Low-power data transmission method for LoRa terminals based on multiple mobile LoRa gateways

Abstract

The present invention discloses a low-power data transmission method for LoRa terminals based on multiple mobile LoRa gateways. The method comprises the following steps: according to the deployment of LoRa terminals, the movement trajectory of each mobile LoRa gateway and the range of terminals it is responsible for serving are determined, and the position of the mobile LoRa gateway at a specified time and the corresponding batch of LoRa terminals that need to perform data transmission are set; the channel activity detection mode is started, the LoRa terminal senses the arrival of the mobile LoRa gateway with low power consumption, enters a sleep mode when no communication is required, and performs data transmission after confirming the arrival of the mobile LoRa gateway; after the multiple mobile LoRa gateways enter the communication range of the LoRa terminal, they collect data with the LoRa terminal, and after receiving the instruction of the mobile LoRa gateway, the LoRa terminal performs data transmission with the mobile gateway according to the transmission parameters indicated by the mobile LoRa gateway; finally, for online applications, the LoRa terminal sends an uplink request data packet to a network server through the mobile LoRa gateway, and the network server integrates the uplink data packets of the LoRa terminal to complete real-time scheduling.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-power wide area networks in the Internet of Things, and mainly relates to a low-power data transmission method for LoRa terminals based on multiple mobile LoRa gateways. Background Art

[0002] With the rapid development of Internet of Things (IoT) technology (especially wireless communication technology), mankind is entering an era of the Internet of Everything. Based on the different communication distances, wireless communication technologies can be mainly divided into two categories: (1) short-range wireless communication technologies, mainly including Wi-Fi, Bluetooth, RFID, etc.; (2) long-range wireless communication technologies, mainly including GSM, 5G, etc. Among them, the former cannot cover wide-area scenarios, and traditional long-range wireless communication technologies often sacrifice a large amount of terminal energy consumption in exchange for communication coverage. Therefore, the demand for wide coverage, low power consumption, and low-cost wireless communication is becoming increasingly urgent. Against this background, Low-Power Wide-Area Networks (LPWAN) technology has emerged. Based on whether the spectrum is licensed, the mainstream LPWAN technologies on the market can be divided into two categories: (1) unlicensed spectrum technologies, mainly including LoRa (Long Range), Sigfox, etc.; (2) licensed spectrum technologies, mainly including NB-IoT, LTE-M, etc. Among them, LoRa has attracted widespread attention from academia and industry due to its advantages such as open architecture, on-demand autonomous networking, miniaturization and easy deployment. Therefore, conducting in-depth and forward-looking research on LoRa networks has important theoretical and application value.

[0003] LoRa terminals, due to their advantages such as autonomous, on-demand networking, have been widely deployed in areas such as smart cities and smart agriculture. A LoRa network primarily consists of terminals, gateways, network servers, and application servers. LoRa terminals are typically battery-powered and communicate with the gateway using specific transmission parameters. The gateway forwards demodulated data packets to the network server via a network such as Ethernet. The network server then uploads the corresponding data to the application server based on application requirements. LoRa terminals are often used in areas such as smart cities, field monitoring, and smart agriculture to collect data. These scenarios often feature numerous obstructions from buildings, harsh environments, and limited network coverage, leading to long communication distances and significant interference between terminals and gateways. For example, in livestock management, LoRa terminals need to relay animal locations to ranchers. However, due to the remote and extensive nature of ranches, signal attenuation is significant, requiring long-range terminals to use higher, more energy-intensive transmission parameters to communicate with the gateway. Consequently, in these complex, wide-area environments, deep within buildings or in remote areas, the actual battery life of LoRa terminals is often only one to two years, far below expectations, and there are also issues such as unequal energy consumption among terminals. The primary reason for this is that in complex wide-area environments, many LoRa terminals are located far from the gateway, necessitating the use of more energy-intensive transmission parameters for data transmission. Furthermore, dense deployments or complex environments with severe environmental interference can lead to severe transmission conflicts between LoRa terminals during data transmission, resulting in low data delivery rates and increased terminal transmission power consumption. LoRa terminals are mostly battery-powered, with limited battery capacity, and in many communication and sensing applications, communication overhead is the primary driver of battery consumption. Therefore, reducing LoRa terminal transmission power consumption in complex wide-area environments to improve battery life and extend the lifecycle of the LoRa network is a core issue that needs to be addressed urgently. Summary of the Invention

