A method for forwarding information in Internet of Vehicles based on named data network

Abstract

The present invention relates to the technical field of vehicle network information forwarding, and discloses a vehicle network information forwarding strategy based on a named data network, which is characterized by comprising: S1, a consumer node sends a beacon to all neighbor nodes within the communication range, obtains the motion state information of all neighbor nodes and the content connection quality value of the naming prefix of the interest packet of the consumer node stored in the neighbor node; S2, finds the Euclidean distance, link duration and content connection quality value of the neighbor node that meets the conditions; S3, finds the most suitable neighbor node as the forwarding node of the interest packet, and transmits the corresponding data packet produced by the producer node to the consumer node according to the reverse path of the interest packet according to the information decision table. The present invention proposes a novel strategy to select the best next hop forwarder node with a small number of hops and a small number of interest packets, while maintaining high reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle network information forwarding, and in particular to a vehicle network information forwarding method based on a named data network. Background Art

[0002] With the rapid development of social economy and the continuous progress of science and technology, vehicles are no longer limited to a single transportation function. By installing various sensors such as GPS devices, radio frequency identification devices (RFID) devices, and cameras on vehicles, and then applying communication technology to vehicles, the functions of vehicles are expanded, so that vehicles can become nodes with communication and computing capabilities in the Internet of Vehicles. These vehicle nodes with communication capabilities and road infrastructure nodes together form the Internet of Vehicles, which is one of the emerging and rapidly developing networks. The current Internet of Vehicles can meet various information needs of users, and these information can be divided into safety information and entertainment information according to the user's sensitivity to delay, such as traffic route planning, forward collision detection and avoidance (FCDA), audio and video multimedia information, etc.

[0003] In the IoV network, each vehicle node has the same state and can act as a communication terminal or a router to forward data packets to other nodes. However, due to the frequent changes in network topology caused by the rapid movement of vehicle nodes and the unreliable quality of wireless communication links, data transmission between vehicles has encountered great challenges. The traditional TCP / IP network structure is not suitable for the IoV, mainly because the IoV based on the IP system has the following problems: 1) IP address problem. Most of the nodes in the IoV are mobile vehicles. Vehicles use wireless channels to communicate with each other. Each device interface needs to obtain an IP address to communicate with other entities. Mobile devices cannot communicate during movement until they obtain another IP address from the newly connected network. In addition, in the IoV, the movement of vehicles will cause frequent changes in the network topology, resulting in high maintenance costs for routing tables; 2) Security issues. Since the communication between nodes is a shared wireless channel, there are many uncontrollable factors, and nodes are vulnerable to denial of service attacks (DoS). Moreover, since security issues were not considered at the beginning of the design of the Internet, the existing security mechanism was added after the network problems occurred, so the security issues have not been well solved.

[0004] Since vehicle users in the Internet of Vehicles can use wireless communication technology (Vehicle-to-Everything, V2X) to obtain the required content from macro base stations, roadside units (RSU) and other vehicle nodes; in addition, vehicle nodes equipped with on-board units (OBU) have the ability to cache resources and calculate data, there can also be communication links to transmit information when vehicles are moving relative to each other.

[0005] The vehicular ad hoc network consists of fixed roadside units (RSU) and mobile vehicles with communication capabilities. RSUs are deployed around points of interest (POIs), such as shopping malls and busy roads. At the same time, RSUs regularly broadcast popular content, and vehicles within the radio range of RSUs can receive and store these popular content. It should be noted that the storage space of RSUs is limited and it cannot cache all the information required by vehicles on the current road section. The safety and travel experience of drivers and passengers are ensured through information sharing between infrastructure and nodes (vehicle users). Compared with the location of vehicles that provide relevant information in the Internet of Vehicles, users are more concerned about the content itself. In addition, the vehicle nodes in the Internet of Vehicles move quickly and the topology changes dynamically. The host-centric TCP / IP network is difficult to adapt to the characteristics of the Internet of Vehicles, which will increase the overhead of information forwarding in the network. In order to ensure the stability of the transmission link and reduce the forwarding overhead, the NDN architecture with content name routing and in-network caching is integrated into the traditional vehicle network.

[0006] The proposed Named Data Network (NDN) solves this problem well. NDN uses named data instead of IP addresses and is data-centric. Consumers only care about what kind of content they need, not which node the message is sent from. The essence of network communication changes from "where to get data from" to "what kind of data they need". Compared with traditional TCP / IP networks, NDN contains different working mechanisms and data structures. Therefore, mobile nodes can get a better content access experience during mobility without the need for new addresses from the connected network, and even if the content producer is unavailable, they can continue to communicate and access content by using NDN's in-network caching function. With the basic use of NDN, especially naming and in-network data caching, NDN may perform better than TCP / IP and may also help cope with mobility and sporadic connection problems.

