A distance vector based routing update method

Abstract

This invention discloses a distance vector-based routing update method, comprising: Step 1, receiving the routing tables and neighbor information tables of neighboring nodes; Step 2, updating the routing table based on the received signal quality (SNR) in the neighbor information table. R The process involves four steps: First, calculating the path cost from the current node to the destination node and combining this cost with the routing entries in the routing tables of neighboring nodes to form a path entry to be updated. Second, if the destination node information is not present in the current node's routing table, the path entry information is inserted into the current node's routing table. If the destination node information already exists, an update check is performed and the path entry is updated. Third, steps two and three are repeated until all entries in the routing table are updated. This invention, when sensing an increase in routing path cost, can predict communication quality and switch to a path with better communication quality in advance, thereby improving the reliability of path selection and reducing packet loss caused by path switching delays.

Description

Technical Field

[0001] This invention belongs to the field of network protocols, specifically relating to a distance vector-based route update method. Background Technology

[0002] Mobile Ad Hoc Networks (MAHC Networks) refer to a multi-hop, temporary, self-organizing network composed of mobile nodes equipped with wireless transceivers. Research on MHACs originated from early military communications, designed to meet the needs of communication in environments where fixed communication infrastructure is impossible, such as battlefields and disaster relief. They do not rely on any existing network infrastructure or centralized management and control center. Nodes in the network are dynamically changing and arbitrarily distributed, interconnected wirelessly, and each node acts as both the communication subject and a router. Due to the multi-hop nature of Ad Hoc networks, traditional Internet-based routing protocols cannot adapt to the rapidly changing topology. Furthermore, routing protocols must consider the low bandwidth, high error rate, and low power consumption requirements of Ad Hoc networks, thus necessitating the design of routing protocols suitable for Ad Hoc networks. Their main characteristics include:

[0003] (1) Highly dynamic network topology. Dynamically changing topology is the most prominent feature of ad hoc networks. When conventional routing protocols are run directly in an ad hoc network, they require a long time and significant overhead to reach convergence after the topology changes.

[0004] (2) Limited wireless transmission bandwidth. Due to the physical characteristics of the wireless channel itself, the network bandwidth it can provide is much lower than that of the wired channel. In addition, considering various factors such as collisions, signal attenuation, noise interference, and inter-channel interference caused by competition for sharing the wireless channel, the actual bandwidth that a node can obtain is far less than the theoretical maximum bandwidth value.

[0005] Existing Ad Hoc routing protocols can be divided into two types: on-demand routing protocols and pre-routing protocols.

[0006] On-demand routing protocols, also known as reactive routing protocols, do not require nodes to maintain timely and accurate routing information. Instead, they only look up routes when data needs to be sent. Each node has a route discovery process and a route maintenance process. The former is responsible for finding the corresponding route, while the latter is responsible for maintaining an established route until the destination node becomes unreachable or no longer needs the route.

[0007] Pre-routing protocols, also known as table-driven routing protocols, involve nodes exchanging routing information by periodically broadcasting routing information packets to maintain updated routes. Each node also maintains a routing table to store routing information to all other nodes in the network. When a node needs to send a data packet, it can immediately find the appropriate route based on the routing information. However, to ensure that route updates keep pace with changes in the network topology, a certain overhead is incurred. But when the number of nodes in an ad hoc network is within a certain range, this overhead is well within acceptable limits.

[0008] DSDV (Destination Sequenced Distance Vector) is a table-driven routing protocol. It avoids routing loops by assigning sequence numbers to each routing packet and uses time-driven and event-driven techniques to control the transmission of routing tables. Each node periodically transmits its local routing table to neighboring nodes. When the routing table changes, it also transmits routing information to neighboring nodes. Upon receiving the modified routing table information, neighboring nodes update their routing tables by comparing routing sequence numbers to maintain the best route. Summary of the Invention

[0009] The purpose of this invention is to provide a distance vector-based routing update method for mobile ad hoc networks, which improves the reliability of routing selection, reduces the time required to detect abnormal paths, and reduces packet loss without increasing the bandwidth occupied by routing on wireless link communication.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A distance-vector-based route update method, applied to mobile ad hoc networks, includes the following steps:

[0012] Step 1: Receive hello packets broadcast by neighboring nodes. These hello packets contain the neighboring nodes' routing tables and neighbor information tables. The routing tables contain several route entries, each including the destination node address, neighbor node address, path sequence number, path hop count, and path cost. The neighbor information tables contain the address information of the current node and its neighbors, as well as the received signal quality (SNR) measured by the neighboring node when it received the hello packet from the current node. R ;

[0013] Step 2: Based on the received signal quality (SNR) R Calculate the path cost from this node to the destination node, and combine it with the routing entries in the routing tables of neighboring nodes to form the path entry to be updated;

[0014] Step 3: If the destination node information for the path entry to be updated is not found in the routing table of this node, then insert the path entry information to be updated into the routing table of this node; if the destination node information already exists, then perform an update check and update the path entry.

