GPSR routing protocol optimization method based on node time-space connectivity index

Abstract

The invention provides a GPSR routing protocol optimization method based on a node time-space connectivity index. The method comprises the following steps: step 1, acquiring position information of a destination node by a source node; 2, judging whether a neighbor node closer to a destination node exists in a neighbor node set of the current node, and if so, performing data transmission by adopting a greedy forwarding strategy; if not, executing the step 3; 3, calculating a time-space connectivity index of each neighbor node in the neighbor node set of the current node, and performing data transmission by taking the node with the maximum time-space connectivity index value as a next-hop routing node of the current node; 4, judging whether a destination node exists in the neighbor node set of the current node or not, and if yes, directly sending the data to the destination node by the current node; and if not, returning to execute the step 2 until the data is transmitted to the destination node.

Description

Technical Field

[0001] The invention relates to the technical field of mobile self-organizing networks, and in particular to a GPSR routing protocol optimization method based on node time-space connectivity index. Background Art

[0002] Greedy Perimeter Stateless Routing protocol (GPSR) is a typical location-based routing protocol that uses two forwarding strategies, greedy forwarding and perimeter forwarding, to complete data transmission. Figure 1 As shown in the figure. Before sending a data packet, the source node first obtains the real location information of the destination node through the GPS positioning service, and then searches among the neighboring nodes of the current node to see if there is a node with a smaller distance from the current node to the destination node. If so, the greedy forwarding mode is used for transmission; if not, it means that the greedy routing algorithm falls into a local optimum (i.e. encounters a routing hole, such as Figure 2 As shown in the figure, GPSR uses peripheral forwarding mode to bypass the holes. When the bypass meets the greedy condition, the greedy forwarding mode is restored; this is repeated until the packet reaches the destination. The use of greedy forwarding strategy and peripheral forwarding strategy to establish routes is efficient, simple and scalable. However, GPSR also has some limitations. Although the peripheral forwarding mode can ensure that data packets can get out of the routing holes, each forwarding requires a flat topology to eliminate cross edges, which reduces routing loops at the cost of increasing the number of forwarding hops. In most cases, the forwarding path is not optimal, so frequent routing holes will cause a sharp decline in the performance of the GPSR algorithm. Summary of the invention

[0003] Aiming at the problems that the typical routing protocol GPSR based on geographic location information has a single routing decision criterion, is prone to routing holes, and has an increased number of hops caused by the peripheral forwarding mode, the present invention provides a GPSR routing protocol optimization method based on the node time-space connectivity index.

[0004] The GPSR routing protocol optimization method based on node time-space connectivity index provided by the present invention comprises:

[0005] Step 1: The source node obtains the location information of the destination node;

[0006] Step 2: Determine whether there is a neighbor node closer to the destination node in the neighbor node set of the current node. If so, adopt the greedy forwarding strategy for data transmission; if not, execute step 3;

[0007] Step 3: Calculate the time-space connectivity index of each neighbor node in the neighbor node set of the current node, and use the node with the largest time-space connectivity index value as the next-hop routing node of the current node for data transmission; wherein the calculation process of the time-space connectivity index of each neighbor node includes: calculating the speed similarity of the neighbor node at adjacent time points, and recording the calculation result as the time correlation index; calculating the speed similarity between the current node and the neighbor node, and recording the calculation result as the space correlation index; respectively calculating the distances between the current node, the neighbor node and the destination node and comparing them, and recording the comparison result as the relative position offset index; obtaining the time-space connectivity index of the neighbor node according to the time correlation index, the space correlation index and the relative position offset index;

[0008] Step 4: Determine whether there is a destination node in the neighbor node set of the current node. If so, the current node sends the data directly to the destination node; if not, return to step 2 until the data is transmitted to the destination node.

[0009] Further, the time correlation index D of node i is calculated according to formula (1): temporal (i,t,t′):

[0010]

[0011] Among them, the time correlation index D temporal (i, t, t′) represents the similarity between the speed of node i at time t and time t′. Represents the velocity vector and The relative directions between Represents the velocity vector and The speed ratio between represents the velocity vector of node i at time t, represents the velocity vector of node i at time t′, and Represent the velocity values ​​of node i at time t and time t′ respectively.

[0012] Further, the spatial correlation index D between the current node i and the neighboring node j is calculated according to formula (2): spatial (i,j,t):

[0013]

[0014] Among them, the spatial correlation index D spatial (i,j,t) represents the similarity between the speed of the current node i and the neighbor node j at time t. Represents the velocity vector and The relative directions between Represents the velocity vector and The speed ratio between represents the velocity vector of the current node i at time t, represents the velocity vector of neighbor node j at time t, and Respectively represent the velocity values ​​of the current node i and the neighbor node j at time t.

