AODV routing method based on geographic position and mobile information

Abstract

The invention relates to an AODV routing method based on a geographic position and mobile information, which is applied to a mobile node and comprises the following steps: acquiring an RREQ message broadcasted by a source node, and judging whether the source node is a destination node according to the received RREQ message, the RREQ message comprising the geographic position and the mobile information of the node and the maximum mobile cost; if the node is the destination node, selecting a routing path to send an RREP message to the source node; and if the RREQ message is not the destination node, calculating a new coverage range of signal transmission provided by the current node according to the geographic position of the node with the previous set hop count in the RREQ message and the geographic position of the RREQ message, if the new coverage range is smaller than a set threshold value, discarding the message, and otherwise, broadcasting and forwarding the RREQ message. According to the invention, redundant broadcast messages in a route discovery process can be reduced, the stability of a route link is effectively improved, and the AODV protocol is more suitable for a mobile network environment.

Description

Technical Field

[0001] The invention relates to the technical field of mobile ad hoc networks, and in particular to an AODV routing method based on geographical location and mobile information. Background Art

[0002] A mobile ad hoc network is a network system composed of wireless mobile nodes that does not require the support of fixed network communication infrastructure and can be quickly deployed when needed. It has the characteristics of being centerless, self-healing, dynamic topology, and high node mobility. The mutual cooperation of network nodes breaks through the limitations of time, location, and equipment. It can be widely used in battlefield communication command and control, disaster relief, temporary gatherings, field construction operations, and other emergency and sudden occasions.

[0003] The Ad-Hoc On-Demand Distance Vector (AODV) protocol is a reactive routing protocol designed for mobile ad hoc networks. It is one of the classic routing protocols in the field of mobile ad hoc networks. It combines the routing discovery (initiating the routing discovery process only when needed) and maintenance mechanism of the Dynamic Source Routing Protocol (DSR) with the multi-hop forwarding routing mechanism and sequence periodic update mechanism of the Destination-Sequenced Distance Vector (DSDV). It can quickly adapt to link conditions, with low processing overhead, low storage overhead, and low routing control overhead.

[0004] Communication nodes in mobile ad hoc networks are allowed to move freely and arbitrarily, which inevitably leads to dynamic changes in network topology, even random, rapid, and unpredictable changes, resulting in unstable network communication, frequent routing breaks, and a large increase in routing control overhead. In the Ad-Hoc On-Demand Distance Vector (AODV) routing protocol, the source node finds the route to the destination node based on the shortest hop count. From the perspective of the link, wireless communication networks are not just two states of on and off. There is a certain quantitative space between on and off. The hop count can only measure on and off, and cannot quantify the quality of the link more. The shortest hop count routing often means the maximization of the average transmission distance. In mobile ad hoc networks, the longer the transmission distance, the more unstable the link and the easier it is to break. In mobile ad hoc networks, the source node finds the route to the destination node by flooding broadcast route request messages. When finding the route, the network is filled with a large number of broadcast messages, but the new coverage brought by the broadcast forwarding of the relay node is limited. The new coverage is too low, indicating that the broadcast is redundant.

[0005] Therefore, an AODV routing method is needed that can reduce redundant broadcast messages in the route discovery process, effectively improve the stability of the routing link, and make the AODV protocol more suitable for mobile network environments. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide an AODV routing method based on geographic location and mobility information, which can reduce redundant broadcast messages in the routing discovery process, effectively improve the stability of the routing link, and make the AODV protocol more suitable for mobile network environments.

[0007] The technical solution adopted by the present invention to solve the technical problem is: to provide an AODV routing method based on geographic location and mobility information, which is applied to a mobile node and includes the following steps: Obtaining the RREQ message broadcast by the source node, and judging whether it is the destination node according to the received RREQ message, wherein the RREQ message includes the node's geographic location and mobility information, as well as the maximum mobility cost; If it is the destination node, it selects a routing path to send a RREP message to the source node; If it is not the destination node, the new coverage range of the signal transmission provided by the current node is calculated based on the geographic location of the node with the previous set number of hops in the RREQ message and its own geographic location. If the new coverage range is less than the set threshold, the message is discarded, otherwise the RREQ message is broadcast and forwarded.

