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: "reflect and transmit array antennas for scalable and energy efficient mmwave massive mimo"
  Abstract: Hybrid analog-digital architectures are promising candidates for implementing millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems since they enable a considerable reduction of the required number of costly radio frequency (RF) chains by moving some of the signal processing operations into the analog domain. Nevertheless, the analog feed network, comprising RF dividers, combiners, phase shifters, and line connections, of hybrid MIMO architectures is not scalable due to its prohibitively high power consumption for large numbers of transmit antennas. In this paper, we study novel massive MIMO architectures, namely reflect-array (RA) and transmit-array (TA) antennas, which consist of few active antennas (i.e., RF chains) and large numbers of passive antennas. We show that the constraints that the precoders for RA and TA antennas have to meet, differ from those of conventional MIMO architectures. Taking these constraints into account and exploiting the sparsity of mmWave channels, we design two efficient precoders for RA and TA antennas; one based on maximizing the mutual information and one based on approximating the optimal unconstrained digital precoder via the orthogonal matching pursuit algorithm. Furthermore, in order to fairly compare the performance of RA and TA antennas against conventional fully-digital and hybrid MIMO architectures, we develop a unified power consumption model. Our simulation results show that unlike conventional MIMO architectures, RA and TA antennas are highly energy efficient and fully scalable in terms of the number of transmit antennas. Therefore, RA and TA antennas are candidates for realizing the potential of \textit{massive} MIMO in practice.

Connected through hyperedge HE-1 (induced by source paper "millimeter wave communications with an intelligent reflector performance optimization and distributional reinforcement learning"):
  with members:
    - "intelligent reflecting surface meets ofdm protocol design and rate maximization"
    - "reflections in the sky millimeter wave communication with uav carried intelligent reflectors"
    - "intelligent reflecting and transmitting surface aided millimeter wave massive mimo"
    - "a vision of 6g wireless systems applications trends technologies and open research problems"
    - "enabling large intelligent surfaces with compressive sensing and deep learning"
    - "performance analysis of large intelligent surfaces liss uplink spectral efficiency and pilot training"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"
    - "fractional programming for communication systems part i power control and beamforming"

Connected through hyperedge HE-2 (induced by source paper "on the impact of phase shifting designs on irs noma"):
  with members:
    - "irs based wireless jamming attacks when jammers can attack without power"
    - "intelligent reflecting surface versus decode and forward how large surfaces are needed to beat relaying"
    - "reflections in the sky millimeter wave communication with uav carried intelligent reflectors"
    - "smart radio environments empowered by ai reconfigurable meta surfaces an idea whose time has come"
    - "intelligent reflecting and transmitting surface aided millimeter wave massive mimo"
    - "a simple design of irs noma transmission"
    - "towards smart and reconfigurable environment intelligent reflecting surface aided wireless network"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"

Connected through hyperedge HE-3 (induced by source paper "beyond max snr joint encoding for reconfigurable intelligent surfaces"):
  with members:
    - "intelligent reflecting surface versus decode and forward how large surfaces are needed to beat relaying"
    - "intelligent reflecting surface with discrete phase shifts channel estimation and passive beamforming"
    - "channel estimation for wireless communication systems assisted by large intelligent surfaces"
    - "reflection probability in wireless networks with metasurface coated environmental objects an approach based on random spatial processes"
    - "capacity characterization for intelligent reflecting surface aided mimo communication"
    - "channel capacity optimization using reconfigurable intelligent surfaces in indoor mmwave environments"
    - "intelligent reflecting surface irs enabled covert communications in wireless networks"
    - "secure transmission strategy for intelligent reflecting surface enhanced wireless system"

Connected through hyperedge HE-4 (induced by source paper "intelligent reflecting surfaces for free space optical communications"):
  with members:
    - "enabling secure wireless communications via intelligent reflecting surfaces"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"
    - "intelligent reflecting surface enhanced wireless network joint active and passive beamforming design"
    - "statistical modeling of fso fronthaul channel for drone based networks"
    - "optimization of free space optical wireless network for cellular backhauling"

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)