Flight ad hoc network method and communication node

Abstract

The invention discloses a flight ad hoc network method and a communication node, which are suitable for automatic networking of aircrafts. The method comprises the steps that a first node determines the relative speed between the first node and at least one adjacent node at first time and obtains at least one relative speed, and the second time is later than the first time; determining the link quality between the first node and the at least one adjacent node according to the at least one relative speed, and obtaining at least one link quality; determining an MPR set according to the at least one link quality, and sending the TC packet through an MPR node in the MPR set; and updating a local networking topology table and a routing table according to the topology information forwarded by the TC packet. Through the method, the situation that links of the nodes and the neighbor nodes are disconnected but data are still transmitted can be reduced as much as possible, and then the packet loss rate and the network overhead are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of self-organizing network routing, and in particular to a flying self-organizing network method and communication node. Background Art

[0002] Self-organizing networks can be realized based on the optimized link state routing (OLSR) protocol. In the process of realizing self-organizing networks based on the OLSR protocol, a routing table is established according to the shortest path. However, the node movement speed in the flying self-organizing network is relatively high, and the routing table may not be updated in time, which may lead to data packet loss. Therefore, a speed-weighted OLSR protocol, namely the SW-OLSR protocol, is proposed.

[0003] The SW-OLSR protocol refers to the introduction of speed weighting into link quality, and determines the best routing path based on the link quality obtained by speed weighting, including two processes: link quality calculation and routing decision. Link quality calculation takes a certain amount of time, and it is possible that the link between the node and the neighboring node has been disconnected, but data is still being transmitted, which eventually leads to packet loss. Summary of the invention

[0004] The present application provides a flying self-organizing network method and communication node, which can reduce the network overhead of routing decisions and effectively reduce the probability of packet loss due to link interruption.

[0005] In a first aspect, a flying ad hoc network method is provided, wherein the execution subject of the method is an aircraft (such as a drone) or a device that can realize a flying function. The method comprises: a first node determines the relative speed between the first node and at least one adjacent node at a second time at a first time, and obtains at least one relative speed, wherein the second time is later than the first time; determines the link quality between the first node and at least one adjacent node according to the at least one relative speed, and obtains at least one link quality; determines a multipoint relay (MPR) set according to the at least one link quality, and broadcasts a topology control (TC) packet through the MPR nodes in the MPR set; and updates the local networking topology table and routing table according to the topology information forwarded by the TC packet.

[0006] In this method, the relative speed between the first node and the adjacent node at the next moment (e.g., the second time) is predicted at the current moment (e.g., the first time), and the link quality between the first node and the adjacent node is determined according to the predicted relative speed, which is suitable for rapidly changing networks. Compared with calculating the link quality of the node by weight according to the current speed, the link quality determined according to the predicted relative speed can increase the link quality usage time, thereby minimizing the selection of routing paths with broken links, thereby reducing the packet loss rate.

[0007] In a possible implementation, determining the MPR set based on at least one link quality also includes: determining the MPR set based on the distance between at least one neighboring node and the first node at the second time, wherein the at least one neighboring node includes a first neighboring node, and if the first neighboring node is within the communication distance range of the first node at the second time, then the first neighboring node can be selected as the MPR node.

[0008] In this method, when determining the MPR set, in addition to considering the predicted relative speed between nodes to calculate the link quality, the distance between the nodes is also considered. In this way, the link quality between the nodes in the MPR set can be guaranteed to be good as much as possible, thereby enhancing the reliability of the network and further improving the success rate of data forwarding. In a possible implementation, determining the MPR set based on at least one link quality also includes: determining a multi-node relay MPR set based on the reachability of at least one adjacent node, wherein the adjacent node with the highest node reachability among at least one adjacent node is used as a node in the MPR set. Among them, at least one adjacent node includes a first adjacent node, and the reachability of the first adjacent node is used to indicate the number of two-hop nodes that the first node can cover through the first adjacent node.

[0009] In this method, suitable MPR nodes are also determined according to the node reachability, which can minimize the number of flooding times and reduce the network overhead of determining the MPR nodes.

[0010] In a possible implementation, the link quality RETX between the first node and the first neighboring node i,j Re the reachability to the first adjacent node j Satisfy between:

[0011]

[0012] Where ε is RETX i,j The weighting factor of j The weighting factor of , and ε+γ=1; represents the distance between node i and node j at the next moment, R represents the communication distance of the node; N w Represents the probability of a node being selected as an MPR node.

[0013] In a possible implementation, the method further includes: sending a first TC packet according to a first time interval; sending a second TC packet according to a second time interval; wherein, within the first time interval, the number of nodes in the MPR concentration that have changed is greater than a first threshold, and the second time interval is different from the first time interval; or, within the first time interval, the number of nodes in the MPR concentration that have changed is less than or equal to the first threshold, and the second time interval is the same as the first time interval.

[0014] In this method, the interval of sending TC packets can be adaptively adjusted according to the degree of change of the nodes in the MPR set. For example, if the link changes greatly, the sending interval is shorter; if the link changes greatly, the sending interval is longer. In this way, the network topology can be forwarded through TC packets as timely as possible, reducing the data packet loss rate.

[0015] In a possible implementation, within a first time interval, the number of nodes in the MPR set that have changed is greater than a first threshold, the second time interval is the sum of the first time interval and a second offset, and the second offset is less than zero.

[0016] In a possible implementation, the first time interval is a set minimum time interval. If the number of nodes in the MPR set that change within the first time interval is 0, the second time interval is the sum of the first time interval and the third offset, and the third offset is greater than 0.

[0017] In a possible implementation, the method further includes: determining a link change degree within a first duration, determining a first offset for sending a Hello message according to the link change degree, and sending a Hello message at a first time. The link change degree is used to indicate the degree to which a link state has changed. The Hello message is used for link perception and neighbor node detection in a network. The first time is the sum of a Hello message sending period and a first offset.