[0007] In named data networks, consumers obtain the required data packets by sending interest packets with unique names, and data packets are generated by producers. The uniqueness of NDN lies in the diversity of its naming and content sources, that is, interest packets may be responded to in different nodes in the network. This feature is more prominently reflected in the NDN Internet of Vehicles: vehicles are divided into content consumers, content producers and information forwarders according to their functions. The functions of content consumers and content producers are consistent with those of normal named data networks, and forwarders are responsible for acting as intermediate nodes to forward data. According to different application scenarios, the process of information forwarding has different classifications, such as Figure 2 As shown:

[0008] 1) Consumers obtain information directly from RSU:

[0009] RSU will store the most popular content in the current period. It can be considered that the content obeys Zipf's law, and the cache space of RSU is limited, so RSU will periodically update the cache content to adapt to the current network and RSU's own cache space. These popular contents are generally information that is not sensitive to delay, such as multimedia files, video files, etc. Figure 2 In the scenario above, consumer C sends an interest packet to request the above content. The latency and number of hops to obtain information from network nodes are unknown, and RSU2 stores the required information. In this scenario, it is more appropriate for consumers to directly request content from RSU. However, vehicle nodes in the vehicle network do not always request these contents, and RSUs are not arranged very carefully on the road, so other scenarios need to be considered.

[0010] 2) Consumers obtain information from RSU through intermediate nodes:

[0011] RSU is another scenario for content producers, such as Figure 2 ,Consumers still need to obtain some popular content, which still needs to be obtained from RSU.,Different from the first scenario, RSU in this case is beyond the communication range of consumers, and needs to use other vehicles as forwarding nodes to forward the interest packet to RSU:,Consumer C sends an interest packet, which is forwarded to RSU3 via vehicle 5, and the data packet returns to the consumer along the reverse path.,Both scenarios have limitations, namely the restrictions on the types of requested content and the layout of roadside units.,Therefore, obtaining information from other nodes in the network is more common, more valuable for research, and more complex;

[0012] 3) Consumers obtain information from other nodes in the network:

[0013] The most complex scenario is that the content producer is other vehicles in the network. As a device with limited cache, RSU cannot update content anytime and anywhere, nor can it cache all the content in the network in its router. When consumer vehicles request some real-time content or scarce content, RSU often cannot play its corresponding role, so it is a real need for consumers to request content from other vehicles. Other vehicles within the communication range of the vehicle become neighbors of the vehicle. This scenario is the process in which consumer vehicle C needs to obtain specific content. If the required content cannot be found within the communication range of C, then other vehicles within the communication range of C will act as forwarders and continue to forward C's interest packets within the network to search for the required content. In this process, the following problems will arise:

[0014] 1. In a highly dynamic network such as the Internet of Vehicles, data packets in the network need to be flooded and forwarded, which increases the network load and causes a broadcast storm. That is, there may be many nodes that need to forward interest packets, and the number of neighboring nodes of these nodes is large. If the interest packets requesting the content are broadcast to these neighboring nodes for forwarding, this will cause a broadcast storm, waste cache space, and increase communication costs;

[0015] 2. Highly dynamically changing nodes will also make the data transmission link unstable. Data transmission failure due to node mobility is also a reality. That is, the vehicle nodes in the Internet of Vehicles have the characteristics of high-speed movement, which makes the network topology always changing. When the node that receives the interest packet has corresponding content, the node will reply to the request with a content unit along the path of the interest packet transmission. However, if the forwarder moves during the process and leaves the communication range of the previous hop node, the data transmission and forwarding will fail. Summary of the invention

[0016] The present invention provides a method for forwarding Internet of Vehicles information based on named data networks to solve the above problems.

[0017] The present invention is achieved through the following technical solutions:

[0018] A method for forwarding information in an Internet of Vehicles based on a named data network, comprising:

[0019] S1. The consumer node sends a beacon to all neighbor nodes within the communication range, obtains the motion state information of all neighbor nodes and the content connection quality value of the naming prefix of the interest packet of the consumer node stored in the neighbor node, and records the content connection quality value and motion state information in the neighbor information table of the consumer node;

[0020] S2, processing the motion state information of the neighbor information table, finding the Euclidean distance, link duration and content connection quality value of the neighbor node that meets the conditions, and storing the found Euclidean distance, link duration and content connection quality value of the neighbor node in the information decision table;

[0021] S3. Find the most suitable neighbor node in the information decision table as the forwarding node of the interest packet, and transmit the corresponding data packet produced by the producer node to the consumer node according to the reverse path of the interest packet according to the information decision table.

