Browsing by Author "Han, Zhu"

Now showing 1 - 4 of 4

An Integrated Affinity Propagation and Machine Learning Approach for Interference Management in Drone Base Stations
(2020-03-01)
Wang, Li-Chun
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Chao, Yung-Sheng
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Cheng, Shao-Hung
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Han, Zhu
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電機工程學系
Drone small cells (DSCs) can provide on-demand air-to-ground wireless communications in various unexpected situations, such as traffic jam or natural disasters. However, a DSC needs to face the challenges such as severe co-channel interference, limited battery capacity, and fast topology changes. Aiming to improve energy efficiency of DSCs and quality of services of customers, this paper presents a learning-based multiple drone management (LDM) framework by controlling the transmission power and the 3-dimension location of DSCs based on location data, and reference signal received power of users. Since the labeled throughput data are typically not available in emergency situations, we develop unsupervised learning DSC management techniques: 1) affinity propagation interference management scheme to mitigate interference and energy consumption, and 2) K-means position adjustment to adjust the new 3-dimension positions of drones. Our numerical results show that the proposed LDM framework combining with affinity propagation clustering and k-means clustering can enhance the energy efficiency of DSCs by 25% and the signal-to-interference-plus-noise ratio of ground users by 56%, respectively.
Data-Driven 3D Placement of UAV Base Stations for Arbitrarily Distributed Crowds
(2019-01-01)
Lai, Chuan-Chi
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Wang, Li-Chun
;
Han, Zhu
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電機工程學系
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Department of Electrical and Computer Engineering
In this paper, we consider an Unmanned Aerial Vehicle (UAV)-assisted cellular system which consists of multiple UAV base stations (BSs) cooperating the terrestrial BSs. In such a heterogeneous network, for cellular operators, the problem is how to determine the appropriate number, locations, and altitudes of UAV-BSs to improve the system sumrate as well as satisfy the demands of arbitrarily flash crowds on data rates. We propose a data-driven 3D placement of UAV-BSs for providing an effective placement result with a feasible computational cost. The proposed algorithm searches for the appropriate number, location, coverage, and altitude of each UAV-BS in the serving area with the maximized system sumrate in polynomial time so as to guarantee the minimum data rate requirement of UE. The simulation results show that the proposed approach can improve system sumrate in comparison with the case without UAV-BSs.
Distributed User-centric Clustering and Base Station Mode Choose in Ultra Dense Networks
(2019-01-01)
Wu, Zhikun
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Fei, Zesong
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Han, Zhu
;
Wang, Li-Chun
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電子工程學系及電子研究所
To cope with the exponential growth of demand, ultra dense networks (UDNs) are a promising technology in future mobile networks. With small cells densely deployed in networks, how to allocate wireless resources in UDNs efficiently becomes a challenging research topic. In this paper, we concentrate on the distributed user-centric clustering and base station (BS) mode choose problem in UDNs. We formulate a combinatorial optimization problem, with the throughput maximization and power consumption minimization jointly considered in the optimization object. In order to reduce the complexity of the problem, we decompose the original problem into two subproblems in terms of user-centric clustering and BS mode choose, and then solve those subproblems by the max-sum algorithm in sequence. The proposed algorithm can be conducted in a distributed way, and the computational complexity grows linearly with the network size. Simulation results show that the performance of proposed algorithm approaches the performance of the exhaustive algorithm well, and outperforms the conventional algorithm significantly.
UAV-Assisted Wireless Charging for Energy-Constrained IoT Devices Using Dynamic Matching
(2020-06-01)
Su, Chunxia
;
Ye, Fang
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Wang, Li-Chun
;
Wang, Li
;
Tian, Yuan
In the emerging Internet-of-Things (IoT) paradigm, the lifetime of energy-constrained devices (ECDs) cannot be ensured due to the limited battery capacity. In this article, unmanned aerial vehicles (UAVs) are served as carriers of wireless power chargers (WPCs) to charge the ECDs. Aiming at maximizing the total amount of charging energy under the constraints of the UAVs and WPCs, a multiple-period charging process problem is formulated. To address this problem, bipartite matching with one-sided preferences is introduced to model the charging relationship between the ECDs and UAVs. Nevertheless, the traditional one-shot static matching is not suitable for this dynamic scenario, and thus the problem is further solved by the novel multiple-stage dynamic matching. Besides, the wireless charging process is history dependent since the current matching result will influence the future initial charging status, and consequently, the Markov decision process (MDP) and Bellman equation are leveraged. Then, by combining the MDP and random serial dictatorship (RSD) matching algorithm together, a four-step algorithm is proposed. In our proposed algorithm, the local MDPs for the ECDs are set up first. Next, using the RSD algorithm, all possible actions can be presented according to the current state. Then, the joint MDP is built based on the local MDPs and all the possible matching results. Finally, the Bellman equation is utilized to select the optimal branch. Finally, simulation results demonstrate the effectiveness of our proposed algorithm.