Research On Formation Communication Technology Of UAV Based On Multi-beam NOMA

Unmanned aerial vehicles(UAV)have been applied more and more widely in various fields due to their low cost,high flexibility and easy deployment.The coordinated operation of UAV formation can make up for the shortcomings of a single UAV’s limited capabilities,making the task execution more efficient,and improving the reliability of the system.The mobile communication network covers a wider range compared to the WIFI network,and the UAV formation system based on the mobile communication network is an inevitable development trend in the future.The non-orthogonal multiple access(NOMA)technology and millimeter-wave Massive MIMO technology in the 5G system provide large connection and high throughput features,which can meet the need of UAV formation communication.However,there are still some problems with these two technologies in UAV formation communication.This paper proposes some improvement schemes to solve these problems.The specific research results and contributions are summarized as follows:The short wavelength of millimeter-wave,large penetration loss,and weak diffraction ability lead to its line-of-sight(LOS)propagation.When the NOMA technology is applied to a millimeter-wave Massive MIMO system,multiple users must be within the coverage of the same beam to transmit using NOMA technology.However,there may be hundreds or thousands of antenna elements in Massive MIMO system,which makes the width of beam generated by the base station beam forming very small.To a large extent,the beam limits the user grouping in the NOMA system,resulting in little performance improvement of the system brought by the NOMA technology.In order to solve this problem,this paper proposed a beamforming scheme that can generate multi-directional beams by dividing the antenna array into sub-arrays,so that users in the NOMA system can be grouped flexibly.At the same time,the proposed multi-beam beamforming scheme is extended from the two-dimensional beamforming system based on ULA to the three-dimensional beamforming system based on URA.The simulation results show that the proposed multi-beam beamforming scheme can generate beams pointing in multiple directions int both 2D and 3D scenes,which indicate the effectiveness of the scheme.When applying the multi-beam beamforming technology to a specific NOMA transmission scenario,it is necessary to allocate resources such as user grouping,antenna elements,and transmission power reasonably in order to obtain optimal system performance.Compared with the single-cell scenario,the resource allocation in the multi-cell scenario is also affected by the interference between the cells.This paper takes the total transmission rate of the system as the optimization goal and establishes a mathematical model of resource allocation in the multi-cell multi-user scenario.In order to reduce the complexity of the algorithm,a two-stage resource allocation algorithm is adopted in this paper.In the first stage,we assume that the user’s power allocation is known,we proposed a user grouping and antenna elements allocation algorithm based on the alliance game theory.In the second stage,based on the results of user grouping and antenna elements allocation in the first stage,an algorithm of user power allocation is proposed.The simulation results show that the two-stage resource allocation algorithm proposed in this paper can allocate system resource effectively,thereby improving the transmission rate of the system.