[0004] The present invention is aimed at the problems of low battery life of LoRa terminals, unfair energy consumption between terminals, and short life cycle of LoRa networks in the prior art. It provides a low-power data transmission method for LoRa terminals based on multiple mobile LoRa gateways. According to the deployment of LoRa terminals, the moving trajectory of each mobile LoRa gateway and the terminal range responsible for providing transmission services are determined, and the position of the mobile LoRa gateway at a specified time and the corresponding batch of LoRa terminals that need to perform data transmission are set; the channel activity detection mode is started, and the LoRa terminal senses the arrival of the mobile LoRa gateway with low power consumption. The LoRa terminal is in sleep mode when no communication is required, and data transmission is performed after the arrival of the mobile LoRa gateway is confirmed; after the multiple mobile LoRa gateways enter the communication range of the LoRa terminal, they collect data with the LoRa terminal, and after receiving the instructions of the mobile LoRa gateway, the LoRa terminal performs data transmission with the mobile gateway according to the transmission parameters indicated by the mobile LoRa gateway; finally, for online applications, the LoRa terminal sends an uplink request data packet to the network server through the mobile LoRa gateway, and the network server integrates the uplink data packets of the LoRa terminal to complete real-time scheduling. The method of the present invention can enable the mobile gateway to freely and flexibly approach the terminal through this scheme, greatly shortening the communication distance, enabling the terminal to achieve data communication with lower transmission power and faster transmission rate, thereby greatly reducing the terminal transmission power consumption and thus extending the life cycle of the entire LoRa network.

[0005] To achieve the above object, the technical solution adopted in the present invention is: a LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways, comprising the following steps:

[0006] S1: According to the deployment of LoRa terminals, determine the movement trajectory of each mobile LoRa gateway and the range of terminals responsible for providing transmission services, and set the location of the mobile LoRa gateway at a specified time and the corresponding batch of LoRa terminals that need to perform data transmission;

[0007] S2: The LoRa terminal is in sleep mode when no communication is required. In the next cycle, the channel activity detection mode is started. The LoRa terminal senses the arrival of the mobile LoRa gateway with low power consumption and transmits data after confirming the arrival of the mobile LoRa gateway.

[0008] S3: After the multiple mobile LoRa gateways enter the communication range of the LoRa terminal, they collect data with the LoRa terminal. After receiving the instructions from the mobile LoRa gateway, the LoRa terminal transmits data with the mobile gateway according to the transmission parameters indicated by the mobile LoRa gateway.

[0009] S4: For online applications, the LoRa terminal sends the uplink request data packet to the network server through the mobile LoRa gateway. The network server integrates the uplink data packet of the LoRa terminal to complete real-time scheduling.

[0010] As an improvement of the present invention, the step S1 is specifically as follows:

[0011] S11: The deployment of LoRa terminals is modeled as a graph G = (V, E), where V represents the set of all LoRa terminals, E represents the set of edges between terminals, and the edges between terminals (v i ,v j ) has a non-negative weight d ij , determine the set of edges that can connect all LoRa terminals into a closed loop, and make the sum of the edge weights of this set as small as possible;

[0012] S12: Randomly select a terminal i as the starting point of the moving trajectory, and select the weight d among the edges connected to this point. ij The smallest edge is used as the first moving trajectory, and terminal j is used as the second moving point. This process can be deduced to obtain a closed loop L consisting of all terminals, and the sum of the edge weights is small.

[0013] S13: Calculate the length l of the closed loop L. The length of the mobile trajectory of each mobile LoRa gateway is l / k±s, where s is the length that makes the trajectory just end at the terminal, and k is the number of mobile LoRa gateways; complete the trajectory planning and communication area division.

[0014] As an improvement of the present invention, step S2 specifically includes:

[0015] S21: In the offline application, the communication time between the LoRa terminal and the mobile gateway is set in advance. The LoRa terminal wakes up in advance before the communication point and enters the channel activity detection mode to listen for the arrival of the mobile gateway.

