Wireless sensor network data transmission method based on minimum convergence delay tree

Abstract

The invention discloses a wireless sensor network data transmission method based on a minimum convergence delay tree. The method comprises the following steps: S1) randomly initializing a data aggregation tree formed by wireless sensor nodes; s2) calculating the minimum convergence time delay of each node in the aggregation tree according to the direction from bottom to top; s3) calculating the latest transmission time slot of each node in the aggregation tree according to the direction from top to bottom; s4) traversing each node in the aggregation tree from top to bottom, and judging whether the node needs to switch a father node to complete the improvement of the data aggregation tree; and S5) after the data aggregation tree is improved, calculating according to the step S2 again to obtain the minimum aggregation time delay of the final aggregation node. According to the wireless sensor network data transmission method based on the minimum convergence time delay tree, not only is the degree of each node considered when the data convergence tree is constructed, but also the influence of the descendant node of the node on the convergence time delay is considered, so that the convergence time delay of data in the WSN is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of wireless sensor networks, and specifically relates to a wireless sensor network data transmission method based on a minimum convergence delay tree. Background Technology

[0002] Wireless Sensor Networks (WSNs) have wide applications in numerous fields, such as forest fire detection and flood monitoring. Sensors can both collect data and act as relay nodes to transmit data to receiving devices. Since the sensor data collected is often correlated, aggregation techniques can reduce the transmission traffic in a WSN. Each sensor node needs to collect data from its neighboring nodes, aggregate the collected data into a single data packet, and continue transmitting it to the receiving device (the final aggregation node). All transmission links in a WSN form a data aggregation tree with the aggregation node as the root node. In multi-hop wireless communication, collisions may occur when data from two or more sensors are transmitted to a neighboring node simultaneously. Therefore, each sensor needs to follow an appropriate transmission time schedule to avoid collisions.

[0003] To rapidly transmit data to the aggregation node, researchers have proposed several forward-looking WSN data aggregation and transmission methods to reduce data transmission latency. These methods typically involve two phases: the first phase is constructing a data aggregation tree, and the second phase is establishing a transmission scheduling mechanism. The data aggregation tree specifies the next-hop node for sensor data transmission, while the transmission scheduling mechanism defines when each node can transmit data to its parent node. Even with the same transmission scheduling mechanism, the data aggregation latency can vary significantly depending on the aggregation tree, making the construction of a good data aggregation tree crucial. Currently, methods used in WSNs to construct data aggregation trees rely solely on local node information, such as the node's degree. These methods ignore the impact of multi-hop data transmission on aggregation latency and cannot prevent data transmission collisions. Therefore, existing data aggregation and transmission methods cannot effectively reduce aggregation latency. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the above shortcomings, the purpose of this invention is to provide a wireless sensor network data transmission method based on a minimum aggregation delay tree. When constructing the data aggregation tree, not only the degree of each node is considered, but also the impact of its descendant nodes on the aggregation delay is taken into account, which greatly reduces the aggregation delay of data in WSN.

[0005] Technical Solution: To achieve the above objectives, this invention provides a wireless sensor network data transmission method based on a minimum convergence delay tree, comprising: S1): Randomly initialize the data aggregation tree composed of wireless sensor nodes; random initialization is simple and easy to implement, reduces the complexity of initial tree construction, and allows starting from any tree structure, avoiding the computational overhead required for pre-optimization; S2): Calculate the minimum aggregation delay of each node in the aggregation tree from the bottom up direction; the bottom-up calculation method recursively determines the delay of each node, ensuring the accuracy and consistency of the delay calculation, and laying the foundation for overall delay optimization.

[0006] S3): Calculate the latest transmission time slot for each node in the aggregation tree in a top-down direction; the top-down time slot allocation ensures the rationality of data transmission scheduling, avoids conflicts and idle time slots, optimizes the utilization of network resources, reduces waiting time, and improves transmission efficiency. S4): Traverse each node in the aggregation tree from top to bottom and determine whether the parent node of the node needs to be switched to complete the data aggregation tree improvement; by traversing and switching the parent node, the tree structure can be dynamically adjusted to achieve local optimization, thereby avoiding the overhead of global reconstruction and reducing the aggregation latency in a targeted manner. S401): The improvement of the data aggregation tree specifically refers to: in the aggregation tree... Find a node k that satisfies the following condition: if it is not a child neighbor node. And satisfy If so, then the parent node of node v will be switched to node k; where Let k be the set of its neighboring nodes. Let k be the set of its child nodes. For the latest transmission slot of node v, For the latest transmission time slot of node k, Let k be the number of child nodes of node k; this ensures that parent node switching only occurs when latency can be reduced, improving the targeting and effectiveness of the improvement, and by utilizing the neighbor set and child node information, it achieves refined local optimization and avoids blind switching; S5): After improving the data aggregation tree, the minimum aggregation latency of the final aggregation node was calculated again according to S2. Recalculating the minimum aggregation latency verified the improvement effect and ensured the accuracy of the final result.

