Research On Energy Efficient Communication Strategies Based On Unmanned Aerial Vehicles

With the development of UAV related disciplines,such as materials sci-ence,control science and communication technology,unmanned aerial vehicle(UAV)technology has gradually matured.UAV can mount relevant equipments to provide aerial photography services,logistics and distribution services,agri-cultural plant protection services,communication services,emergency rescue services and other services,which brings a lot of convenience for people's daily life.In various applications of UAV s,UAV-assisted communications have been the focus of academic and industrial research in recent years.Especially with the commercial use of 5th Generation MobileNetworks(5G),the number of users and the traffic greatly increase and a variety of network services emerge.It is difficult for the traditional ground network communication facilities to guar-antee the communication demand of terminal devices due to the high operation costs,the affect of geographical environment and the poor flexibility.Thanks to the advantages of high mobility,easy deployment and low cost,UAVs can mount communication services related equipment and fly to the specific areas to provide on-demand,flexible and reliable communication services,which ef-fectively makes up for the deficiency of existing network facilities.However,due to the limited size of the UAV,the load of the UAV and the bottleneck of battery related technology,the battery capacity of UAV is limited.Hence,the duration of UAV and the quality of communication network based on UAV are greatly affected.Therefore,under the constraint of the limited lifetime of the UAV,it is important to design energy efficient communication strategies based on UAV to realize the energy efficient dynamic deployment,the energy effi-cient connection establishment and the energy efficient business supply.It is also important to improve the transmission efficiency,the access efficiency and the computation efficiency of the communication network based on UAV to sat-isfy the communication requirements of the ground users under the constraint of the limited lifetime of the UAV.In order to solve the above problems,this paper carries out detailed strate-gies research of transmission efficiency,access efficiency and computation effi-ciency from the aspects of the network deployment,network connection estab-lishment and network services provision based on UAVs.Firstly,considering the communication requirements of ground users,it is necessary to provide en-ergy efficient dynamic network deployment based on UAVs with the goal of reducing the energy consumption of the UAVs and guaranteeing the transmis-sion efficiency in order to provide energy efficient dynamic network deploy-ment based on UAV.Then,to satisfy different communication requirements of massive ground users,the differentiated pre-backoff access design is proposed.The proposed design can effectively reduce the energy consumption to access the network and improve the access efficiency.At last,the energy efficient offloading strategy is proposed to optimize the trajectory of the UAV and the bits allocation with the focus of the computation offloading power consumption in order to enhance the computation efficiency.With regard to the aforemen-tioned three aspects,the main research contents and innovations in this paper are summarized as follows:1.Research on energy efficient and dynamic deployment strategy based on UAVIn order to provide energy efficient communication services based on UAV,how to deploy the UAVs in appropriate positions to provide on-demand com-munication services for ground users and guarantee the transmission efficiency should be firstly considered.Different from the existing research which fo-cus on the covered users or the coverage area of the UAV,this paper proposes energy efficient deployment strategy based on UAV focusing on the energy ef-ficiency of ground users.Besides,this paper first consider the scenario when the multi-UAV based network change,such as a certain UAV leaves for mal-function or drained battery.First of all,by considering the number of trans-mitting data and data transmission energy consumption,the concept of energy efficiency of ground users is introduced and the deployment of multiple UAVs is modeled.The iterative algorithm based on successive convex approximation(SCA)is put forward to get the optimal deployment,the transmitting power of the ground users and the users association.Secondly,by creatively introducing the scenario when the network changes because of the change of the number of UAVs,the energy consumption of the UAV when ensuring the communica-tion quality is modelled.By applying the iterative algorithm based on SCA,the trajectory of the UAV and the users association are jointly optimized.Fi-nally,comparing with the existing strategies,the simulation results verify that the proposed energy efficient deployment strategy can effectively improve the energy efficiency of ground users.And the emergency movement strategy can efficiently reduce the energy consumption of the UAV while ensuring the com-munication quality of ground users compared with the existing strategies.The transmission efficiency is improved and the energy efficient deployment based on UAV is realized.2.Research on the energy efficient network connection establishment strategy based on UAVAfter the communication network based on UAV is deployed,it is nec-essary to establish efficient network connection between ground users and the UAVs.To handle the massive and diverse network access requests,this paper first proposes a independent pre-backoff window division design to satisfy the differentiated requirements of ground users.And the energy efficient strategy of network connection establishment based on the differentiated requirements is proposed to guarantee the network access efficiency.Firstly,ground users are divided into different priorities according to different quality of service(QoS)requirements of business.The ground users are assigned with different pre-backoff windows and perform the pre-backoff process and access process dur-ing the corresponding pre-backoff windows.Secondly,the network connection establishment process is modeled and analyzed to realize the pre-backoff adap-tive adjustment for users with different priorities.The access time of ground users is effectively dispersed and the collision caused by simultaneous access is avoided.Finally,comparing with traditional pre-backoff design,the simulation results verify that the proposed energy efficient network connection establish-ment strategy for differentiated users can effectively guarantee the validity of the network connection establishment.The number of retransmission is de-creased to reduce the energy consumption of the ground users and the UAV.The time of duration when the UAV can provide communication services is pro-longed.The differentiated requirements of ground users are guaranteed while the congestion and overload are alleviated.The energy efficient connections establishment based on UAV is realized.3.Research on efficient binary offloading strategy based on UAVThe communication network based on UAV can provide the offloading services to relieve the computing pressure of ground users after the network connection is established.Different from the existing research only focusing on optimization of the energy consumption of ground users or the UAV,this paper jointly considers the energy limitation of the ground users and the UAV.The paper proposes the energy efficient offloading strategy based on UAV us-ing the binary offloading mode,which can relieve the computing pressure of the ground users and guarantee the energy efficient operation of the offloading system based on UAV.First of all,when all the computing tasks of the ground users are offloaded to the UAV,the energy consumption of the UAV and the ground users are modeled,considering the UAV's energy budget,data causality and speed limits.The trajectory of the UAV and the bits allocation are jointly optimized.Secondly,a two-stage alternating algorithm based on Lagrangian duality is proposed in order to solve the energy minimization problem of the offloading system based on UAV.The optimization problem can be solved by solving two sub-problems which are easy to deal with.Finally,comparing with the other schemes,the simulation results show that the proposed efficient binary offloading strategy based on UAV can effectively reduce energy consumption of the system and improve the lifetime of the system.The efficient binary of-floading services are realized while the computation requirements of the ground users are guaranteed and the computation efficiency is guaranteed.4.Research on efficient partial offloading strategy based on UAVDifferent from the existing research only focusing on the energy consump-tion of the UAV or the number of computation offloading tasks,this paper proposes an energy efficient offloading strategy based on UAV in the partial offloading mode.In this paper,the computation offloading efficiency is in-troduced and the energy efficient partial offloading strategies is proposed to improve the computation efficiency.First of all,considering the total energy consumption of the UAV and the number of offloading bits when the ground users offload part of the tasks to the UAV,the concept of the energy efficiency of the UAV is introduced.The trajectory of the UAV,the ratio of offloading tasks of the ground users and the bits allocation are jointly optimized consid-ering the position constraints and energy constraints of the UAV and the data causality.Secondly,the SCA based iterative algorithm is proposed to solve the energy efficiency maximization problem of the UAV.The non-convex opti-mization problem is simplified by solving two sub-problems.Finally,compar-ing with other strategies,the simulation results show that the proposed energy efficient partial offloading strategy based on UAV-assisted communication can effectively improve the energy efficiency of the UAV.And the computation of-floading efficiency is improved to realize the energy efficient partial offloading based on UAV.