[0018] In this method, the interval for sending Hello messages can be adjusted according to the degree of link change. If the link changes greatly, the interval is shorter; if the link changes greatly, the interval is longer. Compared with sending Hello messages at a fixed period, the link can be sensed more timely or neighbor nodes cannot be detected in time, so that the TC group forwards the network topology in time and reduces the data packet loss rate. It can also reduce the sending of unnecessary Hello messages, reduce network resource overhead, and improve network throughput.

[0019] In a possible implementation, the routing table includes a first path, wherein the first path is a path with the longest link holding time among paths from the first node to all reachable nodes, and the link holding time is the time that two nodes maintain connection.

[0020] In this method, the path with the longest link holding time among the paths from the first node to all reachable nodes can be used as the optimal path, which can reduce the data packet loss rate.

[0021] In a second aspect, a communication system is provided, the system comprising a plurality of nodes, the plurality of nodes comprising a first node. The first node is used to: determine the relative speed between the first node and at least one adjacent node at a second time at a first time, obtain at least one relative speed, the second time being later than the first time; determine the link quality between the first node and at least one adjacent node according to the at least one relative speed, obtain at least one link quality; determine an MPR set according to the at least one link quality, and send a TC packet through a first relay node in the MPR set; and update a local networking topology table and a routing table according to the topology information forwarded by the TC packet.

[0022] In a third aspect, an electronic device is provided, the electronic device comprising a functional module for executing the method of the first aspect. For example, the communication device comprises a processing unit (sometimes also referred to as a processing module or a processor) and / or a transceiver unit (sometimes also referred to as a transceiver module or a transceiver). These units (modules) can perform the corresponding functions in the method example of the first aspect above, and refer to the detailed description in the method example for details, which will not be repeated here.

[0023] Optionally, the communication device further includes a memory, wherein the memory is used to store computer programs, instructions or data, and the processing unit is coupled with the memory and the transceiver unit, and when the processing unit reads the computer program, instructions or data, the communication device executes the method executed by the receiver in the above method embodiment.

[0024] In a fourth aspect, the present application provides a computer-readable storage medium, which stores a computer program. When the computer program is executed, the method in the first aspect is implemented.

[0025] According to a fifth aspect, a computer program product is provided, the computer program product comprising: a computer program code, and when the computer program code is executed, the method in the first aspect is executed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the architecture of a communication system applicable to an embodiment of the present application;

[0027] Figure 2 It is a flow chart of a self-organizing network based on the OLSR protocol;

[0028] Figure 3 Schematic diagram of the process of link awareness based on HELLO packets;

[0029] Figure 4 A schematic diagram of the process of a flight ad hoc network provided in an embodiment of the present application;

[0030] Figure 5 A schematic diagram of the process of selecting an MPR set provided in an embodiment of the present application;

[0031] Figure 6 A schematic diagram of the process of adaptively sending the Hello message interval provided in an embodiment of the present application;

[0032] Figure 7A to Figure 7F Schematic diagram of several formats involved in the OLSR protocol provided in the embodiment of the present application.

[0033] Figure 8 A schematic diagram of a process for optimizing routing provided in an embodiment of the present application;

[0034] Fig. 9 A schematic diagram of the structure of a communication node provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The technical solution provided in the embodiment of the present application can be applied to a flying ad hoc network. A flying ad hoc network refers to an ad hoc network composed of multiple aircrafts, and the aircrafts can exchange information through wireless communication protocols.

[0036] Please refer to Figure 1 , is an exemplary architecture diagram of a communication system applicable to the embodiment of the present application, and the communication system may include multiple aircrafts and base stations. Optionally, the base station may be a ground base station or a satellite base station. Figure 1 For example, the base station includes a ground base station and a satellite base station. The aircraft can be a drone ( Figure 1 Take this as an example), or other devices that may have flight and communication functions. Multiple aircraft can form a network by themselves, and each aircraft can serve as a communication node in the network. Aircraft can communicate with each other, or one aircraft can communicate with other aircraft through another aircraft. In other words, aircraft in the network can act as relays. Communication between source nodes and target nodes can be achieved through one or more aircraft. For example, a ground base station or a satellite base station can send information to any aircraft in the network by connecting to and communicating with a certain aircraft, and can also receive information sent by any aircraft.

[0037] It should be noted that Figure 1 For illustration only, the embodiments of the present application do not limit the type and quantity of aircraft included in the communication system, and do not limit the type and quantity of devices included in the communication system. For example, the communication system may also include terminal devices, etc.

[0038] To facilitate understanding of the solutions provided by the embodiments of the present application, some concepts involved in the embodiments of the present application are first introduced.

[0039] (1)TC Grouping

[0040] TC grouping is a grouping method of the optimized link state routing (OLSR) routing protocol, which is used to establish node topology. For example, in a self-organizing network, TC grouping is to group communication nodes according to different traffic characteristics. Through TC grouping, MPR can be selected and updated to adjust the connection relationship between each node in the network. Usually, the OLSR routing protocol selects the MPR set by maximizing the node connectivity. The MPR nodes in the MPR set forward TC groups to achieve network topology sharing.

[0041] (2) HELLO Group

[0042] HELLO packets refer to a message used for communication between nodes, commonly used in routing protocols and self-organizing networks. HELLO packets are a control message used to discover and maintain neighbor nodes in the network. In other words, HELLO messages are used for link perception and detection of neighbor nodes. Nodes can establish their own local connection database and neighbor information database by exchanging HELLO messages. How to achieve link perception and detection of neighbor nodes based on HELLO messages will be introduced below and will not be introduced here.

[0043] (3) OLSR Routing Protocol

[0044] The OLSR protocol performs link perception and neighbor node detection based on HELLO packets, and selects and updates MPR nodes based on TC packets, thereby achieving the sharing of network topology information and the maintenance of protocol routing.

[0045] See also Figure 2 , shows the process of self-organizing network based on OLSR protocol. Figure 2 As shown in the figure, the operation process of the OLSR routing protocol mainly includes link perception and neighbor node detection process, MPR selection process, TC grouping process and routing table establishment and maintenance process, which are introduced in turn below.