[0007] Furthermore, the calculation of the minimum convergence delay of a non-leaf node in the aggregation tree depends on the minimum convergence delay of its child nodes. For a certain non-leaf node v, let... This represents the sequence of child nodes arranged in ascending order of minimum convergence delay, i.e., (1) in, For children's nodes The minimum convergence delay, For children's nodes The minimum aggregation latency is determined. Child nodes are sorted in ascending order of minimum aggregation latency, and nodes with lower latency are processed first. This optimizes the transmission order, significantly reduces the waiting time of the parent node, and improves efficiency.

[0008] Furthermore, the time slot in which node v transmits data to its parent node is denoted as... Then, the transmission time slot and the minimum aggregation delay have the following relationship: (2) in, This represents the minimum aggregation delay for node v. A direct link between transmission slots and delays is established, providing a mathematical basis for scheduling transmissions.

[0009] Furthermore, the data transmission time slots of the child nodes of node v satisfy the following relationship: (3) For any two child nodes of sensor node v and Based on formulas (1) and (2), the following relationship is obtained: (4) make , represents the latest time slot among all child nodes of node v that transmits data to node v, which can be obtained according to formula (4). (5) For child nodes ,exist The corresponding inequalities (5) are defined. The constraints on the transmission time slots of child nodes are defined to ensure the rationality and conflict-free nature of the transmission order; at the same time, the calculation of the latest time slot helps to further optimize the overall latency.

[0010] Furthermore, the latest time slot among all child nodes of node v that transmits data to node v. satisfy: (6) according to Definition, This can be used to describe the minimum convergence delay of node v, therefore: (7) Take the maximum value of the expression on the right side of equation (7) as ,Right now: (8) in, Let be the minimum convergence delay of node v; For the i-th child node The minimum aggregation delay is calculated. An explicit method for calculating the minimum aggregation delay of nodes is provided, while also considering the worst-case scenario among child nodes, ensuring robustness in delay calculation.

[0011] Furthermore, for the set of child nodes arranged in ascending order of minimum convergence delay... The latest transmission time slot for the i-th child node in the array is... ;in, The latest transmission time slot of its parent node, and the latest transmission time slot of the root node is determined by... Increasing by one ensures that child nodes are transmitted in ascending order, minimizing the idle time of the parent node. By sequentially increasing time slots, transmission overlap is avoided, thus improving scheduling efficiency.

[0012] Furthermore, for the randomly initialized aggregation tree The structure is such that, since leaf nodes do not have child nodes, their minimum convergence latency is set to 0. Setting the latency of leaf nodes to 0 simplifies the computational model, provides a baseline case for recursive computation, and reduces unnecessary complexity.

[0013] As can be seen from the above technical solution, the present invention has the following beneficial effects: 1. The present invention provides a wireless sensor network data transmission method based on a minimum aggregation delay tree. By traversing each node in the aggregation tree from top to bottom and setting the above conditions to determine whether the parent node needs to be switched, the characteristics of the tree structure are not destroyed and the latest transmission time slot of node k is not delayed. 2. The present invention provides a wireless sensor network data transmission method based on a minimum aggregation delay tree. When constructing the data aggregation tree, it not only considers the degree of each node, but also takes into account the impact of its descendant nodes on the aggregation delay, which greatly reduces the aggregation delay of data in WSN. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the steps of a wireless sensor network data transmission method based on a minimum convergence delay tree as described in this invention. Figure 2 This is a schematic diagram illustrating the minimum aggregation delay of the final aggregation node under different numbers of wireless sensor nodes in the embodiment. Detailed Implementation

