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: "rf powered cognitive radio networks technical challenges and limitations"
  Abstract: The increasing demand for spectral- and energy-efficient communication networks has spurred great interest in energy harvesting cognitive radio networks. Such a revolutionary technology represents a paradigm shift in the development of wireless networks, as it can simultaneously enable the efficient use of the available spectrum and the exploitation of RF energy in order to reduce reliance on traditional energy sources. This is mainly triggered by the recent advancements in microelectronics that puts forward RF energy harvesting as a plausible technique in the near future. On the other hand, it has been suggested that the operation of a network relying on harvested energy needs to be redesigned to allow the network to reliably function in the long term. To this end, the aim of this survey article is to provide a comprehensive overview of recent development and the challenges regarding the operation of CRNs powered by RF energy. In addition, the potential open issues that might be considered for future research are also discussed in this article.

Connected through hyperedge HE-1 (induced by source paper "performance analysis of energy harvesting underlay cooperative cognitive radio relay networks with randomly located nodes"):
  with members:
    - "interference aided energy harvesting cognitive relaying with multiple primary transceivers"
    - "wireless energy harvesting in a cognitive relay network"
    - "relay selection in wireless powered cooperative networks with energy storage"
    - "wireless information and power transfer in relay systems with multiple antennas and interference"
    - "opportunistic wireless energy harvesting in cognitive radio networks"
    - "relaying protocols for wireless energy harvesting and information processing"
    - "mimo broadcasting for simultaneous wireless information and power transfer"

Connected through hyperedge HE-2 (induced by source paper "self sustainability of energy harvesting systems concept analysis and design"):
  with members:
    - "performance analysis of ambient rf energy harvesting with repulsive point process modeling"
    - "energy harvesting wireless communications a review of recent advances"
    - "renewable powered cellular networks energy field modeling and network coverage"
    - "wireless networks with rf energy harvesting a contemporary survey"
    - "on green energy powered cognitive radio networks"
    - "a cross layer perspective on energy harvesting aided green communications over fading channels"

Connected through hyperedge HE-3 (induced by source paper "spectrum sharing in rf powered cognitive radio networks using game theory"):
  with members:
    - "distributed power splitting for swipt in relay interference channels using game theory"
    - "information and energy cooperation in cognitive radio networks"
    - "cooperative cognitive networks optimal distributed and low complexity algorithms"
    - "price based resource allocation for spectrum sharing femtocell networks a stackelberg game approach"

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)