[0008] Further, the broadcasting and forwarding of the RREQ message includes: Extract the geographic location and mobility information of the previous node of the current node in the RREQ message, and calculate the single-hop mobility cost based on the geographic location and mobility information of the current node. The single-hop mobility cost is the cost of a single-hop link between two nodes based on quantized mobility calculated based on the location, speed and signal transmission range of the nodes. If the calculated single-hop mobility cost is less than the maximum mobility cost in the RREQ message, the RREQ message is directly broadcast and forwarded; otherwise, the node geographic location and mobility information, as well as the maximum mobility cost in the RREQ message are updated, and the updated RREQ message is broadcast and forwarded.

[0009] Further, the selecting a routing path to send a RREP message to the source node includes: Determine whether there is a routing path to the source node according to the routing table; Calculate link cost metrics based on node location and mobility information in RREQ messages; If the routing path does not exist, a routing path to the source node is established, and the calculated link cost metric is written into the routing table; If the routing path already exists, determine whether the calculated link cost metric is less than the link cost metric in the routing table. If so, update the link cost metric and routing path in the routing table to the calculated link cost metric and its corresponding routing path. Send a RREP message to the source node.

[0010] Further, the link cost metric is calculated based on the node geographic location and mobility information in the RREQ message, including: Calculate the maximum single-hop moving cost in the routing path from the source node to the current node in the RREQ message; The link cost metric is calculated as a weighted sum of the number of hops and the maximum single-hop mobility cost.

[0011] Furthermore, the single-hop mobility cost is calculated by the following formula: in, Represent the Cartesian coordinates of node A and node B respectively, Represent the moving speeds of node A and node B respectively, Respectively represent the moving azimuths of node A and node B, Indicates the radius of the node signal transmission range circle, Indicates the maximum movement speed that a node can achieve. All are intermediate variables.

[0012] Further, the calculating of the new coverage range of the signal transmission provided by the current node according to the geographical location of the node with the previously set number of hops in the RREQ message and the current node's own geographical location includes: Divide the signal transmission range of the current node into several grid units and count the total number of grid units; Counting the grid cells that are not within the signal transmission range of the node with the previously set hop count as the number of uncovered cells; The ratio of the number of uncovered cells to the total number of grid cells is calculated, and a new coverage range of signal transmission provided by the current node is calculated based on the ratio.

[0013] Further, the grid cells that are not within the signal transmission range of the node with the previously set hop count are obtained by the following method: Set the coordinates of the grid cell to the coordinates of its center; For any node with the pre-set number of hops, grid cells whose Euclidean distance to the node is greater than the set value are considered to be grid cells that are not within the signal transmission range of the node.

[0014] Furthermore, the set number of hops is no more than three hops.

[0015] Furthermore, the node geographic location and movement information include a maximum movement cost, a first-hop node location information, a first-hop node movement information, a second-hop node location information, and a third-hop node location information.

[0016] Furthermore, if it is not the destination node, before the step of calculating the new coverage range of the signal transmission provided by the current node based on the geographical location of the node with the previously set number of hops in the RREQ message and its own geographical location, it also includes the step of determining whether the request is a duplicate message based on the source node IP address and the serial number of the RREQ message, and if so, discarding the message.