[0015] Furthermore, if the communication distance D between the current node i and the neighbor node j at time t is i,j (t) is greater than the communication radius R of the current node i, then D spatial (i,j,t)=0.

[0016] Further, the relative position offset index D is calculated according to formula (3): distance (j):

[0017]

[0018] Among them, l(i,d) represents the Euclidean distance between the current node i and the destination node d, and l(j,d) represents the Euclidean distance between the neighbor node j and the destination node d.

[0019] Furthermore, in step 3, the temporal-spatial connectivity index TSC of the neighbor node j is obtained according to the temporal correlation index, the spatial correlation index and the relative position offset index according to formula (4):

[0020] TSC=αD temporal (j)+βD spatial (j)+γD distance (j) (4)

[0021] Among them, D temporal is the time correlation index, D spatial is the spatial correlation index, D distance is the spatial correlation index, and α, β and γ are given weighted judgment coefficients.

[0022] Beneficial effects of the present invention:

[0023] (1) The GPSR routing protocol optimization method based on the node time-space connectivity index provided by the present invention can, firstly, ensure the efficiency of node selection of routes before encountering routing holes according to the greedy algorithm; secondly, by introducing the node time-space connectivity index, the time-space connectivity index can reflect the movement characteristics and topological characteristics of network nodes in time and space. When routing selection encounters a hole, by selecting the next hop node with good time-space connectivity from the neighboring nodes, the probability of falling into the hole again can be reduced while solving the routing hole, thereby reducing the forwarding delay of data packets.

[0024] (2) As a preferred method for calculating time-space connectivity, by using three indexes (including time correlation index, space correlation index and relative position offset index) that can reflect the relative speed, relative direction and time correlation between neighbor nodes and the current node to calculate the time-space connectivity, the efficiency of the selected path can be further improved, and the efficiency and success rate of data packet sending can be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flowchart of node routing of the GPSR protocol provided by the prior art;

[0026] Figure 2 This is a schematic diagram of node locations when encountering routing holes;

[0027] Figure 3 A schematic flow chart of a GPSR routing protocol optimization method based on node time-space connectivity index provided by an embodiment of the present invention;

[0028] Figure 4 A schematic diagram of data path comparison when forwarding encounters a routing hole using a conventional GPSR protocol forwarding method and a method of the present invention provided in an embodiment of the present invention;

[0029] Figure 5 A schematic diagram comparing the routing forwarding paths when a node moves using a traditional GPSR protocol forwarding method and the method of the present invention provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] like Figure 3As shown, an embodiment of the present invention provides a GPSR routing protocol optimization method based on node time-space connectivity index, comprising the following steps:

[0033] S101: The source node obtains the location information of the destination node;

[0034] S102: Determine whether there is a neighbor node closer to the destination node in the neighbor node set of the current node. If yes, adopt a greedy forwarding strategy to perform data transmission; if no, execute step S103;

[0035] S103: Calculate the time-space connectivity index of each neighbor node in the neighbor node set of the current node, and use the node with the largest time-space connectivity index value as the next hop routing node of the current node for data transmission;

[0036] Specifically, the embodiment of the present invention designs a calculation index of the time-space connectivity function (TSC) of neighboring nodes based on the analysis of the movement characteristics and topological characteristics of network nodes in time and space, thereby assisting the node in making the next hop decision when encountering a routing hole.

[0037] As an implementation method, the calculation process of the time-space connectivity index of each neighbor node includes: calculating the speed similarity of the neighbor node at adjacent time points, and recording the calculation result as the time correlation index; calculating the speed similarity between the current node and the neighbor node, and recording the calculation result as the space correlation index; respectively calculating the distances between the current node, the neighbor node and the destination node and comparing them, and recording the comparison result as the relative position offset index; obtaining the time-space connectivity index of the neighbor node according to the time correlation index, the space correlation index and the relative position offset index;

[0038] Among them, the time correlation index reflects the movement characteristics of the node in time, the space correlation index reflects the movement characteristics of the node in space, and the relative position offset index reflects the topological characteristics of the node.

[0039] S104: Determine whether there is a destination node in the neighbor node set of the current node. If so, the current node sends the data directly to the destination node; if not, return to execute step S102 until the data is transmitted to the destination node.

