Research On Power Allocation Technology For UAV-assisted Relay Communication In IoT

The fifth generation(5G)mobile communication is an inter-generational technology and has three application scenarios: enhanced mobile broadband(e MBB),ultra reliable and low latency communication(URLLC)and massive machine type communication(m MTC).The seamless connection between 5G mobile communication technology and internet of things(Io T)technology has further expanded the application scope of Io T,including urban management,medical and health,smart grid,green agriculture,security monitoring,smart home and other fields.Due to the large number of sensor nodes,less energy storage,and long-distance transmission in Io T networks,it is difficult to build a comprehensive and broad coverage Io T communication system.Because the unmanned aerial vehicle(UAV)has good mobility and simple deployment,it can be integrated into the Io T communication technologies to solve the problem of limited coverage of the Io T,thereby achieving more flexible and diversifing Io T applications.As an important resource of the drone communication system,power allocation will directly affect the performance of each link.Therefore,this thesis studies the power control problem of the drone-assisted Io T relay communication system.The main contributions of this thesis are outlined as follows:1.For the UAV-assisted Io T multi-relay communication systems,the optimization problem is established with the constraints of the total transmission power and each relay transmission power and the objective function of maximizing the system throughput.The optimal power allocation(OPA)scheme based on the known complete channel state information(CSI)and statistical CSI is proposed respectively.Then,the selection amplify-and-forward(S-AF)scheme based on partial relay participation is studied.The simulation results show that the performance of the complete CSI-based optimization scheme is better than that of the statistical CSI under low signal-to-noise ratio(SNR)environments,and the OPA scheme can achieve the maximum system throughput when selecting the best relay for transmission under the known complete CSI conditions.2.For the UAV-assisted cognitive Io T relay communication system,firstly,when amplify-and-forward(AF)and decode-and-forward(DF)protocols are used at the relay nodes,and space-time block code(STBC)technologies are combined to collaborate on relay transmission.An optimization problem is established to maximize the throughput of the cognitive Io T relay network under the constraints of cognitive Io T user's transmission power limitation and ensuring the quality of service of the Io T Primary user.Then,using the combination of Lagrange multiplier method and KKT condition,we get the optimal power allocation scheme.Finally,the simulation results show that the throughput of cognitive Io T relay network under the DF relay protocol is better than that under the AF relay protocol.3.For the UAV-assisted relay Io T communication system under the optimal energy efficiency criterion,firstly,the AF protocol is considered at the relay node,and an optimization problem is established,which takes the total relay transmission power and individual relay transmission power constraints as the constraints and maximizes the energy efficiency of the relay node as the objective function.Then,the optimal power allocation scheme is obtained by combining Lagrange multiplier method and KKT condition.Finally,the simulation results show that the proposed power allocation scheme achieves greater system energy efficiency than the equal power allocation scheme and the power allocation scheme designed to optimize the signal-to-noise ratio.