[0022] As an optimization, the content connection quality value is stored in a prefix name tree, the root node of the prefix name tree is the name prefix of the interest packet and / or data packet when the neighbor node first receives the interest packet and / or data packet, and when the vehicle node subsequently forwards the data packet and / or interest packet, the name prefix of the data packet or interest packet is a child of the name prefix of the root node, then the name prefix is ​​recorded in the prefix name tree as a child node of the corresponding root node.

[0023] As an optimization, the root node and child nodes of the prefix name tree also store the number of data packets and / or interest packets forwarded by the node.

[0024] As an optimization, the calculation formula of the content connection quality value of the vehicle node is:

[0025]

[0026] Among them, CCQ j Connect the quality value of the content with name prefix j, D j The number of packets with name prefix j forwarded by neighbor nodes, I j The number of interest packets with name prefix j forwarded to neighbor nodes, ∑ i∈des(j) D i is the number of all packets whose name prefix contains j, ∑ i∈des(j) I i is the number of all Interest packets whose name prefix contains j.

[0027] As an optimization, the motion state information includes the motion speed v of the neighbor node at time t and the current position x. In S2, the specific formula for finding the Euclidean distance of the neighbor node that meets the conditions is:

[0028]

[0029] Where D(m,n) is the Euclidean distance between consumer node m and neighbor node n, (x m ,y m ),(xn ,y n ) are the relative coordinate positions of consumer node m and neighbor node n at time t.

[0030] As an optimization, in S2, the specific formula for finding the link duration of the neighboring node that meets the conditions is:

[0031]

[0032] α=v m cosθ m -v n cosθ n

[0033] β=x m -x n

[0034] γ=v m sinθ m -v n sinθ n ;

[0035] ρ=y m -y n

[0036] Where L(m,n) is the link duration between consumer node m and neighbor node n, θ m ,θ n are the moving directions of consumer node m and neighbor node n at time t, v m ,v n are the speeds of consumer node m and neighbor node n at time t respectively.

[0037] As an optimization, in S2, the specific conditions for finding the Euclidean distance, link duration and content connection quality value of the neighboring node that meets the conditions are:

[0038] A1. Calculate the Euclidean distance between the neighbor node and the consumer node, and find a neighbor node within the communication range of the Euclidean distance as the first backup forwarder node;

[0039] A2. If the vehicle density is high, the forwarding node of the next hop of the neighboring node whose link duration L is greater than the first threshold and whose content connection quality value is the largest is selected in the first standby forwarding node;

[0040] A3. If the vehicle density is low, select the neighbor node with the longest link duration L with the consumer node from the spare forwarder nodes as the next-hop forwarder node.

[0041] As an optimization, the specific steps of S3 are:

[0042] S3.1, along the reverse direction of the interest packet, determine whether the next neighbor node of the vehicle node where the data packet is located communicates normally with the vehicle node where the data packet is located. If normal, jump to S3.2, otherwise, jump to S3.3;

[0043] S3.2, forwarding the data packet to the neighbor node, and returning to S3.1 until the data packet reaches the consumer node;

[0044] S3.3. Find the first backup forwarder node in the information decision table of the vehicle node where the data packet is located, forward the data packet to the first backup forwarder node within the communication range, and return to S3.1 until the data packet reaches the consumer node.

[0045] As an optimization, before S3.1, it also includes adding forward direction ID and reverse direction ID in the interest packet.

[0046] As an optimization, the selection criteria of the first standby forwarder node are:

[0047] B1. Calculate the Euclidean distance between the neighbor node and the first standby forwarder node, and find a neighbor node within the communication range of the Euclidean distance as the first standby forwarder node;

[0048] B2. If the vehicle density is high, the forwarding node of the next hop of the neighboring node whose link duration L is greater than the first threshold and whose content connection quality value is the largest is selected from the first standby forwarding node;

[0049] B3. If the vehicle density is low, a neighbor node with the longest link duration L with the first backup forwarder node is selected from the first backup forwarder node as the next-hop forwarder node.

[0050] As an optimization, a timer is set, and when the timer reaches a second threshold, the information decision table of the vehicle node is cleared.

[0051] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0052] The present invention proposes a vehicle network information forwarding method based on named data network in the NDN vehicle network environment to solve the broadcast storm and packet loss problems caused by the high-speed change of the motion state of vehicle nodes. The conventional motion state information and the inherent naming prefix of NDN are used to solve the problem, which is conventional and authentic.

