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: "cost aware green cellular networks with energy and communication cooperation"
  Abstract: Energy cost of cellular networks is ever-increasing to match the surge of wireless data traffic, and the saving of this cost is important to reduce the operational expenditure (OPEX) of wireless operators in future. The recent advancements of renewable energy integration and two-way energy flow in smart grid provide potential new solutions to save the cost. However, they also impose challenges, especially on how to use the stochastically and spatially distributed renewable energy harvested at cellular base stations (BSs) to reliably supply time- and space-varying wireless traffic over cellular networks. To overcome these challenges, in this article we present three approaches, namely, {\emph{energy cooperation, communication cooperation, and joint energy and communication cooperation}}, in which different BSs bidirectionally trade or share energy via the aggregator in smart grid, and/or share wireless resources and shift loads with each other to reduce the total energy cost.

Connected through hyperedge HE-1 (induced by source paper "a new relation between energy efficiency and spectral efficiency in wireless communications systems"):
  with members:
    - "energy efficient scheduling and power allocation in downlink ofdma networks with base station coordination"
    - "joint energy and spectrum cooperation for cellular communication systems"
    - "framework for link level energy efficiency optimization with informed transmitter"

Connected through hyperedge HE-2 (induced by source paper "energy sustainable paradigms and methods for future mobile networks a survey"):
  with members:
    - "information exchange in randomly deployed dense wsns with wireless energy harvesting capabilities"
    - "a stochastic geometry based demand response management framework for cellular networks powered by smart grid"
    - "fog computing based radio access networks issues and challenges"
    - "a hybrid energy sharing framework for green cellular networks"
    - "recent advances in cloud radio access networks system architectures key techniques and open issues"
    - "green networking in cellular hetnets a unified radio resource management framework with base station on off switching"
    - "online ski rental for on off scheduling of energy harvesting base stations"
    - "dynamic clustering and on off strategies for wireless small cell networks"

Connected through hyperedge HE-3 (induced by source paper "dynamic cross layer beamforming in hybrid powered communication systems with harvest use trade strategy"):
  with members:
    - "energy harvesting wireless communications a review of recent advances"
    - "comp meets smart grid a new communication and energy cooperation paradigm"
    - "a general utility optimization framework for energy harvesting based wireless communications"
    - "a lyapunov optimization approach for green cellular networks with hybrid energy supplies"
    - "cost minimization for fading channels with energy harvesting and conventional energy"
    - "cooperative energy trading in comp systems powered by smart grids"
    - "energy efficient resource allocation in ofdma systems with hybrid energy harvesting base station"
    - "green cellular networks a survey some research issues and challenges"

Connected through hyperedge HE-4 (induced by source paper "optimal energy and data routing in networks with energy cooperation"):
  with members:
    - "joint energy and spectrum cooperation for cellular communication systems"
    - "application of smart antenna technologies in simultaneous wireless information and power transfer"
    - "energy cooperation in energy harvesting communications"
    - "energy cooperation in cellular networks with renewable powered base stations"
    - "wireless information and power transfer architecture design and rate energy tradeoff"
    - "enabling wireless power transfer in cellular networks architecture modeling and deployment"
    - "optimal energy allocation for wireless communications with energy harvesting constraints"
    - "transmission with energy harvesting nodes in fading wireless channels optimal policies"

Connected through hyperedge HE-5 (induced by source paper "wireless information and power transfer design for energy cooperation distributed antenna systems"):
  with members:
    - "throughput optimization for massive mimo systems powered by wireless energy transfer"
    - "multiuser mimo wireless energy transfer with coexisting opportunistic communication"
    - "energy beamforming with one bit feedback"
    - "cost minimization for fading channels with energy harvesting and conventional energy"
    - "multiuser miso beamforming for simultaneous wireless information and power transfer"
    - "optimal power allocation for energy harvesting and power grid coexisting wireless communication systems"
    - "multi antenna wireless powered communication with energy beamforming"
    - "wireless information transfer with opportunistic energy harvesting"

Connected through hyperedge HE-6 (induced by source paper "energy group buying with loading sharing for green cellular networks"):
  with members:
    - "green 5g heterogeneous networks through dynamic small cell operation"
    - "comp meets smart grid a new communication and energy cooperation paradigm"
    - "bargaining based mobile data offloading"
    - "what will 5g be"
    - "joint energy and spectrum cooperation for cellular communication systems"
    - "cooperative energy trading in comp systems powered by smart grids"
    - "energy cooperation in cellular networks with renewable powered base stations"
    - "green cellular networks a survey some research issues and challenges"

Connected through hyperedge HE-7 (induced by source paper "a hybrid energy sharing framework for green cellular networks"):
  with members:
    - "a stochastic geometry based demand response management framework for cellular networks powered by smart grid"
    - "understanding mobile traffic patterns of large scale cellular towers in urban environment"
    - "cooperative energy trading in comp systems powered by smart grids"
    - "energy cooperation in cellular networks with renewable powered base stations"
    - "green cellular networks a survey some research issues and challenges"

Connected through hyperedge HE-8 (induced by source paper "dynamic base station operation in large scale green cellular networks"):
  with members:
    - "green 5g heterogeneous networks through dynamic small cell operation"
    - "energy group buying with loading sharing for green cellular networks"
    - "energy harvesting wireless communications a review of recent advances"
    - "comp meets smart grid a new communication and energy cooperation paradigm"
    - "a general utility optimization framework for energy harvesting based wireless communications"
    - "spatial throughput maximization of wireless powered communication networks"
    - "a lyapunov optimization approach for green cellular networks with hybrid energy supplies"
    - "quantifying potential energy efficiency gain in green cellular wireless 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.IT(Information Theory)