[0040] The routing selection method provided by the embodiment of the present invention can adjust the routing strategy according to the connectivity status and motion status of neighboring nodes. Figure 1Based on the standard GPSR protocol shown in the figure, the present invention comprehensively considers the temporal and spatial movement relationship of nodes, the topological relationship, and the surrounding forwarding mode in routing forwarding, calculates the temporal-spatial connectivity between the current node and the neighboring nodes, and thus selects the more critical and stable nodes among the neighboring nodes as the next hop when encountering routing holes, thereby reducing the number of data packet forwarding hops, reducing the delay of network data packet propagation, and improving the network's packet delivery rate.

[0041] Example 2

[0042] Based on the above embodiments, the embodiments of the present invention specifically describe a design method of a time-space connectivity index.

[0043] In the above embodiment, the time-space connectivity index is mainly determined by three index indicators: time correlation index, space correlation index and relative position offset index. The following is a calculation method of one of the three index indicators.

[0044] (1) Time correlation index

[0045] In the present invention, the time correlation index is defined as the similarity between the speed of a node at time t and time t′, which is a function of the acceleration of the mobile node and the geographical restrictions. It is a measure of the dependence of the movement speed of a node in the network on its speed at a previous time. If the current speed of a node is completely independent of its speed at the previous time, then the mobile node has a smaller time correlation index; however, if the current speed is strongly dependent on the speed at a previous time, then the mobile node has a higher time correlation index.

[0046] Based on the above properties, as one of the preferred calculation methods, the time correlation index D of node i moving from time t to t′ is temporal The calculation formula of (i, t, t′) is as follows:

[0047]

[0048] Among them, the time correlation index D temporal (i, t, t′) represents the similarity between the speed of node i at time t and time t′. Represents the velocity vector and The relative directions between Represents the velocity vector and The speed ratio between represents the velocity vector of node i at time t, represents the velocity vector of node i at time t′, and Represent the velocity values ​​of node i at time t and time t′ respectively.

[0049] Due to the complexity of the environment, limited resources, and limited node energy that self-organizing networks may face, the communication links between nodes are easily affected by factors such as communication interference between nodes, node sleep, and power exhaustion, which can cause the link stability to decrease, increase the packet loss rate, and end-to-end delay. Therefore, the impact of the previous and next moments of the movement state of a single node on network performance needs to be added to the routing decision factors. The nodes with stable movement characteristics have a larger time dependence index. When the node movement stops suddenly, accelerates suddenly, or the node fails, the node movement lacks correlation. If such nodes are used as the destination nodes for data packet forwarding, it may cause the failure of data packet routing, and the accuracy and reliability of node selection and link establishment cannot be guaranteed. The time correlation index can effectively judge the time correlation of a single node movement. Adding time correlation to the routing decision can ensure the stability of the selected next-hop neighbor node, thereby improving the reliability of the link.

[0050] (2) Spatial correlation index

[0051] In the present invention, the spatial correlation index refers to the similarity of the speeds of two communication nodes, reflecting the extent to which the movement of the nodes is affected by each other. When the two communication nodes move in roughly the same direction and at almost similar speeds, the spatial correlation index value is high; however, if the two communication nodes move in opposite directions or have a large difference in movement speed, the spatial correlation index value is small.

[0052] Based on the above properties, as one of the preferred calculation methods, the spatial correlation index D between the current node i and the neighbor node j is spatial The calculation formula for (i,j,t) is as follows:

[0053]

[0054] Among them, the spatial correlation index D spatial (i,j,t) represents the similarity between the speed of the current node i and the neighbor node j at time t. Represents the velocity vector and The relative directions between Represents the velocity vector and The speed ratio between represents the velocity vector of the current node i at time t, represents the velocity vector of neighbor node j at time t, and Respectively represent the velocity values ​​of the current node i and the neighbor node j at time t.

[0055] It should be noted that since the communication range of each node in the wireless network is limited, the movement of the node rarely depends on the distant nodes in space. Therefore, the following limiting conditions are set to focus only on the node relationship within the node communication range. That is, if the communication distance D between the current node i and the neighbor node j at time t is i,j (t) is greater than the communication radius R of the current node i, then D spatial (i,j,t)=0.

[0056] Therefore, if the mobile nodes move independently of each other, the D spatial On the other hand, if the node movement is affected by its nearby nodes so that they move in similar directions and speeds, D spatial The (i,j,t) value will be higher. In the GPSR protocol, nodes obtain the geographical location information of neighbor nodes by periodically receiving broadcast signals from all neighbors. When routing and selecting neighbor nodes for forwarding, the location information of surrounding neighbors obtained in the previous time period is used. At this time, the neighbor may have moved out of the communication range of this node, causing the transmission link to be broken, which in turn causes the data packet to be lost or returned, and the overall network performance is reduced. Considering that the movement speed and direction of a single node cannot fully reflect the spatial relationship between nodes. When a single neighbor node moves at a high speed, if the sending node's movement speed and direction are similar to it at this time, the relative position change between the two is small. On the contrary, if the movement speed of a single neighbor node is low, but the sending node moves in the opposite direction at this time, the relative position change between the two is large. Therefore, the relationship between the movement speed and direction between the sending node and the neighbor node should be comprehensively considered. The spatial correlation index can effectively judge the spatial position change relationship between two moving nodes. When a neighbor node with a large index is selected as the next hop, it can alleviate the link instability caused by node movement and reduce the routing failure caused by obtaining the position of the HELLO packet at a fixed time interval.