[0053] The present invention proposes a novel strategy to select the best next hop forwarder node with a small number of hops and a small number of interest packets while maintaining high reliability, considering all possible nodes in multiple directions, and using parameters defined by the naming prefix to select nodes with higher affinity as forwarding;

[0054] The present invention takes into account the problem of data packet return on the basis of interest packet forwarding, and proposes a method for forwarding information of the Internet of Vehicles based on a named data network, which can solve the problem that data packets cannot reach consumers due to link disconnection, and complete the whole process of interest packet searching for data and successfully returning it, during which a higher interest satisfaction rate and fewer hops can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0056] Figure 1 It is a flow chart of a method for forwarding information of an Internet of Vehicles based on a named data network according to the present invention;

[0057] Figure 2 Schematic diagram of forwarding Interest and Data packets for consumer nodes;

[0058] Figure 3 This is a schematic diagram of the structure of the name prefix tree np;

[0059] Figure 4 A schematic diagram of adding a naming prefix to an interest packet in a beacon;

[0060] Figure 5 It is a schematic diagram of the geographical location coordinates of two vehicle nodes;

[0061] Figure 6 Coordinate diagram for calculating the Euclidean distance between two vehicle nodes and link duration;

[0062] Figure 7 Schematic diagram of forwarding interest packets for vehicle nodes. DETAILED DESCRIPTION

[0063] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0064] Example

[0065] like Figure 1-7 As shown, the general process of the vehicle network information forwarding method based on named data network of the present invention is: the consumer node and its neighbor node exchange their own motion information, and store the motion information obtained by the neighbor node in the neighbor information table (Neighbor Information Table, NIT), and process the motion state information stored in the neighbor information table NIT. At the same time, the consumer node calculates information related to the naming prefix, which will determine the next hop forwarding node. After the interest packet is forwarded, in order to ensure the stability of the reverse path of the data packet, a timer is set to add an alternative forwarding node.

[0066] The specific process is:

[0067] S1. The consumer node sends a beacon to all neighbor nodes within the communication range, obtains the motion state information of all neighbor nodes and the content connection quality value of the naming prefix of the interest packet of the consumer node stored in the neighbor node, and records the content connection quality value and motion state information in the neighbor information table of the consumer node;

[0068] In this embodiment, the content connection quality is defined based on the content name prefix, which is very consistent with the naming mechanism of NDN. Generally, a node with a high content connection quality for a name prefix has good network connectivity, which means that the probability that the interest packet corresponding to the naming prefix gets the corresponding data packet is relatively high. The present invention uses the hierarchical naming of NDN and the availability of network layer application data names to calculate the content connection quality (CCQ) of each name prefix, which means that a node can have different connection qualities for different prefixes.

[0069] However, managing different name prefixes in nodes is a practical problem. The present invention proposes a data structure of a prefix name tree (named prefix tree, np tree) to store the content connection quality of each name prefix. The tree structure can effectively store and retrieve the information of each prefix. Figure 3 An example np tree with a root prefix " / " and its descendants is shown. When a node receives a packet for the first time, it starts to build the np tree, and defines the name prefix " / " of the received packet as the root node. The CCQ at this moment is 0. When the node forwards a data packet or an interest packet later, if the name prefix of the packet is a child of the root prefix, the prefix is ​​recorded in the tree as the corresponding leaf node. As time goes by, the structure of the np tree will gradually improve, and the number of data packets and interest packets forwarded by the node will also be recorded in the tree. Through this data structure, the value of the content connection quality of a certain prefix of a specific node at the current time can be obtained. This method is very beneficial for forwarding strategies.

[0070] The definition of CCQ is as follows:

[0071]

[0072] The calculation method of CCQ of the name prefix is ​​the ratio of the data packets responded to by the node after sending the interest packet to the interest packet sent. j Connect the quality value of the content with name prefix j, D j The number of packets with name prefix j forwarded by the root node of the neighbor node. The score value of all packets with the prefix sent previously is used to determine the sending and receiving status of subsequent packets with the same prefix when they arrive at the node. j The number of interest packets with name prefix j forwarded by the root node of the neighbor node, ∑ i∈des(j) D i is the number of all packets whose name prefix contains j, ∑ i∈des(j) I i is the number of all interest packets that contain name prefix j. Here j is equivalent to the packet with prefix j, and the summed item is considered to be other packets with prefix j, such as / j / video / 01 and / data / b / j are both considered to be packets with prefix j, so the summed item is used. When calculating the CCQ of the name prefix, the count of interest packets and data packets of the descendants of the name prefix is ​​included. In other words, the CCQ of a name prefix represents the average connection quality of all known name prefixes in the name space. In this calculation process, the producer node also needs to add the name prefix to the field of the data packet.