[0016] S22: When the arrival of the mobile LoRa gateway is detected, the LoRa terminal enters the receiving RX mode to receive the downlink data packet sent by the mobile LoRa gateway. The downlink data packet for the LoRa terminal includes the transmission parameters that should be used by the LoRa terminal to send the uplink data packet.

[0017] As another improvement of the present invention, in step S22, the mobile LoRa gateway performs time calibration with the LoRa terminal each time communication occurs.

[0018] As another improvement of the present invention, step S3 specifically includes:

[0019] S31: After entering the communication range of the LoRa terminal, the mobile gateway communicates with the LoRa terminal. Among the transmission parameters of the communication, the spreading factor SF of each LoRa terminal is fixed and the same, and the transmission power TP of each LoRa terminal is fixed;

[0020] S32: The mobile gateway sends a downlink data packet containing channel configuration information to the corresponding LoRa terminal; the channel configuration information includes at least transmission parameter settings, transmission time calibration and LoRa terminal Dev ID;

[0021] S33: The LoRa terminal monitors the LoRa signal sent by the mobile gateway in the CAD mode with low power consumption. If the relevant signal sent by the mobile gateway is monitored, it indicates that the mobile gateway has reached the communication range of the terminal and will collect the data of the terminal. The terminal switches from the CAD mode to the RX mode.

[0022] S34: After the LoRa terminal receives a downlink data packet sent by the mobile gateway in the RX mode, if the downlink data packet contains information for this LoRa terminal, it indicates that this LoRa terminal can perform data transmission in this communication, and the terminal enters the TX mode to start uploading data; if the downlink data packet does not indicate the terminal, the terminal re-enters the RX mode until it receives a downlink instruction data packet for the terminal;

[0023] S35: After completing data transmission, the LoRa terminal goes into sleep mode from TX mode. When the next communication cycle starts, it enters CAD mode from SLEEP mode and starts low-power sensing of the arrival of the mobile LoRa gateway. The mobile gateway collects data from the next batch of LoRa terminals and moves according to the pre-planned trajectory until it enters the communication range of the next batch of LoRa terminals that need to communicate.

[0024] As another improvement of the present invention, in the transmission parameters of step S31, when the spreading factor SF and the transmission power TP are fixed, for the dense distribution of terminals using the same spreading factor SF, every 8 LoRa terminals are used in the same batch for data transmission, and the channel CF of these 8 terminals is randomly allocated. The second batch of LoRa terminal communications is carried out after the first batch ends, and the communication of the remaining LoRa terminals is similar.

[0025] As another improvement of the present invention, step S4 specifically includes:

[0026] S41: The LoRa terminal sends a short prompt message with the maximum transmission parameters (TP, SF) to notify the mobile LoRa gateway within the maximum communication range that there is a data collection demand here, and then enters the channel activity detection mode; the short prompt message includes at least the device ID (DevID) of this LoRa terminal, the geographic location information (GPS) and the length of the data packet to be uplinked;

[0027] S42: After the mobile LoRa gateway receives the short prompt data packet from the LoRa terminal within the communication range, it forwards the data packet to the network server. The network server obtains the information of the LoRa terminal to be communicated based on the short prompt data packet sent by the LoRa terminal. After completing the data transmission, the mobile LoRa gateway stops at the current communication location or the designated charging station according to the application requirements, and waits for the next scheduling instruction from the network server.

[0028] As a further improvement of the present invention, in step S42, the mobile gateway with the largest R value is scheduled to be close to the LoRa terminal according to the following formula: R = a·1 / D+(1-a)·E, where D is the communication distance between the mobile gateway and the LoRa terminal, E is the remaining power of the mobile gateway, and a is the weight of the communication distance and the power of the mobile gateway set by the user according to application requirements.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) For the first time, it is proposed to use mobile LoRa gateways for low-power transmission of LoRa terminals. Compared with the existing fixed gateway-based mode, mobile LoRa gateways can fundamentally solve the problem that long-distance terminals need to use more energy-consuming transmission parameters, thereby reducing transmission power consumption, avoiding energy consumption between terminals, and extending the life cycle of the LoRa network. It is in line with the industry's general trend of green and energy-saving network acquisition and can meet deployment requirements in multiple scenarios.