[0057] (3) Relative position deviation index

[0058] In the present invention, the relative position offset index is defined as the ratio of the distance between the current node i that needs to forward the data packet and the destination node d to the distance between the neighbor node j of node i and the destination node d, that is:

[0059]

[0060] Among them, l(i,d) represents the Euclidean distance between the current node i and the destination node d, and l(j,d) represents the Euclidean distance between the neighbor node j and the destination node d.

[0061] When node i encounters a routing hole during forwarding, node i is the node closest to the destination node within its communication range. Therefore, the D distance (j)<1, and the farther the neighbor node j is from the destination node, the greater the distance The smaller the value of (j), the smaller the value of (j). According to the right-hand rule used by traditional GPSR to deal with routing holes, when a hole is encountered at node i, Figure 1 As shown, the data packets will be forwarded in the order of ixyz; however, in the present invention, the relative position offset index D of node y distance (y) is greater than node x. According to the relative position offset index, node y should be used as the forwarding destination node for the next hop. It can be seen that the relative position offset index can guide the forwarding of data packet transmission, thereby reducing the number of forwarding entries when encountering routing holes and avoiding the occurrence of routing loops.

[0062] In the embodiment of the present invention, the time-space connectivity index calculation adopts the above three decision factors: time correlation index, space correlation index, and relative position offset index; then the three decision factors are assigned appropriate weight coefficients α, β, and γ, and finally the value of the node time-space connectivity index (Time-space connectivity function, TSC) is calculated according to the following formula:

[0063] TSC=αD temporal (j)+βD spatial (j)+γD distance (j) (4)

[0064] Among them, D temporal is the time correlation index, D spatial is the spatial correlation index, D distance is the spatial correlation index, and α, β, and γ are all given weighted judgment coefficients (different weighted judgment coefficients α, β, and γ are given according to different influencing factors of the network in different application scenarios).

[0065] Example 3

[0066] Based on the above embodiments, the GPSR routing protocol optimization method of the present invention is further described below through a specific forwarding scenario.

[0067] As one of the forwarding scenarios, such as Figure 4 As shown in the figure, the current node i is about to forward the data packet to the destination node d. Because there is no neighboring node around node i that is closer to the destination node than itself (i.e., it encounters a routing hole), according to the traditional GPSR routing protocol, the surrounding forwarding mode is started, that is, node i selects node x to forward the data packet according to the surrounding forwarding rule, thus following the path shown in the figure. Figure 4The path ixabcyefgd shown delivers the data packet to the destination node d.

[0068] However, according to the method of the present invention, after encountering a routing hole at node i, node y is the node closest to the destination node d among the neighboring nodes. The value is the largest. After calculating the TSC index of the neighboring node at node i, node y will be selected as the next-hop forwarding node as the forwarding option when the routing hole occurs. After the data packet is forwarded to node y, the greedy forwarding strategy is restored at y by restarting step S102. The data packet is forwarded according to the iyefgd path under the method of the present invention.

[0069] It can be seen from this that although the traditional peripheral forwarding strategy can solve the problem of routing holes, it cannot effectively select the optimal path for data forwarding. The method of the present invention can effectively improve the forwarding efficiency of data packets when facing holes by introducing the TSC index.

[0070] As another forwarding scenario, the node is moving during the process of GPSR protocol data packets being transmitted from the source node to the destination node. Figure 5 As shown in the figure, node i is the node that currently needs to forward the data packet, d is the destination node, x and y are both within the communication range of node i, and node i is facing a routing hole at this time. According to the peripheral forwarding rules of the traditional GPSR routing protocol, node i should choose node x as the next hop. Due to the mobility characteristics of the nodes, and the different directions and speeds of movement, the position of node x has changed dramatically during the time period of updating the neighbor node table, and node x continues to move away from the destination node d, and and In the reverse direction, the distance between node i and node x gradually becomes larger than the communication radius of node i. According to the GPSR forwarding rule, node x is selected as the forwarding node. At this time, the transmission link may be broken, which greatly reduces the probability of successful forwarding.

