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: "power minimization for ofdm transmission with subcarrier pair based opportunistic df relaying"
  Abstract: This paper develops a sum-power minimized resource allocation (RA) algorithm subject to a sum-rate constraint for cooperative orthogonal frequency division modulation (OFDM) transmission with subcarrier-pair based opportunistic decode-and-forward (DF) relaying. The improved DF protocol first proposed in is used with optimized subcarrier pairing. Instrumental to the RA algorithm design is appropriate definition of variables to represent source/relay power allocation, subcarrier pairing and transmission-mode selection elegantly, so that after continuous relaxation, the dual method and the Hungarian algorithm can be used to find an (at least approximately) optimum RA with polynomial complexity. Moreover, the bisection method is used to speed up the search of the optimum Lagrange multiplier for the dual method. Numerical results are shown to illustrate the power-reduction benefit of the improved DF protocol with optimized subcarrier pairing.

Connected through hyperedge HE-1 (induced by source paper "weighted sum rate maximization for downlink ofdma with subcarrier pair based opportunistic df relaying"):
  with members:
    - "on the scale algorithm for multiuser multicarrier power spectrum management"
    - "wsr maximized resource allocation in multiple df relays aided ofdma downlink transmission"
    - "joint subcarrier pairing and power allocation for ofdm transmission with decode and forward relaying"
    - "sum rate maximized resource allocation in multiple df relays aided ofdm transmission"
    - "optimization framework and graph based approach for relay assisted bidirectional ofdma cellular networks"

Connected through hyperedge HE-2 (induced by source paper "novel subcarrier pair based opportunistic df protocol for cooperative downlink ofdma"):
  with members:
    - "weighted sum rate maximization for downlink ofdma with subcarrier pair based opportunistic df relaying"
    - "wsr maximized resource allocation in multiple df relays aided ofdma downlink transmission"
    - "joint subcarrier pairing and power allocation for ofdm transmission with decode and forward relaying"
    - "sum rate maximized resource allocation in multiple df relays aided ofdm transmission"

Connected through hyperedge HE-3 (induced by source paper "on the optimum energy efficiency for flat fading channels with rate dependent circuit power"):
  with members:
    - "weighted sum rate maximization for downlink ofdma with subcarrier pair based opportunistic df relaying"
    - "framework for link level energy efficiency optimization with informed transmitter"
    - "sum rate maximized resource allocation in multiple df relays aided ofdm transmission"

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)