[0031] (2) The key performance indicators of wireless sensor networks are "wide coverage, low cost, and low power consumption". The present invention addresses the large number of transmission conflicts and increased transmission power consumption caused by the complex transmission characteristics of LoRa and the limited parallel receiving capability of the LoRa gateway. While reducing the transmission power consumption of the LoRa terminal, it ensures the reliability and concurrency of the LoRa terminal data transmission, and can meet the "small data, large connection" transmission characteristics of the LoRa network.

[0032] (3) In order to further cope with the ever-increasing application scale and demand, the present invention designs corresponding transmission mechanisms for offline applications and online applications respectively, so as to increase the universality of the method, which can be applied in smart cities, smart factories, smart farms and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1This is a system architecture diagram of the LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways of the present invention;

[0034] Figure 2 The following is a working diagram of a LoRa terminal in a low-power data transmission method of a LoRa terminal based on multiple mobile LoRa gateways of the present invention;

[0035] Figure 3 The present invention is a flowchart of the working process of the LoRa gateway in the LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0037] Example 1

[0038] A low-power terminal data transmission method based on multiple mobile gateways, the specific architecture of which is as follows Figure 1 As shown, the ground station consists of two parts: a drone ground station and a LoRa network server. The ground station controls the drone's flight and data transmission via Ethernet to the LoRa gateway. The drone includes components such as a flight control board and a battery, and carries a LoRa gateway to form a mobile LoRa gateway. The mobile LoRa transmits data with the ground LoRa terminal according to the offline scheduling plan pre-planned by the gateway. The method of the present invention includes the following steps:

[0039] Step S1: Determine the movement trajectory of each of the multiple mobile LoRa gateways and the communication area they are responsible for, that is, determine the terminals that need to provide data transmission services. In offline applications, based on the deployment of LoRa terminals, determine the movement trajectory of each mobile LoRa gateway and the terminal range responsible for providing transmission services, and set the location of the mobile LoRa gateway at a specified time and the corresponding batch of LoRa terminals that need to perform data transmission;

[0040] Before step S1, multiple mobile LoRa gateways need to be built. Use mobile carriers (such as drones, etc.) to carry LoRa gateways close to LoRa terminals for data collection. This allows the gateways to be close to the terminals for data collection, and the LoRa terminals to perform low-power data transmission. The specific process is as follows:

[0041] The LoRa gateway is mounted on a mobile carrier, such as a drone, unmanned vehicle, or unmanned ship, capable of carrying the LoRa gateway for mobility. The LoRa gateway is equipped with a module that allows offline communication with LoRa terminals. In online applications, it can also communicate with the LoRa network server, operating under real-time instructions from the network server. The mobile carrier is equipped with a movement module that allows it to move along a pre-set trajectory. In online applications, it can also communicate in real time with a ground station, operating under real-time instructions from the ground station.

[0042] The specific method of step S1 is as follows:

[0043] Step S11: In offline applications, the service areas of multiple mobile LoRa gateways are first divided, that is, the mobile range of each mobile LoRa gateway and the LoRa terminals that need to be responsible for data transmission by the mobile gateway are determined. Assume that there are k mobile LoRa gateways, which will start from their respective starting points and move along a certain trajectory. In the end, the sum of the trajectories of all mobile LoRa gateways can cover all LoRa terminals, that is, each LoRa is covered by the communication range of at least one mobile LoRa gateway, and the possibility of exhaustion of mobile LoRa gateway movement is small. The deployment of LoRa terminals is modeled as a graph G = (V, E), where V represents the set of all LoRa terminals (vertices) and E represents the set of (arc) edges between terminals. The edges between terminals (v i ,v j ) has a non-negative weight d ij , we need to find a set of edges that can connect all LoRa terminals into a closed loop, and make the sum of the edge weights of this set as small as possible;

[0044] Step S12: Randomly select a terminal i as the starting point of the moving trajectory, and select the weight d among the edges connected to this point. ij The smallest edge is used as the first moving trajectory, and terminal j is used as the second moving point. This process can be deduced to obtain a closed loop L consisting of all terminals, and the sum of the edge weights is small.