[0071] However, according to the method of the present invention, when node i faces a routing hole, after calculating the TSC index value of the neighboring node of node i according to formula (4), TSCy>TSCx, node y will be selected as the next hop forwarding node of node i, and after y is selected as the forwarding node, the data packet can reach the destination node faster, effectively reducing the probability of link breakage.

[0072] The GPSR routing protocol forwarding method provided by the present invention first obtains the position and speed information of the source node, the destination node and the neighbor node through a HELLO packet, calculates the value of the time-space connectivity index TSC of the neighbor node and stores it in the data packet header, and the index is the basis for designing the GPSR optimization protocol; then the GPSR routing protocol forwarding method is optimized based on the time-space connectivity, and according to the positional relationship between the current node, the neighbor node and the destination node, when there is a node closer to the destination node in the neighbor node, a greedy forwarding strategy is adopted, otherwise, according to the TSC index value of the neighbor node, the neighbor node with the largest TSC index value is selected as the next hop forwarding node. The present invention can reduce the number of forwarding hops when the routing encounters a "hole", and reduce the forwarding delay of the node data packet; furthermore, by selecting a node with a large TSC index as the next hop, the probability of encountering a routing hole can be effectively reduced, and the success rate of data packet transmission can be improved.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A GPSR routing protocol optimization method based on node time-space connectivity index, characterized in that: include: Step 1: The source node obtains the location information of the destination node; Step 2: Determine whether there is a neighbor node closer to the destination node in the neighbor node set of the current node. If so, adopt the greedy forwarding strategy for data transmission; if not, execute step 3; Step 3: Calculate the time-space connectivity index of each neighbor node in the neighbor node set of the current node, and use the node with the largest time-space connectivity index value as the next-hop routing node of the current node for data transmission; wherein the calculation process of the time-space connectivity index of each neighbor node includes: calculating the speed similarity of the neighbor node at adjacent time points, and recording the calculation result as the time correlation index; calculating the speed similarity between the current node and the neighbor node, and recording the calculation result as the space correlation index; respectively calculating the distances between the current node, the neighbor node and the destination node and comparing them, and recording the comparison result as the relative position offset index; obtaining the time-space connectivity index of the neighbor node according to the time correlation index, the space correlation index and the relative position offset index; Step 4: Determine whether there is a destination node in the neighbor node set of the current node. If so, the current node sends the data directly to the destination node; if not, return to step 2 until the data is transmitted to the destination node.

2. The GPSR routing protocol optimization method based on node time-space connectivity index according to claim 1, characterized in that, Calculate the time correlation index D of node i according to formula (1): temporal (i,t,t′): Among them, the time correlation index D temporal (i, t, t′) represents the similarity between the speed of node i at time t and time t′. Represents the velocity vector and The relative directions between Represents the velocity vector and The speed ratio between represents the velocity vector of node i at time t, represents the velocity vector of node i at time t′, and Represent the velocity values ​​of node i at time t and time t′ respectively.

3. The GPSR routing protocol optimization method based on node time-space connectivity index according to claim 1, characterized in that, According to formula (2), the spatial correlation index D between the current node i and the neighbor node j is calculated spatial (i,j,t): Among them, the spatial correlation index D spatial (i,j,t) represents the similarity between the speed of the current node i and the neighbor node j at time t. Represents the velocity vector and The relative directions between Represents the velocity vector and The speed ratio between represents the velocity vector of the current node i at time t, represents the velocity vector of neighbor node j at time t, and Respectively represent the velocity values ​​of the current node i and the neighbor node j at time t.

4. The GPSR routing protocol optimization method based on node time-space connectivity index according to claim 3, characterized in that: If the communication distance D between the current node i and the neighbor node j at time t i,j (t) is greater than the communication radius R of the current node i, then D spatial (i,j,t)=0.

5. The GPSR routing protocol optimization method based on node time-space connectivity index according to claim 1, characterized in that: Calculate the relative position deviation index D according to formula (3): distance (j): Among them, l(i,d) represents the Euclidean distance between the current node i and the destination node d, and l(j,d) represents the Euclidean distance between the neighbor node j and the destination node d.

6. The GPSR routing protocol optimization method based on node time-space connectivity index according to claim 1, characterized in that: In step 3, the temporal-spatial connectivity index TSC of the neighbor node j is obtained according to the temporal correlation index, spatial correlation index and relative position offset index according to formula (4): TSC=αD temporal (j)+βD spatial (j)+γD distance (j) (4) Among them, D temporal is the time correlation index, D spatial is the spatial correlation index, D distance is the spatial correlation index, and α, β and γ are given weighted judgment coefficients.

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