[0017] Beneficial Effects Due to the adoption of the above-mentioned technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention adopts a flooding constraint algorithm based on geographic location to determine whether to forward a routing request, thereby excluding nodes that provide new coverage but do not meet the signal transmission requirements, and reducing redundant broadcast messages in the routing discovery process; in addition, by adopting a routing discovery algorithm based on link cost metrics to select routing paths, it can effectively solve the problem that the routing path in a mobile ad hoc network is selected based on the shortest number of hops and the quality of the link cannot be further quantified, resulting in long transmission distances and unstable and easily broken transmission links, effectively improving the stability of the routing link and making the AODV protocol more suitable for mobile network environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of an embodiment of the present invention; Figure 2 is a routing selection flow chart of an embodiment of the present invention; Figure 3 is a schematic diagram of route discovery according to an embodiment of the present invention; Figure 4 is a schematic diagram of broadcast forwarding according to an embodiment of the present invention; Figure 5 is a schematic diagram of a grid filling approximate calculation method according to an embodiment of the present invention; Figure 6 is a flow chart of a geographical location-based flooding constraint algorithm according to an embodiment of the present invention; Figure 7 is a three-dimensional surface diagram of a motion cost function according to an embodiment of the present invention; Figure 8 It is a flow chart of a route discovery algorithm based on link cost metric indicators according to an embodiment of the present invention; Fig. 9 is a schematic diagram of a route request (RREQ) message format according to an embodiment of the present invention; Fig.10 is a schematic diagram of a routing reply (RREP) message format according to an embodiment of the present invention; Fig.11 It is a schematic diagram of the routing table format of an implementation mode of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0020] The embodiment of the present invention relates to an AODV routing method based on geographic location and mobility information, such as Figure 1 As shown, the following steps are included: Step 1) When the source node wants to send data to the destination node, it first queries the routing table to see if there is a route to the destination node. If there is, it uses this route to send the data. If not, the source node starts the route discovery process and broadcasts a route request message RREQ to the network. Step 2) When a node receives a routing request packet from the network, it performs the following processing: 1. If this node is the destination node, jump to step 6; 2. If this node is not the destination node, proceed to step 3; Step 3) Determine whether the request is a duplicate message based on the source node IP address and RREQ sequence number. If it is, discard the message, otherwise proceed to step 4; Step 4) The flood constraint algorithm based on geographic location determines whether to forward the routing request, specifically: Calculate the new coverage range based on the geographical locations of the first K hops (maximum three hops) nodes in the RREQ message and the current node geographical location. If the new coverage range is less than a preset threshold, discard the message, otherwise proceed to step 5; Step 5) According to the location and mobility information of the node in the RREQ message, the single-hop mobility cost is calculated and compared with the maximum mobility cost in the RREQ message. If the former is less than the latter, the mobility cost value is not updated. Otherwise, the maximum mobility cost value is updated, and then the node location and mobility information in the RREQ are updated, and the RREQ message is broadcast and forwarded, and the process ends.

[0021] Step 6) The routing discovery algorithm based on the link cost metric selects the routing path, such as Figure 2 As shown, specifically including: 1) The destination node transmits the RREP message through the reverse route established in the routing selection phase. After receiving the RREP message, the node proceeds to the next step.

[0022] 2) The above receiving node queries the routing table to see whether there is a route to the destination node. If not, a route to the destination node is established and the link cost information is written into the routing table. If so, the link cost information in the routing table and the RREP message is compared and the path with the smaller link cost is selected as the latest path.

[0023] 3) The above receiving node determines whether it is the source node. If so, it transmits the information through the latest path to the destination node and ends the process. If not, it updates and forwards the RREP message and ends the process.

[0024] The overall routing discovery process diagram is as follows: Figure 3 shown.

[0025] The following further describes the flooding constraint algorithm based on geographical location, the route discovery algorithm based on link cost metric, and the route message packet format of this implementation.

[0026] First, the flooding constraint algorithm based on geographical location In a mobile ad hoc network, the wireless signals sent from antennas of different nodes are likely to overlap. Due to the overlap of wireless signal coverage, the cost of broadcast forwarding is very high: mobile node A broadcasts a routing request message, and mobile node B is a relay node, which needs to broadcast and forward this message. , are the wireless signal transmission ranges of mobile nodes A and B respectively. The new coverage range provided by mobile node B is , the node forwarding broadcast diagram is as follows Figure 4 As shown, represents the radius of the mobile node's transmission range, It represents the Euclidean distance between mobile node A and mobile node B. The gray area is the new coverage area provided by mobile node B broadcasting forwarding message.

[0027] It can be deduced that the calculation formula for the shaded area is: when hour, Reaching the maximum value: Obviously, a broadcast forwarding can provide at most 61% new coverage, assuming that mobile node B can be located anywhere within the transmission range of mobile node A; integrating the above gives the average value as follows: According to the above analysis, a broadcast forwarding can only provide 41% coverage area on average. When a routing request message received by a mobile node is forwarded by multiple nodes, to calculate the new coverage area provided by the node broadcast forwarding, it is necessary to calculate the difference between the overlapping union coverage area of ​​multiple intersecting circles and the coverage area of ​​the node, which is very difficult. The present invention uses the grid approximate filling method to calculate the area of ​​the new coverage area.

[0028] The grid filling approximation method is as follows Figure 5 As shown in the figure, X is the current mobile node, A, B, and C are the first three hop nodes, and the gray shaded area is the new coverage range that mobile node X can provide. Taking the coordinates of node X as the center, the transmission range of mobile node X is divided into small squares, and the center of the square is set as the coordinate of the square. The Euclidean distance between each square and nodes A, B, and C is calculated to determine whether the square is within the coverage range of nodes A, B, and C. The number of squares that are not within the coverage range of nodes A, B, and C is divided by the total number of squares within the transmission range of mobile node X to obtain the ratio of the new coverage range that X can provide to the entire transmission range.

