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: "improving energy efficiency through multimode transmission in the downlink mimo systems"
  Abstract: Adaptively adjusting system parameters including bandwidth, transmit power and mode to maximize the "Bits per-Joule" energy efficiency (BPJ-EE) in the downlink MIMO systems with imperfect channel state information at the transmitter (CSIT) is considered in this paper. By mode we refer to choice of transmission schemes i.e. singular value decomposition (SVD) or block diagonalization (BD), active transmit/receive antenna number and active user number. We derive optimal bandwidth and transmit power for each dedicated mode at first. During the derivation, accurate capacity estimation strategies are proposed to cope with the imperfect CSIT caused capacity prediction problem. Then, an ergodic capacity based mode switching strategy is proposed to further improve the BPJ-EE, which provides insights on the preferred mode under given scenarios. Mode switching compromises different power parts, exploits the tradeoff between the multiplexing gain and the imperfect CSIT caused inter-user interference, improves the BPJ-EE significantly.

Connected through hyperedge HE-1 (induced by source paper "rate splitting for multi antenna non orthogonal unicast and multicast transmission spectral and energy efficiency analysis"):
  with members:
    - "energy efficiency of rate splitting multiple access and performance benefits over sdma and noma"
    - "rate splitting multiple access for coordinated multi point joint transmission"
    - "rate splitting for multi antenna non orthogonal unicast and multicast transmission"
    - "gaussian message passing for overloaded massive mimo noma"
    - "rate splitting multiple access for downlink communication systems bridging generalizing and outperforming sdma and noma"
    - "rate splitting for max min fair multigroup multicast beamforming in overloaded systems"
    - "optimal dof region of the k user miso bc with partial csit"
    - "generalized multicast multibeam precoding for satellite communications"

Connected through hyperedge HE-2 (induced by source paper "energy efficiency of rate splitting multiple access and performance benefits over sdma and noma"):
  with members:
    - "rate splitting multiple access for downlink communication systems bridging generalizing and outperforming sdma and noma"
    - "on the total energy efficiency of cell free massive mimo"
    - "energy efficiency in mimo underlay and overlay device to device communications and cognitive radio systems"
    - "energy efficient beam coordination strategies with rate dependent processing power"
    - "sum rate maximization for linearly precoded downlink multiuser miso systems with partial csit a rate splitting approach"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"

Connected through hyperedge HE-3 (induced by source paper "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"):
  with members:
    - "uplink performance of time reversal mrc in massive mimo systems subject to phase noise"
    - "robust estimates of covariance matrices in the large dimensional regime"
    - "low complexity polynomial channel estimation in large scale mimo with arbitrary statistics"
    - "blind pilot decontamination"
    - "massive mimo and small cells improving energy efficiency by optimal soft cell coordination"
    - "capacity limits and multiplexing gains of mimo channels with transceiver impairments"
    - "hardware impairments in large scale miso systems energy efficiency estimation and capacity limits"
    - "linear precoding based on polynomial expansion reducing complexity in massive mimo"

Connected through hyperedge HE-4 (induced by source paper "energy efficiency optimization for mimo broadcast channels"):
  with members:
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "energy efficient iterative waterfilling for the mimo broadcasting channels"
    - "energy efficiency scaling law for mimo broadcasting channels"
    - "framework for link level energy efficiency optimization with informed transmitter"
    - "energy efficient precoding for multiple antenna terminals"
    - "towards a communication theoretic understanding of system level power consumption"

Connected through hyperedge HE-5 (induced by source paper "energy efficient iterative waterfilling for the mimo broadcasting channels"):
  with members:
    - "energy efficiency optimization for mimo broadcast channels"
    - "fundamental tradeoffs on green wireless networks"
    - "energy efficient precoding for multiple antenna terminals"

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)