[0046] (3-1) Link Sensing and Neighbor Node Detection

[0047] A unidirectional link cannot transmit information, so the link between two nodes that can transmit information must be symmetrical. However, due to the uncertainty of wireless propagation, the link between one or some neighboring nodes may be considered unidirectional. Therefore, link sensing is required to ensure that the link between two nodes that can transmit information is symmetrical.

[0048] In one implementation, link awareness can be achieved by periodically exchanging HELLO messages. After receiving a HELLO message, any node updates the local link information table and neighbor information base according to the link state and node type in the HELLO message.

[0049] For example, see Figure 3 , showing the process of link awareness. Figure 3 Take the exchange of HELLO messages between nodes A and B as an example. Node A sends a HELLO message to node B. After receiving the HELLO message from node A, node B puts node A into the neighbor set / neighbor table and marks the state of node A as asymmetric. Then node B sends a HELLO message to node A. After receiving the HELLO message from node B, node A puts node B into the neighbor set / neighbor table and marks the state of node B as asymmetric. Finally, node A sends a HELLO message to node B again. After receiving the HELLO message from node A, node B updates the link state between itself and node A to a symmetric link state, so that node A and node B confirm the link between each other.

[0050] Any node can obtain the one-hop neighbor table of the node through detection of neighbor nodes. The node information contained in the one-hop neighbor table is the information of the one-hop neighbor node of the node.

[0051] (3-2) MPR selection

[0052] After neighbor node detection, each node can obtain the information of one-hop neighbor nodes in the one-hop neighbor table. Figure 3 For example, after nodes A and B become symmetric links, node A sends HELLO messages to all one-hop neighbor nodes except node B, and then obtains the information of two-hop neighbor nodes of node B and obtains the two-hop neighbor table. The MPR set can be calculated based on the one-hop neighbor table and the two-hop neighbor table.

[0053] To calculate the MPR set, you need to obtain the node's reachability. Taking node i as an example, the reachability of node i is the number of two-hop neighbor nodes that node i can reach through its one-hop neighbor node j. When calculating the MPR set, calculate the reachability of each node until all two-hop nodes are covered. Select the node with the highest reachability from the one-hop neighbor nodes as an MPR node to obtain the MPR set.

[0054] (3) TC Group Processing

[0055] The MPR node can forward the TC packet. After the MPR node forwards the TC packet, the node that receives the TC packet updates the topology information table in the node to implement the update of the network topology.

[0056] (4) Routing table creation and maintenance

[0057] In the OLSR protocol, each node needs to calculate and maintain a routing table to forward information. Each node builds a routing table based on the shortest path according to the information stored in the local link information base and the topology information table. Figure 2 The various table items in the local link information base and the topology information table include. Since the routing table is established based on the information in the local link information base and the topology information table, when the topology in the network changes, such as link breakage, topology change, link expiration, etc., the content of the node's local link information base or topology information table will also change accordingly, which will automatically trigger the node to recalculate the routing table.

[0058] As mentioned above, a self-organizing network can be realized based on the OLSR protocol. In the process of self-organizing network based on the OLSR protocol, a routing table is established according to the shortest path. However, the node movement speed in the flight self-organizing network is relatively high, and the routing table may not be updated in time, which may lead to data packet loss. For this reason, a speed-weighted OLSR protocol is proposed, namely the SW-OLSR protocol.

[0059] The SW-OLSR protocol refers to the introduction of speed weighting into link quality, and determines the optimal routing path based on the link quality obtained by speed weighting, which includes two processes: link quality calculation and routing decision.

[0060] (1) Link quality calculation

[0061] The link quality between nodes can be expressed by the expected transmission count (ETX). ETX can also be considered as the expected number of transmissions of a data packet from the source node to the destination node. For example, the link quality between nodes i and j can satisfy formula (2-1):

[0062]

[0063] Where R is the number of routes included in a routing path. It should be understood that there may be multiple routing paths between nodes, and the link quality of each routing path can be calculated according to formula (2-1). f (n) is the probability that a data packet is successfully received after n hops, also known as the forwarding reception ratio; r r (n) is the probability that a data packet is successfully received, also known as the reverse reception ratio.

[0064] The forwarding-receiving ratio can be estimated through the Hello message. For example, the single-hop forwarding-receiving ratio satisfies formula (2-2):

[0065]

[0066] in,

[0067] The α in formula (2-2) is a weight parameter, which is determined by the accuracy of link quality estimation and the response speed. The calculation method of the reverse reception ratio is similar to that of the forward reception ratio, which will not be repeated here.

[0068] Since the calculation of the forwarding-receiving ratio takes a certain amount of time, it is possible that the link between the node and the neighboring node is disconnected, but data is still being transmitted, which eventually leads to packet loss. Therefore, it is proposed to calculate the link quality based on speed weighting, as shown in formula (2-4).

[0069]

[0070] in, It represents the relative speed between node i and node j, β represents the weight of speed weighting, and the value of β determines the proportion of speed factor in EXT.

[0071] (2) Routing Decision

[0072] When making routing decisions, the forwarding and receiving ratio can be first f (n), reverse reception ratio r r (n), speed-weighted The node 3D coordinates are added to the Hello message (also called a new Hello message) and the TC message (also called a new TC message), and then the new Hello message and the new TC message are sent. MPR nodes exchange new TC messages to achieve network topology sharing. After receiving each new Hello message, the speed-weighted EXT is calculated and the location information in the neighbor table is updated.

[0073] When a routing decision needs to be made, selecting a path with a small EXT value for forwarding can effectively improve routing performance. It should be understood that a small EXT requires a large forward acceptance ratio and a large reverse acceptance ratio, and a small numerator after speed weighting. The smaller the speed weighting, the smaller the relative speed. When the relative speed is a negative value, the nodes are close to each other. Therefore, this routing decision is more inclined to select paths that are close to each other and save them in the routing table to improve the success rate of data forwarding.

