LoRa multi-hop network adaptive transmission system and method based on link quality

Abstract

The invention discloses a LoRa multi-hop network adaptive transmission system and method for link quality, and the system comprises a layering module which determines the hop count of each node in a network from a gateway; the routing exploration module is used for determining a father node of each node and selecting according to the signal intensity in a packet in the layering module; according to the parameter optimization module, the gateway calculates SF and BW which can be optimized according to the link quality from the node to the gateway, and if the link quality is good, the node is switched into optimized parameters; and the node management module is used for periodically sending layered messages by each node and periodically updating a neighbor table based on signal intensity so as to manage deletion and addition of the nodes. According to the method, the transmission time is further shortened while the node is ensured to meet the delivery rate through the method for adaptively adjusting the communication parameters based on the link quality, and the reliability of data transmission is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial wireless networks, and in particular relates to a LoRa multi-hop network adaptive transmission system and method based on link quality. Background Art

[0002] As a low-power wide area network radio technology, LoRa has gained wide attention in the field of the Internet of Things. It can provide low power consumption and long-distance communication in the sub-GHz frequency band. LoRaWAN is a medium access control layer protocol based on LoRa. Many existing LoRa applications use the LoRaWAN specification and adopt a star topology, which has a low coverage rate and cannot meet the requirements of large-scale deployment of IoT. In addition, some parameters in LoRa communication, such as the spreading factor, affect the sensitivity and transmission rate. Most LoRa multi-hop protocols usually communicate with fixed parameters and cannot select adaptive parameters according to the link quality, resulting in high packet loss rate and high communication rate. Summary of the invention

[0003] In view of the technical defects of the existing LoRa multi-hop strategy, the present invention proposes a LoRa multi-hop network adaptive transmission system based on link quality, which enables nodes to select adaptive communication parameters, ensuring that the network has a high delivery rate while greatly reducing the transmission time.

[0004] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0005] A LoRa multi-hop network adaptive transmission system based on link quality includes the following modules:

[0006] Hierarchical module, used to confirm the number of hops between nodes and gateways;

[0007] The routing exploration module is used by nodes to confirm their parent nodes;

[0008] Optimization parameter module, used by nodes to adjust their own spreading factor and bandwidth;

[0009] The node management module is used for node deletion and addition management.

[0010] Furthermore, nodes in the network adjust their spreading factor (SF) and bandwidth (BW) based on transmission time and signal strength.

[0011] Furthermore, in the layered module, the gateway broadcasts a data packet containing its own layer number under the parameters of BW of 125kHz and SF of 7. After receiving the data packet, the neighboring nodes within one hop of the gateway update their own layer number and increase the layer number index by 1 and broadcast it again. All adjacent nodes in the network forward the layered message and update their own layer number, thus covering all nodes in the network, so that all nodes are assigned to the corresponding layer number.

[0012] Furthermore, in the routing exploration module, each node in the network needs to find a routing path to find its parent node. The node records the effective signal power (ESP) according to the received layered data packets, sorts them according to the ESP value, and selects the node with the largest ESP value as the best parent node.

[0013] Furthermore, the optimization parameter module optimizes the SF for each node. The node sends an optimization parameter request containing its own layer number, payload size and other information. The node calculates the optimized spreading factor (SF) within the one-hop range (when n is 1) under the premise of reducing the transmission time. opt , the formula for calculating the transmission time is as follows:

[0014] T (sf,pl,n) =n·(t rd(sf) +t pd +t td(sf,pl) )

[0015] Among them, T represents the total transmission time of the node, n represents the layer number of the node, and t rd represents the receiving delay of the node, t pd represents the processing delay of the node, t td Indicates the air transmission time of the node. opt Check whether the ESP value under the current parameter meets the threshold under the current parameter. If it does, switch.