[0015] Step 4: Repeat steps 2 and 3 until all entries in the routing table have been updated;

[0016] Step 5: Periodically maintain the local routing table and delete path entries that have timed out and not been updated.

[0017] Preferably, the calculation of the path cost includes the following steps:

[0018] Step 2-1: Calculate the received signal quality (SNR) from the neighbor information table of the received neighbor nodes. R The transmitted signal quality (SNR) is used as a reference in the neighbor information table of this node. T ;

[0019] Step 2-2: Based on the SNR already recorded at this node, predict the communication quality SNR for the next cycle. next And obtain SNR through covariance next reliability;

[0020] Steps 2-3: When the covariance value meets the requirements, use SNR. next The transmission overhead of neighboring nodes is calculated; when the covariance does not meet the requirements, the actual measured SNR is used. T The transmission cost of all next hops of this node to its neighboring nodes is calculated.

[0021] Steps 2-4: Set SNR T Record the information in the SNR and return to step 2-1 to wait for the neighbor information table of the new neighbor node.

[0022] Preferably, the prediction is a linear prediction: based on the recorded SNRs, the least squares method is used to find a straight line such that the sum of the squares of the vertical distances from all recorded SNRs to that line is minimized.

[0023] Preferably, step three includes the following steps:

[0024] Step 3-1: Combine the neighbor node addresses, path sequence numbers and path hop counts in the neighbor node routing table to select the optimal path for update, and then execute Step 3-2; The optimal path is: when paths switch frequently, the path with faster update speed and equal or lower cost is the optimal path. After the path stabilizes, it is considered the optimal path unless there is a path with lower cost.

[0025] Step 3-2: In the routing table of this node, if the address of the neighbor node leading to the destination node in the routing entry has not changed, then proceed to step 3-3; if it has changed, then proceed to step 3-4.

[0026] Step 3-3: If the path sequence number of the path to be updated is larger, then update the path sequence number, path hop count, and path cost, but do not update the destination node address and neighbor node addresses, and update the path update time; if the path sequence number to be updated is equal to or smaller than the path sequence number, then do not update.

[0027] Steps 3-4: If the sequence number of the path to be updated is larger and the path cost is equal to or better, then update the neighbor node address, path sequence number, path hop count, and path cost in the routing table of this node, but do not update the destination node address, and update the path update time; if the sequence numbers are the same and the path to be updated has better communication quality, then update the neighbor node address, path hop count, and path cost, but do not update the destination node address and path sequence number, and update the path update time; if the local sequence number is larger but the path to be updated has better communication quality, then update the neighbor node address, path sequence number, path hop count, and path cost, but do not update the destination node address, and update the path update time; otherwise, do not update.

[0028] The beneficial effects of this invention are as follows:

[0029] When the increased routing path overhead is detected, this invention can switch to a path with better communication quality in advance by predicting the communication quality, thereby improving the reliability of path selection and reducing packet loss caused by path switching delay. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the routing establishment process of the present invention;

[0031] Figure 2 This is a schematic diagram of the neighbor information table maintenance process of the present invention;

[0032] Figure 3 This is a schematic diagram of the routing update process of the present invention;

[0033] Figure 4 This is a twelve-node simulation topology diagram of the present invention;

[0034] Figure 5 This is a comparison chart of packet loss rates before and after the DSDV transmission overhead calculation optimization of this invention. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0036] Example 1

[0037] A distance-vector-based route update method, applied to mobile ad hoc networks, includes the following steps:

[0038] Step 1: Receive hello packets broadcast by neighboring nodes. These hello packets contain the neighboring nodes' routing tables and neighbor information tables. For example... Figure 1 As shown, the routing table contains several routing entries. Each entry includes the destination node address, neighbor node addresses, path sequence number, path hop count, and path cost. The neighbor information table contains the address information of the current node and its neighbors, as well as the received signal quality (SNR) measured by a neighbor node when it receives a hello packet from the current node. R .

[0039] Step 2: Based on the received signal quality (SNR) R Calculate the path cost from this node to the destination node, and combine it with the routing entries in the routing tables of neighboring nodes to form the path entry to be updated.

