To ensure the thriving development of low-altitude economy, countering unauthorized unmanned aerial vehicles (UAVs) is an essential task. The existing widely deployed base stations hold great potential for joint communication and jamming. In light of this, this paper investigates the joint design of beamforming to simultaneously support communication with legitimate users and countermeasure against unauthorized UAVs based on dual-functional multiple-input multiple-output (MIMO) cellular systems. We first formulate a joint communication and jamming (JCJ) problem, relaxing it through semi-definite relaxation (SDR) to obtain a tractable semi-definite programming (SDP) problem, with SDR providing an essential step toward simplifying the complex JCJ design. Although the solution to the relaxed SDP problem cannot directly solve the original problem, it offers valuable insights for further refinement. Therefore, we design a novel constraint specifically tailored to the structure of the SDP problem, ensuring that the solution adheres to the rank-1 constraint of the original problem. Finally, we validate effectiveness of the proposed JCJ scheme through extensive simulations. Simulation codes are provided to reproduce the results in this paper: https://github.com/LiZhuoRan0. The results confirm that the proposed JCJ scheme can operate effectively when the total number of legitimate users and unauthorized UAVs exceeds the number of antennas.

翻译：为确保低空经济的蓬勃发展，反制非法无人机是一项关键任务。现有广泛部署的基站具备实现通信与干扰联合功能的巨大潜力。鉴于此，本文研究基于双功能多输入多输出（MIMO）蜂窝系统，通过联合波束成形设计，在支持合法用户通信的同时实现对非法无人机的反制。我们首先构建了一个通信与干扰联合（JCJ）问题，通过半定松弛（SDR）将其松弛为一个可处理的半定规划（SDP）问题，SDR为简化复杂的JCJ设计提供了关键步骤。虽然松弛后的SDP问题的解不能直接用于求解原问题，但它为进一步优化提供了重要参考。因此，我们针对SDP问题的结构，专门设计了一种新颖的约束条件，以确保其解满足原问题的秩-1约束。最后，我们通过大量仿真验证了所提JCJ方案的有效性。本文提供了仿真代码以复现结果：https://github.com/LiZhuoRan0。结果证实，当合法用户与非法无人机的总数超过天线数量时，所提JCJ方案仍能有效运行。