[0016] Furthermore, the optimization parameter module optimizes the BW of each node. After optimizing the SF algorithm, the gateway will adjust the BW of the node based on the signal strength, which is given by the following formula according to the sensitivity (S) of the radio receiver at room temperature:

[0017] S=-174+10·log 10 (BW)+NF+SNR

[0018] From the formula, we can see that for a certain SF, increasing BW will reduce the sensitivity of the receiver, but can achieve faster transmission. Taking the commonly used bandwidth of LoRa as an example (125kHz, 250kHz, 500kHz), the above formula shows that for every 125kHz increase in bandwidth, the sensitivity will decrease by 3dB. Therefore, the gateway estimates whether BW can be optimized based on ESP. The calculation formula is as follows:

[0019] esp [margin] =esp-esp [125kHz th]

[0020] Among them, esp [margin] Indicates the redundant ESP value of the node, esp indicates the current value of the node, esp [125kHz th] Indicates the ESP threshold when the BW is 125kHz under the current SF.

[0021] Furthermore, in the node management module, the node periodically updates the ESP value to determine the existence of neighboring nodes. The ESP update formula is as follows:

[0022] esp(t)=α+(1-α)esp(t-1)

[0023] Where esp(t) represents the updated ESP value of the node, and esp(t-1) represents the past ESP value of the node. Update its neighbor table based on the ESP value.

[0024] The present invention also provides a LoRa multi-hop network adaptive transmission method based on link quality, which is used to execute the above system, comprising the following steps:

[0025] S1. Layer the entire network and confirm the number of hops between each node and the gateway;

[0026] S2. Each node obtains a neighbor list based on the ESP value and confirms its parent node;

[0027] S3. The node sends an optimization parameter request to the gateway;

[0028] S4. The gateway calculates the optimized SF based on the link quality and other information and sends it to the requesting node;

[0029] S5. The node sends the optimized SF as a parameter to the gateway. The gateway determines whether the link quality threshold is met based on the ESP value. If so, the node changes the SF.

[0030] S6. After optimizing SF, the gateway continues to determine whether the node can continue to optimize BW, and determines whether the link quality is good based on the difference between ESP and the threshold value at BW of 125kHz. The gateway sends the optimized BW parameters to the node;

[0031] S7. The node sends the optimized BW as a parameter to the gateway. The gateway determines whether the link quality threshold is met based on the ESP value. If so, the node adjusts the BW.

[0032] Compared with the prior art, the present invention adds parameter adaptive optimization based on link quality on the basis of LoRa multi-hop communication; the present invention proposes an optimization parameter algorithm, which adjusts the SF, BW and other parameters of the node through link quality information such as transmission time and signal strength, and further optimizes the parameters to reduce the transmission time while meeting the communication quality; in addition, the present invention uses different SF and BW to reduce conflicts under a single link and ensure the reliability of data transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a structural diagram of a LoRa multi-hop network adaptive transmission system based on link quality provided in Example 1;

[0034] Figure 2 This is a schematic diagram of routing exploration provided in Example 1;

[0035] Figure 3 is a schematic diagram of parameter optimization provided in Example 1;

[0036] Figure 4 This is a schematic diagram of the comparison of three-hop node delivery rates provided in Example 1;

[0037] Figure 5 This is a schematic diagram of the comparison of transmission time of three hop nodes provided in the first embodiment;

[0038] Figure 6 This is a flow chart of a LoRa multi-hop network adaptation method based on link quality provided in Example 2. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0040] The object of the present invention is to provide a LoRa multi-hop network adaptive transmission system and method based on link quality in view of the defects of the prior art.

[0041] Embodiment 1

[0042] like Figure 1 As shown, this embodiment provides a LoRa multi-hop network adaptive transmission system based on link quality, which specifically includes the following modules:

[0043] Hierarchical module, used to confirm the number of hops between nodes and gateways.

[0044] The routing exploration module is used by nodes to confirm their own parent nodes, and the selection is based on the signal strength contained in the packet in the hierarchical module.