[0074] However, the speed-weighted link quality calculation in the SW-OLSR routing protocol takes time, and during this calculation time, data packets may be transmitted on a path with a broken link, resulting in packet loss. In addition, based on formula (2-4), it is also impossible to accurately determine whether two nodes are close to each other.

[0075] In view of this, a solution of an embodiment of the present application is provided. In an embodiment of the present application, the link quality between nodes is predicted based on speed, and the link quality between nodes is weighted and calculated according to the predicted relative speed, which can save the calculation time for determining the MRP set, thereby minimizing the packet loss caused by link interruption during the calculation time. In addition, a suitable MPR node can be determined based on the distance between the nodes to ensure that the link quality between the determined nodes is a good link quality. A suitable MPR node can also be determined based on the node's reachability to minimize the number of flooding times and reduce the network overhead of determining the MPR node.

[0076] The technical solution provided by the embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0077] See also Figure 4 , which is a flow chart of the flight self-organizing network method provided in the embodiment of the present application. The method can be applied to a system composed of multiple aircrafts, and each aircraft can be regarded as a communication node. The method can be executed by any communication node. For the convenience of description, this article takes the method executed by the first node as an example. Specifically, the flow chart of the flight self-organizing network method provided in the embodiment of the present application is as follows:

[0078] S401, determining at a first time a relative speed between a first node and at least one adjacent node at a second time, and obtaining at least one relative speed, wherein the second time is later than the first time.

[0079] The first time can be regarded as the current time, and the second time can be regarded as a time after the first time. The interval between the first time and the second time is not limited in the embodiments of the present application. Before networking, the first node can select other suitable nodes. Specifically, the first node can predict the relative speed between other nodes and the first node at the second time, and determine the node suitable for networking based on the relative speed between the nodes. For example, the first node determines the relative speed between the first node and at least one adjacent node at the second time at the first time, and obtains at least one relative speed.

[0080] It should be understood that the altitude change of the drone is very small when performing a mission, so the following prediction does not consider the impact of altitude change, that is, the position prediction of the two-dimensional plane is considered. The Kalman filter algorithm is used to predict the mobility of the adjacent nodes at the next moment. The actual mobility and predicted mobility of the node at time n are respectively expressed as X(n), The Kalman filter prediction process is regarded as a discrete time state space model, where S(n) is a multidimensional vector that satisfies formula (3.1), p, v, a represent position, velocity and acceleration respectively, and x and y represent the x and y directions of the two-dimensional plane.

[0081] S(n)=[p x ,py ,v x ,v y ,a x ,a y ] T (3.1)

[0082] The state equation and vector corresponding to formula (3.1) satisfy formula (3.2), where A is the state transition matrix, w(n) represents the system noise, which is generally a Gaussian white noise with a mean of 0. Assume that the prediction vector is expressed as formula (3.3).

[0083] S(n+1)=A·S(n)+w(n) (3.2)

[0084]

[0085] The observation vector can be expressed as formula (3.4), where H is the transformation matrix, u(n) is the measured Gaussian white noise, and the mean is 0. Further, the observation vector can be expressed as formula (3.5).

[0086] X(n)=H·S(n)+u(n)(3.4)

[0087]

[0088] Without considering the influence of the system on the estimated value, the prior estimated value can be predicted based on the state equation As shown in formula (3.6), Represents the predicted estimated value at the current time n.

[0089]

[0090] The a priori estimated covariance matrix satisfies formula (3.7), P(n) is the covariance matrix at the previous moment, and Q is the covariance matrix of the system noise w(n), which is known to the system.

[0091]

[0092] The prior estimate can be calculated directly. After obtaining the prior estimate, the Kalman gain can be updated to obtain formula (3.8), where R is the covariance matrix of u(n).

[0093] K(n+1)=P(n+1|n)·H T ·(H·P(n+1|n)·H T +R) -1 (3.8)

[0094] After obtaining K(n+1), the prior estimate can be corrected to obtain the posterior estimate, which is the optimal estimate and satisfies formula (3.9).

[0095]

[0096] The covariance matrix of the posterior estimate satisfies formula (3.10):

[0097] P(n+1)=P(n+1|n)-K(n+1)·H·P(n+1|n)(3.10)

[0098] During the actual mission, the speed of the drone can be regarded as uniformly accelerated motion, so the state transition matrix can satisfy formula (3.11).

[0099]

[0100] Assuming that the GPS positioning vector received by the sensor satisfies formula (3.5), the transformation matrix H can be obtained as follows:

[0101]

[0102] In the specific implementation process, Kalman filtering can be used to calculate the speed information of a node at the next moment. The speed information of all one-hop nodes at the next moment can be obtained through HELLO packet broadcasting, so that the relative speed of two adjacent nodes at the next moment can be calculated.

[0103] In this way, the first node can determine / predict the relative speed between the first node and at least one adjacent node at the second time at the first time, and obtain at least one relative speed.

[0104] S402: Determine a link quality between a first node and at least one adjacent node according to at least one relative speed to obtain at least one link quality.

[0105] In the embodiment of the present application, the link quality between nodes can be weighted and calculated according to the predicted relative speed to reduce the delay of calculating the link quality, thereby reducing the data packet loss rate. For example, the link quality between node i and node j can be calculated according to formula (3.13).

[0106]

[0107] in, Indicates the relative speed at the next moment.

[0108] It should be understood that the smaller the ETX, the better the link quality, and the closer the nodes are, the better the link quality. Therefore, when calculating the link quality between nodes, the distance between the nodes (or whether the nodes are close) can also be considered. For example, determining the MPR set according to at least one link quality also includes: determining the MPR set according to the distance between at least one neighboring node and the first node at the second time, wherein the at least one neighboring node includes a first neighboring node, and if the first neighboring node is within the communication distance range of the first node at the second time, the first neighboring node can be selected as the MPR node.

