Research On Fixed-wing UAV Trajectory Optimization For Data Collection

Unmanned aerial vehicles(UAVs)are expected to play an important role in the future wireless communication systems.Compared with the traditional wireless communications,the UAVs have the ability of on-demand and swift deployment.And the high flexibility makes the UAVs useful to provide wireless connectivity for users out of coverage.In general,UAVs can be classified into fixed-wing UAVs and rotary-wing UAVs according to the architectural difference.The choice of UAVs critically depends on the applications.Firstly,the thesis review recent researches of data collection by UAVs.There are some UAV-to-ground channel models used in researches,like free-space path loss model,altitude-dependent channel model,elevation angle channel parameters and so on.Prior researches on UAV-enabled wireless communications considered the application scenarios where UAVs are employed as mobile base stations(BSs)/relays.The performance metric of UAV Communication including signal to interference-plus-noise ratio,outage probability,communication throughput/delay.In this thesis,it focus on limits of fixed-wing UAV and the requirement of throughput.Secondly,the thesis studies an energy-efficient UAV-enabled wireless communication system with a new trajectory design to collect and forward data between two ground node(GNs)sequentially.Due to limits of fixed-wing UAV,The RT trajectory model consisting of the straight part and circular part is proposed.The objective is to minimize the UAV’ s propulsion energy consumption while ensuring that the communication requirement for the GN is satisfied.Numerical results show that the RT trajectory model can obtain the optimal radius and length with less propulsion energy consumption.And the RT trajectory for UAV can reduce the energy consumption compared to straight line trajectory and circular trajectory.Thirdly,a scene that UAV collect data across many GNs in confined region has been researched.The UAV with communication equipment fly across the GNs to collect the data.Different from the existing works that assume the simplified line-of-sight(LoS)UAV-ground channels,this thesis consider an angle-dependent Rician fading channels between the UAV and GNs with the Rician factors.And then take the outage probability into consideration.The objective is to minimize the UAV’s flying time while ensuring that the communication requirement for GN in each cell is satisfied.As such,the thesis further propose an efficient algorithm to derive its suboptimal solution by using the block coordinate descent technique,which iteratively optimizes the UAV’ s horizontal trajectory,and its vertical trajectory.The light-of-sight channel and Rician channel are compared to study the effect of achievable rate.Numerical results show that adjusting the flying height and horizontal traj ectory can obtain the optimal flying time.Lastly,the innovation points of this thesis are concluded.And there are many significate researches about UAV data collocation in the future.The communication by UAV will be a useful way for future wireless communication.