[0040] The calculation of path cost includes the following steps:

[0041] Step 2-1: Calculate the received signal quality (SNR) from the neighbor information table of the received neighbor nodes. R The transmitted signal quality (SNR) is used as a reference in the neighbor information table of this node. T ;

[0042] Step 2-2: Combining the SNR already recorded at this node, calculate and predict the communication quality SNR for the next cycle based on linear prediction. next The changes are analyzed, and the reliability of the prediction is obtained through covariance.

[0043] Steps 2-3: When the covariance value meets the requirements, use SNR. next The transmission overhead of neighboring nodes is calculated; when the covariance does not meet the requirements, the actual measured SNR is used. T The transmission cost of all next hops of this node to its neighboring nodes is calculated.

[0044] Steps 2-4: Set SNR T Record the information in the SNR and return to step 2-1 to wait for the neighbor information table of the new neighbor node.

[0045] The linear prediction method involves finding a straight line based on the recorded SNRs using the least squares approach, such that the sum of the squared perpendicular distances from all recorded SNRs to this line is minimized. The linear prediction model is y = ax + b, where a and b are calculated using the following formulas:

[0046] (1-1)

[0047] (1-2)

[0048] in

[0049] m - the number of SNRs that have been collected and used for fitting;

[0050] - This represents the SNR data number, ranging from [1, m];

[0051] - is the average value of the SNR data number. ;

[0052] - This refers to the specific SNR value;

[0053] - is the average value of the SNR data number. ;

[0054] A linear prediction model is obtained using this method, and the goodness of fit of the prediction model is obtained by calculating the covariance; the formula for calculating the covariance is as follows:

[0055] (1-3)

[0056] in

[0057] m - the number of SNRs that have been collected and used for fitting;

[0058] - This refers to the specific SNR value;

[0059] - is the fitted value at the corresponding discrete data i;

[0060] - is the average value of the SNR data number. ;

[0061] when Meets expectations Then, the formula is used to calculate and predict the signal-to-noise ratio for the next period (m+1).

[0062] SNR is calculated as follows:

[0063] (1-4)

[0064] in:

[0065] - This refers to the received signal power, measured in dBm.

[0066] - Received noise power, in dBm

[0067] The transmission overhead is calculated using the following formula:

[0068] (1-5)

[0069] in:

[0070] - For transmission overhead

[0071] - The actual minimum received signal-to-noise ratio

[0072] - To achieve the desired maximum received signal-to-noise ratio

[0073] - The signal-to-noise ratio currently detected or predicted.

[0074] Step 3: If the destination node information for the path entry to be updated is not present in the routing table of this node, then the path entry information to be updated is inserted into the routing table of this node; if the destination node information already exists, then an update check is performed and the path entry is updated; this includes the following steps:

[0075] Step 3-1: Combine the neighbor node addresses, path sequence numbers, and path hop counts in the neighbor node routing table to select the optimal path for updating, and then execute Step 3-2. The optimal path is defined as follows: when paths switch frequently, the path with faster update speed (larger sequence number) and equal or lower cost is the optimal path. After the path stabilizes, the optimal path is only considered to be the one with lower cost.

[0076] Step 3-2: If the address of the neighboring node leading to the destination node in the routing table of this node has not changed, then execute step 3-3; if it has changed, then execute step 3-4.

[0077] Step 3-3: If the path sequence number of the path to be updated is larger, then update the path sequence number, path hop count, and path cost, but do not update the destination node address and neighbor node addresses, and update the path update time; if the path sequence number to be updated is equal to or smaller than the path sequence number, then do not update.

[0078] Steps 3-4: If the sequence number of the path to be updated is larger and the path cost is equal to or better, then update the neighbor node address, path sequence number, path hop count, and path cost in the routing table of this node, but do not update the destination node address, and update the path update time; if the sequence numbers are the same and the path to be updated has better communication quality, then update the neighbor node address, path hop count, and path cost, but do not update the destination node address and path sequence number, and update the path update time; if the local sequence number is larger but the path to be updated has better communication quality, then update the neighbor node address, path sequence number, path hop count, and path cost, but do not update the destination node address, and update the path update time; otherwise, do not update.

[0079] Step 4: Repeat steps 2 and 3 until all entries in the routing table have been updated.

[0080] Step 5: Periodically maintain the local routing table and delete path entries that have timed out and not been updated.

[0081] like Figure 4 , Figure 5 As shown, network protocol simulation software was used to simulate the above routing methods with four nodes, eight nodes, and twelve nodes, respectively, obtaining data transmission packet loss statistics before and after optimization. The statistics show that, under the same scenario, the optimized routing transmission cost calculation method results in less packet loss and higher path reliability.

