Browsing by Author "Liu, Yanming"
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Item Joint Beam and Power Control for Millimeter-Wave Multi-Flow Multi-Hop Networks(IEEE Communications Letters, 2024-08-16) Liu, Yanming; Mao, Haobin; Zhu, Lipeng; Xiao, Zhenyu; Xia, Xiang-GenThis letter investigates the joint beam and power control in multi-flow multi-hop networks with millimeter-wave (mmWave) directional transmissions. To guarantee fairness among multiple data flows, an optimization problem is formulated to maximize the minimum of the achievable rates for all flows by jointly optimizing three-dimensional (3D) antenna boresights and transmit powers. To address the non-convex problem, we employ the block coordinate descent (BCD) method to solve two subproblems iteratively. Specifically, each iteration involves solving the transmit power control subproblem by using successive convex approximation (SCA) techniques. Then, suboptimal antenna boresights, including the azimuth and elevation angles for multiple transmitters, are obtained by using a tailored particle swarm optimization (PSO) algorithm. The simulation results reveal the effectiveness and superiority of the proposed algorithm in enhancing the minimum end-to-end achievable rate (E2EAR) compared to the benchmark schemes.Item Joint Resource Allocation and 3D Deployment for Multi-UAV Covert Communications(IEEE Internet of Things Journal, 2023-07-05) Mao, Haobin; Liu, Yanming; Xiao, Zhenyu; Han, Zhu; Xia, Xiang-GenUnmanned aerial vehicles (UAVs) assisted wireless communication will play an important role in the next-generation mobile communication network. However, the inherent open nature of the signal propagation environment may cause illegal eavesdropping and surveillance from adversaries. In addition, the intergroup co-channel interference among different cells further degrades the system performance. Hence, we consider a generic scenario of multiple UAV base stations (UAV-BSs) and ground users, where multiple terrestrial wardens attempt to detect the transmissions from UAV-BSs to users and a UAV-mounted jammer is employed to generate artificial noise to assist the covert communications. To ensure fairness, we formulate an optimization problem to maximize the minimum of the average rate lower bounds of all users by jointly optimizing user association, bandwidth allocation, UAV transmit power control, and UAV three-dimensional (3D) deployment, subject to the constraints of the detection error probability of each warden. To solve this mixed-integer non-convex problem, we propose a suboptimal algorithm by applying block coordinate descent (BCD) method to solve three subproblems iteratively. Specifically, in each iteration, the subproblem of user association and bandwidth allocation is solved by a customized genetic algorithm (GA) first, where a closed-form expression for bandwidth allocation is obtained. Second, the subproblem of UAV transmit power control is solved by using successive convex approximation (SCA) techniques. Finally, suboptimal 3D positions of the UAVs are obtained through particle swarm optimization (PSO) based algorithm. Extensive simulation results demonstrate the effectiveness and superiority of our proposed algorithm compared to benchmark schemes in terms of improving the minimum of the average rate lower bounds of all users.