[0045] Step S13: Calculate the length l of the closed loop L. The length of each mobile LoRa gateway's trajectory is l / k ± s, where s is the length required for the trajectory to terminate exactly at the terminal. For example, if the trajectory is 100 meters long, but the coordinates of the terminals adjacent to the trajectory endpoint are 80 meters and 150 meters, respectively, the trajectory terminates at the terminal at 80 meters, that is, the terminal closest to the trajectory endpoint. The terminal at 150 meters serves as the starting point of the trajectory for the next mobile LoRa gateway, thus forming k mobile LoRa gateway trajectories. Each LoRa terminal selects the mobile LoRa gateway with the closest trajectory as the gateway responsible for its data transmission. After completing trajectory planning and communication area division, the mobile gateway only needs to arrive at the designated location at the specified time to collect data from the corresponding LoRa terminal. If the mobile LoRa gateway starts data transmission at 10:00, the moving speed is 10 m / s, and a LoRa terminal is 100 meters from the starting point, the mobile LoRa gateway must enter the communication range of this terminal around 10:10 (the exact time is affected by the communication time within the 0-100 m range and environmental factors).

[0046] Step S2: Since the mobile gateway's movement is uncertain and it cannot arrive at a certain location at a certain time, the LoRa terminal needs to sense the arrival of the mobile LoRa gateway with low power consumption and transmit data after confirming the arrival of the mobile LoRa gateway. In offline applications, the LoRa terminal is in sleep mode when no communication is needed. It wakes up in advance at the time agreed with the mobile gateway and enters the channel activity detection mode to sense the arrival of the gateway with low power consumption.

[0047] Step S21: In offline applications, the LoRa terminal is in sleep mode when no communication is required and wakes up at the time when data needs to be sent. In offline applications, the communication time between the LoRa terminal and the mobile gateway can be set in advance. The LoRa terminal wakes up in advance before the communication point and enters the Channel Activity Detection (CAD) mode to listen for the arrival of the mobile gateway. If the communication time is set to 10:00, the mobile LoRa gateway will move to the communication range of this LoRa terminal around 10:00 (the exact time is affected by the communication time within the 0-100m range and environmental factors) and send a downlink data packet to the terminal to instruct the terminal to send data with the specified transmission parameters. Taking into account the uncertainty of time offset and gateway movement, the LoRa terminal wakes up from SLEEP mode at 9:55 and enters CAD mode to start monitoring the arrival of the mobile gateway; Step S22: After monitoring the arrival of the mobile LoRa gateway, the LoRa terminal enters receive (RX) mode to receive the downlink data packet sent by the mobile LoRa gateway. The downlink data packet for the LoRa terminal contains the transmission parameters that the LoRa terminal should use to send the uplink data packet, and during each communication, the mobile LoRa gateway will calibrate the time with the LoRa terminal to minimize the time error.

[0048] Step S3: After entering the communication range of the LoRa terminal, the multi-mobile LoRa gateway collects data with the LoRa terminal using transmission parameters that can achieve communication, do not generate transmission conflicts, and have the lowest power consumption. After receiving the instruction of the mobile LoRa gateway, the LoRa terminal transmits data with the mobile gateway according to the transmission parameters indicated by the mobile LoRa gateway;

[0049] After the LoRa terminal senses the arrival of the mobile gateway with low power consumption, it transmits data according to the instructions issued by the gateway. This step can be divided into two parts: the mobile LoRa gateway and the LoRa terminal. The specific process is as follows:

[0050] Step S31: After entering the communication range of the LoRa terminal, the mobile gateway communicates with the LoRa terminal using certain transmission parameters. The transmission parameters are set as follows: the spreading factor (SF) of each LoRa terminal is fixed and identical, and the transmission power (TP) of each LoRa terminal is fixed. Based on the vertical distance from the LoRa terminal to the mobile gateway trajectory / communication location, the SF and TP combination that meets the communication requirements and consumes the least transmission power is selected. For example, when the communication distance is 100m, the combination of SF8 and TP5 can achieve this communication distance with an energy consumption of 0.01187J; the combination of SF9 and TP2 can also achieve this communication distance, but the energy consumption is 0.02117J, so the combination of SF8 and TP5 is selected. Due to the dense deployment of LoRa terminals, there may be a large number of LoRa terminals within the communication range of the mobile gateway, and the terminal channels (CF) need to be allocated to avoid transmission conflicts. When SF and TP are fixed, for the dense distribution of terminals using the same SF, every 8 LoRa terminals are used to transmit data in the same batch. The CF of these 8 terminals is randomly assigned. The second batch of LoRa terminals communicates after the first batch, and the remaining LoRa terminals communicate in the same way.