[0082] Example 2:

[0083] The path cost calculation process of this invention also includes the following steps:

[0084] Step 1: Node A and Node B each broadcast a hello packet. The hello message includes a neighbor information table and a routing information table. The neighbor information table contains the address information of the current node and its neighbors, as well as the received signal quality (SNR) measured when receiving hello packets from each neighbor node. R .

[0085] Step 2: Taking node B as a reference, when node A first receives the hello packet broadcast by node B, calculate and record the SNR of that packet. R The B value is then used to broadcast a local hello message in the next cycle.

[0086] Step 3: After node B receives the hello message broadcast by node A, it checks the SNR returned by A to node B. R Information B: Update the SNR of node B to node A in the local neighbor table. T Value A.

[0087] Step 4: Through multiple data interactions, node B can obtain multiple SNRs for node A.T The A value is used to predict its changing trend linearly, and the latest SNR is obtained based on the calculated covariance. The transmission overhead to the neighboring platform is then obtained based on the SNR.

[0088] It is understood that those skilled in the art can make equivalent substitutions or modifications to the technical solution and inventive concept of the present invention, and all such substitutions or modifications should fall within the protection scope of the appended claims.

Claims

1. A distance-vector-based routing update method, applied to mobile ad hoc networks, characterized in that... Includes the following steps: Step 1: Receive hello packets broadcast by neighboring nodes. These hello packets contain the neighboring nodes' routing tables and neighbor information tables. The routing tables contain several route entries, each including the destination node address, neighbor node address, path sequence number, path hop count, and path cost. The neighbor information tables contain the address information of the current node and its neighbors, as well as the received signal quality (SNR) measured by the neighboring node when it received the hello packet from the current node. R ; Step 2: Based on the received signal quality (SNR) R Calculate the path cost from this node to the destination node, and combine it with the routing entries in the routing tables of neighboring nodes to form the path entry to be updated; Step 3: If the destination node information for the path entry to be updated is not found in the routing table of this node, then insert the path entry information to be updated into the routing table of this node; if the destination node information already exists, then perform an update check and update the path entry. Step 4: Repeat steps 2 and 3 until all entries in the routing table have been updated; Step 5: Periodically maintain the local routing table and delete path entries that have timed out and not been updated.

2. The distance vector-based routing update method according to claim 1, characterized in that... The calculation of the path cost includes the following steps: Step 2-1: Calculate the received signal quality (SNR) from the neighbor information table of the received neighbor nodes. R The transmitted signal quality (SNR) is used as a reference in the neighbor information table of this node. T ; Step 2-2: Based on the SNR already recorded at this node, predict the communication quality SNR for the next cycle. next And obtain SNR through covariance next reliability; Steps 2-3: When the covariance value meets the requirements, use SNR. next The transmission overhead of neighboring nodes is calculated; when the covariance does not meet the requirements, the actual measured SNR is used. T The transmission cost of all next hops of this node to its neighboring nodes is calculated. Steps 2-4: Set SNR T Record the information in the SNR and return to step 2-1 to wait for the neighbor information table of the new neighbor node.

3. The distance vector-based route update method according to claim 2, characterized in that... The prediction is a linear prediction: based on the recorded SNR, the least squares method is used to find a straight line such that the sum of the squares of the vertical distances from all recorded SNRs to this line is minimized.

4. The distance vector-based route update method according to claim 1, characterized in that... Step three includes the following steps: Step 3-1: Combine the neighbor node addresses, path sequence numbers and path hop counts in the neighbor node routing table to select the optimal path for update, and then execute Step 3-2; The optimal path is: when paths switch frequently, the path with faster update speed and equal or lower cost is the optimal path. After the path stabilizes, it is considered the optimal path unless there is a path with lower cost. Step 3-2: In the routing table of this node, if the address of the neighbor node leading to the destination node in the routing entry has not changed, then proceed to step 3-3; if it has changed, then proceed to step 3-4. Step 3-3: If the path sequence number of the path to be updated is larger, then update the path sequence number, path hop count, and path cost, but do not update the destination node address and neighbor node addresses, and update the path update time; if the path sequence number to be updated is equal to or smaller than the path sequence number, then do not update. Steps 3-4: If the sequence number of the path to be updated is larger and the path cost is equal to or better, then update the neighbor node address, path sequence number, path hop count, and path cost in the routing table of this node, but do not update the destination node address, and update the path update time; if the sequence numbers are the same and the path to be updated has better communication quality, then update the neighbor node address, path hop count, and path cost, but do not update the destination node address and path sequence number, and update the path update time; if the local sequence number is larger but the path to be updated has better communication quality, then update the neighbor node address, path sequence number, path hop count, and path cost, but do not update the destination node address, and update the path update time; otherwise, do not update.

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