[0109] Since in formula (3.13) It is impossible to indicate whether the nodes will tend to approach each other at the next moment. Therefore, the link quality between nodes can be further calculated according to formula (3.14).

[0110]

[0111]

[0112] Formula (3.14) and Formula (3.15) show that the link quality is better if the two nodes are close to each other.

[0113] S403: Determine an MPR set according to at least one link quality.

[0114] The first node may determine the MPR set based on the quality of at least one link obtained. Furthermore, the appropriate MPR node may be determined based on the node's reachability, which may minimize the number of flooding times and reduce the network overhead of determining the MPR node. The reachability is used to represent the number of two-hop nodes that can be covered by neighbor node j, which can be expressed as Re j Indicates the reachability of neighbor node j. For example, when determining an MPR set based on at least one link quality, a multi-node relay MPR set is also determined based on the reachability of at least one neighboring node, wherein the neighboring node with the highest node reachability among at least one neighboring node is used as a node in the MPR set. Among them, at least one neighboring node includes a first neighboring node, and the reachability of the first neighboring node is used to indicate the number of two-hop nodes that the first node can cover through the first neighboring node.

[0115] Specifically, the link quality and reachability based on speed prediction are weighted. i,j The changing trend of Re j On the contrary, we take the inverse of the link quality and obtain formula (3.16).

[0116]

[0117] Among them, ε and γ represent weighting factors, satisfying ε+γ=1, and the weights can be adjusted according to actual task requirements. represents the distance between the two nodes at the next moment, and R represents the communication distance of the drone. If drone node j is still within the communication range of node i at the next moment, j may be selected as the MPR node; if drone j is not within the communication range of i at the next moment, j must not be selected as the MPR node. N w The larger the value, the more likely the node is to be selected as an MPR node. In this way, the determined MPR set is more stable and can reduce the network overhead caused by frequent MPR calculations.

[0118] In the specific implementation process, the specific selection process of the MPR set is as follows: Figure 5 As shown. Figure 5 As shown, first, the depth of the one-hop neighbor node can be calculated, and the two-hop neighbor node can be judged to determine whether there is a one-hop neighbor node that has a unique path with the two-hop neighbor node. If there is a one-hop neighbor node that has a unique path with the two-hop neighbor node, then the node is added to the quasi-MPR set, and the covered nodes in the two-hop neighbor node set are removed; and it is determined whether the quasi-MPR set covers all two-hop neighbor tables; if the quasi-MPR set covers all two-hop neighbor tables, then the quasi-MPR set is the final MPR set, and the MPR set selection is completed. If the quasi-MPR set cannot cover all two-hop neighbor tables, or if there is no one-hop neighbor node that has a unique path with the two-hop neighbor node, then the N of each node in the remaining one-hop neighbor nodes is calculated. w。 The largest node in the one-hop neighbor set is added to the quasi-MPR set, and it is determined whether the quasi-MPR set covers all two-hop neighbor tables; if the quasi-MPR set covers all two-hop neighbor tables, the quasi-MPR set is the final MPR set, and the MPR set selection is completed. If the quasi-MPR set cannot cover all two-hop neighbor tables, the largest node in the one-hop neighbor set is continued to be added to the quasi-MPR set, and it is determined whether the quasi-MPR set covers all two-hop neighbor tables until the MPR set selection is completed.

[0119] S404 : Send a TC packet through the first relay node in the MPR set.

[0120] After the first node determines the MPR set, it can send the TC packet through the nodes in the MPR set to forward the network topology. For example, the first node sends the TC packet through the first relay node in the MPR set.

[0121] Since the node movement speed in the flying self-organizing network is relatively high, if the node sends TC packets according to a fixed period, the TC packet forwarding network topology will not be timely, the routing table will not be updated in time, and a higher data packet loss rate will be caused. To this end, the interval for sending TC packets can be adaptively adjusted according to the degree of change of the nodes in the MPR concentration. For example, for example, the first node sends the first TC packet according to the first time interval and sends the second TC packet according to the second time interval. Among them, within the first time interval, the number of changes in the nodes in the MPR concentration is greater than the first threshold, and the second time interval is different from the first time interval. Or, within the first time interval, the number of changes in the nodes in the MPR concentration is less than or equal to the first threshold, and the second time interval is the same as the first time interval. Equivalent to, if the link changes greatly, the sending interval is shorter; if the link changes greatly, the sending interval is longer. In this way, the network topology information can be forwarded through TC packets as timely as possible to reduce the data packet loss rate.

[0122] Among them, within the first time interval, the number of nodes in the MPR set that have changed is greater than the first threshold, and the second time interval is the sum of the first time interval and the second offset, and the second offset is less than 0. This is equivalent to shortening the sending interval when the link changes greatly. If the first time interval is the set minimum time interval, if the number of nodes in the MPR set that have changed within the first time interval is 0, then the second time interval is the sum of the first time interval and the third offset, and the third offset is greater than 0. This is equivalent to increasing the sending interval when the link changes little or even no.

[0123] Specifically, the number of nodes in the MPR cluster can be monitored, and a range can be set for the TC packet time interval. Assume that the current time interval for sending TC packets is TC_H L , the next time interval for sending TC packets is TC_H, which satisfies formula (3.23).

[0124]

[0125] TC_H in [H min ,H max ] range. At the beginning, set the TC grouping time interval to the minimum value H min , monitor the changes of MPR nodes during this time. If the MPR node does not change within the time interval, the sending time interval is increased by 1, and the maximum value cannot exceed H max ; When the number of changed nodes is less than or equal to two, it means that the network topology has changed, but the change is not drastic, and TC packets can continue to be sent at this time interval; when the number of changed nodes is more than two, it means that the network topology has changed drastically and the sending time interval needs to be appropriately reduced, so reduce the current time interval by 1.