[0029] like Figure 6 As shown, the geographical location-based flooding constraint algorithm includes the following steps: Step 1: The source node needs to establish a connection with the destination node. The source node updates its own location to the RREQ message and broadcasts the RREQ message to the entire network.

[0030] Step 2: The relay node receives the RREQ message and calculates the new coverage range that the relay node can provide by broadcasting and forwarding the RREQ message based on the location information of the first k hops (up to three hops) in the RREQ message. , the destination node directly processes the RREQ message when it receives it.

[0031] Step 3: With predefined coverage thresholds Compared with , proceed to step 4. , skip to step 5 to continue.

[0032] Step 4: Update the location and movement information in the RREQ message (storing up to three hops of location information), and broadcast the RREQ message to the network to end the process.

[0033] Step 5: Refuse to forward and discard the RREQ message, ending the process.

[0034] Second, the route discovery algorithm based on link cost metric In the AODV protocol, the source node searches for a route to the destination node based on the shortest number of hops. From the perspective of the link, wireless communication networks do not have only two states: on and off. There is a certain quantitative space between on and off. The number of hops can only measure on and off, and cannot quantify the quality of the link more. The shortest hop routing often means maximizing the average transmission distance. In mobile ad hoc networks, the longer the transmission distance, the more unstable the link and the easier it is to break.

[0035] The present invention proposes a Movement Cost Function (MCF) to quantify the impact of movement on a single-hop link.

[0036] in: In the above formula Represents the Cartesian coordinates of mobile nodes A and B, Indicates the moving speed of mobile nodes A and B, Indicates the moving azimuth of mobile nodes A and B. Indicates the radius of the node transmission range circle, Indicates the maximum movement speed that a node can achieve.

[0037] when =25m / s, the three-dimensional surface diagram of the moving cost function is as follows Figure 7 As shown. Among them: In the above formula It is equivalent to equations (5), (6), (7), and (8).

[0038] Design link cost metrics to replace hop counts in routing decisions. Link cost metrics: in, is the number of hops, is the path movement cost value, which is the maximum value of the single-hop movement cost in the routing path: In formula (11) Represents coefficient weights: like Figure 8 As shown, the link cost metric-based routing discovery algorithm includes the following steps: In the first step, the source node needs to establish a connection with the destination node. The source node updates its own location to the RREQ message and broadcasts the RREQ message to the entire network.

[0039] In the second step, the relay node receives the RREQ message and determines whether to broadcast the message. If forwarded, the mobility cost field in the RREQ message is updated. When the destination node receives the RREQ message, it calculates the link cost metric and proceeds to the third step to process the RREQ message.

[0040] In the third step, if there is no route from the destination node to the source node, a reverse route to the source node is established to end the process; if there is a route to the source node, proceed to the fourth step.

[0041] The fourth step is to compare the link cost index of the path from the destination node to the source node in the routing table with the link cost index of the path passed by the RREQ message, update the path with the lower link cost as the latest path, reply the RREP message to the source node, and end the process.

[0042] Third, routing message packet format 1. Modify the format of the route request message (RREQ). Add several fields to the original route request message (RREQ), such as Fig. 9 As shown, it is now represented by a gray background, and the added fields are explained as follows: (1) Maximum mobility cost: 32 bits in length, indicating the maximum value of the single-hop mobility cost in the routing path from the source node to the node one hop before the current node, used for link cost metric calculation.

[0043] (2) Position of the first hop node in the previous number: 32 bits in length, storing the Cartesian coordinates of the first hop node in the previous number, with the first 16 bits storing the horizontal coordinate value , the last 16 bits store the vertical coordinate value .

[0044] (3) The first hop node movement information: 32 bits in length, the first 16 bits store the movement speed of the first hop node The last 16 bits store the moving azimuth of the first hop node. .

[0045] (4) Second-hop node position: 32 bits in length, storing the Cartesian coordinates of the second-hop node, with the first 16 bits storing the horizontal coordinate value , the last 16 bits store the vertical coordinate value .

[0046] (5) Position of the third hop node from the front: 32 bits in length, storing the Cartesian coordinates of the third hop node from the front, with the first 16 bits storing the horizontal coordinate value , the last 16 bits store the vertical coordinate value .

[0047] 2. Modify the format of the route reply (RREP) message. Add a field to the RREP message format, such as Fig.10 As shown, it is now represented by a gray background, and the added fields are explained as follows: (1) Link cost metric: 32 bits in length, used for comparison and selection of routing paths. The link cost metric in the present invention is .

