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: "wireless power transfer survey and roadmap"
  Abstract: Wireless power transfer (WPT) technologies have been widely used in many areas, e.g., the charging of electric toothbrush, mobile phones, and electric vehicles. This paper introduces fundamental principles of three WPT technologies, i.e., inductive coupling-based WPT, magnetic resonant coupling-based WPT, and electromagnetic radiation-based WPT, together with discussions of their strengths and weaknesses. Main research themes are then presented, i.e., improving the transmission efficiency and distance, and designing multiple transmitters/receivers. The state-of-the-art techniques are reviewed and categorised. Several WPT applications are described. Open research challenges are then presented with a brief discussion of potential roadmap.

Connected through hyperedge HE-1 (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-2 (induced by source paper "optimal and near optimal policies for wireless power transfer in energy limited and power limited scenarios"):
  with members:
    - "battery powered devices in wpcns"
    - "distributed energy beamforming with one bit feedback"
    - "recent advances in joint wireless energy and information transfer"
    - "user cooperation in wireless powered communication networks"
    - "optimal resource allocation in full duplex wireless powered communication network"
    - "energy beamforming with one bit feedback"
    - "optimized training design for wireless energy transfer"
    - "throughput maximization in wireless powered communication networks"

Connected through hyperedge HE-3 (induced by source paper "ambient backscatter communications a contemporary survey"):
  with members:
    - "cooperative ambient backscatter communications for green internet of things"
    - "pixelated vlc backscattering for self charging indoor iot devices"
    - "wirelessly powered backscatter communications waveform design and snr energy tradeoff"
    - "lora backscatter enabling the vision of ubiquitous connectivity"
    - "backscatter communications for internet of things theory and applications"
    - "ambient backscatter networking a novel paradigm to assist wireless powered communications"
    - "backscatter multiplicative multiple access systems fundamental limits and practical design"
    - "scatter radio receivers for extended range environmental sensing wsns"

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)