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: "cooperative strategies for wireless powered communications"
  Abstract: Radio frequency (RF) energy transfer and harvesting has been intensively studied recently as a promising approach to significantly extend the lifetime of energy-constrained wireless networks. This technique has a great potential to provide relatively stable and continuous RF energy to devices wirelessly, it thus opened a new research paradigm, termed wireless-powered communication (WPC), which has raised many new research opportunities with wide applications. Among these, the design and evaluation of cooperative schemes towards energy-efficient WPC have attracted tremendous research interests nowadays. This article provides an overview of various energy-efficient cooperative strategies for WPC, with particular emphasis on relaying protocols for wireless-powered cooperative communications, cooperative spectrum sharing schemes for wireless-powered cognitive radio networks, and cooperative jamming strategies towards wireless-powered secure communications. We also identify some valuable research directions in this area before concluding this article.

Connected through hyperedge HE-1 (induced by source paper "energy efficient wireless powered secure transmission with cooperative jamming for public transportation"):
  with members:
    - "wireless powered cooperative jamming for secure ofdm system"
    - "wireless powered communication opportunities and challenges"
    - "optimal resource allocation in full duplex wireless powered communication network"
    - "on cooperative relaying schemes for wireless physical layer security"
    - "optimal and robust transmit designs for miso channel secrecy by semidefinite programming"

Connected through hyperedge HE-2 (induced by source paper "full duplex cooperative cognitive radio networks with wireless energy harvesting"):
  with members:
    - "a discrete time switching protocol for wireless powered communications with energy accumulation"
    - "ergodic capacity comparison of different relay precoding schemes in dual hop af systems with co channel interference"
    - "full duplex cooperative cognitive radio with transmit imperfections"
    - "wireless information and power transfer architecture design and rate energy tradeoff"

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)