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: "safe and secure wireless power transfer networks challenges and opportunities in rf based systems"
  Abstract: RF-based wireless power transfer networks (WPTNs) are deployed to transfer power to embedded devices over the air via RF waves. Up until now, a considerable amount of effort has been devoted by researchers to design WPTNs that maximize several objectives such as harvested power, energy outage and charging delay. However, inherent security and safety issues are generally overlooked and these need to be solved if WPTNs are to be become widespread. This article focuses on safety and security problems related WPTNs and highlight their cruciality in terms of efficient and dependable operation of RF-based WPTNs. We provide a overview of new research opportunities in this emerging domain.

Connected through hyperedge HE-1 (induced by source paper "specific absorption rate aware beamforming in miso downlink swipt systems"):
  with members:
    - "signal and system design for wireless power transfer prototype experiment and validation"
    - "fundamentals of wireless information and power transfer from rf energy harvester models to signal and system designs"
    - "a learning approach to wireless information and power transfer signal and system design"
    - "wireless information and power transfer over an awgn channel nonlinearity and asymmetric gaussian signaling"
    - "robust resource allocation for mimo wireless powered communication networks based on a non linear eh model"
    - "waveform design for wireless power transfer"
    - "wireless information and power transfer nonlinearity waveform design and rate energy tradeoff"
    - "communications and signals design for wireless power transmission"

Connected through hyperedge HE-2 (induced by source paper "beh indoor batteryless ble beacons using rf energy harvesting for internet of things"):
  with members:
    - "blisp enhancing backscatter radio with active radio for computational rfids"
    - "joint wireless information and energy transfer with reduced feedback in mimo interference channels"
    - "user cooperation in wireless powered communication networks"
    - "wireless networks with rf energy harvesting a contemporary survey"

Connected through hyperedge HE-3 (induced by source paper "robust chance constrained optimization for power efficient and secure swipt systems"):
  with members:
    - "probabilistically robust swipt for secrecy misome systems"
    - "robust resource allocation for mimo wireless powered communication networks based on a non linear eh model"
    - "robust an aided beamforming and power splitting design for secure miso cognitive radio with swipt"
    - "wireless powered communication networks an overview"
    - "multi objective resource allocation in full duplex swipt systems"
    - "secrecy wireless information and power transfer challenges and opportunities"
    - "ambient rf energy harvesting in ultra dense small cell networks performance and trade offs"
    - "secrecy transmit beamforming for heterogeneous networks"

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.NI(Networking and Internet Architecture)