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 and energy efficiency trade offs in cellular networks"
  Abstract: This paper presents a simple and effective method to study the spectral and energy efficiency (SE-EE) trade-off in cellular networks, an issue that has attracted significant recent interest in the wireless community. The proposed theoretical framework is based on an optimal radio resource allocation of transmit power and bandwidth for the downlink direction, applicable for an orthogonal cellular network. The analysis is initially focused on a single cell scenario, for which in addition to the solution of the main SE-EE optimization problem, it is proved that a traffic repartition scheme can also be adopted as a way to simplify this approach. By exploiting this interesting result along with properties of stochastic geometry, this work is extended to a more challenging multicell environment, where interference is shown to play an essential role and for this reason several interference reduction techniques are investigated. Special attention is also given to the case of low signal-to-noise ratio (SNR) and a way to evaluate the upper bound on EE in this regime is provided. This methodology leads to tractable analytical results under certain common channel properties, and thus allows the study of various models without the need for demanding system-level simulations.

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"
    - "an overview of sustainable green 5g networks"
    - "optimal joint power and subcarrier allocation for full duplex multicarrier non orthogonal multiple access systems"
    - "energy efficient heterogeneous cellular networks with spectrum underlay and overlay access"

Connected through hyperedge HE-2 (induced by source paper "interference alignment for downlink cellular networks joint scheduling and precoding"):
  with members:
    - "opportunistic downlink interference alignment"
    - "interference alignment for the k user mimo interference channel"
    - "downlink interference alignment"
    - "degrees of freedom of the k user m times n mimo interference channel"
    - "approaching the capacity of wireless networks through distributed interference alignment"

Connected through hyperedge HE-3 (induced by source paper "spectral and energy efficiency of parallel gaussian broadcast channels"):
  with members:
    - "resource allocation for downlink cellular ofdma systems part i optimal allocation"

Connected through hyperedge HE-4 (induced by source paper "demo non classic interference alignment for downlink cellular networks"):
  with members:
    - "interference alignment for downlink cellular networks joint scheduling and precoding"
    - "interference alignment for the k user mimo interference channel"
    - "downlink interference alignment"
    - "on the achievability of interference alignment in the k user constant mimo interference channel"

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)