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: "kronecker product correlation model and limited feedback codebook design in a 3d channel model"
  Abstract: A 2D antenna array introduces a new level of control and additional degrees of freedom in multiple-input-multiple-output (MIMO) systems particularly for the so-called “massive MIMO” systems. To accurately assess the performance gains of these large arrays, existing azimuth-only channel models have been extended to handle 3D channels by modeling both the elevation and azimuth dimensions. In this paper, we study the channel correlation matrix of a generic ray-based 3D channel model, and our analysis and simulation results demonstrate that the 3D correlation matrix can be well approximated by a Kronecker production of azimuth and elevation correlations. This finding lays the theoretical support for the usage of a product codebook for reduced complexity feedback from the receiver to the transmitter. We also present the design of a product codebook based on Grassmannian line packing.

Connected through hyperedge HE-1 (induced by source paper "advanced quantizer designs for fdd based fd mimo systems using uniform planar arrays"):
  with members:
    - "massive mimo has unlimited capacity"
    - "exploiting the preferred domain of fdd massive mimo systems with uniform planar arrays"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "downlink training techniques for fdd massive mimo systems open loop and closed loop training with memory"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "trellis extended codebooks and successive phase adjustment a path from lte advanced to fdd massive mimo systems"
    - "noncoherent trellis coded quantization a practical limited feedback technique for massive mimo systems"
    - "scalable synchronization and reciprocity calibration for distributed multiuser mimo"

Connected through hyperedge HE-2 (induced by source paper "optimization of massive full dimensional mimo for positioning and communication"):
  with members:
    - "channel estimation and performance analysis of one bit massive mimo systems"
    - "a pessimistic approximation for the fisher information measure"
    - "sectoring in multi cell massive mimo systems"
    - "layered downlink precoding for c ran systems with full dimensional mimo"
    - "positioning for the internet of things a 3gpp perspective"
    - "downlink achievable rate analysis in massive mimo systems with one bit dacs"
    - "optimal fronthaul quantization for cloud radio positioning"
    - "parallel and distributed methods for nonconvex optimization part ii applications"

Connected through hyperedge HE-3 (induced by source paper "downlink precoding for massive mimo systems exploiting virtual channel model sparsity"):
  with members:
    - "spatial temporal bem and channel estimation strategy for massive mimo time varying systems"
    - "low complexity mimo precoding with discrete signals and statistical csi"
    - "linear precoding for the mimo multiple access channel with finite alphabet inputs and statistical csi"
    - "large system analysis of correlated mimo multiple access channels with arbitrary signaling in the presence of interference"
    - "joint spatial division and multiplexing for mm wave channels"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "pilot contamination and precoding in multi cell tdd systems"

Connected through hyperedge HE-4 (induced by source paper "layered downlink precoding for c ran systems with full dimensional mimo"):
  with members:
    - "fronthaul compression and precoding design for c rans over ergodic fading channels"
    - "3d channel model in 3gpp"

Connected through hyperedge HE-5 (induced by source paper "multi layer precoding a potential solution for full dimensional massive mimo systems"):
  with members:
    - "low complexity massive mimo subspace estimation and tracking from low dimensional projections"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "subspace estimation and decomposition for large millimeter wave mimo systems"
    - "massive mimo ten myths and one critical question"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "massive mimo with multi cell mmse processing exploiting all pilots for interference suppression"
    - "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-6 (induced by source paper "dictionary learning based sparse channel representation and estimation for fdd massive mimo systems"):
  with members:
    - "sparse channel estimation for massive mimo with 1 bit feedback per dimension"
    - "compressed sensing for wireless communications useful tips and tricks"
    - "spatially common sparsity based adaptive channel estimation and feedback for fdd massive mimo"
    - "distributed compressive csit estimation and feedback for fdd multi user massive mimo systems"
    - "massive mimo for next generation wireless systems"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"

Connected through hyperedge HE-7 (induced by source paper "an effective limited feedback scheme for fd mimo based on noncoherent detection and kronecker product codebook"):
  with members:
    - "noncoherent trellis coded quantization a practical limited feedback technique for massive mimo systems"

Connected through hyperedge HE-8 (induced by source paper "sum rate and power scaling of massive mimo systems with channel aging"):
  with members:
    - "performance analysis of massive mimo for cell boundary users"
    - "uplink performance of time reversal mrc in massive mimo systems subject to phase noise"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"
    - "massive mimo for next generation wireless systems"
    - "energy efficiency optimization in hardware constrained large scale mimo systems"
    - "what will 5g be"

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)