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: "spectral efficiency and energy efficiency of ofdm systems impact of power amplifiers and countermeasures"
  Abstract: In wireless communication systems, the nonlinear effect and inefficiency of power amplifier (PA) have posed practical challenges for system designs to achieve high spectral efficiency (SE) and energy efficiency (EE). In this paper, we analyze the impact of PA on the SE-EE tradeoff of orthogonal frequency division multiplex (OFDM) systems. An ideal PA that is always linear and incurs no additional power consumption can be shown to yield a decreasing convex function in the SE-EE tradeoff. In contrast, we show that a practical PA has an SE-EE tradeoff that has a turning point and decreases sharply after its maximum EE point. In other words, the Pareto-optimal tradeoff boundary of the SE-EE curve is very narrow. A wide range of SE-EE tradeoff, however, is desired for future wireless communications that have dynamic demand depending on the traffic loads, channel conditions, and system applications, e.g., high-SE-with-low-EE for rate-limited systems and high-EE-with-low-SE for energy-limited systems. For the SE-EE tradeoff improvement, we propose a PA switching (PAS) technique. In a PAS transmitter, one or more PAs are switched on intermittently to maximize the EE and deliver an overall required SE. As a consequence, a high EE over a wide range SE can be achieved, which is verified by numerical evaluations: with 15% SE reduction for low SE demand, the PAS between a low power PA and a high power PA can improve EE by 323%, while a single high power PA transmitter improves EE by only 68%.

Connected through hyperedge HE-1 (induced by source paper "fundamental green tradeoffs progresses challenges and impacts on 5g networks"):
  with members:
    - "spectrum power trading for energy efficient small cell"
    - "power efficient resource allocation for full duplex radio distributed antenna networks"
    - "energy recycling full duplex radios for next generation networks"
    - "energy efficient resource allocation for wireless powered communication networks"
    - "multi objective optimization for robust power efficient and secure full duplex wireless communication systems"
    - "hybrid millimeter wave systems a novel paradigm for hetnets"
    - "coexistence of wi fi and heterogeneous small cell networks sharing unlicensed spectrum"
    - "on the spectral efficiency of full duplex small cell wireless systems"

Connected through hyperedge HE-2 (induced by source paper "on the two user multi carrier joint channel selection and power control game"):
  with members:
    - "toward fully coordinated multi level multi carrier energy efficient networks"
    - "spectrum coordination in energy efficient cognitive radio networks"
    - "on the energy spectral efficiency trade off of the mrc receiver in massive mimo systems with transceiver power consumption"
    - "quantifying potential energy efficiency gain in green cellular wireless networks"
    - "a game theoretic analysis for energy efficient heterogeneous networks"
    - "energy efficient precoding for multiple antenna terminals"
    - "introducing hierarchy in energy games"
    - "femtocell networks a survey"

Connected through hyperedge HE-3 (induced by source paper "toward fully coordinated multi level multi carrier energy efficient networks"):
  with members:
    - "spectrum coordination in energy efficient cognitive radio networks"
    - "on the energy spectral efficiency trade off of the mrc receiver in massive mimo systems with transceiver power consumption"
    - "spectral and energy efficiency trade off with joint power bandwidth allocation in ofdma networks"
    - "a game theoretic analysis for energy efficient heterogeneous networks"
    - "femtocell networks a survey"
    - "energy efficient resource allocation in wireless networks"

Connected through hyperedge HE-4 (induced by source paper "power and load coupling in cellular networks for energy optimization"):
  with members:
    - "data offloading in load coupled networks a utility maximization framework"
    - "analysis of cell load coupling for lte network planning and optimization"
    - "contractive interference functions and rates of convergence of distributed power control laws"
    - "energy efficient relaying over multiple slots with causal csi"
    - "green cellular networks a survey some research issues and challenges"

Connected through hyperedge HE-5 (induced by source paper "energy efficient antenna selection and power allocation for large scale multiple antenna systems with hybrid energy supply"):
  with members:
    - "joint power and antenna selection optimization in large cloud radio access networks"
    - "energy efficient resource allocation in ofdma systems with hybrid energy harvesting base station"
    - "optimal power allocation for energy harvesting and power grid coexisting wireless communication systems"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "on minimizing base station power consumption"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "transmission with energy harvesting nodes in fading wireless channels optimal policies"
    - "optimum transmission policies for battery limited energy harvesting nodes"

Connected through hyperedge HE-6 (induced by source paper "energy efficient large scale distributed antenna system l das for multiple users"):
  with members:
    - "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"
    - "designing multi user mimo for energy efficiency when is massive mimo the answer"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "energy efficiency optimization for mimo broadcast channels"
    - "transmission schemes based on sum rate analysis in distributed antenna systems"
    - "framework for link level energy efficiency optimization with informed transmitter"

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)