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: "blind pilot decontamination"
  Abstract: A subspace projection to improve channel estimation in massive multi-antenna systems is proposed and analyzed. Together with power-controlled hand-off, it can mitigate the pilot contamination problem without the need for coordination among cells. The proposed method is blind in the sense that it does not require pilot data to find the appropriate subspace. It is based on the theory of large random matrices that predicts that the eigenvalue spectra of large sample covariance matrices can asymptotically decompose into disjoint bulks as the matrix size grows large. Random matrix and free probability theory are utilized to predict under which system parameters such a bulk decomposition takes place. Simulation results are provided to confirm that the proposed method outperforms conventional linear channel estimation if bulk separation occurs.

Connected through hyperedge HE-1 (induced by source paper "on the pilot contamination attack in multi cell multiuser massive mimo networks"):
  with members:
    - "pilot spoofing attack by multiple eavesdroppers"
    - "multiple antennas secure transmission under pilot spoofing and jamming attack"
    - "active attack on user load achieving pilot design in massive mimo networks"
    - "user load analysis and pilot sequence design for multi cell massive mimo networks"
    - "the world s first real time testbed for massive mimo design implementation and validation"
    - "multi cell multiuser massive mimo networks user capacity analysis and pilot design"
    - "massive mimo pilot retransmission strategies for robustification against jamming"
    - "subverting massive mimo by smart jamming"

Connected through hyperedge HE-2 (induced by source paper "power scaling laws and near field behaviors of massive mimo and intelligent reflecting surfaces"):
  with members:
    - "intelligent reflecting surface versus decode and forward how large surfaces are needed to beat relaying"
    - "spatially stationary model for holographic mimo small scale fading"
    - "propagation modeling and analysis of reconfigurable intelligent surfaces for indoor and outdoor applications in 6g wireless systems"
    - "beyond max snr joint encoding for reconfigurable intelligent surfaces"
    - "towards smart and reconfigurable environment intelligent reflecting surface aided wireless network"
    - "reconfigurable intelligent surfaces bridging the gap between scattering and reflection"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"
    - "beyond massive mimo the potential of data transmission with large intelligent surfaces"

Connected through hyperedge HE-3 (induced by source paper "data aided secure massive mimo transmission under the pilot contamination attack"):
  with members:
    - "a survey of physical layer security techniques for 5g wireless networks and challenges ahead"
    - "pilot spoofing attack by multiple eavesdroppers"
    - "multiple antennas secure transmission under pilot spoofing and jamming attack"
    - "secure transmission with large numbers of antennas and finite alphabet inputs"
    - "massive mimo pilot decontamination and channel interpolation via wideband sparse channel estimation"
    - "analysis and design of secure massive mimo systems in the presence of hardware impairments"
    - "performance limits of massive mimo systems based on bayes optimal inference"
    - "secure massive mimo transmission with an active eavesdropper"

Connected through hyperedge HE-4 (induced by source paper "a covariance based hybrid channel feedback in fdd massive mimo systems"):
  with members:
    - "downlink precoding with mixed statistical and imperfect instantaneous csi for massive mimo systems"
    - "fdd massive mimo via ul dl channel covariance extrapolation and active channel sparsification"
    - "channel feedback based on aod adaptive subspace codebook in fdd massive mimo systems"
    - "enabling covariance based feedback in massive mimo a user classification approach"
    - "channel estimation for tdd fdd massive mimo systems with channel covariance computing"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "spatially common sparsity based adaptive channel estimation and feedback for fdd massive mimo"
    - "antenna grouping based feedback compression for fdd based massive mimo systems"

Connected through hyperedge HE-5 (induced by source paper "on the spectral efficiency for massive mimo systems with imperfect spacial covariance information"):
  with members:
    - "covariance matrix estimation for massive mimo"
    - "covariance matrix estimation in massive mimo"
    - "massive mimo has unlimited capacity"
    - "superimposed pilots are superior for mitigating pilot contamination in massive mimo"
    - "massive mimo pilot decontamination and channel interpolation via wideband sparse channel estimation"
    - "massive mimo with imperfect channel covariance information"
    - "path loss shadow fading and line of sight probability models for 5g urban macro cellular scenarios"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-6 (induced by source paper "enhanced channel estimation in massive mimo via coordinated pilot design"):
  with members:
    - "pilot contamination mitigation with reduced rf chains"
    - "fractional programming for communication systems part i power control and beamforming"
    - "optimization of mimo device to device networks via matrix fractional programming a minorization maximization approach"
    - "a successive optimization approach to pilot design for multi cell massive mimo systems"
    - "joint pilot design and uplink power allocation in multi cell massive mimo systems"
    - "smart pilot assignment for massive mimo"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-7 (induced by source paper "addressing the curse of mobility in massive mimo with prony based angular delay domain channel predictions"):
  with members:
    - "massive mimo has unlimited capacity"
    - "robust pilot decontamination based on joint angle and power domain discrimination"
    - "massive mimo with multi cell mmse processing exploiting all pilots for interference suppression"
    - "sum rate and power scaling of massive mimo systems with channel aging"
    - "the degrees of freedom region of temporally correlated mimo networks with delayed csit"
    - "effects of channel aging in massive mimo systems"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-8 (induced by source paper "semi blind channel and signal estimation for uplink massive mimo with channel sparsity"):
  with members:
    - "super resolution blind channel and signal estimation for massive mimo with arbitrary array geometry"
    - "bayes optimal joint channel and data estimation for massive mimo with low precision adcs"
    - "bilinear generalized approximate message passing part i derivation"
    - "massive mimo for next generation wireless systems"
    - "expectation maximization gaussian mixture approximate message passing"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "message passing algorithms for compressed sensing"

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)