[0073] The basic idea of ​​the present invention is to select the best neighbor node from different neighbor nodes as the next hop to complete the forwarding of information. As an information sending node, obtaining the relevant parameters of the neighbor node becomes one of the important issues that need to be solved: when the consumer sends an interest packet, it needs to obtain the CCQ information corresponding to the prefix of the interest packet from the neighbor node. Obviously, it is impossible for the consumer node to exchange the CCQ of all its prefixes with each neighbor node, which is a great challenge for delay and storage space. Therefore, the present invention proposes a method for pre-fetching content: when the node forwarding the interest packet sends a beacon to its neighbor node to obtain information such as CCQ and motion state parameters, it adds the naming prefix of the interest packet in the beacon, such as Figure 4 .

[0074] S2, processing the motion state information of the neighbor information table, finding the Euclidean distance, link duration and content connection quality value of the neighbor node that meets the conditions, and storing the found Euclidean distance, link duration and content connection quality value of the neighbor node in the information decision table;

[0075] Take the process of the consumer node sending an interest packet to the next hop for the first time as an example. Figure 4 , consumer nodes periodically send beacons to obtain the motion status information of neighboring nodes. Consumer C sends a beacon with " / a" to one of the nodes N1 to obtain the CCQ value related to the prefix. Node N1 queries the stored different prefixes and returns the CCQ value corresponding to " / a" and the related motion information to C; if the neighboring node does not store the prefix information, a CCQ value of 0 is directly returned. It is worth noting that consumer C will send beacons to all neighboring nodes within the communication range at the same time to obtain this information, so that it can select a good node as the next hop among multiple nodes to complete the stable transmission of information. When consumers send beacons to neighboring nodes, they will not only obtain relevant information about CCQ, but also interact with neighboring nodes about the current state of motion at the current moment, such as the driving speed at the current location.

[0076] S2, processing the motion state information of the neighbor information table, finding the Euclidean distance, link duration and content connection quality value of the neighbor node that meets the conditions, and storing the found Euclidean distance, link duration and content connection quality value of the neighbor node in the information decision table;

[0077] A coordinate system is established for a road section, and the current position is recorded using a rectangular coordinate system, such as Figure 5 shown.

[0078] The motion state information of a vehicle node includes the vehicle's motion speed v at a certain moment, its current position x, and the current time t. The calculation of the state information parameters can derive the Euclidean distance and link duration. These state information parameters and CCQ are used as the basic method for selecting the next hop node. The link duration is defined as follows. A motion model with only two nodes is established to complete the calculation: Assume that m and n on the road are two different nodes, and the two nodes are neighboring nodes, that is, at the current time t, they are within each other's communication range. The two nodes are v m ,v n The speed of m and n is θ respectively. m ,θ n , at this time, the position coordinates of m and n are (x m ,y m ),(x n ,y n ), they exchange motion status information with each other, and the nodes receiving this information maintain their neighbor information table NIT (neighbor information table / list). For example, node m records the information table of its neighbor node n, NIT(n) = (x n ,yn ,v n ,θ n ), based on the above information, vehicle node n can calculate its neighbor node m and its Euclidean distance D(m,n), link stability duration L(m,n),

[0079] The Euclidean distance between nodes is defined and calculated as follows:

[0080]

[0081] The link duration is defined and calculated as follows:

[0082] At time t, nodes m and n are within the communication range of each other. m ,v n The speed continues to move in the original direction. When the distance between m and n reaches time t', it is equal to their maximum communication range. Therefore, time t' is the first threshold of the link duration of m and n. The link duration is L, and L is calculated as follows:

[0083]

[0084] in,

[0085] In this embodiment, in S2, the specific conditions for finding the Euclidean distance, link duration, and content connection quality value of the neighboring node that meets the conditions are:

[0086] A1. Calculate the Euclidean distance between the neighbor node and the consumer node, and find a neighbor node within the communication range of the Euclidean distance as the first backup forwarder node;

[0087] A2. If the vehicle density is high, the forwarding node of the next hop of the neighbor node whose link duration L is greater than the first threshold and whose content connection quality value is the largest will be selected in the first backup forwarding node; the high vehicle density here means that the number of neighbor nodes within the communication range is greater than 5, that is, the vehicle density is high. The first threshold refers to the maintenance time of the communication link between the two vehicle nodes. If the first threshold is 10 seconds, it means that the communication between the two vehicle nodes is interrupted after 10 seconds. Therefore, the node with a link duration greater than the first threshold is selected as the next hop forwarding node to maintain communication for as long as possible. The first threshold can be determined based on the research of the transportation department, which will not be elaborated here.

