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: "pilot beam pattern design for channel estimation in massive mimo systems"
  Abstract: In this paper, the problem of pilot beam pattern design for channel estimation in massive multiple-input multiple-output systems with a large number of transmit antennas at the base station is considered, and a new algorithm for pilot beam pattern design for optimal channel estimation is proposed under the assumption that the channel is a stationary Gauss-Markov random process. The proposed algorithm designs the pilot beam pattern sequentially by exploiting the properties of Kalman filtering and the associated prediction error covariance matrices and also the channel statistics such as spatial and temporal channel correlation. The resulting design generates a sequentially-optimal sequence of pilot beam patterns with low complexity for a given set of system parameters. Numerical results show the effectiveness of the proposed algorithm.

Connected through hyperedge HE-1 (induced by source paper "secure massive mimo communication with low resolution dacs"):
  with members:
    - "optimal multiuser loading in quantized massive mimo under spatially correlated channels"
    - "mimo channel information feedback using deep recurrent network"
    - "quantized constant envelope precoding with psk and qam signaling"
    - "on performance of quantized transceiver in multiuser massive mimo downlinks"
    - "spectral and energy efficiency of multi pair massive mimo relay network with hybrid processing"
    - "power efficient and secure wpcns with hardware impairments and non linear eh circuit"
    - "a tractable framework for performance analysis of dense multi antenna networks"
    - "analysis of one bit quantized precoding for the multiuser massive mimo downlink"

Connected through hyperedge HE-2 (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-3 (induced by source paper "an efficient beam and channel acquisition via sparsity map and joint angle delay power profile estimation for wideband massive mimo systems"):
  with members:
    - "spatial channel covariance estimation for the hybrid mimo architecture a compressive sensing based approach"
    - "channel estimation for tdd fdd massive mimo systems with channel covariance computing"
    - "low complexity massive mimo subspace estimation and tracking from low dimensional projections"
    - "enhancing the estimation of mm wave large array channels by exploiting spatio temporal correlation and sparse scattering"
    - "channel acquisition for massive mimo ofdm with adjustable phase shift pilots"
    - "a generalized framework on beamformer design and csi acquisition for single carrier massive mimo systems in millimeter wave channels"
    - "hybrid beamforming for massive mimo a survey"
    - "spatially common sparsity based adaptive channel estimation and feedback for fdd massive mimo"

Connected through hyperedge HE-4 (induced by source paper "average sep optimal precoding for correlated massive mimo with zf detection an asymptotic analysis"):
  with members:
    - "large scale fading decoding in cellular massive mimo systems with spatially correlated channels"
    - "massive mimo has unlimited capacity"
    - "performance analysis for massive mimo downlink with low complexity approximate zero forcing precoding"
    - "joint pilot design and uplink power allocation in multi cell massive mimo systems"
    - "the world s first real time testbed for massive mimo design implementation and validation"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-5 (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"
    - "massive mimo for next generation wireless systems"
    - "blind pilot decontamination"

Connected through hyperedge HE-6 (induced by source paper "downlink precoding with mixed statistical and imperfect instantaneous csi for massive mimo systems"):
  with members:
    - "massive mimo with imperfect channel covariance information"
    - "a rate splitting strategy for massive mimo with imperfect csit"
    - "massive mimo ten myths and one critical question"
    - "two stage subspace constrained precoding in massive mimo cellular systems"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "dealing with interference in distributed large scale mimo systems a statistical approach"
    - "two tier precoding for fdd multi cell massive mimo time varying interference networks"
    - "downlink training techniques for fdd massive mimo systems open loop and closed loop training with memory"

Connected through hyperedge HE-7 (induced by source paper "performance analysis of large intelligence surfaces liss asymptotic data rate and channel hardening effects"):
  with members:
    - "a vision of 6g wireless systems applications trends technologies and open research problems"
    - "energy efficient multi user miso communication using low resolution large intelligent surfaces"
    - "joint communication and control for wireless autonomous vehicular platoon systems"
    - "beyond massive mimo the potential of positioning with large intelligent surfaces"
    - "capacity degradation with modeling hardware impairment in large intelligent surface"
    - "beyond massive mimo the potential of data transmission with large intelligent surfaces"
    - "reconfigurable intelligent surfaces for energy efficiency in wireless communication"
    - "user assignment with distributed large intelligent surface lis systems"

Connected through hyperedge HE-8 (induced by source paper "pilot contamination mitigation with reduced rf chains"):
  with members:
    - "hybrid analog digital beamforming for massive mimo systems"
    - "partially connected hybrid precoding in mm wave systems with dynamic phase shifter networks"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "smart pilot assignment for massive mimo"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "what will 5g be"
    - "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)