An energy-saving data transmission method for wireless sensor networks in smart cities

Abstract

The present invention discloses an energy-saving data transmission method for a wireless sensor network for smart cities. The method comprises the following steps: based on the high density of base stations in 5G networks, the base station divides the wireless sensor network into multiple candidate clusters based on the distance between nodes and adjusts the nodes in each cluster; during network operation, based on the clustering results, the base station predicts the remaining energy of the clusters and maintains the remaining energy of the clusters; during data transmission, the base station calculates the optimal inter-cluster routing based on the remaining energy of the clusters it maintains; and based on the difference in remaining energy between clusters, the base station adjusts the clusters to which relevant nodes in the network belong to balance the energy between clusters. This method can extend the service life of the wireless sensor network and balance the energy consumption of the cluster head and other sensor nodes in the clustering protocol.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless sensor networks, and in particular relates to an energy-saving data transmission method for wireless sensor networks oriented to smart cities. Background Art

[0002] The Internet of Things (IoT) is an extension of the Internet. Because it eliminates human interaction and enables autonomous data exchange between objects, it has been widely used in various fields within smart cities, including smart healthcare, smart buildings, and smart security. The IoT now assumes the responsibility of sensing the entire city's state. Wireless sensor networks, as a crucial component of the IoT's perception layer, have been widely adopted in numerous fields. According to relevant organizations, the amount of data generated by various information sensors in cities will increase from 13.6 ZB in 2019 to 79.4 ZB by 2025. This indicates that the amount of data in the IoT is enormous and continues to grow rapidly. Transmitting this massive amount of data inevitably consumes significant energy. To effectively reduce energy consumption, research into low-energy data transmission technologies for wireless sensor networks, the perception layer of the IoT, is essential.

[0003] Researchers have proposed various energy-saving methods for wireless sensor network data transmission, such as low-energy MAC protocols, optimal routing protocols, and data compression techniques. Among them, clustering protocols are the most effective and popular energy-saving method in wireless sensor networks, and their representative protocol is LEACH.

[0004] In the LEACH protocol, each cluster node sends monitoring data to the cluster head. After the cluster head receives data from all nodes in the cluster, it transmits it to the base station via a single or multi-hop approach. Compared to other nodes, the cluster head undertakes more work and is therefore more likely to die prematurely.

[0005] To address the imbalance in energy consumption between cluster heads and other nodes, the LEACH protocol stipulates that clustering must be re-clustered and new cluster heads elected every time period, but this method consumes a lot of energy. To this end, researchers have proposed many improvements to the LEACH protocol, such as PEGASIS, GAFOR, and LCP. These optimized protocols all re-cluster the entire network every few time periods. However, none of these protocols take into account the extremely large number of wireless sensor network nodes and the vast geographical area covered in smart city perception applications. Periodic global re-clustering in such large-scale networks would result in enormous energy overhead.

[0006] With the widespread adoption of 5G networks, the number of 5G base station deployments is rapidly increasing. The density is significantly higher than that of 4G base stations, currently exceeding 1.5 million. In urban centers, the average distance between base stations is approximately 300 meters, while in suburban areas, the average distance is around 1,000 meters. With the advancement of wireless communication technology, the transmission distance of sensor nodes can now reach 2,000 meters. Therefore, in a 5G application environment, nodes in a wireless sensor network can communicate directly with one or more nearby base stations.

[0007] Based on the above situation, this application makes full use of the high density of base stations in 5G application scenarios and proposes an energy-saving data transmission method for wireless sensor networks for smart cities. Summary of the Invention

[0008] In order to overcome the above technical defects, the present invention provides an energy-saving data transmission method for wireless sensor networks for smart cities, which extends the service life of wireless sensor networks and balances the energy consumption of cluster heads and other sensor nodes in clustering protocols.

[0009] In order to solve the above problems, the present invention is implemented according to the following technical solutions:

[0010] A wireless sensor network energy-saving data transmission method for smart cities includes the following steps:

[0011] The base station divides the wireless sensor network into multiple candidate clusters according to the distance between nodes and adjusts the nodes in each cluster;

[0012] Based on the clustering results, the base station predicts the remaining energy of the cluster and maintains the remaining energy of the cluster;

[0013] The base station calculates the best inter-cluster routing based on the residual energy of the maintained clusters and broadcasts the best inter-cluster routing to the network;

[0014] The base station adjusts the clusters to which the relevant nodes in the network belong based on the difference in residual energy between clusters to balance the energy between clusters.

