance state and the nodes in the search state that have completed network access form an initial subnet; Step 2. If the node of the initial subnet continuously senses time slot information that is different from the timing of its own subnet, that is, it continuously senses the existence of asynchronous signaling time slots, it determines the merging principle according to the networking control message in the asynchronous signaling time slot; the so-called merging principle means that after the subnet where the node is located and the subnet that sends the asynchronous signaling time slot are merged, the time base of the subnet before the merger is used as the time base of the merged subnet; According to the merging principle, the subnet where the node sending the asynchronous signaling time slot is located is merged; after the merger, all nodes in the two subnets use a unified time base; Step 3. Create or update a gateway node between any two merged subnets, specifically: Step 31. If the node in the current subnet does not receive the inter-network neighbor message from the neighboring subnet, it continues to send inter-network neighbor messages, and the sent inter-network neighbor messages carry the information of the online nodes of the subnet to which the node belongs; The online node information refers to all online nodes currently included in the current subnet; Step 32. When a node receives an inter-network neighbor message from another subnet node, it adds the node information of the node as a candidate inter-network neighbor to the inter-network neighbor message sent by itself and sends it, indicating that it expects to establish a symmetric neighbor relationship with the node; If cross-network neighbor messages from multiple nodes in the same subnet are received, one of the nodes is selected as a candidate cross-network neighbor; Step 33. When the nodes of two different subnets list each other as their own cross-network neighbor, the two nodes successfully establish a cross-network neighbor relationship. The two nodes of different subnets that establish a cross-network neighbor relationship are called symmetric cross-network neighbor nodes; When there is no gateway node, the first pair of symmetric cross-network neighbor nodes formed becomes the gateway node; If there is a gateway node in the current subnet, a link quality judgment is performed. When the node that receives the cross-network message finds that the link quality of the link receiving the cross-network message is better than the link quality of the existing gateway node; the sending node of the cross-network message is used as the node with which the node that receives the cross-network message hopes to establish a cross-network neighbor relationship, and a distributed gateway election is performed to determine whether the gateway node needs to be updated. A new gateway node is obtained through the distributed gateway election, and the new gateway node is used to update the original gateway node.

2. The method for constructing a flat subnet of an ad hoc network according to claim 1, characterized in that: In the step 1, at least one node is set as a master node, the master node is continuously in a maintenance state, and the other nodes are continuously in a search state.

3. The method for constructing a flat subnet of an ad hoc network as claimed in claim 1, characterized in that: The principles for judging merger specifically include: Step 21. First determine whether the number of nodes in the subnets is equal. If not, the time base of the subnet with more nodes is used as the time base of the merged subnet; Step 22. If the number of nodes in two subnets is equal, the time base of the subnet with a smaller master node ID is used as the time base of the merged subnet.

4. The method for constructing a flat subnet of an ad hoc network as claimed in claim 1, characterized in that: In step 32, the screening method is specifically to select the node with the best link quality as the cross-network neighbor, and if the link qualities are the same, select the node with the smallest node ID as the cross-network neighbor.

5. The method for constructing a flat subnet of a self-organizing network as claimed in claim 1, characterized in that: The distributed gateway election method in step 33 is as follows: Step 41: Compare the connection costs between the existing gateway node pair and the symmetric inter-network neighbor node pair. If the connection cost between the symmetric inter-network neighbor node pair is lower, the symmetric inter-network neighbor node pair is updated to become a new gateway node, otherwise it is not updated. Step 42. If the connection costs are the same, compare the sum of the IDs of the gateway node pair and the symmetric cross-network neighbor node pair, and update the pair with the smaller node ID to become the new gateway node, otherwise do not update; Step 43. If the node IDs and are also the same, the node pair containing the node with the smallest ID becomes the gateway node, that is, if the symmetric cross-network neighbor node pair contains the node with the smallest ID, it is updated to become the new gateway node, otherwise it is not updated.

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