[0126] In addition, if the node sends Hello messages according to a fixed period, the network topology will not be updated in time, which will lead to untimely updates of the routing table and a high packet loss rate. To this end, in an embodiment of the present application, the node can adjust the sending interval of the Hello message according to the degree of change in the link. If the link changes greatly, the sending interval is shorter; if the link changes greatly, the sending interval is longer. Compared with sending Hello messages according to a fixed period, the link can be perceived more timely or the neighboring node cannot be detected in time, so that the TC packet forwards the network topology in time and reduces the data packet loss rate. Alternatively, the sending of unnecessary Hello messages can be reduced, the network resource overhead can be reduced, and the network throughput can be improved. In addition, the time interval of the TC packet can be adjusted according to the number of changes in the nodes in the MPR set, so that the TC packet forwards the network topology information in time and reduces the data packet loss rate.

[0127] For example, the first node determines the link change degree within the first duration, determines the first offset for sending the Hello message according to the link change degree, and sends the Hello message at the first time. The link change degree is used to indicate the degree to which the link state has changed. The Hello message is used for link perception and neighbor node detection in the network. The first time is the sum of the Hello message sending period and the first offset.

[0128] Specifically, the link change degree within a transmission interval can be defined as LCC, which indicates the number of link changes within a transmission interval. The link change degree is closely related to the link state change. The change value of LCC is the number of HELLO packets that need to be sent according to the link state change. For example, the link state includes three link states: bidirectional symmetric link (L_SYM_time), unidirectional symmetric link (L_ASYM_time), and failed link (L_time). There may be four changes in the link state, and the corresponding LCC change values ​​also have four values.

[0129] ① When a new neighbor node is added to the local link information table, LCC increases by 3, and the number of added neighbor nodes is L1;

[0130] ② When the state of a link in the local link information table changes from ASYM_time to SYM_time, LCC increases by 1, and the number of links with this state change is L2;

[0131] ③ When the state of a link in the local link information table changes from SYM_time to ASYM_time, LCC increases by 2, and the number of links with this state change is L3;

[0132] ④When a link in the local link information table is deleted or marked as LOST_LINK, LCC increases by 0.

[0133] The link change degree can be defined to satisfy formula (3.20):

[0134] LCC=3L1+L2+2L3(3.20)

[0135] The current link state change is related to the link state change at the previous moment. Considering that the link state change needs to send three HELLO packets at most, the link change degree within three time intervals is weighted averaged, and the weighting factor is given according to the degree of influence on the current link change degree. The link change degree after weighted average is represented by WLCC.

[0136] WLCC=0.5LCC1+0.3LCC2+0.2LCC3(3.21)

[0137] Assume that the time period HELLO_INTERVAL for sending HELLO packets is 2s, then the HELLO packet time interval satisfies formula (3.22), where ΔH represents the increment of the sending time interval (ie, the first offset mentioned above), and the specific value can be determined according to the actual network conditions.

[0138]

[0139] Formula (3.22) divides WLCC into three intervals. When WLCC is less than 1, it means that the current network topology has changed little and is in a stable state, so an increment is added based on the sending interval period; when WLCC is in the interval [1,2], the network is in normal condition, so the time interval is increased or decreased based on the WLCC situation on the basis of the sending interval; when WLCC is greater than 2, it means that the network changes are relatively drastic, and an increment is reduced based on the sending interval period.

[0140] Specifically, the process of adaptively sending the hello message interval is as follows: Figure 6 As shown. Start by initializing LCC and H hello , update the value of LCC and determine whether it is the first time to calculate H hello If the first calculation of H hello , then H hello The value is set to HELLO_INTERVAL. If this is not the first time H is calculated hello , then calculate LCC, and calculate H based on LCC hello Get H hello value to determine whether the protocol is finished. If not, the protocol sends LEEOO packets at an interval updated to H hello .

[0141] It should be understood that the establishment and update of the local link information base, one-hop neighbor node table, two-hop neighbor node table, topology information table and routing table are all achieved by broadcasting Hello messages and TC packets. The first node can adaptively update the local networking topology table and routing table.

[0142] In an embodiment of the present application, during the routing calculation process, the link holding time (i.e., the time that two nodes remain connected) can be considered to monitor the link holding time in real time, and the routing path with a long link holding time can be selected and stored in the routing table, effectively reducing the packet loss caused by link breakage during the transmission process. For example, it can be determined whether there are multiple paths with the same number of hops in the routing table; if there are no multiple paths with the same number of hops, the path with the least number of hops is selected as the transmission path from the source node to the destination node; if there are multiple paths with the same number of hops, the path with the longest link duration is selected as the transmission path from the source node to the destination node. Taking the routing table including the first path as an example, the first path can be the path with the longest link holding time among the paths from the first node to all reachable nodes.

[0143] In the specific implementation process, the link holding time can be defined as LET (Link Expiration Time). Assuming that two adjacent nodes move at a uniform speed in a straight line at their current speed, LET can be estimated by relative motion. For example, LET satisfies formula (3.17)

[0144]

[0145] in,

[0146] a=v ix -v jx ,b=p xi -p xj (3-18)

[0147] c=v iy -v jy ,d=p yi -p yj

[0148] When there are multiple paths from the source node to the destination node, and there is only one shortest hop path, the shortest hop path is selected; when the shortest hop path from the source node to the destination node has multiple hops, the path with the longest link holding time is selected until the paths and link holding times of all reachable nodes are stored in the routing table.

[0149] As mentioned above, the OLSR protocol needs to be modified, for example, the following five information table formats need to be adaptively modified.

[0150] (1) Modify the HELLO group table format

[0151] The current position of the node, the predicted position at the next moment, the current speed, the predicted speed at the next moment, RETX and LTE are added to the original. The modified HELLO packet format is shown in Fig. 7A .

[0152] (2) Modify the local link information table

[0153] The local link information table adds RETX and LTE to the original fields. The modified local link table is shown in Figure 7B .