[0015] Furthermore, the step of dividing the wireless sensor network into a plurality of candidate clusters according to the distance between nodes and adjusting the nodes of each cluster includes the following steps:

[0016] The city is divided into several areas, each area includes a secondary base station and several primary base stations, where the secondary base station is a pre-designated base station BS pre ;

[0017] Each node in the network broadcasts a HELLO message, which includes node coordinates and node ID information;

[0018] Each primary base station creates a tuple based on the received HELLO message. The tuple includes the ID of the node to which the message belongs, the coordinates of the node to which the message belongs, and the ID of the base station itself.

[0019] The primary base station in each area sends the tuple information to the pre-assigned base station BS in the corresponding area. pre , base station BS pre According to the tuple information, the wireless sensor networks in the area are divided into multiple candidate clusters;

[0020] The primary base station counts the number of nodes in the current candidate cluster. If the current number of nodes is lower than the threshold, all nodes in the candidate cluster are assigned to adjacent clusters and the current candidate cluster is disbanded. The adjacent clusters and these nodes can all communicate directly with the same base station.

[0021] Base Station BS pre The cluster adjustment result is broadcast to all primary base stations in the area, and the primary base station broadcasts the cluster adjustment result to all nodes around it.

[0022] Furthermore, the primary base station in each area sends the tuple information to the pre-assigned base station BS in the corresponding area. pre , the base station divides the wireless sensor network in the area into multiple candidate clusters according to the tuple information, including the following steps:

[0023] Base Station BS pre Obtaining from the tuple information and constructing a rectangular monitoring area based on the longitude information and latitude information, wherein the longitude information includes the maximum longitude coordinate and the minimum longitude coordinate, and the latitude information includes the maximum latitude coordinate and the minimum latitude coordinate, and the rectangular monitoring area covers all nodes;

[0024] Base Station BS pre Divide the rectangular monitoring area into several rectangular sub-monitoring areas of the same size;

[0025] Base Station BS pre Based on the coordinate data in the tuple information, each node is assigned to each rectangular sub-monitoring area. The nodes in the same rectangular sub-monitoring area form a candidate cluster, wherein the nodes in the same candidate cluster can directly communicate with the same base station.

[0026] Furthermore, the base station divides the wireless sensor network into multiple candidate clusters according to the distance between nodes and adjusts the nodes of each cluster, further comprising the following steps:

[0027] Check whether all nodes in the current candidate cluster can communicate directly with the same primary base station;

[0028] If not, the node with the largest number of nodes that can directly communicate with the same primary base station is retained, and the other nodes are assigned to adjacent clusters, where both the adjacent clusters and the node can directly communicate with the same primary base station.

[0029] Furthermore, based on the clustering result, the base station predicts the remaining energy of the cluster and maintains the remaining energy of the cluster, including the following steps:

[0030] The cluster head records the actual remaining energy E of the cluster at the end of the first five cycles. ac (j);

[0031] The cluster head uses the least square method to calculate the average energy consumption k of the cluster per cycle, and compares the energy consumption k with the actual remaining energy E at the end of the current cycle. ac (j) sending to a base station;

[0032] Based on the received data, the base station predicts the remaining energy of each cluster in each future cycle. The prediction formula is: E pre (i) = E ac (j)+k·(ij);

[0033] The cluster head records the actual remaining energy E of the cluster in each cycle ac (j) and the predicted remaining energy E pre (i) If the deviation σ1 is greater than the preset deviation threshold δ, the cluster head recalculates the average energy consumption k of the cluster per cycle and compares the newly calculated energy consumption k with the actual remaining energy E at the end of the current cycle. ac (j) Send to the base station.

[0034] Furthermore, the step of calculating the optimal inter-cluster routing of the clusters according to the residual energy of the maintained clusters and broadcasting the optimal inter-cluster routing to the network includes the following steps:

[0035] A set Q is constructed based on all candidate clusters. When a cluster transmits data to the base station, the relationship between the remaining energy of the cluster and a preset energy threshold is determined, where the preset energy threshold is 0.9*the average energy of the cluster.

[0036] When the remaining energy of a cluster is less than the preset energy threshold, the cluster is added to the set L;

[0037] The cluster head of the cluster in set L transmits data to a nearby cluster and adds the cluster to set H, where the remaining energy of the target cluster is greater than the preset energy threshold;

[0038] The clusters of set H send data to the base station, and the base station selects the best inter-cluster route based on data transmission efficiency.