[0045] The parameter optimization module is used for nodes to adjust their own spreading factors and bandwidths. The gateway calculates the optimized SF and BW based on the link quality from the node to the gateway. If the link quality is good, the node switches to the optimized parameters.

[0046] The node management module is used to delete and add nodes. Each node periodically sends hierarchical messages and regularly updates the neighbor table based on signal strength to manage the deletion and addition of nodes.

[0047] The following is a more detailed description of each module.

[0048] In this embodiment, nodes in the network adjust their own spreading factors SF and bandwidths BW based on transmission time and signal strength.

[0049] The gateway sends layer information to neighboring nodes. The neighboring nodes obtain the layer number and increase the layer index by 1 and broadcast it again. All adjacent nodes in the network can relay the layer message and update their own layer number, thus covering all nodes in the network. Therefore, all nodes are assigned to the corresponding layer number.

[0050] like Figure 2 The figure shows the route discovery process. The route discovery process is as follows: The gateway sends hierarchical information, and the adjacent nodes (nodes 1-3) receive and forward the information. After receiving the hierarchical information, node 4 sorts the adjacent nodes according to their ESP values ​​and selects the node with the best link quality to respond. After receiving the response from node 4, node 2 sends a reply, and node 4 confirms that node 2 is its parent node.

[0051] In the parameter optimization module, the gateway optimizes SF and BW for the node sending the request based on the link quality.

[0052] In the parameter optimization module, the gateway optimizes its own SF for the node. The node sends an optimization parameter request containing its own layer number, payload size and other information. The node calculates the optimized spreading factor (SF) within the one-hop range (when n is 1) under the premise of reducing the transmission time. opt , the formula for calculating the transmission time is as follows:

[0053] T (sf,pl,n) =n·(t rd(sf) +t pd +t td(sf,pl) )

[0054] Among them, T represents the total transmission time of the node, n represents the layer number of the node, and t rdrepresents the receiving delay of the node, t pd represents the processing delay of the node, t td Indicates the air transmission time of the node. opt Whether the ESP value under the current parameter meets the threshold under the current parameter, if it does, it switches. After optimizing SF, the gateway continues to optimize the BW for the node. After optimizing the SF algorithm, the node will adjust its BW based on the signal strength. The sensitivity (S) of the radio receiver at room temperature is given by the following formula:

[0055] S=-174+10·log 10 (BW)+NF+SNR

[0056] From the formula, we can see that for a certain SF, increasing BW will reduce the sensitivity of the receiver, but can achieve faster transmission. Taking the commonly used bandwidth of LoRa as an example (125kHz, 250kHz, 500kHz), the above formula shows that the sensitivity will decrease by 3dB for every 125kHz increase in bandwidth. Therefore, the gateway estimates whether BW can be optimized based on ESP. The calculation formula is as follows:

[0057] esp [margin] =esp-esp [125kHz th]

[0058] Among them, esp [margin] Indicates the redundant ESP value of the node, esp indicates the current value of the node, esp [125kHz th] Indicates the ESP threshold when the BW is 125kHz under the current SF.

[0059] like Figure 3 The figure shows the 2-hop node parameter optimization process. Initially, the gateway broadcasts a layer information. After receiving the information, node A uses the information to determine its layer (layer 1) before rebroadcasting the information. After receiving the rebroadcast information, node B determines that it belongs to layer 2. Subsequently, node B sends an optimization parameter request to the gateway. The gateway calculates the optimized SF (SF opt ) and sends it to Node B. Node B receives SF opt After that, use SF opt The gateway uses the new SF to evaluate the link quality. If satisfied, it continues to calculate the optimized BW (BW opt ) and transmits it to Node B. The gateway re-evaluates the link quality and sends an acknowledgment (ACK) to Node B if the quality meets the pre-defined criteria. Compared with traditional multi-hop networks, this adaptive strategy of selecting appropriate BW and SF can significantly reduce the average network delay.

