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: "a new view of multi user hybrid massive mimo non orthogonal angle division multiple access"
  Abstract: This paper presents a new view of multi-user (MU) hybrid massive multiple-input and multiple-output (MIMO) systems from array signal processing perspective. We first show that the instantaneous channel vectors corresponding to different users are asymptotically orthogonal if the angles of arrival (AOAs) of users are different. We then decompose the channel matrix into an angle domain basis matrix and a gain matrix. The former can be formulated by steering vectors and the latter has the same size as the number of RF chains, which perfectly matches the structure of hybrid precoding. A novel hybrid channel estimation is proposed by separately estimating the angle information and the gain matrix, which could significantly save the training overhead and substantially improve the channel estimation accuracy compared to the conventional beamspace approach. Moreover, with the aid of the angle domain matrix, the MU massive MIMO system can be viewed as a type of non-orthogonal angle division multiple access (ADMA) to simultaneously serve multiple users at the same frequency band. Finally, the performance of the proposed scheme is validated by computer simulation results.

Connected through hyperedge HE-1 (induced by source paper "beam squint and channel estimation for wideband mmwave massive mimo ofdm systems"):
  with members:
    - "spatial and frequency wideband effects in millimeter wave massive mimo systems"
    - "beamforming codebook compensation for beam squint with channel capacity constraint"
    - "multi user precoding and channel estimation for hybrid millimeter wave systems"
    - "millimeter wave channel estimation via exploiting joint sparse and low rank structures"
    - "effect of wideband beam squint on codebook design in phased array wireless systems"
    - "channel estimation for millimeter wave multiuser mimo systems via parafac decomposition"
    - "channel estimation for hybrid architecture based wideband millimeter wave systems"
    - "low rank tensor decomposition aided channel estimation for millimeter wave mimo ofdm systems"

Connected through hyperedge HE-2 (induced by source paper "a framework on hybrid mimo transceiver design based on matrix monotonic optimization"):
  with members:
    - "hybrid beamforming via the kronecker decomposition for the millimeter wave massive mimo systems"
    - "spectral and energy efficiency of multi pair massive mimo relay network with hybrid processing"
    - "hybrid analog digital beamforming for massive mimo systems"
    - "hybrid analog and digital beamforming for mmwave ofdm large scale antenna arrays"
    - "codebook based hybrid precoding for millimeter wave multiuser systems"
    - "a novel hybrid beamforming algorithm with unified analog beamforming by subspace construction based on partial csi for massive mimo ofdm systems"
    - "hybrid beamforming for large antenna arrays with phase shifter selection"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"

Connected through hyperedge HE-3 (induced by source paper "inferring remote channel state information cram er rao lower bound and deep learning implementation"):
  with members:
    - "how often should csi be updated for massive mimo systems with massive connectivity"
    - "remote channel inference for beamforming in ultra dense hyper cellular network"
    - "structured compressive sensing based spatio temporal joint channel estimation for fdd massive mimo"
    - "seeing the unobservable channel learning for wireless communication networks"
    - "achievable rates of fdd massive mimo systems with spatial channel correlation"
    - "distributed compressive csit estimation and feedback for fdd multi user massive mimo systems"

Connected through hyperedge HE-4 (induced by source paper "high mobility wideband massive mimo communications doppler compensation analysis and scaling law"):
  with members:
    - "frequency synchronization for uplink massive mimo systems"
    - "high mobility ofdm downlink transmission with large scale antenna array"
    - "angle domain doppler pre compensation for high mobility ofdm uplink with a massive ula"
    - "directivity beamwidth tradeoff of massive mimo uplink beamforming for high speed train communication"
    - "bdma for millimeter wave terahertz massive mimo transmission with per beam synchronization"

Connected through hyperedge HE-5 (induced by source paper "a survey on non orthogonal multiple access for 5g networks research challenges and future trends"):
  with members:
    - "exploiting multiple antenna techniques for non orthogonal multiple access"
    - "achievable rate region of non orthogonal multiple access systems with wireless powered decoder"
    - "on non orthogonal multiple access with finite alphabet inputs in z channels"
    - "spectrum and energy efficient beamspace mimo noma for millimeter wave communications using lens antenna array"
    - "practical power balanced non orthogonal multiple access"
    - "noma based random access with multichannel aloha"
    - "optimal power allocation scheme for non orthogonal multiple access with alpha fairness"
    - "on optimal power allocation for downlink non orthogonal multiple access systems"

Connected through hyperedge HE-6 (induced by source paper "beam tracking for uav mounted satcom on the move with massive antenna array"):
  with members:
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "spatial temporal bem and channel estimation strategy for massive mimo time varying systems"
    - "enabling uav cellular with millimeter wave communication potentials and approaches"
    - "wireless communications with unmanned aerial vehicles opportunities and challenges"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "an esprit based approach for 2 d localization of incoherently distributed sources in massive mimo systems"
    - "five disruptive technology directions for 5g"
    - "scaling up mimo opportunities and challenges with very large 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)