[0088] A3. If the vehicle density is low, select the neighbor node with the longest link duration L with the consumer node from the spare forwarder nodes as the next-hop forwarder node.

[0089] In NDN, consumers obtain content based on the PULL mode. Consumers send named interest packets to obtain content, but the content source that provides the content is often not unique. This is also consistent with the scenario of the connected vehicle network: whether the consumer node requests entertainment content or security content, the content provider may be distributed in different locations in the network. More specifically, the content source may exist in different directions centered on the consumer, which requires consumers to add direction-related entries in the interest packet so that the interest packet can be sent in the forward and reverse directions of the vehicle node. The added entries are as follows: FIPRD (Forwarder ID in the Positive Road Direction) forwarder's positive direction ID, FINRD (Forwarder ID in the Negative Road Direction) forwarder's reverse direction ID, the angle between the positive direction and the consumer's movement direction is 0°, and the angle between the reverse direction and the consumer's movement direction is 180°. The format of the interest packet after adding entries is as shown in the following table.

[0090] Content Name Nonce Selectors FIPRD FINRD

[0091] According to the direction formula, the neighbor nodes in the NIT table are divided into positive direction and negative direction;

[0092] DT NRD (c,n)={n∈NIL|x n <x c &d(x n ,x c ) <R}

[0093] DT PRD (c,n)={n∈NIL|x n >x c &d(x n ,x c ) <R}

[0094] The above formula expresses the directional relationship between node n and consumer node c by constraining the current position and communication radius of consumer node c and neighbor node n: first, the position of neighbor node n must be within the communication range of the consumer, so that the next step of judgment can be made; second, by comparing the current position coordinates of neighbor node n, it can be determined whether the neighbor node and the consumer node are leading to or in the opposite direction; third, the link duration and CCQ (the formula in the above text) of the neighbor node that meets the conditions are calculated and the link duration and CCQ are stored in the information decision table DT;

[0095] According to the above formula, the forwarder node in the opposite direction is selected (because the vehicles on the road travel in both directions, if the consumer node in the middle wants to obtain information, it will obtain it from all directions, rather than being limited to forward or backward. This is why the direction id should be added to the packet at the beginning. The neighboring nodes within the communication range in both directions will be backup options, and both directions must be selected, as shown below). First, in the information decision table DT of the consumer node C NRD The link duration L between the vehicle and consumer C in (c) must be greater than the first threshold ε, and then the node with the highest CCQ value in this direction is selected as the next-hop forwarder node. Otherwise, the vehicle node with the largest L is selected as the next-hop forwarding. Similarly, the forwarder node in the positive direction is selected according to the positive direction node selection formula.

[0096] The specific formula for selecting nodes in the reverse direction is:

[0097]

[0098] Among them, the DT of the first row NRD Represents the forwarding decision table of the neighboring nodes in the opposite direction that meet the conditions, which stores the values ​​of L and CCQ. The meanings of L and CCQ are mentioned above; n p represents the set of all candidate nodes in the reverse direction, ε is the first threshold of link duration, L is the link duration between different nodes and consumer node C calculated based on the data, which needs to be greater than the first threshold, and the subscript n c means consumer node c, subscript n n means the neighbor node n(neighbor) of c;

[0099] The first line of the formula means: when L is greater than the first threshold, Select the decision table DT NRD The neighbor node with the highest CCQ value is used as the next hop forwarding node Otherwise, select the node with the largest L as the next hop (the content of the second line of the formula

[0100] The specific formula for selecting the positive direction node is:

[0101]

[0102] (The positive and negative directions are the same except that q represents the opposite direction and the DT decision table represents the positive direction decision table)

[0103] Consumer C sends the interest packet [Content Name, Selector, Nonce, np, nq] to the best forwarder node.

[0104] As shown in the following table, Table 2 is the NIT table of consumer c and neighbor nodes, Table 3 is the forward decision table DT of consumer c, and Table 4 is the reverse decision table DT of consumer c. The communication radius of consumer C is 100 meters, and x, y, v, and t are traffic data (the meaning has been mentioned above).