[0051] Step S32: After the mobile gateway enters the communication range of the LoRa terminal to be communicated, it sends a downlink data packet containing channel configuration information (such as transmission parameter settings, transmission time calibration, and LoRa terminal Dev ID) to the corresponding LoRa terminal;

[0052] Step S33: The LoRa terminal monitors the LoRa signal sent by the mobile gateway in the CAD mode with low power consumption. If the relevant signal sent by the mobile gateway is monitored, it indicates that the mobile gateway has reached the communication range of the terminal and is about to collect the data of the terminal. Therefore, the terminal switches from the CAD mode to the receiving (RX) mode;

[0053] Step S34: After the LoRa terminal receives the downlink data packet sent by the mobile gateway in the RX mode, if the downlink data packet contains information for this LoRa terminal, it indicates that this LoRa terminal can perform data transmission in this communication, and the terminal enters the transmit (TX) mode to start uploading data; if the downlink data packet does not indicate the terminal, the terminal re-enters the RX mode until a downlink indication data packet for this terminal is received;

[0054] Step S35: After completing data transmission, the LoRa terminal goes into sleep mode, switching from TX mode to SLEEP mode. When the next communication cycle begins, it switches from SLEEP mode to CAD mode, starting low-power sensing of the arrival of the mobile LoRa gateway. The mobile gateway collects data from the next batch of LoRa terminals, moving along a pre-planned trajectory until it enters the communication range of the next batch of LoRa terminals.

[0055] Therefore, the working process of the LoRa terminal in the LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways of the present invention is as follows Figure 2 As shown. The LoRa terminal wakes up from SLEEP mode when there is a need for data transmission. If it is an online application, it directly enters TX mode to send a short communication requirement prompt signal at the maximum communication distance, and then enters CAD mode to monitor the arrival signal of the mobile LoRa gateway. If it is an offline application, it directly enters CAD mode to monitor the arrival signal of the mobile LoRa gateway. After monitoring the arrival signal of the mobile LoRa gateway, the LoRa terminal enters RX mode. If the received downlink data packet contains data transmission information for this LoRa terminal, this LoRa terminal enters TX mode to send data. If it does not contain data transmission information for this LoRa terminal, the LoRa terminal re-listens for downlink data packets sent by the LoRa gateway until it receives information containing information for this LoRa terminal. After the data is sent, the LoRa terminal re-enters SLEEP mode until it wakes up from SLEEP mode when data transmission is required next time.

[0056] Step S4: In online applications, the LoRa terminal sends an uplink request data packet to the network server through the mobile LoRa gateway. The network server integrates the uplink data packet of the LoRa terminal and dispatches the appropriate mobile LoRa gateway in real time to approach the specified LoRa terminal with a certain trajectory and provide it with data transmission services.

[0057] Step S41: In online applications, since the LoRa terminal cannot agree on a time with the mobile gateway in advance, the LoRa terminal wakes up from the SLEEP mode when there is an uplink demand and needs to send a short prompt message with the maximum transmission parameters (TP, SF). The short prompt message contains the device ID (DevID) of the LoRa terminal, geographic location information (GPS), the length of the data packet to be uplinked, etc. This notifies the mobile LoRa gateway within the maximum communication range that there is a data collection demand here, and then enters the channel activity detection mode;

[0058] Step S42: In online applications, after receiving a short notification packet from a LoRa terminal within communication range, the mobile LoRa gateway forwards the packet to the network server. Based on the short notification packet sent by the LoRa terminal, the network server can obtain information about the LoRa terminal to be communicated with (including geographic location, packet size, etc.) and schedule the mobile gateway with the largest R value close to this LoRa terminal according to the following formula: R = a 1 / D + (1-a) E, where D is the communication distance between the mobile gateway and the LoRa terminal, E is the remaining power of the mobile gateway, and a is the weight of the communication distance and mobile gateway power that the user can set according to application requirements. After completing the data transmission, the mobile LoRa gateway can stop at the current communication location or designated charging station according to application requirements, waiting for the next scheduling instruction from the network server.

