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: "energy efficient heterogeneous cellular networks with spectrum underlay and overlay access"
  Abstract: In this paper, we provide joint subcarrier assignment and power allocation schemes for quality-of-service (QoS)-constrained energy-efficiency (EE) optimization in the downlink of an orthogonal frequency division multiple access (OFDMA)-based two-tier heterogeneous cellular network (HCN). Considering underlay transmission, where spectrum-efficiency (SE) is fully exploited, the EE solution involves tackling a complex mixed-combinatorial and non-convex optimization problem. With appropriate decomposition of the original problem and leveraging on the quasi-concavity of the EE function, we propose a dual-layer resource allocation approach and provide a complete solution using difference-of-two-concave-functions approximation, successive convex approximation, and gradient-search methods. On the other hand, the inherent inter-tier interference from spectrum underlay access may degrade EE particularly under dense small-cell deployment and large bandwidth utilization. We therefore develop a novel resource allocation approach based on the concepts of spectrum overlay access and resource efficiency (RE) (normalized EE-SE trade-off). Specifically, the optimization procedure is separated in this case such that the macro-cell optimal RE and corresponding bandwidth is first determined, then the EE of small-cells utilizing the remaining spectrum is maximized. Simulation results confirm the theoretical findings and demonstrate that the proposed resource allocation schemes can approach the optimal EE with each strategy being superior under certain system settings.

Connected through hyperedge HE-1 (induced by source paper "energy and spectral efficiency tradeoff in ofdma networks via antenna selection strategy"):
  with members:
    - "joint user association and resource allocation in the uplink of heterogeneous networks"
    - "energy efficiency maximization via joint sub carrier assignment and power control for ofdma full duplex networks"
    - "multi objective optimization for energy and spectral efficiency tradeoff in in band full duplex ibfd communication"
    - "downlink energy efficiency of power allocation and wireless backhaul bandwidth allocation in heterogeneous small cell networks"
    - "spectral and energy efficiency trade offs in cellular networks"
    - "an overview of sustainable green 5g networks"
    - "optimal joint power and subcarrier allocation for full duplex multicarrier non orthogonal multiple access systems"

Connected through hyperedge HE-2 (induced by source paper "energy efficiency maximization via joint sub carrier assignment and power control for ofdma full duplex networks"):
  with members:
    - "energy efficient power control a look at 5g wireless technologies"
    - "optimal joint power and subcarrier allocation for full duplex multicarrier non orthogonal multiple access systems"
    - "power efficient resource allocation for full duplex radio distributed antenna networks"
    - "throughput analysis for full duplex wireless networks with imperfect self interference cancellation"
    - "power efficient and secure full duplex wireless communication systems"
    - "energy efficient scheduling and power allocation in downlink ofdma networks with base station coordination"
    - "full duplex mobile device pushing the limits"
    - "wireless information and power transfer energy efficiency optimization in ofdma systems"

Connected through hyperedge HE-3 (induced by source paper "joint antenna selection and spatial switching for energy efficient mimo swipt system"):
  with members:
    - "stochastic geometric analysis of energy efficient dense cellular networks"
    - "spatial domain simultaneous information and power transfer for mimo channels"
    - "robust beamforming for secure communication in systems with wireless information and power transfer"
    - "simultaneous wireless information and power transfer in modern communication systems"
    - "wireless networks with rf energy harvesting a contemporary survey"
    - "evolution toward 5g multi tier cellular wireless networks an interference management perspective"
    - "wireless information and power transfer in multiuser ofdm systems"
    - "relaying protocols for wireless energy harvesting and information processing"

Connected through hyperedge HE-4 (induced by source paper "energy efficiency optimization with simultaneous wireless information and power transfer in mimo broadcast channels"):
  with members:
    - "stochastic geometric analysis of energy efficient dense cellular networks"
    - "robust beamforming for secure communication in systems with wireless information and power transfer"
    - "simultaneous wireless information and power transfer in modern communication systems"
    - "wireless networks with rf energy harvesting a contemporary survey"
    - "wireless information and power transfer in multiuser ofdm systems"
    - "relaying protocols for wireless energy harvesting and information processing"
    - "wireless information and power transfer a dynamic power splitting approach"
    - "wireless information transfer with opportunistic energy harvesting"

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)