[0105] Table 2

[0106] ID x y <![CDATA[v x ]]> <![CDATA[v y ]]> t c 1220 8 -10 0 10 1 1235 0 7.5 0 10 2 1338 4 50 0 10 3 1270 8 -5 0 10 4 1220 12 -20 0 10 5 1150 12 -5 0 10 6 1140 8 -20 0 10 7 1170 4 15 0 10

[0107] Table 3

[0108] id L CCQ 1 40.8 0.7 3 10 0.75 4 10 0

[0109] Table 4 Reverse decision table DT

[0110]

[0111]

[0112] According to the above steps, the parameters in the NIT table are calculated and recorded in the NIT table. A decision is made on the information in the NIT table. After calculation, it can be seen that vehicle 2 (ID is 2) has left the communication radius of the consumer, so it is not used as an alternative forwarding node. Then the decision forwarding table in the two directions is determined according to different displacements. According to the above steps, vehicles 3 and 6 are the best forwarding nodes in the two directions respectively. The consumer will forward the interest packet to the selected vehicle. After completing this process, the DT table will not be reset immediately, but will be used for the process of returning the data packet along the reverse path.

[0113] S3. Find the most suitable neighbor node in the information decision table as the forwarding node of the interest packet, and transmit the corresponding data packet produced by the producer node to the consumer node according to the reverse path of the interest packet according to the information decision table.

[0114] In this embodiment, the specific steps of S3 are:

[0115] S3.1. Determine along the reverse direction of the interest packet whether the next neighbor node of the vehicle node where the data packet is located communicates normally with the vehicle node where the data packet is located (the Euclidean distance is within the range, and the communication link time is not interrupted). If normal, jump to S3.2; otherwise, jump to S3.3;

[0116] S3.2, forwarding the data packet to the neighbor node, and returning to S3.1 until the data packet reaches the consumer node;

[0117] S3.3. Find the first backup forwarder node in the information decision table of the vehicle node where the data packet is located, forward the data packet to the first backup forwarder node within the communication range, and return to S3.1 until the data packet reaches the consumer node.

[0118] In this embodiment, the selection criteria of the first standby forwarder node are:

[0119] B1. Calculate the Euclidean distance between the neighbor node and the first standby forwarder node, and find a neighbor node within the communication range of the Euclidean distance as the first standby forwarder node;

[0120] B2. If the vehicle density is high, the forwarding node of the next hop of the neighboring node whose link duration L is greater than the first threshold and whose content connection quality value is the largest is selected from the first standby forwarding node;

[0121] B3. If the vehicle density is low, a neighbor node with the longest link duration L with the first backup forwarder node is selected from the first backup forwarder node as the next-hop forwarder node.

[0122] The consumer node forwards the interest packet to the neighbor node through the above process. The neighbor node that receives the interest packet repeats the above process (S3.1-S3.3) until the corresponding data packet is found. This process requires as small a number of hops and delays as possible (achieved by finding the best forwarding node, thereby achieving a small communication cost). In the process of the data packet reaching the consumer along the reverse path, the forwarder node leaves the link for some reason, resulting in data transmission interruption, causing the data packet to fail to be successfully transmitted back to the consumer node, so the problem of data packet return path interruption also needs to be solved. In this case, the consumer node can of course send the interest packet again to obtain data, but this will increase the delay and affect the traffic conditions. The information decision table DT of the forwarding interest packet can be used to complete the retransmission of the data packet.

[0123] After making a decision in the information decision table DT to select the next hop forwarding, the DT cache is not cleared temporarily. A timer is set (determined by the 802.11p protocol or by the built-in value). The role of the timer is to start the first backup node. If the forwarding node cannot undertake the forwarding task due to an emergency, such as when the communication equipment is damaged or the vehicle is out of the communication range, the data packet cannot be successfully returned to the consumer. At this time, other nodes in DT need to be enabled to undertake the forwarding task. It should be noted that the attributes of the first backup node are not the best in the decision table, so the backup node is used. Forwarding data packets may cause a certain degree of resource loss. If the intermediate node is normal, there is no need to use the first backup node. Wait for the timer to expire and clear DT.

[0124] After the interest packet forwarding mentioned in the previous interest packet forwarding process is completed, the PIT table records the interface for forwarding the interest packet, and the data packet will be returned to the consumer from this interface. However, due to the problem of intermediate link interruption, it is necessary to start the CCQ and L order nodes in the DT table that are not optimal to forward the data packet. For example, if node 6 loses the communication connection, node 7 is selected to relay the data packet and the DT table is cleared after the delayer expires.

[0125] Since vehicles move at high speeds, their motion state information has a relatively obvious timeliness, and the motion state information of vehicle nodes and neighboring nodes will also change continuously. Therefore, both NIT and DT need to be updated and maintained periodically, so that they can assist vehicles in making better decisions and complete information forwarding in the NDN network. Through the above information forwarding strategy, unnecessary traffic in the network is reduced, the stability of the transmission link is increased, the user experience is improved, and the road traffic conditions are maintained.

