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 in 3 way relay channels with circular message exchanges"
  Abstract: Spectral and energy efficiency in 3-way relay channels are studied in this paper. First, achievable sum rate expressions for 3-way relay channels are derived for different relaying protocols. Moreover, an outer bound for the capacity of the 3-way relay channel is presented. Next, leveraging the derived achievable sum rate expressions, two algorithms for joint power allocation at the users and at the relay are designed so as to maximize the system energy efficiency. Numerical results are provided to corroborate and provide insight on the theoretical findings.

Connected through hyperedge HE-1 (induced by source paper "cyclic communication and the inseparability of mimo multi way relay channels"):
  with members:
    - "simultaneous diagonalization on the dof region of the k user mimo multi way relay channel"
    - "beyond one way communication degrees of freedom of multi way relay mimo interference networks"
    - "approximate sum capacity of the y channel"
    - "degrees of freedom for the mimo multi way relay channel"
    - "the deterministic multicast capacity of 4 node relay networks"
    - "the degrees of freedom of the mimo y channel"
    - "optimal transmit power allocation for mimo two way cognitive relay networks with multiple relays"
    - "divide and conquer approaching the capacity of the two pair bidirectional gaussian relay network"

Connected through hyperedge HE-2 (induced by source paper "resource allocation for energy efficient 3 way relay channels"):
  with members:
    - "energy efficiency optimization in relay assisted mimo systems with perfect and statistical csi"
    - "scalar quantize and forward for symmetric half duplex two way relay channels"
    - "the capacity region of multiway relay channels over finite fields with full data exchange"
    - "framework for link level energy efficiency optimization with informed transmitter"
    - "capacity theorems for the awgn multi way relay 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)