Research On Quality Of Service Optimization Technology Of Agricultural UAV Ad Hoc Network

In recent years,more and more electronic equipment has been put into the environment of agricultural production by increasing the research on agricultural Internet of things and intelligent agriculture at home and abroad.This makes the Limited website resources of rural mountain environment more and more tense.In addition,due to the sparsely populated and complex terrain in rural areas,the cost of base station installation in rural mountainous areas is high,the density is low,and the coverage of base station signal is small,so that most of the agricultural environment has a blank area without signal coverage.How to effectively solve the network coverage and service quality of rural agricultural complex environment has become a bottleneck problem in the development of the agricultural Internet of Things.It is more and more important to study a wireless ad hoc network system with wide coverage,high efficiency,low delay and low bit error rate in rural areas.In order to solve the above problems,this paper considers that the micro network base station is carried to every UAV based on the traditional Ad Hoc network.According to the distance perception and measurement between UAVs and the specific network arrangement criteria,the cluster heterogeneous system of UAV Ad Hoc network that fits the actual agricultural environment is built by itself.On the basis of this system,further research is performed on the optimization of spectrum resource allocation and the optimal response strategy between each UAV,so as to improve the spectrum utilization rate and the response capability of the UAV's spectrum perception.At the same time,the optimization schemes of the maximum total transmission rate and the best power allocation between the network of UAV-cluster-heads-to-user-nodes and the network of UAV-usernodes-to-terminal-nodes are also studied separately,thereby improving the network transmission efficiency in the agricultural environment.The specific research work of this paper is as follows:First of all,for the overall design of the cluster heterogeneous system of UAV Ad Hoc network,the clustering criteria,spectrum allocation scheme,and optimal spectrum response strategy of the UAVs are considered.Combined with K-means clustering method,the heterogeneous system is built by using the mutual distance measured by UAVs.On this basis,taking into consideration the spectrum utilization of each UAV and their interrelationships,it is ensured that the idle spectrum is used reasonably.Based on the non-cooperative game bidding,a spectrum allocation strategy model for multiple drones is established,and the best spectrum game bidding scheme under the optimal idle spectrum pricing is obtained to maximize the utility spectrum in the network system.For the optimal spectrum response strategy,various time overheads in each frame of time,false alarm probability and detection probability are introduced to Analyze and establish the relationship of the total system information throughput,the spectrum sensing response time,transmit power,and number of drone cluster heads.The results show that there is a maximum value of the total information throughput,and the optimal transmit power and optimal spectrum sensing response time at this time are obtained.Afterwards,for the resource allocation of single-UAV-cluster-head-to-single-UAV-user-nodes under the condition of multiple clusters,considering the impact of delay and jitter on the transmission performance of the UAVs during flight and hovering,the corresponding delay penalty function and jitter penalty function are introduced.Combined with the admission control of ad hoc network nodes,an orthogonal frequency division multiplexing network(OFDM)model with maximum total transmission rate is established under power allocation.In addition,based on the nonlinear optimization theory,a cognitive power water-filling algorithm is proposed,and the optimal power allocation value under each subcarrier is obtained through iterative updating.In the case of multiple UAV-user-nodes,the above method is generalized and extended,and a subcarrier and power joint allocation water-filling algorithm is proposed based on multi-cluster-heads-tomulti-user-nodes.The results show that this method can reduce the computational complexity and achieve better transmission performance under the same power allocation;the system can also have lower power loss under same transmission performance.Ultimately,aiming at the complex environmental problems of air-to-ground communication,considering the complexity of ground interference,a method of adaptive optimal resource allocation is proposed by combining multiple quadrature amplitude modulation(MQAM)and OFDM between UAV user nodes and terminal nodes.This method can adaptively select the optimal base number for amplitude modulation according to the interference situation of the current network environment.And on the premise of ensuring the transmission rate,it also enhances the anti-interference ability of the network.Then,fast iterative updates are performed by decomposing the Lagrangian function and the sub-gradient dual coefficients to find the optimal power allocation to maximize the average subcarrier transmission rate under satisfying the constraints.The results show the method can not only make up for the problem of low anti-interference of 64 QAM modulation,but also solve the problem of low transmission performance of 32 QAM at some power;moreover,the transmission performance of the method is slightly better than that of the interior point method,and the spectrum utilization rate is higher and the anti-interference is stronger under the method.