[0039] Furthermore, the cluster of step set H sends data to the base station, and the base station selects the best inter-cluster route based on data transmission efficiency, including the following steps:

[0040] Based on the node distance between the node sending data and the node receiving data, the size of the monitoring data and the remaining energy information of each cluster, it is predicted that when cluster i and cluster j in the set H directly send sensor data to the base station, the base station records the first square deviation of the cluster remaining energy after cluster i and cluster j complete the data transmission, and the first transmission energy consumption during the data transmission between cluster i and cluster j;

[0041] Based on the node distance between the node sending data and the node receiving data, the size of the monitoring data and the remaining energy information of each cluster, it is predicted that when cluster i in the set H sends sensor data to cluster j, and cluster j sends its own cluster data and cluster i's data to the base station, the base station records the second square deviation of the cluster remaining energy after cluster i and cluster j complete the data transmission, and the second transmission energy consumption during the data transmission between cluster i and cluster j;

[0042] The base station calculates the first data transmission efficiency based on the first square deviation of the cluster residual energy and the first transmission energy consumption, and calculates the second data transmission efficiency based on the second square deviation of the cluster residual energy and the second transmission energy consumption. The route with the highest data transmission efficiency is selected as the optimal inter-cluster route. The calculation formula for the data transmission efficiency DTE is:

[0043]

[0044] Among them, S 2 (i, j) represents the square deviation of the remaining energy of clusters after cluster i and cluster j complete data transmission, and Cost(i, j) represents the transmission energy consumption during the data transmission between cluster i and cluster j.

[0045] Furthermore, the cluster of step set H sends data to the base station, and the base station selects the best inter-cluster route based on data transmission efficiency, further comprising the following steps:

[0046] The base station calculates the best inter-cluster routes for all cluster heads in set Q and broadcasts the best inter-cluster routes of each cluster to the network;

[0047] The cluster head of each cluster transmits data to the base station according to the optimal inter-cluster routing.

[0048] Furthermore, the base station balances the energy between clusters according to the difference in residual energy between clusters, including the following steps:

[0049] The base station calculates the average residual energy of the cluster set and the average residual energy of the clusters in the network, wherein the clusters located in the same row or the same column constitute a cluster set;

[0050] The base station compares the residual energy of each cluster with the average residual energy of the clusters to balance the energy among the clusters.

[0051] The base station compares the residual energy of each cluster in the cluster set with the average residual energy of the clusters to balance the energy among the clusters;

[0052] The base station broadcasts the inter-cluster energy balancing results to the network, and each node in the network determines whether to change its cluster based on the received message.

[0053] Furthermore, the base station divides the wireless sensor network into multiple candidate clusters according to the distance between nodes and adjusts the nodes of each cluster, further comprising the following steps:

[0054] At the end of each round, the residual energy of the current cluster head is compared with the preset residual energy threshold;

[0055] If the residual energy of the current cluster head is higher than the residual energy threshold, the current cluster head continues to serve as the cluster head for the next cycle; otherwise, the node with the highest residual energy in the current cluster is used as the cluster head for the next cycle.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The present invention discloses an energy-saving data transmission method for wireless sensor networks in smart cities. The method divides the wireless sensor network into multiple candidate clusters based on inter-node distances and adjusts the nodes in each cluster to ensure that each cluster has a certain number of nodes and that all nodes in each cluster can communicate with the same base station. The method also calculates the optimal inter-cluster routing based on the cluster's residual energy, maintaining energy balance during inter-cluster transmission and reducing transmission energy consumption. The method also balances inter-cluster energy, balancing energy consumption between nodes and extending the lifetime of each node. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0059] Figure 1 A flowchart of the energy-saving data transmission method for wireless sensor networks in smart cities described in Example 1;

[0060] Figure 2 FIG2 is a flow chart of the energy-saving data transmission method for a wireless sensor network for a smart city as described in Example 1;

[0061] Figure 3 This is a schematic diagram of step S2 of the energy-saving data transmission method for wireless sensor networks for smart cities described in Example 1;

[0062] Figure 4 This is a schematic diagram of step S4 of the energy-saving data transmission method for wireless sensor networks for smart cities described in Example 1. DETAILED DESCRIPTION

[0063] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0064] Example 1

[0065] Taking advantage of the high density of 5G base stations, such as Figure 1 and 2 This embodiment discloses an energy-saving data transmission method for a wireless sensor network for a smart city, comprising the following steps:

[0066] like Figure 3 ,S1, Based on the high density of 5G network, the base station divides the wireless sensor network into multiple candidate clusters according to the distance between nodes and adjusts the nodes of each cluster.

[0067] Specifically, step S1 includes the following steps:

[0068] S11. Divide the city into several areas, each area includes a secondary base station and several primary base stations, where the secondary base station is a pre-designated base station BS pre By dividing the city into several areas, a preset base station BS is set up in each area. pre , to avoid having only one preset base station BS in the city pre Leading to the preset base station BS pre Too many messages received.