[0059] Therefore, the working process of the LoRa gateway in the LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways of the present invention is as follows: Figure 3 As shown. If it is an online application, the mobile LoRa gateway always listens for the short prompt signal of the LoRa terminal. If a short prompt signal is received, it is forwarded to the network server and moved to the LoRa terminal that needs to communicate according to the instructions of the network server; if it is an offline application, the mobile LoRa gateway moves to the LoRa terminal that needs to communicate according to the pre-planned path and moving speed. After the mobile LoRa gateway moves to the LoRa terminal that needs to communicate, the mobile LoRa gateway sends a downlink data packet to the terminal and receives the downlink data packet sent by the LoRa terminal. After the transmission is completed, it moves to the next LoRa terminal that needs to communicate. If the power of a mobile carrier such as a drone is exhausted, it returns to the charging pile to charge. In summary, the present invention focuses on solving the problem of low battery life of the LoRa terminal, can reduce the transmission power consumption of the LoRa terminal, extend the battery life of the LoRa terminal, reduce the unfairness of energy consumption between terminals, and extend the life cycle of the LoRa network. This method mainly includes four parts: multi-mobile LoRa gateway task scheduling, low-power LoRa terminal sensing of multi-mobile LoRa gateways, low-power data transmission between LoRa terminals and multi-mobile LoRa gateways, and low-power data transmission methods for online applications. The method first performs trajectory planning and task allocation for multi-mobile LoRa gateways based on LoRa deployment for offline applications. Secondly, it designs a mechanism for low-power LoRa terminal sensing of multi-mobile LoRa gateways based on channel activity detection mode. Then, it determines the transmission mechanism between LoRa terminals and multi-mobile LoRa gateways, mainly involving the selection of transmission batches and channels. Finally, to meet different application requirements, the method also supports low-power data transmission in online applications.

[0060] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A low-power data transmission method for LoRa terminals based on multiple mobile LoRa gateways, characterized in that: The process includes the following steps: S1: According to the deployment of LoRa terminals, determine the movement trajectory of each mobile LoRa gateway and the range of terminals responsible for providing transmission services, and set the location of the mobile LoRa gateway at a specified time and the corresponding batch of LoRa terminals that need to perform data transmission; S11: The deployment of LoRa terminals is modeled as a graph G = (V, E), where V represents the set of all LoRa terminals, E represents the set of edges between terminals, and the edges between terminals (v i ,v j ) has a non-negative weight d ij , determine the set of edges that can connect all LoRa terminals into a closed loop, and make the sum of the edge weights of this set minimum; S12: Randomly select a terminal i as the starting point of the moving trajectory, and select the weight d among the edges connected to this point. ij The smallest edge is used as the first moving trajectory, and terminal j is used as the second moving point. Similarly, a closed loop L consisting of all terminals can be obtained, and the sum of the edge weights is minimized. S13: Calculate the length l of the closed loop L. The length of the mobile trajectory of each mobile LoRa gateway is l / k±s, where s is the length that makes the trajectory just end at the terminal, and k is the number of mobile LoRa gateways; complete the trajectory planning and communication area division; S2: The LoRa terminal is in sleep mode when no communication is required. In the next cycle, the channel activity detection mode is started. The LoRa terminal senses the arrival of the mobile LoRa gateway with low power consumption and transmits data after confirming the arrival of the mobile LoRa gateway. S3: After the multiple mobile LoRa gateways enter the communication range of the LoRa terminal, they collect data with the LoRa terminal. After receiving the instructions from the mobile LoRa gateway, the LoRa terminal transmits data with the mobile gateway according to the transmission parameters indicated by the mobile LoRa gateway. S4: For online applications, the LoRa terminal sends the uplink request data packet to the network server through the mobile LoRa gateway. The network server integrates the uplink data packet of the LoRa terminal to complete real-time scheduling.