[0048] 3. Modify the format of the routing table. Add a field to the routing table, such as Fig.11 As shown, it is now represented by a gray background, and the added fields are explained as follows: (1) Link cost metric: 32 bits in length, used for comparison and selection of routing paths. The link cost metric in the present invention is .

Claims

1. An AODV routing method based on geographic location and mobility information, applied to a mobile node, characterized in that: The following steps are involved: Obtaining the RREQ message broadcast by the source node, and judging whether it is the destination node according to the received RREQ message, wherein the RREQ message includes the node's geographic location and mobility information, as well as the maximum mobility cost; If it is the destination node, it selects a routing path to send a RREP message to the source node; If it is not the destination node, the new coverage range of the signal transmission provided by the current node is calculated based on the geographic location of the node with the previous set number of hops in the RREQ message and its own geographic location. If the new coverage range is less than the set threshold, the message is discarded, otherwise the RREQ message is broadcast and forwarded.

2. The method according to claim 1, characterized in that The broadcasting and forwarding of the RREQ message includes: Extract the geographic location and mobility information of the previous node of the current node in the RREQ message, and calculate the single-hop mobility cost based on the geographic location and mobility information of the current node. The single-hop mobility cost is the cost of a single-hop link between two nodes based on quantized mobility calculated based on the location, speed and signal transmission range of the nodes. If the calculated single-hop mobility cost is less than the maximum mobility cost in the RREQ message, the RREQ message is directly broadcast and forwarded; otherwise, the node geographic location and mobility information, as well as the maximum mobility cost in the RREQ message are updated, and the updated RREQ message is broadcast and forwarded.

3. The method according to claim 2, characterized in that The selecting a routing path to send a RREP message to the source node includes: Determine whether there is a routing path to the source node according to the routing table; Calculate link cost metrics based on node location and mobility information in RREQ messages; If the routing path does not exist, a routing path to the source node is established, and the calculated link cost metric is written into the routing table; If the routing path already exists, determine whether the calculated link cost metric is less than the link cost metric in the routing table. If so, update the link cost metric and routing path in the routing table to the calculated link cost metric and its corresponding routing path. Send a RREP message to the source node.

4. The method according to claim 3, characterized in that The link cost metric is calculated based on the node geographic location and mobility information in the RREQ message, including: Calculate the maximum single-hop moving cost in the routing path from the source node to the current node in the RREQ message; The link cost metric is calculated as a weighted sum of the number of hops and the maximum single-hop mobility cost.

5. The method according to claim 3, characterized in that: The single-hop mobility cost is calculated by the following formula: in, Represent the Cartesian coordinates of node A and node B respectively, Represent the moving speeds of node A and node B respectively, Respectively represent the moving azimuths of node A and node B, Indicates the radius of the node signal transmission range circle, Indicates the maximum movement speed that a node can achieve. All are intermediate variables.

6. The method according to claim 1, characterized in that The calculating of a new coverage range of signal transmission provided by the current node according to the geographical location of the node with the previously set number of hops in the RREQ message and the current node's own geographical location includes: Divide the signal transmission range of the current node into several grid units and count the total number of grid units; Counting the grid cells that are not within the signal transmission range of the node with the previously set hop count as the number of uncovered cells; The ratio of the number of uncovered cells to the total number of grid cells is calculated, and a new coverage range of signal transmission provided by the current node is calculated based on the ratio.

7. The method according to claim 6, characterized in that The grid cells that are not within the signal transmission range of the node with the previously set hop count are obtained by the following method: Set the coordinates of the grid cell to the coordinates of its center; For any node with the pre-set number of hops, grid cells whose Euclidean distance to the node is greater than the set value are considered to be grid cells that are not within the signal transmission range of the node.

8. The method according to claim 1, characterized in that The set number of hops is no more than three hops.

9. The method according to claim 8, characterized in that The node geographic location and movement information include maximum movement cost, first hop node location information, first hop node movement information, second hop node location information, and third hop node location information.

10. The method according to claim 1, characterized in that If it is not the destination node, before the step of calculating the new coverage range of the signal transmission provided by the current node based on the geographical location of the node with the previously set number of hops in the RREQ message and its own geographical location, it also includes the step of determining whether the request is a duplicate message based on the source node IP address and the serial number of the RREQ message, and if so, discarding the message.

Images