[0069] S12. Each node in the network broadcasts a HELLO message. The HELLO message includes node coordinates and node ID information. All base stations in the network receive the HELLO message.

[0070] S13. Each primary base station creates a tuple according to the received HELLO message. The tuple includes the ID of the node to which the message belongs, the coordinates of the node to which the message belongs, and the ID of the base station.

[0071] S14. The primary base station in each area sends the tuple information to the pre-designated base station BS in the corresponding area. pre , base station BS pre The wireless sensor networks in the area are divided into multiple candidate clusters according to the tuple information.

[0072] In the above embodiment, step S14 includes the following steps:

[0073] Base Station BS pre Obtain longitude and latitude information from the coordinates of the node to which the message belongs, wherein the longitude information includes the maximum longitude coordinate and the minimum longitude coordinate, and the latitude information includes the maximum latitude coordinate and the minimum latitude coordinate; base station BS preA rectangular monitoring area (M×N) covering all nodes is constructed based on the longitude and latitude information.

[0074] Assume that m×n clusters are formed and each cluster has the same size, then the base station BS pre The rectangular monitoring area is divided into (M / m)×(N / n) rectangular sub-monitoring areas.

[0075] Base Station BS pre Based on the coordinates of the node to which the message belongs, each node is assigned to an appropriate rectangular sub-monitoring area. Nodes in the same rectangular sub-monitoring area form a candidate cluster, where all nodes in the same candidate cluster can directly communicate with the same base station. After clustering, each candidate cluster is associated with a primary base station, meaning each candidate cluster communicates directly with a primary base station, and each primary base station is associated with several candidate clusters.

[0076] S15. The first-level base station counts the number of nodes n in the current candidate cluster. c , if the current number of nodes n c Below the quantity threshold n t , all nodes in the candidate cluster are assigned to the adjacent cluster and the current candidate cluster is dissolved, wherein the adjacent cluster and these nodes can directly communicate with the same primary base station.

[0077] In the above embodiment, step S1 further includes the following steps:

[0078] Check whether all nodes in the current candidate cluster can communicate directly with the same primary base station.

[0079] If not, the node with the largest number of nodes that can directly communicate with the same primary base station is retained, and the other nodes are assigned to adjacent clusters, where both the adjacent clusters and the node can directly communicate with the same primary base station.

[0080] S16. After all clusters in the network have been adjusted, the base station BS pre The cluster adjustment results are broadcast to all primary base stations in the area. Each primary base station then broadcasts the cluster adjustment results to all nodes in its immediate vicinity and direct communication with it. When each node receives the information, it obtains information about the cluster to which it belongs. All nodes in the area receive the cluster adjustment results.

[0081] In the above embodiment, since the energy consumption rate of the cluster head is much faster than that of other cluster members, each node in the cluster must act as the cluster head for a period of time to balance the energy of each node in the network.

[0082] At the end of each cycle, the current cluster head compares its residual energy with the preset residual energy threshold. If the residual energy of the current cluster head is higher than the residual energy threshold, the current cluster head continues to serve as the cluster head for the next cycle; otherwise, the node with the highest residual energy in the current cluster is used as the cluster head for the next cycle.

[0083] The base station divides the network into multiple candidate clusters based on the distance between nodes and adjusts the members of each cluster to ensure that each cluster has a certain number of nodes and all nodes in each cluster communicate directly with the same base station, avoiding excessive energy consumption in the distributed node clustering process.

[0084] Secondary base station BS pre It is only used to implement the division of the ultra-large-scale wireless sensor network in the city into multiple candidate clusters in step S1, so the first-level base station is referred to as the base station in the following.

[0085] The following steps S2, S3, and S4 are all performed based on the clustering result and cluster adjustment result of step S1.

[0086] S2. During network operation, based on the clustering result and cluster adjustment result of step S1, the base station predicts the remaining energy of the cluster and maintains the remaining energy of the cluster.

[0087] Specifically, step S2 includes the following steps:

[0088] The cluster head records the actual remaining energy E of the cluster at the end of the first five cycles. ac (j).

[0089] The cluster head uses the least square method to calculate the average energy consumption k of the cluster per cycle, and compares the energy consumption k with the actual remaining energy E at the end of the current cycle. ac (j) is sent to the base station, and the energy consumption k is calculated as follows:

[0090]

[0091] Where x(i) represents the number of the last five cycles, and y(i) represents the actual remaining energy of the cluster at the end of the x(i)th cycle. is the mean value of x(i) in five cycles, is the mean of y(i) in five cycles.