[0060] In the node management module, the node periodically updates the ESP value to determine the existence of neighboring nodes. The ESP update formula is as follows:

[0061] esp(t)=α+(1-α)esp(t-1)

[0062] Among them, esp(t) represents the ESP value after the node is updated, and esp represents the current value of the node.

[0063] like Figure 3 The figure shows a delivery rate comparison chart, where MPA-LoRa represents the adaptive transmission system, HBRR-LoRa represents the transmission under a fixed SF, and MRT-LoRa represents the transmission using different SFs with different hop numbers. Figure 4 The figure shows a comparison of the average transmission time of nodes, which significantly reduces the transmission time and latency while ensuring the delivery rate.

[0064] In summary, this embodiment provides a LoRa multi-hop network adaptive transmission system based on link quality, and adds parameter-based link quality adaptive optimization on the basis of LoRa multi-hop communication; this embodiment adds parameter-based link quality adaptive optimization on the basis of LoRa multi-hop communication; this embodiment proposes an optimization parameter algorithm, which adjusts the SF, BW and other parameters of the node through link quality information such as transmission time and signal strength, and further optimizes the parameters to reduce the transmission time while meeting the communication quality. In addition, different SF and BW are used to reduce conflicts under a single link, thereby ensuring the reliability of data transmission.

[0065] Embodiment 2

[0066] like Figure 5 As shown, this embodiment is a LoRa multi-hop network adaptive transmission method based on link quality, based on the above system embodiment, which includes the following steps:

[0067] S1. Layer the entire network and confirm the number of hops between each node and the gateway;

[0068] S2. Each node obtains a neighbor list based on the ESP value and confirms its parent node;

[0069] S3. The node sends an optimization parameter request to the gateway;

[0070] S4. The gateway uses the following formula based on the number of layers of the node in the request, the payload size, and other information:

[0071] T (sf,pl,n) =n·(t rd(sf) +t pd +t td(sf,pl) )

[0072] Where T represents the total transmission time from the node to the gateway, pl represents the effective load size, n represents the layer number of the node, and t rd Indicates that the node’s receiving delay is affected by SF, t pd Represents the processing delay of the node, which is a constant, t td It represents the air transmission time of the node, which is related to SF and PL. The total transmission time from this node to the gateway when SF is 7 is calculated and recorded as T 当前 Then calculate the SF value that can reduce the total transmission time within a single hop. That is, use the above formula when n is 1 and SF is 8 to calculate the optimized total time and record it as T 优化 , if T 优化 <T 当前 , record the SF at this time and add 1 to SF and repeat the above steps again. If T 优化 >T 当前 , the algorithm is terminated to obtain the set of optimized SFs, and the largest SF value is selected from the set as the optimized SF and sent to the requesting node;

[0073] S5. The node sends the optimized SF to the gateway. The gateway determines whether the link quality threshold is met based on the ESP value. If so, the node changes the SF; if not, the node does not change the SF.

[0074] S6. After optimizing SF, the gateway continues to determine whether the node can continue to optimize BW, and determines whether the link quality is good based on the difference between ESP and the threshold value under BW of 125kHz. If so, the gateway sends the node the optimized BW parameters; if not, the gateway sends the BW parameters of 125kHz;

[0075] S7. The node sends the optimized BW as a parameter to the gateway, and the gateway determines whether the link quality threshold is met based on the ESP value. If it is met, the node adjusts the BW; if it is not met, the node does not change the BW. Compared with the prior art, the present invention adds parameter adaptive optimization based on link quality on the basis of LoRa multi-hop communication; the present invention proposes an optimization parameter algorithm, which adjusts the SF, BW and other parameters of the node through link quality information such as transmission time and signal strength, and further optimizes the parameters to reduce the transmission time while meeting the communication quality. In addition, different SF and BW are used to reduce conflicts under a single link, thereby ensuring data transmission reliability.