[0015] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. Example

[0016] In this embodiment, as Figure 1 This invention discloses a wireless sensor network data transmission method based on a minimum convergence delay tree, comprising: S1): Randomly initialize a data aggregation tree composed of wireless sensor nodes; S2): Calculate the minimum aggregation delay for each node in the aggregation tree from the bottom up direction; S3): Calculate the latest transmission time slot for each node in the aggregation tree in a top-down direction; S4): Traverse each node in the aggregation tree from top to bottom and determine whether the node needs to switch its parent node to complete the data aggregation tree improvement; For aggregation tree In the context of node k, if the non-child neighbor nodes of this node are... If satisfied If so, then the parent node of node v will be switched to node k; where Let k be the set of its neighboring nodes. Let k be the set of its child nodes. For the transmission time slot of node v, For the transmission time slot of node k, Let k be the number of child nodes of node k; if the transmission time slot of node k is... The larger the number of child nodes The smaller the value, the more likely it is to be selected as the new parent node by node v; to maximize this probability, the latest transmission time slot of the node is defined. Therefore, the improvement of the data aggregation tree described in S401 specifically refers to: in the aggregation tree Find a node k that satisfies the following condition: if it is not a child neighbor node. And satisfy If so, then the parent node of node v will be switched to node k; where Let k be the set of its neighboring nodes. Let k be the set of its child nodes. For the latest transmission slot of node v, For the latest transmission time slot of node k, Let k be the number of child nodes of node k. S5): After the data aggregation tree is improved, the minimum aggregation delay of the final aggregation node is calculated again according to S2.

[0017] Specifically, according to the definition of minimum aggregation latency, data aggregation transmission based on an aggregation tree structure has the following four characteristics: (1) For each sensor node v, at least the time spent After a node completes data aggregation from its subtree, it must wait a specific additional time before transmitting data to its parent node. This is because half-duplex communication and single-channel operation mean that a node can only communicate with one node at a time. The time a node spends before transmitting data to its parent node is called the waiting time. (2) Each node in the aggregation tree will spend a portion of its waiting time receiving data transmitted by its child nodes, and remain idle for the remaining time; (3) If a node receives data transmitted by a new child node while it is in an idle state, the node’s waiting time remains unchanged; (4) If a node changes its parent node, the waiting time of the original parent node may be reduced due to the absence of a child node, which can reduce the minimum convergence delay of the final convergence node (i.e., the root node).

[0018] In this embodiment, in order to further reduce the minimum convergence delay at the root node, it is necessary to modify the aggregation tree. The structure is improved. Assuming a plexiform tree... Node v in the aggregation tree can switch parent nodes. First, the communication link between node v and its current parent node is disconnected. Then, a non-child node k is selected from its neighbors as the new parent node. The original parent node of node v can reduce its minimum aggregation delay by eliminating a child node. If node k does not delay its transmission slots due to the inclusion of the new child node v, the minimum aggregation delay of the root node may decrease. The calculation of the minimum aggregation delay of non-leaf nodes in the aggregation tree depends on the minimum aggregation delay of their child nodes. For a given non-leaf node v, let... This represents the sequence of child nodes arranged in ascending order of minimum convergence delay, i.e., (1) in, For children's nodes The minimum convergence delay, For children's nodes The minimum convergence delay.

[0019] In this embodiment, the time slot in which node v transmits data to its parent node is denoted as . Then, the transmission time slot and the minimum aggregation delay have the following relationship: (2) in, Let be the minimum aggregation delay of node v.

[0020] In this embodiment, since each node uses a half-duplex communication mode, and nodes can only transmit data through one wireless channel, each parent node can only be in a data sending or receiving state at any given time. When in the data receiving state, it can only receive data transmitted by one child node within a time slot; otherwise, a data transmission collision will occur. Therefore, the data transmission time slots of the child nodes of node v satisfy the following relationship: (3) For any two child nodes of sensor node v and Based on formulas (1) and (2), the following relationship is obtained: (4) make , represents the latest time slot among all child nodes of node v that transmits data to node v, which can be obtained according to formula (4). (5) For child nodes ,exist There are corresponding inequalities (5).

[0021] In this embodiment, the latest time slot in which node v transmits data to node v among all its child nodes is specified. satisfy: (6) according to Definition, This can be used to describe the minimum convergence delay of node v, therefore: (7) Take the maximum value of the expression on the right side of equation (7) as ,Right now: (8) in, Let be the minimum convergence delay of node v; For the i-th child node The minimum convergence delay.