[0092] Based on the received data, the base station predicts the remaining energy of each cluster in each future cycle. The prediction formula is:

[0093] E pre (i) = E ac (j)+k·(ij)

[0094] The cluster head records the actual remaining energy E of the cluster in each cycle ac(j) and the predicted remaining energy E pre (i) If the deviation σ1 is greater than the preset deviation threshold δ, the cluster head recalculates the average energy consumption k of the cluster per cycle and compares the newly calculated energy consumption k with the actual remaining energy E at the end of the current cycle. ac (j) Send to the base station.

[0095] The cluster head calculates and records the predicted remaining energy E at the end of the i-th cycle pre (i) Assume that the actual residual energy of a cluster at the end of the jth cycle is E ac (j), and using the energy consumption data of the last five cycles to obtain the average energy consumption of each cycle as k, we can predict the remaining energy E of the cluster at the end of each subsequent time cycle. pre (i).

[0096] During network operation, when the base station receives E ac (j) and k, the base station predicts the remaining energy of each cluster in each future cycle. pre (i) and the actual remaining energy E ac (j) There may be errors. In order to avoid such errors being too large, when the cluster head finds the actual remaining energy E of the cluster in the uth round of time period, ac (j) and the predicted remaining energy E pre When the deviation σ1 of (i) exceeds the specified threshold δ, the cluster head will ac The updated values ​​of (q) and k are sent to the base station, and thereafter, the base station will continue to predict the remaining energy of the cluster according to the new parameters sent by the cluster head.

[0097] S3. During data transmission, the base station calculates the optimal inter-cluster routing based on the residual energy of the maintained clusters.

[0098] Specifically, step S3 includes the following steps:

[0099] S31 . Construct a set Q based on all candidate clusters. When a cluster transmits data to a base station, determine the relationship between the remaining energy of the cluster and a preset energy threshold. The preset energy threshold is 0.9*average energy of the cluster.

[0100] S32: When the remaining energy of the cluster is less than a preset energy threshold, the cluster is added to the set L.

[0101] S33 , the cluster head of the cluster in set L transmits the sensor data to a nearby cluster and adds the cluster to set H, wherein the residual energy of the target cluster is greater than a preset energy threshold.

[0102] S34. The clusters in set H send data to the base station, and the base station selects the best inter-cluster route based on data transmission efficiency.

[0103] In the above embodiment, step S34 includes the following steps:

[0104] According to the energy consumption calculation formula and the node distance between the node sending data and the node receiving data, the size of the monitoring data and the residual energy information of each cluster, it is predicted that when the cluster head of cluster i and the cluster head of cluster j in the set H directly send the sensor data to the base station, the base station records the first square deviation S of the cluster residual energy after cluster i and cluster j complete the data transmission 2 (i, j)1, and the first transmission energy consumption Cost(i, j)1 during the data transmission between cluster i and cluster j.

[0105] According to the energy consumption calculation formula and the node distance between the node sending data and the node receiving data, the size of the monitoring data and the residual energy information of each cluster, the cluster head of cluster i in the prediction set H sends the sensor data to the cluster head of cluster j. When the cluster head of cluster j sends the cluster data and cluster i data to the base station, the base station records the second square deviation S of the cluster residual energy after cluster i and cluster j complete the data transmission. 2 (i, j)2, and the second transmission energy consumption Cost(i, j)2 during the data transmission between cluster i and cluster j.

[0106] When d is the distance between the node sending data and the node receiving data, if the length of the data packet sent is l bits, the energy consumed by the node sending data is recorded as E t (l,d), the energy consumed by the node to receive data is E r (l), the energy consumption calculation formula is:

[0107]

[0108] E R (l) = lE elec

[0109] Among them, E elec represents the energy consumption of the sending and receiving circuits, ∈ fs With ε mp are the power consumption of free space propagation and multipath fading model propagation, is the threshold of the two propagation modes of the node.

[0110] The base station calculates the first square deviation S of the cluster residual energy 2 (i, j)1 and the first transmission energy consumption Cost(i, j)1 calculate the first data transmission efficiency DTE(1), according to the second square deviation S of the cluster residual energy 2(i, j)2 and the second transmission energy consumption Cost(i, j)2 are used to calculate the second data transmission efficiency DTE(2). The route with the highest data transmission efficiency (DTE) is selected as the optimal inter-cluster route, so that the clusters maintain energy balance during inter-cluster transmission and consume less transmission energy. The calculation formula for data transmission efficiency DTE is:

[0111]

[0112] Among them, S 2 (i, j) refers to the square deviation of the remaining energy of clusters after clusters i and j complete data transmission, and Cost(i, j) represents the transmission energy consumption during the data transmission process between clusters i and j.

[0113] The base station calculates the best inter-cluster routes for all cluster heads in set Q and broadcasts the best inter-cluster routes of each cluster to the network.