[0154] (3) Modify the neighbor table

[0155] Add RETX and LTE values ​​to the one-hop neighbor table and the two-hop neighbor table. The modified one-hop neighbor table is shown in Figure 7C , the modified two-hop neighbor table is shown in Fig.7D .

[0156] (4) Modify the TC grouping table format

[0157] Add each node’s RETX to the TC group. The modified TC group table format is shown in Fig. 7E .

[0158] (5) Modify the routing table format

[0159] Add the R_keeping_time field in the routing table to indicate the route keeping time. The modified routing table format Figure 7F .

[0160] S405: Update the local networking topology table and routing table according to the topology information forwarded by the TC packets.

[0161] It should be understood that the establishment and update of the local link information base, the one-hop neighbor node table, the two-hop neighbor node table, the topology information table and the routing table are all achieved by broadcasting HELLO packets and TC packets. Therefore, the first node can update the local network topology table and the routing table according to the topology information forwarded by the TC packet.

[0162] Specifically, the process of optimizing routing is as follows: Figure 8 As shown. First, clear the routing table, add the one-hop neighbor node to the routing table, and determine whether it comes from an unprocessed two-hop node. If there is an unprocessed two-hop node, determine whether there are multiple paths with the same hop count; if there are multiple paths with the same hop count, select the path with the largest link duration; if there are no multiple paths with the same hop count, select this path.

[0163] If there are no unprocessed two-hop nodes, determine whether there is a previous hop table entry to the destination address, and determine whether there are unscanned entries. If there is a previous hop table entry to the destination address, determine whether there are multiple previous hop table entries to the destination address; if there are multiple previous hop table entries to the destination address, determine whether there are multiple paths with the same number of hops; if there are multiple paths with the same number of hops, select the path with the longest link duration; if there are no multiple paths with the same number of hops, select the path with the shortest number of hops. If there are no multiple previous hop table entries to the destination address, select this path.

[0164] If there is no previous hop table entry to the destination address or there is an unscanned table entry, determine whether there is a routing table entry for the destination address. If so, determine whether the link holding time is updated. If the link holding time is not updated, remove the item from the table to be scanned. If the link holding time is updated, update the routing table.

[0165] The following describes the device used to implement the above method in the embodiment of the present application in conjunction with the accompanying drawings. Therefore, the above content can be used in subsequent embodiments, and the repeated content will not be repeated.

[0166] See also Fig. 9 The present application also provides an aircraft for implementing the functions of the above-mentioned various method embodiments. The aircraft at least includes a transceiver module 910 and a processing module 920.

[0167] Among them, the processing module 920 is used to determine the relative speed between the first node and at least one adjacent node at a second time at a first time, and obtain at least one relative speed, wherein the second time is later than the first time; determine the link quality between the first node and at least one adjacent node according to the at least one relative speed, and obtain at least one link quality; determine a multipoint relay (MPR) set according to the at least one link quality, and send a topology control (TC) packet through the first relay node in the MPR set; update the local networking topology table and routing table according to the topology information forwarded by the TC packet.

[0168] In a possible implementation, the processing module 920 is used, in addition to determining the link quality between the first node and at least one adjacent node based on at least one relative speed, to determine the MPR set based on the distance between at least one adjacent node and the first node at a second time, wherein the at least one adjacent node includes a first adjacent node, and if the first adjacent node is within the communication distance range of the first node at the second time, the first adjacent node can be selected as an MPR node.

[0169] In a possible implementation, the processing module 920 is used to determine the link quality between the first node and at least one adjacent node according to at least one relative speed, and further used to: determine a multi-node relay MPR set according to the reachability of at least one adjacent node, wherein the adjacent node with the highest node reachability among the at least one adjacent node is used as a node in the MPR set. The at least one adjacent node includes a first adjacent node, and the reachability of the first adjacent node is used to indicate the number of two-hop nodes that the first node can cover through the first adjacent node.

[0170] In a possible implementation, the link quality RETX between the communication device 900 and the first neighboring node i,j Re the reachability to the first adjacent node j Satisfy between:

[0171]

[0172] Where ε is RETX i,j The weighting factor of j The weighting factor of , and ε+γ=1; represents the distance between node i and node j at the next moment, R represents the communication distance of the node; N w Represents the probability of a node being selected as an MPR node.

[0173] In a possible implementation, the transceiver module 910 is used to send a first TC packet according to a first time interval; send a second TC packet according to a second time interval; wherein, within the first time interval, the number of changes in the MPR centralized nodes is greater than a first threshold, and the second time interval is different from the first time interval; or, within the first time interval, the number of changes in the MPR centralized nodes is less than or equal to the first threshold, and the second time interval is the same as the first time interval.

[0174] In a possible implementation, within a first time interval, the number of nodes in the MPR set that have changed is greater than a first threshold, the second time interval is the sum of the first time interval and a second offset, and the second offset is less than zero.

[0175] In a possible implementation, the first time interval is a set minimum time interval. If the number of nodes in the MPR set that change within the first time interval is 0, the second time interval is the sum of the first time interval and the third offset, and the third offset is greater than 0.

[0176] In a possible implementation, the processing module 920 is further used to: determine the link change degree within the first duration, determine the first offset for sending the Hello message according to the link change degree, and send the Hello message at the first time. The link change degree is used to indicate the degree to which the link state has changed. The Hello message is used for link perception and neighbor node detection in the network. The first time is the sum of the Hello message sending period and the first offset.

[0177] In a possible implementation, the routing table includes a first path, wherein the first path is a path with the longest link holding time among paths from the first node to all reachable nodes, and the link holding time is the time that two nodes maintain connection.

[0178] In an embodiment of the present application, a communication system is also provided, which includes multiple nodes, and the steps performed by the multiple nodes are similar. Taking the multiple nodes including the first node as an example, the first node is used to: determine the relative speed between the first node and at least one adjacent node at a second time at a first time, obtain at least one relative speed, and the second time is later than the first time; determine the link quality between the first node and at least one adjacent node according to at least one relative speed, and obtain at least one link quality; determine the MPR set according to at least one link quality, and send a TC packet through the first relay node in the MPR set; update the local networking topology table and routing table according to the topology information forwarded by the TC packet.