2. the LoRa terminal low-power consumption data transmission method based on multiple mobile LoRa gateways as claimed in claim 1, is characterized in that: Step S2 specifically includes: S21: In the offline application, the communication time between the LoRa terminal and the mobile gateway is set in advance. The LoRa terminal wakes up in advance before the communication point and enters the channel activity detection mode to listen for the arrival of the mobile gateway. S22: When the arrival of the mobile LoRa gateway is detected, the LoRa terminal enters the receiving RX mode to receive the downlink data packet sent by the mobile LoRa gateway. The downlink data packet for the LoRa terminal includes the transmission parameters that should be used by the LoRa terminal to send the uplink data packet.

3. The LoRa terminal low-power consumption data transmission method based on multiple mobile LoRa gateways as claimed in claim 2, wherein: In step S22, the mobile LoRa gateway performs time calibration with the LoRa terminal each time communication occurs.

4. The LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways as claimed in claim 1, wherein: The step S3 specifically includes: S31: After entering the communication range of the LoRa terminal, the mobile gateway communicates with the LoRa terminal. Among the transmission parameters of the communication, the spreading factor SF of each LoRa terminal is fixed and the same, and the transmission power TP of each LoRa terminal is fixed; S32: The mobile gateway sends a downlink data packet containing channel configuration information to the corresponding LoRa terminal; the channel configuration information includes at least transmission parameter settings, transmission time calibration and LoRa terminal Dev ID; S33: The LoRa terminal monitors the LoRa signal sent by the mobile gateway in the CAD mode with low power consumption. If the relevant signal sent by the mobile gateway is monitored, it indicates that the mobile gateway has reached the communication range of the terminal and will collect the data of the terminal. The terminal switches from the CAD mode to the RX mode. S34: After the LoRa terminal receives a downlink data packet sent by the mobile gateway in the RX mode, if the downlink data packet contains information for this LoRa terminal, it indicates that this LoRa terminal can perform data transmission in this communication, and the terminal enters the TX mode to start uploading data; if the downlink data packet does not indicate the terminal, the terminal re-enters the RX mode until it receives a downlink instruction data packet for the terminal; S35: After completing data transmission, the LoRa terminal goes into sleep mode from TX mode. When the next communication cycle starts, it enters CAD mode from SLEEP mode and starts low-power sensing of the arrival of the mobile LoRa gateway. The mobile gateway collects data from the next batch of LoRa terminals and moves according to the pre-planned trajectory until it enters the communication range of the next batch of LoRa terminals that need to communicate.

5. The LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways as claimed in claim 4, wherein: In the transmission parameters of step S31, when the spreading factor SF and the transmission power TP are fixed, for the dense distribution of terminals using the same spreading factor SF, every 8 LoRa terminals are used in the same batch for data transmission, and the channels CF of these 8 terminals are randomly allocated. The second batch of LoRa terminal communications is carried out after the first batch ends, and the remaining LoRa terminals communicate in the same way.

6. The LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways as claimed in claim 5, wherein: The step S4 specifically includes: S41: The LoRa terminal sends a short prompt message with the maximum transmission parameters (TP, SF) to notify the mobile LoRa gateway within the maximum communication range that there is a data collection requirement here, and then enters the channel activity detection mode; the short prompt message includes at least the device ID (DevID) of this LoRa terminal, the geographic location information (GPS) and the length of the data packet to be uplinked; S42: After the mobile LoRa gateway receives the short prompt data packet from the LoRa terminal within the communication range, it forwards the data packet to the network server. The network server obtains the information of the LoRa terminal to be communicated based on the short prompt data packet sent by the LoRa terminal. After completing the data transmission, the mobile LoRa gateway stops at the current communication location or the designated charging station according to the application requirements, and waits for the next scheduling instruction from the network server.

7. The LoRa terminal low-power data transmission method based on multiple mobile LoRa gateways as claimed in claim 6, wherein: In step S42, the mobile gateway with the largest R value is scheduled to be close to the LoRa terminal according to the following formula: R = a·1 / D+(1-a)·E, where D is the communication distance between the mobile gateway and the LoRa terminal, E is the remaining power of the mobile gateway, and a is the weight of the communication distance and the power of the mobile gateway set by the user according to application requirements.

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