[0114] The cluster head of each cluster transmits data to the base station according to the optimal inter-cluster routing.

[0115] When clusters transmit data to the base station, they are added to set L based on the relationship between their actual remaining energy and a preset energy threshold. To reduce the energy consumption of data transmission by clusters in set L, each cluster in set L transmits its sensor data to a nearby cluster with higher actual remaining energy. This cluster is then added to set H, and clusters in set H use aggregation methods for inter-cluster communication. This balances the actual remaining energy of each cluster and reduces the energy consumption of data transmission.

[0116] When a user needs to query monitoring results, the user will first construct a query message, which contains area information and node ID information; this message will be transmitted to all base stations near the monitoring area. Each base station calculates the optimal inter-cluster routing for each cluster based on the cluster where the query target node is located and the maintained residual energy of each cluster, and broadcasts the query target node and the optimal inter-cluster routing information to the network. The nodes of each cluster collect and transmit data based on the received information.

[0117] S4. The base station balances the energy between clusters according to the difference in residual energy between clusters.

[0118] Specifically, since the network is divided into m×n clusters, C[i](i∈{1,…,m}) is used to represent each cluster set in the grid, where clusters located in the same row or column constitute a cluster set; C[i][j](i∈{1,…,m},j∈{1,…,n}) is used to represent each cluster in the grid. Step S4 includes the following steps:

[0119] The base station calculates the average residual energy E of the cluster set C[i](i∈{1,…,m}) in the network avg1 and the average residual energy E of the clusteravg2 , where clusters in the same row or column constitute a cluster set.

[0120] The base station calculates the residual energy E of each cluster set C[i](i∈{1,…,m}) c[i] The average residual energy E of the cluster set avg1 For comparison, when E c[i] <E avg1 When the energy of cluster set C[i] is less than the average residual energy E of the cluster, avg2 The average remaining energy E of the clusters that have not yet been adjusted to the cluster from another set C[k] avg2 Get some energy (represented by nodes) from the adjacent clusters, so that the remaining energy of the cluster set E c[i] Close to the average residual energy E of the cluster set avg1 . When E c[i] >E avg1 When the energy of cluster C[i] is higher than the average residual energy E of the cluster, avg2 The cluster distributes some energy (represented by available nodes) to the adjacent clusters in another set C[k], so that the remaining energy E of the cluster set c[i] Close to the average residual energy E of the cluster set avg1 , balances the energy of each cluster set in the grid.

[0121] The base station calculates the residual energy E of each cluster C[i][j] in the cluster set C[i] c[i][j] The average residual energy E of the cluster avg2 For comparison, when E c[i][j] >E avg2 When E c[i][j] <E avg2 When , cluster C[i][j] obtains some energy (which can be represented by nodes) from the adjacent and unadjusted clusters in the cluster set to balance the energy of each cluster among the cluster sets.

[0122] The base station broadcasts the inter-cluster energy balancing results to the network, and each node in the network determines whether to change its cluster based on the received message.

[0123] The following describes step S4 in conjunction with the specific implementation process:

[0124] Assume that after a wireless sensor network has been running for a period of time, the remaining energy of each cluster is as follows: Figure 4 (a) The average energy E of each set C[i] avg1 is 15J, and the average energy of each cluster in the network is 5J. In the process of energy balance between sets C[i], the energy of set C[1] is 13J, which is lower than Eavg1 Therefore, clusters 1.1 and 1.2 in set C[1] obtain 9 and 1 nodes (to simplify the analysis, assume that a node has 0.2J of energy) from clusters in another set C[2]. After the energy balance of set C[1] is completed, set C[2] is adjusted, and the adjustment process is similar to that of set C[1]. The specific process is as follows: Figure 4 (b) As shown. After all sets (including C[1], C[2] and C[3]) complete the energy balancing process, each cluster in set C[i] initiates energy balancing. For the inter-cluster energy balance in set C[1], the energy of cluster C[1][1] (denoted as cluster 1.1) is the same as the average energy of all clusters in the network. Cluster C[1][1] does not need to be adjusted. Then cluster C[1][2], because the remaining energy is lower than E avg2 , obtain 1 node from cluster C[1][3]. After the inter-cluster balancing process is completed, a similar process is performed in clusters C[2] and C[3]. The specific process is as follows Figure 4 (c) is shown. The inter-cluster energy balance results are shown in Figure 4 As shown in (d), it can be seen that the overall energy balance of each cluster in the network has been achieved.

