human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "optimized training design for wireless energy transfer"
  Abstract: Radio-frequency (RF) enabled wireless energy transfer (WET), as a promising solution to provide cost-effective and reliable power supplies for energy-constrained wireless networks, has drawn growing interests recently. To overcome the significant propagation loss over distance, employing multi-antennas at the energy transmitter (ET) to more efficiently direct wireless energy to desired energy receivers (ERs), termed \emph{energy beamforming}, is an essential technique for enabling WET. However, the achievable gain of energy beamforming crucially depends on the available channel state information (CSI) at the ET, which needs to be acquired practically. In this paper, we study the design of an efficient channel acquisition method for a point-to-point multiple-input multiple-output (MIMO) WET system by exploiting the channel reciprocity, i.e., the ET estimates the CSI via dedicated reverse-link training from the ER. Considering the limited energy availability at the ER, the training strategy should be carefully designed so that the channel can be estimated with sufficient accuracy, and yet without consuming excessive energy at the ER. To this end, we propose to maximize the \emph{net} harvested energy at the ER, which is the average harvested energy offset by that used for channel training. An optimization problem is formulated for the training design over MIMO Rician fading channels, including the subset of ER antennas to be trained, as well as the training time and power allocated. Closed-form solutions are obtained for some special scenarios, based on which useful insights are drawn on when training should be employed to improve the net transferred energy in MIMO WET systems.

Connected through hyperedge HE-1 (induced by source paper "wirelessly powered sensor networks power allocation for channel estimation and energy beamforming"):
  with members:
    - "cluster based wireless energy transfer for low complex energy receivers"
    - "wireless energy beamforming using received signal strength indicator feedback"
    - "on the beneficial roles of fading and transmit diversity in wireless power transfer with nonlinear energy harvesting"
    - "waveform design for wireless power transfer with limited feedback"
    - "distributed wireless power transfer with energy feedback"
    - "robust resource allocation for mimo wireless powered communication networks based on a non linear eh model"
    - "on the feasibility of wireless energy transfer using massive antenna arrays"
    - "waveform design for wireless power transfer"

Connected through hyperedge HE-2 (induced by source paper "a retrodirective wireless power transfer scheme for ambient backscatter systems"):
  with members:
    - "design of ambient backscatter training for retrodirective wireless power transfer"
    - "retrodirective large antenna energy beamforming in backscatter multi user networks"
    - "retrodirective multi user wireless power transfer with massive mimo"
    - "modulation in the air backscatter communication over ambient ofdm carrier"
    - "performance analysis of massive mimo for cell boundary users"
    - "joint wireless information and energy transfer with reduced feedback in mimo interference channels"
    - "energy beamforming with one bit feedback"
    - "joint beamforming design for multi user wireless information and power transfer"

Connected through hyperedge HE-3 (induced by source paper "covert transmission with a self sustained relay"):
  with members:
    - "achieving covert wireless communications using a full duplex receiver"
    - "multi hop routing in covert wireless networks"
    - "covert communication achieved by a greedy relay in wireless networks"
    - "wireless powered dense cellular networks how many small cells do we need"
    - "covert communication in fading channels under channel uncertainty"
    - "covert communications with a full duplex receiver over wireless fading channels"
    - "covert communication with finite blocklength in awgn channels"
    - "on covert communication with noise uncertainty"

Connected through hyperedge HE-4 (induced by source paper "online policies for throughput maximization of energy constrained wireless powered communication systems"):
  with members:
    - "optimization of energy constrained wireless powered communication networks with heterogeneous nodes"
    - "wireless power meets energy harvesting a joint energy allocation approach in ofdm based system"
    - "resource allocation and fairness in wireless powered cooperative cognitive radio networks"
    - "battery powered devices in wpcns"
    - "on optimal policies in full duplex wireless powered communication networks"
    - "an overview of sustainable green 5g networks"
    - "dynamic base station operation in large scale green cellular networks"
    - "optimal design of non orthogonal multiple access with wireless power transfer"

Connected through hyperedge HE-5 (induced by source paper "an energy efficient controller for wirelessly powered communication networks"):
  with members:
    - "swipt using hybrid arq over time varying channels"
    - "optimal and near optimal policies for wireless power transfer in energy limited and power limited scenarios"
    - "joint sum rate and error probability optimization finite blocklength analysis"
    - "joint transfer of energy and information in a two hop relay channel"
    - "optimal energy and data routing in networks with energy cooperation"
    - "battery powered devices in wpcns"
    - "wireless powered relaying with finite block length codes"
    - "on wireless energy and information transfer in relay networks"

Connected through hyperedge HE-6 (induced by source paper "efficient fair and qos aware policies for wirelessly powered communication networks"):
  with members:
    - "online policies for throughput maximization of energy constrained wireless powered communication systems"
    - "optimal and near optimal policies for wireless power transfer in energy limited and power limited scenarios"
    - "optimal hierarchical radio resource management for hetnets with flexible backhaul"
    - "distributed wireless power transfer with energy feedback"
    - "theory and experiment for wireless powered sensor networks how to keep sensors alive"
    - "battery powered devices in wpcns"
    - "capacity of remotely powered communication"
    - "wireless powered communication opportunities and challenges"

Connected through hyperedge HE-7 (induced by source paper "design of ambient backscatter training for retrodirective wireless power transfer"):
  with members:
    - "retrodirective large antenna energy beamforming in backscatter multi user networks"
    - "retrodirective multi user wireless power transfer with massive mimo"
    - "next generation backscatter communication systems techniques and applications"
    - "ambient backscatter communications a contemporary survey"
    - "modulation in the air backscatter communication over ambient ofdm carrier"
    - "inter technology backscatter towards internet connectivity for implanted devices"
    - "communications and signals design for wireless power transmission"
    - "wireless powered communication opportunities and challenges"

Connected through hyperedge HE-8 (induced by source paper "multi user opportunistic beamforming using reconfigurable surfaces"):
  with members:
    - "enabling secure wireless communications via intelligent reflecting surfaces"
    - "mimo assisted networks relying on large intelligent surfaces a stochastic geometry model"
    - "asymptotic max min sinr analysis of reconfigurable intelligent surface assisted miso systems"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"
    - "reconfigurable intelligent surfaces for energy efficiency in wireless communication"
    - "intelligent reflecting surface enhanced wireless network joint active and passive beamforming design"
    - "increasing indoor spectrum sharing capacity using smart reflect array"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.IT(Information Theory)