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: "hybrid block diagonalization for massive multiuser mimo systems"
  Abstract: For a massive multiple-input multiple-output (MIMO) system, restricting the number of RF chains to far less than the number of antenna elements can significantly reduce the implementation cost compared to the full complexity RF chain configuration. In this paper, we consider the downlink communication of a massive multiuser MIMO (MU-MIMO) system and propose a low-complexity hybrid block diagonalization (Hy-BD) scheme to approach the capacity performance of the traditional BD processing method. We aim to harvest the large array gain through the phase-only RF precoding and combining and then digital BD processing is performed on the equivalent baseband channel. The proposed Hy-BD scheme is examined in both the large Rayleigh fading channels and millimeter wave (mmWave) channels. A performance analysis is further conducted for single-path channels and large number of transmit and receive antennas. Finally, simulation results demonstrate that our Hy-BD scheme, with a lower implementation and computational complexity, achieves a capacity performance that is close to (sometimes even higher than) that of the traditional high-dimensional BD processing.

Connected through hyperedge HE-1 (induced by source paper "principal component analysis based broadband hybrid precoding for millimeter wave massive mimo systems"):
  with members:
    - "closed loop sparse channel estimation for wideband millimeter wave full dimensional mimo systems"
    - "periodic analog channel estimation aided beamforming for massive mimo systems"
    - "device to device communications enabled energy efficient multicast scheduling in mmwave small cells"
    - "energy efficient multi user miso communication using low resolution large intelligent surfaces"
    - "wideband hybrid precoding for next generation backhaul fronthaul based on mmwave fd mimo"
    - "hybrid beamforming with selection for multiuser massive mimo systems"
    - "massive mimo channel estimation for millimeter wave systems via matrix completion"
    - "stochastic successive convex optimization for two timescale hybrid precoding in massive mimo"

Connected through hyperedge HE-2 (induced by source paper "channel estimation and hybrid precoding for distributed phased arrays based mimo wireless communications"):
  with members:
    - "modeling and analyzing millimeter wave cellular systems"
    - "framework of channel estimation for hybrid analog and digital processing enabled massive mimo communications"
    - "5g cellular user equipment from theory to practical hardware design"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "codebook design for millimeter wave channel estimation with hybrid precoding structure"
    - "the world s first real time testbed for massive mimo design implementation and validation"
    - "an overview of transmission theory and techniques of large scale antenna systems for 5g wireless communications"

Connected through hyperedge HE-3 (induced by source paper "non uniform quantization codebook based hybrid precoding to reduce feedback overhead in millimeter wave mimo systems"):
  with members:
    - "downlink precoding with mixed statistical and imperfect instantaneous csi for massive mimo systems"
    - "channel feedback based on aod adaptive subspace codebook in fdd massive mimo systems"
    - "spectral and energy efficiency of multi pair massive mimo relay network with hybrid processing"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "structured compressive sensing based spatio temporal joint channel estimation for fdd massive mimo"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "dynamic subarrays for hybrid precoding in wideband mmwave mimo systems"

Connected through hyperedge HE-4 (induced by source paper "millimeter wave massive mimo systems relying on generalized sub array connected hybrid precoding"):
  with members:
    - "spatial lobes division based low complexity hybrid precoding and diversity combining for mmwave iot systems"
    - "non uniform quantization codebook based hybrid precoding to reduce feedback overhead in millimeter wave mimo systems"
    - "on the energy efficiency of mimo hybrid beamforming for millimeter wave systems with nonlinear power amplifiers"
    - "stepwise transmit antenna selection in downlink massive multiuser mimo"
    - "downlink precoding with mixed statistical and imperfect instantaneous csi for massive mimo systems"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "codebook based hybrid precoding for millimeter wave multiuser systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"

Connected through hyperedge HE-5 (induced by source paper "majorization minimization aided hybrid transceivers for mimo interference channels"):
  with members:
    - "a framework on hybrid mimo transceiver design based on matrix monotonic optimization"
    - "hybrid analog and digital beamforming for mmwave ofdm large scale antenna arrays"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "hybrid beamforming for massive mimo a survey"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "two stage subspace constrained precoding in massive mimo cellular systems"
    - "near optimal hybrid processing for massive mimo systems via matrix decomposition"

Connected through hyperedge HE-6 (induced by source paper "mmwave amplify and forward mimo relay networks with hybrid precoding combining design"):
  with members:
    - "low rf complexity technologies to enable millimeter wave mimo with large antenna array for 5g wireless communications"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "transceiver design for dual hop nonregenerative mimo ofdm relay systems under channel uncertainties"
    - "distributed beamforming in wireless multiuser relay interference networks with quantized feedback"
    - "network beamforming using relays with perfect channel information"

Connected through hyperedge HE-7 (induced by source paper "bit interleaved coded multiple beamforming in millimeter wave massive mimo systems"):
  with members:
    - "diversity analysis of millimeter wave massive mimo systems"
    - "hybrid beamforming for large antenna arrays with phase shifter selection"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "on the feasibility of beamforming in millimeter wave communication systems with multiple antenna arrays"

Connected through hyperedge HE-8 (induced by source paper "a hardware efficient analog network structure for hybrid precoding in millimeter wave systems"):
  with members:
    - "hybrid precoding in millimeter wave systems how many phase shifters are needed"
    - "hybrid analog and digital beamforming for mmwave ofdm large scale antenna arrays"
    - "alternating minimization for hybrid precoding in multiuser ofdm mmwave systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "multi layer precoding a potential solution for full dimensional massive mimo systems"
    - "channel estimation for hybrid architecture based wideband millimeter wave systems"
    - "on the number of rf chains and phase shifters and scheduling design with hybrid analog digital beamforming"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"

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)