[0125] The present invention divides a wireless sensor network into multiple candidate clusters based on inter-node distances and adjusts the nodes in each cluster to ensure that each cluster has a certain number of nodes and that all nodes in each cluster can communicate with the same base station. The optimal inter-cluster routing is calculated based on the cluster's residual energy, reducing transmission energy consumption and maintaining energy balance during inter-cluster transmission. Inter-cluster energy is balanced, balancing the energy consumption of the cluster head and other sensor nodes in the clustering protocol, resolving the problem of uneven total energy among cluster nodes, extending the lifetime of each node, and ultimately, the service life of the wireless sensor network.

[0126] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Therefore, any modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A wireless sensor network energy-saving data transmission method for smart cities, characterized in that: The steps include: The base station divides the wireless sensor network into multiple candidate clusters according to the distance between nodes and adjusts the nodes in each cluster; Based on the clustering results, the base station predicts the remaining energy of the cluster and maintains the remaining energy of the cluster; The base station calculates the optimal inter-cluster routing based on the residual energy of the maintained clusters and broadcasts the optimal inter-cluster routing to the network, including the following steps: A set Q is constructed based on all candidate clusters. When a cluster transmits data to the base station, the relationship between the remaining energy of the cluster and a preset energy threshold is determined, where the preset energy threshold is 0.9*the average energy of the cluster. When the remaining energy of a cluster is less than the preset energy threshold, the cluster is added to the set L; The cluster head of the cluster in set L transmits data to a nearby cluster and adds the cluster to set H, where the remaining energy of the target cluster is greater than the preset energy threshold; The clusters in set H send data to the base station. The base station selects the best inter-cluster route based on data transmission efficiency, including the following steps: Based on the node distance between the node sending data and the node receiving data, the size of the monitoring data and the residual energy information of each cluster, it is predicted that when cluster i and cluster j in the set H directly send sensor data to the base station, the base station records the first square deviation of the cluster residual energy after cluster i and cluster j complete the data transmission and the first transmission energy consumption during the data transmission between cluster i and cluster j; Based on the node distance between the node sending data and the node receiving data, the size of the monitoring data and the residual energy information of each cluster, it is predicted that when cluster i in the set H sends sensor data to cluster j and cluster j sends its own cluster data and cluster i's data to the base station, the base station records the second square deviation of the cluster residual energy after cluster i and cluster j complete the data transmission and the second transmission energy consumption during the data transmission between cluster i and cluster j; The base station calculates the first data transmission efficiency based on the first square deviation of the cluster residual energy and the first transmission energy consumption, and calculates the second data transmission efficiency based on the second square deviation of the cluster residual energy and the second transmission energy consumption. The route with the highest data transmission efficiency is selected as the optimal inter-cluster route. The calculation formula for the data transmission efficiency DTE is: Among them, S 2 (i, j) represents the square deviation of the remaining energy of clusters after cluster i and cluster j complete the data transmission, and Cost(i, j) represents the transmission energy consumption during the data transmission between cluster i and cluster j; The base station adjusts the clusters to which the relevant nodes in the network belong based on the difference in residual energy between clusters. The inter-cluster energy balancing includes the following steps: The base station calculates the average residual energy of the cluster set and the average residual energy of the clusters in the network, wherein the clusters located in the same row or the same column constitute a cluster set; The base station compares the residual energy of each cluster set with the average residual energy of the cluster set to balance the energy between the cluster sets: the base station compares the residual energy of each cluster set with the average residual energy of the cluster set. When the residual energy of the cluster set is less than the average residual energy of the cluster set, the cluster with energy less than the average residual energy of the cluster in the cluster set obtains a certain number of nodes from the adjacent cluster in another set that has not yet adjusted to the average residual energy of the cluster; When the residual energy of a cluster set is greater than the average residual energy of the cluster set, a certain number of nodes of the clusters with energy higher than the average residual energy of the clusters in the cluster set will be allocated to adjacent clusters in another set, so that the residual energy of the cluster set is close to the average residual energy of the cluster set; The base station compares the residual energy of each cluster in the cluster set with the average residual energy of the cluster. When the residual energy of a cluster is greater than the average residual energy of the cluster, the cluster allocates some nodes to adjacent and unadjusted clusters in the cluster set. When the residual energy of a cluster is less than the average residual energy of the cluster, the cluster obtains a certain number of nodes from adjacent and unadjusted clusters in the cluster set to balance the energy of each cluster in the cluster set.