[0022] Specifically, if the minimum aggregation delay of node v is known, the child node transmission time slot allocation can be considered as follows: (9) The above transmission time slot allocation ensures that each child node of node v sends data in a different transmission time slot, satisfying inequality (3); substituting equation (9) into inequality (7) yields... , satisfying inequality (2).

[0023] In this embodiment, for the set of child nodes arranged in ascending order of minimum convergence delay... The latest transmission time slot for the i-th child node in the array is... ;in, The latest transmission slot of its parent node; since the final sink node has no parent node (root node), its latest transmission slot is determined by... Add one to get.

[0024] In this embodiment, for the randomly initialized aggregation tree The structure sets its minimum aggregation delay to 0 because leaf nodes do not have child nodes.

[0025] This invention refers to the parent node switching operation method described above as Break and Reconstitution (B&R), and uses B&R to achieve wireless sensor network data collection based on a minimum aggregation delay tree. Link-delay-aware tree (LDAT) and shortest path tree (SPT) are two common methods used for data aggregation and transmission in WSNs. This invention improves the initial aggregation tree based on these two initial aggregation tree structures using the B&R method, as shown in the following figure. Figure 2 As shown, the aggregation trees after B&R all reduce the minimum convergence delay of their root nodes. Furthermore, for SPT-initial aggregation trees, the B&R method demonstrates better performance when the number of sensor nodes is large.

[0026] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for data transmission in a wireless sensor network based on a minimum convergence latency tree, characterized in that: Comprising: S1): randomly initializing a data aggregation tree composed of wireless sensor nodes; S2): calculating the minimum convergence time delay of each node in the aggregation tree according to the bottom-up direction; S3): calculating the latest transmission time slot of each node in the aggregation tree according to the top-down direction; S4): traversing each node in the aggregation tree according to the top-down direction, and judging whether the node needs to switch the parent node, completing the improvement of the data aggregation tree; S401): the data aggregation tree is improved in particular as follows: in the aggregation tree find a node satisfying the following conditions , if its non-child neighbor node , and satisfies , the parent node of node is switched to node ; wherein is the neighbor node set of node , is the child node set of node , is the latest transmission time slot of node , is the latest transmission time slot of node , is the number of child nodes of node ; S5): after the data aggregation tree is improved, the minimum convergence time delay of the final convergence node is calculated again according to S2.

2. The method of claim 1, wherein the method further comprises: The calculation of the minimum convergence latency of a non-leaf node in the aggregation tree depends on the minimum convergence latency of its child nodes, for a certain non-leaf node Let denote the sequence of child nodes in ascending order of minimum convergence latency, i.e., (1) wherein, the minimum convergence latency of the child node, the minimum convergence latency of the child node, the minimum convergence latency of the child node, the minimum convergence latency of the child node.

3. The method of claim 2, wherein: The node The time slot in which the node transmits data to its parent node is denoted as The transmission time slot and the minimum convergence delay exist the following relationship: (2) wherein, is the minimum convergence latency for the node .

4. The method of claim 3, wherein the minimum-convergence-latency tree-based wireless sensor network data transmission method is characterized by: The node The data transmission time slots of the child nodes satisfy the following relationship: (3) For any two child nodes of a sensor node and the following relation is obtained according to equations (1) and (2): (4) Let denote the latest time slot in which a child node of node transmits data to node , which can be obtained according to equation (4) (5) For the child nodes , there are corresponding inequalities (5).

5. The method of claim 4, wherein: The node The latest time slot in which a child node of the node Transmits data to the node Satisfies: (6) According to the definition, the minimum convergence latency of a node may be used to describe the node, thus there is: (7) The maximum value of the right-hand side expression in equation (7) is taken as i.e.: (8) wherein, is the minimum convergence latency for the node ; is the minimum convergence latency for the i-th child node .

6. The method of claim 5, wherein: For the set of child nodes sorted in ascending order of minimum convergence delay The first in Each child node has a latest transmission time slot of 1. ;in, The latest transmission time slot of its parent node, and the latest transmission time slot of the root node is determined by... Add one to get.

7. The method of claim 1, wherein: For the aggregate tree initialized randomly The structure, since the leaf node does not have a child node, sets its minimum convergence latency to 0.

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