[0076] The specific embodiments described above are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. LoRa multi-hop network adaptive transmission system based on link quality, characterized by: Includes the following modules: Hierarchical module, used to confirm the number of hops between nodes and gateways; The routing exploration module is used by nodes to confirm their parent nodes; Optimization parameter module, used by nodes to adjust their own spreading factor and bandwidth; Node management module, used to delete and add nodes.

2. The LoRa multi-hop network adaptive transmission system based on link quality according to claim 1, characterized in that: In the parameter optimization module, nodes in the network adjust their spreading factor SF and bandwidth BW based on transmission time and signal strength.

3. The LoRa multi-hop network adaptive transmission system based on link quality according to claim 2, characterized in that: In the hierarchical module, the gateway broadcasts a data packet containing its own layer number under the parameters of BW of 125kHz and SF of 7; after receiving the data packet, the neighboring nodes within one hop of the gateway update their own layer number and increase the layer number index by 1 and broadcast it again. All adjacent nodes in the network relay the hierarchical message and update their own layer number, thus covering all nodes in the network, and all nodes are assigned to corresponding layer numbers.

4. The LoRa multi-hop network adaptive transmission system based on link quality according to claim 3 is characterized in that: In the routing exploration module, each node in the network needs to find a routing path to find its parent node; the node records the effective signal power ESP according to the received layered data packets, sorts them according to the ESP value, and selects the node with the largest ESP value as the best parent node.

5. The LoRa multi-hop network adaptive transmission system based on link quality according to claim 4 is characterized in that: In the optimization parameter module, the gateway optimizes SF for each node. The node sends an optimization parameter request containing its own layer number and payload size information. The node calculates the optimized spreading factor (SF) within the one-hop range under the premise of reducing the transmission time. opt , the formula for calculating the transmission time is as follows: T (sf,pl,n) =n·(t rd(sf) +t pd +t td(sf,pl) ) Among them, T represents the total transmission time of the node, n represents the number of layers where the node is located, and t rd represents the receiving delay of the node, t pd represents the processing delay of the node, t td Indicates the air transmission time of the node; determines whether the node is in SF opt If the link quality meets the requirement, switch.

6. The LoRa multi-hop network adaptive transmission system based on link quality according to claim 5, characterized in that: The optimization parameter module optimizes the BW of each node. After optimizing the SF, the node adjusts its BW based on the link quality. Based on the change of BW under a fixed SF, the gateway estimates whether the BW can be optimized based on ESP. The calculation formula is as follows: esp [margin] =esp-esp [125kHzth] Among them, esp [margin] Indicates the redundant ESP value of the node, esp indicates the current value of the node, esp [125kHzth] Indicates the ESP threshold when the BW is 125kHz under the current SF.

7. The LoRa multi-hop network adaptive transmission system based on link quality according to claim 6, characterized in that: In the node management module, the node periodically sends hierarchical information and updates the ESP value to determine the existence of neighboring nodes. The ESP update formula is as follows: esp(t)=α+(1-α)esp(t-1) Among them, esp(t) represents the updated ESP value of the node, and esp(t-1) represents the past ESP value of the node; based on the ESP value, the node updates its neighbor table.

8. A LoRa multi-hop network adaptive transmission method based on link quality, used to execute the system described in any one of claims 1 to 7, characterized in that: The steps include: S1. Layer the entire network and confirm the number of hops between each node and the gateway; S2. Each node obtains a neighbor list based on the ESP value and confirms its parent node; S3. The node sends an optimization parameter request to the gateway; S4. The gateway calculates the optimized SF based on the link quality and sends it to the requesting node; S5. The node sends the optimized SF as a parameter to the gateway. The gateway determines whether the link quality threshold is met based on the ESP value. If so, the node changes the SF. S6. After SF optimization, the difference between ESP and the threshold value at BW of 125kHz is used to determine whether the link quality is good. If so, the gateway sends the optimized BW parameters to the node. S7. The node sends the optimized BW as a parameter to the gateway. The gateway determines whether the link quality threshold is met based on the ESP value. If so, the node adjusts the BW.

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