2. The energy-saving data transmission method for wireless sensor networks according to claim 1, characterized in that: The base station divides the wireless sensor network into multiple candidate clusters according to the distance between nodes and adjusts the nodes of each cluster, including the following steps: The city is divided into several areas, each area includes a secondary base station and several primary base stations, where the secondary base station is a pre-designated base station BS pre ; Each node in the network broadcasts a HELLO message, which includes node coordinates and node ID information; Each primary base station creates a tuple based on the received HELLO message. The tuple includes the ID of the node to which the message belongs, the coordinates of the node to which the message belongs, and the ID of the base station itself. The primary base station in each area sends the tuple information to the pre-designated base station BS in the corresponding area. pre , base station BS pre According to the tuple information, the wireless sensor networks in the area are divided into multiple candidate clusters; The primary base station counts the number of nodes in the current candidate cluster. If the current number of nodes is lower than the threshold, all nodes in the candidate cluster are assigned to the adjacent cluster and the current candidate cluster is disbanded. The adjacent cluster and all nodes assigned to the adjacent cluster can communicate directly with the same base station. Base Station BS pre The cluster adjustment result is broadcast to all primary base stations in the area, and the primary base station broadcasts the cluster adjustment result to all nodes around it.

3. The energy-saving data transmission method for wireless sensor networks according to claim 2, characterized in that: Step 1: The primary base station in each area sends the tuple information to the pre-designated base station BS in the corresponding area. pre , the base station divides the wireless sensor network in the area into multiple candidate clusters according to the tuple information, including the following steps: Base Station BS pre Obtaining from the tuple information and constructing a rectangular monitoring area based on the longitude information and latitude information, wherein the longitude information includes the maximum longitude coordinate and the minimum longitude coordinate, and the latitude information includes the maximum latitude coordinate and the minimum latitude coordinate, and the rectangular monitoring area covers all nodes; Base Station BS pre Divide the rectangular monitoring area into several rectangular sub-monitoring areas of the same size; Base Station BS pre Based on the coordinate data in the tuple information, each node is assigned to each rectangular sub-monitoring area. The nodes in the same rectangular sub-monitoring area form a candidate cluster, wherein the nodes in the same candidate cluster can directly communicate with the same base station.

4. The energy-saving data transmission method for wireless sensor networks according to claim 2, characterized in that: The base station divides the wireless sensor network into multiple candidate clusters according to the distance between nodes and adjusts the nodes of each cluster, and further includes the following steps: Check whether all nodes in the current candidate cluster can communicate directly with the same primary base station; If not, the node with the largest number of nodes that can directly communicate with the same primary base station is retained, and the other nodes are assigned to adjacent clusters, where both the adjacent clusters and the node can directly communicate with the same primary base station.

5. The energy-saving data transmission method for wireless sensor networks according to claim 1, characterized in that: Based on the clustering results, the base station predicts the remaining energy of the cluster and maintains the remaining energy of the cluster, including the following steps: The cluster head records the actual remaining energy E of the cluster at the end of the first five cycles. ac (j); The cluster head uses the least square method to calculate the average energy consumption k of the cluster per cycle, and compares the energy consumption k with the actual remaining energy E at the end of the current cycle. ac (j) sending to a base station; Based on the received data, the base station predicts the remaining energy of each cluster in each future cycle. The prediction formula is: E pre (i) = E ac (j)+k·(ij); The cluster head records the actual remaining energy E of the cluster in each cycle ac (j) and the predicted remaining energy E pre (i) If the deviation σ1 is greater than the preset deviation threshold δ, the cluster head recalculates the average energy consumption k of the cluster per cycle and compares the newly calculated energy consumption k with the actual remaining energy E at the end of the current cycle. ac (j) Send to the base station.

6. The energy-saving data transmission method for wireless sensor networks according to claim 1, characterized in that: The cluster of step set H sends data to the base station. The base station selects the best inter-cluster route based on the data transmission efficiency. The steps also include: The base station calculates the best inter-cluster routes for all cluster heads in set Q and broadcasts the best inter-cluster routes of each cluster to the network; The cluster head of each cluster transmits data to the base station according to the optimal inter-cluster routing.

7. The energy-saving data transmission method for wireless sensor networks according to claim 1, characterized in that: The base station adjusts the clusters to which the relevant nodes in the network belong based on the difference in residual energy between clusters to balance the energy between clusters, and also includes the following steps: The base station compares the residual energy of each cluster in the cluster set with the average residual energy of the clusters to balance the energy among the clusters; The base station broadcasts the inter-cluster energy balancing results to the network, and each node in the network determines whether to change its cluster based on the received message.

8. The energy-saving data transmission method for wireless sensor networks according to claim 1, characterized in that: The following steps are also included: At the end of each round, the residual energy of the current cluster head is compared with the preset residual energy threshold; If the residual energy of the current cluster head is higher than the preset residual energy threshold, the current cluster head continues to serve as the cluster head for the next cycle; otherwise, the node with the highest residual energy in the current cluster is used as the cluster head for the next cycle.

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