Browsing by Author "Lin, Jiaru"

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DATA-COGNITION-EMPOWERED INTELLIGENT WIRELESS NETWORKS: DATA, UTILITIES, COGNITION BRAIN, AND ARCHITECTURE
(2018-02-01)
Xu, Wenjun
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Xu, Yue
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Lee, Chia-Han
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Feng, Zhiyong
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Zhang, Ping
With the proliferation of heterogeneous wireless networks, classical information-theoretical methods can no longer provide accurate mathematical models to analyze the complicated network performance for the regulation and optimization of networks. The emerging landscape of big data and machine learning has provided a new paradigm for the design and optimization of intelligent wireless networks. In this article, a general architecture for data-cognition-empowered intelligent wireless networks is proposed. Characteristics of wireless data, the frequently used utilities for data cognition, and data cognition methods are discussed to depict the building blocks and challenges in the exploration of the architecture for data-cognition-empowered intelligent wireless networks.
Energy-Efficient Joint Sensing Duration, Detection Threshold, and Power Allocation Optimization in Cognitive OFDM Systems
(2016-12)
Xu, Wenjun
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Zhou, Xuemei
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Lee, Chia-Han
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Feng, Zhiyong
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Lin, Jiaru
This paper investigates an energy efficiency optimization problem in cognitive orthogonal frequency division multiplexing systems. The goal is to maximize the energy efficiency by adapting the sensing duration, detection threshold, and transmit power to the constraints of the energy consumption of the secondary network and the interference to the primary network in a statistical manner. First, the case of identical detection threshold for all subcarriers is considered. In order to circumvent the intractability of the resulting problem, an alternate iteration framework is proposed to iteratively solve the three decoupled subproblems: sensing duration optimization, detection threshold optimization, and power allocation optimization. By exploiting the characteristics of each subproblem, the proposed framework is proved to be convergent. Then, the case with individual detection threshold for each subcarrier is explored. By proving that the optimal detection threshold is the root of a quadratic equation with one unknown variable, the proposed framework can be applied with minor modification. Simulation results show that the proposed alternating optimization framework can approach rapidly to the optimal solution, with less than 1% gap. Compared with the existing schemes, both the cases with identical and individual detection thresholds can achieve a considerable energy efficiency gain, with the latter further outperforming the former.
Joint Beamforming and Time Duration Optimization for Battery-free-Multi-Antenna-Relay-Assisted WPCN
(2018-01-01)
Yang, Fan
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Xu, Wenjun
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Lee, Chia-Han
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Feng, Zhiyong
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Lin, Jiaru
This paper studies an energy beamforming and time duration joint optimization problem for maximizing the sum-rate of a battery-free-multi-antenna-relay-assisted wireless powered communication network (WPCN). The considered problem is non-convex due to the strongly coupled optimization variables. By introducing new optimization variables and reformulating the problem into a convex problem, the optimal solution is obtained based on convex optimization methods. Furthermore, an alternate iteration algorithm is proposed by decoupling the problem into two subproblems, and a semi-closed form solution of the optimal energy beamforming matrix is derived with given time allocation. Simulation results indicate that the proposed battery-free multiantenna relay architecture can deliver a significant sum-rate gain for the WPCN. In addition, the proposed suboptimal algorithm only has 5% sum-rate loss compared to the optimal solution.
Optimal Beamforming and Duration/Power Allocation for Cooperative PB-enabled WPCN
(2017-01-01)
Shi, Xinxin
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Xu, Wenjun
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Lee, Chia-Han
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Feng, Zhiyong
;
Lin, Jiaru
This paper studies the spectrum efficiency (SE) maximization problem for cooperative multi-antenna power beacon (PB)-enabled wireless powered communication networks (WPCN), where each transmitter harvests energy from surrounding PBs and then transmits data to the corresponding receiver within its allocated duration. The considered problem is formulated as jointly optimizing the energy beamforming vectors of PBs, the transmission duration, and the transmit power of users to maximize the total SE. In order to derive an efficient algorithm, the SE maximization problem is decomposed into two subproblems: the SE maximization problem for data transmission and the energy consumption minimization problem for energy transfer. We prove that the optimal SE is concave with the harvested energy of each user, and based on this concavity, an efficient algorithm is proposed to achieve the optimal solution. Finally, simulation results validate the optimality of the proposed algorithm, and verify the superiority of the proposed scheme-more than 150% performance gain is obtained, compared with the scheme of single PB with single antenna.