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: "are mmwave low complexity beamforming structures energy efficient analysis of the downlink mu mimo"
  Abstract: Future cellular systems based on the use of above-6 GHz frequencies, the so-called millimeter wave (mmWave) bandwidths, will heavily rely on the use of antenna arrays both at the transmitter and at the receiver, possibly with a large number of elements. For complexity reasons, fully digital precoding and postcoding structures may turn out to be unfeasible, and thus suboptimal structures, making use of simplified hardware and a limited number of RF chains, have been investigated. This paper considers and makes a comparative assessment, both from a spectral efficiency and energy efficiency point of view, of several suboptimal precoding and postcoding beamforming structures for the downlink of a cellular multiuser MIMO (MU-MIMO) system. Based on the most recently available data for the energy consumption of phase shifters and switches, we show that there are cases where fully-digital beamformers may achieve a larger energy efficiency than lower-complexity solutions, as well as that structures based on the exclusive use of switches achieve quite unsatisfactory performance in realistic scenarios.

Connected through hyperedge HE-1 (induced by source paper "hybrid combining based on constant phase shifters and active inactive switches"):
  with members:
    - "resolution adaptive hybrid mimo architectures for millimeter wave communications"
    - "millimeter wave receiver efficiency a comprehensive comparison of beamforming schemes with low resolution adcs"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "massive mimo combining with switches"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "massive mimo for next generation wireless systems"
    - "spatially sparse precoding in millimeter wave mimo systems"

Connected through hyperedge HE-2 (induced by source paper "single carrier modulation versus ofdm for millimeter wave wireless mimo"):
  with members:
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "subspace estimation and decomposition for large millimeter wave mimo systems"
    - "on clustered statistical mimo millimeter wave channel simulation"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "what will 5g be"
    - "spatially sparse precoding in millimeter wave mimo systems"

Connected through hyperedge HE-3 (induced by source paper "massive mimo 5g cellular networks mm wave versus mu wave frequencies"):
  with members:
    - "doubly massive mmwave mimo systems using very large antenna arrays at both transmitter and receiver"
    - "subspace estimation and decomposition for large millimeter wave mimo systems"
    - "spectral efficiency of mimo millimeter wave links with single carrier modulation for 5g networks"
    - "cell free massive mimo versus small cells"
    - "on clustered statistical mimo millimeter wave channel simulation"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-4 (induced by source paper "optimal design of energy efficient millimeter wave hybrid transceivers for wireless backhaul"):
  with members:
    - "on clustered statistical mimo millimeter wave channel simulation"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "coverage and rate analysis for millimeter wave cellular networks"
    - "millimeter wave cellular wireless networks potentials and challenges"
    - "spatially sparse precoding in millimeter wave mimo systems"

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)