Research On Uplink Interference Management Technology In Cellular-connected UAV Networks

As a new type of mobile terminal equipment,UAVs are widely used in emergency communication,remote sensing and telemetry,intelligent patrol and other fields.It has become one of the most promising UAVs communication solutions by connecting UAVs to cellular mobile communication system and providing coverage support and mobility management for UAVs with the help of wide-area coverage and ubiquitous interconnection characteristics of cellular network.However,due to the downdip of the traditional deployed base station antenna,the UAVs can only obtain communication services through the side lobe of the base station antenna with low gain,which weakens the uplink signal intensity.At the same time,the line-of-sight propagation characteristics of air-ground channel produce serious interference problem,which affects the uplink transmission performance of UAVs.Aiming at the above problems,this dissertation carried out research on uplink interference management technology of cellular UAVs,and made joint use of Coordinated Multi-Point(Co MP),directional antenna and uplink power control technologies to alleviate the uplink interference of UAVs.The specific research contents and innovative work contents are as follows:(1)Research on Co MP based uplink interference mitigation technology for cellular network UAVs.Firstly,considering the fading characteristics of air-to-ground channel mixed with line-of-sight transmission,an up-Co MP strategy based on average strongest signal receiving power is proposed to determine the cooperative base station set of typical UAVs.Secondly,considering the spatial geometry distribution characteristics of UAVs,the joint probability density function of association probability and link length between typical UAVs and different cooperative base station sets is derived under the ascending Co MP strategy.Furthermore,the geometry geometry theory is used to model the interference distribution of the network,and the theoretical expressions of the uplink coverage and area spectrum efficiency of UAVs are derived.The theoretical and simulation results show that the uplink transmission strategy based on Co MP can effectively suppress intercell interference and improve the uplink coverage and area spectrum efficiency of UAVs.(2)On the basis of research content(1),the application of directional antenna model for UAV is considered to study the mitigation effect of directional antenna technology on uplink interference.First,based on geometry and probability theory,the joint probability density function of association probability and link length between typical UAVs and different cooperative base station sets under directional antenna model is derived.Secondly,using stochastic geometry and calculus theory,the theoretical expressions of uplink coverage and area spectrum efficiency of typical UAVs are derived.The theoretical and simulation results show that the Co MP strategy based on directional antenna technology can further alleviate the uplink cumulative interference and improve the uplink transmission performance of UAVs by adjusting the beam width of directional antenna reasonably.(3)On the basis of contents(1)and(2),the suppression effect of power control technology on uplink interference is studied.Firstly,the transmission power of UAVs under line-of-sight and non-line-of-sight transmission conditions is analyzed after partial power control technology is adopted.Secondly,according to the compensated transmission power,the association probability and joint probability density function of link length from typical UAVs to the cooperative base station set,as well as the theoretical expressions of UAVs uplink coverage and area spectrum efficiency are derived,and the effects of different power control factors on network performance are quantified.The theoretical and simulation results show that the uplink power control technology further inhibits the cumulative interference of the network and improves the transmission performance of the UAVs by reducing the transmitting power of the UAVs.Finally,in the given network scenario with Non Co MP transmission strategy as the benchmark,we analyzed the Co MP strategy,directional antenna strategy and power control strategy of the mitigation and suppression effect of the strongest effect,Co MP strategy alleviate interference effect is strong,power control strategy alleviate interference effect is weak.