[0126] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for forwarding information in an Internet of Vehicles based on a named data network, characterized in that: include: S1. The consumer node sends a beacon to all neighbor nodes within the communication range, obtains the motion state information of all neighbor nodes and the content connection quality value of the naming prefix of the interest packet of the consumer node stored in the neighbor node, and records the content connection quality value and motion state information in the neighbor information table of the consumer node; The calculation formula of the content connection quality value is: Among them, CCQ j Connect the quality value of the content with name prefix j, D j The number of packets with name prefix j forwarded by neighbor nodes, I j The number of interest packets with name prefix j forwarded to neighbor nodes, ∑ i∈des(j) D i is the number of all packets whose name prefix contains j, ∑ i∈des(j) I i is the number of all interest packets whose name prefix contains j; S2, processing the motion state information of the neighbor information table, finding the Euclidean distance, link duration and content connection quality value of the neighbor node that meets the conditions, and storing the found Euclidean distance, link duration and content connection quality value of the neighbor node in the information decision table; S3, find the most suitable neighbor node in the information decision table as the forwarding node of the interest packet, and transmit the corresponding data packet produced by the producer node to the consumer node according to the reverse path of the interest packet according to the information decision table; The specific steps are: S3.1, along the reverse direction of the interest packet, determine whether the next neighbor node of the vehicle node where the data packet is located communicates normally with the vehicle node where the data packet is located. If normal, jump to S3.2, otherwise, jump to S3.3; S3.2, forwarding the data packet to the neighbor node, and returning to S3.1 until the data packet reaches the consumer node; S3.

3. Find the first backup forwarder node in the information decision table of the vehicle node where the data packet is located, forward the data packet to the first backup forwarder node within the communication range, and return to S3.1 until the data packet reaches the consumer node.

2. The method for forwarding information in an Internet of Vehicles based on named data network according to claim 1, characterized in that: The content connection quality value is stored in a prefix name tree, the root node of the prefix name tree is the name prefix of the interest packet and / or data packet when the neighbor node first receives the interest packet and / or data packet, and when the vehicle node subsequently forwards the data packet and / or interest packet, the name prefix of the data packet or interest packet is a child of the name prefix of the root node, then the name prefix is ​​recorded in the prefix name tree as a child node of the corresponding root node, and the root node and child nodes of the prefix name tree also store the number of data packets and / or interest packets forwarded by the node.

3. The method for forwarding information in an Internet of Vehicles based on named data network according to claim 1, characterized in that: The motion state information includes the motion speed v of the neighbor node at time t and the current position x. In S2, the specific formula for finding the Euclidean distance of the neighbor node that meets the conditions is: Where D(m,n) is the Euclidean distance between consumer node m and neighbor node n, (x m ,y m ),(x n ,y n ) are the relative coordinate positions of consumer node m and neighbor node n at time t.

4. The method for forwarding information in an Internet of Vehicles based on named data network according to claim 3, characterized in that: In S2, the specific formula for finding the link duration of the neighboring node that meets the conditions is: α=v m cosθ m -v n cosθ n β=x m -x n γ=v m sinθ m -v n sinθ n ; ρ=y m -and n Where L(m,n) is the link duration between consumer node m and neighbor node n, θ m ,θ n are the moving directions of consumer node m and neighbor node n at time t, v m ,v n are the speeds of consumer node m and neighbor node n at time t respectively.

5. The method for forwarding information in an Internet of Vehicles based on named data network according to claim 4, characterized in that: In S2, the specific conditions for finding the Euclidean distance, link duration and content connection quality value of the neighboring node that meets the conditions are: A1. Calculate the Euclidean distance between the neighbor node and the consumer node, and find a neighbor node within the communication range of the Euclidean distance as the first backup forwarder node; A2. If the vehicle density is high, a neighboring node with a link duration L greater than a first threshold and a maximum content connection quality value is selected as the next-hop forwarding node in the first standby forwarding node; A3. If the vehicle density is low, a neighbor node with the longest link duration L with the consumer node is selected from the first standby forwarder node as the next-hop forwarder node.

6. The method for forwarding information in Internet of Vehicles based on named data network according to claim 5, characterized in that: Prior to S3.1, it also included adding the forward direction ID and reverse direction ID in the interest packet.

7. The method for forwarding information in an Internet of Vehicles based on named data network according to claim 6, characterized in that: A timer is set, and when the timer reaches a second threshold, the information decision table of the vehicle node is cleared.

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