[0179] In an embodiment of the present application, a computer-readable storage medium is also provided, including instructions, which, when executed on a computer, enable the computer to execute the method in the above method example. For details, please refer to the detailed description in the method example, which will not be repeated here.

[0180] In order to realize the functions of the method provided in the above embodiment of the present application, the electronic device for processing space radio signals may include a hardware structure and / or a software module, and the above functions are realized in the form of a hardware structure, a software module, or a hardware structure plus a software module. Whether one of the above functions is executed in the form of a hardware structure, a software module, or a hardware structure plus a software module depends on the specific application and design constraints of the technical solution.

[0181] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device and unit described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0182] In the embodiments of the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0183] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0184] In addition, each functional unit in the embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0185] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor (processor) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: Universal Serial Bus flash disk (USB), mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk and other media that can store program codes.

[0186] The various illustrative logic units and circuits described in the embodiments of the present application can be implemented or operated by a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, a discrete hardware component, or the design of any combination of the above functions. The general-purpose processor can be a microprocessor, and optionally, the general-purpose processor can also be any traditional processor, controller, microcontroller or state machine. The processor can also be implemented by a combination of computing devices, such as a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor core, or any other similar configuration to implement.

[0187] The steps of the method or algorithm described in the embodiments of the present application can be directly embedded in the software unit executed by the hardware, the processor, or a combination of the two. The software unit can be stored in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM or other storage media of any form in the art. Exemplarily, the storage medium can be connected to the processor so that the processor can read information from the storage medium and can write information to the storage medium. Alternatively, the storage medium can also be integrated into the processor. The processor and the storage medium can be arranged in an ASIC.

[0188] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0189] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A flying ad hoc network method, characterized in that: include: Determine at a first time a relative speed between a first node and at least one adjacent node at a second time, respectively, to obtain at least one relative speed, wherein the second time is later than the first time; Determine the link quality between the first node and the at least one adjacent node according to the at least one relative speed, and obtain at least one link quality; determine a multi-node relay MPR set according to the at least one link quality, and send a topology control TC packet through the MPR nodes in the MPR set; Update the local network topology table and routing table according to the topology information of the TC group; Among them, sending the topology control TC packet includes: sending the TC packet at a second time interval according to the number of changes in the MPR concentrated nodes; wherein, within the first time interval, the number of changes in the MPR concentrated nodes is greater than a first threshold, and the second time interval is different from the first time interval; or, within the first time interval, the number of changes in the MPR concentrated nodes is less than or equal to the first threshold, the second time interval is the same as the first time interval, and the first time interval is the time interval for sending the TC packet last time.

2. The method according to claim 1, characterized in that Determining the MPR set according to the at least one link quality also includes: The MPR set is determined based on the distance between the at least one neighboring node and the first node at the second time, wherein the at least one neighboring node includes a first neighboring node. If the first neighboring node is within the communication distance range of the first node at the second time, the first neighboring node can be selected as an MPR node.

3. The method according to claim 1 or 2, characterized in that Determining the MPR set according to the at least one link quality also includes: A multi-node relay MPR set is determined according to the reachability of the at least one adjacent node, wherein the adjacent node with the highest node reachability among the at least one adjacent node is used as a node in the MPR set; the at least one adjacent node includes a first adjacent node, and the reachability of the first adjacent node is used to indicate the number of two-hop nodes that the first node can cover through the first adjacent node.

4. The method according to claim 3, characterized in that The link quality RETX between the first node and the first neighboring node i,j Re the reachability to the first neighboring node j Satisfy between: Where ε is RETX i,j The weighting factor of j The weighting factor of , and ε+γ=1; represents the distance between node i and node j at the next moment, R represents the communication distance of the node; N w Represents the probability of a node being selected as an MPR node.

5. The method according to claim 1, characterized in that In the first time interval, the number of nodes in the MPR set that have changed is greater than a first threshold, the second time interval is the sum of the first time interval and a second offset, and the second offset is less than 0.

6. The method according to claim 5, characterized in that The first time interval is a set minimum time interval. If the number of nodes in the MPR set that change within the first time interval is 0, the second time interval is the sum of the first time interval and a third offset, and the third offset is greater than 0.

7. The method according to claim 1, characterized in that The method further comprises: Determine a link change degree within a first time period, where the link change degree is used to indicate the degree to which a link state has changed; Determine a first offset for sending a Hello message according to the link change degree, where the Hello message is used for link perception and neighbor node detection in the network; When a first time is reached, the Hello message is sent, where the first time is the sum of the sending period of the Hello message and the first offset.

8. The method according to any one of claims 1 to 4, characterized in that The routing table includes a first path, wherein the first path is a path with the longest link holding time among the paths from the first node to all reachable nodes, and the link holding time is the time that two nodes maintain connection.

9. A communication system, characterized in that: The communication system includes a plurality of nodes, wherein the plurality of nodes include a first node; wherein the first node is used to: determine the relative speed between the first node and at least one adjacent node at a second time at a first time, and obtain at least one relative speed, wherein the second time is later than the first time; determine the link quality between the first node and the at least one adjacent node according to the at least one relative speed, and obtain at least one link quality; determine a multi-node relay MPR set according to the at least one link quality, and send a topology control TC packet through the first relay node in the MPR set; and update a local networking topology table and a routing table according to the topology information forwarded by the TC packet; The sending of the topology control TC packet includes: sending the TC packet at a second time interval according to the number of nodes in the MPR concentration that have changed; wherein, within a first time interval, the number of nodes in the MPR concentration that have changed is greater than a first threshold, and the second time interval is different from the first time interval; or, within a first time interval, the number of nodes in the MPR concentration that have changed is less than or equal to the first threshold, the second time interval is the same as the first time interval, and the first time interval is the time interval for sending the TC packet last time.

Images