## 2 Related Work
[PERSON] et al. used a relay UAV to transmit messages from a ground-based remote LoRa node to a remote base station, in response to situations where the wireless network may become congested or completely interrupted after a natural disaster occurs [10]. In [11], a communication strategy between a UAV and ground sensor nodes is designed, with 5 GHz and LoRa communication technology. The LoRa module is adopted to wake up the high-power 5 GHz module or put it to sleep, which achieves data collection with a high transmission rate. It reduces the data transmission time and 5 GHz module energy consumption. Aiming at large data collection of UAV, two heuristic methods are proposed to determine the hovering point of UAV [32]. It also stipulates that the UAV can only collect data from the sensors when it is hovering, and there is no signal transmission when the UAV is moving. On this basis, [PERSON] et al. improved the above two heuristic algorithms for selecting hovering points of a UAV and stipulated two states of collecting data at hovering points and collecting during flight [33]. Specifically, they defined the sequence of hovering points where the UAV had to hover to gather data and defined a subset of sensor nodes that can send data packets to the moving UAV, to reduce the hovering time and the whole data collection time. The above works show that the data transmission rate between UAV and ground nodes has an influence on the flight status. When the ground sensor node, using the low data rate LoRa module, stores a large amount of data, the UAV needs to hover to ensure completing data collection. In [11], the UAV adopts a 5 GHz high-speed communication module for the large data collection problem. Thus, the cost and energy consumption of the hardware in the system increases. Semtech introduced the new long-range 2.4 GHz wireless RF technology and transceiver SX1280 (LoRa 2.4 GHz) in 2017, with the ultra-low current consumption at the higher configurable data rate, compared with the Sub-G LoRa technology. The higher date rate means the lower time on air of the packets, which is conducive to reducing the energy consumption of packet transmission and the probability of channel collision. In the paper, optimization schemes for UAV data collection with LoRa 2.4 GHz technology are proposed to reduce the UAV flight distance and data collection task time. Some properties of this paper which differ from the previous ones are summarized as follows:  
1. An improved clustering algorithm for the LoRa network is proposed, which considers the influence of distance between the cluster heads and the UAV take-off point. 2. We present an improved Genetic Algorithm to obtain the optimal access path of a UAV, which introduces the Teaching-Learning-based Optimization and local search optimization algorithms to improve convergence rate and the path solution. 3. A LoRa 2.4 GHz adaptive data rate strategy with a dual channel is designed based on distance and link quality, to reduce the data transmitting time between the UAV and the cluster head nodes. 4. The UAV's moving status can be adjusted based on data gathering completion status of each cluster head to avoid meaningless flight distances. Real UAV flight paths are obtained to reduce the time of data acquisition tasks.